Relief Header Question

[bkb2665]

This should be simple...just need some clarification. Thermal relief valve (bellows)on a 4" pipe (150# spec), flammable material. Valve is 1x2, 3 gpm required capacity. Relieves into larger pipeline (not technically a relief header) that is 8" (150# spec). This second pipeline is a feed line to a storage tank of the same relieving material.

So, there is 100 psig constant back pressure (feed pump) and that is calculated into the design...but, the 8" feed line can be blocked in.

Should I recommend that the feed line block valve be car-sealed open so that there is a relief path to the storage tank or is the small relief flow not enough to cause a problem with the larger 8" line?

 

[oil198]

I have seen CSO's valved installed between a PSV and a vessel, but a lot of factors need to be taken into consideration...

I found this thread which should answer your questions:

http://www.eng-tips.com/viewthread.cfm?qid=147792&page=13

 

[JoeWong88]

RV is feeding the tank (presumed operate at ATM). Why the constant back pressure is 100 psig ? Any sketch to clarify ?

If the 8" feed line can be blocked in then there is no clear relief path for the relief valve. CSO or LO is required. You wouldn't pass the HAZOP...



JoeWong
Chemical & Process Technology