COMPENSATED FLOW

[samuels]

HELLO,
I am using a Siemens S7 plc to read the flow rate using a Orifice type of transmitter.The client also provides the pressure and temperature of the material in the line as analog values to the PLC.I am required to display a temperature and pressure compensated flow on the HMI.How is this done.Does anyone have a standard formula for the same or is there a standard Function block.

Thanks,
Samuels

 

[Macbeth]

The answer to your questions starts out some thing like this.
Boyles and Charles Law

((P1*V1)/T1)=((P2*V2)/T2)

P= pressure
T= Temperature
V= Volume

Set1 = Known conditions using your orifice plate coefficients
Set2 = Actual conditions

I don’t have enough time but to continue right now. I should have a more complete formula somewhere, if some one else does not post it I will Later.

 

[Macbeth]

OK here is the rest of the stuff I assumed you are metering gas flow. If you are not, then next time include more infomation and describe your process in some detail.

Q = Flow
P = Pressure (PSIA)
T = Temperature (Rankin)

Set1 = Known Flow (calculated from orifice data)
Set2 = Compensated Temp Flow (Substitute new temp)
Set3 = Compensated Pressure Flow (Substitute new press)

Q2 = SQRT(T1/T2) * Q1
Q3 = SQRT(P3/P1) * Q2

Actual Flow = Q3

PSIA = PSIG – 14.73
DegR = DegF + 460