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FCB100, FCB400 COMMISSIONING AND PROVING | PG/CORIOLIS/PROVING-EN REV. A
5 Site and equipment considerations
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Proving
The proving can be influenced by many factors, so it is important
to consider the following:
1. Verification of calibrations on all references should be
done; i.e. pressure, temperature, density, and volume.
2. The repeatability can easily affected by the flow pulsation
of positive displacement pumps.
3. If a valve leakage occurs in the system this can lead to an
incorrect meter zero or allow flow to bypass the prover.
To ensure tightness, double block and bleed isolation
valves are recommended.
4. The same conditions for the normally expected operation
should be used for proving the meter.
5. The flow conditions have to be steady during the proving
run in order to guarantee repeatable results. The
following flow conditions must be at a stable level from
the input of the meter under test to the outlet of the
prover:
•
Pressure
•
Temperature
•
Density
•
Flow rate
6. For mass proving, an error in the density measurement
on the prover leads to a meter factor error. The density
meter factor should be checked using a pycnometer or
hydrometer. For this purpose the following tolerances
should be maintained:
•
The permissible temperature difference should not
exceed 0.2°F
•
Pressure difference should not exceed 1 psi
•
The repeatability of the density meter factor (DMF)
should be 0.05% or better between two pycnometer
measurements in series.
7. Of course, a check of the detector switches of the prover
and the certified measuring section for integrity and
functionality must be done.
8. The run time can be shortened by a higher flow rate; thus,
a larger small volume prover (SVP) may be needed for the
CoriolisMaster. For estimation purposes, 33 % can be
deducted from the maximum flow rate of a small volume
prover sizing chart (Estimated value).
9. Flashing can be avoided by ensuring that there is
sufficient back pressure on the testing meter and the
flow prover.
10. In applications where the pressure fluctuates, the missing
Coriolis pressure compensation can lead to repeatability
and reproducibility problems.
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Zero point adjustment
The perfect meter zero will produce a meter factor near 10000.
Devices in the CoriolisMaster series do not necessarily require
zero point adjustment. Performing a zero point adjustment is
only recommended in the following cases:
•
For measurements in the lower flow range
(below 10 % of Q
max
•
If particularly high accuracies are required
(0.1 % or better).
•
If the operating conditions (pressure and temperature)
deviate greatly from the reference conditions (see data
sheet).
At particularly small flow rates, the meter zero has a major
influence on the meter factor.
1. A zero adjustment is recommended before the first use.
2. The zero adjustment result should be lower than 0,1 %.
3. A new proving meter factor should be determined, if a meter
is re-zeroed.
DN).
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