1 Scope
This International Standard concerns the measurement of calorific value of natural
gas and natural gas substitutes by non-separative methods, i.e. methods that do not
involve the determination of the gas composition nor calculation from it. It describes
the principles of operation of a variety of instruments in use for this purpose, and
provides guidelines for the selection, evaluation, performance assessment, installation
and operation of these.
Calorific values can be expressed on a mass basis, a molar basis or, more commonly,
a volume basis. The working range for superior calorific value of natural gas, on the volume basis, is usually between 30 MJ/m 3 and 45 MJ/m 3 at standard reference conditions (see ISO 13443). The corresponding range for the Wobbe index is usually between 40 MJ/m 3 and 60 MJ/m 3 .
This International Standard neither endorses nor disputes the claims of any commercial
manufacturer for the performance of an instrument. Its central thesis is that fitness-for-purpose
in any particular application (defined in terms of a set of specific operational requirements)
can be assessed only by means of a well-designed programme of experimental tests.
Guidelines are provided for the proper content of these tests.
BS EN ISO 15971:2014 history
2009BS EN ISO 15971:2014 Natural gas. Measurement of properties. Calorific value and Wobbe index