Explosive atmospheres - Part 26: Equipment with Equipment Protection Level (EPL) Ga

IEC 60079-26:2014 is available as IEC 60079-26:2014 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.
IEC 60079-26:2014 specifies alternative requirements for construction, test and marking for electrical equipment that provides Equipment Protection Level (EPL) Ga when single standardised Types of Protection (e.g. Ex "ia", Ex "ma", Ex "da") cannot be applied. This standard also applies to equipment mounted across a boundary where different Equipment Protection Levels may be required. This electrical equipment, within the operational parameters specified by the manufacturer, ensures a very high Level of Protection that includes rare malfunctions related to the equipment or two malfunctions occurring independently of each other. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard takes precedence. This third edition cancels and replaces the second edition published in 2006 and constitutes a technical revision. The numerous changes are identified in the Foreword of the document. Keywords: Equipment Protection Level (EPL) Ga

Atmosphères explosives - Partie 26: Matériel d'un niveau de protection du matériel (EPL) Ga

IEC 60079-26:2014 est disponible sous forme de IEC 60079-26:2014 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.
IEC 60079-26:2014 spécifie les exigences alternatives relatives à la construction, aux essais et au marquage du matériel électrique fournissant le niveau de protection du matériel (EPL, Equipment Protection Level) Ga lorsque des types normalisés uniques de Protection (comme par ex. Ex "ia", Ex "ma", Ex "da") ne peuvent pas être appliqués. La présente norme s'applique au matériel installé en chevauchement sur des emplacements pour lesquels différents niveaux de protection du matériel peuvent être exigés.Ce matériel électrique assure, dans les limites des paramètres de fonctionnement spécifiés par le constructeur, un très haut niveau de protection prenant en compte le cas de rares dysfonctionnements liés au matériel, ou d'apparition simultanée de deux dysfonctionnements indépendants l'un de l'autre. La présente norme complète et modifie les exigences générales de l'IEC 60079-0. Lorsqu'une exigence de la présente norme entre en contradiction avec une exigence de l'IEC 60079-0, l'exigence de la présente norme prévaut. Cette troisième édition annule et remplace la deuxième édition parue en 2006 et constitue une révision technique. Les nombreux changements sont identifiés dans l'avant-propos du document. Mots clés: protection du matériel (EPL) Ga

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Publication Date
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IEC 60079-26
Edition 3.0 2014-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 26: Equipment with Equipment Protection Level (EPL) Ga
Atmosphères explosives –
Partie 26: Matériel d'un niveau de protection du matériel (EPL) Ga
IEC 60079-26:2014-10(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60079-26
Edition 3.0 2014-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 26: Equipment with Equipment Protection Level (EPL) Ga
Atmosphères explosives –
Partie 26: Matériel d'un niveau de protection du matériel (EPL) Ga
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX Q
ICS 29.260.20 ISBN 978-2-8322-1903-4

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 ----------------------
– 2 – IEC 60079-26:2014 © IEC 2014
CONTENTS

FOREWORD ......................................................................................................................... 3

1 Scope ............................................................................................................................ 6

2 Normative references..................................................................................................... 6

3 Terms and definitions .................................................................................................... 7

4 Requirements for design and construction ...................................................................... 7

4.1 Protection measures against ignition hazards of the electrical circuits .................... 7

4.1.1 General ......................................................................................................... 7

4.1.2 Application of two independent Types of Protection providing EPL Gb ............. 7

4.1.3 Application of a Type of Protection providing EPL Gb and a separation

element ......................................................................................................... 8

4.2 Equipment with moving parts ............................................................................... 12

4.2.1 Frictional heating ......................................................................................... 12

4.2.2 Damage arising from failure of moving parts ................................................. 12

4.2.3 Light metals ................................................................................................. 12

4.3 Process connection ............................................................................................. 13

5 Type tests ................................................................................................................... 13

5.1 Standardized types of protection ......................................................................... 13

5.2 Separation elements ........................................................................................... 13

5.3 Temperature evaluation ....................................................................................... 13

6 Marking ....................................................................................................................... 14

6.1 General ............................................................................................................... 14

6.2 Examples of marking ........................................................................................... 14

7 Instructions.................................................................................................................. 14

7.1 Separation elements: .......................................................................................... 14

7.2 Process connection: ............................................................................................ 15

7.3 EPL allocation ..................................................................................................... 15

Bibliography ....................................................................................................................... 16

Figure 1 – Example of a partition wall with a conductor bushing considered as gas

diffusion tight ........................................................................................................................ 9

Figure 2 – Example of a separation element with a cylindrical shaft joint and

naturalventilation ................................................................................................................ 12

Table 1 – Separation elements ............................................................................................ 11

---------------------- Page: 4 ----------------------
IEC 60079-26:2014 © IEC 2014 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 26: Equipment with Equipment Protection Level
(EPL) Ga
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

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

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

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

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

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

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 60079-26 has been prepared by IEC technical committee 31:

Equipment for explosive atmospheres.

This third edition cancels and replaces the second edition published in 2006 and constitutes a

technical revision.
---------------------- Page: 5 ----------------------
– 4 – IEC 60079-26:2014 © IEC 2014

This edition includes the following significant changes with respect to the previous edition:

Type
Changes Clause Minor and Extension Major
editorial technical
changes changes
Notes deleted 1 X
Reference to associated apparatus deleted 1 X
Additional normative references included 3 X
Requirements against mechanical and
electrostatic ignition hazards deleted (now 4.1 X
covered in IEC 60079-0)
Requirement for separation element detailed
4.1.3.2 X
regarding external influences
Intrinsic safety Ex ia as single type of protection
4.2.2
including associated apparatus deleted (now X
(ed.2)
covered by EPL)
Encapsulation Ex ma as single type of protection 4.2.3
deleted (now covered by EPL) (ed.2)
Conditions a) and b) linked with an “and” ,
therefore requirement of “flameproof joint” deleted
in following clause. Both requirements already 4.3 X
covered by separation elements and standardised
process connections.
Process connection requires a sufficiently tight
4.3 X
joint: IP66 added alternatively to IP67
Requirement for isolated conductive components 4.4
deleted (now covered in IEC 60079-0) (ed.2)
Requirements for non-conductive enclosures 4.5
deleted (now covered in IEC 60079-0) (ed.2)
Test of partition walls according to 4.1.3.2 b) is
5.2 C1
specified in more detail
Marking example for associated apparatus deleted 6.2 b) X
Note 3 with an additional example added 6.2 X
Specification of material of partition wall required
7 X
in instructions (also required in 4.1.3.2)
Alternative risk assessment method deleted (is AnnexA
now generally introduced) (ed.2)

NOTE The technical changes referred to include the significance of technical changes in the revised IEC

Standard, but they do not form an exhaustive list of all modifications from the previous version.

Explanation of the types of 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.
---------------------- Page: 6 ----------------------
IEC 60079-26:2014 © IEC 2014 – 5 –
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: Introduction of type tests for separation elements according to “4.1.3.2 b)”
The text of this standard is based on the following documents:
FDIS Report on voting
31/1146/FDIS 31/1155/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.

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.
---------------------- Page: 7 ----------------------
– 6 – IEC 60079-26:2014 © IEC 2014
EXPLOSIVE ATMOSPHERES –
Part 26: Equipment with Equipment Protection Level
(EPL) Ga
1 Scope

This part of IEC 60079 specifies alternative requirements for construction, test and marking

for electrical equipment that provides Equipment Protection Level (EPL) Ga when single

standardised Types of Protection (e.g. Ex “ia” , Ex “ma”, Ex “da”) cannot be applied. This

standard also applies to equipment mounted across a boundary where different Equipment

Protection Levels may be required.

EXAMPLE: Equipment installed in the wall of a storage vessel containing Zone 0 (requiring EPL Ga) inside an

area defined as Zone 1 (requiring EPL Gb).

This electrical equipment, within the operational parameters specified by the manufacturer,

ensures a very high Level of Protection that includes rare malfunctions related to the

equipment or two malfunctions occurring independently of each other.

NOTE A malfunction may result from a failure of the component parts of the electrical equipment or from

anticipated externally applied influences. Two independent malfunctions which may occur more frequently and

which, separately, would not create an ignition hazard but which, in combination, could create a potential ignition

hazard, are regarded as occurring together to form a rare malfunction.

This standard supplements and modifies the general requirements of IEC 60079-0. Where a

requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of

this standard takes precedence.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60079-0, Explosive atmospheres − Part 0: Equipment − General requirements

IEC 60079-1, Explosive atmospheres − Part 1: Equipment protection by flameproof enclosures

"d"

IEC 60079-11, Explosive atmospheres − Part 11: Equipment protection by intrinsic safety "i"

IEC 60695-11-10, Fire hazard testing − Part 11-10: Test flames − 50 W horizontal and vertical

flame test methods
IEC 60529, Degrees of protection provided by enclosures (IP Code)
---------------------- Page: 8 ----------------------
IEC 60079-26:2014 © IEC 2014 – 7 –
3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC 60079-0 and the

following apply.

NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426.

3.1
separation element

mechanical element inside the equipment, which separates different parts of the equipment

with different EPLs

Note 1 to entry: A separation element consists of a mechanical partition wall, which may be combined with a

flameproof joint or a natural ventilation
4 Requirements for design and construction
4.1 Protection measures against ignition hazards of the electrical circuits
4.1.1 General

The equipment shall comply with the requirements of 4.1.2 or 4.1.3 in the event of a failure of

one equipment means of protection, by the provision of a second independent means of

protection.

NOTE 1 Types of Protection according to EPL Ga do not require a second independant means of protection, e.g.

Ex “ia” (IEC 60079-11), Ex “ma” (IEC 60079-18), Ex “da” (IEC 60079-1).

Electrical connections and permanently connected cables of the equipment sited within an

area requiring EPL Ga equipment shall comply with the same Level of Protection required by

this standard, for example a cable suitable for EPL Gb containing non-Ex “ia” circuits

additionally protected by a flameproof conduit or a cable suitable for EPL Gb provided with

earth leakage protection.

NOTE 2 Detailed cable and installation requirements for Types of Protection accepted as achieving EPL Ga

beyond intrinsically safe circuits are under consideration in IEC 60079-14.

NOTE 3 Because of ignition hazards which can arise from faults and/or transient circulating currents in the

potential equalization system, galvanic isolation in the power and signal connections to the equipment according to

4.1.2 and 4.1.3 is commonly applied along with minimizing the effect of transient fault currents in the potential

equalization network by the use of electrical protection equipment such as sensitive earth leakage monitors.

4.1.2 Application of two independent Types of Protection providing EPL Gb

Electrical equipment shall comply with the requirements of two independent Types of

Protection that provide EPL Gb. If one Type of Protection fails, the other Type of Protection

shall continue to function. The independent Types of Protection shall not have a common

mode of failure, except as specified in this clause. Combined types of protection providing

EPL Gb shall depend on different physical protection principles.

NOTE 1 An example of a common mode of failure is if an Ex “d” enclosure containing arcing components is

installed inside an Ex “e” enclosure. Should the Ex “d” enclosure be compromised, it would also compromise the

Ex “e” enclosure.

NOTE 2 The combination of Ex “d” and Ex “q” both depend on the avoidance of flame propagation (same physical

protection principle) and may not be useful in combination. In practice, some combinations may not be useful, for

example the combination of oil immersion “o” and powder filling “q”.

Where combined types of protection are used, it shall be possible for each Type of Protection

to be tested individually (see 5.1).

Both Types of Protection shall be assessed using the most arduous fault condition of the

other Type of Protection. When combining intrinsic safety, Type of Protection “ib”, with other

---------------------- Page: 9 ----------------------
– 8 – IEC 60079-26:2014 © IEC 2014

Types of Protection, the second Type of Protection shall be assessed, with the most arduous

fault condition applied to the intrinsically safe circuit. Thermal dissipation shall be considered

in case of a fault of one Type of protection.

When using two Types of Protection, which both rely on the same parameter (for example, the

creepage distance combining Ex “ib” with Ex “e”), the most stringent requirement of both

Types of Protection shall be applied.

If two Types of Protection are combined which both rely on the enclosure, one of the following

shall be met:

a) if two enclosures are used (one totally enclosed within the other), each enclosure shall

comply with the requirements of the respective Type of Protection; or

b) if only one enclosure is used, the enclosure and the cable glands shall meet the impact

test requirements of IEC 60079-0, using the Group I values.

Examples of relevant combinations of two independent Types of Protection are as follows:

– inductive transmitters (for example proximity switches, electrical position sensors) with

intrinsic safety “ib” enclosed by encapsulation “mb”. The connections to intrinsically safe

“ib” circuits can be protected by the increased safety “e”;

– a luminaire designed as increased safety “e”may be included in a flameproof enclosure

“d”:

– measuring transducers with intrinsic safety “ib” and a flameproof enclosure “d”;

– equipment with electrical circuits of intrinsic safety “ib”, additionally protected by powder

filling “q”;

– electromagnetic valves with encapsulation “mb”, enclosed by a flameproof enclosure “d”;

– increased safety “e”, with pressurized equipment “pxb”.

4.1.3 Application of a Type of Protection providing EPL Gb and a separation element

4.1.3.1 General

Equipment which is mounted through or forms part of the boundary wall to an area requiring

EPL Ga and contains electrical circuits which do not comply with EPL Ga shall comply with at

least one of the Types of Protection providing EPL Gb. Additionally, it shall contain a

mechanical separation element as part of the equipment to separate the electrical circuits of

the equipment from the area requiring EPL Ga.
If the Type of Protection fails, the separation element shall:

a) prevent flame propagation through the equipment into the area requiring EPL Ga,

b) maintain its safety characteristics,

c) not exceed the maximum surface temperature of the specified temperature class of the

equipment (see 5.3).
4.1.3.2 Partition walls
Partition walls shall be constructed of either:
a) corrosion-resistant metals, glass or ceramics,

b) other materials which can be verified to provide the same level of safety. In this case, the

certificate number shall include the "X" suffix in accordance with the marking requirements

of IEC 60079-0.

If the wall thickness is less than 1 mm, the certificate number shall include the "X" suffix in

accordance with the marking requirements of IEC 60079-0 and the Specific Conditions of Use

---------------------- Page: 10 ----------------------
IEC 60079-26:2014 © IEC 2014 – 9 –

listed on the certificate shall indicate that the material shall not be subject to environmental

conditions which might adversely affect the partition wall.

If the partition wall is under constant vibrational stress (for example vibrating membranes), the

minimum endurance limit at maximum amplitude shall be defined in the documentation (see

Clause 7). Due to specified process pressure, loads or temperature, the separation element

shall not impair the Type of Protection.

A wall thickness less than 1 mm is only permitted in combination with intrinsic safety “ib”, or a

flameproof joint or natural ventilation (see 4.1.3.3). For glass or ceramics, a minimum

thickness of 1/10 of the diameter/maximum dimension but not less than 1 mm is required.

In addition to the requirements of 4.1.3.1 to 4.1.3.3, metallic partition walls with a thickness

≥ 1 mm may be provided with suitable conductor bushings (see Figure 1).

To avoid a critical concentration of explosive gas atmosphere diffusing from the area requiring

EPL Ga into the enclosure containing the electrical circuits, the leakage rate through the

bushing shall be low compared to the leakage rate from the enclosure into the free

atmosphere. For example this could be done using a standard enclosure with an IP67 rating

according to IEC 60529, a bushing with a leakage rate equivalent to a helium-leakage rate

-2 –4 5

less than 10 Pa×l/s (10 mbar × l/s) at a pressure difference of 10 Pa (1 bar). This can be

achieved, for example, by using a glass or ceramic bushing as shown in Figure 1.
Metallic sleeve, corrosion
resistant (wall thickness ≥ 1 mm)
Bushing insulator (e.g. melted
≥ 10 mm glass, brazed ceramics)
Less hazardous
area
“ia” circuit
Area
Ex “ia” circuit
requiring
Non-“ia”
EPL Ga
Non-“ia” supply circuit
circuit
(e.g. Ex “e”)
Partition wall
Welded
(t ≥1 mm)
(joint ≥ 1 mm)
Electrical equipment
IEC
Figure 1 – Example of a partition wall with a conductor bushing
considered as gas diffusion tight
4.1.3.3 Requirements depending on the thickness of the partition wall
...

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