ISO INTERNATIONAL STANDARD 15971 First edition 2008-12-15 Natural gas Measurement of properties Calorific value and Wobbe index Gaznaturel-MesuragedespropriétesPouvoircalorifiqueet indice de Wobbe Referencenumber ISO 15971:2008(E) @ISO2008 Not for Resale ISO15971:2008(E) PDFdisclaimer This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In accepts noliabilityinthisarea. Adobe is a trademark of Adobe Systems Incorporated. Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by IsO member bodies. In the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below. COPYRIGHTPROTECTEDDOCUMENT ?ISO2008 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either isO at the address below or isO's memberbody in the country of the requester. ISO copyright office Casepostale56.CH-1211Geneva20 Tel.+ 4122749 0111 Fax + 41 22 749 09 47 E-mail copyright@iso.org Web www.iso.org Published inSwitzerland @ ISO 2008 -All rights reserved without license from IHS Not for Resale ISO15971:2008(E) Contents Page Foreword. Introduction 1 Scope 2 Normative references 3 Terms and definitions.. 3.1 Calorific value and Wobbe index. 3.2 Water content of gas .... 3.3 Performance classification. 3.4 Terms from metrology... 4 Principles of measurement.. 4.1 Introduction.... 4.2 Directcombustioncalorimetry...... 4.3 Indirect methods..... 5 4.4 Inferential methods. 5 Performance assessment and acceptance tests.. 5.1 Performanceassessmentforinstrument selection.. 5.2 Factoryandsiteacceptancetests...... 20 6 Samplingand installation guidelines 21 6.1 Sampling.... 21 6.2 Installation guidelines 22 7 Calibration.. 25 7.1 Calibration procedures. 25 7.2 Calibration gases.... 8 27 8.1 Verification procedures.. 27 8.2 Verification gases .... .28 9 Maintenance .29 9.1 Preventivemaintenance. 29 9.2 Correctivemaintenance. 10 Quality control.... 10.1 General.. 29 10.2 Environmental parameters and ancillary equipment.. 31 10.3 Instrumental factors..... 32 Annex A (normative) Symbols and units... AnnexB(informative)Examplesoftype-approvalandtechnicalspecifications.. .34 Annex C (informative) Class 0 mass-basis calorimetry ... AnnexD(informative)Direct combustion calorimetry .40 AnnexE(informative)Stoichiometric combustion devices... AnnexF(informative)Effect ofnon-alkanegaseson stoichiometriccombustion devices... 47 AnnexG (informative)MeasurementofWobbe index... 48 Bibliography.... .49 Copyright International Oorganization forstandardization'ghts reserved ili efrom IHS Not for Resale