PSV Testing - Back pressure (Bellows) 1

[CarlosEstinos]

Hello All,
I'm conducting a back-pressure test on a PSV fitted with bellows, testing at 30psi (air) as per ASME Viii.
The valve manufacturer tag plate shows the set pressure of the valve, but also the back pressure, in this case 22psi for the latter. I’m assuming that the back pressure stated on the tag plate means the test pressure, but it’s not something I usually see on a tag plate. The stated back pressure could also imply that it has been sized for an application with 1.5bar back pressure, either built up or superimposed.
ASME Viii states that the minimum test pressure for the second cavity of the PSV should be 30psi. Is that test pressure sensible based on the fact the tag plate shows 22psi for back pressure (this could be for sizing applications or the manufactures test limit for their bellows).
It’s a small testing anomaly, but bellows are quite fragile so I don’t want to kill them!

Any insight on this would be much appreciated.

Thanks in advance

 

[The Obturator]

Hi.

Your question would most probably been answered by now, if you had posted it in the specific SRV Forum "Safety Relief Valve Engineering (PSV). Please note for future.

The test you reference, is that to test the integrity of the bellows ?ie., to ascertain if the bellows are not ruptured/split/damaged? If so, you will pressurise the outlet of the SRV and see if there is any leakage out of the bellows vent. 30 PSIG is normal for that test, though I would refer to the manufacturers instructions. Please advise if you are conducting a different test, as other comments apply.

The back pressure you find on the nameplate, is the back pressure the SRV will be seeing in service. It is used for sizing and selecting the SRV. It is not a test pressure.

Hope that helps.

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