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Dual Rating and PSVs

Dual Rating and PSVs

Dual Rating and PSVs

We occasionally run into equipment that was originally stamped at two or more coincident MAWP/MAWTs.

For instance, an ASME Section VIII Div 2 vessel was originally rated and stamped (on the nameplate and data report) for 1500 psi @ 100 °F and 1000 psi @ 700 °F.

How does ASME (or any other authority such as API NBIC etc) address pressure relief on such an item.  If you decide to use the 1500 psi @ 100 °F MAWP/MAWT can you set the relief valve for 1500 psi considering the vessel is also rated for a maximum of 1000 psi at a different temperature?

Do you have to provide any type of thermal protection to ensure that the vessel does not exceed its MAWT for a given MAWP?

Any references to areas of API ASME NBIC etc. such as interpretations would be greatly appreciated.


RE: Dual Rating and PSVs

I encounter the same on ansi valves,
designs are for its intended use an dthe dual cert makes a lot of sense to caution the user.

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