ISO 3085:2019
(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
This document 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. This document can also be applied for the purpose of checking the precision of sampling, sample preparation and measurement separately.
Minerais de fer — Méthodes expérimentales de contrôle de la fidélité de l'échantillonnage, de préparation des échantillons et de mesurage
General Information
Relations
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 3085
Fifth edition
2019-08
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 3085:2019(E)
©
ISO 2019
---------------------- Page: 1 ----------------------
ISO 3085:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 3085:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 General conditions . 2
5.1 Sampling . 2
5.1.1 General. 2
5.1.2 Number of lots . 2
5.1.3 Number of increments and number of gross samples . 2
5.2 Sample preparation and measurement . 2
5.3 Replication of experiment . 2
5.4 Record of the experiment . 2
6 Method of experiment. 3
6.1 Sampling . 3
6.1.1 Systematic sampling . 3
6.1.2 Stratified sampling . 4
6.2 Sample preparation and measurement . 5
6.2.1 General. 5
6.2.2 Method 1 . 5
6.2.3 Method 2 . 6
6.2.4 Method 3 . 6
7 Analysis of experimental data . 7
7.1 General . 7
7.2 Method 1. 7
7.3 Method 2. 9
7.4 Method 3.11
8 Interpretation of results and action .12
8.1 Interpretation of results .12
8.2 Actions .13
8.2.1 Checking for changes in quality variation .13
8.2.2 Increasing number of increments .13
8.2.3 Increasing mass of increments .13
8.2.4 Checking the sample preparation and measurement procedures .13
9 Test report .13
Annex A (informative) Example of experiment on systematic sampling by method 1 .14
Bibliography .18
© ISO 2019 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 3085:2019(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron,
Subcommittee SC 1, Sampling.
This fifth edition cancels and replaces the fourth edition (ISO 3085:2002), which has been technically
revised. The main change compared to the previous edition is the use of the mean square difference
between assay pairs, as described in the Introduction.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 3085:2019(E)
Introduction
The key change between this document and the previous edition is the use of the mean square
difference between assay pairs to estimate the numerical value of the precision instead of the mean
difference between assay pairs, noting that the use of mean square differences was included in
ISO 3085:1996, Annex B, as an alternative method only. The use of mean square differences avoids
overestimating the sampling system’s capability, thereby limiting the opportunity for improvement.
In addition, when possible measurement outliers are identified, the process (such as sampling, sample
preparation or measurement) under investigation may not be in a state of statistical control and should
be checked in order to detect assignable causes. If these assignable causes can be identified, then the set
of measurements should be repeated after the assignable causes have been corrected. Otherwise, data
assessment should proceed without eliminating the outliers.
© ISO 2019 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 3085:2019(E)
Iron ores — Experimental methods for checking
the precision of sampling, sample preparation and
measurement
1 Scope
This document 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.
This document can also be applied for the purpose of checking the precision of sampling, sample
preparation and measurement separately.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3082:2017, Iron ores — Sampling and sample preparation procedures
ISO 3084, Iron ores — Experimental methods for evaluation of quality variation
ISO 11323, Iron ore and direct reduced iron — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11323 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
Sampling from 20 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.
Comparison of the estimated precision with that specified in ISO 3082:2017, Table 1, and necessary
action taken if the estimated precision does not attain these specified values.
© ISO 2019 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 3085:2019(E)
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, namely
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
1
sample is made up from these increments, the number of increments required for the experiment shall
be 2n and two gross samples shall be constituted.
1
Alternatively, if the experiment is carried out as part of routine sampling, n increments may be taken
1
and two gross samples constituted, each comprising n /2 increments. In this case, the sampling
1
precision obtained will be for n /2 increments. The precision thus obtained shall be divided by 2 to
1
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
1 1
shall be 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.
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.
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.
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).
2 © ISO 2019 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 3085:2019(E)
6 Method of experiment
6.1 Sampling
6.1.1 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 using mass basis sampling, the sampling intervals, Δm, in
1
tonnes, shall be calculated by dividing the mass, m , of the lot by 2n , i.e. giving intervals equal to one-half
L 1
of the sampling interval for routine sampling, see Formula (1):
m
L
Δ=m (1)
2n
1
Alternatively, when the experiment is carried out as part of routine mass basis sampling and n
1
increments are taken, the sampling interval, Δm, shall be calculated by dividing the mass, m , of the lot
L
by n , see Formula (2):
1
m
L
Δm= (2)
n
1
The sampling intervals thus calculated may be rounded down to the nearest 10 t.
6.1.1.3 When 2n increments are taken using time basis sampling, the sampling intervals, Δt, in
1
minutes, shall be calculated using Formula (3), i.e. giving intervals equal to one-half of the sampling
interval for routine sampling:
60m
L
Δt= (3)
2qn
max 1
where q is the maximum flow rate, expressed in tonnes per hour, of ore on the conveyor belt.
max
Alternatively, when the experiment is carried out as part of routine time basis sampling and n
1
increments are taken, the sampling interval, Δt, shall be calculated using Formula (4):
60m
L
Δt= (4)
qn
max 1
The sampling intervals thus calculated may be rounded down to the nearest minute.
6.1.1.4 The increments shall be taken at the sampling interval determined in 6.1.1.2 or 6.1.1.3, with a
random start.
6.1.1.5 The increments shall be placed alternately in two containers. Thus, two gross samples, A and B,
will be constituted.
EXAMPLE 1 See Figure 1.
A lot of 19 000 t is transferred by belt conveyors and the number of increments determined in accordance with
ISO 3082 for routine mass basis sampling, n , is 60.
1
When 2n increments are taken, the sampling interval for the experiment, Δm, is given by the formula:
1
© ISO 2019 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 3085:2019(E)
m
L 19000
Δm== =→158 150
2n 60×2
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 are taken at the point 20 + iΔm,
where i = 1, 2, ., 2n (170 t, 320 t and so on). Since the whole lot size is 19 000 t, 126 increments are taken.
1
The increments are placed alternately in two containers, and two gross samples, A and B, are constituted, each
composed of 63 increments.
NOTE 1 Solid circles indicate increments taken from strata.
NOTE 2 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
3
number of strata, n , forming one lot and the number of increments determined in accordance with
4
ISO 3082, n , using Formula (5):
1
n
1
n = (5)
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
1
increments 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
1
taken, n increments shall be taken from each stratum and be separated at random into two partial
3
samples, each of n /2 increments.
3
4 © ISO 2019 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 3085:2019(E)
6.1.2.3 The two partial samples from each stratum shall be combined into two gross samples, A and B,
respectively.
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 2 See Figure 2.
A lot is divided in 11 strata each of 60 t and the number of increments, n , determined for the entire lot
1
(60 × 11 = 660 t) in accordance with ISO 3082 is 20. Thus, the number of increments to be taken from each
stratum is shown by the formula:
n 20
1
n == =→1,82
3
n 11
4
NOTE 1 Boxes indicate strata.
NOTE 2 Solid circles indicate increments taken from strata.
NOTE 3 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
1 3
separated at 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 in 6.2.2 to 6.2.4.
6.2.2 Method 1
The two gross samples A and B shall be divided separately. The resulting four test samples, A , A , B
1 2 1
and B , shall be tested in duplicate. The eight tests shall be run in random order. See Figure 3.
2
NOTE Method 1 allows the precision of sampling, sample preparation and measurement to be separately
estimated.
© ISO 2019 – All rights reserved 5
---------------------- Page: 10 ----------------------
ISO 3085:2019(E)
Figure 3 — Flowsheet for method 1
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
1 2
prepared 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.
Figure 4 — Flowsheet for method 2
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.
6 © ISO 2019 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 3085:2019(E)
Figure 5 — Flowsheet for method 3
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 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 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 ,
111 112
x , x , and x , x , x , x .
121 122 211 212 221 222
7.2.3 Calculate the mean, x , and the range, R , for each pair of duplicate measurements using
ij. 1
Formulae (6) and (7), respectively:
1
xx=+ x (6)
()
ij. ij12ij
2
Rx=−x (7)
11ij ij2
where
i = 1 and 2 and stands for A and B gross samples;
j = 1 and 2 and stands for test samples.
© ISO 2019 – All rights reserved 7
---------------------- Page: 12 ----------------------
ISO 3085:2019(E)
7.2.4 Calculate the mean, x , and the range, R , for each pair of duplicate test samples, using
i . 2
Formulae (8) and (9), respectively:
1
xx=+ x (8)
()
ii. 12.i
2
Rx=−x (9)
21ii.2
7.2.5 Calculate the mean, x , and the range, R , for each pair of gross samples, A and B, using
3
Formulae (10) and (11), respectively:
1
xx=+ x (10)
( )
12. .
2
Rx=−x (11)
31. 2.
2 2 2
ˆ ˆ ˆ
7.2.6 Calculate the overall mean, x, and the variances, σ , σ and σ using Formulae (12) to (15):
1 2 3
1
x = x (12)
∑
n
1
2 2
ˆ
σ = R (13)
∑
1 1
8n
1
2 2
ˆ
σ = R (14)
∑
2 2
4n
1
2 2
ˆ
σ = R (15)
∑
3 3
2n
where n is the number of lots.
Calculate the control limits for ranges as follows and construct range control charts.
ˆ ˆ ˆ
The upper control limits for the R-charts are 3,64 σ for R , 3,64 σ for R and 3,64 σ for R .
1 2 3
1 2 3
The factor 3,64 (i.e. 2,576 × √2) gives the 99 % limit for the difference between two independent
measurements from the same normal distribution, because the difference has twice the original
variance.
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
3 2 1
indication 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,
3 2 1
the process (such as sampling, sample preparation or measurement) under investigation may not be in a
state of statistical control and should be checked in order to detect assignable causes. If these assignable
8 © ISO 2019 – All rights reserved
---------------------- Page: 13 ----------------------
ISO 3085:2019(E)
causes can be identified, then the set of measurements should be repeated after the assignable causes
have been corrected. Otherwise, the computation should proceed without eliminating the outliers.
7.2.8 When 2n increments are taken, calculate the estimated values of the standard deviations of
1
ˆ ˆ ˆ
measurement, σ , sample preparation, σ , and sampling, σ using Formulae (16) to (18), respectively:
M P S
2 2
ˆˆ
σσ= (16)
M 1
1
2 2 2
ˆˆ ˆ
σσ=− σ (17)
P 2 1
2
1
2 2 2
ˆˆ ˆ
σσ=− σ (18)
S 3 2
2
2 2 2 2
ˆ ˆ ˆ ˆ
If σ or σ as calculated from Formulae (17) and (18) is found to be negative, σ or σ shall be
P S P S
replaced by zero. When n increments are taken in accordance with 5.1.3, the estimated value of the
1
ˆ
standard deviation of sampling, σ from Formula (18) shall be divided by 2 to obtain the standard
S
deviation of sampling for gross samples comprising n increments. The estimated values of the standard
1
deviations of measurement and sample preparation may be calculated using Formulae (16) and (17).
ˆ
7.2.9 Calculate the estimated values of the precision of sampling βσ= 2 , sample preparation
()
SS
ˆ ˆ
βσ=2 and measurement βσ=2 .
() ()
PP MM
7.2.10 Calculate the estimated value of the overall precision of sampling, sample preparation and
ˆ
measurement βσ=2 , using Formula (19):
()
SPMSPM
222
ˆ ˆˆˆ
σ =+σσσ+ (19)
SPMS PM
7.3 Method 2
7.3.1 The estimated values of precision of sampling, sample preparation and measurement shall be
calculated in accordance with 7.3.2 to 7.3.10.
7.3.2 Denote the four measurements as follows:
x , x are the duplicate measurements of test sample A prepared from gross sample A;
1 2 1
x is the single measurement of test sample A prepared from gross sample A;
3 2
x is the single measurement of test sample B prepared from gross sample B.
4
7.3.3 Calculate the mean, x , and the range, R , for each pair of duplicate measurements using
1
Formulae (20) and (21):
1
xx=+ x (20)
()
12
2
© ISO 2019 – All rights reserved 9
---------------------- Page: 14 ----------------------
ISO 3085:2019(E)
Rx=−x (21)
11 2
7.3.4 Calculate the mean, x , and the range, R , using Formulae (22) and (23):
2
1
xx=+ x (22)
()
3
2
Rx=−x (23)
23
7.3.5 Calculate the mean, x , and the range, R , for each pair of gross samples, A and B, using
3
Formulae (24) and (25):
1
xx=+ x (24)
4
2
Rx=−x (25)
34
2 2 2
ˆ ˆ ˆ
7.3.6 Calculate the overall mean, x , and the variances, σ , σ and σ using Formulae (26), (27),
1 2 3
(28) and (29), respectively:
1
x = x (26)
∑
n
1
2 2
ˆ
σ = R (27)
∑
1 1
2n
1
2 2
ˆ
σ = R (28)
∑
2 2
2n
1
2 2
ˆ
σ =
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.