
Custody Gas Orifice Meter Plate CalculationCustody orifice plate calculations for gases (pressure and temperature compensated) are based on the ReaderHarris Gallagher equation for the orifice coefficient found in the Third Edition of the Manual of Petroleum Measurements Standards, Chapter 14  Natural Gas Fluids Measurements, Section 3  Concentric SquareEdged Orifice Meters, Part 3  Natural Gas Applications. Flow is corrected back to a base (or contract) flowrate by compensation for base temperature, base pressure and base compressibility. Correction is also made for thermal expansion of the orifice plate and the pipe from a base temperature of 20°C (or 68°F). Note that when solving for orifice bore the calculations may not converge for a beta ratio greater than 0.8. References: Custody Gas Orifice Meter Plate CalculationCopyrighted 2001, 2003
