Pig Launcher PSV Sizing
Pig Launcher PSV Sizing
(OP)
Hi
I have been looking into the sizing of an Offshore Pig Launcher PSV. API 521 indicates that I should size using 100% liquid inventory as if the vessel contains gas the metal temperature will exceed strength of the vessel and cause and explosion.
The Client wants the PSV sized for gas is this normal and if so which part of API do I use?
Thanks in Advance
I have been looking into the sizing of an Offshore Pig Launcher PSV. API 521 indicates that I should size using 100% liquid inventory as if the vessel contains gas the metal temperature will exceed strength of the vessel and cause and explosion.
The Client wants the PSV sized for gas is this normal and if so which part of API do I use?
Thanks in Advance





RE: Pig Launcher PSV Sizing
Often, there would be intervening protected equipment (separators, dehy's, treaters, etc.) whose PSV would have to fail to operate before you could exceed the MAWP of the launcher so there is often no credible scenario (i.e., a scenario that does not require multiple unrelated failures simultaneously) for the launcher to be overpressured while gas filled. There is generally a credible scenario for a launcher or receiver to end up isolated while liquid filled (launchers often stretch credibility a bit, but receivers ending up liquid full are pretty common) and you only need thermal relief which is usually a very small PSV.
The answer to your client is a credible scenario evaluation which has been required by API for over 25 years and the Oil & Gas Industry is just beginning to discover.
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
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RE: Pig Launcher PSV Sizing
If you have a jet fire when there are ten guys launching the pig the PSV is the last of your problems.
RE: Pig Launcher PSV Sizing
RE: Pig Launcher PSV Sizing
David
RE: Pig Launcher PSV Sizing
RE: Pig Launcher PSV Sizing
RE: Pig Launcher PSV Sizing
I feel that any scenario that only requires one person to skip one procedural step (or to stop a procedure early) is credible. Even if Exxon, BP, Conoco, and the DOT signed off on replacing barrel thermal reliefs (I'm not even talking about fire case here) with 1/4 inch lines and valves, I wouldn't stamp it with my stamp for receivers.
Launchers are kind of a different basket of fish. It is hard to come up with a credible scenario that leaves them liquid full and isolated. Every scenario that I can come up with that leaves a launcher barrel liquid full and isolated requires too many unrelated things to go wrong simultaneously (like Clancy's The Sum of All Fears where 7 totally unrelated things have to go wrong on the same Sunday, and they do until Jack Ryan saves the world yet again).
David