Q the application's flow in sccm standard conditions are 14.70 psia and 20oC)
Pi the inlet pressure in psia (atmosphere + psig)
K a constant for gases other than nitrogen =(28.0/MWgas))1/2 or see table
Po the outlet pressure in psia (if known)
Then calculate (Q/Pi) x (34.7/K) the nitrogen flow at 20 psig from the desired orifice
Look up the orifice ID from best match in Flow Table.
Note: If Po > Pi /2 substitute Q/[Po(Pi -Po)]1/2 for (Q/Pi)and 17.35/K for 34.70/K. Also, multiply Q by (Tgas/293)1/2 with T in Kelvins, if the temperature of the application gas differs significantly from 20oC.
Flow Table
Note: Helium does permeate PCTFE at a low rate
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