Section 501.250  Sample Testing of Diaphragm Meters

a)         A utility may, at its option and upon giving notice to the Commission, adopt scientific sample procedures for new and in-service diaphragm meters.

b)         A utility shall develop sample testing lots for new meters that consist of meters of a single type and size that were manufactured under the same conditions and at essentially the same time. All sample testing procedures shall be in accordance with Inspection Level II of ANSI/ASQ Z1.4-2008.

c)         A utility shall establish meter sample testing lots for in-service meters that consist of meters of a similar type, size and year of installation or year of purchase. In the ninth and every subsequent year thereafter that the meters are in service, a utility shall test their accuracy in accordance with Inspection Level II of ANSI/ASQ Z1.4-2008.

d)         In order to comply with the accuracy limits of Section 501.170, a utility's sample testing plan for new meters shall provide an acceptable quality limit not to exceed 1.0% in order to assure a process average of at least 99%.

e)         A manufacturer shall test a new meter, and the resulting test record shall accompany the meter to retirement. A utility shall use the manufacturer's test as the initial test of the meter. However, if a utility tested the new meter prior to placing it into service, then the utility shall use its test as the meter's initial test.

f)         A utility's sample testing plan for meters in service shall provide an acceptable quality limit of 6.5% in order to assure a process average of at least 93.5%. A meter is deviant if the average of its check-rate and capacity-rate accuracy test results in accuracy more than 3.0% fast or 3.0% slow. A utility must complete all sample tests by the end of the calendar year in which the tests are due for completion.

g)         If a utility determines that a meter lot has failed sample testing, the utility shall remove all remaining meters in the failed lot from service within 24 months after completion of the current year's sampling.

(Source:  Amended at 41 Ill. Reg. 351, effective December 29, 2016)