This part of API MPMS Ch. 14.3/AGA Report No. 3 has been developed as an application guide for the calculation of natural gas flow through a flange-tapped, concentric orifice meter, using the U.S. customary (USC) inch-pound system of units.

For applications involving international system (SI) of units, a conversion factor can be applied to the results (Qm, Qv , or Qb) determined from the equations in 4.3. Intermediate conversion of units will not necessarily produce consistent results. As an alternative, the more universal approach specified in API MPMS Ch. 14.3.1/AGA Report No. 3, Part 1 can be used. The meter has to be constructed and installed in accordance with API MPMS Ch. 14.3.2/AGA Report No. 3, Part 2.