Scope
This Guideline provides a method to verify that installed liquid densitometers
are functioning correctly at a single point. This is achieved by comparing the
actual transducer periodic time ‘in air’ against the value recorded on the
transducer calibration certificate as the “air check” periodic time.
Frequency As needed.
LIQUID DENSITOMETER CALIBRATION AND VERIFICATION TEST
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 Densitometer Air Check Test Sheet, attached.
Ensure the oil densitometer has a valid calibration certificate and that the serial number on the certificate corresponds with the installed densitometer. Ensure that the serial and tag numbers are recorded on the test sheet.
Check that the test equipment serial numbers and certification dates are accurately recorded on the test sheet and correspond with the test equipment used.
CALIBRATION EQUIPMENT:
A) Frequency Counter / Timer
PROCEDURE:
The oil densitometer shall be checked using the following procedure:
a) Close the densitometer inlet and outlet isolation valves, drain
vent the densitometer and disconnect from the pipeline.
b) Clean and dry the wetted parts of the transducer and leave
them open to the ambient air.
c) Connect a timer/counter across the output from the densitometer.
d) Switch the power on and allow the output to stabilise.
e) Note the periodic time of the output signal.
f) Complete the Liquid Densitometer Air Check Test Sheet. If
the measured periodic time and certified periodic time are
within tolerance, the test is complete.
g) If the measured periodic time and certified periodic time are
out of tolerance investigate the reason and attempt corrective
action. I.e. cleaning of the tubes with a solvent.
h) Once the measured and certified periodic times are within
tolerance complete the test sheet. The test is now complete
and the densitometer may be re-installed.
i) Enter details of all tests in the Metering Log Book. Record if
the densitometer has been replaced and the replacement
number of the replacement unit.
LIQUID DENSITOMETER AIR CHECK TEST SHEET
