ISO/FDIS 13909-8
(Main)Coal and coke — Mechanical sampling — Part 8: Methods of testing for bias
Coal and coke — Mechanical sampling — Part 8: Methods of testing for bias
ISO 13909-8:2016 sets out principles and procedures for testing the bias of test samples of hard coals or cokes, taken in accordance with ISO 13909: 2016 (all parts). NOTE In the text, the term "fuel" is used where both coal and coke would be applicable in the context and either "coal" or "coke" where only one is applicable.
Charbon et coke — Échantillonnage mécanique — Partie 8: Méthodes de détection du biais
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ISO/TC 27/SC 4
Coal and coke — Mechanical
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sampling —
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Methods of testing for bias
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Charbon et coke — Échantillonnage mécanique —
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Reference number
FINAL DRAFT
International
Standard
ISO/TC 27/SC 4
Coal and coke — Mechanical
Secretariat: SABS
sampling —
Voting begins on:
Part 8:
Methods of testing for bias
Voting terminates on:
Charbon et coke — Échantillonnage mécanique —
Partie 8: Méthodes de détection du biais
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
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Phone: +41 22 749 01 11
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Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 1
5 Pretest inspection . 2
6 Reference methods . 2
7 Test design . 3
7.1 Choice of test parameters .3
7.2 Number of paired samples .3
7.3 Selection of sample pairs .3
7.3.1 Composition of sample pairs .3
7.3.2 Paired-increment samples .4
7.3.3 Paired-batch samples .4
7.4 Choice of fuel for test .4
7.5 Coke .4
8 Conduct of the test . 4
8.1 General .4
8.2 Collection and preparation of test samples .5
9 Outline of test procedure . 5
9.1 General .5
9.2 Special precautions for moisture-test samples .5
9.3 Documentation .6
10 Statistical analysis and interpretation . 6
10.1 Outline of statistical procedure .6
10.2 Calculations .6
10.2.1 Statistical procedure for identifying outliers .6
10.2.2 Disposition of outliers .7
10.2.3 Calculation of confidence intervals and determining bias .8
10.2.4 Review of the 95 % confidence region for the bias .11
11 Test report .11
Annex A (informative) Example calculations.13
Bibliography .26
iii
Foreword
ISO (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. 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 International 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 different types
of ISO document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 4, Sampling.
This third edition cancels and replaces the second edition (ISO 13909-8:2016), which has been technically
revised.
The main changes are as follows:
— the main title has been modified and aligned with the ISO 13909 series;
— requirements in reference methods have been clarified;
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
It is not possible to lay down a standard method for field work by which a sampling procedure can be tested
for bias, because details of the procedure will inevitably be affected by local conditions. However, certain
principles can be specified which ought to be adhered to whenever possible and these are discussed in this
document.
Testing for bias can be a tedious and expensive process. All bias tests therefore include a thorough pretest
inspection, with appropriate action taken regarding any system deficiencies likely to cause bias.
In the text, the term “fuel” is used where both coal and coke would be applicable in the context and either
“coal” or “coke” where only one is applicable.
v
FINAL DRAFT International Standard ISO/FDIS 13909-8:2025(en)
Coal and coke — Mechanical sampling —
Part 8:
Methods of testing for bias
1 Scope
This document sets out principles and procedures for testing the bias of test samples of coals or cokes, taken
according to the ISO 13909 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 13909-1, Coal and coke — Mechanical sampling — Part 1: General introduction
ISO 13909-4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 13909-6, Coal and coke — Mechanical sampling — Part 6: Preparation of test samples of coke
ISO 13909-7, Coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of sampling,
sample preparation and testing
ISO 21398, Hard coal and coke — Guidance to the inspection of mechanical sampling systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13909-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principles
The testing of a sampling system for bias is based on taking a series of pairs of samples of essentially the sa
...
Date: 2025-04-07
ISO/TC 27/SC 4
Secretariat: SABS
Date: 2025-05-09
Coal and coke — Mechanical sampling — —
Part 8:
Methods of testing for bias
HouilleCharbon et coke — Échantillonnage mécanique —
Partie 8: Méthodes de détection du biais
FDIS stage
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic 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 ISO'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland.
ii
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principles . 1
5 Pretest inspection . 2
6 Reference methods . 2
7 Test design . 3
8 Conduct of the test . 5
9 Outline of test procedure . 6
10 Statistical analysis and interpretation . 7
11 Test report . 12
Annex A (informative) Example calculations . 13
Bibliography . 30
iii
Foreword
ISO (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. 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
International 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 different types of
ISO document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 4, Sampling.
This third edition cancels and replaces the second edition (ISO 13909--8:2016), which has been technically
revised.
The main changes are as follows:
— — the main title has been modified and aligned with the ISO 13909 series;
— — requirements in reference methods have been clarified;
— —
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
It is not possible to lay down a standard method for field work by which a sampling procedure can be tested
for bias, because details of the procedure will inevitably be affected by local conditions. However, certain
principles can be specified which ought to be adhered to whenever possible and these are discussed in this
document.
Testing for bias can be a tedious and expensive process. All bias tests therefore include a thorough pretest
inspection, with appropriate action taken regarding any system deficiencies likely to cause bias.
In the text, the term “fuel” is used where both coal and coke would be applicable in the context and either
“coal” or “coke” where only one is applicable.
v
Coal and coke — Mechanical sampling — —
Part 8:
Methods of testing for bias
1 Scope
This document sets out principles and procedures for testing the bias of test samples of coals or cokes, taken
in accordance withaccording to the ISO 13909 series.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 13909--1, Coal and coke — Mechanical sampling — Part 1: General introduction
ISO 13909--4, Coal and coke — Mechanical sampling — Part 4: Preparation of test samples of coal
ISO 13909--6, Coal and coke — Mechanical sampling — Part 6: Preparation of test samples of coke
ISO 13909--7, Coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of
sampling, sample preparation and testing
ISO 21398, CoalHard coal and coke — Guidance to the inspection of mechanical sampling systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 13909--1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
4 Principles
The testing of a sampling system for bias is based on taking a series of pairs of samples of essentially the same
fuel; one member of each pair being sampled by the system or component under test, the other member being
obtained by a reference method. For each pair, the difference between the analytical results is determined.
The series of differences between the analytical results thus obtained are subjected to statistical analysis.
The sensitivity of the statistical test is dependent on the number of pairs compared, the variability of the
differences between members of the pairs, and the number of parameters used for the test.
The statistical analysis to which results will be subjected assumes the following three conditions:
— — a multivariate normal distribution of the variables;
— — independence of the errors of measurement for the individual parameters;
— — homogeneity of the data.
5 Pretest inspection
The primary sources of information regarding compliance with the sampling standard are the equipment
specifications and drawings.
A thorough examination of the sampling system and a review of its component specification shall be made, in
accordance with ISO 21398.
The party performing the test shall, however, verify performance by field measurements and observations.
The operation of the sampling system shall be observed both dynamically with fuel flowing and statically with
no fuel flowing. Some components will need to be actuated in static mode.
Pretest inspections of all operations and equipment, both static and under load, shall be carried out by persons
experienced in the sampling of segregated, heterogeneous, and lumpy bulk materials. It is recommended that
operation under normal conditions be observed for an entire lot.
Do not execute a test for bias until all conditions known to cause bias are corrected unless it is necessary to
establish the performance of a system or component as it stands. In the latter case, the pretest inspection
provides essential documentation of what the conditions were at the time of the test.
6 Reference methods
To test overall system bias, the use of a reference method which is known to be intrinsically unbiased is
required. The preferred method is the stopped-belt method, i.e. the collection of increments from a complete
cross-section of the fuel on the conveyor belt by stopping the belt at intervals. When properly collected from
the primary fuel stream, the stopped-belt increment can be considered as a reference increment.
NOTE If it is not possible to collect stopped-belt increments, other reference methods can be used but, in these cases,
an apparent absence of a lack of bias relative to the reference method might notcan be conclusiveinconclusive and the
use of such methods can compromise the validity and authority of the findings.
With collection of stopped-belt increments, some disruption of normal operations can occur, and therefore,
the plan of execution may need to be coordinated with the normal operations and organized to minimize such
disruption. It must be recognized that the conveyor system involved may be used for only a few hours per day
for normal operations and cannot be operated solely for bias tests unless the fuel can be diverted to another
discharge point. This can extend the time necessary for completion of the field work and require special
arrangements for supplying fuel to the system for testing.
Stopped-belt increments shall be taken with a sampling frame (see Figure 1Figure 1),), or equivalent, from a
complete cross-section of the solid mineral fuel on the belt at a fixed position, for a length along the belt which
is at least three times the nominal top size of the fuel.
Figure 1 — Sampling frame
The sampling frame (or equivalent) shall be placed on the stationary belt at the predetermined position so
that the separator plates at each end are in contact with the belt across its full width. All particles lying inside
the sampling frame end plates shall be swept into the sampling container.
Particles obstructing the insertion of the end plate on the left-hand side shall be pushed into the increment,
while those obstructing the insertion of the end plate on the right-hand side shall be pushed out of the
increment or vice-versa. Whichever practice is used initially, this practice shall be implemented throughout
the test.
Care shall be taken to minimize the risk of bias being introduced in the course of preparation of the increments
and samples and all sample division equipment and procedures shall be checked for bias with respect to
relevant test parameters.
It is recommended that the mass of all increments/samples be determined immediately after collection. Pay
close attention to minimizing unintended mass losses.
Report all observed mass losses.
7 Test design
7.1 Choice of test parameters
The standard test for general purposes shall include moisture and ash (ash on a dry basis). Use of these two
parameters will generally suffice. Other variables can be included if desired. However, given a fixed number
of sample pairs, the test often becomes less sensitive to detection of a bias as additional variables are included.
Bias in ash on a dry basis is most commonly caused by errors in size distribution. Bias in moisture content
may be caused by a wide variety of factors, including, but not limited to, errors in size distribution, moisture
losses associated with crushers, excessive ventilation within the sampling system, less than the closest
possible coupling between system components, excessive retention time in the system, or any combination of
these.
Direct tests on particle size di
...
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