This manual discusses gas flow measurement based on philosophies expressed in AGA (American Gas Association) and API (American Petroleum Institute) guidelines. NOTE: AGA and API do not certify manufacturers’ equipment for flow measurement. Products of The Flow Computer Division of Emerson Process Management are in compliance with AGA and API guidelines. The American Gas Association (AGA) has published various reports describing how to measure the flow of natural gas, starting with AGA Report No. 1, issued in 1930, describing the measurement of natural gas through an orifice meter. This report was revised in 1935 with the publication of AGA Report No. 2 and again in 1955 with the publication of AGA Report No. 3. The report was revised again in 1969, 1978, 1985, and 1992, but has remained AGA Report No. 3 — Orifice Metering of Natural Gas and Other Related Hydrocarbons. Thus, AGA3 has become synonymous with orifice metering. In 1975, the American Petroleum Institute (API) adopted AGA Report No. 3 and approved it as API Standard 2530 and also published it as Chapter 14.3 of the API Manual of Petroleum Measurement Standards. In 1977, the American National Standards Institute (ANSI) also approved AGA Report No. 3 and referred to it as ANSI/API 2530. Thus references to API 2530, Chapter 14.3 and ANSI/API 2530 are identical to AGA Report No. 3. In 1980 (revised in 1984 and in 1996), AGA Report No. 7– Measurement of Fuel Gas by Turbine Meters–was published, detailing the measurement of natural gas through a turbine meter. While AGA No. 3 and AGA No. 7 detail methods of calculating gas flow, separate documents have been created to explain the calculation of the compressibility factor, used in both AGA No. 3 and AGA No. 7. The older method, called NX-19, was last published in 1963. A more comprehensive method was published in 1985 as AGA Report No. 8. This report was revised in 1992. In 1992, the API released Chapter 21, Section 1, which addressed the application of electronic flow meters in gas measurement systems. It addresses the calculation frequency and the method of executing the AGA calculations.
EMERSON (2005) Flow Measurement