Page 225 - Water Loss Control

198 Cha pte r T w e l v e

Fire Line Meter Evaluation
Meter Size Test Data Possible Cause
Bypass Meter
6"Compact fire line 192% @ 4 gpm • Broken Rotor Blades
96% @ 45 gpm • Adjusting vane moved to (−)
99% @ 500 gpm • Rotor Bearings and/or thrust bearings worn
• Debris caught in blade
Detector Check Valve
• Worn seat
• Debris preventing closure
Large Meter
6"Compact fire line 100% @ 4 gpm • Jetting from strainer and/or installation
100.3% @ 45 gpm • Adjusting vane moved to (+)
105% @ 500 gpm • Coating on rotor and/or chamber
6"Compact fire line 100% @ 4 gpm • Leaking downstream isolation valve
103.3% @ 45 gpm
101% @ 100 gpm
100% @ 500 gpm
Bypass Meter
• Adjusting vane moved to (+)
• Coating on rotor and/or chamber

Source: Water Loss Control Manual, 1st ed.
TABLE 12.10 Evaluating Customer Meter Accuracy Test Results (Continued)

To properly evaluate a tested meter, a high level of confidence is needed in the
integrity of the test data. It is, therefore, essential that meter testing procedures are fol-
lowed carefully in conducting the meter accuracy test. Sensus allows a +/− 1½% accu-
racy spread on Turbo (turbine) meters, fire line meters, and compound meters tested at
normal operating ranges. At low flows and crossover flow rates on compound meters,
Sensus allows +1½ to −5% accuracy. These limits are more stringent than AWWA stan-
dards. See AWWA standards C701, C702, C703, and C704 for additional guidelines. 11–14
When meter accuracy test results indicate questionable meter performance, be cer-
tain to review whether the test process included testing at low, medium, and high flows
(manufacturer’s or AWWA recommendations), and confirm a minimum duration of
one sweep on the tested meter register. If these conditions were not met during the test-
ing, then the test process should be repeated with particular attention paid to these test
requirements.
When reviewing the meter accuracy test results, be mindful to look for:

• Normal operating range tests. Is the minimum flow test 95 to 101.5%? If either
one is not within the range, the meter should not be geared or adjusted to meet
specifications without repair. A complete meter replacement may be required.