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High RhoV2 at relief valve discharge (not discharge piping)

High RhoV2 at relief valve discharge (not discharge piping)

High RhoV2 at relief valve discharge (not discharge piping)


I have a balanced relief valve to verify in flarenet.

The valve is 4P6. The downstream piping is 10" to give a rhov2 less than 150,000kg/m/s2 and mach no < 0.75 in the downstream tailpipe.

The expander is flange to flange with the relief valve, but has sonic velocity at the inlet (/relief valve nozzle) and rhov2 > 200,000.

Backpressure is ok.

There are no AIV issues.

Is this typically acceptable? All guidance talks about downstream *piping*, not so much the conditions at the valve discharge itself. If there are no weak fittings and just straight pipe between the valve discharge and expander, is there actually a mechanism for failure? Considering the force at any restriction is proportional to rhov2*d2, but there is no 'd2' term for the fluid momentum to act against.

RE: High RhoV2 at relief valve discharge (not discharge piping)


Consider deleting this and re-posting in the "Safety Relief Valve Engineering" forum.

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