ISO 4701:2008

INTERNATIONAL ISO
STANDARD 4701
Third edition
2008-10-01
Iron ores and direct reduced iron —
Determination of size distribution by
sieving
Minerais de fer et minerais de fer préréduits — Détermination de la
granulométrie par tamisage
Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Principles and planning . 2
4.1 General. 2
4.2 Purpose of the analysis . 2
4.3 Impact of ore and DRI properties . 2
4.4 Nature of sample. 4
4.5 Choice of sieving method . 4
4.6 Maximum particle size permitted on a sieve.5
4.7 Specified loading of sieves. 5
4.8 Sieving time. 6
5 Apparatus . 7
5.1 Sieve media . 7
5.2 Sieving machines. 8
5.3 Accessories for wet sieving . 8
5.4 Drying equipment . 8
5.5 Equipment for the determination of mass. 8
6 Samples . 10
6.1 Derivation of size sample. 10
6.2 Mass of test sample(s) for sieving. 10
7 Procedures . 11
7.1 Drying. 11
7.2 Division . 12
7.3 Preparation and maintenance of sieves for test or nest sieving . 12
7.4 Sieving . 12
7.5 Determination of mass . 17
7.6 Determination of sieving end point. 17
8 Verification . 18
8.1 General. 18
8.2 Checking of division. 18
8.3 Verification of sieve media . 18
8.4 Verification of sieving machines. 18
8.5 Verification of weighing devices . 18
9 Results . 19
9.1 Evaluation of results. 19
9.2 Calculation and expression of results. 19
9.3 Repeatability and acceptance of results . 20
10 Test report and working log . 21
11 Precision. 21
11.1 Overall precision, β . 21
SPM
11.2 Precision of preparation and measurement, β . 21
PM
Annex A (informative) Steps for establishing the operating conditions for the determination of
size distribution using a single sieve or a nest of sieves. 23
Annex B (normative) Scheme of sample preparation and sieving procedure. 24
Annex C (normative) Maximum mass to be retained on a sieve at completion of batch sieving (m)
in order to obtain good sieving efficiency. 25
Annex D (informative) Size apertures in R20 and R40/3 series (taken from ISO 565) . 27
Annex E (informative) Typical batch sieving apparatus. 28
Annex F (informative) Desirable features of mechanical sieving machines . 29
Annex G (normative) Procedure for determining the minimum mass of sample used for sieving . 33
Annex H (normative) Flowsheet of the procedure for the acceptance of analytical values for test
portions. 36
Annex I (informative) Additional information. 37
Annex J (normative) Determination of the average particle size (APS). 39

iv © ISO 2008 – All rights reserved

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 4701 was prepared by Technical Committee ISO/TC 102, Iron ore and direct reduced iron, Subcommittee
SC 1, Sampling.
This third edition cancels and replaces the second edition (ISO 4701:1999), which has been technically
revised.
INTERNATIONAL STANDARD ISO 4701:2008(E)

Iron ores and direct reduced iron — Determination of size
distribution by sieving
1 Scope
This International Standard specifies the methods to be employed for determination of size distributions by
sieving of iron ore and direct reduced iron (exclude briquetted iron), utilizing sieves having aperture sizes of
36 µm or larger. The size distribution is expressed in terms of mass and percentage mass, passed or retained
on selected sieves. The purpose of this International Standard is to provide a basis for any testing of iron ore
and direct reduced iron involving size determination for use by contracting parties in the sale and purchase of
these materials.
When this International Standard is used for comparative purposes, agreement should be reached between
the concerned parties on selection of the detailed method to be employed in order to eliminate sources of
subsequent controversy.
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 2591-1, Test sieving — Part 1: Methods using test sieves of woven wire cloth and perforated metal plate
ISO 3082, Iron ores — Sampling and sample preparation procedures
ISO 3085, 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 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, Iron ores for blast furnace and direct reduction feedstocks — Determination of bulk density
ISO 10835, Direct reduced iron and hot briquetted iron — Sampling and sample preparation
ISO 11323, Iron ore and direct reduced iron — Vocabulary
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 11323 apply.
4 Principles and planning
4.1 General
The determination of size distribution of iron ores and direct reduced iron (DRI) may be carried out on a “dry”
or “natural” (or “as-received”) basis. Before a particle size determination is carried out, it is necessary to plan
the entire sequence of procedures to be followed.
The basis for determination and the sequence of procedures will depend on:
a) the purpose of the size analysis;
b) the properties of the iron ore and DRI to be evaluated;
c) the form in which the iron ore and DRI is received, e.g. gross sample, increments or partial samples;
d) the apparatus available.
A typical decision tree to determine the sequence of procedures necessary to perform size analysis is shown
in Figure 1. The guidelines for practical application of this International Standard are provided in Annex A.
General principles of sieving are given in ISO 2591-1.
4.2 Purpose of the analysis
The principal purposes of particle size determination are as follows.
a) To measure the mass and calculate the percentage mass of an ore or DRI passing or retained on one or
more specification sieves.
The choice of sieve aperture sizes shall be determined by the specification size(s) required together with the
necessity for introducing intermediate aperture sizes to satisfy the maximum particle size and sieve loading
constraints. See 4.6 and 4.7.
b) To generate an overall size distribution curve.
The choice of sieve apertures will depend on the resolution required for the curve and the need to satisfy
sieve loading constraints.
4.3 Impact of ore and DRI properties
4.3.1 Effect of moisture content
The effect of the moisture content of the size sample on sample division and sieving should be assessed
before the commencement of the size determination procedure.
When it is difficult to conduct sample division due to sample being adhesive or excessively wet, the sample
shall be dried to constant mass in accordance with 7.1.
NOTE Partial drying of a sample for the purpose of size distribution analysis is not acceptable, as residual moisture
might affect the effective separation of the individual size fractions.
2 © ISO 2008 – All rights reserved

Figure 1 — Typical decision tree for selecting size determination procedure

4.3.2 Degradation of material
Certain iron ores, particularly lump ore, and DRI may be subject to significant degradation during the sampling
and size analysis sequences. Furthermore, different sampling and size analysis processes can cause
degradation of ores and DRI to different extents. Consequently this may lead to significant variation in results
for the same lot.
It is therefore essential that any degradation should be minimized through the correct design of handling,
sampling and size analysis systems.
Sampling systems should be designed in accordance with the guidelines set out in ISO 3082 and ISO 10835.
4.3.3 Magnetic ores
For iron ores with pronounced magnetic properties and DRI that has been handled by magnets, it is desirable
to ensure that the size sample be demagnetized or that the sieves are non-magnetic.
4.4 Nature of sample
The sample may be received in the form of a gross sample, several partial samples or increments.
The procedures for sampling of iron ores and direct reduced iron (ISO 3082 and ISO 10835) will generally
provide quantities of material in excess of the requirements for sieving.
If it is undesirable to sieve the entire mass, division of the following is permissible:
a) gross sample;
b) partial samples;
c) increments;
d) fractions obtained during sieving.
Methods governing the division and the mass of sample to be sieved are provided in Clause 6.
4.5 Choice of sieving method
4.5.1 Two different sieving methods are available to perform particle size analysis (see Annex I):
a) dry sieving, i.e. sieving without the application of water;
b) wet sieving, i.e. sieving with a sufficient application of water to ensure the passage of undersize particles
through the sieve apertures.
A table summarizing the sample preparation and sieving procedure is given in Annex B.
4.5.2 The results of these methods may not be the same. No specific preference is given in this
International Standard for either method when sieving iron ore samples. For DRI, dry sieving is recommended.
4.5.3 The choice of sieving method (see 4.5.5) for each part of a size determination shall be made on the
basis of attaining the defined precision of testing (see 11.1). Details on the procedure shall be recorded in the
working log.
4.5.4 If a combination of any of the sieving methods is employed for different parts of the same overall size
distribution, the changeover from dry to wet sieving shall be clearly indicated on the report sheet
(see Clause 10).
4 © ISO 2008 – All rights reserved

4.5.5 The following factors should be taken into account when making the choice of sieving method.
a) For dry sieving on a natural basis sample, the moisture content of the charge shall be sufficiently low so
as not to introduce any bias beyond acceptable limits.
b) Wet sieving should be used:
1) if there is a tendency for a significant proportion of fine particles to adhere to the larger ones, or if the
ore has a tendency to cake on drying;
2) if the fine particles of iron ore tend to become charged with static electricity during the sieving
operation and adhere tenaciously to the sieve.
4.6 Maximum particle size permitted on a sieve
0,7
To avoid damage to sieves, the maximum particle size in any charge shall not exceed 10 W , where W is
the sieve aperture size, in millimetres.
Examples of the relationship between maximum particle size and sieve aperture size are given in Table 1.
Table 1 — Maximum particle size permitted on a sieve
Sieve aperture size
Approximate size of
largest particle
W
25 mm 95 mm
11,2 mm 55 mm
4 mm 26 mm
1 mm 10 mm
3,8 mm
250 µm
45 µm 1,2 mm
36 µm 1,0 mm
4.7 Specified loading of sieves
4.7.1 General
The loading of a sieve or nest of sieves or continuous sieving machine shall be limited as prescribed in 4.7.2
and 4.7.3 and requires previous information about the size distribution of the sample to be sieved.
4.7.2 Batch sieving with a single sieve or nest of sieves
4.7.2.1 General
The mass of sample that may be loaded onto any sieve is limited by the conditions covering the mass to be
retained and by the need to avoid undue degradation. It may be necessary to sieve a sample in several
portions. The results shall be combined. The maximum mass retained shall not exceed the values tabulated in
Annex C or as determined in 4.7.2.2 or 4.7.2.3.
The maximum loading is defined as that corresponding to the maximum mass retained but shall not exceed
twice the maximum mass retained.
4.7.2.2 Apertures W 4 mm
The loading of the sieve shall be such that the maximum mass of sample retained on any sieve at the
completion of sieving shall be in accordance with formulae (1) and (2) below or the visual rule c).
a) Apertures W 22,4 mm
mW=+(40,005 0,000 )ρA (1)
b
b) For apertures < 22,4 mm and W 4 mm
mW= 0,000 7 ρA (2)
b
where
m is the maximum mass to be retained on the sieve, in kilograms;
W is the sieve aperture size, in millimetres;
ρ is the bulk density of the sample, in kilograms per cubic metre, determined in accordance with
b
ISO 3852;
A is the area of the sieve, in square metres.
The formulae apply only if the open area of the sieve (incomplete apertures are regarded as blanked-off
areas) exceeds 40 %. For open areas of less than 40 %, the values of m shall be reduced pro rata.
c) Alternative visual rule
On completion of sieving, the particles spread out as a single layer shall cover not more than three-quarters of
the floor area of the sieve.
4.7.2.3 Apertures < 4 mm
For sieves in the − 4 mm range, the maximum mass of sample retained shall be as given in Annex C.
4.7.3 Loading of continuous sieving machines
In the case of continuous sieving machines, the rate of feed shall be constant and so adjusted that during the
sieving operation, a maximum of 50 % of any sieve area is covered by the material.
4.8 Sieving time
4.8.1 General
The practicable sieving time is mainly influenced by:
a) the properties of the sample;
b) the volume of the initial charge;
c) the sieving intensity;
d) the nominal aperture size of the sieve;
e) the acceptable limits of accuracy.
No exact time can be defined at which a sieving process is completed. Where possible, sieving time shall be
based on strict application of the end point ruling. However, in some cases, strict application of the end point
ruling may be impractical. In such cases, fixed time sieving based on experience may be agreed.
6 © ISO 2008 – All rights reserved

Examples in Table 2 are given as a general indication of times for dry batch sieving of stable iron ores and
DRI.
Table 2 — Examples of dry sieving times for stable ores and DRI using batch methods
Sieve aperture size Sieving time
mm min
4 and larger 3
− 4 to 1
− 1
4.8.2 End point ruling
The method for determining the sieving end point in accordance with ISO 2591-1 is given in 7.6 (see Annex I).
4.8.3 Retention time for continuous sieving machines
Retention time depends on the material feed rate and the rates at which particles pass through the sieves and
move forward across the surface of the sieving media. It depends on the type of machine, the inclination of the
sieve media and the nature of the sample sieved.
The procedure parameters shall be optimized in order to minimize material degradation and maximize sieving
efficiency in order to satisfy the requirements defined in 5.2.
5 Apparatus
5.1 Sieve media
5.1.1 Shape of aperture
The sieve media shall have square apertures in accordance with ISO 565.
5.1.2 Size of aperture
The nominal size of aperture to be utilized shall be selected from the R20 and R40/3 series given in ISO 565
(see Annex D).
5.1.3 Construction of sieve media
The sieve media shall be in accordance with ISO 3310-1 or ISO 3310-2 and the requirements of a) to d) below.
(See Annex I.)
a) For aperture sizes u 4 mm, woven wire shall be used.
b) For aperture sizes > 4 mm and u 16 mm, either woven wire or perforated plate shall be used [see also d)].
c) For all sizes > 16 mm, perforated plate is preferred; woven wire may be used, but it should be recognized
that the tolerances on aperture size are wider than those for perforated plate.
d) Within a size determination, one change-over point from wire to perforated plate is allowed. This shall be
established for each size determination procedure and shall be adopted for all subsequent determinations.
5.1.4 Sieve frames for hand or mechanical nest sieving
Test sieves used for hand or mechanical nest sieving shall have frames in accordance with ISO 3310-1 and
ISO 3310-2. Frames may be either round or rectangular. A typical nest sieving apparatus is shown in Annex E.
Sieves other than test sieves shall have frames that nest snugly with each other and with the lid and receiver.
The frame should be smooth and the seals of the sieves so constructed as to avoid lodging of particles and
loss of fines.
5.2 Sieving machines
Any type of apparatus is acceptable, provided that the results obtained with reference to the specification size
selected, or other designated aperture size, are unbiased in relation to those obtained by methods described
in 7.4.3 or 7.4.4. Sieving machines shall be tested for bias in accordance with the procedures given in
ISO 3086 and will be acceptable if no significant bias against the reference procedure performed in
accordance with 7.4.3 or 7.4.4 is proven.
The sieve media shall be kept unblocked (see Annex F).
5.3 Accessories for wet sieving
When wet sieving is carried out, in addition to the apparatus mentioned in 5.1 and 5.2, it is necessary to have
available a controllable supply of water, a spray nozzle and, where appropriate, a collecting tank. A simple
arrangement is shown in Figure 2. When wet sieving on sieves having apertures < 125 µm, it is preferable
that:
a) the sieve be constructed of stainless steel;
b) the medium have a backing to prevent possible sagging and distortion caused by water pressure; this
backing may typically consist of a sieve medium having 2 mm square apertures;
c) the backing be made so that the particles cannot get trapped between two sieve media;
d) the water pressure be adjusted as gently as possible in order to avoid damage to the sieve media.
5.4 Drying equipment
Any form of ventilated equipment is acceptable for drying, provided that it be fitted with a temperature control
apparatus capable of regulating the temperature in the equipment to ± 5 °C of the desired temperature and
shall be so designed as to maintain this temperature. Loss of dust from the equipment shall be avoided.
It is recommended that the parties concerned with the iron ore and DRI use the same drying procedure in
order that the effect on the size determination be similar.
5.5 Equipment for the determination of mass
Each device for the determination of mass shall have a sensitivity of at least 0,1 % of its rated capacity and a
level of accuracy such that the mass of the test sample and of each size fraction may be determined to a
precision of ± 0,1 % or better of the test sample mass.

8 © ISO 2008 – All rights reserved

Key
1 spray nozzle
2 pressure gauge
3 regulating valve
4 water supply from reservoir tank
5 sieve
6 collecting tank
Figure 2 — A simple arrangement of wet sieving apparatus

6 Samples
6.1 Derivation of size sample
6.1.1 The size sample shall have been taken in accordance with the specifications of ISO 3082 and be in
the form of a gross sample, partial samples or increments.
6.1.2 The sample shall be composed of ore that has not been previously used for other tests or purposes
that in any way modify the mass and the particle size distribution.
6.1.3 For replicate size determinations, the corresponding number of size samples shall be provided.
6.1.4 Increments or partial samples may be combined into a gross sample or into new partial samples.
6.1.5 Where it is not required to sieve the total mass, one or more test samples for sieving shall be
extracted from the gross sample, or from each increment or partial sample, by division (see 6.2).
6.1.6 When testing increments or partial samples, only the combined size analysis of all the increments or
partial samples shall be representative of the lot.
6.2 Mass of test sample(s) for sieving
6.2.1 General
The mass of the test samples used for sieving shall be equal to or greater than the minimum mass defined in
6.2.2.
6.2.2 Minimum mass
For specified precision of preparation and measurement (see Clause 11) the required minimum mass is the
same whether the test sample used for sieving is obtained by dividing the gross sample or by dividing
increments or partial samples and combining those divided increments or partial samples.
The minimum mass to be used for sieving depends on the required precision of preparation and measurement,
β , which is twice the standard deviation of preparation and measurement, and shall be calculated by means
PM
of the formula shown in Annex G. The level of precision, β , to be used shall be determined so that the
PM
overall precision specified in Table 3 shall be met.

10 © ISO 2008 – All rights reserved

Table 3 — Comparison of overall sizing precision, β , with the precisions of sampling, β , and
SPM S
sample preparation and measurement, β
PM
− 31,5 + 6,3 mm ore
− 200 mm and − 50 mm ore + 6,3 mm fraction
Mass of lot
− 10 mm fraction Sinter feed
(1 000 t)
− 6,3 mm fraction
β β β β β β
SPM S PM SPM S PM
> 270 3,4 1,55 3,0 1,7 0,77 1,5
210 - 270 3,5 1,61 3,1 1,75 0,80 1,6
150 - 210 3,6 1,69 3,2 1,8 0,84 1,6
100 - 150 3,7 1,77 3,3 1,85 0,88 1,6
70 - 100 3,9 1,86 3,4 1,95 0,92 1,7
45 - 70 4,0 1,98 3,5 2,0 0,98 1,7
30 - 45 4,2 2,11 3,6 2,1 1,05 1,8
15 - 30 4,4 2,28 3,8 2,2 1,13 1,9
5,0 2,5 4,3 2,5 1,24 2,2
< 15
Pellet feed Pellets
− 45 µm fraction − 6,3 mm fraction

β β β β β β
SPM S PM SPM S PM
> 270 1,7 0,47 1,6 0,68 0,47 0,50
210 - 270 1,75 0,48 1,7 0,70 0,48 0,51
150 - 210 1,8 0,51 1,7 0,72 0,51 0,51
100 - 150 1,85 0,53 1,8 0,74 0,53 0,52
70 - 100 1,95 0,56 1,9 0,78 0,56 0,54
45 - 70 2,0 0,59 1,9 0,80 0,59 0,54
30 - 45 2,1 0,63 2,0 0,84 0,63 0,55
15 - 30 2,2 0,68 2,1 0,88 0,68 0,55
< 15 2,5 0,75 2,4 1,00 0,75 0,66

7 Procedures
7.1 Drying
If drying is specified, the iron ore and direct reduced iron shall be dried in air or by the use of drying equipment
in accordance with 5.4. The maximum temperature setting shall be 105 °C so that the actual temperature shall
not exceed 110 °C. The sample shall be dried to constant mass.

7.2 Division
One or more of the following methods of sample division shall be conducted individually or jointly; the
applicability of each method for division of the particular ore and DRI shall be determined by reference to
ISO 3082 and ISO 10835:
a) mechanical increment division;
b) other mechanical division methods (e.g. mechanically charged riffle divider);
c) manual division.
7.3 Preparation and maintenance of sieves for test or nest sieving
The preparation of sieves shall be carried out in accordance with the specifications of ISO 2591-1. Before use,
each sieve medium and frame shall be degreased and cleaned. The cleaning of a sieve shall be carried out
with great care so that the sieve medium is not damaged. For sieves with apertures W 500 µm, cleaning shall
be undertaken by the application of a soft brass wire brush to the underside of the sieve. For sieves with
apertures < 500 µm, ultrasonic cleaning is the preferred method. Cleaning shall not entail brushing of the
sieve media. The frame should be tapped gently to assist in freeing trapped particles. At times it may be
necessary to wash fine sieves in a warm soft soap and water solution. After washing or after ultrasonic
cleaning the sieves shall be dried thoroughly.
7.4 Sieving
7.4.1 General
The procedure shall employ one or more of the following methods:
a) hand placing on individual sieves (minimum aperture size is 40 mm);
b) hand sieving and assisted hand sieving;
c) mechanical batch sieving;
d) wet sieving;
e) continuous machine sieving.
Of the above, the hand sieving method performed in accordance with 7.4.3 or 7.4.4 is the reference method
that shall be used for bias assessments and in settling of between-laboratory disputes.
7.4.2 Hand placing on individual sieves
The minimum aperture size at which this method is considered to be applicable is 40 mm.
a) Gently shake the sieve by hand until separation seems complete.
b) Check the particles remaining on the sieve one by one in all orientations without applying force. Particles
which pass through the sieve openings are included in the passing fraction.
c) Weigh the separated size fractions individually.
NOTE The percentage of passing fractions obtained by the hand placing method tend to be greater than those
obtained by hand or mechanical sieving. Hand placing measures minimum diameters, while hand or mechanical sieving
measures intermediate diameters.
12 © ISO 2008 – All rights reserved

7.4.3 Hand sieving in the − 40 mm to +1 mm range
This procedure is applicable using a single sieve or a sequence of individual sieves.
a) Use an individual sieve with a receiver pan. When using a sequence of individual sieves, start with the
largest aperture. Place it on a smooth platform (to minimize attrition).
b) Place the charge on the sieve.
c) Take the sieve in both hands and slide it back and forth on the platform about 120 times per minute at an
amplitude of about 120 mm. If the particles are difficult to sieve, especially in the size fractions − 4 mm to
+ 1 mm, the back and forth movement should be interrupted three times per minute by a circular motion in
case of a round sieve, or by a sequence of movements lifting each side of the sieve in case of a square
sieve. A periodic vertical shake may be given when using a round sieve.
d) Sieving is terminated either on satisfying the end point rule or at completion of a fixed sieving time.
See 4.8 and 7.6.
e) The materials passing the sieve constitute the charge for the test sieve with the next smallest aperture.
f) Weigh the separated particle size fractions individually.
Examples of alternative methods for use of individual sieves are given in Figure 3.
7.4.4 Hand sieving in the − 1 mm range
This procedure is applicable to round sieves with 200 mm and 300 mm diameters, using a single sieve or a
sequence of individual sieves. In this size range, a sieve together with a lid and receiver pan shall be used.
a) Use an individual sieve with a receiver pan. When using a sequence of individual sieves, start with the
largest aperture.
b) Place the charge on the sieve and fit the lid.
c) Take the sieve in one hand and tap approximately 120 times per minute against the other hand at an
inclination of 10° to 20°, with the grasped point tilted downwards. After 30 taps, put the sieve into the
horizontal position, turn 90° and give a hard tap by hand against the sieve frame. A periodic vertical
shake may be given. If the particles are difficult to sieve or when using fine sieves, the underside of the
sieve medium shall be cleaned gently with a soft brush in order to loosen trapped particles. The resulting
dust or particles released below the sieve are added to the undersize material.
d) Terminate sieving either on satisfying the end point rule or at completion of a fixed sieving time. See 4.8
and 7.6.
e) Weigh the separated particle size fractions individually.
Method 1 (− 11,2 mm) Method 2 (− 11,2 mm)
Key
1 charge M
2 charge P
3 charge R
4 retained x
5 retained y
6 retained z
7 sieve A
8 sieve B
9 sieve C
10 receiver pan
a
M − (x + y + z) = undersize through sieve C.
b
R − z = undersize through sieve C.
NOTE 1 Sieve A has the largest aperture size.
NOTE 2 Replicate charges M, P and R in method 2 are produced by careful sample division.
Figure 3 — Alternative methods for use of individual sieves for samples − 11,2 mm to + 1 mm

14 © ISO 2008 – All rights reserved

7.4.5 Mechanical batch sieving
This procedure is applicable to any size of iron ore and DRI using a single sieve or nest of sieves. The
machine shall satisfy the criteria given in 5.2.
a) Assemble the nest of sieves with the largest aperture at the top and the receiver pan at the base.
b) Place the charge on the top sieve and fit the lid.
c) Attach the nest of sieves to the mechanical shaker.
d) Terminate sieving either on satisfying the end point rule or at completion of fixed sieving time. See 4.8
and 7.6.
e) Weigh the separated particle size fractions individually.
7.4.6 Wet sieving of coarse and fine samples
The general procedural rules applicable to dry sieving (see 7.4.2 to 7.4.5) also apply to wet sieving.
Arrange the sieving system so that an entire charge is subjected to a copious flow of clean water. Apply the
water at low velocity and also low pressure. Take care that water does not flow over the side of the sieve.
Take care to avoid damage to the sieve medium or cause degradation by the application of excessive water
pressure. If the sample has been dried prior to wet sieving, wet the sample by mixing with a small quantity of
water before agitating the sieves in order to reduce dust losses.
For manual wet sieving using individual sieves, an alternative method is to submerge the charge in water
during the agitation of the sieve. On using this method, care shall be taken to ensure that water does not flow
over the side of the sieve.
Method 1 described in Figure 3 shall be used if only a limited quantity of material is available. The sample may
be washed successively through a nest of sieves with the finest aperture size at the bottom of the nest. The
suspension that washes through the coarser sieve shall be placed directly on the next sieve. If the sample is
large, a number of individual charges may be used in accordance with method 2 indicated in Figure 3. At
completion, dry the sieves together with the retained oversize material under the same conditions as those
specified in 7.1.
A schematic diagram of a reliable procedure for wet sieving of fine samples is shown in Figure 4.
7.4.7 Continuous machine sieving
Due to the diversity of type and configuration of continuous sieving machines, no specific procedural guide is
provided in this International Standard. It is recommended that the manufacturer's instructions be strictly
adhered to.
Continuous sieving machines shall be tested for bias in accordance with 5.2.
NOTE If a subsequent size distribution of the total undersize product (superfine sample) is needed, the undersize
product should be wet sieved until the water emerging from the underside of the bottom sieve attains absolute clarity on
visual inspection.
Figure 4 — Suggested wet sieving procedure for fine samples (− 11,2 mm)

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7.5 Determination of mass
7.5.1 General
At all stages of operation, the mass of the charge and products shall be determined using equipment in
accordance with 5.5 and then recorded. These operations cover drying, division and sieving.
7.5.2 Wet sieving — Determination of mass of solids-content in washings
The following procedures are permissible.
a) The charge is dried before and after wet sieving so that the loss of sample in the washings (which need
not be collected) can be obtained by difference.
b) The charge is sieved in the “as-received” state, but the washings are collected to enable the solids to be
extracted by filtering (or by another efficient method), dried and their mass measured.
c) The charge is sieved in the “as-received” state and the washings are not collected. Instead, the moisture
content of the charge needs to be known, and this is obtained in accordance with ISO 3087. Hence, the
loss of sample in the washings can be obtained by weight difference as in procedure a).
7.6 Determination of sieving end point
7.6.1 Dry sieving
7.6.1.1 Procedure when using a nest of sieves
a) Position the specification sieve immediately above the pan; add larger aperture size sieves as required
then fit the lid. If there is no specification sieve, the end point ruling shall be applied to the sieve having
the smallest aperture size.
b) Place the charge on the top sieve of the nest of test sieves and sieve for 1 min.
c) Remove the sample, which passes into the pan, and determine its mass.
d) Replace the empty receiver pan and continue the sieving operation for a second one-minute period.
e) Determine the mass of the sample that passes into the pan during the second one-minute interval.
f) Repeat this sequence of sieving for one minute and determine the mass of undersize until the quantity of
material passing the specification sieve in any one minute is less than 0,1 % of the mass of the initial
charge or until the collective sieving time reaches 30 min.
g) Adopt the duration of sieving to reach the end point for the specification sieve as the sieving time for all of
the sieve size fractions of the sample being tested. If an end point is not reached within 30 min, then
adopt an arbitrary sieving time.
7.6.1.2 Procedure for using a sequence of individual sieves
This procedure simulates sieving with a nest of sieves.
a) Use an individual sieve with a receiver pan and lid.
b) Place the charge on the sieve with the largest aperture size, and sieve for 1 min. The sample passing the
sieve constitutes the charge for the test sieve with the next smallest aperture size. Sieving for 1 min is
performed at successively smaller sieve aperture sizes down to the specification sieve.
c) Remove the sample, which passes from the specification sieve into the pan, and determine its mass.
d) Continue this “sieve to sieve” sequence of operation until the quantity of sample passing the specification
sieve in 1 min is less than 0,1 % of the initial charge or until the collective sieving time reaches 30 min.
e) Adopt the duration of sieving to reach the end point for the specification sieve as the sieving time for all
sieve size fractions of the sample being tested. If an end point is not reached within 30 min, then adopt an
arbitrary sieving time.
7.6.2 Wet sieving
A wet sieving operation on an individual sieve is considered to be complete when the liquid used is practically
clear when it flows through.
8 Verification
8.1 General
Regular checking of apparatus and procedures is essential to verify the test results. Checks shall be carried
out prior to the commencement of a routine size analysis and at regular intervals thereafter. The frequency of
checking is a matter for each laboratory to determine. A detailed record of all verification activities shall be
maintained and re
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