2 replies to this topic

[domiBod]

Dear all,

 

I was expecting that the equations for PRV sizing liquid and PRV sizing subcooled liquid with 100% liquid are similar or very close.

By the fact there are almost similar except that the liquid sizing equation considers the specific gravity and subcooled liquid equation considers the liquid density.

 

we have something like

 

liquid : A = coeff * Q * SQRT(G/(P1-P2))

subcooled liquid : A = coeff * Q *SQRT(liquidDensity/(P1-P2))

 

Is there something I have misunderstood ?

 

Thanks for your support

Regards

Dominique

[domiBod]

To be more precise on this topic. I consider the sizing equations of the API 520. In the above formula, G stands for specific gravity.

 

In the API 520, Ninth edition, July 2014, the number of the equations is:

Liquid: equation (C.29)                  --> A = 11.78 * Q * SQRT(G1 / (P1-P2)) / (Kd.Kw.Kc.Kv)

Subcooled liquid: equation (C.46) --> A = 11.78 * Q * SQRT(rho_lo / (P0-P)) / (Kd.Kb.Kc.Kv)

 

where G1 is the specific gravity of the liquid and rho_lo is the liquid density.

 

Thanks again for your support

[domiBod]

I got it .. I think ...

 

for liquid the unit is kPa and for the subcooled liquid the unit is Pa. So it becomes coherent