1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN ISO 6974-2:2012Natural gas Determinationof composition andassociated uncertainty by gaschromatographyPart 2: Uncertainty calculations (ISO6974-2:2012)BS EN ISO 6974-2:2012
2、BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN ISO6974-2:2012. Together with BS EN ISO 6974-1:2012, it supersedesBS EN ISO 6974-1:2001 and BS EN ISO 6974-2:2002, which arewithdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/
3、15, Natural Gas and Gas Analysis.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institutio
4、n 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 78387 6ICS 75.060Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 October 2012.Amendments issued sin
5、ce publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6974-2 May 2012 ICS 75.060 Supersedes EN ISO 6974-2:2002English Version Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 2: Uncertainty calculations (ISO 6974-2:
6、2012) Gaz naturel - Dtermination de la composition et de lincertitude associe par chromatographie en phase gazeuse - Partie 2: Calculs dincertitude (ISO 6974-2:2012)Erdgas - Bestimmung der Zusammensetzung und der zugehrigen Unsicherheit durch Gaschromatographie - Teil 2: Unsicherheitsberechnungen (I
7、SO 6974-2:2012) This European Standard was approved by CEN on 14 May 2012. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliog
8、raphical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsib
9、ility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece
10、, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Ma
11、nagement Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 6974-2:2012: EBS EN ISO 6974-2:2012EN ISO 6974-2:2012 (E) 3 Foreword This document (EN ISO 6974-2:2012) has been prepared b
12、y Technical Committee ISO/TC 193 “Natural gas“. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2012, and conflicting national standards shall be withdrawn at the latest by November 2012.
13、 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 6974-2:2002. According to the CEN/CENELEC Internal Re
14、gulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg,
15、Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 6974-2:2012 has been approved by CEN as a EN ISO 6974-2:2012 without any modification. BS EN ISO 6974-2:2012ISO 6974-2:2012(E) ISO
16、2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms and definitions . 14 Symbols . 14.1 Symbols . 14.2 Subscripts . 25 Calculation of uncertainty . 25.1 General considerations . 25.2 Principles . 55.3 Step 9 Calculation of uncertainty of mole
17、fractions . 55.4 Step 10 Calculation of the expanded uncertainty of mole fractions 11Annex A (informative) Calculation of processed component uncertainties for the methane-by-difference approach .12Annex B (normative) Uncertainties of relative response factors 13Annex C (informative) Alternative cal
18、culation of the uncertainty of the value of the unknown 14Bibliography .16BS EN ISO 6974-2:2012ISO 6974-2:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards
19、is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take pa
20、rt in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to pr
21、epare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that
22、some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 6974-2 was prepared by Technical Committee ISO/TC 193, Natural Gas, Subcommittee SC 1, Analysis of natural gas.This second edition of ISO 697
23、4-2, together with ISO 6974-1:2012, cancels and replaces ISO 6974-1:2000 and ISO 6974-2:2001, which have been technically revised.ISO 6974 consists of the following parts, under the general title Natural Gas Determination of composition and associated uncertainty by gas chromatography: Part 1: Gener
24、al guidelines and calculation of composition Part 2: Uncertainty calculations Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C8using two packed columns Part 4: Determination of nitrogen, carbon dioxide and C1to C5and C6+hydrocarbons for a laborator
25、y and on-line measuring system using two columns Part 5: Determination of nitrogen, carbon dioxide and C1to C5and C6+hydrocarbons for a laboratory and on-line process application using three columns Part 6: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C1to C8hydrocarbons u
26、sing three capillary columnsFuture subsequent parts of ISO 6974 are planned.iv ISO 2012 All rights reservedBS EN ISO 6974-2:2012ISO 6974-2:2012(E)IntroductionISO 6974 describes methods of analysis of natural gas and methods for calculating component mole fractions and uncertainties. ISO 6974 (all pa
27、rts) is intended for the measurement of H2, He, O2, N2, CO2and hydrocarbons, either as individual components or as a group, for example all hydrocarbons above C5, defined as C6+. This approach is suitable for a range of end applications, including calibrating gas mixtures and providing natural gas c
28、omposition and uncertainty data to be used in the calculation of calorific value and other additive physical properties of the gas. Details of these end applications are provided in ISO 6974-3 and subsequent parts of ISO 6974.ISO 6974-1 gives guidelines for calculating the mole composition of natura
29、l gas, determined using one of the gas chromatographic methods described in ISO 6974-3 and subsequent parts of ISO 6974. ISO 6974-1 also describes all the essential steps for setting up an analysis, including outlining the structure of the analysis, defining the working ranges and establishing the a
30、nalytical procedure. This part of ISO 6974 describes the steps required to calculate the uncertainty of the component mole fractions of natural gas determined using gas chromatography.ISO 6974-3 and subsequent parts of ISO 6974 describe different gas chromatographic methods. These methods cover both
31、 daily practice in the laboratory and on-line field applications. ISO 6974-1:2012, Annex A, provides a comparison of the characteristics of the analytical methods described in ISO 6974-3 and subsequent parts of ISO 6974.It is intended that this part of ISO 6974 be used in conjunction with ISO 6974-1
32、 and a method of analysis, e.g. ISO 6974-3 or subsequent parts of ISO 6974.ISO 6974-1:2012, 5.5, describes the conventional normalization approach for calculating processed mole fractions from raw mole fractions. When conventional normalization is used for multiple operation methods without bridging
33、, the uncertainties of the calculated mole fractions will be conservative. If a more accurate assessment of uncertainty is required, an alternative approach to normalization, using the generalized least squares (GLS) method, can be used; this is described in ISO 6974-1:2012, Annex B. Further alterna
34、tive approaches are available for calculating processed mole fractions, including methane-by-difference (see ISO 6974-1:2012, Annex C) and data harmonization (see Reference 1). ISO 2012 All rights reserved vBS EN ISO 6974-2:2012BS EN ISO 6974-2:2012Natural gas Determination of composition and associ
35、ated uncertainty by gas chromatography Part 2: Uncertainty calculations1 ScopeThis part of ISO 6974 describes the process required to determine the uncertainty associated with the mole fraction for each component from a natural gas analysis in accordance with ISO 6974-1. 2 Normative referencesThe fo
36、llowing referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 6974-1:2012, Natural gas Determination of compositio
37、n and associated uncertainty by gas chromatography Part 1: General guidelines and calculation of compositionISO/IEC Guide 98-3, Uncertainty of measurement Part 3: Guide to the expression of uncertainty in measurement (GUM:1995)3 Terms and definitionsFor the purposes of this document, the terms and d
38、efinitions given in ISO 6974-1 apply.4 Symbols4.1 Symbolsbzparameters of the regression function (z = 0, 1, 2 or 3)bzmean parameters of the regression function (in “mean normalization” method)Cisensitivity coefficientk coverage factorK relative response factor with respect to the reference component
39、nitotal number of components (direct plus indirect, but excluding “other components”)njtotal number of gas standards or mixturesnltotal number of injections (and therefore total number of responses)s standard deviationT total mole fraction of all raw componentsINTERNATIONAL STANDARD ISO 6974-2:2012(
40、E) ISO 2012 All rights reserved 1BS EN ISO 6974-2:2012ISO 6974-2:2012(E)u() standard uncertainty (of the quantity in parentheses)U() expanded uncertainty (of the quantity in parentheses)x normalized mole fractionx*raw mole fractionx mole fraction calculated using the methane-by-difference approach A
41、nnex Ax adjusted mole fraction Annex Cy instrumental response of the specified analytey mean instrumental response (in “mean normalization” method)y adjusted instrumental response Annex CY instrumental response Annex C intercept of a first-order calibration function Annex C gradient of a first-order
42、 calibration function Annex C gradient of the calibration curve Annex Cmean of the distribution of non-linearity errors4.2 Subscriptscal calibration Annex Ai componentind components or groups of components to be analysed by indirect measurementj gas standard/mixturel injectionoc other componentsp, q
43、 indices defining a regression coefficientref reference (component or pressure)s index defining a componentwms working measurement standard5 Calculation of uncertainty5.1 General considerationsThe process of setting up a gas chromatograph for the analysis of natural gas consists of the steps outline
44、d in the flowcharts in Figures 1 and 2.Steps 1 to 8 are covered in ISO 6974-1. This part of ISO 6974 covers steps 9 and 10.2 ISO 2012 All rights reservedBS EN ISO 6974-2:2012ISO 6974-2:2012(E)START Primary calibration Determine analysis function: (a) Selection of reference gases (b) Measurement of r
45、eference gases (c) Regression analysis (d) Selection of regression function Performance evaluation Determine initial analysis function (a) Selection of reference gases (b) Measurement of reference gases (c) Regression analysis Step 4 Is primary calibration or performance evaluation required? Type 1
46、or Type 2 analysis? No Yes Type 1 Type 2 Are there any indirect components? No Yes Step 1: Define the working range ISO 6974-1:2012, 6.2Step 2: Define the requirements of the analytical method Step 5: Assign relative response factorsStep 3: Select equipment and working conditions FLOWCHART B ISO 697
47、4-1:2012, 6.3ISO 6974-1:2012, 6.4ISO 6974-1:2012, 6.5ISO 6974-1:2012, 6.6Figure 1 Procedure for determining mole fraction and uncertainty Steps 1 to 5 ISO 2012 All rights reserved 3BS EN ISO 6974-2:2012ISO 6974-2:2012(E)START FROM FLOWCHART A QA with a WMSRC with a WMS QA check RC Step 6 Quality ass
48、urance(QA) check or routine calibration (RC)?Yes Step 8: Calculation of component mole fractions Step 7: Analysis of samplesWill the analyser be used for routine operation?No Are uncertainties of component mole fractions required? FINISH Yes No Step 9: Calculation of uncertainty in mole fractions St
49、ep 10: Calculation of the expanded uncertainty in mole fractionsFINISH ISO 6974-1:2012, 6.7ISO 6974-1:2012, 6.7.3.2 ISO 6974-1:2012, 6.7.3.3ISO 6974-2:2012, 5.4ISO 6974-1:2012, 6.9ISO 6974-1:2012, 6.8ISO 6974-2:2012, 5.3Figure 2 Procedure for determining mole fraction and uncertainty Steps 6 to 104 ISO 2012 All rights reservedBS EN ISO 6974-2:2012ISO 6974-2:2012(E)5.2 PrinciplesUncertainties associated with the component mole fractions shall be calculated in accordance wi
