Is it necessary to assembly a PSV at the pig launcher&receiver
Is it necessary to assembly a PSV at the pig launcher&receiver
(OP)
Hi guys:
There is a natural gas transmitting pipeline,with the design pressure 10Mp and 26" in diametre.Is it necessary to assembly a PSV at the pig launcher&receiver.
On looking for some project,i found some with PSV and the other without.i dont make sense why.
yours
pipingX
There is a natural gas transmitting pipeline,with the design pressure 10Mp and 26" in diametre.Is it necessary to assembly a PSV at the pig launcher&receiver.
On looking for some project,i found some with PSV and the other without.i dont make sense why.
yours
pipingX





RE: Is it necessary to assembly a PSV at the pig launcher&receiver
Good luck,
Latexman
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
Some folks still do design the barrels to ASME Section VIII Division 1, particularly for automated pig launchers. ASME would probably force the overpressure protection in the form of pressure relief.
Regards,
SNORGY.
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
I've seen pig barrels designed to ASME VIII Div 1 (or more usually the closures) but I haven't myself seen one to which the ASME Code stamp has been applied (which would then necessitate a PSV).
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
I recently saw a situation where a pig arrived (with a full load of water) about quitting time. The operator didn't want to deal with it that late so he opened the side valve, and shut the barrel isolation and bypass valves. In the morning there was a production meeting, followed by a team lunch. By early afternoon the receiver had drained itself through a 10 inch long split in the barrel. A vessel full of liquid will increase pressure about 100 psig for every 1F increase. Doesn't take much sun to cause a real mess. A tiny PSV would have prevented that. A procedure (which was followed) that prohibited leaving the receiver full and pressurized would have prevented it. One or the other was required even if the code calls it a "pipeline accessory" and doesn't require a code stamp--we're Engineers for god sake, when did we discard our analytical sense in favor of a discussion of which code to blindly follow?
David
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
If thermal only, perhaps then the relief valve discharge disposition could be a 1" o-let on the pipeline side of the main barrel isolating valve (routing expanded liquids back into the pipeline). That would get around the need to install a lit flare (for a sour site) or a pop tank near the barrel. What have you done in similar situations?
Regards,
SNORGY.
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
I've also used procedures that prohibited leaving a barrel isolated. I like leaving the kicker/bypass open when not doing pigging operations, but that bothers some folks too. Other people like to leave the barrel vented. This works, but fugitive emissions from a weeping isolation valve can be big.
For the folks who don't trust procedures, a small PSV that exhausts to the process seems to work. The required relieving capacity is teaspoons.
David
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
To be honest, I don't think I've seen a pig trap with a thermal relief on it before and none of the standard pig trap drawings that I've seen used have shown this detail. Doesn't mean it's right though. Perhaps it hasn't been an issue as with the climate around here, the contents would probably tend to cool rather than heat up.
I believe the Canadian Association of Petroleum Producers is currently working on a guidance document around pigging and pigging procedures. No idea when it might be published though.
I took a quick look at the Norsok Specifications (the Process Systems document) as it has design requirements for pig traps and while it addresses interlocks, vents, drains, pig detectors, etc, it doesn't talk about relief so I'm guessing they are relying on the pigging procedures as well. I also looked up the Oliver Compact Pigging Systems (CPS), a complete packaged solution, and it isn't equipped with thermal relief either.
On balance, I think most people rely on procedures.
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
Mike McCann
MMC Engineering
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
Regards,
SNORGY.
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
I regularly design systems where all the liquid from a pig run is routed into the downstream piping to be subsequently pigged out of that line. This daisy chain goes on until you reach a line drip or a plant inlet scrubber. The scheme works well.
If we're talking about a liquids batching pig then all the decisions are different.
David
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
RE: Is it necessary to assembly a PSV at the pig launcher&receiver
Either a thermal relief, or as dcasto says, a check (with a locked open backup block valve for when the trap is open), going back into the pipeline would be fine, if is a liquid line and there is no oily water drain around, otherwise a drip pan might have to do.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/