ISO 13909-6:2025

International
Standard
ISO 13909-6
Third edition
Coal and coke — Mechanical
2025-07
sampling —
Part 6:
Preparation of test samples of coke
Charbon et coke — Échantillonnage mécanique —
Partie 6: Préparation des échantillons pour essai de coke
Reference number
© ISO 2025
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ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Precision of sample preparation . 2
5 Constitution of a sample . 2
5.1 General .2
5.2 Combination of increments .2
5.3 Combination of samples .2
6 Division . 3
6.1 General .3
6.2 Mechanical methods . 13
6.2.1 General . 13
6.2.2 Mass of cut . 13
6.2.3 Interval between cuts .14
6.2.4 Division of individual increments .14
6.2.5 Minimum mass of divided increment .14
6.2.6 Division of samples. 15
6.3 Manual methods . 15
6.3.1 General . 15
6.3.2 Riffle method . 15
6.3.3 Flattened-heap method .16
6.3.4 Strip-mixing and splitting method .18
7 Preparation of samples for specific tests . 19
7.1 Types of test sample . .19
7.2 Preparation of samples for determining total moisture .21
7.2.1 General .21
7.2.2 Procedure .21
7.2.3 Wet samples .21
7.2.4 Reduction of total moisture test sample . 22
7.2.5 Division . 22
7.2.6 Determination of total moisture . 22
7.2.7 Reserve sample . 22
7.3 Preparation of sample for general analysis . 22
7.3.1 General . 22
7.3.2 Segregation errors (preparation error) . 22
7.3.3 Reduction . 23
7.3.4 Division . 23
7.3.5 Preparation errors . 23
7.4 Storage . 23
7.5 Physical test sample . 23
7.6 Samples for special properties . 23
8 Design of equipment for preparation .24
8.1 Dividers .24
8.2 Design of cutters for falling-stream dividers .24
8.2.1 General .24
8.2.2 Cutter velocity .24
8.3 Crushers . 25
8.3.1 General . 25
8.3.2 Examples of crushers . 25
8.4 Preparation systems . 25

iii
8.4.1 General . 25
8.4.2 Design criteria . 26
8.4.3 Normal operation. 26
8.4.4 Abnormal operation . 26
8.4.5 Provision for checking for precision . 26
8.4.6 Provision for testing for bias . 26
Bibliography .27

iv
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 13909-6:2016), which has been technically
revised.
The main changes are as follows:
— the title has been modified and aligned with the rest of the ISO 13909 series;
— the scope has been revised to specifically refer to coke;
— the references have been updated;
— legends for Formulae (1) and (3) have been updated;
— requirements have been specified throughout the document.
A list of all parts in the ISO 13909 series can be found on the ISO website.
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.

v
Introduction
The objective of sample preparation is to prepare one or more test samples from the primary increments
for subsequent analysis. The requisite mass and particle size of the test samples depend on the test to be
carried out.
Examples of tests which require different masses are shatter index (ISO 616), Micum and Irsid Index
(ISO 556), reactivity tests (ISO 18894), density (ISO 567, ISO 1013) and size distribution (ISO 728, ISO 2325).
The process of sample preparation can involve constitution of samples, reduction, division, mixing and
drying, or all, or a combination of these.
Primary increments can be prepared individually as test samples or combined to constitute samples either
as taken or after having been prepared by either reduction or division, or both. Samples can either be
prepared individually as test samples or combined on a weighted basis to constitute a further sample.

vi
International Standard ISO 13909-6:2025(en)
Coal and coke — Mechanical sampling —
Part 6:
Preparation of test samples of coke
1 Scope
This document describes the preparation of samples of coke from the combination of primary increments to
the preparation of samples for specific tests.
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 579, Coke — Determination of total moisture
ISO 687, Coke — Determination of moisture in the general analysis test sample
ISO 13909-1, Coal and coke — Mechanical sampling — Part 1: General introduction
ISO 13909-5, Coal and coke — Mechanical sampling — Part 5: Sampling of coke from moving streams
ISO 13909-7, Coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of sampling,
sample preparation and testing
ISO 13909-8, Coal and coke — Mechanical sampling — Part 8: Methods of testing for bias
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 Precision of sample preparation
From the formulae given in ISO 13909-7, the estimated absolute value of the precision of the result obtained
for the lot at the 95 % confidence level, P , for continuous sampling is given by Formula (1):
L
V
I
+V
PT
n
P =2 (1)
L
m
where
2 is a conversion factor from the sample estimate of the population standard deviation to an
index of precision, dimensionless;
V is the primary increment variance;
I
n is the number of increments in the sample;
V is the variance of preparation and testing for both off-line and on-line systems;
PT
m is the number of sub-lots.
The procedures given in this document are designed to achieve levels of V of 0,05 or less for moisture
PT
tests. Better levels may be expected for other chemical characteristics.
For some preparation schemes, however, practical restrictions can prevent the preparation and testing
variance being as low as this. Under these circumstances, the user shall decide whether to achieve the
desired overall precision by improving the preparation scheme or by dividing the lot into a greater number
of sub-lots.
The errors occurring in the various stages of preparation and analysis, expressed in terms of variance, can
be checked by the methods given in ISO 13909-7.
5 Constitution of a sample
5.1 General
Examples of the constitution of samples are shown in Figure 1.
Primary increments shall be taken in accordance with the procedures specified in ISO 13909-5.
Individual increments are usually combined to form a sample. A single sample may be constituted by
combination of increments taken from a complete sub-lot or by combining increments taken from individual
parts of a sub-lot. Under some circumstances, e.g. size analysis or bias testing, the sample consists of a single
increment which is prepared and tested.
Samples may also be prepared by the combination of other samples.
5.2 Combination of increments
The mass of the primary increments shall be proportional to the flow rate at the time of sampling. The
primary increments may be combined into a sample, either directly as taken or after having been prepared
individually to an appropriate stage by fixed-ratio division (see Clause 6).
5.3 Combination of samples
When combining samples, the mass of the individual samples shall be directly proportional to the mass of
the coke from which they were taken in order to obtain a weighted mean of the quality characteristic for the
sub-lot. Prior to combination, division shall be by fixed-ratio (see Clause 6).

a) Example 1
b) Example 2
Figure 1 — Examples of the constitution of samples
6 Division
6.1 General
Since the cutter aperture is at least three times the nominal top size, this results in a very large increment mass
in many cases. The handling and preparation of such large increments can be either manpower or equipment
intensive. Division prior to further treatment may be necessary to provide a manageable sample mass.
Sample division can be:
— on-line mechanically; or
— off-line mechanically or manually.
Whenever possible, mechanical methods are preferred to manual methods to minimize human error.
Examples of dividers are shown in Figures 2 to 10.
Mechanical dividers are designed to extract a part of the coke in a number of cuts of relatively small mass.
When the smallest mass of the divided sample that can be obtained in one pass through the divider is greater
than that required, further passes through the same divider or subsequent passes through further dividers
are necessary.
Manual division is normally applied when mechanical methods would result in loss of integrity (e.g. loss of
moisture or size degradation). Manual division of coke is also applied when the nominal top size of the coke
is such as to make the use of a mechanical divider impracticable. Manual methods may themselves result in
bias, particularly if the mass of coke to be divided is large.
In the rotating disc type of mechanical divider in Figure 2, the material from a mixing container is fed by
scrapers to the centre of the dividing disc. From there it is discharged over the range of the disc through
special clearing arms. The sample falls through adjustable slots into chutes; the reject is carried away
through a cleaning conduit. The whole interior space is cleaned by scrapers.
For the rotating cone type of divider in Figure 3, a stream of coke is allowed to fall onto a rotating cone, the
adjustable slot with lips in the cone allows the stream to fall directly onto the sample receiver for part of
each revolution.
In the container type dividers in Figure 4, the coke stream flows to the hopper and this flow is intercepted
by the top edge of a number of sector-shaped containers dividing the flow into equal parts. Either the hopper
or the containers may rotate. The machine can be controlled for the following operations:
1) for dividing;
2) for collecting duplicates:
3) for collecting replicates.
For the chain bucket type divider in Figure 5, a chain mechanism as shown is equipped with buckets spread
at equal pitch. The buckets travel in a single direction or change direction at preset time periods. The bucket
intercepts the free-falling coke stream to extract cuts which discharge to sample as the bucket inverts.
The slotted-belt type divider in Figure 6 comprises an endless belt as shown having slots spaced at equal
pitch with lips that act as cutting edges passing below a feed chute. The coke stream is fed to the chute and,
as each slot passes through the stream, a cut is taken. The stream which falls onto the plain part of the belt
is carried to rejects.
The rotating plate divider in Figure 7 consists of a flat plate with lipped slots spaced at equal pitch rotating
beneath a feed chute. Coke is fed into the feed chute, then, falls onto the rotating plate to form a ribbon bed
which is carried to the plough and discharged to rejects. As a slot passes through the stream, a cut is taken.
The rotating chute type divider in Figure 8 incorporates a hollow shaft with a rotating conical hopper and
chute which distributes the coke to one or more stationary cutters within a housing as shown. Each cutter is
designed to take cuts from the coke stream and the rejects are discharged through the hollow shaft.
The rotating cutter divider in Figure 9 comprises one or more rotating cutters taking cuts from the coke
stream as it is fed into the housing through a feed chute as shown. Coke not collected by the rotating cutters
is directed to reject at the bottom of the housing.
Finally, the cutter-chute type divider in Figure 10 incorporates a cutter-chute that traverses the full coke
stream and diverts a portion from the stream. When the coke stream is not being cut by the chute, it is
deflected by the angle plate to reject.

Key
1 feed
2 reject
3 divided sample
Figure 2 — Rotating disc type divider

Key
1 feed
2 rotating cone
3 adjustable slot
4 divided sample
5 reject
Figure 3 — Rotating cone type divider

Key
1 feed
2 divided sample in rotating receivers
Figure 4 — Container type divider

Key
1 feed
2 reject
3 divided sample
Figure 5 — Chain bucket type divider

Key
1 slotted belt
2 feed
3 inclined chute
4 divided sample
5 reject
Figure 6 — Slotted-belt type divider

Key
1 feed
2 reject
3 divided sample
Figure 7 — Rotating plate type divider

Key
1 feed
2 reject
3 divided sample
Figure 8 — Rotating chute type divider

Key
1 feed
2 divided sample
3 reject
Figure 9 — Rotating cutter type divider

Key
1 feed
2 divided sample
3 reject
Figure 10 — Cutter-chute type divider
6.2 Mechanical methods
6.2.1 General
Mechanical sample division may be carried out on an individual increment or a sample. Where samples are
for moisture or general analysis, it is permissible to install on-line crushing to a nominal top size of 16 mm
followed by sample division. Division shall be by fixed-ratio division subject to the conditions set out in 6.2.2
and 6.2.3.
When crushing on-line, the risk of moisture loss shall be considered, particularly if the coke is hot.
The uses to which the sample is to be put, the numbers, masses and size distribution of the test samples
required shall also be taken into account when deciding on the minimum mass of the sample.
When a coke is regularly sampled under the same conditions, the precision obtained for all the required
quality parameters shall be checked using the procedures of ISO 13909-7 and the minimum mass adjusted
accordingly. The masses shall not be reduced, however, below the minimum requirements laid down in the
relevant analysis standards.
6.2.2 Mass of cut
The flow of coke to the divider shall be controlled so that the required number of cuts of approximately
uniform mass can be taken throughout the division of an increment. The cutting aperture and speed of the
...