Explosive atmospheres - Part 20-2: Material characteristics - Combustible dusts test methods

ISO/IEC 80079-20-2:2016 is published as a dual logo standard and describes the test methods for the identification of combustible dust and combustible dust layers in order to permit classification of areas where such materials exist for the purpose of the proper selection and installation of electrical and mechanical equipment for use in the presence of combustible dust. The standard atmospheric conditions for determination of characteristics of combustible dusts are:
- temperature -20 °C to 60 °C,
- pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar) and
- air with normal oxygen content, typically 21 % v/v. The test methods defined do not apply to:
- recognized explosives, propellants (e.g. gunpowder, dynamite), or substances or mixtures of substances which may, under some circumstances, behave in a similar manner or
- dusts of explosives and propellants that do not require atmospheric oxygen for combustion, or to pyrophoric substances. This first edition cancels and replaces the first edition of IEC 61241-2-1 published in 1994, the first edition of IEC 61241-2-2 published in 1993 and the first edition of IEC 61241-2-3 published in 1994, combining the requirements into a single document, and is considered to constitute a technical revision. Significant changes with respect to IEC 61241-2-1:1994, IEC 61241-2-2:1993 and IEC 61241-2-3:1994 can be found in the foreword of the document.
The contents of the corrigendum of March 2017 have been included in this copy.
Keywords: combustible dust

Atmosphères explosives - Partie 20-2: Caractéristiques des produits - Méthodes d'essai des poussières combustibles

ISO/IEC 80079-20-2:2016 est publiée en tant que norme sous double logo et décrit les méthodes d'essai pour l'identification des poussières combustibles et des couches de poussières combustibles afin de permettre le classement des emplacements où de tels produits existent, et ce, pour un choix et une installation corrects des équipements électriques et mécaniques à utiliser en présence de poussières combustibles. Les conditions atmosphériques normales pour la détermination des caractéristiques des poussières combustibles sont les suivantes:
- température de -20 °C à 60 °C,
- pression de 80 kPa (0,8 bar) à 110 kPa (1,1 bar) et
- air avec teneur normale en oxygène, généralement égale à 21 % v/v. Les méthodes d'essai définies ne s'appliquent pas aux:
- explosifs proprement dits, agents propulseurs (par exemple, poudre à canon, dynamite) ou substances ou mélanges de substances qui, dans certaines conditions, peuvent se comporter de manière semblable ou
- aux poussières d'explosifs et agents propulseurs qui n'exigent pas d'oxygène atmosphérique pour leur combustion, ou aux substances pyrophoriques. Cette première édition annule et remplace les premières éditions de l'IEC 61241-2-1, de l'IEC 61241-2-2 et de l'IEC 61241-2-3 parues respectivement en 1994, 1993 et 1994, en regroupant les exigences dans un seul document. Cette édition constitue une révision technique. Modifications majeures par rapport à l'IEC 61241-2-1:1994, l'IEC 61241-2-2:1993 et l'IEC 61241-2-3:1994 et sont identifiés dans l'avant-propos du document.
Le contenu du corrigendum de mars 2017 a été pris en considération dans cet exemplaire.
Mots clés: poussières combustibles

General Information

Status
Published
Publication Date
17-Feb-2016
Current Stage
PPUB - Publication issued
Start Date
18-Feb-2016
Completion Date
18-Feb-2016
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ISO/IEC 80079-20-2
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 20-2: Material characteristics – Combustible dusts test methods
Atmosphères explosives –
Partie 20-2: Caractéristiques des produits – Méthodes d’essai des poussières
combustibles
ISO/IEC 80079-20-2:2016-02(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
ISO/IEC 80079-20-2
Edition 1.0 2016-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 20-2: Material characteristics – Combustible dusts test methods
Atmosphères explosives –
Partie 20-2: Caractéristiques des produits – Méthodes d’essai des poussières
combustibles
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 13.230; 29.260.20 ISBN 978-2-8322-3179-1

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

---------------------- Page: 3 ----------------------
– 2 – ISO/IEC 80079-20-2:2016
 ISO/IEC 2016
CONTENTS

FOREWORD ......................................................................................................................... 5

1 Scope ............................................................................................................................ 8

2 Normative references..................................................................................................... 8

3 Terms and definitions .................................................................................................... 8

4 Dust sample requirements ............................................................................................. 9

4.1 Receipt of sample for testing ................................................................................. 9

4.2 Characterisation of sample .................................................................................... 9

4.3 Preparation of sample ......................................................................................... 10

4.4 Test conditions .................................................................................................... 10

5 Combustible dusts and combustible flyings determination ............................................. 10

5.1 Test sequence .................................................................................................... 10

5.2 Tests to determine whether material is a combustible dust or combustible

flying ................................................................................................................... 10

5.2.1 Visual inspection .......................................................................................... 10

5.2.2 Determine particle distribution ...................................................................... 11

5.2.3 Ignition test in the Hartmann tube ................................................................. 11

5.2.4 Ignition test in the 20-litre sphere ................................................................. 11

6 Procedure for characterisation of combustible dust or combustible flying ...................... 11

7 Test methods for determination of whether a material is a combustible dust or a

combustible flying ........................................................................................................ 14

7.1 Modified Hartmann tube ...................................................................................... 14

7.1.1 General ....................................................................................................... 14

7.1.2 Test equipment ............................................................................................ 14

7.1.3 Test procedure ............................................................................................. 15

7.2 20-litre sphere ..................................................................................................... 15

7.2.1 General ....................................................................................................... 15

7.2.2 Test equipment ............................................................................................ 15

7.2.3 Test procedure ............................................................................................. 16

7.3 Alternative method to 20-litre sphere for small test material quantities .................. 16

7.3.1 General ....................................................................................................... 16

7.3.2 Test equipment ............................................................................................ 17

7.3.3 Test procedure ............................................................................................. 17

8 Test methods for combustible dust determinations ....................................................... 17

8.1 MIT of a dust cloud ............................................................................................. 17

8.1.1 General ....................................................................................................... 17

8.1.2 GG furnace .................................................................................................. 17

8.1.3 BAM furnace ................................................................................................ 18

8.2 Test for MIT of dust layer .................................................................................... 19

8.2.1 General ....................................................................................................... 19

8.2.2 Heated surface ............................................................................................ 19

8.2.3 Dust layers .................................................................................................. 20

8.2.4 Dust layer temperature ................................................................................. 20

8.2.5 Ambient temperature measurements ............................................................ 20

8.2.6 Dust layer temperature test method .............................................................. 20

8.2.7 Recording of results ..................................................................................... 21

8.3 Method for determining minimum ignition energy of dust/air mixtures ................... 22

---------------------- Page: 4 ----------------------
ISO/IEC 80079-20-2:2016 – 3 –
 ISO/IEC 2016

8.3.1 General ....................................................................................................... 22

8.3.2 Test equipment ............................................................................................ 22

8.3.3 Test procedure ............................................................................................. 23

8.3.4 Calibration for determination of minimum ignition energies (MIE) by

electrically generated high-voltage d.c. sparks .............................................. 24

8.3.5 Recording of test results .............................................................................. 24

8.4 Test on resistivity ................................................................................................ 24

8.4.1 General ....................................................................................................... 24

8.4.2 Test equipment ............................................................................................ 25

8.4.3 Test procedure ............................................................................................. 25

8.4.4 Recording of test results .............................................................................. 26

9 Test report................................................................................................................... 26

Annex A (normative) Measurement of temperature distribution on the surface of the

hot plate ............................................................................................................................. 27

Annex B (informative) Godbert-Greenwald oven (GG) ......................................................... 28

Annex C (informative) Examples of spark-generating systems ............................................ 29

C.1 General ............................................................................................................... 29

C.2 Triggering by auxiliary spark using three-electrode system ................................... 30

C.3 Triggering by electrode movement ....................................................................... 31

C.4 Triggering by voltage increase (trickle-charging circuit) ........................................ 32

C.5 Triggering by auxiliary spark, using normal two-electrode system – Trigger

transformer in discharge circuit ............................................................................ 33

Annex D (normative) Vertical tube (modified Hartmann tube) apparatus .............................. 34

Annex E (informative) 20-litre sphere ................................................................................. 35

Annex F (informative) BAM oven ........................................................................................ 37

Annex G (informative) Data for dust explosion characteristics ............................................. 38

Annex H (informative) 1 m vessel ..................................................................................... 39

H.1 Test principle ...................................................................................................... 39

H.2 Test apparatus .................................................................................................... 39

H.3 Test conditions .................................................................................................... 43

H.4 Test procedure .................................................................................................... 43

Bibliography ....................................................................................................................... 45

Figure 1 – Protocol for characterisation of combustible dust or combustible flying ................ 12

Figure 2 – Tests to define ability to form explosive dust atmosphere (combustible

dust/combustible flyings) ..................................................................................................... 13

Figure 3 – Tests to characterise combustible dust or combustible flying ............................... 14

Figure 4 – Modified Hartmann tube ..................................................................................... 23

Figure 5 – Measuring cell for powder resistivity ................................................................... 25

Figure A.1 – Typical surface temperature distribution (method A) ......................................... 27

Figure B.1 – Vertical cross-section through the Godbert-Greenwald oven ............................. 28

Figure C.1 – Circuit – Triggering by high-voltage relay, using a two-electrode system .......... 29

Figure C.2 – Apparatus for determining the minimum ignition energies of dust

(schematic) – Triggering by auxiliary spark using three-electrode system ............................. 30

Figure C.3 – Apparatus for determining the minimum ignition energies of dust

(schematic) – Triggering by electrode movement ................................................................. 31

Figure C.4 – Apparatus for determining the minimum ignition energies of dust

(schematic) – Triggering by voltage increase ....................................................................... 32

---------------------- Page: 5 ----------------------
– 4 – ISO/IEC 80079-20-2:2016
 ISO/IEC 2016
Figure C.5 – Apparatus for determining the minimum ignition energies for dust

(schematic) – Trigger transformer in discharge circuit .......................................................... 33

Figure D.1 – Vertical tube apparatus (modified Hartmann tube) ........................................... 34

Figure E.1 – Test equipment 20-litre sphere (schematic) ...................................................... 35

Figure E.2 – Cross-sectional view of rebound nozzle ........................................................... 36

Figure E.3 – Plan view of rebound nozzle ............................................................................ 36

Figure E.4 – Cross-sectional view of dispersion cup ............................................................ 36

Figure F.1 – Cross-sectional arrangement of BAM oven ....................................................... 37

Figure H.1 – 1 m vessel (schematic) .................................................................................. 40

Figure H.2 – Location of the 6 mm holes in the semicircular dust dispenser ......................... 41

Figure H.3 – Rebound nozzle .............................................................................................. 42

Figure H.4 – Dispersion cup ................................................................................................ 43

Table 1 – Example of ignition test report ............................................................................. 21

---------------------- Page: 6 ----------------------
ISO/IEC 80079-20-2:2016 – 5 –
 ISO/IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 20-2: Material characteristics –
Combustible dusts test methods
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard ISO/IEC 80079-20-2 has been prepared by subcommittee 31M: Non-

electrical equipment and protective systems for explosive atmospheres, of IEC 31: Equipment

for explosive atmospheres.
It is published as a double logo standard.

This first edition cancels and replaces the first edition of IEC 61241-2-1 published in 1994, the

first edition of IEC 61241-2-2 published in 1993 and the first edition of IEC 61241-2-3

published in 1994, combining the requirements into a single document, and is considered to

constitute a technical revision.
---------------------- Page: 7 ----------------------
– 6 – ISO/IEC 80079-20-2:2016
© ISO/IEC 2016
The text of this standard is based on the following documents:
FDIS Report on voting
31M/102/FDIS 31M/108/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table. In ISO, the standard has been approved by 15 P-members

out of 21 having cast a vote.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

"A list of all parts in the IEC 60079 series, under the general title Explosive atmospheres, as

well as the International Standard 80079 series, can be found on the IEC website."

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum of March 2017 have been included in this copy.
---------------------- Page: 8 ----------------------
ISO/IEC 80079-20-2:2016 – 7 –
 ISO/IEC 2016
Significant changes with respect to IEC 61241-2-1:1994, IEC 61241-2-2:1993 and
IEC 61241-2-3:1994
Type

Explanation of the significance of the Clause Minor and Extension Major technical

changes editorial changes changes
Normative references 2 X
Terms and Definitions 3 X
Dust sample Requirements 4 X
Combustible Dust Determination 5 X
Procedure for Characterisation of combustible 6 X
dust or combustible flying
Test methods for determination of a 7 X
combustible dust or a combustible flying
MIT of a dust cloud 8.1 X
MIT of a dust layer 8.2 X
MIE of a dust/air mixture 8.3 X
Tests on resistivity 8.4 X
Measurement of temperature distribution on Annex X
the surface of the hot plate A
Godbert-Greenwald oven Annex X
Examples of spark-generating systems Annex X
Vertical tube apparatus Annex X
20-litre sphere Annex X
BAM oven Annex F X
Data for dust explosion characteristics Annex X
1m vessel Annex X
---------------------- Page: 9 ----------------------
– 8 – ISO/IEC 80079-20-2:2016
 ISO/IEC 2016
EXPLOSIVE ATMOSPHERES –
Part 20-2: Material characteristics –
Combustible dusts test methods
1 Scope

This part of ISO/IEC 80079 describes the test methods for the identification of combustible

dust and combustible dust layers in order to permit classification of areas where such

materials exist for the purpose of the proper selection and installation of electrical and

mechanical equipment for use in the presence of combustible dust.

The standard atmospheric conditions for determination of characteristics of combustible dusts

are:
• temperature –20 °C to +60 °C,
• pressure 80 kPa (0,8 bar) to 110 kPa (1,1 bar) and
• air with normal oxygen content, typically 21 % v/v.
The test methods defined do not apply to:

• recognized explosives, propellants (e.g. gunpowder, dynamite), or substances or mixtures

of substances which may, under some circumstances, behave in a similar manner or
• dusts of explosives and propellants that do not require atmospheric oxygen for
combustion, or to pyrophoric substances.
2 Normative references
None.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
combustible dust

finely divided solid particles, 500 µm or less in nominal size, which may form explosive

mixtures with air at standard atmospheric pressure and temperatures
Note 1 to entry: This includes dust and grit as defined in ISO 4225.

Note 2 to entry: The term 'solid particles' is intended to address particles in the solid phase but does not preclude

a hollow particle.
3.1.1
conductive dust

combustible metal dusts and other combustible dusts with electrical resistivity equal to or less

than 1 × 10 Ω⋅m

Note 1 to entry: Metal dust is treated as conductive dust because it is assumed that surface oxidation cannot be

depended upon to always ensure electrical resistivity greater than 1 × 10 Ω⋅m
---------------------- Page: 10 ----------------------
ISO/IEC 80079-20-2:2016 – 9 –
 ISO/IEC 2016
3.1.2
non-conductive dust
combustible dust with electrical resistivity greater than 1 × 10 Ω⋅m
3.2
combustible flyings

solid particles, including fibres, where one dimension is greater than 500 µm in nominal size,

which may form an explosive mixture with air at standard atmospheric pressure and

temperature
Note 1 to entry: The ratio of length to width is 3 or more.

Note 2 to entry: Examples of flyings include carbon fibre, rayon, cotton (including cotton linters and cotton waste),

sisal, jute, hemp, cocoa fibre, oakum and baled waste kapok.
3.3
explosive dust atmosphere

mixture with air, under atmospheric conditions, of combustible substances in the form of dust,

fibres, or flyings which, after ignition, permits self-sustaining propagation
3.4
minimum ignition temperature of a dust layer

lowest temperature of a hot surface at which ignition occurs in a dust layer under specified

test conditions
3.5
minimum ignition temperature of a dust cloud

lowest temperature of a hot surface on which the most ignitable mixture of the dust with air is

ignited under specified test conditions
3.6
minimum ignition energy (of a combustible dust/air mixture)

lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect

ignition of the most sensitive dust/air mixture under specified test conditions
4 Dust sample requirements
4.1 Receipt of sample for testing
A material safety data sheet or equivalent with the sample.

The test material shall be provided in suitable packaging, labelled according to relevant

guidelines labelled according to relevant guidelines, and appropriate transportation.

NOTE It is usual to provide a quantity of at least 0,5 kg for testing. If sample preparation is required this may be

insufficient. If only a smaller volume of material is available then the full range of testing may not be possible.

4.2 Characterisation of sample

The sample shall be representative of the material as it appears in the entire process

operated.

NOTE Many unit operations such as extract systems will separate dust into finer fractions than seen in the main

processing equipment and this is accounted for when taking the sample.

If the sample is not representative of the material as found in the process then sample

preparation shall be carried out to apply the worst case conditions.
At least the following information about the sample shall be provided:
---------------------- Page: 11 ----------------------
– 10 – ISO/IEC 80079-20-2:
...

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