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Orifice Sizing Equations

Orifice Sizing Equations

Orifice Sizing Equations

Hi all,

Can someone guide me to a reliable technical resource that has equations for calculating temporary pressure loss, permanent pressure loss, max velocity across an orifice?

I’ve seen some equations in the past that take into account orifice details such as thickness, sharp edge etc but I cannot find them. Any help is greatly appreciated.

My fluid is liquid but it would be good to have a reference for gas orifice sizing as well.


RE: Orifice Sizing Equations

This is an FAQ for choked flow through an orifice. https://www.eng-tips.com/faqs.cfm?fid=1201

If you're doing it for measurement there are specific calcs for that which normally limit DP to 1000mbar

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Orifice Sizing Equations

hi, a search with your favorite engine should be the ultimate resource.

RE: Orifice Sizing Equations

Thanks guys

RE: Orifice Sizing Equations

For natural gas, I used the AGA Report No. 3 or Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids— Concentric, Square-edged Orifice Meters
Part 1: General Equations and Uncertainty Guidelines

I size the orifice dP for a max orifice dP at 100-inH2O, simply to minimize pressure loss and noise generated. Check orifice dP at min/norm/max flows and size orifice accordingly.

Fyi, I stumbled across an orifice plate at 4" in 8-inch pipe with 450-inH2O dP across the orifice. Noise was absolutely terrible. Increase plate size to max beta size and a "normal" conversation could be had in the gas turbine/compressor enclosure.

RE: Orifice Sizing Equations

Quote (oilman11)

Can someone guide me to a reliable technical resource that has equations for calculating temporary pressure loss, permanent pressure loss, max velocity across an orifice?
See chap. 4 Idelchik's Handbook
In case if you are looking for a calculations of orifices having design the same as flow measuring orifices then you should consult your instrumentation&ocontrol engineer for codes applicable in particular project. You might take a better comments if share with us what kind(s) of orifices and how you are going to use those.

RE: Orifice Sizing Equations

First question is: Is it a restriction orifice or an orifice for measuring flow?

First one: Use something along the API 520 for a PSV
Second: Theres an ISO standard (and many other possible) - although i cant remember what no.

There is a lot of difference between the two methods mostly due to the required accuracuy i would think.

--- Best regards, Morten Andersen

RE: Orifice Sizing Equations

Here is a link to a calculator:


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