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Orifice Plate

  1. Jun 23, 2011 #1
    We have a situation where we have air in front of the dry pigs and need to control the pig speed

    Medium is air, pressure is 17 barg upstream and 0.2 barg downstream and pig speed target is O.5 m/s for the pig in the 48" pipeline with a pressure of 17 barg.

    need to find the following:

    Orifice profile (hole) size?
    Plate thickness
  2. jcsd
  3. Jun 28, 2011 #2
    For these upstream and downstream conditions the flow is critical, sonic, or "choked" which means the velocity is limited by the speed of sound in the orifice throat.

    So a quick estimate is to calculate the speed of sound in the pipeline:

    v_sonic = sqrt (k R Tstar)

    k = isentropic exponent
    R = gas constant
    Tstar = 0.8333 Tgas

    The volumetric flow is:

    V_flow = v_sonic * A_orifice

    and solve for A_orifice which is the area of the orifice. Then you can find the orifice bore size from this area.
    Last edited: Jun 28, 2011
  4. Jul 3, 2011 #3
    thanks , i have tried to model it on massflow and Cd as 0.8 landed around 63 mm dia
  5. Jul 3, 2011 #4
    Glad to hear you have this running. I think CD of .6 is closer for an orifice.
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