ISO 11794:2017

INTERNATIONAL ISO
STANDARD 11794
Second edition
2017-06
Copper, lead, zinc and nickel
concentrates — Sampling of slurries
Concentrés de cuivre, de plomb, de zinc et de nickel —
Échantillonnage des schlamms
Reference number
ISO 11794:2017(E)
©
ISO 2017

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ISO 11794:2017(E)

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ISO 11794:2017(E)

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principles of sampling slurries . 2
4.1 General . 2
4.2 Sampling errors . 3
4.2.1 General. 3
4.2.2 Preparation error, PE . 4
4.2.3 Delimitation and extraction errors, DE and EE . 4
4.2.4 Weighting error, WE . 6
4.2.5 Periodic quality-fluctuation error, QE .
3 6
4.3 Sampling and total variance . 6
4.3.1 Sampling variance. 6
4.3.2 Total variance . 6
4.3.3 Sampling-stage method of estimating sampling and total variance . 8
4.3.4 Simplified method of estimating sampling and total variance . 9
4.3.5 Interleaved sample method of measuring total variance .10
5 Establishing a sampling scheme .11
6 Minimization of bias and unbiased increment mass .16
6.1 Minimization of bias .16
6.2 Volume of increment for falling-stream samplers to avoid bias.17
7 Number of increments .17
7.1 General .17
7.2 Simplified method .18
8 Minimum mass of solids contained in lot and sub-lot samples .18
8.1 Minimum mass of solids in lot samples .18
8.2 Minimum mass of solids in sub-lot samples .18
8.3 Minimum mass of solids in lot and sub-lot samples after size reduction .18
9 Time-basis sampling .19
9.1 General .19
9.2 Sampling interval .19
9.3 Cutters .19
9.4 Taking of increments .19
9.5 Constitution of lot or sub-lot samples .19
9.6 Division of increments and sub-lot samples .20
9.7 Division of lot samples .20
9.8 Number of cuts for division .20
10 Stratified random sampling within fixed time intervals.20
11 Mechanical sampling from moving streams .21
11.1 General .21
11.2 Design of the sampling system .21
11.2.1 Safety of operators .21
11.2.2 Location of sample cutters .21
11.2.3 Provision for duplicate sampling .21
11.2.4 System for checking the precision and bias.21
11.2.5 Avoiding bias .21
11.3 Slurry sample cutters .22
11.3.1 General.22
11.3.2 Falling-stream cutters .22
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ISO 11794:2017(E)

11.3.3 Cutter velocities .23
11.4 Mass of solids in increments .23
11.5 Number of primary increments .23
11.6 Routine checking .23
12 Manual sampling from moving streams .23
12.1 General .23
12.2 Choosing the sampling location .24
12.3 Sampling implements .24
12.4 Mass of solids in increments .25
12.5 Number of primary increments .25
12.6 Sampling procedures .25
13 Sampling of stationary slurries .25
14 Sample preparation .25
14.1 General .25
14.2 Sample division.25
14.3 Sample grinding .26
14.4 Chemical analysis samples . .26
14.5 Physical test samples .26
15 Packing and marking of samples .26
Annex A (normative) Sampling-stage method for estimating sampling and total variance .27
Annex B (informative) Examples of correct slurry sampling devices .34
Annex C (informative) Examples of incorrect slurry sampling devices .37
Annex D (normative) Manual sampling implements .41
Bibliography .42
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ISO 11794:2017(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 on 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 the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 183, Copper, lead, zinc and nickel ores and
concentrates.
This second edition cancels and replaces the 2010 edition (ISO 11794:2010), of which it constitutes
a minor revision. The main changes are the deletion of reference ISO 20212, which has not yet been
published, and the replacement of “should” with “shall” where the criteria and/or requirements are
mandatory.
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INTERNATIONAL STANDARD ISO 11794:2017(E)
Copper, lead, zinc and nickel concentrates — Sampling of
slurries
WARNING — This document may involve hazardous materials, operations and equipment.
It is the responsibility of the user of this document to establish appropriate health and safety
practices and determine the applicability of any other limitations prior to use.
1 Scope
This document sets out the basic methods for sampling particulate material that is mixed with a liquid,
usually water, to form a slurry. In industry and in the mining and mineral processing literature, slurry is
also referred to as pulp, but this term is not used in this document. At very high ratios of fine particulate
solids to liquids where material assumes a soft plastic form, the mixture is correctly termed as a paste.
Sampling of pastes is not covered in this document.
The procedures described in this document apply to sampling of particulate materials that are
transported in moving streams as slurries, but not pressurized slurries. These streams may fall freely
or be confined in pipes, launders, flumes, sluices, spirals or similar channels. Sampling of slurries in
stationary situations, such as a settled or even a well-stirred slurry in a holding vessel or dam, is not
recommended and is not covered in this document.
This document describes procedures that are designed to provide samples representative of the slurry
solids and particle-size distribution of the slurry under examination. After draining the slurry sample of
fluid and measuring the fluid volume, damp samples of the contained particulate material in the slurry
are available for drying (if required) and measurement of one or more characteristics in an unbiased
manner and with a known degree of precision. The characteristics are measured by chemical analysis,
physical testing or both.
The sampling methods described are applicable to slurries that require inspection to verify compliance
with product specifications, determination of the value of a characteristic as a basis for settlement
between trading partners or estimation of a set of average characteristics and variances that describes
a system or procedure.
Provided that flow rates are not too high, the reference method against which other sampling
procedures are compared is one where the entire stream is diverted into a vessel for a specified time or
volume interval. This method corresponds to the stopped-belt method described in ISO 12743.
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 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
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ISO 11794:2017(E)

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 12743, ISO 12744 and
ISO 13292 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
4 Principles of sampling slurries
4.1 General
In this document, a slurry is defined as “any fluid mixture of a solid of nominal top size < 1 mm that
is mixed with water, which is frequently used as a convenient form to handle solids in bulk”. Slurry
flows are found in many mineral processing plants, with the water and entrained solids mixture being
transported through the plant circuits by means of pumps and pipelines and under gravity in sluices,
flumes and launders. In a number of operations, ore is transported to the mill in slurry form, and in
others concentrates are transported long distances in slurry pipelines. Tailings from wet plants are also
discharged as slurries through pipelines to the tailings dam. In many of these operations, collection of
increments at selected sample points is required for evaluation of the particulate material in the slurry.
A lot sample is constituted from a set of unbiased primary increments from a lot. The sample container is
weighed immediately after collection and combination of increments to avoid water loss by evaporation
or spillage. Weighing is necessary to determine the percentage of solids by mass in the slurry sample.
The sample may then be filtered, dried and weighed. Alternatively, the sample may be sealed in plastic
bags after filtering for transport and drying at a later stage. The liquid removed during filtration should
be retained if it needs to be analysed.
Test samples are prepared from samples after filtering and drying. Test portions may then be taken
from the test sample and analysed using an appropriate and properly calibrated analytical method or
test procedure under prescribed conditions.
The objective of the measurement chain is to determine the characteristic of interest in an unbiased
manner with an acceptable and affordable degree of precision. The general sampling theory, which is
based on the additive property of variances, can be used to determine how the variances of sampling,
sample preparation and chemical analysis or physical testing propagate and hence determine the
total variance for the measurement chain. This sampling theory can also be used to optimize manual
sampling methods and mechanical sampling systems.
If a sampling scheme is to provide representative samples, all parts of the slurry in the lot must have
an equal opportunity of being selected and appearing in the sample for testing. Hence, slurries are to
be sampled in such a manner that all possible primary increments in the set into which the slurry can
be divided have the same probability of being selected. Any deviation from this basic requirement can
result in bias. A sampling scheme with incorrect selection techniques, i.e. with non-uniform selection
probabilities, cannot be relied upon to provide representative samples.
Sampling of slurries should preferably be carried out by systematic sampling on a time basis (see
Clause 9). If the slurry flow rate and the solids concentration vary with time, the slurry volume and the
mass of dry solids for each increment will vary accordingly. It needs to be shown that no systematic
error (bias) is introduced by periodic variation in quality or quantity, where the proposed sampling
interval is approximately equal to a multiple of the period of variation in quantity or quality. Otherwise,
stratified random sampling should be used (see Clause 10).
Best practice for sampling slurries is to cut freely falling streams mechanically (see Clause 11), with
a complete cross-section of the stream being taken during the traverse of the cutter. Access to freely
falling streams can sometimes be engineered at the end of pipes or, alternatively, a full-stream sample
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ISO 11794:2017(E)

by-line can be added to a pipe that diverts the slurry into a holding tank, or weirs can be incorporated in
launders, sluices and flumes. If samples are not collected in this manner, non-uniform concentration of
solids in the slurry due to segregation and stratification of the solids may lead to bias in the sample that
is collected. Slurry flow in pipes can be homogeneous with very fine particles, such as clays, dispersed
uniformly in turbulent suspension along the length and across the diameter of the pipe. However, more
commonly, the slurry in a pipe will have significant particle concentration gradients across the pipe and
there may be particle concentration fluctuations along the length of the pipe. These common conditions
are called heterogeneous flow. Examples of such flow are full-pipe flow of a heterogeneous suspension,
or partial-pipe flow of a fine particle suspension above a slower moving or even stationary bed of
coarser particles in the slurry.
For heterogeneous flow, bias is likely to occur where a tapping is made into the slurry pipe to locate
either a flush-fitting sample take-off pipe or a sample tube projecting into the slurry stream for
extraction of samples. The bias is caused by non-uniform radial concentration profiles in the pipe and
the different trajectories followed by particles of different masses due to their inertia, resulting in
larger or denser particles being preferentially rejected from, or included in, the sample.
In slurry channels such as launders, heterogeneous flow is almost always present, and this non-
uniformity in particle concentration is usually preserved in the discharge over a weir or step. However,
sampling at a weir or step allows complete access to the full width and breadth of the stream, thereby
enabling all parts of the slurry stream to be collected with equal probability.
Sampling of slurries in stationary situations, such as a settled or even a well-stirred slurry in a tank,
holding vessel or dam, is not recommended, because it is virtually impossible to ensure that all parts
of the slurry in the lot have an equal opportunity of being selected and appearing in the lot sample for
testing. Instead, sampling shall be carried out from moving streams, as the tank, vessel or dam is filled
or emptied.
4.2 Sampling errors
4.2.1 General
The processes of sampling, sample preparation and measurement are experimental procedures, and
each procedure has its own uncertainty appearing as variations in the final results. Where the average
of these variations is close to zero, they are called random errors. More serious variations contributing
to the uncertainty of results are systematic errors, which have averages biased away from zero. There
are also human errors that introduce variations due to departures from prescribed procedures for
which statistical analysis procedures are not applicable.
The characteristics of the solids component of a slurry can be determined by extracting samples from
the slurry stream, preparing test samples and measuring the required quality characteristics. The
total sampling error TSE can be expressed as the sum of a number of independent components (Gy,
1992; Pitard, 1993). Such a simple additive combination would not be possible if the components were
correlated. The sampling error, expressed as a sum of its components, is given by Formula (1):
TSEQ=+EQEQ++EWED++EEEP+ E (1)
12 3
where
QE is the short-range quality-fluctuation error associated with short-range variations in quality
1
of the solids component of the slurry;
QE is the long-range quality-fluctuation error associated with long-range variations in quality of
2
the solids component of the slurry;
QE is the periodic quality-fluctuation error associated with periodic variations in quality of the
3
solids component of the slurry;
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ISO 11794:2017(E)

WE is the weighting error associated with variations in the slurry flow rate;
DE is the increment delimitation error introduced by incorrect increment delimitation;
EE is the increment extraction error introduced by incorrect increment extraction from the slurry;
PE is the preparation error (also known as accessory error) introduced by departures (usually
unintentional) from correct practices, e.g. during constitution of the lot sample, draining and
filtering away the water, and transportation and drying of the sample.
The short-range quality-fluctuation error consists of two components, as shown by Formula (2):
QE =+FE GE (2)
1
where
FE is the fundamental error due to variation in quality between particles;
GE is the segregation and grouping error.
The fundamental error results from the composition heterogeneity of the lot, i.e. the heterogeneity that
is inherent to the composition of each particle making up the solids component of the lot. The greater
the differences in the compositions of particles, the greater the composition heterogeneity and the
higher the fundamental error variance. The fundamental error can never be completely eliminated.
It is an inherent error resulting from the variation in composition of the particles in the slurry being
sampled.
The segregation and grouping error resul
...