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8 comments
Guest

Flow Measurement

10/08/2009 11:13 AM

I have a task where im going to measure flow with a dp cell and flow orifice. First i have to calibrate the dp cell. I dont know anything about the pressure before the flow orifice, my plan was to measure the pressure before the flow orifice and use that as the range. For example, if i measure 500 millibar before the flow orifice, would it then be correct to set the measuring range to 0-500 millibar?

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Guest
#1

Re: Flow Measurement

10/09/2009 12:30 AM

Sorry but no. You need to use flow differential calculations to arrive at a correct diff to calibrate the DP cell to. If you want to do it without calcs, measure the diff across the orifice at max flow and that will be the DP Cell calibration 100% figure, it may be only 20kPa when the line pressure could be 6000kPa.

Rok

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#2

Re: Flow Measurement

10/09/2009 6:36 AM

Differential-pressure-across-an-orifice is so 1972.

Why not use a vortex-shedding meter instead, with all the features and a linear 4-20mA signal 2-wire capability built in, perhaps?

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Guest
#3

Re: Flow Measurement

10/09/2009 8:24 AM

Calibrate the DP with a stand pipe or two.

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#4

Re: Flow Measurement

10/09/2009 8:33 AM

Pick your range...calibrate your tx...and size your plate according to the flow.

Commentator
India - Member - ADIL MOULA Engineering Fields - Instrumentation Engineering - Adil Moula

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#5

Re: Flow Measurement

10/09/2009 9:49 AM

try turbinemeter /rotameter, why dp cell ?

Guest
#6

Re: Flow Measurement

10/12/2009 2:27 PM

DP cells are cheap, "Vortex Shredding" flow meters are not. Alot of companies are cheap, ie. the one I work for. Therfore you'll find alot of DPs kicking around.

Guest
#7

Re: Flow Measurement

10/12/2009 2:28 PM

typo sorry "Shedding"

Guest
#8

Re: Flow Measurement

10/12/2009 11:38 PM

If you know the pipe ID and the Orifice size, you can use a program to predict the DP.

if this is a liquid application it easy, if gas, pressure and gas compostion is needed.\

you can obtain a decent calculation program by going to this link, free and they are one of the oldest suppliers of orifice meters.

http://www.emersonprocess.com/daniel/Products/gas/orifice/orifice_flow_cal.asp

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find2am (1), Guest (5), InstrumentKyle (1), PWSlack (1)

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