ASME code pressure exclusion requirements
ASME code pressure exclusion requirements
(OP)
We have a 15,000 gallon liquid nitrogen storage tank that is operated at 14 psig. The tank is enclosed in a vacuum casing under a full vacuum, therefore the outer pressure on the liquid storage tank is 0 psia. Under these conditions the net pressure on the liquid storage tank is 28.7 psi, (14 + atmospheric pressure of 14.7). Does this tank meet the code pressure exclusion requirement because it is operated at 14 psig or does it fall under the code because it is being operated at 28.7 psi.





RE: ASME code pressure exclusion requirements
RE: ASME code pressure exclusion requirements
First off, you need to review the rules or regulations where the vessel will be installed. If in the US, there is a division of boiler/pressure vessel safety that establishes rules for regulating boilers and pressure vessels.
If this vessel will be installed in any of the Jurisdictions in the US, which use the ASME Boiler and PV Code, the answer to your question is most likely no.
You can still design and fabricate to Section VIII, Div 1 requirements (which I would recommend). The only difference is that you do not need to have it stamped.
RE: ASME code pressure exclusion requirements
I'll put myself in an unusual position by disagreeing with metengr. I would argue that this vessel is within the scope of VIII-1; jurisdictional requirements will vary.
You do not get the "not more than 15 psi" excemption from the scope due to:
Note that the wording of this part has changed, I believe first published in A06.
The shell should have been designed to handle the differential pressure.
Was the shell designed for 29+ psi differential pressure?
Finally, Appendix 9 places you in its scope based on combined pressure:
Based on the above, I'd say that this vessel is within the scope of Section VIII Div. 1.
jt
RE: ASME code pressure exclusion requirements
You place yourself in great peril by choosing to disagree with metengr. But, I believe you have picked your times wisely. I concur with your disagreement. The design pressure for the inner vessel is about 29 psig.
Joe Tank
RE: ASME code pressure exclusion requirements
Having an external casing (could be sheet metal or fiberglass) to me in this application provides a vacuum necessary for zero heat transfer (no heat gain to warm the liquid nitrogen). Without further information as to the actual function of the casing and it's design, I agree with the above.