Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
(OP)
I have a pressure vessel that has a U-1 form (as well as the nameplate) that has two different MAWPs and MDMTs.
One MAWP is 250 psi @ 300F to -20F and the other MAWP is 85 psi @ -20 to -50F.
We operate this vessel between -30F and -40F.
The vessel contains anhydrous ammonia and is operated at around 9"hg.
Questions:
Which MAWP do I set my RV's to? 250 psi or 85 psi or something else?
Can I operate the vessel at the conditions of -40F (with an MAWP assigned of 85 psi) with 250 psi RV?
If yes, where in ASME UG-125 does it permit this design?
I understand that manufacturers can provide additional MAWP and MDMTs, but how does an owner/operator comply? I have upload the U-1 form.
One MAWP is 250 psi @ 300F to -20F and the other MAWP is 85 psi @ -20 to -50F.
We operate this vessel between -30F and -40F.
The vessel contains anhydrous ammonia and is operated at around 9"hg.
Questions:
Which MAWP do I set my RV's to? 250 psi or 85 psi or something else?
Can I operate the vessel at the conditions of -40F (with an MAWP assigned of 85 psi) with 250 psi RV?
If yes, where in ASME UG-125 does it permit this design?
I understand that manufacturers can provide additional MAWP and MDMTs, but how does an owner/operator comply? I have upload the U-1 form.





RE: Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
Your ammonia temperature at 9" Hg is approximately -40 deg F.
Thus your relief valve should be set at 85 psig.
RE: Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
RE: Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
RE: Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?
The vessel was built for and used only in ammonia refrigeration process.
RE: Can a Relief Valve Set Point be set higher than the MAWP (Dual Stamped)?