12.9 MB
UFC 3-410-06N
16 January 2004
UNIFIED FACILITIES CRITERIA (UFC)
IN
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CENTRAL HEATING PLANTS
OPERATION AND MAINTENANCE
APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED
UFC 3-410-06N
16 January 2004
UNIFIED FACILITIES CRITERIA (UFC)
CENTRAL HEATING PLANTS
OPERATION AND MAINTENANCE
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Any copyrighted material included in this UFC is identified at its point of use.
Use of the copyrighted material apart from this UFC must have the permission of the
copyright holder.
U.S. ARMY CORPS OF ENGINEERS
NAVAL FACILITIES ENGINEERING COMMAND (Preparing Activity)
AIR FORCE CIVIL ENGINEER SUPPORT AGENCY
Record of Changes (changes are indicated by \1\ ... /1/)
Date
Dec 2005
Location
FOREWORD
IN
Change No.
1
This UFC supersedes Military Handbook 1125/1, dated October 1995.
UFC 3-410-06N
16 January 2004
FOREWORD
\1\
The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides
planning, design, construction, sustainment, restoration, and modernization criteria, and applies
to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance
with USD(AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and
work for other customers where appropriate. All construction outside of the United States is
also governed by Status of forces Agreements (SOFA), Host Nation Funded Construction
Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.)
Therefore, the acquisition team must ensure compliance with the more stringent of the UFC, the
SOFA, the HNFA, and the BIA, as applicable.
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UFC are living documents and will be periodically reviewed, updated, and made available to
users as part of the Services’ responsibility for providing technical criteria for military
construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities
Engineering Command (NAVFAC), and Air Force Civil Engineer Support Agency (AFCESA) are
responsible for administration of the UFC system. Defense agencies should contact the
preparing service for document interpretation and improvements. Technical content of UFC is
the responsibility of the cognizant DoD working group. Recommended changes with supporting
rationale should be sent to the respective service proponent office by the following electronic
form: Criteria Change Request (CCR). The form is also accessible from the Internet sites listed
below.
UFC are effective upon issuance and are distributed only in electronic media from the following
source:
•
Whole Building Design Guide web site http://dod.wbdg.org/.
Hard copies of UFC printed from electronic media should be checked against the current
electronic version prior to use to ensure that they are current. /1/
AUTHORIZED BY:
______________________________________
DR. JAMES W WRIGHT, P.E.
Chief Engineer
Naval Facilities Engineering Command
______________________________________
KATHLEEN I. FERGUSON, P.E.
The Deputy Civil Engineer
DCS/Installations & Logistics
Department of the Air Force
______________________________________
Dr. GET W. MOY, P.E.
Director, Installations Requirements and
Management
Office of the Deputy Under Secretary of Defense
(Installations and Environment)
IN
______________________________________
DONALD L. BASHAM, P.E.
Chief, Engineering and Construction
U.S. Army Corps of Engineers
UFC 3-410-06N
16 January 2004
CONTENTS
Page
CHAPTER 1 INTRODUCTION
1-1
1-2
1-2.1
1-2.2
1-2.3
1-2.4
1-3
MIL-HDBK 1125/1…...…………...................…………………… A-1
IN
APPENDIX A
PURPOSE AND SCOPE ....................................................... 1-1
APPLICABILITY..................................................................... 1-1
General Building Requirements ............................................. 1-1
Safety .................................................................................... 1-1
Fire Protection ....................................................................... 1-1
Antiterrorism/Force Protection ............................................... 1-1
REFERENCES ...................................................................... 1-1
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Paragraph
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UFC 3-410-06N
16 January 2004
CHAPTER 1
INTRODUCTION
1-1
PURPOSE AND SCOPE. This UFC is comprised of two sections.
Chapter 1 introduces this UFC. Appendix A contains the full text copy of the previously
released Military Handbook (MIL-HDBK) on this subject. This UFC serves as criteria
until such time as the full text UFC is developed from the MIL-HDBK and other sources.
This UFC provides general criteria for operating and maintaining heating
systems.
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Note that this document does not constitute a detailed technical design,
and is issued as a general guide to the considerations associated with operating and
maintaining heating systems.
1-2
APPLICABILITY. This UFC applies to all Navy service elements and
Navy contractors; Army service elements should use the references cited in paragraph
1-3 below; all other DoD agencies may use either document unless explicitly directed
otherwise.
1-2
APPLICABILITY. This UFC applies to all DoD agencies and contractors
preparing designs of maintenance facilities for ammunition, explosives and toxins.
1-2.1
GENERAL BUILDING REQUIREMENTS. All DoD facilities must comply
with UFC 1-200-01, Design: General Building Requirements. If any conflict occurs
between this UFC and UFC 1-200-01, the requirements of UFC 1-200-01 take
precedence.
1-2.2
SAFETY. All DoD facilities must comply with DODINST 6055.1 and
applicable Occupational Safety and Health Administration (OSHA) safety and health
standards.
IN
NOTE: All NAVY projects, must comply with OPNAVINST 5100.23 (series), Navy
Occupational Safety and Health Program Manual. The most recent publication in this
series can be accessed at the NAVFAC Safety web site:
www.navfac.navy.mil/safety/pub.htm. If any conflict occurs between this UFC and
OPNAVINST 5100.23, the requirements of OPNAVINST 5100.23 take precedence.
1-2.3
FIRE PROTECTION. All DoD facilities must comply with UFC 3-600-01,
Design: Fire Protection Engineering for Facilities. If any conflict occurs between this
UFC and UFC 3-600-01, the requirements of UFC 3-600-01 take precedence.
1-2.4
ANTITERRORISM/FORCE PROTECTION. All DoD facilities must
comply with UFC 4-010-01, Design: DoD Minimum Antiterrorism Standards for
Buildings. If any conflict occurs between this UFC and UFC 4-010-01, the requirements
of UFC 4-010-01 take precedence.
1-1
UFC 3-410-06N
16 January 2004
APPENDIX A
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MIL-HDBK 1125/1
OPERATION AND MAINTENANCE: CENTRAL HEATING PLANTS
A-1
EEEl
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MIL-HDBK-1125/l
15 OCT~
HANDBooK
OF CENTRAL
HEATING
PLANTS
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MILITARY
AND OPERATION
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MAINTENANCE
AMSC N/A
~:
DISTRIBUTION
ARSA
APPROVED
IS UNLIMITED.
FOR PUBLIC
RELEASE;
FACR
MIL-HDBK-1125/l
ABSTRACT
A modern power plant requires that a very diverse mixture of
These
technology and hardware combine to form unique systems.
systems must then be integrated and developed into a complete
By understanding
these individual
systems, plant
power plant.
personnel are better able to perform the correct operation and
maintenance procedures needed to run a plant efficiently and
safely.
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This handbook was developed
for personnel who work in the field
performing operation and maintenance work on equipment.
It
should be used along with manufacturer’
literature to gain a
better understanding
of the different types of equipment
available within the power plant.
ii
MIL-EDBK-1125/l
(
FOREWORD
This military handbook is approved for
agencies of the Department of Defense.
use
by all departments
and
VE
Beneficial comments (recommendations,
additions, deletions) and
any pertinent data which may be of use in improving this document
should be addressed to: Commander,
Atlantic Division, Naval
Facilities Engineering Command, Code 161B, 1510 Gilbert Street,
Norfolk, VA, 23511-2699, telephone commercial (804) 322-4625, by
using the self-addreseed Standardization
Document Improvement
or
Proposal (DD Form 1426) appearing at the end of this document
by letter or by e-mail to [email protected]
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The purpose of this publication
is to provide practical
information on the equipment operation and maintenance of central
heating and power plant facilities.
It is primarily directed to
the personnal in the field who actually supenise
and perform the
operations and the maintenance work.
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Although the general subject of steam and power is highly
technical, this publication has been written in nontechnical
language, brief and direct, so that the reader will have the
basic information required for the intelligent handling of field
situations.
This publication has been written,
not only to be read, but more
important, to be used.
To obtain maximum benefit, it ehould be
consulted together with the equipment
manufacturerar instruction
manuala, parts lists, and drawings.
Much of the data contained
herein has originated at activity level and represents the actual
experiences of field personnel.
In addition, the latest
information operation and maintenance
procedures have been
collected and included.
THIS NANDBOOK SHALL NOT BE USED AS A RKFERENCE DOCUMSNT FOR
PROCUREMENT OF FACILITIES CONSTRUCTION.
IT IS TO BE USED IN THE
PURCBASE OF FACILITIES ENGINEERING
STUDIES AND DESIGN (FINAL
PLANS, SPECIFICATIONS,
AND COST ESTIMATES).
DO NOT REFERENCE
IT
IN MILITARY OR FEDERAL SPECIFICATIONS
OR OTHER PROCUREMENT
DOCUMENTS .
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MAINTENANCE
AND OPERATION
OF CEN’3VUL
HEATING
PLANTS
CONTENTS
Section
1
1.1
1.2
Section
2
2.1
INTRODUCTION
Scope ................... ..... ............... 1
Application ............. .. .................. 1
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CENTRAL BOILER PLANTS
Introduction .......... ..... ................. z
General Considerat~ons. . ... ................. 2
;::.1
Types of Central Boiler [email protected] .............. 2
2.2.2
Comparison of High Temperature
Water and
Steam ................... .... ............,...
2.2.2.1
Energy Loesee From a Steam Syetem ............ :
2.2.2.2
Pressure Reducing Valves and Vent
Condenser . ............. .................... 3
2.2.2.3
Heat Balance for a High Temperature
Water
(HTW) System ................................ 5
2.2.2.4
Corrosion ................... ................ 5
2.2.2.5
Stored Thermal Energy... ..... ............... 6
2.2.2.6
Safety ............... ..... . . . . . . . . . . . . . . . . .
2.2.2 .-) Water Treatment ........... . . . . . . . . . . . . . . . . . :
2.2.2.8
Loss of Steam Pressure and Quality .......... 7
LOW Temperature Water (L~, . ................ 1
2.2.3
2.3
Equipment ................. ................. 7
2.3.1
Heat-Absorbina
EauiDment. . ................. 7
2.3.2
Fuel-Eandling-Eq~ip~ent.
... ................. 7
2.3.3
Combustion Equipment.. ... ................... 8
2.3.4
Air-HandlingE quipment.
... .................. 8
2.3.5
Controls and Instrumentation . ............... 8
2.3.6
Pollution Control Equipment .. ............... 8
Water Treatment Systems. .... .............. .. 8
2.3.7
2.3.8
Water Supply Equipment. . ... ................. 9
2.3.9
Distribution
Systeme. ... .. .................. 9
2.3.10
Miscellaneous ........... .................... 9
Elementary Combustion
Principles ............ 9
2.4
Fossil Fuele ............... ................. 9
2.4.1
2.4.1.1
Coal ......#............ .... ................. 9
2.4. 1.2
Oil ......................... .............. ..10
2.4.1.3
Natural Gae ............... .......... ........14
2.4.1.4
Alternate Fuels ............ .................14
2.4.2
Combustion ................ ...... ............14
2.4.2.1
Chemical Reactions ........ ..................15
Air Requirements ........ ............ ........16
2.4.2.2
Excess Air Example ...... ....................16
2.4.2.3
2.4.2.4
Higher Heating Valuee (HHvs) .... .... ........17
2.4.3
Combustion of Coal ...... ....................17
2.4.4
Combustion of Oil .....,..... ................18
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2.5.2.7
3
3.1
3.1.1
3.1.2
3.1.3
3.1.3.1
3.1.3.2
3.1.3.3
3.1.4
3.1.5
3.1.5.1
3.1.5.2
3.1.5.3
3.1.5.4
3.1.5.5
3.1.5.6
3.1.6
3.1.7
3.1.8
3.2
3.2.1
3.2.2
3.2.3
3.2.4
3.2.5
3.2.5.1
3.2.5.2
DESCRIPTION OF EQUIPMENT
Boilers and Beat Exchangers .................37
Boiler Classifications . .............. .......37
Boiler Design Requirements ..................37
Fabrication .... .... ... ......................38
Drums, Shells, Readers . ... ..................38
Boiler Tubes. .. .... .... .....................38
Bafflee ......,.. .... .... ,.....,.............39
Fire Tube Boilers .... .... .. .................39
Water Tube Boilers ... ................ .......42
Refractory Furnaces.. ... ....................43
Water Wall Construction. ....................43
Steam Drum Internals .... ....................45
Generating
Surface. .... .....................45
Superheaters ..... .... ..... ........... .......
Package Boilers . . .... ..... ..................;:
Hot Water Generators.. . .....................48
Economizers .... .... ..... .....................49
Air Heaters . .... .... .... ............. .......53
Boiler Ac~essories
and Fittings .............53
ASMERequlrements
.... .......................53
Gage Glass, Gage Cocks ......................55
Water Columns .. ... ... .......................56
Pressure Gage, Temperature
Gage .............56
Safety Valves ... . .... ...... ,................57
Types of Safety Valvee ......................58
Safety Valve Capacity.. .....................60
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2.5.1
2.5.2
2.5.2.1
2.5.2.2
2.5.2.3
2.5.2.4
2.5.2.5
2.5.2.6
Combustion
of Natural Gas. ..................18
soot and Smoke .. ...... ......................19
soot ............ ....... .....................19
Smoke ........... ........ ....................19
Stack Opacity .... ..... . .....................20
Flue Gas Analysi~ and Temperature ...........2O
Combustion Efficiency ... ....................
Boiler Efficiency ........ ...................:!
Central Boiler Plant Efficiency .............28
principles of Steam and Hot Water
Generation ..,......... ......................29
Basic Principles ... .. ...... .................29
Heat Transfer .. ..... ...... ............. .....31
Radiation ...... ...... ... .. ..................31
Conduction ...... ... .. ... ....................31
Convection ..... ..... ..... ...................32
Gas Flow Considerations . .. ..................32
Water Circulation
Considerations. ...........32
Heat Transfer to Boiler Tubes and Water
by Convection ... ...... ... ....................33
Optimizing
Heat Transfer .. ..................33
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2.4.5
2.4.6
2.4.6.1
2.4.6.2
2.4.6.3
2.4.7
2.4.8
2.4.9
2.4.10
2.5
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Safetv Valve Settinae.
... ...................61
.
Boiler Outlet Valves.. ... ...................61
Blowoff Valves and Piping ...................63
Fusible Pluge . .... .. .... ....................63
Fire-Actuated
Plug . .... .....................
Steam-Actuated
Plug... . .....................::
Soot Blowere .... ... .. .......................64
Brushes, Scrapere,
and Band Lances ..........65
Mechanical Soot Blowers . ....................65
Fuel-13andling and Combetion
Equipment. ..,..66
Coal Combustion
Equipment ...................66
Stokers ... .. .... ... . ..... ...................67
Underfeed Stokere .. .... .....................67
Spreader Stokers . .. ..... ....................70
Traveling Grate and Chain Grate Stokers .....74
Vibrating Stokere .. .. ... ....................75
Pulverizer.
.... .. .. .. ......................
Fluidized Bed ... .. .. .. ......................::
Coal-Bandling
Equipment . ....................81
Storage ...... ... .. .. .. ......................82
Coal Flandling in Plant. . ................. ...82
Ash Bandling Equipment. . ....................85
Pneumatic Ash Handling. ............ .........86
17ydraulic Ash Rankling. .....................87
Mechanical Ash Handling .....................87
Oil-Firing
Equipment .. ......................88
Types of Oil Atomizers. . .,..................88
Typeeof
Burnere .. .. .. ......................90
Oil Storage and Handling. ...................92
Fuel Oil Preparation..
.. ....................93
Safety Equipment . . .. .... ....................93
Gas-Firing Equipment . .......................97
Liquefied Petroleum
Gae (LPG) ...............97
Controls and Instrumentation
.......... ......97
Feedwater-Drum Level Controls ...............99
Pofiitive Displacement ... .......,............99
Thermohydraulic . .. .. .. ......................99
Thermostatic .. .. ... . ... ....................1OO
Drum Level Transmitter .....................102
Combustion Controle. ... ....................105
Control Concepts .. . . ... ....................106
Controls for Stoker-Fired
Boilers ..........l12
Controls for Oil- and Gas-Fired Boilers ....ll4
Boiler Safety Control ... ...................117
Control Logic ... .. .. .. .. ...................118
Low Water Fuel Cutoff. . ....................119
Pressure and Temperature
Switches ..........ll9
Flame Scanners .. .. .. ... ....................124
tinunciatore .. ... .. . ... ....................124
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3.2.5.3
3.2.6
3.2.7
3.2.8
3.2.8.1
3.2.8.2
3.2.9
3.2.9.1
3.2.9.2
3.3
3.3.1
3.3.1.1
3.3.1.2
3.3.1.3
3.3.1.4
3.3.1.5
3.3.1.6
3.3.1.7
3.3.2
3.3.2.1
3.3.2.2
3.3.3
3.3.3.1
3.3.3.2
3.3.3.3
3.3.4
3.3.4.1
3.3.4.2
3.3!5
3.3.5.1
3.3.5.2
3.3.6
3.3.7
3.4
3.4.1
3.4.1.1
3.4.1.2
3.4.1.3
3.4.1.4
3.4.2
3.4.2.1
3.4.2.2
3.4.2.3
3.4.3
3.4.3.1
3.4.3.2
3.4.3.3
3.4.3.4
3.4.3.5
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Additional Controls and Instrumentation ....125
Air-Flow Steam-Flow Meter ... .. .............125
Temperature Controls.. ..; .. ... .............125
Pressure Controls ......... .... .............127
Flow Meters ................ .. ..............133
Pressure Gages ............ .... .............~~~
Draft Gages ............... ... ..............
Flue Gas Analyzers ......... ... ..............144
Temperature Gages ......... ... ..............146
Recorders ................ .... ..............146
Pollution Control Equipment .. .. ............146
Pollution Regulations .... .... .. ............146
Point Source Regulation . .... ... ... .’
. ......147
Ambient Air Quality Standards .. ............147
Types of Pollutant
and Control Methods ....l48
Oxides of Nitrogen ......... .... ............148
Oxides of Sulfur ........... ... .............148
Particulate .............. .... ..............151
Pollutants from Natural Gas .. ..............l5l
Pollutant
frOm Oil ...... .... ..............152
Pollutants frOm COal.. ... .... ..............152
Mechanical Collectors .... .... ..............153
Single Cyclone .......... ...... .............153
Multicyclones ..... ...... ..... ..............153
Other Cyclones .......... ...... .............153
Collection Efficiency of Cyclones ..........l56
Pressure Drop and Energy Requirements ......l57
Cyclone Performance ..... .... ... ............158
Application for Particulate
Collection. ....158
Application as Precleaners .. ...............158
Application for Reinfection ................159
Effect of Firing Modee. . .... ... ............159
Fabric Filters .......... .... ...............159
Housing Design .......... .... ...............159
Filter tirangement ...... .... ...............159
Filter Cleaning Methode. ..... ..............160
Energy Requiremente ...... ..................162
Application of Fabric Filters . .............l63
Electrostatic
Precipitators ... .............163
Electrode Design .......... .... .............163
Precipitator Location .. .... ... .............165
Cleaning and Dust Removal .. ... .............165
Energy Requirements .... .... ... .............165
Application of Electrostatic
Precipitators.166
Wet Scrubbers .......... .... ................166
Auxiliary Equipment.. .. .... ................166
Feedwater Eeaters ....... .. .... .............167
Pumps and Injectors .... ... .... .............167
Installation .............. ... ..............168
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3.4.4
3.4.4.1
3.4.4.2
3.4.4.3
3.4.4.4
3.4.4.5
3.4.4.6
3.4.4.7
3.4.4.8
3.4.4.9
3.5
3.5.1
3.5.1.1
3.5.1.2
3.5.2
3.5.2.1
3.5.2.2
3.5.2.3
3.5.2.4
3.5.2.5
3.5.2.6
3.5.3
3.5.3.1
3.5.3.2
3.5.3.3
3.5.3.4
3.5.3.5
3.5.3.6
3.5.3.7
3.5.3.8
3.5.3.9
3.5.3.10
3.5.4
3.5.4.1
3.5.4.2
3.5.4.3
3.5.4.4
3.5.4.5
3.5.5
3.5.5.1
3.5.5.2
3.5.5.3
3.5.5.4
3.5.5.5
3.5.6
3.6
3.6.1
3.6.2
3.6.2.1
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Centrifugal Pumps ..........................
Reciprocating
Piston Pumps .................173
Rotary Positive Displacement
Pumps.........l74
JetPumps/Injectors
.......... ..............177
Boiler Feed Pumps ..........................179
Condensate Pumps ...........................179
Vacuum Pumps ...............................180
Forced Draft (PO) Fans .....................180
Induced Draft (ID) Fana ....................183
Stacks, Fluee, and Duct . ................. .183
Stack Construction .........................183
Flueeand
Ducte ............................184
Steem Turbinee .............................184
Electric 140tore.............................185
Electrical Equipment. ......................186
Variable Speed Drivee. .....................186
Air Compreseore ............................186
Reciprocating Compressors ..................186
Rotary Screw Compreesore ...... .............186
Capacity of Air Compreeeors ................187
Aftercoolere ...............................187
Air Dryere ................... ..............187
Air Receivere ..............................188
Steam Traps ................................188
Thermostatic Steam Traps ...................188
Float and Thermostatic
Steam Traps .........189
Disc/Thermodynamic
Steam Trape .............190
Inverted Bucket Steam Trape ................190
Piping Systems .............................192
Design Codee ................. ..............192
Materiale ..................................193
Sizing ............. ........................193
Fittinge and Jointe. ... ....................196
Pipe Supporta ..............................196
Valvee .....................................198
Insulation .................................204
4
4.1
4.2
4.2.1
4.2.1.1
4.2.2
4.2.3
4.2.4
4.2.4.1
4.2.4.2
4.2.4.3
4.2.4.4
OPERATION
Introduction ...............................205
Preliminary operating Procedures ...........2O5
Plant Operation Considerations .............205
Boiler Plant Operating Loge ................205
Inspection .................................205
Applicable Codes ...........................206
Preparation for Start-up ...................206
Instrumentation ............................206
Internal Inspection ............. ...........206
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3.6.2.2
3.6.2.3
3.6.2.4
3.6.2.5
3.6.2.6
3.6.2.7
3.6.2.8
3.6.3
3.6.4
3.6.5
3.6.5.1
3.6.5.2
3.6.6
3.6.7
3.6.8
3.6.9
3.6.10
3.6.10.1
3.6.10.2
3.6.10.3
3.6.10.4
3.6.10.5
3.6.10.6
3.6.11
3.6.11.1
3.6.11.2
3.6.11.3.
3.6.11.4
3.6.12
3.6.12.1
3.6.12.2
3.6.12.3
3.6.12.4
3.6.12.5
3.6.12.6
3.6.12.7
Section
Combustion Equipment. ......................206
“
Puel Supply ................................206
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Furnace Purge ..............................207
Starti.ngFire ..............................208
Rand Firing Coal ...........................208
Stoker Firing Coal.... .....................208
Pulverized Coal Firing. ....................208
Oil F~r$ng .................................208
Gas Fumg
.................................209
Warm-Up Time ...............................210
Placing a 13igh Pressure Steam Boiler in
Service ..... ...............................210
Control of Water Level. ....................210
Checking Safety Valves. ....................210
Operation of Header Valves .................211
Activate Controle ..........................211
Placing a Hot Water Boiler in Service. .... .211
Procedure for a Single Boiler ..............211
Action in Case of Abnormal Conditione ......213
Placing Additional
Boilers into Service. ...213
Operating Adjustments
and Procedures ........2l3
Boiler Operation ...........................213
Maintaining
Pressure or Temperature ........213
Feedwater and Boiler Water Treatment .......214
Controlling
Feedwater ......................214
Boiler Accessories .........................214
Water Column and Gage Glass ................2l5
Safety Valves ..............................215
Blowoff Lines .. ......................... ...217
Soot Blowers ... ............................217
Coal Firina Procedures. ....................218
Iland Fi.rin~ -Coking. ......................218
Hand Firing - Alternate Method .............219
Hand Firing - Spreader Method ..............219
Cleaning Hand-Fired
Furnaces .............. .219
Combustion Rate Regulation in Hand-Fired
Furnace . ............ ......................219
Underfeed Stoker Firing ....................220
Spreader Stoker Firing. ................. ...221
Traveling Grate Stoker Firing ..............222
Oil-Firing Procedures ......................224
Sludge Control .............................224
Air Leakage ................................224
Oil Strainere ..............................225
Oil Heating ................................225
Oil Temperature
at Burner ................. .225
Oil, Atomizing
Steam, and Combustion
Air at Burner ..............................226
IN
AC
4.2.7.1
4.2.7.2
4.2.7.3
4.2.7.4
4.2.8
4.2.8.1
4.2.8.2
4.2.8.3
4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.5.1
4.3.5.2
4.3.5.3
4.3.5.4
4.3.6
4.3.6.1
4.3.6.2
4.3.6.3
4.3.6.4
4.3.6.5
Water Supply ...............................
Water Column and Gage Glass ................207
Boiler Safety Control.. ....................207
TI
VE
4.2.4.5
4.2.4.6
4.2.4.7
4.2.4.8
4.2.5
4.2.5.1
4.2.5.2
4.2.5.3
4.2.5.4
4.2.5.5
4.2.6
4.2.7
4.3.6.6
4.3.6.7
4.3.6.8
4.3.7
4.3.7.1
4.3.7.2
4.3.7.3
4.3.7.4
4.3.7.5
4.3.7.6
x
MIL-13DBK-1125/l
TI
VE
Burner Adjustments ...... ............... ....226
Daily Operation ......
. ... ...................227
Gaa-Firing
Proceduree. .....................227
Pressure Regulation.. ... ...................227
Burner Adjustment
.........................227
Daily Operation ......... ...................227
Combustion
Controla ........................228
Fuel/Air Ratio Adjustment ..................228
Standard Operating Procedures ..............228
Boiler Safety Controls. ....................230
Centrifugal
Pumps ........ .............. ....230
Operating Centrifugal Pumps in Parallel ....23l
Controlling Leakage. ... . ...................231
Lubrication ............................ ....231
Direct-Acting
Pumps... .....................231
Operation ............... ...................232
Lubrication ............. ............. ......232
Leakage ....................................232
Steemor
Air Binding.. .. ............. .. ....232
Injector . ........... ......................232
Fans . .................................. ....233
Lubrication ................................233
Water-Cooled
Bearings ... ............... ....233
Regulation .................................233
Common Difficulties ..... ............... ....233
Feedwater Heating and Treatment ............234
Economizers,
Air Heaters, and Pollution
Control Equipment ...... .............. .. ....234
Emergency Procedure - Abnormal Water Level.234
Low Water Level ........................ ....235
High Water Level (Steam Boilers] ....... ....235
Emergency Procedure - Boiler Tube Failure. .235
Procedure
for Gae- or Oil-Fired Boilers ....235
Procedure
for Stoker-Fired
Boilers ..... ....236
Emergency Procedure - Fan Failure ..... .. ...237
Emergency Procedure - Electric System
Failure ................. .............. .....237
Emergency Procedure - Flame Failure .... ....238
Removing a Boiler From Service ....... ......238
Optimizing
Central Plant Efficiency .... ....239
Optimizing
Combustion Efficiency ....... ....239
Soot Blowing/Cleaning
to Reduce Flue Gas
Temperatures ........... .............. ... ...239
Waterside
Cleaning.. .................. ....240
Setting Leaks .......................... ....240
Baffles ................ .............. .. ....240
Fuel/Air Ratio Optimization ............ ....240
Optimizing
Boiler Efficiency, ........ ......241
Reduce Radiation Loseee . ............... ....242
AC
4.3.7.7
4.3.7.8
4.3.8
4.3.8.1
4.3.8.2
4.3.8.3
4.3.9
4.3.9.1
4.3.9.2
4.3.10
4.3.11
4.3.11.1
4.3.11.2
4.3.11.3
4.3.12
4.3.12.1
4.3.12.2
4.3.12.3
4.3.12.4
4.3.13
4.3.14
4.3.14.1
4.3.14.2
4.3.14.3
4.3.14.4
4.3.15
4.3.16
IN
4.3.17
4.3.17.1
4.3.17.2
4.3.18
4.3.18.1
4.3.18.2
4.3.19
4.3.20
4.3.21
4.3.22
4.4
4.4.1
4.4.1.1
4.4.1.2
4.4.1.3
4.4.1.4
4.4.1.5
4.4.2
4.4.2.1
xi
MIL-HDBK-1125/l
Reduce Blowdown Loeses. ....................242
Reduce Unburned Carbon Losses ..............242
Stabilize Combustion Controls.. ............242
Optimizing
Central Boiler Plant Efficiency.243
Boiler Selection .... ................. ......243
Deaerato~ Control ,....................... ..243
Steem-Driven
Auxiliaries .............. .....243
Plant Building Consemation
......... .., ....244
Equipment Modifications
or Addition”s. .. ....244
Distribution
System Effects on Plant
Efficiency ..........................~......245
IN
AC
TI
VE
4.4.2.2
4.4.2.3
4.4.2.4
4.4.3
4.4.3.1
4.4.3.2
4.4.3.3
4’.4.3.4
4.4.3.5
4.4.3.6
Section
5
5.1
5.1.1
5.2
5.2.1
5.2.2
5.2.3
5.2.3.1
5.2.3.2
5.3
5.4
5.5
5.6
5.6.1
5.6.1.1
5.6.1.2
5.6.2
5.6.2.1
5.6.2.2
5.6.2.3
5.7
5.7.1
5.7.2
5.7.3
5.8
5.9
5.9.1
5.9.2
5.10
5.10.1
5.10.2
5.10.3
5.10.4
5.10.5
5.10.6
5.10.7
5.10.8
INSPECTION AND PREVENTIVE MAINTENANCE.
Purpose and Scope ................... .......246
References .......................... .......246
Types of Maintenance .......................246
Breakdown Maintenance ............... .. .....246
Prev~ntive
Maintenance .....................247
Pred~ctive
Maintenance ............... ......247
Benefits . .............. ............ .. ......247
Vibration Analysis .................... .....248
Responsibility ...................... .......248
Inspection .................................248
Housekeeping ...............................249
Utilities
Inspection and Service Records. ..249
Records ....................................249
Computerized
Maintenance
Management System.249
Data Entry .......................... .......252
Assignment
of Work.... ............. ........253
Chief Operator/Supervisor
.............. ....253
Regular Operators ................... .......253
Maintenance
Men ....................... .. ...254
Tools ............................... .......254
Special Tools .,. .................... .......254
Care of Tools ......................... .....254
Tool Board ........................... ......254
Spare Parts..., ..................... .... ...254
Special Supplies ...................... .....255
Lubricants ............................ .....255
Cleaning Solvents ........ ........... ... ....255
Scheduled Preventive Maintenance ...... .....255
Scheduling
and Use of the Information. . ....255
Boilers .............................. ......256
Economizers ......................... ... ....260
Air Heaters ........ ................ .. ......260
Water Columns ........................ ......261
Safety Valves ............ .......... ... .....262
Fusible Plugs ........................ ......262
Soot Blowers ............. ............ ......263
xii
HIL-HDBK-1125/l
TI
VE
Stokers . .... ... ............................263
Pulverized Coal Equipment ..................265
Lubrication ... ..... ........................265
Ball Mills ... .. ............................265
..........266
Bowl Milla ...... ..................4
Ball-Race Pulverizer .......................267
Attrition
Pulverizer .... ...................268
Coal-Handling
Equipment ....................269
Ash-Handling
Equipment .....................271
Oil Burners ... . .......... ..................271
Oil-Eandling
Equipment .....................272
Gaa Burners .. .. .......... ..................273
Feedwater/Drum
Level Controls..............273
Combustion
Controla ..................~ .....274
Boiler Safety Controla. ....................275
Instrumentation ............................275
Mechanical
Collectors ......................276
Stacke ....... .. ........................... .276
Zeolite Water Softeners ....................277
Hot Lime-Soda
Softeners ....................278
Deaerating
Heatera and Deaerators ..........279
Pumps ....... .. .............................280
Centrifugal
Pumps ........ ....,.............281
Reciprocating
Pumps ........................282
Steam Injectors .......... ..................284
Steam Turbines
(Noncondensing) .............284
Air Compresaore ............................286
Steam Traps ... .............................287
Electric Motora ......... ...................288
Forced Draft (FD) and Induced Draft (ID)
Fans . ......... ......... ....................289
Command Inspections ........................290
Procedure ..... .............................290
AC
5.10.9
5.10.10
5.10.10.1
5.10.10.2
5.10.10.3
5.10.10.4
5.10.10.5
5.10.11
5.10.12
5.10.13
5.10.14
5.10.15
5.10.16
5.10.17
5.10.18
5.10.19
5.10.20
5.10.21
5.10.22
5.10.23
5.10.24
5.10.25
5.10.26
5.10.27
5.10.28
5.10.29
5.10.30
5.10.31
5.10.32
5.10.33
IN
5.10.34
5.10.34.1
5.10.34.2
5.10.35
5.10.35.1
5.10.35.2
Follow-uP
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...290
Technical
Inspection .......................290
Procedure ..... .......... ...................29I
Follow-up .... .. ............................291
APPENDIX
APPENDIX
A
Heat
Balance
Calculations
..................292
FIGURES
FIGURE
1
2
3
100-psi Steam Heat Balance .................
15-pai Steam Heat Balance. .................
High Temperature
Water Heat Balance ........
xiii
4
5
6
4
5
6
7
8
9“
IN
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
AC
TI
20
21
22
VE
10
11
12
13
14
15
16
17
18
19
MIL-HDBK-1125/l
(
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
IN
73
74
75
76
77
78
79
80
81
82
TI
VE
52
Fuel Oil Pumping and Heating Equipment ..... 94
Safety Equipment,
Oil-Fired Water Tube
Boiler ........ . .. .......................... 95
Safety Equipment,
Gaa- or Oil-Fired Water
Tube Boiler ... .. .. ......................... 96
Safety Equipment,
Natural Gae-Fired Water
Tube Boiler .. .. . . .......................... 98
Positive Displacement
Feedwater Regulator. .100
Vapor-Generator/Thermohydraulic
Feedwater
Regulator .... .. . ...........................101
Thermostatic/Metal
Expansion Feedwater
Regulator .... .. . ...........................102
Drum Level’Transmitter
- Connection and
Calibration .. .. . ...........................103
Two-Element Feedwater Controls .............lOS
Control Valve With Pneumatic Actuator ......lO7
Control
. . Valve With Pneumatic Actuator and
pos~tloner .... . . ...........................108
Steam Pressure Control System ... ...........lO9
Proportional Control ............ ...........110
proportional
Response ............ ..........111
Proportional
Plus Integral Response ........ll2
Parallel Positioning
Control System ........ll3
Series/Parallel
Control ....................115
Jackshaft Control System ...................115
parallel Metering control ..................116
Oxygen
Trim Control System .................117
Electronic Programming
Control in a Boiler
Panel ....... .. . . ...........................120
Float/Magnet
Low Water Fuel Cutoff .........l2l
Resistive Type Low Water Fuel Cutoff .......l22
Mechanical Type Pressure Switch .. ..........l22
Diaphragm Pressure Switch ..................123
Temperature
Switch .........................123
U-V Flame Scanner ..........................124
Annunciator . .. . . ...........................125
Direct-Acting
Temperature
Regulator ........l26
Pilot-Operated
Temperature Control Valve. ..l27
Pilot-Operated
Pressure-Reducing
Valve.. ...129
Diaphragm Actuator
Pressure-Reducing
Valve.130
Self-Contained
Diaphragm Pressure-Reducing
Valve ........ . . ..................... .......131
Differential
Pressure-Reducing
Valve .......l32
Steam Differential
Pressure-Reducing
Valve.133
Orifice, Flow Nozzle, and Venturi ..........l3S
Steam Flow Recorder.. ......................136
Pneumatic Differential
Pressure
Transmitter .. . . .. ..........................137
Pitot Tube Design and Installation .........l37
AC
50
51
83
84
85
86
87
88
xv
MIL-HDBK-1125/l
11OA
11OB
111
112
113
114
VE
IN
115
116
117
118
119
120
121
122
123
124
125
126A
126B
127
128
129
130
131
132
A-1
TI
106B
107
108
109
Vortex Shedding Phenomenon .................138
Positive Displacement
Meter. .............. . 139
Turbine Meter .............’.................140
Bourdon Tube Preseure Gage ............ ... ..142
Opposed Bellows Differential
Pressure Gage.142
Inclined/U-Tube
Manometer .............. ....143
Diaphragm Draft Gage. .... .............. .. ..144
Zirconium Oxide Oxygen Analyzer .....~ ... . ..l45
Strip Chart Recordera.. .. ............... ...147
Medium Efficiency Cyclone Configuration . ...l54
Multicyclone
Configuration .............. ....155
Cyclone Fractional Efficiency Curve .... ....l57
Reverse Flow Baghouse.. .. ............... ...161
Pulse Jet Baghouse. ...... .............. ... .162
Electrostatic
Precipitator ............. ....164
Wet Approach Venturi Scrubber .......... .. ..167
U-Tube Heat Exchanger. ................. ....168
Maintain Proper Slope to Suction Line .... ..l69
Suction Line Installation ............... ...170
Centrifugal
Pump ......... ................ . . 171
Reciprocating
Piston Pump ................ . .174
Two Methods of Providing Lost Motion .... ...l75
Rotary Screw Pumps... .... ............ .... . .176
Rotary Gear Pumpa ........ ............ ......177
Steam Injector .......... ...................178
Forced Draft Fan With Inlet Damper .... ... ..l8l
Typical Outlet Fan Dampers ............ ... ..l8l
Fan Curves for Different Inlet Vane
Positions .. ............. ................ ...182
Fan Curve for Fan with Outlet Dsmper ... .. ..l82
Single-stage
Impulse Noncondensing Turbine.185
Thermostatic
Steam Trap ................ . ...189
Float and Thermostatic
Steam Trap ....... . ..l9O
Disc/Thermodynamic
Steam Trap .......... .. ..l9l
Inverted Bucket Steam Trap .............. . ..l92
Standard Ranger Types for Piping Syetems. ..l97
Solid Wedge Disc Gate Valve .......... ... . . .199
Single-Port Globe Valve ............... .. ...200
Nonlubricated
Plug Valve ............... . ...201
Butterfly Valve ........................ ....202
Swing Check Valve.... .................. . ...203
Y-Type Spring Lift Check Valve ........ .. . ..2O3
Oil Viscosity Versus Temperature ...... .. . . .226
Smoke Density Versue Percent Oxygen ... .. ...229
Fuel/AirRatioBiasing.
................ ....230
Boiler Efficiency Versus Load ......... .. ...244
Hot Water Beating Boiler Log ......... ... . ..25O
Steam Heating Boiler Log. ............ ... ...251
100-psi Steam Beat Balance .......... .... ...292
AC
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106A
xvi
MIL-HDBK-1125/l
A-2
A-3
15-psi Steam Heat Balance ..................296
High Temperature Water (HTW) Beat Balance..299
TABLES
8
9
10
11
12
IN
AC
13
Classification
of Coal.... ................. 11
Standard Specification
for Fuel Oils ....... 12
Range of Analysea of Fuel Oils ..... ........ 13
Combustion Efficiency for Natural Gas ...... 23
Combustion Efficiency for No. 2 Oil ........ 24
Combustion Efficiency for No. 6 Oil ........ 25
Combustion Efficiency for Coal, 3.5 Percent
MOiBtUre, Bituminous . ...................... 26
Combustion Efficiency for Coal, 9.0 Percent
Moisture, Bituminous ......... .............. 27
WaterlSteam Characteristics ................ 30
Feedwater Control Symbols ..................104
Comparison of NO, Reduction Techniques. ....149
Performance Characteristics
of Flue-Gas
Desulfurization
Systems ....................ISO
Performance Characteristics
of Particulate
Control Devices ............................I52
Characteristics
of Mechanical Dust
Collectors .................................I56
Removal Efficiencies
of Uncontrolled
Particulate Emisaione From Combustion
Processes . .................................157
Permissible Maximum Suction Lifts and
Minimum Suction Heads in Feet for Various
Temperatures
and Altitudes .................169
Piping Codes and Standards for Boiler
Plants ..... .............,........,.........194
Typical Piping 14aterial Applications .......l95
Flue Gas Analysis at 25 Percent,
50 Percent, and 100 Percant Load for
Natural Gas, No. 2 Oil, No. 6 Oil,
and Stoker Coal.... ........................241
VE
1
2
3
4
5
6
7
TI
Table
15
16
17
18
19
BIBLIOGRAPHY
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REFERENCES
...........................................303
GLOSSARY
.............. .............................306
xvii
301
—
HIL-HDBK-1125/l
(
Section
1:
INTRODUCTION
TI
VE
1.1
S=?12e. The purpose of this hendbook is to provide
information
and guidance on installation,
operation, and
maintenance
of U.S. Navy central boiler plant equipment.
Efficient plant operation becomes more important
with each
increase in cost of fuel and equipment.
The central plant
and maintaining
operator has an important job in achieving
maximum efficiency
of plant operation.
Information
and guidance
in this handbook should be reviewed as a first etep toward
achieving efficient plant operation.
Coneult manufacturers’
literature to obtain information specifically
related to your
plant.
IN
AC
1.2
. The primary purpose of a central boiler
plant is to economically
produce energy for distribution.
This
energy may be in the form of steam, hot water, or occasionally,
compressed air or electric power.
A distribution
system is
necessary to carry this energy to buildings,
hospitals, kitchens,
and laundries where it is used for heating, cooling, process,
sterilization,
and production of domestic
hot water.
Condensate
or hot water is returned to the central boiler plant where it is
reheated in a boiler and returned to the distribution
eystem to
be recycled.
1
.
MIL-HDBK-112511
Section
2:
CENTRAL
BOILER
PLANTS
VE
The purpose of this handbook is to
2.1
In production.
provide information and guidance on installation, operatio~ii~nd
maintenance of U.S. Navy central boiler plant equipment.
handbook is generic
in nature because it is intended for use in
It is limited to basic theory
Naw
shore steamlheatinq
plants.
and-concepts,
typical equipment,
generally accepted operating
procedures, proven maintenance
principles, and practices common
to most installations.
TI
The primary purpose of this
2.2
General Considerations.
manual ie to inform and guide the plant staff in operation and
maintenance of the overall plant and associated equipment;
ranging from small sensitive
instruments to rugged pumps and
boilers.
This manual meets the needs of both plant operators
and
maintenance
staff by providing
a better understanding
of the
With a
inner workings and purpose of every piece of equipment.
common understanding,
each discipline
can communicate well and
assist each other to achieve efficient and reliable plant
operations.
IN
AC
It Is essential that each plant
have in place all
material from manufacturers
pertinent to specific items of
equipment.
Identical plants do not exist, consequently
one
manual cannot be written to meet the complete needs of all
plants.
Most major manufacturers
publish informative booke,
booklets, bulletins, or pamphlets
dealing with their products.
They are in a wide range of physical sizes from small pocket
books to encyclopedias.
In addition, there are several thermal
plant oriented books, pamphlets,
and periodicals available.
These publications can provide viable, up-to-date information
on
central beating plant equipment
and should be available to the
plant staff.
2.2.1
process
~
1’
use i: generally
ts.
Energy
in one of three
produced
a) Low temperature
and less than 160 psig)
water
for heating
forms:
(LTW) (up to 250 degrees
or
F
b) High temperature
water (HTW) (pressure exceeding
160 psig andlor temperature
exceeding 250 degrees F)
water (MTW) (200 to 300 degrees
c) Medium temperature
F and 150 psig to 300 psig), i.e., overlaps ASME ranges for LTW
and HTW generators
2
MIL-HDBK-1125/l
VE
The type of central boiler plant dependa upon
For applications
requirements of the specific installation.
involving only space heating and domestic water, a LTW plant ia
If eteem ia required for large process
generally sufficient.
loads or electric generation,
a steam plant must be constructed.
For most other installation,
ah economic evaluation must be
performed to compare the costs of a HTW system to those of a
steam system.
Such an evaluation usually shows the HTW plant to
be more economical.
The following paragraphs provide a brief
comparison of the major typee of central heating plant systems.
and Stew . Major
2.2.2
of H~
advantagea of HTW and MTW systems result from the closed-loop
distribution
system.
The closed-loop
eystem recycles unused
energy in the water which results in very small system water
loeses.
By comparison,
steam distribution
systems include
condensate return syetems with potentially
significant energy and
water lessee due to steam flashing, defective traps, defective
pressure reducing valvee, pipe leake, and unreturned procees
steam.
Advantages
of HTW and MTW systems are further discuesed
in the following paragraphs.
IN
AC
TI
(
2.2.2.1
~.
Fi9ures 1 and 2
illustrate the heat balance at a heat exchanger for a 100-psig
and 15-psig steem/condensate
system, respectively.
When 100-peig
eteem is supplied to a heat exchanger, condensed water is at a
temperature of 338 degrees F and contains 26 percent of the
energy originally
supplied in the steam.
When condensate
discharges from the trap, 13 percent of the water flashee to
eteam and the remaining
condensate
is at a temperature of 212
degrees F. When 15-psig eteam ie supplied, condensed water
contains 19 percent of the original energy at a temperature
of
250 degrees F. When condensate discharges
from the trap, 4
percent of the water flashes to steam.
Energy losses and makeup
water requirement
of the low pressure system are thue lower,
making the low pressure
system preferable if a steam system is
used.
2.2.2.2
Valves and Vent Cond~.
The
m= sure [email protected]
pressure reducing valve supplies the heat exchanger with low
pressure steam, thus minimizing
flash losses.
If a vent
condenser is not eupplied,
flaeh-off steam is lost.
If a portion
of condensate ie not returned to the central boiler plant for any
reason, the portion of energy remaining in the condensate
is
lost . For example,
if a 100-psig eyetem has 20 percent
condensate loss, 5.2 percent (0.20 x 0.26 = 0.052) of total
energy produced is wasted.
In addition, 20 percent treated
makeup water ie needed to keep the system operating.
3
AC
TI
VE
MIL-HDBK-1125/l
Figure
Steam
IN
100-psi
4
1
Heat Balance
MIL-HDBK-1125/l
1-
TI
VE
,Hlm,,nw”;nn
AC
Figure 2
15-psi Steam Heat Balance
IN
e Water lHTWl Svst em.
a
2.2.2.3
Fiqure 3 illustrates
a heat balance for a HTW system at a heat
ex;hanger.
It is informative to compare the high temperature
In both cases, 1,125
water system with a 100-psig steam system.
pounds of water is heated from 50 to 140 degrees F by the heat
The HTW system returns 56 percent of energy input to
exchanger.
the heat exchanger while the steam eystem returns 14 percent.
The HTW ayetem does not have steam flashing losses or condensate
losses.
The HTW system is clearly a more efficient means of
distributing
energy from a central boiler plant, if process
requirements
of the system are such that it is applicable.
Appendix A provides heat balance calculations
explaining these
numbers.
2.2.2.4
A major advantage of the HTW closed-loop
c rro~.
distributio~
system is an inherent reduction in distribution
system corrosion
as compared to steamlcondensate
distribution
systems.
Maintenance,
pipe replacement,
and energy costs
associated
with line leaks are thereby reduced, resulting in a
significant
savinge.
5
MIL-HDBK-1125/l
112S L=
[email protected]
k
tizsLms.
WA7ERINO 50”F
HEAT
EXCHWQER
m
RETURNTO CENT8AL
~lLERFUMT
E07L= WATERO 240%
MW EFIERGY
TI
1
VE
M7 1= WA7ERO [email protected]
100!4
ENERGYINPUT
m
Heat
Balance
AC
Figure 3
High Temperature
Water
The large amount of stored
2 .2.2.5
Stored Thermal Energy.
thermal energy in HTW and MTW distribution
systems allows for
more effective response to short-duration
peak load requirements.
Boiler load swings are reduced, and more accurate combustion
control is possible.
HTW and MTW plants are generally
sized for
peak loads 10 to 20 percent less than steam plants because of
st6red thermal capacity in the system.
IN
If a line
2.2.2.6
HTW systems are safer than steam.
~.
ruptures, stored thermal energy in the water is dissipated
by
accelerating
the water to higher velocities
and flashing it to
steam.
A fine spray of 180 degree F water occurs, ending 1 to 2
feet from the rupture.
The amount of energy exiting a ruptured
HTW line is only 5 to 10 percent of the energy exiting a ruptured
steam line of the same size.
2.2.2.7
Water Tr eatment.
Due to low makeup water requirements,
the capacity of a water treatment system for an HTW and MTW plant
This
is a small fraction of that required for a steam plant.
provides cost savings in equipment, maintenance,
and chemical use
requirements.
Steam plants require more complex water treatment
systems, including a deaerator
(not required in HTW or MTW
plants) to provide oxygen-free
water.
If not carefully
controlled,
the deaerator can vent steam, resulting
in energy
losses.
Steam boilers also require blowdown to maintain
6
MIL-HDBK-1125/l
(
acceptable
water quality, which contributes
to makeup water
Lese blowdown ie needed
requirements
and plant energy lessee.
(or not required at all) in a hot water boiler.
. If distribution
and
reductions in steam pressure and
quality (100 percent quality = 100 percent steam, 90 percent
quality = 90 percent eteam and 10 percent liquid water, etc.) can
occur
due to line friction and heat lessee.
2.2.2.8
lines
significant
2.3
major
categories
TI
VE
2.2.3
~.
L~
plants have the basic
In addition,
advantages
of HTW plants relative to steam plants.
the lower system preeaure aaeociated with LTW providee a coet
advantage due to the lower pressure ratings required for boilers,
accessories,
and piping.
However, LTW plants cannot provide
energy at temperature
required for many process, hospital, and
laundry application,
thus eliminating
them from consideration
for many installation.
A central boiler plant is comprised
of equipment,
as described below.
of 10
AC
2.3.1
Heat (energy) from
lisat-Abs~!diRmmk.
combustion
of fuel is transferred
to boiler water to generate
steam or hot water in the furnace and generating
sections of the
boiler.
Economizers
are sometimes provided to recover
heat from
boiler flue gases (products of combustion)
and transfer it to the
feedwater.
Heat from flue gases can also be absorbed by air
heaters for tranefer to combustion
air before it enters the
furnace through the burner or stoker grate.
Plant efficiency is
closely related to ability of the boiler, economizer,
or air
heater to absorb heat from the products of combustion.
2.3.2
Coal-burning plants require
NJ l-iiand~.
facilities f~r storage of coal, and equipment for moving coal to
storage and reclaiming and transferring it at the boiler.
Provisions are usually made to move coal directly from the
IN
.
Loss ox Steam ~ure
are long,
delivery point to the boiler.
Mechanical,
pneumatic, or
hydraulic ash removal systems are necessary in coal-burning
plants to dispose of ash from the boiler, stoker, and duet
collector hoppers.
Oil-burning
plants require one or more oil
storage tanka with associated
transfer pumps, tank heatere,
connecting piping, tank lever meters, flow
meters, and day
tanks.
Pumping equipment
and piping to burners will be required
and oil heatere may be required depending upon oil used.
Ash
removal equipment may be required in some cases.
Gas-burning
plants will have a gas pressure reducing station (shutoff valve,
strainer, pressure reducing valve, safety relief valve, and gas
meter) to reduce incoming line pressure required in distribution
piping and burnere.
7
MIL-HDBK-1125/l
Combustion equipment for oil and
2.3.3
Combustion !3auiDment.
gas firing consists of safety shutoff valves, safety devices or
interlocks,
control valves, and burner(s).
The function of the
burner is to ignite and burn fuel by efficiently and completely
Coal may be fired
mixing it with combustion
air in the furnace.
manually
on grates or automatically
by stokers, or burned in
suspension
in a pulverized
furnace or fluidized bed.
VE
fiir-Handlinq Eq ui D ment.
To achieve efficient
2.3.4
combustion
of fuel, the amount of air delivered ta the burner or
Forced
stoker must be properly matched to the amount of fuel.
draft (FD) fans with associated
control dampers are ueed to
Overfire air and reinfection fane for
provide combustion air.
etokers and primary air fans for pulverizers may also be
required.
Induced draft (ID) fans are used to pull flue gas from
the furnace through the boiler bank and any ductwork, economizer,
air heater, or dust collector provided.
IN
AC
TI
Controls and Instrumental ion.
Since operator safety
2.3.5
and protection
of the boiler are of great importance, boiler
feedwater controle and burner safety controls are required to
guard against failures due to low bailer water or explosion.
Combustion
controls regulate fuel and airflow to maintain
The high price of boiler fuel which
efficient
combustion.
justifies
improved combustion
controls also justifies use of”
recorders
and meters to monitor combustion
and ensure optimum
plant operation.
Combustion of fuel may
2.3.6
P ollution Control Ea iDment.
generate a variety of pollutan~s
in excess of limits
set by
regulatory
agencies.
Major pollutant
emissions of present
concern are particulate,
carbon monoxide (CO), oxides of sulfur
(S0,), and oxides of nitrogen
(NOX).
Use of a fuel lower in ash
or sulfur content and modifications
to the combustion process can
be effective in reducing
these emissions.
If these fuels are too
expensive or combustion modifications
are only partially
effective,
pollution control systems can also be used to bring
Typical pollution control
emissions within acceptable
limits.
systems are mechanical collectors,
fabric filters, electrostatic
precipitators,
wet scrubbers,
flue gas recirculation,
and tall
etacks.
fia
2.3.7
~ e
NAVFAC MO-225, lmdustrial
ent Svst ms.
Water Treatment, pravides thorough coverage of water treatment
subjects and should be referenced
if greater detail is required.
Proper water treatment prevents scale formation on internal
surfaces of the boiler and reduces boiler and distribution
system
corrosion.
Water treatment is often a combination of external
and internal techniques.
External water treatment includes
removal of suspended matter with clarifiers and filters;
8
MIL-HDBK-1125/l
reduction of water hardnese with lime or zeolite softeners or
demineralizere;
and reduction of corrosive gases with deaeratore.
Internal water treatment
involves injection of chemicals directly
into the boiler to control any impurities remaining after
external treatment.
These chemicals include cauetic to aid
precipitation,
phosphate
for hardness removal, and dispereants
to
aid precipitate
removal by blowdown.
Specific equipment is also
required for boiler blowdown systems and testing purposes to
monitor and maintain a functional water treatment
system.
TI
VE
. Feedwater ia supplied to ateem
2.3.8
Mater s~
boilers by means of centrifugal
or reciprocating
pumps.
Centrifugal
pumps are aleo typically used to circulate water
through HTW boilers and their associated distribution
systems.
2.3.9
~
svstqmR. Energy produced in the central
boiler plant, whether in the form of eteam or hot water, must be
transferred
to other buildings through a distribution
system.
The distribution
system also returns unused energy in the form of
The
hot water or condensate
to the central plant for recycle.
distribution
system consiets of insulated, weatherproofed
Steam
pipelines, valves, pumpe, regulators, and heat exchangers.
systems also include trape and condensate handling equipment.
2.4
AC
2.3.10
~
. Each central boiler plant has its own
unique set of maintenance
tools and spare parts inventory; an
electric power distribution
system; air compreeaors;
and
emergency- generator
eeta.
E.iementarv
.
.
comb~
2.4.1
Fossil fuels are derived from remains of
Fos sil Fua.
plant and animal organiems.
These organisms used carbon dioxide
(CO:), minerals, water, and energy from sunlight to grow.
Over
millions of years this material accumulated and original
carbohydrates
and other organic materiale were buried and
These
converted to hydrocarbon
or fossil fuels we use today.
fossil fuels are found in solid, liquid, and gaseous form.
IN
.
2.4.1.1
Characteristics
of”
Coal is a solid fossil fuel.
Cr?d.
coal are directly affected by age, since the plant matter from
which it was formed firat changes to peat, then with sufficient
heat, pressure, and time to brown coal or lignite, subbituminous
coal, bituminous coal, and finally anthracite - the oldeet of
coals.
If anthracite
were submitted to additional
pressure and
heat, graphite and eventually
diamonds would be produced.
In the United States, lignite is found primarily in
North Dakota, Montana, and Texas, with proven resemes
of 447
billion tons.
Subbituminous
coal is found in Montana, Wyoming,
9
MIL-HDBK-l125/l
Washington, and Alaska with proven reserves of 437 billion tons.
Bituminous coal is found in at least 28 states with proven
Anthracite ie found in
.reservee of over 800 billion tons.
Pennsylvania,
Alaeka, Arkansas,
and Virginia”with
proven reservee
Because of its widespread availability
and
of 25 billion tone.
subsequently
lower transportation
costs, bituminous coal is most
Table 1 outlines the classification
of coals ae
frequently ueed.
given by the American Society for Testing and Materials
(ASTM)
of Coale bv Rank . Thie etandard
D388, Standard Classification
establishes
ranges for fixed carbon, volatile matter, and heating
TI
VE
value for each class and group of coals.
AC
Most of its heating
Coal is a highly complex fuel.
value exiete in the form of carbon, which is present in two
Volatile matter
forms, fixed carbon and volatile matter.
The
consiets of eaeily gasified carbohydrates
and hydrocarbon.
relationship
between these two forms of carbon is one of the
primary factore in determining
how readily a particular
coal
burne.
Coal analyses may be provided in one of two forms,
A proximate analysis includes moisture,
proximate and ultimate.
volatile matter,
fixed carbon, ash, and sulfur on a percent by
weight basis.
An ultimate analysis includes moisture, carbon,
hydrogen, eulfur, nitrogen, oxygen, and ash.
These analyses may
be given on either an as-received
or dry basis, or occasionally
on a moisture and ash free basis.
Coal is also analyzed for
heating value, in British thermal units per pound (Btu/lb), and
sometimes for ash chemical analysis and fusion temperatures.
Ash-fusion temperatures
are important because they are related to
elag and ash depoeits which can cause operational problems within
the boiler or furnace.
IN
2.4:1.2
u.
Oil ie a liquid fossil fuel, normally found far
underground
(to a depth of 5 miles or more).
Oil and natural gas
are as old or older than coal and are products of marine plants
and organisms which were buried and transformed by bacteria and
chemical action into complex hydrocarbons.
Oil and gas moved
through the sedimentary
rock in which it was buried until it was
trapped in pockets below solid rock.
In general, the deeper in
the ground oil and gas are found, the higher their age and
quality.
Oil we burn today can come from paraffin base, asphalt
base, naphthene base, or mixed base crude oil.
This oil ie
refined by fractional distillation
at low temperatures
and
pressures to separate light ends (etraight run No. 1 and No. 2
oil) from heavier residual oil.
Residual oil may be further
processed by cracking, catalytic
reforming, or other processes
to
produce lighter oils such as cracked No. 2 distillate.
Cracked
oil contains more olefinic and aromatic hydrocarbons
and is more
difficult to burn than paraffinic
and naphthenic hydrocarbons
found in straight run oil.
Fuel oils are defined in ASTM D396,
Standard Specification
for Fuel Oils.
Table 2 establishes
limits
10
.
25/1
MIL-HDBK-1
for many of the key properties
of fuel oil for various standard
Table 3 defines a range of analysis for different grades
gradee.
For additional
information
on fuel oils and
of fuel oils.
special circumstance,
refer to NAVFAC MO-911, ~
. .
and NAVFAC MO-230,
~avv—~
as ~
.
fixed Eatiwn
L{mits,
Percmt
(my, nineralRrAter-Frst
Gasis)
.
Class
GrwFI
Equs 1
or
Great w
Than
Anthrec itic
1. Lou
volatile
bituminous
COfll
2. nedium
vdat~te
bituninow
con1
3. High
wlatile
A
bituairmus
cm 1
6. Him
vdaiile
8
bituainow
coat
5. nigh
vo(atile
C
bituninwa
cm 1
leas
Than
subbitusirmw
1. Ligni
tic
Greeter
lb.
Equsl
or
Less
Thsm
92
8G
9a
92
:
G
14
?a
e6
14
22
FG
22
31
69
31
69
1. subbiwsircu$
4 Cwt
2. sutbiwaimua
0 c-l
3. 241bbiwainous
c ccal
1. Lignite
.?. Lignite
Volati(e
matter
LimS1s, Percent
(Lh-y, ninerali!mter-$res
Gssis)
EalOrif*c
value
Limits,
Bt. Per
Rud
(naist,
Mlrwal-lsst
terfree Zasis)
Equsl
or
Greater
than
Less
T3Mn
14,WI
-
2
IN
:1.
of Coal
9a
AC
0{ Iunims
1. netacmthracite
2. Anthracite
3. Seai anthracite
1
TI
VE
Table
Classification
A
B
11
13, COI
14,5X3
11, XSI
10,5OI
13,CUJ
11,50)
10,5M
11,500
9,3C0
10,3OG
8, 3C0
9,5m
6,S03
8,SOJ
6, Sol
MIL-HDBK-1125/l
Standard
Table 2
Specification
U8ter
and
scdimnt
Vol
(percent)
Flash
Point
Pear
Point
(::)
(::)
Hi”
flax
38
(lm)
-19
(0)
0.05
,te
38
(Ire)
-6
(m)
0.05
Ite
55
(130)
-6
(20)
0.50
55
(130)
-
55
(130)
-
Grade
of
Fuel
I.ca
2.m
Saybolt
Viscosity,
IN
Hax
(wrc~t)
ml!
37.9
45
125
125
3m
3m
m
~
~=pce”t
Point
ma
nin
262
(540)
26s
(550)
338
(6U3)
0.10
0.10
0.10
Specific
Gravity
Mldwf
(Degree
API)
5
iurol
at so-c
(122-F)
flin
I!ax
!sidual
:sidual
23
40
4s
3m
!sidua(
9Cm
Max
0.35
Bte
m
p~,~~”~
215
(420
are
32.6
,0
POi nt
0.15
Universa L
at 38, F
[lWF)
Hin
Distillation
re~ratures,
Y (v)
TI
VE
to
(140)
I.co
Oils
Ash
Ueight
ha
Max
AC
e
Carton
Residue
al 10
Percent
MC tom
(percent)
for Fuel
esid.al
12
Copper
strip
Corrosion
-.
Sutfur
(percent )
Max
nax
O..%w
(35 in)
NO. 3
0.5
0.8762
(30 -in)
no. 3
0.5
Hax
MIL-EDBK-1125/l
(
Range
Table
of Analyses
3
of Fuel
Oils
—
Grede of
ight,
fuel
m. 1
Oit
w.
2
4
m.
5
m.
6
percent:
sulfur
o.m-o.s
0.03-1.0
0.2-2.0
Hydrcgen
13.3-14.1
11. s-13.9
[email protected]
1O.5-12.OI
9.S-12.W
Ce.rbm
85.9-s6.7
a6.1-aa.2
a6.s-a9.a
e&5-s9.a
S&s-w.a
ox~wl
.y:
LO-44
Os.a API
O.azs-o.am
Specific
6.87-6.71
Lb per gal
w
Point,
0 to
f
-30
scmity:
sw
a 122f
!er
ml
6 scckinent,
%
.:ing
0
to
-40
value:
per lb,
l!_EwL-
19,67C19,260
o.m4.5
1s-30
14-22
7-22
8.06-7.30
-loto +50
1.9-3.0
0.972-0.922 1.0224.922
8.m-7.ta
-loto +s0
65-203
10.5-65
a.5t-7.a
+15to.85
260-750
65.303
m-m
20-40
0-0.1
IN
01.
7.s9-6
.87
3.?-32
625 a Imf
0-0.1
0.s274.225 0.96-0.876
AC
1.6-2.2
Cmtistokes
a Imf
Za-Lo
04.1
TI
wi;
0.7-3.s
Nilal
NiI-O.l
Ash
0.5-3.0
VE
Nitrogen
.
m.
tr
to1.0
18,2s0.
19,6m
19,17019,730
0.03-1.0
“18,1m19,020
0.03-2.0
17,&1&
18,%=3
●Estimated.
Note:
To obtain
Btu/gal,
multiply
heating
value
by density:
(Btu/lb) (lb/gal) = Btu/gal
Knowing the grade and specifications of an oil is only
a start toward understanding
its handling and combustion
characteristics.
Because sulfur limits are often imposed on fuel
oil, refiners and distributora
may blend different oils to meet
sulfur limits.
For example, low sulfur No. 4 oil could be a
blend of low sulfur No. 2 and high or medium sulfur No. 6 oil.
Problems associated with blended oils may include widely varying
viscosity, sludge precipitation,
and stratification
of different
13
MIL-HDBK-1125/l
components.
Fairly recent problems
have been related to No. 4
Paraffin wax from
oil refined from imported paraffin
base crude.
oil can plate out and clog strainers,
even though oil is fluid.
Heating oil to 90 to 100 degrees F will usually solve this
With oil coming from literally
every corner of the
problem.
world, the possible variations
are endless and can change with
Some of the more common problems are further
each new tankful.
discussed
in Section 4.
AC
TI
VE
Natural gas is formed by the same
2.4.1.3
Natural Gas.
Compared with coal and oil, natural
processes
that produce oil.
gas is a simple fuel consisting
primarily
of methane (CH4, 77
percent to 90 percent by volume) and ethane (C2H6, 5 percent to
Propane and other more complex
15 percent by volume).
hydrocarbons
are present in small quantities,
and inert
components
such as carbon dioxide and nitrogen may range from 1
Typical natural gas has a higher
percent to 9 percent by volume.
heating value of 1,000 Btu per cubic foot and a specific gravity
Care is required in handling of natural
of 0.6 relative to air.
If leaks in piping exist, gas will
gas in the vapor state.
Commercial
escape and can be explosive if allowed to collect.
pipeline natural gas has a distinctive
“sweet” smell which helps
to identify any leakage.
2.4.1.4
Due to rising fuel costs and
Al ternate Fuels.
occasional
shortages, it is becoming common to utilize wood, wood
waste, municipal waster agricultural
by-products,
and other
These alternate fuels
wastes to supplement our fossil resources.
may be mixed with more conventional
fuels or burned by themselves
This trend will
to reduce consumption of coal, oil, or gas.
undoubtedly
continue and accelerate.
IN
Combustion.
2.4.2
Combustion
can be defined as rapid
oxidation
of fuel.
It is a chemical
reaction in which energy is
released,
in the form of heat and light, when fuel and oxygen
combine.
Rapid oxidation will not occur without heat to start
the reaction.
Fuel, oxygen, heat, and a chemical reaction are
necessary
for comhstion
to take place.
If any one of these
elements is removed, combustion
stops.
During combustion in a
boiler it is important to control fuel, oxygen, and heat so that
use
is
made
of its
the fuel is completely burned and maximum
energy.
To achieve controlled
and efficient combustion three
factors must be considered:
time, temperature,
and turbulence.
Although oxidation is rapid, several seconds may be required to
start and complete the combustion
process.
Temperature varies
temperatures
occurrina
durina the combustion =—..–
Drocess with minimum
at th~ beginning and end.
is neces~ary to allow fuel”
Turbulence
to be intimately mixed with oxygen.
14
MIL-HDBK-1125/l
. The following general chemical
ae combustible
carbon (C-molecular weight (~) =
-MW = 2), and sulfur (S-14W = 32) combine with
~~~~e~y~~~~
~Hf2) to form carbon dioxide [COg;fW = 44) , water
(H20-f4W = 18), and sulfur dioxide (S02 - MW =
:
2.4.2.1
reactions
occur
C+02-C02;121bC~
321b02=441bC02
2H2 + 02 = 2H20; 4 lb H2 + 32 lb 02 = 36 lb H20
These
equatione
lb02=641bS02.
TI
VE
S+02=S02;321bS+32
may also be written
on a weight
basis
1 lb C + 2.66 lb 02 = 3.66 lb C02 + 14,093
1 lb H2 + 7.94 lb 02 = 8.94
1 lb S + 1.00 lb 02 = 2.00
Btu
lb H20 + 61,100
lb S02 + 3,983
as follows:
Btu
Btu
when the
The following general chemical reactions occur
simplest hydrocarbon
gases, methane (CH4 - MW = 16), ethane (C2H6
- MW = 30), and propane (C3H8 - MW = 44) are oxidized:
16 lb CH4 + 64 lb 02 = 44 lb C02 +
AC
CH4 + 202 = C02 + 2H20;
36 lb H20
C2H6 + 3.502
C02 + 54 lb H20
= 2C02 + 3H20;
C3H8 + 502 = 3C02 + 4H20;
C02 + 72 lb H20
On the basis
as follows:
of weight
30 lb C2H6 + 112 lb 02 = 88 lb
44 lb C3H8 + 160 lb 02 = 132 lb
per pound
of fuel, these
IN
(
23,87;
lb Ch4 + 3.99 lb 02 = 2.74
Btu
1 lb C2H6 + 3.74 lb 02 = 2.93
22,320 Btu
lb C02 + 2.25
lbC02
equations
appear
lb E20 +
+ 1.80 lb H20 +
1 lb C3H8 + 3.63 lb 02 = 2.99 lb C02 + 1.64 lb H20 +
21,661 Btu
In some cases, carbon only partially oxidizes to form
carbon monoxide
(CO) which can then oxidize to form carbon
dioxide.
A large number of intermediate
compounds of carbon,
hydrogen, and oxygen may also form between the atart of the
combustion
procese and the final products of combustion
listed
15
MIL-HDBK-1125/l
VE
above.
These intermediates
are of little practical intereet to
the boiler operator.
The heat of combustion listed above for
each reaction ie in Btu and is called higher heating value (HHV).
(970 Btu per 1 lb H20 produced) is
Some of the heat of combustion
If this
used to form water and keep it in the vapor state.
amount of heat is subtracted
from the heating values shown above,
The
a quantitY called lower heating value (LHV) is obtained.
common pract~ce In the United States is to use HHV in combustion
General
calculations,
while LHV is typically used in Europe.
chemical reactions are a good way to calculate fuel and air
requirements.
They begin to explain combustion and boiler
efficiency.
2.4.2.2
&ir Requirements. Air we breathe is 76.7 percent
nitrogen and 23.3 percent oxygen by weight or 79 percent nitrogen
and 21 percent oxygen by volume. We use air to obtain oxygen for
the combustion process. Each pound of air contains 0.233 pounds
of oxygen.
To obtain one pound of oxygen requires 4.29 pounds of
air.
This
is calculated
as follows:
lb air
TI
0.233 lb 02
4.29
= 1.0 lb 02
1.0 lb air
IN
AC
Each 4.29 pounds of air contains 1.0 pound of oxygen
and 3.29 pounds of nitrogen. Nitrogen is not chemically active
in the combustion process; however, it lowers flame temperature
by absorbing heat and carrying it away from the boiler in flue
gas.
The combustion
equation given in the previous paragraph can
be used to calculate
the exact quantity of oxygen, and hence air,
This
required to completely
react with a given amount of fuel.
quantity of air is called theoretical
air.
Unfortunately,
use
and control of the combustion
process in a boiler is not perfect
and an additional
quantity of air called excess air is needed to
achieve complete combustion.
2.4.2.3
Combustion of 1 pound of No. 2 oil
Excess Air EXaIIID~e.
with an analysis of 87 percent carbon, 12 percent hydrogen, 0.5
percent sulfur, and 0.5 percent nitrogen requires theoretical
air
as determined
below:
0.87 lb C X 2.66 lb 02/lb C
= 2.31 lb 02
0.12 lb H2 X 7.94 lb 02/lb H2 = 0.95 lb 02
S
0.005 lb S X 1.00 lb02/b
= 0.01 lb 02
Theoretical
Oxygen
= 3.27 lb 02
16
MIL-HDBK-1125/l
In a moderately
well controlled burner, approximately
20 percent excess air is typically required to eneure complete
combustion.
Theoretical
air - 3.27 lb 02 x 4.29 lb air/lb 02 =
14.0 lb air.
Total combustion
air per pound of fuel required
thus becomes:
14.0 lb air + (14.0 lb air x 0.20) = 16.8 lb air
VE
If the combustion
process is not well controlled,
50
percent excess air may enter the furnace through the burner.
Total combustion air per pound of fuel then becomes:
14.0 lb air + 1 (14.0 lb air x 0.50) = 21.0
lb air
HHVS of fuela are best
2.4.2.4
HeatJ..ng Va l“ues 1HH v~ .
determined
by a calorimeter
test.
If the ultimate analysis of an
oil or coal is known, Dulong’s formula may be used to determine
the HHV of a liquid or solid fuel.
Dulong’s formula is given
below and may be considered
accurate to within 2 or 3 percent.
HHV = 14,544 C + 62,028 (H2-02/8) + 4050 S. Carbon, hydrogen,
oxygen, and sulfur come from the ultimate analysis and are
expressed in percent by weight.
Coefficients represent
approximate
heating values of constituents
in Btu/lb and the
result obtained is also in Btu/lb.
The 02/8 is a correction
applied to hydrogen in fuel to account for the fact that some of
The
the hydrogen is already combined with oxygen to form water.
Dulong formula is not suitable for gaseous fuels because the heat
of formation of constituents
like methane and ethane is not
considered.
by
For gaseous fuels the HHV may be determined
taking a weight average of heating values for each gaseous
constituent.
Care must be taken in evaluating the heating value
of fuel oils.
A No. 6 fuel oil may have a LHV than a No. 2 oil
when measured on a Btu/lb basis, but since it is more dense, the
No. 6 oil could well have more Btu/gallon.
This is significant
since oil is normally purchased by the gallon rather than by the
pound.
Table 3 provides a comparison
of the API gravity,
specific gravity, Btu/lb, and Btu/gallon for ranges of fuel oils.
IN
AC
TI
(
2.4.3
of cQd .
Fundamental
of coal
combustion
on a hand-fired
grate are described below.
A uniform
fuel bed 8 inches thick is maintained on the grate.
About 50
percent of the air required for combustion enters from below the
grate and pasaes through a layer of ash.
Oxygen in this air is
consumed while paseing through the first few inches of burning
fixed carbon.
This is called the oxidizing zone.
Heat from
burning the fixed carbon rises and drives moisture and volatile
matter from raw coal in the oxygen-deficient
reducing zone at the
top of the bed.
Remaining
fixed carbon from the top of the bed
later burns in the bottom of the bed as additional raw coal is
17
MIL-HDBK-l125/l
Volatile matter in vapor form and carbon
added to the top.
monoxide
just above the bed must be fully mixed with overfire
to complete the combustion process.
air
IN
AC
TI
VE
At low firing rates it is important to minimize the
amount of overfire air to prevent cooling of volatile matter
resulting
in incomplete combustion
and soot formation.
At
intermediate
and high firing rates, the ability to fully mix
volatile matter, carbon monoxide, and overfire air determines
completeness
of combustion and practical excess air levels that
Rate of combustion
is controlled
by the
can be maintained.
Efficiency of combustion
is determined
underfire combustion air.
Stokers
by effective turbulent use of overfire combustion
air.
may use fans, ducts, air compartments,
modulating
air dampers,
cinder reinfection
systems, coal feeders, and moving or vibrating
grates to provide better control of the firing rate and
In some stokers, a portion of
efficiency
of coal combustion.
coal may be burned in suspension before it falls onto the grate.
In underfeed stokers, raw coal is delivered from below the
burning coal.
Pulverized coal firing systems utilize pulverizers
to grind coal to a fine dust.
This dust is conveyed by primary
combustion
air to a burner which serves to ignite the coal and
mix additional
secondary combustion
air with the stream of
primary air and coal.
Pulverized
coal is completely
burned in
suspension.
Principles of coal combustion
remain the same for
be
any of these variations.
Moisture and volatile matter must
driven
off before fixed carbon can be burned and combustion
air
must be effectively mixed with volatile vapors to efficiently
complete combustion.
2.4.4
Combustion of Oil.
Combustion
of fuel oil occurs after
liquid oil is vaporized.
The time required for combustion
is
initially dependent upon ‘the ability of the burner to atomize the
The
oil into fine droplets and provide heat to vaporize the oil.
vapor is then ignited and turbulently
mixed with combustion
air
to stabilize ignition in an ignition zone.
Heavy hydrocarbons
crack to give the oil flame its yellow color.
The burner must
SUPPly
additional air to mix with remaining fuel with adequate
time, temperature,
and turbulence
for complete combustion.
Careful control and adjustment of the flow of air, oil, and
atomizing steamlair are needed to achieve maximum efficiency
at
boiler loads.
2.4.5
Combustion of Natural Gas.
Natural gas consists mainly
of simple hydrocarbons methane and ethane, and is the easiest
fuel to burn, although it can also be the most dangerous.
Given
the proper time, temperature,
turbulence,
and excess air, gas can
sometimes burn without a visible flame or with a blue flame.
If
some of the hydrocarbons
crack, a yellow flame will be present.
One danger of natural gas combustion
is that carbon monoxide,
18
MIL-HDBK-1125/l
2.4.6
fj~
ok~ .
VE
which is poisonous in very low concentrations,
may be produced if
For eafety and
there is insufficient
air or insufficient
mixing.
efficiency
reasons, incomplete combustion
should be avoided by
proper control of fuel and air.
There is a range of air-gas
Thie range varies
mixtures which burn violently and explosively.
between 8 and 13 percent gas by volume, depending upon the
Leaner mixtures,
O to 7 percent, do not
particular
hydrocarbon.
explode or burn, while richer mixtures typical of the ignition
zone in the combustion
process burn more slowly and do not
explode.
If a rich concentration
of vapor existe, however, it
will gradually diffuse into the air and will at some time be
within the explosive range.
If this mixture comes in contact
with a spark or open flame, an explosion can occur.
In order to
prevent build-up of such concentrations,
safety shutoff valves
systems and are
are installed on natural gas and oil combustion
very important.
Purging of the boiler setting both before and
after combustion
of any fuel is also extremely
important in the
prevention
of explosions.
Understanding causes of soot and smoke
IN
AC
TI
(
is the first
step in prevention.
2.4.6.1
~.
Soot is unburned carbon from fuel.
Finely
divided soot particles give flue gases a black color.
In
refining of oil, heavy hydrocarbons
are crackad into simpler
hydrocarbons,
carbon, and hydrogen.
This cracking (thermal
decomposition)
process is also one of the reactions that occurs
when a fuel is burned.
For example, if methane gas is slowly
heated and mixed with air, the gas burns with no visible flame or
a blue flame.
Methane is oxidized without cracking and several
intermediate
carbonlhydrogenloxygen
compounds
are formed.
However, if methane is heated quickly, the gas is cracked into
hydrogen and carbon.
Carbon particles glow when burnt, giving
off a yellow color.
If this yellow flame comes in contact with a
boiler tube, carbon in the flame can be cooled and deposited on
the tube as soot.
If a flame containing
elemental carbon is not
given enough time and proper temperature
for combustion,
soot
will form as the carbon cools.
For example, when a boiler is
fired beyond its rated capacity, it ie required to burn more fuel
When this happens, the time available for
in the same furnace.
combustion
is shortened and may become so short that complete
combustion
is not possible.
Another potential
time for soot to
form is during start-up of a cold boiler or while operating at
low fire.
Under these conditions,
enough heat may be transferred
from the flame to cool it below its ignition temperature and
cause the formation of soot.
2.4.6.2
S.mQ)L9. Smoke seen in boiler flue gas results from the
presence of soot and ash from the combustion
process.
It is
difficult to make natural gas fire,smoke,
but oil and coal, if
19
MIL-HDBK-1125/l
TI
VE
not properly controlled,
will smoke readily due to more rapid
While heat loss from
cracking of their complex hydrocarbons.
unburned carbon may not be significant
(tenths of a percent of
efficiency),
smoke formation indicates a waste of fuel and a
possible soot build-up in the furnace and convection passes.
Such build-ups can result in large efficiency
losses associated
with reduced heat transfer and higher boiler exit gas
Smoke color other than black is less noticeable
temperatures.
Blue smoke from an oil-fired boiler
but can be just as wasteful.
indicates that a portion of the oil is not being cracked, while
white smoke generally indicates high excess air levels.
In
It is common
either case, a major burner problem ia indicated.
practice, when adjusting the combustion
process, to start with
At some lower range of excess
high excess air and white smoke.
air no smoke will be visible and finally, at still lower excess
Coal-fired
boilers often
air levels, black smoke will occur.
generate white smoke related to ash in the coal.
Flue Gas Analvsis and Temperature.
Performance
of a
and boiler can largely be determined
by analysis and
Flue gas temperature
at the boiler,
temperature
of flue gas.
economizer,
or air heater outlet provides information
on boiler
cleanliness,
firing rate, and efficiency.
Flue gas analysis
establishes
the amount of oxygen, carbon dioxide, and carbon
monoxide in flue gas.
This analysis is generally on a dry basis
by volume since water vapor is condensed before analysis.
Given
the type of fuel being burned and the oxygen or carbon dioxide
level, Tables 4 through 8 can be used to determine combustion
efficiency and percent of excess air in flue gas for natural gas,
No. 2 oil, No. 6 oil, and coal.
IN
2.4.7
burner
AC
s~y
. Operating with a minimum practical
2.4.6.3
level of smoke as measured by stack opacity indicates a generally
Stack opacity is measured on a O percent
well run boiler plant.
(clear) to 100 percent (completely opaque) scale.
A practical
level of smoke would be less than local opacity limits (typically
10 to 20 percent) and based upon obtaining optimum boiler
efficiency.
A slight decrease in opacity may not be acceptable”
When
if it must be obtained with a large increase in excess air.
burning coal, the amount of carbon in the stoker and collection
hoppers should be considered when reviewing excess air and
opacity levels.
2.4.8
efficiency
~y
. Boiler combustion
can be determined
if proper information
is available on fuel
analysis, flue gas analysis, combustion
air temperature,
and
stack temperature.
American Society of Mechanical
Engineers
(ASME) PTC 4.1, Steam Gene r at”na Units, P ower T est C odes,
contains industry standards for calculating
efficiencies
of steam
Figure 4 contains a heat balance for steam
generating units.
20
MIL-HDBK-1125/l
TI
VE
generation.
Note that this heat balance is greatly simplified
when nonapplicable
items are set equal to zero.
The following
paragraphs contain simplified
methods and tables used to
When calculating
efficiency using the
calculate efficiencies.
heat loss method, loss of heat in flue gas, on a percentage
basis, is subtracted from 100 percent to provide the percentage
combustion
efficiency.
The heat lost with flue gas ia determined
by its temperature and chemical
analysis.
Amounts of excess air
and water vapor are most important in determining
their leas.
Water is contained in flue gas in its vapor state.
Each pound of
water vapor requires 970 Btu of energy supplied to the boiler to
maintain it in its vapor atate.
In addition to this 970 Btu/lb,
water vapor also contains 80 percent more energy per pound than
other flue gas constituents,.
The effect of this water vapor on
boiler efficiency can be illustrated
by comparing a natural gasfired boiler to one fired by oil.
AC
For identical levels of excess air, combustion
air
temperature,
and stack temperature,
the natural gas-fired boiler
will have a lower combustion
efficiency
than the oil-fired
boiler.
This happene because natural gas containa more hydrogen,
which reacts with oxygen in air to form water, than oil and thus
water in flue gae.
Using Tables 4 and 6, at 15 percent
has more
excess air, 70 degrees F combustion
air temperature,
and 530
degrees F stack temperature,
combustion
efficiency of a natural
gas-fired boiler ie 78.9 percent as compared with 83.4 percent
Tables 4 through 8 are combustion
for a NO. 6 oil-fired boiler.
efficiency tables for natural gas, No. 2 oil, 110.6 oil, coal
with 3.5 percant moisture,
and
coal
with 9.0 percent moisture,
respectively.
Combustion
efficiency
for No. 4 oil may be
considered the average of combustion
efficiencies
for No. 2 oil
and No. 6 oil.
Expanded versiona of tablea presented here may be
found in the Boiler Efficiency
Institute book entitled, poileK
vemer&.
encv
ImDrO
IN
(
2.4.9
Boiler efficiency is simply defined
as the amount of energy in steam or hot water leaving the boiler
(E out, Btu/lb x lb/hr = Btu/hr) minus energy in feedwater
(E fw,
Btu/lb x lb hr) divided by the amount of energy in fuel used
(E fuel, Btu/lb x lb/hr).
Boiler
Efficiency
= JEout-Ef
E fuel
w~
I
MIL-HDBK-1125/l
HEAT 1)4FuEL (lilt (cHENICbL)
INPUT
e.
.eA, w ~mrc,mc.,.
‘r
B,
.c.rr..rcwzw. SYEU
,emv,,E “CA,,*,“tL
,W”tn,zt,
.,CmJ,”E,
●O.*,
~ ;:
90#Lemc#mcln.7)”.
8,
P*,”.*,
B,
.,,
,-
?“.0 .0.[.
+ cncmrs
.O.C*
0. .
*eel DcLn-.fWG r,., ,AIl PO. f*
.1., ,“,,t, fo e, .Olirum
,“ !W, c,,”r, ,,,
B.
.[.7
,“ COO,,MG
.,,
(8 I
C*
.
IN
AC
TI
VE
1
,..
[,0.,
v
.[.,
:
a
,. ,,,”4,
? ,, C,”
M., t.otw.tm.s.,t...,re.MDC1*CU.ll”CPU”*S”ll
CTIOM..1C*
“E.,,“,ttDwL,c,
.c.,I.SLO.W.. ..0cfmcut.
r,.c..- .c...
o). .Iri!
“1.,,.,,!..r~m.!,CCL’’”(O”I
“1!}
“c., ,..i”c.r ,,[..W1
“!.,,..a*,”*{@”[.
,[@..7[.
.<.,l“ml.c.,,,C..I.
L..
L.
L.,
L“
L ..
L,
LOSSES (L)
““S”*.,,C.QBO”In.,,”,,
.1A19”D*Vc.,
!.0,,7”8[
,“r“[L
-1,1”.E sm.”8“,.,.
C”,O*CZ.
“0,,,”.[ ,.,,,
.C.T ,..TO.OZ,.G,
TC..
::: ::::,::’;,,”
“.QROC.980”,
LU.C Ule”n.co
L>
..ot.,
m. U.Oca.vcc,m.
L.
,.0,.,,0.
,0 ,* ,,,,
%L.G&,.li”l
.1.,0,
L,
,C”s?mc “c.,
L.
L.
.[.
L.
Ioor SLO.OMO
EFFICIENCY
MEAT BALANCE:
H,+B
w FLUE w,?
[email protected],
Zl”mf,rcl,
.1.,!.COOLI”G
...t,
OIJTPU1
OEPINITION:
,t.,, sL, .C., !.
,“,,e. or %.G
, !.
= INPUT
IPERCEM1l
. OuTPuT+L
- LOSSES
= 3,1RI
. -
. 100 = -
OR ?6 [%1 =
[1
I-H+B
Figure 4
Heat Balance of Steam
22
. IC.J
Generator
. IW
MIL-HDBK-1125/l
Table 4
Efficiency
for Natural
Combustion
EXCCS8
Air
(x)
Percmt Ccduatim
Efficl.etw
Tuoerature
ninu, EcdW;t{lm
. flue (%
(:)
-
1
19.7
,s.8
9.5
!4.3
—
2.0
2.s
3.0
3.5
4.0
4.$
S.o
5.s
6.0
6.S
7.0
7.s
8.0
9.0
10.0
11.0
12.0
13.0
14.0
— 15.0
10.4
10.1
9.8
9.6
9.3
9.0
8.7
8.L
8.2
7.9
7.6
7.3
6.7
6.2
S.6
5.1
4.5
3.9
w
85.8
85.7
85.7
85.6
85.5
85.4
85.2
85.1
85.0
84.9
64.7
84.5
84.6
84.0
83.5
83.0
82.3
81.S
80.4
—79.0
AC
9.5
12.1
15.0
18.0
21.1
2L.5
28.1
31.9
35.9
to.3
L4.9
W.9
)5.3
57.3
!1.6
f6.7
11.8
11.2
10.7
0.0
1.0
Wo
— 3.4
220
260
X0
340
85.3
85.1
86.9
&.8
86.5
84.2
83.6
83.4
83.1
63.0
82.8
22.6
82.5
82.3
82.1
81.9
81.7
81.5
81.2
eo.9
80.7
eo.o
79.3
78.3
77.2
73.8
74.0
—71.7
82.8
82.5
82.2
82.0
8~.8
81.7
81.5
81.3
86.0
340
TI
VE
0.0
4.5
Gas
83.9
3::
84.5
84.3
84.2
84.1
83.9
83.7
83.5
63.4
83.1
82.7
82.1
81.5
80.6
79.6
78.3
—76.6
:::
83.s
83.3
83.2
83.0
22.8
62.6
82.4
82.2
81.9
97.4
80.7
79.9
78.9
n.7
76.2
—74.1
81.1
80.8
80.6
8n.3
80.0
79.7
79.4
7a.
7
77.8
76.8
75.5
73.9
71.9
—69.2
_
81.9
81.6
81.2
81.1
20.9
80.7
m. 5
20.2
80.0
79.7
79.5
79.2
78.8
78.5
78.1
n.s
76.4
75.2
73.8
72.0
69.7
6.3.7
—
Excess
co,
Air
(x)
(x)
420
0.0
1.0
2.0
2.s
3.0
IN
0.0
4.5
9.5
12.1
15.0
18.0
21.1
24.3
28.1
31.9
35.9
40.3
L4.9
&9.9
55.3
67.3
81.6
98. ?
119.7
14S.8
179.5
2L.3
[
flue
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
?.5
8.0
9.0
-
10.0
11.0
12.0
13.0
14.0
15.0
—
11.8
11.2
10.7
10.4
10.1
9.8
9.6
9.3
9.0
8.7
:::
7.9
7.6
7.3
6.7
6.2
5.6
5.1
4.5
3.9
3.4
81.0
80.7
80.3
80.1
79.9
79.7
79.4
79.2
78.9
78.6
78.3
78.0
77.6
n.3
76.9
76.0
76.9
-
460
500
540
80.1
79.3
78.9
78.4
78.2
78.4
77.9
79.8
79.4
79.1
78.9
78.7
78.4
78.1
77.8
77.
s
n.9
77.6
n.b
77.1
76.7
76.4
76.0
73.6
75.2
74.8
74.3
73.2
71.9
70.
b
68.5
66.2
n.z
76.8
76.4
76.0
73.6
74.6
%:
%:
70.1
67.5
64.2
—
I
Percmt
CGdu$tim
Efficiency
601 Temperature Rinua Cccbustim
Air Tecverature
(“F)
2::
65.3
61.7
—
63.1
59.1
—
This table is based m the following
fuel analysis
(X by weight):
3.2.%, Oxygen-1.2X,
Carbm diomide-o. ax.
The w
is 2f,7C0 Btultb.
23
n.5
n.z
76.9
76.6
76.3
76.0
73.6
75.3
74.9
74.5
74.0
73.
s
73.0
71.8
70.4
M.8
66.7
:::
—56.5
58n
620
n.5
76.6
76.1
75.5
75.2
74.9
74.6
7L.2
77.0
76.5
76.2
75.9
73.6
75.3
74.9
74.5
74.1
73.7
n.3
72.8
72.2
71.7
70. L
68.9
67.1
64.9
62.2
58.7
Sf..o
—
n.8
n.4
n.o
_
72.5
72.o
71.5
71.0
70.4
69.0
67. L
65.5
63.1
60.2
S6. L
51.&
[email protected] .8%, hydrcgen-23 .4%, nitrogcn-
MIL-HDBK-112511
Table 5
Efficiency for No. 2 Oil
percent
cmtwst~mEfficiency
I
Excess
Air
CO*
02
(%)
(%)
(%)
flue
1-
Air
15.6
‘74.9
14.1
0.0
1.0
2.0
92.4
90.2
%7.1
89.6
89.6
89.2
89.1
89.0
88.9
88.7
88.6
88.5
TT
I
11.0
12.0
13.0
14.0
1s.0
13.8
13.4
13.0
32.6
12.3
11.9
11.5
13.2
10.8
10. I,
10.0
9.7
8.9
8.2
7.4
6.7
9U. O
89.9
89.8
89.7
89.6
89.5
88.3
88.1
89.1
88.9
88.7
88.6
2a.2
87.7
87.1
ea.3
88.1
ea.o
87.8
8?.6
87.4
86.9
E!6.3
85.6
-d_l_
-1__
L
—
B.8
83.7
22.4
20.6
IN
AC
Excess
Air
(%)
260
(%)
88.8
89.6
88.3
88.2
WI
87.9
87.8
87.6
87.4
8s.0
87.7
87.4
87.3
87.1
87.0
86.8
86.6
84.4
87.3
87.
~
e4.9
86.6
86.4
86.2
85.6
.%.9
84.1
86.2
86.0
85.8
85.5
85.2
.%.9
84.3
83.5
82.6
83.1
81.9
80.3
78.2
81.4
80.0
78.2
75.7
—
Air
620
T
0.0
0.0
L.?
1,0
9.9
12.6
15.6
18.7
22,0
25.5
29.2
33.2
37.6
L1.9
66.8
2.0
52.0
57,6
70.2
85.0
102.9
124.7
152.0
187.0
?33
.7
1
This
0.1%,
tabLe
is
2.5
3.0
3.5
4.0
4.5
S.o
5.5
6.0
6.5
7.0
7.5
8.0
9.0
10.0
11.0
1.?.0
13.0
14.0
15.0
bdsed on the
sulfur-O.8%.
15.6
14.9
~1..q
.95.5
85.2
84.8
84.6
84.3
84.1
83.9
83. b
83.3
83.0
62.7
82.6
62.0
81.7
81.2
80.3
79.2
77.9
76.3
74.3
71.7
6a.2
I
73,6
13.
L
13.0
12.6
12.3
11.9
11.5
11.2
10.8
10.4
10,0
9.7
8.9
8.2
7.4
b.7
6.0
5.2
L.5.
foLbawing
The HUV is
300
87. J
86.9
86.6
86.4
86.2
86.0
85.8,
85.6
85.L
85.2
84.9
N.6
84.4
84.’7
83.7
83.0
82.1
81.0
79.7
78.1
—
86.3
2-5.0
85.7
85.5
85.3
85.
~
84.9
M.6
.34.4
84.1
83.8
83.5
83.2
82.9
82,5
81.6
80.6
79.5
78.0
76.2
Percent Combustion Efficiency
Flue Gas Temperature Minus C.mbustim
C02
02
(%)
Cmbusc im
(“F)
TI
2.5
3.0
3.5
4.0
4.5
3.0
5.5
6.0
6.5
?.0
7.5
8.0
9.0
10.0
Minus
Temperature
-
220
180
0.0
4.7
9.9
12.6
15.6
18.7
?2.0
?5.5
?9.2
!3.2
37.6
$1.9
$6.8
S2.O
57,6
70.3
95.0
12.9
24.7
S2. O
37,0
33.7
Gas Temperature
VE
:ombustion
19,5W
fuel
ana(ysis
tltul
84.7
e4.3
83.9
83. b
83.4
83.1
82.9
82.6
82.3
62.0
83.6
81.3
8a.9
80.4
80.0
79.0
77.8
7b.3
74.5
72.3
69.5
—
b5.7
24
(“F)
540
5m
83.8
83.6
82.9
82.7
82.4
82.2
81.9
81. b
81.2
2n.9
2n.5
89.1
79.7
83.0
82.5
82.0
.91.8
83.5
81.2
80.9
80.5
80.2
79.8
79.6
79.0
78.5
79.2
78.7
77.6
76.3
74.7
72.8
77.5
76.2
74.8
73.1
71.0
70.4
63.6
67.3
— 63.1
65.0
— tQ.6
(% by weight):
lb.
Temperature
7.3.0
tartan-85.7%,
80.2
79.8
79.5
79.’I
78.7
78.3
77.8
77.3
7b.7
7b.2
74.9
75.3
71.5
69.2
66.4
hydrogen-12.4%,
81.3
8Q.7
80.2
79.9
79.5
79.2
78.8
78.4
78.0
77.6
77.1
76.6
76.1
75.5
74.9
75.5
71.8
b9.9
67.6
64.4
nitrogen-
MIL-HDBK-1125/l
(
Table
6
:Ombus
—
0.0
0.0
4.7
10.0
*2.8
15.8
18.9
22.3
2s.8
29.6
33.6
37.9
42.4
47.3
52.6
58.2
71.0
86.0
04.1
Z6. I
53.7
29.1
56.6
—
-
E,cess
Aif
0.0
IN
11.0
12.0
13.0
14.0
— 15.0
tabi e
220
91.2
91.o
W.4
90.2
90.0
89.9
89.8
89.7
89.5
29.4
89.2
89.1
88.9
88.7
88.6
88.3
88.1
87.6
87.0
%:
W.7
9U.6
$0.5
m.&
W:3
9U.1
90.0
89.8
89.7
89.5
89.3
2.2.9
88.5
87.9
87.2
—
86.3
85.2
83.7
2::
84.4
83.0
81.2
—
Flue
—
16.5
15.7
IL.9
14.5
14.1
13.8
11.6
13.0
12.6
12.2
11.8
11.4
11.0
10.6
10.2
9.4
8.6
7.9
7.1
6.3
5.5
4.7
nirws
89.6
89.4
89.1
89.0
88.9
88.7
88.6
88.4
88.2
88.0
87,8
87,6
87.4
87.2
86.9
86.3
8s.6
84.8
83.8
82.3
80.9
78.7
8f..6
&.3
84.1
83.8
83.6
83.1
82.7
82.3
81.9
81.0
79.6
—
78.5
76.8
74.7
72.1
68.5
is bdsed on the following fur[analysis
.78.
The w
i, 18, XU Btu/ib.
—
m
88.8
88.$
88.2
88.1
87.9
87.8
87.6
87.6
87.2
87.0
86.8
86.5
8.5.3
85.0
83.7
85.0
84.2
83.2
82.1
80.6
78.7
76.2
—
(%
—
lecgcrature
:::
83.7
83.4
83.2
82.9
:::
81.9
81.6
81.2
80.8
80.3
79.9
79.4
78.2
76.9
75.2
n.3
70.8
67.6
63.3
—
by weight):
‘utf”r4
25
87.9
87.7
87.3
87.2
87.0
86.8
M.6
86.4
86.2
8S.9
85.7
85.6
85.1
84.8
84.4
83.7
82.7
81.7
80.3
78.6
76.5
—..
86.4
m. 3
&.1
85.8
85.6
85.4
—n.b
85.1
84.8
8&6
iii
83.9
83.6
83.2
82.3
81.3
21
1
76.7
7t.3
71.1
(“f)
540
5W
83.4
85.1
U.6
84.4
84.1
23.9
83.6
83.3
83.0
82.7
82.3
81.9
81.5
81.1
8n.6
79.6
78.3
76.9
73.0
72.8
69.8
65.9
340
Percmt Cocbust ian [I ficicncy
@s Tecpr.rature Rims Cmbust ion
w
86.3
85.9
8s.5
85.3
85.1
24.9
Cdttion
(of)
Tecpermure
260
Air
(8)
0.0
1.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.$
7.0
7.5
8.0
9.0
10.0
4.7
10.0
12.8
15.8
18.9
22.3
25.8
29.6
33.6
37.9
&z.&
47.3
52.6
54.2
71.0
86.0
OL.1
26.1
53.7
B9.I
M.&
—
This
180
C02
%
(%)
(%)
0.9%,
36.>
15,7
14.9
Its
14.1
13.8
13.6
13.0
12.6
12.2
11.8
11.4
11.0
10.6
10.2
9.4
8.6
7.9
7.1
6.5
5.5
4.7
Alr
AC
—
1.0
2.0
2.5
3.0
3.s
4.0
4.s
S.o
5.5
6.0
6.5
7.0
7.s
8.0
9.0
10.0
11.0
12.0
13.0
14.0
1s.0
Oas leq.wmwe
E
(%)
(a)
Flue
cot
(8)
02
TI
V
E.teas
Air
—
::;
82.8
82.5
82.2
81.9
81.6
81.2
80.9
20. s
80.0
79.6
79.1
78.6
78.1
76.8
7s.4
73.6
71.5
68.8
65.5
m.7
carbm-88.4%,
580
82.9
82.4
81.8
81.5
81.2
80.9
20.5
80.2
79.8
%;
78. &
77.9
n.4
76.8
7s.4
73.9
72.0
69.6
M.8
63.0
58.1
—
hydrc.aen-10.0~,
1
22.0
B1.5
82.9
80.6
69.2
79.9
79.5
79.1
78.7
72.2
77.7
77.2
76.7
76.1
n.s
7L.O
72.
s
70.3
67.8
fA.7
m.7
5s.4
nitrWen-
MIL-HDBK-1125/l
Excess
&$r
Table 7
Combustion
Efficiency
for Coal,
rcent
Moisture;
Bituminous
3.5
E
—
Cm&mtim
Efficimcy
Percent
F We Oas Tmpemture
l!inus Comtust ion
C02
Air Temperature (“F)
(%1
02
(%)
(%)
180
2.0
3.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7,5
16..?
22a
26.4
30.3
34.4
sa.
a
43.5
48.5
53.9
59.7
65.9
72.7
20.1
62.1
06.6
29.2
57.5
93a
1.2.2
—
a.o
a.s
9.0
9.5
10.0
11.0
12.0
13.0
14.0
15.0
—
—
02
(%)
(%)
9~.2
91.0
90. a
90.5
93.2
90.1
a9.9
a9.a
a9.6
a9.4
a9.2
68.9
88.7
Za. h
aa.2
a7.9
87.5
aa. a
a5. a
84.6
83.1
all
Coz
(%)
420
0,0
1.0
2.0
3.0
4.0
1.,5
S.o
5.5
6,0
6.5
?.0
7.5
a.o
a.s
9.0
9.5
10.0
11.0
12.0
13.0
14.0
15.0
7a.6
17.6
16.7
15. a
14.9
14.5
14.0
73.6
13.2
12.7
12.3
11.9
11.4
11.0
10.5
10.1
9.7
a.a
7.9
7.0
6.1
5.3
aa. a
86.4
e6. o
a5.5
a5. o
84.7
84.4
84.0
83.7
IN
0>0
L.a
10.2
16.2
22.8
26.6
30.3
36.6
3a.a
1.3,5
48. s
53.9
59.7
65.9
72.7
60.1
68.1
06.6
29.2
57.5
93.8
42.2
—
,is
—
teb Le is
5.12%,
36.14%,
—
based m the f.a(lowim
cmbon-77 .13%,
FC-55.36%,
imist.
R-3.5%,
re-3.5
ash-5.0%.
a3.3
82.9
a2.5
—
az.o
81.5
81.0
ao.6
79.7
78,2
76.4
76.2
71.2
67.4
89.5
a9.2
88.9
8a. 5
88.2
69a
89.5
89.2
89.0
88a
88.6
aa.h
88.2
a7.9
a7.7
a7.4
a7.1
e6.7
a6.4
86.0
85.1
84.0
82.6
ao.a
7a.4
87.0
86.7
86.6
86.1
a5.7
a5.3
84.9
84.6
a3. &
M.6
82.3
a7.9
a7.5
ar .,I
a6.9
86.6
84.3’
86.7
as.a
a5.4
85.1
84.7
a4.3
a3.9
83.4
82.9
81.7
82.1
80.2
80.5
7a.4
75.7
76.0
72.9
a7.9
a7.7
a7.5
a7.2
—
Percent Cornbus ~ncy
Flue Gas Temperature flinus
-
-
92.3
W.1
AC
Excess
Air
92.0
91.9
91.7
91.5
91.3
91.1
91.0
w. 9
90.7
92.6
W.4
9U.2
93.0
89.8
a9.6
a9.3
a9.o
68.4
a7.7
86.7
a5.5
a3.a
lab
17.6
16.7
15a
14.9
14.5
14.0
13.6
13.2
12.7
12.3
11.9
11,6
11.0
10,5
10.1
9.7
a.a
7.9
7.0
6.1
5.3
1.0
—
Air
5a3
85.9
85.5
a5. o
84.5
83.9
a3.6
83.2
82.9
22.5
82.1
81.6
all
80.6
W2.1
79.5
7a.8
78.1
76.5
74.5
72.0
6a. a
64.5
85.0
84.5
34.0
83.6
—
(% by we
The HHV of this
26
a3.6
83.0
a2.4
al.7
81.3
30.9
ao.5
80.0
79.5
79.0
class
7a.5
—
77.9
77.2
76.5
75.7
76.9
73.0
70.6
67.7
63.9
5a.9
ht)
: ash. o%,
mygen-6 .84 % .
Combustion
W..l
82.4
az.1
al.7
al.3
ao.a
80.3
79a
79.2
78.6
7a.o
77.3
76.5
74.7
72.6
69.9
.%.4
61.7
-
540
82a
A
7a.4
(“F)
Temperature
Lto
, nit rc.gen-l .49%,
87.7
a7.3
24.9
%.5
W.o
as.a
ass
a5.2
.94.9
W.5
84.2
.33.8
23. G
82.9
82.4
al.9
al,3
M.o
78,3
76.3
73,6
70.1
VE
~.a
70..?
TI
0.0
0.0
32.0
300
620
63.1
82.6
82.0
81.3
80.6
80.2
79.7
79.3
78a
78.3
77.7
77.1
76.5
75a
a2.2
al.6
al. o
80.3
79.5
79.0
7a.6
78.1
77.6
n.o
76.6
75.7
75.0
76.3
73.5
72.6
71.6
69.4
66.7
63.3
58.9
53.1
75.0
76.2
73.3
74.2
ta.
?
65.5
6~.4
56.0
— .~
1.92%,
sulfur
The proximre
1 Grcup 3 bitumi”nws
580
cd
hydrqm-
analysis
is v%
is 13,750
S:./ Lb.
MIL-HDBK-1125/l
Table 8
Combustion Efficiency
for Coal.
rcent
Moisture,
Bituminous
9.0
—
Effic\mcY
PertmtCdxstim
Air
(8)
12U
0.0
Excess
Air
(%)
83.5
2s.3
08.1
87.8
89.5
89.3
89.1
83.9
88.7
83.5
88.2
Z&o
87.3
86.5
85.6
84.3
—82.6
87.6
87.3
87.0
86.7
24.4
—
02
co>
(%)
(%)
1’ table
ased m
18.4
17.6
16.7
15.8
%4.9
14.5
14.0
~3.6
13.2
12.7
12.3
11.9
11.4
11.0
10.5
10.1
9.7
8.8
7.9
7.0
6.1
5.3
—
4.48%,
53.36%,
the
carbm-67 .60%,
FC-L9.14%,R-9.0%,
mist.
following
Air
Teepermure
re-9. W%,
ash-8.0%
.
analysis
nitrcgm-l
me w
86.5
86.2
85.8
85.3
(8
.31%,
n.&
71.5
69.1
66.1
62.2
of
this
asfI-8 .0%,
oxmen-7.9U%.
class
2-I
-
sulfu
7he proximte
11 Group b bitmi
620
520
81.7
81.1
M.3
80.0
79.6
79.1
78.7
78.2
Tf.6
n.1
76.4
75.8
75.1
7L.3
by weight):
:::
84.3
84.0
83.6
83.3
82.9
82.5
82.1
81.6
81.1
80.6
20.0
78.6
77.0
74.9
72.2
63.6
(“;1
1540
76.7
fue(
320
8?.6
87.1
26.2.
24.4
83.9
83.7
83.4
83.2
84.9
84.6
84.2
23.9
83.5
83.1
82.6
82.1
81.6
20.4
78.9
n.o
74.6
71.5
M.6
2b.3
86.1
85.8
83.5
8s.2
84.9
IX.5
04.1
IN
0.0
1.0
2.0
3.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
11.0
12.0
13.0
14.0
15.0
—
340
300
I
—
Percmr
CoE61Jstim Efficief .CY
Flue Gas Temperature minus Ctiitim
4z0146015m
0.0
6.8
10.2
16.2
!2.8
!6. 4
10.3
)4.4
I&a
i3.5
a.s
13.9
;9.7
15.9
‘2.7
10.1
I&l
kl. b
9.2
7.3
5.8
,22
_
(or)
all-l-i
AC
—
H
8.5
9.0
9.5
10.0
11.0
12.0
13.0
16.0
15.0
::
$0.0
89.8
89.7
260
I
91.0
W.8
9U.7
$0.5
18.4
17.6
16.7
15.8
14.9
14.5
l&.o
13.6
13.2
12.7
12.3
11.9
11.L
11.0
10.5
10.1
9.7
8.8
7.9
7.0
6.1
5.3
1.0
2.0
3.0
4.0
4.5
5.0
5.5
6.0
6.5
7.0
220
minus Cti;tlm
Teqmrc.ture
TI
0.0
4.8
lo.,?
16.2
22.8
26.4
30.3
34.4
38.8
43.5
L8. s
53.9
59.7
6S.9
72.7
80.1
WI
D&b
29.2
5?.5
?3.8
L2.2
_
Gas Ttmerature
VE
(%)
flue
C02
02
(%)
Air
81.8
.31.3
80.6
Zn.o
79.2
78.8
78.3
77.9
n.6
76.8
76.3
73.7
73.0
?4.5
n.5
72.7
71.7
W.6
67.0
63.8
59.7
—54.1
J
.91%, hy
,m-
analysis
nous coal is
89.9
20.3
79.6
78.9
78.1
77.6
77.1
76.6
76.1
75.5
74.9
74.3
73.5
is
12,030
72.8
71.9
71.0
70.1
67.8
65.0
61.6
57.1
51.2
VRBtullb.
MIL-HDBK-1125/l
Boiler efficiency muet always be less than combustion
efficiency.
Typical boiler efficiencies
range from 75 to 85
percent.
The main boiler loss ia heat lost in flue gas as
Other energy losses are
discussed
in the previous paragraph.
associated
with heat radiated from the boiler casing, heat
carried away by the blowdown water, and heat lost because of
To achieve maximum boiler efficiency the
incomplete
combustion.
operator must:
Minimize
excess
air to reduce
stack
losses.
IN
AC
TI
VE
a)
b) Clean the gas side and water side of boiler
maximum absorption
of heat and reduced stack
to ensure
temperatures.
c)
minimize
Minimize
to reduce
d)
Perform maintenance
unburned fuel.
A more detailed
Section 4.
2.4.10
blowdown
discussion
blowdown
on burners
of boiler
losses.
and controls
efficiency
tubes
to
is provided
in
Central Boiler Plant Efficiency.
The amount of ‘energy
in steam or hot water leaving the plant (E out of plant, Btu/lb x
lb/hr) minus the amount of energy in condensate or hot water
return (E return, Btu/lb x lb/hr), divided by the amount of
energy in fuel (E fuel, Btu/lb x lb/hr) used to produce that
steam or hot water is the central boiler plant efficiency.
Plant
Efficiency
=
~~E out of
E fuel
return
Boiler selection,
deaerator control, steam trap
maintenance,
use of steam driven auxiliaries,
and plant building
energy conservation
are important contributing
elements to boiler
plant efficiency.
Energy losses and use should be controlled to
keep plant efficiency as close as possible to boiler efficiency.
Use of steam-driven auxiliaries
reduces the amount of energy sent
out of the central plant and steam losses can result if exhaust
steam cannot be used in the deaerator or building heating system.
Distribution
system losses from the central boiler plant should
also be monitored and reported.
While distribution
system losses
are not a part of central plant efficiency,
they greatly affect
the efficiency of the system.
Any makeup water required to
replace distribution
losses must be heated to feedwater
temperature.
This requires additional
steam to be generated by
boilers, thus using
additional
fuel and lowering plant
efficiency.
More information
ia provided in Section 4.
28
MIL-HDBK-l125/l
2.5
IN
AC
TI
VE
2.5.1
Generation
of steam occurs as a
result of two separate processes:
(1) combustion,
release of
heat by burning fuel, and (2) heat tranefer, absorption of heat
into water.
Combustion was discussed in the previous section.
A
study of the heat transfer process can be made with an elementary
boiler as shown in Figure 5. The boiler system can be
represented
as a container equipped with an outlet pipe and
valve, a preaaure gage, and a thermometer
immersed in water.
If
a fire is built under the unit and water at 32 degreea F is put
into the container with the valve left open, water temperature
will rise steadily as the fire burns until a temperature of
At this time, the
approximately
212 degrees F. is reached.
temperature
will rise no further, but the water will gradually
boil off and, if firing is continued
long enough, the water will
evaporate.
If the heat content of the fuel source ia accurately
measured,
it can be demonstrated
that to raise the temperature
from 32 degrees F to the boiling point, the heat input was 180
Btu for each Dound of water.
It would also be ahown that 970
additional
Bt~ for each pound of water is required to boil o f
the water.
This additional heat is called the latent heat o:
vaporization
and represents heat required to convert the sma 1
volume of liquid into a large volume of eteam.
w_
dMf-
F,.
Figure 5
“Elementary Boiler
29
MIL-HDBK-1125/l
o
0
0
15
30
m
90
100
110
120
130
1)
140
150
200
250
300
32 degl
temperc
Energy in
Water
(Btu/lb)
m
IN
40
50
60
70
80
Saturation
Temp
(Degrees F)
AC
Pressure
(psig)
Table 9
Characteristics
TI
Water/Steam
VE
With the valve in a closed position and using another
batch of water, the process is repeated and pressure is allowed
to build up to 100 psig, then the valve is throttled
so that
The temperature
in the
pressure is maintained
at 100 psig.
container is now approximately
338 degrees F. This is called the
Heat input
saturation temperature
for 100-psig pressure.
required to raise 1 pound of water from 32 degrees F up to this
Energy expended in boiling 1
saturation temperature
is 309 Btu.
pound of water to 338 degrees F at 100 psig is 880.6 Btu.
The
temperature
required to boil water increases as preesure
increases.
The amount of heat put into the liquid to raise it to
this boiling point temperature
is greater and the latent heat of
Table
vaporization
is progressively
less as pressure increases.
9 Drovides a summarv of saturation temperatures,. ener9y”in watert
energy in steam, and latent heat of vaporization
for pressures
from O to 300 psig.
Reference standard steam tables.
331
338
344
350
356
m
302
309
316
322
328
n
m
1188
1190
1191
1192
1193
1195
1196
1199
1202
422
399
1203
I
s F and 60 degrees F are saturation
res
of water
at O psig.
30
886
881
875
870
865
862
857
837
820
804
MIL-HDBK-1125/l
2.5.2
Heat transfer is accomplished
by three
~.
lill three
methods:
radiation, conduction,
and convection.
methods are used within a boiler.
The heating surface in the
‘“s
furnace area receives.heat
primarily by radiation.
The remaining
heating surface in the boiler receives heat by convection
from
Heat received.by
the heating surface travels
hot flue gases.
Heat is then transferred
from the
through metal
by conduction.
Each of these methods ia discussed
metal to water by convection.
in more detail below.
TI
VE
Radiation
is the most important method of
2.5.2.1
~.
The amount of heat transfer
heat tranafer in the furnace.
depends on the area of heating surfacea and hot surfaces in the
furnace, the difference
of the fourth powers (T4) of temperatures
of the flame and heating surfacee, and the nature of the flame.
For the same temperatures,
a coal flame ie more radiant
than an
oil flame and an oil flame is more radiant than a natural gas
flame.
The same phyeical laws governing transmission
of light
aleo apply to transfer of radiant heat:
a)
Heat ie transmitted
b)
Heat can be reflected
c)
Heat ie radiated
in straight
lines
and refracted
AC
in all directions
Radiant heat can be transmitted
through a vacuum, most
gaees, some liquids, and a few solids.
Solid boiler tubes absorb
radiant heat from the flame and radiate a emall portion of that
heat back to the furnace.
IN
In conduction,
heat is transferred
through
2.5.2.2
a material in which individual
particles etay in the same
position.
Heat flowing along an iron bar when one end of the bar
is held in a fire is a eimple example of thie process.
Conduction occurs when material, called a conductor, is in
physical contact with both the heat source and the point of
delivery.
Heat flows from the hot end to the cold end of the
conductor.
It makes no difference
if the conductor is straight,
crooked, inclined, horizontal,
or vertical.
Material which it is
made of has a great effect, however.
Metals conduct heat readily
while liquids and gases conduct heat more slowly.
Some materials
conduct heat very poorly, and are called insulators.
Common
examples of insulators are asbestoe, fiberglass, wood, and some
types of plastics.
Asbeetoe
ie no longer used as an insulator
because of health risks.
The amount of heat transmitted
also
varies with the length of the path, contact area, and temperature
difference,
31
MIL-HDBK-1125/l
2.5.2.3
Transfer of heat by convection occurs, for
Con vectim.
exanmle.
when
water
flows
over a heated surface causina the
.
.
surface to cool.
In convection
heat transfer, the gas-or liquid
medium receives heat from the source, expands, and is pushed away
Fluid that receives
by colder, heavier particles
of the medium.
heat then transfers heat to a new location, losing some heat in
the process.
Heat transfer by convection
normally occurs from a
However, transfer in any direction
lower to a higher elevation.
may take place if an external force, such as fans, pumps, or a
pressure drop, is applied.
AC
TI
VE
In most boilers, a large
2.5.2.4
Gas F1 ow Consideratione.
amount of absorbed heat is given up by hot flue gases which sweep
Heat transfer takes place by
over heat-absorbing
surfaces.
convection.
The quantity of heat transferred
can be varied by
Usually both
controlling
temperature
or quantity of flue gases.
are controlled.
Ability of materials
to resist damaging effects
of high temperatures
is the limiting factor in the first case,
and the force available for causing flow through the boiler is
the limiting factor in the second case.
Boiler draft loss or
resistance
ta flow is the force or pressure drop required for
gases to flow through a boiler.
Draft loss is commonly called”
draft and may be supplied by a chimney, forced draft fan, or
induced draft fan.
Draft, which is measured in inches of water,
depends primarily on velocity and density of flowing gases, and
cross-sectional
area and length of gas passage.
Draft loss
increases with the square of velocity and directly with length of
the passage.
IN
It is important to keep velocity at a minimum,
consistent
with requirements
of good convective
heat transfer, if
maximum output of a boiler installation
is to be attained.
The
cross-sectional
area, baffle arrangement,
and length of the gas
passage are usually fixed.
If gas passages are kept free of soot
and ash accumulation,
gas velocity and draft loss will depend
solely on quantity of gas flow which in turn depends on quantity
of air supplied to burn fuel.
A minimum air supply consistent
with good combustion practice therefore minimizes draft loss and
helps to maximize heat transfer and boiler output.
2.5.2.5
Water Circulation
Considerations.
Water circulates
in
a steam boiler because the deneity of water is greater than the
density of the water/steam
mixture
(Figure 6). Within the
boiler, denser water falls while the less dense mixture rises.
Natural circulating
forces are reduced as operating pressure of a
boiler increases, and increased as percent of steam in the
mixture increases.
Hot water boilers normally use pumps to force
circulation
of water ,through the boiler, because the density
32
MIL-HDBK-1125/l
difference
between cold and hot water is not large enough to
cause natural circulation
with velocities
necessary
for good heat
transfer.
AC
TI
VE
.
2.5.2.6
Heat transfer by convection
depends on temperature
and velocity
of gases on one side of the boiler tube and velocity of water on
Increasing velocity of water aids convection and
the other side.
This is due to a very thin film of
increases heat transfer.
This
stagnant water which is in contact with the boiler tube.
can be demonstrated
by a simple experiment
using a Bunsen burner
and a metallic vessel containing boiling water as shown in Figure
Place the lighted burner under the vessel and observe it
6.
cloeely.
Note that the flame spreads into a eheet about 1/30 to
the
1/40 inch from the vessel. Because of its high conductivity,
temperature
of the tube is only a few degreea hotter than the
water while the temperature
of the burner flame is much higher.
Therefore,
there must be a large temperature
drop through the
This principle
thin film between the flame and the vessel.
Heat in
applies to both the water and gas sides of the veeeel.
the boiler tube must be conducted through the thin stagnant film
Heat
of water before the active convection
process begins.
transfer can be greatly increased if this film is reduced in
Usually, this is
thickness, or eliminated
completely.
accomplished
by increasing
flow velocity across the surface and
Unfortunately,
as waa mentioned
scrubbing the film away.
earlier, increasing
velocities
increases draft losses and power
requirements.
The thin film does not affect radiant or
conductive
heat tranefer but only convective
heat tranafer.
IN
Boiler furnace heat is
2.5.2.7
~.
absorbed by a combination
of radiation, convection,
and
Water in boiler tubes is heated
conduction
through boiler tubes.
by convection.
Tubes and other heating surfaces close to fire
that do not have a high rate of gas flowing across them receive
Heating surfaces close
practically
all their heat by radiation.
to the furnace and across which gas flow is high receive heat by
Surfaces distant from the furnace
both radiation and convection.
Heat transfer can be optimized
receive their heat by convection.
by controlling
excess air, keeping boiler tubes clean, and
maintaining
optimum gas and water velocities.
Maintaining
low excess air
Excess Air Control.
a)
levels in a boiler is important because any air above the
required air for combustion
is heated and lost up the stack.
Theoretical
air is the exact amount of air required for
combustion.
Excess air is additional
air above theoretical
air.
Plant operators should maintain 02 levels as low as possible
while maintaining
smoke-free
operations.
A 1.3 percent reduction
in 02 increases efficiency
by approximately
1 percent.
33
AC
TI
VE
MIL-HDBK-1125/l
11-
Eunu.Bum.r
A
IN
o
—
G. Sumlv
Figure 6
Water Circulation
The amount of excess air directly affects flame
temperature
E. The rate at which radiant heat is transmitted
varies as the fourth power of temperature.
The amount of heat
transmitted
by radiation doubles when the absolute temperature of
the radiating
source is increased by approximately
19 percent.
The rate at which heat is transmitted
bv radiation from an oil
the temperature of
flame can increase by 42 percent by inc~easing
the visible flame from 1725 to 1925 degrees F. Reducing excess
air used to burn fuel causes the flame temperature
to increase.
Maximum flame temperature is normally obtained with approximately
34
MIL-HDBK-1125/l
3 to 5 percent excess air.
A moderate increase in furnace
temperature
resulting from an excess air reduction can markedly
affect the amount of radiant heat absorbed by boiler surfaces.
Heat loss due to
b) Maintaining
Clean Boiler Tubes.
high exit gas temperatures
up the stack constitutes
one of the
major efficiency losses.
A 40 degreee F increase in gae
temperature
up the stack will reduce efficiency
by approximately
1 percent.
Gas temperature
leaving the economizer
ie controlled
by soot blowing which cleans eurfaces and improvee heat transfer.
TI
VE
The amount of heat transferred by conduction
depends on
type, thickness, and condition of conductive material as well as
the difference in temperature.
Heat is readily conducted
through
Figure 7
metal, while ash, soot, and scale are poor conductors.,
illustrates
the effects of soot and scale.
If heating surfaces
become coated with soot, scale, or other material,
the firing
rate of the boiler must be increased to raise gas temperatures
Any deposit on
and maintain the same amount of heat transfer.
either side of the heating surface increases maintenance
costs,
reducee efficiency, and may cauee operator injuries or boiler
damage if a tube overheats and ruptures.
AC
Keeping gas
Gas and Water Passages.
‘=) Maintaining
passages free from accumulations
of soot and ash, and maintaining
gae baffles in good repair help to ensure proper gas velocities
to heat transfer surfaces.
Keeping water passages free from
accumulations
of sludge and scale ensures proper water
flow and
velocity for cooling of heat transfer surfaces and generating
steam or hot water.
Maximum
d) Maximum Vereus Economical Heat Transfer.
and economical heat transfer are not the same.
It is rarely
high enough to
Possible to ooerate a boiler at temperatures
obtain the maximum heat transfer rate because of material
limitations, particularly
furnace brickwork.
The maximum
temperature that can be safely maintained
is determined
by, among
other considerations,
the kind of firebrick used, furnace
construction
(self-supporting
or supported),
quantity and kind of
ash in the fuel, furnace size, and amount and tvDe of coolina of
furnace walls (air cooled or water cooled).
It-is important-to
maintain a low gas temperature
at the boiler outlet since this
resulta in high boiler efficiency.
However, the rate of heat
IN
(
35
MIL-HDBK-1125/l
BO 1LER
TUBE
METAL WALL
BO1LER TUBE
METAL WALL
m
&.
J
TI
SOOT
. .. ti”i4i#
EiiNlw.1
AC
‘//A
VE
transfer may be relatively
low in this area because temperature
There is a practical
limit on the velocity
differences
are low.
of flue gas based on reasonable
fan horsepower
requirements
and
Water velocity is fixed by boiler design and
capabilities.
Reduced water
cleanliness
for any particular
firing rate.
velocity at a lower boiler firing rate resulte in reduced but
Most
of the above factors
more economical heat transfer rates.
It is the responsibility
are determined
by design of the boiler.
of the boiler manufacturer
to balance requirements
of maximum
heat transfer with economics and produce a cost-effective
design.
IN
~////&WAlZI
Effects
UV1
of Soot
Figure 1
and Scale
36
on Heat
Transfer
MIL-HDBK-1125/l
Section
DESCRIPTION
3:
OF EQUIPMENT
3.1
. .
.
forced
a)
Type of water
circulation.
b)
Type of steam
c)
Method
d)
Type of use:
e)
Type of fuel:
circulation:
produced:
of assembly:
erected.
package,
stationary,
coal,
f) Method of combustion:
pulverized
coal.
natural
eaturated,
oil,
circulation,
superheated.
modular,
marine,
gas,
spreader
AC
bed,
TI
VE
er c~
. There are a few fundamental
3.1.1
tvDes of boilera and manv variationa
of each tvDe.
Boilers are
Boilers
g~;erally classified
as ~ither fire tube or wa~~r tube.
are also classified
by the form of energy produced;
low or high
Other methods of
pressure steam; low or high temperature
water.
classifying
boilers are listed below:
field
power,
heating.
other.
stoker,
fluidized
Boiler capacity:
up to 20,700.pounds
per hour (up
9)
to 600 hp
for fire tube boilers; up to 10 million pounds per
hour for water tube boilers; up to 200 million Btu per hour for
hot water boilers).
a)
desired
A boiler
r De~.
requirements:
IN
3.1.2
following
b)
rate,
Operational
must meet
safety.
Generation of clean steam or hot water
pressure, and temperature.
c)
Economy
d)
Conformance
the
of operation
at the
and maintenance.
to applicable
codes.
A set of rules for the construction
and operation of
boilers, known as the ASME
and
u re Vess 1 Code , has
been widely adopted by insurance underwriters
and G~vernment
agencies.
Section I of the Code contains requirements
for power
boilers including methods of construction
and installation,
materials to be used, design, accessories,
and inspection.
Section IV of the Code contains requirements
for heating boilers.
I
37
MIL-HDBK-1125/l
Low pressure steam boilers and LTW boilers are classified
as
heating boilers.
Section VI of the Code provides recommended
rules for care and operation
of heating boilers, and Section VII
Other
provides recommended
rules for care of power boilers.
sections of the Code provide material specifications,
nuclear
equipment requiremente,
inspection requirements,
and welding
qualifications.
TI
VE
Boilers, superheaters,
economizers,
and
Fabrication.
3.1.3
other pressure parts must be built using materials and”
construction
methods specified by the applicable
sections of the
Repairs to boilers must
ASME Boiler and Pressure Vessel Code.
Equipment
alao be made in accordance
with Code requirements.
built and inspected
in accordance with the Code must have an ASME
is stamped on heating boilers.
An
stamp.
An “H’” in a cloverleaf
“S” in a cloverleaf
is stamped on power boilers.
AC
Boiler drums, shells, or
Drums, Shells. or Headers.
3.1.3.1
headers are used to collect steam or hot water generated
in the
These
boiler and distribute
it within the boiler tubes.
components must be strong enough to contain the steam or hot
water and to hold the boiler tubes as they expand and contract
with changes in temperature.
The shells of fire tube boilers may
be reinforced by the use of stays to hold the boiler heads in
These components
are generally fabricated with welded
place.
seams and connections.
Riveted seams are no longer used,
although many old riveted boilers are still in operation.
IN
3.1.3.2
Boiler Tubes.
Boiler tubes carry water, steam, or flue
gases through the boiler.
Boiler tubee are installed by
expanding or welding them into seats in the drums or headers.
The expander tool consists of a tapered pin which fits into a
A different
size expander
cage containing
several small rollers.
is required for each size tube.
During installation,
the
expander is slipped into the end of the tube and the tapered pin
is pushed into the cage until the rollers are against the tube
walls . Then the pin is turned with a wrench or motor, forcing
the rollers out against the tube, and simultaneously
moving the
cage into the tube.
This action distorts and stretches the tube,
The
forcing it to make a tight seal against the tube sheet.
expander often has a stop which helps prevent overexpanding.
Boiler tubes are installed with ends projecting
slightly beyond
the tube sheets.
Projecting
ends are flared slightly in water
tube boilers and allowed to remain because they are surrounded
and cooled by water or steam.
Since the tube ends of a fire tube
boiler are surrounded
by hot gases, they would soon burn off if
allowed to project.
They are therefore beaded and hammered until
flat against the tube sheet.
This process also increases the
holding power of the tube.
It must, however, be performed
carefully to avoid damaging the tube.
38
MIL-tJDBK-1125/l
TI
VE
3.1.3.3
~.
Baffles are thin walls or partitions
installed in water tube boilere to direct the flow of gases over
the heating surface in the desired manner.
The number and
position of bafflee have a marked effect on boiler efficiency.
A
leaking or missing baffle permite gases to short-circuit
through
the boilers.
Heat that should have been absorbed by the water is
With a leaking baffle, tubes may be
then dissipated
and lost.
damaged by the “blow torch”’ action of the flame or hot gas
sweeping across the tube at high velocity, especially if the leak
is in or near the furnace.
Baffles may be made of iron castings,
sheet metal strips, brick, tile, or plastic refractory.
IN
AC
Provisions must be made to permit movement between the
baffle and setting walls while etill maintaining a gas-tight
seal.
Iron castings are made in long, narrow sections. to fit in
the tube lanea and around the tubes.
They can be installed only
while the boiler ia being erected or assembled, and their use is
limited by the temperatures
they can withstand.
Sheet metal
strips are formed to fit around the tubes and are easily
installed after tubes are in the boiler.
Their primary uses are
to help distribute
flue gaa within a pass and to maintain proper
tube spacing, rather than to function aa baffles between adjacent
passes.
This type baffle cannot be used in the high temperature
areas of the boiler.
Brick or tile baffles, made of specially
shaped forms which fit between and around the tubes, can be
installed after the boiler has been erected and can be used in
any area of the boiler.
Castable
plastic refractory baffles are
usually installed by building a form and pouring the refractory
like concrete.
The forms are then removed after the refractory
has set.
This type of baffle can be used at any location in the
boiler and, if properly deeigned,
can remain gas-tight for long
periods.
It may be used to repair or replace other types of
baffles.
Born.
3.1.4
Fire ~be
Many of the first steam boilers
produced were designed with the products of combustion paasing
inside the tubes.
Fire tube boiler design has developed
primarily in the direction of the Scotch-type boiler shown in
Figure 8. The Scotch boiler is, shop fabricated and is capable of
supplying saturated steam at pressures below 250 psig at
capacities usually below 20,000 lb/hr.
At pressuree above 250
psig, the natural circulation
of water and steam in this design
is not adequate for good heat transfer.
At capacities above
20,000 lb/hr, the shell diameter
becomes too large to be
economical.
Scotch boilers come in two, thrae, and four gas pass
designs, as illustrated
in Figure 9. With more gas passes and
more heat transfer surface,
boiler exit qas temperatures
are
lower and efficiencies
are higher.
Wet Lack co~struction
in a
Scotch boiler means that a waterwall
is provided at the outlet of
the first pass or furnace.
Wet back construction
reduces the
39
MIL-HDBK-l125/l
IN
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costs
often
associated
with
dry back
designs.
high maintenance
Scotch-type
fire tube boilers can effectively
fire natural gas
and fuel oils.
Coal is a less desirable fuel because the first
tubes are not easily cleaned and ash removal is restricted.
Advantages
of the Scotch boiler include the ability to respond to
rapid load swings due to the large volume of stored waterlsteam
in
the shell, low initial cost, low maintenance
costs, and
Disadvantages
include the difficulty
general ease of control.
of producing
superheated steam and pressure and capacity
Scotch boilers are also used to Droduce low
limitations.
The other common type of f~re tube boiler is
temperature
water.
the horizontal
return tubular (HRT) design, illustrated in
The firebox in this type of boiler permits the
Figure
10.
burning of coal using stokers or fluidized beds.
Figure 8
Four-Pass Scotch
40
Boiler
MIL-HDBK-1125/l
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#
2 PASS
4 PASS
3 PAS2
VE
Figure 9
and Four-Paaa Scotch
Boiler
AC
TI
Two- , Three-
I
IN
(
Horizontal
Figure
Return
41
10
Tubular
Boiler
Deaigna
MIL-HDBK-1125/l
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IN
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3.1.5
Water tube boilers were developed
Water Tube Boilers.
for a variety of reasona, including
the need for higher
pressures,
higher capacities,
superheated
steam, faster response
to load changes, and increased
safety due to’reduced water
volume.
Water tube boilers have water inside the tube and flue
gases on the outside.
Early straight tube design boilers were
replaced with today’s bent tube designs to increase the amount of
available heat transfer surface, to solve mechanical problems,
Figure 11 illustrates
a fourand for general economic reasone.
drum boiler with a water-cooled
back wall.
The bottom drum is
called a mud drum because of the tendency of boiler sludge to
collect in this low area.
Upper drums are called steam drums.
Water enters the top rear drum, passee through tubes to the
bottom drum, and then up through tubes to two front drums.
A
mixture of steam and water is discharged
into these drums; steam
returns to the top rear drum through the upper row of tubes while
water travels through tubes in lower rows.
Steam is removed near
the. top of the,rear drum by a dry pipe extending across the drum,
and is discharged through the steam outlet header.
Baffles are
arranged to encourage flue gas flow over boiler tubes for good
heat transfer.
Two-drum boilers have generally replaced threeand four-drum units in modern construction,
because they are less
expensive to c Istruct.
Four-Drum
Figure 11
Water Tube Boiler
42
MIL-HDBK-1125/l
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~.
Early boiler designs utilized
3.1.5.1
refractory
furnacea as combustion
zones.
Some furnacea used
arches and bridge walls to reflect heat and maintain high
temperatures
in specific zones for burning anthracite and other
hard coals.
Since prolonged exposure
to high temperature damages
refractory
material, it is necepsary
to maintain the heat
liberation
rate (Btu per hour per cubic foot of furnace volume)
of refractor
furnaces within reasonable
limits.
These limits
depend upon ~he”type of refractory
used, type of fuel, firing
method, type of heating surface exposed to the radiant heat, and
type of cooling mechaniam used.
Maximum heat liberation ratea
for refractory
furnacea are in the ranges of 25,000 to 35,000 Btu
per hour per cubic foot at full load.
In refractory wall
construction,
it is important to allow for the thermal expansion
which occurs as the refractory
is heated to operating
temperatures.
Figure 12 illustrates
typical expansion joint
arrangements.
The development
of high alumina super-duty
insulating firebrick,
block insulation, castable
firebrick,
refractory,
and plastic refractory
have greatly improved
refractory
life and reduced radiation
loaaes from boiler
furnacea.
AC
a
IN
(
Floor
1
1
to Wall Expansion
I
Jointa
Corner Construction
Staggered Expansion
Joints (18” Wall)
With
J
Refractory
Figure 12
Expansion
3.1.5.2
HaterWall Construct
allow the use of higher firing
.
WaterWalls were developed to
rates
43
Joints
and higher
furnace
heat
MIL-HDBK-112511
VE
release ratee, while reducing heat losses and maintenance.
Improvements
to watkrwall
furnaces and associated casings and
lagging also reduced air infiltration
into the boiler, reducing
excess air levels and improving boiler efficiency.
The four
types of waterwall construction
are: tube and tile, tangent tube,
The tube and tile
studded tube, and membrane wall (Figure 13).
construction,
which was developed
first, provided only a partial
solution to the maintenance
and heat loss problems.
Minimum
practical tube spacing was limited by the ability to economically
limited
the
roll the tubes into drums or headers.
This, in turn,
amount
of
heat
transfer
surface
added and the amount of
protection
given to the refractory,
thus limiting the
practicality
of tangent tube construction.
1
IN
AC
TI
Studded tube construction
was then developed
and was
highly effective.
In areas with high heat releases
such as
bridge walls and arches, studded tubes covered with refractory
are especially
effective.
Flue gas can still leak through
studded tube wall construction
under some circumstances,
resulting in corrosion of boiler tubes, and lagging.
To obtain
completely
gas-tight construction
and maximize heat transfer,
membrane waterwall construction
was developed and remains the
best, though the most expensive,
waterwall design.
I’1’lJom.n
NM
Figure 13
Waterwall
Construction
44
MIL-tiDBK-1125/l
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Combinations
of baffles, cyclone type separators,
corrugated
scrubbers,
and perforated plates are now used to
effectively
separate watet and steam.
Figure 14 illustrates
Cyclones are arranged in a row and
modern steam drum internals.
receive the water/steam
mixture tangentially
from the boiler
waterwall and generating
tubes.
Water is spun to the outside of
the cyclone and exits through the open bottom of the cyclone.
Steam is less dense and thus stays in the center and exits
Scrubbers
further reduce
through the open top of the cyclone.
the amount of water entrained.
Solids in condensed
steam from a
well-designed
steam drum should be less than 3 ppm.
AC
3.1.5.4
Boiler tubes that connect the
na Surface.
uPPer and lower drums are called generating
surfaces and are
the total
Included with the waterwall
surface in computing
heating surface.
Many different
tube spacings are used,
The tubes may be independing on the type of fuel being fired.
line or staggered.
A staggered tube arrangement
would not be
acceptable
for coal-fired
or heavy oil-fired boilers due to its
susceptibility
to ash build-up; however, it provides better heat
transfer for gas-fired or light oil-fired units.
3.1.5.5
~.
Some processes and turbines require
steam that is superheated
above the saturated eteam temperatures.
Figure 15 illustrates
a two-drum boiler equipped with a
spreader stoker, and economizer.
Steam
superheater,
waterwalle,
from the steam drum is directed to a superheater
inlet header and
then through superheater
tubes to the outlet header and steam
outlet.
A superheater
can be arranged in many ways and may be
located behind a row of generating
tubee.
These tubee cool
furnace gasee somewhat before reaching the superheater
tubes and
shield the superheater
tubes from radiant heat.
IN
.
3.1.5.3
~.
Steam drums are equipped with
mechanical
separators
to ensure that the eteam leaving the boiler
does not contain solids or other impurities and that steam-free
water is made available to continu”e the natural circulation
process in the boiler.
A dry pipe, the earliest device used, was
placed inside the shell or drum just below the eteam outlet
nozzle.
Numerous small holes drilled in the upper half of the
The trend
dry pipe cause separation
of the steam from the water.
in boiler design toward ever higher heat transfer rates makes
separation of water and steam more difficult and limits the
application
of the dry pipe.
45
MIL-HDBK-1125/l
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3.1.5.6
Packaged water tube boilers are
packaQe Bo ilers.
factory assembled, complete with combustion
equipment, mechanical
These
draft equipment,
automatic controls,
and accessories.
factory assembled packages can be purchased
in capacities
Package boilers are available in three
exceeding
200,000 lb/hr.
Figure 17
basic configurations:
‘“D,“ ‘“A,” and “’O” (Figure 16).
illustrates
a type “D” package boiler arranged for oil and gae
firing.
Note that the flame travels lengthwise
down the furnace
Flue gases then make a 180-degree
where combustion
is completed.
turn and come back to the burner end of the boiler, exiting from
Historically,
package
the side of the generating bank tubes.
boilers have been designed to fire only natural gas and oil.
Coal firina has not been practical due to the high ash content of
Package
coal which-would
plug the-boiler
generating
banks.
boilers have been widely and successfully
applied for central
boiler plant service.
IN
AC
TI
1A
Steam
Figure 14
Drum Internals
46
MIL-HDBK-1125/l
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1
IN
Figure 15
Superheater
in Two-Drum
Boiler
47
Figure 16
Boiler Configurations
IN
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Package
VE
MIL-HDBK-1125/l
I
Figure 17
,$Du*package Boiler
Hot water generators .are
~.
. often
Hot Wate
3.1.6
called hot water boilers, even though litt~e Or nO bo~l~ng
Modified Scotch boilere and a var~ety of package boilers
occurs.
These boilers have limited and uneven water
are available.
is utilized
circulation
characteristic
if natural circulation
48
.
.
MIL-HDBK-1125/l
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becauae of the small natural circulation
forces available.
Special boilera have been developed
that use forced circulation
The main difference in a water
to improve heat tranefer ratea.
tube hot water generator is the eteem and mud drums are replaced
with headers.
The hot water generator
is connected to a hot
water distribution
syetem.
Ae water is heated in the hot water
When the hot water is distributed
generator,
the water expands.
to various heat exchanger,
the water cools and contracta.
Figure 18 illuatratee some typical end ueea for a low temperature
water ayatem.
An expansion tank, preeeurized
by either steam, a
static water head, or inert gas, is provided to adjuat for theee
volume changes.
One or more centrifugal
pumps are required to
Figure 19 illustrates a high
circulate water through the eystem.
temperature
water eystem equipped with an expansion tank, a
and a circulating pump for
circulating
pump for the generator,
the distribution
ayetem.
Many other arrangement
are poaeible.
AC
3.1.7
~.
Economizer
are used to recover heat from
the boiler flue gaeee and thereby increaee boiler efficiency.
The heat absorbed by the economizer
ie transferred to the boiler
feedwater flowing through the ineide of the economizer tubee.
Becauee feedwater temperature
are much lower than saturated
eteam temperature, an effective
temperature
differential exiate,
enabling good heat tranefer and low economizer exit gae
Bare
temperatures.
Continuous
tube construction
is common.
tubes are used for coal-fired
boilers, while fin tubes or
extended eurfaces are commonly
ueed on gas- and oil-fired units.
Figure 21
Figure 20 shows a continuous
bare tube economizer.
The
illustrates
a eteel-finned
extended
eurface economizer.
extended eurface promotes heat tranafer
from the gas by providing
more heating surface.
Care must be taken when selecting the
number of fine per inch.
Extended
eurface economizers on natural
gae-fired boilers may uae up to nine fins per inch, while only
two fina per inch would be ueed for heavy oil-fired application.
IN
(
Provision for cleaning
with coot blowere is necessary
for economizers on coal-fired
boilere or some oil-fired boilera.
Economizers
are ueually arranged with gas flow down and water
flow up.
Thie maximizea heat tranefer and helps to avoid water
hammer.
Economizer
are usually designed with water temperatures.
below the saturated temperature
of the water to avoid producing
eteam.
Economizers should be e’quipped with a three-valve bypaes
on the water aide to allow servicing or bypassing water at low
boiler loads.
This helps to minimize economizer corrosion when
high sulfur fuels are burned.
Figure 22 provides curves which
establish minimum metal temperatures
allowable for corroeion
protection in economizers
and air heatere.
Methode for avoiding
corroeion
during idle or standby periode are diecueaed in par.
4.3.16.
Economizers are preeeure
parte and, ae euch, must be
manufactured
and stamped in accordance
with the ASME ~
Pr e aeure Veseel CO*.
49
MIL-HDBK-1125/l
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Figure
Hot Water
50
18
End Uses
VE
MIL-HDBK-1125/l
IN
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Figure 19
High Temperature
Hot Water
Distribution
System
Bare
Figure 20
Tube Economizer
I
51
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MIL-HDBK-1125/l
IN
AC
Figure 21
Extended Surface Economizer
(1 ppm)
(10 ppm)
Sulfur
(100 ppm)
in Fuel, % by Weight (as fired)
Figure 22
cold End Corrosion
- Minimum
Temperatures
52
Metal
t41L-HDBK-1125/l
3.2
AC
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VE
. Air heatere, like economizer,
are used
3.1.8
~
to recover heat from boiler flue gases and thereby increase
the
boiler efficiency.
Heat absorbed by the air heater ia
transferred
to the combustion air before the air entera the
burnere and boiler.
This preheated air not only improvee
efficiency
by recovering otherwise lost heat, but also can
improve the combustion
of some fuele by promoting
higher furnace
temperatures.
There are two general types of air heatera:
Recuperative
air heatere, like
recuperative
and regenerative.
the tubular air heater illustrated
in Figure 23, transfer heat
from the hot flue gases on one side of the tube to the combustion
Regenerative
air heaters,
air on the other side of the tube.
like the rotary heat wheel illustrated
in Figure 24, transfer
heat indirectly
by heating a plate with the hot gae and then
rotating that hot plate into the cool combustion
air which then
absorbs the heat.
Rotary heat wheels are equipped with seals
that separate the flue gas side from the combustion
air side of
the wheel.
Air infiltration
from the air aide to the gas side ie
minimized but not eliminated, and is a factor that must be
Provisiona
considered
when sizing forced and induced draft fans.
for soot blowers are required if dirty or high ash fuels are
being fired.
Cold end corrosion ia more of a problem in an air
heater than an economizer because of the low entering combustion
air temperatures.
Figure 22 establishes
minimum allowable metal
temperature
if corrosion is to be controlled.
Cold air bypass
ducts and dampers, hot air recirculation,
steam coil air heaters,
and low level economizers are examplea of methode for preheating
These
the combustion
air before it enters the air heater.
methods help control cold end corrosion
but also reduce the
efficiency of the system by raising exit gas temperatures.
To ensure safe operation, the ASME
3.2.1
ASME [email protected]
er and
od ~ requirea that boilers be equipped
ressure Vessel
with a water gage glass and gage cocks, water column, pressure
gage, and safety valves.
Forced circulation,
HTW boilers that
have no water line do not require a gage glase and gage cocks,
but a temperature
gage ia required.
Detailed requirements
for
the location and installation of these accessories
on power
boilers are found in Section I of the Code, and requirements for
heating boilers are in Section IV.
Section IV requires each
boiler to be equipped with two controls to cut off the fuel
supply to prevent steam pressure or water temperature
from
exceeding boiler limits.
Theee controls are pressure operated
for steam boilers and temperature operated for hot water boilers.
Low water fuel cutoff instrumentation
is also required.
Oil- and
gas-fired boilers must be equipped with suitable
flame safeguard
controls, safety limit controls, and burners which are approved
by a nationally
recognized organization.
IN
(
53
MIL-HDBK-l125/l
cold
VE
Wln
H
TI
{rim
Filltil
AC
u
S-
G“ lnlct
or ad..
t
IN
E-n
G-
1.
Figure 23
Tubular Air Heater
54
Hc.w+r
_
MIL-HDBK-1125/l
(
Transiiim
❑
✝✍
Msin&l
3
‘“”’”
Uom Sumxml
/Ciolmfertmul
seal
km
/
TI
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HeJtins
SuriZm
liii—
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1
AC
feremial
S4
Und
Figure 24
Regenerative
Air Heater
IN
3.2.2
Each boiler must have at least
Gac?e Glass. Gatae Coch.
one water gage glass.
If the operating
prassure is 400 psig or
greater, two gage glasses are required
on the same horizontal
line.
Each gage glass must have a valved drain, and the gage
must
not
be
less
than
l/2-inch nominal
glass and pipe connections
pipe size (NPS).
The lowest visible part of the gage glass must
be at leaat 2 inches above the lowest permissible water level,
which ie defined as the lowest level at which there is no danger
of overheating
any part of the boiler during operation.
For
horizontal
fire tube boilera, the gage glass is set to allow at
least 3 inches of water over the higheet point of the tubes,
fluee, or crown eheet at its loweet reading.
Figure 25
illustrates
a typical water gage.
Each gage consists of a strong
glass tube connected
to the boiler or water column by two special
fittings.
have an automatic shutoff
These fittings sometimes
device that functions if the water glass falls.
Requirements
for
the fabrication
of these shutoff devices are also given in the
ASME Code.
When the boiler operating
pressure exceeds 100 psig,
the gage glasa must be furnished with a connection to install a
55
I
L
MIL-HDBK-1125/l
valved drain to some safe discharge
point.
Each boiler must have
three or more gage or try cocks located within the visible length
of the gage glass.
Gage cocks are used to check the accuracy of
They are
the boiler water level as indicated by the gage glass.
opened by handwheel, chainwheel,
or lever, and are closed by
hand, a weight, or a spring.
The middle cock is usually at the
normal water level of the boiler; the other two are spaced
equally above and below it.
Spacing depends on the size of the
boiler.
IN
AC
TI
VE
3.2.3
Water Columns.
A water column is a hollow cast iron,
malleable
iron, or steel vessel having two connections
to the
boiler.
The top connection
entere the steam space of the boiler
through the top of the shell or head, and the water connection
enters the shell or head at least 6 inches below the lowest
permissible
water level.
Pipe used to connect the water column
to the boiler may be brass, iron, or steel, depending on the
pressure;
it must be at least 1 inch in diameter.
Valves or
cocks are used in these connecting
lines if their construction
prevents stoppage by eediment deposits and.if the positiOn of the
operating mechanism indicates whether they are open or closed:
Outside screw-and-yoke
gate valves are generally used for this
Lever lifting gate valve or stop cocks with permanently
service.
attached levers arranged to indicate open or closed position may
also be used.
These valves or cocks must be locked open.
Crosses are generally used in place of elbows or tees on piping
between the water column and the boiler to facilitate cleaning
the line.
A valved drain or blowdown line is connected to the
water column for removal of mud and sediment from the lines and
column.
Ends of blowdowns
should be open and located for ease of
inspection.
The water column shown in Figure 25 is equipped with
high and low water alarms which operate a whistle to warn the
operator.
The whistle is operated by either of the two floats.
3.2.4
Pressure Gaae, Temperature
Gaae.
Every boiler must be
equipped with an easily readable pressure gage.
The pressure
gage must be installed so that it indicates pressure in the
boiler at all times.
Each steam boiler must have the pressure
gage connected to the steam space or to the steam connection of
the water column.
A valve or cock must be placed in the gage
connection
adjacent to the gage.
An additional valve or cock may
be located near the boiler, provided that it is locked or sealed
in the open position.
No other shutoff valves may be located
between the gage and the boiler.
The pipe connection
must be of
ample size and arranged so that it may be cleared by blowing out.
For a steam boiler, the gage or connection must
contain
a syphon
or
equivalent
device which will develop and maintain a water seal
to prevent steam from entering the gage tube.
Pressure gage
connections
must be stiitable for the maximum allowable working
pressure and temperature.
Connections
to the boiler must not be
56
MIL-HDBK-1125/l
AC
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VE
less than l/4-inch NPS.
Where steel or wrought iron pipe or
tubing is used, it must be at least l/2-inch inside diameter.
The dial of the pressure gage must be graduated to approximately
double the pressure at which the safety valve is set, and it
should never be less than 1-1/2 times this pressure.
Every hot
water boiler must also have a temperature
gage located and
The temperature
gage must be
connected
for easy readability.
installed ao that it indicates the boiler water temperature at ox
near the outlet connection
at all times.
--
----l=!=
L-
(0)
Fire Tube Boiler
IN
(
Water
Figure 25
Gage Glass, Water
(b)
Eater Tube Br.iler
Column
3.2.5
Safety valves are installed to
S.afetv Val v-.
prevent excessive pressure build-up in the boiler, superheater,
or economizer.
Safety valves are designed to quickly pop to the
full open position when the steam pressure rises to the set
point, and to quickly close when the pressure drops a preset
amount (blowdown or blowback).
They must close tightly without
chattering
or leakage, and remain tightly closed after reseating.
Their construction,
installation,
and performance
are rigidly
prescribed
in the ASME Code.
No valve or stop is permitted
between the boiler and safety valve, and the discharge line must
be supported separately to prevent any undue stress on the valve.
57
MIL-HDBK-1125/l
VE
A recommended
method of installation
is shown in Figure 26. Any
economizer
which may be shut off from the boiler must have one or
Every superheater
must also have one or more
more safety valves.
A safety
“safety valves located near the superheater outlet.
valve is defined as an “automatic pressure relief device actuated
by a static pressure upstream of the valve and characterized
by
full opening pop action.”
A safety valve is used for gas or
vapor service, including steam.
Hot water boilers use a safety
relief valve which is defined as an “automatic pressure actuated
relief device suitable for use either as a safety valve or relief
Safety valves and safety
valve, depending on the application.”
relief valves are constructed
so that the failure of any part
cannot obstruct the free and full discharge of steam or water
from the valve.
Safety relief valves, like safety valves, must
be manufactured
and stamped in accordance with the ASME Code.
IN
AC
TI
3.2.5.1
One common type of safety
Tvn es of Safetv Valves.
valve is the huddling chamber safety valve illustrated
in Figure
27.
This safety valve opene rapidly because of the additional
area on which steam pressure is exerted as soon as the valve
starts to lift from the seat, and because of the reaction of the
steam on the seat.
This second action resembles the action which
causes a free air, water, or steam hose to whip around when the
discharge
velocity is high.
The area between the valve seat and
the adjusting ring is called the huddling chamber.
As seen in
Figure 27, the clearance between the inside of the adjusting ring
and the feather is comparatively
small.
The boiler pressure is
exerted on the area of the feather which is equal to the inside
area of the seat bushing.
As soon as the seat is slightly
displaced,
steam starts to flow through the valve because of the
excessive
boiler pressure.
The steam cannot escape between the
feather and the adjusting ring as fast as it is flowing through
the seat.
As a result, pressure builds up under the feather.
This, in turn, increases the force available for pushing the
valve off the seat.
The flow of steam is turned by the feather,
and this also exerts a force to open the valve.
These two forces
cause the valve to pop open.
Because of the larger area
subjected
to the steam pressure and the reactive force of the
flowing steam, the valve does not close until the ‘pressure drops
below the pressure that caused it to open.
The difference
between the set or popping pressure and the cloeing pressure is
Jet flow and nozzle reaction safety valves
called the blowdown.
are other common types.
58
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MIL-HDBK-1125/l
Safety
Figure 26
Valve Installation
59
MIL-HDBK-1125/l
R,kac NW
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,Wnliml Screw
F“uu, G
F“th., G“i,j,
TI
1-
Stilah
of Rim Pi” 1, so”
Ftiq
Th, 0.,,,,
toTh9W* mm
<
IN
AC
F..,tw
SniBu.tliol \
Sbtl F*
x-W.T.Fol mu”
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Huddling
H=’2UL.
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Figure
Chamber
27
Safety
Valve
3.2.5,2
Safetv Valve CaDacity.
The safety valve capacity for
each boiler must be such that the valve or valves will discharge
the steam that can be generated by the boiler without allowing
the pressure to rise more than 6 percent above the highest
pressure at which any valve is set, and in no case tO more than 6
allowable
working
pressure.
percent above the rnaxi.mum
The safety
valve capacity must be in compliance
with the ASME Code and, must
60
MIL-HDBK-1125/l
.
not be less than the maximum deeigned eteaming capacity as
The required eteem relief
determined
by the manufacturer.
capacity
(in lb/hr) of the eafety relief valvee on a high
temperature water boiler is determined by dividing the maximum
output in Btu/hr at the boiler nozzle by 1,000.
Economizer
safety valve capacity is calculated
from the maximum heat
absorption
in Btu/hr divided by 1,000.
AC
TI
VE
One or more safety valves on
3.2.5.3
Valve Settings.
the boiler proper must be eet at or below the maximum allowable
working pressure.
If additional
valves are used, the highest
preseure setting muet not exceed the maximum allowable working
The complete range of pressure
preesure by more than 3 percent.
settings of saturated steam safety valves on a boiler must not
exceed 10 percent of the highest pressure to which any valve ie
set.
The pressure setting of safety relief valves on high
temperature water boilere may exceed thie 10 percent range
because safety relief valvea in hot water service are more
susceptible to damage and subsequent leakage than eafety valves
relieving steam.
It is recosssended that the maximum allowable
working pressure of the boiler and the safety relief valve
setting for HTW boilers be selected substantially
higher than the
desired operating pressure to minimize the frequency of safety
relief valva lift.
IN
3.2.6
~er
Outle t Valves.. Each steam discharge outlet from
a boiler, except the safety valve and superheater connections,
must have a stop valve.
If the valve ie over a 2-inch pipe size,
it must be the outside screw and yoke rising-spindle
type; the
spindle position indicates whether the valve is open or closed
(Figure 28).
A plug-type cock may be used if the plug is held in
place by a gland or guard, if it allows remote indication
of
opening or closing, and if it is used with a show-opening
mechanism.
When two or more boilers are connected to a common
header, the steam connection
from each boiler having a manhole
opening must be fitted with two stop valves and a free blow drain
between them.
Stop valves ehould consist, preferably,
of one
nonreturn valve set next to the boiler area, and a second valve
of the outside screw and yoke type.
However, two outside screw
and yoke type valves may be used.
The nonreturn valve is a type.
of check valve which can be held closed (Figure 29).
It can be
opened only by preesure in the boiler, and it closes when the
boiler pressure is lower than the header pressure, a condition
which may be caused by a burst tube, loss of fire, etc.
The
valves require a very emall difference in pressure for proper
operation.
A dashpot is ‘provided to prevent chattering
or rapid
movement of the valve.
Ladders and catwalks, chains, or other
means for operating the valves from the operating floors in
boiler rooms should be provided.
61
MIL-HDBK-l125/l
no.
0C6CRIPTION
1
80DV
1
BONNST GASKSI
d
BONNIT 80L1
1
BOIINIT
5
BONNET ~Ll
6
1
Disc
DISC PIN
NUT
1
DISC RltlG-lRIM
9
IIANDWH1[L
HANOWW[[L NUT
PACKING
VE
11
12
6
PKL
14
PI(G GLANO FL.%
1$
fvfBOLl
16
L_Ii80LT
11
SYf801T
1:
IISPKG. S[AT
19
SiAl
TI
13
Toil
?3
VOK[ BOLT
Z5
YOKEBUSHIHG
AC
SlfM
21
[b)
Figure 29
Nonreturn
Check
62
8USHING
RING
Figure 28
Screw and Yoke Gate Valve
(o)
NuT
.
RIvET
10
IN
Outside
CLANO
Valve
MIL-HDBK-1125/l
TI
VE
. Each boiler must have at
3.2.7
off Valves
least one blowoff connection installed at the lowest water space
The pipe used must not be
available
to allow removal of sludge.
Extra-strong
pipe must be
2-1/2 inches.
less than 1 inch or over
The blowoff line must be
used for pressures above 100 psig.
protected
from direct furnace heat by brickwork
or other heatresisting material which is constructed
to allov for inspection
of the pipe.
This is necessary because sediment collects in the
blowoff line and, since there is no circulation
of the water, the
Care must be
pipe may easily become overheated and burn out.
taken to ensure ample room for expansion
and contraction
at the
One slow opening valve may
junction of the pipe and the setting.
be used in the blowoff line for pressures
up to 100 psig.
Two
slow opening valves, or a slow opening valve and cock, are
A typical blowdown valve
required
for pressures above 100 psig.
set is shown in Figure 30. A slow opening valve requires at
least five complete turns of the operating
mechanism to change
from the completely
open to the completely
closed positions and
is used to avoid shock to the piping and possible injury to
Valves that have dama or pockets where sediment can
personnel.
Boiler blowdown
is provided for the
collect must not be used.
control of dissolved and suspended solids that concentrate
in
steam boilers.
AC
3.2.8
Fusible plugs are sometimes used on
Hds.ible Plugs.
fire tube boilers to provide added protection
against low water.
They are constructed
of bronze or brass with a tapered hole
drilled lengthwise through the plug and filled with a low melting
There are two types of fusible
alloy consisting
mostly of tin.
plugs, fire actuated and steam actuated.
IN
3.2.8.1
&e-Ac~.
Fire-actuated
plugs are filled
with an alloy of tin, copper, and lead with a melting point of
445 to 450 degrees F. They are screwed into the shell or a
special tube at the lowest possible water level.
One side of the
plug is in contact with the fire or hot gases, and the other side
with water.
As long as the plug is covered with water, the tin
does not melt.
If the water level drops below the plug, the tin
melts and is blown out.
The boiler must then be taken out of
service to replace the plug.
Fusible plugs of this type are
renewed regularly once a year.
The old castings
should not be
reused, but should be replaced with new plugs obtained from the
boiler manufacturer.
63
AC
TI
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MIL-HDBK-1125/l
Figure 30
Blowdown Valve
Set
IN
The steam-actuated
plug is
Steam-Actuated
Pluq.
3.2.8.2
The other end
installed on the end of a DiDe outside the drum.
of the pipe, which is open; Is at the lowest permissible
water
level.
A valve is usually installed between that of the steam in
The pipe ie small enough to prevent water from
the boiler.
Water around the
circulating
inside it and cooling the plug.
plug is much cooler than the water in the boiler as long as the
However, if the water
end of the pipe is below the water level.
level drops below the open end of the pipe, cool water runs out
Steam melte the
of the pipe and steam condensee on the plug.
This type of
plug and steam blows out, warning the operator.
plug can be replaced without taking the boiler out of service by
closing the valve in the plug line.
Soot Blowere.
Soot, fine ash, and cindere can collect
3.2.9
on boiler tubes and cause a substantial
decrease in the heat
transfer rate.
These substances
are very poor conductors
of
heat; in addition, when excessive amounts are deposited
on the
tubes, passages become plugged and gas flow is restricted.
64
MIL-HDBK-1125/l
Brushes, scrapera, hand lancee, and occasionally
soot blowere are
Hand lances
used to remove these deposite in fire tube boilers.
and mechanical
soot blowers are used to clean water tube boilere.
TI
VE
Brushes and
3.2.9.1
a. Scracx2rs. @.ru2Hand L anc~.
They
scrapers are made in various sizea to fit the boiler tubes.
are fastened to a long handle, usually a piece of pipe, and
pushed through the tubes.
Automatic
brushing syateme with vacuum
A hand
dust collecting
attachment
are effective
and common.
lance ia a piece of pipe supplied with compressed
air or steam.
The
Occasionally,
a special head is attached to the hand lance.
hand lance may be needed to remove deposits of aah or slag even
on boilers equipped with mechanical
soot blowers.
Permanently
mounted
3.2.9.2
These
mechanical
soot blowers are used on water tube boilers.
or
boiler supporting
blowers are mounted on the setting wane
structure at several points, to clean as much of the surface as
ia practical.
Blowers conaiat of a head that admita eteem or air
and turns the element, the element itself that distributes
the
steam or air, and the neceaeary bearings,
piping, and other
eupports.
AC
.
The head consiets of an operating mechanism, usually a
for turning the element
chain or handwheel operating two gears,
within a limited arc; a poppet valve for admitting and
controlling
the flow of steam or air to the element; and a cam
for opening and closing this valve (Figure 31).
The poppet valve
is adjusted at start-up to obtain proper steam or air regulation.
The cam ia cut or adjusted to establish
the proper blowing arc
and prevent steam or air from striking and cutting the baffles,
drums, tubes, or headers.
IN
of
nozzles.
Elemants are tubes containing
a number
These nozzles are spaced along the element to blow between the
boiler tubee for lance blowing, ”or at a number of tubes for maes
blowing.
When elements are installed
for lance blowing, it is
important that the nozzle epacing fit the boiler tube spacing and
that the elements are located properly.
Failure to observe these
precautions
may result in cut tubee because of the high velocity
of discharge
from the nozzles.
Elemente are made of plain,
carburized,
or alloy steel, depending
on the temperature to which
they are to be subjected; elements are supported at regular
intervals by bearinga clamped on the boiler tubes.
The distance
between these bearings is determined
by flue gas temperature in
that specific area.
.
f
65
MIL-HDBK-1125/l
/’vv’y=F
.,”!0”
VALVE mm’
Hcml”lmm
DMC
TI
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.,..,
:
IN
:
AC
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)
0)
“0,2..
,“
I
.. .
w<”’’”’””
VALVC ❑sc -
STC*”’IMC1
Figure 31
Mechanical
Soot Blower
3.3
Fuel -Handling
and Combustion
Coal Combust ion Eauirment.
3.3.1
four methods:
66
EcIui~ment
Coal
may be fired by one of
MIL-HDBK-1125/l
a)
Manually
on stationary
gratee
b)
Automatically
by stoker
c)
In suspension
ae pulverized”coal
d)
In a fluidized
bed
TI
VE
Manuel firing of coal using stationary grates ie not
used in modern central heating plants becauae of the limited
capacity of hand-fired
gratee and the amount of labor necessary
to operate the equipment.
Thie handbook contains no further
diecueeion
of manual firing.
The following paragraphs
deecribe
the combustion
equipment
required for the other methods of coal
firing and typical coal specifications
applicable to each method.
IN
AC
3.3.1.1
~.
Stokers were developed to automate and
Automatic
increase the capacity
of the simple hand-fired grate.
fuel feed and ash dieposal systems were added to reduce the labor
requirements,
and capacity wae increased by the addition of
forced draft fans, control dampers, and air compartments
to
promote better fuel and air mixing.
The result is that stokers
have several advantages
over hand firing:
they permit the use of
cheaper gradee of fuel, maintain better furnace conditions,
increaae combustion
efficiency,
require less labor, and increase
the boiler capacity.
Stokera may be divided into four general
classes:
underfeed,
spreader, traveling or chain grate, and
vibrating grate.
Spreader, traveling, chain, and vibrating
stokers are overfeed
stokers, in that fuel is fed from above the
bed.
Each type has its own application,
depending primarily on
the characteristics
of the fuel used.
The choice of the proper
stoker also depende upon factors such as the size and capacity of
the boiler, the ash content and clinkering characteristics
of
fuel, and the amount of draft available.
3.3.1.2
eed Stem.
Underfeed stokers receive their
name from the fact that fresh fuel ie supplied below the burning
zone.
freeh or green coal
The fuel bed consiets of three zonea:
on the bottom, the coking zone in the middle, and the
incandescent
or burning zone on the top.
Fresh fuel enters the
bottom of one end of a retort, is distributed
over the entire
retort, and ie forced to move gradually to the top where it
burns.
As the coal travels up from the bottom of the retort, its
temperature
gradually
risee, causing the volatile matter to
distill off, mix with the air eupply, and pase up through the
hotter zones of the fuel bed.
The temperature of the mixture of
volatile matter and air gradually increases until the mixture
ignites and burns.
The mixture may burn just below the surface
of the fuel bed or immediately
above it. The coke remaining
after the volatile matter has distilled off continues
to move to
67
MIL-HDBK-1125/l
the top; its temperature
gradually
rises above its ignition
temperature
and burns.
The vertical movement of the coal through
the bed is accompanied by movement of the burning coke toward the
ash discharge area.
The combustion
process is practically
completed by the time the remaining material reaches thie area.
The remaining combustible
matter or fuel completes its combustion
in this area before the ash is removed.
Air enters through
openings in the stoker called tuyeres, which are usually located
at the top or sides of the retort.
TI
VE
Underfeed stokers may be classified by the number of
retorts (single, double, or multiple) and the method of feeding
(screw or ram).
Single retort’ stokers may be screw or ram feed.
Figure 32 illustrates a single retort, screw feed ram distributor
stoker.
Multiple retort stokers usually combine a gravity or
overfeed action with the underfeed,
and are always ram feed.
They are used only on large boilers.
Coal sizing requirements
are established by the stoker manufacturer,
with a top size of
1-1/2 to 2 inches and not more than 50 percent slack being
typical.
The principal elements of an underfeed stoker are
Each is
hoppers, feeders, retorts, and a combustion air fan.
discussed
in the following paragraphs.
AC
Hoppers with a capacity of several
a) Hoppers.
hundred to several thousand pounds of coal are provided to supply
fuel to the feeder.
Some hoppers are equipped with agitators but
most depend on the slope of hopper sides to prevent coal from
bridging.
Offset hoppers are occasionally
used to permit access
to the boiler front.
IN
b) Feeders.
Feed screws or reciprocating
rams may be
used to deliver coal from the hopper to the stoker retort as
shown in Figure 32.
Even distribution
of coal is obtained by the
shape of the screw, shape of the retort, and the stroke of
distributing
rams.
The coal feed rate is controlled by a drive
mechanism which adjusts the speed of the screw or ram.
An
electric motor or steam turbine is used to drive the stoker via a
mechanical
or hydraulic apeed reducer.
Ram feed stokers may
utilize oil, air, or steam driven cylinders to move the ram, and
are generally set up to allow multiple feed rates.
Shear pins or
relief valves are provided to protect the equipment against
overload or binding.
Belt guards and gear and shaft covers are
provided for operator protection.
68
MIL-1lDBK-1125/1
mm9.
,~
v
=
-:
.-..
-
d-
VE
:..”
TI
Y—
Figure 32
Single-Retort
Stoker
AC
Screw-Fed
IN
Retorts.
Size and shape of the retort depends on
c)
Retorts in the smaller
the coal-burning
capacity of the stoker.
units are nearly square, while thoee in larger units are oblong.
The tuyeres or tuyere blocks through which air ia admitted to the
fuel bed are made in comparatively
small sections to allow for
expansion and to minimize thermal atress.
The tuyere blocks form
by either dead plates or
the top of the retort and are surrounded
dump plates.
Dump plates are ordinarily made to permit air to
pass through them.
Tuyere blocks may be high and slope away from
the retort, or receaeed below the dead plate.
They may be of
either stationary
or movable design.
d) Combustion
Centrifugal
or axial fans are’
Air Fan.
used to supply air to a windbox under the retort and to overfire
air ports.
The windbox may be divided into zones to permit
better control of combustion air.
Volume of the air supplied is
controlled
by inlet or outlet control dampers on the fan.
Airflow should be controlled automatically
to correspond to
changes in the firing rate.
Methods of control are discussed in
par. 3.4.2.
69
MIL-HDBK-1125/l
.
TI
VE
In practical application,
f=) Fuel Characteristics.
fuels ranging from lignite to anthracite have been burned
However, this
.auccessfully on single retort underfeed stokers.
type of stoker is most widely used for Eastern caking and mildly
caking bituminous coals and many of the Midwestern
free burning
coals, especially
those having an ash fusion temperature
sufficiently
high for successful utilization
in the relatively
For
thick fuel beds that characterize
underfeed burning.
satisfactory
stoker operation, coal sizing is as important as
coal analysis.
The size of coal best suited for single retort
stokers is that designated commercially
as l-inch to l-1/2-inch
nut and slack, preferably containing
not more than 50 percent
slack.
Slack is defined as coal of a size that will pass through
For multiple retort underfeed
a l/4-inch round hole screen.
stokers, the ideal coal should vary in size from 2 inches to
The volatile content
slack, with not more than 50 percent slack.
should preferably
be between 20 and 30 percent, the aeh content
should range between 6 and 8 percent, and the ash softening
temperature
should be above 2400 degrees F in a reducing
atmosphere.
Iron content of the ash should not be more than 20
percent as Fe-Ol for this range of softening temperatures
and not
more than 15 percent if the softening temperature
is between 2200
and 2400 degrees F.
IN
AC
Spreader stokers combine some of the
3.3.1.3
SDreader Stokers.
This
best features of hand and pulverized coal-firing
methods.
method of coal feed permits smaller particles to burn h
suspension
in the furnace, approximating
the action of pulverized
on
top of
coal firing.
The remainder of the coal is deposited
the burning coal, as in hand firing.
Other similarities
to
pulverized
coal firing are the presence of fly ash in flue gases,
the wide range of fuel which can be handled, and responsiveness
to rapid load fluctuation.
Spreader stokers are not affected by
the caking or noncaking properties
of coal to the same extent as
other types of stokers, and they can handle coal ranging in size
from dust to about 1-1/4 inches.
The furnace volume to permit
fines to be burned in suspension is usually about 50 percent
that required for an underfeed stoker.
larger than
The depth of
the grate is limited by the ability of the stoker to spread coal
evenly, and its width is limited by the width of the boiler;
however, several stoker units can be placed side by side to
provide the necessary capacity.
Spreader stokers with combined
traveling grates have been applied to boilers with capacities
up
to 400,000 pounds of steam per hour.
Although the ability to
burn inexpensive
coal screenings is one of the chief advantages
of spreader stokers, fly ash emissions increase
greatly as the
percentage of fines is increased.
Thusr under most conditions,
spreader stokers require some type of dust collectors.
Spreader
stokers operate with comparatively
thin fuel beds, are sensitive
to load changes, and are well adapted to regulation
by automatic
70
MIL-HDBK-1125/l
The thin fuel bed ie a decided
combustion control equipment.
advantage in following fluctuating
loade.
Figure 33 illustrates
The principal elemente of
a Power dumping type spreader stoker.
a spreader stoker are described
below.
AC
TI
VE
The feed mechanism consiste of the
a) Feed Mechanism.
feeder and the epreader.
The spreader is constructed
with either
An overthrow rotor receives
an underthrow or overthrow rotor.
An underthrow
the coal directly and throwe it into the furnace.
rotor picke coal out of a circular tray and throwe it into the
furnace.
Figure 34 illustrate
a chain type feeder with an
overthrow rotor.
Paddles (rotor blades) are ueually set in
either two or four rows around the rotor, with those in one row
twisted at an angle to throw the coal to the right, and those in
In some designs,
the next row arranged to throw it to the left.
the paddle ie curved to provide uniform crosswise distribution.
An oscillating plate or ratchet-driven
roll feeder ie used to
supply coal to the rotor.
The rate at which coal is fed is
regulated by varying the length of the etroke of the oscillating
plate or the speed at which the roll ie turned.
Speed or
position adjustments
are also
provided to regulate distribution
of fuel along the length of the grate.
The feeder mechanism,
grates, and air supply are ueually constructed
to operate as a
unit.
Feedere are usually driven from a single line shaft, with
When dumping grates are used,
each having its own drive gearing.
sections of the fire can be cleaned alternately
by shutting off
fuel to one feeder and allowing
fuel to burn out in that section
of grate before dumping.
Variable speed-driven
mechanisms are
eimilar to those found on underfeed
stokers.
Variable speed
motors often replace mechanical
gearing to drive the individual
feeder and distribution
shaft on newer designs.
b) Overfire Air Fan.
A separately driven centrifugal
fan is provided to supply overfire air necessary to maintain
proper fuel and air mixing and complete combustion.
A portion of
the overfire air may also be used to cool the feed mechanism and
aid in distribution
of coal.
IN
If
\
System.
Since the spreader
c) Cinder Reinfection
stoker burns a significant
percentage
of coal in suspension,
carry-over of unburned coal is common.
To improve boiler
efficiency by reducing this unburned carbon lose, fly ash and
coal can be collected
in a mechanical
collector at the boiler
outlet and put back into the boiler furnace.
This is done by use
of a cinder reinfection
fan and aspirator which picks up fly ash
and coal and pneumatically
conveye it back to the furnace via
special piping and reinfection
ports.
71
AC
TI
VE
MIL-HDBK-1125/l
Dump
Figure
Grate
33
Spreader
IN
Power
72
Stoker
.
CM,”
F**e,,
TI
VE
MIL-HDBK-1125/l
AC
B
Figure 34
Chain-Type
Overfeed
1)
Spreader
IN
d) Gratee.
Stationary,
dumping, vibrating, and
traveling grates may be used with a spreader stoker installation.
Traveling grates are most commonly used on modern installations.
Provision is made under the grates for proper air distribution
and ash collection.
Fiqure 35 illustrates
a soreader stoker with
traveling grate installation.
Air Fan.
As with all stokers,
e) Combustion
combustion
air under pressure is needed to ensure complete
efficient combustion and control.
Inlet or outlet dampers
provided to control the airflow rate.
73
and
are
IN
AC
TI
VE
MIL-HDBK-1125/l
Traveling
Figure
Chain
35
Grate
Stoker
Spreader stokers were
f) Fuel Characteristics.
developed
to burn lower grades of coal, but they are capable of
handlinq all ranks from semi-anthracite
to lignite, plus numerous
waste a;d by-product fuels.
As might be expected, spreader
The
stoker performance is best when quality and sizing are good.
fuel bed requires
a relatively small size
thin, quick-burning
fuel.
The spreader stoker will burn fuel ranging from slack or
carbon, all through 118- or l/4-inch screen, to l-1/4-inch or
l-1/2-inch
nut and slack.
Considerable
range in size content is
necessary
for satisfactory distribution,
and if there is a good
balance between coarse and fine particles
the burning rate and
ash bed thickness are practically
uniform over the entire grate
surface.
These types
3.3.1.4
3ra velina Grate and Chain Grate Stokers.
of stokers consist of an endless belt grate which moves slowly
and conveys the burning coal from the feed end to the ash
discharge
end of the stoker.
With chain grate stokers, links are
assembled
so that as they pass over the rear idler drum, a
scissor-like
action occurs between links.
This action helps to
break loose clinkers which may adhere to the grate surface.
74
MIL-HDBK-1125/l
Traveling grate stokers do not have this scissor action and
Figure 35
therefore are not normally used with clinkering
coals.
Traveling
or chain
illustrates
a traveling chain grate stoker.
gratea may be used with the spreader feedere diacuased
above, or
coal may be placed directly on the stoker, as described
below.
VE
a) Feed Mechanism. . A hopper on the front of the
stoker has an adjustable
gate that regulates
the depth of the
fuel bed.
The rate of feeding coal to the furnace ie regulated
The amount of
by changing the speed at which the grate travels.
aah carry-over
from the furnace ie kept to a minimum with this
feeding method, and fly ash injection, typical.of
spreader
stokers, is not required.
Figure 35 illuatratee
the overfeed of
coal onto a chain grate.
TI
b) CombustionAir.
Space between the grates is
divided into zones and flow of air to each of these zones is
This is necessary if uniform combustion
controlled
by dampers.
is to be attained, because resistance of the fuel bed to flow of
It would be
air decreasea as grates move to the rear.
practically
impossible
to get proper air distribution
if these
Overfire air is alao provided to
zones were not provided.
complete combustion of volatile matter driven off from the fuel
bed.
AC
Fuels moat widely used on
c) Fuel Characteristics.
traveling grate stokers are anthracite,
semi-anthracite,
noncaking or free-burning
bituminous coal, subbituminous
coal,
lignite, and coke breeze.
Some bituminous
coals of the caking
type may be burned on traveling grate stokers if coal is of an
optimum size, has been allowed to weather,
and is tempered to
Coal sizing for traveling
approximately
15 percent moisture.
grate stokera may be related to the ASTM classification
of coal
by rank (ASTM D388).
IN
(
. In this type of stoker, grates are
3.3.1.5
Vibra~
Stok~
inclined at an angle of about 14 degrees.
Coal ie fed from a
hopper at the front of the furnace.
The fuel bed is progreased
by intermittent grate vibrations.
Ash is discharged
over the end
of the grate (Figure 36).
Furnace water tubes are positioned
under stoker grates to cool grate bars; and air compartments
are
provided to control combustion
air.
Overfire air is generally
provided at two elevations.
The firing rate is controlled
by
adjustment of a hopper faed gate, frequency of grate vibration,
combustion air dampers, and overfire air dampers.
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Water
Cooled
Figure 36
Vibrating
Grate
Stoker
The water cooled vibrating
Fuel Characterietice.
a)
grate stoker is suitable for burning a wide range of bituminous
and lignite coals.
Even with coals having a high free swelling
index, gentle agitation and compaction
of the fuel bed tende to
keep the bed porous without the formation
of large clinkers
A
generally associated with low ash fusion temperature coals.
well-distributed,
uniform fuel bed can be maintained without blow
holes or thin spots.
3.3.1.6
pulve rizerq
The function
of a pulverized coal system
a) General.
is to pulverize coal, .deliver it to the fuel-burning equipment,
Burning
and burn it in the boiler with a minimum of excess air.
pulverized coal becomes cost effective
in large capacity systems
76
MIL-HDBK-1125/l
(over 100,000 lb/hr steam flow)
over stoker coal, such aa:
(1)
Ability
to achieve
much
2)
Ability
to use coal
3)
Improved
several
higher
sizes
advantages
capacities.
from fires UP
2 inches.
exceaa
air
rec
to load changes.
4) Increased thermal efficiency
irements and lower carbon leas.
(5)
c)
response
Types
because
of lower
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to
and can offer
Less manpower
requirements.
of Pulverizers
AC
(1) Ball Mill.
The ball mill consists of a
horizontal
rotating cylinder filled with a charge of steel balls
The
of various sizes to a level just below the halfway mark.
interior of the cylinder is fitted with cast iron liners and is
rotated at epeeds of 20 to 30 rpm.
Balls are carried part way
around the circumference
of the cylinder and fall toward the
Hot air
center.
Coal intermingling
with balls ia pulverized.
passing through the cylinder dries the coal and removes the
fines.
IN
(2) Bowl Mill.
Material fed to the pulverizer
falls to the center of the revolving bowl where it is thrown by
centrifugal
force between the grinding ring in the revolving
bowl, and the rolls.
Pressure for grinding is imparted to the
rolls by springs.
A typical bowl mill is shown in Figure 37.
Air enters the mill housing below the bowl and passes upward past
coal that
the bowl, where it picks up the partially pulverized
has been discharged over the edge of the grinding ring.
The air
and pulverized
coal mixture is carried into an adjustable
classifier
where a spinning action is imparted to the mixture.
The degree of spin determines
the sizing of the finished product.
The oversize is returned to the bowl from regrinding.
(3) Ball-Race Pulverizers.
In ball-race
pulverizers
(Figure 38), balls used as the grinding element are
confined between two races.
The balls are driven by rotating the
race in the case of
uppe~ or lower race, or the intermediate
multl-ring
units.
Pressure for crushing is supplied by springa
forcing the race together.
Coal circulation
is affected by means
of preheated air under preaaure supplied by a blower.
Fines and
coarse particlea are carried to a classifier.
Coarse particles
are returned for regrinding while fines are carried onto burners.
Fineness of coal at the outlet of the classifier
ie regulated by
adjustable
vanes.
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Figure 37
Bowl Mill
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MIL-HDBK-112511
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Oischa,go Opminps
(Individual Burner (.m~)
IN
Figure 38
Ball Race
(4)
Figure
39
illustrate=
Attrition
Pulverizers.
.
.
a
Pulv=l~er
that
comlnnes xmpact and attrition forces.
Coal and
pr~mary au enter the unit through a feed chute.
A series of
hammers makea up the primary pulverizing
stage which breaks down
and lumps to a granular eize.
Partly ground coal passes around
the outside of the rotor into the final pulverizing
stage, which
consists of stationary and rotating pegs.
Coal in the turbulent
airstream rubs against the pegs and other coal particles to be
reduced by attrition.
79
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MIL-HDBK-l125/l
(b)
(a)
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Figure 39
Attrition
Fluidized bed codustion
is a
3.3.1.7
~
ed.
relatively
new method of burninq coal while complvinq with sulfur
dioxide e;ission regulations.
in fluidized bed-c~mb~stion,
coal
is introduced
into a bed of limestone or sand particles which is
kept in a fluidized state by a flow of high pressure air from
The
Combustion takes place in the bed.
forced draft (FD) fans.
sulfur in the fuel combines chemically with limestone in the bed,
forming calcium sulphate and calcium sulphite which can be
removed with the ash handling system, eliminating
the need for
scrubbers to clean flue gases.
The main advantage
of the
fluidized bed boiler ie its ability to control sulfur dioxide
emissions.
However, it also has the ability to burn a wide
variety of fuels as discussed below.
The disadvantages
of
fluidized bed boilers are added electrical operating costs
associated with larger combustion air fans necessary
for
fluidizing the bed, higher particulate and unburned carbon
carryover
from the furnace, and high initial cost.
Figure 40
illustrates
a fluidized bed fire tube boiler.
Fluidized bed
water tube boilers are also available.
Note that a baghouse or
precipitator
is required for particulate control.
Fluidized
bed boilers may be
a) Fuel Characteristics.
used to burn almost any fuel, including not only bituminous
and
anthracite
coals but also lignite, refuse, wood, and various
solid waste fuels.
80
.MIL-HDBK-1125/l
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Figure 40
Bed Fire Tube Boiler
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Fluidized
3.3.2
. A great many types of coalhandling equipment with capacities ranging from a few tons to
several hundred tona per hour are available.
The kind of
equipment selected is determined
by such factors as size of
Plant, total amount of fuel to be burned, method of receiving
the
coal (rail, truck, or water), regularity of delivery,
kinds of
coal available, and relative locations of the plant and storage
areas.
It is usually advantageous
to keep a certain amount of
coal in storage, in case deliveries
are delayed for any reason.
The amount of coal stored depends on the rate at which it is
burned, space available
for storage, and frequency of delivery.
The quantity stored should’ normally be sufficient to operate
for
90 days or longer at peak demand.
,
81
MIL-HDBK-112511
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3.3.2.1
Storaae.
coal may be stored in covered bine or
bunkers, in silos, or in the open.
Only relatively
small amounts
of coal can be stored in bunkers and silos.
The amount that can
be stored on the ground is limited only by the space and coal
If coal is to be stored on the
handling equipment available.
ground, the selected area should be prepared to reduce loss of
fuel due to mixing with foreign material.
The site may be
leveled and firmly packed, stabilizing
materials
may be used, or
Silo etorage is
a concrete or asphalt surface may be laid.
The dead storage in silos
divided between live and dead storage.
Where obvious heating
should be shifted at least once per month.
occurs, shifting of dead storage should be as often as required
to minimize spontaneous
heating and to avoid fires.
Figure 41 illustrates
a
3.3.2.2
Coal Handlina in Plan t.
It includes the following major,
typical coal handling system.
components:
tractor truck hopper, feeder, bucket elevator or
conveyor,
bunker or silo, and a coal weighing device.
IN
AC
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Hoppers receive c,oa.1from trucks or coal
a) Hoppers.
Hoppers
cars and deliver it to a feeder or conveyor system.
usually have grates made of steel rods or bars to prevent passage
of oversized material that could plug or damage the conveying
equipment.
b)
Feeders.
Many types of feeders are available to
convey and regulate the flow of coal from the hopper to the
bucket elevator or other parts of the system.
Apron feeders and
flight feeders are continuous chain feeders that are often used.
Final selection is dependent on the particular
site
characteristics.
Bucket Elevators.
A bucket elevator consists of an
c)
endless chain, twin chains, or belt to which buckets are
attached.
It is used to lift coal vertically.
The three most
common types of bucket elevator discharges
are centrifugal,
perfect, and continuous
(Figure 42).
Elevator boots are provided
with cleanout doors for removing dropped coal.
Some bucket
elevators can also convey coal horizontally.
Belt conveyors and
drag-type
flight conveyors are other effective devices for
delivering coal to bunkers.
Bunkers and Silos.
d)
Bunkers and silos provide
covered storage of coal.
Bunkers are made of steel and are often
lined with a protective coating to minimize corrosion
and
abrasion.
Hopper bottom and discharge
gates are provided to
remove coal from the bunker.
Silos are constructed
of either
steel or concrete and are often provided with live storage
sections and reserve storage sections.
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MIL-HDBK-1125/l
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Figure 41
Handling System
IN
Coal
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PERFECT
CENTRIFUGAL
Typee
CONTINUOUS
Figure 42
of Bucket Elevators
IN
Knowledge
of quality and quantity
e) Coal Weighing.
of coal used is essential for efficient
operation of a boiler
No standard method of weighing
coal can be prescribed,
plant.
since many types of equipment are available
for doing the job
manually
or
automatically.
Coal may be weighed directly with
weighing
equipment, or indirectly
with equipment
that measures
its volume.
Weighing equipment ordinarily
consists of automatic
or semiautomatic
weigh larries.
As shown in Figure 43, a weigh
larry consists of a framework that supports a hopper mounted on
scale beams.
The framework can be moved over various bunkers.
The coal hopper of the larry is filled and the weight determined
and recorded.
The larry is then moved to desired stoker hopper
and dumped.
Coal scales that weigh coal automatically
are also
available.
One type of scale consists
of three major assemblies:
a belt feeder, weigh hopper with bottom dump gate, and weigh
lever with controls.
A mechanical
register
is provided to record
amount of coal delivered.
A belt feeder transfers coal into the
weigh hopper until the weigh lever is balanced.
The weigh hopper
is then dumped and the cycle is repeated.
84
MIL-HDBK-1125/l
3.3.3
Ash typically
requires removal
from several collection
points in the boiler.
Ash that is
removed directly from the furnace or stoker ie termed “bottom
ash” and may be in hard, agglomerated
Ash that is
clinkers.
removed from various dust collection points is termed “fly ash”
and tends to be light, fluffy, and relatively
free flowing.
Ash
is generally handled together and disposed of in a permitted
landfill, especially
on small systems.
Depending
on individual
circumstances,
it may be desirable to segregate
the bottom and
fly ash and handle them separately.
This could be advantageous,
for instance, if a commercial
market existed for one of the
products (fly ash may be used in the manufacture
of concrete;
Medium
bottom ash may be used as a winter road treatment,
etc.).
and large plants generally
employ complete ash disposal
systems,
while small plants may use.simpler
and less automatic
equipment.
The three general types of ash handling $ystema are pneumatic,
hydraulic, and mechanical.
Combinations
of these three systems
are often used.
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(
Figure 43
Weigh Larry
85
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MIL-HLIBK-llZ>I1
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Figure 44 illustrates
a
3.3.3.1
P neumatic Ash Handling.
vacuum-type
pneumatic
ash handling
system.
In this illustration,
the vacuum is created by a steam exhauster; however, motor-driven
vacuum pumpe are also available.
Intake hoppers provided at
desired locations admit ash to the system.
One end of the ash
created by the exhauster
conveying line ie open, and suction
Dry ash”is admitted
causes a rapid flow of air through the line.
to primary and secondary ash receivers,
which are equipped with
counterbalanced
drop doors.
A timer limits the period of
operation to short cycles to permit dumping ashes into “the silo.
As the system goes into operation,
negative pressure in the
receivers closes and seals the drop doore.
At the end of each
when pressure is equalized,
And drop
cvcle,
.
. the doors ewinq open
The a]r washer condenses incoming
ashes into the silo b~lo~.
steam from the exhauster,
washing
out ash and dust particles
exhausted to the atmosphere..
The, mixture of water. and dust
passes to a sump, where dust settles and water is drawn off to
waste.
[
Figure
Pneumatic Ash
44
Handling
System
It is necessary to clean the sump periodically
to
prevent clogging the sew~r.
exhaust sile;cer is ava;lable
for
this system where desired.
An unloader is usually provided and
consists of an inclined revolving
drum containing water sprays
that wet the ashes as they are discharged
from the bottom of the
eilo.
are
limited in the distance they can move
Vacuum systems
ash effectively,
and pressurized
pneumatic systems or combination
vacuumlpressure
systems are available
if the conveying distances
86
MIL-HDBK-1125/l
become too great.
conveying
fly ash
on small systems.
Pneumatic
but
are
also
systems
are most commonly used
used for bottom
occasionally
for
ash
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3.3.3.2
A6 h [email protected] . Figure 45 illustrates a
hydraulic
aeh handling system.
Thie is a pressure velocity
system in which force is provided by a series of high pressure
When the system operates, ash is taken from the ash
water jets.
jet hopper beneath the boiler.
Sprays and water jet nozzles
flush material out of the hopper and through a grid which retains
any large clinkere for breaking.
Some systems are equipped with
clinker grinders.
The ash is then jetted through an abrasion
Fly ash and
resistant
sluice gate to a sump pit or landfill.
dust are aspirated pneumatically
from dust hoppers by water jet
exhausters
and passed through an air separator where air is
collected
and vented to the atmosphere.
Finally, the mixture of
fly ash, dust, and water is discharged through the sluice qate to
th~ sump pit or landfill.
Hydrauli~ systems-are
normally ;sed
for bottom ash conveyinq.
Thev are used infreauentlv
on new
tallations due to-en,~ironme~tal and water u;age regulations.
..
i(l
-.“..
. . . . . . . . . . .
Hydraulic
Figure 45
Ash Handling
I
System
3.3.3.3
Drag, screw, and bucket
conveyors
can
be
used
to
move
ash
from
boiler ash pits to storage
..
..
C.ins, SLlos, or container.
Mechanical systems are used
primarily with small stoker fire boilers, and may be utilized for
either bottom ash or fly ash.
87
MIL-HDBK-1125/l
Oi.1-F~na
3.3.4
EauiDment . Oil has a number of advantages
cost of fuel
over coal when used to generate eteam or hot water:
VE
handling ie lower, less labor is required for operation and
maintenance,
leee storage space is required, initial cost of the
oil system is lower, and higher efficiencies
are possible.
In
addition, oil does not normally deteriorate
in storage; it is a
A disadvantage
of oil
clean burning fuel and is easy to control.
is the greater danger of explosions
(which leads to more
elaborate
flame safety controls), and its cost (which is two or
Refer to
three times higher than coal on a heating value basis).
of fuel
pars. 2.4.1.1 and 2.4.5 for a gore detailed discussion
oil and the combustion
process, and to Table 3, which presents
The operator
physical properties
of common grades of fuel oil.
should be familiar with the fundamental principles
of combustion
to make the best use of this concentrated
and,valuable
fuel.
~
A omizers. Burners in central heating
3.3.4.1
plants utilize three types of atomizers: atomizers using steam
AC
TI
The
or
air,
pressure atomizers,
and rotary cup atomizers.
purpose of atomization
is to break fuel into fine particles that
Fuel then burns with a clean
readily mix with combustion
air.
hot flame, being vaporized and oxidized by the resulting
combustion
before cracking takes place.
In pressure atomizing
burners, the fineness of spray increases as pressure increases
When NO. 6 oil is burned, a
and as viscosity
is lowered.
pulsating
flame may result if viscosity is reduced to a point
The burner
where the preheat temperature
tends to vaporize fuel.
manufacturer
should recommend a proper viscosity operating range.
Proper preheating
of oil will be discussed in par. 4.3.6.
IN
Fluid Atomizers.
Fluid atomizers use either steam
a)
or air to break fuel oil into a fine mist.
Steam atomizers
operate by mixing oil and steam inside the atomizer tip under
pressure.
As the steam and oil mixture leaves the tip, steam
rapidly expands, breaking oil into small droplets to begin the
combustion
process.
Figure 46 illustrates
a steam atomizer.
Steam is supplied to the atomizer at a pressure of between 10 and
20 psi above oil pressure.
Under normal conditions,
a steam
atomizer uses approximately
1/10 pound of steam to atomize 1
pound of oil.
This amounts to about 2/3 of 1 percent of the
boiler steam output.
Some modern atomizers use as little as 0.03
pounds of steam while older designs may use more steam.
Compressed
air may also be used in place of steam to atomize oil.
An air atomizer uses energy developed by the air compressor
to
replace energy in steam generated in the boiler.
Air atomizers
are commonly used when steam is not available,
on smaller boilers
generating
less than 20,000 pounds of steam per hour, and for
firing more easily atomized oils, such as NO. 2 and No. 4 grades.
Air atomizers are often used for cold start-up of a boiler, then
replaced by eteam units as the plant pressure builds up.
Both
88
MIL-HDBK-1125/l
steam and air atomizers are effective when used with a good
burner to control combustion
air mixing.
Automatic control of
the firing rate is possible over a range of 15 to 100 percent of
capacity.
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Pressure atomizere use
b) Pressure Atomizere.
pressures of 600 psig or more to accelerate oil into the furnace
Oil is spun inside the tip and leaves
through the atomizer tip.
as a cone of oil that thins out and breaks apart into fine
The advantage of pressure atomizere
ie
droplets for combustion.
The disadvantagee
are high
the simplicity of the system.
pressure required and the fact that the turn down range ie
limited to 75 to 100 percent of capacity if effective atomization
Thie type of atomizer is also sensitive to
is to be maintained.
oil viscosity, and small passagea
in the atomizer tips tend to
frequently used on
Preseure atomizers
are not
clog and’ wear.
modern central heating plants.
..
4
“’w
IN
L
AC
~,’
It
~
new.,.Ca
!*
,
II
,
\
b,,”
s,.,mw
%,.
1,.mu
Figure 46
Steam Atomizer
The rotary atomizer uses energy
c) Rotary Atomizer.
from a apinning cup and primary air from a small fan.
A thin
cone of oil is spun off the end of the cup and, aided by the
primary air, thins out, and breaks apart into fine droplets.
Rotary atomizers can be fairly effective when combined with
burne~s using forced draft fa~s.
Natural draft rotary atomizer
burners, as developed in.the 1930’s, do not compare favorably
with modern forced draft burners and, in general, rotary
atomizers do not have any significant
advantage
over fluid and
pressure types.
They have disadvantages
of limited capacity and
electric horsepower requirements
for driving
the rotary cup and
89
MIL-HDBK-1125/l
.
the primary air fan.
They generally become uneconomical
for
boiler capacities
above 20,000 pounds of steam per hour, and are
seldom
used in modern burners.
VE
3.3.4.2
Once oil is effectively
atomized,
e.
3YDe s of B~
the next step ie to effectively mix it with comhstion
air.
Three general types of burners are available:
register, low
excess air, and package burners.
These burners incorporate an
igniter for automatic light-off and a provision
to mount flame
scanners to prove igniter andlor main flame.
Effectiveness
of a
burner is measured by its ability to complete combustion of fuel
with a minimum of excess air throughout
the firing range,. Excess
air levels at 100, 75, 50, and 25 percent load should be
determined
when evaluating burner effectiveness.
Refer to par.
4.4.1 and Table 19 for more information.
IN
AC
TI
Regieter
burners are
a) Register Burners.
characterized
by one or more circular
registers
that admit
combustion
air into the burner throat as shown in Figure 47.
An
impeller is provided to protect the atomizer
from the direct
blast of combustion air and to provide a zone to stabilize
ignition.
The refractory throat helps to control airflow and
velocity, and the hot refractory helps to stabilize ignition by
radiating heat back into the base of the flame.
Adjustment of
air registers, either initially or continually
with load swings,
helps to ensure that optimum air velocities
are available for the
combustion
process.
Register burners may be used with ambient or
preheated
air, oil atomizers, and/or gas burning equipment.
Capacities
from 10 to 200 million Btu/hr are common.
b) Low Excess Air (LEA) Burners.
LEA burners were
developed
to achieve lower excess air levels, throughout the
burner load range, than are possible with register burners.
A
venturi section ensures uniform airflow at the burner outlet.
An impeller is used to swirl a portion of air into atomized oil.
The remainder of air moves axially through the burner at a
velocity designed to cause it to mix later with fuel and impeller
swirled air.
The advantage of the LEA burner is its ability to
operate at LEA levels, with subsequent
improvements
in
efficiency.
The main disadvantage
is a long, narrow flame which
furnace configurations.
is not well suited for many
Very
accurate combustion controls are needed to take advantage of this
burner’s LEA capability.
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MIL-HDBK-1125/l
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Furnace wail
47
Burner
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Figure
Register
IN
Low-NOx Burners.
To meet environmental
c)
regulations,
manufacturers
have developed burners that are
without adversely affecting
capable of reducing NOX emissions
These
10W-NOX burners control mixing
efficiency or performance.
of fuel and air in a pattern
that keeps the flame temperature
Whereas conventional
burners
down and dissipates heat quickly.
mix secondary air with the primary
fuel air stream as soon as
they are injected into the furnace, creating a high intensity
separate
combustion
process, 10W-NOX burners establish distinctly
primary and secondary combustion
zones, thereby staging the flame
at the burner.
Basically, the same techniques
for NOX reduction apply
to the burner as were used in the furnace.
Thus, almost all
burner modifications
rely on some form of LEA staged combustion
andlor internal flue gas recirculation
to reduce NO emissions.
Overfire air in combination
with 10W-NOX burners of #ers even
further reduction.
d)
Package Burners.
Package burners include the
forced draft fan and its air control damper, oil andlor gas
control valves, actuators,
igniters,
flame safety system, and
combustion controls as a shop assembled unit.
Cost and
performance capability of package burnera vary widely.
Not all
packages are suitable for every application.
Every burner
application
requirea careful consideration to ensure that the
proper burner, controls, and accessories are applied.
91
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MIL-ZIDBK-1125/l
burners should be capable of automatic
start-up, shutdown, and
Package burners are available for firing
modulating
firing rate.
rates of several gallons to several hundred gallons per hour.
Either register or LEA burners may be supplied as packages; and
rotary, pressure, or fluid atomizers
may be used.
AC
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. Aboveground
3.3.5
Oil Storaa
and Hanand underground
fuel storage tanks a~e available
as illustrated
in Figures 48 and
49.
These tanks are provided with some or all of the following
fill, vent, return, sludge
auxiliary
equipment and connections:
pump-out,
low suction, high suction, steam smothering,
firefighting
connections,
gage” connection,
suction box, suction
or tank heater, steam connection,
level indicator, temperature
indicator,
access manholes,
ladders, piping, valves, and double
wall containment
for underground
fuel etorage tanks not shown in
Figure 49. The amount of storage capacity installed depends on
the mission of the base, availability
of dependable
supply, and
Storage tanks and oil-burning
equipment
frequency of delivery.
must be installed in accordance
with the National Fire Protection
Association
(NFPA) 30, F~uids
Code,
tallation of Oil-Burnti
and NFPA 31, ~hs
Ea uiom ent.
,,,,
am,
r.;, *;..
IN
.
Pt.. VI,” m Tu,, Em,na.”
Figure 48
Arrangement
of Aboveground
Fuel Oil Tank
92
MIL-HDBK-1125/l
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I
, .A--U7.
c-ol
n-Am
“-#ii
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—P.
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n-t
-w-cd
n r- 1-
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C.*%Vtieti
.
AC
TI
sznl Pbmsmlx-
Figure 49
Underground Fuel Oil Storage Tank
IN
. No. 2 and No. 4 oil normally
3.3.5.1
Fuel Oil ~
only require a pump set to tranefer oil from storaqe to the
Paraffin base No. 4 oil may also require i small amount
burner.
of heating.
Use of day tanks and transfer pumps may be necessary
No. 5
if main storage tanke are located remotely from the plant.
and No. 6 oil require pumping and heating equipment to prepare
Figure 50 illustrates
and move oil to the combustion
equipment.
A pressure regulatory valve is
a duplex pumping and heating set.
provided to return unneeded oil to the etorage or day tank before
it is heated.
This avoids overheating
of storage tanks in
Insulation of
addition to maintaining
the desired oil pressure.
oil, eteam, and condensate
linee ie required, and electric or
steam heat tracing of lines may be required in some applications.
I
3.3.5.2
requirements
The NFPA establishes
&afetv Ea~.
for safe boiler operation for boilers with 10,000 pounde of steam
per hour and larger.
These requirements
are contained in NFPA
8501,
Figures 51
and 52 show schematic arrangement
of safety equipment for oilfired water tube and fire tube boilers,
respectively.
Standards
for oil-fired multiple burner boilers are found in NFPA 8502,
ns/Imc)losions in
or the Pre v~o
Standard
. For boilers rated less than
r Bo~
93
MIL-HDBK-1125/l
.
Inc.,
10,000 pounds of steam per hour, Underwriters Laboratories
Underwriters
Laboratories
of Canada, or other nationally
recognized
organizations
establish safety requirements
and tests,
and approve safety equipment.
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Pumping
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IN
Fuel Oil
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Figure 51
Fuel Oil-Fired
95
Water
Tube Boiler
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MIL-HDBK-1125/l
.
schematic Ammr._nt
of Safety Eq.ipmc.t.
Am.mmtic (rc+ing)
Cu. ..d OI~i%cd (akerytdll
or A.tmn*u. (..n-~chnti
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Boiler With One (1] Burner,
IN
AC
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Gas-
Fiaure 52
and ‘Oil-Fired
96
Water
Tube
Boiler
UIL-HDBK-1125/l
for Automatica.llv F~
organizations.
TI
VE
3.3.6
. Natural gaa is an easy and clean
fuel to burn and requires less equipment and maintenance
than
coal or oil aysteme.
Its disadvantages
include higher cost than
coal, uncertain and limited availability,
and a greater danger of
explosion.
Pars. 2.4.1.3, 2.4.6, and 2.4.6.1 describe
the
potential for explosiona
and some of the necessary precautions.
Early gas-firing
equipment used gas velocity to aspirate air into
the burner throat, where it wae premixed with the gas before
The
burning.
Premix burnera are now used for igniter service.
advent of forced draft fans and the need for increased
burner
capacity brought about the development
of nozzle mix gae burners.
Nozzle mix burners are capable of handling gas over a wide range
of preesures depending
on the design.
Typeo of nozzle mix
burners include ring, gun, and multiple spud.
NFPA 8501
establishes
requirements
for safe operation of gas-fired
boilers.
Figures 52 and 53 show schematic arrangements
of safety equipment
Standards
for
for gas-fired fire tube and water tube boilers.
natural gas-fired multiple burner boilers are found in NFPA 8502.
For boilers rated less than 10,000 pounds of steam per hour,
standards are set by Underwriters
Laboratories
Inc., Underwritera
Laboratories
of Canada, ASNE CSD-1,
tv De vices
# and other nationally recognized
IN
AC
3.3.7
~ed
Pe~Gas
(LP~ . LPG ia used for igniter
service and occasionally
as a standby fuel for natural gas or
oil-fired installations.
LPG is also used on smaller remotely
located boilers where natural gas service is not available.
LPG
is a combination
of propane and butane maintained
in a liquid
state through storage under pressure.
NFpA 58, ~
a of
Petroleum Ga seR and NFPA 54,
and
Part 2 establish
requirements
for
Gas CO*
storage and handling o; LPG.
3.4
. Controls and
instrumentation
are an integral and essential part of central
boiler plants.
They serve to ensure safe, economic,
and reliable
operation of equipment.
They range from the simplest of manual
devices to completely
automated, microprocessor-based
systems for
control of boilers, turbines, and even end users of energy.
The
subjects of controls and instrumentation
are so intimately
related that they are difficult to separate, and are discussed in
parallel in the following section.
Only those systems and items
which are commonly used in central boiler plants are discussed.
Uany of the controls existing in Navy power plants are pneumatic;
however, nearly all new “controls are electronic
based with
microprocessors.
97
MIL-HDBK-l125/l
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Safety Equipment,
Figure 53
Natural Gas-Fired
98
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TI
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Tni-1
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Water
Tube
Boiler
MIL-HDBK-1125/l
. The importance of an
3.4.1
adequate,
properly controlled supply of feedwater to a boiler
cannot be overemphasized.
Boiler feedwater
pumps and injectors
(par. 3.6.3), low water fuel cutoffs
(par. 3.4.3), and feedwater
heaters
(par. 3.6.2) are part of an effective
feedwater system.
Steam boilers also require drum. level controle
to maintain the
water level within limits eetabliehed
by the manufacturer.
Operating
with water levels that are too high may cause carryover
with levels that are too
of water from the drum, while operating
low can result in boiler tube failuree
due to insufficient
cooling.
Feedwater regulator
are used to adjust the feedwater
flow rate and maintain proper levels.
Five types of feedwater
regulators
are commonly ueed:
positive
displacement,
thermohydraulic,
thermostatic,
pneumatic
level transmitter/
controller,
and electronic level transmitter/controller.
Each is
described
below.
VE
(
AC
TI
. The positive displacement
3.4.1.1
~
feedwater regulator
(Figure 54) is connected
to the boiler drum
or water column so that the average water level in the chamber is
in line with that of the drum.
The rise and fall of the float
with the water level actuatee a balanced
feed valve through a
suitable system of levers, and reduces or increases flow of water
to the boiler.
The entire mechanism
is in the pressure space and
there are no etuffing boxes to leak or bind.
The float ia
of
alcohol,
which vaporizes
initially charged with a small amount
and pressurizes
in the float to counteract
boiler pressure
exerted on the outside of the float.
The valve and linkage are
designed
to give a gradual and continuous
change in water flow
between high and low limits.
This type of control will maintain
a different water level for each steam flow produced by the
boiler.
IN
3.4.1.2
Operation
of the thermohydraulic
or
vapor generator type of feedwater regulator
(Figure 55) depends
upon the principle that steam occupies
a greater volume than the
water from which it was formed.
The equipment consists of a
generator,
a diaphragm operated valve, and the necessary
connecting
pipe and tubing.
The central
tube of the generator is
connected
to the boiler drum or water column, with the tube
inclined so that normal drum water level is slightly above the
center of the generator.
The generator,
tubing and diaphragm
chamber are filled with hot water.
In operation, heat from steam
in the upper portion of the inner tube raises the temperature of
water surrounding
that portion of the tube and converts part of
it to steam.
This increases pressure
in the generator, forcing
part of the water out of the generator
until the water level .is
the same in both the inner and outer tubes.
Water that is forced
out of the generator moves the diaphragm
and opens the valve.
When water level in the boiler rises, some of the steam in the
(
99
MIL-HDBK-1125/l
generator condenses and lowers the pressure. The spring on the
valve forces water into the generator, closing the valve in the
process.
Fins are installed on the generator to radiate away
some of the heat absorbed, thus preventing
excessive pressures in
the generator
circuit and increasing the speed of response of the
regulator.
This type of regulator establishes
a relationship
between water level in the drum and the valve opening.
Therefore,
for each stream flow rate, a slightly different water
level will be maintained.
IN
AC
TI
VE
3.4.1.3
Thermostatic.
Operation of the metal thermostat or
expansion
type of regulator
(Figure 56) depends upon expansion
and contraction
of an inclined metal tube.
The expansion tube is
mounted on a steel frame in such a way that it is under constant
tension.
It is connected to steam and water spaces of the boiler
so that it contains only steam when water is at its lowest level.
length.
As water level
The tube is then expanded to its maximum
in the boiler rises, water also rises in the tube, causing it to
cool and contract.
The tube is connected to a balanced valve in
the feedwater
line by a system of levers that move the valve as
the tube length changes. The feedwater valve ie at its maximum
opening when water level ie low and the tube is filled with
steam, and closes as water level rises and the tube shortens.
Note that all of the above regulators increase the flow of water
as the level drops.
Figure 54
Positive Displacement
Feedwater Regulator
100
IN
AC
TI
VE
MIL-HDBK-1125/l
Figure 55
Vapor-Generator/Thermohydraulic
Feedwater Regulator
101
AC
TI
VE
MIL-HDBK-1125/l
Figure 56
Thermostatic/Metal Expansion Feedwater Regulator
3.4.1.4
Drum Level Transmitter. A typical arrangement of a
drum level measuring transmitter is shown in Figure 57. The
IN
transmitter
is a differential
pressure device in which the output
signal increases as differential
pressure decreases.
Typically,
the differential
pressure range is approximately
30 inches with a
zero suppression
of several inches.
To determine the measuring
instrument
calibration,
necessary design data are the location of
upper and lower pressure taps into the boiler drum with respect
to normal water level, operating pressure of the boiler drum, and
ambient temperature around external piping.
With these data and
the desired range span of the transmitter,
exact calibration
can
be calculated
by using the standard thermodynamic
properties
of
steam and water.
On the high pressure side of the measuring device,
effective
pressure equals boiler drum pressure plus the weight of
a water column at ambient temperature,
and having a length equal
to distance between two drum preaeure connections.
On the low
preseure side, effective pressure equals boiler drum pressure,
plus the weight of a column of saturated steam having a length
from the upper drum pressure connection
to the water level.
102
MIL-HDBK-1125/l
i
Condensate
reservoir
‘-’J,
I
h(2).
h(3)—
70* walercolumn
/et Ifansmilter
=ts(3)-(h(l)
VE
=%
i(l),
equivalent
pressure
+h(2)]
differential
bL
L
Trar
I
nitter
Pneumatic
Tranamitter/Controller.
As boiler firing
a)
ratea increaeed with the development
of the modern water cooled
furnaces, water etorage capacity decreased and feedwater control
became more difficult.
A steam drum in a modern boiler can be
emptied of water in minutee if the supply ie shut off.
Changes
in steam pressure
result in expansion or swelling of the
steam/water mixture and false water level indications.
Mechanical controls
discussed previously have limited
capabilities
and slow response times, and pneumatic controls were
drum
level
control.
developed to provide more accurate
Basic to
pnaumatic systems are a drum level transmitter
to sense level, a
manual/automatic
station to allow manual control during start-up,
and,a controller
to determine the adjustment
required to the
feedwater valve.
Single-, two-, and three-element
feedwater
controls are available.
IN
I
AC
TI
Figure 57
Drum Level Transmitter
Connection
and Calibration
b)
Electronic
Transmitter/Controller.
One-, two-, and
three-element
feedwater control systems are also available
utilizing electronic
transmitter,
manual/automatic
stations, and
controllers
(Table 10). Electric or pneumatic actuators
can be
used aa final control drives for the feedwater control valve.
An
electro-pneumatic
(1/P) transducer
ie required to convert the
electric signal into a pneumatic signal when pneumatic
actuators
are used.
103
MIL-HDBK-1125/l
Table 10
Control
Feedwater
Symbols
@
Flow indicotinq
@
Level indicating tmnsmt:er
Q
Mon. ol
find
T
CC.ntrd!n,
Ho”a/outOmotic
@
~
;
S.b(,oCling
<
1K
m
I Frc::rmcl
J
generator
~
SIy,l
station
:mw.ller
-olus-,n(t;rcl
contrder
log..
AC
summer
control
.“it
Proo,rtiono!
(-=jJ
f“”ch”
TI
VE
~
signal
tr...tir:g.g
IN
single-element
controls use a
Element.
(1) Single
-“
- ‘-’
drum level transmitter”with
a manual/automatic
station and
controller
to send a siqnal to position the feedwater control
valve.
The controller ;an be a~justecl to provide responsive and
accurate control.
Single-element
control is adequate for systems
with gradual load changes.
In two-element
controls, both
(2) Two Element.
drum level and steam flow levels are measured
and used to control
the feedwater
(Figure 58).
Becauae steam flow is measured, this
control system can eense and respond to load changes before they
result in drum level changes.
The system can thus compensate
for
swelling and shrinking in the boiler and drum which occur as the
pressure changes during load swings.
Two-element
control is
load changes.
recommended
for systems with frequent and large
104
MIL-HDBK-1125/l
TI
V
E
(
r
A
A
+?...._—
w
..——
AC
Figure 58
Two-Element
Feedwater Controls
with permission
of Babcock h Wilcox,
h USR I 39th Ed.)
(reprinted
XiLS Ge~n
from ~team.
IN
(3)
Three Element.
Three-element
controls sense
Threefeedwater flow in addition to drum level and steam flow.
element systems can compensate
for changes in feedwater flow that
may occur due to feedwater pressure,
temperature
change, or
feedwater valve inaccuracies.
This level of control ia not
normally necessary except for very large boilers used in eystems
with large load changes, or in boilers producing superheated
steam for use in a turbine.
combustion
controls adjust fuel
3.4.2
and airflows to satisfy boiler demand.
Steam pressure, which
changes with changes in demand, serves as the input signal by
which the boiler firing rate is controlled.
In hot water
leaving the boiler is used as the
boilers, water temperature
input signal.
A combustion
control system must maintain an
efficient
fuellair ratio.
For boilers equipped with induced
draft fans or tall stacks, combustion
controls must also adjust
fan inlet dampers or boiler outlet dampars to control furnace
draft.
Combustion controle syetems are comprised of the
following general types of components:
seneing elements,
t
105
MIL-1lDBK-1125/1
actuators, transmitters,
control drives, controllers,
control
valves, indicators, dampers, and recorders.
These components
be combined in an endless variety of arrangement
to provide
almost any degree of sophistication
required.
d
may
AC
TI
VE
Open-1oop and closed-loop control
3.4.2.1
Control Conceots.
Open-1oop control (also
are both used in the boiler plant.
called feed-forward)
takes an input demand signal and generates a
single output in response to the demand.
The result of the
Closed-loop
(or “feedback”)
control action is not considered.
control monitors a system variable and automatically
generates an
output to adjust the system.
If the system remains out of
balance, the control will continue to change its output until the
desired result is obtained.
A simple pneumatic actuator on a
valve is an example of open-loop control (Figure 59).
The
actuator receives a eignal and generates an output, the movement
of” its shaft.
This same pneumatic actuator could be converted
to
closed-loop control by equipping it with a positioner
(Figure
60).
The actuator receives a signal and generates an output to
move the shaft.
The shaft position is measured as feedback.
If
the shaft is not in the desired position, the output from the
positioner is automatically
readjusted,
and the shaft is moved
A basic advantage of
again until it is in the correct position.
closed-loop
control is that it provides more accuracy of
adjustment due to its ability to overcome hysteresis losses.
Hysteresis losses are caused by friction in linkages, valves,
actuators, and other mechanical
items.
The effect of hysteresis
is to cause a valve or mechanism to etop at a slightly different
adjustment each time.
A typical open-loop control may be able to
whereas
control position within k5 percent of a desired setting,
a closed-loop control can typically control to approximately
fl
percent.
two-,
or
Closed-loop
control is available as one-,
three-mode control using proportional,
integral, or derivative
responses.
These different
responsee are discussed below.
IN
Proportional
control (also called
a) Proportional.
gain control) is the simplest form of closed-loop control.
In
proportional
control,
the difference
between a setpoint and a
system variable is measured,
and corrective
actionis
taken by
adjusting the control output.
A proportional
steam pressure
control system is illustrated
in Figure 61. Steam pressure
setpoint and actual steam pressure are compared, and an output ie
generated in proportion
to the difference.
Figure 62 illustrates
proportional
control.
For a proportional
gain setting of 5, the
fuel valve is opened 5 percent for each 1 percent drop in steam
pressure.
proportional
gain, or simply gain, is defined as “the
control output change, in percent, divided by the system variable
change, in percent.”
106
.
141L-iIDBK-1125/l
Gain = (percent change.in control
change in system variable)
Proportional
percent.
band
is
the
Proportional
= (l/gain)-X
eystem variable)/(percent
inverse
output)/(percent
of gain, expressed
100 = (percent change in
change in control output)
x 100
AC
TI
VE
.-
IN
(
Figure 59
Control Valve With
Pneumatic Actuator
107
in
IN
AC
TI
VE
MIL.HDBK-1125/l
Figure 60
control Valve with
pneumatic Actuator
and Positioner
108
MIL-HDBK-1125/l
----------
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Sum
PmulJ,,
,
Smf%d
:
titmlk
b
i
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K
CL
_-________j
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L___
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Figure
Pressure
61
Control
IN
AC
Steam
TI
VE
----------; A:
7
~
109
System
MIL-HDBK-1125/l
140
m?:t
-----------—
TI
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.
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50
160
0
%
Fuel+fal.e
+lopsl
103
Opening
AC
Figure 62
Proportional Control
IN
Thus , a gain of 5 iS equivalent to a proportional
band
of 20.
Figure 63 Illustrates
the response of a steam pressure
control system to a change in steam flow.
Note that offset or
deadband is the difference
between setpoint and steam pressure.
The following observations
should be noted about proportional
control:
(1) Proportional
control operates and establishes
because
a difference
exists between the
steady-state positions
setpoint and system variable.
In the example shown in Figure 62,
only at the 50 percent fuel valve position would steam pressure
exactly match the setpoint.
At other fuel valve positions,
a
difference of up to 10 psi from setpoint would be required to
-intain
the fuel valve position that would satisfy a steam flow
demand.
(2)
proportional
band)
control to changee
deadband.
The larqer the gain (or the smaller the
of a cofitrol, the greater the response of the
in the system variable, and the smaller the
110
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Figure 63
Proportional
Response
(3) The smaller the gain (or the larger the
proportional
band), the smaller the response to changes in the
system variable, and the larger the deadband.
(4) A large gain may not be stable.
A fuel valve
cycling between full open and full closed is an example of
unstable operation.
IN
b) Integral.
Integral (also called reset) control was
developed to improve the accuracy of proportional
control.
Integral action works to eliminate the deadband which ie inherent
in proportional
control.
Integral control adjusts the control
output in steps based upon the offeet and the time the offeet has
existed.
Adjustment continues until the aetpoint and the system
variable are the same or until maximum or minimum output is
reached.
plus integral
Figure 64 illustrates proportional
control response to” a change in steam flow.
Proportional
plus
integral control is also called two-mode control.
Reducing the
integral time increases the integral control response, while
increasing
the
integral
time
reduces
111
the
control
response.
MIL-HDBK-1125/l
1
Proportional
Figure
Plus
VE
Time —
64
Integral
Response
AC
TI
Derivative. Derivative is a mathematical term that
c)
In some systems, derivative
(or
considers the rate of change.
rate) response can improve the speed and accuracy of the control
by anticipating a trend before an actual change occurs.
Proportional
plus integral plus derivative control is called
three-mode control; it is rarely used in a steam heating plant
but can be very effective in a hot water plant by recognizing.
For example, when the
change in direction of a system variable.
rising boiler outlet water temperature
starts to fall, the fuel
valve should be opened to supply heat to satisfy the new demand
for hot water, even though the setpoint may not have been reached
Reducing the derivative
time increases the derivative
yet.
control
response, while increasing
the derivative
time decreases
the response.
Too much derivative
control can dampen other
control responses.
IN
~
. Combustion controls
3.4.2.2
Cotos
for etoker-fired boilers must have the ability to adjust the
fuellair ratio to compensate
for changes in coal heating valuee,
forced draft fan performance,
and
moisture, bed thickness,
Spreader
stokers,
which
burn
a
portion
of
ambient air changes.
coal in suspension,
react differently
than underfeed,
traveling,
Spreader stokers respond best to a
chain, and vibrating stokers.
change in fuel feed rate, while grate burning stokers respond
Two types of control, parall”el
in
airflow rates.
well to changes
positioning control and series/parallel
control, are commonly
used with stokers.
112
MIL-HDBK-1125/l
VE
Parallel Positioning
Control.
Figure 65
a)
illustrates a parallel positioning
control system.
A deviation
of steam pressure from setpoint results in the master controller
and
overfire
air
signaling the fuel actuator and the combustion
actuators to reposition
themselves to a higher firing rate.
TWO
fuel/air ratio control stations are provided to allow the
operator to adjust and trim the combustion and overfire air
supply . A furnace pressure controller monitors the furnace
pressure and adjusts the induced draft (ID) fan inlet damper to
maintain a slightly negative pressure in the furnace.
Manual/automatic
stations are provided to allow manual control.
STEAMMfAOC#
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MIA UAMUAU~UTQWIC
Parallel
Figure
Positioning
65
Control
System
b) Series/Parallel
Control.
Figure
66 illustrates the
series/parallel
system.. In this system, steam pressure is used
to control fuel feed rate and steam flow to control the airflow
rate.
airflow and steam flow meter is discussed in
A combination
par. 3.4.4.
Operators use this type of meter as a guide to
fuel and
control the relationship
between air required to burn
air actually supplied.
The eteam generation
rate is used as a
measure of air required, while the flow of gases through the
113
MIL-HDBK-1125/l
IN
AC
TI
VE
boiler
setting is used as a measure of air supplied.
By
comparing
the two, a check on the air-to-fuel
ratio in the
This type of meter has been in use for
furnace can be obtained.
The
many
years and is commonly called a “boiler. meter.”
series/parallel
control combines positioning
control for fuel
Initial calibration
and
with metering control for airflow.
Overfire
repeatability
of the airflow signal are very important.
air fans are also modulated with boiler load to obtain best
combustion
results at the lowest possible excess air levels.
Although
this feature has not been shown in Figure 66, it would
be provided
for many applications.
‘_“
Parallel
3.4.2.3
~ed
~
positioning
and p~ra~lel metering combustion con~~ols are
available for oil- and gas-fired boilers. Either type may be
equipped with trimming controls to adjust fuellair ratio based
Pneumatic,
electric,
upon the oxygen level in flue gas.
electronic,
and computer
operated
controls
are available.
With the compactness
a) Parallel Positioning Control.
of modern oil- and gas-burner packages,
it is possible to use a
single
set of jackshaft and levers to control both fuel and air.
The master
Figure 67 illustrates a typical jackshaft system.
regulator
is a proportional
control that senses steam pressure
and generates a rotary output, which moves the jackshaft.
Adjustable
valves are used to control and characterize
fuel and
gas flow.
These valves, together with the mechanical
linkage
that connects them to the forced draft (FD) dampers, establish
the fuel/air ratio.
This system is effective
if fuel and air
conditions
remain constant and the linkage is tight and
Some
parallel positioning
control systems
accurately
adjusted.
replace the jackshaft by using a pneumatically
or electronically
generated
fuel/air ratio and individual
actuators for each fuel
valve and fan damper.
This approach, which is illustrated in
Figure 65, can be more accurate and more easily adjusted or
Positioning control systems assume that fuel and air
trimmed.
flows always change the same amount for each change in valve or
damper position.
They are open-loop control systems.
b) Parallel Metering Controls.
If fuel and air flow
to the burner are metered, a controller
can be used that receives
feedback
from the metering device and further adjusts the fuel or
air actuator.
This ensures that when a specific fuel or air flow
is demanded,
it is actually delivered to the fire.
This becomes
a closed-loop
control system and is known as parallel metering
control.
A parallel metering system is illustrated
in Figure 68.
This type of system is commonly used on larger sizes of steam
boilers.
114
MIL-HDBK-1125/l
TI
VE
(
Control
IN
AC
Figure 66
Series/Paralle”l
RCGULATOR
+
@
MAh’UAL/AUT~ATK
.- ..,””
Figure 67
Jackshaft Control
115
System
MIL-HDBK-1125/l
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STEAM
HEAoEn
\
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AC
TI
VE
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Control
IN
Figure 68
Parallel Metering
On most modern oil- and gasc) Oxygen Trim Control.
fired boilers, as well as many coal-fired units, oxygen analyzers
Oxygen content
are used as co~ustion
guides for the operators.
Control systems have
in flue gas verifies proper air/fuel ratio.
been developed to allow automatic
adjustment of air/fuel ratio,
These systems are
based upon the reading of the oxygen analyzer.
Figure 69 illustrates
a
called oxygen trim control
systems.
typical oxygen trim control,
although many other arrangements
are
These controls
are not applicable to all systems
also available.
If accuracy of an actuator
because trim adjustments
are small.
is ?S percent and the trim required is 2 percent, oxygen trim
will not be effective.
The following conditions must exist
before oxygen trim can be effectively
added to a boiler:
(1) Air infiltration
into the boiler must be
minimal, since the trim controller
cannot distinguish
between air
The flame
that entered through the burner and infiltration air.
116
MIL-HDBK-1125/l
could be starved for air at the burner and produce smoke, while
still registering
excess air at the analyzer.
Trim control can
also become unstable if the leakage rate changea.
operation
manually.
at a low
(2) Combustion equipment muet be capable of
at the new air/fuel ratio.
This can be tested
A burner cannot be expected to operate automatically
oxygen
level if it cannot do eo manually.
Wllme.
VE
(3) Existing combustion
control components must be
able to operate accurately.
Oxygen trim can be expected to
compound any deficiency
in an existing system.
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Figure 69
Trim Control
System
3.4.3
Boilers are equipped with
safety devices to minimize the risk of low water- and exploaionrelated damage.
Figures 51 through 53 illustrate
typical safety
systems.
A typical oil- or gae-fired boiler safety control
system includes the following components:
a)
Low water
fuel cutoff
117
switch.
MIL-HDBK-1125/l
b)
High steam pressure or high water
c)
Flame scanner(s).
d)
Gas supply
high
e)
Gas supply
low pressure
f)
Combustion
airflow
9)
Purge airflow
h)
Fuel safety
i)
Fuel control
j)
Manual
k)
Atomizing
temperature
switch.
pressure
switch.
switch.
shutoff
valves
induced
valves,
steam
Atomizing
steam
P)
cocks,
position
low fire position
strainers,
switch.
and trape.
or air switch.
or air shutoff
Low oil pressure
n) Hiah furnace
draft fa~s).
0)
with
with closed
AC
TI
m)
valves
VE
switches.
switches.
1)
switch.
Fan motor
Control
and control
valves.
switch.
Dressure
switch
(for boilers
with
switch.
logic.
IN
NFPA 8501 (for single burner systems), NFPA 8502 (for
multiple burner gas-fired systems and for multiple burner oilfired systems), and ASME CSD-1 establish rules for operation of
the equipment listed above.
Notes on some of the more important
items are given below.
3.4.3.1
following
Control Loqic.
actions:
a)
Prepurging
b)
Proper
c)
Low-fire
Control
logic provides
the boiler
operation
start
below
of limits
aid release
light-off.
and interlocks.
to modulation
d) Trial for igniter flame sequence.
shut off at the end of the trial for main flame.
118
for the
sequence.
The igniter
ia
&lIL-HDBK-1125/l
e)
Trial
for main
f)
Main
flame
g)
Safe
shutdown
h)
Boiler
flame ignition
or normal
post
of
the
sequence.
operation
system.
purge.
TI
VE
Electronic controls are available that receive flame
scanner eignala and provide the control aequencea lieted above
when connected to the proper switchee, valvea, and motor
startera.
Electronic controls are equipped with self-checking
circuits that prove the controls to be operational.
Figure 70
ahowa an electronic programming
control incorporated
into a
eimple control cabinet typical of a fire tube boiler application.
Note that motor etarters, draft control, and a draft indicator
are included.
Relay logic has been commonly used in the past on
multiple burner applications,
but many new syatema are operated
and monitored by programmable
controllers.
3.4.3.2
Low Watg.r FUP1 ~.
Float/magnet
and electrode
low
water fuel cutoff devicee are commonly used (Figuree 71 and 72).
Their purpose is to eliminate the major cause of boiler failure,
i.e., firing a boiler with a low water level.
If such a
condition exista, the limit circuit is opened and fuel to the
boiler is ahut off.
Because of its importance,
the low water
fuel cutoff is a device that requires manual reset.
The
electrode type low water fuel cutoff uses probes or electrodes
to
When
the
water
level is above the low
sense the water level.
water electrode, electricity
ia conducted to ground and a sensing
relay coil ia energized.
Another relay is used to provide the
manual reset feature required.
Momentary electric circuitry can
be provided to bypass the low water fuel cutoffs to allow
blowdown of the equipment without disrupting
normal operation.
IN
AC
(
3.4.3.3
ure and
. A variety of
Swidifferent typee of pressure switches are required to measure the
wide range of pressures
present in a boiler.
Pressuree range
from a few inches of water in the furnace to hundreds of pounds
per square inch in the steam drum.
Fiqure 73 illustrates
a
mechanical type pressure element with a mercury-filled
switch
typically used for applications
in the range of 5 to a few
hundred psig.
Diaphragm-type
mechanisms with snap action
switches, ae shown in Figure 74, are ueed for air pressure
measurements in the inchee of water range.
In both cases, a
pressure causes the eensing element to deflect,
change in system
activating the switch mechanism,
Temperature
switches can use
liquid- or vapor-filled
bulbs or bimetallic
elements to activate
similar switch mechanisms
(Figure 75).
119
, M5
.
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MIL-EDBK-1125/l
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Tcsl palm
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cowl tleblnar
IN
Tnndomlm
Electronic
Figure 70
Programing Control
120
Ctmsb Rcblnlna ScraW
in a Boiler
Panel
r
~
/$
VE
.
MIL-HDBK-1125/l
~
hllq Lwd
OPERATING
PRINCIPLE
AC
TI
@
Figure 71
Low Water Fuel Cutoff
IN
Float/Magnet
121
MIL-HDBK-1125/l
TI
VE
J!il!li
72
Low Water
L?i.gure
Type
AC
Resistive
.
IN
. . .. .
Fuel
Figure 73
Mechanical Type
pressure Switch
122
Cutoff
1
VE
MIL-HDBK-1125/l
Switch
IN
AC
TI
Figure 74
Diaphragm Pressure
Figure 75
Temperature
Switch
123
MIL-HDffK-1125/l
3.4.3.4
Fl ame ScanneU . Flame scanners that view the
Lead
ultraviolet
range of light are commonly called W scanners.
sulfide scanners that view the infrared and visible range of
Self-checking
scanners,
like the W
light are also common.
scanner shown in Figure 76, are equipped with shutters that allow
the scanner’s electronic controls to prove that the ecanner
New types of scanners and
components
are properly functioning.
electronics
are also available which measure the frequency of the
light observed and account for the fact that the base of a flame
generates
light at a frequency of many hundred cycles per second,
light less than 60 cycles per second.
while the tips generate
Frequency
scanners are especially effective
in multiple burner
flames
from various
burners.
I
UV Detector -
Shutter
~.
VE
applications be:ause they can discriminate well between the
Amplificf
-----
ho
B-]
Sc,znnw
Flame Being
Monitored
Shu?ter
Driving
- “kCircuit
Ralaw
TI
.
-
Control
Sdf-Chtcking Control DeenargizesFlame Relay If:
AC
1. Any Ektfonic Compmwnt F-ill
2. Flame Signalij Absent or Continuous
For Any Other Rumn
_——
1
Figure
U-V Flame
76
Scanner
IN
3.4.3.5
Annunciators. Figure 77 illustrates a typical
annunciator system. Annunciators are frequently used in boiler
plants
to perform
the following
functions:
Provide continuous monitoring
of important
a)
operating conditions
such as temperature,
pressure level,
vibration,
main flame,
bearing cooling, and other conditions
associated
with the boiler safety control and plant systems.
b)
Alert
operators
c) Require
condition(s) .
d)
Advise
operator
operator
to off-normal
acknowledgment
when
normal.
124
condition(s).
of off-normal
the condition
returns
to
MIL-HDBK-1125/l
~::.-
-
VE
..,..-4 . 7--”
-.
.
TI
Figure 77
Annunciator
AC
There are
3.4.4
many types of controls and instruments
that are applied to Navy
boiler plants.
Some provide only measurement
functions, while
Some of the common
others provide both measurement
and control.
types of instrumentation
for measurement
and control are
d~hcussed below.
IN
3.4.4.1
~ir-Flow Steam-Flow MeteK.
The air-flow steam-flow
meter, which is also commonly called a “boiler meter,n is
typically applied in series/parallel
combustion control systems
to provide the operator with a auide to control the relationship
between the air ~equired to efficiently
burn fuel and air
“
actually supplied.
A more detailed
discussion on flow meters is
contained in par. 3.4.4.4.
3.4.4.2
l’emoerature Con tro~.
Direct-acting,
pilot-operated,
and pneumatic or electronic temperature
controls are available.
Direct-acting
temperature control regulators, shown in Figure 78,
consist of a bellows-operated
valve directly connected by
capillary tubing to a temperature
bulb.
The bellows, capillary,
and bulb systems are filled with a liquid, gas, or liquid-vapor
combination.
The bulb is ,inserted wherever temperature
is to be
controlled,
as in a feedwater heater or hot water heater, and the
valve is mounted in the steam or hot water line supplying the
heat.
Temperature changes at the bulb produce an expansion or
contraction
of the bellows and subsequent movement of the valve
An adjustable compression
spring opposes expansion of the
stem.
125
MIL-HDBK-1125/l
.
.
bellows and provides a means to adjuat the controlled
temperature.
Direct-acting
regulators, while simple, reliable,
and inexpensive, are of limited capacity, and the valve and bulb
must be located within the practical length ‘of the capillary.
VE
Pilot-operated
valves are
Valves.
a) Pilot-Operated
available for larger capacity
and more flexibility of
Pilot-operated
valves may be operated by either
installation.
A bulb and capillary system
internal or external pilot valves.
Variable loading
controls the movement of a small pilot valve.
of the
pressure produced by the pilot valve controls movement
Figure 79 shows a pilot-operated
temperature
control valve.
Both direct-acting
and pilot-operated
temperature
control valve.
regulators are proportional
devices.
AC
TI
b) Pneumatic and Electronic Temperature
Controllers.
accuracy,
two-mode (proportional plus
For improved control
integral) temperature controllers
are available using either
Filled bulbs, hi-metal
pneumatic or electronic components.
elements, thermocouples,
and resistance temperature devices
The pneumatic or electronic
(RTDs)
are used as sensina elements.
.––.
controllers compare the s~nsed temperature-with
a setpoint and
The actuator
generate an output to control an actuatOr/valve.
may be either pneumatic or electric.
vUlorPreswmTwe
———
IN
I
L
Direct-Acting
‘e
!
Figure 78
Temperature
126
Regulator
.
MIL-HDBK-1125/l
Smsi.q Etmm*n
AC
TI
VE
I!llilr
I
IN
s
Figure 79
Pilot-Operated
Temperature
Control Valve
3.4.4.3
~ure
C~.
Preseure controllers may be divided
into two general typee.
One type maintains a set pressure in one
part of the system while pres8ure in the other part fluctuates or
changes within certain limits,
An example of this tvDe of
control is a pressure-reducing
valve, which maintain~-a
set
pressure on the discharge side by controlling
the flow of steam,
air, or gae.
The second type of control maintains a constant
pressure differential
between two points and also controls the
flow.
This type of control is often applied to a boiler
feedwater system to maintain a fixed differential
between the
pressure of water supplied at the feed valve and tbe pressure in
127
MIL-HDBK-1125/l
VE
The pressure controller may consist of either a
the steam drum.
self-contained
device which operates the regulating valve
directly, or a pressure-meaauring
device, such ae a Bourdon tube,
The controller positione
which operatea a pneumatic controller.
the regulating valve or mechanism to maintain desired conditions.
Operation of preesure-reducing
and differential-pressure
valves
depends upon a load applied to a diaphragm or piston, balancing
The pressure load is applied to
the force exerted by a spring.
both sides of the diaphragm or pieton in a differential pressure
valve, but to only one side in a pressure-reducing
valve.
A
spring or weight ia used to balance the valve in either case.
IN
AC
TI
The valve
Preaeure-Reducing
Valve.
a) Pilot-Operated
ehown in Figure 80 ia a self-contained pressure-reducing valve,
The deliver pressure acts on the
which operates as follows:
This movement ia
bottom of the diaphragm,
tending to push it up.
a position
opposed by the spring, and the diaphragm aasumes
The pilot valve is held against
dependent
upon these two forces.
the diaphragm by a spring, so any movement of the diaphragm
One side of the pilot valve ia
causee the pilot valve to move.
connected
to the eupply pressure, and the’ other to the top of the
The spring on
piston which is in contact with the main valve.
the bottom of the main valve holds the valve against the piston
and supplies the force necessary to move the piston up. When the
valve is in equilibrium
(that is, when flow through ~t is
sufficient
to maintain discharge pressure at the desired level),
any drop in pressure on the discharge side causes the spring to
push the diaphragm down and open the pilot valve further.
The
pilot valve, in turn, transmits a pressure to the chamber above
This opens
the piston and causes the piston to move downward.
the main valve and increases the flow, building up discharge
The
pressure until the valve is once again in equilibrium.
Discharge pressure
reverse occurs if discharge pressure rises.
setpoint is regulated by adjusting the spring.
128
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Figure 80
Pressure-Reducing
Valve
The valve in
b)
Diaphragm
Pressure-Reducing
Valve.
Figure 81 is equipped with a diaphragm actuator and is used for
many purposes.
connected to a pneumatic
It is commonly
controller to serve as a pneumatic control valve. When used as a
pressure-reducing
valve, the pressure to be controlled is applied
to the top chamber and a movement of the diaphragm is transmitted
directly to the control valve.
An increase in pressure pushes
the diaphragm out against the resistance of the spring and closes
the valve until equilibrium
is established.
The controlled
pressure can be varied by adjusting the compression in the
spring.
Figure 82 illustrates
a self-contained
diaphragm
pressure-reducing
valve;
The outlet pressure balances the force
of the spring within the valve body.
The remote pressure sensing
capability
of the previous valve is eliminated by the simplicity
of this valve.
129
MIL-HDBK-1125/l
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IN
AC
c
Diaphragm
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Figure 81
Actuator Pressure-Reducing
Valve
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Figure 82
;elf-Contained
Diaphragm
Pressure-Reducing
Valve
IN
In the valve
Differential Pressure-Reducing
Valve.
c)
shown in Figure 83, a pressure-tight
chamber is provided on each
aide of the diaphragm, and a spring is used to control the
differential
between the two pressures.
The top and bottom
chambers
are
connected
to
the
two
pressures
to
be
controlled.
When the force on the top chamber of the diaphragm is equal to
the force on the bottom plue the spring force, the valve is said
to be in equilibrium.
If the bottom chamber pressure changes,
the spring acts on the diaphragm
to cause the pressurea to vary
simultaneously,
maintaining a constant differential.
d)
Steam Differential
Pressure-Reducing
Valves.
pressure-reducing
valve
Figure 84 illustrates a differential
An oil
atomizing
steam
to oil
burners.
typically
used to control
The
sensing line ia connected to the top chamber of the valve.
pressure of the oil and epring are added together to balance the
pressure
of the steam and to adjuat the valve position.
Force
applied by th: spring establishes
the differential pressure
between the 011 and steam,
131
MIL-HDBK-1125/l
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IN
AC
Figure 83
Differential
Pressure-Reducing
Valve
132
MIL-HDBK-1125/l
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IN
mm In
3.4.4.4
are
Figure 84
Steam Differential
Pressure-Reducing
Valve
F.low MeL~.
typically
found
Strom Out
Eight
in
central
a)
Differential
b)
Pitot
c)
VOrtex
d)
variable
e)
Volumetric/positive
types
heating
pressure
of flow measuring
plants:
(orifice)
tubes
shedders
area
displacement
133
elements
MIL-HDBK-l125/l
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..
indicators,
operation.
f)
Propeller
and turbine
9)
Weirs
flumes
h)
Electromagnetic flow meter
and
These measuring
or totalizers
elemente may be connected to recorders,
to provide information
on plant
AC
TI
VE
(1) Differential
Pressure Meters (Orifice).
Differential
pressure flow meters measure pressure loss created
by fluid flow through a pipeline restriction
such as an orifice,
Water, steam, or gas
flow nozzle, or venturi (Figure 85).
flowing through a restriction
increases in velocity and decreases
in pressure.
The pressure drop increases by the square of flow
or velocity.
Thus,
if an orifice has a preesure drop of 100
inches of water at 100 percent flow, the pressure drop is only 1
This explains why it is
inch of water at 10 percent flow.
difficult
for differential
flow meters to provide accurate
Figure 86 illustrates
a steam
information
at low flow rates.
The Ledoux bell is
flow recorder equipped with a Ledoux bell.
shaped to take the square root of a signal from the line
restriction.
Movement of the bell is transmitted
through a
system of levers and links to a pen which records the flow on a
chart.
Pneumatic transmitters
like the one shown in Figure 87
Very
are available to replace the function of the Ledoux bell.
accurate electronic
transmitters
are also available.
(2) Pitot Tubes.
Pitot tubes are used to measure
in ducts and pipes.
They are portable and are ueed where
are
well
suited
Pitot tubes
checks of flow are required.
Flow does not
for
low
to
medium
flow
in
large
ducts
(Figure
88).
instead
it
impacts
on
the
pitot
and
pass through the pitot tube;
causes
higher
pressure.
The difference
between higher impact
pressure and static pressure relates to velocity of the fluid.
IN
flow
spot
(3) Vortex Shedder Flow Metere. Vortex shedders
operate over a wide flow range with high accuracy.
They are
unaffected
by changes in viscosity and density of fluid, and they
are relatively
easy to install.
They operate on the principle
that a bluff body immersed in a flow sheds vortices alternately
from its sides (see Figure 89).
Vortices impart an oscillating
motion to fluid flow.
Since there is a direct relationship
between velocity and the frequency of vortex shedding, this
method can be utilized for flow measurement.
(4) Variable Area Meters.
In a variable area or
rotameter,
fluid passee upward through a,tapered meter tube which
contains a float.
Float position indicatee rate of fluid flow.
134
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Figure 85
Flow Nozzle,
IN
Orifice,
135
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MIL-HDBK-1125/l
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Figure 86
Flow Recorder
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Differential
n
PIVOT
1.
NOZZLE
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IN
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INSTRUMENTS
Figure 88
Pitot Tube Design
Installation
137
and
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Shedding Phenomenon
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Vortex
IN
AC
Volumetric
or positive
(5) Volumetric
Meters.
..
displacement
meters are frequently used to measure gas, OL1, or
water and are equipped with a dial register that indicates
the
Figure 90 illustrates
a positive
total volume of flow.
These meters can also be
displacement
meter for oil service.
equipped to generate flow rate signals.
In turbine meters, the
(6) Turbine Meters.
rotational
velocity of the propeller or turbine is proportional
to fluid velocity or flow.
Flow rates are measured by electronic
equipment which senses this rotational velocity and converts
it
to a volumetric
reading.
Figure 91 illustrates
a turbine meter.
Changes of liquid flow
(7) Weirs and Flumes.
rates through the weir or flume cause a change in.the uPstream
liquid level.
Float-actuated
level indicators are used to
indicate
flow rate.
(8) Electromagnetic
Flow Meter.
A magnetic
flow
meter consists of a transmitter
and a primary flow tube
A process fluid moving
surrounded
by electromagnetic
coils.
through the magnetic field generates a voltage, which is
proportional
to fluid velocity.
The transmitter
converts these
voltages to an appropriate
output signal.
138
MIL-HDBK-1125/l
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Figure 90
Displacement
IN
Positive
139
Meter
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Figure 91
Turbine MeteI
A number
Pressure Gaaes.
The Bourdon tube
pressure.
in boiler plants.
IN
3.4.4.5
measure
applied
of devices may be used to
is the one most commonly
The measuring element
Bourdon Tube Pressure Gage.
a)
of the Bourdon tube gage (Figure 92) is a tube of oval cross
section bent into an arc which is closed at one end and connected
This oval cross section
to the source of pressure at the other.
When pressure within
changes its shape with changes in pressure.
the tube increases, the cross section tends to become circular
Movement of the free end of
and causes the tube to straighten.
the Bourdon tube ia transmitted
through a gear and pinion to a
The shape of the
pointer which indicates the change in pressure.
tube and the material from which it is made depend upon the
pressure range for which the gage is to be used.
This type of
gage can be used to measure pressures
either above or below
140
MIL-HDBK-1125/l
VE
b)
Other Types of Pressure Gages.
Diaphragm gages are
used for measurement
of small differentials
in inches of water
where total preseure does not exceed about 1 psig.
For high
etatic pressures,
oppoeed bellows gages (Figure 93) are available
to read a wide range of differential
preseures.
They are
suitable for reading fluid pressure drops through boiler circuits
and can be used to measure differentiale
from 2 to 1,000 psi at
pressures up to 6,000 psig.
More aophieticated
devices for
measurement
of pressures and differential
pressures
are also on
the market.
Generally
described as transducers,
they are based
on a variety of principles.
Some examples are transducer
using
a strain gage mounted on a diaphragm, or those using a crystal
which undergoes a change in electrical resistance
ae the element
is deformed.
Since such elements require elaborate
and frequent
calibration,
they have not historically
been used as basic
instruments
in boiler plants.
However, with their rapidly
increasing
reliability
and ease of application,
pressure
transducers
are finding wider application
and will become more
frequently seen.
AC
TI
.
When using a gage to measure steam pressure, a
atmospheric.
siphon or water leg must be used to ensure that hot steam does
not come into direct contact with the tube.
3.4.4.6
t Gaaes.
A draft gage is a form of pressure gage
R.4Laf
that measures pressures
in the range of inches of water column.
Draft gages typically are used to measure air pressures at the
furnace, windbox, and boiler outlet. Inclined and U-tube
manometers
and diaphragm
draft gages are common.
Manometers.
Figure 94 shows an inclined and U-tube
a)
manometer.
The inclined manometer consists of an inclined leg
and a reservoir filled with gage oil.
In a typical inclined
manometer,
the length of the ecales is 12 inches for each inch of
water draft measured.
It is important to use the gage oil for
which the manometer was designed to obtain accurate readings,
since the gage reading is dependent on the density of the oil.
This information
is normally stamped on the manometer
body.
IN
(
b)
Diaphragm
Oraft Gages.
The draft gage shown in
Figure 95 uses a thin metal diaphragm fastened to a flat
cantilever
spring.
Atmospheric
pressure is exerted on top of the
diaphragm,
and draft on the bottom.
This pressure differential
causes the diaphragm
to move down.
Downward movement is resisted
by the cantilever
epring.
Motion of the cantilever
spring is
transmitted
through a chain to the counterbalanced
pointer and
produces an indication
on the scale which is directly
proportional
to the draft.
The pointer in this gage moves in an
arc.
The area of the diaphragm is large, thus greatly magnifying
the force available
for moving the pointer.
141
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Pressure
PIN
Gage
IN
AC
Bourdon
CONNEC7:OP
,..,
”.
. .
Opposed
.
.
c-x”,,”
Bellows
Figure 93
Differential
ware P?cduasco.
Pressure
1
Gage
.
142
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IN
AC
Figure 94
Inclined/V-Tube
Manometer
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Figure 95
Diaphragm Draft
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3.4.4.7
F1 ue Gas Analv zere.. A variety of flue gas analyzers
Their purpose is to
may be installed
in central boiler plants.
allow the operator to more efficiently
monitor and operate the
plant and to ensure compliance with environmental
regulations.
IN
The percentage
of oxygen in
a) Oxygen Analyzer.
boiler flue gas is an effective combustion
guide.
Continuous
monitoring
of oxygen levels can be accomplished
by using a
zirconium oxide oxygen analyzer .as shown in Figure 96. The
analyzer consists of a sampling system which pulls flue gas into
the zirconium oxide cell located in an electric furnace.
At
approximately
1,700 degrees F, the cell responds to the
percentage
of oxygen in flue gas by generating
a small electric
current.
Analyzer electronics
evaluate the electric current from
the cell and produce an output signal to an indicator, recorder,
or combust~on
trim control system.
144
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Figure 96
Zirconiuti Oxide Oxygen
Analyzer
IN
AC
TI
b) Carbon Monoxide Analyzer.
Carbon monoxide
(CO) in
flue gae indicates incomplete combustion due to either a lack of
sufficient combustion
air or inefficient mixing of fuel and air.
Modern boiler plants may be equipped with CO analyzers to provide
CO in
the operator with an indication of how much CO exiate.
flue gas is converted to an electric signal through oxidation on
the surface of a catalyst-coated
element and measurement
of the
heat produced.
Analyzer electronics
provide an output signal
proportional
to the concentration
of CO in the sample stream.
The output is sent to a recorder, or occasionally
used as a
trimming input to the combustion
control system.
Historically,
reliability
has been a problem with CO analyzers.
However, as
technology
improves, their reliability
is expected to improve,
in combustion
control
systems will become more
and their use
common.
CO trim ia applicable
only to oil- and gas-fired
boilers, and its use is limited by essentially
the same criteria
as those noted for oxygen trim systems.
Smoke Density Indicator.
Coal- and oil-fired
c)
plants are often provided with smoke density indicators and
recordere.
These units usually consiet of a light source and
photoelectric
cell mounted on opposite sides of the stack, an
electronic
system to condition the cell signal, and an indicator
or recorder mounted on the panel.
d)
Continuous monitoring
of
S02 and NOX Analyzers.
pollutants
is sometimes required by environmental
regulations.
Sulfur dioxide (S02) and oxides of nitrogen (NOX) are the
pollutants most commonly required to be monitored.
Several
different types of analyzers are available to monitor pollutants
by extractive means:
non-dispersive
infrared (NDIR), ultraviolet
photometric
(UV), and electrochemical
analyzers for both S02 and
145
I
MIL-HDBK-1125/l
analyzers
for No , flame photometric
and
Nox , chemiluminescence
Each o? these analyzers has its
fluorescence
analyzers
for S02.
own advantages
and disadvantages,
and the technology
is rapidly
A detailed analysis of up-to-date
technology and
changing.
environmental
agency requirements
is recommended before analyzers
of this type are installed.
VE
Temperature
is measured by a number
3.4.4.8
Ternperature Gaaes.
of devices, the most common of which is the mercury- or liquidWhen remote indication or
filled industrial
thermometer.
recording of temperature
is needed, for example to monitor flue
gas temperature
leaving the boiler, then bulb/capillary,
pneumatic,
or electronic
sensors and transmitters
can be provided
Temperature
devices
and connected to an indicator or recorder.
can also be used to provide feed-forward
or feedback “signals to a
control system.
IN
AC
TI
Recorders.
A variety of recorders are available to
3.4.4.9
provide
a permanent record of almost any variable that can be
measured.
Some recorders may be connected directly to the
instrumentation
which provides the recorded signal, such as the
Others are remotely mounted and
air-flow steam-flow meter.
receive an electronic
or pneumatic
signal from the
Typical strip chart recorders are
instrumentation
element.
These models can record up to three
illustrated
in Figure 97.
separate process variables on a 4-inch-wide
strip chart, while
Both strip charts
other models may record up to 20 variables.
and circular charts in typical use in boiler plants generally
record two to four variables.
3.5
Pollut”o
1 n Control
EauiDment
Poll ution Regulations.
Control of pollutants
from
“3.5.1
combustion
of fossil fuels in central boiler plants may be
required.
Boiler plant emission regulations
are issued by
agencies, with the most
Federal, State, and local environmental
Two general types of
stringent regulation
usually being imposed.
point source regulations
and ambient air
regulations
exist:
quality standards.
With recent enactment of the Clean Air Act
and increasing
emphasis on the environment,
regulations
are
becoming very strict.
It is important to have a complete
understanding
of regulations
and environmental
impacts prior to
specifying
new plant equipment.
146
MIL-HDBK-1125/l
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Strip
Figure 97
Chart Recorders
IN
3.5.1.1
~.
Point source regulations
place limits upon the quantity of pollutant which may be emitted
from any stack, regardless
of its relationship
to local air
quality.
These regulations
should be considered
to be the
minimum regulations,
and, if applicable,
must always be met.
For
regulations,
most Federal, State, and local agencies have minimum
size limitations.
3.5.1.2
~
Air Ou~.
Ambient air quality
etandards may be applicable
to any size boiler.
These standards
require that emissions
from the unit be considered,
aa they
affect the air quality of the surrounding
area.
Consideration
must be given to meteorological
effects and other pollution
sources in the area in determining
allowable emission levels.
Emission levels determined
under ambient air quality standards
may be the same as, more etringent than, or less stringent than
147
MIL-HDBK-1125/l
applicable
point source regulations
for a given boiler plant.
Actual determnat~on
of applicable
limits usually warrants a
separate study by a consultant.
T YD es of P o llutants and Con t rol Methods .
3.5.2
installation
and operation of air pollution control
discussed
in U.S. Army Technical Manual (TM) 5-815,
Control Svstems for Boilers and Incinerat ors.
Details on
systems are
Air Pollut ion
IN
AC
TI
VE
NOX is the generic name for a
Oxides of Nitroaen.
3.5.2.1
group of pollutants
formed from various combinations
of nitrogen
The principal form generated by boilers is nitric
and oxygen.
NO is formed when the nitrogen in fuel and air reacts
oxide, NO.
It can be
at high temperature
with oxygen from the air.
controlled
in existing boilers by careful adjustments
and
modification
to burners aimed at lowering peak flame temperatures
in the furnace and by minimizing
the amount of free oxygen
New
available
in the highest temperature combustion
zones.
boilers purchased to meet specific NOX emission regulations
will
generally
have these modifications
deeigned into them.
In
addition, they will also be designed with larger furnaces and
more water cooled surface in the burner zone to improve heat
transfer characteristics
and to further reduce the peak
Flue gas recirculation
is
combustion
temperature
attained.
Some of the modifications
and
another form of NOX control.
adjustments
that can be implemented
are listed in Table 11, as
well as advantages
and disadvantages
of each and the anticipated
reduction
in NOX emissions.
The primary oxide of sulfur (SOX)
Oxides of Sulfur.
3.5.2.2
formed by combustion
of fossil fuel is sulfur dioxide or S02.
S02 is formed when sulfur from fuel combines with oxygen from the
In a conventional
air in high temperature
zones of the furnace.
boiler, essentially
all the sulfur that enters with the fuel
No practical
form of combustion modification
converts to SO~.
has been developed
to reduce S02 generation in the furnace.
To
control the release of S02 emissions to the atmosphere,
it is
necessary to either burn a fuel having a lower sulfur content, or
use some type of flue gas desulfurization
equipment
(also called
The
scrubbers)
to remove the S02 after it leaves the boiler.
most common types of scrubbers used on boilers are lime or
limestone slurry types, magnesium oxide slurry, double alkali,
and lime dry scrubbers.
Some of the performance
characteristics
of these are summarized
in Table 12. The S02 removal systems
mentioned
above are expensive both to purchase and to operate,
and in most cases they cost more than the entire boiler plant.
For this reason, they are not cost effective and generally not
rarely seen
They are very
used unless dictated by regulations.
on smaller plants, because compliance with regulations
are
generally by means of low sulfur fuel.
Atmospheric
fluidized bed
148
MIL-HDBK-1125/l
boilers are also becoming more commonly applied when control
SO emissions is required.
These are generally more cost
ef $ ective than scrubbers but have not been commonly applied
because of their limited operating experience
(refer to
par. 3.3.1.7).
Tecfmique
wd Rcductim
w Escess Afr
.2A )
Potential
NOx
Rcd”ct{m
(%)
25-tO
firing
15-40
Table 11
of NOX Reduction
of
Techniques
oisadvantaQes
Adwnt ages
VE
Comparison
Eali(y
krlkcllted;
m
edditimat
equlpem
requ{red
[email protected]{m
Increased
efficiency
A sdxstinn
cmtml
sy$:es which
closely
mnitors
and cmtrots
fuetlair
ratios
*S required;
possib(e increase in particulate
eoiaslons;
increased sla; ;:.ss and
ash derms itim
with cml-f ired
units.
Luiter
Ih.xcml
pass4bte
in toiler
IN
AC
TI
i
in generating
capacity;
rcductim
thernat efficimcy.
m-50
tloiler
.irnilaes
IS.JS1be designed
for this application.
NM
mc-erdcd
fer mat-tired
nits.
rurna.e corrosion md pmt ic.lale
●nimims
my increase.
!f-scoichionetric
tistion
(coal)
1545
Cmtrol
of alternate
fuel-rich
and
fuel-lean
burners ODY be a prcblm
durirq transient
load corditims.
!dUced Cabilstion
r Preheat
lo-m
war applicable
to Ceal-fird
units;
reducticm in bolter
therml
efficiency;
increase $n emit gas
votuae and temperature;
reduction
in boiler
lwd.
,ue GM
!cimul atim
20-50
m-stage
C-stim
Po$$ ible i6provenent
in
cmbustim
efficiency
ard
reductim
+. particulate
emissions
149
Sailer
UiMIW
rust be mdified
to
handle the additional
gas .ohme;
ductmrk,
fans, and controls
required.
MIL-HDBK-1125/l
Table 12
Performance Characteristics
of
Flue-Gas Desulfurization
Systems
RetrOfit
Sox
Sy.te.
TYPe
CY
(%)
wsme,
‘.bber
jection
>e
30-40
Pressure
0rop
( i mhes of
water)
Operot i.na 1
Reliability
Recovery ad
Regenerat ion
of
Greater Norecovery
High reliability;
m Lwi Ler
scaling.
Low
●ff iciency;
scaling and
plugging of
iwzzles ad
surfaces in
scrubber
solids
disposal.
Yes
High efficiemy;
m Lwi Ler
sca(ing;
(e%s
scaling
in
scrubber than
( imstone
i. some
case5,
LOW
reliabi~ity;
solids
di swsa 1 to
k.ndfi Li.
Yes
High
●fficiency;
no
$oLids disposa L.
Low
re~iability;
corrosion and
eros ion of
scrubber ad
piping;
need
prec lea. i q of
flue gos.
Unknown
Yes
Absorpt ion
efficiency
POte”tiakty
higher than othe r
system;
scaling
problems reduced ;
produces soLid
rather than
liquid
waste.
solids buildup
in reactor
system;
problems with
de.ate ring
system..
unproven
but
~tentiolly
high
Yes
Lower cost;
relatively
sirnp Le
operation;
produces solid
waste; takes
advantage of
a(kali
content of
ccal ash; uses
existing
technc.lcgy.
Unproven
operational
reliability;
opp(i. abte
only 10 lowl
medium s.tf.r
.-1;
must b.
used in
conjunction
92+
Greater
than 6’4
No recovery
lime
gnesi.,a
i de
W+
Greater
than 6“
Reco.ery of H.O
and su(furic
acid
LOW
)ubCe
,kaii
,Stems
90-95
Rqenerarion
of
sodium
hydroxide and
scdi..
su(fit es
7C-$U
Low
TI
of
AC
IN
irne, Dry
:r.bbing
8°< - 10”
inchding
bagh..se
Di.ad.anta9e
Yes
High
lime
v.bber
jection
p.
Advantage
lnstallatims
than 6“
❑,
‘0
Exist<Y
Li.elli.estone
My be
recovered
VE
Rmoval
Efficjen-
withbaghw
se,
precipitator.
150
MIL-HDBK-1125/l
VE
3.5.2.3
Particulate
matter, also called fly ash,
is the pollutant that ia of most concern to boiler operators.
It
is comprised
primarily of unburned carbon and the portion of ash
The
that is carried through the boiler by the flue gas stream.
quantity of particulate
matter generated is strongly dependent
In general, the higher the
upon the characteristic
of the,fuel.
aah content of fuel, the higher the particulate
emissions.
Therefore,
coal produces a large amount of fly ash,. natural gas
produces essentially
none, and fuel oil produces a moderate but
widely varying amount, depending upon its grade and
characteristic.
AC
TI
Particulate
emiaeions may be controlled
to ii certain
extent by careful attention to burners and combustion
However, control of this type is
characteristics
of the boiler.
essentially
limited to oil firing, eince the total particulate
matter produced from oil is low and usually contains a large
Proper combustion
control can
percentage
of unburned carbon.
minimize this unburned carbon and thus substantially
reduce the
With coal, incoming fuel may contain
total particulate
emission.
10 to 12 percent ash, as much as 80 to 90 percent of which may be
carried out as fly ash.
This aeh far outweigha the small
percentage
of unburned carbon which is produced in the furnace
due to incomplete combustion.
Changes and adjustments
to
burners that minimize the unburned carbon are, therefore,
largely
ineffective
in reducing total particulate
emissions.
(This is
not meant to imply that proper burner adjustment
and operation
ehould be ignored on coal-fired
boilers, since gains in thermal
efficiency
can still ba realized due to a decrease in unburned
carbon and reductions
in excess air. )
When coal ie to be fired in a boiler, it is necessary
to provide particulate
emission control by means of a collection
device in the flue gas stream between the boiler and the stack.
Several suitable types of devices exist, as itemized in Table 13
and discussed
in pare. 3.5.3 through 3.5.6.
In addition to these
devices, under some circumstance,
tall stacks may be considered
Although they do not remove
a Pa:tlculate
control device.
part~culate
matter, tall stacks can cause particulate
to be more
widely dispersed in the atmosphere,
and thus can be a means of
meeting ambient air quality regulations.
IN
(
3.5.2.4
~.
of the fuels commonly
burned, natural gas is the cleanest.
The only pollutant
generally associated with natural gas is NOX.
Since natural gas
contains no ash or sulfur, there is no generation
of particulate
matter or S0.2.
151
MIL-HDBK-1125/l
Table 13
Performance
Characteristics
of
Particulate
Control Devices
echmic.1
tectrosta
recipitat.r
Collector
tic
Maxim.
Remva t
Efficiency
93-95 %
w%+
Typi m 1
Preswre
Drop
3-d
0.2-0.8
Advantages
High reliability;
proven; compact.
Dimdvantages
well
on SM1(
Lou ●fficiency
particle
sizes.
High ●fficiency
over a
wide range of particle
sizes; well proven;
reliable;
lW pressure
drop
High capital
cost; very
sensitive
to ash anatysis.
VE
Device
~i(ter
99%+
3-6
reliab~e
High ●fficiency;
if properly designed;
i nsens$ t ive to ma 1 type.
Potentially
high m.intenance; high capital
cost;
rmt
compatible with
oil-only
firing;
maxim.
operating
tew.wature
of
550 degrees F.
et Scrubber
99%
20-25
High efficiency;
cm
hmd(e high temperatures
and heavy
[cadiws.
High capital
cost; high
W
cost; soiid waste
disposa( problem;
comp(icatd
control
syste.;
water SUPP!Y and
disposal
prob[erns;
.eatherprmf
ing my be.
rquired.
IN
AC
TI
nbric
3.5.2.5
Pollutants
From Oil.
When oil is burned in a boiler, a
variety of pollutants
can be formed including NOX, SOX, and
particulate..
The grades, of oil most commonly burned are No. 2,
and No. 6. No. 2 oil is a hiqhlv refined, clean-burning
oil
having little ash or sulfur, ~nd-emissions
can generally be
controlled
by burner adjustments
without resorting to specialized
pollution
equipment.
No. 6 oil ie less refined and therefore
cheaper.
It can contain up to about 0.5 percent ash and 3.5
percent sulfur.
These higher amounts of ash and sulfur lead to
higher emission levels.
Particulate
emission levele from No. 6
oil often become high enough to warrant use of particulate
While S02 emissions can also become high enough
control devices.
to violate regulations,
use of scrubbing equipment with small
boilers ie not generally cost effective,
and regulations
are
usually met by conversion
to an oil having a lower sulfur
content.
3.5.2.6
Pollutants
From Coal.
Boilers burning coal will almost
NOX
always require a device to control particulate
emissions.
and S02 emissions will also be high from most coals.
Whether or
not control of NOX and S02 is required depends upon the
regulation
in effect in the particular
locality in question.
Control of NOX emissions is accomplished
by proper design, proper
152
MIL-1iDBK-1125/1
adjustment,
and proper boiler and burner operation.
Control of
S02 emissions would usually be achieved by the use of low sulfur
coal.
In very few instances would use of S02 scrubbing equipment
be cost effective on small boilers.
TI
VE
3.5.3
The term “mechanical collector”
refers to a widely used type of particulate-collection
device in
which dust-laden
gas enters tangentially,
into a cylindrical
or
conical chamber or series of chambers and leaves through a
central opening.
The resulting vortex motion or spiraling gas
flow pattern createa a strong centrifugal
force which separates
dust particles
from the carrier gas stream by virtue of their
inertia.
The particles migrate to the cyclone walls by means of
gas flow and gravity and fall into a hopper.
Because of the
pattern of gas flow through the collector,
mechanical collectors
are often referred to as cyclones.
Cyclones may be classified
according to their gaa inlet design, duet discharge design, gas
handling capacity, collection efficiency,
and their arrangements.
TWO common types of cyclones are the conventional
mediumefficiency
single cyclone, and the multicyclone.
AC
3.5.3.1
~.
Single cyclones are used to collect
coarse particlea when high collection
efficiency
and space
requirements
are not major considerations.
Collection
efficiencies
of 50 to 80 percent of particles greater than 10
microns are common.
A typical configuration
is shown in Figure
98.
Single cyclones are 4 to 12 feet in diameter and are limited
to about 20,000 actual cubic feet per minute gas flow.
More than
one unit can be combined in parallel to accept greater gas flows.
3.5.3.2
When higher collection
efficiencies
or
higher gas flows are required, it is common to employ the
multicyclone.
This device combines into a single plenum a large
number of small diameter cyclones
(6 to 12 inches) of a type
ehown in Figure 99.
Due to the small diameter, higher inertial
forces are generated and collection
efficiencies
are higher.
In
addition,
it ie possible to design multicyclones
to handle
virtually any gae flow simply by adding more cyclone tubes and
mounting more than one unit in parallel into the gas stream.
IN
(
3.5.3.3
Other types of cyclones leas commonly
~.
used are the high-efficiency
single cyclone and the wetted
cyclone.
The principal characteristics
of the four types of
cyclones are summarized
in Table 14.
153
MIL.HDBK-1125/l
Ait
IN
AC
TI
VE
Cl...
Figure 98
Medium Efficiency Cyclone
Configuration
154
MIL-HDBK-1125/l
(
I
cl,,”
bit
0“:!
G#l
out
VE
rub.
TI
b.Tvpir.t!
Multicwt.n.
C.n(i~,.zim
AC
0“1..
vent.
IN
Innet
Vol’w.
I
I ..
C..
own
fiwratim
OftWi.id.al
CVdm.Tub.
FromMultkvdoIw
Figure
Multicyclone
155
99
Configuration
MIL-HDBK-112511
Table 14
of Mechanical
Characteristics
-
_
Gas
MY
‘9’ I
(ft
)iameter
(ft)
.ni”]
velocity
0. 5-.?
20-70
l,Lru-
6-12
Medi.mEfficiency
Singte
Cyc lone
Pressure
Orop
(inH20)
Inlet
(ftls)
COllectim
I
Efficiency
(%)
50-s0
I
Application
Ifater
ial
handling
20,m
Exhaust sas
pre. leaner
HighEfficiency
S$ngle
Cyclone
Less
than 3
R.lti Cycl.a”es
0.5-1
Wet ted
cyclone
Less
than 3
7m2,CO0
30,m-
2-6
30-m
3-6
50-70
.
1w2,m
2-6
50
-
I
Large headrm
requi .ements.
Limited to large,
.00. s. pa. tictes;
Large grain
lcadi~s.
so-95
lnd.srri.al
toiler
particulate
control
smal le. space requirement;
parallel
arrangement;
in(et
vane flow cent rols
needed cent i.was
dust renaval system
purge opetati.m.
90-95
Indusrria(
and uti[ity
Lni ler
part iculate
cant rol
P(c”.ms required.
Problems:
gas
recirculation
fouling;
continuous
dust renwva[
system, f(o.
controt.
L!mi[er
application
( low sulfur
tuel)
(to.
temperature)
Uate. rate 5315
gal/1, ~
ft /
rein; corrOsio.resistant
marerinls.
AC
TI
lL!O,
WI
I
Other
VE
Type
Dust Collectors
91-95
Note:
Cyclone collection
efficiency must be evaluated
for each
specific application,
due to the sensitivity of cyclone
p&formanc;-on
gas and dust properties and loadings.
IN
3.5.3.4
Collection
Ef ficiencv of Cvclones.
The ability of a
cyclone to separate and collect particles from a gas stream is
dependent primarily upon the design of the cyclone, size and
quantity of dust particles, and the pressure drop through the
cyclone.
Typical collection efficiencies
for various types of
cyclones, operating in various applications,
are given in Tables
estimates for a given application
can be
14 and 15. Efficiency
made bv utilizinq the cyclone manufacturer’s
fractional
efficiency
curve;.
An &xample of a typical fractional
efficiency
curve is shown in Figure 100.
These curves are determined
by
actual testing of similar prototypes
in the manufacturer’s
Total collector efficiency
is determined
by
laboratory.
multiplying
the percent weight of particles in each size range by
the collection
efficiency corresponding
to that size range, and
determining
the sumof
the collected weights as a percentage
of
the total weight of dust entering the collector.
156
MIL-HDBK-112511
Table 15
Removal Efficiencies
of Uncontrolled
Particulate
Emissions From Combustion
Processes
Efficiency)
(Percent Removed, Medium
Fuel/Firing
Mode Cyclone
Multicyclone
30-40
40-50
75-85
50-70
90-95
85-90
VE
Oil/steam or mechanical
atomizer
Coal/spreader
stoker
Coal/chain
grate or underfeed
stoker
Coal/pulverized
Coal/cyclone
85-90
40-50
TI
50-70
30-40
IN
AC
(
PAI?
TICLC SIZC, MICRONS
Cyclone
Figure
Fractional
100
Efficiency
Curve
3.5.3.5
Through any
given cyclone, there will be a 10SS in static pressure of gas
between the inlet and outlet.
This preesure drop is the result
157
MIL-HDBK-11251’1
VE
of entrance and exit losses, frictional
losses, and loss of
The cyclone
rotational
kinetic energy in the exiting gas stream.
,pressure drop increases approximately
as the square of the inlet
velocity.
Energy requirements
ii the form of fan horsepower
are
directly proportional
to the volume of gas handled and the static
A rule of thumb estimate of fan energy
pressure drop.
requirements
is that one quarter of one horsepower is required
per 1,000 actual cubic feet per minute of gas per l-inch water
pressure drop.
Thus, a mechanical
collector applied to a 40,000
lb/hr boiler (approximately
16,000 actual cubic feet p’er minute
flue gas flow) and designed to operate at 3.O-inch water pressure
drop would require about 12 horsepower
in fan POwer.
AC
TI
3.5.3.6
Cyclone Performan ce.
For cyclone installation., it is
desirable
to have as high a collection
efficiency
and as low a
pressure drop as possible.
Actual in-plant performance
will vary
from day to day due to changes in operating conditions
such as
In general, changes that
gas flow, dust load, and particle size.
inc”rease pressure drop or particle size will improve the
collection
efficiency,
and changes that decrease pressure drop or
particle size will decrease efficiency.
Mechanical
3.5.3.7
ADplicatiOn
for Part j.culate Collection.
collectors
are used as primary particulate
collection
devices
when the particulate dust is coarse, when inlet loading is heavy,
or when high collection efficiency
is not a critical requirement.
Since collection efficiencies
are low compared to other types of
control devices, mechanical
collectors
are not usually suitable
as the primary means of control when emission regulations
are
stringent.
In this case, one of the devices discussed later in
this section must be applied.
IN
3.5.3.8
~
Another common application
ecleaners.
of cyclones is as a precleaned
in solid fuel combustion
systems,
such as stoker-fired
and pulverized
coal-burning
boilers.
In
these units, large coarse particles may be generated and a
cyclone collector may be installed ahead of an electrostatic
In the case
precipitator
or baghouse to remove these particles.
of a stoker/baghouse
combination,
a mechanical
collector is
almost mandatory, since hot or burning particles are often
carried over the fuel bed and could ignite the bags.
A
combination
installation
is also ideal from a performance
standpoint
when applied to a precipitator,
because the cyclOne
exhibits increased collection
efficiency
during high gas flow and
dust loading conditions, while the precipitator
shows an increase
in efficiency during decreased gas flow and dust loading.
The
two devices complement each other to provide good efficiency
over
a wide range of gas flow and dust loading conditions.
158
MIL-HDBK-1125/l
3.5.3.9
Fly aah carried over from
a spreader stoker often containe a high percentage
of unburned
carbon.
This constitutes
a lose in heating value and, therefore,
efficiency.
Since the particlee are fairly coarse, a medium
efficiency
cyclone can collect them effectively
with a minimum of
added fan horsepower.
An additional
small fan can then be used
to reinject the collected material into the furnace for more
This type of cyclone arrangement
ie
complete combustion.
typically used ahead of a precipitator
or baghouse, which serves
as the final collection
device.
3.5.3.10
The method by which fuel is
t of
fired can have a major effect on the suitability
of a mechanical
This is due to differences
in
collector
for the application.
particle eize distribution
in the flue gae from the different
firing modes.
Thue, if the same coal were to be fired in two
identical boilere, one using a epreader etoker and the other
using a chain grate stoker, the mechanical
collector could
collect the ash from the spreader etoker-fired
boiler more
Table 15
efficiently,
because it generates coarser fly ash.
illustrates
the optimum expected performance
of mechanical
collectors
for particulate
removal in various combustion
process
applications.
IN
AC
TI
VE
(,
Fabric filters, commonly called
3.5.4
baghouses,
are used to remove particulate
from the flue gaa
stream.
Filters are made of woven or felted high temperature
fabric, such as fiberglass or Teflon.
They are normally
manufactured
in the form of a cylindrical
bag, although other
configurations
are possible.
These elements are contained in a
metal housing which has gas inlet and outlet connections,
a dust
storage hopper, and a cleaning mechanism.
In operation,
dustladen gas flows through cloth filters, and dust is removed from
the gae stream as it pasaes through the filter cloth.
Filters
are cleaned periodically.
3.5.4.1
For practical reasons, most baghouses
a D-.
used for boiler flue gas are designed to operate on negative
pressure and are located between the last heat trap and the
induced draft fan.
Pressurized
baghouses are very rare.
Negative pressure baghouees are constructed
with a welded steel,
gas-tight houeing.
It ia usually divided into two or more
compartments,
each having a duet collection
hopper beneath it.
Hoppers and housing are ineulated, and the fan is located on the
clean eide of the collector.
3.5.4.2
~.
Filters are usually cylindrical
but may also be of the flat panel type.
The cylindrical
types
have the advantage of maximizing
total cloth area per square foot
of floor area, since they can be’made very long.
They typically
159
MIL-HDBK-1125/l
They can be
have a length to diameter ratio of about 30:1.
arranged to collect the dust on either the inside or the outside
Flat panel filters consist of large, flat areas
of the cylinder.
Flow direction
is
of cloth stretched over adjustable
frames.
usually horizontal.
Flat panel filters have the advantages
of
Flat panel
frames.
Flow direction is usually horizontal.
filters have the advantages
of allowing slightly more filter area
per cubic foot of collector volume and of allowing the panels to
be manually cleaned by brushing if excessive dust build-up
occurs.
are
VE
ods . Dust may be remove~ from
r~
3.5.4.3
The most common methods applied
filters by several methods.
shaking, reverse gas flow, and reverse Pulse.
A few baghouse designs use a rigid frame
Shaking.
a)
and a motor-driven
oscillator
mechanism to gently shake dust
Howeverr this is rarely used on modern
loose from the bags.
design units because it increases
bag wear and shortens bag life.
AC
TI
See Figure .101. The reverse gas
b)
Reverse Gas F1ow.
flow cleaning method uses a fan to gently backwash the bags with
high volume, low pressure, clean flue gas taken from the baghouse
outlet.
This causes dust which has accumulated
on the bags .to
drop off into the hoppers.
Baghousea of this design use low airto-cloth
ratios and thus require more bags and a larger housing
In addition, a spare compartment
to handle the same gas flow.
must be provided,
since the compartments
must be taken off-line
for cleaning.
IN
The pulse jet cleaning
See Figure 102.
Pulse Jet.
c)
method utilizes a short blast of high pressure air (90 to 100
psig) to blow backwards through the bag and dislodge dust so that
it can drop into the collection
hopper.
This design has several
advantages
over the reverse gas flow method and is gradually
Its primary
becoming the dominant design in the industry.
advantages
relate to its higher air-to-cloth
ratio and
This leads to lower initial
subsequently
smaller physical size.
cost, fewer bags, and lower space requirements.
Other advantages
are lower horsepower
requirements
for generating
the cleaning
air, fewer moving parts, and the fact that compartments
may be
cleaned either on- or off-line.
Its main disadvantage
ia that
the bags, although fewer in number, must be considerably
heavier,
and therefore more expensive,
to withstand the severe cleaning
cycles.
160
-#
AC
TI
VE
MIL-HDBK-1125/I
IN
Figure 101
Reverse Flow Baghouie
161
MIL-HDBK-l125/l
7
J
IN
AC
TI
VE
‘“’’’”-::
Figure 102
Pulse Jet Baghouee
The primary energy requirement
of
3.5.4.4
Enerav Requirements.
a baghouse is the fan horsepower
necessary to move flue gas
Resistance
to flow arises from the pressure
through the unit.
drop across the filter cloth, friction losses through ducts and
Power is also required to
damDers, and turbulent flow losses.
dri;e the cleaning equipment.
162
MIL-HDBK-1125/l
..
,
. Properly designed
3.5.4.5
of F~
fabric filters may be applied to most coal-fired boiler
applications,
either as part of a new installation
or on a
retrof~t basis.
The flue gas temperature into the fabric filter
must be maintained
above the sulfuric acid dew point but below
the maximum permissible
filter-cloth
temperature.
Temperature
requirements
are discussed mora fully in Section 4. Application
to oil-fired boilers is not generally recommended,
since unburned
oil tends to cause the filters to plug or blind.
A bypasa around
the baghouse is generally utilized for boilere that must burn
both coal and oil.
VE
(
AC
TI
3.5.5
An electrostatic
precipitator
(ESP) is a device that ramoves particles
from a gaa
stream by means of an electric field [Figure 103).
The electric
field imparts a positive or negative charge to the particle and
attracts it to an oppositely
charged plate.
Provision is also
made to remove dust particles from collection plates to dust
hoppers located below the precipitator.
The entire precipitator
is enclosed in a metal housing which has a flue gas inlet and
outlet and is connected
into the boiler lines between the boiler
and stacks.
ESPS may be operated under either pressure or
suction conditions,
with gas flow either horizontal or vertical.
Many configurations
are possible, depending upon the desired
application.
Common application
are discussed below.
IN
3.5.5.1
Most electrostatic
precipitators
are
de De~.
of the parallel plate design with horizontal gas flow.
The
plates carry a positive charge and act ae the collecting
electrode.
A large number of negatively charged high voltage
discharge electrodes
are spaced between the plates.
These
electrodes
impart a negative charge to the particles in the gas
etream which are then attracted to the positively charged
collection
plates. The particles adhere to the platea until they
are removed by the cleaning system.
This electrode system can be
designed in two basic configurations.
a) Weighted Wire.
In the weighted wire design, both
plates and wires are suspended from the top and allowed to hang
vertically
by gravity.
Weights are attached to the wire to
maintain proper tension.
Precise alignment is necessary so that
both seta of electrodes
maintain the relationship
required for
best efficiency.
Weighted wire construction
has been used for
many years, and is well proven and relatively inexpensive.
,
163
MIL.HDBK-1125/l
IN
AC
TI
VE
m
1
Figure 103
Electrostatic
Precipitator
Some modern precipitators
use rigid
Rigid Frame.
b)
In this type of construction,
both the
frame construction.
positive and negative electrodes
are rigidly mounted at top and
This is somewhat more
bottom to maintain precise alignment.
expensive,
but is advantageous
when extremely high collection
It also reduces maintenance
costs by
efficiencies
are required.
minimizing
or eliminating
electrode wire breakage.
164
MIL-HDBi(-1125/l
(
3.5.5.2
Precipitators
may be located
~cioitator
Location.
either in hot regions of the flue gas stream, where temperatures
are above 600 degrees F, or after the last heat trap, where
temperatures
are between 300 and 350 degrees F. These two
locations are termed hot and cold, respectively.
TI
VE
Hot Precipitators.
Hot precipitators
are generally
a)
applied to units designed for low sulfur coal because the
characteristics
of ash from this type of coal make it difficult
to collect in a cold precipitator.
Particle resistance
to
The ability to
collection
decreasea at the higher temperature.
remove particles from the plates and hoppers ia alao increased at
these temperatures.
Hot precipitator
are more expensive,
however, because they must be larger to handle the higher
specific volume of the gas stream.
Material selection, design
for proper expansion,
and structural considerations
also become
more critical at higher temperatures.
Finally, radiation leases
from the precipitator
housing increase at higher temperatures,
fleCeSS~ttItiflg
either more insulation or a reduction
in boiler
operating efficiency.
AC
b) Cold Precipitators.
Cold precipitators
are
designed to operate at temperatures
between 300 to 350 degrees F
They are smaller in construction
and therefore cheaper than hot
units for the same boiler size.
However, they are not as
effective in collecting
ash from low sulfur coal.
In addition,
they must be resistant to corrosion due to condensation
of
sulfuric acid at lower temperatures.
IN
3.5.5.3
Dust ~.
Dust is removed from
electrodes
by rappers.
Rappers can consist of electromagnetic
solenoids, motor-driven
cams or motor-driven
hammers which
vibrate or impact upon the tops of the plates and wirea.
This
causes collected dust to slide down the electrode,
eventually
reaching the dust collection
hopper at the bottom of the unit.
Once collected in the hoppers, dust is removed by the fly ash
removal system.
3.5.5.4
The main uses of energy in an
electrostatic
precipitator
are the fan horsepower
to move flue “
gas through the unit and the power required to maintain the
electrostatic
field.
These two power usages are approximately
equal.
A typical electrostatic
precipitator
on a 30,000 lblhr
boiler would require about two to three brake horsepower
in fan
power consumption
and two to three kilowatts to maintain the
electrostatic
field.
The rappers and dust removal systems are
other sources of power consumption.
165
MIL-HDBK-112511
3.5.5.5
Pr eciDi t ators.
A 9D~l“ca tl“on 0 f Electrostatic
Electrostatic
precipitators
can be designed to function
either for a new or retrofit
,efficiently on almost any boiler,
However, It
installation,
if sufficient physical space exists.
is important to have a good knowledge of the fuel analysis that
will actually be burned, since this has a major effect upon the
design of the precipitator.
Once the precipitator
has been
designed and sized for a given fuel, major inefficiencies
and
operating problems can result from fuel changes.
AC
TI
VE
3.5.6
w~
. A wet scrubber is a device designed to
use a liquid to separate particulate
contaminants
from a flue gas
stream.
Wet scrubbers have some potential application
and
advantages
over other types of particulate
control devices and
Most wet scrubber
are thus discuesed
in this handbook.
applications
to Navy b-oilers would be of the wet approach venturi
type (Figure 104). It is very compact and has the capability
to
collect particles down to submicron size with about 99 percent
efficiency,
or even more if necessary.
Its principle of
operation is somewhat similar to a mechanical
collector,
but it
adds the action of liquid scrubbing to centrifugal
and inertial
forces.
The incoming gas steam accelerates
and atomizes the
liquid droplets.
These atomized droplets then wash dust out of
the gas stream in the same manner that a severe rainstorm can
wash dust out of the atmosphere.
Pressure drop through a wet
scrubber increases with decreasing
particle size and increasing
collection
efficiency.
IN
For a venturi scrubber applied to a coal-fired
boiler,
pressure drop typically ranges from 20 to 25 in water.
This
creates a significant
penalty in fan horsepower
requirements
and
is “one of the primary reasons that wet scrubbers are seldom
Other types of scrubbers can lower
appl~ed to smaller boilers.
th~s horsepower
requirement,
but their collection
efficiencies
are also lower.
The other major disadvantage
of the wet scrubber
is its water usage.
The cost of pretreating
water and the cost
and complexity
of treating the waste slurry from the ecrubber
discharge can be significant.
The primary advantages
of a wet
scrubber are its compact size and its tolerance
for extremely
high gas temperatures.
These two characteristics
make it
potentially
useful for retrofit application
where other types of
control devices might not be applicable
due to efficiency
or
space requirements.
3.6
~
ui ment
166
MIL-HDBK-1125/l
VE
(
W,t,flsluart
out
TI
L
AC
Figure 104
Wet Approach Venturi
Scrubber
IN
3.6.1
Feed water He-.
Cloeed feedwater heaters of the
tube and shell type are used to preheat feedwater going to
deaerators
and hot water boilers as well as for deaerating
heating.
These closed feedwater heatere can make use of turbine
exhaust steam or waste heat generated in the boiler plant to
improve overall plant efficiency.
Figure 105 illustrates
a
closed U-tube heat exchanger used for feedwater heating.
3.6.2
pU~DS and
The selection and replacement
of
pumps require consideration
of capacity and pressure
requirements,
the type and temperature
of fluid to be handled,
and the type of pump best suited for the job requirements.
Performance
characteristics
vary widely, even among pumps of the
same type and capacity.
Pumps can be classified
into four
groups:
centrifugal
pumps, reciprocating
piston pumps, rotary
positive displacement
pumps, and jet pumps/injectors.
The
characteriatice
of these groupe are discussed
later.
167
VE
MIL-HDBK-1125/l
or cmanml
Figure 105
Heat Exchanger
AC
TI
U-Tube
IN
3.6.2.1
Selection of a pump for a particular
job
In stall ation.
involves many considerations,
but once the pump is selected,
successful performance
depends upon details of the installation.
This is particularly
true where the pump must lift the fluid or
when the fluid is heated.
Greater care must be exercised
in
design and installation
of the suction line than of the pump
discharge.
A strainer is required to prevent foreign objects
from entering and clogging the pump or piping.
The maximum
suction lift or minimum suction lift or minimum suction head
depends to a great extent upon the temperature
of the water and
distance of the pump above sea level, as noted in Table 16. The
following rules should be observed when installing
a suction line
to a pump.
Disregarding
any of the following rules may lead to
unsatisfactory
operation
or complete failure:
The line must be tight.
A leak in the discharge
a)
line may be annoying, but a leak in the suction line may lead to
inoperation
of the pump.
b)
from the pump
Keep the suction lift, or the vertical distance
to the water supply, as small as possible.
168
MIL-HDBK-1125/l
Table 16
Permissible
Maximum Suction Lifts and
Minimum Suction Heads in Feet
for Various Temperatures
and Altitudes
Altiuld,
uat.rTemperature
At se. tevet
2,020 fc abave
6,CC0 f t ~tOVC
10,OOJ ft @Ove
Note:
-22
-19
-1s
-11
Sa
-17
-1s
-11
-7
(-) indicates
of pump above
(+) indicates
below water.
1)
Im
120
140
la
1s0
Zro
210
-13
-11
-6
-2
-8
-4
-2
+3
+7
+0
.3
.7
+11
.s
.?
412
+16
.10
+12
+16
-
.tz
●15
lift,
or distance
maximum
water”.
suction
::
●2
VE
60
(degrqes
suction
head,
or distance
of pump
TI
Keep the suction line as short as possible.
Keep
c)
the number of fittings, such as ells, tees, reducers, and valves
to 25 minimum.
To prevent formation of air pockets, maintain
e)
proper slope on horizontal
sections of pipe.
Slope the line away
from the pump for a suction lift and toward the pump for a
suction head (Figure 106A).
IN
f
AC
d)
To reduce losses caused by pipe friction and high
velocity, keep the diameter of the suction line as large ae
practical.
I
POO.O**ign
God O*tian
Maintain
Figure 106A
Proper Slope to Suction
169
Line
MIL-HDBK-1125/l
f) Do not use fittings that permit the formation of
An air chamber is occasionally
Note:
air pockets (Figure 106B).
used on the suction line of a pump to smooth out pressure
These must be carefully designed and
‘fluctuations or surges.
installed to ensure proper operation.
“s-lIn-/
VE
~q~”
FLOW
Figure 106B
Line Installation
AC
TI
Suction
9) To keep the line and pump full of water when the
pump is idle, install a foot valve on the inlet end of a suction
A foot valve is a special type of check valve made for
line.
Very little force is required to operate it, and a
this purpose.
A foot valve has no value when
strainer is usually incorporated.
the pump is located below the source of water supply.
h) properly guard gears, belts,
moving parts exposed to hazardous contact,
from pump bases.
shafts, and other
and provide drains
IN
Centrifugal
pumps use a rotating
~
3.6.2.2
Pumvs.
This type of
impeller to give velocity and pressure to fluid.
pump ie widely used in boiler feed and condensate
pumping
applications.
Figure 107 illustrates
a horizontal
split case
Centrifugal
pumps are available in
type of centrifugal
pump.
many configurations,
including
single and double suction, single
Although these
and double volute, multistage,
and vertical.
pumps look different,
they have basically the same components
and
operate similarly.
They are compact, of simple construction,
discharge
at a uniform rate of flow and pressure, contain no
valves or pistons, operate at a high speed, and can handle dirty
water.
comparatively
low
They have two major disadvantages:
However,
efficiency,
and inability to discharge air or vapor.
The
their advantages more than offset the lower efficiency.
inability
to discharge air can be overcome by proper installation
and operating practices.
170
MIL-HDBK-1125/l
(
.—.
MO1lZOmAUV
lA~CE
lTwmyJI
11
1!
ADIUSIAU1
\
If
LAcT1rNw4
ItAll
VE
..lll-!$%UY
NC1’iOM
ANDOISCSACG1
mnt.:ow#
NAU
.wuNo:v
TI
Figure 107
Centrifugal
Pump
AC
Construction,
The pump shown in Figure 107
a)
consiets of the rotating element called an “impeller,” the
casing, shaft, and parts used for sealing the pump against
leakage.
IN
(1) The impeller consists of two disks separated
by a number of vanes which form passages for water and are
connected
to the hub.
This impeller may be of cast iron, bronze,
steel, or other alloys, depending upon the fluid to be handled.
Its diameter depends on ita operating speed and the difference
between suction and discharge pressurea.
The pressure difference
is usually called the “pump head” and is measured in feet.
An
impeller may be either single or double suction.
The one shown
ie the double suction type, in which water enters from both
sides.
(2) The casing ia split on the horizontal center
line and contains the inlet and outlet passages.
Inlet and
outlet connections
are usually in the bottom half of the casing,
permitting
disassembly
and repair of the pump without disturbing
pipe connections
or pump alignment.
The casing guides water from
the inlet connection
to the impeller and from the impeller to the
discharge connection.
The casing, although usually made of cast
iron, can be made of other materials if necessary to handle
special fluids.
171
MIL-HDBK-1125/l
(3) The shaft supports and drives the impeller and
Babbitt-type
bearings are
is, in turn, supported by bearings.
used in the pump shown in Figure 107, though many pumps use ball
bearings.
b]
Operation
TI
VE
14) The imneller is held firmlv bv shaft sleeves
that also help’t& seal it-against
air leakage-in~o the pump.
Sleeves are held in place by two nuts, one of which has a rightPacking is
hand thread and the other a left-hand thread.
sometimes provided between these nuts and the sleeves to ensure a
tight seal.
Stuffing boxes are provided where the shaft passes
through the casing.
Stuffing boxes are filled with packing held
A brass or bronze lantern, ring is
in place by packing glands.
often inserted between two adjacent rings of packing to provide a
The sealing water lubricates and
channel for the sealing water.
cools the packing and shaft sleeve and helps seal against air
leakage into the pump.
It may be supplied directly from the
The casing has
pump, as shown, or from an outside source.
renewable
rings to reduce leakage from the discharge to the inlet
side of the impeller.
Renewable
bearings are occasionally
installed
on the impeller.
IN
AC
(1) When the pump is operating, the impeller
rotates at high speed, drawing water into its center, near the
The resultant centrifugal
force imparts energy to the
shaft.
As this occurs, the partial
water, which is forced outward.
The casing
vacuum produced at the inlet draws additional water.
must transform the velocity of water leaving the impeller into
This is done in the pump shown by
pressure with minimum loss.
making the casing in the form of a spiral, called a “volute,” and
gradually
increasing
its cross-sectional
area from i,ts beginning
to the pump discharge.
The pump shown is called a “single-stage
Multistage
pump” because water passes through only one impeller.
pumps are used when it is necessary to operate against higher
heads.
In a multistage
pump, water travels through successive
impellers
or stages until it has reached the desired head.
(2) The output of a centrifugal
pump can be
controlled
by regulating the pump speed, providing a controlled
recirculation
line, or throttling
the discharge.
The
recirculation
line, or bypass, consists of a valved line between
the pump discharge and suction.
The output of the pump is
decreased
by opening this valve and recirculating
water through
the pump.
Throttling
the discharge
increases pressure at the
pump outlet, causing some of the fluid to stop and remain in the
pump casing.
Any of. these control methods can be manual or
automatic.
A centrifugal
pump must be equipped with a check
valve on the discharge side to prevent backflow of water when the
172
UIL-HDBK-1125/l
Centrifugal
pumps are designed to deliver a
pump is inoperative.
given quantity of fluid against a specified discharge pressure or
head.
Every centrifugal
pump has a maximum or shutoff head,
This fact should
above which it ia unable to deliver any fluid.
be taken into consideration
when an increase in delivery pressure
is contemplated.
The ehutoff head can sometimes be increased by
substitution
of a larger impeller, although a larger motor may
also be required.
VE
.
.
The direct-acting,
ateam3.6.2.3
~.
driven duplex pump is widely used becauee of its low initial
cost, low maintenance,
simple operation, and positive action.
in
Simplex pumps are rarely ueed because of the wide fluctuation
fluid pressure at the pump discharge.
AC
TI
A horizontal duplex piston pump is shown in Figure 108.
This type of pump coneista of two single-cylinder
pumps mounted
The piston rod of one pump operates the steam
side by eide.
valve of the other through a system of bell cranks, rocker arms,
Pistons move alternately
ao that the resultant
or links.
discharge of water is essentially continuous.
Steam ie admitted
for the full stroke and is not used expansively,
resulting in
Each
high steam consumption
for the amount of water handled.
cylinder has two ports in each end, one of which admits steam
while the other discharges
it.
This minimizes
the required valve
travel but leaves sufficient bearing surface between the steam
ports and the main exhauat port to prevent steam leakage from one
to the other.
Steam which ia trapped in the cylinder when the
exhaust stroke neare completion providee a cushion to prevent the
Some pumps also have
piston from striking the cylinder heads.
small hand operated valvea on the side of the steam chest to
regulate the amount of cushioning by controlling
the eecape of
the steam from the cylinder.
Maximum cushioning
is desired with
the pump operating at high speeds, and ie obtained by closing the
hand valve.
IN
(
Valves of a duplex pump do not overlap the edges of the
ports with the valve in its mid-position.
Valvea are held to
their seats by the pressure differential
acting on the two sides
of the valve.
Figure 109 showe the relative position of the
working parts when the pump and valve are in mid-position.
The
illustrations
indicate that valves are not fastened rigidly to
the stem and that there is lost motion between the valve and the
This lost motion ie provided to force the pump to take a
stem.
full stroke; otherwise,
it would make only about a quarter
stroke.
The typical operationa of the pump are alaodue
to this
When one piston has completed its etroke, it pausee
lost motion.
and goes into reverse only after the second piston has reached
the end of its stroke and moved its valve.
One pieton ia always
in position to move ao that the pump goes into operation as soon
as the steam valve is opened.
173
MIL-HDBK-1125/1
.
-II ABM
SILaMI.4ul
M!LL!
lxJuv-
(
S’ruM
mm-
LOgMO1!ON
VALVI
iOO>
A
A
WAR8OtKMA#Gi
AC
TI
WO[VALV1
VE
~
mDs . Rotary positive
3.6.2.4
J70ta
acement
displacement
pumps use gears, screws, or sliding vanes to move a
volume of fluid through the pump (Figure 11OA and 11OB).
Rotary
positive displacement
pumps are most commonly used in boiler
plants to pump fuel oil.
Very close tolerances
are maintained
between the pump internals to minimize slippage of fluid.
Slippage in a positive displacement
pump may be less than 0.5
percent, while slippage of 50 percent or more is common in
centrifugal
pumps.
These pumps can thus operate at high
efficiencies
and pressures.
Rotary positive displacement
pumps
should be equipped with relief valves to protect against over
pressurization.
While centrifugal
pumps may be cOntrOlled
by
pumps are controlled
throttled
flow, rotary positive displacement
by recirculating
a portion of the pumped fluid back to the tank
or the pump suction.
IN
Figure 10I3
Reciprocating, Piston Pump
174
- nutw[t
—MU-IS
MIL-HDBK-1125/l
I
Losz Motion
I
I
1
VE
lAi-
AC
St
TI
PO,
Figure 109
‘lMo Methods of Providing
Motion
IN
(
175
Lost
MIL-HDBK-1125/l
VE
8ECTION
O*CVLINDCU
T?(0)MNOLC-SCRN
,/ /
@
@
.OFCIL1.DtR
TI
SUCTION
(,%)
DWOLE-lDLCRITPE
(b)rwtm+cncwmsi#o~z-)D~gn
T,u
IN
AC
Figure 11OA
Rotary Screw Pumps
176
MIL-HDBK-1125/l
Rfng Gear with Two More
Teeth Than Pinion and
with Stationary Crescent
IN
AC
TI
VE
Ring Gear with One More
Tooth Than P{nfon
I
Lobe Pump (two-lobe type)
Simple
Gear
Pump
Figure 11OB
Rotary Gear Pumps
3.6.2.5
. An injector is a jet pump used to
$et P~
feed water into a boiler, where its high thermal efficiency
justifies its use.
Most of the heat, in the form of steam, used
to operate the pump is returned to the boiler with the water.
The injector is convenient,
cheap, compact, efficient,
and has no
moving parts.
It delivers warm water into the boiler without
preheating,
and has no exhaust to dispose of.
It cannot be used
to pump hot water and can handle a maximum water temperature
of
about 140 degrees.
Excessive preheating
of feedwater passing
through the injector often causes impurities
to drop into the
tubes, scaling them so heavily that the injector faile to
function.
Essential
parts of an injector are the steam tube,
combining and delivery
tubes, and the necessary casing to guide
water to and from these tubes (Figure 111).
The shape of the
steam tube is designed
in the ehape of a venturi to increase the
velocity of the steam passing through the tube.
As a result of
this high velocity,
air is partially evacuated from the inlet
177
MIL-HDBK-1125/l
suction
line,
and
fluctuating
pressures.
VE
line, causing the water to rise until it contacts steam at the
entrance of the combining tube.
Steam is condensed and imparts
considerable
velocity to water.
The condensing steam reduces its
volume and thus maintains the vacuum.
The combining tube further
increases the velocity of the moving mass of water, enabling it
to cross the opening to the delivery tube.
The water velocity
opens a check valve and water enters the boiler against the
boiler pressure.
An overflow is provided to remove water when
No water should appear at the overflow
the injector is started.
if the injector is operating properly.
Injectors can be hand
starting, automatic,
single tube, or double tube.
An automatic
injector will resume its flow after an interruption without any
attention
from the operator.
The injector operates
satisfactorily
under a constant load ,and pressure but becomes
unreliable
when operating with fluctuating
pressure.
Due to this
fact and to low temperature
limitations,
injectors are rarely
used on modern installations.
Injector failures are most often
caused bv excessive suction lift, hot water.,–...cloaaed strainer or
w
IN
0
AC
TI
—
F.dwm*[email protected]
Figure 111
Steam Injector
178
in
,
MIL-HDBK-1125/l
VE
The boiler feed pump is probably
3.6.2.6
&&ler
Feed -.
the single most important auxiliary in the boiler plant. It must
be operated continuously
when the boiler is in operation, and at
The AS?4E
a rate of discharge
equal to the rating of the boiler.
Code requires the boiler to have two methods of feeding water, to
ensure that an adequate supply ,is available at all times.
Reciprocating
and jet pumps can be used for thie purpose, but
centrifugal
pumps are most commonly used in modern stationary
Centrifugal
pumps have the advantages
of small size,
practice.
high speed, low chance of boiler water contamination
with oil,
and continuous
steady flow.
IN
AC
TI
The area of the
Reciprocating
Pump Application.
a)
steam cylinder of a reciprocating
pump ranges from two to three
times that of the water piston or plunger to allow for friction
losses and to permit the pump operation at reduced steam
A boiler feed pump is required to pump against a
pressures.
total head ranging from 1.1 to 1.5 times the boiler pressure.
A
reciprocating
pump must be eized to provide the desired water
discharge
capacity with the pump operating at approximately
oneThis allowa for pump wear and
half the maximum stroke rate.
provides a margin in an emergency,
such as low water or ruptured
Reciprocating
pumps of the direct-acting
duplex type are
tubes.
They
sometimes used for small capacities and moderate pressures.
consume approximately
5 percent of the eteam produced by the
boiler, but since the exhaust, is utilized to heat the feedwater,
the net heat consumed by the pump can be less than 1 percent.
b)
Centrifugal
Pump Application.
Centrifugal
pumps
for boiler feed applications
must be sized to develop enough head
and capacity to feed the boiler under all conditions.
A
centrifugal
pump may be driven by a steam turbine or a variableThe method ueed to control output
or constant-speed
motor.
Any centrifugal
depends primarily on the type of drive used.
pump used to pump hot water must be provided with an adequate
flow of water at all times.
Centrifugal
pumps quickly become
steam-bound
and stop pumping under certain conditions,
and may be
damaged if permitted to operate under those conditions
for any
length of time.
3.6.2.7
~.
Reciprocating,
positive-displacement
Heating
rotary, and centrifugal
pumps are used for this service.
systems generally use an automatic float-operated
centrifugal
pump.
The condensate
drains to a return tank or reservoir, and a
float operates a motor switch which starts and stops the
centrifugal
pump.
the motor ia on top of the
In one arrangement,
tank and the pump ia at the bottom.
In another arrangement,
the
pump and motor are mounted outside and below the return tank.
I
179
MIL-HDBK-1125/l
VE
3.6.2.8
Vacuum Pumvs.
Reciprocating,
jet, and positivedisplacement
rotary pumps may be used for vacuum service.
A
centrifugal
pump can be used to supply water to the jet, which
Reciprocating
pumps, arranged to
actually maintains
the vacuum.
remove both condensate
and air at the same time, are called wet
vacuum pumps.
This is a common arrangement
and is used with
Smaller clearances
in the
small condensing
turbines or engines.
A pump which
water end characterize
pumps used for this service.
The vacuum pump
removes only air is known as a dry vacuum pump.
in a vacuum return heating system must handle both air and water.
One method of doing this is to use a pump with two impellers
mounted on a shaft.
One impeller handles water and the other
Condensate
flows into the receiver and enters the pump.
An
air.
automatic control actuated by the water level and pressure in the
receiver
(which is below atmospheric)
starts and etops the pump
as required.
This arrangement
can maintain a vacuum of 10 to 18
inches of mercury in a system which is reasonably
free from
leaks.
IN
AC
TI
3.6.3
Forced Draft [FDI Fans.
FD fans are applied to push
combustion
air through the burner into the furnace.
If an ID
fan is not supplied, the FD fans mu,st also push the products of
combustion
through the boiler to the stack.
Both centrifugal
and
axial fans are used, with centrifugal
units being more common.
Centrifugal
fans include the following blade designs:
radial,
forward curved, forward curvedlbackward
inclined, backward
inclined,
and airfoil/backward
inclined.
Backward inclined and
airfoil/backward
inclined fans are most commonly used for FD fan
service because of their high efficiency,
stable operation,
and
nonoverloading
horsepower characteristics.
FD fans are required
to operate over a load range of approximately
25 to 100 percent
capacity.
This is accomplished
primarily by use of dampers.
Three types of dampers are used:
inlet dampers, parallel blade
outlet dampers, and opposed blade outlet dampers.
Figure 112
illustrates
a FD fan equipped with inlet vane dampers.
Figure
113 illustrates
a typical parallel blade outlet damper.
Inlet
vane dampere control airflow through the fan by prespinning
the
entering air.
Each position of an inlet vane damper in effect
creates a new fan and horsepower curve, as shown in Figure 114.
This results in improved control range and horsepower
savings
over outlet damper applications
by creating a static pressure on
the fan.
Increased static pressure reduces flow and causes the
operating
point to move back up the fan curve (Figure 115).
Opposed blade outlet dampers provide a greater control range than
parallel blade outlet dampers, which operate best in the 70 to
100 percent capacity range.
180
TI
VE
(
Forced
Draft
1
IN
1
Figure 112
Fan With Inlet Damper
AC
4
1lk-----4u
IF-----AN
w-
,
#
Typical
Figure
Outlet
181
113
Fan Dampers
I
I
MIL-HDBK-1125/l
I
I
90Oq (Wid9OP*I+
Sv8t9m Cum
Th,[email protected] Point
.
]:
F.m S.latio.
::
.o.mp**_
‘i
Es
;X
.::
::
lnm
SUP Oanw.r
—POd,
io”, -
Figure 114
for Different
Positions
AC
Fan Curves
TI
AI, FIOW. CFM —
.0 o,.i~
Icldl
VE
;2
‘m
%2:
Inlet
Vane
‘o”~~..,
ml
e saloclion
IN
?=
~:
-~-
SP
[=[
M=
6!
Zm
0
I
AIsFIow,
CFM —
Fan Curve
Figure 115
for Fan With
182
Outlet
Damper
MIL-HDBK-1125/l
VE
ID fans are used to exhaust
3.6.4
~.
the products of combustion
from the boiler.
Maintaining
balanced
draft conditions
in the furnace improves boiler operation
and
provides energy to move flue gases at velocities
needed for good
heat tranafer.
ID fana are subjected to more severe service
conditions
than FD fana, because they must handle larger volumes
Physical
of gas at high temperature
and contain ash particlea.
characteristics
of ID fana must therefore be different
from those
Airfoil bladea are not recommended
for ID fan
of FD fana.
service.
Backward inclined fans are acceptable
for nonabrasive
gaa servica, while radial or radial tip bladea and forward
curvedlbackward
inclined fans are recommended
for abrasive
service.
The higher temperature
of gaaea handled by the ID fan
sometimes makes it neceesary to use water cooled bearinga to
prevent overheating.
Inlet damper controls or variable speed
drives are used to control ID fan capacity.
AC
TI
3.6.5
~.
Stacka or chimneys are
necessary to discharge
the products of combustion
at a
sufficiently
high elevation
to prevent nuisance due to low flying
smoke, soot, and ash.
A certain amount of draft is alao required
to conduct flue gases through the furnace, boiler, tubes,
economizers,
air heaters, and dust collectors,
and the stack can
The height of the stack
help to produce part of this draft.
necessary to meet the first requirement
ia often enough to alao
produce the draft necessary
to meet the second requirement.
The
amount of draft available
from a etack dependa on the height and
diameter of the stack, the amount of flue gas flowing through it,
the elevation above sea level, and the difference
between
temperature
of the outaide air and average temperature
of gases
inside the stack.
Excessive
stack temperature
are undesirable,
because they repraaent a heat loss and efficiency
reduction.
3.6.5.1
Stacks are built of steel plate,
masonry, and reinforced
concrete.
Caged laddera should be
installed.
Stack guys should be kept clear of walkwaye and roads
and, where subject to hazardoua contact, should be properly
guarded.
Stacks are provided with the means of cleaning ash,
soot, or water from thei,r base, the meane depending mainly on the
size of the stack.
IN
(
The advantages
of ateel stacks over masonry
a) Steel.
or reinforced concrete are reduced construction
time, lower
weight, smaller wind surface, and lower initial coat.
Major
diaadvantages
are higher maintenance
cost and shorter life.
Steel stacka may be either self-aupporting
or guyed, single-wall
or double-wall
construction,
and lined or unlined.
Unlined guyed
stacks usually are used on smaller installationa.
This type of
etack can be supported by the boiler smoke box, the building
structure, or a separate foundation.
Two aeta of four guy wires
183
MIL-HDBK-1125/l
VE
Steel etacks over
each are usually used to hold the stack erect.
They are
72 inches in diameter are normally self supporting.
typically
lined with refractory
or insulation
to protect the
metal from the corrosive attack of flue gases and to improve
performance
of the stack by minimizing
cooling of flue gases.
The eelf-supporting
stack is usually mounted on its own
Stub and
foundation
or on the building structure framework.
venturi stacks are typically of steel construction
and usually
When these stacks
extend no more than 20 feet above the boiler.
are used they contribute
little to the draft requirements,
which
must then be supplied entirely. by FD andlor ID fans.
Brick.
The modern brick chimney built of special
b)
radial brick or block is very satisfactory,
its major
This type of stack is
disadvantage
being its higher cost.
normally
lined with fire brick for about one-fifth of its height
and must be protected
from lightning.
AC
TI
and
Ducts
.
Flues are used to interconnect
boiler
F1 ues
3.6.5.2
Ducts are used to
air heaters, and stacks.
outlets, economizers,
interconnect
forced draft fans, air heaters, and windboxea or”
combustion
air plenums.
Flues and ducts are usually made of
steel.
Expansion
joints are provided to allow for expanaion and
Flues or ducts carrying heated air or gases should
contraction.
Outside insulation
is
be insulated to minimize radiation losses.
Flues and ducts are designed
preferred
for its maintainability.
to be as short as possible, free from sharp bends or abrupt
changes in cross-sectional
area, and of adequate cross-sectional
area to minimize draft loss at the design flow rates.
IN
~.
3.6.6
The reciprocating
steam engine with
its need for oil lubrication
and resulting contaminated
steam has
Steam
been replaced by steam turbines and electric motors.
turbine-driven
boiler plant auxiliaries
are generally economical
only if exhaust steam can be used for feedwater or other heating
applications.
The steam turbine uses a rotating wheel, with
buckets or blades uniformly spaced around its circumference
to
tranaform
the heat energy of steam into mechanical
energy or
work.
Steam, expanding through a nozzle, is directed against
these buckets and causes the wheel to turn.
Various types of
steam turbines differ in the construction
and arrangement of the
nozzles,
steam pasaagesr and buckets.
The steam turbine is
essentially
a high-speed machine; it is best used with direct
connection
to electric generators,
pumps and fans, and with
geared connection
to low-speed machinery.
The common
noncondensing
turbine operates at an efficiency
of only 20
percent.
Only special circumstances,
euch as the necessity for
oil-free exhaust steam, can justify use of a small turbine for
any purposes other than standby or emergency.
Figure 116 shows a
single-stage
impulse noncondensing
steam turbine.
184
MIL-HDBK-1125/l
(
CJ,ln,,
u ,34u,rtwce
Umcm1*, .0c4J1
Smrm OJciii!l
Lbtfvp,
wfmnma
ifltaCiu
.!nwt
,,,*,
v 6MS,
Cu. Iau*lq
,mq
Nut IX*O
45)
VE
etafq
u“ %,,1
BI,
L-5,, ,&y
Stzlt&C*,CI
ffotw
Imlrnl cum,
IM! ,lbTiieat;
r“Irq Iml Iota
nt
6fb1 M t,,,,lia,
IN
AC
TI
4
h
Clrmlfm
OlaAiil
bmm,o
S*
raw
Single-Stage
WIUI
II&d
S&t,,ILK,.
Kt!Jttld,
tit’
mrtanbtmti d&tmlflc4t4kk
d!wlilluciq
Luniu tlmmii
rslm
Figure 116
Impulse Noncondensing
.—
Turbine
.
3.6.7
Electric motors can be grouped into
three general classes based on power source.
These classes are
direct current,
single-phase
alternating
current (AC), and threephase AC.
Three-phase
motors are available in squirrel cage,
synchronous,
and wound rotor.
The squirrel cage motor has become
dominant because of its low cost, high reliability,
high
efficiency
over a wide load range, and high starting torque, and
it is estimated
that 90 percent of electric motor energy is
185
MIL-HDBK-1125/l
Not all squirrel
consumed by three-phase
squirrel cage motors.
When
the
need to replace
cage motors perform equally, however.
or install a new motor exists, modern higher efficiency
and
Economic
higher power factor designs should be considered.
analysis usually justifies the slightly higher initial coet of
high-efficiency
motors.
VE
~t
. Electrical equipment used in
3.6.8
central plants
includes motors, motor starters, controls, circuit
breakers,
switchgear,
transformers,
fire protection,
lighting,
Operation of these devices involves use of
conduit, and wiring.
Operating personnel must
voltages that are dangerous
to life.
~L
observe safety regulations
found in NAVFAC P-106O, E
ibutio
etv
Manual..
ansmi
sion
a
d
ist
T~
TI
Variable Sneed Drives.
Electrical,
mechanical,
and
3.6.9
Electrical drives
fluid variable speed drives are available.
include multiple speed motors, variable frequency controls, and
variable voltage controls.
Development
of solid state components
has allowed the design of variable frequency controls which can
Mechanical
operate at high efficiency
over a wide load range.
variable speed drives include belts with adjustable pulleys, gear
Fluid drives include a
reducers,
and geared transmission.
variety of hydraulic couplings.
IN
AC
3.6.10
Air Compressors.
Three basic types of air compressors
reciprocating,
rotary, and centrifugal.
are available:
Air
compressors
may be further classified as oil free or lubricated.
Air compressors
used in Navy installations
are comparatively
small units, with final discharge pressures of approximately
100
They are typically
of rotary screw or single- or tWO-Sta9e
psi,
reciprocating
design.
These two types are discussed below.
NAVFAC MO-209, ~
Mainte an e of Stea
Distribution
Svstems may be referenced
for additional
information
on compressed
air systems.
3.6.10.1
~
The reciprocating
Compressors.
compressor
is a piston, positive displacement
machine.
Air
volumes can range up to approximately
6,000 cfm.
Two-stage
compressors
are frequently
used, because they require less power
to compress a given quantity of air than do single-stage
machines.
Cylinders
and intercoolers
of two-stage machines may
be cooled by either air or water.
The need for ehielding or
baffling structures
for noise attenuation
requires investigation
when reciprocating
compressors
are to be used.
3.6.10.2
Rotary screw compressors
are
~ ota
ressora.
also classified
as poeitive displacement
machines.
They operate
by passing the inlet air through an inlet valve, and then
compressing
it throuqh the action of two helical screws rotating
186
MIL-HDBK-1125/l
VE
against one another.
Filr volukes can range as high aa 3,000 cfm
Packaged
but are more typically in the 100- to 150-cfm range.
units are readily available in sizes up to 500 cfm which
incorporate
necessary filters, coaleecera,
and coolers into a
single, factory-designed
and aeaembled unit.
Liquid sealed
rotary screw-type
unita are available up to about 300 cfm and can
provide oil-free air.
This type of compressor is recommended
in
food processing
or health care facilities but is not often used
It is more common to provide oil-free air to
in boiler plants.
boiler plants by means of filters and separatora in combination
with one of the compressor
types discussed above.
Total air requirement
3.6.10.3
should be based not upon the total of individual maximum
requirements
but upon the aum of average air conaumpti.on of airoperated devices.
Compressor capacity should be based upon the
calculation
procedure explained in NAVFAC MO-209.
TI
In the process of compressing
air,
3.6.10.4
~.
approximately
80 percent of energy delivered by the electric
motor becomes heat energy stored in compressed air at elevated
temperatures.
Aftercoolera
are required to cool the air to a
more usable temperature.
An aftercooler
is a heat exchanger
which ia sized to cool the air below the dew point so as to allow
water and oil vapors to condense.
A moisture separator is
attached to remove condensed vapora.
The aftercooler
is normally
cooled with water, but it may also use air as its heat exchanger
medium.
IN
AC
(,
3.6.10.5
~.
Some compressed
air applications
require
moisture removal in addition to that provided by the aftercooler.
Such applications
in the boiler plant include pneumatic tools,
operation of pneumatic drives on dampers or valves, and
instrument
air.
For these applications,
a supplemental
dryer is
required.
Three basic categories
exist:
refrigeration
dryers,
regenerative
dryers, and deliquescent
dryers.
Regenerative
dryere are the type usually used in boiler plants, and are
discussed
here.
Information
on the other types may be obtained
from manufacturers
or from NAVFAC MO-209.
Regenerative
dryers
are further broken down into three types:
heatless desiccant,
heat regenerative,
and low temperature
regenerative.
Heatless Desiccant Dryers.
Heatless desiccant
a)
regeneration
paeses a quantity of dried (purged) air through the
offstream bed.
No external heat is applied.
This type should be
selected with a field-adjustable
purge control so that the purge
rate (and therefore the preseure dew point) can be adjusted to
accommodate
seaeonal variations
in ambient temperature,
thereby
reducing operating coate.
Heatless dryers are capable of
providing
-150 degrees F pressure’dew
point.
Maintenance
costs
187
MIL-HDBK-1125/l
With adequate
are low, since there are few moving parts.
prefiltering
to remove oil, desiccant replacement
requirements
are minimal.
b)
Heat Regenerative
Dryers.
Heat regenerative
dryers
utilize heat from an external source (either electric or steam)
in conjunction
with purged air to regenerate
the offstream tower.
By reducing the amount of purged air required to regenerate,
the
heat regenerative
dryer operating costs can be outweighed by
maintenance
costs and downtime.
TI
VE
Low
Low Temperature ’Regenerative
Dryers.
c)
temperature
regenerative
(heat pump) dryers utilize thermal
energy from the inlet air to heat the offstream tower for
This type
regeneration.
NO electric heaters or steam are used.
of dryer provides the economy of refrigerated
drying and the low
Refrigeration
pressure dew point capability of desiccant drying.
cooling is used to remove most of the incoming moisture and to
This
cool the onstream tower for high adsorption
efficiency.
system saves energy, since the heat energy removed from the inlet
stream is recycled by the refrigeration
compressor
and discharged
to the offstream tower for regeneration.
Stable pressure dew
points down to -100 degrees F are realized with this type.
IN
AC
3.6.10.6
Air Receivers.
Air receivers are steel pressure
vessels, constructed
in accordance with the ASME Boiler and
~,
Section VIII, which are sized to dampen
pulsations
entering the compressor discharge
line, to serve as a
reservoir
for sudden or unusually heavy demands in excess of
compressor
capacity, to prevent too frequent loading and
unloading
of the compressor,
and to allow moisture and oil vapor
carryover
from the aftercooler to precipitate.
Drainage valves
and piping, safety valves, and pressure gages must be installed
in accordance with the Code.
~team ‘J!raD
3.6.11
s. Steam traps are used to discharge
condensate
and air but not steam from a pipeline or heat
exchanger
(refer to NCEL UG-0005, ~
St a
ra
uide).
No
single type of trap is ideal for every situation.
The four major
types of steam traps are thermostatic., float and thermostatic,
disc/thermodynamic,
and inverted bucket.
These are discussed
below.
Orifice or impulse traps are also produced but operate by
discharging
steam continuously
and are therefore
not recommended.
This waste, as well as the wasting of steam from defective or
damaged traps, represents an energy loss that is not acceptable.
Proper maintenance
of steam traps is discussed
in Section 5.
3.6.11,1
Thermostatic
traps can be
Th ermostatic Steam Trarm.
further subdivided into balanced-pressure
thermostatic
traps,
liquid expansion traps, and bimetallic
traps.
All three subtypes
188
MIL-HDBK-1125/l
work by sensing the difference between steam temperature
and
cooler condensate
temperature,
utilizing an expanding bellows or
They usually discharge
bimetal strip to operate a valve head.
condensate
below steam temperature and therefore require a
collecting
leg before the trap to allow for some condensate
A balanced pressure thermostatic
trap is illustrated
in
cooling.
Thermostatic
traps are typically used in low and
Figure 117.
medium pressure applications
euch as steam radiators,
submerged
heating coils, and steam tracing lines.
r
AC
TI
VE
-1
-1
Figure
Thermostatic
117
Steam
Trap
IN
Float and
3.6.11.2
E.lost and ~static
Steam=.
thermostatic
steam traps (Figure 118) are recommended
for use
wherever possible.
Their valve seat is always under water,
preventing
any eteam loss.
The discharge is continuous
and
modulates with the condensing
rate, and it is unaffected
by
changes in inlet pressure.
A separate thermostatic
air vent
independently
purges air, giving a faat start-up, and discharges
in parallel with the main valve aeat without affecting its
TypiCal
applications
of float and thermostatic
traPs
operation.
are air unit heaters, hot water heaters, heat exchangers,
and
converters.
189
MIL-HDBK-1125/l
!’!!-
Figure 118
and Thermostatic
Steam Trap
AC
TI
Float
VE
outlet
IN
3.6.11.3
pisc/Thermodynamic
Steam TraDs.
Oisc/thermodynamic
traps (Figure 119) are widely used due to their small size, wide
pressure range, one moving part, and resistance to water hammer
and corrosion.
Because operation
of each model depends on the
manufacturers
seat and disc design, results may widely vary.
Many are prone to air binding on start-up, operate below steam
temperature
(causing water logging), have a relatively
short life
due to soft seat and disc materials,
and contain a bleed slot
which causes rapid cycling and steam loss.
Properly designed
di’sclthermodynamic
traps can overcome these problems and allow
effective and efficient operation.
They are typically used on
high pressure or superheated
steam drip legs, steam trace lines,
and unit heaters.
3.6.11.4
aDs . Inverted bucket traps
J~
(Figure 120) have been in existence
for many years, and their low
initial cost helps keep them popular, although in every
application
superior results can be obtained with another type of
trap.
They consume a small amount of steam in operation and can
blow fully open if they lose their prime due to oversizing
or a
rapid drop in inlet pressure.
Their discharge is intermittent,
not continuous.
Typical applications
include high pressure
indoor steam main drips and submerged
heating coils.
190
MIL-HDBK-1125/l
(
Olec
Cond.n.at(
VE
Steam
w
lW
TI
—
IN
AC
Figure 119
Disc/Thermodynamic
Steam
191
Trap
MIL-HDBK-1125/l
—
VE
--
IN
AC
TI
:ond. namte
Figure 120
Inverted Bucket Steam
Trap
3.6.12
~ina
svstems.
Piping (and tubing) systems are used
in the central boiler plant to transport a wide variety of
water, steam, oil, natural gas,
fluids, including,
among others:
and compressed
air.
The following section is intended to provide
a brief overview of some of the components
and considerations
that are involved in piping and tubing systems.
The word
“piping” in this handbook can generally be assumed to mean both
pipe and tube.
Strictly speaking, however, there is a difference
between pipe and tube, and this is discussed briefly in
par. 3.6.12.3.
3.6.12.1
D
ian Codes.
Design of boiler plant piping is
generally g%rned
by design codes and industry standards.
ASME ~
Bo” e a d
od , Section I, which was
192
The.
MIL-HDBK-1125/l
discussed
in par. 3.2.1 as it applies to boilers and accessories,
also covers certain portions of the piping around the boiler.
Much of the balance of the piping in a boiler plant ie covered by
the American National Standarda
Institute (ANSI) B31.1, ~
Some
additional
design
codes
and their applicability
are
RiQi.D9.
given in Table 17. These design codes generally specify
materials
that may be used wi,thin their scope, how piping sizee
and thicknesses
must be determined,
how pipe must be supported,
what types of fittings,
joints, and accessories may be used, and
other provisions.
Although these codes are written primarily for
the piping designer or engineer, a general knowledge of their
provisions
is useful to the operator as well.
IN
AC
TI
VE
(
3.6.12.2
Piping materials are generally specified by
The most common
the design code under which the eystem is built.
Steel pipe is
piping material in the boiler plant is steel.
strong, relatively
easily worked, and available in a wide variety
of sizes to fit most application
of pressure, temperature,
and
fluid.
Other piping materials which are used for specific
aeeliyations
include copper, stainless steel, cast iron, and
plastlc.
Some common applications
of various materials are
included in Table 18.
3.6.12.3
x.
Standard specification
of size is the primary
difference
between pipes and tubes.
Pipe size is specified by
nominal pipe size (NPS) and schedule.
Tube size is given by
outside diameter
(OD) and wall thickness.
Pipe Size.
Nominal pipe size (or NPS) refers to
a)
the diameter of the pipe.
Nominal pipe sizes range from 1/2 inch
up to at least 30 inches, in standard increments.
The OD for a
given NPS is always the same, while the inside diameter varies
depending
upon the schedule.
Schedule refers to the wall
thickness and is generally
listed as Schedule 40, Schedule 80,
Schedule 160, etc.
Earlier practice, which is still used on
occasion, was to refer to schedules by designation
such as
Standard
(STD), Extra Strong (XS), or Double Extra Strong (XXS).
Dimensions
and tolerances
corresponding
to nominal sizes and
schedules are established
by ANSI standards.
There is no easy
way, other than referring
to a chart, to determine the actual
dimensions
of a given nominal pipe size.
For instance, l-inch
NPS, Schedule 80 pipe has an outside diameter of 1.315 inches, a
wall thickness of 0.179 inches, and an inside diameter of 0.957
inch.
193
MIL-HDBK-1125/l
--,
Piping
Codes
Table 17
and Standards for Boiler
Title
.
Plants
Coverage
I
I
Rules
ha.er 85i Lers
construct
for
ian
ofpower
%.irene.t.
fo.h-tiw
N
Ieatirtq
Section
VI
:are of Heating
ml lers
Section
VII
:are of Po.er
‘ressure
Remhmended ru(es for the care and
operation
of heating bsi lers
Recommended r.kes
ki lers
soilers
Ru(es for
Vessels
uelding
Ietding
oualif~cati.ms
Sect ion 1X
~ouer Test
PA
procedures
of pre.ssu+e vesse(s
and quaiificatians
TI
units
ALI boiler
jurisdiction
plant piping beyond the
of AS14EWV 1
~ower Piping
B36 Series
[ron and Stee(
Pipe
Ifatmials
anddimensions
B16 Series
Pipe, FLangea,
Fittings
and
Hater iaLs, dimensims,
stresses,
pressurelt ●mperature ratings
IN
AC
MA
the Csre of WJer
S31.1
B18 Series
TH
for
construction
Steam generation
Codes
ASHE L.1
SI
~i~-~
soilers
VE
Section
biler.
Bolts
SnLted connections
and Nuts
resti~
Physica[ properties
of msreria(s
~“ ASME and ANsI cedes
f!nterials
TUG and SI!20
steam Turbines
30
Comb.st ion Liquids
[de
31
3il
8501
Fuel Oi ( and Natural
Gas
8urning
and
I
Allouab(e
turbines
specified
reactions
and movements on
from piping
Flamcwb[e and co.busrib~e
Standards for the
equipment
i.sta[lat
liquids
cede
ion of oi t
Equipmentbvr.inq
85B
Natural
Burners
85D
Fuel Oil
Ewrner.
85E
Pu(verizc-d
Coal
8503
Pulverized
F“e[
Gas f!uLti D[e
Ilultipt
194
Standards for prevention of furnace
explosions
in fuel oi( and natural
gas
fired
single burner boiler
furnaces
Standards for prevention
of furnace
cxp(osions
in natural gas fired multiple
burner boiler
furnaces
Standards for prevention of furnace
explosions
in full oi( fired multiple
burner boiler
furnaces
Standards for prevention of furnace
explosions
in pulverized
coa~ fired
multiple
burner boiler
furnaces
Standards
operation
for the instal(aticn
of pulverized
fuel
and
systems
MIL-HDBK-1125/l
(.
Typical
Material
Typical
I
Piping
Table 18
Material
Application
Typical
Applications
Jointe*
Screwed, socket- or
butt-welded,
flanged
High preseure eteatn, water,
fuel oil, compressed air,
and natural gae. Almoet any
fluid, with the exception of
certain corrosive types, up
to about 750 degrees F
,OW Alloy
;teel
Superheated
eteam,
1,000 degreee F
;tainless
iteel
Chemical and corrosive
applications**,
eteam above
1,000 degreee F, instrument
tubing
Socket- or butt-welded,
flanged; tubing may us<
flared or compression
fittings
:ast Iron
Floor and roof drains; water
supply, eanitary piping; low
pressure and temperature
applications
Bell
Plumbing, potable
instrument
tubing
Soldered, flared, or
compression fittings
Helded
and
TI
Plastic
(Pvc, ASS)
●
up to
water;
AC
Copper
II
VE
:arbon
;teel
Sanitary drains, nonpotable
water; miscellaneous
low
lpressure applications
mechanical
spigot,
groove-lock
jointa
Solvent
welded
..
IN
Selection of proper joint must be based on design code.
‘+ Extreme care must be used in selection of proper alloys
for corrosive
service.
b)
Tubing Size.
Tubing size is specified by OD and
wall thickness.
Although
tubing theoretically
is available
in
almost anv diameter.
ranaina from a few hundredths of an inch UD
to severai feet, in”prac~ic~,
tubing in a boiler plant is limit~d
to sizes of about 1/8 to 1 inch.
Tubing in common use in the
boiler plant is generally either copper or stainless steel.
The
major exception to this rule ia within the boiler itself.
Boiler
manufacturers
generally use tubing rather than pipe, and for the
most part use carbon or low alloy steel.
be sized
quantity
Determination
of Proper Size.
Piping systems must
c)
with regard to a number of criteria, including type and
of fluid to be transported,
pressure and temperature
195
MIL-HDBK-1125/l
These
conditions,
allowable velocities,
and Pressure 10ss.
calculations
can become quite sophisticated
and are outside the
The pertinent design codes should be
scope of this handbook.
consulted
for guidance.
VE
~.‘tt”
Pipe and tubing may be joined in
3.6.12.4
a variety of ways, including threading,
welding, flanges, a
variety of mechanical coupling joints, eoldering
(for copper and
These methods are
brass), and solvent welding (for plaetics).
common, and the type used in a particular
application
ie ueually
In steel piping, high pressure
specified by the design code.
systems such as steam or boiler feedwater commonly use welded
joints, as do systems which are larger than approximately
2 to 3
inchee in diameter.
Smaller diameter systems in eteel pipe may
Flanges are often used when
be threaded or socket welded.
piping must be disassembled
periodically,
for instance to Perform
Fittings and flanges
maintenance
on valves or other components.
are available in materiale and thicknesses
to correspond
to
pressure and temperature
requirements
of the piping eystem.
TI
Proper support of piping systems
3.6.12.5
PiDe SUDD orts.
requires sophisticated
design calculations
and is outside the
scope of this handbook.
Some of the general criteria that must
be considered
in making these calculations
are discussed below.
AC
The design codes for each
a) Allowable Stress.
application
generally provide allowable
stress levele for each
material.
These levels have been determined
by experience
to
have adequate safety margin, and they must be adhered to.
Allowable
stress for a given material is a function of
temperature
and decreases at higher temperatures.
IN
As the temperature
of a
b) Expansion/Flexibility.
pipe changes, the pipe moves due to expansion and contraction.
Provisions
must be made in the piping support system to
accommodate
this movement by providing piping flexibility
through
joints.
The required amount
bends , expansion loops, or expansion
of expaneion must be determined
by calculating
the stress level
in the pipe and ensuring that it is less than the allowable
stress.
An almost infinite variety
c) Anchors and Supports.
of anchors, hangers, and supports may be seen in central boiler
plants.
A variety of hanger types has been standardized
by the
Manufacturers
Standardization
Society (MSS), and some of these
are illustrated
in Figure 121.
Custom designed supports using
structural
steel shapes and standard hardware are aleo common.
196
MIL-HDBK-1125/l
(
1
I
EM
VE
.
UVI1 PIN
EM
AmoPe!l
Ialufsllw.)
AC
I
TI
m
nnlns wm
II?Qlol)
IN
I
ml
—.
4
PIE
MLm
SPRING H4NGER
Standard
Figure 121
Hanger Types for Piping
197
Systems
MIL-HDBK-1125/l
VE
Valves are available in a wide variety of
3.6.12.6
Valves.
types, materials,
and pressureltemperature
ratings to correspond
‘to the system in which they are used and their purpose in that
Some types of specialized
valves ark discussed elsewhere
system.
in the manual (gage cocks, par. 3.2.2; safety valves, par. 3.2.5;
boiler outlet valves, par. 3.2.6; blowoff valves, par. 3.2.7;
Several additional common types are
control valves, par. 3.4.1).
Specific applications
should be discussed with
discussed below.
the manufacturers
representative
to ensure the correct. body and
internal materials,
seat design, packing design and material, and
other details.
Valves can serve many different
Function.
a)
Broad categories
of valve” function
functions in a piping system.
(on-off), throttling
(control), backflow
include: isolation
prevention,
pressure relief, and regulation.
AC
TI
Gate
Valves.
The gate valve is the simplest in
b)
Gate
design and operation and is commonly used in boiler plants.
They
valves are used where minimum pressure drop is important.
are employed where the valve will operate in a wide open or fully
Gate valves
closed position and is to be operated infrequently.
are not designed for throttling
operation,
and under prolonged
use in a partially open position damage to the seat or disc may
A solid wedge type of gate valve is illustrated
in
occur.
Figure 122.
IN
The globe valve is used primarily
Globe Valves.
c)
for throttling
or positioning
to create a definite pressure drop.
Globe valves are available in the common partial globe and seat
contact type, the small needle type, and numerous variations
such
post-guided,
angle, Y-pattern,
fluted, and cageas top-guided,
guided.
Because of their inherent ability to exhibit repeatable
flow curves, they are the most commonly used type of valve for
control valve application.
Globe valves can also be used in onoff service where pressure drop in the fully open position is not
of primary importance.
Normally, globe valves are installed with
the flow under the disc, but in certain cases where it is
desirable to have line pressure assist in maintaining
seat
closure, flow may be directed over the disc.
In motor- and airactuated valves, this flow direction
is very important in sizing
the actuator.
A standard single-port
globe valve is illustrated
in Figu”re 123.
198
MIL-HDBK-1125/l
VE
i
Olsc
AC
TI
o
Figure 122
Wedge Disc Gate
Valve
IN
Solid
199
MIL-HDBK-l125/l
[email protected]
PACKING GLANO
PACKING
/[email protected]?
TI
VE
018C
mov
F
Figure 123
Single-Port
Globe
Valve
IN
AC
d)
Pluq Valves.
The plug valve is a refinement of the
Basically,
it is a 90-degree
earliest known vaive, the spigot:
rotation from open to cloeed position of a tapered inner valve.
The downward thrust of the plug taper exerts a compression
load
on the side wall, thus ensuring a continuous
circumferential
sealing surface.
Like the gate valve, it is used primarily in
The plug valve has the added benefit of
on-off service only.
bubble-tight
sealing, thus making it ideal for gaseous service.
because of its large unobstructed
flow passage, the
In addition,
A typical plug
plug valve is ideally suited for slurry service.
valve is illustrated
in Figure 124.
Butterfly valves have been used
Butterfly Valves.
e)
in industry for decades, performing well-defined
tasks in which
Some
they show distinct advantages
over other valve types.
butterfly
valve designs can provide dependable
bubbletight
shutoff, and others are ideally suited for throttling or control
applications,
having an equal percentage
flow characteristic,
Butterfly
valves are quick opening and highly efficient, can be
operated manually or automatically,
and can be used in handling a
variety of media, including liquids, solids, slurries, gases, and
vapor (steam) . Figure 125 illustrates
a typical butterfly valve.
200
VE
MIL-HDEIK-1125/I
[
INSERT
TI
‘=A1
IN
AC
Figure
Nonlubricated
201
124
Plug Valve
MIL-HDBK-1125/l
.
.
AC
TI
VE
~ua
Figure 12S
Butterfly Valve
IN
Check valves are designed for use in
f) Check Valves.
a piping system where protection
against the reversal of fluid
During operation,
liquid or gas pressure will
flow is desired.
move the disc off the valve seat and allow fluid to flow through
If the fluid flow ceases
m~nimum
pressure drop.
the valve with
or reverses direction,
the reverse fluid flow and design of the
disc assembly will force the disc against the seat to prevent
The disc weight, seat configuration,
and
fluid back flow.
internal spring assistance
(if provided) contribute
to the ease
with which the disc opens or closes and to a leak tight seal when
Check valves can be obtained in a wide
in the closed position.
Two of the more
variety of styles to fit specific applications.
common types (swing check and spring-loaded
lift check) are
illustrated
in Figure 126A and 126B.
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MIL-IiDBK-1125/l
(
VE
Hinq8
TI
Disc
IN
AC
Figure 126A
swing Check valve
Y-Type
Figure 126B
Spring”Lift
Check
203
Valve
MIL-HDBK-1125/l
IN
AC
TI
VE
3.6.12.7
Insulation.
Insulation is used to reduce heat loss
from hot piping, eliminate condensation,
reduce heat gain on cold
Insulation types
piping, and provide personnel protection.
typically used in central boiler plant piping systems include
Jacketing or
fiberglass,
mineral wool, and calcium silicate.
vapor barrier is usually incorporated
over insulation to p~otect
insulation
material.
Common jacket materials
include alummum,
fiberglass cloth, and various other fabrics.
Asbestos insulation
The Navy
is no longer used because of potential health hazards.
has been removing and replacing asbestos materials in older
plants.
Prior to removing any insulation,
be sure that it has
been certified
asbestos-free.
204
MIL-flDBK-1125/l
Section
4:
OPERATION
IN
AC
TI
4.2
VE
4.1
This section discusses operation of
equipment that haa been deecribed”in
Section 3. Operational
recommendations
are made for steam and hot water boilers with
capacities
less than 200,000 pounds per hour of steam or lese
Comments are generally
than 250 million Btu per hour output.
based upon steam boilers producing saturated steam, although in
some cases, specific differences
are noted for hot water boilers.
Vessel code , Section VI or VII, NFPA 85
ASME ~ure
series standards, ASME CSD-1, and manufacturers
operating and
maintenance
instructions
should be carefully considered
in
addition to the following text.
Safe and reliable operation is
dependent to a large extent upon the skill and attentiveness
of
Operating
skill
the operation and maintenance
personnel.
requires knowledge of fundamental,
familiarity
with equipment,
and a suitable background
of training and experience.
4.2.1
Standard operating
Con_tiontz.
procedures
(SOP’s) should be prepared and posted in the boiler
The SOP should clearly indicate the sequence of actions to
room.
be performed for each unusual condition which could create a
hazard operational
interruption.
Examples of such unusual
conditions
include flame failure, loss of water, tube failure,
sudden loss of load, steam line failure, loss of electric power,
or control malfunction.
The exact order in which each valve,
control, and piece of equipment should be operated for a
Valves
particular
type of failure should be stated in the SOP.
The SOP
and equipment should be marked for easy identification.
MSY also be used to describe normal actions necessary to maximize
bo~ler and plant efficiency.
4.2.1.1
~
. Boiler plant operating
logs provide a means of recording data and maintaining
a history
of boiler plant performance.
Information
should be recorded at
specified time intervals.
This information
should include the
following:
date, time, operating equipment,
relative parameters
(pressure, temperature,
flow), energy in (fuel), energy out
(steam, electricity),
water quality, efficiency,
equipment
problems, and any work performed on equipment.
These data should
be compiled at the end of each month and reported on a monthly
log .
4.2.2
A boiler is eubject to damage and must be
tieDectim.
periodically
inspected by a qualified inepector to ensure that it
is in safe operating condition.
Boilers . muet
.
.be inspected as
required by MO-324,
on and Certtitlon
of Boilers and
~e
V~.
Details are included in Section 5.
205
MIL-HDBK-1125/l
Daily operation
requires the operator to be aware of normal
operation and to perform daily inspections
to ensure that
Abnormal operation
equipment is operating properly and safely.
should be logged and reported.
ales. The following codes provide rules
4.2.3
ica
ml
and practical guidance for the safe and effective operation
of
boilers and boiler accessories:
ende
~~
ende
ASME
Boiler
b)
ASME
es
Boiler and Pr essur e Vessel
ilera.
are
c)
14FPA National
Fire Codes,
d)
NFPA
National
Fire Codes,
e) NFPA National
Fuel Svs t ems.
Fire Codes,
Section VI,
Boil rs.
Code,
Section
NFPA
8501.
NFPA
8502.
NFPA
8503, ~ox
VII,
IN
AC
TI
P u 1ve rized
and Pressur e Veesel Code,
eati
tio
a)
VE
~ 0
Re
f)
ASME
CSD-1.
Specific plant SOP’s should
4.2.4
P r e D a r at”Ion for Start-uo.
be prepared and followed in preparing
for boiler start-up.
In
general, before lighting fire in a boiler the following steps
should be taken.
If possible,
4.2.4.1
Check instrumentation.
~nstrumentation.
operate control devices to prove operation,
freedom of movement,
Check that the boiler pressure
and function of limit switches.
gage cock is open.
4.2.4.2
Internal Insr)ectio n . Check that personnel and tools
Inspect furnace walls, boiler
have been removed from the boiler.
tubes, and flues to confirm that they have been cleared of slag,
soot, and deposits which could act as insulation,
thus reducing
heat transfer and boiler efficiency.
Slag, soot, and ash should
Check that
be removed as discussed in pars. 4.3.5 and 4.3.6.
doors and openings are closed.
Inspect and test operation of
4.2.4.3
Combustion
Eauioment.
combustion
equipment without lighting a fire.
Careful inspection
of a stoker or burner and their accessories
helps to prevent
forced outages.
4.2.4.4
Check the fuel storage system to ensure
Fuel SUDDly.
that there is enough fuel to meet boiler requirements.
For solid
fuels, check the fuel level in the hopper, as well as its size
206
MIL-HDBK-1125/l
and moisture content.
For oil, measure the quantity of fuel oil
by stick or gage.
Ensure that valves are properly aligned, and
that necessary pumps and regulating
valves are in operation.
Check that fuel oil ia available at the required pressure and
temperature.
If atomizing
air or steam is required, confirm its
availability.
For gas fuel, chedk for correct gas pressure and
valve positions, and for any signs of gas leakage from piping or
valves.
VE
4.2.4.5
Ensure that an adequate supply of
M=JdwEw.
Check
treated feedwater is available
at the proper temperature.
the level and temperature
of water storage tanks or deaerator.
.Check valve alignment
and boiler feedwater pump availability.
AC
TI
4.2.4.6
~.
check Operation’ and close
blowoff valves, water column, gage glass drains, and gage cocks.
Ensure that the gage glass is clean and well lighted.
Open the
drum vent and drain valve between header and nonreturn valves.
Open feedwater valves and admit water to the boiler slowly until
the water level is just above the lowest safe level.
Blow down
the water column and operate the cock ae a further check of water
level and to ensure that these appliances are in good working
condition.
If provided, check the operability
of the low-water
fuel cutoff.
On forced circulation
hot water boilers, start the
circulating
pump and, if a proof of water flow switch is
provided, prove switch operating
by shutting off and then
restarting
the pump.
4.2.4.7
-r
when provided.
Safetv C~.
Check limit
Clean the flame scanner
switches to prove operation.
lens
IN
4.2.4.8
~ce
purq~.
The furnace, boiler bank, economizer,
air heater, ducts, and pollution equipment must be adequately
purged before starting a fire.
CAUTION:
Many disastrous
explosions
are caused by
failure to vent the furnace and setting completely
before
attempting
to start a fire.
Explosive mixtures of air and gases
[email protected] accumulate and ignite if a fire is started without first
venting the furnace and setting.
To avoid this danger, open the
etack damper and operate necessary fans and dampers to purge the
furnace and attached equipment.
The purge air should be at a sufficient
rate to provide
adequate velocity to clear dead spots or i.nacti.ve pockets and
sweep the entire unit.
Purge airflow ratea of 25 to 75 percent
and purge time of 3 to 5 minutes, or eight air changes are
considered adequate.
A boiler must also be purged after an
accidental
loss of ignition.
207
MIL-HDBK-1125/l
After completing
the preparatory
steps
Startina Fire.
4.2.5
outlined above, combustion
equipment may be started.
recommendations
for equipment
start-up should be
Manufacturers’
reviewed and carefully
followed for each type of equipment and
General recoxmnendations are provided below.
fuel.
TI
VE
Ensure that ashes and clinkers are
4.2.5.1
Ht!d..
If lump coal is available,
spread a layer 3
removed from grates.
to 6 inches thick on grates to prevent fines from sifting
through.
When ash content of coal is low (under about 7
percent),
spread about an inch of ashes on grate before
introducing
coal.
Spread dry” wood, shavings,
or live coals from
naphtha,. or other
Gasoline,
an adjacent boiler on top of coal.
highly flammable liquids should never be used as kindling.
Partly open the stack damper and ash-pit doors to induce airflow
Light the kindling,
leaving the fire door
through the furnace.
After
partly open to admit air over the fire and reduce smoke.
regulate
the
damper
and
ash-pit
doors
to
the fire is started,
Supply
additional
maintain a draft and accelerate
combustion.
coal as required and control the rate of combustion
by regulating
airflow through the fuel bed.
IN
AC
Stoker Firina Coai.
TO start a fire on a mechanical
4.2.5.2
stoker, supply coal to the furnace by operating
the feed
Place enough coal
mechanism
or shoveling coal into the furnace.
into the furnace to cover the tuyeres of an underfeed stoker to a
6
inches, or the grates of a spreader stoker to
depth of about
Place wood, shavings,
or kindling on top of the
about 2 inches.
coal, and open the stack damper or operate the induced draft fan.
Maintain a slightly negative furnace pressure to remove products
Light shavings and regulate the draft as required
of combustion.
plante, fires may also be
In some
to keep the fire burning.
As soon as the
started with live coals from another furnace.
coal burns freely, operate the FD fan and regulate airflow to the
furnace with the blast gate or damper to control the rate of
combustion.
If the boiler heats up too rapidly, operate fans at
Do not add more
lower ratings or stop them for a ehort time.
When neither
coal to the furnace until the fire burns freely.
steam nor electric power is available to operate the fan and
stoker, feed the coal by hand and use natural draft until steam
pressure is high enough to operate the auxiliary eguipment.
When firing pulverized coal,
4.2.5.3
Pulverized
Coal Firing.
follow the procedures
outlined in NFPA 8502 and NFPA 8503, and
refer to the plant’s specific SOP.
4.2.5.4
Oil Firing,
Oil firing procedures
vary with the type
of burner, controls,
and fuel oil.
Some plants use No. 2 fuel
oil with pressure or steam atomizing burners, automatic controls,
and electric spark ignition.
Many installations
use No. 4, 5, or
208
MIL-HDBK-112511
(
6 fuel oils with either air, semiautomatic,
or automatic ignition
procedures.
In every procedure an important step is the
If ignition is delayed,
purging of the boiler furnace.
immediately
determine the cause and correct the problems.
TI
VE
Heavy oils (Nos. 5 and 6,
the Fuel Oil.
a) Preheating
and sometimes 4) require heating to reduce the oil viscosity to a
point where pumping is practical.
Additional
heating may also be
required to optimize atomization.
Pump and burner manufacturer
viscosity
recommendations
should be followed.
Steam or electric
tank heaters are ueed to heat oil to a temperature
of 90 to 110
degreee F, with oil preheater
supplying additional
heat as
needed.
To determine
the amount of preheat temperature
necessary
for a given oil, consult the burner manufacturer
for an initial
recommendation.
Experimentation
ia often necessary to determine
the temperature
that works best for the particular
installation.
One hundred to 300 Saybolt seconds universal
(SSU) viscosity is
usually desirable
for Nos. 5 and 6 fuel oils.
No. 4 may also
need some preheating
depending
on the type of atomizerfburner
and
the particular
oil.
No. 2 oil rarely needa preheating,
but
outside storage in cold climates may necessitate
preheating to
room temperature.
Gas igniters or pilots are usually used to light off
light oil burners.
These igniters typically use an electric
spark to ignite the gas.
If the igniter flame is seen by the
flame scanner within a 10-second trial for ignition, the oil
safety shut-off valve is opened, either manually or
automatically.
The oil control valve should be at its low fire
position and is often interlocked
in this position.
Fifteen
seconds after the oil shutoff vale is opened, the igniter is shut
off.
If the flame scanner still seee flame, the burner will
continue to operate.
If no main flame is seen at this time, the
The boiler should be repurged before a
shutoff valve is closed.
second trial for ignition ie made.
LOSS of main flame or other
safety interlock limits as shown on Figures 51 and 52 will result
in the safety shutdown of a burner.
IN
.
AC
b) Lighting Burnera.
Before lighting off a burner,
always check for proper oil pressure, temperature,
and atomizing
air or steam pressure.
Purgs the unit and establish airflow
suitable for light-off.
4.2.5.5
Gas F-.
The ignition of a gaa burner is always
accomplished
with the use of a gas igniter, flame scanner, and
flame safeguard control.
Purging the boiler is required before a
trial for ignition.
Proper gas pressure should be available to
both the igniter and main burner, and the gaa control valve
should be in its low fire position.
The semiautomatic
or
automatic
light-off sequence is identical to that for oil burners
209
MIL-HDBK-1125/l
except the trial for ignition of main flame is only 10 seconds.
Loss of flame or boiler and burner limits shown on Figure 52 or
The boiler
Figure 53 will result in the shutdown of a burner.
be
repurged
before
a
new
trial
for
ignition
may
be
furnace must
attempted.
AC
TI
VE
The time required to bring a boiler up
“ e.
4.2.6
K5Kllt4~
to line pressure or temperature
is dependent on many things,
including the size and type of boiler, its operating pressure or
temperature,
the combustion
equipment,
and whether or-not it is
Manufacturer’s
detailed
equipped with a superheater.
instructions
should be followed to minimize thermal atr,eases as
In general, boilers out of
the boiler heats up and expands.
service long enough to cool down to room temperature
require 1/2
If a new boiler or one
to 2-1/2 houra to reach line Pressure.
with extensive
repairs to the furnace or setting is being placed
in service, sufficient
time must be allowed for brickwork to dry
out . Operate the boiler on low fire for several days before it
If the boiler is equipped with
is actually placed into service,
take extra precautions
to prevent it from
a superheater,
overheating
by firing at a low rate during the warm-up period,
and by allowing a small amount of steam to flow through the
superheater.
Leave the outlet drain from the superheater open so
that some steam flows through the tubes as pressure builds up.
This steam will help to cool the superheater
metal, and prevent
tube damage.
IN
When
P 1ac”n
I a a Hiqh Pressure Steam Boiler in Servi c e.
4.2.7
steam
is
discharged
from
the
water in the drum begins to boil,
When boiler pressure reaches about 25 psig, air will
drum vent.
If the bo~ler
have been removed, and the vent should be closed.
does not have a vent, use the gage cocks to allow air to escape.
Carefully
observe the fire while the pressure is increased, and
If the firing rate ia
maintain minimum stable firing conditions.
too high on multiple burner boilers, shut off some of the
Rotate operation of burners to promote uniform heating.
burners.
If the firing rate is too high on a stoker-fired
boiler, shut off
the FD fan for a period and operate on natural or ID only.
Observe water level frequently
t
evel.
4.2.7.1
~
Increasing
temperature and the
during the warm-up period.
To avoid
formation of steam causea the boiler water to expand.
high water levels, start the boiler with the water level just
above the lowest safe level.
If necessary,
open the blowdown
valvee and remove water to prevent high level conditions.
Valves.
~ he
4.2.7.2
“
Safety valves should be tested
Do this when steam preesure
periodically
by hand lifting them.
in the boiler is at least 75 percent of the set pressure of the
lowest safety valve.
Care should be taken to hold the valve open
210
MIL-HDeK-1125/l
VE
wide and release the hand lever briskly, so that the valve closes
with a enap.
At intervals, ae required by the Authorized
Inspector,
safety valves muet be teeted by raising the boiler
pressure to the set pressure of the safety valve to ensure that
When a safety valve fails to
it pops and reseats correctly.
operate, do not attempt to free,it by etriking the body or other
If a safety valve leaks or fails to operate
. parta of the valve.
properly,
remove the boiler from service immediately and repair
or replace the valve.
Checking of safety valves by raising
pressure on the boiler must be under direct supervision of a
designated,
qualified employee.
AC
TI
4.2.7.3
er Val veQ . When placing a boiler into
service, care must be taken to avoid water hammer and expansion
When
stresses associated with large temperature
differentials.
other boilers on a header are already operating, the steam line
from the boiler being started must be brought up to temperature
by operating
the bypass and drain valves-to create a flow of
When the line is up to temperature and
steam from the header.
pressure,
the header gate valve may be opened wide and the bypass
closed.
The nonreturn valve should be opened to a 25 percent
position until the boiler etarts to supply steam to the header,
after which it may be fully opened.
In the absence of a
nonreturn valve, the boiler stop valve should be opened slowly
when pressure in the boiler and header are approximately
equal.
If a boiler is being put into service on a header which is not
under pressure, it is desirable
to warm up both the boiler and
steamline/header
together.
In this case, open both the stop and
nonreturn valves and make sure the steam header drain valves are
open to remove any condensate
formed.
4.2.7.4
When the boiler is producing steam
&ct ivate Con~.
and is properly connected to the header, place the feedwater and
combustion
controls into automatic operation in accordance with
the manufacturer’s
recommendations
and instruction.
IN
(
4.2.8
ter
Ser L.Gf4. The following
general procedures
should be followed for p~acing a single LTW,
MTW, or HTW boiler into service.
Procedures are aleo included
for placing additional boilers into service on multiple boiler
installations.
4.2.8.1
for a
after lay up, proceed as follows:
of burner
Review manufacturer’s
a)
and boiler.
b)
Fill boiler
and
When
recommendation
system;
system.
211
starting
a boiler
for start-up
vent air at high point
in
MIL-HDBK-1125/l
d)
regulator
and high
“OPEN”
e) Make
dampers
f)
Check
9)
Vent
h)
Clean
switch
availability
glass
to ensure
in “OFF” position.
sure fresh air to boiler
are open.
combustion
tank
room
is unobstructed
of fuel.
chamber
on flame
to remove
scanner,
unburned
gases.
if provided.
of water pressure
i) Observe proper functioning
and turn circulator pumps on electrically.
.
for proper setting.
j) Check temperature control(s)
k) Check manual
limit temperature
1) Set manual
position.
m)
position.
n)
reset button
control.
fuel oil supply
Place
circuit
Place
boiler
Place
on.
boiler
breaker
Do
emergency
not
on low water
or manual
gas valve
or fuse disconnect
switches
fuel cutoff
in
in “ON’”
in “ON” position.
control starting switch in “ON” or
stand in front of boiler doors or
IN
0)
“START” posit
breaching. )
TI
V
and manual
Set control
gage and expansion
E
c) Check altitude
is properly filled.
AC
system
Do not leave boiler unattended
until it reaches the
establishe~’cutout
point to ensure that controls shut off the
burner.
and pressure build-up period,
q) During temperature
walk around the boiler frequently to observe that associated
equipment and piping is functioning properly.
Visually check
burner for proper combustion.
after burner shuts off, inspect water
r) Immediately
pressure and
open the highest vent to determine that system is
completely
full of water.
s)
Enter
(1)
in log book:
Date and time
of start-up.
212
MIL-HDBK-1125/l
(2)
action
established
observed
and corrective
(3) Time when controls shut off burner
temperature,
tests performed etc.
(4)
Perform
Any irregularities
taken.
Signature
t) Check safety
try lever test.
at
of operator.
relief
valve
for evidence
of leaking.
VE
If any abnormal
4.2.8.2
conditions
occur during light off or temperature
build-up,
immediately
open emergency ,switch.
Do not attempt to restart the
unit until difficulties
have been identified and corrected.
AC
TI
. .
~Q”
. When placing
4.2.8.3
a boiler on the line with other boilers which are already in
service, start the boiler using the above procedures,
but have
Bring the second
ite supply and return stop valves closed.
boiler to the same temperature
as the operating boiler and
partially open the supply valve(s).
If there is no unusual
disturbance,
such as noise, vibration,
etc., continue to open the
valve slowly until it is fully open.
Open the valve in the
return line.
Caution:
When the stop valve at the boiler outlet is
closed, the stop valve in the return line of that boiler must
alao be closed.
4.3
and Proc~
IN
4.3.1
Basic boiler operation consists of
supplying fuel to generate steam (or hot water) as required by
system demand, and supplying air in the correct proportion
to
efficiently
burn the fuel.
The rate of fuel feed used to
maintain steam pressure or water temperature may be controlled
either manually or automatically.
In supplying air to the burner
or furnace, both the quantity and its point of application
for
optimum combustion
must be considered.
Other facets of boiler
operation
include feedwater supply, which must be introduced
in
proportion
to quantity of eteam discharged,
and operation of
pumps, fans, dampers valvea, controllers
and fuel handling
equipment,
all of which are used to maintain proper flow of
materials
to and from boiler.
4.3.2
. Pressure gages
indicate the difference
between pressure inside the boiler and
atmospheric
pressure.
Pressure on each square inch of internal
surface ia expressed ae pounds per equare inch gage (psig).
For
213
MIL-HDBK-l125/l
VE
steam boilers the pressure gage indicates if the firing rate h
If the rate of steam flow from a boiler
properly adjusted.
“increases, the pressure drops because heat i? carried away faster
than it is being supplied, and the firing rate must be increased.
If steam flow decreases,
the pressure increases and the firing
For hot water boilers, the temperature
rate must be decreased.
If the boiler
gage is used to indicate the proper firing rate.
outlet temperature
falls below the set point, the firing rate
If the outlet temperature
rises above the
needs to be increased.
If manual control
set point, the firing rate must be decreased.
is being used, the operator notes changes to pressure or
temperature
and adjusts the fuel and air supply accordingly.
Automatic combustion
controls, as discussed
in par. 3.4.2, sense
pressure or temperature
changes and automatically
adjust” fuel and
Automatic
systems relieve the operator of the
air supplies.
tedious and continuous
adjustment
necessary with each change in
demand.
AC
TI
Feedwate r and Boiler Wate r Tr eatmen t . Feedwater must
4.3.3
be supplied to the boiler at an acceptable
temperature
to avoid
thermal shock and excessive stresses on the boiler pressure
Water must also be treated to minimize corrosion and
parts.
scale formation in the boiler and the distribution
system and
Refer to MO-225.
optimize heat transfer and boiler efficiency.
IN
Feedw ter.
~
Hot water boilers operate with
4.3.4
constant water flow rates and do not require feedwater controls.
Water flow to steam boilers must be regulated
so that 1 pound of
The gage glass,
water replaces each pound of steam generated.
try cocks, and other water level indicators
are used as guides in
Visible water level is not
controlling
water flow to a boiler.
always a true indication
of the amount of water in a boiler
because steam bubbles, as well as water, are contained
in the
water space and cause the water to swell.
If the steaming rate
decreases, the amount of steam bubbles decreases,
the water
shrinks, and the water level drops.
The tendency of water level
to vary with steaming rate is known as “swell” and “shrink.”
Swell and shrink must be taken into consideration’in
controlling
water flow so that the flow varies properly with steam output.
The types of feedwater controls available are discussed in par.
3.4.1.
Most feedwater controls on small boilers are of the
Although they
single-element
type, and sense only water level.
do a very good job on most boilers, they cannot compensate
for
swell and shrink.
Where swell and shrink become a problem, twoand three-element
feedwater controls are available to provide
improved control.
Boiler Accessories.
4.3.5
columns, gage glasses, safety
blowers are outlined below.
Operating
procedures
for water
valves, blowoff lines, and soot
214
MIL-HDBK-1125/l
. If water level is too
4.3.5.1
If water
low, the boiler may be severely damaged by overheating.
level is too high, water may be carried out with steam, resulting
in damage to enginea and turbines and causing deposits to form in
A gage glasa, try cocks,
piping, valves, and other equipment.
high- and low-level alarms, and. various other indicating and
recording devices are used as guides in maintaining
proper water
level.
The gage glass and try cocks are the most reliable and
should be used as the final check when the various devices
dieagree.
Leaks.
b)
glasses to avoid
Promptly repair leaks in pipee,
false water level indication.
valves,
or
TI
gage
VE
Removing Sediment.
Sediment collects in the water
a)
so the gage
column and, in time, will obstruct the connection
To ensure correct
glass and try cocks do not show correct level.
the water column and gage glass must be blown down
indication,
Once per shift is the recommended
interval.
Lines
regularly.
from the boiler drum to indicating
and recording devices should
be blown down daily.
AC
Gage glasses have valvee at both top and
c1 Valves.
bottom.
Hand-operated
valves are ueually supplied with chain
operatora
so that if the glass breaks, the operator can close
valves and avoid danger of burns from escaping steam and hot
water.
Some gage glaas valves are automatically
closed by the
Determine the type
rush of steam and water if the glass breaks.
of valves employed on gage glasses and decide in advance what to
do in case of breakage.
To replace a broken
d)
Replacement
of Gage Glass.
gage glass, remove packing nuts, packing, and broken pieces of
Tighten packing nuts
glaes.
Insert new glass and packing.
carefully.
Turn on upper steam valve first to heat the new glass
uniformly.
Goggles and wire mesh or canvas screen should be
provided when first putting pressure on gage glass.
IN
(
If valves are
e) Valves in Water Column Line.
supplied in the lines from the drum to the water column, they
must be sealed or locked open.
4.3.5.2
Valv~.
Safety valves are designed to remain
=etv
If load drops and fuel
closed under normal operating condition.
supply is not readjusted quickly enouqh, the eafety valve opens
to relieve the increased pressu;e.
Opening of saf&ty valvei
causes discharge of steam or hot water into the atmosphere
and
results in a loss of heat,
Although it may be assumed that the
215
MIL-HDBK-1125/l
original safety valves were of sufficient capacity,
larger
capacity may be required when a coal-fired boiler is converted
oil or gas firing.
to
IN
AC
TI
V
E
Adjustment
and sealing of safety
a) Adjustment.
valves must be performed
only by properly trained and authorized
personnel,
such as qualified
boiler inspectors and factory
A safety valve normally requires two
representatives.
For boilers
adjustments,
popping pressure and blowdown.
operating
at pressures of 250 psig or below, the popping pressure
can be adjusted over a range of 10 percent above or below the
pressure for which the valve is designed, by varying the
A new spring must be. installed
compression
of the valve spring.
Blowdown is varied
if the desired adjustment
exceeds 10 percent.
e
The ASME $3
by means of an adjusting
ring.
~
Co e requires that safety valves be adjueted to close
after blowing down not more than 4 percent of the set pressure
It also requires that the blowdown be
but not less than 2 psi.
not less than 2 percent for pressures between 100 and 300 psig.
Lifting levers are provided to lift the valve manually to check
When using” the
its action and blow any dirt away from the seat.
lift lever, the boiler pressure should be at least 75 percent of
Use these levers to test safety valves.at 30the set pressure.
day intervals to ensure that the valve disc does not stick to “the
seat.
Once a year, a test should be made by actually raising the
When
boiler pressure to check the valve setting and blowdown.
the lifting lever is used, raise the valve disc sufficiently
to
This
ensure that foreign matter is blown from around the seat.
will help to prevent leakage after the valve is closed.
Testing clamps or gags
b)
Hydrostatic
Test Caution.
are often used to hold the valve discs on their seats during
hydrostatic
tests.
When this is done, ensure that the clamps are
Also
not over tightened,
as damage to the valve stem may occur.
take every precaution
to ensure that the clamps are removed as
soon as the test is completed.
Never use a test clamp to gag a
valve that is leaking.
of the safety valve(s) must
by the boiler without
allowing pressure to rise more than 6 percent above the maximum
allowable working pressure.
This capacity may be checked by
closing steam outlets and forcing the fire to the maximum.
If
pressure builds up more than 6 percent, additional valve capacity
is needed.
Safety valve capacity
for each boiler must not be
Vess
Code
less than the minimum ASME 0~ ‘ e
d
requirements.
When changing
from coal to oil gas firing, do not
overlook the increased safety valve requirements.
Capacity
c)
be
sufficient
Capacity.
to
discharge
The capacity
steam
generated
216
MIL-HDBK-112511
checks must be authorized
by the Public Works Officer and made
under the direct supervision
of a designated qualified employee,
an authorized
insurance ~nspector,
or a factory representative.
TI
VE
off
Boilers are equipped with blowoff lines
4.3.5.3
at the lowest point in the water system.
These lines are
neceesary
for draining and also to help control concentration
of
Thie concentration
ie determined by an
solids and sludge.
analysis of the boiler water and should be a routine part of
Blow down a specific quantity of water each
operating procedure.
Frequency
time, usually a few inches ae measured on gage glass.
of blowdown is based on results of water analysis.
Blowdown Procedure.
Open the quick-opening
valve
a)
Then open the slow-opening
valve fully until the
or cock firet.
required quantity of water ie discharged.
Do not open valves too
rapidly, as undue stress or damage to blowoff piping and
connections
may result.
Blowdown when the boiler is banked or
steaming at low rate is most effective in removing sludge and
Bottom blowoff connections
must be used to remove
solids.
sludge.
AC
Continuous
Blowdown.
b)
Surface blowoff connections
are also provided on moat steam boilers and when used on a
continuous
basis, are the most effective and economical means of
controlling
dissolved
solids.
Recovery of come of the heat from
the blowdown water can be accomplished
by use of a heat
If continuous
blowdown is used, the bottom blowdown
exchanger.
valves should still be used at intervals to prevent them from
becoming stuck or otherwise inoperative,
and to remove sludge.
The quantity and frequency of manual blowdowns are determined
by
the degree to which sludge accumulates
in mud drums and headers.
4.3.5.4
Flue gases carry ash and soot that act
~.
as insulators
and, when deposited
on boiler heating surfaces,
reduce the rate of heat transfer.
The extent of soot deposit
depends upon the fuel burned , completeness
of combustion,
and the
rating at which the boiler is operated.
When coal-fired boilers
are operated at high rating, aah and slag may deposit on tubes to
such an extent that gas flow is restricted
and draft loss through
the boiler increases.
Oil-fired
boilers seldom build up enough
ash to restrict gas flow, but heat transfer efficiency can be
affected,
Several cleaning methods are discussed below.
IN
(
Swinging-Pipe
Soot Blower.
Fire tube boilers may
a)
be cleaned while in operation by meane of steam jets operated
from outside the boiler setting.
Steam is applied to the pipe of
a swinging-pipe
soot blower with steam jets directed into the
boiler tubes.
The coot blower is rotated to direct the jets into
217
MIL-HDBK-112511
each tube.
After completing
the blowing operation,
the soot
,blower is moved to a position where it is protected from heat or
gases.
Fire tube boiler tubes should be cleaned daily.
VE
Swinging-pipe
soot blowers for
b)
Long-Handled
Brush.
fire tube boilers are convenient but are not satisfactory
when
Soot can be effectively
removed from the
boiler tubes are long.
The brush
tubes of fire tube boilers with a long-handled
brush.
should be just large enough to pass through the tubes.
Frequency
Goggles and
of cleaning depends upon operating conditions.
respiratory
protection
equipment should be used when cleaning
boiler tubes.
AC
TI
Many water tube boilers
Mechanical
Soot Blowers.
c)
These should be
are supplied with mechanical
soot blowers.
operated once every 8 hours, or an interval dictated by operating
To operate a soot blowing system, open the piping
experience.
system drains first, then slowly open the steam valve to admit
steam.
Completely
preheat and drain the piping system before
admitting
steam to the soot blower elements, as a small quantity
of water introduced
into a hot soot blower element can cause
serious damage.
Drain valves may be throttled but not closed
while the elements are being operated.
Increase the draft in the
boiler and furnace during soot blowing periods to prevent smoke
Soot blower
and to carry away material removed from tubes.
elements are operated by a handwheel or chain or in some cases by
an electric motor.
As the element is rotated, an automatic valve
opens and admits steam.
TWO rotations of the element are usually
Rotate
sufficient;
more rotations only result in wasted steam.
the element slowly for maximum effect.
Start the soot blowing
sequence near the furnace and progress toward the boiler outlet.
IN
d}
Hand Lancing.
If mechanical
soot blowers are not
A
available
or cannot be used, hand lancing must be employed.
practical
hand lance can be made from a section of l/2-inch pipe
of suitable length attached to a hose and supplied with 100 psig
air pressure.
When using a hand lance, care must be exercised to
prevent damage to furnace walls and baffles.
4.3.6
~
hand firing,
grate stoker
underfeed
follow.
Procedures for firing coal by
Procedures.
stoker, spreader stoker, and traveling
4.3.6.1
~
- Coki q. Coking allows time for escape of
volatile gases before coal is placed directly on the fuel bed.
First, place coal on the dead plate where radiant heat causes the
gases to be distilled off.
These gases mix with secondary air
coming through the damper in the fire door and burn as they pass
Coked coal is later distributed
over the
~~;
~~d hot fuel bed.
. Disadvantages
of this method are that smoke is
218
MIL-HDBK-1125/l
produced and the introduction
ok air causes ash and burning coke
However,
to mix and create clinkers, wasting both time and fuel.
this method of firing may be successfully
applied to small
furnacee operating at low rating.
VE
4.3.6.2
Satisfactory
Alt~.
na
combustion
can be obtained by use of an alternate method of
firing.
A layer of green coal is applied to one side of the
furnace.
Heat generated by combustion on the opposite side
causes volatile gases to be distilled off and accelerates
combustion.
The aeh-pit door should be closed during and
immediately
after firing to reduce smoke.
Keep the fire door
open about 1 inch for 1 to 3 minutes to supply sufficient
eecondary air to allow the volatile gases to burn off.
Despite
these precaution,
gasee may etill be distilled off more rapidly
than they can be burned due to the large eurface of green coal
exposed.
AC
TI
4.3.6.3
Sm~.
Spreader firing
na
conaiets of distributing
coal over the entire fire bed.
Thin
epots are obeerved by their bright appearance and additional
fuel
When
should be applied to keep the fuel bed uniformly thick.
correctly used, this method permits operation at high ratings.
Be sure to supply sufficient overfire air, as volatile gases are
quickly liberated.
Agitation of the fuel bed causes ash to come
into contact with the hot portion of fire, forming clinkers.
If
coal is properly placed, firing proceede without resorting to
agitation of the fuel bed.
4.3.6.4
Coarse pieces of ash and
clinkers that do not fall through the grates must be removed at
sufficiently
short intervals, or the air passages can become
restricted
and the rate of combustion
reduced.
One method of
cleaning grates consists of pushing burning coal against the
bridge wall, after which ash and clinkers can be removed from the
front.
This method has the advantage of being quick, but does
not remove all ash, as some always remains at the bridge wall.
A
more complete cleaning is accomplished
by the “side” method,
which consists of pushing good coal to one side of the furnace
and exposing ash and clinkers, which are then readily removed.
Burning coal ie then moved to the aide which has been cleaned and
remaining ash and clinkere are removed.
When shaking grates are
employed, a greater percent of aeh can be discharged
to the ash
pit and the work of cleaning fires is materially
reduced.
IN
(
4.3.6.5
Rate of combustion
is controlled
by the quantity of air passing
through the fuel bed, while efficiency of combustion
is
controlled
by the quantity and distribution
of overfire air.
To
regulate the rate of combustion,
change the furnace draft by
219
MIL-HDBK-1125/l
The fuel bed must be kept light (6
controlling
the stack damper.
If holes develop
to 8 inches) so that airflow is not retarded.
in the fuel bed, air will follow the path of least resistance
and
pass through the holes rather than the active portion of fuel.
Underf eed Stoker Firing.
Underfeed stokers admit coal
4.3.6.6
Gases distilled
from the
from underneath
the burning fuel bed.
Single
fuel pass up through the bed to accelerate combustion.
retort underfeed stokers are horizontal,
with coal being moved
Multiple
into the furnace and distributed
by mechanical motion.
retort underfeed stokers are inclined and coal movement is caused
by mechanical motion and force of gravity.
IN
AC
TI
VE
Adjust the stoker feeding
a) Adjusting Feed.
mechanism
(screw or ram) so that coal is fed to meet consumption
requirements.
If the stoker has an off-and-on control, adjust
the fuel and air feed so that the stoke? operates most of the.
Adjust the coal distributing
mechanism
(secondary arm) as
time.
If the
necessary to maintain sufficient coal to fill the retort.
After dumping ashes,
fire burns back, it will damage the stoker.
cover the ends of the grate bars adjacent to the dump grates with
coal.
The depth of the fuel bed above the tuyeres of singleretort stokers varies from 8 to 14 inches, and from 12 to 24
If the fuel bed
inches on high-rating
multiple retort stokers.
is too thin, increase coal feed without increasing
air until
normal conditions
are restored.
If the fuel bed is irregular,
Many
adjust the secondary feeding mechaniem or air distributor.
stokers have dampers that vary the supply of air to different
zones.
If a hole appears in the fire, the condition may be
If the fuel bed
corrected by reducing the airflow to that area.
is of correct thickness,
the rating is changed by varying both
air and fuel supply.
b) Ash Removal.
The procedure
for removing aeh
depends on whether stationary
grates, dumping grates, or clinker
grinders are used.
In all cases, burn coke thoroughly
before
dumping refuse into the ash pit.
Air must be passed through the
coke and ash for some time before discharging.
Do not introduce
too much air as fuel losses may result.
In cleaning the fires,
do not remove aches from the grate bars, instead, let them move
down by stoker action for removal at the next cleaning.
Underfeed
stokers
c) Agitation and Clinker Formation.
of
agitation
given
the fuel bed.
vary in the amount
In some
designs, coal is forced into the furnace and passed over
stationary tuyeres and grate; in others these parts move and
agitate the burning fuel bed.
Stokers that supply agitation are
best suited for burning coals having extreme coking tendencies
as
the movement tends to retard coke formation.
Burning coal of low
ash fusion temperature
on these stokers cauees clinkers when the
220
MIL-HDBK-1125/l
(
Clinkering
is
ash is pushed into the high temperature
zone.
greatly accelerated
when the stoker is operated at high ratings.
Work the fire as little as possible” to reduce clinker formation,
and remove clinkers that adhere to grates or side walla at once
with the least possible agitation of the fuel bed.
VE
d)
Underfeed stokers are operated with
Air Supply.
relatively
thick fuel bede and require a FD fan to supply air.
Best
The windbox preaaure varies from 1 to 7 inches of water.
results are usually obtained by operating with a slight draft in
the furnace. . Regulate windbox pressure to eupply the required
quantity of combustion
air and regulate the ID fan or stack
damper to produce the necessary draft to overcome resistance of
the boiler.
Thie draft regulation
ia often accomplished
automatically.
AC
TI
Lubricate moving parta according to
e) Operation.
manufacturer’s
instructions.
Keep efficient
coal in the retort
Do not
to prevent fire from reaching this section of the stoker.
Inepect windboxes each
permit ashes to fill the ash pit.
When
operating shift and remove any accumulation
of siftings.
banking the boiler, feed sufficient coal and renew the coal
Make frequent
supply as required during long banking periods,
inspections
of stoker and brickwork and report unusual conditions
so that repairs can be made before equipment ia seriously
damaged.
of
IN
4.3.6.7
Spreader stokers permit
burning of fine coal particles i; suspension
and the remainder
the coal on gratee.
Thie permite faster load response and
reduces clinker formation since the fuel bed on the grates is
quite thin.
Coal inventory in the furnace laata only a few
minutes.
Check the thickness of the fuel bed by stopping the
coal feed and noting the rate at which fuel on the grates is
burned.
If ashes are ready to dump after 3 to 5 minutes, the
thickness of the fuel bed is correct.
Adjust the
a) Adjusting Spreading Mechanism.
spreading mechaniam
for a uniform thickness of fuel over the
gratee to optimize mixing of fuel and air.
At the came time,
adjust the rate of fuel and air feed in correct proportions
for
efficient combustion.
1
b) Effect of Coal Size on Operation.
Spreader stokere
are not suitable for burning coal particles
larger than 1-1/2
inches, as they hinder operation of the feeding mechanism.
The
meet efficient eize of coal ie 1/4 inch, with not more than 40
percent passing through a 114-inch ecreen.
Satisfactory
results
can be obtained with sizes up to 1-1/2 inches.
The fine coal
burne in suspension with larger particlea
falling to the grates
221
MIL-HDBK-1125/l
where combustion
is completed.
Too much coal overloads the
grates.
In passing through bunkers or chutes, coal sometimes
If this occurs, the
segregates
into coarse and fine particles.
stoker will burn practically
all “fines” atone
time and all
coarse at another, resulting in variable and inefficient
operation.
E
Clean the fires at regular intervals,
c) Ash Removal.
usually twice each operating
shift or when ashes are from 3 to 6
inches deep on grates.
If the grates are divided, clean one zone
at a time.
Shut off the coal flow and wait 3 to 5 minutes with
the FD fan on for the remaining coal to burn.
Do not allow the
bed to become too thick or clinkers will form.
Remove the ash
deposit promptly from the ash pit to prevent fires.
TI
V
Allow some accumulation
of ash
d)
Banking Procedures.
on the grates before banking a spreader stoker.
Reduce the air
supply and adjust the feeder mechanism to deliver coal to the
front of the stoker to build up the fuel bed in that area.
Maintain a alight draft in the furnace during the time the
furnace is banked.
IN
AC
Overfire Draft.
The best operating results are
e)
usually obtained with an overfire draft from 0.03 to 0.07 inch of
water.
This reduces air leakage to a minimum without causing
overheating
of furnace walls, doors, or other parts subjected to
heat.
Adjust the air supply so that it is just sufficient
to
prevent smoking.
This should result in approximately
11 to 14
percent carbon dioxide in flue gas.
Examine the furnace
Low carbon
frequently to ensure that it is not overheated.
dioxide and inability to secure proper draft through the boiler
are often due to air leakage through the boiler setting.
Maintain
flue gas temperature
at the minimum level consistent
with good operation.
Some packaged boilers are operated with
positive pressure in the furnace.
These boilers should be
operated in accordance
with the manufacturer’s
operating
instructions.
f) Operation.
Examine the windbox periodically
and
keep it clean.
Check the operation of feeding mechanisms
to
ensure equal distribution.
If wet coal sticks in the hopper,
Lubricate bearings
push it into the feeder with a rod.
frequently
in accordance
with manufacturer’s
requirements.
~g ve ‘
. Traveling grate atokera
4.3.6.8
T.
provide a means of burning very fine coal or coal having a low
ash fusion temperature.
They are not generally suitable for
burning caking or coking coal.
Control is obtained by varying
the rate of feed either by changing the thickness of coal feed
ribbon to the stoker or by changing the rate of grate movement.
222
MIL-HDBK-1125/l
VE
The method employed is determined
by trial to suit the ekill of
the individual
operator.
Adjustment
of grate epeed must be done
with care.
The usual speed varies from 2-1/2 to 3-1/2 feet per
minute.
The fuel must be completely
burned before it reaches the
end of the grate to prevent excess carbon loss to the aeh pit.
Excessive burning of link ends is an indication that an
appreciable
amount of burning combustible
ie paeeing over the
refuse end of the etoker.
However, if the fuel ie burned too far
before the end of the grate, too much air will be admitted
through the uncovered
grate and an excessive quantity of heat
will be carried away with the flue gasee.
This condition can be
Additional
determined
by observation
and flue gaa analyeia.
regulation of the fuel-bed level is obtained by uee of section
air control dampers under the stoker.
Use theee dampere to
reduce the supply of air to thin sections.
Note that if the ash
has a low fueion temperature,
excessive
agitation of the fuel bed
can result in clinker formation.
Traveling grate etokers are used with
a) Air Control.
either natural or FD boilers, with modern units being almost all
FD type.
FD is neceseary when the use of fine coal increases the
resistance of the fuel bed or when the grate openinge are small
in eize.
Greater control and high rates of combustion are also
obtained with the use of FD.
Operation,
in either case, remains
essentially
the came.
Draft lees through the fuel bed varies
from 0.25 to 0.60 inch of water with natural draft and from 1 to
4 inches with FD.
IN
AC
TI
(
b)
Draft Control.
An overfire draft of 0.03 to 0.07
inch of water should be maintained.
This minimizes air leakage,
overheating
of furnace walla, doors, and other parts exposed to
heat.
Storing Coal.
Do not segregate coarse and fine
c)
coal in bunkere or hoppers, as this will result in irregular
burning and holee in the fuel bed.
d)
Adjueting Grate Tension.
Adjust tension on the
grate with tension screws at the back sprocket bearing.
Adjust
the ecrewe on both aidea until chain or grate bars are tight,
then loosen the screws slightly.
Ledge-Plate
Clearance.
Many stokers are supplied
e)
with ledge plates on the sidea to prevent excessive air leakage.
Ensure that ledge plates have approximately
l/8-inch clearance.
If proper clearance
is not maintained,
excees air levels increase
and boiler efficiency
ia reduced.
grate
f)
stoker,
Banking Procedure.
To bank
allow the fire to burn down,
223
fire on a traveling
reducing draft as much
MIL-EDBK-1125/l
Introduce a bed of coal approximately
1 foot thick.
as possible.
The stoker should be run ahead at hourly intervals during the
banked period.
Frequency of this operation depends upon the rate
In starting from bank, break up any coke which has
of burning.
formed, introduce air, allow the coke to burn, and wait until
furnace walls are heated before resuming normal operation.
Oil-Firinq
Efficient
4.3.7
Pro cedur es.
fired burners requires careful oil storage,
burner adjustment.
operation of oiloil preparation,
and
IN
AC
TI
VE
Good bunkering practices greatly
4.3.7.1
S1 u da e Control.
However, occasional
reduce sludge accumulation
in storage tanks.
When sludge reaches the level that it may
cleaning is necessary.
enter the pump suction line, the tank must be emptied and the
The most practical method of reducing sludge
sludge removed.
This consists
formation to a minimum is controlled
bunkering.
basically
of extending the fill, suction, and return lines to
Keep the
within one to two pipe diameters of the tank bottom.
fill line on the opposite end of the tank from the suction and
This piping arrangement
helps to prevent heavy
return lines.
sludge deposits by sweeping the bottom of the storage tank.
Sludge conditions
in storage tanks are aggravated by the
following:
a)
b)
storage tank,
fractions.
Return
to the tank
of overheated
oil.
Maintaining
the oil temperature
too high in the
causing separation
of the light and heavy
c)
Leakage
of ground
d)
Storing
oil
water
in tanks for
into the tank.
excessively
long periods.
4.3.7.2
Air Leakaae.
A small air leak in a c.umn suction line
can cause a areat
deal of trouble.
~—––.
Such leaks”ca~ occur around
valve stems, screwed or flanged fittings, and strainer gaskets.
Test for such leakage by applying a small quantity of light oil
to the joint or part in question.
Oil is drawn into the suction
line if leakage is present.
If air does get into lines, it
should be released from bleed points.
If bleed points are not
available,
check burner operation closely until air is completely
Air coming through the burner may cause fires to go
cleared.
out . If oil flow is then resumed, explosive ignition can occur
from the hot furnace walls.
Do not allow oil storage tanks to be
emptied to the level where the suction line may draw air, except
when necessary for annual cleaning.
224
MIL-HDBK-1125/l
4.3.7.3
pil Str~.
Strainers are provided in oil suction
and distribution
piping to protect pumps and burner atomizera
Theee atrainere remove
from being damaged or clogged.
Strainer baakets should be
particulate
and sludge from the oil.
checked and cleaned on a weekly basis, while daily cleaning may
be required for heavy oils.
AC
TI
VE
When heating oil in a storage tank or
4.3.7.4
~.
suction line before tranafer to supply pumps, do not heat the oil
to a temperature
where vapora are given off, since vapor locking
Day
of pumps and unpredictable
burner operation can result.
tanks may be effectively
used if significant quantities of heated
oil are circulated
through a distribution
header with only a
portion of that oil ueed.
When a pumping and heating set is part
of an installation,
it is important to adjust the pressure
control valve to maintain a constant oil supply pressure and
recirculate
oil to the tank ahead of the heaters.
Oil
temperature
control can often be improved by reducing the steam
pressure or water temperature
to the oil heater.
This is
particularly
important if oil flows through the heater are less
than the design conditions.
IN
4.3.7.5
Qi.1 Te
The beat oil temperature
for atomization
is dependent upon the type of oil and the burner
manufacturer’e
recommendation.
The burner manufacturer
will
recommend a viscosity
range in which to operate.
Typically, a
range of 35 to 150 SSU is recommended
for pressure atomizers, 35
to 250 SSU for eteam or air atomizers, and 35 to 300 SSU for
rotary atomizers.
An atomizer for a LEA burner may require an 80
5, or No. 6 oil.
to 120 SSU range for No. 4, No.
Refer to
par. 2.4.1.2, Table 2, and Table 3 for further information.
Figure 127 illustrates
typical viscosity limits for various oils
as a function of temperature.
This chart can be used to plot a
viscosity curve for a particular oil.
Semi-logarithmic
graph
paper must be used.
If the viscosity at one temperature
is
known, a curve can be plotted by assuming that the slope of the
line is the same as the standard slopes.
An example is shown on
Figure 127.
However, with the blended oils common today, it is
beat to know the viscosity at two different temperatures
and draw
a straight line through those two points.
When the viscositytemperature
curve is known, the proper operating temperature
range can be read from the chart.
Maintaining
a constant and
stable viscosity
to the oil control valve is also important if
accurate control of oil flow over the burner control range is to
be maintained.
Host control systems do not compensate
for
viscosity changee, and fuel/air ratio control becomes difficult
if viscosity
is not held constant.
225
MIL-HDBK-1125/l
50,000
Zo.cm
10.OW
5000
] Zoca
j lCQO
500
300
2CQ
VE
100
so
$
50
40
35
AC
TI
33
120
Temperature.
160
200
240
280
F
Figure 12.7
Oil Viscosity Versus Temperature
IN
Qil, Atomizina Steam. and Combustion Air at Burne<.
4,.3.1.6
Oil, atomizing steam (or atomizing air), and combustion
air must
be supplied to the burner at the pressures recommended
by the
manufacturer.
Oil atomizers using steam or air for atomization
normally maintain a differential
pressure with the pressure of
steam or air being above the oil pressure throughout the firing
range.
Atomizing steam lines should be well drained and trapped
to ensure that no water is delivered with the steam.
Combustion
air also must be controlled
at the preesures and quantities
necessary
for complete and efficient combustion.
The energy in
the oil pressure, atomizing steam or air, and combustion
air are
used to mix fuel and air for efficient combustion.
4.3.7.7
~
ius ment . Burner adjustments
are necessary
to ensure that the atomized fuel and combustion
air mix
completely
and efficiently.
The positions of the atomizer,
and register baffles are adjusted to optimize burner
diffuser,
performance.
Some control systems change the regieter positions
automatically
throughout the firing range to maintain LEA
levels.
If automatic adjustment
is not part of your system and
226
MIL-HDBK-1125/l
(.
boiler load variee significantly
over the year, optimum burner
adjustment
for the low and high load rangea ehould be determined
and burnera and controls adjuated accordingly.
IN
AC
TI
VE
Oil burners should be inspected
4.3.7.8
~.
daily.
The atomizer should be “removed and cleaned in accordance
with manufacturer’s
recommendations.
For No. 6 oil firing, this
may be a daily procedure, while for No. 2 oil, a weekly cleaning
is usually sufficient.
A visual inspection of the burner flame
and furnace condition
should be made.
The flame ehould be clean,
smokeless, and steady with a yellow to yellow-orange
color.
There should be minimal or no flame impingement
on the furnace
walla, no smoke or eparklere in the fire, no slanting or lazinese
in the flame, and no brilliant color.
If any of these conditions
exist, check the excess air levels, oil pressure and temperature,
water in oil, atomizing eteam or air differential
preesure,
and
the
atomizer
for
wear.
Take
corrective
burner adjustments.
.
action or request assistance.
Fuel/air ratio control is
discussed in par. 4.3.9.1.
4.3.8
fired
Gas
burners
requires
PrOc~.
proper
Efficient operation
gas handling and burner
of gasadjustment.
4.3.8.1
Gas is supplied under pressure.
-ssure
Requld&2n.
A strainer, preesure regulating valve, and gaa meter are commonly
supplied at the inlet of gas service to reduce line pressure and
1
meter
the gas.
A second gas pressure regulating
valve is then
supplied to maintain a constant pressure in the distribution
piping
to the burnere.
Accurate gae preeeure regulation
is
I
important for the proper functioning
of the gas control valve and
for maintaining
the proper fuel/air ratio.
Gas distribution
pressure
should
be
checked each shift.
A higher than normal gas
!
pressure
reduces the amount of excess air, while a lower pressure
I
increases the excess air.
4.3.8.2
Burner adjustments
are required to
(
ensure
that the gas and combustion
air mix completely
and
1
efficiently.
Gas burner poeition
(if movable), diffuser
position,
and regieter/baffle
positions must be adjuated to
I
I
optimize
burner performance
in that specific furnace.
Some
(
control
systems automatically
change the register positions
f
throughout
the burner firing range to maintain LEA levels.
If
d
automatic
adjustment
is not part of your system and boiler load
1
varies
significantly
over the year, optimum burner adjustment
for
1
the
low and high load ranges should be determined
and burners and
(
controls
adjusted accordingly.
d
~V
4.3.8.3
Ooe. Gaa burnera ehould be inspected
<
daily.
A visual inspection of the flame and furnace conditions
f
should
be made.
Traditionally,
gas flamea have been blue in
221
MIL-HDBK-1125/l
color with yellow tips.
However, modern burners, designed for
LEA and/or NOX control, may vary in color from almost invisible
The burner flame should be clean and
to luminescent
yellow.
steady, with minimal impingement
on the furnace walls, and no
smoke, flaring, instability,
brilliance,
shortness,
or flashback.
If any of these conditions exist, check excess air levels, gas
pressure, burner adjustments,
and furnace pressure.
Take
Fuel/air
corrective
action or request assistance,
as required.
ratio control is discussed in par. 4.3.9.1.
VE
4.3.9
Operate combustion
controls in
c ombustion Controls.
Review
the fully automatic mode whenever possible.
und=st.dnd
the
manufacturer’s
operating instructions
to fully
operating characteristics
of your particular
control system.
Inspect control drives and linkages daily for smooth operation
and tight connections.
IN
AC
TI
When the amount of excess
4.3.9.1
Fuel /Ai r Ratio Adjustment.
air observed in flue gas exceeds the amount determined
as proper
for your system, the fuel/air ratio should be adjusted.
TO
determine
the proper fuel/air ratio, the,boiler
should be
operated at four different loads; apPrOxlmately
20 percent, 40
percent, 70 percent, and full load.
Data should be taken at each
load, after adjusting the burner for optimum operation.
The data
should include steam flow or Btu output, fuel flow, fuel valve
position,
fuel pressure, fuel temperature,
atomizing steam or air
pressure
(of oil), overfire air pressure
(if coal), Bacharach or
Ringleman
smoke density, combustion
air pressure, combustion
airflow if available,
fan damper position(s),
furnace pressure,
percent oxygen or carbon dioxide in flue gas, and flue gas
temperature.
At each load, a curve of smoke density versus
percent oxygen or carbon dioxide should be developed.
Figure 128
illustrates
such a curve.
When the desired operating positions
are known for the four loads, the controllers
and linkages should
be adjusted to duplicate the settings.
When compromise
is
necessary due to control limitations,
the system should be
arranged for best control throughout
the normal operating range
of the boiler.
4.3.9.2
Standard Operatina Procedur es.
Simple biasing of the
fuel/air ratio is often possible to allow the operator to
compensate
for changes in fuel, air, or other operating
characteristics.
This involves increasing or decreasing
the
amount of airflow by a fixed amount.
Biasing of airflow does not
change the basic fuel/air ratio.
Figure 129 illustrates
fuel/air
ratio biasing.
When simple biasing of the fuel/air ratio is
possible, a Standard Operating Procedure should be developed to
detail and authorize actions to be taken by the operator.
Each
time corrective
action is taken, it should be noted in the boiler
log .
228
MIL-HDBK-1125/l
NO.6OIL.1OWLOAO
>
(o~
Figure 128
Density Versus Percent
IN
AC
Smoke
OXYGEN
TI
PERCENT
VE
-t
=,
229
Oxygen
MIL-HDBK-1125/l
i
%+
s
——
:
2
+.9$02
.—
-.5%
02
81AS
I
t
RATIO
AC
TI
o~
--
01.4s
BASE FUEL/AIR
------
VE
-1
o
25
50
PERCENTLOAO
15
100
Figure 129
Fuel/Air Ratio Biasing
IN
The water column discussed in
ontrols.
4.3.10
~
B “ e
par. 4.3.5.1 is equipped with a low water cutout ewitch
Historically,
interlocked
to shut down the fuel to the boiler.
Tube rupture
this is the most important boiler safety control.
failure due to low hater level is one of the most common and most
The water column must be blown down’
dangerous
types of failure.
each shift to improve operation and ensure that sediment does not
prevent normal operation.
High steam pressure or high water
temperature
switches, flame scanner function, and other safety
switches as shown in Figures 51, 52, or 53 must also be tested
periodically.
Tests can best be performed during the normal
start-up
shutdown procedures.
4.3.11
Centrifugal
PumDs ,
in heating plants and require
Centrifugal
pumps are widely used
Small,
of
attention.
a minimum
electrically
driven
centrifugal
pumps are started by closing the
motor-starting
switch.
Discharge valves of large pumps should be
closed before the pump is started to reduce power required for
starting.
After the pump has started, slowly open the discharge
valve.
Pumps can be safely operated for a few minutes with the
230
.,.
.
MIL-HDBK-112511
(
VE
discharge valve closed, but continued
operation without water
Open casing vents
circulation
will cause the pump to overheat.
Some centrifugal
to remove air or gases trapped in the casing.
pumps are driven at constant epeed with output controlled
by
throttling
a discharge valve either manually or automatically.
When centrifugal
boiler feed pumpe are used, pump control may
In all cases
consist of the boiler feedwater control valve.
where automatic
regulation is employed,
be sure to prevent the
discharge
valve from closing off completely,
as”this would result
in overheating
of the pumps.
Large hot water distribution
pumps
are often equipped with variable
epeed drives to economically
Centrifugal
pumps are built to operate
control water flow.
“ against a given head or discharge
pressure for a specified apeed.
If there is stoppage, or if for any reason discharge pressure
becomes higher than the rated value, the pump will stall and a
no-flow condition will exist.
Immediately
investigate
and
correct the cause of the increaeed pressure.
TI
AC
4.3.11.2
For a pump not using mechanical
seal, pack the pump shaft with the recommended
packing material
to minimize leakage.
In tightening
the packing, be sure to take
it up evenly, but not so tight as to produce excessive friction
and cause overheating.
4.3.11.3
If centrifugal
pump bearings are
lubricated
by oil rings, ensure that the oil level is maintained
Check the rings to see that
high enough to come up to the rings.
they are turning.
Drain the oil occasionally,
flush out the
bearings, and add new oil.
Centrifugal
pumps that have roller
bearings packed with grease require infrequent attention.
Do not
When
overgrease
the bearings as this may result in overheating.
adding grease to a roller bearing, remove the drain plug or use a
safety fitting to prevent overgreasing.
Inspect pumps daily for
proper operation and bearing temperatures.
IN
.
If
4.3.11.1
centrifugal
pumps are operated in parallel, each pump must have
the same characteristic,
otherwise
the pump with the greateat
This results in
head will pump all or most of the water.
Exercise care in
overheating
of the low lower head pump.
selecting the required number of pumps to meet load conditions.
4.3.12
~rect-Ac~.
Direct-acting
pumps (duplex and
simplex) may be used where steam of 60 psig or more is available
and where the exhaust eteam may be utilized for heating.
These
pumps are not economical when exhaust is discharged
to the
atmosphere.
Neglecting
leakage, direct-acting
pumps deliver a
given amount of water per stroke,
The maximum pressure which a
given pump develops depends on the, steam pressure supplied, and
it is necessary to regulate the speed of the pump to control
231
MIL-HDBK-1125/l
is accomplished
by controlling
the rate of
output . Regulation
steam flow to the pump with a hand-operated
globe valve or a
This
regulating
valve actuated by pump discharge
preseure.
control varies the pump speed and thereby maintains constant
Some duplex pumps are supplied with cushion
discharge
pressure.
valves to regulate the length of stroke; when the pumP begins tO
short-etroke
the cushion valve is opened to compensate.
If
cushion valves are not supplied, the length of stroke is
regulated by adjusting the valve-gear
10st mOtion; this
adjustment
cannot-be made during pump operation.
VE
4.3.12.1
ODeration.
To starta
direct-acting
steam pump, drain
Open the
the steam line and ensure that no water is present.
Ensure that valves on inlet
drain cocks on the steam cylinders.
Admit
and outlet water lines and exhaust steam lines are open.
steam to the pump and allow the cylinder drain cocks to remain
Adjust cylinder
lubricators
to
open until the pump operates.
feed the required amount of cylinder oil.
AC
TI
There are two principal
types of
4.3.12.2
~.
Hydrostatic
hydrostatic
and mechanical.
lubricators:
lubricators
depend upon pressure created by a column of water’to
A mechanical
force oil into the cylinder against steam pressure.
lubricator
consists of a small plunger pump operated by the
Avoid excessive
lubrication so
reciprocating
motion of the pump.
that oil does not find its way into the boiler by mixing with the
condensate.
Leakage of packing and valves results in
4.3.12.3
Leakaqe.
Valve leakage is
decreased
capacity of displacement
pumps.
Replace the packing
usually accompanied
by irregular operation.
or repair valves as necessary.
IN
Steam or air binding is a common
Steam or Air Bindinq.
4.3.12.4
When
cause for failure of displacement
pumps to deliver water.
suction lift is too great or water too hot, flashing takes place
within the suction pipe and pump cylinder, and steam expand? and
To correct this
contracts
as the piston or plunger operates.
If air
condition,
decrease suction lift, or cool the water.
leaks into the suction line past the packing, the.cy:inder
will
Since alr IS a
become filled with air instead of water.
compressible
gas, its presence prevents the pump from operating.
When the pump has a suction line, ensure that the suction pipe is
absolutely
tight.
~.
Injectors used in stationary
practice are
4.3.13
J
To operate, open
usually of the self-starting
automotive
type.
Water is first discharged
the water and steam supply valves.
When the injector starts to deliver water,
through an overflow.
the overflow valve is automatically
closed by the vacuum
232
MIL-HDBK-1125/l
(
Rate of flow is then controlled by means of either
produced.
water or eteam supply valvee.
Some of the common difficulties
encountered
in operation of injectors are:
a)
Water
too hot.
b)
Suction
c)
Leaka
in auction
d)
Scale
deposits
e)
Worn
f)
Clogged
91
Fluctuating
lift too great.
in injector
caused
nozzlee
by impurities
foot “valve, strainer,
steam
and body.
VE
nozzlee
piping.
in water.
or suction
piping.
pressure.
IN
AC
TI
4.3.14
In many older plants, natural draft created by a
EaDs.
stack was used to tnove air through the boiler.
The need for more
positive control and safety resulted in use of FD fans and ID
fans.
4.3. 14.1
Sleeve bearings are lubricated by oil
rings.
Oil rings are larger in diameter than the shaft and dip
into an oil well under the bearing.
Rotation of the shaft causea
rings to turn and carry oil to the bearing.
It is important that
proper oil level in the well be maintained.
If the ring fails to
touch oil, the bearing will not be lubricated.
Roller bearings
require leee attention
than sleeve bearings.
Pack roller
bearings with grease every 6 months to 1 year, depending on
service.
Use manufacturer’s
recommended
grease only and use care
to prevent overgreasing.
4.3.14.2
For fans handling high
&iter-Cooled
Beati.
temperature
air or gases, water-cooled
bearinge may be required.
Ensure that cooling water is maintained
on the bearings.
A
bearing operating
temperature
of 130 degrees F or less is
considered
satisfactory.
4.3.14.3
Output of a fan can be regulated either by
changing its speed or by adjusting inlet or outlet dampers.
Damper adjustment
is usually employed to avoid the expense of
supplying a variable-speed
drive for the fan.
Dampers may be
manually or automatically
controlled.
In either case, means are
provided to regulate airflow to meet eystem requirements.
4.3.14.4
encountered
in fan operation
Some common
are:
233
difficulties
MIL-HDBK-1125/l
a)
“bearings,
or
caused
by unbalanced
b) Misalignment
resulting
and wear of couplings.
‘=)
failure
Vibration
Incorrect
overheating
rotor.
in vibration,
or insufficient
of bearings.
lubrication
vanes,
d)
Improper regulation
due to fouled
dampers, and control mechanisms.
fouled
e) Reduced fan efficiency
with dust, dirt, or grease.
f) Fan rotor and casing
laden with fly ash and other
resulting
or worn
and capacity
of
in
control
due to blades
VE
gases
overheating
erosion due to handling
abrasive material.
of
AC
TI
In the simplest
4.3.15
Feedwater Heatino and Tr eatment.
systems a closed feedwater heater may be used to heat the
feedwater to an acceptable temperature,
usually 180 to 220
degrees F.
air or
IN
4.3.16
Economizers,
Air Heaters, and Poll ution Control
EauiDment.
This equipment is located between the boiler outlet
and the stack.
Gas pressure and temperature through this
equipment
should be closely monitored,
as they are good
indicators
of performance,
both for individual items of equipment
When soot blowers or other
and for overall boiler installation.
cleaning devices are provided they should be operated once a
Moving parta such
shift or as recommended
by the manufacturer.
as dampers,
linkages or air heater drives should be lubricated as
Ash hoppers should be emptied
recommended
by the manufacturers.
Care must be taken to
daily or more frequently,
if required.
maintain
gas temperature
above the acid dew point (Figure 22) to
minimize corrosion.
Daily inspection
is required.
Manufacturer’s
shutdown instructions
should be incorporated
into
When an economizer or air heater
the boiler shutdown procedure.
will not be operated for more than 2 days, clean the fire side to
minimize corrosion problems.
Correct
~r
Level.
4.3.17
E e enc
water level is maintained
either manually or automatically.
Automatic
control is an aid but cannot always replace the
operator for reliability.
Low water level can result in burned
tubes and boiler plates with the possibility
of destructive
explosion.
High water level causes water to be carried out with
the steam and causes damage or destruction
to engines, turbines,
valves, or piping.
Abnormal water level (high or low) can be
234
MIL-HDBK-1125/l
caused by operator carelessness,
failure of a regulator or pumps,
broken piping, boiler leaks, failure of an indicating device, or
failures in the water circulating
system.
TI
VE
If the water level is below the
4.3.17.1
~.
vieible range of the gage glaqs, shut off fuel flow, purge the
boiler, and ehut off fans.
Continue to feed water slowly until
normal level is restored.
If there is any possibility
that the
boiler has been damaged, it should be cooled and thoroughly
The underlying
inspected before being put back into service.
cause of the low water condition should be determined
and
appropriate
corrective
action taken before attempting
to resume
Water level should be controlled
manually
normal operation.
until the automatic control is known to be functioning correctly.
AC
If water is above
4.3.17.2
~vel
the vieible range of the gage glass, shut off feedwater and fuel,
For hand-fired
purge the boiler, and shut off combustion
air.
boilers, smother the fire by covering the grate with green coal
or wet ashes.
For stoker-fired
boilers, shut down the stoker,
cut off the air supply, and open the furnace doors.
If the water
level does not recede into the visible range of the gage glass
operate
the
main
blowdown valves ae required.
within 2 minutes,
The underlying
cause of the high water ehould be determined and
appropriate
corrective
action taken before attempting
to resume
Water level ehould be controlled
manually
normal operation.
until the automatic control is known to be functioning correctly.
4.3.18
. If
Tube FaM
relatively
cold water is introduced into the empty drum of a hot
boiler, the drum and tube jointe are subjected to severe thermal
straine which may result in cracke or loosened tubes.
Should the
water get too low while heat is still applied, serious damage to
tubes and boiler structures may result.
Leakage may become so
great that available water is not efficient
to maintain the
required level.
If a feedwater regulator ie used, it will open
wide when the level drops.
This results in a large flow of water
to that boiler and may cause other boilers on the same header
system to develop low water conditions.
The correct remedial
procedure varies, depending on how rapid the fire can be
extinguished.
IN
(
4.3.18.1
If the leak
red
Pro ce dure for Gae- or OL1“-”
Boiler s.
ie ao serious that immediate removal of the boiler is necessary,
proceed as follows for gas- or oil-fired boilers:
a)
Shut
off fuel.
235
MIL-IiDBK-1125/l
b) Close the steam outlet valves if only one boiler is
in operation.
Do this quickly to prevent a sudden pressure drop
For a multiple boiler
and corresponding
temperature
drop.
installation
when more than one is in eervice, the header
preseure and the nonreturn valve will automatically
isolate the
disabled boiler from the header.
to carry
d) Maintain minimum
away steam discharged
f=) After
VE
Shut off the supply of feedwater to the boiler,
c)
provided there is not enough hot refractory to cause overheating.
In the case of boilers with refractory
furnaces, adjust the
feedwater flow to the maximum consistent with the protection
of
Attempt to maintain a normal
supply to other operating boilers.
water level until the overheating
hazard is past, then shut off
the feedwater.
airflow through
from the leak.
15 or 20 minutes,
the boiler
shut down
setting
the FD fans.
TI
Proceed with the normal method of cooling
f).
boiler.
Do not drain the unit until the furnace is cool
to enter.
the
enough
AC
Inspect boiler and pressure parts completely.
9).
Be sure the boiler is
Repair the boiler, ae required.
hydrostatically
tested and approved by an Authorized
Inspector
before returning to service.
4.3.18.2
Boilers.
Pr ocedure for Stoker-Fired
units, the following procedure is recommended
occurs:
For stoker-fired
if tube failure
IN
Shut off the fuel feed and gradually reduce
a).
Also , use whatever means
airflow as the fuel bed decreases.
been predetermined
or are available to smother the fire
effectively
without danger of explosion.
b)
Close
the
steam
outlet
have
valves.
c) Adjust the feedwater flow to the maximum
Shut off
permissible
and attempt to maintain normal water level.
the feedwater after the setting has cooled to a point where no
danger of overheating
exists.
d) Adjust airflow to minimum safe level consistent
with preventing water or steam from flowing into the boiler room
and minimizing
the rate of cooling.
236
MIL-1iDBK-1
Inspect the boiler completely and make the
e)
necessary repairs.
Be sure the boiler is hydrostatically
tested
and approved by an Authorized
Inspector before returning to
service.
AC
TI
VE
The flow of air and
4.3.19
Fan
ure
gases through the boiler depends upon the action of the FD and ID
fans.
The greateat difficulty
occurs when ID fans stop for any
to
operate
when the
reason.
If the combustion
system continues
ID fan fails, smoke, combustion
gases, or fire are discharged
into the boiler room.
The FD fan and fuel feed should be
Most boilers are
immediately
stopped when the ID fan trips.
equipped with safety interlocks
that do this automatically.
Safety interlocks are also normally provided to stop the fuel
feed if the FD fan fails. . If such interlocks are not provided,
If the ID fans
the operator must take these actions manually.
have tripped for any reason, slowly open dampers in the air and
flue gas passages to their wide open position to create as much
natural draft aa possible to ventilate the setting.
Opening the
dampera should be timed or controlled
to avoid excessive pressure
transients during fan coast-down.
Maintain this condition
for a
period that will result in not less than five volume changes, but
in any case not lass than 15 minutes.
At the end of this period,
close the flow control dampers and immediately
start the fan(s).
Gradually increase the airflow to at least 25 percent of full
load flow and purge the setting for 5 minutes.
These general
recommendations
should be adhered to unless adequate tests on a
specific boiler demonstrate
that different values should be used.
4.3.20
E~.
Auxiliary equipment in some plants is equipped with both steam
and electric drivers.
In case of the failure of one, the other
can be quickly put into service.
If auxiliary equipment
is
electrically
driven and.there
is no gasoline or steam engine
backup, or emergency source of auxiliary power, electrical
failure causes a complete outage.
While power is being restored,
prepare the boiler equipment so that operation may be immediately
resumed when power is available.
Prepare and follow a schedule
for testing operation of standby equipment.
Some boilers may be
operated at reduced rating with natural draft.
Steam-driven
pumps may be used to supply feedwater.
If this is possible, some
of the steam service may be able to be maintained.
Arrange a
schedule so that the least important service is shut off during
an emergency.
Study the plant and determine how, in case of
electric power failure, the following services may be continued:
IN
(
25/1
a)
Water
supply
b)
Operation
to the boilers.
of ID fan.
237
MIL-HDBK-1125/l
c)
Fuel
supply
to the furnace.
d)
Combustion
e)
Operation
of automatic
f)
Operation
of valvea
air supply.
controls.
and safety
devices.
TI
VE
4.3.21
F1 ame Failur e. Oil and, gas
dur
E eraen Cv Pro
burners aremprovided
wi~~ fl~me scanners and safety controls
which will safely shut down a burner within 2 to 4 seconds of
flame failure, and post purge the furnace before shutting off the
fans.
Manual systems require that the operator take these
actione.
If fans are operating after a safety shutdown, continue
If the
the operation.
Do not immediately
increase the airflow.
airflow is above 25 percent of full load flow, it should be
gradually decreased to this value for a post-firing
purge of at
least 5 minutes.
If the flow is below 25 percent at the time of
the shutdown, it should be continued at that rate for 5 minutes,
then
increased
to
the
25
percent level, and held there for an
additional
5 minutes.
Refer to NFPA 85 series or ASME CSD-1, as
applicable,
for additional
information.
firing
a)
rate.
Reduce
the load on the boiler
to the minimum
stable
b) Open the bottom blowdown connection
for a
time to remove sludge from the mud drum.
IN
sufficient
AC
4.3.22
Removina a Boiler From Service.
When removing a boiler
from service, care must be taken to prevent rapid temperature
This helps to decrease the
changes and resulting thermal stress.
possibility
of future forced outages and reduces maintenance
costs . The procedure for removal is as follows:
With oil or gas firing, the fuel shutoff valve
c)
should be tripped at the appropriate
time and manual valves at
burners closed immediately.
With stoker-fired
boilers, the
stoker hoppers should be emptied and the fuel bed burned out.
d) The setting and boiler should be cooled down
without exceeding the maximum rate prescribed
by the
manufacturer.
As a general guide it is advisable to wait until
furnace refractory
is black before using higher rates of airflow
for cooling.
Exercise care when using the ID fan for cooling.
The ID fan and motor are designed to handle hot gases, and cooler
gases, if not controlled,
can cause the motor to overload.
238
MIL-HDBK-1125/l
(
e) On high pressure steam boilers, after the feedwater
flow ceases and the nonreturn valve has closed, close the
Run down the stem on
feedwater valves and main steam stop valve.
Where two stop
the nonreturn valve to hold the disc on ita aeat.
valves are used, open the drain between them to ensure that it is
clear and bleede off any pressur~ in the line.
f) When eteam pressure falls below
drum vent(s) to prevent formation of a vacuum
subsequent leakage of gasketed joints.
g) On hot water boilers, maintain water circulation
the boiler is sufficiently
cooled, then etop circulation,
the inlet and outlet water valves, and open a vent valve.
VE
until
close
TI
h) The boiler should be inspected and cleaned in
Procedures
for
accordance with instructions
in par. 5.10.2.
removing low preesure steam and low temperature
water heating
boilers from service can be found in ASME ~K~
v,
~
Section VI.
4.4
AC
,,
4.4.1
comb~
. With cost of fuel
continuously
increasing,
the need to operate central boiler
plants efficiently
becomes more important all the time.
Procedures
for optimizing
operating efficiencies
are discussed in
this section.
An operator should review the elementary
combustion
principles
and principles of steam and hot water
generation
found in Section 2. To optimize boiler efficiency,
the combustion
efficiency
must firat be optimized.
Combustion
efficiency
is a function of the type of fuel burned, flue gas
temperature,
and the amount of excess air in flue gas.
For a
given fuel, the operator must take action to optimize combustion
efficiency by maintaining
as low a flue gas temperature
and
excess air level as is possible.
IN
.*
25 psig, open the
that might cause
4.4.1.1
to
e Gas Temperatures.
Soot Blo wins/~a
Boilers equipped with soot blowers should be operated as needed
to maintain clean heat transfer surfaces.
Once a shift is the
recommended
interval when oil or coal is being fired, although
experience may dictate a different interval for a particular
unit.
Note the flue gas temperature before and after soot
blowing.
A reduction
in temperature of 35 to 40 degrees F
corresponds
to an efficiency
improvement
of 1 percent.
See
Tablee 5 through 8 for the specific improvement
at the actual
temperatures
and excess air levels at which you are operating.
For fire tube boilers not equipped with soot blowers, a record of
flue gas temperatures
at the normal firing rate of the boiler
should be kept.
When flue gas temperature
exceeds the clean
239
MIL-HDBK-1125/l
boiler flue gas temperature
by more than 70 degrees F, the boiler
Fire tube boilers
should be taken out of service and cleaned.
should, as a minimum, be cleaned during the quarterly inspection.
IN
AC
TI
VE
Maintaining
the water side of a
Water Side Clea~.
4.4.1.2
boiler is equally as important as maintaining
the fire side.
Scale on the water side reduces heat transfer juet as soot does,
and thereby increases flue gas temperature
and reducee
efficiency.
Quarterly inspection
and mechanical cleaning may be
The
required.
Chemical cleaning may be required occasionally.
operator should know the flue gas temperature
of the boiler at
its normal firing rate and excese air level, with the gas and
Any major change in temperature at those
water side clean.
firing conditions
indicates a problem, typically dirty’ gas Or
water side heat transfer surfaces.
ea s. Air leakage into the boiler system
4.4.1.3
s~
Any air
increases
excess air levels and reduces efficiency.
drawn into the boiler through leaks in the furnace setting,
casing, or flues must be heated from room temperature
to the flue
gas temperature,
using heat that could otherwise be transferred
to the steam.
Normal maintenance
should greatly reduce the
The operator
number and size of leaks (refer to par. 5.10.2).
should ensure that doors, ports, and openings into the furnace
The furnace draft should be maintained
at a
are tightly closed.
This
slightly negative level of -0.03 to -0.10 inch of water.
When the draft is
practice helps to minimize air leaks.
increased
for soot blowing, take care to return it to its normal
The use of a continuous
level after soot blowing is complete.
oxygen analyzer to traverse the stack or flue can sometimes help
to locate an air leak by showing a higher than normal excess air
level.
4.4.1.4
Baffles.
To obtain maximum heat absorption, baffles
are often used to help direct the hot gaaes over the tubes.
Arrangements
vary widely, depending
upon tube arrangement.
Baffles restrict the flow of gases and affect draft flow required
Defective baffles allow gases to short circuit so
by the boiler.
Leaking
they do not pass over the entire heating surface.
baffles result in high outlet gas temperature,
and decreased
efficiency.
Leaking baffles can usually be distinguished
from
fouled heat transfer surfaces by their effect on draft loss:
leaking baffles decrease gas loss, while fouled surfaces increase
draft loss.
Always investigate
and report a change in flue gas
temperature
or draft lose.
4.4.1.5
Ratio ODtimizatioq.
Refer to par. 4.3.9.1.
EW ellti
When
Know the proper excese air levels for each firing rate.
proper levels are known, corrective
action can be taken if the
Some corrective actions,
fuel/air ratio is out of adjustment.
240
MIL-HDBR-1125/l
VE
such as returning
the oil header pressure or temperature to the
correct operating point, adjusting the stoker feed, returning the
furnace draft to the operating point, or biasing the fuel/air
ratio may be taken by the operator. “ If additional corrective
action is required,
note this in the boiler log and inform the
responsible
personnel.
The optimum fuellair ratio for a winter
load is probably not optimum for a summer load.
Determine the
optimum ratio over the full load range of the boiler, and post a
chart where it can be readily accessed by the operators.
Table
19 gives recommended
oxygen, carbon dioxide, and excess air
levels at full load, 50 percent load, and 25 percent load for
typical equipment.
Boilers will not be able to operate at these
levels, but thie level of performance
is possible with modern,
correctly adjusted equipment.
Plant modifications
to reach these
levels may be economically
justified based on fuel savings
resulting from improved combustion
efficiency.
I
AC
TI
Table 19
Flue Gas Analysis at 25 Percent,
50 Percent, and 100 Percent Load
for Natural Gas, No. 2 Oil, No. 6 Oil, and Stoker
I
Fuel
Natural
Gas
No. 2 Oil
IN
No. 6 Oil
Load
(Percent)
Stoker
Coal
I
Flue Gas
Coal
(Percent)
Excess
Air
02
co~
25
50
100
4.0
3.0
2.0
9.6
10.1
10.7
21.1
15.1
9.5
25
50
100
5.0
4.0
2.5
11.9
12.6
13.8
29.2
22.0
12.6
25
50
100
5.5
4.5
3.0
12.2
13.0
14.1
33.6
25.8
15.8
25
50
100
7.0
6.0
5.0
12.4
13.3
14.2
48.5
38.8
30.3
,.
4.4.2
. Boiler efficiency
a Bo~
accounts for the energy loss included in combustion
efficiency
plus energy losses associated with heat radiated from the boiler
casing, heat removed with blowdown, and heat lost due to
incomplete combustion.
Boiler efficiency
is affected by the
stabiiity of the combustion controls.
Boiler efficiency is
always less than combustion
efficiency.
241
MIL-HDBK-1125/l
Inspect, maintain, and
J7educe Radiation Lo sses.
4.4.2.1
Improved insulation
improve boiler, flue, and pipe insulation.
Radiation losses
is often available and economically
justified.
can be minimized by the proper selection of ,operating and standby
boilers, and the temperature at which standby boilers are
maintained.
For some plants operating with noncritical
load, a
Close
standby boiler need not be maintained
in hot condition.
This will
the inlet and outlet dampers of any standby boilers.
the
natural
draft
airflow which will cool the
help to minimize
boiler.
AC
TI
VE
Reduce Blowdown Lo s se s. Blowdown is necessary to
4.4.2.2
control steam boiler water quality and minimize scale formation.
Reduced scale formation helps to maintain combustion efficiency
near clean boiler levels and reduces water side maintenance.
Blowdown is a form of preventive maintenance
that should be
Continuous blowdown is recommended
for
carefully
controlled.
steam boilers because blowdown heat exchangers can be used to
recover much of the heat in the blowdown water by preheating
makeup water.
Automatic control of continuous blowdown is also
recommended
to improve the accuracy of the blowdown procedure and
help minimize losses.
IN
4.4.2.3
Reduce Unburned Carbon Losses.
Unburned carbon losses
from oil- and gas-fired boilers are usually negligible because
the fuels burn easily and excess air levels and smoke are easily
Unburned carbon losses for stoker-fired
boilers,
controlled.
Stokers should be carefully
however, can be significant.
Ash
maintained
and operated to minimize unburned carbon losses.
reinfection
systems are an important part of a spreader stoker
system which must be maintained
in good operative condition.
Overfire air is also very important on any stoker system to
obtain proper mixing of air and combustion gases.
Refer to
operation procedures
in par. 4.3.6.
4.4.2.4
Stabil ize Combustion Controls.
The combustion
control
system must accurately establish the correct fuel/air ratio to
Combustion controls are designed
optimize combustion
efficiency.
to regulate fuel and airflows to satisfy load demand, establish
correct fuellair ratio, and minimize the time spent at
Combustion controls are
inefficient
firing conditions.
stabilized
by making the proper adjustments
to the proportional
band, integral, and rate settings to best respond to the load
conditions.
It is common that the best settings for winter load
conditions
are not best for summer conditions.
The assistance
of
the control manufacturer
may be required to determine the best
settings.
Settings should be changed only by trained and
authorized
personnel.
242
MIL-HDBK-1125/l
. .
4.4.3
c.
Overall
Cen~
Refer
plant efficiency
is alwaye less than boiler efficiency.
par. 2.4.10 for an initial discussion of central boiler plant
efficiency.
After individual
boiler efficiency is optimized,
then consideration
must be given to proper boiler selection,
deaerator control, use of steam-driven
auxiliaries,
building
energy conservation,
and modifications
or additiona to plant
equipment.
to
TI
VE
4.4.3.1
~
. The best use of available boilers is
necessary to optimize plant efficiency.
A curve of efficiency
versue load should be developed
for each boiler based upon the
data obtained when the fuellair ratios were developed.
Figure
130 illustrates
euch a curve.
With this information
it is
possible to select which boiler or group of boilers is best
suited to operate at a given load.
For a steam demand of 30,000
pph, operation of boilers No. 1 and No. 2 would be most
economical.
If efficiency
of a particular boiler is good over a
very small range, it may be best to baseload that boiler in that
range and allow the other boiler(s) to handle load swings.
l%o
boilers operating at partial load may be more efficient than one
boiler operating near its design capacity.
A SOP should be
developed
establishing
which boilers should operate for a given
load.
AC
4.4.3.2
Deaerators consume a significant
~.
amount of stecm to heat and deaerate feedwater.
Some of the
eteam is vented to atmosphere
and lost.
The amount vented ranges
from 1/10 percent to 1 percent of the plant load and is dependent
upon both the original design of the deaerator and vent condenser
and their proper operation.
With poor operation or design, 5
percent or more of the plant load can be vented through the
deaerator.
If operation
alone does not resolve excessive
venting, equipment modification
or replacement
should be
considered.
IN
(
4.4.3.3
~ven
Steam-driven
fans and pumps
may be useful in providing a plant that can be operated in case
of electric failure.
Care must be taken, however, in utilizing
such drives, because they can have a significant
effect on plant
efficiency.
The efficiency
of a noncondensing
steam turbine is
only about 20 percent.
Suitable uses for exhaust steam must,
therefore,
be developed
if steam turbines are to be used
effectively.
Operate steam drivea only when a use for low
preesure exhaust steam is available.
243
MIL-HDBK-1125/l
90
‘-
80
8
BOILER
I
! 70
1:
BOILER
NO.
BOILER
NO. Z
300 HP, 4 PASS FIRFTLISE
30,000
PPH, WAIERTUBE
BOILER
NO. 3:
40,000
PPtl, WATERTUSE
\
TI
~
T
NO. 3J
VE
;
I
I
10
30
20
POUNO OF STEAM PER HOUR X 1~
I
o
AC
o
Boiler
Figure 130
Efficiency
Versus
I
40
Load
IN
4.4.3.4
Plant Buildina Conservation.
Overall plant efficiency
can be improved by minimizing the use of plant-generated
energy
for building heating.
Use waste heat from condensate
return,
blowdown water, or boiler radiation whenever possible.
Insulate
the building.
Maintain building steam traps and repair water or
steam leaks immediately.
Provide vent condensers
on condensate
wells, deaerators
or deaerating
heaters, and use the minimum
steam pressure practical in heat exchangers
(refer to
par. 2.2.2.1).
EaUiDIIEnt
Modifications
or A d ditions.
Existing
4.4.3.5
equipment
that does not operate efficiently
should be modified or
replaced if economically
justified.
Consider use of economizers
or air heaters for boilers that normally operate with flue gas
temperatures
above 500 degrees F, if these boilers operate for
significant
periods of the year.
Five percent improvement
in
boiler efficiency
is common and can often economically
justify
the addition of such equipment.
Improvements
to external water
treatment may be justified if significant
reductions
in blowdown
244
MIL-HDBK-1125/l
be realized.
Addition of a blowdown heat recovery system should
be considered.
Also consider use of vent condensers,
condensate
heat recovery systems, improved steam flow and upgraded boiler
combustion controls.
The economice of such modifications
should
be carefully reviewed, but it will often be found that the
potential energy savinga will quickly pay back the capital
investment required.
IN
AC
TI
VE
. .
4.4.3.6
~
If
svst~ts
on P~.
less water is returned to the central plant than was supplied in
the form of steam or hot water, plant efficiency
is reduced.
Makeup water must ba heated from its supply temperature,
usually
about 60 degrees F, while condensate
return water needs only to
be heated from ite already.elevated
temperature
of 150 to 180
degrees F.
It is important to monitor eupply and return flows as
well as makeup flow and determine if exceesive
loseea occur.
Note that temperature
compensation
is required for accurate flow
comparison.
If losses are determined
to be excessive or other
problems develop, appropriate
personnel ehould be alerted so
repairs to the distribution
eystem can be made.
Distribution
system losses should not exceed 5 to 10 percent of supplied flow
in a steam system and 1 percent in a hot water system.
245
MIL-HDBK-1125/l
Section
5:
INSPECTION
AND PREVENTIVE
MAINTENANCE
VE
.5.1
PurD ose and Scone.
This section is presented to cover
general information
and provide guidance to those responsible
for
It establishes
a system
maintenance
of boiler plant equipment.
of maintenance
assignments
and records sufficiently
flexible to
Although this
be applicable
to most boiler plant installations.
handbook schedules most of the maintenance
called for by
manufacturers,
it is not intended to take the place of
Each plant must maintain for
manufacturer’s
instruction
sheets.
ready reference and use a manufacturer’s
instruction
file on
installed equipment.
5.2
of Maintenance
AC
TvDes
TI
5.1.1
preferences.
Along with manufacturers’
instructions,
ASME Boiler and Pr essure Vessel Code, Sections VI and VII provide
general procedures
for care and operation of boilers.
NAVFAC
Instruction
11300.37, Enerqv and Util ities Po licy, providee Navy
policy for maintenance
of plant equipment,
NAVFAC MO-324 provides
guidelines
for inspection and certification
of boilers and
unfired pressure vessels, and the National Board of Boiler and
Pressure Vessel Inspectors
(NBBI), National Board Inspection Code
provides national board inspection codes for construction,
repair, and alterations
of boilers.
IN
5.2.1
Forced outages for repair or
Breakdown Maintenance,
replacement
of equipment parts that have failed in service can
be, and often are, very costly.
Through the application
of
proper operating procedures
and careful inspection,
it is
possible to increase the length of time over which a boiler can
be carried on the line before any repairs are required.
This, in
turn, will prolong the useful life of the equipment and minimize
forced maintenance.
The principal causes of forced outages and
excessive maintenance
are:
a)
Sustained
and
b)
Operating
with
c)
Fouling
d)
Inadequate
e)
Improper
frequent
overloading
of fuel burning
equipment
improper
of external
water
airflow
heating
conditioning
lubrication
246
conditions
surfaces
MIL-HDBK-1125/l
(
Forced maintenance
is outeide the scope of this
Normally, forced maintenance
and major overhauls are
handbook.
not performed by operating pereonnel,
but rather by aeaigned
maintenance
personnel or outeide contractors.
VE
Preventive maintenance
can be
5.2.2
Prwen~.
defined as the systemic and periodic inspection and servicing
required to keep equipment
in proper operating condition.
Maintenance
tasks are based on elapsed time or houre of service.
Preventive maintenance
means fixing things before they break,
thus keeping equipment in continuous
service or ready for
service.
The life of boiler plant equipment depende largely upon
its maintenance,
and the cost of operation in a well maintained
plant is consistently
lower than in a poorly maintained one.
In
addition, proper preventive
maintenance
results in improved
working conditions
and better employee morale.
TI
Preventive maintenance
has
5.2.3
Predict ive Mai~.
~iO doubt
been the mainstay of maintenance
practice for decades.
it is better than breakdown maintenance,
but with the advent of
modestly priced computer systems and software it can be augmented
with a more refined procedure
known as predictive
maintenance.
For example, with predictive
maintenance,
wearing parts of
equipment are maintained
in step with their actual maintenance
needs rather than arbitrary assumptions
based on the passage of
time or hours of use.
IN
AC
“
Predictive maintenance
can be described as follows:
predictive
maintenance
involves equipment condition monitoring
along with data tracking and trending to predict failures.
Condition monitoring
information
is gathered from vibration
monitoring,
infrared imaging, oil and wear particle analysis,
visual inspections,
and other
ultrasound
detection,
nondestructive
testing.
Predictive
maintenance
information
is
scanned, by computer analysis software or other methods, and
A technician
tracks the
potential problems are diagnosed.
severity of the problems, orders necessary parts, and schedules
maintenance
accordingly.
Depending on the severity, equipment
with problems can be scheduled
for repairs during the next outage
With this method, breakdown
or taken out of service immediately.
maintenance
is avoided.
5.2.3.1
. A predictive
maintenance
program used in
conjunction
with a good preventive
maintenance
program can reduce
machinery cost and improve safety.
These savings are realized as
follows:
247
MIL-HDBK-1125/l
By monitoring
a machine’s actual
Avoid Breakdowns.
a)
condition,
forced outages and the additional problems associated
with a catastrophic
failure are avoided.
Maintenance
is
b)
Reduced Maintenance
Requirements.
performed only as needed and not according to assumptions
based
on passage of time.
With the ability
Reduced Spare Parts Inventory.
c)
determine what equipment,
tools, and labor will be required,
spare parts inventories
can be. reduced.
to
VE
Early detection of,incipient
d)
Longer Machine Life.
machine problems and prevention
of catastrophic
failures will
increase machine life.
Verification
of New Equipment
e)
Equipment can be checked for problems prior
service or accepting contracted
services.
and Repairs.
to returning
to
AC
TI
Vibration analysis is presently
Vibration
Anal vsis.
5.2.3.2
It has
the most widely used predictive maintenance
technique.
been used in the Navy, mostly on submarines,
since the early
With the availability
of microcomputers
and advanced
1960’s.
programs, vibration
analysis is now cost effective in smaller
Vibration
analysis products range in complexity
from
plants.
pocket size single point level indicators to continuous
on-line
It is important to understand
the available
diagnostic
systems.
equipment before implementing
a program.
IN
The chief operator or plant supervisor
Responsibility.
5.3
has the ultimate responsibility
for boiler plant equipment,
its
proper operation,
and the scheduling and performance
of
The chief operator should assign to himself
maintenance.
responsibility
for inspection and servicing required for plant
He will assign other operating or maintenance
personnel
safety.
the responsibility
for maintenance
of specific pieces of
equipment as required.
Some items listed for daily inspection by
an assigned individual
also require hourly inspections
by the
These hourly inspections
do not relieve the
operating personnel.
assigned operator of his responsibility
to inspect, service, and
record the equipment condition.
InsDe ctiom.
5.4
Inspection is the first step in a
preventive
maintenance
program. The early detection of a problem
can greatly reduce the amount of damage, simplify maintenance,
The key to effective inspection
is a
and prolong equipment life.
complete understanding
of the equipment’s
operating
The operator should know the condition,
sound,
characteristics.
temperature,
pressure, speed, vibration, and performance
248
MIL-HDBK-1125/l
(.
characteristics
of each piece of equipment in the plant, and
Any
particularly
those that are his assigned responsibility.
change in normal characteristics
should be immediately
reported,
investigated,
and corrected.
VE
5.5
A neat boiler plant generally indicates
a well run plant.
The boiler plant should be kept free of
unnecessary
material and equipment.
Good housekeeping
should be
encouraged
and procedures
established
to maintain the desired
Sometimes
level of cleanliness.
Equipment should be kept clean.
cleaning is all that is required to keep equipment in troublefree operation.
bugs, and oil in
Moisture, dirt, duet, cobwebs,
the wrong place are enemies of mechanical and electrical
Leaks not
equipment.
Stop leaks as coon as they are detected.
repaired at best represent waste and at worst may cause extensive
damage.
AC
TI
5.6
Insr.ection and Ser vice Records . Preventive
maintenance
programa are effective only if careful, accurate, and
complete
records are kept.
In no other way can the maintenance
manager ensure that personnel are carrying out their
properly maintained.
responsibilities
and that equipment is being
Figures 131 and 132 are examples of the typea of log sheets that
should be maintained
at each plant.
IN
5.6.1
accurate and
Aa discussed above, maintaining
[email protected]
complete
records is an essential part of a good preventive
maintenance
program.
Record data cards provide an effective
method for smaller plants; however, for larger more complex
plante, new software programs are available for record keeping.
A computerized
maintenance
management
system (CMMS) provides the
maintenance
department
with a method of handling large amounts of
data.
5.6.1.1
svs~.
There are many maintenance
software packagea available on the
commercial
market with different options available.
A typical
CMMS is used to plan scheduling,
issue work brders, track costs,
and provide inventory control for maintenance
tacks.
Maintenance
personnel
perform equipment
inspections,
maintenance,
and
functional checks at specified time intervals.
The program
prints predictive maintenance
task sheets specifying work
required on the equipment,
then updates a history file when the
work is complete.
Reports provide managera with equipment,
maintenance,
personnel,
and coat information.
This exchange of
information
helps coordinate
management and maintenance
personnel.
Maintenance
can also uee these programe to track
predictive
maintenance
tasks and history files.
249
AC
TI
VE
MIL-HDBK-1125/l
IN
1
Figure
Hot
Water
131
Heating
250
Boiler
Log
NJ
W
.
IN
T
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Iv
.
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AC
WEEK4
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MIL-HDBK-1125/l
Whether using a CNMS or record cards, care
5.6.1.2
Data En try.
The following
is required when initially filling in entry data.
outlines basic information
that should be included when
establishing
maintenance
records:
enough
b)
detail
VE
The equipment number is made up
a) Equipment Number.
The first part is
of three separate parts separated by dashes.
The second and
the boiler plant building or location number.
third parts are equipment classification
codes used to
distinguish
between similar pieces of equipment.
Description.
Describe equipment briefly
so that it can be readily identified.
but in
TI
Show the job
Preventive
Maintenance
To Be Done By.
c)
title and name of the person responsible
for maintenance;
this
should normally be the person who actually operates the
equipment.
He is also responsible
for reminding the chief
operator,
superintendent,
or other supervisor of any special
semiannual
or annual inspections
required, and for ensuring that
the supervisor
makes the appropriate
entry on the card afterthe
inspection
is completed.
Identify each operation with the
f=) Item Number.
item number.
Usually the item number is the subparagraph
unless an item number is noted.
Where the came item
is used to identify more than one operation,
differentiate
them by adding a letter to one of the numbers; thus, if
used twice, write one of them as “la.”
IN
proper
number
number
between
“1” is
AC
d)
Work To Be Done.
Study the handbook and the
equipment manufacturer’s
manual, noting inspection and service
required.
Enter in this space the paragraph or subparagraph
heading describing
the operation.
Add any operations
not covered
Ensure that
in the manual but needed to maintain the unit.
necessary
inspections
and services are shown on the record card.
List operations
in order of frequency of performance,
with daily
service first.
reference
Insert paragraph
f) Reference.
to the appropriate
manual.
numbers
to facilitate
Frequency.
Record frequency of operations,
as
9)
shown in Time-Schedule
columns.
Modify suggested frequencies
required to fit local conditions.
252
as
MIL-HDBK-1125/l
Show specific day or month when service ia
h) Time.
Stagger quarterly,
semiannual,
and annual inspections
so as
due.
Choose the
to minimize rush perioda and schedule conflicts.
season when the work can be beat accomplished.
Mark an “X” at the top of
i) Tab Index.
alongside each month during which work is to be done
submitted.
This helps to schedule operationa,
since
required in a given month can be quickly determined
to the tab index.
the form
or a report
overall work
by reference
TI
VE
On the back of the card, record
j) Service Record.
the date and item number whenever maintenance
ia performed, and
initial.
If service is required beyond the ability or authority
of the inspector,
he must request the proper help and enter the
request in the Work Done column.
For example, if inspection of a
motor reveals a grooved commutator,
the entry would read
“’Electrician needed to complete Item 51 - commutator
grooved.””
The work order number is entered under the column headed Signed
When
and ia initialed.
apacea on the Service Record are filled
in, a blank card should be stapled to the original.
of [email protected] . Only general rules covering
5.6.2
assignment of preventive
maintenance
work are given here.
Actual
assignment
will necessarily
depend upon the specific plant and
Work loads of
the qualification
of operating personnel.
personnel ehould be substantially
equal, and duties assigned must
be in keeping with the qualifications
of the individual.
A coal
handler, for example, may inepect the stack and breeching for
fly-ash accumulation,
and examine guy wires, coal bunkers,
elevators, and conveyors.
He should not be expected to maintain
and adjuat flow meters or combustion
controls.
IN
AC
(
5.6.2.1
~
v“
. The chief operator is
charged with overall responsibility
for the plant.
Therefore,
inspections
having to do with safety of operation or the
possibility
of serious damage to equipment are assigned to him.
These items must be checked at frequent intervals.
Likewise,
items of major importance
such as internal inspection of boilers
and furnaces should be under his personal supervision.
5.6.2.2
Shift operatora,
firemen, or other
~.
qualified personnel usually have maintenance
duties in addition
to their regular assignments.
The man to whom a given piece of
equipment is assigned should perform the required maintenance
during whatever shift he happens to be working on a given day.
During this man’s time off, the relief operator or the chief
operator performs the scheduled maintenance.
Maintenance
activity can sometimes be assigned entirely to day shif$
253
MIL-HDBK-1125/l
This arrangement necessitates
close supervision
operators.
guard against neglect, but maintenance
work during daylight
is more pleasant and frequently more effective.
to
hours
~aintenance
Men.
In plants where regular maintenance
5.6.2.3
men are available,
assignment of preventive maintenance
work is
However, certain
Here day-shift work is usual.
simplified.
special items should still be assigned to skillful operators.
VE
Tools
Proper preventive
maintenance
requiies proper
5.7
Review the operations
listed on the
tools and ~~ments.
maintenance
cards and determine the tools required for each
There is no eingle list of tools which will apply to
operation.
However, each plant should be equipped with a
all plante.
workbench
with a pipe vise, a machinist’s
vise, and a tool board.
AC
TI
Some maintenance
operations
require
5.7.1
SDecial Tools.
tools that would be used too infrequently
to justify their
If possible, such tools
purchase
for the central boiler plant.
should be borrowed from other departments
on the base; otherwise,
Indicate on the maintenance
card the
requisition
them.
department
from which they may be borrowed.
Maintain tools in first ClaSs
Care of Tools.
5.7.2
Take defective tools out of service immediately
and
condition.
Use tools properly. If the proper tool
repair or replace them.
for an operation
is not available,
immediate arrangements
should
be made for its procurement.
IN
Tool Board.
Keep tools on a well planned tool board or
5.7.3
Keeping tools on a
tool box, not in bins, benches, or drawers.
tool board helps prevent loss and makes them instantly available
when required.
Locate the tool board in a conspicuous
place,
convenient
to the majority of operators.
Space should be
The
provided on the board for additions to the tool supply.
shape or size of a tool should not prevent its being installed on
the tool board.
Extension cords, oil cans, flashlights,
and
electric drills can be installed on the board by use of special
brackets.
The outline of each tool should be painted on the
board in a contrasting
color to assist in replacing tools in
their proper place and to serve as a ready check on missing
tools.
SDare Parts.
5.8
Preventive maintenance
requires an
adequate stock of spare parts.
Service conditions,
the
importance
of the part to service continuity,
and the ease of
procurement
help to determine the kind and number of spare parts
kept in stock.
Examine the equipment requirements
in the plant
.
254
MIL-HDBK-1125/l
(.
.
Do not neglect to include
and prepare a spare parts inventory.
small parte such as nuts, bolts, shear pins, steam traps,
gaskets, valve seats, packing, and cotter pins.
Lubricants and cleaning solvents are
5.9
needed for proper equipment
opdration and long life.
Clean,
properly lubricated
equipment
is required for aucceaaful plant
operation.
AC
Cleaning solvents such as mineral
5.9.2
Solvm.
spirits, kerosene, and Varsol can be used in central boiler
plants.
Petroleum derivatives
such as naphtha and gasoline
present an explosion
and fire danger and must never be used.
Benzene especially
must never be used, as it not only has a low
Follow the precautions
flashpoint,
but is alao extremely toxic.
for use and storage that are provided with the solvents.
Material Safety Data Sheets must be readily available to
employees in accordance
with OSHA Regulation 29 CFR 1910.1200.
When using cleaning solvents, be sure the solvent is completely
evaporated
before placing the equipment back into service.
When
using solvents for cleaning electrical equipment,
first remove
loose dirt and dust, then dip a rag into the solvent and wipe the
insulation.
When spraying solvents, extra precautions
against
When cleaning bearings
fire or health hazards must be observed.
or machined parts, place the cleaned parts on clean rags or
paper, allow them to dry and immediately dip them in oil or apply
lubricant.
Do not allow rust-susceptible
parts to remain exposed
to air after cleaning.
IN
I
TI
VE
Lubricants
are frequently referred to in
5.9.1
par. 5.10.~ Because of the extreme variations in equipment and
service conditions,
the types of lubricants required for a given
Determine lubricant
plant must be determined
locally.
requirements
from the equipment manufacturer
instructions,
or
advice from lubricant manufacturers.
5.10
d Prev~
5.10.1
The following
and Use of the
Sche dQina
sections provide suggested preventive maintenance
schedules for
many types of central boiler plant equipment.
The subparagraph
designates
the frequency
for preventive maintenance:
daily,
weekly, monthly, quarterly,
semiannually,
and annually. The
second subparagraph
numbers are numbered consecutively
and can be
used as index numbers on the record cards.
The lists of
inspection and work presented
here should not be considered
to be
complete.
Review the manufacturer’s
operating and maintenance
instructions
and add additional
required items.
Review the
Vessel Code
applicable
section of the ASMS ~
and the NBBI ~
Cod s, along with NAVFAC
255
MIL-HDBK-1125/l
Other
MO-324 for additional
requirements
and suggestions.
equipment will be found which is not discussed in this section.
Such equipment
should be researched with the manufacturer
and
The frequency euggested here
~LJprOPriate record cards prepared.
Modify the suggested frequency to
IS based on good practice.
best match local conditions
and experience.
a)
Daily
(1)
Check
(a)
Water
(b)
Steam
stability.
tests.
blowdown
Adjust
(e)
Water
or steam
at two loads,
(f)
Air leaks
dioxide
levels
leaks.
in casing,
ducts,
or setting.
(2) Take water samples and psrform necessary
internal treatment and continuous blowdown.
(3) Blow down steam boilers
connection
to remove sludge.
b)
action
temperature
(d) Flue gas oxygen or carbon
compared with baseline data.
(4)
par.
or water
pressure
(c) Flue gas temperature
boiler temperatures.
IN
at two loads,
and take
of a
of
level.
AC
to clean
conditions
the following
as required:
compared
TI
VE
The successful
operation and maintenance
Boi 1ers.
5.10.2
boiler is greatly dependent on the operation and maintenance
Boiler operation and boiler preventive
its auxiliaries.
maintenance
involve inspection of the boiler operating
conditions.
Clean
boiler
through
the bottom
exterior.
Month ly
(1)
Lever
test
safety
(2
Check
boiler
valves
(refer to
5.10.6).
drain
and closing.
256
valvea
for proper
opening
r41L-HDBK-1125/l
(3)
Check
boiler
drains
room floor
for proper
function.
One of the auarterlv inspections
should
the annual ~nspecti~n by-the Authorized
c)
Quarterlv.
be timed to’co~ncide
with
Inspector.
(1) Internally and externally
to semiannual and annual procedure.
(2)
Clean
the fire
inspect
the boiler.
side of the boiler.
VE
Refer
Semiannually
or as required by
d)
Semiannually.
NAVFAC MO-324, an external inspection of the boiler by an
With the boiler operating,
Authorized
Inspector is required.
inspect for the following:
vibration,
Any evidence
(2)
Pressure
(3)
Safety
(4)
Water
(5)
Pressure
(6)
Low water
of steam
gage
or water
accuracy
(7) Steam,
proper rating,
or safety
level
gage
controls
leakage.
and function.
AC
TI
function.
(1)
relief
valves.
function.
function.
fuel cutoff
and level
control
water, and blowdown piping
and freedom to expand.
for leakage,
IN
(8) Review the boiler log, maintenance
records,
and water treatment records to ensure that regular end adequate
testa have been made.
Annual inspections
are required by
e) Annually.
NAVFAC MO-324.
Boiler inspections
are to be made in accordance
with rules for inspections
in Section VII of the ASMS Boiler and
An
Authorized
Inspector is required.
~.
Preparation
for an annual inspection is discussed
in the next
subparagraph.
The most recent copy of Boiler Inspection
Report,
NAVFAC Form 9-11014/32
(3/67), muet be posted for each boiler in
the plant.
and repair
(1) Inspect
as required:
the boiler
251
for the following;
clean
.- —..
MIL-HDBK-llz5/l
(a) Water side of tubes for deposits caused
Remove excessive deposits by
by water treatment,
scale, or oil.
mechanical
or chemical means.
(b)
Stays
Repair
and stay bolts.
or replace
as required.
(c) Water side of tubes
and cracks.
grooving,
the boiler
(d) Manholes,
for cracks, corrosion,
(e)
signs of thinning,
Fusible
spalling,
Boiler
Test
(h) Fire
corrosion
supports
Inspector,
and setting
side of tubes
or erosion.
(i) Setting
and leakage.
for cracks,
(j) Safety valves
the safety valves.
(k)
Baffles.
(1)
Blowdown
(m)
Boiler
IN
piping.
annually.
for
for freedom
for bulging,
AC
TI
bricks,
Replace
plugs.
(f) Tube sheets, tube ends and drums
leaking, corrosion,
or cracks.
(9)
leaks,
for
internals,
and connections
to
erosion and clean passagee.
of expansion.
blistering,
and boiler
VE
corrosion,
settlement,
and their
loose
connections
and
piping.
appliances.
(n) When required by the Authorized
hydrostatically
test the boiler.
[0)
Review
past
inspection
reports
and plant
records.
(p) Make any other inspection
required by the
ASMS Boiler and Pressure Vessel Code or NBBI National Board
In snection Code.
(2) Preparation
for an annual inspection.
Make
Other
the following preparations
for annual inspection.
preparations
may also be required by the ASME Boiler and Pr essure
sne ction Code.
Vessel Code or NBBI ~LD
a
258
MIL-HDBK-1125/l
(
soot before
reducing
(a) Where soot blowers are installed,
boiler load below 50 percent.
blow
VE
(b) Shut down the boiler in accordance
with
par. 4.3.22.
Shut off fuel supply lines and lock when possible.
Sufficiently
cool the boiler before draining the water.
Internally wash the boiler to remove sludge deposits, suspended
solide eediment, and loose ecale. Do not clean drums or tubes
until after the inspection
unless prior agreement has been
reached with the Authorized
Inspector.
(c) Before opening or entering any part of
the boiler, ensure that the nonreturn
and atop valves are
closed, tagged, and preferably
padlocked and drain valves between
The feed and check valves must be closed,
the two are opened.
tagged, and padlocked and drain valves between the two must be
opened.
After draining the boiler blowoff valvea must be cloeed
and padlecked.
Drain and vent lines should be opened.
be thoroughly
lighting
should
(e) The fire side walls, baffles,
swept and aeh and soot removed.
IN
AC
should
(d) Proper low voltage
for internal inspection.
TI
provided
be
and tubes
(f)
If the installation
burns coal, remove
the grate bars, and clean the firebox plates along the grate
line until the bare metal is exposed.
Take care not to damage
the metal during the cleaning.
(g) Have available a supply of gaskets for
manholes and hand holes, and suitable wrenches for removing and
replacing covers.
(h)
Replace
fusible
plugs.
inscribed
carefully
(i) If insulation
conceals manufacturers
data, remove the lagging and clean the surface
so that die-cut letters and figures can be easily
to assist
the Inspector
(j).
Assign a qualified boiler
throughout
the tests.
plant
read.
operator
(k) Be prepared to run a hydrostatic
pressure
test.
A hand pump should be provided for this test if required.
Provide gags to prevent safety valvea from lifting when teet
pressure ia applied.
If hydrostatic
pressure tests on more than
one boiler are contemplated,
sufficient
gags should be provided
259
-—.
.
MIL-HDBK-1125/l
If boiler gages and controls are not designed
for the boilers.
for the proposed test pressure, be prepared to isolate or remove
them and plug the openings.
(1)
Have boiler
records
available.
~conom izers.
5.10.3
Refer
VE
Whenever a boiler
f) Taking a Boiler Out of Service.
is to be out of service for more than 2 days, thoroughly clean
the fire side of the boiler, flues, economizer
and air heater.
Dry ash and soot are not
Ash and soot deposits must be removed.
corrosive
but moisture in combination
with the ash and soot of
To avoid acid attack and corrosion of
sulfur bearing fuel is.
the metal, ash and soot must be removed.
to par.
3.1.7.
b)
Monthly.
conditions:
Check
the following
(1)
Water
pressure
(2)
Draft
losses
drop
across
AC
increase
normally
TI
Inspect for leaks in piping, valves,
Daily.
a)
packings,
gasketed joints, hand-hole openings, casing, etc.
repairs as required.
under
through
identical
Make
load
the economizer.
the economizer.
(3) Gas temperature
drop across the economizer.
in, draft loss and a decrease in gas temperature
drop
indicates a fouling condition.
During
c) Annually.
and inspect the economizer.
the annual
boiler
overhaul,
An
clean
IN
(1) Externally
look for signs of overheating,
Check the baffles
leakage, wear, or corrosion in pressure parts.
and tubes in the area of soot blowers for signs of abrasion
Check the elements of the
caused by fly ash or steam cutting.
soot blower.
sludge
5.10.4
(2) Internally
look for corrosion,
deposits,
or oil in tubes and headers.
p.i
~.
a)
duct , casing,
Refer
to par.
erosion,
scale,
3.1.8.
Daily
(l)” Inspect the air heater
gasketed joints, etc.
260
for gas or air leaks
in
MIL-HDBU-1125/
(.
(2)
rotary
air
Inspect
1
for abnormal
air or gas temperatures.
(3)
Inspect for mechanical
air heaters, if supplied.
heaters
b)
drive
problems
on
(4) Establish a lubrication
schedule for rotary
in accordance
with manufacturer’s
recommendations.
Monthly.
Check
the following
under
identical
load
air
Air and gas
(2)
Gas
(3)
air hanging
heaters
side draft
temperature
drop
losses.
through
Inspect for mechanical
heaters, if supplied.
drive
the air heater.
problems
on
(4) Establish a lubrication
schedule for rotary
in accordance
with manufacturer’s
recommendations.
TI
rotary
(1)
VE
conditions:
AC
(5) Air temperature
rise through the air heater.
An increase in gas side draft losses combined with a decrease in
air temperature
rise indicates excessive soot deposits in the
tubes or gas passages.
(6) Make an oxygen analysis of flue gas at the air
heater inlet and outlet.
The difference
in total air content
between the analyses indicates air leakage.
Repair if leakage is
excessive.
c)
Annually
IN
(1)
During the boiler
the air heater. Look for indications
leakage, and wear.
overhaul, clean and inspect
of corrosion,
erosion,
In rotary regenerative
air heaters, inspect
(2)
the motor drive, speed reducer, auxiliary air motor if provided,,
lubricating
system, cooling system, bearings, rotor seals, etc.
washing
5.10.5
(3)
equipment.
~.
a)
Check
the condition
Refer
to par.
Daily
261
of soot blowers
3.2.3.
and
MIL-HDBK-1125/l
11) Blow down and inspect water columns, gage
glasses, level’indicators,
and level-alarm devices for leaks,
‘correct operation,
correct level indication,
and adequate
Repair leaks immediately.
lighting.
gage
glass
(2) Check to see that valves
free and operational.
to ensure
between
boiler
and
(3) When provided, test high and low automatic
Repair when faulty.
that it is in perfect order.
IN
AC
TI
VE
alarm
are
During annual boiler overhaul, or more
b) Annually.
often if necessary,
dismantle, clean, and inspect parts such as
valves, alarm linkages, floats, chains, alarms, glasses,”
Replace or repair damaged or worn
diaphragms,
or electrodes.
parts as required to ensure proper functioning.
Safetv
5.10.6
a)
Valves.
Refer
to par.
3.2.5.
Daily
(1) Check for steam leakage indicating damaged
Immediately correct euch
seat, defective
parts or lodged scale.
faults as leaking, simmering, or chattering.
(2)
to ensure
that
Check
supports
and anchors
(3) Check the drain
it is open and will
of discharge
line from safety valve
function when needed.
pipe.
outlet
b)
Monthly.
Check each safety valve by raising the
valve off the seat by lifting the lever.
Keep the valve wide
open for at least 10 seconds to blow dirt and scale clean from
the seat.
Close the valve by suddenly releasing the lever.
Annually.
c)
generator
inspection
and
valves.
Testing is also
back ring has been reset
5.10.7
should
Before and after the annual stesm
overhaul, test the operation of safety
required whenever the spring or blow
or adjusted.
Fusible Pluas.
These items
Refer to par. 3.2.8.
be put on the boiler record card where applicable.
a) Quarterly.
Inspect fusible plugs during boiler
Scrape the surface clean and bright.
inspections.
Replace if
the metal does not appear sound.
b)
Annually.
Replace
fusible
year.
262
plugs
at least
once a
MIL-HDBK-1125/l
(
5.10.8
~.
a)
Refer
~opar.
3.2.9.2.
Daily
if required.
(1)
Check
for leaks.
Repair
(2)
Check
for correct
operation
of the system
components.
(1) During the boiler outages,
items and repair if required:
or otherwise
[a) Defective
damaged).
Worn,
(c)
Incorrect
blowing
(d)
Incorrect
location
(e)
Alignment
and tightness
AC
control
system
(2)
Repack
Sts2&di.
Refer
a)
to par.
cotroded,
nozzles
of elements
glands
or
of the supporting
control
of abraaion
and adjust
the
and adjustment.
of soot blowsr
Condition
(h) Evidence
of the jet.
IN
5.10.9
or defective
chains,
(f) Defective
components.
(g]
impingement
loose,
(warped,
(b)
nozzles.
bearings.
elements
inspect
TI
following
eroded,
Semiannually
VE
b)
valves,
piping
caused
and
system.
bv
to prevent
leakage.
3.3.1.1.
Daily
(1)
Clean
exposed
parts
of the stoker.
(2) Inspect accessible parts.
Pay special
attention
to bolts and connections
in shear pins or safety
release mechanisms.
Be sure there is no binding that may keep
protective
devices from functioning.
Operating personnel should
inspect the following items hourly:
(a)
Hot bearings.
263
MIL-HDBK-1125/l
Foreign
(c)
Mechanical
(d)
Damaged,
(e)
Oil leaks.
(f)
Proper
(9)
Correct
(h)
Clinkers.
in coal.
linkages.
overheated,
oil level
or burned
out parts.
and condition
of
systems.
temperature.
schedule
material
oil pressures
and oil
TI
VE
hydraulic
(b)
(3) Establish lubrication
requirements
and a
in accordance with manufacturer’s
requirements.
b)
Quarterly.
Make
and overhaul whenever a boiler
the following general inspection
is removed from service.
part”s.
(a)
Clearances
between
grate
(b)
Tightness
of nuts,
bolts,
elements.
and holding
(c) Drive mechanism and drive unit.
any damage to gears and other components.
IN
and repair
AC
Check for wear
(1) Inspect the complete stoker.
on surfaces of feeder-box sides, conveyor areas, and moving
Replace
parts.
Check alignment and condition of the grates.
broken, warped, or distorted parts promptly.
Check the
following:
(d)
Bearings
of drive
unit.
(e)
Electrical
(f)
Fan and its bearings.
Clean
Lubricate
as
required.
lubricate
worn
areas
controls
and connections.
Check
and
bearings.
(9) ~ly-ash reinfection
system.
and plugged llnes.
Repair if required.
(h)
Air seals.
264
Repair
Look
if required.
for
MIL-HDBK-1125/l
(
(2) Remove slag from furnace walla adjacent to
Take care to avoid injury to the
stoker or fuel bed surface.
brickwork.
Preventive maintenance
equipment are as followe.
5.10.10
Pul verized Coal
procedures
for pulverized coal
5.10.10.2
daily
TI
VE
Establish
a definite lubrication
schedule
5.10.10.1 ~.
for pulverizer
installations
and assign definite responsibility
Frequency of lubrication
and
for the periodic lubrication.
lubricant
used should be approved by both the pulverizer
and
lubricant manufacturer.
The operator
Daily.
a)
for the following:
Unusual
(2)
Driver
noise
(3) Correct
and levels.
the installation
or vibration.
lubricating
(4)
Hot bearinga.
(5)
Correct
cooling
(6)
Correct
coal
(7)
Proper
IN
upon
inspect
overload.
AC
temperatures,
(1)
shall
water
level
operation
(8)
Correct
(9)
Proper
mill
(1)
Liner
(2)
Mill
(3)
Exhauster
(4)
Correct
(5)
Bearings
liner
of coal
feeder
and controls.
temperature.
of exhauster.
a year,
inspect
bolte
temperatures.
in mill.
outlet
operation
b) Annually.
Once
the severity of eervice,
oil pressures,
or as required, depending
the mill for the following:
for tightness.
for wear.
blades
ball
and liners
charge.
for wear
265
and dirt.
for erosion.
MIL-HDBK-1125/l
(6
Gear
drives
for wear.
(7
Coal
valves
and lines
(8)
Check
for wear
and dirt
accumulations.
system
General
(1)
Add
(2)
Tighten
(3)
Repair
(4)
annually.
insta
to ball charge
mill
liner
or replace
Thoroughly
Repair
clean
bolts
worn
and
or replace
frequently.
or defective
flush
worn
parts.
lubricating
or damaged
coal
oil
valves.
Bowl Mills
Daily.
The operator shall
a)
lation daily for the following:
(1)
Hot bearings.
(2)
Motor
(3)
Unusual
noise
(4)
Correct
lubricating
Proper
(6)
Correct
(7)
Proper
setting
(8)
Correct
mill
operation
(2
Mill
oil
levels,
pressures
and
of exhauster.
roll pressure.
b) Annually.
Once
the severity of service,
Rolls
the mill
or vibration.
(5)
(1
inspect
overheating.
IN
temperatures.
upon
as required.
AC
TI
(5)
5.10.10.3
alignment.
VE
c)
coupling
of classifier
outlet
a year,
inspect
and grinding
liners
valves.
temperature.
or as required, depending
for the following:
rings
for wear.
266
deflector
for wear.
MIL-HDBK-1125/l
(
(3) Exhauster blades, deflectors,
vanes for erosion and damage.
directional
4
Bearings
and gears
5
Coal
6
Check
bolts
(7)
Check
coupling
for wear.
and air-
Check
setting
of
gears.
valves
and lines
for wear
and dirt
accumulations.
for tightness.
VE
alignment.
IN
AC
TI
General.
Worn or defective mill liners,
c)
deflectors,
and air-directional
vanea should be repaired or
Do not leave finished surfacea beaded when
replaced as required.
Lips resulting
from
building up worn surfaces with weld metal.
wear to rolls and grinding rings may be trimmed, making it
possible to use either the trimmed rolls with the trimmed ring,
the trimmed rolls with a new ring, or new rolls with the trimmed
ring.
Rolls are made of chilled cast iron, chilled to a depth of
Should the wear on the roll have progressed
below
about 1 inch.
the chill, nothing can be gained by trimming the lip.
Trimming
must be done by melting with a l/2-inch to 3/4-inch carbon
electrode at 300 to 400 amperes, ueing reverse polarity on the
machine.
It is not necessary to obtain a smooth surface.
The
grinding ring can be trimmed using an acetylene torch.
This cut
also does not have to produce a smooth finish.
Trimming can be
accomplished
by fastening the torch in a suitable fixture and
setting the torch to cut the lip at the desired angle.
The bowl
can be turned by turning the mill shaft.
An alternate method ia
to trim the lip by hand burning, the bowl being turned
intermittently
aa required.
5.10.10.4
~Pulv~
Daily.
The operator shall
a)
installation
daily for the following:
(1)
Unusual
noise
(2)
Hot bearings.
(3)
Motor
(4)
Correct
lubricating
(5)
Correct
spring
inspect
the pulverizer
and vibration.
overheating.
oil levels,
pressures,
temperatures.
267
loading
on grinding
elements.
and
MIL-HDBK-1125/l
(6)
Proper
operation
(7)
Proper
setting
(8)
Correct
mill
(9)
Proper
of blower.
of classifier
vanee,
if
adjustable.
Once
(1)
Balls
(2)
Classifier
(3)
Blower
(4)
Bearings
(5)
Check
of coal
a year,
and grinding
vanes
inepect
rings
and gears
and controls.
the installation
for wear.
for erosion
for wear.
bolts
feeder
VE
b) Annually.
following:
operation
temperature.
and wear.
for wear.
for tightness.
AC
TI
for the
outlet
(6)
Check
coupling
alignment.
IN
Renew worn balls and races as required.”
‘=) General.
It is good practice in this type of pulverizer
to wear down two
complete sets of balls with one eet of grinding rings to obtain
When new balls and races
maximum life of the grinding elements.
allow the ball diameter to reduce 1/4 inch and
are installed,
Allow the second set to
then replace with a second set of balls.
wear down 1/2 inch and then change to the first set and allow
By following this
them to wear an additional
1/2 inch.
procedure,
the balls are kept within 1/4 inch of each other in
If one set of
diameter and close to the contour of the races.
balls is allowed to wear to the minimum eize, the effect on the
races will be such that the races will have to be replaced
The maximum permissible
ball wear is 7-1/2-inch
prematurely.
balls worn to 5 inches. 9-1/4-inch
balls worn to 6-1/4 inches, or
Extra or fill-in
10-1/2-inch
balls worn’to a“7-inch diameter.
balls should be added as wear increases, but the addition of a
ball must not reduce the average clearance between balls to less
than 5/8 inch.
Grinding rings may be worn to a thickness of from
1 inch to 1-3/4 inches.
New top and bottom grinding rings should
be installed at the same time so as to provide mating ring
surfaces for proper ball contact.
5.10.10.5
daily
~q
Daily:
The operator
a)
for the following:
268
shall
inspect
the installation
MIL-HDBK-1125/l
(
(1)
Hot bearings.
(2)
Driver
(3)
Unusual
(4)
Proper
(5)
Correct
(6)
Proper
(7)
Check. rpm on turbine
overload.
noise
or vibration.
lubricating
oil
levels,
pressures
and
temperatures.
operation
Annually
temperature.
of coal
stationary
feeder
driven
pega,
and controls.
machines.
hammer,
TI
(1) Inspect
for erosion and wear.
(2)
Check
housing
(3)
Inspect
rejector
(4)
Inspect
fan bladea
IN
AC
pegs
outlet
VE
b)
mill
liners
arms
and moving
for wear.
for erosion
and damage.
for wear.
(5)
Check
bearinga
for wear
and dirt.
(6)
Check
coupling
alignment.
(7)
Check
bolts
for tightness.
General.
Replace stationary peg bases when bolts
c)
that hold peg tips are exposed and in danger of being cut off.
Replace stationary
peg tips when approximately
1 inch has been
worn off the total length.
Replace moving pegs when
approximately
one-third of the face area has been chipped or worn
away.
Replace rotor wearing plates when it appears that
continued
operation might result in failure.
Fan blades can be
kept in service until the blades are cut through at the tip.
Pulverizer
liners should be replaced when it appears that
continued
operation will result in coal cutting through to the
houeing.
5.10.11
.
a)
Refer
to par.
3.3.2.
Daily
(1)
Inspect
for the following
269
hourly:
..-
MIL-HDBK-1125/l
Unusual
noise or vibration.
(b)
Motor
(c)
Hot bearings.
(d)
Coal
(e)
Correct
chain or belt
teneion.
(f)
Damaged
or loose drag
flights
(9)
Damaged
chain,
(h)
Proper
operating
(i)
Oil or water
(j)
Proper
overheating.
Clean
as required.
or buckets.
VE
accumulation.
chain
Repair
as required.
levels.
and
(2) Establish
lubrication requirements
as required by manufacturer’s
instructions.
(3)
Monthly.
scales
Inspect
for zero load balance.
for the following:
IN
AC
b)
Inspect
or belts.
conditions.
leaks.
lubricant
sprocket,’
TI
schedule
(a)
(1) Gear boxes, sheaves, rollers, shafts for
lubrication,
freedom of movement, and bearing play.
proper
clean
(2)
as required.
Screens
for holes or plugging.
loose
[3) Structural
or damaged’joints.
frame for broken
Repair
or bent
or
parts
(4)
Proper
alignment
of pulleys
and other
(5)
Proper
operation
of control
and safety
and
parts.
devices.
c)
Semiannually.
Inspect
for the following:
(1)
Corrosion
or erosion
(2)
Damage
of hoppers,
chutes,
and
gates.
and bearings.
of lining
and protective
(3) Wear or damage of scale levers,
Repair or replace as required.
270
coatings.
knife
edges,
MIL-HDBK-1125/l
(4)
d)
Cracks
or other
Prepare
Annually.
damage
of concrete
applicable
metal
structures.
eurfaces
and
repaint.
.
~
a)
Refer
to par.
3.3.3.
Daily
(1)
Inspect
for the following:
VE
, 5.10.12
(a)
Piping
leaks.
(b)
Proper
operation
of steam
(c)
Proper
operation
of air waaher,
(d)
Proper
operation
of aah gates
(e) Proper
controls,
operation
including
of automatic steam
maintenance
of correct
exhauater.
immediately.
or mechanical
. .
IN
AC
TI
provided.
Repair
if
and clinker
grinders.
valves and automatic
steam pressure.
b)
for accumulated
necessary.
Quarterly
(1) Inspect conveyor piping, especially at elbows,
ash and eroeion.
Rotate, repair, or replace as
(2)
Inspect
steam
exhaueter
for corrosion
and
erosion.
accumulation,
necessary.
5.10.13
(3)
Inspect washer internals for wear,
and nozzle condition.
Clean and repair
~.
a)
Refer
to pars.
3.3.4
aeh
as
and 4.3.7.
Daily
(1)
Inspect
for the following
(a)
Oil,
steam,
(b)
Unburned
or air
hourly:
leaks.
Repair
immediately.
burner
oil deposits
parts.
271
and overheating
of
MIL-HDBK-
125/1
for proper
(c)
Burner
flame
(d)
Proper
operating
shape,
color
and
stability.
pressures
and
temperatures.
Remove
(3
Clean
(4)
etrainers.
b)
and clean
burner
the oil atomizer.
exterior.
the established
Follow
Annually
(1)
remove
Completely
igniter.
schedule
for cleaning
VE
burner
(2
and clean
the burner
and
been
AC
TI
(2) Inspect air register and burner parts for
Repair or replace as
freedom of movement, warpage, and wear.
The services of a
Adjust parts for proper operation.
required.
burner serviceman may be required.
3) Replace atomizer tips or nozzles
service with new tips or nozzles.
in normal
4)
gages.
5.10.14
4.3.7.
Calibrate
Oil-Handlina
EG uic.ment.
pressure
Refer
and temperature
to pars.
3.3.5
and
Daily
IN
a)
burner
that have
(1
Inspect
for the following:
(a)
Oil,
steam,
water,
or air
(b)
Proper
operation
of traps,
(c)
Proper
operating
pressures,
leaks.
Repair
immediately.
controls,
and
instrumentation.
and
temperatures,
levels.
[2)
Clean
(3)
Establish
equipment
as required.
a schedule
272
for cleaning
strainers.
MIL-HDBK-1125/l
pars.
(4)
Inspect and maintain
5.10.26, and 5.10.27.
5.10.25,
b)
pumps
as outlined
in
Annually
(1)
Inspect and clean heaters and tanks internally
and externally.
InsDect carefullv for corrosion,
erosion.
pitting, plug~ed tub&,
damaged b~ffles, sludge deposits,”water
accumulations,
and scale deposits.
(2)
Inspect for damage
or repaint as required.
Repair
protective
to
coatings,
IN
AC
TI
VE
paint.
(3)
Test
relief
(4)
Clean,
valve
inspect,
settings
or
and operation.
and calibrate
controls
and
instrumentation.
5.10.15
Refer
~.
a)
to pars.
Inspect
Daily.
3.3.6
and 4.3.8.
for the following
(1)
Gas or air
leaks.
Repair
(2)
Proper
gas and air pressures.
(3)
Burner
flame
hourly:
immediately.
for proper
shape,
color,
or binding
of burner
and
stability.
(4)
b)
Overheating
parts.
Annually
(1)
Completely
remove
and clean
the burner
and
igniter.
(2)
Inspect burner parts for freedom of movement,
warpage, and wear.
Repair or replace as
Inspect gas nozzles.
required.
Adjust parts for proper operation.
The services of a
burner serviceman
may be required.
(3)
5.10.16
Calibrate
burner
~.
a)
pressure
gages,
Refer
to par.
3.4.1.
Daily
(1)
Inspect
for water
273
leaks.
Repair
immediately.
MIL-HDBK-1125/l
(2) Observe
any malfunctions
and repair
operation
of control
immediately.
devices.
(3) Establish a calibration
schedule
components
in the control system in accordance with
manufacturer’s
recommendations.
b)
Report
for
Annually
(2)
Check
VE
(1) During the boiler overhaul, or more often if
Look for signs
necessary,
clean and inspect control components.
of corrosion,
erosion, or wear and for deposits, leaks, and
Repair as required.
defective parts.
settings,
adjustments,
components.
Combustion
a)
Repair
Daily
(1)
immediately.
(2)
Inspect
compressed
AC
(4)
Inspect
(5)
Clean
3.4.2
to pars.
oil,
(3) Check jack shafts,
and freedom of movement.
for stable
exterior
and 4.3.9.
gas, and water
air drip
dampers
legs
and
and proper
of
leaks.
and
linkages
foz
operation.
of controls.
(6) Establish
lubrication
requirements
and
in accordance with manufacturer’s
instructions.
IN
schedule
for air,
Blow down
filters.
slippage
Refer
Controls.
TI
5.10.17
and operation
internally.
b)
Monthly.
c1
Annually
Replace
or clean
system
filters.
(1) Inspect and completely
clean control devices
Replace any worn, corroded,
or damaged parts.
(2) Test
for correct
required.
274
calibration.
Adjust
as
MIL-HDBK-1125/l
(3) Test control settings under operating
Optimize control function to improve plant
conditions.
efficiency.
(4) Obtain the assistance
of a fully trained
combustion
control service engineer as required to calibrate,
clean and adjuet the controls. ‘
a)
cleanliness.
low water
Refer
~.
to pars.
3.4.3 and
Daily
VE
5.10.18
4.3.10.
(1) Inspect eafety controls
Repair and clean immediately.
for leaks
(2) Blow down the water column, gage
Test function.
fuel cutoff each shift.
Monthly
and
glass,
and
TI
b)
AC
(1) Inspect safety controls for such problems as
dirty switch contacts, defective diaphragm
or sensing elements,
loose wires, dirty flame scanner lens, or flame rod.
Clean or
repair immediately.
(2)
Teet
safety
controls
for proper
calibration
and operation.
5.10.19
Refer
a)
to par.
3.4.4.
Daily
(1)
Inspect
for leaks.
IN
(
Repair
immediately.
[2) Check for proper operation.
Report any
malfunction.
Only trained personnel
should place in service,
remove from service, calibrate,
or maintain instruments.
lighting,
(3)
IIISDeCt for undue
and ~eadabil~ty.
vibration,
broken
alaee,
.
.
Once .? year, or more often if neceesary,
b)
Annually.
and gages for
make a thorough inspection of Instruments
Inspect carefully for the
corrosion,
deuosits,
or other defects.
following:
(1
Ruptured
(2’
Incorrect
or distorted
calibration
275
pressure
parts.
or adjuetmenta.
I
MIL-HDBK-1125/l
(3)
Badly
worn
pins
or bushings.
(4)
Damaged
or burned
(5)
Leaking
or damaged
(6)
Mercury
separations
(7)
Loose
(8)
Broken
(9)
Plugged
thermocouple
wire
insulation.
diaphragms,
bellows,
and
gaskets.
(11)
operation.
5.10.20
or tubing.
or damaged
Defective
screws.
adjustment
clockwork
assemblies.
mechanism
Refer
to par.
or electric
3.5.3.
Daily
readings
are being
(1) Observe draft gage readings
for that operating condition.
(2) Check dust level in hopper
emptied on a regular basis.
b) Quarterly.
following:
At the time
and compare
to ensure
of boiler
outage,
IN
for the
Broken
piping
Mechan ical Collectors.
a)
normal
balance-arm
AC
TI
motor
pointers.
VE
(10)
in thermometers.
damaged
(1) Check gasketed joints for leaks.
or defective
gaskets as required.
with
hoppers
inspect
Replace
(2) Check the interior of dust collector
for caked
deposite,
corrosion,
erosion, loose parts, and other damage.
Clean and repair as required.
damaged parts,
required.
c)
5.10.21
~.
(3) Check the exterior
paint, corrosion,
etc.
Annually.
Refer
Paint
of dust collector
Clean and repair
the entire
to par.
3.6.5.
276
assembly.
for
as
MIL-HDBK-1
Inspect for possible defects, leaks,
Daily.
al
damage, deterioration
of iining, c;acks, or settlement
in
foundation.
Report promptly any such observation.
b)
Quarterly
(1) Make a more thorough examination
of the
chimney exterior using high powered binoculars quarterly or after
corrosion,
loose
every severe storm to look for cracks, spans,
guy wires (if provided),
damaged lightning rod and connectors,
loose parta, etc.
IN
AC
TI
VE
(.
25/1
(2)
Remove
soot and fly-ash
accumulation
from base
of stack.
(3) Clean accumulation
of soot and fly ash from
connecting
fluee and inspect them for corrosion,
erosion, and
Remove
If moisture is found, clean more frequently.
moisture.
the cause of water formation if possible.
Carefully examine stack supports
Semiannually.
c)
corrosion,
crackinq,
or movement of anchor blocks, and proper
wire tension.
Check for corrosion of the ladder.
d)
Annually.
and externally.
Inspect
connections.
Paint.
5.10.22
te Water
a)
Check
regenerant
solution,
maintained.
for length of time
operations.
pressure
when
for the following:
(a) Flow rates.
and rinse rates
Service, backwash,
should be carefully
(b) Adherence to manufacturers
instructions
for backwash, regeneration,
and rinse
(c)
gagear
Proper operation of flow regulators,
temperature
indicators.
Chemical
or water
leaks.
(e) Hardness
to regenerate.
of water
leaving
(d)
determine
sof~
Daily
(1)
meters,
Clean and inspect the stack internally
lightning rod tips and ground
277
softener
to
for
quy
. .
MIL-HDBK-1125/l
(f)
Density
(9)
Sump
of brine.
for zeolite
carryover.
(2) Establish lubrication
in accordance with manufacturers
schedule
b)
requirements
and
recommendations.
Semiannually
(1) Inspect ion exchange
for corrosion, rust, and peeling
vessel
uneven
(2) Drain and internally
inspect the ion exchange
for loss of resin, dirt, slime, or oil fouling of the bed,
bed, or corrosion or erosion in distributor
piping.
c) Annually.
as required.
5.10.23
~~
a)
ime-SO
Calibrate
Softeners
Daily
(1)
Check
instruments
(a) Alkalinity
and hardness several
day to determine proper chemical additions.
(b)
Chemical
feed
(c)
Plugging
of feed lines.
(d)
Chemical
proportioner
(e)
verify heater function.
degrees F at sea level.
pressure
determine
and
or more
for the following:
IN
AC
each
annually
TI
often
vessel, valves;
of paint.
VE
piping
pump
times
for operation.
for operation.
Temperature
of water in reaction tank to
Temperature
should be greater than 212
(f)
Heater
(q]
.
Live
vent
steam
for proper
makeup
venting.
valve
for operation
and
control.
necessity
h) Pressure differential
of backwashing.
i)
Chemical
solution
required.
278
across
tank.
filters
Add chemicals
to
as
MIL-HDBK-1125/l
(
(j)
Lines and
valves
for leakage.
Repair
or
immediately.
(2) Blow down reaction
to sludge accumulation.
according
manufacturers
b)
tank daily
(3) Lubricate mdtors and pumps
directions
and schedule.
often
according
to
Monthly
(1)
Clean
chemical
solution
(2)
Clean
and flush chemical
(3)
Lubricate
strainer.
and adjust
tank.
Clean
outlet
feed pump..
chemical
TI
V
c)
or more
E
replace
proportioner.
Semiannually
(1) Open and clean heater.
Level and adjust trays
Repack and
and spray nozzles. Clean and drain vent condenser.
in regulator
reeeat live eteam regulator valve. Check diaphragm
and replace if worn.
Adjust regulator.
Repack and reseat water
inlet control valve.
;
(2) Open, examine, clean, and recharge
with manufacturer’e
recommendations.
AC
accordance
d)
filters
in
Annually
IN
(1) Drain, open, and clean reaction tank.
Repair
or replace damaged insulation.
If corrosion
is excessive on
interior of tank, scrape thoroughly and apply protective
paint or
other similar coating.
If exterior is exposed, paint after
thoroughly cleaning.
(2)
Dismantle,
[3)
Repack
(4)
Paint
5.10.24
clean,
valves.
exposed
surfaces.
Heat~
a)
overhaul,
Daily
279
and repack
pumps.
MIL-HDBK-1125/l
(1) Check for correct operation of relief valve,
steam pressure reducing valve, overflow, controls, alarms, and
Report any
steam pressure and temperature
indicators.
malfunctions
immediately.
(2)
Inspect
for steam
and water
leaks.
Repair
immediately.
once a year, or more often under severe
b) Annually.
conditions,
clean the unit and inepect the following:
(1) Spray
seating.
vaives
and proper
(2) Water
and wear.
discharge
corrosion,
instruments.
(6)
Condition
of gage
7)
Condition
of piping
IN
Condition
EW!.E!=. Refer
a)
Daily.
Inspect
pressure
and check
Check
Unusual
noise
(2)
Electric
(3)
Hot bearings.
(4)
Abnormal
(5)
Hot stuffing
alarms,
for cracks
hourly:
for overheating.
suction
box.
280
and
for corros. on,
or vibration.
motors
for
r“educ.inq,
.
3.6.2.
for the following
(1)
of heater
controls,
of insulation.
to par.
and
and valves.
Open
8) Vent condenser.
of tubes, and scaling.
(9)
peeling.
glass,
Remove
interior
steam
Condition of relief,
(5)
.,
and overflow valves.
clogging
scaling,
for clogging,
Inspect
(4) Oil separator.
of oil, corrosion,
or scaling.
vent,
5.10.25
nozzles
AC
TI
evidence
wear,
erosion,
(3) Trays (on tray type units).
for corrosion, warping, and scaling.
inspect
float,
for corrosion,
VE
service
or discharge
pressures.
and
MIL-HDBK-1125/l
(
(6)
Abnormal
leakage
through
glands/seals.
Inspect external gear and bearing
b)
Monthly.
houeings for correct lubricant condition.
Establish lubrication
requirements
and schedule in accordance with manufacturer’s
recommendations.
Completely disassemble,
for the following:
Annually.
c)
Check
the pump.
(1)
Excessive
(2)
Hot and cold
(3)
Corrosion
or erosion
(4)
Excessive
wear of shafts,
alignment.
Cracks,
5.10.26
scrapes,
Inspect
b)
(1)
Abnormal
vibration
(2)
Abnormal
preesure
(3)
Excessive
(4)
Hot bearings.
(5)
Hot stuffing
of gear
3.6.2.2.
hourly:
and noise.
and flow conditions.
or inadequate
packing
leakage
box.
Semiannually
(1) Check
unit at stand-still
flush,
to par.
bearings,
or corrosion
for the following
IN
AC
Daily.
sleeves,
wastage,
Refer
a)
of parts.
TI
(5)
if provided.
and
clearances.
and seals.
teeth
clean,
VE
inspect
alignment of pump and driver with
and normal operating temperature.
(2)
Check
shaft
(3)
Replace
sleeves
packing
for scoring.
if required.
(4) Drain .the oil from oil-lubricated,
and refill with clean oil.
281
the
bearings,
----
MIL-HDBK-1125/l
Do not
drain plug
(5) Check grease-lubricated
bearings.
When adding greaee, remove
overgreaae
the bearings.
or use a safety fitting to prevent overgreasing.
c) Annually.
the pump.
Check
manufacturer’s
and 0.025 inch
required,
seals,
Completely
disassemble,
for the following:
(2) Bearing wear and clearances.
Overhaul
according to manufacturer’s
instructions.
for scoring,
Impellers
for corrosion,
(5)
Calibrate
pressure
(6)
Suction
cleanliness.
erosion,
gages,
and discharge
PumDs.
Refer
IN
AC
ReCiDr ocatina
or wear
if
at
or excessive
strainers
to par.
for
3.6.2.3.
Daily
(1)
Inspect
for the following
(a)
Abnormal
speed.
(b
Improper
stroke
(c
Defective
(d
Ineffective
(e
Improper
(f)
Steam
hourly:
length.
operation
of lubricator.
operation
action
and water
of governor.
of the air chamber.
leaks.
(2) Establish
lubrication
requirements
and
in accordance with manufacturer’s
instructions.
b)
0.005
thermometers,
TI
flow meters.
a)
corrosion,
(4)
wear.
schedule
and
(1) Wearing ring clearances
according to
instructions.
Diametric clearance between
is usual.
(3) Shaft
and alignment.
5.10.27
clean,
VE
inspect
Monthly.
(1)
Inspect
Scoring
for the following:
of piston
282
rods.
and
MIL-HDBK-1125/l
(
if required;
Binding
(3)
Lost
(4)
Tilted
(5)
Defective
glands
in stuffing
condition
Check
the
following
boxes.
of strainers.
a year
Condition
(b)
Condition
(c)
Piston
rings
(d)
Piston
rod packing.
(e)
Relief
valve,
Alignment.
(9)
Strainers,
often
end:
of valves,
springs,
of cylinder
liner.
TI
AC
(f)
or more
in the liquid
(a)
bolts.
and
or packings.
if used,
and setting.
if used.
IN
erosion, or excessive
(3) Also look for corrosion,
and for transmission
of strains from piping to
(4
valvea
mechanism.
motion.
1) Dismantle the pump once
c ean and inspect the pump.
wear of paints,
pump.
slide
operating
Annually
(2)
retaining
of valve
VE
c)
(2)
and
Check
(a)
seals.
the following
Condition
(b)
Alignment.
(c)
Clearance
(d)
Lubricator.
(e
Governor.
liner.
283
in the steam
of pistons
between
end:
and piston
piston
rings,
and cylinder
MIL-HDBK-1125/
cheet, scoring
excessive wear
(5) Check for plugged steam passages in steam
of shoulders or cylinders,
corrosion,
erosion,
of parts.
(6)
Calibrate
(7)
Replace
Steam
a)
packings.
Refer
In ie ctors.
to par,
(1
Inspect
for steam
(2)
Check
for correct
(3)
Check
for correct
(4)
Check
for erratic
and water
leaks.
feedwater
flow.
temperature
b)
Annually.
following:
(1)
wear, and clogging
nozzles.
Dismantle
Injectors
passages.
(2) Valves
Check packing.
as
and pressure
injector.
Clean
and inspect
for corrosion,
erosion, excessive
Pay particular
attention to
for corrosion,
excessive
for corrosion,
scaling,
(3)
Piping
(4)
Insulation.
IN
Repair
overflow.
AC
TI
readings.
leakage.
3.6.2.5.
Da. ly
required.
for the
and
instruments.
VE
5.10.28
1
wear,
and
and erosion.
5.10.29
Steam Turbines
Refer to par. 3.6.6.
(Noncondensina)..
Institute preventive maintenance
schedule in accordance with
manufacturer’s
recommendations.
The following program is
suggested
for a single-stage
impulse noncondensing
steam turbine
typically used to drive auxiliary equipment.
a)
Daily
(1)
Inspect
for the following:
(a)
Proper
oil levels,
(b)
Hot bearings.
temperatures.
284
pressures,
and
MIL-HDBK-1125/l
(
(c)
Dirty
or emulsified
(d)
Unusual
(e)
Steam,
water,
(f)
Proper
operation
of governor
(9)
Proper
operation
of instruments,
no>ae
oil.
or vibration.
Repair
and oil leaks.
as
necessary.
varying
valve.
in accordance
(2) Eetablish lubrication
requirements
with manufacturer’s
instructions.
b)
Weekly
(1)
Blow down
steam
(2)
Lubricate
govarnor
linkagss.
(3) Trip
its operability.
(1]
bearings,
and
Change
bearing
strainer
valve
by hand
oil and clean
coupling
trip
trip lever
reservoir.
of governor
for looseness,
to
wear,
parts,
and
IN
Check
and schedule
connection.
and overspeed
(2) Make visual inspection
linkage for lost motion.
(3)
alignment.
emergency
AC
Monthly
c)
gages,
TI
VE
and throttle
check
under
load.
d)
Annually.
Make a thorough inspection of the unit
after the first year of operation.
Subsequent
internal
inspection
intervals should be baaed upon operating conditions
and the operating
record of the machine.
Follow manufacturers
recommendations
for such inspections.
The following may be
adopted as guidelines
for an annual overhaul:
play
(1)
in linkage.
operation.
(2)
Repair
Dismantle
speed
Check overspeed
if neceseary.
285
governor
and check
trip governor
and rectify
for proper
MIL-HDBK-1125/l
(3
etc.
stem,
Clean and examine governor
Replace stem packing.
(4)
thrust
bearing
(6)
Clean
steam
(7)
Clean
and inspect
(8)
Inspect
buehing,
for end play.
(5I
Clean
and examine turbine
,– ,
.–
damage, erosion, and debris.
for cracks,
axial
Check
valve,
blades
and shrouds
strainer.
packing
rings
for damage
and
rubs.
TI
VE
valve
turbine
necessary.
5.10.30
Air COmrJressors.
a)
Daily
(1)
Inspect
(a)
air,
consistency.
for the
Unusual
if
3.6.10.
following:
noise
or vibration.
Abnormal temperature
and pressure
water, or lubricating
oil.
(c)
Proper
operation
(d)
Hot bearings
(e)
Correct
of
of unloader.
and stuffing
lubricating
box.
oil level and oil
(2) Establish lubrication
requirements
and
in accordance with manufacturer’s
recommendations.
IN
schedule
(b)
cooling
to par.
AC
compressed
Refer
Change
bearings.
b)
Quarterly.
Inspect
(1)
Compressor
(2)
Operation
(3)
Belts
(4)
Cleanliness
(5)
Tightness
for the following:
valves
for wear,
dirt,
and improper
seating.
of safety
for tension,
valves.
wear,
of air intake
of cylinder
286
and deterioration.
filter.
head bolts
and gaskets.
MIL-tIDBK-1125/l
(
c)
Annually
(1)
Check
cylinders
for wear,
scoring,
corrosion,
and dirt.
scoring,
(2) Inspect pistons and rings for leakage,
security to the piston rod, and head clearances.
for wear
(3) Inspect crank
and proper operation.
Check
alignment
and crank
shaft
of the compressor
bearings
with
VE
(4)
shaft
to the driver.
wear,
respect
5.10.31
Refer to par. 3.6.11.
Establ.+ah a
~.
comprehensive
and coordinated
maintenance
and inspect~on program
for eteam trape, strainers, and separator.
As a minimum, the
following must be done for central boiler plants.
the traps,
Piping
(2)
Correct
leaks.
(4)
baskets.
and oil
Repair
as necessary.
Abnormal
preaeure
drop
acrose
etrainere.
Unusual
accumulations
of foreign
(5) Unusual
from separators.
and excessive
discharge
strainer
(6)
and
operation.
IN
AC
(1)
(3)
etrainere,
TI
Inspect
Daily.
a)
for the following:
separators
Damage
to insulation
at trapa.
matter
in
of condensate
Repair
as
necessary.
b)
Monthly
(1)
B1OW down
steam
trap to eliminate
dirt
accumulations.
accumulated
c)
(2)
air.
Open
the air vents
(3)
Test
traps
on float
for correct
Annually
287
traps
operation.
to vent
MIL-HDBX-1125/l
..
them
carefully
(1) Completely
disassemble
for the following:
(a)
Cracked,
steam
corroded,
traps
broken,
and
inspect
loose,
or worn
parts.
of valves
(b) Excessive
and seats.
(c)
wear,
Defective
(2)
Replace
(3)
Reassemble
bellows,
or’ repair
and orifices.
E lectric
a)
Inspect
Cleanliness.
(b)
Overheating.
(c)
Hot bearings.
(d)
C&rect
(e)
proper
(f)
Unusual
(h)
operation.
3.6.7.
lubrication.
operation
noise
Continuous
Loose
of instruments
or excessive
belts,
b)
bars.
and
or vibration.
sparking
at
if provided.
(2) Establish lubrication
and motor
with manufacturer’s
recommendations.
accordance
linkages,
for the following:
(a)
(9)
or brushes.
commutator
or floats.
gaskets,
for proper
to par.
AC
IN
controls
bearings
Refer
buckets,
defective
and test
Daily
[1)
loose
Motors.
and wire
TI
5.10.32
grooving,
VE
drawing
maintenance
Annually
(1)
Check
Inspect squirrel cage rotors for broken
for loose or broken fan blades.
(2) Thoroughly
for wear and dirt.
inspect
288
ball,
roller,
or
and sleeve
in
MIL-HDBK-1125/l
Check
and record
insulation
(4)
Check
windings.for
(5)
Check
coupling
dirt,
resistance.
moisture,
cracks,
and
wedges.
5.10.33
to pars.
t IFDI
and 3.6.4.
3.6.3
a)
Refer
Daily
(1)
Inspect
for the following:
(a)
Abnormal
noises.
(b)
Abnormal
(c)
Overheating
vibrations.
(d)
(e)
(f)
(9)
schedule
Abnormal
bearing
Condition
Proper
temperature.
of oil and bearing
flow and temperature
AC
water.
of drive.
TI
.
cooling
alignment.
VE
loose
(3)
Freedom
of damper
oil
level.
of bearing
motion.
(2) Establish
lubrication
requirements
and
in accordance with manufacturer’s
recommendations.
Quarterly
IN
b)
(1)
Examine
water
cooling
system
for corrosion
and
clogging.
(2) Clean rotor and casing and inspect for
corrosion,
erosion, and damage.
Check clearances
between rotor
and casing.
(3)
Check
alignment
of shaft
and coupling;
inspect
coupling.
(4) Check condition of foundation and tightness
bearing and foundation bolts.
Defective
foundation”or
loose
bolts may promote heavy vibration.
(5)
Inspect
bearings.
289
of
MIL-HDBK-1125/l
After
Annually, or more often if required,
c) Annually.
and perform the following maintenance
work:
replacing
(1)
Completely
(2)
Clean
overhaul
and flush
bearings.
cooling
system.
(3) Repair or replace fan blades,
blades, rebalance rotor.
(4)
Repair
or replace
(5)
Repair
insulation.
defective
as required.
parts.
TI
VE
inspect
Command inspections
are a
5.10.34
COmm and In sDections.
They are made to determine
function of commanding
officers.
general condition and effective use of central boiler plant
equipment,
causes of neglect or carelessness,
and need for
additional
instruction
or training of operating personnel.
Command inspections
may be formal, informal, or spot checks.
the
walls,
AC
Command inspections
are made on accessible
5.10.34.1 procedure.
central boiler plant equipment at any time that causes the leaet
Equipment,
possible interference
with boiler plant routine.
accessories,
and connections
are checked during formal
inspections;
equipment is selected at random for informal
Inspectors
look for the following:
inspections
and spot checks.
a) Cleanliness
and instruments.
b)
leaks
from water,
Neat and orderly
c)
and fuel.
IN
supplies,
Any
of equipment,
d)
Deficiencies
e)
Methods
pipes,
steam,
storage
and procedures
oil,
tools,
of equipment,
used
walks,
or air equipment.
spare
working
floors,
parts,
order
of parts.
in hazardous
operations.
5.10.34.2
personnel
noted.
i?OllOW-UD.
are advised
After inspections
have been completed,
of the deficiencies
and irregularities
Technical
5.10.35
Technical
inspections
are made
In sDectim.
to determine
the general condition of boiler plant equipment,
effectiveness
of preventive maintenance,
and need for additional
instruction
or training of maintenance
personnel.
290
MIL-HDBK-1125/l
Boiler p“lant equipment is selected at
5.10.35.1 [email protected]
random and inspected without previous notification
so that the
overall condition of equipment and efficiency
of maintenance
personnel can be determined.
Technical
inspections
are
preferably
made while equipment is being dismantled
for routine
inspection.
In thoroughness,
Ghe technical inspection
should
equal inspections
made by insurance or other authorized
The following are checked at each piece of
inspecting
agenciee.
boiler plant equipment
inspected:
included
in command
5.10.~i).
b)
Adequacy
of preventive
performed.
inspections
(refer
VE
Items
par.
maintenance
to
as it is being
AC
TI
5.10.35.2
On completion
of the technical
inspection,
the Public Works Officer will take the steps necessary to correct
indicated deficiencies
in preventive
maintenance
inspection and
eervice procedures.
He will arrange to have any indicated
maintenance
work done at once.
IN
(
291
MIL-HDBK-1125/l
APPENDIX
HEAT BAIANCE
CALCULATIONS
See Figure
100-9sia Steam Heat Balancq.
figure is a duplicate of Figure 1.)
this
1125LSS.WATER
!
1
WATEFII?EO”F <
4
L
IWM ENERGY ‘
~
!2 LM.
WATER
HEAT
EXCHANGER
AC
I
[email protected]
1%EMEROV
●
I
i
1
i
100LSSWAIER
o 3*F
2SSENERGY
I
1
1
P
.
—
I
I
I
PUMP
RETURNTO
CENTRAL
SOILER
?LAFAT
;!\Lr5F
WATER
IN
—.—
“b
14UEMEROY
CO#OEIISAIE
WELL
100-psi
conditions
CONOENSER
TI
100L= ~AM
a)
vENT
I
1
mmm
(OFTIOMALI
PHE=URE
REOUCING
VALVE
(Note
y
[email protected] 140+
i
~&l=---
A-1.
VE
A.1
that
A
The following
Figure
Steam
A-1
Heat
assumptions
Balance
have been made:
(1)
100 lb of steam at 100 psig saturated
will heat water from 50 to 140 degrees F.
292
MIL-HDBK-l12s/l
steam
input
piping,
flash
(2) Percent energy is based
to the heat exchanger.
in the
(3) Negligible
heat” is lost from the insulated
exchanger,
vent condenser,
or condensate
tank.
heat
steam
on the energy
(4) The vent condenser condenses 91 percent
and cools the condensate
to 100 degrees F.
of the
b)
The following
utilized:
steam
100 psig
eteam
enthalphies
hg100
in Btu/lb
(1)
For
(2)
For O psig steam
(3)
For water
at 50 degrees
(4)
For water
at 100 degrees
F hf100
= 68.0
(5)
For water
at 140 degrees
F hf140
= 107.9
(6)
For water
at 198 degrees
F hf198
= 166.0
= 309.0
exchanger
table
= 1189.7
hgO = 1150.4
TI
hf100
been
AC
have
VE
(5) The amount of flash steam releaeed is not
with
affected by the water returned from the vent condenser.
this aaaumption,
our example aervee to establiah flaah steam
losaea for systems without vent condenaera.
Base Energy
= M x hg100
at the heat
= 100 lb x 1189.7
(2) Energy at heater exchanger
= 100 lb X 309.0 Btu/lb = 30,900 Btu
IN
and hfO = 180.0
F hf50 = 18.0
Percent energy in saturated water
c)
outlet is calculated
ae follows:
(1)
and
outlet
Btu
= M x hf100
[3) Percent energy at heat exchanger out = (energy
at heat exchanger outlet divided by base energy) x 100 = (30,900.
divided by 118,970) x 100 = 26 percent
d)
Energy from the 100-paig saturated water at 309
Btu/lb and 338 degrees F reaches a new equilibrium
after it exits
the steam trap at O psig, 180 Btu/lb, and 212 degrees F by
flaehing a portion of ite mass to steam at O psig.
The pounds of
flaah steam Fa released is calculated
aa follows:
(1)
M X hf100
= FS X hgO + (M-Fs) X hfO
293
MIL-HDBK-1125/l
Btu/lb)
100 lb X 309.0 Btu/lb
(2)
= (100 lb-Fs) X 180 Btu/lb
+ 180 Btu/lb
e)
= FS = (100 lb-Fs
(3)
X FS
30,900
Btu 1150 Btu/lb
(4)
12,900
Btu = 970 Btu/lb
(5)
13.3 lb = Fs.
Percent
energy
X f,e + 18,000
1150
Btu
X fs
Use Fs = 13 lb for Figure
in flash
steam
ia calculated
A-1.
as
TI
VE
follows:
(1) Energy in flash steam
13.3 lb X 1150 Btu/lb = 15,295 Btu
= MF x hgo =
(2) Percent energy in flash steam = (energy in
flash steam divided by base energy) x 100 (15,295 Btu divided by
118;970 Btu) x 100 = 12.86 percent
(3)
1.2 lb.
f)
Pounds
Use 1 lb.
13 percent
of flash
in Figure
steam
0.91
X
A-1.
lost = 0.09 x 13.3 lb =
Percent energy in flash steam lost = (MFlost x hgO
9)
by base energy) x 100 = (1.2 lb x 1150 Btu/lb divided by
Btu) x 100 = 1.16 percent. Use 1 percent.
IN
AC
divided
118,970
Use
h)
Pound of condensate returned
Use 12 lb.
13.3 lb = 12.1 lb.
from vent
condensel
i) Percent energy in condensate return from vent
condenser = (MCR x hf100 divided by base energy) x 100 = 12.1 lb
Use 1
x 68 Btu/lb divided by 118,970 Btu) x 100.69 percent.
percent.
have
]) Condensate return
characteristics
calculated
flash
~~ndenser)
to the central
as follows:
boiler
plant
will
(1) The mass flow to the plant will equal (water
steam out = condensate returned from the vent
Use 99 lb.
= 100 lb - 13.3 lb = 12.1 lb = 98.8 lb.
(2) The energy in the condensate well will equal
the energy in the 86.7 lb of condensate
from the heat exchanger
at 180 Btu/lb and 212 degrees F = 12.1 lb of condensate
from the
vent condenser at 68 Btu/lb and 100 degrees F = (86.7 lb x 180
Btu/lb = 12.1 lb X 68 Btu/lb) = (15,606 + 823) = 16,428 Btu.
294
MIL-HDBK-1125/l
(3) The temperature
of the condensate
can be
calculated
from the energy of the condensate
and the steam
tables.
Energy in condensate
divided by lb of condensate
=
(16,428 Btu divided by.98.8 lb) - 166.3 Btu/lb.
This
corresponds
to 198 degrees F.
(energy
divided
(4) Percent energy in the condensate
return is
in condensate divided by base energy) x 100 = (16,428 Btu
Use 14 percent.
by 118,970 Btu) x 100 = 13.8 percent.
from 50 to 140 degrees
is calculated
as
F
VE
k) The amount of water heated
in the heat exchanger and vent condenser
follows:
IN
AC
TI
(1) The energy available for heating the water
equals the energy in the incoming steam (base energy) minus the
energy lost by vented steam (subpar. f) minus energy return
(subpar. i) = (118,970 Btu - 1,380 Btu - 16,428 Btu) =
101,162 Btu.
(2) The energy required to heat water from 50 to
140 degrees Fis (hf140 - hf50) = (107.9 Btu/lb) - 18 Btu/lb =
89.9 Btu/lb.
divided
(3) The pounds of water
by 89.9 Btu/lb) = 1,125
b.
1) The temperature
is calculated:
X (1150.4
at the outlet
(1) 14Fcond. x (hgO-hfO)
Btu/lb - 180 Btu/lb) divided
Btu/lb.
From
of 60 degrees
heated
(2) h50 + 10.44
the steam tables
F.
is (101,162
of the vent
Btu
condenser
divided by Mw = 12.1 lb
by 1125 lb = 10.44 Btu/Lb.
= 18 Btu/lb + 10.44 Btu/lb = 28.44
this corresponds
to a temperature
A.2
See Figure A-2.
(This
figure is a duplicate of Figure 2.)
This heat balance is based
on the came assumptions
listed in par. A.1 except now 15-psig
saturated eteam is utilized for heating water.
have been
The following
a).
utilized:
(1
For
(2
For water
eteam
15 psig
table
steam
enthalphies
hg15
= 1164.0
in Btu/lb
and
hf15 = 219.0
at 50 degrees
.295
F hf50 = 18.0
MIL-HDBK-l125/l
F-F
l:’’’”s”
l“W%”
&x-(omollAL)
PRESURE
REOUCIMG
VALVE
4 l=
WATER
● lorr
HEAT
EXCHANGER
MO LBSWATER
.-l
25a”F
lENENERGY
exchanger
Btu/lb
I
1
I
1
I
1
1
:.
RETURMTo
CENTRAL
BOILER
PLANT
100LM.WATER
O ME”F
15%ENERGY
-IF
w
TRAP
AC
IN
15-psi
4LUATEAM
4WEWI!R8Y
TI
●
I
,
VE
&“
100la SPEAN
O 15~G
IGGNENERGY
1
PUMP
1
1
I
.
Figure A-2
Steam Heat Balance
(3)
For water
at 140 degrees
F hf140
= 107.9
(4)
For water
at 208 degrees
F hf208
= 176.0
Percent energy in saturated water
b)
outlet is calculated
as follows:
(1) Base Energy
= 116,400 Btu
= M x hg15
(2) Energy at heat exchanger
(100 lb X 219.0 Btu/lb) = 21,900 Btu
296
at the heat
= (100 lb x 1164.0
outlet
= M x hf15
=
MIL-HDBK-1125/l
(3) Percent energy at heat exchanger outlet
= (Energy at heat exchanger outlet divided by base energy)
= (21,900 divided by 116,400) x 100 = 18.8 percent.
Use 19 percent.
x 100
Energy from the 15-psig saturated water at 219
c)
Btu/lb and 250 degrees F reaches a new equilibrium
after it exits
the steam trap at O psig, 180 Btu/lb, and 212 degrees F by
The pounds of
flashing a portion of its mase to eteam at O paig.
flash steam Fs released is calculated
as follows:
MX
hf15
= Fs X hgO+
(3)
- 180 Eltu/lb X F
d)
21,900
3,900
(5)
4.0 lb = Fs
Percent
energy
(1) Energy
=4,600 Btu
X Fs + 18,000
Btu
Btu = 970 Btu lb X Fs
in flash
AC
X 1150 Btu/lb
= FS X 1150 Btu/lb
Btu = 1150 Btu/lb
(4)
follows:
Btu/lb
X hfO
TI
V
(2)
100 lb X 219.0
= (100 lb - Fs) X 180 Btu/lb
(M-Fs)
E
(1)
in flash
steam
steam
is calculated
as
= MF x hgO = 4.0
lb
(2) Percent energy in flash steam = (energy in
flash steam divided by base energy) x 100 = (4,600 Btu divided
116,400 Btu) x 100 = 4.0 percent.
e)
= 0.36
Pounda
of flash
steam
divided
116,400
lost = 0.09
x 4.0
by
lb
lb.
IN
\
f) Percent energy in flash steam lost = (Flost x hgO
by base energy) x 100 - (.36 lb x 1150 Btu/lb divided by
Btu) x 100 = 0.36 percent.
0.91 X 4.0gib
Pound of condensate
returned
= 3.64 lb.
Uae 3.6 lb.
from vent condenser
=
h)
Percent energy in condensate
return from vent
condenser = (MMCR x hf100 divided by base energy) x 100 = 3.64 lb
x 68 Btu/lb divided by 116,400 Btu) x 100 = 0.21 percent
return
i) Condensate
have characteristics
calculated
to the centra
as follows:
297
boiler
plant
will
MIL-HDBK-1125/l
(1) The mass flow to the plant will equal (water
steam out = condensate
returned from the vent
Use 100 lb.
= 100 lb - 4.0 lb + 3.6 lb = 99.6 lb.
in - flash
,condenser)
(2)
the energy in the
at 180 Btu/lb and
vent condenser
at
Btu/lb + 3.6 lb X
The energy in the condensate well will equal
96.0 lb of condensate
from the heat exchanger
212 degrees F + 3.6 lb of condensate
from the
68 Btu/lb and 100 degrees F = (96.0 lb x 180
68 Btu/lb) + (17,280 + 245] = 17,525 Btu.
(4) Percent energy in the condensate
return is
in condensate
divided by base energy) x 100 = (17,525 Btu
by 116,400 Btu) x 100 = 15 percent.
j)
in the heat
follows:
The amount of water heated
exchanger
and vent condenser
from 50 to 140 degrees
is calculated
as
F
TI
(energy
divided
VE
(3) The temperature
of the condensate
can be
calculated
from the energy of the condensate and the steam
tables.
Energy in condensate
divided by pounds of condensate
=
(17,525 Btu divided by 99.6 lb) = 176 Btu/lb.
This corresponds
to 208 degreea F.
AC
(1)
The energy available for heating the water
equals the enerqv in the incominq steam (base enerqy) minus the
e~ergy lost by ~~nted steam (subpar. f) minus ener~~ return
(aubpar. i) = (116,400 Btu - 414 Btu - 17,525 Btu) = 98,461 Btu.
(2) The energy required to heat water from 50 to
140 degrees F is (hf140 - hf50) = (107.9 Btu/lb - 18 Btu/lb) =
89.9 Btu/lb.
divided
(3) The ~ounds of water heated is (98, 461 Btu
by 89.9 Etu/lb)’=
1,095 lb.
Use 1,100 lb:
IN
k) The temperature
is calculated:
x (1150.4
of the vent condeneer
(1) MFcond. x (hgO - hfO) divided by Mw = 3.64 lb
Btu/lb - 180 Btu/lb) divided by 1,095 lb = 3.22 Btu/lb.
Btu/lb.
From
of 53 degrees
A.3
A-3
at the outlet
Hl!
(identical
(2) hf50
the steam
F.
+ 3.22 = 18 Btu/lb + 3.22 Btu/lb = 21.22
tables this corresponds
to a temperature
Temnerat re Wat
to Figure 3).
ea
298
Balance.
See Figure
MIL-HDBK-1125/l
11Z2LB
[email protected]
A
207l= WA7ER O -F
lWXENERGV INPUT
112sL=.
WATER INO SO-F
m
TI
VE
HEAT
EXCHANGER
I
L
I
fiE7U7iNT0
CENTRAL
‘lLERPLANT
CU7l= WATER (3z4dF
22’!4
ENERGY
compare
AC
Figure A-3
High Temperature
Water (HTW) Heat
The following assumptions
are made so we can
a)
the HTW system with the 100-psig steam system:
(1)
140 degrees
1126 lb of water
have
with
an heat
been
will
be heated
from
50 to
F.
(2) The heat exchanger will be designed to heat
a 400 degrees F inlet and 240 degrees F outlet
IN
the water
HTW .
piping
Balance
(3) Negligible
exchanger.
b)
The following
utilized:
heat
steam
is lost
table
from the insulated
enthalphies
in Btu/lb
(1)
For water
at 50 degrees
(2)
For water
at 140 degrees
F hf140 = 107.9
(3)
For water
at 240 degrees
F hf240
299
F hf50 = 18.0
= 208.3
MIL-HDBK-1125/l
(4)
High temperature
water (Hi?’w)flow
d)
by the following energy balance:
(1)
Btu/lb
Energy
added
= Energy
(2)
101,138 Btu = MHTW
- 208.3 Btu/lb)
(3)
boiler
F hf400
= 375.0
MU X (hf140
Energy added to water is calculated:
18.0
Btu/lb)
=
101,138
Btu.
= 11~~ lb X (107.9 Btu/lb -
calculated
(375.0
at 400 degrees
MHTW
= 606.7
lb.
rate
released
X (hf400
ie
by HTW
- hf240)
= MHTW X
VE
hf50
For water
Use 607 lb.
Percent energy in water returned
e)
plant is calculated
as follows:
to the central
IN
AC
TI
(Energy in water returned divided by energy in water
supplied) x 100 = (MHTW x hf4GO) x 100 = 606.7 lb X 208.3 Btu/lb
Use 56
divided by 606.7 lb x 375 Btu/lb) x 100 = 55.5 percent.
percent.
300
-
MIL-HDBK-1125/l
BIBLIOGRAPHY
HANDBOOK
MIL-HDBK-loo3/7
NAVFAC
MAINTENANCE
MO-221
NAVFAC
Steam
Power
AND OpEMTION
- Fossil
Plants
Fuel
(no) MANUAL
Metering
GUIDE
5pECIFICAT10NS
VE
MILITARY
15551
Watertube
Oil/Gas
(Packaged)
NFGS
15553
Steam Heating Plant
Coal/Oil or Coal
NFGS
15554
NFGS
15631
Boilers,
Oil or
Watertube
(Shop)
TI
NFGS
Steam Heating Plant Watertube
Coal/Oil or Coal
(Field)
IN
AC
Steam Boilers and Equipment
(500,000-18,000,000
Btu/hr)
NFGS
15632
Steam Boilers and Equipment
(18,000,000-60,000,000
Btu/hr)
NFGS
15852
Mechanical Cyclone Dust Collector
Flue Gas Par~iculates
NFGS
5853
Electrostatic
Particulate
NFGS
5854
Fabric Filter Dust Collector
Particles in Flue Gae
NFGS
5877
Dust and Gas Collector,
Fabric Filter Type
NFGS
15972
Direct
NFGS
15997
Testing
Digital
Dust Collector
Control
Industrial
of
of Flue Gae
of Flyash
Dry Scrubber
Syateme
Ventilation
Systems
(Unless otherwiee
indicated, copies are available from the
Defense Printing Service Detachment office, Bldg. 4D (Customer
Service),
700 Robbins Avenue, Philadelphia,
PA 19111-5094. )
301
and
MIL-HDBK-1125/l
NON-GOVERNMENT
AMERICAN
PUBLICATIONS:
SOCIETY
FOR TESTING
AND MATERIALS
(ASTM)
ASTM
D197
Standard
Fineness
Test Method for Sampling
Test of Pulverized
Coal
ASTM
D1066
Standard
Practice
for Sampling
and
Steam
IN
AC
TI
VE
(Unless otherwise indicated,
copies are available from the
American Society for Testing and Materials
(ASTM), 1916 Race
Street, Philadelphia,
PA 19103.)
302
MIL-HDBK-1125/l
(
REFERENCES
NOTE : THE FOLLOWING REFERENCED
DOCUMENTS FORM A PART OF THIS
USERS OF THIS HANDBOOK
HANDBOOK TO THE EXTENT SPECIFIED HEREIN.
SHOULD REFER lY3 THE I.ATEST REVISIONS OF CITED DOCUMENTS UNLESS
OTHERWISE
DIRECTED.
~VFAC
: u~
AND
:
Unless otherwise indicated, coDies are available
from the Naval
Publications
and Forms Center,- Standardization
Documents Order
PA
Desk, Buildinq 4D, 700 Robbins Avenue, Philadelphia,
1911i-5094.
-
Mo MANUALS
VE
.
ANCE AND OP~UALS
MO-209
Maintenance
of Steam, Hot Water and
Compressed
Air Distribution
Systems.
MO-225
Industrial
MO-230
Petroleum
MO-324
Inspection and Certification
of Boilers
and Unfired Pressure Vessels.
MO-911
Utilization
of Navy-Generated
as Burner Fuel.
Treatment.
TI
Water
Facilities.
AC
Fuel
Waste
Oils
P-PUBLICATIONS
P-106O
Electrical Transmission
Safety Manual
and Distribution
IN
GOVERNMENT
TM 5-815-1
.
Air Pollution Control Systems
Boilers and Incinerators.
(Unless otherwise indicated, copies
U.S. Army Publications
Distribution
St. Louis, MO 63114.)
UG-0005
Steam
Trap
are available
from
Center, 1655 Woodaon
Users
for
Road,
Guide.
(Unless otherwise indicated, copies are available
from Commanding
Officer, Naval Facilities Engineering
Service Center (NFESC), 560
Center Drive, Port Hueneme, CA 93043-4328. )
303
MIL-HDBK-1125/l
NAVFAC
11300
37
Energy
and Utilities
Policy.
(Unless otherwise
indicated, copies are available
from Naval
Documente Ordex
Publications
and Forms Center, Standardization
PA
Desk, Building 4D, 700 Robbins Avenue, Philadelphia,
19111-5094. )
UBLIC
N~
ANERICAN
NATIONAL
TIONS:
STANDARDS
INSTITUTE
(ANSI)
B16
Pipe,
Flanges,
and Fittings.
ANSI
B31.1
Power
Piping.
ANSI
B36
Iron and Steel
IN
AC
TI
VE
ANSI
Pipe.
(Unless otherwise indicated, copies are available from the
American National Standards Institute
(ANSI), 11 W. 42nd Street,
New York, NY 10036.)
ANERICAN
ASME
SOCIETY
Boiler
OF MECHANICAL
and Pressure
Section,I
Rules
ENGINEERS
Vessel
(ASNE)
Code.
for Construction
of Power
for Heating
Boiler. ”
Section
IV
Requirements
Section
VI
Recommended
Rules for Care
of Heating Boilers.
and Operation
Section
VII
Recommended
Boilers.
of Power
Section
VIII
Pressure
Section
IX
Welding
Rules
Boilers.
for Care
Vessels.
and Brazing
ASNE
CSD-1
Controls and Safety
Automatically
Fired
ASNE
PTC 4.1
Steam
Generating
Qualifications.
Devices for
Boilers.
Units.
(Unless otherwise indicated, copies are available from the
American Society of Mechanical Engineers,
United Engineering
Center, 345 East 47th Street, New York, NY 10017.)
304
(.
MIL-HDBK-1125/l
AMSRICAN
OF TESTING
AND MATERIALS
(ASTM)
ASTM
D388
Standard
Rank.
Classification
of Coals
ASTM
D396
Standard
Claaaification
for Fuel Oila.
by
NATIONAL
BOARD
National
OF BOILER
Board
AND
VE
(Unless otherwise
indicated,
copies are available
from the
American Society of Teeting and Materials,
1916 Race Street,
Philadelphia,
PA
19103.)
PRESSURE
Inspection
VESSEL
INSPECTORS
(NBB1)
Code.
NATIONAL
FIRE PROTECTION
30
NFPA
31
ASSOCIATION
Flammable
(NFPA)
and Combustible
Liquida
Standard for the Installation
Burning Equipment.
AC
NFPA
TI
(Unless otherwise indicated,
copies are available
from the
National Board of Boiler and Pressure Vessel Inspectors,
1055
43229. )
Crupper Avenue, Columbus,
OH
Code.
of Oil-
NFPA
54
National
NFPA
58
Standard for the Storage and Handling
Liquefied
Petroleum Gases.
NFPA
8501
Standard for Single
Operation.
IN
.
SOCIETY
Fuel Gas Code.
Burner
of
Boiler
NFPA
8502
Standard for the Prevention
of Furnace
Explosions/Implosions
in Multiple Burner
Boiler-Furnaces.
NFPA
8503
Standard
for Pulverized
Fuel
Systems.
(Unless otherwise indicated,
copies are available
from the
National Fire Protection
Association,
1 Batterymarch
Park, P.O.
Box 9101, Quincy, MA 02269-9101. )
305
MIL-HDBK-1125/l
GLOSSARY
The
~.
reduction
in degree
of intensity
Pressure above
Absolute DressuKe.
gage and atmospheric
pressures.
~.
Alternating
of pollution.
zero pressure,
the sum of the
current.
Bctual cubic foot . A cubic foot referring
to the actual
Usually abbreviated
temperature
and pressure of the gas.
Actuatina
aiqna~.
A signal
function or position itself
temperature
and
expressed as
VE
Actual volume.
The volume of a gas at its actual
pressure.
In the United States, this is normally
actual cubic feet.
ACF.
which causes a control
accordingly .
element
to
1.
AC
TI
Adiabatic
temperature.
The theoretical
temperature
that would
attained by the products of combustion
provided the entire
chemical energy of the fuel,, the sensible heat content of the
fuel, and combustion
air above the datum temperature
were
transferred
to the products of combustion.
This assumes:
Combustion
2.’ There
is complete.
is no heat
loss.
3.
There
is no dissociation
of the gaseous
4.
Inert
gases
in the reaction.
Aeration
play
To circulate
no part
oxygen
through
compounds.
a substance.
An air pollution control device
organic gases by incineration.
IN
Afterburner.
undesirable
be
that removes
Af tercoolez.
A device used for lowering the temperature
of a
fluid.
Typically
used on air compressors
or to reduce the
temperature
of boiler blowoff discharge
before it enters the
building drain.
Aoqlomerating.
A caking
characteristic
of a coal.
A i r atomizinq oil burner.
A burner for firing oil in which the
oil is atomized by compressed air which is forced into and
through one or more streams of oil, breaking the oil into a fine
spray.
306
MIL-HDBK-1125/l
~a
short
The
period,
through
which
flow of air at’a
A refractory
air passes.
high velocity,
wall
of hollow
usually
for a
construct, on
. .
Insufficient
air in an air-fuel mixture to
def~.
supply the oxygen theoretically
required for complete combustion
of the fuel.
.
The ratio
fuel.
The
boiler,
or duct.
of the weight,
leakage
.
See
of air to
furnace,
in the air.
The presence of contaminant
do not disperse properly and interfere
Air Doxk .
to 85
Monitoring.
AC
that
.
or volume
of air into a setting,
Air moist.ue. The water vapor suspended
.
&&umukum
exposed
TI
VE
Condition
of coal after sample has been
to 95 degrees F air until weight is constant.
An opening
through
which
substances
with human
in the air
health.
air passes.
. A heat exchanger that transfers
Air rm=heater or air ~
heat from a high temperature
medium such as hot gas, or steam,
an incoming air stream.
D~
removing
to
w.
An automatically
controlled
soot blower
ash, refuse, or soot from heat-absorbing
surfaces.
IN
(
The removal
of undesired
matter
by replacement
with
air.
An area designated
by the Federal
rol rem.
Government
in which communities
share a common air pollution
problem, sometimes involving several states.
that cannot
area.
through
any
be exceeded
The level of pollutants prescribed
by law
during a specified time in a defined
The opposition
fl~w path.
offered
307
to the passage
of air
MIL-HDBK-1125/l
A valved opening for venting air from the top of the
Rir vent.
highest drum of a boiler or pressure vessel.
Abi.m . A suitable
operated will give
condition.
horn, bell, light or other device which when
suitable notice of malfunction
or off-normal
IN
AC
TI
VE
The maximum pressure for which the
Allowable workina Pr essure.
the maximum gage pressure on
boiler was designed and constructed;
a complete boiler and the basis for setting of the pressure
relieving devices protecting the boiler.
Am~r
. The air that surrounds
The temperature
Ambient temperature.
equipment.
the equipment.
of the air surrounding
the
Analvsis, Droximate.
Analysis of a solid fuel determining
moisture, volatile matter, fixed carbon and ash expressed as
percentage
of the total weight of sample.
sis
ultimate.
Chemical analysis of a fuel determining
Jii
carbon, hydrogen,
sulfur, nitrogen, chlorine, oxygen, and ash as
percentages
of the total weight of sample.
dry fixed carbon
Anthracite.
ASTM coal classification
by rank:
92 percent or more and less than 98 percent; and dry volatile
matter 8 percent or less and more than 2 percent on a mineralmatter-free
basis.
AQLfe.K.
stone
that
An underground
bed or layer of earth,
contains water.
gravel,
or porous
Area source. In air pollution, any small individual fuel
combustion
source, including vehicles.
A more precise legal
definition
is available in Federal Regulations.
Arch-fu mace.
A substantially
horizontal
into the furnace, to serve as a deflector
As-f ired fuel,.
equipment.
&h.
The
Fuel
in the condition
incombustible
solid matter
as fed to the fuel burning
in fuel.
Ash bed.
A layer of refuse left on grates
furnace floor after, the fuel is burned.
308
structure extending
of the gases.
or deposited
on a
MIL-HDBK-1125/l
ee bh
. The method of reporting fuel analysis whereby
ash is deducted and other constituents
are recalculated
to total
100 percent.
A gate or valve
an aeh pit or coot hopper.
Aahs?ax.
from
ash pits
which
refuse
ie removed
A trench or channel used for transporting
to a disposal point by means of water.
Ueed
from
refuse
The ratio of width to depth in a rectangular
in calculating
resistance
to flow.
IN
AC
TI
VE
or elbow.
through
duct
Compressed
air supplied at pressures
sufficiently
above furnace pressure to prevent flow of combustion
gases from escaping the boiler.
~.
A burner in which the fuel in a gaseous or
finely divided form is burned in suspension, the air for
combustion
being supplied by bringing into contact with the fuel
air drawn through one or more openings by the lower static
pressure created by the velocity of the fuel stream.
Atmos.L21EKS. The body of air surrounding
the earth.
The barometer reading
Atmo D~by t~e atmosphere;
at sea level, 14.7 pounds
29.92 inches of mercury.
very
A device
fine spray.
by means
of which
of pressure exerted
per square inch or
a liquid
is reduced
to a
Apparatus
for reducing and controlling
the
temperature
of a superheated
vapor or of a fluid.
Also called
desuperheater.
~.
between
con~.
a measured
A device which cauaea the difference
property and its set point to diminish.
.
.
. .
Ewtomatlc
Lwhter
or Ag,cu!xx. A means for starting ignition of
fuel without manual intervention.
Usually applied to liquid,
gaseous or pulverized
fuel (see Igniter).
Additional
air, either hot or cold, which may be
introduced
into the exhauster inlet or burner lines to increase
the primary air at the burner.
~.
The draft which may be utilized to cause the
flow of air for combustion
or the flow of producte of combustion.
309
MIL-HDBK-1125/l
Avai Labilitv facto~.
The fraction
unit ia in operable condition.
Axial fan.
Consists
cylinder discharging
level.
Background
present in ambient
of the time during
which
the
of a propeller or disc wheel within’ a
the air parallel to the axis of the wheel.
In air pollution,
the level
air from natural sources.
of pollutants
IN
AC
TI
VE
Backina ring.
A ring of steel or other material placed behind
the welding groove when joining tubes or pipes by welding, to
confine the weld metal.
umbeK.
p~
ExaJs.
A plate
Q.
1.
firetube
2.
See Smoke
or wall
A deep bulge
boiler.
A single
Spot Number.
for deflecting
in the bottom
fabric
filter
gaaes
of the
unit
Baaho use.
An air pollution abatement
particulate
by filtering gas streams
usually made of glass fibers.
or liquids.
or furnace
shell
of a
in a baghouse.
device used to trap
through large fabric
bags
Balanced draft.
The maintenance
of a fixed value of draft in a
furnace at combustion
rates by control of incoming air and
outgoing products of combustion.
Banking.
maintain
Burning
ignition
solid
only.
fuels on a grate
at rates
ive ~. Operating boilers at combustion
BEi
sufficient
to maintain normal operating pressure
of no load demand.
p~Ll
Barometric
barometer.
.
A furnace
wall having
bare
sufficient
rates
under
to
just
conditions
tubes.
Atmospheric
pressure as determined
Dr essure.
Usually expressed in inches of mercury.
by a
Baae load.
The term applied to that portion of a boiler
load that is essentially
constant for long periods.
plant
L3atterv aetti n g. A type of setting
share common division walla.
boilers
310
in which
two or more
MIL-HDBK-1125/l
(
metal ie formed
rolled.
The rounded end of a rolled tube when the tube
over against the sheet in which the tube ie
See Flared
~.
air or gas
Tube-End.
A eeal in the shape
leakage.
of a bellows
used
to prevent
matter-free
basis
VE
A system in which fuel is pulverized,
etored in
bins, and subsequently
withdrawn
through feedera to the burnere
in amounte sufficient to satisfy load demanda.
ASTM coal classification
by rank
and with bed moisture only.
on a mineral-
1. Low volatile:
dry fixed carbon 78 percent or more, and
less than 86 percent; and dry volatile matter 22 percent or less,
and more than 14 percent.
3.
High volatile:
TI
2. Medium volatile:
dry fixed carbon 69 percent or more,
and less than 78 percent; and dry volatile matter 22 percent or
less, and more than 31 percent.
moist,
(b) Btu value 13,000 or more
mineral-matter-free
basis.
moist,
11,500
(c) Btu value 11,000 or more and less than 13,000
mineral-free
baais commonly agglomerating,
or 8,300 to
Btu agglomerating.
IN
.
AC
(a) Dry fixed carbon less than 69 percent, and dry
volatile matter more than 31 percent Btu value equal to or
greater than 14,000 moist, mineral- matter-free
basis.
Ewdihfd.
A head,
without
a manhole,
and
less than
14,000
at the end of a boiler
drum.
A nipple,
or a short
piece
of pipe
or tube,
closed
at one end.
A raised area on the surface of solid metal produced
pressure thereon while the metal is hot and plaatic due to
overheating.
311
by
MIL-HDEiK-1125/l
Usually a rectangular-shaped
casting
w.
heat-conducting
material made to fit closely
Also a refractory
shape
furnace side walls.
lining and cooled by air.
of metal or of high
on or cast to
used as a furnace
The difference
between the pressures
B1 owback.
valve opens and closes, usually about 3 percent
pressure.
at which a safety
of the opening
TI
VE
A valve generally used to continuously
regulate
B1 OW down valve.
concentration
of solids in theboiler
(not a drain valve).
Typically
used
Rkk!.eZ. A fan used to force air under pressure.
to force air through a pulverizer
or to force primary air through
an oil or gas burner register.
A local
B~.
disproportionately
area in a burning fuel bed through
large quantity of air passes.
which
a
A vented and drained container equipped with
Blo woff se~ara to~.
baffles or an apparatus
for the purpose of separating moisture
from flash steam as it passes through the vessel.
AC
A specially designed, manually operated, valve
Blowoff valve.
connected to the boiler for the purpose of reducing the
concentration
of eolids in the boiler or for draining purposes.
IN
IIQiJ&K. A closed vessel in which water is heated, steam is
generated,
steam is superheated,
or any combination
thereof,
The term
under pressure or vacuum by the application
of heat.
does not include such facilities that are an integral part of a
continuous
processing
unit but does include units supplying
heating or vaporizing
liquids other than water where these are
separate from processing
systems and are complete within
themselves.
1. High
in excess of
temperatures
of 160 pounds
pressure - a boiler furnishing
steam at pressures
15 pounds per square inch or hot water at
in excess of 250 degrees F or at pressures in excess
per sguare inch.
hot water at
2. Low pressure - a boiler furnishing
pressures not exceeding
160 pounde per square inch or at
temperatures
not more than 250 degrees F or steam at pressures
not more than 15 pounds per square inch.
water (HTW) - a water heating boiler
3. fii.ghtemperature
operating at a pressure exceeding
160 psig or temperatures
exceeding 250 degrees F.
312
MIL-HDBK-1125/l
(
and
4. Water tube - a boiler in which the tubes contain
steam, the heat being applied to the outside surface.
water
5.
Bent tube - a water tube boiler consisting of two or
more drums connected by tubes, practically
all of which’are bent
near the ends to permit attachment
to the drum ehell on radial
lines.
VE
6. Horizontal
- a water tube boiler in which the main bank
of tubes are etraight and on a slope of 5 to 15 degrees from the
horizontal.
7.
Sectional header - a horizontal
boiler of the
longitudinal
or cross drum.type,
with the tube bank comprised of
multiple parallel sections, each section made up of a front and
rear header connected by one or more vertical rows of generating
tubes and with the sections or groups of eections having a common
steam drum.
TI
8.
Box heater - a.horizontal
boiler of the longitudinal
crose drum type consietin>
of a front and rear inclined
rectangular
header connected by tubes.
or
AC
9. Cross drum - a sectional header or box boiler in which
the axis of the horizontal drum ie at right angles to the center
lines of the tubes in the main bank.
10.
Longitudinal
drum - a sectional header or box header
boiler in which the axie on the horizontal
drum or drums is
parallel
to the tubes in a vertical plane.
11.
Low head - a bent tube boiler having
relatively
short tubes in a vertical plane.
.
IN
12.
Firetube - a boiler
surrounded
by water and eteam
combustion
paes.
three drums
with
with straight tubes, which are
and through which the products of
13.
Horizontal return tubular - a firetube boiler
consisting
of a shell, with tubes inside the shell attached to
both end closures.
The producte of combustion
pass under the
bottom half of the shell and return through the tubes.
14.
Locomotive
- a horizontal
firetube boiler with an
internal furnace the rear of which ie a tube eheet directly
attached to a shell containing
tubee through which the products
of combustion
leave the furnace.
313
MIL-HDBK-1125/l
15. Horizontal
firebox - a firetube boiler with an internal
furnace the rear of which is a tube sheet directly attached to a
shell containing
tubes. The first-pass bank of tubes is connected
The secondbetween the furnace tube sheet and the rear head.
pass bank of tubes, passing over the crown sheet, is connected
between the front and rear end closures.
VE
16.
Refractory
lined firebox - a horizontal
firetube
boiler, the front portion of which sets over a refractory or
water-cooled
refractory
furnace, the rear of the boiler shell
having an integral or separately connected section containing the
first-pass
tubes through which the products of combustion
leave
the furnace, then returning through the second-pass
upper bank of
tubes.
TI
17. Vertical
- a firetube boiler consisting
of a
cylindrical
ehell, with tubes connected between the top head and
The
the tube sheet which forms the top of the internal furnace.
products of combustion
pass from the furnace directly through the
vertical tubes.
IN
AC
18.
Submerged vertical - the same as the vertical type
above, except that by use of a water leg construction
as part of
the upper tube sheet, it is possible to carry the waterline at a
point above the top ends of the tubes.
19. Scotch boiler - a cylindrical
steel shell with one or
more cylindrical
internal steel furnaces located generally in the
lower potion and with a bank or banks (passes) of tubes attached
to both end closures.
In Stationary
Service, the boilers are either of the dryback, or wet-back type (see Boiler Dry-Back and Boiler Wet-Back).
In Marine Service, the boilers are generally of the wet-back
type.
Boiler blowoff Diving.
the blowoff valves.
~.
Bo” e
water is discharged
blowoff line.
Also
The piping
connections
from the boiler
A vented and drained container into which
above atmospheric
pressure from a boiler
called flash tank.
~k “
. A group of two or more rows of tubes
forming part of a water boiler circulatory
system and to which
heat is transmitted
mainly by convection
from the products of
combustion.
J30
314
to
MIL-HDBK-1125/l
(
The baffle provided in a firetube boiler
joining the furnace to the second pass.
Constructed
to be
separate from the pressure vessel and constructed
of heatresistant material- (generally refractory and insulating
material) .
Boiler
boiler fluid
source(a) .
divided
The ratio of the net energy output of the
by the input of the primary energy
IN
AC
TI
VE
The evaporation
of 34-1/2 pounds of water per
hour from a temperature
of 212 degrees F into dry saturated steam
at the same temperature.
Equivalent
to 33,472 Btu/hr.
wet
A completed water-cooled
baffle provided in a
firetube boiler or water leg construction
covering the rear end
of the furnace and tubes.
The products of combustion
leaving the
furnace are turned in this area and enter the tube bank.
.BQDA. A retaining
a joint
or holding high-temperature
cement
brick or adjacent courses of brick.
between
for making
IwuLG9d.
Coal from that part of a seam which has a very high
ash content.
In connection
with anthracite,
any material which
haa between 40 and 75 percent fixed carbon.
A device
(see Blower).
[email protected]
gas
for increasing
the pressure
of flow of a
A raised portion of metal of small area and limited
thickneaa
on flat or curved metal surfaces.
RQsE.
Bottom ~
traveling
weching.
combustion
stack.
.
.
grate
.
.
stoker
A duct
between
-Wt?iu. A wall
tid
combustion
pass.
partially
absorbing
A method of introducing
under the stoker.
air to a chain
or
for the transport of the products of
parta of a steam generating unit or to the
in a furnace
over which
the products
of
The accumulation
of noncombustible
matter and slag
or completely
blocking spaces or orifices between heat
tubea.
315
MIL-HDBK-l125/l
The mean British thermal unit is 1/180 of
British thermal un it.
the heat required to raise the temperature
of 1 pound of water
from 32 to 212 degrees F at a constant atmospheric
preseure.
It
is about equal to the quantity of heat required to raise 1 pound
of water 1 degree F (abbreviated
Btu).
Broken coal.
Anthracite
coal
3-1/4-inch
round mesh screen.
classification
Buckstav stiace K. A spacer for separating
which are used as a buckstay.
Anthracite
Buckwheat.
coal
2. Number 2 (Rice)
mesh screen.
round
3. Number 3 (Barley)
mesh screen.
- through
- through
according
a pair
over
to rank now
of channels
9/16-inch,
5/15-inch,
- through
AC
round
inches,
size:
Number 1 (Buckwheat)
mesh screen.
1.
round
4-3/8
TI
VE
A former coal
Brown coal.
included in Lignite B.
size - through
over
3/16-inch,
4.
screen.
Number
4 - through
3/32-inch,
over
5.
Number
5 - through
3/64-inch,
round
over
3/16-inc.h
over
3/64-inch
mesh
5/16-inch
3/32-inch
round
mesh
screen.
IN
Bulae.
A local distortion
or outward swelling caused by internal
pressure on a tube wall or boiler shell while overheated.
Also
applied to similar distortion
of a cylindrical
furnace due to
external pressure when overheated provided the distortion
is of a
degree that can be driven back.
BLUDQ. A raised or flattened
shell formed
attachments.
by fabrication,
Bunker C oil.
Residual
viscosity
commonly used
plants.
portion of a boiler drum head or
generally used for nozzle or pipe
fuel oil (No. 6 fuel oil) of high
in marine and stationary
steam power
Burner.
A device for the introduction
of fuel and air into a
furnace at the desired velocities,
turbulence,
and concentration
to establish and maintain proper ignition and combustion
of the
fuel.
316
MIL-HDBK-1125/l
1. Automatic
automatically.
fuel
burner
- a burner
that
stops
and starts
2. Burner, automatically
ignited - one where
is automatically
turned on and ignited.
3. Burner,
burner is turned
main burner
manually ignited - one where fuel to the main
on only by hand and ignited under supervision.
- a burner
pressure.
where
air for combustion
VE
4. Burner, forced draft
is supplied above atmospheric
5. Burner, natural draft type - a burner which depends
principally
upon
the natural draft to induce into the burner
air required for combustion.
TI
A plenum chamber around a burner in which
Fwn er windb x
pressure is ~a~ntained
to ensure proper distribution
and
discharge of secondary air.
The air pressure
windbox
or plenum
maintained
the
air
in the
chamber.
AC
A narrow strip of boiler plate overlapping
~.
of two butted plates, used for connecting
by riveting.
the joint
a portion or all of
E!YIxWt. A passage for a fluid, permitting
the fluid to flow around certain heat-absorbinq
surfaces over
which it would normally pass.
[email protected]$l.
and form
Property of certain coals
large masses of coke.
a fuel burned
to become
plastic
when
heated
The number of heat units liberated Der unit of
in a calorimeter
under prescribed condi~ions.
IN
(
Apparatua
for determining
the calorific
value
of a
fuel.
The manufacturers
stated output rate over a period
CaDacity.
time for which the boiler is designed to operate.
of
Cavacitv fact=.
The total output over a period of time divided
by the product of the boiler capacity and the time period.
QLKbQJ3. An element.
most
The” principal
fuels.
317
combustible
constituent
of
MIL-HDBK-1125/l
~y
the fuel carbon
Carbonization.
removing other
Carbon
energy
fuel.
compounds
.
An indictor of the degree
are oxidized to C02.
The procese
ingredients.
of converting
coal
to carbon
to which
by
10 Ss. The loss representing
the unliberated
thermal
occasioned by failure to oxidize some of the carbon in the
VE
Carbon residue.
The carbon residue of a fuel is a measure of the
carbonaceous
material left after the volatile compounds
are
vaporized
in the absence of air.
Casing.
A covering of sheets of metal or other material such as
fire-resistant
composition
board used to enclose all or a portion
of a steam generating
unit.
~
force
c
to remove
ctoK.
A mechanical
system using centrifugal
aerosols from a gas stream or to dewater sludge.
TI
Centr ifuaal faq.
A type of fan using a rotor or wheel
scroll type housing and discharging
the air at a right
the axis of the wheel.
Checker
furnace
AC
Chain arate stoker.
A stoker which has a moving
a grate surface, onto which coal is fed directly
work.
An arrangement
with openings through
within a
angle to
endless chain as
from a hopper.
of alternately
spaced brick
which air or gas flows.
Chemical feed uioe.
A pipe inside a boiler drum through
chemicals
for treating the boiler water are introduced.
The material
which
forms the
inner
which
surface
of
IN
Chimnev lining.
the chimney.
in a
Cinder.
Particles of partially burned fuel from .which volatile
gases have been driven off, which are carried from the furnace by
the products of combustion.
Circular burner.
having a circular
A liquid, gaseous, or pulverized
fuel burner
opening through the furnace wall.
CjJg&__ator.
A pipe or tube to pass steam or water between boiler
drums or headere.
Also ueed to apply to tubes connecting
headers
of horizontal water tube boilers with drums.
~.
Rank of coal.
318
MIL-HDBK-1125/l
(
A door placed” so the accumulated
from a boiler setting, flue or chimney.
~.
removed
C.LinkK.
furnace,
A hard congealed
usually slag.
of which
Any water-cooled
wall
is in contact with the edges
The
formation
of fuel matter
fused
Computerized
CMMs.
may be
in the
eurface, the major
of the fuel bed.
portion
of clinkers.
IN
AC
TI
VE
.
mass
refuse
Maintenance
Management
System.
Solid hydrocarbon
fuel formed by ancient decomposition
substance under conditions
of heat and pressure.
CQfd.
woody
electricity
source.
of
The production
of steam (or hot water) andlor
for uee by multiple users generated
from a single
CQkiDf3.
The conversion
by heating carbonaceous
fuel,
particularly
certain bituminous
coals, in the absence or near
absence of air to a coherent,
firm, cellular carbon product known
as coke.
passee
before
A plate adjacent to a grate through which no air
and on which coal is placed for distilling
the volatiles
the coal is moved onto the grate.
QmhuAkk
. The heat producing
constituent
of a fuel.
Combustible
matter in the solid refuee
resulting from the incomplete combustion
of fuel.
It may occur
in the flue dust discharge
from the stack or collected
in
hoppers, as well as in ash-pit refuse.
Tha loss representing
108Q.
Combustible
energy occasioned
by failure to oxidize
combustible
matter in the fuel.
combustible
heat.
Also
called
the unliberated
thermal
completely
some of the
The rapid chemical combination
of oxygen with
elements of a fuel resulting in the production
The space
a furnace.
in which
319
comhation
takes
the
of
place.
MIL-EIDBK-1125/l
Combu stio n eff iciency.
A measure of the completeness
of
It is usually quantified
as the
oxidation of fuel compounds.
ratio of actual heat release by combustion
to the maximum heat of
combustion
available.
stio
safe
~~d
. A system for sensing the presence
or absence of flame and indicating,
alarming or initiating
control action.
One of two or more air chambers
under the stoker from which air can be passed
quantities.
Comnl ete comb ustio~.
The complete
constituents
of a fuel.
in a windbox or
in controlled
VE
UmEd=mt.
oxidation
of the combustible
Condu ction.
The transmission
of heat through and by means
matter unaccompanied
by any obvious motion of the matter.
of
A pilot,
the main
usually gas, that remains lighted
burner is in operation or not.
at
AC
ianitioq.
Constant
full volume whether
TI
co
The amount of heat (Btu) transmitted
in one hour
~y
.
through one square foot of a homogeneous
material
l-inch thick
for a difference
in temperature
of 1 degree F between the two
surfaces of the material.
Con tinuous blowdow~.
The uninterrupted
removal of concentrated
boiler water from a boiler to control total solids concentration
in the remaining water.
IN
Control.
Any manual or automatic device for the regulation
of a
machine such as a boiler, to keep it at normal operation.
If
automatic,
the device is motivated by variations
in temperature,
pressure,
water level, time, light, or other influences.
Control element.
A device
produces a physical change
(usually a valve or damper) which
according to an actuating
signal.
Control,
limit.
An automatic
safety control responsive
to
changes in liquid level, pressure, or temperature
or position
limiting the operation of the controlled
equipment.
for
Control,
safetv.
Control
(including relays, switches, and other
auxiliary
equipment used in conjunction
therewith to form a
safety control system) which is intended to prevent unsafe
operation
of the controlled
equipment.
320
MIL-HDBK-1125/l
A device designed to regulate the fuel, air,
water, or electrical
supply to the controlled
equipment.
It may
be automatic,
semi-automatic,
or manual.
A valve
~.
used
to control
the flow of
air,
oil, or
gas.
~.
The transmission
liquid or a gas euch as air.
forced.
of heat by the circulation
of a
Convection may be natural or
a boiler
dioxide,
.
The wasting
usually caused
or an acid.
VE
A method of firing liquid, gaseous, or pulverized
fuel in which the burners are lccated in the corners of the
furnace.
Also called tangential
firing.
away of metale due to chemical action
by the presence of oxygen, carbon
of complex
hydrocarbons
in
into
TI
The thermal decomposition
compounds
or elements.
simpler
AC
A wedge-shaped
member of refractory or other
Crick et.
construction
used to subdivide a channel into hopper-ahaped
pockets.
The standards that the Environmental
Protection
Agency
(EPA) has established
for certain pollutants,
which not only
limit the concentration,
but aleo eet a limit to the number of
violations
per year.
Qgwn
sheet.
the furnace.
In a firebox
boiler,
the plate
forming
the top of
. . .
cross lAmlaa9.
A feature of some full metering systems which,
by means of high-low select controls, prevents fuel flow from
exceeding airflow under conditions
of load changes or flow
changee of either air or fuel.
IN
(
Unrefined
QuibeK.
maximum
A machine
size.
petroleum.
to reduce
lumps of solid
CYdQo.e.
A device which usee centrifugal
of materials of different densities.
~.
large
particlea
fuel to a desired
action
A device that uees centrifugal
from polluted air.
321
for separation
force
to pull
I
I“
I
I
I
DamIx=.
regulating
1.
A device for introducing
a variable resistance
the volumetric
flow of gas or air.
Butterfly
type
- a single
blade
pivoted
about
its
center.
2. Curtain type - a damper, compoeed of flexible
moving in a vertical plane as it is rolled.
each
3.
Flap type - a damper
pivoted about one edge.
consisting
material,
of one or more
blades
4. Louvre type - a damper consisting
of several blades each
pivoted about its center and linked together for simultaneous
operation.
I
moves
I
Deaeration.
Removal of air and gases
to ita introduction
to a boiler.
5. Slide type
substantially
Dead Dla te.
A grate
Coking Plate).
- a damper consisting
normal to the flow.
or plate
through
of a single
which
prior
AC
p~
.
Removal
to its introduction
of air and gases
to a boiler.
of a stream
from boiler
p~
combustion.
A continuation
of combustion
(see also Secondary Combustion).
izer.
An ion exchange
device
which
(see
feedwater
su~e
eat.
The number of degrees between
ee 0
pl
temperature
and saturated temperature
corresponding
pressure.
P laved
f~rnace
blade
no air passes
from boiler
Defl ectoz.
A device for changing direction
of a mixture of pulverized
fuel and air.
IN
I
damper
for
TI
VE
I
MIL-HDBK-112511
prior
of air or
feedwater
steam
to the steam
beyond
used to remove
the
solids
from
water.
~
De
controlled.
A controller
in which the output
signal level is directly proportional
to the rate of change of
the error.
This type of control is rarely used without integral
and/or proportional
control modes.
Derivative control tends to
be hypersensitive
to noise and other high frequency disturbances.
[email protected]
designed,
. The load for which steam generating unit is
usually considered
the maximum load to be carried.
322
MIL-HDBK-1125/l
(
The preseure”ueed
in the design of a boiler for
the purpose of determining
the minimum permissible
thickness or
physical characteristics
of the different parts of the boiler.
. The temperature
of steam
or reheater is designed.
m t~
superheater,
boiler,
The
~.
removal
of slag which
has adhered
for which
a
to heat-absorbing
surfaces.
kww=ku=.
The temperature
~.
head
TI
VE
See Attemperator.
or tube
header,
at which
condensation
A brace used in firetube
;heet and the shell.
boilers
starts.
between
a flat
A partition of metal or other material placed
duct, or pipe to separate portions thereof.
1 (on/off
end “cut-out” points.
.
The difference
between
in a
““cut-in”’
AC
A device used to distribute airflow within the burner
to promote stable ignitions andlor enhance fuel/air mixing.
Also
called impeller.
A system in which fuel is
pulverized
in proportion
to the load demand and conveyed directly
from the pulverizers
to the burners.
IN
A control system that utilizes a microprocessor
or computer to process and determine control decisions.
Analog
signals are converted
to digital words, processed,
and then
converted
to analog signals to ultimately be transmitted
to final
control elements.
down
The process by which
simpler constituents.
into
Ri.smlv d
Gases
are in solution
compound
breaks
in water.
scd.i.da.Those solids in water which are in eolution.
from crude
.
Light fraction of oil which
oil by fractional distillation.
.
volatile
which
a chemical
constituents
hae been
separated
The region, in a solid fuel bed, in which
of the fuel are vaporized.
323
MIL-HDBK-1125/l
p~
with
wat r. Water
a resulting
higher
produced
purity.
by vaporization
and condensation
by
Distributed
diaital contr 01.. A control system, characterized
the integration
of a central digital control area with one or
more remote digital control areas that are partially dedicated
to
perform specified control, within their realm of operation.
Specified
levels of communication
and operation may be controlled
The concept of
from the central area or any remote area.
distributed
digital control is to prevent complete system failure
due to a failure in any one area.
ine
i
te. A grate consisting
and inclined to form a Figure “V.”
A tube or pipe
Downcomex.
system through which fluid
Ika-fL. The difference
between atmospheric
pressure and some
in the furnace or gas passages of steam
Draft control. barometric.
A device that controls draft
of a balanced damper which bleeds air into the breeching
changes of pressure to maintain a steady draft.
in static
Draft aaae.
water.
draft,
IN
AC
The difference
Pr aft differential.
two points in a system.
A device
eo
in a boiler or waterwall circulating
See Supply Tube.
flows downward.
TI
lower pressure existing
generating
unit.
of two parts,
VE
P~ uble
placed
for measuring
pressure
usually
by means
on
between
in inches
of
Draft 10ss.
The drop in the static pressure of a gas between two
points in a system, both of which are below atmospheric
pressure,
and caused by resistance to flow.
A device which functions to maintain a desired
Praf t reaulat Oz.
draft in the appliance by automatically
controlling
the chimney
draft to the desired value.
A plate beneath a traveling
Pr a a D1 ate,
used to support the returning grates.
or chain
grate
etoker
Drac! seal.. In a chain grate stoker the hinged plate resting
against the returning chain and used to seal the air
compartments.
main.
piping
A valved connection
at the lowest
system for the removal of water.
324
point
of the boiler
or
MIL-HDBK-112511
An apparatus
for the removal
or moisture from fuel or air.
Rx&x.
RKw!l. A cylindrical shell closed
withstand internal preeaure.
of part or all of the water
at both ends designed
to
A plate or series of platea or acreena placed
Mm-balk.
within a drum to divert or change the direction of the flow of
water or water and steam.
A plate
closing
Apparatus
the steam drum
the end of a boiler
drum
or shell.
TI
VE
RKIMLkd.
within
a drum.
The pressure
or steam-and-water
drum
of the steam maintained
in
of a boiler in operation.
This term is
Air with which no water vapor is mixed.
used comparatively,
since in nature there is always some water
vapor included in air, and such water vapor, being a gas, is dry.
lwu=tl.
granular
Noncombustible
dust form.
matter
in the solid
state,
usually
AC
The method of reporting fuel analysis
Drv. ash
ash and moisture eliminated
and remaining constituents
recalculated
to total 100 percent.
in
with
ulb t~.
The temperature
of the air indicated by
thermometer
not affected by the water vapor content of the air.
IN
The method of reporting
Prv. fuel ba&.
moisture eliminated
and other constituents
100 percent.
~.
Gaa containing
no water
fuel analysis
recalculated
with
to total
vapor.
The loss representing
the difference
between the
heat content of the dry exhaust gases and their heat content at
the temperature of ambient air.
~.
Dry
limestone
gaaes.
to absorb
. An air pollution control method that usea
the sulfur oxidea in furnaces and stack
The method of reporting fuel
analyais with moisture and aah, plus other mineral matter
eliminated and remaining constituents
recalculated
to total 100
percent.
325
MIL-HDBK-1125/l
Pry steam.
is usuallv
moisture.
Commercially
dry steam
Steam containing
no moisture.
said to contain not more than one-half of 1 percent
.D!l.Gt.A passage
for air or gas flow.
pumv ar ate stoker.
One equipped with movable ash trays, or
at any
grates, by means of which the ash can be discharged
desirable
interval.
Fine
m.
grain
particles
light
from which ashes
of the Plate.
may
be
VE
DumD D1 ate.
An ash supporting plate
discharged
by rotation frOm one side
enough
to be suspended
in air.
oven.
A furnace that extends forward of the wall of a
P~ tc
boiler setting. It is usually of refractory
construction
with
low roof, although in some cases the roof and side walls are
water cooled.
AC
TI
Economize.
A heat recovery device designed to transfer
to boiler feedwater.
from the products of combustion
a
heat
Eiector.
A device which utilizes the kinetic energy in a jet of
water or other fluid to remove a fluid or fluent material from
tanks or hoppers.
A boiler
El ectric boiler.
as the source of heat.
in which
electric
heating
El ec tr o nic control.
A control system which primarily
electronic
signals and solid state control devices.
means
serve
uses
m~
IN
Electrostatic
Drecin itator [E SP1.. An air pollution control
device that imparts an electrical
charge to particles in a gas
stream causing them to collect on an electrode.
steam
being
t cracking.
A form of metal failure that occurs in
boilers at riveted joints and at tube ends, the cracking
predominantly
intercrystalline
in nature.
Emission fa CtoI.
The relationship
between the amount of
pollution produced and the amount of fuel burned or raw material
processed.
inventory.
A listing, by source, of the amounts of air
pollutants
discharged
into the atmosphere
of a community daily.
It is used to establish emission standards.
~
326
MIL-HDBK-1125/l
allowed
. The maximu”m amount of discharge
from a single source, mobile or stationary.
The conveying
of particles
water by the steam.
the boiler
~.
of water
The sum of external conditions
and survival of an organism.
development,
legally
or solids
affecting
the
from
life,
IN
AC
TI
VE
~ct
stat~.
A document required of Federal
agenciea by the National Environmental
Policy Act for major
They are used in making
projects or legislative
proposala.
decisions about the positive and negative effecte of the
undertaking,
and liet alternativea.
~.
into a pneumatic
A transducer
eignal.
Connection
used to convert
betwaen
parts
a voltage
of a boiler
signal
to equalize
pressures.
typically
The wearing away of refractory or of metal
by the action of slag or fly ash.
The difference
between
point.
This error calculation
automatic controller.
a meaaured
ia usually
EUQK.
~
condensate
..
Distilled water
for boiler feedwater.
~.
unit
The number
used
of pounde
parts,
property and ita set
an integral part of an
to supplement
of water
returned
evaporated
in a
of time.
EwwLsQd.
An expanding connection on the outlet
in an airflow paseage for the purpose of converting
energy to potential energy, i.e., velocity pressure
pressure.
Excess air.
theoretically
Edfwikx.
Air supplied for combustion
in excess
required for complete oxidation.
A fan used
Exhau s ‘c steam.
Steam
to withdraw
discharged
air or gases
from a prime
.,
Eimnded
IOMU . The preesure-tight
tube end in a tube .eeat.
327
joint
of a fan or
kinetic
into static
of that
under
suction.
mover.
formed
by enlarging
a
MIL-HDBK-1125/l
A joint to permit
~xD ansion ioin~.
without undue etress.
movement
due to expansion
Uncontrolled
combustion
which proceeds
EXD1OS ion.
that a high pressure ie generated. suddenly.
A door in a furnace or boiler
Eml osion dooc.
to be opened by predetermined
gas pressures.
so rapidly
setting
designed
Treatment
Ex ternal treatment.
introduction
into the boiler.
A
or gases
Em.
ringe,
VE
end d surfa C!e. Heating surface in the form of fins,
studs , added to heat absorbing elements.
of boiler
feedwater
prior
machine consisting
of a rotor and housing
at relatively
low pressure differentials.
or
to its
for moving
air
A pipe
through
which
water
IN
AC
Feed DiDe .
boiler.
TI
Feedback.
A eignal produced by a measuring device which is
proportional
to the magnitude of a controlled
variable or
When combined with a set point
position of a control element.
signal, the required amount of control of a variable is indicated
and serves as an input to an automatic controller.
is conducted
Feedwate<.
Water introduced
into a boiler
includes makeup and return condensate.
during
into
operation.
treatment.
The treatment
of boiler feedwater
addition of chemicals to prevent the formation of scale
eliminate
other objectionable
characteristics.
~
a
by the
or
A short metallic ring rolled into a tube hole to
ELxSLk
d~creas; in diameter or rolled inside of a rolled tube end.
a short metallic ring for making up handhole joints.
EiJ&!2z. Porous material
mixtures
are passed
Filtration.
Removing
through which
to separate matter
particles
Ei.n. Usually a strip of steel
circumferentially
to a tube.
materials
longitudinally
from
fluids.
or
Fineness.
The percentage
by weight of a standard eample of a
pulverized
material which passes through a standard screen of
specified mesh when subjected to a prescribed
sampling and
screening procedure
(ASTM D197).
328
Also
fluids or fluid and solid
held in suspension.
of solid
welded
It
MIL-HDBK-1125/l
Ei.Lies.Sizes below a specific
Fin
tube.
A tube with
range.
one or more” fins.
Spaced waterwall
Fin tube walJ.
extensions
are welded in a plane
tubee on which flat metal
parallel to the wall.
The equivalent
of a furnace.
furnaces of locomotives
and similar
shell,
A term ueually used
typea of boilers.
for
A crack etarting on the heated side of a tube,
or header resulting from exceaaive temperature
stresses.
VE
the
A pressure vessel in which eteem or hot
e vesa~.
water is generated by the application
of heat resulting from the
combustion
of fuel.
solid
TI
Fire tube. A tube in a boiler having water on the outside
carrying the products of combustion
on the inside.
dooc . A door in a furnace through which
fuel is introduced
into the furnace.
and
coal or other
A pressure or temperature
flow controller
which controls the firing rate of a burner according to the
deviation
from pressure or temperature
set point.
IN
AC
(
E.i.xedad.
vegetation
The portion of the ash derived from the original
including intimately contained minerals.
Fixed [email protected]&UI. A component of the proximate analyais of a solid
The carbonaceous
residue Iesa the ash remaining in the
fuel.
test container after the volatile matter has been driven off.
EL-d
q.m&.
A grate
which
does
not have movement.
A device which indicatea if fuel ia burning or
if ignition hae been lost.
The indication may be transmitted
to
a signal or to a control system.
~.
Flame
[email protected] .
The
technique
of shaping
the geometry
of a flame.
The substantially
continuous
contact upon a
surface by flame which results in formation of hard carbonaceous
deposits and which may result in localized incomplete combustion.
Flame impingement
ia a condition of firing which may cauae
failure and/or exceseive maintenance
of combustion
chamber wall
aurfacee.
Susceptibility
to combustion.
329
MIL-HDBK-1125/l
composition
of a
the mixture will
limit represents
burn without the
limit represents
burn without the
The limiting (upper and lower) homogeneous
combustible
mixture of gas and air beyond which
The lower
not ignite and continue to burn.
proportion of gas in air that can
the smallest
The higher
continuous
application
of heat.
the largest proportion of gas in air that can
continuous
application
of heat.
The projecting end of a rolled
Flared tube end.
expanded or rolled to a conical shape.
Steam produced
into a region
by discharging
water
of lower pressure.
is
at saturation
VE
E’1ashinq.
temperature
tube which
The flash point of a liquid ie an indication of the
Flash point.
maximum temperature
at which it can be stored and handled without
serious fire hazard.
See Boiler
Fla sh tadi.
A passage
for products
Tank.
of combustion.
AC
TI
E!JE.
Blowoff
The particles of gas-borne
F1 ue dust.
the products of combustion.
F1 ue aas.
stack.
The gaseous
products
eolid
of combustion
matter
carried
in
in the flue to the
F lue qas recir culatio n i The reintroduction
of part of the
combustion
gas at a point upstream of the removal point in the
furnace for the purpose of controlling
steam temperature
or for
NO, control.
IN
Fluidized
bed combustion.
A process where a fuel is burned in a
bed of granulated
particles which are maintained
in a mobile
suspension
by the forward flow of air and combustion products.
ELJuA1.
Suspended
Flv ash CO1l ector.
form from flue gas.
ash particles
A device
carried
designed
in the flue gas.
to remove
fly ash in dry
Foaminq.
The continuous
formation of bubbles which have
sufficiently
high surface tension to remain as bubbles beyond
disengaging
surface.
d
l?~n
f~e~ burning
A fan supplying
equipm%.
330
air under
pressure
the
to the
MIL-HDBK-1125/l
~.
through
means.
the grate
is caueed
A itoker in which the flow of air
by a pressure produced by mechanical
The accumulation
of solid matter in gas paasages or on
E!UliIN.
heat absorbing surfaces which results in undesirable
restrictions
to the flow of gas or heat.
See Surface
discharged
feed.
-
. A stoker
qe sfrom the qrate surface
Fuel -“ r
air.
&!ua-bd.
The ratio
Layer
Fuel bed re~.
fuel bed.
a.
containing
combustible
of the weight
of burning
The
matter,
Any hydrocarbon
or volume
fuel on a furnace
etatic
or break
into
so arranged that refuse is
at the eeme end as the coal
AC
TI
A substance
w.
generating
heat.
Fuel
of a coal to crumble
pieces.
VE
The tendency
emall
Moisture.
pressure
oil as defined
and used
for
of fuel to
grate.
differential
by ASTM
across
a
D396.
intended
1. Grade No. 1 is a light distillate
Fu el oil arad~.
for use in burners of the vaporizing
type in which the oil is
converted
to a vapor by contact with a heated surface or by
radiation.
High volatility
ie necessary to ensure that
evaporation
proceeds with a minimum of residue.
IN
(
2. Grade No. 2 is a heavier distillate
than grade No. 1.
It is intended for use in atomizing type burners which spray the
oil into a combustion chamber where the tiny dropleta burn while
in suspension.
This grade of oil ia used in most’domestic
burners and in many medium capacity commercial-industrial
burners
where ite ease of handling and ready availability
sometimee
justify its higher cost over the residual fuels.
3. Grade No. 4 (light) is usually residual but it aometimee
is a heavy distillate.
It is intended for use both in pressureatomizing commercial-industrial
burners not requiring higher cost
distillate
and in burners equipped to atomize oils of higher
viscosity.
Its permissible
viscosity range allows it to be
pumped and atomized at relatively
low etorage temperatures.
331
MIL-HDBK-1125/l
4.
Grade No. 4 is usually” a light residual, but it is a
It is intended for use in burners equipped
heavy distillate.
with devices that atomize oils of higher viscosity than domestic
Its permissible viscosity
range allows it to
burners can handle.
be pumped and atomized at relatively low etorage temperatures.
Thus, in all but extremely cold weather, it requires no
preheating
for handling.
TI
VE
5. Grade No. 5 (light) is residual fuel of intermediate
viscosity
for burners capableof
handling fuel more viscous than
grade No. 4 without preheating.
Preheating may be necessary in
some types of equipment for burning and in colder climates for
handling.
6. Grade No. 5 (heavy) is a residual fuel more viscous than
grade No. 5 (light) and is intended for use in similar service.
Preheating
may be necessary in some types of equipment for
burning and in colder climates for handling.
AC
7. Grade No. 6, sometimes referred to as “Bunker C,” is a
high-viscosity
oil used mostly in commercial
and industrial
heating.
It requires preheating in the storage tank to permit
pumping, and additional preheating at the burner to permit
atomizing.
The extra equipment and maintenance
required to
handle this fuel usually preclude its use in small installations.
Combustion control system in which air-to-fuel
Full metering.
ratios are maintained
by measuring both air and fuel with a flow
measuring device.
Full metering systems can contain many other
features such as cross limiting or oxygen trim.
Furn ace.
See Combustion
Chamber.
IN
The draft in a furnace, measured
Fur nace draft.
immediately
in front of the furnace outlet.
at a point
Furnace liberation rate.
The total quantity of thermal energy
above a fixed datum introduced into a furnace by the fuel,
considered
to be the product of the hourly fuel rate, and its
high heat value, divided by furnace volume, expressed in Btu per
hour per cubic foot of furnace volume.
r ~.
ace
The heat available per square foot of heat
absorbing surface in the furnace.
That surface is the projected
area of tubes, and extended metallic surfaces on the furnace side
including walls, floor, roof, partition walls, and platens and
the area of the plane of the furnace exit which is defined as the
entrance to the convection tube bank.
332
MIL-EIDBK-1125/l
(
~.
tubes
A screen formed by one or ❑ ore rows of
arranged across a furnace gas outlet, serving to create an
ash cooling zone for the particlee suspended in the products of
combustion
leaving the furnace.
The cubic
~.
Slag which
Fu sed
mass by fusing.
contents
of the furnace
has coalesced
or combustion
into a homogeneous solid
HI sibu.
homogeneous
Property
mass.
Euai.Qn. The melting
Qw2Q2Gk.
I
II
I
A valve attached
water level.
material
to a water
such as ash.
column
or drum
for
The transparent
part of a water gage assembly
directly or through a water column to the boiler, below
the water line, to indicate the water level in the
~.
The pressure
above
atmospheric
pressure.
Gaa. safetv va lv~.
A clamp designed to prevent a safety
from lifting while applying a hydrostatic test at higher
than the safety valve setting.
The determination
mixture.
IN
I1“
of a solid
into a
GMfukui.
connected
and above
boiler.
I
of slag to fuse and coalesce
AC
checking
TI
VE
D1U9
A hollowed threaded plug having the hollowed
portion fill~d with a low melting point material, usually located
at the lowest permissible
water level.
GudumEx.
~.
into
A burner
a gaseous
arranged
throat.
for use with
gaaeous
of a gaseous
fuel.
The process of converting
solid or liquid
fuel such as the gasification
of coal.
fuel
A circular device with multiple openings or orifices
to admit or dietribute
gaseous fuels into a burner
.
Glwk.
of the constituents
valve
pressure
A tube
in which
Coal classification
steam
according
333
is generated,
to quality.
MIL-HDBK-1125/l
Grain loading.
The rate at which particles are emitted from a
pollution
source; measurement
ie made by the number of graine per
Also called particulate
loading.
,cubic foot of gas emitted.
Gr anular
[email protected]
through
aeh.
Small particles
of dry ash.
The surface on which fuel ie supported
which air is passed for combustion.
Grate bars.
Those parts of the
to admit air for combustion.
and burned,
fuel supporting
surface
and
arranged
IN
AC
TI
VE
liquid petroleum products
1. Weight index of fuels:
Gravi.Q!.
expressed either as specific or API (American petroleum
Institute)
gravity.
2. Weight
related to air
3.
to water
index of gaseous fuels as specific
under specific conditions.
Weight index of solid fuels
under specific conditions.
as specific
gravity
gravity
related
Gro oved
grooves
tube seat.
A tube seat having one or more shallow
into which the tube may be forced by the expander.
Qgl_Q.
A subclassification
of coal
by rank.
etation~.
A device for routing a control
The signal can be from a
signal to a final control element.
control system (auto position) or be entered manually to any
desired level (manual position).
p~
Hand fired ar ate.
A grate on which
usually by means of a shovel.
~.
exceeding
pandhole
fuel
An opening in a pressure part
6 inches in longest dimension.
cover.
A handhole
is placed
manually,
for accese,
usually
not
closure.
A manually manipulated
length of pipe carrying air,
Han d lan ce.
steam, or water for blowing ash and slag accumulations
from heat
absorbing
surfaces.
~.
B
in boiler
as CaCo2.
A measure of the amount of calcium
water.
Usually expressed as grains
334
and magnesium
salts
per gallon or ppm
MIL-HDBK-1125/l
[email protected]@22z.
amount which
lather.
Water which contains calcium
requires an excessive amount
or magnesium
in an
of soap to form a
A chamber for the collection
and/or distribution
ikackx.
. fluid to or from a multiplicity
of parallel flow parts.
of
TI
VE
The thermal energy above a fixed datum that is
&at
a vaw.
capable of being abaocbed for useful work.
In boiler practice,
the heat available
in the furnace is usually taken to be the
higher heating value of the fuel for combustion
corrected by
subtracting
radiation losses, unburned combustible,
latent heat
of the water in the fuel or formed by the burning of hydrogen,
and adding sensible heat in the air, all above ambient.
temperatures.
An accounting
and output.
HmLkbmE.
input
A vessel
~.
of the distribution
in which
heat
of the heat
is transferred
from one
medium
to another.
medium
That surface which is exposed to the heating
for absorption
and transfer of heat to the heat medium.
rec. v erv bow.
See Waste
AC
&at
Heat Boiler.
Metallic elements such as mercury, chromium,
cadmium, araenic, and lead, with high molecular
weights.
They
can damage living things at low concentrations
and tend to
accumulate
in the food chain.
WwLmw&i.
A switch
to stop the burner
if the gas
IN
aas Dressure a lt~.
sure is too hig~.
lHHV~.
The total heat obtained
from the
combustion
of a specified amount of fuel which is at 6 degrees F
when combustion
starts, and the combustion
products of which are
cooled to 60 degrees F before the quantity of heat released is
measured
(see also Calorific Value and Lower Heat Value).
HQR.PQK. A changer
or bin used
for holding
solid
fuel or refuse.
HODDer bottom furn ace.
A furnace bottom with one or more
inclined sides forming a hopper for the collection
of ash and
the easy removal of same.
335
for
MIL-HDBK-1125/l
A means of firing liquid, gaseous or
pulverized
fuel, in which the burners are so arranged in relation
to furnace as to discharge the fuel and air into the furnace in
approximately
a horizontal direction.
Hm.
Horizontal
HYk==bl.
Kidr-tat
pressure
return
tubular.
A chemical
compound
of hydrogen
ic test.
A strength and tightness
vessel by water pressure.
and carbon.
test
of a closed
Iqnition.
The
initiation
TI
VE
A burner smaller than the main burner, which is ignited
by a sp~rk or other independent
and stable ~9nition.source?
and
which provides proven ignition energy required to llght off the
main burner.
of combustion.
arch or surface located over a fuel
Jan ition arch . A refractory
Usually used
bed to radiate heat and the rapidity of ignition.
with a low volatile fuel such as anthracite coal.
Iqn ition
Deriod.
See Trial
for Ignition.
Ian ition
AC
Lowest temperature
Xa nition temperature.
combustion
becomes self sustaining.
torch.
~n
JncOm
constituents
See Lighting-Off
Torch.
. The partial
of a fuel.
Induced draft (ID) fan.
absorbing equipment.
oxidation
A fan exhausting
IN
Incombustible
Inert oa seous constituents.
which may be present in a fuel.
. .
lnhlb~tu.
action.
Iniecto~.
A substance
which
feedwater
A device utilizing
into a boiler.
W,q
or inlete
. An integral part
to permit attachment
of a fuel at which
selectively
a steam
of the combustible
hot gases
gases
retards
from
such as nitrogen
a chemical
jet to entrain
of a fan enclosing the
of the fan to the duct
336
the heat
and deliver
fan inlet
system.
.
MIL-HDBK-1125/l
(
certain
reduce
A small door in the outer enclosure so that
of the interior of the apparatus may be observed.
parts
heat
A material
losses.
of low thermal
conductivity
used
to
~tent
intervals.
A device to prove
and to furnish that
blowdown.
and while the main
the main burner.
The
the physical etate of a required
proof to the primary safety control
blowing
down
AC
~.
directly
IN
~.
between
A charged
negative.
km.
at
a mixing chamber in
on jeta of incoming
in a completely
The treatment of boiler
into the boiler.
ted
and which is shut off
the main burner.
discharging
water
An igniter which burna during light-off
burner is firing, and which is shut off with
A burner having
which high velocity steam or air impinges
liquid fuel.
The fuel ia then discharged
atomized form.
chemicala
of boiler
TI
~.
condition
circuit.
VE
A controller
in which the rate of
~.
change of the output is directly proportional
to the error.
An
integral controller
will alwaya attempt to drive the error to
zero.
The units of the constant of proportionality
are usually
expressed either in repeata per minute or minutes per repeat.
water
by introducing
An igniter which burns during light-off,
(interrupted)
during normal operation of
A burner which terminates
in nozzle
adjacent waterwall
tubes.
atom
or radical
which
may be positive
or
A reversible
process by which ions are
interchanged
between solids and a liquid, with no substantial
structure changes of the solid.
mu=dwue.
directing
A short tube connection for bypassing,
the flow of fluid as desired.
Lca$&n9.
material,
A covering,
on boilers,
Jmux4uk.
usually metallic
pipes, or ducts.
337
to protect
routing,
insulating
or
MIL-HDBK-1125/l
L~K c
.
for cleaning
A door through which
heating surfaces.
a hand
A control to prevent
h tch switch.
burner is not secured in the firing
.LEA- Low excess
lance may be inserted
fuel valve
position.
opening
if the
air.
The uncontrolled
quantity of fluid which enters
through the enclosure of air or gas passage.
or
Leak-as.
The minimum cross
Lioa ment.
shell, or tube sheet between
section of solid metal
two adjacent holes.
in a header,
VE
leaves
A torch used for igniting fuel from a
Liah tins-off torch:
The torch may consist of asbeatos wrapped around an iron
burner.
rod and saturated with oil or may be a small oil or gas burner.
TI
JLianite A.
A coal of low ASTI.1classification
by rank with
calorific
value limits on a moist, mineral-matter-free
basis
between 6,300 and 8,300 Btu per pound.
by rank with
Liqnite B. A coal of lowest ASTM classification
calorific value limits on a moist, mineral-matter-free
basis less
than 6,300 Btu per pound.
Lidn.9.
~.
AC
The material used on the furnace eide of a furnace wall.
It is usually high grade refractory tile or brick or plastic
refractory
material.
An element
of the chain
L,ive steaq.
Steam which
which it was generated.
IN
Lca!i. The actual
of a chain
has not performed
instantaneous
output
grate
stoker.
any of the work
for
rate of a boiler.
~J
. A burner from which the fuel emerges in such
Lo
a condition,
or one in which the air for combustion
is admitted
in such a manner, that the two do not readily mix, resulting in a
comparatively
long flame.
Low d raft switch.
draft is too low.
A control to p“revent burner operation
Used primarily with mechanical draft.
if the
~L
. The higher heating value (HHV) minus the
Lowe
latent heat of vaporization
of the water formed by the oxidation
of hydrogen bearing compounds in the fuel and the vaporization
of
water in the fuel.
338
.
MIL-HDBR-1125/l
The firing of”a burner with controls in a lowLO -“ re Stti.
fi~e position to provide cafe operating condition during
light-off.
operation
Liquefied
LZli.
Low temperature
petroleum
L!dS1. Any projection
the burner
to stop the burner
gas.
water.
used
Emissive
for supporting
power
if gas
. A control to
of the oil ia too
if the temperature
. A device
Low water Cu
conditions
in the boiler.
w.
to stop
VE
LOW oil
prevent burner
low.
A control
.
kow aasa.uxmue
preesure is too low.
with
respect
on unsafe
water
or grasping.
IN
AC
TI
(
to visible
radiation.
M.&E!dE. The water added to boiler feed to compensate
lost through exhaust, blowdown, leakage, etc.
for that
The head
[email protected]
having a manhole.
vessel
of a boiler
drum or other
The opening in a pressure
M!mkl&!.
permit a man to enter.
distributing
Me chanical
means.
Mechanic~.
of sufficient
size to
A pipe or header for collecting a fluid from, or the
of a fluid to a number of pipes or tubes.
Any device
Mess urina de vicq.
property
(euch as flow rate).
preseure
veseel
pressure
. .
at~
of the oil
.
011
A burner
for atomizing.
dre.f.$. The negative
. .
used to indicate
pressure
the magnitude
which
created
The ratio of power
output
uses
of a
the
by mechanical
to power
input.
cal stok~ . A device consisting of a mechanically
operated fuel feeding mechanism and a grate, used for the purpose
of feeding solid fuel into a furnace, distributing
it over a
grate, admitting air to the fuel for the purpose of combustion,
and providing a means for removal or discharge of refuse.
339
MIL-HDBK-1125/l
1. Overfeed stoker - a stoker in which fuel is fed onto
grates above the point of air admiseion to the fuel bed.
Overfeed stokers include:
(a) Front feed, inclined
is fed from the front onto a grate
rear of the stoker.
grate - a stoker in which
inclined downwards toward
fuel
the
(c) Chain
endless grate which
where it is burned,
TI
VE
(b) Side feed, double inclined grate - a stoker in
which fuel is fed from both sides onto grates inclined downwards
towards the centerline of the stoker.
or traveling grate - a stoker having a moving
conveys fuel into and through the furnace
after which it discharges the refuse.
(d) Vibragrate
- an inclined vibrating stoker in which
fuel is conveyed into and through the furnace where it is burned,
after which it discharges
the refuse.
onto
AC
2. Spreader stoker - a stoker that distributes
fuel into
the furnace from a location above the fuel bed with a portion of
the fuel burned in suspension and a portion on the grates.
Spreader stokere include:
(a) Stationary grate
a fixed position grate.
nonmoving
of refuse
- a stoker
in which
fuel is fed
(b) Dump grate - a etoker in which fuel is fed onto a
grate which is arranged to allow intermittent
discharge
through tilting action of the grate bars.
IN
(c) Continuous ash discharge or traveling grate - a
stoker in which fuel is fed onto a moving endless grate which
conveys the fuel into and through the furnace where it ia burned,
after wh~ch it discharges the refuse.
3. Underfeed stoker - a stoker in which fuel is introduced
through retorts at a level below the location of air admiesion to
Underfeed stokers are dividad into three general
the fuel bed.
classes, as follows:
(a) A side ash discharge underfeed stoker is a stoker
having one or more retorts which feed and distribute
fuel onto
side tuyeres or a grate through which air is admitted for
combustion,
and over which the ash is discharged at the eide
parallel to the retorts.
340
..-.
.—.
.
f41L-HDBK-1125/l
(b) A rear discharge underfeed stoker is a stoker
having a grate composed of transversely
spaced underfeed retorts,
which feed and distribute solid fuel to intermediate
rows of
tuyeres through which is admitted air for combustion.
The ash is
discharged
from the stoker across the rear end.
VE
(c) A continuous aah discharge underfeed stoker is one
in which the refuse is discharged continuously
from the normally
stationary
stoker ash tray to the aeh pit, without the uee of
mechanical
means other than the normal action of the coal feeding
and agitating mechanism.
Highest coal classification
according to rank.
Dry fixed carbon 98 percent. or more and dry volatile matter 2
percent or less, on a mineral-matter-free
baeie.
AC
TI
ticronroceseor
Utilizee a emall microcomputer
chip to
perform requirements
of a system control package.
The
microprocessor
containers support chips to store necessary
control system instruction
in what is called memory.
Usually,
changes in system logic can be performed without any rewiring or
component changea.
free bati.
The method of reporting coal analysis
whereby the ash plus other minerale which are in the original
coal are eliminated and the other constituents
recalculated
to
total 100 percent.
klsdsture. Water in the liquid or vapor phase.
free
See Dry, Ash Free Basis.
expressed
.
Method
of reporting
in
Particles of water
as the percentage by weight.
IN
(
carried
coal
analysis.
in steam.
Usually
e los~.
The loss representing
the difference
in the heat
content of the moisture in the exit gasee and that at the
temperature
of the ambient air.
level
Periodic
of pollution.
c baa.
or continuous
A baffle
sampling
of poured
or rammed
material.
Mss.
Manufacturers
Mm.
Medium
Standardization
temperature
water.
341
to determine
Society.
refractory
the
MIL-HDBK-1125/l
m.
Molecular
weight.
Mu~
drum.
A pressure chamber of a drum or header type
located at the lower extremity of a water-tube
boiler convection
bank which is normally provided with a blowoff valve for periodic
blowing off of sediment collecting in the bottom of the drum.
A burner by means of which more
el burn er.
can be burned either separately or simultaneously,
pulverized
fuel, oil, or gas.
surfaces
one
as
fuel
so baffled
IN
AC
TI
VE
Multi-pa ss arrangement.
Heat absorbing
provide two or more passes in series.
than
such
as to
~ t’
).lU
t stoker.
An underfeed stoker consisting
of two or
more retorts, parallel and adjacent to each other, but separated
by,a line of tuyeres, and arranged so that the refuse is
discharged
at the ends of the retorts.
Wtiuort
A burner having
buu.
fuel and air are discharged.
a number
of nozzles
from which
Natural circulation.
The circulation
of water in a boiler
by differences
in density; also referred to as thermal or
thermally induced circulation.
caused
~Eatu a d
. A stoker in which the flow of air through
the grate is caused by the difference of pressure between the
furnace and the atmosphere.
~
~.
as.
Gaseous
Non-dispersive
fuel occurring
infrared.
pet fan reauirements.
The calculated
fan excluding tolerances.
fleut
~
nor reduce
NQx .
e. An atmosphere
immersed materials.
A notation
in nature.
meaning
oxides
operating
which
tends
conditions
neither
for a
to oxidize
of nitrogen.
w, Dort six.
Air that is added downstream
of the primary
combustion
zone to achieve off-stoichiometric
combustion
and
reduce NO, emissions.
on a drum or
[email protected] A short flanged or welded neck connection
shell for the outlet or inlet of fluids; also a projecting
spout
for the outlet or inlet of fluids; also a projecting
spout
through which a fluid flows.
342
MIL-HDBK-1125/l
Nominal
pipe
size.
w.
Anthracite
coal
15/16-inch round meeh
by some chosen screen
~.
inchee
ml.
designation
through l-5/8-inches
over
Bituminous
coal size designation
screen.
mesh size aa 2 inches by 3/4 inch.
A combination
of nut and slack coal, such as 2
by 3/4 inch nut plus 3/4 inch by slack (see Slack).
Outside
diameter.
A burner
for firing
VE
ms.
oil.
9il wn-e. The cone of finely atomized
atomizer.
SW
heat= . A heat exchanger
oil discharged
from an oil
utilizing
steam, hot water,
to heat oil to the desired viscosity.
electricity
.
See Pump
and Heater
TI
Q&J heakb.w and EWWQUK&
or
Set.
ODen f~.
traveling
AC
The degree to which emissions
reduce the transmission
QQ!3&&.
of light and obscure the view of an object in the background.
Usually defined as a number between O and 100 percent.
At O
percent, light is completely
unobstructed
and at 100 percent,
light is completely
obstructed
(opacity numbers with respect to
boiler emissions are not intended to include the effect of
condensing
water vapor). See Smoke Number, Ringlemann
and Smoke
Spot Number, Bacharach.
grate
IN
i
living
A furnace, particularly
as applied to chain
stoker containing
essentially
no arches.
Compounds
containing
carbon
often
derived
or
from
organisms.
~.
1. The opening from the whirling chamber of a
mechanical
atomizer or the mixing chamber of a steam atomizer
through which liquid fuel is discharged.
drop
2. A device inserted into
to be used for the purpose
a pipeline to create a pressure
of measuring
fluid flow.
A gas-analysis
apparatus
in which certain gaseous
w.
constituents
are measured by absorption
in separate chemical
solutions.
~.
point
above
Air for combustion
the fuel bed.
343
admitted
into
the furnace
at a
MIL-HDBK-1125/l
.
A fan used
alr h.
above the fuel bed.
chamber
to provide
. A substance containing
air to produce a new eubstance.
Chemical
Oxidation.
oxygen
combination
with
tmosoher
. An atmosphere
of immersed materials.
9~ idizi
oxidation
Oxvaen attack.
oxygen.
Corrosion
or pitting
air to a combustion
that
reacts
chemically
in
oxygen.
which
tends
to promote
the
VE
.
in a boiler
caused
~ cka e
enerator.
A boiler equipped and shipped
with fuel burning equipment, mechanical
draft equipment,
automatic controls and accessories.
by
complete
See
pressure
Boss.
vessel.
A pad is larger
than a boss
AC
m.
TI
Packed tower.
A pollution control device that forces dirty air
through a tower packed with loose pellet-like
material of various
shapes or a fixed grid type material, while liquid is sprayed
over the packing material.
Pollutants
in the air stream either
dissolve or chemically
react with the liquid.
and is attached
to a
~.. alle
A type or class of burners which includes
F
the venturi burner.
The burner is characterized
by the lack of
register spin louvers and normally has a venturi section to
straighten,
balance, and in some cases, meter airflow.
The flame
is stabilized by either a diffuser, spinner, or bluff body.
IN
p~
ositioning.
Fuel and air control elements have
separate actuators responding to the same load signal
simultaneously.
At least one of the actuators
has a positioner
to set air-fuel ratio with load.
Particulate.
smoke, mist,
Fine
fumes,
liquid or solid particles
such as dust,
or smog found in the air or emissions.
EEEia. A confined passageway through which a fluid, gas, or
products of combustion
flows in essentially
one direction.
Anthracite
or bituminous coal size.
In anthracite through
&a.
13/16 inch over 9/16 inch round hole screen; in bituminous
3/4
inch by 3/8 inch.
peak
load.
The maximum
load carried
344
for a stated
period
of time.
~1125/1
E=fLhQk.
A small
E.&uamm.
Naturally
occurring
of hydrocarbons.
predominately
hole
in a door covered
minerel
by a movable
cover.
oil consisting
A measure of the acidity or alkalinity of a material,
liquid, or solid. ptl is represented on a scale of O to 14 with
being a neutral state, O most acid and 14 most alkaline.
@i.
7
Ei.b2L. See Igniter.
VE
. .
The length of time fuel is permitted
l?i.lotflame est~.
to be delivered
to a proved pilot before the flame-sensing
device
is required to detect pilot flame.
Eilot . nro VQ$ . A pilot
failure controle.
flame which
has been
detected
by flame
TI
D-.
A time interval synonymous on most
Pilo t et~t~on
systems today with timed trial for pilot ignition.
Hodern
programmers
prevent main valve operation for a specified number
of seconds after commencement
of trial for pilot ignition even
though pilot is immediately
proved.
AC
A concentration
attack
chemicals on a boiler, producing
metal surface.
EkmuI!. An enclosure
relatively
primary
between
usually
through
low velocities.
~.
conduit
by oxygen or other corrosive
a localized depression
in the
which
gas or air passes
at
Utilizes gas pressure (usually air) as the
motive force for control elements, and as the signal
control devices.
The maximum and minimum pressures are
3 and 15 psig, but can be other values as well.
IN
(
The transportation
of fuel through
a
by air.
B?x.L. An opening
determining
I?our o int .
liquid”fuels
gravitational
The preesure
through
a control
which
A device
element
An indication
can be stored
forces.
at which
a safety
valve
opens.
fluid passes.
which provides
position.
means
for
of the lowest temperature at which
and still be capable of flowing under
345
MIL-HDBK-1125/l
wer
inDut.
The energy required to drive auxiliary equipment,
delivered to shaft or kilowatts to
expressed
in brake horsepower
drive motor.
m
er slillj,gm. A method of expressing tiny concentrations.
P!?
In air or flue gas, usually a volume/volume
ra~io; may alao be
used as a weight/weight
or a weightlvolume
ratio [abbreviated
ppm ).
by the
The material
IN
AC
TI
VE
To separate materials
from a solution
Pre cin itate.
formation of insoluble matter by chemical reaction.
which is removed.
Precin itato~.
electrostatic
An ash separator
type.
and collector
Preheated air.
ambient air.
Air at a temperature
Pr essure dreg.
a system.
The difference
exceeding
in pressure
Products of combustion.
The gases,
from the combustion
of fuel.
of the
vapors,
that of the
between
two points
and solids
resulting
co t olleq.
ab
Similar to microprocessor
control,
E!?oara
utilizina a Simplified method of enterinq instructions
into
memory (~bbrevi~ted PC).
proaram t im e c. A timing device which
switches in programmed
sequence.
actuates
proiected
arate
stoker grate.
projected
area.
The horizontal
in
a series
but
of
area of the
contro~.
A mode of control in which there is a
Pr ovortional
continuous
linear relation between value of the controller
variable and position of the final control element (modulating
control) .
ontrolle~.
ort”o a
A controller in which the position of
?l
the output is directly proportional
to the error.
The constant
of nro~ortionalitv
is called qain and usually expressed in
perken;.
In practice, propor~ional
controllers are usually
combined with integral action to eliminate residual error (see
Integral (Reset) Controller).
[email protected]
A minor
eetting.
combustion
explosion
346
within
the boiler
furnace
or
MIL-HDBK-1125/l
Rapid
~.
euitable
fluctuations
in furnace
A machine which reduces
for burning in suspension.
pressure.
a solid
fuel to a fineness
Assembled unit consisting
of oil heater,
~.
fuel pump, strainer, valve, and piping and temperature controls.
May be either simplex or duplex arrangements.
VE
.
.
A pump which automatically
pumps oil from
PumD. aut~.
the supply tank and delivere the oil under a constant head to an
oil-burning
appliance.
An oil pump, automatically
or manually
PumD. ~.
operated, which transfers through continuous
piping from a supply
tank to an oil burning appliance or to an auxiliary tank.
TI
To introduce air into the furnace and the boiler flue
m.
pasaage in such volume and manner as to completely
replace the
air or gas-air mixture contained therein.
IN
AC
A flow meter ao arranged that an airflow
through the furnace above a minimum amount must exist for a
definite
time interval before the interlocking
system will permit
an automatic
igniter to be placed in operation.
A method of scavenging the furnace and boiler
~.
paeses to remove combustible
gaaes after flame failure controls
have sensed pilot and main burner shutdown and eafety shutoff
valves are closed.
E3wae.
boiler
syetem
. . .
Dr~
. A method of scavenging
the furnace and
passes to remove combustible
gases before the ignition
can be energized.
The degree
-.
materials.
to which
Eu&lheK. A device for giving
motion, such as moving block
A compound
a substance
is free of foreign
motion to fuel bed by recivrocatinq
in the bottom of a r;tort.”
of iron and sulfur
naturally
occurring
in
coal.
A comprehensive” term used in a boiler unit heat
balance to account for the conduction,
radiation, and convection
heat losses from the settings to the ambient air.
A form of plunger used in connection with underfeed
to introduce fuel into retorte.
See aleo Pusher.
Em.
347
etokers
.
MIL-HDBK-1125/l
Rank.
Method of coal classification
based on the deqree of
in
the natural series from lignite b to
progressive
alteration
meta-anthracite.
The limits under classifications
according to
rank are on a mineral-matter-free
basis.
Ra te of bl owdow~ . A rate normally
the incoming water.
I?aw watec.
Water
supplied
expressed
to the plant
as a percentage
before
of
treatment.
VE
stoker.
A stoker so arranged that refuse is
Re ar discharae
discharged
from the grate surface at the end opposite the coal
fuel.
KeciDrocati.na a ra t~. A grate element which has reciprocating
motion, usually for the purpose of fuel agitation.
line.
fluid
Piping and connections
on a heat exchanger
is returned from the outlet to the inlet.
TI
Recirculating
through which
fleducina atmosphere.
An atmosphere which”tends
removal of oxygen from immersed materials.
peduction.
Removal
of oxygen
from a chemical
to promote
compound.
refractory.
Material that will withstand temperatures
degrees F without distortion or deterioration.
IN
AC
the
above
50
A type or class of burner.
Air is admitted
Rea ister burnez.
through one or multiple zones of adjustable louvers which impart
a rotary motion to the air.
The flame is stabilized
by the
swirling air from the register louvers and internal eddies
generated downstream
of the diffuser and external eddies
generated downstream
of the throat exit.
~~
etort. ‘A trough or channel
extending within the furnace, through
into the fuel bed.
in an underfeed
stoker,
which fuel is forced upward
fleaulator. a
A spring-loaded,
dead-weighted
or
Dr
r
pressure-bal~;cede~~~i~e
which will maintain a nearly constant
gae pressure to the burner supply line.
. The ratio of the weight of water vapor
E ~y
p;esent in a unit volume of gas to the maximum possible weight
water vapor in unit volume of the same gas at the same
temperature
and pressure.
348
of
MIL-HDBK-1125/l
Utilizes electro-mechanical
relays to perform
logic function (on/off status) as burner sequencing and/or safety
control.
A relay control system u9ually incorporates
timers
andlor motor-driven
program timers in addition.to
relays.
~.
Oils which are too heavy to be evaporated
in any
normal evaporation
or distillation
process and are thus left over
from that process. Such oils are frequently cracked (high
temperature
fractionation)
or catalytically
cracked
(fractionation
in presence of alumina-silica
catalyst).
IN
AC
TI
VE
A straight or helical strip inserted in a firetube
Rsiar&x.
primarily to increase the turbulence
and improve heat transfer.
Also called turbulator.
“
~.
can be mechanically
boiler.
A soot blower in which the blowing element
extended- into and retracted out of the
flo w o~
. A mechanical
atomizing oil burner in
which part of oil supplied to the atomizer is withdrawn and
returned to storage or to the oil line supplying the atomizer.
Rke.
Anthracite coal size, otherwise known as No. 2 Buckwheat
through
5/16 inch over 3/16 inch round mesh screen.
-
.
A series of four rectangular
grids of black
lines of varying widths printed on a white background,
used as a
criterion of blackness for determining
smoke density.
umber.
See Smoke
A tube through
uPPer
Number,
which
Ringlemann.
steam
and water
passes
from an
wate~all header to a drum.
.
.
ed -lo&J&. A joint made
roller expander.
by expanding
a tube
into a hole
by a
. A burner
Rt. rv 011 b~
b; feeding oil to the inside
in which atomization
is accomplished’
of a rapidly rotating cup.
Ii12. Resistance
device.
Run of S&M.
mine.
~.
purpose
temperature
Unscreened
bituminous
A casting, fabricated
of support.
coal
chair,
349
as it comes
or member
used
from the
for the
I
~q et
. The action of shutting off fuel and ignition
Sa
energy to the burner by means of safety control or controls such
that restart cannot be accomplished
without operator action.
I’sv
The removal
of a portion
of a material
for, examination
or analysis.
eats. Steam
temperature.
S5
saturation
Saturated
~
water.
Water
VE
saturated
air.
Air which contains the maximum amount of water
vapor that it can hold at its temperature
and pressure.
at the pressure
at its boiling
SGs.k.
surfaces
Screen.
mounted
to its
point.
temperature.
The temperature
at a particular
pressure.
occurs
at which
A hard coating or layer of chemical
of boiler pressure parts.
evaporation
materials
on internal
A perforated plate, cylinder or mesh fabric, usually
on a frame for separating coarser from finer parts.
Scre eninq.
The undersized coal
inch or smaller, bituminous) .
Screw
corresponding
TI
I
m
ing.
s.a-E!L_
feed.
A means
from a screen
of introducing
[email protected] A device to close openings
leakage.
IN
I
I
I
valve.
A spring loaded valve that automatically
opens
afet
Used to prevent
when pressure attains the valve setting.
excessive pressure from building up in a boiler.
AC
I
MIL-HDBK-1125/l
process
fuel by rotation
between
structures
(often -3/4
of a screw.
to prevent
Sealinq air.
Air at a pressure slightly exceeding boiler
internal gas pressures used to prevent flow of combustion
from escaping the boiler, usually taken from a FD fan.
Seal weld.
leakage.
A weld
used primarily
to obtain
tightness
gases
and prevent
seam.
The joint between
SeEm.
origin
clay.
A continuous
tubular deposit of vegetal or sedimentary
bedded between parallel strata of sandstone,
shale, or
two plates
350
welded
or riveted
together.
..
-—=
._.
..-.
. .
MIL-HDBK-1125/l
(
Secon~
ignition at a point
Combustion).
. Combustion which occurs as a result
beyond the furnace (see also Delayed
of
Matter in water which is in suspension
and can be
removed by gravity or mechanical meana.
Noncombustible
solid
matter which settles out at the bottom of an oil tank; a small
percentage
is present in residual fuel oils.
TI
VE
Dry
.
A coal classification
according
to rank.
fixed carbon 85 percent or more and less than 92 percent and dry
volatile matter 14 percent or leae and more than 8 percent, on a
mineral matter-free
basis.
Semi“-””
bltummmfi . A former coal classification
including
low volatile
Se mi-fused slag.
have partly fused
according
Hard slag masses
together.
of particles
consisting
A device for separating solid matter
fluid; an electromagnetic
device for the removal
or tramp iron from coal.
SeRa=wK.
r
ice wate~.
General purpose water
treated for a special purpose.
value
AC
s
b~e~
A control reference
of a measured property.
point
which
from a conveying
of magnetic ores
which
may or may not have
which
represents
a desired
A grate from which refuse is removed by motion
the grate causing the refuse to sift through openings in or
between the grate.
IN
I
to rank,
bituminous.
StEu.
The
joint
between
two plates
welded
or riveted
Side air adm issio~.
Admission of air to the underside
from the sides of a chain or traveling grate stoker.
. A stoker ao arranged
Side dumo atr?.kez
from a dump
plate
that
at the side of the stoker.
Q12L!2. A laboratory
apparatus
finer particles of a substance
the coarser particlee.
.
Fine particles
refuse
together.
of a grate
is discharged
with meshes through which the
are passed to separate them from
of solid
grate.
351
fuel which
of
sift through
a
MIL-HDBK-1125/l
.
-,
QsIIId.
A continuous
level of information,
transmitted
to or
from control devices, from which there exists a maximum and
minimum value defined by the transmission
method and control
interpretation.
For example, an electronic signal may be based
on 4 to 20 milliamperes
(mA) of which 4 MA = the minimum or O
percent and 20 mA = the maximum or 100 percent.
S.iJ&. Finely divided
cleaning
anthracite
obtained
as a residue
from
process.
Fuel and air control elements are
mechanically
linked to a common actuator which medulatea
the two
Fuel air ratio
control elements as a unit in response to load.
is varied with firing rate by means of a mechanical
cam
arrangement.
VE
e Doint DO siti-.
Siinal
Sinale re tort stoker.
An underfeed stoker
in the assembly of a complete stoker.
SL?&k.
2-1/2
Screening,
inches.
SL.a9. Molten
down
or fused
SL!2exe. A tubular
pipe
or fine coal;
of friable
or other
solid
member
connections.
contact
maximum
IN
AC
Slackinq.
Breaking
moisture contents.
in direct
envelope.
one retort
with
TI
Skin casing.
Casing located
used to maintain an airtight
using
coals
top size
boiler
seldom
due to changes
only
tubes
above
in
matter.
through
a wall
to permit
Sli9 seal.
A seal between members designed
either member by slipping or sliding.
passage
to permit
of
movement
of
ShK1.
A large “dose” of internal chemical treatment applied
intermittently
to a steam boiler.
Also sometimes used instead
“priming”’ to denote a discharge
of water from a boiler steam
outlet in relatively
large intermittent
amounts.
S.mQ9. Air pollution
associated
of
with oxidants.
m.
Small gas-borne particles of carbon or soot, less than 1
micron (0.001 mm) in size, resulting from incomplete combustion
of carbonaceous
materials and in sufficient number to be
observable.
352
MIL-HDBK-1125/l
An integer between O and 5 that ,is
used todeacribe
the “darkness density” or degree of blackness of
The technique involves comparing standard
a visible etack plume.
Ringlemann charta to the stack plume visually.
A smoke number of
O indicates complete nonblack and a 5 indicates complete black.
An integer between O and 9 that is
used to indicate the relative emoke deneity of stack flue gas.
The technique ie to draw a specified amount of stack gas through
filter paper and compare the “smoke spot” to standard shaded
smoke spots.
magnesium
TI
VE
~.
The act of removing scale-forming
impurities
from water.
calcium
and
Water which contains little or no calcium or
soft water.
magnesium salts, or watsr from which ecale-forming
impurities
have been removed or reduced.
Ssu&.
AC
Utilizes solid state semiconductor
components
in a hardwirad system to perform logic and sequencing
control and/or process control.
Any changes in system logic
usually require rewiring, relocation/replacement
of components,
addition of components,
or any combination
thereof.
Carbon
dust
formed
by incomplete
A mechanical device
Soot blo w=.
clean heat absorbing
surfaces.
Scu?. Standard
w,.
A notation
operating
meaning
combustion.
for discharging
steam or air to
procedure.
oxides
of sulfur.
IN
(
The breaking off of the surface refractory material
a result of internal stresses resulting from an excessive
temperature
gradient.
to raise
as
heat.
The quantity of heat, expressed in Btu, required
the temperature
of 1 pound of a substance 1 degree F..
Sd=Ldss.
An abrasion-resistant
metal plate, forming the
back of an elbow in a pulverized
fuel and air line, against which
the fluidized material strikes and ia dispersed
for the purpose
of obtaining uniform distribution
in the succeeding line or
burner.
.
Platea epaced in an elbow of a duct
[email protected]
guide the flow of fluid through the elbow with
distribution
and to minimize pressure drop.
353
so disposed
uniform
as to
MIL-HDBK-1125/l
sDona
e
ash.
structures
Accumulation
of dry ash particles
having a spongy appearance.
into soft
~n
. Ignition of combustible
following slow oxidation without the application
temperature
from an external source.
material
of high
A metal plate
wer
nlate.
atomizer of an oil burner.
A nozzle
S4mv
n Ozzle.
the form of a spray.
VE
SDrav anql e. The angle included between the sides of the cone
formed by liquid fuel discharged frDm mechanical,
rotary
atomizers,
and by some forms of steam or air atomizers.
used to atomize
from which
a liquid
the fuel in an
fuel is discharged
in
burner.
A type of gas burner
orifices.
The enda of hollow
SDun ends.
rigidly in position.
m.
Saybolt
consisting
AC
Spud
with
TI
@rav
towec.
A duct through which liquid particlea flow countercurrent to a column of gaa:
a fine apray is used when the object
is to concentrate
the liquid, a coarse spray when the object ia
to remove solids and objectionable
materials from gaaes.
seconds
members
closed
of several
pipes
by rolling
members
universal.
Stack . A vertical conduit to discharge
—
the atmosphere.
Also called chimney.
combustion
products
to
IN
Stack effect.
Hot gases, as in a chimney, that move upward
because they are warmer than the surrounding atmosphere.
Standard cubic foot . A standard cubic foot ia referred to 60
degrees F and 14.696 pounds per square inch pressure.
A dry
cubic fDot of air at these conditions weighs 0.0763 pound and has
a specific gravity of 1.00.
Ueually abbreviated
SCF.
~
~ta
d d te
standard volume
STP .
1.
standard
of gases
essur . Conditions at which a
is defined.
Sometimes abbreviated
Boilers (U.S.) - Standard
pressure is 14-7 psia.
temperature
is 60 degrees
2. Air pollution control (U.S.) - Standard
70 degrees F,
standard pressure is 14.7 psia.
354
temperature
aa
F,
is
MIL-HDBK-1125/l
(
Other - standard
is 14.7 psia.
3.
pressure
temperature
is 32 degrees
F, standard
The volume of a gas at standard temperature
and
~.
pressure.
In the U.S., this is normally expressed as standard
cubic feet.
.
SQ3Y.
“
A tensile strese
in position.
having
member
no moving
parts.
to hold material
or other
IN
AC
TI
VE
rigidly
A grate
A bolt threaded through or welded
~.
two spaced eheete of a firebox or box header
surfaces againet internal pressure.
The vapor
S&em.
phase
of water
members
at each end, into
to support flat
substantially
unmixed
with other
gases.
~
. A pressure chamber located at the upper
extremity of a boiler circulatory
system in which the steam
generated in the boiler ie eeparated from the water and from
which steam is discharged at a position above a water level
maintained
therein.
~~q
atomized
type.
. .
.
. A burner for firing oil which is
oil bu~
by steam.
It may be of the internal or external mixinq
SLfwkwoled
superheater
wall.
A wall partly
or reheater tubes.
or completely
covered
with
A receptacle riveted or welded to the top sheet of a
firetube boiler through and from which the steam is taken from
the boiler.
[email protected]
A
SumukuK.
.
steam
is paseed
[email protected]
Steam
water
~.
series of screens, wires, or plates
to remove entrained moisture.
A gage for indicating
CUM&&Y.
mixture.
the pressure
The percent
by weight
of vapor
A device
for removing
through
of steam.
in a steam
the entrained
and
water
The complete oxidation of the
the exact,
combustible
constituents
of a fuel, utilizing
theoretically
required amount of” oxygen.
355
which
from
.
MIL-HDBK-1125/l
(
SMlkeL.
See Mechanical
Stoker.
An element of a stoker, placed at the point of
entrance of fuel into the furnace and by means of which the depth
of fuel on the stoker grate may be controlled.
It is generally
used in connection with chain or traveling grate etokere and has
the form of guillotine.
~.
That part of the etoker within the space defined
by the walls of the furnace at the fuel bed level which forms the
bottom of the furnace and supports the fuel bed.
On a chain or
traveling grate stoker, the fuel bed ie considered
to be
eupported only to the center line of the rear shaft or its
equivalent.
VE
~.
.
A device, such as filter,
allowing a liquid to pasa,
particles
of withstanding
AC
TI
A weld capable
tllbg. Vertical tubes
wuwt
which act as supports for horizontally
surface.
A ehort
~.
extension.
to retain
SQd.d. A projecting
solid
a design
stress.
containing water or steam
oriented convection
tube welded
to a preesure
part
for field
pin serving
as a support
or means
etuds welded
to it.
of
attachment.
[email protected]
short
A tube wall covered with refractory
tube wall.
in place by stud anchors attached to the tubes.
IN
Stud
held
A tube having
Sub -“”
bkwuumus
coal.
Coal classification
according
1.
Moist
Btu 10,500 or more
2.
Moist
Btu 9,500 or more
and less
3.
Moist
Btu 8,300 or more
and less than
~.
and less
than
than
which
to rank:
11,500
10,500
9,500
saturation
saturation
To raise the temperature
of steam above ite
temperature.
.The temperature
in excess of its
temperature.
~.
saturation
Steam
temperature.
at a higher
356
temperature
is
than
its
. .
MIL-HDBK-11251’1
Superb eate~.
A group of tubes which absorb heat from the
products of combustion
to raise the temperature
of the vapor
passing through the tubes above its saturation
temperature.
suPD
lV
tube.
A tube which
carries
water
to the
inlet
water
header.
wof~.
~
Removal of water, foam, etc., from the surface
at the water level in a boiler.
The equipment
for such removal.
ax&E.
vessel
The sudden
or drum.
displacement
or movement
Sw2.u.. A slight weep in a boiler
to form drops.
joint,
not in sufficient
The sudden increase in the volume
mixture below the water level.
Temperina moisture.
A load that changes
intervals.
Water added to certain coals
insufficient
moisture content for proper
IN
100,000
of the steam
to the furnace
au.
The quantity of air required
Also called stoichiometric
air.
‘l!lsm5.A unit of heat applied especially
amount
to
for perfect
to gas.
One therm
=
Btu.
T hermal sleeve.
A spaced internal sleeve lining of a connection
for introducing
a fluid of one temperature
into a vessel
containing
fluid at a substantially
different
temperature,
used
to avoid abnormal stresses.
mrQa2.
Burner exit, geometrically
designed to provide
proper air-fuel expansion for flame shaping and flame
stabilization,
sometimes referred to as the quarl.
357
in
at relatively
short
which, as received, have
combustion
on stokers.
~ertiarv
air.
Air for combustion
supplied
supplement
the primary and secondary air.
~eoretical
combustion.
in a closed
in boiler water.
from a warm saturated
AC
Swinqina load.
the water-steam
of water
TI
Undissolved
solid
SusDended solids.
Sweat
The
condensation
of
moisture
—
.
atmosphere
on a cooler surface.
which
VE
~e.
That portion of the moisture in the coal
comes from external sources as water seepage, rain, snow,
condensation,
etc.
the
MIL-HDBK-1125/l
-1
A brace
Thro uah stay.
or tube sheets.
used
in firetube
Tie bar.
A structural member
furnace waterwall tubes.
T~e
to hold
m.
other
od .
A tension
member
which
between
A baffle
formed
to maintain
buckstays
the heads
the spacing
a bolt or tie rod
of
is passed,
or tie plates.
usually
A preformed burner refractory,
than standard brick.
Tile baffle.
shapes.
between
applied
to shapes
VE
T.~
. A plate, through
brick in place.
designed
boilers
of preformed
burner
refractory
Total air.
The total quantity of air supplied to the fuel and
products of combustion.
Percent total air is the ratio of total
air to theoretical
air expressed as percent.
Total moisture.
The
moisture in coal.
sum of
~n0
suspended
expressed
. The weight of dissolved and
in a un t weight of boiler water, usually
and surface
TI
moisture
IN
AC
impurities
in ppm.
nherent
~q
. A device to convert information
T
from one form to
another.
The usual application
is converting
physical states
such as pressure, temperature,
etc., into a pneumatic or
electronic
signal.
y~
ate st
with the exception
on, and driven by,
may be required to
ke~.
A stoker similar to a chain grate stoker
that the grate is separate from, but supported
chains.
Only enough chain strands are used as
support and drive the grate.
Water which has been chemically
Tr eated wate~.
it suitable for boiler feed.
treated
to make
ial for ianition.
That period of time during which the
‘1’r
programming
flame failure controls permit the burner fuel valves
to be open before the flame sensing device is required to detect
the flame.
22&!.e. A hollow
T’K
hammering,
cylinder
for conveying
. A device for cleaning
or by rotating cutters.
358
fluids.
tubes
by brushing,
..
MIL-HDBK-1125/l
(
A door in a boiler”or
may be removed or new tubes
furnace
paseed.
WkrdQQK.
tubes
TAkdlQk.
accommodate
A hole in a drum,
a tube.
~.
contact.
That
header,
part of a tube
wall
or tube
hole with
through
sheet
which
which
to
a tube makes
.
the tube holes.
-to tube wall. A waterwall in which
substantially
tangent to each other with
between the tubes.
me
Tube
driven
rotary
the tubea are
essentially
no space
. The act of cleaning a tube by means
device which passes through the tube.
of a power-
XMKwbMu.
TI
The optical obstruction
to the passing of a ray of
TU rbi~.
light through a body of water, caused by finely divided suepended
matter.
See Retarder.
Forms of grates,
air ie introduced.
XuYeK!=.
which
AC
A burner in which fuel and air are mixed
discharged
into the furnace in such a manner as to produce
turbulent
flow from the burner.
~.
located
See Analysis,
adjacent
to a retort,
and
through
Ultimate.
Ma ccoun ted for 10 se. That portion of a boiler heat balance
which represents
the difference
between 100 percent and the sum
of the heat absorbed by the unit and the classified
losses
expressed as percent.
IN
,
containing
VE
The plate
~.
is not completely
The combustible
oxidized.
portion
See Combustible
of,the
fuel which
Loas.
red -ssure
vess~ . A vessel designed to withstand internal
pressure, neither subjected to heat from products of combustion
nor an integral part of a fired pressure vessel system.
ufdkxsK.
The
in that period.
ratio
of hours
in operation
359
to the total
hours
.—
141L-HDBK-1125/l
(
An automatically
or manually operated
Yalve,
device consisting
essentially of a regulating valve and an
It is used to” regulate fuel flow.
operating mechanism.
YAll!2. A fixed or adjustable plate inserted
stream used to change the direction of flow
.
~.
provide
A set of movable vanes in the inlet of a fan to
regulation
of air or gae flow.
The change
from liquid
or solid phase
Flue
that are visible
to the vapor
IN
AC
TI
VE
,
in a gas or air
(see also Splitter).
phaae.
~.
water
gasea
becauae
they contain
droplets.
Y!2.l&. An opening in a veeael
removal of gas or vapor.
or other
enclosed
epace
for the
. .
Vertic~.
An arrangement
of a burner such that air and
fuel are discharged
into the furnace, in practically
a vertical
direction,
either up or down.
Viscosj.&y.
The measure of the internal friction of a fluid or of
its resistance
to flow.
In fuel oil, it is highly significant
since it indicates both the relative ease with which the oil will
flow or may be pumped, and the eaee of atomization.
Vitreous
Glassy
slag.
ma
tile matte~.
Those products
or vapor, determined
by definite
Volat~,
~.
waterwall
2
given off by a material
prescribed methods.
as gas
See Vaporization.
heat
A short retractable
blower
absorbing surfaces.
for cleaning
adjacent
A structure in a wall of a eteam generator throuqh
[email protected]
which apparatue,
such aa coot blowere, extend into tile setiing.
Ya te heat. Sensible heat in noncombustible
le~ving furnaces used for proceeding metals,
materials.
Waste heat boil.ex. A boiler that recovers
and converts it to ueable heat.
360
gases, such as gases
ores, or other
normally
unused
energy
—-—.
.
MIL-HDBK-1125/l
~.
Wate
Appreciable
of handling
Moisture and foreign matter in liquid fuel.
amounts of water and sediment tend to cause fouling
equipment.
One or more horizontal water tubee located over and
M&eLkQk.
laterallv across the ash discharqe end of a stoker to prevent ash
adhesion-to
the wall and to reduie.air leakage from the ash pit
into the furnace.
w ater cooled baffl e.
spaced boiler tubes.
A baffle
VE
A vertical tubular member connected at its top and
water column.
bottom to the steam and water space respectively of a boiler, to
which the water gage, gage cock=, and high and iow level alarms
may be connected.
composed
essentially
of closely
~r
w
TI
Water cooled burner throat.
Burner throat water cooled by
waterwall
tubes bent to conform to the throat and covered by
refractory.
. A stoker having tubes in or near the grate
surface
through
which
Water
cooled
wall.
Hater
aaae.
The gage
water
is passed
A furnace
containing
and its fittings
AC
glass
wall
for cooling
the grates.
water
tubes.
for attachment.
Hat er ham.er . A sudden increase in pressure of water
instantaneous
conversion
of momentum to pressure.
due to an
IN
A vertical or nearly vertical box header, sectional
Hater leg.
header, or water cooled sides of an internal firebox composed of
flat or circular surfaces.
Ha ter level.
boiler.
The elevation
of the Surface
of the water
in a
Water seal.
A seal against leakage of air into a furnace
consisting
of a metal sheet, the lower edge of which is submerged
in a trough containing water.
Water tube.
A tube in a boiler having the water
inside and heat applied to the outside.
A synonym for steam,
Water vaDOq.
of low absolute pressure.
leathering.
Same
a“s slacking.
361
usually
and steam
used to denote
on the
steam
. .
..—
MIL-HDBK-1125/l
H!=a2.
which
A term usually applied to a minute leak in a boiler
forms droplets (or tears) of water very slowly.
joint
~~,u.
. A furnace closure wall made up of closely spaced
waterwall
tubes welded to each other or to an intermediate
fin to
form a continuous
airtight structure.
Wet bulb temDeratur e. The lowest temperature
which a water
The
wetted body will attain when exposed to an air current.
temperature
of adiabatic saturation.
steam.
heating
wet
A term used to designate the percentage of water in
Also used to describe the presence of a water film on
surface interiors.
steam.
Steam
containing
moisture.
of supplying
a water
film to the water
side
TI
Wetting.
The process
of a heating surface.
VE
[email protected] tness.
Wide ranae mechan ical atomizinq oil burn e~.
A burner having an
oil atomizer with a range of flow rates greater than that
obtainable
with the usual mechanical
atomizers
(see also Return
Flow
Oil Burner).
Windbox
burner,
AC
Windbox.
A chamber below the grate or surrounding
a burner,
through which air under pressure is supplied for combustion
of
the fuel.
pressure.
The static pressure
firing system or stoker.
in the windbox
of a
IN
WraDger sheet.
The outside plate enclosing the firebox in a
Also the thinner sheet in the
firebox or locomotive boiler.
shell of a two thickness boiler drum.
Zone control.
stoker.
The control
of airflow
into
Zo:es.
Divisions of the stoker windbox
ma~ntained
at different and controllable
CUSTODIAN:
NAVY - YD2
individual
zones
of a
in which air can be
pressures.
PREPARING ACTIVITY:
NAVY - YD2
PROJECT NO.
FACR-111O
362
STANDARDIZATION
DOCUMENT
(
IMPROVEMENT
PROPOSAL
INSTRUCTIONS
1.
The preparing acsivity mwt complete blocki 1.2. 1. and 8, In block 1, both the dosument
letter fhould be given.
2.
The wbmitter
3.
The preparing acIivity mu!: provide a reply within 30 days from receipt of the form.
of this form mu$tcomplete
number and rew!,on
bldck$ d, 5.6, and 7.
NOTE: This form may not be u~ed 10 requeil copms of ddcument$ nor to reque!t waivers. or dari Iication
requiremems on current contracts. Commenh submitted on thi$ form do not constitute or imply authorization
waive any portion of the referenced document
or to amend contractual requirements.
.,
RECOMMEND
00CUMtNT
A CHANGE:
‘“ O“’’M;l~#;;
.
lllL1
MAINTENANCE
OF
CHANG1
(kl,noly
P4,ag,,#I
AND
tw,nbct
L
,,25,,
00CUMIN1
OA1l
OPERATION
,IM
tilud,
OF
-d
CENTRAL
,,wm,.
lVVMMOOJ
9S1OI5
if
HEATNG PIANTS
POWtJ,.
AIwch
en,,
UI,,l,
,,
nrrdrd)
AC
NAWIU
.
TI
VE
*
of
to
I
IN
RI ASON POR RfCOMMINOA1,Oll
SuBMlrTEn
NAME [l~R.
Flm4 Mkb7Q [email protected]
AOCHESS (-
@
b
Codt)
oRowo’Anoti
d rslzn+ow W&
,.
&** cd)
7. pmwamco
~1) Commaicisl
U) iuTOVON
‘ ofaPP7r*t4
PRIPA RING ACliVllY
COMMANDEK
ATLANTIC DIVISION
NAVAL FACILITIES ENGINEERING COMMAM2
CODE 161B
N~l
AYJRES$
(I,xlti,
2,0 Cd]
1510 GILBERT STREET
NORFOLK VA
23511.2699
F..- U%
.— m-..-,
b,
1[LCP)40NE
(bxh.dc
A/,,
Cod,]
(21AUTOVON
(’lCmme’ci”’
26246?5
(S0S) 322-4625
1? YOU 00
NOT RICIWI
A REPLY
WIHIN
hfmx
Ou.!ir, and S:.nd..d#z.l,on
S1OI lembulg PIk*. S“LIR 1403. ~,lt,
T,!.pllm,
4S D&YS. CONTACT,
Office
Chum.
VA 2SOS1.MS6
(701)
7s6.2140
Aulovota
2s9.23a
-... ..................
....
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