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Orifice Plate Flow

Orifice Plate Flow

Orifice Plate Flow

(OP)
How do you calculate the flow through an orifice plate?  They want to replace an existing orifice plate with one that has a smaller bore size.  How can I calculate what the flow through the new plate is going to be?

RE: Orifice Plate Flow

Flow is proportional to the square of the bore for a given meter d/p, so

Q1/Q2 = d1^2/d2^3

you can rerange the d/p measurement though it is sqrt(h1)/sqrt(h2) ...

lots of parameters are ignored, so this is a just a plant calculation for what its worth...

RE: Orifice Plate Flow

(OP)
Maybe I am having a blonde day...

I have the following information for the existing plate:

Fluid: Air
Specific Gravity: 1.0
Viscosity: 0.0192 cPS
K (CP/CV): 1.41
Barometer: 14.7 PSIA

Base Conditions:
Temperature: 60.0 Deg. F
Pressure: 14.73 PSIA
Compressibility: 0.9991

Flowing Conditions:
Temperature: 110.0 Deg. F
Pressure: 26.7 PSIA
Compressibility: 0.9993

Line Size: 6.0"
Differential Range: 0-20"H2O

My new orifice plate is 316SST, 150# flange rating, 6.0", Bore Size: 1.3543

What is the expected flow through this plate?

RE: Orifice Plate Flow

You might also search for "orifice" on this site.  This question comes up a lot.

Although I have a question about the data you posted.  Suppose somebody here took it and came back with an answer "you need an orifice with an orifice of 1.15 inches." (This is a totally bogus number.  Do NOT use it!!)

How would you justify using that value to your management? Do you really think saying "Someone on a free Internet site told me the answer" would work?

You'd be a lot better off asking "where can I find out how to calculate this myself. (and,by the way, do you have a copy of Crane's Technical Paper 410, "Flow of Fluids Through Valves, Fittings, and Pipes?")

Sorry, rant over.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

RE: Orifice Plate Flow

(OP)
Thanks for all of your help!  I will use your info to come up with a flow.  

About the "info"... I posted it because I thought that someone who saw it might have the sizing program and be able to quickly pop out the flow I can expect to get.  I already have an orifice plate, I just don't know what kind of flow I will get through it.  

Unfortunately, I am not very familiar with orifice plates and do not have the software to help me.

 

RE: Orifice Plate Flow

Lisa,

Appologies for the delay, I come up with 135.5 scfm at the conditions you've provided for flange or close-up taps and a square-edged orifice plate.





 

RE: Orifice Plate Flow

(OP)
Thanks hacksaw!!  You're a life saver.  

I just downloaded the program that rikiraph2 suggested.  I'm going to try to duplicate your answer on my own so that I will know how to do if myself next time.

Thanks again!!!

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