How to choose pressure relief device for piping pneumatic leak test

[Sean_Wei]

Hello guys, one question has confused me for a long time.
As the requirement of ASME B31.3 345.5.2, a pressure relief device shall be provided during pneumatic leak test.
1. What cases will cause the test pressure to increase, the misoperation of pressure - raising equipment? Or uncontrolled test temperature rise?
2. How to evaluate these pressure increase cases quantitatively and give the clear information for selection of PSVs?

 

[LittleInch]

Usually the biggest is simply the pressurising device, be it a compressor / bottle supply or similar goes flat out / full open regualtor.

For a pressure test the temperature rise should be fairly low and also a fairly lor percent. Remember the P1V1/T1 equation for temperature uses absolute temperature so even say a 30 C rise is only a 10% increase in pressure starting at sat 10C / 283K

So do the maths and work out which is the biggest flow case and its almost certainly the max flow in from your pressure raising equipment assuming the controls have failed or no one turns it off.