How to calibrate steam flow DP transmitter
Material
Data sheet
Pressure calibrator (std)
Multimeter (std)
Hart communicator
Step
*Ask panel man to put the controller in manual mode for control loop and to put it on MOS for ESD loop.
*Hook up HART Communicator and verify some parameters by refer to data sheet. Typical parameters are, tag number, PV, LRV and URV.
*Isolate the instrument from the process.
*Release both pressure and drain low and high side liquid throughout manifold drain.
*Connect pressure calibrator to high side of manifold
*Expose the low side to atmosphere
*Hook up a multimeter in series with the signal to the DCS to measure current signal.
*Apply pressure as per data sheet LRV (normally 0mmH2O)
Multimeter should show 4mA
If not, do zero adjustment at transmitter using HART Communicator
*Apply pressure as per data sheet URV
Multimeter should show 20mA
If not, do span adjustment at transmitter using HART Communicator
*Verify the linearity by increasing and decreasing the pressure (0%,25%,50%,75%,100%,75%,50%,25% and 0%of range)
*Fill up back water until half of seal pot.
*After completion of the job ask panel operator to put loops back in normal mode or normalize the MOS
Example calculation
Instrument calibrated range: 0 – 2500 mmH2O
Process calibrated range: 0 – 7000 kg/h
Q =K P
0% 0 mmH2O = ( 0/2500) x 7000
= 0 kg/h
50% 1250 mmH2O = ( 1250/2500) x 7000
= 4949.75 kg/h
100% 2500 mmH2O = ( 2500/2500) x 7000
= 7000 kg/h
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