PSV

You will need to know several things to do this.

1. set pressure of the PSV

2. Downstream pressure (back pressure) on the PSV

3. orifice size of the relief valve.

4. molecular weight of the gas.

Typically you can assume an ideal gas and be fairly close to the answer. Many relief valve manufacturers provide free software for sizing relief valves and this can be used to determine the flow rate from the valve. Just check with crosby or whoever manufactured your valve and they probably have a link on their website to download the program.

If not, then you can use the ASME formulas (which I don't have handy at the moment) to calculate the relief rate.

Hi, i advise you to read API 520 in determining the right calculation to use depending on your relief scenario.