Natural gas measurement today is accomplished through the use of two different classifications of gas meters. The first consists of inferential type meters, including, orifice, ultra-sonic and turbine meters, and the second is the positive displacement meters, which consist of diaphragm and rotary displacement meters. The inferential type meters are so-called because rather than measuring the actual volume of gas passing through them, they “infer” the volume by measuring some other aspect of the gas flow and calculating the volume based on the measurements. The positive displacement type meters are so-called because they measure the actual volume of gas displaced through them.
The reliability of the rotary positive displacement meter, rangeability, long-term accuracy, and ease of installation, maintenance and testing have made this meter a favorite among gas utilities for billing purposes in industrial and commercial applications. Rotary meters have continue to gain popularity in the production and transmission markets.
This document briefly discusses the concepts of rotary positive displacement meters and the related operating principles, sizing practices, accuracy and rangeability, along with the installation, start-up and maintenance of the meters.
Principles of Operation