ISO 349:2020

INTERNATIONAL ISO
STANDARD 349
Second edition
2020-01
Hard coal — Audibert-Arnu
dilatometer test
Houille — Essai au dilatomètre Audibert-Arnu
Reference number
ISO 349:2020(E)
©
ISO 2020

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ISO 349:2020(E)

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© ISO 2020
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ISO 349:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
5.1 Apparatus for preparing the coal pencil . 3
5.2 Dilatometer and accessories . 3
5.3 Other apparatus . 3
5.4 Calibration of apparatus . 4
5.5 Inspection . 4
5.5.1 Dilatometer . 4
5.5.2 Mould . 4
6 Preparation of sample . 5
7 Procedure. 5
7.1 Preparation of the coal pencil . 5
7.2 Determination of dilatation . 6
7.3 Cleaning of the tube and piston . 6
7.3.1 Tube and plug . 6
7.3.2 Piston . 6
8 Expression of results . 6
9 Precision of determination . 7
9.1 Repeatability . 7
9.2 Reproducibility . 7
10 Test report . 7
Annex A (informative) Types of dilatation curves . 8
Annex B (informative) Inspection of dilatometer tubes. 9
Bibliography .15
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ISO 349:2020(E)

Foreword
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This document was prepared by Technical Committee ISO/TC 27, Solid mineral fuels, Subcommittee
SC 5, Methods of analysis.
This second edition cancels and replaces the first edition (ISO 349:1975), which has been technically
revised. The main changes are the following:
— Reformatting of the figures in the main document and annexes.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 349:2020(E)

Introduction
The Audibert-Arnu dilatometer test is used to determine the coking properties of hard coal or hard coal
blends on the laboratory scale.
In principle, the test is not designed, nor can it be used, to indicate the pressures exerted by hard coals
on the walls of industrial carbonization ovens.
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INTERNATIONAL STANDARD ISO 349:2020(E)
Hard coal — Audibert-Arnu dilatometer test
1 Scope
This document specifies a method for determining the swelling properties of hard coal when heated
under standard conditions in a dilatometer.
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 1213-2, Solid mineral fuels — Vocabulary — Part 2: Terms relating to sampling, testing and analysis
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1213-2 and the following apply.
3.1
softening temperature
temperature of initial contraction
temperature at which the downward movement of the dilatometer piston is 0,5 mm
Note 1 to entry: See temperature T in Figure 1.
1
3.2
temperature of maximum contraction
temperature at which the dilatometer piston reaches its lowest point
Note 1 to entry: See temperature T in Figure 1.
2
3.3
temperature of maximum dilatation
temperature at which the dilatometer piston reaches its highest point
Note 1 to entry: See temperature T in Figure 1.
3
3.4
maximum contraction
maximum downward movement of the dilatometer piston, measured from the zero point
Note 1 to entry: Maximum contraction is expressed as a percentage of the initial test-piece length.
Note 2 to entry: See a in Figure 1.
3.5
maximum dilatation
maximum upward movement of the dilatometer piston after contraction, measured from the zero point
Note 1 to entry: Maximum dilatation is expressed as a percentage of the initial test-piece length.
Note 2 to entry: See b in Figure 1. The value can be either positive or negative.
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ISO 349:2020(E)

3.6
repeatability
r
maximum acceptable difference between two determinations which are carried out in the same
laboratory, by the same operator with the same apparatus, on test pieces prepared from the same test
sample and tested simultaneously in two different retorts during the same heating cycle or separately
in the same retort during different heating cycles
3.7
reproducibility
R
maximum acceptable difference between the means of two determinations which are carried out in
each of two laboratories, on representative portions taken from the same gross sample, after the last
stage of sample preparation
4 Principle
A pencil made of powdered (pulverised) coal formed under pressure is inserted into a precisely
calibrated narrow tube and topped by a calibrated steel rod (piston) which slides in the bore of the tube.
The whole assembly including the tube, pencil and piston is heated at a constant and definite rate.
Upon taking regular readings of the displacement of the piston as a function of the temperature and
expressing the displacements observed as percentages of the original length of the pencil, a curve of the
type shown in Figure 1 can be plotted.
Key
T temperature at which the piston has moved down 0,5 mm (or one division, if the scale is calibrated in percentage
1
of the standard length of pencil) softening temperature or initial contraction temperature
T temperature at which the piston reaches its lowest point: temperature of maximum contraction
2
T temperature at which the piston reaches its highest point: temperature of maximum dilatation
3
Y piston displacement (or dilatation) in %
a maximum contraction of length of pencil in %.
b maximum dilatation of length of pencil, %.
Figure 1 — Piston displacement with temperature
Different types of dilatation curves are represented in Annex A.
NOTE The principal factors capable of distorting the results of this empirical test are the following:
a)  Deterioration/oxidation of the coal, consequent on bad storage or faulty drying;
b)  Deviation from the tolerances of
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ISO 349:2020(E)

    1)  the internal dimensions of the dilatometer tube,
    2)  the clearance between tube and piston,
    3)  the mass of the piston,
    4)  the dimensions of the mould;
c)  Deviation from the specified mean rate and regularity of heating;
d)  Deviation from the specification for the preparation of the sample in respect of maximum particle size, or for
the pencil in respect of its length after tamping.
5 Apparatus
5.1 Apparatus for preparing the coal pencil
5.1.1 Mould, polished internally, with accessories; see Figure B.1.
5.1.2 Gauge.
5.1.3 Ram, of which Figure B.2 shows an example.
5.1.4 Press, of which Figure B.3 shows an example.
5.2 Dilatometer and accessories
5.2.1 Dilatometer tubes and pistons, see Figure B.4.
5.3 Other apparatus
5.3.1 Electric furnace, example shown in Figure B.5, consisting of a block of metal resistant to
oxidation and of sufficiently high melting point. A suggested material is aluminium bronze. The metal
block is pierced by at least two holes of 15 mm diameter by 350 mm deep to take the dilatometer
tubes and one hole 320 mm deep to take a temperature-measuring device, which intends to keep the
thermojunction of the thermocouple in the middle position of the inserted coal
...