Which medium to use? 1

[Enkelaar]

Hello,

I am currently designing the safety valve for a gasfilter system. My sizing case will be when the blowback valves (of the cleaning system) will fail.

The filtervessel itself is approximately 35 m3 and filled with the process gas.

When the blowback valve fails, approximately 200 kg/hr / 165 Nm3/hr of plant air might set off the PSV. What is the medium I will design my PSV for?

Thank you for thinking along in advance!

 

[don1980]

Enkelaar, first I suggest checking to see if it's safe for this process vapor to be suddenly mixed with air. It depends on the fluid, but in most cases that will generate the risk of a flammable mixture. If so, that's a scenario you probably ought to prevent from happening, by using a SIS or HIPS.

Back to your original question.....the PSV should be sized for the fluid(s) that will actually pass through the valve during the worst case scenario. In cases like this you might have one scenario involving process vapor and another involving air. The PSV size must be based on the scenario that requires the largest orifice.