Hi all,

I know this issue is an old discussion in this forum, but I have a lot of doubts yet. I read a lot of thread but no one solved my problem. I didn't find threads considering open discharge system for liquids. So, I'm here again. I'll be glad if someone can answer any question.

First, my system consists in a single PSV (PRV to be more exact) in a pipeline with water and Open Discharge System.

My question is:

I contacted some vendors and everybody said me the same: "For open discharge system, the pressure at exit pipe is almost atmospheric". I think CAESAR II uses ASME B31.1 equation for force calculations:

F1 = (W*V1)/gc + (P1 - Pa)*A1

Being, P1 the static pressure at exit pipe, and this value is almost 1 kgf/cm2, the second term will be zero.

So,

F1 = (W*V1)/gc

In other words this force may be calculated only with mass flow vs fluid sonic velocity?

Someone knows any equation that I can calculate pressure at exit pipe and fluid sonic velocity for liquid? All equations that I saw is specific for vapor/gases.

Vendors said me also, for liquids the PSV don't "pop". Is this right?

For conclude, the only reaction force that acts in this system is F1 and this force is applied in last elbow of pipe exit?

Thanks in advance,

Miyamoto