XI. General Planning for Maintenance
A 12-month maintenance interval is recommended for general service
conditions. For severe service applications, a 3 to 6 month inspection and
test interim may be more appropriate. The specific plant's operating and
service history will better determine this frequency. Baker Hughes encourages
preventive maintenance.
The 2900 series Pilot Operated Safety Relief Valve (POSRV) is easily
maintained. Normal maintenance usually involves:
• Removal of pilot valve from main valve
• Disassembly of both the pilot and main valve
• Cleaning
• Component Inspection
• Parts Replacement as Needed
• Reassembly
• Setting, Testing and Resealing the Valve
Occasionally, remachining the nozzle may be necessary to extend the service
life of the valve. Keep all parts for each valve separated to ensure replacement
in the same valve.
Note: Insure there is no pressure in the inlet of the valve before
attempting to remove it from the piping system.
XII. Recommended Installation Practices
A. Mounting Position
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.
Decontaminate or
clean if necessary
before pretesting or
disassembly. Safety
and environmental
precautions must
be taken for the
decontamination or
cleaning method used.
Do not interchange
parts from one valve
to another.
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