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Orifice Plate for Flow Measuring

01/07/2016 6:25 AM

Hi to all

I have a question that is about an orifice plate for flow for any things such as (Steam , air and fuel…Etc..) , How can I know this orifice plate is suitable for that…

My issue that how I can make a calculation and choose the right one .

So pls advice me about this topic and also how many types there are ??

Y our feedback and answers really appreciated.

Best wishes

Omar Aboosh

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#1

Re: Orifce plate for flow measuring

01/07/2016 6:33 AM

Orifice plates are sooooo 1973. Go for a vortex-shedding unit instead from a reputable manufacturer (names withheld).

Selection is best done over the telephone with a Sales Engineer.

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#6
In reply to #1

Re: Orifce plate for flow measuring

01/08/2016 3:05 AM

I wonder if someone could explain why a vortex shedding meter might be better than an orifice plate for the OP's situation.

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#8
In reply to #6

Re: Orifce plate for flow measuring

01/08/2016 4:29 AM

Sales Engineers can, certainly, and they are on the other end of a phone.

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#13
In reply to #8

Re: Orifce plate for flow measuring

01/08/2016 3:23 PM

Sorry, I should have mentioned that I am not the OP and I am not in the market for a device, but merely wishing to add to my general knowledge.

This website has something to say about vortex meters:

Vortex Meter Advantages
• Vortex meters can be used for liquids, gases and steam
• Low wear (relative to turbine flow meters)
• Relatively low cost of installation and maintenance
• Low sensitivity to variations in process conditions
• Stable long term accuracy and repeatability
• Applicable to a wide range of process temperatures
• Available for a wide variety of pipe sizes
Vortex Flow Meter Limitations
• Not suitable for very low flow rates

• Minimum length of straight pipe is required upstream and downstream of the vortex meter

So how does that list distinguish vortex flow meters from orifice flow meters?

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#2

Re: Orifce Plate for Flow Measuring

01/07/2016 7:41 AM

As cited by PWslack, the following youtube video of Endress-Hausser might help you

See application

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#3

Re: Orifce Plate for Flow Measuring

01/07/2016 10:10 PM

Orifice Plates are sized according to flow rate range being measured and type of fluid being measured.

You must go to your vendor of choice and review their offerings based on the application requirements.

If you have difficulty understanding all of the information and/or the requirements contact the applications group of your preferred vendor and they will be more than happy to help you so that you purchase their equipment.

If they are not willing to do so, simply go to a different vendor.

I have never experienced anything but good advice from any major instrument suppliers such as ABB, Siemens, Emerson-Rosemount, Endrus-Hauser, Vega.

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#4

Re: Orifce Plate for Flow Measuring

01/07/2016 11:51 PM

You will need to carry this work out in two stages.

Firstly prepare the engineering (process) data. Most importantly this will include the range of operating conditions that you need to cover

Typically you will need flowrate, density, viscosity, temp and pressure and you should have made an assessment of the pipe size.

You will also need to know the accuracy for which the measurement is needed.

All of this work is carried out with no knowledge of the metering technique.

Once you can give a vendor all this information in Stage 2 they will be able to advise on a suitable metering technology

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#5
In reply to #4

Re: Orifce Plate for Flow Measuring

01/08/2016 1:58 AM

Very good answer!

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#7
In reply to #4

Re: Orifce Plate for Flow Measuring

01/08/2016 3:42 AM

Thanks ,if I think there is an Equation by it that we can know size of orfice plate .

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#9
In reply to #7

Re: Orifce Plate for Flow Measuring

01/08/2016 4:33 AM

Yes, there is, and it can be looked up in any Process Engineering textbook [try "The Chemical Engineer's Handbook" by Perry, any edition]. However, it is not necessarily the optimal measuring technique for every situation, which is why a telephone discussion with equipment suppliers is essential before selecting the technique.

Technology moves on. Orifice plates don't.

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#10
In reply to #7

Re: Orifce Plate for Flow Measuring

01/08/2016 5:49 AM

There isn't just one equation. It depends on the flow regime (Reynolds No. etc) and can get quite complicated when dealing with compressible flow or steam. If you haven't got a feel for fluid properties, flow, energy etc you're likely to find it hard going.

One drawback of OP (or any DP generating meter) is DP varies as square of flow, so accuracy suffers if you have a big turndown. Another option for gas flow is thermal mass type, which also gives negligible pressure loss, and reads directly in normal, std etc flow units, no need to correct for actual pressure and temperature.

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#11
In reply to #10

Re: Orifce Plate for Flow Measuring

01/08/2016 11:43 AM

Not quite any DP meter. The Fleisch pneumotachograph (used in medicine and physiology to measure respiratory airflows) has a resistance element consisting of multiple small parallel tubes. The flow is almost laminar and the pressure-flow calibration curve is almost linear.

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#12
In reply to #11

Re: Orifce Plate for Flow Measuring

01/08/2016 12:51 PM

OK, but I doubt he had such a low-flow application in mind!

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