PSV for flasing liquid

[GeorgeGrande]

Hello,

My question is about the following model.

I have a 22 bara vaporizer with organic fluid. a 2" pipe is connected to the bottom of the HE (with blocking valve) for filling and evacuation service when process is shut and no pressure at HE. This pipe is connected to a pneumatic pump with 8 bar casing.
I want to protect the pump in case of valve opening when process is on (lets say full opening by mistake).
In that case fluid will flash and i will get gas flow in pipe. Sonic velocity value is 178.8 m/s but i dont know if i can apply this value in this case. I also tried to use Fauske correlation for discharge of flashing saturated liquid but it refers only to discharge to atm.

To focus my problem, I want to size a PSV for this system and i dont know how to calculate the expected flow. Using 2" nozzle PSV will be reasonable but i need a way to justify it.

Your help will be appreciated.

Thanks.

 

[MortenA]

I can "visualize" your problem:

The evaporator operates below atm. pressure?
Your worries are they concerning the design pressure of the pump or the fact that 2 phase gas might get into the pump?

Best regards

Morten

 

[GeorgeGrande]

Morten,

The vaporizer works at 22 bara. liquid is flashing via 2" pipe connected to the bottom of the vaporizer (liquid area). How can i calculate the gas flow in this pipe in order to calculate PSV that fits the pump casing pressure (8 bara).

Hope i am clear.