Supercompressibility factor

Figure 12-76. Basic horsepower for a machine with intake of 14.5 psia, with k value for air (1.396) and supercompressibility factors neglected. (Used by permission Cole, S. L. Oil and Gas Journal, V. 58, No. 6, 1960. PennWell Publishing Company. All rights reserved.)...

For determining supercompressibility factors of natural gas mixtures, see Manual for the Determination of Supercompressibility Factors for Natural Gas, American Gas Association, New York, 1963 and A.G.A Gas Measurement Committee Report No. 3, 1969. 

Because the value of Z for natural gas is significantly less than unity at ambient temperatures and at pressures greater than 1 MPa (145 psia), the compressibility must be taken into account in gas measurement gas purchased at high line pressure will give a greater volume when the pressure is reduced than it would if the gas were ideal. Natural gas pipeline operators use a. supercompressibility factor, also called Z, but defined as... 

An inaccurate method of sample heating value or the application of average figures can cost a s company millions of dollars in lost revenue and/or contribute to the lost and unaccounted for volumes. Proper sampling philosophy can also lend accuracy to the sample analysis chemical composition in determining the correct supercompressibility factors in place of system averages. 

There are three modules that perform the necessary calculations required for flow measmement FL WRAT, AGAFPV, and ORFLC. The first is the orifice flow rate calculation, C. (See APPENDIX A for detailed information.) For this calculation the operator can select tap location, UPSTREAM or DOWNSTREAM for flange taps. Note pipe taps were not considered since they are not used. The second is the supercompressibility factor, Fpv. Finally, the gas flow rate is calculated in MMCFD and MMBTUD. 

Compressibility factor is also known as gas deviation factor, supercompressibility, or z-factor. Sometimes the reciprocal of compressibility factor is called supercompressibility. 

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