PSV Sizing, 2-phase flow prediction/test

As far as I remember SimSci Inplant is able to predict firecase too.

I think you'll find that example of 2 phase flow sizing is not for Pressure-relief Valves. Your best approach for 2 phase flow PRV sizing is in the first 2 references provided by Shvet above. These are the best and up to date 2 phase flow calculators for PRV's following API-520 from two of the largest manufacturers whom have been involved deeply in 2 phase flow sizing for PRV's.


*** Per ISO-4126, the generic term
'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

Shvet and The Obturator, thanks for the input. I'll have a look on these links.

pb, I am literally in the middle of putting together an analysis sheet using an old journal article from Larry Simpson. I wonder if you have the article from Forrest and Fisher that you could share, or at least let me know the date of the article. It may be a more recent article than Simpson's.

To clarify the approach... First step is to determine if at allowed over pressure is there two phase flow or vapor only flow. For example the Simpson approach (pretty long math) looks first at the loss of liquid and vapor during the first phase of relief - up to the allowed OVP. Then checks to see if flow during phase 2 (at allowed OVP) will be vapor only. Not sure the Emerson and Leser first check to determine if vapor only, as your doc above seems to do.

probably your manufacturer can propose the right tool (the reason being that there are many specific factors as valve's internals etc. which can affect results in complex models as for example non-homogeneous, non-equilibrium models)
said that, there are many tools available and, since you mention Excel, there is Prode Properties,


which includes methods able to solve single and two-phases flow with different models (homogeneous and non homogeneous equilibrium etc.), also you can use Prode library to calculate the speed of sound (single and two-phase flow) to verify your lines...