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Calculating SCFM

  1. Jul 9, 2015 #1
    I am trying to calculate the SCFM of helium through five feet of SS tubing (1/4" OD x .035" wall). The helium would be flowing from a pressure vessel at 250 psig, through a pressure regulator set to 4psi, and into a compressor crankcase. What, if any, other information is required to calculate the SCFM? Once I have all of the info needed, how do I calculate it? I appreciate the help!
  2. jcsd
  3. Jul 12, 2015 #2


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    Hi randync. Welcome to the board.

    I'm afraid you haven't really provided enough information. I'm sure you have a very good reason for wanting to put a blanket purge on the crankcase, so if you could explain a bit about your application it might help.

    If you're pressurizing a cranckase to 4 psi, you may have helium leaking out of the crankcase somewhere. How much leaks out depends on how well seals are working, both static and dynamic ones along with any other leak paths there might be. Crankcase pressure could also be affected by volume change, for example if you have a reciprocating compressor, the volume the piston displaces affects the overall volume and therefore the pressure in the crankcase. So I assume you're trying to maintain 4 psig by putting gas in as fast as it's escaping and there's really no way of knowing what the flow will be until you test it.
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