NRV positioning
NRV positioning
(OP)
Hi Guys,
I have a set of PIDs with me and it seems the designer has put NRV before discharge valve in all pumps. Dont u think this can be a problem due to thermal expansion of the liquid trapped in between the NRV and the discharge valve (when the discharge valve is closed)? Actually, I have seen many gaskets rupturing due to thermal expansion in my previous refinery experience. It not only eats away time of manpower constrained plants but also adds fire hazards. What dya say?
-SB
I have a set of PIDs with me and it seems the designer has put NRV before discharge valve in all pumps. Dont u think this can be a problem due to thermal expansion of the liquid trapped in between the NRV and the discharge valve (when the discharge valve is closed)? Actually, I have seen many gaskets rupturing due to thermal expansion in my previous refinery experience. It not only eats away time of manpower constrained plants but also adds fire hazards. What dya say?
-SB





RE: NRV positioning
As long as the distances are short, which they should be, thermal expansion should be limited.
Cheers,
Joerd
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: NRV positioning
saxon
RE: NRV positioning
Thnx guys!
RE: NRV positioning
saxon has outlined the reason why check valves/NRv's are upstream of the discharge valve. If thermal expansion is a cause of concern - will depend on the fluid, a bypass around the check valve will help during the situation when the discharge block valve is closed.Whenever the discharge block valve is closed "keep the NRV bypass valve open". This would take care of your thermal expansion concerns. Having said this, in case your system has a standby pump with auto cut in feature,take care to ensure that operating procedures ensure that NRV bypass is kept close during normal operation.
hope this helps.
RE: NRV positioning
RE: NRV positioning
Similarly, on cryogenic systems it can be VERY desirable to ensure that the trapped volume between checkvalve and isolating valve can relieve back to the pump side. A heavily spring-loaded checkvalve in reverse can fix it.