SIST EN ISO 21178:2020

SLOVENSKI STANDARD
SIST EN ISO 21178:2020
01-julij-2020
Nadomešča:
SIST EN ISO 21178:2013
Naprave za kontinuirni transport - Lahki trakovi tračnih transporterjev -
Ugotavljanje električnih upornosti (ISO 21178:2020)
Light conveyor belts - Determination of electrical resistances (ISO 21178:2020)
Leichte Fördergurte - Bestimmung der elektrischen Widerstände (ISO 21178:2020)
Courroies transporteuses légères - Détermination des résistances électriques (ISO
21178:2020)
Ta slovenski standard je istoveten z: EN ISO 21178:2020
ICS:
53.040.20 Deli za transporterje Components for conveyors
SIST EN ISO 21178:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 21178:2020

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SIST EN ISO 21178:2020


EN ISO 21178
EUROPEAN STANDARD

NORME EUROPÉENNE

February 2020
EUROPÄISCHE NORM
ICS 53.040.10 Supersedes EN ISO 21178:2013
English Version

Light conveyor belts - Determination of electrical
resistances (ISO 21178:2020)
Courroies transporteuses légères - Détermination des Leichte Fördergurte - Bestimmung der elektrischen
résistances électriques (ISO 21178:2020) Widerstände (ISO 21178:2020)
This European Standard was approved by CEN on 18 January 2020.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21178:2020 E
worldwide for CEN national Members.

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SIST EN ISO 21178:2020
EN ISO 21178:2020 (E)
Contents Page
European foreword . 3

2

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SIST EN ISO 21178:2020
EN ISO 21178:2020 (E)
European foreword
This document (EN ISO 21178:2020) has been prepared by Technical Committee ISO/TC 41 "Pulleys
and belts (including veebelts)" in collaboration with Technical Committee CEN/TC 188 “Conveyor belts”
the secretariat of which is held by SNV.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2020, and conflicting national standards shall
be withdrawn at the latest by August 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 21178:2013.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 21178:2020 has been approved by CEN as EN ISO 21178:2020 without any modification.

3

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SIST EN ISO 21178:2020

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SIST EN ISO 21178:2020
INTERNATIONAL ISO
STANDARD 21178
Third edition
2020-02
Light conveyor belts — Determination
of electrical resistances
Courroies transporteuses légères — Détermination des résistances
électriques
Reference number
ISO 21178:2020(E)
©
ISO 2020

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Electrical surface resistances . 2
5.1 Method A: Measurement of surface resistance, R , omni-directionally . 2
OA
5.1.1 Applicability . 2
5.1.2 Principle . 2
5.1.3 Apparatus (see Figure 1) . 2
5.1.4 Test piece . 4
5.1.5 Procedure . 5
5.1.6 Expression of results . 6
5.1.7 Test report . 6
5.2 Method B: Measurement of surface resistance R in longitudinal and transverse
OB
directions . 6
5.2.1 Applicability . 6
5.2.2 Principle . 6
5.2.3 Apparatus (see Figure 4) . 6
5.2.4 Test piece . 8
5.2.5 Procedure . 9
5.2.6 Expression of results . 9
5.2.7 Test report . 9
6 Electrical surface resistivity ρ .10
s
6.1 General .10
6.2 Principle .10
6.3 Apparatus .11
6.4 Test piece .12
6.4.1 Material .12
6.4.2 Dimensions .12
6.4.3 Number .12
6.4.4 Cleaning .12
6.4.5 Conditioning .12
6.4.6 Preparation .12
6.5 Procedure .12
6.6 Expression of results .13
6.7 Test report .13
7 Electrical volume resistances .13
7.1 Volume resistance, R , perpendicular to plane of belt.13
D
7.1.1 Principle .13
7.1.2 Apparatus .13
7.1.3 Test piece .14
7.1.4 Procedure .15
7.1.5 Expression of results .15
7.1.6 Test report .15
7.2 Volume resistance, R , in longitudinal and transverse directions parallel to plane
Di
of belt .16
7.2.1 Principle .16
7.2.2 Apparatus .16
7.2.3 Test piece .17
7.2.4 Procedure .18
7.2.5 Expression of results .19
© ISO 2020 – All rights reserved iii

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

7.2.6 Test report .19
8 Electrical volume resistivity, ρ .19
D
8.1 Procedure .19
8.2 Expression of results .19
8.3 Test report .20
Bibliography .21
iv © ISO 2020 – All rights reserved

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SIST EN ISO 21178:2020
ISO 21178:2020(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.
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 41, Pulleys and belts (including veebelts),
Subcommittee SC 3, Conveyor belts, in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 188, Conveyor belts, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 21178:2013), which has been technically
revised. The main changes compared to the previous edition are as follows:
— addition of terms and definitions;
— modifications to the figures and formulas;
— technical changes to the Clauses 5, 6 and 7;
— deletion of Annex A;
— editorial modifications.
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.
© ISO 2020 – All rights reserved v

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SIST EN ISO 21178:2020

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SIST EN ISO 21178:2020
INTERNATIONAL STANDARD ISO 21178:2020(E)
Light conveyor belts — Determination of electrical
resistances
1 Scope
This document specifies test methods for determining the electrical resistances of light conveyor belts
according to ISO 21183-1. The resistances are surface resistance, volume resistance perpendicular
to the belt plane, and longitudinal and transverse volume resistance parallel to the belt plane. This
document also specifies two test methods for determining the surface resistivity and the volume
resistivity.
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 18573, Conveyor belts — Test atmospheres and conditioning periods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
electrical surface resistance
quotient of a direct-current voltage applied between two electrodes on the same surface of a test piece
and the current between the electrodes
Note 1 to entry: It is expressed in ohms (Ω).
3.2
electrical surface resistivity
measured surface resistance calculated to apply to a square
Note 1 to entry: It is expressed in ohms (Ω) and the size of the square is immaterial.
3.3
electrical volume resistance
quotient of a direct-current voltage applied between two electrodes in contact with opposite faces of a
test piece and the current between the electrodes, excluding current along the surface
Note 1 to entry: It is expressed in ohms (Ω).
3.4
electrical volume resistivity
measured volume resistance calculated to apply to a cube of unit side
Note 1 to entry: It is expressed in ohm metres (Ωm).
© ISO 2020 – All rights reserved 1

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

4 Symbols
Symbol Description Unit
R Electrical surface resistance, method A Ω
OA
R Electrical surface resistance, method B Ω
OB
R Electrical surface resistance for the determination of ρ Ω
OG s
R Electrical volume resistance perpendicular to the plane of the belt Ω
D
R Electrical volume resistance in longitudinal and transverse direction parallel Ω
Di
to the plane of the belt
ρ Electrical surface resistivity Ω
s
ρ Electrical volume resistivity Ωm
D
d Diameter of electrode mm
1/2/3
d Middle of the gap diameter mm
m
g Width of the gap mm
2
A Surface of the electrode mm
h Thickness of test piece mm
1/2
NOTE The SI unit of surface resistivity, ρ , is the ohm (Ω). In practice, this is sometimes referred to as “ohm/
s
square” or “Ω/sq” . The size of the square is immaterial.
5 Electrical surface resistances
5.1 Method A: Measurement of surface resistance, R , omni-directionally
OA
5.1.1 Applicability
This method is applicable to belts which are electrically two-dimensionally isotropic in the plane of
the belt.
5.1.2 Principle
An electric current of specified voltage is passed via electrodes through a suitably prepared test piece
taken from the belt.
5.1.3 Apparatus (see Figure 1)
5.1.3.1 Sheet of insulating material, a little larger than the test piece.
5.1.3.2 Two cylindrical and coaxial electrodes (see Figure 1), with contact surfaces machined flat
and polished, as follows.
5.1.3.2.1 Electrode 1, circular.
5.1.3.2.2 Electrode 2, annular.
5.1.3.2.3 Material of electrodes, either brass or stainless steel.
10
5.1.3.3 Ohmmeter, having a measuring range up to 10 Ω and accurate to within ±5 %.
2 © ISO 2020 – All rights reserved

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

5.1.3.4 Source of direct current, adjustable up to 500 V, and not permitting a current greater than
10 mA.
Key
1 electrode 1
2 electrode 2
3 test piece
4 sheet of insulating material
5 ohmmeter
Figure 1 — Test arrangement for measurement of electrical surface resistance R
OA
© ISO 2020 – All rights reserved 3

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

5.1.4 Test piece
5.1.4.1 Material
Test piece material shall be new, unused (“virgin”), but shall not be tested sooner than five days after
manufacture. It shall be free from contamination and superficial damage.
5.1.4.2 Dimensions
The test pieces shall be square, 300 mm × 300 mm minimum, and shall be cut from the full thickness of
the belt.
5.1.4.3 Number
Three test pieces shall be taken. One test piece shall be taken from the middle of the belt, the other two
test pieces shall be taken in the area between 100 mm to 400 mm from each of the belt edges. The test
pieces shall be selected in accordance with Figure 2.
Dimensions in millimetres
Key
b belt width
Figure 2 — Distribution of test piece selection
5.1.4.4 Cleaning
If necessary, clean both surfaces of the test pieces by rubbing with fuller's earth (hydrated magnesium-
aluminium silicate), for example, using a clean cloth. After cleaning away all traces of the powder, wipe
the surface with a clean cloth moistened with distilled water and then dry with a clean cloth.
5.1.4.5 Conditioning
Before testing, condition the test pieces in accordance with ISO 18573, Atmosphere B, for 24 h, except
that, if the light conveyor belt consists of materials with a high absorption of moisture, for example
cotton or polyamide, condition the test piece for 48 h.
5.1.4.6 Preparation
To ensure good contact between electrodes and test piece a contact medium as described in 5.1.4.7 can
be used if necessary.
4 © ISO 2020 – All rights reserved

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

If contact medium is used, paint two areas of the test piece as shown in Figure 3. Take care to ensure
the accuracy of the dimensions of the painted areas, although the symmetry of the centre is not critical.
Dimensions in millimetres
Key
1 contact medium
Figure 3 — Design to be painted on the test piece
5.1.4.7 Contact medium
4
The electrical surface resistivity of the contact medium shall not be higher than 10 Ω. For checking
this value, use the same electrode arrangement as described in Clause 6. Examples for suitable contact
media are silver lacquer or a jelly.
NOTE A jelly having the following composition is suitable:
— Anhydrous polyethylene glycol of molecular mass 600: 800 parts by mass;
— Water: 200 parts by mass;
— Potassium chloride: 10 parts by mass;
— Soft soap (pharmaceutical quality): 1 part by mass.
5.1.5 Procedure
The temperature and relative humidity in the test room shall be in accordance with ISO 18573,
Atmosphere B.
Measure the temperature and relative humidity in the test room.
Place the test piece on the sheet of insulating material, with the test surface upwards.
© ISO 2020 – All rights reserved 5

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

Apply the test voltage to the electrodes, starting with a low voltage to protect very fine antistatic layers
against damage.
Read the value of the electrical resistance 1 min after applying the test voltage.
5.1.6 Expression of results
For each surface of the belt subjected to test, record the electrical resistance, in ohms, measured for
each test piece, and calculate the mean of the values recorded for that surface for the three test pieces.
Record the electrical resistance for the two surfaces of the belt separately.
5.1.7 Test report
The test report shall include the following information:
a) complete designation of the tested light conveyor belt material and the manufacturing date;
b) reference to this document, i.e. ISO 21178;
c) test room temperature and relative humidity;
d) conditioning period;
e) contact medium, if applied;
f) voltage applied to the electrodes;
g) results of the tests;
h) date of test;
i) any deviations from the standard test.
5.2 Method B: Measurement of surface resistance R in longitudinal and transverse
OB
directions
5.2.1 Applicability
This method is applicable to belts which have electrically varying properties in the plane of the belt,
especially those where fabrics have conducting threads in the longitudinal direction which can be
exposed on the belt surface.
5.2.2 Principle
An electric current is passed via electrodes clamped in a suitable arrangement to the surface of a test
piece of the belt material.
5.2.3 Apparatus (see Figure 4)
5.2.3.1 Earthed screen plate
5.2.3.2 Bottom plate, made of insulating material, such as polymethylmethacrylate,
polytetrafluoroethylene or similar, having dimensions 600 mm × 200 mm × 20 mm.
5.2.3.3 Electrodes (see Figure 4), with connection points for the ohmmeter connecting cables, as
follows.
5.2.3.3.1 Contact area, 100 mm × 10 mm.
6 © ISO 2020 – All rights reserved

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SIST EN ISO 21178:2020
ISO 21178:2020(E)

5.2.3.3.2 Material of electrodes, either brass or stainless steel.
5.2.3.4 Electrode holders
10
5.2.3.5 Ohmmeter, having a measuring range up to 10 Ω and accurate to within ±5 %.
5.2.3.6 Source of direct current, adjustable up to 500 V, and not permitting a current greater than
10 mA.
NOTE The source current can be either an accumulator or a rectified, stabilized AC power supply.
Dimensions in millimetres
Key
1 s
...

SLOVENSKI STANDARD
oSIST prEN ISO 21178:2019
01-julij-2019
Naprave za kontinuirni transport - Lahki trakovi tračnih transporterjev -
Ugotavljanje električnih upornosti (ISO/DIS 21178:2019)
Light conveyor belts - Determination of electrical resistances (ISO/DIS 21178:2019)
Leichte Fördergurte - Bestimmung der elektrischen Widerstände (ISO/DIS 21178:2019)
Courroies transporteuses légères - Détermination des résistances électriques (ISO/DIS
21178:2019)
Ta slovenski standard je istoveten z: prEN ISO 21178
ICS:
53.040.20 Deli za transporterje Components for conveyors
oSIST prEN ISO 21178:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN ISO 21178:2019

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oSIST prEN ISO 21178:2019
DRAFT INTERNATIONAL STANDARD
ISO/DIS 21178
ISO/TC 41/SC 3 Secretariat: SAC
Voting begins on: Voting terminates on:
2019-04-26 2019-07-19
Light conveyor belts — Determination of electrical
resistances
Courroies transporteuses légères — Détermination des résistances électriques
ICS: 53.040.10
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 21178:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2019

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2019
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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Electrical surface resistances . 2
5.1 Method A: measurement of surface resistance R omni-directionally . 2
OA
5.2 Method B: measurement of surface resistance R in longitudinal and transverse
OB
directions . 6
5.2.1 Applicability . 6
5.2.2 Principle . 6
5.2.3 Apparatus (see Figure 4) . 6
5.2.4 Test piece . 7
5.2.5 Procedure . 9
5.2.6 Expression of results . 9
5.2.7 Test report . 9
6 Electrical surface resistivity ρ . 9
s
6.1 General . 9
6.2 Principle . 9
6.3 Apparatus (see Figure 6) .10
6.4 Test piece .11
6.4.1 Material .11
6.4.2 Dimensions .11
6.4.3 Number .11
6.4.4 Cleaning .11
6.4.5 Conditioning .11
6.4.6 Preparation .11
6.5 Procedure .11
6.6 Expression of results .12
6.7 Test report .12
7 Electrical volume resistances .12
7.1 Volume resistance R perpendicular to plane of belt .12
D
7.1.1 Principle .12
7.1.2 Apparatus (see Figure 8) .12
7.1.3 Test piece .13
7.1.4 Procedure .14
7.1.5 Expression of results .14
7.1.6 Test report .14
7.2 Volume resistance, R , in longitudinal and transverse directions parallel to plane
Di
of belt .15
7.2.1 Principle .15
7.2.2 Apparatus (see Figure 9) .15
7.2.3 Test piece .16
7.2.4 Procedure .17
7.2.5 Expression of results .18
7.2.6 Test report .18
8 Electrical volume resistivity ρ .18
D
8.1 Procedure .18
8.2 Expression of results .18
8.3 Test report .18
Annex A (informative) Comparative values for electrical resistances .20
© ISO 2019 – All rights reserved iii

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

Bibliography .21
iv © ISO 2019 – All rights reserved

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(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.
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 on 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 the following URL: www .iso .org/iso/foreword .html.
ISO 21178 was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts),
Subcommittee SC 3, Conveyor belts.
This third edition cancels and replaces the second edition (ISO 21178:2013), of which it constitutes a
full revision.
The main changes compared to the previous edition are as follows:
— According to ISO/TC 41/SC 3 N 1216
© ISO 2019 – All rights reserved v

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oSIST prEN ISO 21178:2019

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oSIST prEN ISO 21178:2019
DRAFT INTERNATIONAL STANDARD ISO/DIS 21178:2019(E)
Light conveyor belts — Determination of electrical
resistances
1 Scope
This International Standard specifies test methods for determining the electrical resistances of light
conveyor belts according to ISO 21183-1. The resistances are surface resistance, volume resistance
perpendicular to the belt plane, and longitudinal and transverse volume resistance parallel to the
belt plane. This International Standard also specifies two test methods for determining the surface
resistivity and the volume resistivity.
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 18573, Conveyor belts — Test atmospheres and conditioning periods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
electrical surface resistance
quotient of a direct-current voltage applied between two electrodes on the same surface of a test piece
and the current between the electrodes
Note 1 to entry: It is expressed in ohms (Ω).
3.2
electrical surface resistivity
measured surface resistance calculated to apply to a square
Note 1 to entry: It is expressed in ohms (Ω) and the size of the square is immaterial.
3.3
electrical volume resistance
quotient of a direct-current voltage applied between two electrodes in contact with opposite faces of a
test piece and the current between the electrodes, excluding current along the surface
Note 1 to entry: It is expressed in ohms (Ω).
3.4
electrical volume resistivity
measured volume resistance calculated to apply to a cube of unit side
Note 1 to entry: It is expressed in ohm metres (Ω•m).
© ISO 2019 – All rights reserved 1

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

4 Symbols
Symbol Quantity Unit
R Electrical surface resistance, method A Ω
OA
R Electrical surface resistance, method B Ω
OB
R Electrical surface resistance for the determination of ρ Ω
OG s
R Electrical volume resistance perpendicular to the plane of the belt Ω
D
R Electrical volume resistance in longitudinal and transverse direction parallel to the Ω
Di
plane of the belt
ρ Electrical surface resistivity Ω
s
ρ Electrical volume resistivity Ω•m
D
d Diameter of electrode mm
1/2/3
d Middle of the gap diameter mm
m
g Width of the gap mm
2
A Surface of the electrode mm
H Thickness of test piece mm
NOTE The SI unit of surface resistivity, ρ , is the ohm (Ω). In practice, this is sometimes referred to as “ohm/
s
square” or “Ω/sq” or “Ω/□”. The size of the square is immaterial.
5 Electrical surface resistances
5.1 Method A: measurement of surface resistance R omni-directionally
OA
5.1.1 Applicability
This method is applicable to belts which are electrically two-dimensionally isotropic in the plane of
the belt.
5.1.2 Principle
An electric current of specified voltage is passed via electrodes through a suitably prepared test piece
taken from the belt.
5.1.3 Apparatus (see Figure 1)
5.1.3.1 Sheet of insulating material, a little larger than the test piece
5.1.3.2 Two cylindrical and coaxial electrodes (see Figure 1), with contact surfaces machined flat
and polished, as follows.
5.1.3.2.1 Electrode 1, circular.
5.1.3.2.2 Electrode 2, annular.
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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

5.1.3.2.3 Material of electrodes, either brass or stainless steel.
10
5.1.3.3 Ohmmeter, having a measuring range up to 10 Ω and accurate to within ±5 %.
5.1.3.4 Source of direct current, adjustable up to 500 V, and not permitting a current greater than
10 mA.
Dimensions in millimetres
Key
1 electrode 1
2 electrode 2
3 test piece
4 sheet of insulating material
5 ohmmeter
Figure 1 — Test arrangement for measurement of electrical surface resistance R
OA
© ISO 2019 – All rights reserved 3

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oSIST prEN ISO 21178:2019
ISO/DIS 21178:2019(E)

5.1.4 Test piece
5.1.4.1 Material
Test piece material shall be new, unused (“virgin”),
...