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Homework Help: Calculating whether the force of a flow rate is sufficient to move a disc

  1. Aug 9, 2012 #1
    1. The problem statement, all variables and given/known data

    There is a vertical 10 inch pipeline with a disc hanging in it. The disc weighs 7.3 kg. There is a flow coming from the opposite direction (water with density 1017.17 kgm/m3) coming at 2250 gpm at 198 psi in the opposite direction (moving up through a pipe). Is there sufficient force to open the free hanging disc? What is the minimum flow rate (in gpm) needed to raise the disc? Delta P is 5 to 7 psi.

    b. how about 1680 gpm at 122 psi ?

    2. Relevant equations

    None provided, but equations used below.

    3. The attempt at a solution

    First I calculated the Force of the disc which would be 7.3kg (9.81 m/s2) = 71.613 kg m/s2

    The flow rate of 2250 gpm was converted to 0.142 m3/s

    0.142 m3/s * 1017.17 kg/m3 = 144.43 kg/s

    The area of the pipe is A=∏r2 , so 78.5398 in2 or 0.05067 m2

    I am not sure what the next step would be in comparing a Force (exerted by the disc and gravity) to the Force exerted by a flow rate.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
    Last edited: Aug 9, 2012
  2. jcsd
  3. Aug 9, 2012 #2
    What is the dynamic pressure of the flow? What should it be to open the disk?
  4. Aug 9, 2012 #3
    The delta P is 5 to 7 psi. and the piping is ASME Class150, so the pressure would never exceed 290 psig in the pipe. The only effects on the disc is gravity.
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