Vacuum Relief Valve: maximum vacuum a tank can handle

[Subystud]

An inverted check valve is used for vacuum relief of a pressure vessel during emptying of the tank.

What would be a recommended maximum vacuum for purposes of selecting a check valve? The operating pressure is 35 psig, the tank will firstly be depressurized, and then emptied. The depressurization line is not sufficient for emptying the tank at the desired rate.

The appropriate size is 2" valve. 316SS is required material. The lowest opening pressure I have found on a check valve is 0.5 psi. Would a vacuum of 0.5 psi be non-consequential?

Thanks.

 

[JStephen]

Allowable vacuum can vary from approximately "none" to full vacuum. If you have the original design information on the tank, it may state a design vacuum. If not, if you have the geometry, it would likely be possible to calculate the allowable vacuum per ASME or other codes. It is likely to be over the 0.5 psi, but there's no way to know for sure without checking.