Backpressure calculation
Backpressure calculation
(OP)
hello. i need to supply some back pressure to a control valve i am trying to size. currently the downstream pressure is atmosphere, so my control valve is cavitating. How can i size an orifice plate to give me the required backpressure on my valve?





RE: Backpressure calculation
If you can't lower the upstream pressure, you need to raise the downstream pressure. Put your orifice plate downstream, or increase downstream pressure by some other means.
If you can't raise the downstream pressure, lower the upstream pressure hitting the valve; try putting your orifice plate there.
Be aware that putting in any orifice plate will have some flow reduction implications, so a review of overall pressure drop and flow and possibly a resize of the valve may become necessary.
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RE: Backpressure calculation
Good luck,
Latexman
RE: Backpressure calculation
Forsizing an orifice plate would you treat the orifice plate as a sudden contraction and a sudden expansion in a pipe for calculating the pressure drop across it?
I will be honest ive never sized one, but thats the only method i can think of to account for an orifice plate, but it just seems a little too simple...
RE: Backpressure calculation
Basically, for the dP calculation you use the orifice bore (rather than the pipe ID when calculating the piping pressure loss) with a discharge coefficient for the orifice (which is a function of the Re number in the main piping).
For higher Re numbers and small bore to pipe diameter ratios the discharge coefficient is close to 0.6 but for it can also be significantly different for lower flow cases. Crane has a chart of C versus Re and the beta ratio.
RE: Backpressure calculation
Good luck,
Latexman
RE: Backpressure calculation
RE: Backpressure calculation
No it's not. You need methods specifically for an orifice.
Good luck,
Latexman
RE: Backpressure calculation
RE: Backpressure calculation
RE: Backpressure calculation