This International Standard provides the means for determining the energy of natural gas by measurement or calculation, and describes the associated techniques and the necessary measures to be taken. The calculation of thermal energy is based on the separate measurement of the quantity of gas transferred, expressed in mass or volume, and on its measured or calculated calorific value. It also provides the general means for calculating uncertainties.
NF X20-516:2014 Referenced Document
ISO 6976 Natural gas - Calculation of calorific values, density, relative density and Wobbe indices from composition*， 2016-08-01 Update