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VII. Pre-Installation and Installation Instructions
Pre-Installation and Installation
When POSRVs are uncrated and the flange protectors or sealing plugs are removed, exercise
meticulous care to prevent dirt and other foreign materials from entering the inlet and outlet
ports while bolting the POSRV in place.
Mounting Instructions
The POSRVs should be mounted in a vertical upright position (in accordance with API RP 520).
Installing a pilot operated safety relief valve in any position other than vertical (±1 degree)
will adversely affect its operation as a result of induced misalignment of moving parts. A stop
valve may be placed between the pressure vessel and its relief valve only as permitted by code
regulations. If a stop valve is located between the pressure vessel and POSRV, the stop valve
port area should equal or exceed the nominal internal area associated with the pipe size of the
POSRV inlet. The pressure drop from the vessel to the POSRV shall not exceed 3% of the valve's
set pressure, when flowing at full capacity. Ensure the flanges and sealing faces of the valve and
connective piping are free from dirt, sediment, and scale. Ensure all flange bolts are drawn evenly
to prevent distortion of the valve body and the inlet nozzle. Position the POSRVs for easy access
and/or removal so that servicing can be properly performed. Ensure sufficient working space is
provided around and above the valve.
Hydrostatic Testing
Prior to hydrostatic test of the pressure vessel system, the pilot-operated safety relief valve
should be removed and the mounting flange for the valve blocked.
Service Considerations
For best performance, pressure relief valves should be serviced annually unless maintenance
history dictates otherwise. They should be located for easy access and removal for service.
Remote Sensing
If the pressure drop between the source of pressure in the equipment to be protected and
the pressure at the relief valve inlet exceeds 3%, the sensing line to the pilot valve should be
connected directly to the equipment being protected. The optional sensing ring should not be
installed. For remote sensing, .375" (9.53 mm) diameter tubing is adequate for distances up to 10
feet, (3.048 m).
For block valve and other special installation features consult API 520 or the factory.
Ramp Rate
As with all pilot operated relief valves, the ramp rate should be carefully controlled in order
to minimize the adverse effects of extreme pressure surges. With many years of operational
experience along with research and development, the importance of proper ramp rate has been
established as one of the primary contributors to many avoidable valve problems. Based on
testing and operating experience, a ramp rate of about 2% of valve set pressure per second or the
equivalent of a consistent increase in pressure over a one minute interval was shown to have no
adverse effects due to water hammer during the pressurization. This has been shown to provide
the best balance between quick start up procedures while eliminating the chance of avoidable
valve damage. For applications where pressurization rates are expected to be high, a Nitrogen
bottle (connected to the field test connector) pre-charged up to 97% of set pressure may be used.
Pre-fill
During pre-fill of the economizer before pressurization, the prefill pressure is recommended not
to exceed 15-25 psi (1-1.5 bar). For pressures exceeding this limit, a Nitrogen bottle (connected to
the field test connector) precharged up to 97% of set pressure may be used.
14 | BHGE
Prevent dirt from entering
outlet or inlet port.
Always install valve
in a vertical, upright
position.
Decontaminate or clean
if necessary before
pretesting or disassembly.
Safety and environmental
precautions must be taken
for the decontamination
or cleaning method used.
© 2019 Baker Hughes, a GE company. All Rights Reserved.
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