ISO 13909-4:2001
(Main)Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples
Hard coal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples
Houille et coke — Échantillonnage mécanique — Partie 4: Charbon — Préparation des échantillons pour essai
L'ISO 13909-4:2001 décrit la préparation des échantillons de charbon, de la combinaison de prélèvements primaires à la préparation d'échantillons pour des essais spécifiques.
Črni premog in koks - Mehansko vzorčenje - 4. del: Premog - Priprava preskusnih vzorcev
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INTERNATIONAL ISO
STANDARD 13909-4
First edition
2001-12-15
Hard coal and coke — Mechanical
sampling —
Part 4:
Coal — Preparation of test samples
Houille et coke — Échantillonnage mécanique —
Partie 4: Charbon — Préparation des échantillons pour essai
Reference number
ISO 13909-4:2001(E)
© ISO 2001
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ISO 13909-4:2001(E)
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ISO 13909-4:2001(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Precision of sample preparation . 1
5 Constitution of a sample . 2
6 Division . 4
7 Reduction . 17
8 Mixing . 18
9 Air-drying . 19
10 Preparation of samples for specific tests . 19
11 Reserve sample . 25
12 Design of equipment for preparation . 25
Bibliography. 29
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ISO 13909-4:2001(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.
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 13909-4 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels,
Subcommittee SC 4, Sampling.
ISO 13909 cancels and replaces ISO 9411-1:1994, Solid mineral fuels — Mechanical sampling from moving
streams — Part 1: Coal and ISO 9411-2:1993, Solid mineral fuels — Mechanical sampling from moving streams —
Part 2: Coke, of which it constitutes a technical revision. It also supersedes the methods of mechanical sampling of
coal and coke given in ISO 1988:1975, Hard coal — Sampling and ISO 2309:1980, Coke — 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 13909-4:2001(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 sample depend on the test to be carried out.
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.
When difficulty in handling the coal or coals being sampled is expected at a particular stage in sample preparation,
or if there is a likelihood of losing moisture by evaporation, it is necessary to withdraw the sample or increment from
the on-line system at the stage immediately prior to the point of difficulty and proceed off-line.
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INTERNATIONAL STANDARD ISO 13909-4:2001(E)
Hard coal and coke — Mechanical sampling —
Part 4:
Coal — Preparation of test samples
1 Scope
This part of ISO 13909 describes the preparation of samples of coal 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.
Hard coal — Determination of total moisture.
ISO 589:1981,
ISO 3310-1:2000, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.
Hard coal and coke — Mechanical sampling — Part 1: General introduction.
ISO 13909-1:2001,
ISO 13909-2:2001, Hard coal and coke — Mechanical sampling — Part 2: Coal — Sampling from moving streams.
ISO 13909-3:2001, Hard coal and coke — Mechanical sampling — Part 3: Coal — Sampling from stationary lots.
ISO 13909-7:2001, Hard coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of
sampling, sample preparation and testing.
ISO 13909-8:2001, Hard coal and coke — Mechanical sampling — Part 8: Methods of testing for bias.
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
s
V
I
+V
PT
n
P = 2 (1)
L
m
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ISO 13909-4:2001(E)
where
V is the primary increment variance;
I
n is the number of increments per sub-lot;
V is the preparation and testing variance 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 ofV of 0,2 or less for both ash and
PT
moisture tests. Better levels are expected when using mechanical dividers.
For some preparation schemes, however, practical restrictions may prevent the preparation and testing variance
being as low as this. Under these circumstances, the user will have to 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 method given in ISO 13909-7.
5 Constitution of a sample
5.1 Introduction
Primary increments shall be taken in accordance with the procedures specified in ISO 13909-2 and ISO 13909-3.
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. Examples of the constitution of samples are shown in Figure 1.
The procedures for increment combination (5.2) may vary according to whether the primary increments were taken
using a time-basis (5.2.1) or a mass-basis (5.2.2) sampling scheme.
Samples may also be prepared by the combination of other samples (see 5.3).
5.2 Combination of increments
5.2.1 Time-basis sampling
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).
5.2.2 Mass-basis sampling
If the primary increments are of almost uniform mass (see note), they 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).
NOTE Almost uniform mass has been achieved if the coefficient of variation of the increment masses is less than 20 % and there
is no significant correlation between the flow rate at the time of taking the increment and the mass of the increment (see
ISO 13909-2:2001, annex B).
If the primary increments are not of almost uniform mass, they may only be combined into samples after having been
divided individually by fixed-mass division (see clause 7).
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ISO 13909-4:2001(E)
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 coal
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).
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ISO 13909-4:2001(E)
6 Division
6.1 General
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 one or more parts of the coal 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.
Coal which is visibly wet may not run freely through or may tend to adhere to the surfaces of a sample divider. In such
circumstances, it may be necessary to air-dry the sample as described in clause 10 before sample division is
undertaken.
Manual division is normally applied when mechanical methods would result in loss of integrity, e.g. loss of moisture
or size degradation. Manual methods may themselves result in bias, particularly if the mass of coal 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 which has been crushed, if
necessary, to an appropriate nominal top size. Division shall be either by fixed-mass division or by fixed-ratio division
subject to the conditions set out in 6.2.3.
NOTE The procedures described for fixed-ratio division are the simplest to implement. Other procedures may be used, however,
provided that the mass of the divided sample is proportional to the mass of the feed, e.g. the number of cuts could be kept
constant by making the feed rate of each division proportional to the mass of coal to be divided.
6.2.2 Mass of cut
The cuts shall be of uniform mass throughout the division of an increment. In order to achieve this, the flow of coal to
the divider shall be uniform and the cutting aperture 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 coal to be divided.
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 cutting
interval. For secondary and tertiary dividers, the cycle time shall not be evenly divisible into the cycle time of the
cutter which precedes it.
For fixed-mass division, the interval between taking cuts shall be varied proportionally to the mass of coal to be
divided so that divided samples having almost uniform mass are obtained.
For fixed-ratio division, the interval between taking cuts shall be constant, irrespective of the variations of masses of
coal to be divided, so that the divided-sample masses are proportional to the mass of the feed.
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ISO 13909-4:2001(E)
Key
1Feed
Key 2 Rotating cone
1Feed 3Adjustableslot
2 Reject 4 Divided sample
3 Divided sample 5 Reject
The material from a mixing container is fed by
scrapers tothe centre of thedividingdisc. From
there it is discharged over the range of the disc via
specialclearingarms. Thesamplefalls through A stream of coal is allowed to fall onto a rotating cone;
adjustable slots into chutes; the reject is carried the adjustable slot with lips in the cone allows the
away via a cleaning conduit. The whole interior stream to fall directly onto the sample receiver for part
space is cleaned by scrapers. of each revolution.
a) Rotating disc type b) Rotating cone type
Figure 2 — Examples of dividers
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ISO 13909-4:2001(E)
Key
1Feed
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:
1) for dividing;
2) for collecting duplicates;
3) for collecting replicates.
c) Container type
Figure 2 — Examples of dividers (continued)
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ISO 13909-4:2001(E)
Key
1Feed
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 pre-set time periods. The bucket intercepts the free-falling coal stream to extract cuts which discharge to sample as
the bucket inverts.
d) Chain-bucket type
Figure 2 — Examples of dividers (continued)
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ISO 13909-4:2001(E)
Key
1 Slotted belt
2Feed
3 Inclined chute
4 Divided sample
5Reject
An endless belt having slots spaced at equal pitch with lips that act as cutting edges passes 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 — Examples of dividers (continued)
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ISO 13909-4:2001(E)
Key Key
1Feed 1Feed
2 Reject 2 Reject
3 Divided sample 3 Divided sample
A flat plate with lipped slots spaced at equal pitch
rotates beneath a feed chute. Coal is fed into the
feed chute, then falls onto the rotating plate to form A hollow shaft which is attached to one or more cutters
a ribbon bed which is carried to the plough and rotates within a housing as shown. Each cutter is
discharged to rejects. As a slot passes through the designed to take cuts from the coal stream and to
stream, a cut is taken. discharge via the hollow shaft.
f) Rotating plate type g) Rotating chute type
Figure 2 — Examples of dividers (continued)
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ISO 13909-4:2001(E)
Key
1Feed Key
2 Rotating hopper 1Feed
3Reject 2 Divided sample
4 Divided sample 3Reject
A rotating hopper receives a coal flow and dis-
charges through a spout. Stationary cutters are
positioned in the path of the spout outlet, cuts are The cutter-chute traverses the full coal stream and diverts a portion from
takenaseachcutterispassed.Oneormorecutters the stream. When the coal stream is not being cut by the chute, it is
may be fitted. deflected by the angle plate to reject.
h) Rotating hopper and spout i) Cutter-chute type
Figure 2 — Examples of dividers (continued)
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ISO 13909-4:2001(E)
6.2.4 Division of individual increments
6.2.4.1 Number of cuts
The number of cuts for dividing an increment shall be determined as follows.
a) For fixed-mass division, the minimum number of cuts for dividing primary increments shall be four. An equal
number of cuts shall be taken from each primary increment in the sub-lot.
b) For fixed-ratio division, the minimum number of cuts for dividing a primary increment of mean mass shall be four.
c) For subsequent division of individual divided primary increments, a minimum of one cut shall be taken from each
cut from the preceding division.
Examples of procedures for division of individual increments, and subsequent sample division are shown in Figure 3.
a) Example of division of individual increments (minimum number of cuts)
Figure 3 — Examples of procedures for division of increments and samples
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ISO 13909-4:2001(E)
b) Example of two-stage division of individual increments
Figure 3 — Examples of procedures for division of increments and samples (continued)
6.2.4.2 Minimum mass of divided increment
The minimum mass of a 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 purpose for which the
sample has been taken and 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.
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ISO 13909-4:2001(E)
6.2.5 Division of samples
6.2.5.1 Number of cuts
The sample constituted from all increments, or divided increments, 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 to 20.
If the mass is too low, an alternative manual method of division should be used.
6.2.5.2 Minimum mass of divided samples (see Table 1)
For most parameters, particularly size analysis and those that are particle-size related, the precision of the result is
limited by the ability of the sample to represent all the particle sizes in the mass of coal being sampled.
The minimum mass of divided samples is dependent on the nominal top size of the coal, the precision required for
the parameter concerned and the relationship of that parameter to particle size. The attainment of the required
minimum mass after division will not, in itself, guarantee the required precision, because division precision is also
dependent on the number of cuts taken during division (see 6.2.4.1 and 6.2.5.1).
Values for the minimum mass of divided samples for general analysis to reduce the variance due to the particulate
nature of the coal to 0,01, corresponding to a precision of 0,2 % with regard to ash, are given in column 2 of Table 1
[1]
(see CSIRO report ). Column 3 of Table 1 gives the corresponding minimum masses of divided samples for total-
20 %
moisture analysis, which are approximately of the minimum masses for general analysis, subject to an absolute
minimum of 0,65 kg. Values for the minimum mass of divided samples for size analysis are given in columns 4 and 5
1% 2%
of Table 1 for division precisions of and respectively. These masses have been calculated on the basis of the
precision of the determination of oversize, i.e. the coal above the normal top size. The precision for other size
fractions will normally be better than this. Note that, in each case, the overall division precision is determined by the
sum of the division variances for each sample-division stage.
The minimum mass of divided samples,m , for other desired levels of precision may be calculated from the following
S
equation:
� �
2
P
0
m =m (2)
S S,0
P
R
where
m is the minimum mass of sample after division specified in Table 1 for a given nominal top size;
S,0
P is the precision for a given division stage specified in Table 1;
0
P is the required precision for a given division stage.
R
When a coal is regularly sampled under the same circumstances, the precision obtained for all the required quality
parameters shall be checked (see ISO 13909-7) and the masses may be adjusted accordingly. However, the masses
shall not be reduced below the minimum requirements laid down in the relevant analysis standards.
When preparing coal to produce samples for multiple use, account shall also be taken of the masses and size
distribution of the test samples required for each test.
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ISO 13909-4:2001(E)
Table 1 — Minimum mass of sample after division
Nominal top size of General-analysis and Total-moisture analysis
Size-analysis samples
coal common samples samples
mm kg kg 1% 2%
300 15 000 3 000 54 000 13 500
200 5 400 1 100 16 000 4 000
150 2 600 500 6 750 1 700
125 1 700 350 4 000 1 000
90 750 125 1 500 400
75 470 95 850 210
63 300 60 500 125
50 170 35 250 65
45 125 25 200 50
38 85 17 110 30
31,5 55 10 65 15
22,4 32 7 25 6
16 20 4 8 2
11,2 13 2,5 3 0,7
10 10 2,0 2 0,5
8 6 1,5 1 0,25
5,6 3 1,2 0,5 0,25
4 1,5 1,0 0,25 0,25
2,8 0,65 0,65 0,25 0,25
2,0 0,25 — — —
10,1 — — —
< 0,5 0,06 — — —
NOTE 1 The masses for the general-analysis samples and common samples have been determined to reduce the variance due to the
particulate nature of coal to 0,01, corresponding to a precision of 0,2 % ash.
NOTE 2 These values are generally suitable for off-line division but, for nominal top sizes of 16 mm and below, the masses may not be
sufficient to maintain the integrity of the sample when performing on-line division.
6.3 Manual methods
6.3.1 Riffle method
A riffle (see Figure 4) is a sample divider that will, in a single pass of a sample, divide it into halves, one of which is
retained and the other normally rejected. The device is normally portable and, for sample division, is usually fed
manually, the coal being evenly distributed along it's length. Adjacent slots feed opposite receivers.
The slot width shall be at least 3 times the nominal top size of the coal. Each half of the riffle shall have the same
number of slots, which shall be at least eight and preferably more. All the surfaces on which the coal might rest shall
�
have a slope of at least 60 to the horizontal.
The coal shall be allowed to fall steadily into the riffle, ensuring that it is evenly distributed over all the slots. The coal
shall be allowed to fall freely, i.e. not towards one side of the riffle, and the rate of feed shall be controlled such that
the slots are never choked. Closed riffles are preferred.
Care shall be taken to minimize loss of dust and moisture. To this end, the receiver shall fit closely against the body
of the riffle and, for dry coals and moisture samples, closed-type riffles shall be used.
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ISO 13909-4:2001(E)
When a stage of sample division requires two or more steps or passes, the sample retained at each step shall be
taken alternately from each side of the riffle.
Key
1 Even number of slots
a) Open type b) Closed type
Figure 4 — Examples of riffles
6.3.2 Flattened-heap method
Theprocedure,whichisillustratedinFigure5,is as follows.
The sample is mixed thoroughly and spread to form a rectangle of uniform thickness on a mixing plate which is a
smooth, non-absorbent and non-contaminating surface. The maximum thickness shall be 3 times the nominal top
size of the coal. Avoid moisture loss from wet coals which can result from over-mixing.
If the mass of the coal is greater than can be formed into a heap of 2m� 2,5 m, two or more heaps of equal mass
shall be formed and separate samples shall be taken from each heap.
A matrix is marked on the spread sample to give a minimum of 4� 5 equal parts. An increment is taken, at random,
from each of the parts by inserting a scoop with a bump plate (see the last paragraph of this subclause) to the bottom
of the matrix layer. The increments are combined into a divided sample. It is essential that these operations be
performed quickly if loss of moisture is to be prevented.
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ISO 13909-4:2001(E)
The increments shall be of uniform mass. The minimum mass required for each nominal top size is the mass of the
divided sample (see Table 1) divided by the number of parts of the flattened heap. This mass is determined by using
a scoop of appropriate dimensions.
The scoop shall be flat bottomed and the width of the entry shall be at least three times the nominal top size of the
coal. The side walls shall be higher than the height of the heap and the depth shall be sufficient to allow the required
mass of increment to be taken.
a) Spread the crushed sample into a rectangle with a
maximum thickness of three times the nominal top size.
b) Arrange into 20 equal parts, e.g. into five equal parts
lengthwise and four equal parts breadthwise.
c) Take a scoopful of samples at random from each of
the 20 parts by inserting the scoop to the bottom of the
sample layer. Combine the 20 scoopfuls into a divided
sample.
d) Detail of taking an increment by using the bump
plate shown in c).
Figure 5 — Flattened-heap method
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ISO 13909-4:2001(E)
Take the scoop sample with the aid of a bump plate which is inserted vertically through the flattened heap until it is in
contact with the bottom of the sample layer. The scoop is then inserted to the bottom of the spread coal and moved
horizontally until its open end comes into contact with the vertical bump plate. The scoop and bump plate are lifted
together to ensure that all particles are collected off the top of the mixing plate and that none fall off during lifting.
6.3.3 Strip-mix
...
SLOVENSKI STANDARD
SIST ISO 13909-4:2002
01-junij-2002
ýUQLSUHPRJLQNRNV0HKDQVNRY]RUþHQMHGHO 3UHPRJ3ULSUDYDSUHVNXVQLK
Y]RUFHY
Hard coal and coke -- Mechanical sampling -- Part 4: Coal -- Preparation of test samples
Houille et coke -- Échantillonnage mécanique -- Partie 4: Charbon -- Préparation des
échantillons pour essai
Ta slovenski standard je istoveten z: ISO 13909-4:2001
ICS:
73.040 Premogi Coals
SIST ISO 13909-4:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST ISO 13909-4:2002
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SIST ISO 13909-4:2002
INTERNATIONAL ISO
STANDARD 13909-4
First edition
2001-12-15
Hard coal and coke — Mechanical
sampling —
Part 4:
Coal — Preparation of test samples
Houille et coke — Échantillonnage mécanique —
Partie 4: Charbon — Préparation des échantillons pour essai
Reference number
ISO 13909-4:2001(E)
© ISO 2001
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SIST ISO 13909-4:2002
ISO 13909-4:2001(E)
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tronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's mem-
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SIST ISO 13909-4:2002
ISO 13909-4:2001(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Precision of sample preparation . 1
5 Constitution of a sample . 2
6 Division . 4
7 Reduction . 17
8 Mixing . 18
9 Air-drying . 19
10 Preparation of samples for specific tests . 19
11 Reserve sample . 25
12 Design of equipment for preparation . 25
Bibliography. 29
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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 13909-4 was prepared by Technical Committee ISO/TC 27, Solid mineral fuels,
Subcommittee SC 4, Sampling.
ISO 13909 cancels and replaces ISO 9411-1:1994, Solid mineral fuels — Mechanical sampling from moving
streams — Part 1: Coal and ISO 9411-2:1993, Solid mineral fuels — Mechanical sampling from moving streams —
Part 2: Coke, of which it constitutes a technical revision. It also supersedes the methods of mechanical sampling of
coal and coke given in ISO 1988:1975, Hard coal — Sampling and ISO 2309:1980, Coke — 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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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 sample depend on the test to be carried out.
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.
When difficulty in handling the coal or coals being sampled is expected at a particular stage in sample preparation,
or if there is a likelihood of losing moisture by evaporation, it is necessary to withdraw the sample or increment from
the on-line system at the stage immediately prior to the point of difficulty and proceed off-line.
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Hard coal and coke — Mechanical sampling —
Part 4:
Coal — Preparation of test samples
1 Scope
This part of ISO 13909 describes the preparation of samples of coal 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.
Hard coal — Determination of total moisture.
ISO 589:1981,
ISO 3310-1:2000, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth.
Hard coal and coke — Mechanical sampling — Part 1: General introduction.
ISO 13909-1:2001,
ISO 13909-2:2001, Hard coal and coke — Mechanical sampling — Part 2: Coal — Sampling from moving streams.
ISO 13909-3:2001, Hard coal and coke — Mechanical sampling — Part 3: Coal — Sampling from stationary lots.
ISO 13909-7:2001, Hard coal and coke — Mechanical sampling — Part 7: Methods for determining the precision of
sampling, sample preparation and testing.
ISO 13909-8:2001, Hard coal and coke — Mechanical sampling — Part 8: Methods of testing for bias.
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
s
V
I
+V
PT
n
P = 2 (1)
L
m
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where
V is the primary increment variance;
I
n is the number of increments per sub-lot;
V is the preparation and testing variance 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 ofV of 0,2 or less for both ash and
PT
moisture tests. Better levels are expected when using mechanical dividers.
For some preparation schemes, however, practical restrictions may prevent the preparation and testing variance
being as low as this. Under these circumstances, the user will have to 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 method given in ISO 13909-7.
5 Constitution of a sample
5.1 Introduction
Primary increments shall be taken in accordance with the procedures specified in ISO 13909-2 and ISO 13909-3.
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. Examples of the constitution of samples are shown in Figure 1.
The procedures for increment combination (5.2) may vary according to whether the primary increments were taken
using a time-basis (5.2.1) or a mass-basis (5.2.2) sampling scheme.
Samples may also be prepared by the combination of other samples (see 5.3).
5.2 Combination of increments
5.2.1 Time-basis sampling
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).
5.2.2 Mass-basis sampling
If the primary increments are of almost uniform mass (see note), they 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).
NOTE Almost uniform mass has been achieved if the coefficient of variation of the increment masses is less than 20 % and there
is no significant correlation between the flow rate at the time of taking the increment and the mass of the increment (see
ISO 13909-2:2001, annex B).
If the primary increments are not of almost uniform mass, they may only be combined into samples after having been
divided individually by fixed-mass division (see clause 7).
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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 coal
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).
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6 Division
6.1 General
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 one or more parts of the coal 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.
Coal which is visibly wet may not run freely through or may tend to adhere to the surfaces of a sample divider. In such
circumstances, it may be necessary to air-dry the sample as described in clause 10 before sample division is
undertaken.
Manual division is normally applied when mechanical methods would result in loss of integrity, e.g. loss of moisture
or size degradation. Manual methods may themselves result in bias, particularly if the mass of coal 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 which has been crushed, if
necessary, to an appropriate nominal top size. Division shall be either by fixed-mass division or by fixed-ratio division
subject to the conditions set out in 6.2.3.
NOTE The procedures described for fixed-ratio division are the simplest to implement. Other procedures may be used, however,
provided that the mass of the divided sample is proportional to the mass of the feed, e.g. the number of cuts could be kept
constant by making the feed rate of each division proportional to the mass of coal to be divided.
6.2.2 Mass of cut
The cuts shall be of uniform mass throughout the division of an increment. In order to achieve this, the flow of coal to
the divider shall be uniform and the cutting aperture 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 coal to be divided.
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 cutting
interval. For secondary and tertiary dividers, the cycle time shall not be evenly divisible into the cycle time of the
cutter which precedes it.
For fixed-mass division, the interval between taking cuts shall be varied proportionally to the mass of coal to be
divided so that divided samples having almost uniform mass are obtained.
For fixed-ratio division, the interval between taking cuts shall be constant, irrespective of the variations of masses of
coal to be divided, so that the divided-sample masses are proportional to the mass of the feed.
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Key
1Feed
Key 2 Rotating cone
1Feed 3Adjustableslot
2 Reject 4 Divided sample
3 Divided sample 5 Reject
The material from a mixing container is fed by
scrapers tothe centre of thedividingdisc. From
there it is discharged over the range of the disc via
specialclearingarms. Thesamplefalls through A stream of coal is allowed to fall onto a rotating cone;
adjustable slots into chutes; the reject is carried the adjustable slot with lips in the cone allows the
away via a cleaning conduit. The whole interior stream to fall directly onto the sample receiver for part
space is cleaned by scrapers. of each revolution.
a) Rotating disc type b) Rotating cone type
Figure 2 — Examples of dividers
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Key
1Feed
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:
1) for dividing;
2) for collecting duplicates;
3) for collecting replicates.
c) Container type
Figure 2 — Examples of dividers (continued)
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Key
1Feed
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 pre-set time periods. The bucket intercepts the free-falling coal stream to extract cuts which discharge to sample as
the bucket inverts.
d) Chain-bucket type
Figure 2 — Examples of dividers (continued)
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Key
1 Slotted belt
2Feed
3 Inclined chute
4 Divided sample
5Reject
An endless belt having slots spaced at equal pitch with lips that act as cutting edges passes 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 — Examples of dividers (continued)
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Key Key
1Feed 1Feed
2 Reject 2 Reject
3 Divided sample 3 Divided sample
A flat plate with lipped slots spaced at equal pitch
rotates beneath a feed chute. Coal is fed into the
feed chute, then falls onto the rotating plate to form A hollow shaft which is attached to one or more cutters
a ribbon bed which is carried to the plough and rotates within a housing as shown. Each cutter is
discharged to rejects. As a slot passes through the designed to take cuts from the coal stream and to
stream, a cut is taken. discharge via the hollow shaft.
f) Rotating plate type g) Rotating chute type
Figure 2 — Examples of dividers (continued)
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Key
1Feed Key
2 Rotating hopper 1Feed
3Reject 2 Divided sample
4 Divided sample 3Reject
A rotating hopper receives a coal flow and dis-
charges through a spout. Stationary cutters are
positioned in the path of the spout outlet, cuts are The cutter-chute traverses the full coal stream and diverts a portion from
takenaseachcutterispassed.Oneormorecutters the stream. When the coal stream is not being cut by the chute, it is
may be fitted. deflected by the angle plate to reject.
h) Rotating hopper and spout i) Cutter-chute type
Figure 2 — Examples of dividers (continued)
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6.2.4 Division of individual increments
6.2.4.1 Number of cuts
The number of cuts for dividing an increment shall be determined as follows.
a) For fixed-mass division, the minimum number of cuts for dividing primary increments shall be four. An equal
number of cuts shall be taken from each primary increment in the sub-lot.
b) For fixed-ratio division, the minimum number of cuts for dividing a primary increment of mean mass shall be four.
c) For subsequent division of individual divided primary increments, a minimum of one cut shall be taken from each
cut from the preceding division.
Examples of procedures for division of individual increments, and subsequent sample division are shown in Figure 3.
a) Example of division of individual increments (minimum number of cuts)
Figure 3 — Examples of procedures for division of increments and samples
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b) Example of two-stage division of individual increments
Figure 3 — Examples of procedures for division of increments and samples (continued)
6.2.4.2 Minimum mass of divided increment
The minimum mass of a 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 purpose for which the
sample has been taken and 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.
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6.2.5 Division of samples
6.2.5.1 Number of cuts
The sample constituted from all increments, or divided increments, 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 to 20.
If the mass is too low, an alternative manual method of division should be used.
6.2.5.2 Minimum mass of divided samples (see Table 1)
For most parameters, particularly size analysis and those that are particle-size related, the precision of the result is
limited by the ability of the sample to represent all the particle sizes in the mass of coal being sampled.
The minimum mass of divided samples is dependent on the nominal top size of the coal, the precision required for
the parameter concerned and the relationship of that parameter to particle size. The attainment of the required
minimum mass after division will not, in itself, guarantee the required precision, because division precision is also
dependent on the number of cuts taken during division (see 6.2.4.1 and 6.2.5.1).
Values for the minimum mass of divided samples for general analysis to reduce the variance due to the particulate
nature of the coal to 0,01, corresponding to a precision of 0,2 % with regard to ash, are given in column 2 of Table 1
[1]
(see CSIRO report ). Column 3 of Table 1 gives the corresponding minimum masses of divided samples for total-
20 %
moisture analysis, which are approximately of the minimum masses for general analysis, subject to an absolute
minimum of 0,65 kg. Values for the minimum mass of divided samples for size analysis are given in columns 4 and 5
1% 2%
of Table 1 for division precisions of and respectively. These masses have been calculated on the basis of the
precision of the determination of oversize, i.e. the coal above the normal top size. The precision for other size
fractions will normally be better than this. Note that, in each case, the overall division precision is determined by the
sum of the division variances for each sample-division stage.
The minimum mass of divided samples,m , for other desired levels of precision may be calculated from the following
S
equation:
� �
2
P
0
m =m (2)
S S,0
P
R
where
m is the minimum mass of sample after division specified in Table 1 for a given nominal top size;
S,0
P is the precision for a given division stage specified in Table 1;
0
P is the required precision for a given division stage.
R
When a coal is regularly sampled under the same circumstances, the precision obtained for all the required quality
parameters shall be checked (see ISO 13909-7) and the masses may be adjusted accordingly. However, the masses
shall not be reduced below the minimum requirements laid down in the relevant analysis standards.
When preparing coal to produce samples for multiple use, account shall also be taken of the masses and size
distribution of the test samples required for each test.
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Table 1 — Minimum mass of sample after division
Nominal top size of General-analysis and Total-moisture analysis
Size-analysis samples
coal common samples samples
mm kg kg 1% 2%
300 15 000 3 000 54 000 13 500
200 5 400 1 100 16 000 4 000
150 2 600 500 6 750 1 700
125 1 700 350 4 000 1 000
90 750 125 1 500 400
75 470 95 850 210
63 300 60 500 125
50 170 35 250 65
45 125 25 200 50
38 85 17 110 30
31,5 55 10 65 15
22,4 32 7 25 6
16 20 4 8 2
11,2 13 2,5 3 0,7
10 10 2,0 2 0,5
8 6 1,5 1 0,25
5,6 3 1,2 0,5 0,25
4 1,5 1,0 0,25 0,25
2,8 0,65 0,65 0,25 0,25
2,0 0,25 — — —
10,1 — — —
< 0,5 0,06 — — —
NOTE 1 The masses for the general-analysis samples and common samples have been determined to reduce the variance due to the
particulate nature of coal to 0,01, corresponding to a precision of 0,2 % ash.
NOTE 2 These values are generally suitable for off-line division but, for nominal top sizes of 16 mm and below, the masses may not be
sufficient to maintain the integrity of the sample when performing on-line division.
6.3 Manual methods
6.3.1 Riffle method
A riffle (see Figure 4) is a sample divider that will, in a single pass of a sample, divide it into halves, one of which is
retained and the other normally rejected. The device is normally portable and, for sample division, is usually fed
manually, the coal being evenly distributed along it's length. Adjacent slots feed opposite receivers.
The slot width shall be at least 3 times the nominal top size of the coal. Each half of the riffle shall have the same
number of slots, which shall be at least eight and preferably more. All the surfaces on which the coal might rest shall
�
have a slope of at least 60 to the horizontal.
The coal shall be allowed to fall steadily into the riffle, ensuring that it is evenly distributed over all the slots. The coal
shall be allowed to fall freely, i.e. not towards one side of the riffle, and the rate of feed shall be controlled such that
the slots are never choked. Closed riffles are preferred.
Care shall be taken to minimize loss of dust and moisture. To this end, the receiver shall fit closely against the body
of the riffle and, for dry coals and moisture samples, closed-type riffles shall be used.
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When a stage of sample division requires two or more steps or passes, the sample retained at each step shall be
taken alternately from each side of the riffle.
Key
1 Even number of slots
a) Open type b) Closed type
Figure 4 — Examples of riffles
6.3.2 Flattened-heap method
Theprocedure,whichisillustratedinFigure5,is as follows.
The sample is mixed thoroughly and spread to form a rectangle of uniform thickness on a mixing plate which is a
smooth, non-absorbent and non-contaminating surface. The maximum thickness shall be 3 times the nominal top
size of the coal. Avoid moisture loss from wet coals which can result from over-mixing.
If the mass of the coal is greater than can be formed into a heap of 2m� 2,5 m, two or more heaps of equal mass
shall be formed and separate samples shall be taken from each heap.
A matrix is marked on the spread sample to give a minimum of 4� 5 equal parts. An increment is taken, at random,
from each of the parts by inserting a scoop with a bump plate (see the last paragraph of this subclause) to the bottom
of the matrix layer. The increments are combined into a divided sample. It is essential that these operations be
performed quickly if loss of moisture is to be prevented.
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The increments shall be of uniform mass. The minimum mass required for each nominal top size is the mass of the
divided sample (see Table 1) divided by the number of parts of the flattened heap. This mass is determined by using
a scoop of appropriate dimensions.
The scoop shall be flat bottomed and the width of the entry shall be at least t
...
NORME ISO
INTERNATIONALE 13909-4
Première édition
2001-12-15
Houille et coke — Échantillonnage
mécanique —
Partie 4:
Charbon — Préparation des échantillons
pour essai
Hard coal and coke — Mechanical sampling —
Part 4: Coal — Preparation of test samples
Numéro de référence
ISO 13909-4:2001(F)
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ISO 13909-4:2001(F)
Sommaire Page
Avant-propos. iv
Introduction . v
1 Domaine d'application. 1
2 Références normatives . 1
3 Termes et définitions. 1
4 Fidélité de la préparation de l'échantillon . 2
5 Constitution d'un échantillon . 2
6 Division . 4
7 Réduction . 19
8 Homogénéisation. 20
9 Séchage à l'air. 21
10 Préparation des échantillons pour des essais spécifiques . 21
11 Échantillon de réserve. 28
12 Conception de l'équipement pour la préparation. 29
Bibliographie . 32
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Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes nationaux de
normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est en général confiée
aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude a le droit de faire partie du
comité technique créé à cet effet. Les organisations internationales, gouvernementales et non
gouvernementales, en liaison avec l'ISO participent également aux travaux. L'ISO collabore étroitement avec
la Commission électrotechnique internationale (CEI) en ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles données dans les Directives ISO/CEI,
Partie 3.
La tâche principale des comités techniques est d'élaborer les Normes internationales. Les projets de Normes
internationales adoptés par les comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 % au moins des comités membres
votants.
L'attention est appelée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable de ne
pas avoir identifié de tels droits de propriété et averti de leur existence.
L'ISO 13909-4 a été élaborée par le comité technique ISO/TC 27, Combustibles minéraux solides,
sous-comité SC 4, Échantillonnage.
L'ISO 13909 annule et remplace l'ISO 9411-1:1994, Combustibles minéraux solides — Échantillonnage
mécanique sur minéraux en mouvement — Partie 1: Charbon et l'ISO 9411-2:1993, Combustibles minéraux
solides — Échantillonnage mécanique sur minéraux en mouvement — Partie 2: Coke, dont elle constitue une
révision technique. Elle remplace également les méthodes d'échantillonnage mécanique du charbon et du
coke données dans l'ISO 1988:1975, Charbons et lignites durs — Échantillonnage et l'ISO 2309:1980,
Coke — Échantillonnage.
L'ISO 13909 comprend les parties suivantes, présentées sous le titre général Houille et coke —
Échantillonnage mécanique:
Partie 1: Introduction générale
Partie 2: Charbon — Échantillonnage en continu
Partie 3: Charbon — Échantillonnage sur lots statiques
Partie 4: Charbon — Préparation des échantillons pour essai
Partie 5: Coke — Échantillonnage en continu
Partie 6: Coke — Préparation des échantillons pour essai
Partie 7: Méthodes pour la détermination de la fidélité de l'échantillonnage, de la préparation de
l'échantillon et de l'essai
Partie 8: Méthodes de détection du biais
iv © ISO 2001 – Tous droits réservés
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ISO 13909-4:2001(F)
Introduction
L'objectif de la préparation des échantillons est de préparer un ou plusieurs échantillons pour essai à partir
des prélèvements primaires pour une analyse ultérieure. La masse requise et la granulométrie de l'échantillon
pour essai dépendent de l'essai à effectuer.
Le processus de préparation des échantillons peut comprendre l'ensemble des opérations suivantes ou
certaines d'entre-elles combinées: constitution, réduction, division, mélange et séchage des échantillons.
Les prélèvements primaires peuvent être préparés individuellement en tant qu'échantillons pour essai ou en
combinaison pour constituer des échantillons soit tels quels, soit après une préparation par réduction et/ou
division. Les échantillons peuvent être préparés soit individuellement en tant qu'échantillons pour essai, soit
en combinaison sur une base pondérée afin de constituer un autre échantillon.
Lorsque la manipulation du ou des charbons à échantillonner risque d'être problématique à une phase
donnée de la préparation des échantillons, ou s'il est probable qu'il y a une perte d'humidité par évaporation, il
est nécessaire de retirer l'échantillon ou le prélèvement du système en ligne à la phase qui précède
immédiatement le point de difficulté et de procéder hors ligne.
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NORME INTERNATIONALE ISO 13909-4:2001(F)
Houille et coke — Échantillonnage mécanique —
Partie 4:
Charbon — Préparation des échantillons pour essai
1 Domaine d'application
La présente partie de l'ISO 13909 décrit la préparation des échantillons de charbon, de la combinaison de
prélèvements primaires à la préparation d'échantillons pour des essais spécifiques.
2 Références normatives
Les documents normatifs suivants contiennent des dispositions qui, par suite de la référence qui y est faite,
constituent des dispositions valables pour la présente partie de l'ISO 13909. Pour les références datées, les
amendements ultérieurs ou les révisions de ces publications ne s'appliquent pas. Toutefois, les parties
prenantes aux accords fondés sur la présente partie de l'ISO 13909 sont invitées à rechercher la possibilité
d'appliquer les éditions les plus récentes des documents normatifs indiqués ci-après. Pour les références non
datées, la dernière édition du document normatif en référence s'applique. Les membres de l'ISO et de la CEI
possèdent le registre des Normes internationales en vigueur.
ISO 589:1981, Houille — Détermination de l'humidité totale
ISO 3310-1:2000, Tamis de contrôle — Exigences techniques et vérifications — Partie 1: Tamis de contrôle
en tissus métalliques
ISO 13909-1:2001, Houille et coke — Échantillonnage mécanique — Partie 1: Introduction générale
ISO 13909-2:2001, Houille et coke — Échantillonnage mécanique — Partie 2: Charbon — Échantillonnage en
continu
ISO 13909-3:2001, Houille et coke — Échantillonnage mécanique — Partie 3: Charbon — Échantillonnage
sur lots statiques
ISO 13909-7:2001, Houille et coke — Échantillonnage mécanique — Partie 7: Méthodes pour la détermination
de la fidélité de l'échantillonnage, de la préparation de l'échantillon et de l'essai
ISO 13909-8:2001, Houille et coke — Échantillonnage mécanique — Partie 8: Méthodes de détection du biais
3 Termes et définitions
Pour les besoins de la présente partie de l'ISO 13909, les termes et définitions donnés dans l'ISO 13909-1
s'appliquent.
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ISO 13909-4:2001(F)
4 Fidélité de la préparation de l'échantillon
À partir des équations données dans l'ISO 13909-7, la valeur absolue estimée de la fidélité du résultat obtenu
pour le lot à un niveau de confiance de 95 %, P , pour l'échantillonnage continu est donné par l'équation
L
suivante:
V
I
+ V
PT
n
P = 2 (1)
L
m
où
V est la variance primaire du prélèvement;
I
n est le nombre de prélèvements par sous-lot;
V est la variance de la préparation et des essais à la fois pour les systèmes en ligne et hors ligne;
PT
m est le nombre de sous-lots.
Les modes opératoires expliqués dans la présente partie de l'ISO 13909 ont pour objectif d'arriver à des
niveaux de V équivalant à 0,2 ou moins tant pour les essais des cendres que pour l'humidité. Si des
PT
diviseurs mécaniques sont utilisés, de meilleurs niveaux peuvent être atteints.
Toutefois, dans certains programmes de préparation, la variance de la préparation et des essais peut ne pas
être aussi faible en raison de restrictions d'ordre pratique. Dans ce cas, l'utilisateur devra décider s'il veut
obtenir la fidélité globale souhaitée en améliorant le programme de préparation ou en divisant le lot en un
nombre supérieur de sous-lots.
Les erreurs se produisant aux diverses étapes de la préparation et de l'analyse, exprimées en termes de
variance, peuvent être vérifiées à l'aide de la méthode décrite dans l'ISO 13909-7.
5 Constitution d'un échantillon
5.1 Introduction
Des prélèvements primaires seront recueillis conformément aux modes opératoires décrits dans
l'ISO 13909-2 et l'ISO 13909-3.
Les prélèvements individuels sont généralement combinés pour former un échantillon. Un simple échantillon
peut être constitué de la combinaison de prélèvements pris sur l'intégralité d'un sous-lot ou en combinant des
prélèvements pris sur des parties individuelles d'un sous-lot. Dans certains cas comme l'analyse
granulométrique ou la détection du biais, l'échantillon est constitué d'un seul prélèvement qui est préparé et
soumis à l'essai. Des exemples de constitution des échantillons sont représentés à la Figure 1.
Les modes opératoires relatifs à la combinaison de prélèvements (5.2) peuvent varier selon que les
prélèvements primaires ont été effectués à l'aide d'un programme d'échantillonnage basé sur le temps (5.2.1)
ou basé sur la masse (5.2.2).
Des échantillons peuvent également être préparés grâce à la combinaison d'autres échantillons (voir 5.3).
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ISO 13909-4:2001(F)
5.2 Combinaison de prélèvements
5.2.1 Échantillonnage basé sur le temps
La masse des prélèvements primaires doit être proportionnelle au débit au moment de l'échantillonnage. Les
prélèvements primaires peuvent être combinés pour former un échantillon, soit pris directement tels quels,
soit après les avoir préparés individuellement à une étape appropriée par une division à taux fixe (voir
Article 6).
5.2.2 Échantillonnage basé sur la masse
Si les prélèvements primaires ont une masse quasi uniforme (voir la Note), ils peuvent être combinés pour
former un échantillon, soit pris directement tels quels, soit après les avoir préparés individuellement à une
étape appropriée par une division à taux fixe (voir Article 6).
NOTE Une masse quasi uniforme est obtenue si le coefficient de variation de la masse des prélèvements est
inférieur à 20 % et s'il n'y a pas de corrélation importante entre le débit au moment du prélèvement et la masse du
prélèvement (voir l'ISO 13909-2:2001, Annexe B).
Si les prélèvements primaires n'ont pas une masse quasi uniforme, ils ne peuvent être combinés pour former
des échantillons qu'après avoir été divisés individuellement par une division à masse constante (voir Article 7).
a) Exemple 1
Figure 1 — Exemples de constitution des échantillons
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ISO 13909-4:2001(F)
b) Exemple 2
Figure 2 (Suite)
5.3 Combinaison des échantillons
Lors de la combinaison des échantillons, la masse des échantillons individuels doit être proportionnelle à la
masse du charbon dans lequel ils ont été prélevés afin d'obtenir une moyenne pondérée de la caractérisation
de la qualité pour le sous-lot. Avant la combinaison, une division à taux fixe doit être effectuée (voir Article 6).
6 Division
6.1 Généralités
Une division peut être effectuée
mécaniquement en ligne, ou
mécaniquement hors ligne ou manuellement.
Chaque fois que c'est possible, il y a lieu de privilégier les méthodes mécaniques aux méthodes manuelles
afin de réduire au minimum toute erreur humaine. Des exemples de diviseurs sont illustrés à la Figure 2.
Les diviseurs mécaniques sont conçus pour extraire une ou plusieurs parties du charbon dans un certain
nombre de coupes de masse relativement petite. Lorsque la plus petite masse de l'échantillon divisé pouvant
être obtenue par un seul passage dans l'appareil est plus importante que celle requise, d'autres passages
dans le même appareil ou dans d'autres appareils peuvent s'avérer nécessaires.
Le charbon visiblement humide peut ne pas passer librement dans le diviseur et avoir tendance à adhérer aux
surfaces. Dans ce cas, il peut être utile de sécher l'échantillon à l'air comme décrit à l'Article 10 avant de
procéder à un sous-échantillonnage.
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ISO 13909-4:2001(F)
Une division manuelle est généralement opérée lorsque les méthodes mécaniques risquent d'entraîner une
perte d'intégrité (par exemple: perte d'humidité ou dégradation dimensionnelle). Les méthodes manuelles
peuvent elles-mêmes provoquer un biais, en particulier si la masse du charbon à diviser est importante.
6.2 Méthodes mécaniques
6.2.1 Généralités
Une division mécanique d'un échantillon peut être effectuée sur un prélèvement individuel ou un échantillon
qui a été broyé, au besoin pour atteindre une dimension nominale supérieure appropriée. Leur division doit
être effectuée à masse constante ou à rapport constant en fonction des conditions définies en 6.2.3.
NOTE Les modes opératoires décrits pour la division à rapport constant sont plus simples à mettre en œuvre.
D'autres modes opératoires peuvent être utilisés pour autant que la masse de l'échantillon divisé soit proportionnelle à la
masse d'entrée. Le nombre de coupes peut être maintenu constant en utilisant, pour chaque division, un débit d'entrée
proportionnel à la masse du charbon à diviser.
6.2.2 Masse de la coupe
Les coupes doivent présenter une masse uniforme tout au long de la division d'un prélèvement. Pour ce faire,
le débit de charbon au niveau du diviseur doit être uniforme et l'ouverture de coupe doit être constante. La
méthode d'alimentation du diviseur doit être étudiée de manière à minimiser la ségrégation causée par le
diviseur.
L'ouverture de coupe doit au moins être égale à trois fois la dimension maximale nominale du charbon à
diviser.
6.2.3 Intervalle entre coupes
Afin de minimiser le biais, la première coupe pour chaque masse à diviser doit être effectuée de manière
aléatoire dans le premier intervalle. En ce qui concerne les dispositifs de coupe secondaires et tertiaires, la
durée du cycle opératoire ne doit pas être divisible par la durée du cycle opératoire d'un dispositif de
prélèvement situé en amont.
Pour une division à masse constante, l'intervalle entre deux coupes doit être déterminé en fonction de la
masse de charbon à diviser, de manière à ce que les échantillons divisés présentent une masse quasiment
uniforme.
Pour une division à rapport constant, l'intervalle entre deux coupes doit être constant, quelles que soient les
variations des masses de charbon à diviser, de manière que la masse des échantillons divisés soit
proportionnelle à la masse d'alimentation.
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ISO 13909-4:2001(F)
Légende Légende
1 alimentation 1 alimentation
2 rejets 2 cône rotatif
3 échantillon divisé 3 fente réglable
4 échantillon divisé
Le matériau d'un mélangeur est orienté par des racloirs
5 rejets
vers le centre du disque. Il est ensuite réparti sur la
surface du disque par des dispositifs spéciaux.
Un écoulement de charbon tombe sur un cône rotatif; une
L'échantillon tombe par des fentes réglables dans des
fente réglable avec rebords ménagée dans le cône
goulottes; les rejets sont évacués par un conduit de
permet à l'écoulement de tomber directement sur le
nettoyage. L'espace intérieur est nettoyé par des racleurs.
collecteur d'échantillons pendant une partie de chaque
révolution.
a) Diviseur à disque rotatif b) Diviseur à cône rotatif
Figure 2 — Exemples de diviseurs
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ISO 13909-4:2001(F)
Légende
1 alimentation
2 échantillon divisé dans des collecteurs rotatifs
Le charbon est déversé dans la trémie puis l'écoulement de charbon est intercepté par l'arête supérieure d'un certain
nombre de récipients disposés en secteurs, permettant de diviser l'écoulement en portions égales. Soit la trémie ou soit
les récipients peuvent tourner. La machine peut être contrôlée pour les opérations suivantes:
1) division;
2) collecte des échantillons dédoublés;
3) collecte des subdivisés.
c) Diviseur à récipients
Figure 2 (Suite)
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ISO 13909-4:2001(F)
Légende
1 alimentation
2 rejet
3 échantillon divisé
Comme illustré, un mécanisme à chaîne est muni de godets répartis à égale distance. Les godets se déplacent dans un
seul sens ou le sens de déplacement change à intervalles de temps prédéterminés. Le godet intercepte l'écoulement du
charbon tombant en chute libre afin d'en extraire des coupes qui sont recueillies comme échantillons lorsque le godet se
renverse.
d) Diviseur à chaîne à godets
Figure 2 (Suite)
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ISO 13909-4:2001(F)
Légende
1 bande fendue
2 alimentation
3 goulotte inclinée
4 échantillon divisé
5 rejet
Une bande sans fin comportant des fentes équidistantes dont les lèvres servent de dispositifs de prélèvement défile sous
une goulotte d'alimentation. L'écoulement du charbon s'effectue dans la goulotte et, une coupe est prélevée chaque fois
qu'une fente passe sous l'écoulement. La portion de l'écoulement qui tombe sur la partie pleine de la bande est dirigée
vers le rejet.
e) Diviseur à bande avec fentes
Figure 2 (Suite)
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ISO 13909-4:2001(F)
Légende Légende
1 alimentation 1 alimentation
2 rejet 2 rejet
3 échantillon divisé 3 échantillon divisé
Une plaque comportant des fentes équidistantes tourne Un arbre creux, relié à un ou plusieurs dispositifs de
sous une goulotte d'alimentation. Le charbon est chargé prélèvement, tourne dans une enceinte, comme illustré.
dans la goulotte d'alimentation et tombe ensuite sur la Chaque dispositif de prélèvement est conçu pour
plaque rotative pour former un ruban qui passe sous un effectuer des prélèvements sur l'écoulement de charbon
racloir et est dirigé vers le rejet. Une coupe est prélevée et pour les décharger par l'intermédiaire de l'axe creux.
chaque fois qu'une fente passe sous l'écoulement.
f) Diviseur à plaque rotative g) Diviseur à goulotte rotative
Figure 2 (Suite)
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ISO 13909-4:2001(F)
Légende Légende
1 alimentation 1 alimentation
2 trémie rotative 2 rejets
3 rejets 3 échantillon divisé
4 échantillon divisé
Une goulotte de prélèvement traverse entièrement
l'écoulement de charbon et en dévie une portion.
Une trémie rotative reçoit un écoulement de charbon et le
L'écoulement de charbon qui n'est pas prélevé par la
décharge dans une goulotte. Des dispositifs de
goulotte est dévié par la plaque inclinée vers le rejet.
prélèvement fixes sont placés sur le trajet de l'orifice de
sortie de la goulotte. Les coupes sont prélevées à chaque
passage au-dessus d'un dispositif de coupe. Le diviseur
peut être muni d'un ou de plusieurs dispositifs de coupe.
h) Diviseur à trémie et goulotte rotatives i) Diviseur à goulotte de prélèvement
Figure 2 (Suite)
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ISO 13909-4:2001(F)
6.2.4 Division de prélèvements individuels
6.2.4.1 Nombre de coupes
Le nombre de coupes pour la division d'un prélèvement doit être déterminé comme suit.
a) Pour une division à masse constante, le nombre minimal de coupes pour la division de prélèvements
primaires doit être de 4. Un nombre égal de coupes doit être pris sur chaque prélèvement primaire dans
le sous-lot.
b) Pour une division à rapport constant, le nombre minimal de coupes pour la division d'un prélèvement
primaire de masse moyenne doit être de 4.
c) Pour une division ultérieure de prélèvements primaires individuels divisés, une coupe au minimum doit
être prélevée sur chaque coupe résultant de la division précédente.
Des exemples de modes opératoires de division de prélèvements élémentaires individuels et de division
ultérieure d'un échantillon sont illustrés à la Figure 3.
a) Exemple de division de prélèvements individuels (nombre minimal de coupes)
Figure 3 — Exemples de modes opératoires pour la division de prélèvements et d'échantillons
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ISO 13909-4:2001(F)
b) Exemple de division des prélèvements individuels en deux étapes
Figure 3 (Suite)
6.2.4.2 Masse minimale du prélèvement élémentaire divisé
La masse minimale d'un prélèvement élémentaire divisé doit être telle que les masses combinées de tous les
prélèvements divisés dans le sous-lot doivent, à chaque étape, être supérieures à la masse indiquée dans le
Tableau 1, selon l'usage pour lequel l'échantillon a été prélevé et en fonction de la dimension maximale
nominale. Si la masse du prélèvement est trop faible pour satisfaire cette exigence, le prélèvement divisé doit
être concassé avant une nouvelle division.
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ISO 13909-4:2001(F)
6.2.5 Division des échantillons
6.2.5.1 Nombre de coupes
L'échantillon constitué de tous les prélèvements, ou de prélèvements divisés, doit être divisé en prenant au
minimum 60 coupes.
NOTE Si, au cours de la préparation, l'échantillon est entièrement homogénéisé et s'il peut être établi que la fidélité
requise peut être atteinte, ce nombre peut être ramené à 20.
Si la masse est trop faible, il convient d'utiliser une autre méthode manuelle de division.
6.2.5.2 Masse minimale d'échantillons divisés (voir le Tableau 1)
Pour la plupart des paramètres, en particulier l'analyse granulométrique et ceux relatifs à la taille des grains,
la fidélité du résultat est limitée par l'aptitude de l'échantillon à représenter toutes les tailles de grains dans la
masse du charbon échantillonné.
La masse minimale des échantillons divisés dépend de la dimension maximale nominale du charbon, de la
fidélité requise pour le paramètre concerné et de la relation de ce paramètre par rapport au calibre du grain.
Le fait d'atteindre la masse minimale requise après la division ne garantira pas en soi la fidélité requise, étant
donné que la fidélité de la division dépend également du nombre de coupes prises au cours de la division
(voir 6.2.4.1 et 6.2.5.1).
Les valeurs pour la masse minimale des échantillons divisés pour analyse générale afin de réduire la variance
due à la nature des particules du charbon à 0,01, ce qui correspond à une fidélité de 0,2 % en ce qui
[1]
concerne les cendres, sont indiquées dans la colonne 2 du Tableau 1 (voir le rapport du CSIRO ). La
colonne 3 du Tableau 1 détaille les masses correspondantes des échantillons divisés pour l'analyse de
l'humidité totale; elles représentent environ 20 % des masses minimales pour analyse générale, sous réserve
d'un minimum absolu de 0,65 kg. Les valeurs concernant les masses minimales des échantillons divisés pour
l'analyse granulométrique sont indiquées dans les colonnes 4 et 5 du Tableau 1 pour une fidélité de division
de respectivement 1 % et 2 %. Ces masses ont été calculées sur la base de la fidélité de la détermination du
refus, c'est à dire le charbon dépassant la dimension maximale nominale. La fidélité pour les autres fractions
dimensionnelles sera normalement meilleure que celle-ci. Il faut noter que dans tous les cas la fidélité globale
de la division est déterminée par la somme des variances de division à chaque étape de la division des
échantillons.
La masse minimale des échantillons divisés, m , pour d'autres niveaux de fidélité peut être calculée à partir
S
de l'équation:
2
P
0
mm= (2)
SS,0
P
R
où
m est la masse minimale d'un échantillon après division spécifiée dans le Tableau 1 pour une
S,0
dimension maximale nominale donnée;
P est la fidélité pour une étape donnée de la division stipulée dans le Tableau 1;
0
P est la fidélité requise pour une étape donnée de la division.
R
Lorsque du charbon est échantillonné régulièrement dans les mêmes circonstances, la fidélité obtenue pour
tous les paramètres de qualité requis doit être vérifiée (voir l'ISO 13909-7) et les masses peuvent être
ajustées en conséquence. Cependant, les masses ne doivent pas être réduites en dessous des exigences
minimales indiquées dans les normes d'analyse correspondantes.
Lorsque du charbon est préparé pour produire des échantillons à usage multiple, il faut également tenir
compte des masses et de la composition granulométrique des échantillons pour essai nécessaires pour
chaque essai.
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ISO 13909-4:2001(F)
Tableau 1 — Masses minimales d'un échantillon après division
Échantillons pour
Échantillons pour
Dimension maximale analyse générale
analyse de l'humidité Échantillons pour analyse dimensionnelle
nominale du charbon et échantillons
totale
communs
mm kg kg 1 % 2 %
300 15 000 3 000 54 000 13 500
200 5 400 1 100 16 000 4 000
150 2 600 500 6 750 1 700
125 1 700 350 4 000 1 000
90 750 125 1 500 400
75 470 95 850 210
63 300 60 500 125
50 170 35 250 65
45 125 25 200 50
38 85 17 110 30
31,5 55 10 65 15
22,4 32 7 25 6
16 20 4 8 2
11,2 13 2,5 3 0,7
10 10 2,0 2 0,5
8 6 1,5 1 0,25
5,6 3 1,2 0,5 0,25
4 1,5 1,0 0,25 0,25
2,8 0,65 0,65 0,25 0,25
2,0 0,25 — — —
1 0,1 — — —
< 0,5 0,06 — — —
NOTE 1 Les masses pour les échantill
...
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