PRV Set Pressure 2

[Instnapp05]

Hi All,

It's understood that the computed set pressure for a pressure relief valve during pop test is the average of at least the last three measured set pressures once established and stabilized. Based on the "average set pressure" achieved, the valve repair shop performing the test should stamp on the repair tag the average set pressure or the nameplate set pressure?

Example: Average is 170.6 PSI
Nameplate Set Pressure: 169 PSI

Thanks and appreciate your feedback.

 

[The Obturator]

Never heard of this in all my years of SRV's. It may be just a company's test standard. Set Pressure is simply a predetermined set point that the valve has to open at. You state "pop test" and this will apply to those SRV's on compressible fluid. Liquid service should only be tested on liquid and no pop happens. Note also that any set pressure will have a an allowable tolerance per API/ASME. The manufacturers will follow this or better it. I do know they have to repeat the test themselves until the set pressure is within limits over several pops. Stamped set pressure will be as predetermined, not what was achieved.

Per ISO, only the term Safety Valve is used regardless of application or design.

 

[JAlton]

Based on 44 years of Pressure Relief Valve Assembly, Repair and Testing, including 20 years as a member of ASME Sub-Committee Safety Valve Requirements, Past Chair of Sub-Group Testing and PTC25, as well as Vice Chair of the National Board Sub-Committee Pressure Relief Devices, I can tell you that the Average of at least the last three tests (Definition of Set Pressure as determined by the Manufacturer) is the actual Set Pressure. If that actual set pressure is within the tolerance permitted by the applicable ASME Code, then the Nameplate Set Pressure is stamped on the Repair Nameplate.

Per your example, the Repair Nameplate would be stamped 169 PSI.
Example: Average is 170.6 PSI
Nameplate Set Pressure: 169 PSI

I hope this is helpful.

JAC