Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?
Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?
(OP)
I am working on the design of a test rig for a screw compressor and I have been looking into the use of a safety relief valve in our system. At the discharge side we are planning to have 2 control globe valves :
Excuse my ignorance in this field as I am new to engineering. I have read through API 521 and 520 to get some insight into this, but maybe I missed something?
- 1 for controlling the bypass flow back into the suction side of the compressor
- 1 for controlling the back pressure at the compressor discharge
Excuse my ignorance in this field as I am new to engineering. I have read through API 521 and 520 to get some insight into this, but maybe I missed something?





RE: Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?
RE: Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?
Failure position, either FC or FO, is referred to failure of incoming instrument air or electrical signal and doesn't cover the case in which the valve may get stuck in the closed or open position. Hence upstream of the valve should be protected against overpressure due to stuck close situation if the upstream design pressure is lower than the source pressure.
RE: Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?
If whatever is controlling these valves gets incorrect data or simply fails to adjust then the valves can close or close more than they should. They have not failed.
A PD compressor can see very rapid rises in presure if flow is restricted even by a small amount.
A Pressure Relief Valve is essential in this arrangement.
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RE: Is a Safety Relief Valve required if protecting against a Fail-Open Valve failure?