Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation

IEC 60079-28:2015 is available as IEC 60079-28:2015 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60079-28:2015 specifies the requirements, testing and marking of equipment emitting optical radiation intended for use in explosive atmospheres. It also covers equipment located outside the explosive atmosphere or protected by a Type of Protection listed in IEC 60079-0, but which generates optical radiation that is intended to enter an explosive atmosphere. It covers Groups I, II and III, and EPLs Ga, Gb, Gc, Da, Db, Dc, Ma and Mb. This standard does not cover ignition by ultraviolet radiation and by absorption of the radiation in the explosive mixture itself. Explosive absorbers or absorbers that contain their own oxidizer as well as catalytic absorbers are also outside the scope of this standard. This second edition cancels and replaces the first edition, published in 2006, and constitutes a technical revision. Refer to the Foreword of the document for a complete listing of the technical changes between edition 2.0 and previous edition of the document. Keywords: equipment emitting optical radiation intended for use in explosive atmospheres
The Interpretation sheet 1 of November 2019 have been included in this copy.

Atmosphères explosives - Partie 28: Protection du matériel et des systèmes de transmission utilisant le rayonnement optique

L'IEC 60079-28:2015 est disponible sous forme de IEC 60079-28:2015 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
L'IEC 60079-28:2015 spécifie les exigences, les essais et le marquage du matériel émettant des rayonnements optiques destiné à être utilisé dans des atmosphères explosives. Elle couvre également le matériel situé à l'extérieur de l'atmosphère explosive ou protégé par un mode de protection indiqué dans l'IEC 60079-0, mais qui génère des rayonnements optiques qui sont destinés à pénétrer dans une atmosphère explosive. Elle couvre les Groupes I, II et III, et les EPL Ga, Gb, Gc, Da, Db, Dc, Ma et Mb. La présente norme ne couvre pas l'inflammation par rayonnement ultraviolet et par absorption du rayonnement dans le mélange explosif lui-même. Les absorbeurs explosifs ou absorbeurs qui contiennent leur propre oxydant/comburant de même que les absorbeurs catalytiques sont également hors du domaine d'application de la présente norme. Cette deuxième édition annule et remplace la première édition, parue en 2006. Cette édition constitue une révision technique. Reportez-vous à l'avant-propos du document pour une liste complète des modifications techniques entre l'édition 2.0 et édition précédente du document. Mots clés: matériel émettant des rayonnements optiques destiné à être utilisé dans des atmosphères explosives.
Le contenu de la feuille d'interprétation 1 de novembre 2019 a été pris en considération.

General Information

Status
Published
Publication Date
26-May-2015
Current Stage
PPUB - Publication issued
Start Date
27-May-2015
Completion Date
27-May-2015
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IEC 60079-28
Edition 2.0 2015-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical
radiation
Atmosphères explosives –
Partie 28: Protection du matériel et des systèmes de transmission utilisant le
rayonnement optique
IEC 60079-28:2015-05(en-fr)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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---------------------- Page: 2 ----------------------
IEC 60079-28
Edition 2.0 2015-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 28: Protection of equipment and transmission systems using optical
radiation
Atmosphères explosives –
Partie 28: Protection du matériel et des systèmes de transmission utilisant le
rayonnement optique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-2679-7

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.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
IEC 60079-28:2015/ISH1:2019 – 1 –
 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-28
Edition 2.0 2015-05
EXPLOSIVE ATMOSPHERES –
Part 28: Protection of equipment and
transmission systems using optical radiation
INTERPRETATION SHEET 1

This interpretation sheet has been prepared by IEC technical committee 31: Equipment for

explosive atmospheres.
The text of this interpretation sheet is based on the following documents:
DISH Report on voting
31/1496/DISH 31/1508/RVDISH

Full information on the voting for the approval of this interpretation sheet can be found in the

report on voting indicated in the above table.
___________

Interpretation sheet to the 6 paragraph of the Scope of IEC 60079-28:2015 (Edition 2)

Various interpretations are being made by IECEx ExCB -and ExTL staff regarding the

consideration of the risk of ignition from optical sources, and the applicability of IEC 60079-28

in the context of Subclause 6.6.4 of IEC 60079-0:2017. In addition to assistance provided to

date on IECEx Decision Sheet DS2018/004, the Liaison with IECEx has indicated that an

interpretation sheet addressing the applicability of IEC 60079-28 is required to clarify which

equipment that falls into the scope and what does not.

This interpretation is made available for Edition 2 of this standard due to the current use of

that standard by manufacturers, conformity assessment schemes and national bodies by

means of this “Interpretation Sheet” as follows:
ICS 29.260.20
IEC 60079-28:2015-05/ISH1:2019-10(en)
---------------------- Page: 4 ----------------------
– 2 – IEC 60079-28:2015/ISH1:2019
 IEC 2019
Details of interpretation:

IEC 60079-28:2015 (Edition 2: Protection of equipment and transmission systems using

optical radiation
Interpretation of the 6 paragraph of the Scope:

Question: The 6 paragraph including the items 1) to 5) describes the equipment excepted

from the Scope of this standard. The understanding of the listed exceptions is ambiguous.

Therefore, it is possible that IEC 60079-28 is not applied in all situations where it is relevant.

In addition, the potential confusion can be compounded by the wording of the exceptions.

When should the requirements of IEC 60079-28 be applied to Ex Equipment, including

Equipment assemblies and Ex Components that include an optical radiation source based on

Subclause 6.6.4 “Lasers, luminaries, and other non-divergent continuous wave optical

sources” in IEC 60079-0:2017 (Edition 7)?
Interpretation:
This standard applies to
i) laser equipment; and
ii) optical fibre equipment; and

iii) any other convergent light sources or beams where light is focussed in one single point

within the hazardous area.

NOTE 2 Some optical elements such as lenses and reflectors are able to convert divergent light into a

convergent beam.
This standard does not apply to:

1) laser equipment for EPL Mb, Gb or Gc and Db or Dc applications which complies with

Class 1 limits in accordance with IEC 60825-1; or

NOTE 3 The referenced Class 1 limits are those that involve emission limits below 15 mW measured at a

distance from the optical radiation source in accordance with IEC 60825-1, with this measured distance

reflected in the Ex application.

2) divergent light sources or beams where light is not focussed within the hazardous area; or

3) Single or multiple optical fibre cables not part of optical fibre equipment if the cables:

a) comply with the relevant industrial standards, along with additional protective means,

e.g. robust cabling, conduit or raceway (for EPL Gb, Db, Mb, Gc or Dc); or
b) comply with the relevant industrial standards (for EPL Gc or Dc).; or

4) Optical radiation sources as defined in i. to iii. above where the optical radiation is fully

contained in an enclosure complying with one of the followings Types of Protection

suitable for the EPL, or the minimum ingress protection rating specified:
a) flameproof "d" enclosures (IEC 60079-1); or

NOTE 4 A flameproof “d” enclosure is suitable because an ignition due to optical radiation in combination

with absorbers inside the enclosure is contained.
b) pressurized "p" enclosures (IEC 60079-2); or

NOTE 5 A pressurized “p” enclosure is suitable because there is protection against ingress of an

explosive atmosphere.
c) restricted breathing “nR” enclosure (IEC 60079-15); or

NOTE 6 A restricted breathing “nR” enclosure is suitable because there is protection against ingress of

an explosive atmosphere.
d) dust protection "t" enclosures" (IEC 60079-31); or

NOTE 7 A dust protection “t” enclosure is suitable because there is protection against ingress of an

explosive dust atmosphere.
---------------------- Page: 5 ----------------------
IEC 60079-28:2015/ISH1:2019 – 3 –
 IEC 2019
e) an enclosure that provides a minimum ingress protection of IP 6X and where no

internal absorbers are to be expected and complying with “Tests of enclosures” in

IEC 60079-0.

NOTE 8 An enclosure of a minimum ingress protection of IP 6X and complying with “Tests of enclosures”

in IEC 60079-0 is suitable because there is protection against the ingress of absorbers. It is anticipated

that when the enclosures are opened, entrance of any absorbers is avoided.
---------------------- Page: 6 ----------------------
– 2 – IEC 60079-28:2015 © IEC 2015
CONTENTS

FOREWORD ........................................................................................................................... 4

INTRODUCTION ..................................................................................................................... 8

1 Scope .............................................................................................................................. 9

2 Normative references .................................................................................................... 10

3 Terms and definitions .................................................................................................... 10

4 General requirements .................................................................................................... 13

5 Types of protection ........................................................................................................ 13

5.1 General ................................................................................................................. 13

5.2 Requirements for inherently safe optical radiation “op is” ...................................... 14

5.2.1 General ......................................................................................................... 14

5.2.2 Continuous wave radiation ............................................................................. 14

5.2.3 Pulsed radiation ............................................................................................. 18

5.2.4 Ignition tests .................................................................................................. 19

5.2.5 Over-power/energy fault protection ................................................................ 19

5.3 Requirements for protected optical radiation “op pr” .............................................. 20

5.3.1 General ......................................................................................................... 20

5.3.2 Radiation inside optical fibre or cable ............................................................ 20

5.3.3 Radiation inside enclosures ........................................................................... 21

5.4 Optical system with interlock “op sh” ..................................................................... 21

6 Type verifications and tests ........................................................................................... 22

6.1 Test set-up for ignition tests .................................................................................. 22

6.1.1 General ......................................................................................................... 22

6.1.2 Test vessel .................................................................................................... 22

6.1.3 Criteria to determine ignition .......................................................................... 23

6.2 Verification of suitability of test set-up for type tests ............................................. 23

6.2.1 Reference gas ............................................................................................... 23

6.2.2 Reference absorber ....................................................................................... 23

6.2.3 Reference test for continuous wave radiation and pulses above 1 s

duration ......................................................................................................... 23

6.2.4 Reference test for pulsed radiation below 1 ms pulse duration ....................... 23

6.3 Type tests ............................................................................................................. 24

6.3.1 Ignition tests with continuous wave radiation and pulses above 1 s

duration ......................................................................................................... 24

6.3.2 Ignition tests with single pulses less than 1 ms duration ................................ 24

6.3.3 Tests for pulse trains and pulses from 1 ms to 1 s duration ............................ 24

6.3.4 Absorber targets for type tests ....................................................................... 24

6.3.5 Test acceptance criteria and safety factors .................................................... 25

7 Marking ......................................................................................................................... 25

Annex A (informative) Reference test data ........................................................................... 27

Annex B (informative) Ignition mechanisms .......................................................................... 28

Annex C (normative) Ignition hazard assessment ................................................................. 33

Annex D (informative) Typical optical fibre cable design ...................................................... 35

Annex E (normative) Flow diagram for the assessment of pulses ......................................... 36

Bibliography .......................................................................................................................... 37

---------------------- Page: 7 ----------------------
IEC 60079-28:2015 © IEC 2015 – 3 –

Figure 1 – Optical ignition delay times and safe boundary curve with safety factor of 2 ........ 22

Figure B.1 – Minimum radiant igniting power with inert absorber target (α
1064

=83 %, α =93 %) and continuous wave-radiation of 1064 nm ................................. 31

nm 805 nm
Figure B.2 – Minimum radiant igniting power with inert absorber target
(α nm=83 %, α nm=93 %) and continuous wave-radiation (PTB: 1064 nm,
1 064 805

HSL: 805 nm, [8]: 803 nm) for some n-alkanes ..................................................................... 32

Figure C.1 – Ignition hazard assessment .............................................................................. 33

Figure D.1 – Example Multi-Fibre Optical Cable Design For Heavy Duty Applications ........... 35

Figure D.2 – Typical Single Optical Fibre Cable Design ........................................................ 35

Figure E.1 – Flow diagram for the assessment of pulses according to 5.2.3 .......................... 36

Table 1 – EPLs achieved by application of types of protection for optical systems ................ 13

Table 2 – Safe optical power and irradiance for Group I and II equipment, categorized

by Equipment Group and temperature class .......................................................................... 15

Table 3 – Safe optical power and irradiance for Group III equipment ..................................... 15

Table 4 – Safe limit values for intermediate area, Group I or II, constant power, T1 –

T4 atmospheres, equipment Groups IIA, IIB or IIC (Data derived from Figure B.1

including a safety factor) ....................................................................................................... 16

Table A.1 – Reference values for ignition tests with a mixture of propane in air at

40 °C mixture temperature .................................................................................................... 27

Table B.1 – AIT (auto ignition temperature), MESG (maximum experimental safe gap)

and measured ignition powers of the chosen combustibles for inert absorbers as the

target material (α =83 %, α =93) .................................................................. 30

1 064 nm 805 nm
Table B.2 – Comparison of measured minimum igniting optical pulse energy
i,min
(Q ) at 90 µm beam diameter with auto ignition temperatures (AIT) and
e,p

minimum ignition energies (MIE) from literature [9] at concentrations in percent by

volume (ϕ) ............................................................................................................................ 32

---------------------- Page: 8 ----------------------
– 4 – IEC 60079-28:2015 © IEC 2015
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 28: Protection of equipment and transmission
systems using optical radiation
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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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

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services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

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

International Standard IEC 60079-28 has been prepared by IEC technical committee 31:

Equipment for explosive atmospheres.

This second edition cancels and replaces the first edition, published in 2006, and constitutes

a technical revision.

The significance of the changes between IEC 60079-28, Edition 2.0 (2015) and IEC 60079-28,

Edition 1.0 (2006), is as listed below:
---------------------- Page: 9 ----------------------
IEC 60079-28:2015 © IEC 2015 – 5 –
Significance of changes with respect to IEC 60079-28:2006
Type
Significant Changes Clause Minor and Extension Major
editorial technical
changes changes
Scope: Expansion to include Group III and EPLs Da, Db and x
Scope: Clarification and list of exclusions for optical 1 x
radiation sources
Normative references: Deletion of IEC 60079-10, and 2 x
addition of IEC 60050-426 and 60050-731
Terms and definitions: Some definitions not used in the 3 x
standard deleted. New definitions added.
General requirements: Introduction of an ignition hazard 4 x
assessment moved to 4, statement for presence of
absorbers added, Explanation of EPLs deleted
Table 1: EPLs versus protection types moved from 5.5 to 5.1 x x
5.1, table modified and extended
Structure of Table 2 changed and extended explanation in 5.2.2.1 x
the notes, but with the same limit values
Table 3 for Group III added 5.2.2.1 x
Table 4 replaces Figure 1 for better application 5.2.2.1 x
Detailed requirements for the measurement of optical power 5.2.2.2 x
added
Detailed requirements for the measurement of optical 5.2.2.3 x
irradiance added
Requirements for the assessment of optical pulses for 5.2.3.1 x
Group II much more detailed 5.2.3.2
5.2.3.3
5.2.3.4
Requirements for the assessment of optical pulses for 5.2.3.5 x
Group I and Group III added
Ignition tests: Notes 1 and 2 added 5.2.4 x
Over-power/energy fault protection: Title changed and 5.2.5 x
wording modified for clarity
Radiation inside optical fibre or cable: requirements added, 5.3.2 C1
e.g. pull test
Radiation inside enclosures: IP 6X enclosures, “p” or “t” 5.3.3 x
enclosures added
Optical system with interlock “op sh” 5.4 x
Table 3 deleted, Figure 1 with interlock cutoff delay times
added
Type verifications and tests: structure changed (editorial, 6 x
without changing the requirements)
Marking: markings required by IEC 60079-0 deleted. 7 x
Examples of marking: example with combination of op is
with other types of protection added
Ignition hazard assessment: Flow chart in Figure C.1 Annex C x
modified for better understanding
Old Annex E (Introduction of EPLs) deleted. New Annex E Annex E x
provides a flow chart for the assessment of pulses
according to 5.2.3
Relevant IEC-Standards moved to Clause 2 Formerly x
Annex F
---------------------- Page: 10 ----------------------
– 6 – IEC 60079-28:2015 © IEC 2015
Explanation of the Types of Significant Changes:
A) Definitions
1) Minor and editorial changes: – Clarification
– Decrease of technical requirements
– Minor technical change
– Editorial corrections

These are changes which modify requirements in an editorial or a minor technical way. They include changes of

the wording to clarify technical requirements without any technical change, or a reduction in level of existing

requirement.
2) Extension: Addition of technical options

These are changes which add new or modify existing technical requirements, in a way that new options are given,

but without increasing requirements for equipment that was fully compliant with the previous standard. Therefore,

these will not have to be considered for products in conformity with the preceding edition.

3) Major technical changes:
– addition of technical requirements
– increase of technical requirements

These are changes to technical requirements (addition, increase of the level or removal) made in a way that a

product in conformity with the preceding edition will not always be able to fulfil the requirements given in the later

edition. These changes have to be considered for products in conformity with the preceding edition. For these

changes additional information is provided in clause B) below.

Note These changes represent current technological knowledge. However, these changes should not normally

have an influence on equipment already placed on the market.
B) Information about the background of ‘Major technical changes’

C1 For the protection concept “protected radiation op pr” some requirements like a pull test for optical fibres or

cables have been added.
The text of this standard is based on the following documents:
FDIS Report on voting
31/1178/FDIS 31/1193/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.

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

A list of all parts in the IEC 60079 series, published under the general title Explosive

atmospheres, can be found on the IEC website.
---------------------- Page: 11 ----------------------
IEC 60079-28:2015 © IEC 2015 – 7 –

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 interpretation sheet of November 2019 have been included in this copy.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
---------------------- Page: 12 ----------------------
– 8 – IEC 60079-28:2015 © IEC 2015
INTRODUCTION

Optical equipment in the form of lamps, lasers, LEDs, optical fibers etc. is increasingly used

for communications, surveying, sensing and measurement. In material processing, optical

radiation of high irradiance is used. Where the installation is inside or close to explosive

atmospheres, the radia
...

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