Section 501.180  Diaphragm Meters

a)         A utility shall install a new diaphragm meter set and revisions to an existing diaphragm meter set in accordance with the recommendations of ANSI B109.1, XQ0008 (June 2000) for diaphragm meters with a rated capacity less than 500 cubic feet per hour and in accordance with ANSI B109.2, XQ0009 (June 2000) for diaphragm meters with a rated capacity of 500 cubic feet per hour or greater.

b)         A utility furnishing natural gas service with diaphragm meters shall ensure the use of suitable meter proving or testing equipment to determine the accuracy of the meter. The average accuracy of a diaphragm meter is determined by averaging the accuracy of the check and open flow rates.

1)         The open rate is 95% to 105% of the rated capacity.

2)         The check rate is 20% to 33% of the rated capacity.

3)         The maximum allowable accuracy spread between the open and check rates' accuracy is 1.0%.

c)         A utility shall conduct periodic accuracy tests on all installed diaphragm meters at least every 120 months unless the utility has provided notification to the Commission regarding its plans to conduct sample testing in accordance with Section 501.250.

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