Relief Capacity Rupture disc + relief valve

[martane]

I have a 10" Rupture disc with relief valve set at 180psig installed to protect my pipe. What is the total relief capacity (gpm) would this provide? Assuming the fluid is water flowing at 140F. This is vented out into the atmosphere. What equation should I use to determine the capacity?

 

[AWloo]

You will need to know the flow coefficient, Cv, from the valve manufacturer.

The flow rate [GPM] Q=Cv*sqrt((P2-P1)/SG)

Where the pressure is in psi and is the upstream and downstream pressure of the valve. SG is the specific gravity of the fluid relative to water at 60 Deg F.

 

[martane]

I used the equation by ASME and by Crane but I Alway get 2 different answer. ASME eq. Lb/hr = 2407*A*sqrt((P1-P2)/w) where: w is the specific weight. P1 is the set perssure*1.1+14.7psi. P2 is the discharge pressure.

Crane's eq: GPM = 22.8*A*sqrt(deltaP/SG) where deltaP is set pressure*1.1, SG is the specific gravity.
Then i would convert gpm to lb/hr

These two equations would give me different answers. For the 10" rupture disc i would get 10200 Klb/hr from Cranes eq. And 2150 Klb/hr from ASME.

 

[ione]

martane,

Are you sure to be using the right formulas, I mean for liquid service, as in your OP you've specified the fluid involved is water?