ISO 13909-6:2016
(Main)Hard coal and coke — Mechanical sampling — Part 6: Coke — Preparation of test samples
Hard coal and coke — Mechanical sampling — Part 6: Coke — Preparation of test samples
ISO 13909-6:2016 describes the preparation of samples of coke from the combination of primary increments to the preparation of samples for specific tests.
Houille et coke — Échantillonnage mécanique — Partie 6: Coke — Préparation des échantillons pour essai
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 13909-6
Second edition
2016-07-01
Hard coal and coke — Mechanical
sampling —
Part 6:
Coke — Preparation of test samples
Houille et coke — Échantillonnage mécanique —
Partie 6: Coke — Préparation des échantillons pour essai
Reference number
ISO 13909-6:2016(E)
©
ISO 2016
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ISO 13909-6:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
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ISO 13909-6:2016(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Precision of sample preparation . 1
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 . 9
6.2.1 General. 9
6.2.2 Mass of cut .10
6.2.3 Interval between cuts .11
6.2.4 Division of individual increments .11
6.2.5 Minimum mass of divided increment .11
6.2.6 Division of samples .12
6.3 Manual methods .12
6.3.1 General.12
6.3.2 Riffle method .12
6.3.3 Flattened-heap method .13
6.3.4 Strip-mixing and splitting method .15
7 Preparation of samples for specific tests .16
7.1 Types of test sample .16
7.2 Preparation of samples for determining total moisture .18
7.2.1 General.18
7.2.2 Procedure .18
7.2.3 Wet samples .18
7.2.4 Reduction of total moisture test sample .19
7.2.5 Division .19
7.2.6 Determination of total moisture .19
7.2.7 Reserve sample .19
7.3 Preparation of sample for general analysis .19
7.3.1 General.19
7.3.2 Preparation errors .19
7.3.3 Reduction .20
7.3.4 Division .20
7.3.5 Preparation errors .20
7.4 Storage .20
7.5 Physical test sample .20
7.6 Samples for special properties .20
8 Design of equipment for preparation .21
8.1 Dividers .21
8.2 Design of cutters for falling-stream dividers .21
8.2.1 General.21
8.2.2 Cutter velocity .21
8.3 Crushers .22
8.3.1 General.22
8.3.2 Examples of crushers .22
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ISO 13909-6:2016(E)
8.4 Preparation systems .22
8.4.1 General.22
8.4.2 Design criteria .23
8.4.3 Normal operation .23
8.4.4 Abnormal operation .23
8.4.5 Provision for checking for precision .23
8.4.6 Provision for testing for bias .24
Bibliography .25
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ISO 13909-6:2016(E)
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 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 shall 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 is 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 ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT), see the following URL: Foreword - Supplementary information
The 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 13909-6:2001), which has been
technically revised.
ISO 13909 consists 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 — Preparation of test samples
— Part 7: Methods for determining the precision of sampling, sample preparation and testing
— Part 8: Methods of testing for bias
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ISO 13909-6:2016(E)
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 may involve constitution of samples, reduction, division, mixing and
drying or all or a combination of these.
Primary increments may be prepared individually as test samples or combined to constitute samples
either as taken or after having been prepared by reduction and/or division. Samples may either be
prepared individually as test samples or combined on a weighted basis to constitute a further sample.
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INTERNATIONAL STANDARD ISO 13909-6:2016(E)
Hard coal and coke — Mechanical sampling —
Part 6:
Coke — Preparation of test samples
1 Scope
This part of ISO 13909 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, in whole or in part, are normatively referenced in this document and are
indispensable for its application. 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, Solid mineral fuels — Coke — Determination of moisture in the general analysis test sample
ISO 13909-1, Hard coal and coke — Mechanical sampling — Part 1: General introduction
ISO 13909-5, Hard coal and coke — Mechanical sampling — Part 5: Coke — Sampling from moving streams
ISO 13909-7, Hard coal and coke — Mechanical sampling — Part 7: Methods for determining the precision
of sampling, sample preparation and testing
ISO 13909-8, Hard 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.
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
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ISO 13909-6:2016(E)
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 part of ISO 13909 are designed to achieve levels of V of 0,05 or less for
PT
moisture tests. Better levels may be expected for other chemical characteristics.
For some preparation schemes, however, practical restrictions may prevent the preparation and testing
variance being as low as this. Under these circumstances, the user should 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,
may 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).
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ISO 13909-6:2016(E)
a) Example 1
b) Example 2
Figure 1 — Examples of the constitution of samples
6 Division
6.1 General
Since the cutter aperture will be at least three times the nominal top size, this will result in a very large
increment mass in many cases. The handling and preparation of such large increments would 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 Figure 2.
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ISO 13909-6:2016(E)
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 may be 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.
Key Key
1 feed 1 feed
2 reject 2 rotating cone
3 divided sample 3 adjustable slot
4 divided sample
5 reject
The material from a mixing container is fed by As stream of coal is allowed to fall onto a
scrapers to the centre of the dividing disc. From rotating cone; the adjustable slot with lips in the
there, it is discharged over the range of the disc cone allows the stream to fall directly onto the
through special clearing arms. The sample falls sample receiver for part of each revolution.
through adjustable slots into chutes; the reject
is carried away through a cleaning conduit. The
whole interior space is cleaned by scrapers.
a) Rotating disc type b) Rotating cone type
Figure 2 — (continued)
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ISO 13909-6:2016(E)
Key
1 feed
2 divided sample in rotating receivers
The coal 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:
a) for dividing;
b) for collecting duplicates;
c) for collecting replicates.
c) Container type
Figure 2 — (continued)
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ISO 13909-6:2016(E)
Key
1 feed
2 reject
3 divided sample
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 coal
stream to extract cuts which discharge the sample as the bucket inverts.
d) Chain bucket type
Figure 2 — (continued)
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ISO 13909-6:2016(E)
Key
1 slotted belt
2 feed
3 inclined chute
4 divided sample
5 reject
An endless belt as shown having slots spaced at equal pitch with lips that act as cutting edges passing
below a feed chute. The coal 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.
e) Slotted-belt type
Figure 2 — (continued)
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ISO 13909-6:2016(E)
Key Key
1 feed 1 feed
2 reject 2 reject
3 divided sample 3 divided sample
A flat plate with lipped slots spaced at equal pitch A hollow shaft with a rotating conical hopper and
rotates beneath a feed chute. Coal is fed into the chute which distributes the coal to one or more
feed chute, then, falls onto the rotating plate to stationary cutters within a housing as shown.
form a ribbon bed which is carried to the plough Each cutter is designed to take cuts from the coal
and discharged to rejects. As a slot passes through stream and the rejects are discharged through the
the stream, a cut is taken. hollow shaft.
f) Rotating plate type g) Rotating chute type
Figure 2 — (continued)
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ISO 13909-6:2016(E)
Key Key
1 feed 1 feed
2 divided sample 2 divided sample
3 reject 3 reject
One or more rotating cutters take cuts from the The cutter-chute traverses the full coal stream and
coal stream as it is fed into the housing through diverts a portion from the stream. When the coal
a feed chute as shown. Coal not collected by the stream is not being cut by the chute, it is deflected
rotating cutters is directed to reject at the bottom by the angle plate to reject.
of the housing.
h) Rotating cutter type i) Cutter-chute type
Figure 2 — Examples of dividers
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
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ISO 13909-6:2016(E)
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 should 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 cutter shall be constant. The method of feeding the divider shall be designed to minimize any
segregation caused by the divider.
The cutting aperture shall be at least three times the nominal top size of the coke to be divided.
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ISO 13909-6:2016(E)
6.2.3 Interval between cuts
In order to minimize bias, the first cut for each mass to be divided shall be made at random within the
first interval. For secondary and tertiary dividers, the cycle time shall not be evenly divisible into the
cycle time of the cutter which precedes it.
The interval between taking cuts shall be constant, irrespective of the variations of masses of coke to
be divided so that divided sample masses are proportional to the mass of the feed. The ratio shall be
fixed for the whole sub-lot.
6.2.4 Division of individual increments
6.2.4.1 Number of cuts
When dividing an uncrushed increment, the minimum number of cuts from an increment of mean mass
at any stage shall be four. If the divided increments are crushed, a minimum of one cut shall be taken
from each cut from the preceding division.
6.2.5 Minimum mass of divided increment
The minimum mass of the divided increment shall be such that the combined masses of all the divided
increments in the sub-lot shall, at each stage, be greater than the mass given in Table 1, corresponding
to the nominal top size. If the increment masses are too low to satisfy this requirement, the divided
increment shall be crushed prior to further division.
For moisture samples, there is a restriction of 70 kg on the maximum mass of sample to be crushed at
one time during off-line preparation.
NOTE The masses given in Table 1 are for guidance on the minimum mass for unknown or heterogeneous
cokes. While they can usually be reduced for the moisture sample, they may be inadequate for the determination
of, for example, oversize to 1 % division precision, particularly on very large cokes.
Table 1 — Minimum mass of sample after division
Nominal top size Minimum mass
mm kg
>125 2 000
125 1 000
90 500
63 250
45 125
31,5 60
22,4 30
16,0 15
11,2 8
10,0 6
8,0 4
5,6 2
4 1
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ISO 13909-6:2016(E)
6.2.6 Division of samples
6.2.6.1 Number of cuts
The sample shall be divided by taking a minimum of 60 cuts.
NOTE If, during preparation, the sample is thoroughly mixed and it can be established that the required
precision can be achieved, the number may be reduced, with a minimum of 20. The required precision is easier to
achieve if the coke has been sized.
6.2.6.2 Minimum mass of divided sample
The mass of the divided sample shall not be less than the minimum mass in Table 1.
6.3 Manual methods
6.3.1 General
For the manual division methods given in 6.3.2 to 6.3.4, the mass of the divided sample shall not be less
than the minimum
...
DRAFT INTERNATIONAL STANDARD
ISO/DIS 13909-6
ISO/TC 27/SC 4 Secretariat: SABS
Voting begins on: Voting terminates on:
2014-07-08 2014-10-08
Hard coal and coke — Mechanical sampling —
Part 6:
Coke — Preparation of test samples
Houille et coke — Échantillonnage mécanique —
Partie 6: Coke — Préparation des échantillons pour essai
ICS: 75.160.10
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 13909-6:2014(E)
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 SUPPORTING DOCUMENTATION. ISO 2014
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ISO/DIS 13909-6:2014(E)
Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as
permitted under the applicable laws of the user’s country, neither this ISO draft nor any extract
from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means,
electronic, photocopying, recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s
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E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2014 – All rights reserved
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ISO/CD 13909-6
Contents Page
Foreword .v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Precision of sample preparation.1
5 Constitution of a sample.2
5.1 Introduction.2
5.2 Combination of increments.2
5.3 Combination of samples.3
6 Division.3
6.1 General .3
6.2 Mechanical methods .4
6.2.1 General .4
6.2.2 Mass of cut.4
6.2.3 Interval between cuts.10
6.2.4 Division of individual increments .11
6.2.5 Minimum mass of divided increment .11
6.2.6 Division of samples.11
6.3 Manual methods .12
6.3.1 General .12
6.3.2 Riffle method.12
6.3.3 Flattened-heap method .12
6.3.4 Strip-mixing and splitting method .15
7 Preparation of samples for specific tests .16
7.1 Types of test sample .16
7.2 Preparation of samples for determining total moisture .16
7.2.1 General .16
7.2.2 Procedure.16
7.2.3 Wet samples.16
7.2.4 Reduction of total moisture test sample.17
7.2.5 Division.17
7.2.6 Determination of moisture.17
7.2.7 Reserve sample .17
7.3 Preparation of sample for general analysis.18
7.3.1 General .18
7.3.2 Segregation errors .18
7.3.3 Reduction .18
7.3.4 Division.18
7.3.5 Preparation Errors.20
7.3.6 Storage .20
7.4 Physical test sample .20
7.5 Samples for special properties .20
8 Design of equipment for preparation .20
8.1 Dividers.20
8.2 Design of cutters for falling-stream dividers.21
8.2.1 General .21
8.2.2 Cutter velocity.21
8.3 Crushers.22
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ISO/CD 13909-6
8.3.1 General. 22
8.3.2 Examples of crushers . 22
8.4 Preparation systems . 22
8.4.1 General. 22
8.4.2 Design criteria. 23
8.4.3 Normal operation . 23
8.4.4 Abnormal operation. 23
8.4.5 Provision for checking for precision . 23
8.4.6 Provision for testing for bias. 23
Bibliography………………………………………………………………………………………………………….….25
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ISO/CD 13909-6
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
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 some of the elements of this part of ISO 13909 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13909-6 was prepared by Technical Committee ISO/TC 27, Solid mineral
fuels, Subcommittee SC 4, Sampling.
ISO 13909 consists 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 — Preparation of test samples
— Part 7: Methods for determining the precision of sampling, sample preparation and testing
— Part 8: Methods of testing for bias
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ISO/CD 13909-6
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 778, ISO 2355).
The process of sample preparation may involve constitution of samples, reduction, division, mixing and drying
or all or a combination of these.
Primary increments may be prepared individually as test samples or combined to constitute samples either as
taken or after having been prepared by reduction and/or division. Samples may either be prepared
individually as test samples or combined on a weighted basis to constitute a further sample.
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DRAFT INTERNATIONAL STANDARD ISO/CD 13909-6
Hard coal and coke – Mechanical sampling – Part 6: Coke –
Preparation of test samples
1 Scope
This part of ISO 13909 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 normative documents contain provisions which, through reference in this text, constitute
provisions of this part of ISO 13909. For dated references, subsequent amendments to, or revisions of, any of
these publications do not apply. However, parties to agreements based on this part of ISO 13909 are
encouraged to investigate the possibility of applying the most recent editions of the normative documents
indicated below. For undated references, the latest edition of the normative document referred to applies.
Members of ISO and IEC maintain registers of currently valid International Standards.
ISO 579:1999, Coke — Determination of total moisture.
ISO 687:1974, Coke — Determination of moisture in the analysis sample.
ISO 13909-1, Hard coal and coke — Mechanical sampling — Part 1: General introduction.
ISO 13909-5, Hard coal and coke — Mechanical sampling — Part 5: Coke — Sampling from moving streams.
ISO 13909-7, Hard coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of
sampling, sample preparation and testing.
ISO 13909-8, Hard coal and coke — Mechanical sampling — Part 8: Methods of testing for bias.
ISO 21398:2007, Guide to the inspection of mechanical sampling systems.
3 Terms and definitions
For the purposes of this part of ISO 13909, the terms and definitions given in ISO 13909-1 apply.
4 Precision of sample preparation
From the equations 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:
L
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ISO/CD 13909-6
a) Example 1
b) Example 2
Figure 1 — Examples of the constitution of samples
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 division(see Clause 6).
6 Division
6.1 General
Since the cutter aperture will be at least three times the nominal top size, this will result in a very large
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ISO/CD 13909-6
increment mass in many cases. The handling and preparation of such large increments would 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 Figure 2.
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 may be 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.
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 should 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
cutter shall be constant. The method of feeding the divider shall be designed to minimize any segregation
caused by the divider.
The cutting aperture shall be at least three times the nominal top size of the coke to be divided.
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ISO/CD 13909-6
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.
a) Rotating cone type
Figure 2 — Examples of dividers
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ISO/CD 13909-6
Key
1 Feed
2 Divided sample in rotating receivers
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:
a)for dividing;
b)for collecting duplicates;
c)for collecting replicates.
b) Container type
Figure 2 — Examples of dividers(continued)
6 © ISO 2008 – All rights reserved
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ISO/CD 13909-6
Key
1 Feed
2 Reject
3
...
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