ISO 7936:2022

INTERNATIONAL ISO
STANDARD 7936
Second edition
2022-08
Coal — Determination and
presentation of float and sink
characteristics — General directions
for apparatus and procedures
Charbon — Détermination et présentation des caractéristiques
de flottation et d'enfoncement — Principes directeurs relatifs à
l'appareillage et aux modes opératoires
Reference number
© ISO 2022
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’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and symbols .1
4 Sampling . 1
4.1 General . 1
4.2 Sample mass . 2
4.3 Coal preparation plant products . 3
4.4 Plant control testing . 4
4.5 Comprehensive plant efficiency test . 4
4.6 Core samples. 4
4.7 Preliminary treatment . 4
4.8 Size analysis . 5
4.9 Pilot testing . 5
5 Separation media . 6
5.1 General . 6
5.2 Organic solutions . 6
5.2.1 General . 6
5.2.2 Limitations on accuracy . 6
5.3 Inorganic solutions . 7
5.3.1 General . 7
5.3.2 Formate solutions . 7
5.4 Aqueous suspensions . . 8
5.4.1 General . 8
5.4.2 Zirconium dioxide . 8
6 Apparatus .10
6.1 General . 10
6.2 Coarse coal apparatus . 12
6.3 Fine coal apparatus . 16
7 Float and sink testing procedures.16
7.1 General . 16
7.2 Relative densities of test media . 16
7.3 Testing of coarse size fractions . 17
7.3.1 General . 17
7.3.2 Procedure . 18
7.3.3 Air drying. 19
7.4 Testing of fine size fractions . 19
7.4.1 General . 19
7.4.2 Procedure . 19
8 Test report .22
Annex A (informative) Drop shatter .24
Annex B (informative) Wet tumbling .36
Annex C (informative) Sample masses for float and sink testing .38
Annex D (normative) Validation of data .43
Annex E (informative) Interpretation of data .45
Annex F (informative) Guide to the safe use of organic solutions .49
Annex G (informative) Calibration of hydrometers .52
iii
Bibliography .54
iv
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 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 1,
Coal preparation: Terminology and performance.
This second edition cancels and replaces the first edition (ISO 7936:1992), which has been technically
revised.
The main changes are as follows:
— addition of new procedures for the use of inorganic solutions, such as caesium and potassium
formates, and for aqueous suspensions, such as zirconium dioxide for float and sink analysis.
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.
v
Introduction
The results of float and sink testing, presented in tabular and graphical form, are the basis for the
provision of washability data.
The results of float and sink data from coal seam samples provide an estimation of the future quality
and yield of washed coal from the area of the coal lease where the samples were taken.
The results of float and sink data from coal seams and preparation plants are also used when designing
a new plant and /or redesigning an existing plant, and also in predicting, controlling and assessing the
performance of an existing plant in total or in part.
Where tests other than those for routine control purposes are carried out, it is essential that there
is precise instruction regarding size ranges and relative density fractions to establish the scope of
information and accuracy required.
The following annexes provide new additional information in this revision as follows:
Annex A  Drop shatter – A pre-treatment of samples for float and sink testing;
Annex B  Wet tumbling – A pre-treatment of samples for floa
...