Re: [foxboro] Typical Orifice Flowmeter Compensation Calculations

I'd use a CHARC block using T and P as inputs to get the multiplicative
compensation factors (assuming not water, as density is relatively invariant
with P).  The compensation factors are the ratio of densities at P (or T) to
the "base point" density.  What I mean is that the flowmeter is calibrated
at a specific density (and therefore T and P; possibly STP); the ratios
should be the ratio of density at that T or P to the density at the
calibration T or P (base point) from a set of physical property tables.
Examples of these tables are steam tables, chemical property tables, etc.
Note that often the inverse of the density (specific volume) is listed in
the tables.  For many fluids, you can use the density at a given T as the
liquid saturation T density, as liquids are mostly incompressible.

Now, in a CALCA block, multiply the two ratios together.  Then, send this
value to KSCALE on the AIN block.  At the calibration T and P, the KSCALE
should be 1.0000.  

Jim

-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx] On
Behalf Of kirk.d.carver@xxxxxxxxxxxxxx
Sent: Sunday, January 22, 2006 5:32 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Typical Orifice Flowmeter Compensation Calculations 

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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