BS EN ISO 15971:2014

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Principles of measurement
5 Performance assessment and acceptance tests
6 Sampling and installation guidelines
7 Calibration
8 Verification
9 Maintenance
10 Quality control
Annex A (normative) - Symbols and units
Annex B (informative) - Examples of type-approval and
        technical specifications
Annex C (informative) - Class 0 mass-basis calorimetry
Annex D (informative) - Direct combustion calorimetry
Annex E (informative) - Stoichiometric combustion devices
Annex F (informative) - Effect of non-alkane gases on
        stoichiometric combustion devices
Annex G (informative) - Measurement of Wobbe index
Bibliography

Specifies 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 calculations from it.

This InternationalStandard concerns the measurement of calorific value ofnaturalgas 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 varietyof instruments in use forthis purpose, and providesguidelines for the selection, evaluation, performance assessment, installation andoperation 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 calorificvalue of natural gas, on the volume basis, is usuallybetween 30MJ/m³and 45 MJ/m³ at standard reference conditions (see ISO13443). The corresponding range for the Wobbeindex is usuallybetween 40 MJ/m³ and 60 MJ/m³.

This International Standard neitherendorses nor disputes the claims of any commercial manufacturer for theperformance of an instrument. Its central thesis is that fitness-for-purpose in anyparticular application (defined in terms of a set ofspecific operational requirements) can be assessed onlybymeans of a well-designed programme of experimental tests. Guidelines are provided for the proper content of these tests.