1、DD ISO/TS29041:2008ICS 71.040.40NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWDRAFT FOR DEVELOPMENTGas mixtures Gravimetricpreparation Mastering correlationsin compositionThis Draft for Developmentwas published under theauthority of the StandardsPolicy and StrategyCommittee o
2、n 28 February2009 BSI 2009ISBN 978 0 580 61975 5Amendments/corrigenda issued since publicationDate CommentsDD ISO/TS 29041:2008National forewordThis Draft for Development is the UK implementation of ISO/TS29041:2008 and corrigendum 1:2009.This publication is not to be regarded as a British Standard.
3、It is being issued in the Draft for Development series of publications andis of a provisional nature. It should be applied on this provisional basis,so that information and experience of its practical application can beobtained.Comments arising from the use of this Draft for Development arerequested
4、 so that UK experience can be reported to the internationalorganization responsible for its conversion to an international standard.A review of this publication will be initiated not later than 3 years afterits publication by the international organization so that a decision can betaken on its statu
5、s. Notification of the start of the review period will bemade in an announcement in the appropriate issue of Update Standards.According to the replies received by the end of the review period,the responsible BSI Committee will decide whether to support theconversion into an international Standard, t
6、o extend the life of theTechnical Specification or to withdraw it. Comments should be sent tothe Secretary of the responsible BSI Technical Committee at BritishStandards House, 389 Chiswick High Road, London W4 4AL.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/15, N
7、atural gas and gas analysis.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard ca
8、nnot confer immunityfrom legal obligations.uReference numberISO/TS 29041:2008(E)ISO 2008TECHNICAL SPECIFICATION ISO/TS29041First edition2008-02-01Gas mixtures Gravimetric preparation Mastering correlations in composition Mlanges de gaz Prparation gravimtrique Matrise des corrlations en composition D
9、D ISO/TS 29041:2008ISO/TS 29041:2008(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes 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
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12、ariat at the address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 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 writin
13、g from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2008 All rights reservedDD ISO/TS 29
14、041:2008ISO/TS 29041:2008(E) ISO 2008 All rights reserved iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Normative references . 1 3 Symbols and abbreviated terms . 1 4 Mixture preparation by gravimetry 2 5 Unit conversion. 5 6 Inclusion of purity data 5 7 Gas property calculation 8 8 Summ
15、ary and recommendations 10 Annex A (normative) Generic approach to uncertainty calculation . 11 Bibliography . 14 DD ISO/TS 29041:2008ISO/TS 29041:2008(E) iv ISO 2008 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards
16、bodies (ISO member bodies). The work of preparing International Standards 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 organizat
17、ions, governmental and non-governmental, in liaison with ISO, also take part 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 th
18、e ISO/IEC Directives, Part 2. The main task of technical committees is to prepare 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
19、the member bodies casting a vote. In other circumstances, particularly when there is an urgent market requirement for such documents, a technical committee may decide to publish other types of document: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical exper
20、ts in an ISO working group and is accepted for publication if it is approved by more than 50 % of the members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical committee and is accepted for publication if it is
21、approved by 2/3 of the members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is review
22、ed again after a further three years, at which time it must either be transformed into an International Standard or be withdrawn. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying an
23、y or all such patent rights. ISO/TS 29041 was prepared by Technical Committee ISO/TC 158, Analysis of gases. This document is not to be regarded as an “International Standard”. It is proposed for provisional application so that information and experience of its use in practice may be gathered. Comme
24、nts on the content of this document should be sent to the ISO Central Secretariat. DD ISO/TS 29041:2008ISO/TS 29041:2008(E) ISO 2008 All rights reserved vIntroduction ISO/TC 158 decided at its meeting in Prague (October 2002) to investigate the influence of possible correlations (both extrinsic and
25、intrinsic) on the uncertainty calculation(s) for mixture composition and gas mixture property data. Methods should be developed for taking all existing correlations into account, and exemplified appropriately. This Technical Specification describes the tools needed for full accounting of correlation
26、s, and exemplifies how these tools should be applied to practical examples. Some recommendations are given which are intended to provide support to the decision on whether or not, and in which situations, the full calculatory scheme as described herein should be applied in practice, and in which sit
27、uations simplified approaches as given in ISO 6142 are considered sufficient for the intended purpose. DD ISO/TS 29041:2008DD ISO/TS 29041:2008TECHNICAL SPECIFICATION ISO/TS 29041:2008(E) ISO 2008 All rights reserved 1Gas mixtures Gravimetric preparation Mastering correlations in composition 1 Scope
28、 In this Technical Specification, the gravimetric mixture preparation as given in ISO 6142 is investigated for influences of a priori existing, as well as correlations introduced by data processing. All calculations refer to an example which consists in the preparation of a synthetic natural gas of
29、a target composition as follows: 1,4 mol % N2, 1,8 mol % CO2, 9,4 mol % ethane, 3,4 mol % propane, 1 mol % n-butane, and 83 mol % methane. All considerations given for this example concerning mixture feasibility, choice of preparation procedure, and weighing steps and sequences are the same as given
30、 in ISO 6142. This also applies to all estimates for basic uncertainty sources and the purity tables of the gases used for preparation. All calculations follow the principles, and use the tools and algorithms laid down in Annex A. For the sake of simplicity, procedural steps such as matrix transform
31、ation, inversion or matrix calculus are not detailed each time they are used in the calculations. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest
32、 edition of the referenced document (including any amendments) applies. ISO 6142, Gas analysis Preparation of calibration gas mixtures Gravimetric method 3 Symbols and abbreviated terms CVi calorific value of gas component i, i = 1, , n CV calorific value of the gas mixture G system of model equatio
33、ns describing the measurand J Jacobian m mass mg mass of the gas component in the mixture cylinder, as determined by gravimetry mm mass difference, as determined, between mixture and reference cylinder after the corresponding filling step mx mass difference corrected between mixture and reference cy
34、linder after the corresponding filling step DD ISO/TS 29041:2008ISO/TS 29041:2008(E) 2 ISO 2008 All rights reservedMimolar mass of gas component i, i = 1, , n M molar mass of the gas mixture Q transfer matrix U(x) expanded uncertainty of a value x u(x) standard uncertainty of a value x u2(pi, pj) va
35、riance (for i = j) of a value pi, or covariance (for i j) of two values piand pjuB buoyancy correction (see Note) uexp correction accounting for cylinder expansion um uncertainty of balance indication (cumulated estimate) uR correction for residual gas in the cylinder after evacuation V variance/cov
36、ariance matrix for a set of results or parameters wg mass fraction of a component as determined by gravimetry ximole fraction of gas component i in the final mixture, i = 1, ., n pur,ikx mole fraction of gas component k in pure gas i used for gravimetric preparation NOTE ISO 6142 uses symbols with l
37、ower-case letter “u” (e.g. uB) for variables other than uncertainties, namely for corrections made for influential factors in the gravimetric mixture production process, e.g. buoyancy. This symbol assignment to variables is also retained for the purposes of this document. The reader should be carefu
38、l not to confound values and value uncertainties. The uncertainty of, say, uBis u(uB). 4 Mixture preparation by gravimetry For the weighing steps and sequence as described in the example, the values for the mxand their corresponding uncertainties (as given in Table 1) can be obtained from the raw da
39、ta and uncertainty source estimates. Estimates for the corrections and their uncertainties are the same as in the CO in N2example in ISO 6142. DD ISO/TS 29041:2008ISO/TS 29041:2008(E) ISO 2008 All rights reserved 3Table 1 Component weighing data and their uncertainties for the gas mixture Component
40、Masses and their uncertainties Vacuum n-Butane Propane Ethane CO2N2Methane mm g 50,000 21 37,999 302 7,999 707 50,000 21 65,999 937 73,999 78 345,998 422 um g 0,011 0,157 0,731 0,299 0,052 0,065 0,13 uB g 0,007 45 0,005 66 0,001 19 0,007 45 0,009 84 0,001 1 0,051 58 uexp g 0,001 49 0,015 9 uR g 0,00
41、3 3 u(mm) mg 0,015 0,019 3 0,010 8 0,015 0,020 2 0,015 1 0,06 u(um) mg 2,3 2,3 2,3 2,3 2,3 2,3 2,3 u(uB) mg 0,019 0,014 0,003 0,019 0,025 0,028 0,13 u(uexp) mg 0,86 9,16 u(uR) mg 1,9 mx g 49,996 660 38,161 962 7,269 897 49,708 660 66,063 267 74,065 880 346,199 202 u(mx) mg 2,300 128 2,300 124 2,300
42、027 2,300 127 2,455 735 2,300 220 9,634 630 The following reasoning applies to possible correlations: it is assumed that umis a random variable governed by a common distribution, and each realisation is a drawing from the distribution. Under this assumption, there is no reason for making allowances
43、for correlation(s) since the realisations are independent. The uncertainty sources for the uBestimates are the same, namely pressure, temperature, and humidity. This causes correlation, but the common sources are not quantified in ISO 6142. There is no reason for assuming correlations for the uexpes
44、timate, and uRoccurs only once for methane. For mm, a clear correlation exists since the same mass pieces are used, but their combinations are unknown (except for some cases). Usually, these correlations are small and may be neglected in practice. Here, for demonstrating the principle of the method
45、they are included where obvious. The corresponding variance-covariance matrix for the data table is given in Table 2. Table 2 Variance-covariance matrix for the weighing data in Table 1 V(mx) Vacuum n-Butane Propane Ethane CO2N2Methane Vacuum 5,290 586 0 0 0,000 225 0,000 225 0,000 225 0 n-Butane 0
46、5,290 568 49 0 0 0 0 0 Propane 0 0 5,290 125 64 0 0 0 0 Ethane 0,000 225 0 0 5,290 586 0,000 225 0,000 225 0 CO20,000 225 0 0 0,000 225 6,030 633 04 0,000 225 0 N20,000 225 0 0 0,000 225 0,000 225 5,291 012 01 0 Methane 0 0 0 0 0 0 92,826 1 DD ISO/TS 29041:2008ISO/TS 29041:2008(E) 4 ISO 2008 All rig
47、hts reservedValues in Table 1 are exemplified for the N2column: The uncertainty of the mxvalue for N2is combined from the contributing sources of uncertainty according to the usual uncertainty propagation rule. It holds 2222mmB() ( ) () ()xum um uu uu=+ (1) delivering a value of 2,300 3 mg. The corr
48、esponding variance is 5,291 012 01 mg2and contained in the sixth row of the N2column. The mmvalues for the N2and the methane filling step are quite different, it was assumed that different mass pieces were used. Other common sources of uncertainty are the corrections umand uBfor which either an abse
49、nce of correlation is assumed, or the correlations are negligible or unknown. Thus, the covariance term is set to zero (seventh row of the N2column). The same reasoning holds for the n-butane/N2and the propane/N2pairs (second and third row of the N2column). The mmvalues for the initial weighing (vacuum) and the ethane and CO2filling step are quite similar or at least in the region of 50 g, so it can be assumed that the same mass pieces were used. For simplicity, the covariance arising f
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