ISO 3085:2002
(Main)Iron ores — Experimental methods for checking the precision of sampling, sample preparation and measurement
Iron ores — Experimental methods for checking the precision of sampling, sample preparation and measurement
Minerais de fer — Méthodes expérimentales de contrôle de la fidélité de l'échantillonnage, de préparation des échantillons et de mesurage
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 3085
Fourth edition
2002-03-01
Iron ores — Experimental methods for
checking the precision of sampling, sample
preparation and measurement
Minerais de fer — Méthodes expérimentales de contrôle de la fidélité de
l'échantillonnage, de préparation des échantillons et de mesurage
Reference number
ISO 3085:2002(E)
©
ISO 2002
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ISO 3085:2002(E)
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ISO 3085:2002(E)
Contents Page
Foreword.iv
1 Scope .1
2 Normative references.1
3 Definitions .1
4 Principle.1
5 General conditions .2
6 Method of experiment .3
7 Analysis of experimental data.7
8 Interpretation of results and action .12
9 Test report .12
Annex A (informative) Example of experiment on periodic systematic sampling by method 1.14
Annex B (informative) Alternative method for analysis of experimental data .20
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ISO 3085:2002(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.
The main task of technical committees is to prepare International Standards. 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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 3085 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron, Subcommittee
SC 1, Sampling.
This fourth edition cancels and replaces the third which has been technically revised.
Annexes A and B of this International Standard are for information only.
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INTERNATIONAL STANDARD ISO 3085:2002(E)
Iron ores — Experimental methods for checking the precision of
sampling, sample preparation and measurement
1 Scope
This International Standard specifies experimental methods for checking the precision of sampling, sample
preparation and measurement of iron ores being carried out in accordance with the methods specified in ISO 3082
and the relevant ISO standards for measurement.
NOTE This International Standard may also be applied for the purpose of checking the precision of sampling, sample
preparation and measurement separately.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard 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 3082:2000, Iron ores — Sampling and sample preparation procedures
ISO 3084:1998, Iron ores — Experimental methods for evaluation of quality variation
1)
ISO 11323:— , Iron ore and direct reduced iron — Vocabulary
3 Definitions
For the purposes of this International Standard, the definitions given in ISO 11323 apply.
NOTE The precision of sampling is defined mathematically in annex A of ISO 3082:2000.
4 Principle
Sampling from twenty lots or more, preferably taking twice as many increments as specified in ISO 3082 and
placing the increments alternately into two gross samples. If this is impracticable or the precision testing is carried
out in conjunction with routine sampling, the normal number of increments specified in ISO 3082 may be used.
Preparation of separate test samples from each gross sample and determination of relevant quality characteristics.
Analysis of the experimental data obtained and calculation of the estimated value of the precision of sampling,
sample preparation and measurement for each selected quality characteristic.
1) To be published. (Revision of ISO 11323:1996)
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ISO 3085:2002(E)
Comparison of the estimated precision with that specified in Table 1 of ISO 3082:2000 and necessary action if the
estimated precision does not attain these specified values.
5 General conditions
5.1 Sampling
5.1.1 General
The sampling procedure to be followed shall be selected from the two methods of sampling, viz. periodic
systematic sampling or stratified sampling, depending on the method of taking increments from the lot in
accordance with ISO 3082.
5.1.2 Number of lots
To reach a reliable conclusion, it is recommended that the experiment be carried out on more than 20 lots of the
same type of iron ore. However, if this is impracticable, at least 10 lots should be covered. If the number of lots for
the experiment is not sufficient, each lot may be divided into several parts to produce more than 20 parts in total for
the experiment, and the experiment should be carried out on each part, considering each part as a separate lot in
accordance with ISO 3082.
5.1.3 Number of increments and number of gross samples
The number of increments required for the experiment shall preferably be twice the number specified in ISO 3082.
Hence, if the number of increments required for routine sampling is n and one gross sample is made up from
1
these increments, the number of increments required for the experiment shall be 2n and two gross samples shall
1
be constituted.
Alternatively, if the experiment is carried out as part of routine sampling, n increments may be taken and two gross
1
samples constituted, each comprising n /2 increments. In this case the sampling precision obtained will be for n /2
1 1
increments. The precision thus obtained must be divided by 2 to obtain the precision for gross samples
comprising n increments (see clause 7).
1
When the experiment is carried out with n increments and n is an odd number, an additional increment shall be
1 1
taken in order to make the number of increments even.
5.2 Sample preparation and measurement
Sample preparation shall be carried out in accordance with ISO 3082. The measurement shall be carried out in
accordance with the relevant ISO standards for chemical analysis, moisture content and size analysis of iron ores.
NOTE 1 For chemical analysis it is preferable to carry out a series of determinations on test samples for a lot over a period of
several days, in order to maintain the independence of test results.
NOTE 2 The method of determination of any quality characteristic should remain the same throughout the experiment.
5.3 Replication of experiment
Even when a series of experiments has been conducted prior to regular sampling operations, the experiments
should be carried out periodically to check for possible changes in quality variation and, at the same time, to control
the precision of sampling, sample preparation and measurement. Because of the amount of work involved, it
should be carried out as part of routine sampling, sample preparation and measurement.
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ISO 3085:2002(E)
5.4 Record of the experiment
For future reference and to avoid errors and omissions, it is recommended that detailed records of experiments be
kept in a standardized format (see clause 9 and annex A).
6 Method of experiment
6.1 Sampling
6.1.1 Periodic systematic sampling
6.1.1.1 The number of increments, n , shall be determined in accordance with ISO 3082.
1
6.1.1.2 When 2n increments are taken, the sampling intervals, ∆m, in tonnes, shall be calculated by dividing
1
the mass, m , of the lot by 2n , i.e. giving intervals equal to one-half of the sampling interval for routine sampling.
L 1
m
L
∆=m
2n
1
Alternatively, when the experiment is carried out as part of routine sampling and n increments are taken, the
1
sampling interval, ∆m, shall be calculated by dividing the mass, m , of the lot by n .
L 1
m
L
∆=m
n
1
The sampling intervals thus calculated may be rounded down to the nearest 10 t.
6.1.1.3 The increments shall be taken at the sampling interval determined in 6.1.1.2, with a random start.
6.1.1.4 The increments shall be placed alternately in two containers. Thus, two gross samples, A and B, will
be constituted.
EXAMPLE 1 See Figure 1.
Suppose that a lot of 19 000 t is transferred by belt conveyors and the number of increments determined in
accordance with ISO 3082 for routine sampling, n , is 60.
1
When 2n increments are taken, the sampling interval for the experiment, ∆m, is given by the equation
1
m
19 000
L
∆=m = = 158→ 150
26n 0×2
1
Thus, increments are taken at 150 t intervals. The point for taking the first increment from the first sampling interval
of 150 t is determined by a random selection method. If the point for taking the first increments is determined as
20 t from the beginning of handling the lot, subsequent increments should be taken at the point 20 + i∆m, where
i = 1, 2, ., 2n (170 t, 320 t and so on). Since the whole lot size is 19 000 t, 126 increments shall be taken.
1
The increments are placed alternately in two containers, and two gross samples, A and B, are constituted, each
composed of 63 increments.
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ISO 3085:2002(E)
Key
Solid circles indicate increments taken from stratum.
Open circles indicate gross samples.
Figure 1 — Schematic diagram for example 1
6.1.2 Stratified sampling
6.1.2.1 The number of increments, n , to be taken from each stratum shall be calculated from the number of
3
strata, n , forming one lot and the number of increments determined in accordance with ISO 3082, n , using the
4 1
equation
n
1
n =
3
n
4
NOTE Examples of strata, based on time, mass or space, include production periods, production masses, holds in vessels,
wagons in a train or containers.
The number of increments thus calculated shall be rounded up to the next higher whole number if 2n increments
1
are taken, or to the next higher whole even number if n increments are taken.
1
6.1.2.2 When 2n increments are taken, 2n increments shall be taken from each stratum and shall be
1 3
separated at random into two partial samples, each of n increments.
3
Alternatively, when the experiment is carried out as part of routine sampling and n increments are taken, n
1 3
increments shall be taken from each stratum and be separated at random into two partial samples, each of n /2
3
increments.
6.1.2.3 The two partial samples from each stratum shall be combined into two gross samples, A and B,
respectively.
NOTE If the mass varies from stratum to stratum, the number of increments to be taken from each stratum shall be varied
in proportion to the mass of ore in each stratum. This method is called “proportional stratified sampling”.
EXAMPLE 1 See Figure 2.
Suppose that a lot is divided in 11 strata each of 60 t and the number of increments, n , determined for the entire
1
lot (60 × 11 = 660 t) in accordance with ISO 3082 is 20. Thus, the number of increments to be taken from each
stratum is
n
20
1
n== = 1,8→ 2
3
n 11
4
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ISO 3085:2002(E)
Key
Boxes indicate strata.
Solid circles indicate increments taken from stratum.
Open circles indicate gross samples.
Figure 2 — Schematic diagram for example 2
When 2n increments are taken, four (2n = 2 × 2) increments are taken from each stratum and separated at
1 3
random into two partial samples, each consisting of two increments.
The two partial samples from each of the 11 strata are combined into two gross samples, A and B respectively,
each comprising 22 (2n = 2 × 11) increments.
4
6.2 Sample preparation and measurement
6.2.1 General
The two gross samples A and B taken in accordance with 6.1 shall be prepared separately and subjected to testing
by either method 1, method 2 or method 3 described below.
6.2.2 Method 1
The two gross samples A and B shall be divided separately. The resulting four test samples, A , A , B and B ,
1 2 1 2
shall be tested in duplicate. The eight tests shall be run in random order. See Figure 3.
NOTE Method 1 allows the precision of sampling, sample preparation and measurement to be separately estimated.
6.2.3 Method 2
Gross sample A shall be divided to prepare two test samples, A and A and one test sample shall be prepared
1 2
from gross sample B. See Figure 4.
Test sample A shall be tested in duplicate and single tests shall be conducted on test samples A and B.
1 2
NOTE Method 2 also allows the precision of sampling, sample preparation and measurement to be separately estimated.
However, the estimates are less precise than those obtained by method 1.
6.2.4 Method 3
One test sample shall be prepared from each of the two gross samples A and B, and single tests shall be
conducted on each sample. See Figure 5.
NOTE Using method 3, only the overall precision of sampling, sample preparation and measurement is obtained.
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ISO 3085:2002(E)
Figure 3 — Flowsheet for method 1
Figure 4 — Flowsheet for method 2
Figure 5 — Flowsheet for method 3
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ISO 3085:2002(E)
7 Analysis of experimental data
7.1 General
The method for analysis of experimental data shall be as specified in 7.2 to 7.4 depending on the method of
sample preparation and measurement, regardless of whether the method of sampling is periodic, systematic or
stratified.
7.2 Method 1
7.2.1 The estimated values of precision at the 95 % probability level (hereinafter referred to simply as precision)
of sampling, sample preparation and measurement shall be calculated according to 7.2.2 to 7.2.10.
Annex A shows an example of application of method 1.
7.2.2 Denote the four measurements (such as % Fe), for the two gross samples A and B, as x , x , x ,
111 112 121
x , and x , x , x , x .
122 211 212 221 222
7.2.3 Calculate the mean, x , and the range, R , for each pair of duplicate measurements using equations (1)
ij. 1
and (2) respectively.
1
xx=+x (1)
()
ij.1ij ij2
2
R=−xx (2)
11ij ij2
where
i = 1 and 2 and stands for A and B gross samples;
j = 1 and 2 and stands for test samples.
7.2.4 Calculate the mean, x , and the range, R , for each pair of duplicate samples, using equations (3) and (4)
i. 2
respectively.
1
xx=+x (3)
()
ii. 1.i2.
2
R=−xx (4)
21ii. 2.
7.2.5 Calculate the mean, x, and the range, R , for each pair of gross samples, A and B, using equations (5) and
3
(6) respectively.
1
xx=+x (5)
()
1. 2.
2
R=-xx (6)
31. 2.
7.2.6 Calculate the overall mean, x, and the means of ranges, R , R and R , using equations (7) to (10).
12 3
1
xx= (7)
∑
n
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ISO 3085:2002(E)
1
R = R (8)
11∑
4n
1
R = R (9)
22∑
2n
1
R = R (10)
33∑
n
where n is the number of lots.
Calculate the control limits for ranges as follows and construct range control charts.
Upper control limits for R-charts
D R (for R ), D R (for R ), D R (for R )
41 1 42 2 43 3
where D = 3,267 (for a pair of measurements).
4
7.2.7 When all of the values of R , R and R are within the upper control limits of the R-charts, it is an indication
3 2 1
that the processes of sampling, sample preparation and measurement of samples are in a state of statistical
control.
On the other hand, when several values of R , R or R fall outside the respective upper control limits, the process
3 2 1
(such as sampling, sample preparation or measurement) under investigation is not in a state of statistical control
and should be checked in order to detect assignable causes. Such values should be excluded and the means of
ranges recalculated.
7.2.8 When 2n increments are taken, calculate the estimated values of the standard deviations of
1
measurement, σˆ , sample preparation, σˆ , and sampling, σˆ , using equations (11) to (13) respectively:
M P S
2
2
σˆ = Rd (11)
()
M12
2
1
22
σσˆˆ=−Rd (12)
()
P22 M
2
2
11
222
σσˆˆ=−Rd −σˆ (13)
()
S32 P M
24
where 1/d = 0,886 2(for a pair of measurements).
2
2 2 2 2
If σˆ or σˆ as calculated from equations (12) and (13) is found to be negative, σˆ or σˆ must be replaced by
P S P S
zero. When n increments are taken in accordance with 5.1.2, the estimated value of the standard deviation of
1
sampling, σˆ from equation (13) shall be divided by 2 to obtain the standard deviation of sampling for gross
S
samples comprising n increments. The estimated values of the standard deviations of measurement and sample
1
preparation may be calculated using equations (11) and (12).
NOTE As an alternative to using ISO 3084, the quality variation, σ , can be determined from the standard deviation of
W
sampling, σ , as follows:
S
σ = nσ
W1S
7.2.9 Calculate the estimated values of the precision of sampling (2βσ= ˆ), sample preparation βσ= 2 ˆ
( )
SS PP
and measurement βσ=2.ˆ
( )
MM
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ISO 3085:2002(E)
7.2.10 Calculate the estimated value of
...
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