In natural gas measuring techniques, the natural gas mass flow rate is usually measured employing experimental facilities for density calculation, volume flow meters and other peripheral equipment such as temperature and pressure sensors. In order to simplify natural gas mass flow metering at natural gas pressure drop stations (CGS), this work presents an easy and precise method for measuring natural gas density. The method is based on a correlation that calculates the molecular weight and density of natural gas stream as a functional of the temperatures and pressures of natural gas before and after a throttle valve. These easily measurable properties at the natural gas pressure drop station are employed to calculate, firstly, the Joule Thomson (JT) coefficient and then density based on a developed correlation. For developing the corresponding correlation and also validating the results, a huge database including the practical data of 6 selected main natural gas fields of Iran is used. In fact, 50% of the available experimental data (three fields) have been used to develop the correlation and the remaining 50% (the other three fields) are used in accuracy assessment step. The results show that the error in calculating density doesn't exceed 1.2%, while for more than 70% of the states the error is even less than 0.6% and the average error is less than 0.4%. MAE (mean absolute error) and STD (standard deviation of absolute error) are also employed in order to validate the correlation results. The validation shows satisfactory calculation accuracy.

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