Meter Calibration - TCS 700-30 Installation, Operation & Maintenance Manual

TCS900003, Rev.6
04/26/2016
Page 13

Meter Calibration

The method of proving should be selected, and necessary provisions made, during the design stage of the
installation. Of the most commonly used systems, portable provers have the advantage of more closely reproducing
the conditions under which the product is normally delivered.
Use an Accurate Prover
Scientifically designed provers are commercially available for proving meters, and no other kind should be used.
Scientifically designed test measures have proper drainage means built into them, a calibration gauge glass neck
and protection against deformation (which would cause volume changes).
Scientifically designed provers are not merely truck compartments or drums. A "homemade" prover, whether a
drum or a tank is not likely to be satisfactory, and may cause expensive errors due to inaccurate meter calibration.
Even scientifically designed provers should be checked periodically for accuracy. Weights and Measures officials
have been very cooperative in giving assistance to checking privately owned volumetric provers.
Recommended size of test measure
The prover capacity should be equal to at least one minute's flow through the meter at its maximum rate.
Setting the Prover
The prover should be set level, using the levels provided on the prover, or separate leveling means. This insures
consistent results when moving the prover from meter to meter and provides the basis for accurate readings on the
prover scale.
Where to Test a Meter
The best place to test a meter is in its normal operating position, instead of a test stand. In this way, the correctness
of the installation and of the operating conditions of the system will be verified by the test. Always test a meter with
the same liquid it is to measure. Even slight differences in viscosity, temperature or system plumbing can have a
significant effect on meter accuracy.
Discharge Line from Meter
Where a portable prover is used, the liquid is generally discharged into the prover in the same manner as a normal
delivery would be made (with a hose reel and nozzle, for example). Where a special delivery test connection is
used, the discharge line must be arranged to drain to the same point on each test. The meter flow rate and start and
stop must be controlled at the end of the discharge line.
Wetting the Prover
Reset the meter register to zero, and fill the prover to the zero line or 100% marking of the scale. Disregard this
meter reading. Drain the prover and reset the register. The reason for disregarding the first meter reading is that
the prover must be wetted. The calibrated capacity of the prover has been determined by its manufacturer based its
wet measure capacity. Once wetted, the prover will be wet for all the subsequent tests to be run.
Allow the prover to drain for a set amount of time before closing the dump valve. 30 seconds is a commonly used
time interval. However, you must ensure that the prover is completely empty prior to closing the dump valve. This
time interval must be the same for each test to ensure uniform results. If a considerable length of time is to elapse
between tests (lunch break or phone call), the wetting operation can be eliminated by allowing the prover to remain
full until the next test is to be run.
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