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I don't know if you can help me, or if I am asking my question correctly but your feedback will be greatly appreciated. I have a 2" piping system that connects a scrubber that is rated for 675 psi (36" OD x 7'-4") to another scrubber rated for 75 psi (84"ID X 24'- 0") ; there is a .3/8" orifice plate in the system and roughly 100 ft of schedule 40 steel pipe between the vessels. The system does have high and low pressure alarms but I am trying to prove that in the remote case that the high pressure scrubber reaches 675 psi there will be enough pressure drop at the currently installed orifice plate to make the 75 psi scrubber safe. I know it will be safe because the low pressure scrubber has a 12" pipe going to a Flare but I want to make sure that we will never reach 75 psi if the high pressure scrubber reached operating limits.

How would you guys approach this situation? The gas flowing through the system is methane at 60F, I have estimated the flow by using a quick formula that estimates the amount of gas blown through a line puncture and it gave me 96,989 scf/Hr; I calculated this by assuming that the orifice was a line puncture of a system at 675 psi. This will be the choked flow rate at the orifice so this it should be the most flow rate that the system will see. I can then use that flow rate to calculate the Pressure drop due to piping friction but I am having a struggle calculating the pressure drop across the orifice.

Am I approaching the problem wrong? Or any ideas on how to calculate the DP?

In advance, thank you!

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# Calculate the pressure drop of air across an orifice?

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