ISO 4701:1999

INTERNATIONAL ISO
STANDARD 4701
Second edition
1999-03-01
Iron ores — Determination of size
distribution by sieving
Minerais de fer — Détermination de la granulométrie par tamisage
A
Reference number
ISO 4701:1999(E)

---------------------- Page: 1 ----------------------
ISO 4701:1999(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Definitions . 2
4 Principles and planning . 2
5 Apparatus . 6
6 Samples . 7
7 Procedures . 8
8 Verification . 11
9 Results. 12
10 Test report and working log . 13
11 Precision. 13
Annex A (normative) Maximum mass of iron ore to be retained
on a sieve at completion of batch sieving (m) in order to obtain
good sieving efficiency . 19
Annex B (normative) Procedure for determining the minimum
mass of sample used for sieving . 20
Annex C (normative) Flowsheet of the procedure for
the acceptance of analytical values for test samples . 23
Annex D (informative) Sieve apertures in the R20 series
(taken from ISO 565). 24
Annex E (informative) Typical batch sieving apparatus. 25
Annex F (informative) Desirable features of mechanical
sieving machines. 26
Annex G (informative) Additional information. 29
©  ISO 1999
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 the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii

---------------------- Page: 2 ----------------------
© ISO
ISO 4701:1999(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.
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.
International Standard ISO 4701 was prepared by Technical Committee
ISO/TC 102, Iron ores, Subcommittee SC 1, Sampling.
This second edition cancels and replaces the first edition (ISO 4701:1985),
which has been technically revised.
Annexes A, B and C form an integral part of this International Standard,
annexes D, E, F and G are for information only.
iii

---------------------- Page: 3 ----------------------
INTERNATIONAL STANDARD  © ISO ISO 4701:1999(E)
Iron ores — 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, utilizing sieves having aperture sizes of 36 μm or larger. The size distribution is to be 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 involving size determination and for use by contracting parties in the
sale and purchase of this material.
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 standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings.
ISO 2591-1:1988, Test sieving — Part 1: Methods using test sieves of woven wire cloth and perforated metal plate.
ISO 3082:1998, Iron ores — Sampling and sample preparation procedures.
ISO 3085:1996, Iron ores — Experimental methods for checking the precision of sampling.
ISO 3086:1998, Iron ores — Experimental methods for checking the bias of sampling.
ISO 3087:1998, Iron ores — Determination of moisture content of a lot.
1)
ISO 3310-1:— , Test sieves — Requirements and tests — Part 1: Metal wire cloth sieves.
2)
ISO 3310-2:— , Test sieves —Requirements and tests — Part 2: Perforated metal plate sieves.
ISO 11323:1996, Iron ores — Vocabulary.

1)  To be published. (Revision of ISO 3310-1:1990)
2)  To be published. (Revision of ISO 3310-2:1990)
1

---------------------- Page: 4 ----------------------
© ISO
ISO 4701:1999(E)
3 Definitions
For the purpose of this International Standard, the definitions given in ISO 11323 apply.
4 Principles and planning
4.1 General
Before a particle size determination is carried out, it is necessary to plan the entire sequence of procedures to be
followed. In some cases agreement between parties will be necessary.
This sequence of procedures will depend on:
a) the purpose of the size analysis;
b) the properties of the iron ore to be evaluated;
c) the form in which the iron ore 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.
Sieving of iron ores shall be carried out in accordance with 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 percentage mass of an ore 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 and the need to satisfy sieve loading
constraints.
4.3 Properties of ore to be evaluated
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.
It may be desirable to dry or partially dry the size sample before carrying out sample division or sieving. Drying of
iron ores in accordance with 7.1, or wet sieving in accordance with 7.4.5 may result in changes of internal moisture
which may affect the masses of size fractions. Under such circumstances reliable masses can only be obtained by
drying the fractions at 105 °C and cooling under anhydrous conditions. Some iron ores readily absorb moisture and
should not safely be allowed to come into equilibrium with laboratory atmospheres. These ores shall be handled in
such a way as to reduce to a minimum the duration of their contact with the atmosphere.
2

---------------------- Page: 5 ----------------------
© ISO
ISO 4701:1999(E)
4.3.2 Friable ores
For iron ores subject to significant degradation during the size analysis sequence it is essential that any mechanical
sizing procedure be checked for bias against hand placing and sieving in accordance with the procedure given in
ISO 3086 (see 5.2).
4.3.3 Magnetic ores
For iron ores with pronounced magnetic properties it may be desirable that the size sample be demagnetized.
4.4 Nature of sample
The sample may be received in the form of a complete size sample, several partial samples or increments.
The procedures for sampling of iron ores (ISO 3082) 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) the size 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 wet or dry sieving
4.5.1  The results of dry and wet sieving may not be the same. No specific preference is given in this International
Standard for either method.
4.5.2  The choice of dry or wet sieving (see 4.5.4) 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 procedure shall be recorded in the working log.
4.5.3  If a combination of dry and wet sieving 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).
4.5.4  The following factors should be taken into account when making the choice between dry and wet sieving:
a) For dry sieving, 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 lumps, 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.
3

---------------------- Page: 6 ----------------------
© ISO
ISO 4701:1999(E)
4.6 Maximum particle size permitted on a sieve
To avoid damage to sieves, the maximum particle size in any charge shall not exceed:
0,7
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
250 μm 3,8 mm
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 below.
4.7.2 Batch sieving with a single sieve or nest of sieves
The mass of ore that may be loaded on to 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 A or as determined
in 4.7.2.1 or 4.7.2.2.
The maximum loading is defined as that corresponding to the maximum mass retained but shall not exceed twice
the maximum mass retained.
4.7.2.1 For apertures larger than or equal to 500 μm
The loading of the sieve shall be such that the maximum mass of iron ore retained on any sieve at the completion of
sieving shall be in accordance with formulae a) and b) below or the visual rule c).
a) Apertures larger than 22,4 mm
mW=+(0,005 0,000 4 )ρA
b) For apertures less than 22,4 mm and larger than or equal to 500 μm
mA= 0,000 7Wρ
where
m is the maximum mass to be retained on sieve, in kilograms;
W is the sieve aperture size, in millimetres;
ρ is the bulk density of iron ore, in kilograms per cubic metre;
A is the area of the sieve, in square metres.
4

---------------------- Page: 7 ----------------------
© ISO
ISO 4701:1999(E)
The formulae apply only if the open area of the sieve (incomplete apertures are regarded as blanked-off area)
exceeds 40 %. For open areas of less than 40 %, the values of m shall be reduced pro rata.
c) Alternatively the following visual rule may be applied.
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.
4.7.2.2 Apertures smaller than 500 μm
For sieves in the 2500 μm range, the maximum mass to be loaded on a sieve shall not exceed twice the maximum
permitted mass of residue given in annex A.
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 characteristics of the ore;
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, strict application of the end point ruling may be impractical. In
such cases hand placing or fixed time sieving based on experience may be agreed.
Examples in table 2 are given as a general indication of times for dry batch sieving of stable iron ores.
Table 2 — Examples of sieving times for stable ores using batch methods
Time by
Time by
Sieve aperture size
hand sieving
mechanical sieving
min min
mm
4 and larger 3 3
4 to 1 variable 5
2
1 variable 20
2
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.
5

---------------------- Page: 8 ----------------------
© ISO
ISO 4701:1999(E)
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 ore being sieved.
The procedure parameters must be optimized 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 R 20 and R 40/3 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) – d) below.
a) For aperture sizes of 4 mm or smaller, woven wire shall be used.
b) For aperture sizes greater than 4 mm and up to and including 16 mm, either woven wire or perforated plate
shall be used (see also d) below).
c) For all sizes above 16 mm perforated plate is preferred; woven wire may be used but it should be recognized
that the tolerances on aperture size is 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 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. 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 hand placing or hand
sieving. Sieving machines shall be tested for bias in accordance with the procedures given in ISO 3086 and will be
acceptable if no significant bias is proven.
It may be necessary for an operator to keep the sieve media unblocked (see annex F).
6

---------------------- Page: 9 ----------------------
© ISO
ISO 4701:1999(E)
5.3 Accessories for wet sieving
When wet sieving is carried out, in addition to the apparatus mentioned above 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 of less than 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 within 6 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 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
6 0,1 % or better of the test sample mass.
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 composite size sample, partial samples or increments.
6.1.2  The sample shall be composed of ore which has not been used previously for other tests or purposes which
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 single size 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 size sample, or from each increment or partial sample by division. (See 6.2.)
6.1.6  Only the combined size analysis of all the increments or partial samples shall be representative of the lot.
6.2 Division and derivation of test sample(s) for sieving
6.2.1 Mass of the test samples
The mass of the test samples used for sieving shall be equal to or greater than the minimum mass defined in 6.2.2.
7

---------------------- Page: 10 ----------------------
© ISO
ISO 4701:1999(E)
6.2.2 Minimum mass
For a specified precision of division and measurement (see clause 11) the required minimum mass is the same
whether the test sample used for sieving is obtained by dividing the size 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 division and measurement β and
PM
shall be calculated by means of the formula shown in annex B. The level of precision β to be used shall be
PM
determined so that the overall precision specified in table 1 of ISO 3082:1998 shall be met.
7 Procedures
7.1 Procedure for drying iron ore
Iron ores 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.
7.2 Procedure for 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 shall be determined by reference to ISO 3082:
a) mechanical increment division;
b) other mechanical division methods (e.g., mechanically charged riffle divider);
c) manual division.
7.3 Procedure for the 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 equal to or greater than 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 of less than 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 Procedures for 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 22,4 mm);
b) hand sieving and assisted hand sieving;
c) mechanical batch sieving;
d) wet sieving;
e) continuous machine sieving.
7.4.2 Hand placing on individual sieves
The minimum aperture size at which this method is considered to be applicable is 22,4 mm.
8

---------------------- Page: 11 ----------------------
© ISO
ISO 4701:1999(E)
a) Gently shake the sieve by hand until separation seems complete.
b) Check the iron ore 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.
7.4.3 Hand sieving and assisted hand sieving in the 2222,4 mm 111 mm range
This procedure is applicable using a single sieve or nest of sieves.
a) Assemble the nest of sieves with the largest aperture at the top.
b) Place the charge on the sieve with the largest aperture.
c) Take the sieve or nest of sieves in both hands and move to and fro horizontally about 60 times a minute at an
amplitude of about 70 mm. If the ore is difficult to sieve, especially in the size fractions 2 4 mm + 1 mm the to
and fro movement should be interrupted three times per minute by a circular motion. A periodic vertical shake
may be given.
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) Weigh the separated particle size fractions individually.
Examples of alternative methods for use of individual sieves are given in figure 3.
22
7.4.4 Hand sieving and assisted hand sieving in the 1 mm range
This procedure is applicable using a single sieve or nest of sieves. In this size range, a sieve or nest of sieves
together with a lid and receiver pan shall be used.
a) Assemble the nest of sieves with the largest aperture at the top and attach the receiver pan.
b) Place the charge on the sieve with the largest aperture and fit the lid.
c) Take the sieve or nest of sieves in one hand and tap approximately 120 times a 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, turned 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 fixed sieving time. See 7.6.
e) Weigh the separated particle size fractions individually.
7.4.5 Mechanical batch sieving
This procedure is applicable to any size of iron ore 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 7.6.
9

---------------------- Page: 12 ----------------------
© ISO
ISO 4701:1999(E)
e) Weigh the separated particle size fractions individually.
7.4.6 Procedures for wet sieving of coarse and fine ores
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 overflow 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 iron ore
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. In using this method, it is necessary to apply an adequate end point ruling and as in the
preferred method care shall be taken to ensure that water does not overflow 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 which 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 ores 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 the standard. It is recommended that the manufacturer's instructions be strictly adhered to.
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, sieving and division.
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 ore 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 content to be
extracted by filtering (or by another efficient method), dried and 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
iron ore in the washings can be obtained by weight difference as in procedure a).
7.6 Procedures for determining sieving end point
7.6.1 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.
10

---------------------- Page: 13 ----------------------
© ISO
ISO 4701:1999(E)
c) Remove the iron ore which passes into the pan and determine its mass. In the case of wet sieving, dewater
and dry the product before weighing.
d) Replace the empty receiver pan and continue the sieving operation for a second one-minute period.
e) Determine the mass of the ore which passes into the pan during the second one-minute interval.
f) Repeat this sequence of sieving for one minute and determine its mass of
...