ISO 11790:2010
(Main)Copper, lead, zinc and nickel concentrates — Guidelines for the inspection of mechanical sampling systems
Copper, lead, zinc and nickel concentrates — Guidelines for the inspection of mechanical sampling systems
ISO 11790:2010 sets out recommended practices for the inspection of mechanical sampling systems. It serves as a reference for conformance with applicable International Standards for copper, lead, zinc and nickel concentrates. ISO 11790:2010 covers general considerations, including precision, quality variation, bias, establishment of inspection systems and inspection procedures.
Concentrés de cuivre, de plomb, de zinc et de nickel — Lignes directrices pour le contrôle des systèmes mécaniques d'échantillonnage
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11790
First edition
2010-09-15
Copper, lead, zinc and nickel
concentrates — Guidelines for the
inspection of mechanical sampling
systems
Concentrés de cuivre, de plomb, de zinc et de nickel — Lignes
directrices pour le contrôle des systèmes mécaniques d'échantillonnage
Reference number
ISO 11790:2010(E)
©
ISO 2010
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ISO 11790:2010(E)
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ISO 11790:2010(E)
Contents Page
Foreword .iv
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 General consideration.2
4.1 Precision.2
4.2 Quality variation.2
4.3 Bias.2
4.4 Operation of the sampling system .3
5 Establishment of inspection system .3
5.1 General.3
5.2 Audits.4
5.3 Mechanical inspections .4
5.4 Operational inspections.4
6 Procedures.4
6.1 Audits.4
6.2 Mechanical inspections .5
6.3 Operational inspections.6
6.4 Control charts.7
6.4.1 General.7
6.4.2 Sampling ratio.7
6.4.3 Extraction ratio.7
6.5 Sampling records.10
6.6 Operator's inspection report.10
Annex A (informative) Example of a sampling checklist for copper ore.11
Annex B (informative) Example of sampling plant operator's inspection report on a shift basis.14
Annex C (informative) Example of sampling-system operations inspection summary .18
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ISO 11790:2010(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 11790 was prepared by Technical Committee ISO/TC 183, Copper, lead, zinc and nickel ores and
concentrates.
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INTERNATIONAL STANDARD ISO 11790:2010(E)
Copper, lead, zinc and nickel concentrates — Guidelines for the
inspection of mechanical sampling systems
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 sets out recommended practices for the inspection of mechanical sampling
systems. It serves as a reference for conformance with applicable International Standards for copper, lead,
zinc and nickel concentrates.
This International Standard covers general considerations, including precision, quality variation, bias,
establishment of inspection systems and inspection procedures.
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
ISO 12744, Copper, lead, zinc and nickel concentrates — Experimental methods for checking the precision of
sampling
ISO 13292, Copper, lead, zinc and nickel concentrates — Experimental methods for checking the bias of
sampling
ISO 20212, Copper, lead, zinc and nickel sulfides — Sampling procedures for ores and smelter residues
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12743, ISO 12744, ISO 13292 and
ISO 20212 and the following apply.
3.1
audit
critical review of a mechanical sampling system, undertaken by a suitably qualified person not directly
involved in the operation of that system, which measures its compliance with stipulated operating
specifications
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ISO 11790:2010(E)
3.2
mechanical inspection
comparative record of observations and measurements of physical parameters against design criteria, and
records of subsequent changes or improvements undertaken by a suitably qualified person not involved in the
day-to-day operation of the system
3.3
operational inspection
record of observations and inspections undertaken by the system operator before, during and after the
sampling of a lot
NOTE The operator is the person taking the sample.
4 General consideration
4.1 Precision
Precision checks are recommended for each material type sampled by the system. If there is a significant
change in material type or a new material type is introduced, a precision check should be carried out. The test
should outline the precision of sampling, preparation and analysis of each material type sampled by the
system. These tests are to be in accordance with ISO 12744.
4.2 Quality variation
2
The variance between increments, s , is a measure of the heterogeneity of the lot and is the variance of the
b
2
quality characteristics of increments taken from the lot. The value of s shall be measured experimentally for
b
each material type for each handling plant under normal operating conditions, in accordance with ISO 12743
and ISO 20212.
The entire material-handling system up to the mechanical sampling system should be examined to determine
whether any unloading, storage, or reclaiming procedures produce a cyclical pattern which could cause the
increment collection to get in phase with the sequence of material variability. Variations in the physical
characteristics, such as particle-size distribution, surface moisture, extraneous matter and oversized material,
could become cyclical and could even be in phase with mass-based or time-based increment collection.
Where such cyclical variations occur in the material stream, the source of the variations should be
investigated to determine the practicability of eliminating the variations. If there is no practical way to eliminate
the variations, the interval between primary cuts should be adjusted so that the collection of increments is not
in phase with the cyclic variation. Alternatively, stratified random sampling may be used.
4.3 Bias
After commissioning and auditing of a new system or any major engineering modifications of an existing
system, a bias test should be carried out in accordance with ISO 13292 to confirm the correct operation of the
system. In multi-material-type facilities, it is recommended that the material having the highest variability be
chosen for the bias test.
It is recommended that, on a regular basis, further bias sample pairs be taken to confirm that the initial bias
result is still relevant. If a significant change is made to the sampling system, or a new material having more
difficult sampling characteristics is introduced, the need for a new bias test should be considered.
NOTE Provided that the mechanical sampling system satisfies the criteria outlined in ISO 12743 and ISO 20212,
bias tests are not mandatory. However, quality-assurance principles at individual plants might require bias tests.
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ISO 11790:2010(E)
4.4 Operation of the sampling system
The mechanical sampling system should be started at some time in advance of the start of conveying the
material to be sampled, so that any foreign substances (including water) are purged. Where hydraulic drives
are used, sufficient time should be allowed for the hydraulic oil and the associated system to attain
temperature equilibrium. It is recommended, particularly in multi-material-type sampling systems, that one
primary cut be allowed to pass through the mechanical system as a conditioner before sampling commences.
It is recommended that the operator review any sampling-system records maintained by the previous operator.
These records should include such things as quantities of material handled and sampled, and notations as to
system malfunctions, stoppages, blockages, or other deficiencies. The operator should use a suitable
checklist, such as the example in Annex A. It is recommended that the operator complete all items on a
suitable checklist designed for the particular system. For large multi-user systems, an operator's inspection
report, such as the example in Annex B, should be developed.
Sufficient suitably designed inspection points should be available to observe that the falling-stream and cross-
belt cutters cut the full stream of material, and cutter apertures can be inspected for blockages and blinding.
5 Establishment of inspection system
5.1 General
To ensure reliable operation, it is recommended that a sampling checklist (Annex A) and operator's sampling
record (Annex B) be developed with input from the following sources:
a) original design criteria and records of any subsequent changes or improvements;
b) sampling equipment operating and maintenance manuals;
c) management responsible for the system;
d) personnel operating or maintaining the system;
e) for a new system, the designers and commissioning personnel.
The general method for establishing these procedures is as follows.
1) Refer to ISO 12743 and ISO 20212 to ascertain the correct sampling scheme.
2) Refer to the equipment supplier's operating and maintenance manuals to ascertain correct
procedures for operation and intervals for routine maintenance. The manuals can provide useful
information on the basis of the system design. Information such as conveyor rates, conveyor speeds
and material parameters (particularly sizing and variability) are significant data and should always be
kept in mind when changes are contemplated.
3) Examine existing sampling and maintenance records for an extended period. This information will
provide guidance for operators to ensure that the required level of inspection and maintenance is
carried out to ensure reliable operation, and will possibly alert operators to any inappropriate
maintenance or modifications that may have been made to the equipment.
4) Seek the personal experience of maintenance, operational and sampling personnel with respect to
the sampling system. This information, together with that obtained from the above, will enable an
appropriate operator's manual, operator's sampling record and system checklist to be prepared.
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ISO 11790:2010(E)
5.2 Audits
A scheme for regular audits of the sampling system should be established. Reference should be made to the
original operating parameters and equipment supplier's design data, as well as any records of any subsequent
changes or improvements, in order to establish conformance with current applicable International Standards.
Annex A provides a typical reference list.
NOTE 1 Correct operation of all new systems needs to be confirmed by an audit following the commissioning stage
before being accepted as operational.
NOTE 2 The design and operation of the system need to be confirmed by an audit prior to any bias test.
5.3 Mechanical inspections
A scheme for routine inspections of the sampling system by operators should be established, similar to the
example in Annex A. The frequency and detail of inspections will be determined by factors such as, but not
limited to, reliability of the system, handling characteristics of the sampled material, frequency of use of the
system and purpose of sampling (e.g. process control compared to large multi-user port facilities).
5.4 Operational inspections
Operational procedures and inspections should be established and carried out immediately before, during and
immediately after operation of the sampling system for a given lot or sub-lot, similar to the example in Annex A.
These procedures and inspections will be less extensive than those undertaken as audits or mechanical
inspections, as given in 5.2 and 5.3, respectively. They should be designed to be simple inspections of the
integrity of the sampling process. For large multi-user facilities, it is recommended that a system of operational
reports be developed and an example of such a report is provided in Annex B.
6 Procedures
6.1 Audits
When assessing the conformance of a mechanical sampling system, an auditor should refer to Annex A, the
relevant parts of ISO 12743 or ISO 20212, and the design flow chart of the particular system being evaluated.
It is recommended that an audit be carried out at least once per year by a suitably qualified person who is not
directly involved in the operation and management of that particular sampling system.
It is essential that reference be made to the original operational parameters upon which the sampling system
was designed, as well as records of any changes or improvements. Operational conditions, such as conveyor
capacity, belt speed or material top size, could have been altered without due regard to the impact on the
operation and conformity of the sampling system.
Common examples of such alterations and their potential consequences are as follows.
a) An increase in the capacity of a conveyor could result in an excessive primary increment mass that will no
longer be entirely contained by the primary sample cutter.
b) A change in conveyor speed could affect the trajectory of material at a transfer point which could result in
a part of the material stream being missed by the sample cutter.
c) A change in nominal top size of the concentrate/ore could result in the original cutter aperture no longer
being large enough (i.e. three times the nominal top size of the material being sampled) to conform to
ISO 12743 or ISO 20212.
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ISO 11790:2010(E)
Items that should be covered as a minimum are as follows.
1) Safety requirements of site.
2) Original and current operating parameters.
3) Selection of appropriate sampling procedure.
4) General condition of the equipment, including build-up of material or blockages in chutes, cutters and
sample loss or sample contamination.
5) Comparison of design and actual increment masses for all cutters at several flow rates on the
product belt, up to the maximum.
6) Condition of cutters, cutter apertures and cutter lips. Check for foreign material, such as wood, rags,
stones and material that may be blinding the cutter apertures.
7) Conformance to ISO 12743 and/or ISO 20212, in particular:
i) minimizing bias;
ii) correct design and operation of sample cutters;
iii) the number of primary increments and sub-lots required;
iv) the methods of taking primary increments and division of gross samples, partial samples and
increments.
8) Ongoing precision monitoring using ISO 12744.
9) Crusher condition (inspect jaw plates, rolls and screens for wear and blinding).
10) Nominal top size of feed and crusher products.
11) Staff training and procedures for manual assessment.
12) Previous mechanical and operational inspections.
6.2 Mechanical inspections
It is suggested that the inspector start at the primary cutter and follow through the system to the final on-line
sample-collection point. The mechanical inspection should be made both with and without material running
through the system. Mechanical inspections should be carried out at more frequent intervals than audits. For
systems in daily use, it is recommended that mechanical inspections be carried out at least once per month by
the management of the sampling system, and not by the direct operators of the system.
The following items should be inspected.
a) The falling-stream and/or cross-belt cutter apertures to determine that they comply with the requirements
of ISO 12743 or ISO 20212 and with the design flow chart of the system.
b) The speed in both directions of all cutters. Check that the speed is constant for both time-based and
mass-based sampling. For mass-based sampling, it is also possible to use a variable-speed cutter. In this
case, check the speed at several flow rates to ensure that the speed is proportional to the flow rate. All
weighing devices must be checked regularly to ensure their reliability.
c) The movement of all cutters to verify uniform speed while in the material stream.
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ISO 11790:2010(E)
d) For all cutters, that the proper number of increments is taken to satisfy the requirements of ISO 12743 or
ISO 20212. It should also be determined that the time or mass interval between primary cuts is correct to
ensure that the minimum number of increments are collected for the lot being sampled during the
inspection based on maximum attainable feed rates.
e) That all cutters are parked out of the stream in the “at rest” position and that no material is entering the
cutter opening. There should be no holes in the baffle plates, dust doors, or seals that may cause leaking
of material into the primary sample hopper.
f) For falling-stream and/or cross-belt cutters, that the masses of increments conform with ISO 12743 or
ISO 20212.
g) Belt feeders (sample conveyors) and vibrating feeders for good condition. This is especially important for
sample integrity. The correct tracking of belts, condition of belts, skirt rubbers and belt scrapers can have
a significant impact on sample integrity. Check that the belt scrapers and skirts are adjusted properly to
avoid spillages. Check the flow rate settings of vibrating belt feeders.
h) The general condition of crushers, including measurement of crusher gaps, and the particle size of
crushed products. Variations in product size over time can indicate that maintenance is required to
screens, jaw plates, and rolls and gaps in roll crushers. Ensure that the crusher body and chutes are not
spilling material from the system.
i) The canisters of rotary sample dividers to ensure that they are free of distortions, perforations and cracks
in welds to guarantee correct distribution of material and prevent any material loss.
j) The final sample collector to determine the general condition. Checks should be made to ensure that
sample integrity is not being compromised through contamination, sample loss or moisture loss.
k) Records of previous operations and inspections.
6.3 Operational inspections
Operational inspections should be carried out immediately prior to, during and immediately after each
sampling operation. This inspection would be due at changes of shift or concentrate/ore type, or for each lot.
The emphasis of operational inspections should be on ensuring that the sampling system is operated at
correct settings and that reliable operation will be achieved during the sampling period. It is recommended that
operational inspections be carried out by the direct operators of the system. The following points should be
checked and reported.
a) Operational settings are correct, taking into account the lot size, number of primary increments and
sample-collection interval.
b) All equipment and sample chutes are clear of material build-up or blockages. Evidence of chute damage
due to damage to external walls or scraping should be recorded.
c) All equipment and sample chutes are clear of foreign material, such as wood, paper, rags, rocks or metal,
and there is no contamination from water that may have entered the sampling system.
d) All drives have been checked for correct operation, with attention paid to smooth operation of sample
cutter drives. Any unusual noises or vibrations should be reported.
e) All drives, including hydraulic systems, have been started well before sampling is required. Hydraulic
systems require a period of time to attain temperature equilibrium.
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ISO 11790:2010(E)
f) The sampling system has been “conditioned” by passing one or more primary increments through the
sampling system before commencing or recommencing sampling. Any sample collected during
conditioning should be discarded.
g) Control charts have been maintained in accordance with 6.4. This will provide evidence of restricted flow
through the system, should this occur. An example of this inspection summary can be found in Annex C.
6.4 Control charts
6.4.1 General
In addition to the operator's sampling record, it is recommended that control charts also be maintained. Two
types of control charts are recommended: for sampling ratio and for extraction ratio.
6.4.2 Sampling ratio
The sampling ratio, R , is the actual mass of sample, m , in kilograms, divided by the mass of material that it
S A
represents, m , in tonnes, expressed by the following equation:
SL
1000m
A
R =
S
m
SL
The sampling-ratio control chart is a plot of the sampling ratio as a function of increments sampled.
Sampling-ratio comparisons should be made only for similar system settings (same cutter apertures, timer
settings, sub-lot size and mass flow rate through the system), so a separate control chart is required for each
set of system settings used. Samples having a sampling ratio out of control are suspect and should be
investigated for validity. When there is a significant variation in the sampling ratio, the reasons for this should
also be investigated. An example of an inspection summary and the associated sampling-ratio control chart is
shown in Table 1 and Figure 1, respectively.
6.4.3 Extraction ratio
The extraction ratio, R , is the actual mass of the sample, m , in kilograms, divided by the mass of sample, m ,
e A C
in kilograms, calculated from the material flow rate, frequency of cuts, cutter aperture and cutter speed as
expressed by the following equation:
m
A
R =
e
m
C
The extraction ratio can be applied to primary increments or at any convenient subsequent sampling stage.
The example shown in Figure 1 is calculated for a single lot from the data in Table 1. However, in practice
extraction-ratio control charts are constructed for multiple lots to indicate long-term trends. Thus, each point
on an extraction-ratio control chart represents one lot sampled. The data are plotted over many lots, and long-
term trends for a particular system can be monitored. Control limits for the extraction ratio are based on the
average moving range. The aim in practice should be set at unity (1), not to the average of the data. When the
extraction ratio differs significantly from one, the system should be audited and investigated.
The extraction ratio is useful in determining whether there are long-term problems with a particular system.
For example, if a cutter speed decreased over several weeks due to a faulty drive, the mass of sample
passing through the system would increase and the long-term extraction-ratio data would indicate a problem
with the system. When system settings are changed, the extraction ratio is less likely to change than the
sampling ratio, so it is more useful in comparing the effectiveness of different sampling systems. An example
of an inspection summary and the associated extraction-ratio control chart is shown in Table 1 and Figure 1,
respectively.
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ISO 11790:2010(E)
Table 1 — Inspection summary outlining the mass of each sub-lot sample collected and
sampling/extraction ratios determined at a mechanical sampling system during the loading of a lot
Vessel “Copper Trader”
Lot 40 000 tonnes
Sampling frequency One (1) primary increment every 60 s
Loading rate 4 000 t/h
Number of sub-lot samples 20
Partial sample design mass 20 kg
Sub-lot sample Sub-lot sample Design sub-lot Sub-lot mass Sampling ratio Extraction ratio
number mass sample mass
kg kg t
1 13,5 18,3 3 668 3,68 0,74
2 18,4 20,7 4 135 4,45 0,89
3 16,7 19,3 3 857 4,33 0,87
4 27,5 19,7 3 945 6,97 1,40
5 24,5 20,7 4 139 5,92 1,18
6 19,4 20,4 4 084 4,75 0,95
7 21,3 20,3 4 065
...
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