Difference PRV Opening Pressure On Test Bench and in Line
Difference PRV Opening Pressure On Test Bench and in Line
(OP)
Hi
I am Commissioning Engineer on a Gas Plant Project. A piloted PRV is installed at the discharge of a firewater diesel pump. We tested the PRV (equipped with a pilot) on a certified test bench with air so that the opening pressure was set to 13.7 barg as specified in the PRV's datasheet.
When we installed the PRV and did a online test with the diesel firewater running increasing engine RPM but the PRV had still not opened at 15 barg.
The PRV's opening during inline test with firewater pump running was witnessed through an inline side-glass connected to the discharge flange of the PRV.
We decided to set the pilot in line with the pump running so that the PRV would open at 13.7 barg.
Then we dismantled the PRV to bring it back to the bench to test it again with air. The PRV opened at 12.1 barg instead of 13.7 barg.
The PRV discharge line goes back to the top of the Firewater tank, but The PRV is piloted so we can rule out any back pressure effect on the opening set pressure.
I am trying to find an explanation as why there is a difference in the opening pressure between the bench and inline?
Thanks
Seb
I am Commissioning Engineer on a Gas Plant Project. A piloted PRV is installed at the discharge of a firewater diesel pump. We tested the PRV (equipped with a pilot) on a certified test bench with air so that the opening pressure was set to 13.7 barg as specified in the PRV's datasheet.
When we installed the PRV and did a online test with the diesel firewater running increasing engine RPM but the PRV had still not opened at 15 barg.
The PRV's opening during inline test with firewater pump running was witnessed through an inline side-glass connected to the discharge flange of the PRV.
We decided to set the pilot in line with the pump running so that the PRV would open at 13.7 barg.
Then we dismantled the PRV to bring it back to the bench to test it again with air. The PRV opened at 12.1 barg instead of 13.7 barg.
The PRV discharge line goes back to the top of the Firewater tank, but The PRV is piloted so we can rule out any back pressure effect on the opening set pressure.
I am trying to find an explanation as why there is a difference in the opening pressure between the bench and inline?
Thanks
Seb





RE: Difference PRV Opening Pressure On Test Bench and in Line
I wouold present this to the manufacturer and ask them to give you a valve that works.
Several years ago one of the major manufacturers had a significant quality control problem with their pilot operated valves. That problem has sense been corrected. If this is a new valve, that's probably not the explanation. Regardless, this ought not be happening - I'd let the manufacturer figure it out.
RE: Difference PRV Opening Pressure On Test Bench and in Line
RE: Difference PRV Opening Pressure On Test Bench and in Line
RE: Difference PRV Opening Pressure On Test Bench and in Line
I forgot to mention that the gauge in the field was calibrated.
I wrote to the manufacturer of the valve. He answered a that "the pressure relief valve is preset only with water. Air is prohibited to adjust valves. The priming and depriming of the loading chamber will cause huge delay in valve reaction"
RE: Difference PRV Opening Pressure On Test Bench and in Line
Can you expalin further ->"They behave a LOT differently. I'll bet that the mfr will not guarantee setpoints established using air on one of his liquid, incompressible flow, PRV's"
RE: Difference PRV Opening Pressure On Test Bench and in Line
Previously we test it using air/gas.
Thank you