Metrological performance of diaphragm gas meters in distribution networks

• In natural gas distribution networks almost totally diaphragm gas meters are installed.
• Knowing the errors of the existing meters is relevant in consumer protection.
• Knowing the errors of the existing meter is relevant for unaccounted for gas estimation.
• The results of metrological tests on 402 diaphragm gas meters are presented.

In natural gas distribution networks a great number of domestic diaphragm gas meters are currently installed (about 15 million in Italy) and most of them are very old meters. Furthermore, some National Authorities nowadays impose strict roll-out procedures of the existing meters with new smart meters. To this aim, diaphragm meters in “hybrid” configuration equipped with electronic and transmission devices are supposed to be widely installed by natural gas distribution companies in the first roll-out campaigns, since they present a fully developed technology despite of the new ultrasonic and thermal mass meters.In this paper the author presents the results of a wide experimental study aimed to assess how metrological performance of diaphragm gas meters worsen over time as function of age, installation conditions, manufacturing technology, etc.The results of the experimental analysis show that a significant number of the meters investigated failed subsequent verification and presented a not excellent stability. On the other hand, the average percentage errors and the weighted mean error of the meters were measured basically close to zero, also for very old meters.