Scope: This Guideline provides a method to check that the liquid density calculation is functioning correctly by injecting simulated density signals.
Frequency: As needed
LIQUID DENSITOMETER CALCULATION TEST PROCEDURE
PREPARATIONS:
If stable density 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 Liquid Density Computation 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 flow computer tag and serial numbers are recorded on the test sheet.
CALIBRATION EQUIPMENT:
A) Densitometer Simulator
B) Frequency Counter / Timer
PROCEDURE:
The liquid densitometer calculation shall be checked using the following procedure: –
a) Isolate all power supplies to the densitometer and disconnect the field wiring for the input to be tested at the field terminals.
b) Connect the densitometer simulator to the field terminals. Set the timer counter to measure periodic time and connect it to the simulator.
c) Confirm that the densitometer constants displayed on the current densitometer calibration certificate are exactly the same as the constants entered in the flow computer.
d) Record on the liquid density calculation test sheets the values for densitometer pressure and temperature.
e) From the densitometer calibration certificate select a periodic time that will simulate a density within the normal operating range of the system and enter this periodic time on the simulator.
f) Record on the test sheet the value of periodic time displayed on the timer counter and the value of periodic time and density displayed on the flow computer.
g) If the If the displayed and expected densities are in tolerance, the test is complete.
h) If the displayed and expected densities are out of tolerance, investigate the reason and attempt corrective action.
NOTE: If the periodic time is correct but the calculated density is wrong, the flow computer data/configuration should be checked.
k) Once the corrective action has been taken and the displayed and expected densities are within tolerance, complete the test sheet. The test is now complete and the flow computer should be returned to the ‘As Found’ condition.
l) Repeat steps e) to k) for a second and third value of periodic time.
m) Enter details of all tests in the Metering Log Book.