Orifice Plate Max Size 3

[prdav86]

Currently we have a 15.125" orifice size on a 24" line. This is causing a 3psi pressure drop. What is the largest bore size that you can install to reduce this pressure drop to a minimum and how do you calculate this?

 

[zdas04]

In API 14.3 (I can't remember which annex) there is a comprehensive review of the components of uncertainty in gas measurement. They are all pretty well behaved between a beta ratio of about 0.3 and 0.72 and get very large outside that range. If you buy that then a 17.25 bore would keep you in a reasonable uncertainty range. The standard allows going to 0.8 beta ratio, but that limitation was put in place before the committee did the uncertainty work.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[prdav86]

What equation are you using to find this or is there a good online calculator to use?

 

[zdas04]

0.72*24??????????????

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[zcman91]

There are several calculators out there to use and I believe most utilize the RW Miller equation. However, in my experience in sizing an orifice I would talk with an Orifice manufacturer (like Rosemount or their representative) as the size you calc may be different than what they can either make or sell.

 

[georgeverghese]

If we want to maintain accuracy and keep within acceptable industry practice, a beta ratio of 0.8 may be as far as you can go. Else go for a V cone (short or long cone venturi). Dont remember if the turndown limits for a V cone are as good or better that an orifice plate.

 

[LittleInch]

You need to be clear what the plate is for - the (very good) answers above assume you're using it for flow measurement of ? gas? liquid?

3 psi doesn't sound a lot - what has happened for you to want to change it?

If you want no pressure drop look at other forms of non intrusive measurement - multi path UT e.g. or mag flow for a liquid.

all depends on what you're trying to do, if its a meter what is your accuracy / uncertainty aim as a percent?

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