Spirax Sarco 25T User manual

IM-P235-04-US Issue 1 1
Type 25T Pilot Operated Temperature Regulator
1. Safety information
2. Installing the valve
3. How it works
4. Valve sizes ½” - 4”
5. 6" Valve only
6. Troubleshooting
© Copyright 2021
Printed in US
Type 25T
Pilot Operated Temperature Regulator
Installation and Maintenance Instructions
IM-P235-04-US
Issue 1

IM-P235-04-US Issue 1
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Type 25T Pilot Operated Temperature Regulator
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. Safety information

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Type 25T Pilot Operated Temperature Regulator
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 normalize after isolation to avoid the 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
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).
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.
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.

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Type 25T Pilot Operated Temperature Regulator
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.
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.
Prevention of tensile stressing
Pipe misalignment:
Installing products or re-assembling after maintenance:
Do not over tighten.

1
1
4 2
3
8
2
6
3
7
Flange bolts should be gradually tightened across
diameters to ensure even load and alignment.
5
4

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Type 25T Pilot Operated Temperature Regulator
Prevention of waterhammer
Steam trapping on steam mains:
Steam Mains - Do's and Don'ts:
Steam Steam
Flow Flow
100 - 150 ft intervals
Gradient 1:100
Gradient 1:100
Trap set
Trap set
Trap set
Condensate
Condensate
Condensate
Steam
Steam

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Type 25T Pilot Operated Temperature Regulator
Thermal expansion:
Guides
Guides
Limit
rods
Limit rods
Fixing point
Medium
distance
Small lateral
movement
Small lateral
movement
Large lateral
movement
Large lateral
movement
Short
distance Fixing point
Axial
movement
Axial movement
Guides
Guides

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Type 25T Pilot Operated Temperature Regulator
2. Installing the valve
Important: Step by step instructions on the following pages should be read carefully before
installing the valve.
2.1 Unpack carefully
Do not lift the regulator by the tubing or temperature pilot. Grasp the body of the valve firmly when
lifting. Do not bend sharply or kink the flexible tubing.
2.2 Piping
1. 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.
2. 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.
3. Determine the correct installation situation and direction of fluid flow.
4. 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.
2.3 Bypass
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 temperature regulating valve.
2.4 Steam Line Drain Trap
To insure proper operation of the valve and avoid premature wear, it is recommended that a steam
trap be installed on the steam supply line. (See Figs. 1 and 2.)
2.5 Pipeline Strainers
1. It is strongly recommended that strainers be installed before the temperature regulating valve
and steam traps. (See Figs. 1 and 2.)
2. Make certain adequate clearance is provided for screen removal and blowdown connection
between strainer and regulating valve body.
2.6 Stop Valves
All stop valves on the supply side, as well as on the downstream side of the temperature regulating
valve, should be of the gate type so as to insure full rated capacity and good control.
2.7 Calibrated Adjustment Dial
Depending upon the installation, the position of the calibrated dial on the valve, as received, may not
be easily observed by the operating personnel. To change the calibrated dial position loosen hexagon
nut (K) and rotate the entire adjustment assembly to a position that can be easily observed. Re-tighten
hexagon nut (K).

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Type 25T Pilot Operated Temperature Regulator
2.7 Thermostatic Bulb and Tubing
1. Carefully uncoil the flexible tubing avoiding sharp bends and kinks.
2. Support flexible tubing to protect it against mechanical damage.
3. Keep flexible tubing away from hot pipe lines or other hot surfaces.
4. Install thermostatic bulb to unit to be controlled. Make certain that the entire bulb is exposed
to the medium being controlled. Accuracy of regulation depends on the bulb being located in a
representative location with adequate circulation over it.
5. If a separable socket is used for the temperature bulb, it is recommended that the socket be packed
with a heat transfer compound to minimize lag in response to temperature changes caused by
the insulating air layer between bulb and socket.
2.8 Thermometer
An accurate thermometer should be installed in very close proximity to the temperature regulating
bulb.
Fig. 1 Temperature Control of Warm-up and Running Loads at Storage Tank
Fig. 2 Controlling Temperature of Large Open Tank Heated by Direct Steam Injection

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Type 25T Pilot Operated Temperature Regulator
3. How it works
3.1 How it works
Normal positions before startup are with the main valve closed and the pilot valve held open by
spring force.Entering steam passes through the pilot valve into the 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 the medium being heated
approaches the pre-selected temperature, liquid in the bulb expands through the capillary tubing into
the bellows and throttles the pilot valve (3E). Control pressure maintained in the diaphragm chamber
positions the main valve to deliver required steam flow. When heat is not required, the main valve
closes tight to provide dead-end shutoff. The temperature setting can be changed by turning the
calibrated adjustment dial.
3.2 Start-up
1. First, make certain that all stop valves as closed.
2. Adjust the temperature pilot to the temperature required by turning the red adjustment knob 3C.
Caution: Do not loosen Allen set-screw in the red temperature knob.
3. Open stop valves in the following order:
a. Open stop valve ahead of steam trap on steam supply line. This will insure condensate free
steam at the regulator inlet.
b. Open downstream stop valve.
c. Slowly open inlet stop valve.
4. After the system has stabilized itself, check thermometer temperature. Readjustment of the
temperature pilot (red knob 3C) may be necessary.
Note: In the event the temperature indicated on the calibrated dial does not agree with the
thermometer, the temperature pilot can be recalibrated to match the thermometer as described
on page 11.
5. Important: Re-tighten all pilot flange connections to insure steam tight joints.
3.3 Maintenance
3.1.1 General inspection
While a program of planned maintenance is always to be recommended, the Spirax Sarco 25T
temperature regulator 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 a few days later. Check
the following:
1. Clean all pipeline strainers (remove screens to clean).
2. Check the main valve seat and protective screen (1D).
3. Inspect and clean orifices (E) and (H).
4. Check all joints for leakage.

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Type 25T Pilot Operated Temperature Regulator
3.1.2 Servicing Procedure (Refer to Fig. 4 and 5)
To determine which part of a malfunctioning temperature regulator requires maintenance, refer to
the troubleshooting chart and follow this servicing procedure to check the tightness of the seats.
1. With all stop valves closed and the valve cooled down, remove the copper tubing from connectors
(L) and (N) for ½” - 2” valves, being careful not to bend them.
2. Close the pilot valve (K) by turning the temperature adjustment (3C) counter-clockwise until the
spring is completely compressed.
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.
4. Open and close the pilot valve a few times by turning the temperature adjustment and observe
the steam
flow from tubing connectors (N) for ½” - 2” valves. 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 is faulty and must be replaced.
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 (L). Steam flow from this connector
indicates that the main valve head and seat are leaking and require servicing.
3.1.3 Inspecting and Replacing Pilot Valve Head and Seat
(Refer to Figs. 4 and 5)
Note: Inspecting and replacing parts, if necessary, can be done without removing the pilot from the
main valve. However, if more convenient, the entire pilot can be removed from the main valve by
removing the four pilot flange cap screws.
Exception: To replace the seat in low pressure (5 psi and below) 2½”, 3”, and 4” valves, the entire
pilot must be removed from the main valve or mounting bracket.
1. Unscrew hexagon nut (K) and remove temperature adjustment assembly.
2. The pilot valve head assembly (3E), which includes the springs, Teflon seal, and valve head, can
then be withdrawn and inspected.
3. If it is found after inspection that the head is worn, the entire assembly should be replaced.
4. The pilot valve seat can be removed for inspection using a ½” hexagon socket wrench.
5. If the seat shows signs of wear, the seat should be replaced including a new seat gasket.

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Type 25T Pilot Operated Temperature Regulator
4. Valve sizes ½” - 4”
4.1 Inspecting and Replacing Main Valve Head and Seat
(Refer to Figs. 4 and 5)
1. Unscrew copper tubing connection at (J) and (N).
2. Remove main valve cover cap screws (1A).
3. Remove main valve cover, strainer screen, and head spring.
4. Head can then be removed by simply withdrawing with a pliers or similar tool.
5. Inspection should then be made to determine if scale or other foreign material prevented tight
closure of the head and seat. Check for body erosion at the seat threads.
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 ½” to 2”.) When replacing the valve seat, a new gasket
should be used to insure a tight joint. 2½” valves contain raised lugs for removal and seal metal-
to-metal without a gasket. Replacement heads and seats should be lapped in.
4.2 Inspecting and Replacing Main Valve Main Valve Diaphragms
(Refer to Figs. 4 and 5)
1. Unscrew copper tubing connection (G).
2. Remove main valve diaphragm bolts (1C).
3. This will allow the lower diaphragm case to be removed.
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.
5. At the same time any accumulation of dirt of foreign material should be removed from the
diaphragm case.
6. The valve stem (1F) 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.
7. Before reassembling diaphragms, main valve head must be in place and held in closed position
with the return spring and main valve cover.
8. Make certain pressure plate (1G) is set properly. (Refer to Fig. 3)
9. Care should be taken in centering the diaphragms properly and equalizing bolt take-up uniformly.
Size ½” and ¾” 1” 1-¼” and 1-½ 2” 2-2½” 3” 4”
Dim A ” ””” 
Head on seat
Adjustment and locknut
Pressure Plate 1G
Note: In ½” - 4” sizes, top of valve must be
completely assembled and head must be on
seat when measuring dimensions “A” and when
reassembling diaphragms.
Fig. 3

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Type 25T Pilot Operated Temperature Regulator
5. 6" Valve only (refer to Fig. 6)
5.1 Inspecting and Replacing Main Valve Diaphragms, Seat
and Head Assembly
5.1.1 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.
4. H).
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.
8. Check for body erosion around the seat ring.
9. Replacement heads, should be lapped in, and minor wear of seats can be corrected by lapping

10. On re-assembly be sure diaphragm plate (1G) is set at 27/64" and set screw securely tightened.
5.1.2 Recalibration of Temperature Adjustment Dial
The temperature adjustment dial can be recalibrated after servicing or to match the calibration of a
thermometer on a particular application installed next to the temperature bulb. To recalibrate,
proceed as follows:
1. The control bulb must be immersed in a temperature within the range of the calibrated dial.
2. With steam pressure on the valve, turn temperature adjustment knob (3C) slowly clockwise until
󰀨
3. Turn temperature adjustment knob (3C) counter- clockwise slightly just enough to start a slight

4. Loosen small Allen set screw in red temperature adjustment knob (3C) using a 3/32" hex Allen
󰀨
5. Rotate red temperature knob until temperature on dial matches temperature reading at the control
bulb, then push knob downwards over the rubber support.
6. Retighten Allen set screw. Note: No attempt should be made to recalibrate the temperature pilot
for temperatures beyond the range shown on the calibrated dial. If the temperature range is to
be changed, the entire pilot assembly including the thermostatic system must be replaced.
(Refer to Spirax Sarco Replacement Parts Reference Guide.)
5.1.3 Replacement of Thermal System
1. Loosen hexagon nut (M) and withdraw thermostatic bellows.
2. Insert replacement system in a similar manner making certain to tighten hexagon nut (M).
Caution: Do not overtighten.
3. All replacement systems are interchangeable for the same range and generally adjustment of the
temperature dial is not required. However, should this be necessary, follow the instructions as
described under “Recalibration of Temperature Adjustment Dial”.

IM-P235-04-US Issue 1 13
Type 25T Pilot Operated Temperature Regulator
Symptom Cause Check and Cure
Controlled temperature
overrides set point.
Control not set properly; or
may have been tampered with.
Readjust temperature knob (3C).
Temperature bulb not in
representative location.
Check actual temperature at bulb with glass
thermometer. If necessary, relocate bulb.
Dirt under pilot valve head or
pilot valve spindle (3E) sticking.
Remove and, if necessary, replace or
clean.
Valve oversized. Check actual load against valve rating.
E) or (H). Inspect and clean.
Dirt or foreign material under
main valve head (1E). Seat
worn, body casting eroded at
seat threads
Set temperature knob (3C) to lowest
temperature. Disconnect tubing at (G).
Valve should close. If not, remove bolts
(1A) and clean or repair main valve.
Defective thermal system.
(Rare).
Experience over the years has shown that
failure of the thermal system (other than
mechanical damage) is very rare. Only
after all of the “checks” listed on the
troubleshooting chart have been pursued,
should the following test be made to
determine if the thermal system is
defective.
i. Disconnect copper tubing connection
at (J).
ii. Immerse thermal system bulb in a
temperature 20° above dial setting. Allow
to saturate for approximately 5 minutes.
iii. Open steam supply stop valve to allow

iv. Under these conditions steam should

(J) which shows that the thermal system
is satisfactory.
v. If steam should flow from tubing
connection (J), exert pressure downward
with thumb on thermal system elbow
connection (3A). If this pressure seats
                         
thermal system is probably defective.
Bypass valve leaking. Check and correct.
6. Troubleshooting

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Type 25T Pilot Operated Temperature Regulator
Symptom Cause Check and Cure
Temperature too low or
valve does not open.
Control not properly set or may
have been tampered with.
Adjust temperature knob (3C) to higher
setting.
Thermostatic bulb not in
representative location.
Check actual temperature at bulb with
glass thermometer. If necessary, relocate
bulb.
Valve undersized. Check actual load against rating of valve.
Main valve diaphragm (1H)
cracked.
Remove copper tubing at (G) and crack
bypass valve. If steam blows from
diaphragm case at (G) connection,
replace diaphragm.
H) blocked. 
and clean.
Steam pressure too low. Check and correct.
Valve strainer (1D) blocked. Remove bolts (1A). Inspect strainer and
clean.
Line strainer partially or
completely blocked.
Inspect and clean.
Pilot valve spindle (3E) sticking
in guide.
Remove thermal system by loosening
nut (M).
Apply pressure to spindle, observe up
and down motion. If necessary, clean
or replace spindle assembly.
Steam trap draining equipment
may not be functioning properly.
Check and repair, if necessary.
Erratic control Thermostatic bulb is not
installed in the proper location.
Check actual temperature at bulb with
glass thermometer. Relocate bulb, if
necessary.
Heating surface may be
waterlogged due to defective
steam trap.
Inspect and repair, if necessary.
Valve size may not be correct. Check actual load against valve rating.

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Type 25T Pilot Operated Temperature Regulator
3A
M
3A
1A
N
1E
1C
H
G
1G
1H
L
1F
1D
J
K
3E
E. Orifice with
Cleaning Wire
1G
1F
E
L
J
1D
K
3c
3A
M
1G
1A
Fig. 4 - ½” - 2” Sizes
Fig. 5 - 2½” - 4” Sizes GHH1

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Type 25T Pilot Operated Temperature Regulator
M
3E
3C
K
E
J
L
1HG H
1G
1C
1F
1E
Figure 6 - 6” Sizes
SPIRAX SARCO, INC. • 1150 NORTHPOINT BLVD. • BLYTHEWOOD, SC 29016
spiraxsarco.com/global/us
PHONE [phone] • FAX [phone]