ISO 3082:2009

INTERNATIONAL ISO
STANDARD 3082
Fourth edition
2009-06-01
Iron ores — Sampling and sample
preparation procedures
Minerais de fer — Procédures d'échantillonnage et de préparation des
échantillons
Reference number
©
ISO 2009
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2009
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2009 – All rights reserved

Contents Page
Foreword .vi
1 Scope .1
2 Normative references.1
3 Terms and definitions .2
4 General considerations for sampling and sample preparation .4
4.1 Basic requirements .4
4.2 Establishing a sampling scheme.4
4.3 System verification.5
5 Fundamentals of sampling and sample preparation .6
5.1 Minimization of bias .6
5.1.1 General .6
5.1.2 Minimization of particle size degradation .6
5.1.3 Extraction of increments .6
5.1.4 Increment mass .7
5.2 Overall precision.8
5.3 Quality variation.10
5.4 Sampling precision and number of primary increments.11
5.4.1 Mass-basis sampling .11
5.4.2 Time-basis sampling .11
5.5 Precision of sample preparation and overall precision .12
5.5.1 General .12
5.5.2 Preparation and measurement of gross sample.12
5.5.3 Preparation and measurement of partial samples.12
5.5.4 Preparation and measurement of each increment.13
6 Methods of sampling.13
6.1 Mass-basis sampling .13
6.1.1 Mass of increment .13
6.1.2 Quality variation.14
6.1.3 Number of primary increments .14
6.1.4 Sampling interval.14
6.1.5 Methods of taking increments.14
6.2 Time-basis sampling .15
6.2.1 Mass of increment .15
6.2.2 Quality variation.15
6.2.3 Number of increments .15
6.2.4 Sampling interval.15
6.2.5 Methods of taking increments.15
6.3 Stratified random sampling within fixed mass or time intervals.16
6.3.1 Fixed mass intervals .16
6.3.2 Fixed time intervals .16
7 Sampling from moving streams.16
7.1 General .16
7.2 Safety of operations .17
7.3 Robustness of sampling installation.17
7.4 Versatility of sampling system.17
7.5 Primary samplers.18
7.5.1 Location.18
7.5.2 Types of primary sampler.18
7.5.3 General design criteria for primary cutters .18
7.5.4 Cutter aperture of primary sampler . 22
7.5.5 Cutter speed of primary sampler . 22
7.6 Secondary and subsequent samplers. 23
7.7 On-line sample preparation . 23
7.7.1 Arrangement for sample preparation . 23
7.7.2 Crushers . 23
7.7.3 Dividers. 23
7.7.4 Dryers. 27
7.8 Checking precision and bias . 27
7.9 Cleaning and maintenance . 27
7.10 Example of a flowsheet . 27
8 Sampling from stationary situations . 29
8.1 General. 29
8.2 Sampling from wagons . 29
8.2.1 Sampling devices. 29
8.2.2 Number of primary increments . 30
8.2.3 Method of sampling. 30
8.3 Sampling from ships, stockpiles and bunkers . 30
9 Stopped-belt reference sampling. 30
10 Sample preparation . 31
10.1 Fundamentals. 31
10.1.1 General. 31
10.1.2 Drying. 32
10.1.3 Crushing and grinding . 32
10.1.4 Mixing. 32
10.1.5 Sample division. 33
10.1.6 Mass of divided sample. 33
10.1.7 Split use and multiple use of sample. 36
10.2 Method of constituting partial samples or a gross sample. 36
10.2.1 General. 36
10.2.2 Method of constitution for mass-basis sampling. 36
10.2.3 Method of constitution for time-basis sampling . 38
10.2.4 Special procedure for moisture content. 38
10.3 Mechanical methods of division . 39
10.3.1 Mechanical increment division. 39
10.3.2 Other mechanical division methods. 40
10.4 Manual methods of division . 40
10.4.1 General. 40
10.4.2 Manual increment division. 40
10.4.3 Manual riffle-division method. 43
10.5 Preparation of test samples for chemical analysis . 43
10.5.1 Mass and particle size. 43
10.5.2 Preparation to − 250 µm . 46
10.5.3 Final preparation. 46
10.5.4 Grinding to −100 µm or −160 µm . 47
10.5.5 Distribution of samples for chemical analysis . 48
10.6 Preparation of test samples for moisture determination. 48
10.7 Preparation of test samples for size determination . 49
10.8 Preparation of test samples for physical testing . 49
10.8.1 Selection of sample preparation procedure. 49
10.8.2 Extraction of test samples . 49
10.8.3 Reserve samples. 58
11 Packing and marking of samples. 58
Annex A (informative) Inspection of mechanical sampling systems. 59
Annex B (normative) Equation for number of increments. 67
Annex C (informative) Alternative methods of taking the reference sample . 70
iv © ISO 2009 – All rights reserved

Annex D (normative) Procedure for determining the minimum mass of divided gross sample for
size determination using other mechanical division methods.76
Annex E (normative) Riffle dividers .79
Bibliography.81

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 3082 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 edition (ISO 3082:2000), of which it constitutes a technical
revision.
vi © ISO 2009 – All rights reserved

INTERNATIONAL STANDARD ISO 3082:2009(E)

Iron ores — Sampling and sample preparation procedures
WARNING — This International Standard may involve hazardous materials, operations and equipment,
and does not purport to address all the safety issues associated with its use. 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 gives
a) the underlying theory,
b) the basic principles for sampling and preparation of samples, and
c) the basic requirements for the design, installation and operation of sampling systems
for mechanical sampling, manual sampling and preparation of samples taken from a lot under transfer, to
determine the chemical composition, moisture content, size distribution and other physical and metallurgical
properties of the lot, except bulk density obtained using ISO 3852:2007 (Method 2).
The methods specified in this International Standard are applicable to both the loading and discharging of a lot
by means of belt conveyors and other ore-handling equipment to which a mechanical sampler may be
installed or where manual sampling may safely be conducted.
The methods are applicable to all iron ores, whether natural or processed (e.g. concentrates and
agglomerates, such as pellets or sinters).
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 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ISO 3084, Iron ores — Experimental methods for evaluation of quality variation
ISO 3085:2002, Iron ores — Experimental methods for checking the precision of sampling, sample
preparation and measurement
ISO 3086, Iron ores — Experimental methods for checking the bias of sampling
ISO 3087, Iron ores — Determination of moisture content of a lot
ISO 3271, Iron ores for blast furnace and direct reduction feedstocks — Determination of the tumble and
abrasion indices
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310-2, Test sieves —Technical requirements and testing — Part 2: Test sieves of perforated metal plate
ISO 3852:2007, Iron ores for blast furnace and direct reduction feedstocks — Determination of bulk density
ISO 4695, Iron ores for blast furnace feedstocks — Determination of the reducibility by the rate of reduction
index
ISO 4696-1, Iron ores for blast furnace feedstocks — Determination of low-temperature reduction-
disintegration indices by static method — Part 1: Reduction with CO, CO , H and N
2 2 2
ISO 4696-2, Iron ores for blast furnace feedstocks — Determination of low-temperature reduction-
disintegration indices by static method — Part 2: Reduction with CO and N
ISO 4698, Iron ore pellets for blast furnace feedstocks — Determination of the free-swelling index
ISO 4700, Iron ore pellets for blast furnace and direct reduction feedstocks — Determination of the crushing
strength
ISO 4701, Iron ore and direct reduced iron — Determination of size distribution by sieving
ISO 7215, Iron ores for blast furnace feedstocks — Determination of the reducibility by the final degree of
reduction index
ISO 7992, Iron ores for blast furnace feedstocks — Determination of reduction under load
ISO 8371, Iron ores for blast furnace feedstocks — Determination of the decrepitation index
ISO 11256, Iron ore pellets for shaft direct-reduction feedstocks — Determination of the clustering index
ISO 11257, Iron ores for shaft direct-reduction feedstocks — Determination of the low-temperature reduction-
disintegration index and degree of metallization
ISO 11258, Iron ores for shaft direct-reduction feedstocks — Determination of the reducibility index, final
degree of reduction and degree of metallization
ISO 11323, Iron ore and direct reduced iron — Vocabulary
ISO 13930, Iron ores for blast furnace feedstocks — Determination of low-temperature reduction-
disintegration indices by dynamic method
3 Terms and definitions
For the purposes of this document, the terms and definitions contained in ISO 11323, as well as those given
below, apply.
3.1
lot
discrete and defined quantity of iron ore and direct reduced iron for which quality characteristics are to be
assessed
3.2
increment
quantity of iron ore and direct reduced iron collected in a single operation of a device for sampling or sample
division
3.3
sample
relatively small quantity of iron ore and direct reduced iron, so taken from a lot as to be representative in
respect of the quality characteristics to be assessed
2 © ISO 2009 – All rights reserved

3.4
partial sample
sample comprising of less than the complete number of increments needed for a gross sample
3.5
gross sample
sample comprising all increments, entirely representative of all quality characteristics of a lot
3.6
test sample
sample prepared to meet all specific conditions for a test
3.7
test portion
part of a test sample that is actually and entirely subjected to the specific test
3.8
stratified sampling
sampling of a lot carried out by taking increments from systematically specified positions and in appropriate
proportions from strata
NOTE Examples of strata include production periods (e.g. 5 min), production masses (e.g. 1 000 t), holds in vessels,
wagons in a train, or containers and trucks representing a lot.
3.9
systematic sampling
sampling carried out by taking increments from a lot at regular intervals
3.10
mass-basis sampling
sampling carried out so that increments are taken at equal mass intervals, increments being as near as
possible of uniform mass
3.11
time-basis sampling
sampling carried out so that increments are taken from free falling streams, or from conveyors, at uniform time
intervals, the mass of each increment being proportional to the mass flow rate at the instant of taking the
increment
3.12
proportional mass division
division of samples or increments such that the mass of each retained divided portion is a fixed proportion of
the mass being divided
3.13
constant mass division
division of samples or increments such that the retained divided portions are of almost uniform mass,
irrespective of variations in mass of the samples or increments being divided
NOTE 1 This method is required for sampling on a mass basis.
NOTE 2 “Almost uniform” means that variations in mass are less than 20 % in terms of the coefficient of variation.
3.14
split use of sample
separate use of parts of a sample, as test samples for separate determinations of quality characteristics
3.15
multiple use of sample
use of a sample in its entirety for the determination of one quality characteristic, followed by the use of the
same sample in its entirety for the determination of one or more other quality characteristics
3.16
nominal top size
particle size expressed by the smallest aperture size of the test sieve (from a square opening complying with
the R20 or R40/3 series in ISO 565), such that no more than 5 % by mass of iron ore is retained on the sieve
4 General considerations for sampling and sample preparation
4.1 Basic requirements
The basic requirement for a correct sampling scheme is that all parts of the ore in the lot have an equal
[1]
opportunity of being selected and becoming part of the partial sample or gross sample for analysis (Gy ;
[2]
Pitard ). Any deviation from this basic requirement can result in an unacceptable loss of trueness and
precision. An incorrect sampling scheme cannot be relied on to provide representative samples.
The best sampling location to satisfy the above requirement is at a transfer point between conveyor belts.
Here the full cross-section of the ore stream can be conveniently intercepted at regular intervals, enabling
representative samples to be obtained.
In-situ sampling of ships, stockpiles, containers and bunkers is not permitted, because it is impossible to drive
the sampling device down to the bottom and extract the full column of ore. Consequently, all parts of the lot do
not have an equal opportunity of being sampled. The only effective procedure is sampling from a conveyor
belt when ore is being conveyed to or from the ship, stockpile, container or bunker.
In-situ sampling from stationary situations such as wagons is permitted only for ores with nominal top size less
than 1 mm, provided the sampling device, e.g. a spear or an auger, penetrates to the full depth of the
concentrate at the point selected for sampling and the full column of concentrate is extracted.
Sampling shall be carried out by systematic sampling either on a mass basis (see 6.1) or on a time basis (see
6.2), provided no bias is introduced by periodic variation in quality or quantity. If this is not the case, stratified
random sampling within fixed mass or time intervals shall be carried out (see 6.3).
The methods used for sampling and sample preparation depend on the final choice of the sampling scheme
and on the steps necessary to minimize possible biases and obtain acceptable overall precision.
Moisture samples shall be processed as soon as possible and test portions weighed immediately. If this is not
possible, samples shall be stored in non-absorbent airtight containers with a minimum of free air space to
minimize any change in moisture content, but should be prepared without delay.
4.2 Establishing a sampling scheme
The procedure for establishing a sampling scheme is as follows:
a) identify the lot to be sampled and the quality characteristics to be determined;
b) ascertain the nominal top size;
c) determine the sampling location and the method of taking increments;
d) determine the mass of increment considering the nominal top size, the ore-handling equipment and the
device for taking increments;
e) specify the precision required;
4 © ISO 2009 – All rights reserved

f) ascertain the quality variation, σ , of the lot in accordance with ISO 3084, or, if this is not possible,
W
assume “large” quality variation as specified in 5.3;
g) determine the minimum number of primary increments, n , to be taken from the lot for systematic or
stratified random sampling;
h) determine the sampling interval in tonnes for mass-basis sampling or in minutes for time-basis sampling;
i) take increments having almost uniform mass for mass-basis sampling or having a mass proportional to
the flow rate of the ore stream at the time of sampling for time-basis sampling. Increments are to be taken
at the intervals determined in (h) during the entire period of handling the lot;
j) determine whether the sample is for split use or multiple use;
k) establish the method of combining increments into a gross sample or partial samples;
l) establish the sample preparation procedure, including division, crushing, mixing and drying;
m) crush the sample, if necessary, except for the size sample and some physical testing samples;
n) dry the sample, if necessary, except for the moisture sample;
o) divide samples according to the minimum mass of divided sample for a given nominal top size, employing
constant mass or proportional division for mass-basis sampling, or proportional division for time-basis
sampling;
p) prepare the test sample.
Special attention shall be given to the total mass of sample required for physical tests to be carried out on the
gross sample or partial samples (see 10.1.6.3). When the mass of the gross sample or partial samples is
expected to be less than that required for preparation of test samples for physical testing, the number and/or
mass of increments to be taken shall be increased to give the required mass. It is preferable that the number
of increments be increased, rather than the increment mass.
4.3 System verification
Stopped-belt sampling is the reference method for collecting samples against which mechanical and manual
sampling procedures may be compared to establish that they are unbiased in accordance with procedures
specified in ISO 3086. However, before any bias tests are conducted, sampling and sample preparation
systems shall first be inspected to confirm that they conform to the correct design principles specified in this
International Standard. Inspections shall also include an examination of whether any loading, unloading or
reclaiming procedures could produce periodic variations in quality in phase with the taking of increments.
These periodic variations could include characteristics such as particle size distribution and moisture content.
When such cyclic variations occur, the source of the variations shall be investigated to determine the
practicability of eliminating the variations. If this is not possible, stratified random sampling shall be carried out
(see 6.3).
An example of a suitable inspection procedure and checklist is provided in Annex A. This will quickly reveal
any serious deficiencies in the sampling or sample preparation system and may avoid the need for expensive
bias testing. Consequently, sampling systems shall be designed and constructed in a manner that facilitates
regular verification of correct operation.
NOTE Further details can be found in ISO/TC 102 Technical Committee Report No.14, Iron ores and direct reduced
[3]
iron — Guide to the inspection of mechanical sampling systems .
Regular checks of quality variation and precision shall also be carried out in accordance with ISO 3084 and
ISO 3085 to monitor variations in quality variation and to verify the precision of sampling, sample preparation
and measurement. This is particularly important for new products or new sampling systems or when
significant changes are made to existing systems.
5 Fundamentals of sampling and sample preparation
5.1 Minimization of bias
5.1.1 General
Minimization of bias in sampling and sample preparation is vitally important. Unlike precision, which can be
improved by collecting more increments or repeating measurements, bias cannot be reduced by replicating
measurements. Consequently, the minimization or preferably elimination of possible biases should be
regarded as more important than improvement of precision. Sources of bias that can be completely eliminated
at the outset by correct design of the sampling and sample preparation system include sample spillage,
sample contamination and incorrect delineation and extraction of increments, while sources that can be
minimized but not completely eliminated include change in moisture content, loss of dust and particle
degradation (for size determination).
5.1.2 Minimization of particle size degradation
Minimization of particle size degradation of samples used for determination of size distribution is vital in order
to reduce bias in the measured size distribution. To prevent particle size degradation, it is essential to keep
free-fall drops to a minimum.
5.1.3 Extraction of increments
It is essential that increments be extracted from the lot in such a manner that all parts of the ore have an equal
opportunity of being selected and becoming part of the final sample for analysis, irrespective of the size, mass,
shape or density of individual particles. If this requirement is not respected, bias is easily introduced. This
results in the following design requirements for sampling and sample preparation systems:
a) a complete cross-section of the ore stream shall be taken when sampling from a moving stream (see 7.5);
b) the aperture of the sample cutter shall be at least three times the nominal top size of the ore, or 30 mm
for the primary sampling and 10 mm for subsequent stages, whichever is the greater (see 7.5.4);
c) the speed of the sample cutter shall not exceed 0,6 m/s, unless the cutter aperture is correspondingly
increased (see 7.5.5);
d) the sample cutter shall travel through the ore stream at uniform speed (see 7.5.3), both the leading and
trailing edges of the cutter clearing the ore stream at the end of its traverse;
e) the lips on the sample cutter shall be parallel for straight-path samplers and radial for rotary cutters
(see 7.5.3), and these conditions shall be maintained as the cutter lips wear;
f) changes in moisture content, dust losses and sample contamination shall be avoided;
g) free-fall drops shall be kept to a minimum to reduce size degradation of the ore and hence minimize bias
in size distribution;
h) primary cutters shall be located as near as possible to the loading or discharging point to further minimize
the effects of size degradation;
i) a complete column of ore with nominal top size less than 1 mm shall be extracted when sampling iron ore
concentrate in a wagon (see 8.2).
Sampling systems shall be designed to accommodate the maximum nominal top size and flow rate of the ore
being sampled. Detailed design requirements for sampling and sample preparation systems are provided in
Clauses 7, 8, 9 and 10.
6 © ISO 2009 – All rights reserved

5.1.4 Increment mass
The increment mass required to obtain an unbiased sample can be calculated for typical sampling situations
[see Equations (1), (2) and (3)]. Comparing the calculated masses with the actual increment masses is useful
for checking the design and operation of sampling systems. If the difference is significant, the cause shall be
identified and corrective action taken to rectify the problem.
5.1.4.1 Increment mass for falling stream sampling
The mass of increment, m , in kilograms, to be taken (mechanically or manually) by a cutter-type sampler from
I
the ore stream at the discharge end of a conveyor belt is given by:
ql
m = (1)
l
3,6v
C
where
q is the flow rate, in tonnes per hour, of ore on the conveyor belt;
l is the cutter aperture, in metres, of the sampler;
v is the cutter speed, in metres per second, of the sampler.
C
The minimum increment mass that can be taken, while still avoiding bias, is determined by the minimum cutter
aperture specified in 7.5.4 and the maximum cutter speed specified in 7.5.5.
For practical reasons, e.g. in the case of lumpy ore, it may be necessary for the cutter aperture to exceed
three times the nominal top size of the ore.
5.1.4.2 Increment mass for stopped-belt sampling
The mass of increment, m , in kilograms, to be taken manually from a stopped-belt is equal to the mass of a
I
complete cross-section of the ore on the conveyor. It is given by the equation:
ql
m = (2)
l
3,6v
B
where
q is the flow rate, in tonnes per hour, of ore on the conveyor belt;
l is the length, in metres, of the complete cross-section of ore removed from the conveyor;
v is the speed of the conveyor belt, in metres per second.
B
The minimum increment mass that can be taken, while still avoiding bias, is determined by the minimum
length of ore removed from the conveyor, i.e. 3d, where d is the nominal top size of the ore, in millimetres,
subject to a minimum of 30 mm for primary sampling and 10 mm for subsequent stages.
5.1.4.3 Increment mass for manual sampling using spear or auger
The mass of increment, m , in kilograms to be taken from a wagon in a lot using a spear or an auger of
I
diameter, l , in millimetres, is given by:
πρlL
m = (3)
l
4 000
where
ρ is the bulk density of the ore with nominal top size < 1 mm, in tonnes per cubic metre;
L is the depth of ore with nominal top size < 1 mm in the wagon, in metres.
The minimum increment mass that can be taken, while still avoiding bias, is determined by the minimum
diameter of the spear or auger, i.e. 30 mm.
This method of extracting increments is only applicable to sampling ore with nominal top size < 1 mm.
5.2 Overall precision
This International Standard is designed to attain the overall precision, β , at a probability level of 95 %,
SPM
given in Table 1 for the total iron, silica, alumina, phosphorus, and moisture contents and the percent size
fraction of the lot. Greater precision may be adopted if required. The precision shall be determined in
accordance with ISO 3085.
Table 1 — Overall precision, β (values as absolute percentages)
SPM
Quality characteristics Approximate overall precision
β
SPM
Mass of lot
t
Over 210 000 150 000 100 000 70 000 45 000 30 000 15 000 Less
270 000 to to to to to to to than
270 000 210 000 150 000 100 000 70 000 45 000 30 000 15 000
Iron content 0,34 0,35 0,37 0,38 0,40 0,42 0,45 0,49 0,55
Silica content 0,34 0,35 0,37 0,38 0,40 0,42 0,45 0,49 0,55
Alumina content 0,11 0,12 0,12 0,13 0,14 0,15 0,16 0,18 0,20
Phosphorus content 0,003 4 0,003 5 0,003 6 0,003 7 0,003 8 0,004 0 0,004 2 0,004 5 0,004 8
Moisture content 0,34 0,35 0,37 0,38 0,40 0,42 0,45 0,49 0,55
Size − 200 mm ore − 10 mm fraction
3,4 3,5 3,6 3,7 3,9 4,0 4,2 4,4 5,0
mean 20 %
Size − 50 mm ore
Size − 6,3 mm fraction
− 31,5 + 6,3 mm ore mean 10 %
Size − Sinter feed + 6,3 mm fraction
1,7 1,75 1,8 1,85 1,95 2,0 2,1 2,2 2,5
mean 10 %
Size − Pellet feed − 45 µm fraction

mean 70 %
Size − Pellets − 6,3 mm fraction
0,68 0,70 0,72 0,74 0,78 0,80 0,84 0,88 1,00
mean 5 %
NOTE The values of β for silica, alumina and phosphorus content are indicative and subject to confirmation through international testwork.
SPM
NOTE The overall precision for other physical characteristics and metallurgical properties is not specified in this
International Standard, because they are used to qualitatively compare the behaviour of iron ores during handling and
reduction processes.
8 © ISO 2009 – All rights reserved

The overall precision, β , is a measure of the combined precision of sampling, sample preparation and
SPM
measurement, and is twice the standard deviation of sampling, sample preparation and measurement, σ ,
SPM
expressed as an absolute percentage, i.e.:
22 2
σ =+σσσ+ (4)
SPM S P M
22 2
β ==22σσ+σ+σ (5)
SPM SPM S P M
σ
W
σ = (6)
S
n
where
σ is the sampling standard deviation;
S
σ is the sample preparation standard deviation;
P
σ is the measurement standard deviation;
M
σ is the quality variation of the ore;
W
n is the number of primary increments.
Equations (4), (5) and (6) are based on the theory of stratified sampling (see Annex B for details). The number
of primary increments to be taken for a lot is dependent on the sampling precision required and on the quality
variation of the ore to be sampled. Thus, before the number of primary increments can be determined, it is
necessary to define:
a) the sampling precision, β , to be attained;
S
b) the quality variation, σ , of the ore to be sampled.
W
When on-line sample preparation takes place within the sample plant away from the preparation laboratory,
the distinction between the terms sampling and sample preparation becomes unclear. The precision of on-line
sample preparation may be included in either the sampling precision or in the sample preparation precision.
The choice depends on how easy it is to separate the precision of secondary and tertiary sampling from that
of primary sampling. In any event, sample preparation also constitutes a sampling operation, because a
representative part of the sample is selected for subsequent processing.
The most rigorous approach is to break up the sampling standard deviation into its components for each
sampling stage, in which case Equation (4) becomes:
2 222 2
σ =σσ+++σ σ+σ (7)
SPM S1 S2 S3 P M
where
σ is the sampling standard deviation for primary sampling;
S1
σ is the sampling standard deviation for secondary sampling;
S2
σ is the sampling standard deviation for tertiary sampling.
S3
Using this approach, the precision of each sampling stage can be separately determined and optimized,
resulting in a fully optimized sampling and sample preparation regime.
5.3 Quality variation
The quality variation, σ , is a measure of the heterogeneity of the lot and is the standard deviation of the
W
quality characteristics of increments within strat
...