1、BS ISO 13909-7:2016Hard coal and coke Mechanical samplingPart 7: Methods for determining theprecision of sampling, sample preparationand testingBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS ISO 13909-7:2016 BRITISH STANDARDNational forewordThis British Standard
2、is the UK implementation of ISO 13909-7:2016.It supersedes BS ISO 13909-7:2001 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/16, Solid mineral fuels.A list of organizations represented on this committee can beobtained on request to its secretary.T
3、his publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016. Published by BSI StandardsLimited 2016ISBN 978 0 580 83180 5ICS 73.040; 75.160.10Compliance with a British Standard cannot
4、confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 June 2016.Amendments issued since publicationDate Text affectedBS ISO 13909-7:2016 ISO 2016Hard coal and coke Mechanical sampling Part 7: Methods for dete
5、rmining the precision of sampling, sample preparation and testingHouille et coke chantillonnage mcanique Partie 7: Mthodes pour la dtermination de la fidlit de lchantillonnage, de la prparation de lchantillon et de lessaiINTERNATIONAL STANDARDISO13909-7Second edition2016-07-01Reference numberISO 139
6、09-7:2016(E)BS ISO 13909-7:2016ISO 13909-7:2016(E)ii ISO 2016 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in SwitzerlandAll rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic
7、 or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCh. de Blandonnet 8 CP 401CH-1214 Vernier, Gen
8、eva, SwitzerlandTel. +41 22 749 01 11Fax +41 22 749 09 47copyrightiso.orgwww.iso.orgBS ISO 13909-7:2016ISO 13909-7:2016(E)Foreword ivIntroduction v1 Scope . 12 Normative references 13 Terms and definitions . 14 General 15 Formulae relating to factors affecting precision . 25.1 General . 25.2 Samplin
9、g . 36 Estimation of primary increment variance 46.1 Direct determination of individual primary increments 46.2 Determination using the estimate of precision. 57 Methods for estimating precision . 57.1 General . 57.2 Duplicate sampling with twice the number of increments. 57.3 Duplicate sampling dur
10、ing routine sampling . 87.4 Alternatives to duplicate sampling 97.5 Precision adjustment procedure . 98 Calculation of precision 108.1 Replicate sampling 108.2 Normal sampling scheme . 119 Methods of checking sample preparation and testing errors 129.1 General 129.2 Target value for variance of samp
11、le preparation and analysis .129.2.1 General. 129.2.2 Off-line preparation 139.2.3 On-line preparation 139.3 Checking procedure as a whole . 139.4 Checking stages separately 149.4.1 General. 149.4.2 Procedure 1 . 159.4.3 Procedure 2 . 189.4.4 Interpretation of results . 219.5 Procedure for obtaining
12、 two samples at each stage 229.5.1 With a riffle 229.5.2 With a mechanical sample divider 229.6 Example 22Annex A (informative) Variogram method for determining variance 26Annex B (informative) Grubbs estimators method for determining sampling precision .34Bibliography .43 ISO 2016 All rights reserv
13、ed iiiContents PageBS ISO 13909-7:2016ISO 13909-7:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees
14、. 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 part in the work. ISO collaborates closely with the Intern
15、ational Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the diffe
16、rent types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shal
17、l not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document i
18、s information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT)
19、, see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 27, Solid mineral fuels, Subcommittee SC 4, Sampling.This second edition cancels and replaces the first edition (ISO 13909-7:2001), which has been technically revised.ISO 13909 consists
20、 of the following parts, under the general title Hard coal and coke Mechanical sampling: Part 1: General introduction Part 2: Coal Sampling from moving streams Part 3: Coal Sampling from stationary lots Part 4: Coal Preparation of test samples Part 5: Coke Sampling from moving streams Part 6: Coke P
21、reparation of test samples Part 7: Methods for determining the precision of sampling, sample preparation and testing Part 8: Methods of testing for biasiv ISO 2016 All rights reservedBS ISO 13909-7:2016ISO 13909-7:2016(E)IntroductionTwo different situations are considered when a measure of precision
22、 is required. In the first, an estimate is made of the precision that can be expected from an existing sampling scheme and, if this is different from that desired, adjustments are made to correct it. In the second, the precision that is achieved on a particular lot is estimated from the experimental
23、 results actually obtained using a specifically designed sampling scheme.The formulae developed in this part of ISO 13909 are based on the assumption that the quality of the fuel varies in a random manner throughout the mass being sampled and that the observations will follow a normal distribution.
24、Neither of these assumptions is strictly correct. Although the assumption that observations will follow a normal distribution is not strictly correct for some fuel parameters, this deviation from assumed conditions will not materially affect the validity of the formulae developed for precision check
25、ing since the statistics used are not very sensitive to non-normality. Strictly speaking, however, confidence limits will not always be symmetrically distributed about the mean. For most practical uses of precision, however, the errors are not significant.NOTE In the text, the term “fuel” is used wh
26、ere both coal and coke would be applicable in the context and either “coal” or “coke” where that term is exclusively applicable. ISO 2016 All rights reserved vBS ISO 13909-7:2016BS ISO 13909-7:2016Hard coal and coke Mechanical sampling Part 7: Methods for determining the precision of sampling, sampl
27、e preparation and testing1 ScopeIn this part of ISO 13909, formulae are developed which link the variables that contribute to overall sampling precision. Methods are described for estimating overall precision and for deriving values for primary increment variance which can be used to modify the samp
28、ling scheme to change the precision. Methods for checking the variance of sample preparation and testing are also described.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references,
29、 only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 13909-1, Hard coal and coke Mechanical sampling Part 1: General introductionISO 13909-2, Hard coal and coke Mechanical sampling Part 2: Coal Sampling from mov
30、ing streamsISO 13909-3, Hard coal and coke Mechanical sampling Part 3: Coal Sampling from stationary lotsISO 13909-4, Hard coal and coke Mechanical sampling Part 4: Coal Preparation of test samplesISO 13909-5, Hard coal and coke Mechanical sampling Part 5: Coke Sampling from moving streamsISO 13909-
31、6, Hard coal and coke Mechanical sampling Part 6: Coke Preparation of test samplesISO 13909-8, Hard coal and coke Mechanical sampling Part 8: Methods of testing for bias3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 13909-1 apply.4 GeneralWhen design
32、ing a sampling scheme in order to meet a required precision of results, formulae are necessary that link certain fuel and sampling characteristics to that precision. The main factors to be considered are the variability of primary increments, preparation and testing errors, the number of increments
33、and samples taken to represent the lot, and the mass of the samples. These formulae are derived in Clause 5. Methods for estimating the parameters used in those formulae are given in Clause 6.Once a sampling system has been designed and installed, the precision which is being achieved on a routine b
34、asis should be checked. An estimate of the precision can be obtained from the primary increment variance, VI, the numbers of increments, n, and sub-lots, m, (see Clause 5) and the preparation and testing variance, VPT. The preparation component of VPTis made up of on-line sample processing and off-l
35、ine sample preparation.INTERNATIONAL STANDARD ISO 13909-7:2016(E) ISO 2016 All rights reserved 1BS ISO 13909-7:2016ISO 13909-7:2016(E)Sampling variance is a function of product variability, so the same number of increments, sub-lots, and preparation and testing errors will yield different precision
36、with fuels that exhibit different product variability.Depending on the extent to which serial correlation exists and which method of estimating primary increment variance is used, such an estimate could represent a considerable overestimate of the numerical value of the precision (i.e. indicate that
37、 it is worse than is really the case). In addition, in order for the results to be meaningful, large numbers of increments (in duplicate) would need to be prepared and analysed for the estimation of VI and VPT.Quality variations obtained in the form of primary increment variances on existing systems
38、 are not absolute and therefore designers should exercise caution when using such results in a different situation. The estimated value of the primary increment variance, VI, should be derived experimentally for each fuel and at each sampling location.Whenever a sampling scheme is used for determini
39、ng increment variance, the operating conditions should be as similar as possible to the conditions known, or anticipated, to prevail during the sampling for which the increment variance is needed, whether it be carried out by the same or by a different sampling system.An estimate of the precision ac
40、tually achieved can be obtained by taking the sample in a number of parts and comparing the results obtained from these parts. There are several methods of doing this, depending ona) the purpose of the test, andb) the practical limitations imposed by the available sampling procedures and equipment.W
41、here a sampling system is in existence, the purpose of the test is to check that the scheme is in fact achieving the desired precision (see Clause 7). If it is not, it may need to be modified and rechecked until it meets the precision required. In order to do this, a special check scheme should be d
42、evised which may be different from the regular scheme but which measures the precision of the regular scheme.For regular sampling schemes, the most rigorous approach is that of duplicate sampling of sub-lots. In many existing mechanical sampling systems, however, the capacity of individual component
43、s and the interval between increments in the regular scheme is insufficient to allow the taking of extra increments. In such cases, duplicate samples can be constituted from the normal number of increments and the result adjusted for the smaller number of increments in each sample (see 7.3).The need
44、 may arise to sample a particular lot and to know the precision of the result obtained (see Clause 8). Once again, a special check scheme needs to be devised, but in this case, it is the precision achieved by that scheme on that lot which is required. For the measurement of the precision achieved fo
45、r a particular lot, replicate sampling is the best method.Methods for detailed checking of preparation and testing errors are given in Clause 9. The results may also be used to provide data for the formulae used in Clause 5.5 Formulae relating to factors affecting precision5.1 GeneralPrecision is a
46、measure of the closeness of agreement between the results obtained by repeating a measurement procedure several times under specified conditions and is a characteristic of the method used. The smaller the random errors of a method, the more precise the method is. A commonly accepted index of precisi
47、on is two times the sample estimate of the population standard deviation and this index of precision is used throughout this part of ISO 13909.2 ISO 2016 All rights reservedBS ISO 13909-7:2016ISO 13909-7:2016(E)If a large number of replicate samples, j, are taken from a sub-lot of fuel and are prepa
48、red and analysed separately, the estimated precision, P, of a single observation is given by Formula (1):Ps V= =22SPT(1)wheres is the sample estimate of the population standard deviation;VSPTis the total variance.The total variance, VSPT, in Formula (1) is a function of the primary increment varianc
49、e, the number of increments, and the errors associated with sample preparation and testing.NOTE The components of primary increment variance are the variance of sample extraction and the variance contributed by product variability. The variance contributed by product variability is generally, but not always, the largest source of variance in sampling.For a single sample, this relationship is expressed by Formula (2):VVnVSPTIPT=+ (2)whereVlis the primary increment variance;VPTis the p
