Scope : This Guideline provides a method to check that the meter and prover pressure indicators are functioning correctly. This is achieved by applying known pressures to the indicators and comparing them to the actual pressures.
Frequency: 3 months
PRESSURE INDICATOR CALIBRATION PROCEDURE
PREPARATIONS:
This test may be performed with the metering stream in service.
Give a brief description of the test in the Metering Log Book.
Record the results of this test on the Pressure Indicator Calibration Test Sheet, attached.
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. Pressure Source
PROCEDURE:
The Pressure Indicator shall be checked using the following procedure: –
a) Isolate the indicator from the main process line and return it to the instrument workshop.
b) Connect the tester pressure source to the indicator. The pressure source may be a dead weight tester or a pneumatic pressure comparator (example; Truck pressure calibrator).
c) Apply pressure to the indicator at the following nominal points on its span, with both rising and falling pressure:
0%, 25%, 50%, 75% and 100%.
d) Over-range the indicator to approximately 105% between the rising and falling pressures.
e) Complete the pressure indicator test sheet. Record the pressure indications and the actual pressures.
f) If the calibration check is within tolerance, the test is complete.
g) If the calibration check is out of tolerance indicator adjustment is required.
h) Adjust the zero and span to calibrate the indicator then repeat steps c) to e).
i) Complete the pressure indicator test sheet and return the pressure indicator to service.
j) Check all impulse lines for leaks.
PRESSURE INDICATOR TEST SHEET
