This Guideline provides a method to check that the meter and prover pressure transmitters are functioning correctly. This is achieved by applying known pressures at the transmitters and comparing them to the displayed pressures.
Frequency: 3 months
PRESSURE TRANSMITTER CALIBRATION PROCEDURE
PREPARATIONS:
If stable pressure conditions exist, and a manual value can be input at the flow computer, then this test may be performed with the metering stream in service. Otherwise, ensure that the meter stream is off-line and out of service.
Give a brief description of the test in the Metering Log Book.
Record the results of this test on the Pressure Transmitter Calibration Test Sheet.
Verify that the certificates for the test equipment are valid.
Check that the test equipment serial numbers and certification dates are accurately recorded on the test sheet and correspond with the test equipment used. Ensure the instrument tag and serial numbers are recorded on the test sheet.
CALIBRATION EQUIPMENT:
A) Dead Weight Tester
B) Digital Multimeter
PROCEDURE:
The Pressure Transmitter shall be checked using the following procedure: –
a) Isolate the transmitter from the main process line by closing the isolation valve at the main line.
b) Vent/drain the transmitter by slowly opening the instrument impulse line fitting.
c) Connect the deadweight tester pressure source to the transmitter at the instrument impulse line fitting.
d) Monitor the current in the instrument loop, at back of panel in the control room, using the certified digital
multimeter.
f) Apply pressure to the transmitter at the following nominal points on its span, with both rising and falling pressure: 0%, 25%, 50%, 75% and 100%.
g) Over-range the transmitter to approximately 105% between the rising and falling pressures.
h) Complete the pressure transmitter test sheet. Record the current at the DMM and the pressure reading at the flow computer.
i) If the calibration check is within tolerance, the test is complete.
j) If the calibration check is out of tolerance transmitter adjustment is required.
k) Adjust the zero and span to calibrate the transmitter then repeat step e).
l) Complete the pressure transmitter test sheet, re-instate the loop and return to service.
m) Check all impulse lines for leaks.
n) Enter details of all tests in the Metering Log Book.
PRESSURE TRANSMITTER TEST SHEET
