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Flow Calculation

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#1 Venkat1989


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Posted 21 July 2022 - 08:21 AM

Dear all,

As panel engineer, I always find flow transmitters getting faulty, during such situation before getting it attended through instrument team, is it possible to calculate flow if I know the upstream(14kgf/cm2g) Debutanizer column and downstream pressure(2kgf/cm2g) flow towards storage tank across the control valve, whose opening is 55%?

If so, what data I need to use to get the flow?


Edited by Venkat1989, 21 July 2022 - 08:22 AM.

#2 latexman


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Posted 21 July 2022 - 09:32 AM

I recommend you refer to your university fluid flow textbook, or obtain Crane Technical Paper No. 410.

#3 breizh


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Posted 21 July 2022 - 10:07 PM


I think Latexman is spot on with his recommendations.

As a panel engineer you should be able to explain your thoughts based on DCS trends thus ask support from I&E team.


Note : You should be able to ask your process engineer to come and use a portable  non intrusive flowmeter to support you ( doppler flowmeter device) . This is a cheap investment for a plant and can help a lot to troubleshoot units and get data .


Good luck


#4 Said Salim

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Posted 22 July 2022 - 01:15 AM

You can use your historical data before flow transmitter failure and plot flow reading against CV opening and derive the correlation.

#5 Pronab


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Posted 24 July 2022 - 02:25 AM

Usually there are flow vs valve opening at specified CV provided by the manufaturere where you can find out the flow at your desire valve opening.

#6 breizh


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Posted 24 July 2022 - 11:26 PM


I still believe the best way is to use an external flowmeter to validate your suspicion of a faulty flowmeter or valve , see my initial reply..

Anyway you will find a excel sheet with equations and methodology to support your query . To perform the exercise you need information about the valve (CV) together with its type of response ( see attached document) and piping arrangement ( length, fittings).

Good luck


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