Gas blow-by

[korn]

I am trying to size a PSV located on an Amine Surge Drum. I have several gas blow-by cases (failure opening of upstream control valves, resulting in loss of liquid level and subsequent high pressure gas flow to the low pressure Amine Surge Drum). However, should the gas blow-by case be considered if the high pressure source is from a centrifugal pump? The upstream high pressure gas would have to travel through the pump and control valve after liquid inventory is lost in the upstream high pressure vessel. Is this a scenario anyone has considered before? If so, how did you model the gas flow through the pump?

Thanks,

 

[TD2K]

Yes, you should consider it. You could talk to the vendor and get a feel for the dP through the pump when free flowing liquid. Calculate the equivalent number of feet of piping and then add that to your gas blowby case. Or ignore it and get a conservative answer.

For the control valve, you need to see what 'should' happen to the control valve during gas blowby. If the control action should open the valve, you assume that happens. If the control valve should close the valve, you assume it does not and the valve remains in its normal position.

 

[korn]

Thanks for the confirmation. Now I have to convince all of the "because we just don't" co-workers about this scenario.

Thanks,