Table of Contents
Advertisement
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 common used systems, portable provers have the advantage of more closely re-
producing the condition under which the product is normally delivered.
Use Accurate Prover
Scientifically designed provers are commercially available for proving meters, and no other kind should
be used. 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 volumet-
ric 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.
These provers are not merely truck compartments or drums, but are scientifically designed test measures,
having proper drainage means built into them, a calibration gauge glass neck, and protection against de-
formation (which causes volume changes).
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.
Setting a Prover
The prover should be set level, using the levels provided on the prover, or separate ones. This insures con-
sistent results when moving the prover from meter to meter.
Where to Test a Meter
The best place to test is in its normal operating position, instead of a test stand. In this way, the correct-
ness of the installation and of the operation conditions will be verified by the test. Always test a meter
with the same liquid it is to measure, because a difference in viscosity, temperature and system plumbing
slightly affects meter accuracy.
Discharge Line from Meter
Where a portable prover is used, the liquid is generally discharged in to the prover in the same manner, as
a normal delivery would be made. Where a special test connection is used, the discharge line must be ar-
ranged to drain to the same point on each test. The meter flow rate and off/on is controlled at the end of
the discharge line.
Wetting the Prover
Reset the meter register to zero, and fill the prover to the zero or 100% marking of the scale. Disregard
the meter reading. Drain the prover, and reset the register. The reason for disregarding the first meter
reading is that the prover must be wetted, as its calibrated capacity is determined on its wet measure ca-
pacity by its manufacturer, and because the prover will be wet for the subsequent tests to be run.
Advertisement
Table of Contents
Troubleshooting
