Air pressure vessel safety valve size

[guideonl]

Hi everyone,

I have to determine the size of safety valve for an air pressure vessel. I found in ASME and BS 5500 a procedure to calculate the size of safety valve, which relates the mass flow capacity to the: pressure, temprature, discharge area, s.v coefficient, and air parameters. This can be helpfull if the flow capacity is known, so you can get the discharge area (valve size). But if the flow capacity is unknown (such in case manufacturing perss. vessels without compression units).
The next question is there any relation between the discharge capacity of the s.v to the compression unit flow capacity? I suppose yes, but is it equal/higher? how much?

Thank you,
Guideon

 

[anorlunda]

If it is all air, no liquid, then mass flow out = mass flow in. If there is zero mass flow in, then even a small valve is able to make the pressure start reducing immediately.

If temperature in the tank is increasing then use volume flow out = volume flow in.