Pump casing protection

[GeorgeGrande]

This is the case i am dealing with:

A 2" pipe connecting a pressure vessel (200.5 psia) to a pump. The pump is designed to fill and evacuate the cold and not pressurized fluid. I must protect the pump from 145 psia. In case of leaking (or open from some reson) 2" valve there will be high pressure flow to the pump.
I took worst case scenario for gas flowing through 2" pipe in sonic velocity and calculated the volume flow from pipe flow area and the velocity.
I am getting very large PSV for 2" pipe.

P=200.5 psia
T=287 oF
Tb= 97oF @ atm.
Vsonic=164 m/s

 

[Latexman]

How did you calculate it? Did you calculate sonic velocity at upstream conditions and then apply that to the cross sectional area of 2" pipe without considering the frictional effects of the pipe and fittings? That's easy and conservative, and yes, you'll get a PSV with about a 2" nozzle. I assume the sizing pressure (set pressure + overpressure) at the pump is 145 psia, right.

Good luck,
Latexman