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Title: Overall Measurement Accuracy
Author: Robert W. Carson
Source: 1986 Gulf Coast Measurement Short Course (Now called ASGMT)
Year Published: 1986
Abstract: How many times in the recent past has your conversation turned to the cost of natural gas? What I would give to be a fly on the wall of a measurement superintendents office when he or she sits down to balance the books or to determine if the sales volume equals the purchase volume. According to the most recent AGA Gas Facts publication the average residential gas bill in 1960 was 104.46. Today it is close to 600.00 and according to my own gas bills, this seems conservative. No doubt about it we are talking about an expensive commodity. Measurement accuracy is a must. Invariably when the word measurement is mentioned, most measurement types immediately turn their thoughts to the meter. The meter certainly contributes to the science of measurement but it is not the only consideration. Besides metering there is instrumentation, pressure and temperature correction, and the rate structure. Natural gas is a compressible fluid, changing its volume with changes in pressure and temperature but not always uniformally depending on the composition of the gas. Generally the basic gas laws can be used for the application of correction factors, but there are also deviations from the basics called supercompressibility factors or super-expansibility factors. These factors are based on the chemical composition of the gas and the actual flowing temperature and pressure experienced at the meter.