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ASME Code and LPG vessels

ASME Code and LPG vessels

ASME Code and LPG vessels

(OP)
Dear All:

ASME Section VIII has an exception to the rule of installing relief valves with an overpressure of 10%: UG-125 3), allows in some cases (for products like LPG and in some specific situations), to install relief valves with overpressure of 20%.  One of the conditions required is that the vessel should not have “permanent supply connection”. It is clear that this is the case with all commercial tanks with LPG filled by tank trucks, however, in the case of vessels installed terminals that receive LPG through pipelines, does the multiple block valves normally installed between vessels and pipelines count to be considered as “not permanently connected”?  If this is not allowed, then all vessels in LPG terminals would need valves set at 10% plus valves for fire case set at 21%.

Anybody with experience in LPG storage/terminals has an idea about what is the interpretation of the Code and what is the normal practice in these cases?

RE: ASME Code and LPG vessels

The LPG pipeline isolation valves, their local and remote operation seems to be fairly extensively specified by the majors like Shell, Mobil and other users of large storage tanks of LPG. The Shell DEP tends to not regard the mentioned block valves as positive isolation and further, they include a valve reaction time and count on the LPG residence in the feed or interconnecting pipes. Unlike the short lines for filling the stationary LPG tanksor mobile ones connected to a filling arm which are not permanently connected, those lines in refinery or terminals are thus considered permanently connected. Hence the need of both type of relief valve.
gr2vessels

RE: ASME Code and LPG vessels

(OP)

Thanks gr2vessels. Just to clarify my understanding, you are saying that is common for LPG tanks in pipeline terminals to have safety relieve capacity for overfilling scenario and not only fire scenario?

Under this assumption, could the same relief valve provide protection for both situations, considering that thre would be a "liquid" discharge?  Could the discharge still be vented to air?

RE: ASME Code and LPG vessels

Garfio

You should have look to ICG code.

Good luck

Idontknowit

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