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Custody Gas Orifice Meter Plate Calculation


Custody orifice plate calculations for gases (pressure and temperature compensated) are based on the Reader-Harris 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 Square-Edged 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 20C (or 68F). Note that when solving for orifice bore the calculations may not converge for a beta ratio greater than 0.8.


References:

  • "Third Edition of the Manual of Petroleum Measurements Standards, Chapter 14 - Natural Gas Fluids Measurements, Section 3 - Concentric Square-Edged Orifice Meters, Part 3 - Natural Gas Applications," American Petroleum Institute (August 1992).

    Custody Gas Orifice Meter Plate Calculation
    Copyrighted 2001, 2003
    Last updated 04May03