IM-P006-07
CTLS Issue 12
26
7.1 Preliminary check
Before undertaking the following trouble tracing procedure, ensure the valve has been isolated and that
upstream and downstream pressures are zero. Possible fault checks are given in a logical order below.
7.2 Downstream pressure zero or too low
If downstream pressure drops below set pressure or is zero, check the following:
1.
No high pressure steam reaching the reducing valve. Check that the steam is turned on and that the
strainer is clear. (To assist with commissioning and fault finding it is recommended to fit an upstream
pressure gauge).
2.
Pressure adjustment spring broken.
3.
Pipe assembly blocked. Remove by uncoupling the union nuts and blow through to clear obstruction.
4.
Control orifice blocked. Unscrew from the outlet port and clear out obstruction. For identification this
coupling has a groove around the hex.
5.
Main diaphragms fractured. Replace diaphragms following Section 5.8.
6.
Pilot valve plunger too short. Check as Section 5.5, step 13.
7.
Valve capacity insufficient for downstream conditions.
a
) Check that the upstream pressure is correct. If it is low, the capacity of the valve will be reduced.
b
) Ensure that the balance pipe is fitted as recommended in Section 3.8 and if necessary fit an external
pressure sensing pipe as described. If the downstream pressure is still too low, then a larger valve
with more capacity is required.
7.3 Downstream pressure too high
If the pressure on the downstream side of the reducing valve has risen above the required set
pressure check the following:
1.
External pressure sensing pipe blocked. Dismantle and blow through.
2.
Control orifice blocked. Unscrew the pipework from the side of the body and clean it out. For
identification this coupling has a groove around the hex.
3.
Pilot valve diaphragms fractured. Check and replace (see Section 5.7).
4.
Pilot valve or pilot valve plunger is sticking. Follow steps in Section 5.5.
5.
Main valve not seating. Follow Section 5.8.
6.
Main valve pushrod sticking. Follow Section 5.9, steps 9 to 13.
7.
Pilot valve plunger too long. Check as Section 5.5, step 13.
8.
Pilot valve not seating. Follow steps in Section 5.5.
7. Fault finding
Содержание DP143
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