API 620 R.3.2 Temperature metal design.

[Chavita]

Hi everybody,

API 620 R.3.2 defines the Temperature metal design as the minimum temperature to which the tank contents will
be refrigerated.

I want to have my tank content at -17°F. But, I also want to have a PSV that works when more vacum is present, in that case, the content tank temperature slows down to -45°F.

What would be the Temperature metal design then?

hope you understand my English and help me.

Thanks a Lot.


Chavita.

 

[JStephen]

There in R.3.2, it says "including the effect of subcooling at reduced pressure."

I would think that it would not be critical to maintain toughness when a tank is subject to vacuum, but there doesn't seem to be an exemption for that case, either. Unlike ASME, which lets you vary the MAWP with the temperature.