Q & A > Question Details
If any reciprocating compressor is stopped, what is the condition of suction unloader valve? Suppose discharge loader valves pass why pressure not increase up to discharge pressure but same as suction pressure.
02/04/2015 A: Manikandan S, SIP, maniazhar@gmail.com
According to my experience, If reciprocating compressor is stopped/shutdown, the unloader valve shall be in open position, provided a Relief valve at compressor suction side. The purpose of relief valve is to avoid over-pressurisation of compressor suction side due to reverse flow/in case of any passage of gas from discharge side.
21/10/2013 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Reciprocating compressor "unloaders", whether they are manual or automatic, adjust the compression volume of the cylinder. When a compressor shuts down, the position(s) remain in place. Has nothing to do with the suction and discharge valves in the piping.
18/10/2013 A: Nandhakumar Duraikkannan, TAKREER, nnandha3@gmail.com
As Singh highlighted, close compressor suction valves (installed in suction line) in order to register pressure rise in suction line, in case of compressor discharge valve passes.
Suction valves remains in unload condition while tripping/stopping the compressor for all designs except certain old design Instrument air compressors (no instrument air is available for un loader during block out start)
17/10/2013 A: Narendra Naidu, Bapco, nbpnnaidu@gmail.com
When the Reciprocating compressor trips/Stopped, the Suction unloaders should unload, this should be the fail safe position.
The discharge valves of the compressors act as a Check valve, hence the suction and the cyclinders should be under suction pressure, when the compressor is not running.
If the Discharge valves are passing then the efficiency of the machine comes down and also causes overheating of the valves, hence the passing discharge valve/s on the Reciprocating machines needs to replaced.
17/10/2013 A: jagjit singh, indian oil, singhj5@iocl.co.in
Suction valves remains in unload condition while tripping/stopping the compressor, if discharge loaders are passing it will results reverse flow of gas from discharge to suction, if you will isolate the suction valve in such case you will find the pressure in suction same as discharge pressure....