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How to size an orifice on a vent line

  1. Oct 2, 2014 #1
    I would like to install a vent stone on a 3/4" vent line. The line vents upwards of 1500 psig of stored gasous nitrogen in under 1 second. The vent stones are only rated for 300 psig, so I'd like to add an orifice just upstream to limit the exit flow rate to a point where it can handle the pressures from venting the GN2. What are useful formulas for this application? I was thinking perhaps the equation for mass flow rate with choked flow (http://www.grc.nasa.gov/WWW/k-12/airplane/mflchk.html), and also the equation for flow coefficient (http://www.fnwvalve.com/FNWValve/assets/images/PDFs/FNW/tech_AboutCv.pdf). Then I started thinking about the equation for dynamic pressure (http://www.grc.nasa.gov/WWW/k-12/airplane/dynpress.html), but I am struggling with applying these equations to get the information I need. Either I am not using the right approach, or I am not using these correctly.

    Thanks for any insight!

  2. jcsd
  3. Oct 7, 2014 #2
    Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Oct 9, 2014 #3
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