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TRU/FLO Compound Meter Installation and Maintenance Guide
If a low flow accuracy test shows poor results, it can indicate one of
several things:
•
The T-10 strainer is clogged and requires cleaning.
•
The T-10 chamber needs to be replaced.
•
The o-ring in the outlet of the T-10 chamber needs to be
replaced.
•
The mainline valve is damaged or is wearing out and needs to
be replaced.
A poor accuracy test needs to be repeated to make sure that there
was not an error in the test setup to cause the poor results.
Acceptable in-field low flow accuracy test results are reported in the AWWA
M6 manual.
2
Second, run a test at medium flow or high flow. This ensures that
the turbine measuring assembly is working properly.
A poor accuracy test with high flow can indicate one of the
following:
•
The calibration vane needs adjustment based upon the high
flow results.
•
The turbine measuring assembly needs maintenance:
a. Examine the magnet drive for damage.
b. Examine the calibration vane assembly for damage.
c. Examine the rotor assembly for damage.
d. Clean the bronze strainer.
•
The register on the meter can be the wrong size.
•
The meter has an up-flow obstruction.
•
The meter is not installed with the proper install procedures.
When the meter transitions from low flow to high flow, there is a
flow range called crossover. During crossover, the water is
measured by both the T-10 chamber and the turbine. A brief dip in
accuracy is seen when transitioning through crossover.
When performing an accuracy test, be aware of the crossover range. If
an accuracy test results in less than the allowable range for low flow and
high flow, you might be testing in the crossover range. Accuracy can not
dip below 90% in the crossover range. The crossover range can also
cover a small flow range. For more details see AWWA C702.
For more information, please consult the TRU/FLO Field Testing Guide
and AWWA's M6 manual.
Why Maintenance is Important
29
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