Relief Valve response to Pulsation from Positive Displacement Pump
Relief Valve response to Pulsation from Positive Displacement Pump
(OP)
A relief valve set for 1250 psi on a system with a positive displacement pump (2500 rpm) sees pressure spikes of 1275 psi every 1.5 seconds. However, the RV does not lift. Does anyone know why it does not respond to the pressure spikes?
J. Alton Cox
www.delucatest.com





RE: Relief Valve response to Pulsation from Positive Displacement Pump
RE: Relief Valve response to Pulsation from Positive Displacement Pump
A Direct Acting Relief Valve will respond faster that a Pilot Operted type but both have to move a mechanical part that is spring loaded and that requires time. A Pilot operated Relief valve can have as much as twice the pressure setting override each time it is forced to open.
You must be reading the 1,275 PSI peaks with a digital gauge so you can see what the pressure spike is if you block pump outlet suddenly.
I always use a small bladder or diaphragm type accumulator as a pulsation dampener and locate it as close as possible to the pump discharge port. Set the pre-charge pressure at or slightly under the relief valve setting and there will be very little pressure spikes in the line to the circuit.
Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com
http://www.fluidpower1.us
RE: Relief Valve response to Pulsation from Positive Displacement Pump
RE: Relief Valve response to Pulsation from Positive Displacement Pump
RE: Relief Valve response to Pulsation from Positive Displacement Pump
10% overpressure does not imply anything about the pressure the PSV will start to open.
RE: Relief Valve response to Pulsation from Positive Displacement Pump
J. Alton Cox
www.delucatest.com
RE: Relief Valve response to Pulsation from Positive Displacement Pump
RE: Relief Valve response to Pulsation from Positive Displacement Pump
Is this similar to the 'pop' effect for valves in vapor service. I haven't heard of this though I'm not saying it's not true. My impression was that liquid valves basically open in proportion to the overpressure.
ASME certified liquid valves are fully open at 10% overpressure. The older overpressure used to be 25% overpressure to get full flow and the PSV manuals had derating factors in them for their capacity at 10% overpressure.
RE: Relief Valve response to Pulsation from Positive Displacement Pump