Type 25P & 25PA Pressure Reducing Valves

Type 25P & 25PA Pressure Reducing Valves
INSTALLATION AND MAINTENANCE INSTRUCTIONS
IM-3-000-US October 2015
Type 25P & 25PA Pressure Reducing Valves
Safety Information
Safe operation of these products can only be guaranteed if
they are properly installed, commissioned, used and maintained
by qualified personnel (see Section 1.11) in compliance with
the operating instructions. General installation and safety
instructions for pipeline and plant construction, as well as the
proper use of tools and safety equipment must also be complied
with.
1.1 Intended use
Referring to the Installation and Maintenance Instructions,
name-plate and Technical Information Sheet, check that the
product is suitable for the intended use / application.
i) The products have been specifically designed for use on
steam, air or water/condensate. The products’ use on other
fluids may be possible but, if this is contemplated, Spirax
Sarco should be contacted to confirm the suitability of the
product for the application being considered.
ii) Check material suitability, pressure and temperature and
their maximum and minimum values. If the maximum
operating limits of the product are lower than those of the
system in which it is being fitted, or if malfunction of the
product could result in a dangerous overpressure or
overtemperature occurrence, ensure a safety device is
included in the system to prevent such over-limit situations.
iii) Determine the correct installation situation and direction
of fluid flow.
iv) Spirax Sarco products are not intended to withstand external
stresses that may be induced by any system to which they
are fitted. It is the responsibility of the installer to consider
these stresses and take adequate precautions to minimise
them.
v) Remove protection covers from all connections and
protective film from all name-plates, where appropriate,
before installation on steam or other high temperature
applications.
1.2 Access
Ensure safe access and if necessary a safe working platform
(suitably guarded) before attempting to work on the product.
Arrange suitable lifting gear if required.
1.3 Lighting
Ensure adequate lighting, particularly where detailed or intricate
work is required.
1.4 Hazardous liquids or gases in the pipeline
Consider what is in the pipeline or what may have been in the
pipeline at some previous time. Consider: flammable materials,
substances hazardous to health, extremes of temperature.
1.5 Hazardous environment around the product
Consider: explosion risk areas, lack of oxygen (e.g. tanks, pits),
dangerous gases, extremes of temperature, hot surfaces, fire
hazard (e.g. during welding), excessive noise, moving
machinery.
1.6 The system
Consider the effect on the complete system of the work
proposed. Will any proposed action (e.g. closing isolation
valves, electrical isolation) put any other part of the system or
any personnel at risk?
Dangers might include isolation of vents or protective devices
or the rendering ineffective of controls or alarms. Ensure
isolation valves are turned on and off in a gradual way to avoid
system shocks.
1.7 Pressure systems
Ensure that any pressure is isolated and safely vented to
atmospheric pressure. Consider double isolation (double block
and bleed) and the locking or labelling of closed valves. Do not
assume that the system has depressurised even when the
pressure gauge indicates zero.
1.8 Temperature
Allow time for temperature to normalise after isolation to avoid
danger of burns.
1.9 Tools and consumables
Before starting work ensure that you have suitable tools and / or
consumables available. Use only genuine Spirax Sarco
replacement parts.
1.10 Protective clothing
Consider whether you and / or others in the vicinity require any
protective clothing to protect against the hazards of, for example,
chemicals, high / low temperature, radiation, noise, falling
objects, and dangers to eyes and face.
1.11 Permits to work
All work must be carried out or be supervised by a suitably
competent person. Installation and operating personnel should
be trained in the correct use of the product according to the
Installation and Maintenance Instructions.
Where a formal ‘permit to work’ system is in force it must be
complied with. Where there is no such system, it is recommended
that a responsible person should know what work is going on
and, where necessary, arrange to have an assistant whose
primary responsibility is safety.
Post ‘warning notices’ if necessary.
1.12 Handling
Manual handling of large and/or heavy products may present
a risk of injury. Lifting, pushing, pulling, carrying or supporting
a load by bodily force can cause injury particularly to the back.
You are advised to assess the risks taking into account the
task, the individual, the load and the working environment and
use the appropriate handling method depending on the
circumstances of the work being done.
1.13 Residual hazards
Steam Mains - Do's and Dont's:
In normal use the external surface of the product
may be very hot. If used at the maximum
permitted operating conditions the surface
temperature of some products may reach
temperatures in excess of 300°C (572°F).
4
7
4
7
4
7
4
7
4
7
Many products are not self-draining. Take due
care when dismantling or removing the product
from an installation (refer to 'Maintenance
instructions').
1.14 Freezing
Provision must be made to protect products
which are not self-draining against frost
damage in environments where they may be
exposed to temperatures below freezing point.
Steam
1.15 Disposal
Unless otherwise stated in the Installation
and Maintenance Instructions, this product
is recyclable and no ecological hazard is
anticipated with its disposal providing due
care is taken.
1.16 Returning products
Customers and stockists are reminded that
under EC Health, Safety and Environment Law,
when returning products to Spirax Sarco they
must provide information on any hazards and
the precautions to be taken due to contamination
residues or mechanical damage which may
present a health, safety or environmental risk.
This information must be provided in writing
including Health and Safety data sheets relating
to any substances identified as hazardous or
potentially hazardous.
1.17 Working safely with cast iron
products on steam
Cast iron products are commonly found on
steam and condensate systems. If installed
correctly using good steam engineering
practices, it is perfectly safe. However, because
of its mechanical properties, it is less forgiving
compared to other materials such as SG iron or
carbon steel. The following are the good
engineering practices required to prevent
waterhammer and ensure safe working
conditions on a steam system.
Prevention of tensile stressing
Pipe misalignment:
Installing products or re-assembling after maintenance:
1
Safe Handling
Cast Iron is a brittle
material. If the product
is dropped during
installation and there
is any risk of damage
the product should
not be used unless it
is fully inspected and
pressure tested by the
manufacturer.
4
7
Do not over tighten.
Use correct torque figures.
Prevention of water hammer
Steam trapping on steam mains:
30 - 50 metre intervals
Gradient
Steam
1:100
Trap set
Condensate
Gradient
1:100
Trap set
Condensate
Steam
Trap set
Condensate
2
7
3
2
1
3
5
6
4
2
8
Flange bolts should be gradually tightened across
diameters to ensure even load and alignment.
Thermal expansion:
Guides
Limit rods
Guides
Medium
distance
Axial movement
Short
distance
Small
lateral
movement
Large
lateral
movement
Fixing point
Fixing point
Axial movement
Guides
Limit rods
Guides
Small
lateral
movement
Large
lateral
movement
Installing the Valve
4.Install a small gate valve in the sensing line so that this
can be closed when servicing the regulator.
Do not lift the regulator by the tubing. Grasp the body of
the valve firmly when lifting.
5.The sensing line must be pitched downward from the
main valve to insure proper drainage.
Piping
6.To permit accurate setting of the pressure regulator,
a pressure gauge should be installed as close as possible to the pilot sensing line connection.
2.Piping on the downstream side of the valve should be
increasedso as not to restrict flow.
Bypass
Unpack Carefully
1.Typical hookup sketches as shown in Figs. 1 and 2 will
aid in planning a correct installation.
3.Swage nipples are recommended for changes in pipe
sizes.
4.Before installing the valve make sure the piping is free
of foreign material, scale, etc.
5.Make certain the arrow cast on valve body is pointing
in the direction of flow.
6.Valve should always be installed in a horizontal position. (See Figs. 1 and 2.)
7. Pressure Gauges must be installed on both sides of the reducing valve.
Assembling Pilot to Valve Body
1.Remove all protective caps from ports if present.
2. Remove the package of square gaskets from the pilot box and install on the main valve cover assembly (A).
3.
Install pilot on top of gasket just placed on main valve cover assembly (A) so that the sensing line is pointing
in same direction as the valve outlet connection. Be
sure that the guide pin in the cover assembly (A) fits
securely in the guide hole in the pilot. Be sure the pilot
bolts are secured to the valve cover assembly (A) and
tightened.
1.A bypass connection, as shown in Figs. 1 and 2, is
recommended so that the valve can be serviced without shutting down the equipment.
2.The bypass valve should be the same size as the
pressure reducing valve.
Steam Line Drain Trap
1.To insure proper operation of the valve and avoid
premature wear, it is recommended that a 1/2” Spirax
Sarco thermodynamic steam trap be installed on the
steam supply line. (See Figs. 1 and 2.)
2.A steam trap should also be installed in the downstream piping at the heel of each rise, between all
reducing valves installed in series, and ahead of any
manual or automatic valve. This will prevent condensate accumulation that can result in waterhammer
damage.
Pipeline Strainers
1.It is strongly recommended that strainers be installed
before the reducing valve and steam traps.
2.Make certain adequate clearance is provided for
screen removal and blowdown connection between
strainer and valve body.
Stop Valves
Pilot Pressure Sensing Line
All stop valves on the supply side, as well as on the
downstream side of the pressure reducing valve and
sensing line, should be of the gate type so as to insure full
rated capacity and good control.
2.Connect the sensing line to a straight portion of the
piping 10 pipe diameters from nearest fitting downstream from the valve and approximately 1 foot from
elbows, tees, valves and other restrictions. (See Figs. 1
and 2.)
Separators
1.Copper tubing (1/4” OD) can be used for the sensing
line with suitable compression fittings or as alternative
1/4” piping can be used.
3.When the reducing valve is serving a single piece of
equipment, the sensing line can be connected to the
steam space of the equipment.
It is recommended that a line size separator is installed
before all pressure reducing stations where the pipeline
supply is longer than 50 ft from a trapping station or
where exposure or piping configurations lead to the accumulation of significant amounts of condensate ahead of
the PRV station.
Safety
Valve
Steam
Supply
Moisture
Separator
Drip
Pan
Elbow
Strainer
Reduced
Steam
Pressure
Pilot Operated
Pressure Control Valve
Spira-tec
Loss
Detector
Strainer
Check
Valve
Fig. 1
Float &
Thermostatic
Steam Trap
Select inlet piping for reasonable velocity and expand downstream for equal flow rate.
Typical Pressure Reducing
Valve Station
Safety
Valve
/3
2
Pressure
Sensing
Line
Drip
Pan
Elbow
Strainer
Pilot Operated
Pressure Control Valve
/3
1
Steam
Supply
Pressure
Sensing
Line
Moisture
Separator
Reduced
Steam
Pressure
Strainer
Spira-tec
Loss
Detector
Set lead valve (1/3) 2 psi above
desired set pressure and set
lag valve ( 2 / 3 ) 2 psi below
desired set pressure.
Strainer
Check
Valve
Pilot Operated
Pressure Control Valve
Fig. 2
Float &
Thermostatic
Steam Trap
Parallel Operation of
Pressure Reducing Valves
Pressure
Sensing
Line
Pressure
Sensing
Line
Moisture
Separator
Steam
Supply
Pilot Operated
Pressure Control Valve
Spira-tec
Loss
Detector
Strainer
Note: Intermediate pressure takeoff
requires an additional safety valve.
Drip
Pan
Elbow
Reduced
Pilot Operated
Pressure Control Valve Steam
Pressure
Strainer
Strainer
Safety
Valve
Strainer
Check
Valve
Float &
Spira-tec Thermostatic
Loss
Steam Trap
Detector
Check
Valve
Fig. 3
Float &
Thermostatic
Steam Trap
Series Pressure Reducing Valve
Station for High Turndown Rations
4
Safety
Valve
Drip
Pan
Elbow
5/16” Copper
Tubing or 1/4” Pipe
Moisture
Separator
Noise Diffuser
(if required)
Steam
Supply
Strainer
Reduced
Steam
Pressure
Main
Control Valve
1/2” Pipe
Limit pilot to 15 ft.
drop below main valve
and drain all supply tubing. If pilot is
mounted above main
valve, pilot line drip
traps can be eliminated. For longer distance an air loaded
pilot should be used.
Remote
Pressure
Pilot
Check
Valve
Check
Valve
Check
Valve
Strainer
Float &
Thermostatic
Steam Trap
Float &
Thermostatic
Steam Trap
Float &
Thermostatic
Steam Trap
Hook-up for Remote Operation of
25 PRM Pressure Reducing Valve
Start-up
1.First make certain that all stop valves are closed.
Pressure Adjustment,
Spring or Air
Air
Pilot
Pressure
Pilot
Pressure Diaphragm
Orifice
Downstream
Pressure
Sensing Line
2.Remove pilot spring cover then turn the pressure pilot
adjustment (2D) counter-clockwise until spring is slack.
Make certain spring remains in vertical position and
centered in its retainers.
Air loaded PA pilots must have no air pressure
supplied to them.
3.Open stop valves in the following order:
MPC2
Filter Regulator
Main Valve
Control Pressure
Main Diaphragm
a.Open stop valve ahead of steam trap on steam
supply line. This will insure water free steam at the
regulator inlet when put into operation.
b.Open small gate valve on pressure sensing line.
c. Slowly open inlet stop valve.
4.Slowly adjust pilot spring at (2D) turning clockwise until
reduced pressure required is indicated on pressure
gauge downstream of valve.
How the 25P & 25PA Work
Normal positions before start-up are with the main valve
closed and the pilot valve held open by spring force or
air pressure. Entering steam passes through the pilot
valve into the main diaphragm chamber and also out
through the control orifice. As flow through the pilot
valve exceeds flow through the orifice, control pressure increases in the diaphragm chamber and opens the
main valve. As steam flows through the main valve, the
increase in downstream pressure feeds back through the
pressure sensing line to the underside of the pressure
diaphragm. When the force below that diaphragm balances the compression force of the spring above it, the
pilot valve throttles. The control pressure maintained in
the main diaphragm chamber positions the main valve to
deliver just enough steam for the desired delivery pressure. Adjustment of the spring or air pressure above the
pressure diaphragm changes the downstream pressure
set point. When steam is no longer required, the sensing
line pressure increases closing the pressure pilot and the
control pressure bleeds back through the control orifice.
This allows the main valve to hold the desired reduced
pressure, and it may close tight for a dead-end shutoff.
5.Once the system has stabilized itself, slowly open
down-stream isolation valve. It may be necessary
to make re-adjustment of pilot spring (2D). Replace
spring cover then tighten adjustment locknut.
6.Important­––Retighten all pilot flange connections to
insure steam tight joints.
7. Air Loading PA Pilot requires air loading as indicated
in the following table.
Desired Outlet Steam
Pressure P2 psig
Inlet Pressure
P1 psig
Approximate
Air Set Pressure
psig
5
5
10
25
50 75
100
10 psig to 100 psig
11 16 31 56 80 102
to to to to to
to
13.516.833.558 81 103
Troubleshooting
(Refer to Figs. 6, 7 and 8)
Cause
Symptom
Check and Cure
1. Controlled pressure over-
1. (a) Dirt or foreign material between pilot
1. (a) Loosen screw (2D). Remove copper
shoots under normal valve seat and head.
tubing connections at (J & L). With
load conditions
steam on valve, if steam flows from
copper tubing connections at (J & L)
remove pilot head and seat assembly
(2H) and clean or replace.
(b) Foreign particles between main valve
head and seat.
(b) Inspect and clean head and seat
(c) Orifices (B) and (H) or pressure sensing
line may be plugged.
(c) Remove, inspect and clean.
2. Controlled pressure 2. (a) Main valve head and seat worn or dirt
2. (a) Inspect and clean head and seat.
overshoots only on between them.
light loads.
(b) Valve may be severely oversized.
(b) Adjust screw (2D) to give desired
pressure under light loads.
(c) Bypass valve not shut tightly or leaking.
(d) Dirt or foreign material on main valve
stem and guide (1F).
(c) Check and repair as required.
(d) Remove, inspect and clean.
3. Valve fails to open.
3. (a) Main valve diaphragm ruptured.
3. (a) Unscrew copper tubing connection at (G) and crack bypass valve. If steam flows from main valve diaphragm case, diaphragm is defective and must be replaced.
(b) Orifice (H) is plugged
(b) Remove and clean.
(c) Pilot valve seat is plugged with dirt.
(c) Remove head and seat assembly (2H). Inspect and clean or replace.
(d) Screen (1D) is plugged.
(d) Inspect screen and clean.
(e) Pipeline strainer blocked.
(e) Inspect and clean.
(f) Pilot valve adjustment (2D) or air loading
(f) Adjust screw (2D) to desired pres pressure not properly adjusted.
sure. Check air supply to PA pilots.
4. Delivery pressure low.
4. (a) Pilot valve adjustment (2D) not
4. (a) Adjustment screw (2D) to desired
properly adjusted.
pressure.
(b) Valve undersized.
(b) Check actual load against valve
rating.
(c) Steam supply pressure too low.
(c) Check and correct.
(d) Main valve diaphragm ruptured.
(d) Unscrew copper tubing connection (G) and crack bypass valve. If steam
flows from diaphragm case, dia
phragm is defective and must be
replaced.
5. Valve fails to close.
(e) Bleed orifice (B) missing.
5. (a) Bypass valve open or leaking.
(e) Replace proper fitting.
5. (a) Check and repair as required.
(b) Pilot sensing line blocked (or not installed).
(b) Remove, inspect, clean or install.
(c) Pilot ruptured (water or steam coming
from pilot at spring retainer area).
(c) Replace pilot diaphragm assembly.
(d) Pilot assembly or main valve seat
(d) Check casting in seat area for threads leaking.
erosion.
(e)
Main valve diaphragm reassembled
(e) With main valve cover installed,
without return spring and main valve
loosen all main valve diaphragm
cover holding valve head closed.
bolts (1C) and then retighten.
(1/2” thru 4” sizes only).
6
Maintenance
4.If it is found that either the head or seat is worn, the
entire assembly should be replaced.
General Inspection
While a program of planned maintenance is always to be
recommended, the Spirax Sarco 25P valve will give long
and trouble-free service if correctly selected, installed and
kept reasonably free of dirt and foreign matter. Dirt and
foreign matter are most likely to collect during installation
and later trouble can be avoided by inspecting the installation after a few days. Check the following:
Inspecting and Replacing Pilot Valve
Diaphragms (Refer to Fig. 6 and 9)
1.Turn adjustment screw (2D) counterclockwise until
spring is slack. Air loaded PA pilots must have no air
pressure supplied to them.
2.Remove cap screws (2C). Pilot yoke (2B) can then be
removed.
1.Clean all pipeline strainers. (Remove screens to clean.)
2.Check the main valve seat (1E) and protective screen
(1D).
3.The 2 metal diaphragms (2F) can then be inspected for
distortion or possible fracture as a result of abnormal
operation.
3. Inspect and clean orifices (B) and (H).
4.At the same time any accumulation of dirt or foreign
material should be removed from the lower diaphragm
pilot case.
4. Check all joints for leakage.
Servicing Procedure (Refer to Fig. 6 and 9)
To determine which part of a malfunctioning pressure
reducing valve requires maintenance, refer to the troubleshooting chart and follow this servicing procedure to
check the tightness of the seats.
5.When replacing diaphragms, make certain casting surface is clean to insure a steam tight joint. Application
of a plastic compound on the casting surface, such as
Garlock 101, is recommended.
1.With all stop valves closed and the valve cooled down,
remove the copper tubing from connectors (J) and (L)
being careful not to bend them.
6.Position pilot yoke on lower diaphragm pilot casting
making certain that the yoke is properly centered.
7. Tighten all cap screws uniformly. To an assembly torque of 15-20 ft/lbs.
2.Close the pilot valve (2H) by turning the pressure
adjustment (2D) counter-clockwise until the spring is
slack. (No air pressure supplied to the type PA pilot).
Valve Sizes 1/2” Thru 4”
Inspecting and Replacing Main Valve Head
and Seat (Refer to Figs. 6, 7, and 9)
3.Stand clear of the tubing connectors and open the inlet
stop valve slightly so that a small amount of steam
reaches the valve inlet and pilot.
1. Unscrew copper tubing connections at (J) and (L).
4.Open and close the pilot valve a few times by turning
the pressure adjustment (2D) and observe the steam
flow from tubing connectors (J) and (L). When the pilot
valve is closed, there should be no steam flow from
the connectors; if there is some steam flow, it indicates
that the pilot valve assembly (2H) is faulty and must be
replaced.
2. Remove main valve cover cap screws (1A).
5.With the copper tubing removed the main valve head
and seat are held closed and should not pass any
steam. Observe the downstream orifice connector (B).
Steam flow from this connector indicates that the main
valve head and seat are leaking and require servicing.
5.Inspection should then be made to determine if scale
or other foreign material prevented tight closure of the
head and seat.
3.Remove main valve cover, strainer screen (1D), spring
support disc and head spring.
4.Head can then be removed by simply withdrawing with
a pliers or similar tool.
6.If it is necessary to replace the valve seat, this can be
removed from the valve body using a standard hexagon socket. (Valve sizes 1/2” to 2”.) When replacing
the valve seat, a new gasket should be used to insure
a tight joint.
Inspecting and Replacing Pilot Valve Head
and Seat (Refer to Fig. 6 and 9)
1.Remove 4 pressure pilot flange cap screws and lift off
pressure pilot. Visual examination can be made of the
pilot valve head and seat.
2-1/2” thru 6” valves contain raised lugs for
removal and seal metal-to-metal without a gasket.
Replacement heads and seats should be lapped
in.
2.Pilot valve head and seat are contained in one complete assembly. (See Fig. 6.)
3.To remove head and seat assembly (2H), unscrew
hexagon, using 11/16” hex wrench.
7
Valve Sizes 1/2” Thru 4”
Inspecting and Replacing Main Valve
Diaphragms (Refer to Figs. 5, 6, 7, and 9)
Servicing the Main Valve Head and Seat
5.Loosen the diaphragm plate set screw and remove
the diaphragm plate (1G).
6.Remove the top cover bolts (1A) and cover.
7.Remove the stem and head assembly from the valve.
Inspect the head and seat for wear.
1.Unscrew copper tubing connection at (G).
2. Remove main valve diaphragm bolts (1C).
3. This will allow the lower diaphragm case to be removed.
8.Check the body erosion around the seat ring.
4.The 2 metal diaphragms (1H) should be inspected to
insure that they have not become distorted or possibly
fractured as a result of abnormal operating conditions.
9.Replacement seats and heads should be lapped in,
and minor wear can be corrected by lapping with 400
grit compound.
5.At the same time any accumulation of dirt or foreign
material should be removed from the diaphragm case.
10.On re-assembly be sure diaphragm plate (1G) is set
and set screw securely tightened.
6.The valve stem should also be checked to make sure
it is free to move and that there is no scale or foreign
material lodged in the guide bushing (1F).
NOTE:For replacement parts refer to Spirax Sarco
Replacement Parts Reference Guide.
7.Before reassembling diaphragms in 1/2” thru 4”
sizes, main valve head must be in place and head
in a closed position with the return spring and
main valve cover.
Head on Seat
8.Make certain pressure plate (1G) is set properly.
(Refer to Fig. 5.)
9.Care should be taken in centering the diaphragms
properly and equalizing bolt take-up uniformly.
Adjustment
& Locknut
6” Valve Only
Inspecting and Replacing Main Valve
Diaphragm, Seat, and Head Assembly (Refer
to Fig. 8)
Pressure Plate
1G
Diaphragms
1.Unscrew copper tubing connections (G) to lower diaphragm chamber.
2.Remove main valve diaphragm bolts (1C) and drop
lower diaphragm case.
3.The 2 metal diaphragms (1H) should be inspected and
replaced if they have become distorted or fractured.
Fig. 5––Note in 1/2” and 4” sizes, top of valve must be
completely assembled and head must be on seat when
measuring dimension “A” and when re-assembling
diaphragms.
4.Clean any accumulation of dirt from the diaphragm
case and orifice (H).
Size
1/2” & 3/4” 1” 1-1/4 & 1-1/2” 2” 2-1/2” 3” 4”
Dim. A
1/16”
5/64”
3/32”
1/8” 13/64” 13/64”1/4”
8
2D
2D
Figure 6
Figure 7
2B
1/2” thru 2” sizes
2-1/2” thru 4” sizes
2H
2C
2F
2G
1A
J
1A
1D
L
2H
J
1D
1E
1F
1F
B Orifice
1C
1G
G
1C
1H
H
H
G
1A
Figure 9
1D
2A
1A
1A
2” Class 300,
25 Valve
Components
Figure 8
1B
6” size
1D
2D
1E
B
1F
1G
1F
1G
1H
G
1C
H
1H
G
9
H
1C
Spare Parts – Main Valve
1/2” thru 2”
C
M
N
Cover Assembly w/ Cap Screws & Gasket
Diaphragm Case Bolts & Nuts
Screen, Spring Support Disc,
Valve Spring & Cap Gasket
Cap Gasket, Valve Head, Seat
& Seat Gasket (2)
specify regular or reduced port “S” valve
Valve Stem Guide & Gasket
Diaphragm Plate
Diaphragms (2 ply)
Transmission Tubing w/ Assembly
Gasket Kit
Rebuild Kit B
O
W
P
A
Q
R
J
T
V
A,B, C
G,H
M, N, O, C
C, P, Q, R
J, S, T
K
L
U, V
C, R, S, W
B, C, L, M,
O, P, Q, R
U, V, W
S
H
U
K
L
L
G
2-1/2” thru 4”
Spare Parts – Main Valve
M
N
C
W
O
B
A
E4
P
Q
U
X
S
J
D1
T
K
L
L
H
C1
C1
B1
G
A1
10
Cover Assembly w/ Cap Screws & Gasket
Diaphragm Case Bolts & Nuts
Screen, Spring Support Disc,
Valve Spring & Cap Gasket
Cap Gasket, Valve Head, Seat
& Seat Gasket (2)
specify regular or reduced port “S” valve
Diaphragms (2 ply)
Transmission Tubing w/ Assembly
Gasket Kit
Damping Assembly
Diaphragm Plate
Lower Stem & Guide
Relief Tube
Rebuild Kit
A,B, C
G,H
M, N, O, C
C, P, Q, X
L
U
S, W, C
A1, B1, C1
K
J, T
D1
B, C, L, M, O,
P, Q, R, U, W
Transmission Tubing
U
Spare Parts – Main Valve
6”
Main Valve Spring
& Lower Diaphragm Cover Gaskets
Diaphragm Plate & Set Screws
Transmission Tubing with Fittings
Diaphragms (2 per set)
Gasket Kit
Head, Stem & Seat Assembly
“S” Head, Stem & Seat Assembly
Screen Assembly
Cover Bolt Kit
Diaphragm Case Bolt Kit
C
P
Q
B
Spares Kits
W
J
U
D
K
G
K, D
U*
L*
C, S, W*
P, Q, C
P, Q, C
I, J
B
G, H
* A standby set of spares for general maintenance
purposes includes all spares marked
O
I
O, S
S
L
S
H
11
How to Size Piping for
25-Series Regulators
Principle
When steam pressure is lowered through a
reducing valve, the steam expands creating
a higher velocity. The extreme velocities that
must exist across reducing valve seats cannot
be tolerated in pipes supplying the valves and
leading from them. Erosion and noise would be
prohibitive.
It is recommended practice in heating systems
to limit velocities to between 4,000 and 6,000
feet per minute. Higher velocities are often
acceptable outdoors and in plants where the
environment is already noisy.
This chart lists steam capacities of pipes under
various pressure and velocity conditions.
Example
Given a steam heating system with a 100 psig
inlet pressure ahead of the pressure reducing
valve and a capacity of 1,000 pounds per hour
at a reduced pressure of 25 psig, find the smallest sizes of upstream and downstream piping
for reasonable steam velocities.
Upstream Piping
Enter the velocity chart at point A for 1,000
pounds per hour. Proceed horizontally to point
B where the 100 psig diagonal line intersects.
Follow up vertically to point C where an intersection with a diagonal line falls inside the 4,000
to 6,000 feet per minute velocity band. Actual
velocity (see point D) is about 4,800 feet per
minute for 1-1/2 inch upstream piping.
Downstream Piping
Enter the velocity chart at point A for 1,000
pounds per hour. Proceed horizontally to point
E where the 25 psig diagonal line intersects.
Follow up vertically to point F where an intersection with a diagonal line falls inside the 4,000
to 6,000 feet per minute velocity band. Actual
velocity (see point G) is about 5,500 feet per
minute for 2-1/2 inch downstream piping.
Spirax Sarco Applications Engineering Department
Toll Free at:
1-800-575-0394
SPIRAX SARCO, INC. • 1150 NORTHPOINT BLVD. • BLYTHEWOOD, SC 29016
PHONE 803-714-2000 • FAX 803-714-2200
12
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