Re: [foxboro] Typical Orifice Flowmeter Compensation Calculations

The equation is only valid for gas. It gives only an approximate value, not 
good for fiscal measurements, only operative. It doesn't account for gas 
composition, liquid contents, etc.
What's the use of this, then?..... Well, for a lot of things this simple 
calculation is enough, for example, to know how much fuel gas you are using 
or how much you are sending to the flare, to take intermediate measurements 
inside your plant, for a turbine anti-surge control, etc.
Pablo Lioi
TOTAL AUSTRAL
Argentina


>From: "Jim Mowrey" <jmowrey@xxxxxxxxxxxxx>
>Reply-To: foxboro@xxxxxxxxxxxxx
>To: <foxboro@xxxxxxxxxxxxx>
>Subject: Re: [foxboro] Typical Orifice Flowmeter Compensation Calculations
>Date: Tue, 24 Jan 2006 23:26:20 -0500
>
>I haven't looked this up or derived it, but isn't this applicable for a gas
>only?   I think this comes out of Bernoulli's equation and the ideal gas
>law, assuming an adiabatic expansion across the orifice.
>
>The equation would be different for a liquid, correct?
>
>Jim
>
>-----Original Message-----
>From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
>Behalf Of Pablo Lioi
>Sent: Monday, January 23, 2006 5:13 AM
>To: foxboro@xxxxxxxxxxxxx
>Subject: Re: [foxboro] Typical Orifice Flowmeter Compensation Calculations
>
>Kirk,
>Hope this helps:
>
>CALCA BLOCK
>
>RI01  FIxxxx.PNT
>RI02  PIxxxx.PNT
>RI03  TIxxxx.PNT
>
>M01 1.013      (Base Pressure, Bar)
>M02 273.15    (Base Temp, Kelvin)
>M03 298.15    (Reference Temp, in Kelvin)
>M04 18.103    (Reference Pressure, Bara)
>M05 350        ( max differential pressure, mBar)
>M06 6.39       (Flow @ max dif pressure, Ref. Pressure and Ref. Temp)
>
>ADD RI02 M01
>ADD RI03 M02
>DIV
>MUL M03
>DIV M04
>MUL RI01
>DIV M05
>SQRT
>MUL M06
>OUT RO01
>END
>
>
>The formula is
>
>Qcomp = Qref Sqrt[( FI/FImax) ((PI+1.013)/(Pref + 1.013)) *
>((Tref+273.15)/(TI+273.15))]
>
>Pref+1.013 is stored in M04
>Tref+273.15 is stored in M03
>FImax is stored in M05
>Qref is stored in M06
>
>Determine Qref with a flow calculation program, using FI = max differential
>pressure, P = work pressure T = work temperature
>
>Pref is the work pressure and Tref the work temperature
>
>Note in the above formula that if (FI=FImax, PI = Pref and TI = Tref) then
>Qcomp = Qref, so the formula compensates for the deviations from the
>reference pressure and temperature.
>
>You can put this formula in Excel and make a table of Qcomp vs. P and Qcomp
>vs. T and compare results against your flow calculation program to see how
>it works
>
>I am using SI units. If you need otherwise, just change the values in
>M01-M06
>As you see, the transmitter is not calculating the square root of the diff
>pressure.
>
>If you have square root at the transmitter then the MUL RI01 line has to be
>moved after the SQRT, leaving the rest unchanged (you still need the SQRT
>for the FI range, pressure and temp).
>
>Good luck
>Pablo Lioi
>System Engineer
>TOTAL AUSTRAL
>ARGENTINA
>
> >From: kirk.d.carver@xxxxxxxxxxxxxx
> >Reply-To: foxboro@xxxxxxxxxxxxx
> >To: foxboro@xxxxxxxxxxxxx
> >Subject: [foxboro] Typical Orifice Flowmeter Compensation Calculations
> >Date: Sun, 22 Jan 2006 16:32:17 -0600
> >
> >I am comparing some different configurations on our project and wanted to
> >get a quick survey of how others perform flowmeter compensation in I/A.
> >
> >Assuming two flavors of 4-20mA flowmeter signal:
> >a) in H2O (or psi) differential
> >b) volumetric flow (square root in the transmitter)
> >How do you compensate the flow for pressure and temperature?
> >
> >Calc block steps would be appreciated.
> >
> >
> >Hook 'Em,
> >Kirk
> >
> >Kirk Carver, PE
> >ExxonMobil Development Company
> >Facilities -  Instrumentation and Controls
> >12450 Greenspoint Drive
> >GP6-315
> >Houston, TX 77060
> >(281) 654-4881 (Greenspoint Office)
> >(713) 350-1158 (Worley Parsons)
> >(713) 962-2549 (mobile)
> >kirk.d.carver@xxxxxxxxxxxxxx (best chance of contacting me)
> >
> >
> >
> >_______________________________________________________________________
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> >Systems (formerly The Foxboro Company). Use the info you obtain here at
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> >
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>
>
>
>
>_______________________________________________________________________
>This mailing list is neither sponsored nor endorsed by Invensys Process
>Systems (formerly The Foxboro Company). Use the info you obtain here at
>your own risks. Read http://www.thecassandraproject.org/disclaimer.html
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>
>
>
>_______________________________________________________________________
>This mailing list is neither sponsored nor endorsed by Invensys Process
>Systems (formerly The Foxboro Company). Use the info you obtain here at
>your own risks. Read http://www.thecassandraproject.org/disclaimer.html
>
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