ISO 23873

ISO/FDIS 23873:2024(en)
ISO/TC 27/SC 5
Secretariat: SA
Date: 2025-03-2006-12
Hard coal — Method for the measurement of the swelling
properties using a dilatometer
Houille — Méthode pour le mesurage du gonflement de la houille au moyen d'un dilatomètre

FDIS stage
ISO/FDIS 23873:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland.
iv
ISO/FDIS 23873:2025(en)
Contents Page
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Materials . 2
6 Apparatus . 2
6.1 Mould and accessories . 2
6.2 Dilatometer . 3
6.3 Dilatometer furnace . 4
6.4 Temperature controller . 4
6.5 Temperature recorder . 5
6.6 Retort and piston . 5
6.7 Means of recording piston movement . 5
6.8 Cleaning instruments . 5
6.9 Balance . 5
7 Procedure . 6
7.1 Temperature calibration . 6
7.2 Preparation of test sample and test pieces. 6
7.3 Determination . 8
8 Expression of results . 9
9 Precision . 9
9.1 General . 9
9.2 Repeatability . 10
9.3 Reproducibility . 10
10 Test report . 10
Bibliography . 13

v
ISO/FDIS 23873:2025(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 27, Coal and coke, Subcommittee SC 5, Methods
of analysis.
This second edition cancels and replaces the first edition (ISO 23873:2010), which has been technically
revised.
The main changes are as follows:
— — clarified units of measure in Figures 1figures 1 and 22 and Table 1table 1;
— added specifications for temperature recorder;
— added balance to apparatus clauseClause 6.
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.
vi
ISO/FDIS 23873:2025(en)
Introduction
The dilatation of coal has been primarily measured by two different standard procedures: the Ruhr
dilatometer and the Audibert-Arnu dilatometer. Both methods are very similar, with the same basic apparatus
and heating rate, but use different initial masses of coal arising from the method of pencil preparation.
This document combines the two previous procedures by adjusting the equipment specification to define a
single acceptable method.
vii
ISO/FDIS 23873:2025(en)
Hard coal — Method for the measurement of the swelling properties
using a dilatometer
1 Scope
This document describes a method for the measurement of the swelling properties of hard coal using 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 Coal and coke — Vocabulary — Part 2: Terms relating to sampling, testing and
analysis
ISO 13909--4, Hard coalCoal and coke — Mechanical sampling — Part 4: Coal — Preparation of test samples of
coal
ISO 18283, Coal and coke — Manual sampling
3 Terms and definitions
For the purposes of this document, the terms and definitions given in given in ISO 1213-2 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
3.1 3.1
softening temperature
temperature at which the downward movement of the dilatometer piston is 0,5 mm, also known as
temperature of initial contraction
Note 1 to entry: See temperature θ in Figure 3Figure 3.
3.2 3.2
temperature of maximum contraction
temperature at which the dilatometer piston reaches its lowest point
Note 1 to entry: See temperature θ in Figure 3Figure 3.
3.3 3.3
temperature of maximum dilatation
temperature at which the dilatometer piston reaches its highest point
Note 1 to entry: See temperature θ in Figure 3Figure 3.
ISO/FDIS 23873:2025(en)
3.4 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 c in Figures 3Figures 3 and 44.
3.5 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 d in Figures 3Figures 3 and 44. The value can be either positive or negative.
4 Principle
A test piece, in the form of a pencil prepared from powdered coal, is heated at a constant rate in a steel retort
positioned in a furnace. Two reference metals of known melting points have been used to calibrate the
temperature monitoring system. The change in level of a piston resting upon the test piece is observed
continuously, and a record is produced which is characteristic of the swelling properties of the coal.
5 Materials
The following materials are required for temperature calibration (7.1(7.1).).
5.1 5.1 Graphite pencils, 30 mm long, base diameter 7,4 mm, top diameter 6,8 mm, with a small
cylindrical reservoir drilled in the narrow end of each pencil.
5.2 5.2 Metal balls, of the following reference metals:
a) a) lead, of analytical reagent grade, assay (Pb) 99,98 % minimum, melting point 327,0 °C;
b) b) zinc, assay (Zn) 99,87 % minimum, melting point 419,3 °C.
5.3 5.3 Water-based blacking.
6 Apparatus
6.1 Mould and accessories
6.1.1 6.1.1 Mould (see Figure 1Figure 1),), made from steel, case-hardened after machining. The bore
shall be polished after hardening and the bore and uniformity of taper (i.e. 1 in 50) shall conform to the
dimensions given in Table 1Table 1.
6.1.2 6.1.2 Mallet, plastics head, mass about 200 g.
6.1.3 6.1.3 Ram (see Figure 1Figure 1).).
6.1.4 6.1.4 Press (see Figure 1Figure 1).).
6.1.5 6.1.5 Load cell (see Figure 1Figure 1),), capable of registering a load of 0 kN to 15 kN.
6.1.6 6.1.6 Pencil gauge (see Figure 1Figure 1).).
ISO/FDIS 23873:2025(en)
Dimensions in millimetres
Key
1 mould cylinder 6 press mould-support
2 mould plug 7 press base-plate
3 mould base 8 load cell
4 ram 9 pencil gauge
5 press plunger
1 mould cylinder
2 mould plug
3 mould base
4 ram
5 press plunger
6 press mould-support
7 press base-plate
8 load cell
9 pencil gauge
Figure 1 — Mould, press and accessories
Table 1 — Dimensions of mould – dimensions in millimeters
Bore
Distance from wide end
mm
mm
(tolerance: −0,00, +0,05)
0 7,4
10 7,2
20 7,0
30 6,8
40 6,6
50 6,4
60 6,2
70 6,0
6.2 Dilatometer
A general arrangement of suitable dilatometer apparatus giving critical dimensions is shown in
Figure 2Figure 2.
Dimensions in millimetres
Key
1 heated block 7 thermocouple
2 holes for retorts (∅ 15,0 ± 0,1) 8 refractory insulation
3 threaded plug for retort 9 pen mechanism
4 test piece 10 recording-drum stand
5 piston 11 recording drum with chart
6 retort
1 heated block
ISO/FDIS 23873:2025(en)
2 holes for retorts (∅ 15,0 ± 0,1)
3 threaded plug for retort
4 test piece
5 piston
6 retort
7 thermocouple
8 refractory insulation
9 pen mechanism
10 recording-drum stand
11 recording drum with chart
Figure 2 — Typical dilatometer apparatus
6.3 Dilatometer furnace
A furnace capable of heating two or more retorts
...