ISO 13292:2006

INTERNATIONAL ISO
STANDARD 13292
Second edition
2006-03-15

Copper, lead, zinc and nickel
concentrates — Experimental methods
for checking the bias of sampling
Concentrés de cuivre, de plomb, de zinc et de nickel — Méthodes
expérimentales de contrôle de l'erreur systématique d'échantillonnage




Reference number
ISO 13292:2006(E)
©
ISO 2006

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ISO 13292:2006(E)
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ii © ISO 2006 – All rights reserved

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ISO 13292:2006(E)
Sommaire Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 General requirements and recommendations . 1
4 Sampling and sample processing methods . 2
4.1 Sampling. 2
4.1.1 General. 2
4.1.2 Checking bias in mechanical sampling. 3
4.1.3 Checking difference between sampling at different locations . 3
4.2 Sample processing and analysis . 3
5 Analysis of experimental data . 3
5.1 Statistical basis. 3
5.2 Determination of the mean difference and its standard deviation . 4
5.3 Determination of the required number of data sets . 4
5.4 Statistical test. 6
Annex A (informative) Numerical examples of determining the bias of sampling . 7
Bibliography . 11

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ISO 13292:2006(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 2.
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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 13292 was prepared by Technical Committee ISO/TC 183, Copper, lead, zinc and nickel ores and
concentrates.
This second edition cancels and replaces the first edition (ISO 13292:1997), which has been technically
revised.
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INTERNATIONAL STANDARD ISO 13292:2006(E)

Copper, lead, zinc and nickel concentrates — Experimental
methods for checking the bias of sampling
WARNING — This International Standard may involve hazardous materials, operations and equipment.
It is the responsibility of the user of this International Standard to establish appropriate health and
safety practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies methods for checking whether there is any bias in the sampling of
copper, lead, zinc and nickel concentrates, where the sampling is carried out in accordance with the methods
specified in ISO 12743. These methods can also be used for comparing alternative sampling regimes,
checking whether there is any bias in sample processing and for checking possible significant differences in
sampling at different places, e.g. at loading and discharge points, or the analysis of exchange samples.
Numerical examples are given in Annex A.
2 Normative references
The following referenced documents are indispensable for the application 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 12743, Copper, lead, zinc and nickel concentrates — Sampling procedures for determination of metal and
moisture content
3 General requirements and recommendations
The procedures specified in this International Standard are applicable to paired data only. The results
obtained from the method to be checked for bias (referred to as Method B) are compared with the results for a
reference method (referred to as Method A), which is considered to produce unbiased results from technical
and empirical viewpoints. If there is no significant difference between the results obtained using Method B and
Method A, then Method B may be adopted as a routine method.
While the procedures specified in Clause 5 are principally designed for checking bias against a reference
method, separate measurements of quality characteristics, e.g. using different sampling regimes, sampling at
loading (Method A) and discharge (Method B), or analyses of exchange samples, may also be compared to
check whether there is a statistically significant difference between the results.
Mechanical sampling systems, or manual sampling methods, are tested for bias by comparing the test results
for final system or manually collected samples (Method B) with the test results for reference increments
collected from a stopped conveyor belt (Method A). Analytical methods or test procedures are checked
against certified reference materials.
The standard method of taking reference increments from a stopped conveyor belt presents operational
difficulties, even if the handling system is capable of being restarted with a fully loaded belt. The main
problems are losses in production tonnage and the difficulty experienced in the sequence of starting the
handling system. During a ship's loading or unloading operation, this can cause delays in the turnaround time
of the ship.
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ISO 13292:2006(E)
Alternative reference methods, which are also expensive, divert the ore flow onto a transfer conveyor belt to
produce a material bed section identical to that from the main belt on which the mechanical primary sampler
(Method B) is installed. Stopped-belt sampling is then carried out on the transfer belt to collect reference
increments (Method A). The transfer conveyor belt should be of sufficient length to allow the establishment of
a material bed section that is not influenced by any longitudinal segregation introduced by the diversion plate.
The primary sampler and the point of diversion to the transfer belt should be as close as possible.
Sampling and sample processing procedures are more prone to bias than analytical techniques and test
methods. As system samples and reference increments are progressively reduced in mass and particle size,
lot samples, subsamples and test samples become increasingly vulnerable to sample loss and contamination.
Therefore, systematic errors occur more frequently during sample processing than during sampling, so
different stages of the sample processing procedure may require testing for bias.
Where testing for bias, the number of paired sets of measurements (data sets) shall be not less than 20. The
number of data sets required depends on the variance of the differences between the two methods and on the
value of the bias, δ, to be detected.
Any chemical or physical characteristic may be used to check whether any bias is present, e.g. copper, lead,
zinc, nickel or moisture content. Bias may not always be present for just one parameter. Therefore, several
parameters to reduce the effect of short-term variations in quality, preferably including all those that are likely
to be of interest, should be examined to determine whether bias exists. Characteristics to be tested for the
presence of bias need to be decided before the test work begins.
If the purpose of the bias check is to assess the performance of the sampling equipment, it is recommended
that increments for Method A and Method B be taken from closely adjacent portions of the concentrate to
reduce the effect of short-term variations in quality, and that sample processing and analysis be carried out on
each increment individually. This is likely to reduce the number of data sets required to detect a given bias in
the sampling equipment.
On the other hand, if the purpose of the bias check is to determine whether the selected sampling regime is
biased, e.g. due to the presence of periodic variations in quality, it is recommended that increments for
Method A and Method B be taken completely independently.
Even after a bias check has been conducted, further checks should be carried out at regular intervals. Bias
checks should also be carried out when sampling equipment is changed.
4 Sampling and sample processing methods
4.1 Sampling
4.1.1 General
The method to be checked (Method B) shall be compared with a designated reference method (Method A)
using the same type of concentrate. Method A may also be an alternative method that is being compared with
Method B. As specified in Clause 3, at least 20
...