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Pressure rating at higher T
- Thread starter SELM005
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ASME B31.1 would be the governing code.
Look up your alloy and the look at the allowable stress per temperature.
Simplistically, if the allowable stress is 20% less at 190C, it would be a pretty good conservative estimate to de-rate the vessel accordingly. A registered professional engineer could evaluate the vessel and possibly find that its stress does not meet B31.1's limits at the previous rating. In which case you could have a licensed pressure vessel tester re-rate the vessel to a pressure corresponding to the max allowable stress.
Look up your alloy and the look at the allowable stress per temperature.
Simplistically, if the allowable stress is 20% less at 190C, it would be a pretty good conservative estimate to de-rate the vessel accordingly. A registered professional engineer could evaluate the vessel and possibly find that its stress does not meet B31.1's limits at the previous rating. In which case you could have a licensed pressure vessel tester re-rate the vessel to a pressure corresponding to the max allowable stress.
Remember not to panic!
Your fault condition is perhaps fire? In that case your temperature should correspond to the boiling temperature of the liquid in the vessel at reliving pressure (PSV set point +21%).
As far as I understand the vessel is not considered suitable for use folloing a fire where deluge has failed and the PSV has relived. Therefore the higher pressure allowed, and is shall have been checked using calculations that the vessel will not rupture, but without the normal margins added by the code (maybe not entirely correctly explained but the general idear i hope is correct).
Best regards
Morten
Your fault condition is perhaps fire? In that case your temperature should correspond to the boiling temperature of the liquid in the vessel at reliving pressure (PSV set point +21%).
As far as I understand the vessel is not considered suitable for use folloing a fire where deluge has failed and the PSV has relived. Therefore the higher pressure allowed, and is shall have been checked using calculations that the vessel will not rupture, but without the normal margins added by the code (maybe not entirely correctly explained but the general idear i hope is correct).
Best regards
Morten
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