How to Install Piston‑Type Steam Pressure Reducing Valves
Add time：2017/8/20 14:33:00 Page views：2910
During installation and commissioning of the steam pressure‑reducing valve, fill the condenser with cold water fully, open the globe valve on the bypass pipeline, and drain condensate and steam‑water mixture inside the pipeline. This prevents water hammer damage to the pressure‑reducing valve upon valve opening. After confirming no abnormalities, slowly turn the adjusting screw clockwise to set the outlet pressure to the required value (refer to the gauge pressure downstream of the valve). Upon completion of adjustment, tighten the lock nut and fit the protective cap.
A filter shall be installed upstream of the pressure‑reducing valve to prevent impurities in the medium from entering the valve and impairing its performance.
Before installing the steam pressure‑reducing valve, the piping system must be flushed and cleaned. Weld slag, scale and other contaminants shall be kept from flowing into the valve cavity, which would damage the sealing surfaces and interfere with normal valve operation.
The steam pressure‑reducing valve shall be installed in an accessible location for operation and maintenance. It must be mounted upside‑down on a horizontal pipeline. Ensure the medium flow direction in the pipeline matches the arrow marked on the valve body (same as for ball valves and hydraulic control valves); reverse installation is prohibited. For steam service valves, upside‑down installation is mandatory. The supplied condenser shall be positioned above the actuator, so that the actuator can be filled with condensate to protect the diaphragm and extend service life.
Straight pipe sections shall be reserved both upstream and downstream of the installed pressure‑reducing valve. The upstream straight‑pipe length shall be approximately 600 mm, and the downstream straight‑pipe length approximately 1 m.
General pressure‑reducing valves require a pressure differential between inlet and outlet of no less than 0.2 MPa.
Pressure‑reducing valves are commonly available in sizes DN15 ~ DN400. The upstream working pressure is less than 1 MPa, and the downstream working pressure ranges from 0.1 MPa to 0.5 MPa. The pressure‑regulating tolerance is ±5 % ~ 10 %.
Troubleshooting
Downstream pressure fluctuates with upstream pressure variation
Causes
Valve core jammed by foreign matter
Valve stem or push rod stuck
Inlet pipeline blocked
Remedies
Disassemble and reassemble to remove foreign matter
Readjust the valve
Clear the blockage
Downstream pressure cannot be reduced and keeps fluctuating above the set value
Causes
Excessively high stiffness of setting spring
Oversized valve nominal size
Excessive upstream pressure and too‑large pressure‑reduction ratio
Remedies
Replace the spring
Adopt a smaller‑size valve
Where the ratio of upstream pressure to downstream pressure exceeds 10:1, apply two‑stage pressure reduction
Downstream pressure cannot rise and keeps fluctuating below the set value
Causes
Insufficient stiffness of setting spring
Undersized valve nominal size
Too‑small pressure‑reduction ratio
Remedies
Replace the spring
Adopt a larger‑size valve
Where the ratio of upstream pressure to downstream pressure is lower than 1.25, raise the upstream pressure
Upstream pressure cannot rise and operates persistently below the set value
Causes
Insufficient stiffness of setting spring
Valve core jammed by foreign matter
Valve stem or push rod stuck
Damaged valve core and valve seat with excessive leakage
Oversized valve nominal size
Remedies
Replace the spring
Disassemble and reassemble the valve
Readjust the valve
Re‑lap or replace worn components
Adopt a smaller‑size valve
Upstream pressure cannot drop and operates persistently above the set value
Causes
Excessively high stiffness of setting spring
Undersized valve nominal size
Seizure of valve core, valve stem or push rod
Remedies
Replace the spring
Adopt a larger‑size valve
Eliminate seizure causes and readjust the valve
Frequent fluctuation of upstream or downstream pressure
Causes
Oversized valve nominal size
Too‑small volume of actuator diaphragm chamber
Remedies
Select properly‑sized valve
Install a damper on the inlet pipeline
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