Guide to Operation of Steam Receivers

Guide to Operation of Steam Receivers
GUIDE TO OPERATION OF
STEAM RECEIVERS
This guide is prepared by the
Occupational Safety and Health Branch
Labour Department
This edition
May 2012
This guide is issued free of charge and can be obtained from office of the
Boilers and Pressure Vessels Division of the Occupational Safety and
Health Branch or downloaded from website of the Labour Department at
http://www.labour.gov.hk/eng/public/content.htm. Addresses and telephone
numbers of the offices can be found in the website of the Department at
http://www.labour.gov.hk/eng/tele/index.htm.
This guide may be freely reproduced except for advertising, endorsement
or commercial purposes. Please acknowledge the source as “Guide to
Operation of Steam Receivers”, published by the Labour Department.
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OPERATION OF STEAM
RECEIVERS
(INCLUDING KIERS)
Labour Department
CONTENTS
Foreword................................................................................................1
1.General ..........................................................................................2
2.
Registration and Examination ........................................................2
3.
Competent Person .........................................................................2
4.
Steam Receivers ...........................................................................3
5.
Cone and Fabric Kiers ...................................................................5
6.
Principle of Operation for Kiers ......................................................5
7.
Fittings for Steam Receivers and Kiers..........................................8
8.
Operating Precaution for Steam Receivers....................................9
9.
Points to be observed when putting the Steam Receivers in Use...10
10. Points to be observed when opening the Receiver for Inspection.... 11
11. Other Important Points to be observed by Operators and Owners .. 13
12. Enquiries and Complaints ............................................................14
FOREWORD
This guide explains briefly the main provisions of the Boilers and
Pressure Vessels Ordinance, Chapter 56, as applicable to various types of
steam receivers.
Steam receivers are extensively used in industry, particularly textile.
Using the equipment by personnel without sufficient knowledge about its
operation and maintenance may cause serious accidents. All personnel
engaged in the use of such equipment are strongly advised to familiarise
themselves with the contents of this guide.
While every care has been taken in the preparation of this guide, the
Ordinance itself remains the sole authority for the provisions of the law
explained.
On request, the Labour Department will also offer further advice to
owners and operators regarding such equipment.
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1. GENERAL
The Boilers and Pressure Vessels Ordinance also governs, among other
things, the use of steam receivers. Steam receiver means any vessel used
for containing steam under pressure greater than atmospheric pressure
and covers equipment such as a vessel used to store steam for heating of
other materials (i.e. dryers, steam rolls etc.), or for heating of fluid under
pressure in a vessel as kiers.
2. REGISTRATION AND EXAMINATION
• The steam receiver must be registered with Boilers and Pressure
Vessels Division, Labour Department.
• An appointed examiner must examine the steam receiver and the
auxiliary equipment, and the owner shall submit application for
registration at least 30 days prior to the steam receiver being put in
use.
• The maximum permissible working pressure of the steam receiver
must be approved by this Department and be allotted with a
Registration Number.
• An appointed examiner must set and seal the safety valve at the
approved maximum pressure and issue a Certificate of Fitness.
• Regular periodic examination must be carried out at every 26 months
interval by an appointed examiner for the issue of a Certificate of
Fitness.
• Operation of a steam receiver without a valid Certificate of Fitness
is an offence and the owner may be fined a maximum of HK$50,000
[Level 5 of Schedule 8 to the Criminal Procedure Ordinance, Cap 221]
for the contravention of the Ordinance.
3. COMPETENT PERSON
• Incorrect operation of steam receiver and its fittings can cause
accidents resulting in injury or loss of life. Therefore, a competent
person must be present at all times when the steam receiver is in
operation to ensure safety in its operation and to comply with Boilers
and Pressure Vessels Ordinance.
• The competent person who operates or supervises the operation of
steam receivers must be in possession of a Certificate of Competency
awarded by the Boilers and Pressure Vessels Division of Labour
Department.
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• The competent person who possesses a Certificate of Competency
to operate steam receiver is also qualified to operate kiers. He must,
therefore, understand the principle and operation of a kier.
4. STEAM RECEIVERS
• Different types of steam receivers, such as steam rolls for calendering,
or dryers for heating and drying other materials, or kiers for dyeing
purposes, or sterilizers used in the preparation of food etc.
• All steam receivers have certain common fittings/mountings, e.g.
safety valves, pressure gauges, valves, steam traps etc.
• Some steam receivers may have vent valves, working door/cover etc.
• A thermostatic sensor locking device which is approved by the maker
may be fitted for additional safety in operation.
GENERAL ARRANGEMENT OF
STEAM RECEIVERS
1. Pressure gauge
2. Safety valve
3. Stop valves (inlet and outlet)
4. Pressure reducing valve
5. Vent valve
6. Drain valve
7. Steam trap
3
GENERAL ARRANGEMENT OF MULTI-CYLINDER DRYERS
1. Pressure gauge
2. Safety valve
3. Stop valves
4. Pressure reducing valve
5. Steam trap
4
5. CONE AND FABRIC KIERS
• Cone kiers may be completely flooded or partly filled up with dyeing
liquor.
• Compressed air may be used to form an 'air pad' for pressurisation.
• Different types of kiers are used according to the type of material being
treated.
• These kiers use high pressure steam to heat up the dyeing liquor.
• All these kiers have certain common mountings, e.g. safety valve,
pressure gauge, valves, heating coils, vent and drain etc.
6. PRINCIPLE OF OPERATION FOR KIERS
A. Fabric Dyeing Kiers
• The fabric to be dyed forms a loop in the vessel and is circulated inside
the vessel with the help of liquor circulation and the lifter reel.
• The dye stuff and chemicals are added at the appropriate temperature
after the cover is closed.
• The vessel is pressurised by compressed air or by the vapour pressure
of steam.
• The temperature and pressure inside the vessel varies for different
dyestuff and chemicals used.
B. Cone Dyeing Kiers
• Cone fabric to be dyed is mounted on a carrier.
• The dyeing liquid is mixed in the side tank and circulated through the
cones by a circulating pump.
• This type of kier may have three modes of operation, i.e. low/medium/
fully flooded mode.
• The first two modes are pressurised by air while the last mode is
pressurised by the pump.
5
GENERAL ARRANGEMENT OF FABRIC KIER
1. Service door
9. Water inlet valve
2. Lifter reel
10. Compressed air inlet valve
3. ELPO nozzle
11. Depressure valve
4. Service tank
12. Mixing valve
5. Dyestuff feed pump
13. Cooling water outlet valve
6. Filter & heat exchanger
14. Steam inlet valve
7. Circulation pump
15. Cooling water inlet valve
8. Drain valve
16. Safety valve
17. Pressure reducing valve
6
GENERAL ARRANGEMENT OF CONE KIER
1. Kier cover
7. Steam inlet valve
11.Lid valve
2. Dye tank
8. Cooling water inlet
valve
12.Drain valve
3. Circulation pump
(main pump)
4. Heating coil
5. Overflow valve
6. Drain valve
9. Condensate outlet
valve
10.Cooling water outlet
valve
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13.Injection pump
14.Service tank
15.Safety valve
16.Pressure reducing
valve
7. FITTINGS FOR STEAM RECEIVERS AND KIERS
(a)
STEAM TRAP —
It is used to drain out the
condensate from the steam
receiver. As the water level
rises, the float in the trap will
move up and in turn, connect
some leverage to open the
valve and drain the water away.
When the level falls, the float
will come down and the drain
valve will be closed.
(b) PRESSURE REDUCING
VALVE —
It is used to reduce the steam
pressure supplied from the
boiler. Usually boiler generates
steam at a pressure higher than
normally required for steam
receiver operation. Pressure
reducing valve can control and
maintain the pressure in the
steam receiver. This valve also
has a throttling effect which
minimise the water droplets
in the steam. The bellow in
the reducing valve should be
checked periodically to ensure
the safe operation of the
equipment at the receiving end.
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(c)
SAFETY VALVE —
It prevents the pressure in the
vessel from going above a
safe working pressure by its
automatic opening to release
the excess pressure when the
set point is reached. This guards
against possible explosion from
excessive pressure.
8. OPERATING PRECAUTION FOR STEAM RECEIVERS
When steam is supplied to cold steam pipe with condensate, steam
condenses as it comes in contact with cold pipe wall or the condensate
causing water hammering as illustrated below:
Fig.(A)
Fig.(B)
Fig.(C)
Fig.(D)
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FIG. (A) & (B) Steam is supplying to the pipe which contains condensate
with the stop valve closed, and the draining of condensate
from the pipe has not been completed. As steam enters
the pipe and disturbs the surface of water and causes the
formation of waves.
FIG. (C) & (D) When the condensate level falls, the turbulence increases
rapidly and breaks the crest of the waves forming bubblelike enclosures containing steam. The pressure causes
the bubble to collapse with some noise and force. A
surging wave may be big enough to block the pipe. Steam
condenses on the other side of the waves creating partial
vacuum together with the incoming steam behind the wave
forcing the water at high velocity towards the stop valve or
other obstruction. This action causes rupture of steam pipe
or the valve body.
To prevent water hammer in steam pipe, open the drain valve to drain the
condensate completely and crack-open the stop valve to allow warming up
the steam pipe. When the steam pipe is warmed up and steam comes out
through the drain cock, the drain cock can be closed and the steam stop
valve can be opened slowly.
9. P O I N T S T O B E O B S E R V E D W H E N P U T T I N G T H E
STEAM RECEIVER IN USE
• Periodically check the validity of Certificate of Fitness, to ensure
statutory inspections have been carried out at the right time.
• Periodically examine the safety devices, attachments, auxiliary fittings
and control equipment to ensure their proper functioning. Defective
parts may be the cause of accidents.
• Check all the fittings are properly mounted and there are no leaky
joints.
• For bolted covers, the practice of tightening or loosening only a few
bolts must be prohibited.
• All swing bolts must be completely free and the cover loosened before
swinging the bolts clear.
• Drain the condensate in the steam pipe completely before the steam
stop valve is opened slowly to prevent water hammer.
• Check the pressure in steam receiver is not higher than the pre-
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determined working pressure to ensure the function of the pressure
reducing valve.
• Always ensure that the operating pressure indicated in the pressure
gauge should not exceed the red line which indicates the maximum
permissible working pressure as specified in the Certificate of Fitness.
• Check the steam trap is functioning properly, and that condensate only
is discharged from it.
10.P O I N T S T O B E O B S E R V E D W H E N O P E N I N G T H E
RECEIVER FOR INSPECTION
• The steam receiver should be isolated by closing all its inlet and outlet
valves. Drain and vent valves are fully opened to release the pressure
or vacuum inside. If drain is connected to a common manifold with
other steam receivers or apparatus, then drain valves should be closed
after drainage is completed.
• Check pressure gauge is working correctly and indicating zero
pressure.
• When no pressure remains inside the receiver, slacken all the nuts and
slightly open the cover/inspection door. The nuts must not be swung
clear unless no steam comes out from the cover.
• A responsible person must be stationed close by to prevent accidental
opening of steam isolating valve or closing the cover when someone is
working inside the steam receiver. The steam isolating valve should be
locked shut or labelled ‘DO NOT OPEN’.
• Appropriate measures to be taken to comply with the Factories and
Industrial Undertakings (Confined Spaces) Regulation, Cap. 59AE,
Laws of Hong Kong.
In Addition to the operating precaution for steam receivers, the
following points should also be observed when operating kiers:
• The cover should never be opened when pressure still exists inside the
shell and its operating temperature is above 80°C. This is especially
important in the fully flooded mode of cone dyeing kiers where the
pressure inside the shell can be released quickly while the liquid inside
the shell is still above boiling point.
• The vent, drain, connection of pressure gauge and level gauge glass
are checked for blockage before each dyeing operation.
11
• Do not by-pass and/or interfere with the function of the interlocking
devices.
• After loading the kier and before the door is closed, all foreign matter,
spillage, etc., should be cleaned from the locking parts of the door,
and the door jointing should be examined to ensure that it is seating
properly in its groove.
• Care should be taken to ensure that the locking ring does not bind
during rotation. The entire ring may, otherwise, rotate about this
fulcrum with the result that the ring does not remain concentric leading
to unequal overlap of the locking lug.
• In case of quick closing doors, where locking is by means of a single
handle, the use of a piece of steel tubing or other similar arrangements
to unduly increase the joint tightness is prohibited.
• In using eye bolts for lifting the cone carrier, the liquid in the shell must
be completely drained first. The attendant should prevent the carrier
from turning during lifting. Hooks for lifting should be fitted with safety
latch.
• In all cases, the manufacturer's recommended method of operation
should be strictly followed. Instructions for loading, taking sample and
unloading should also be in easy reach of operators, or prescribed
procedures, in written orders, are available for observance.
• Concentricity of the rotating ring is maintained by the clearance of
the fit. Such clearance should not give way to possible excessive
displacement from use of undue force. If the ring has not been rotated
to the pre-determined position, the mechanical interlock will prevent
the kier from proper functioning and the operator cannot start the
process.
• Dyeing chemicals containing chlorine should not be used in stainless
steel vessels/kiers without consulting equipment manufacturers.
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11. OTHER IMPORTANT POINTS TO BE OBSERVED BY
OPERATORS AND OWNERS
• Operators must obtain the relevant certificate of competency before
operating any steam receiver.
• Do not tamper with the
seal of the safety valve
or increase the working
pressure beyond the
approved maximum
working pressure. This
endangers the safety, as
over-pressure can cause
accident and injuries
to operator and other
persons.
• The cover or locking
device should never
be forced into position.
If there is any unusual
resistance to smooth
operation, the matter
should be reported
to the maintenance
engineer for immediate
investigation.
• Repairing or servicing
should only be carried
out by qualified
engineers approved by
the makers and under
supervision of appointed
examiners.
• In case of accident, owners must ensure the steam receiver and its
auxiliaries are shut down immediately and report the accident to the
Boilers and Pressure Vessels Authority within 24 hours. The owner
can be prosecuted and the maximum fine for this breach of the law is
$10,000.
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12. ENQUIRIES AND COMPLAINTS
For other enquiries, such as the application for registration, safe
operation of steam receivers, approved list of appointed examiners etc.,
please contact the Boilers and Pressure Vessels Division of the Labour
Department through:
Address: Unit 01-02, 20/F
Millennium City 6
392 Kwun Tong Rd
Kowloon
Telephone: 3107 3458
Fax:
2517 6853 / 2517 0875
E-mail:equiry@labour.gov.hk
Information on the services offered by the Labour Department is available
on its website at http://www.labour.gov.hk
Information on the services offered by Occupational Safety and Health
Council can be obtained through hotline 2739 9000.
If you have any complaints about unsafe workplaces and practices, please
call the Labour Department's occupational safety and health complaint
hotline on 2542 2172. All complaints will be treated in the strictest
confidence.
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Published by the Labour Department
5/2012-3-BPVB17a
Printed by the Government Logistics Department
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