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[bmicky]

Hello all

2 questions if I may regard subcooled liquid sizing which goes through flashing inside the PSV.

1)      PSV Discharge nozzle sizing :

Is there a sizing criteria for the discharge nozzle of a PSV ?

I didn’t see any relation to that nozzle . All the sizing equations and scenarios always relate to the inlet nozzle and the orifice size. Why isn’t the discharge being treated?

Should a criteria of 0.7 x sonic velocity ? ( or sonic velocity ) be used ?

This is especially important in cases where the inlet is subcooled and PSV it goes partial/full flashing inside the PSV.

In that case, to the best of my judgment, a substantial difference should be between inlet nozzle and outlet nozzle

 

2)      Subcooled liquid flashing - sizing :

I have a specific case that I am debating for a while on how to size it.

This is a subcooled liquid that goes through flashing through the PSV.

 

To the best of my judgment, section C 2.3 of API 520,part I should be used.

Do you agree?

In that case, when I check omega and all criteria, its seems I am in the “high sub cooling region” which require using equation: C.42 ( or D.11 in older versions of the code):

 

G= 96.3 [density_l_0(P0-P)^1/2]

 

Do you agree?

What will be the correct sizing for that valve( especially outlet nozzle ? ) and why isn’t the vapor criteria any factor in this kind of sizing ?

 

Below are the exact data for my case, I will appreciate your help for the correct sizing:

-          Water ( with small amount of soluble CO2,~ 0.2% wt ).

-          Vapor pressure of composition: 70.3 psia

-          PSV set pressure : 200psig @ 300 F

-          Block flow scenario (110%), Ambient pressure : 11.5 psia, therefore :

-          Reliving pressure :  231.5 psia

-          Operating temperature: 283 F

-          Volumetric  Flow : 4500 GPM

-          Mass Flow : 2,051,325 lb/Hr

-          Liquid density : 56.833  lb/ft^3

-          Density at 90% of saturation pressure   ( P=63.27 psia ) :

Vapor density =0.18 lb/ft^3,liquid density = 56.8 lb/Ft^3

 

 

Thank you all in advance

 

 

 

[latexman]

1) Not really.  Once the nozzle is sized and you look at the choices from different manufacturers in the pressure class(es) required, what you see is what you get.