Transcription of EQUATIONS FOR FLOW THROUGH ORIFICES
1 Drw 10999/28/92 rev 971014; 090805 PSEQUATIONS FOR FLOW THROUGH ORIFICESThe following EQUATIONS give an approximate flow THROUGH ORIFICES and short tubes basedon orifice size, pressures and gas involved. They are simple EQUATIONS that provide onlyan estimate of flow rate and Aqua Environment Co. Inc. makes no representation orwarrenties concerning these EQUATIONS . They should not be depended on in criticalapplications. They can be used for round ORIFICES or short tubes where the length doesnot exceed more than a few times the tube DOWNSTREAM PRESSURE IS LESS THAN 1/2 THE UPSTREAM PRESSURE FOR AIRQ = 11 Pu D2 D = (Q/Pu)1/2 Where: Q is the flow rate in SCFMPu is the upstream pressure going to the orifice or hole in PSID is the orifice or hole inside diameter in inchesThe superscript "2" means square the valueThe superscript "1/2" mean take the square root of thevalue in parenthesisWHEN DOWNSTREAM PRESSURE IS MORE THAN 1/2 THE UPSTREAM PRESSURE APPLYTHE FOLLOWING press.
2 As % Correction - multiplyof upstream press. Q by:0 to 50% GASES OTHER THAN AIR ARE USED MULTIPLY THE ABOVE Q BY:Helium gas APPROXIMATE CONVERSION OF ORFICE DIAMETER TO CV VALUE IS GIVEN BY:Cv = 15 D2where D is the orfice diameter in Environment Inc.
