oSIST IEC 60079-0:2018

IEC 60079-0 ®
Edition 7.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 0: Equipment – General requirements

Atmosphères explosives –
Partie 0: Matériel – Exigences générales
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IEC 60079-0 ®
Edition 7.0 2017-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Explosive atmospheres –
Part 0: Equipment – General requirements

Atmosphères explosives –
Partie 0: Matériel – Exigences générales

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-5065-5

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-0
Edition 7.0  2017-12
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment – General requirements

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
31/1455/DISH 31/1464/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 of Subclause 16.6 of IEC 60079-0:2017
The TC31/CAG requested (Resolution 2 of 2018-04-19) that WG22 prepare an interpretation
sheet based on IECEx Decision Sheet DS2018/002 addressing the assignment of entry point
and branching point temperatures of electrical rotating machines.
Details of interpretation:
requirements
Interpretation of Subclause 16.6: Temperature at branching point and entry point:
Question: Subclause 16.6 of IEC 60079-0:2017 states “When the temperature under rated
conditions is higher than 70 °C at the entry point or 80 °C at the branching point of the
conductors, information shall be marked on the equipment exterior to provide guidance to the
user on the proper selection of cable and cable gland or conductors in conduit.”
ICS 29.260.20
– 2 – IEC 60079-0:2017/ISH1:2019
 IEC 2019
It is not normal practice for electrical rotating machines to be tested with the cable entry
devices and cables that might be used in an actual installation, but with the cables available
at the manufacturer’s test area. In many cases, there will be no formal entry device as the
cables will enter via the space reserved for fixing of a gland plate.
How shall the relevant entry point and branching point temperatures be determined?
Interpretation: The use of the maximum internal air space temperature to represent the
maximum service temperature of terminal box gaskets and seals, the cable branching point
temperature, and the entry point temperature reflects the normal practice of testing electrical
rotating machines without prior knowledge of the actual glands and cables to be used for
installation. The production of heat from the electrical rotating machine connections is
generally insignificant with respect to the production of heat from the machine windings and
core.
Further amplification:
1) The entry point of the cable where the temperature is measured should be sealed so far
as possible to ensure that there is minimum air-circulation which can reduce the measured
temperature.
2) This is not intended to apply to any gasket between the terminal box and the frame of the
electrical rotating machine, where higher temperatures may be recorded, but only to the
gasket between the terminal box and its lid.
Although written in the context of electrical rotating machines, there may be other types of
equipment where an equivalent approach is applicable

 IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
IEC 60079-0
Edition 7.0  2017-12
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment – General requirements

INTERPRETATION SHEET 2
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
31/1469/DISH 31/1486/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.

___________
Question:
How shall marking be shown for equipment covered by both the electrical and non-electrical
standards (IEC 60079 and ISO 80079 series)?
Answer:
Equipment which includes both an electrical part and a non-electrical part shall have
combined marking. For example:
Ex db h IIA T4 Gb
Ex h tb IIIC T135 °C Db
ICS 29.260.20
– 2 – IEC 60079-0:2017/ISH2:2019
 IEC 2019
It will be clearer for the user that the combined risk of the electrical part and the non-electrical
part, covered by a single certificate, has been assessed for the complete equipment, stating
one EPL, one equipment Group and one temperature class for Gas and the same for Dust
(but showing a maximum surface temperature instead of a temperature class). It is also noted
that Ex Components are not marked with either a temperature class (Group II) or a maximum
surface temperature (Group III).
For equipment where separate certificates have been prepared, with one for the electrical
parts, and one for the non-electrical parts, it is appropriate to have separate electrical and
non-electrical marking strings, each with its own associated certificate number.
NOTE Additional guidance on the marking of assemblies is given in IEC TS 60079-46.

– 2 – IEC 60079-0:2017  IEC 2017
CONTENTS
FOREWORD . 8
1 Scope . 15
2 Normative references . 16
3 Terms and definitions . 18
4 Equipment grouping . 36
4.1 General . 36
4.2 Group I . 36
4.3 Group II . 36
4.4 Group III . 36
4.5 Equipment for a particular explosive gas atmosphere . 37
5 Temperatures . 37
5.1 Environmental influences . 37
5.1.1 Ambient temperature . 37
5.1.2 External source of heating or cooling . 37
5.2 Service temperature . 37
5.3 Maximum surface temperature . 38
5.3.1 Determination of maximum surface temperature . 38
5.3.2 Limitation of maximum surface temperature . 38
5.3.3 Small component temperature for Group I or Group II electrical

equipment. 39
5.3.4 Component temperature of smooth surfaces for Group I or Group II
electrical equipment . 40
6 Requirements for all equipment . 41
6.1 General . 41
6.2 Mechanical strength of equipment . 41
6.3 Opening times . 41
6.4 Circulating currents in enclosures (e.g. of large electric machines) . 42
6.5 Gasket retention . 42
6.6 Electromagnetic and ultrasonic energy radiating equipment . 42
6.6.1 General . 42
6.6.2 Radio frequency sources . 42
6.6.3 Ultrasonic sources . 43
6.6.4 Lasers, luminaires, and other non-divergent continuous wave optical
sources. 44
7 Non-metallic enclosures and non-metallic parts of enclosures . 44
7.1 General . 44
7.1.1 Applicability . 44
7.1.2 Specification of materials . 44
7.2 Thermal endurance . 45
7.2.1 Tests for thermal endurance . 45
7.2.2 Material selection . 46
7.2.3 Alternative qualification of elastomeric sealing O-rings . 46
7.3 Resistance to ultraviolet light . 46
7.4 Electrostatic charges on external non-metallic materials . 47
7.4.1 Applicability . 47
7.4.2 Avoidance of a build-up of electrostatic charge for Group I or Group II . 47

7.4.3 Avoidance of a build-up of electrostatic charge for Group III . 49
7.5 Attached external conductive parts . 50
8 Metallic enclosures and metallic parts of enclosures . 51
8.1 Material composition . 51
8.2 Group I . 51
8.3 Group II . 51
8.4 Group III . 52
8.5 Copper Alloys . 52
9 Fasteners . 52
9.1 General . 52
9.2 Special fasteners . 53
9.3 Holes for special fasteners . 53
9.3.1 Thread engagement . 53
9.3.2 Tolerance and clearance . 53
9.4 Hexagon socket set screws . 54
10 Interlocking devices . 54
11 Bushings . 54
12 (Reserved for future use) . 54
13 Ex Components . 54
13.1 General . 54
13.2 Mounting . 55
13.3 Internal mounting . 55
13.4 External mounting . 55
13.5 Ex Component certificate . 55
14 Connection facilities . 55
14.1 General . 55
14.2 Type of protection . 56
14.3 Creepage and clearance . 56
15 Connection facilities for earthing or bonding conductors . 56
15.1 Equipment requiring earthing or bonding . 56
15.1.1 Internal earthing . 56
15.1.2 External bonding. 56
15.2 Equipment not requiring earthing . 56
15.3 Size of protective earthing conductor connection . 56
15.4 Size of equipotential bonding conductor connection . 57
15.5 Protection against corrosion . 57
15.6 Secureness of electrical connections . 57
15.7 Internal earth continuity plate . 57
16 Entries into enclosures . 57
16.1 General . 57
16.2 Identification of entries . 57
16.3 Cable glands . 58
16.4 Blanking elements. 58
16.5 Thread adapters . 58
16.6 Temperature at branching point and entry point . 59
16.7 Electrostatic charges of cable sheaths . 59
17 Supplementary requirements for electric machines . 60
17.1 General . 60

– 4 – IEC 60079-0:2017  IEC 2017
17.2 Ventilation. 60
17.2.1 Ventilation openings . 60
17.2.2 Materials for external fans . 60
17.2.3 Cooling fans of rotating electric machines . 60
17.2.4 Auxiliary motor cooling fans . 61
17.2.5 Room ventilating fans . 61
17.3 Bearings . 62
18 Supplementary requirements for switchgear . 62
18.1 Flammable dielectric . 62
18.2 Disconnectors . 62
18.3 Group I – Provisions for locking . 63
18.4 Doors and covers . 63
19 Reserved for future use . 63
20 Supplementary requirements for external plugs, socket outlets and connectors for
field wiring connection . 63
20.1 General . 63
20.2 Explosive gas atmospheres . 64
20.3 Explosive dust atmospheres . 64
20.4 Energized plugs . 64
21 Supplementary requirements for luminaires . 64
21.1 General . 64
21.2 Covers for luminaires of EPL Mb, EPL Gb, or EPL Db . 64
21.3 Covers for luminaires of EPL Gc or EPL Dc . 65
21.4 Sodium lamps . 65
22 Supplementary requirements for caplights and handlights . 65
22.1 Group I caplights . 65
22.2 Group II and Group III caplights and handlights . 65
23 Equipment incorporating cells and batteries . 66
23.1 General . 66
23.2 Interconnection of cells to form batteries . 66
23.3 Cell types . 66
23.4 Cells in a battery . 69
23.5 Ratings of batteries . 69
23.6 Interchangeability . 69
23.7 Charging of primary batteries . 69
23.8 Leakage . 69
23.9 Connections . 69
23.10 Orientation . 69
23.11 Replacement of cells or batteries . 69
23.12 Replaceable battery pack . 70
24 Documentation . 70
25 Compliance of prototype or sample with documents . 70
26 Type tests . 70
26.1 General . 70
26.2 Test configuration . 70
26.3 Tests in explosive test mixtures . 70
26.4 Tests of enclosures . 71
26.4.1 Order of tests . 71

26.4.2 Resistance to impact . 73
26.4.3 Drop test . 74
26.4.4 Acceptance criteria . 75
26.4.5 Degree of protection (IP) by enclosures . 75
26.5 Thermal tests . 76
26.5.1 Temperature measurement . 76
26.5.2 Thermal shock test . 78
26.5.3 Small component ignition test (Group I and Group II) . 78
26.6 Torque test for bushings . 79
26.6.1 Test procedure . 79
26.6.2 Acceptance criteria . 80
26.7 Non-metallic enclosures or non-metallic parts of enclosures . 80
26.7.1 General . 80
26.7.2 Test temperatures . 80
26.8 Thermal endurance to heat . 80
26.9 Thermal endurance to cold . 81
26.10 Resistance to UV light . 81
26.10.1 General . 81
26.10.2 Light exposure . 82
26.10.3 Acceptance criteria . 82
26.11 Resistance to chemical agents for Group I equipment . 82
26.12 Earth continuity . 83
26.13 Surface resistance test of parts of enclosures of non-metallic materials . 84
26.14 Measurement of capacitance . 85
26.14.1 General . 85
26.14.2 Test procedure . 85
26.15 Verification of ratings of ventilating fans . 86
26.16 Alternative qualification of elastomeric sealing O-rings . 86
26.17 Transferred charge test . 86
26.17.1 Test equipment . 86
26.17.2 Test sample . 87
26.17.3 Test procedure . 87
27 Routine tests . 88
28 Manufacturer's responsibility . 88
28.1 Conformity with the documentation . 88
28.2 Certificate . 89
28.3 Responsibility for marking . 89
29 Marking . 89
29.1 Applicability . 89
29.2 Location . 89
29.3 General . 89
29.4 Ex marking for explosive gas atmospheres . 90
29.5 Ex marking for explosive dust atmospheres . 92
29.6 Combined types (or levels) of protection . 95
29.7 Multiple types of protection . 95
29.8 Ga equipment using two independent Gb types (or levels) of protection . 95
29.9 Boundary wall . 95
29.10 Ex Components . 95
29.11 Small Ex Equipment and small Ex Components . 96

– 6 – IEC 60079-0:2017  IEC 2017
29.12 Extremely small Ex Equipment and extremely small Ex Components . 96
29.13 Warning markings . 96
29.14 Cells and batteries . 97
29.15 Electric machines operated with a converter . 97
29.16 Examples of marking . 98
30 Instructions . 101
30.1 General . 101
30.2 Cells and batteries . 102
30.3 Electric machines . 103
30.4 Ventilating fans . 103
30.5 Cable glands . 104
Annex A (normative) Supplementary requirements for cable glands . 105
A.1 General . 105
A.2 Constructional requirements . 105
A.2.1 Cable sealing . 105
A.2.2 Filling compounds . 106
A.2.3 Clamping . 106
A.2.4 Lead-in of cable . 106
A.2.5 Release by a tool . 107
A.2.6 Fixing . 107
A.2.7 Degree of protection . 107
A.3 Type tests . 107
A.3.1 Tests of clamping of non-armoured and braided cables . 107
A.3.2 Tests of clamping of armoured cables . 110
A.3.3 Type test for resistance to impact . 111
A.3.4 Test for degree of protection (IP) of cable glands . 112
A.4 Marking . 113
A.4.1 Marking of cable glands . 113
A.4.2 Identification of cable-sealing rings . 113
A.5 Instructions . 113
Annex B (normative) Requirements for Ex Components . 115
Annex C (informative) Example of rig for resistance to impact test . 118
Annex D (informative) Electric machines connected to converters . 119
Annex E (informative) Temperature evaluation of electric machines . 120
Annex F (informative) Guidance flowchart for tests of non-metallic enclosures or non-
metallic parts of enclosures (26.4) . 123
Annex G (informative) Guidance flowchart for tests of cable glands . 124
Annex H (informative) Shaft voltages resulting in motor bearing or shaft brush
sparking Discharge energy calculation . 125
H.1 General . 125
H.2 Assessment of the risk of ignition using ignition energy calculation . 125
H.3 Shaft voltage determination for a rotating machine . 126
H.4 Capacitance “C” calculation for a rotating machine . 126
H.5 Energy “E” calculation for a rotating machine . 129
H.6 Assessment using reference curves . 129
Bibliography . 131

Figure 1 – Typical battery examples . 20

Figure 2 – Typical battery compartment . 21
Figure 3 – Typical replaceable battery pack . 22
Figure 4 – Tolerances and clearance for threaded fasteners . 53
Figure 5 – Contact surface under head of fastener with a reduced shank . 54
Figure 6 – Cable gland . 59
Figure 7 – Conduit entry . 59
Figure 8 – Assembly of test sample for earth-continuity test . 84
Figure 9 – Test piece with painted electrodes . 85
Figure 10 – Compression set of an O-ring . 86
Figure A.1 – Illustration of the terms used for cable glands . 106
Figure A.2 – Rounded edge of the point of entry of the flexible cable . 107
Figure A.3 – Example of rig for resistance to impact test . 112
Figure C.1 – Example of rig for resistance to impact test . 118
Figure F.1 – Non-metallic enclosures or non-metallic parts of enclosures . 123
Figure H.1 – Capacitance stored in bearing clearance of sleeve bearing Between
journal and outer bearing housing . 128
Figure H.2 – Air-gap between stator and rotor . 128
Figure H.3 – Typical surfaces that form capacitors from the motor shaft to ground . 129
Figure H.4 – Capacitive ignition curves . 130

Table 1 – Ambient temperatures in service and additional marking . 37
Table 2 – Classification of maximum surface temperatures for Group II electrical
equipment . 38
Table 3 – Assessment of temperature classification according to component size . 40
Table 4 – Assessment of temperature classification Component surface area ≥ 20 mm . 40
Table 5 – Threshold power . 43
Table 6 – Threshold energy . 43
Table 7 – Limitation of surface areas . 48
Table 8 – Maximum diameter or width . 49
Table 9 – Limitation of thickness of non-metallic layer . 49
Table 10 – Maximum acceptable transferred charge . 49
Table 11 – Maximum capacitance of unearthed conductive parts . 51
Table 12 – Minimum cross-sectional area of PE conductors . 57
Table 13 – Primary cells . 66
Table 14 – Secondary cells . 68
Table 15 – Tests for resistance to impact .
...

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Eksplozivne atmosfere - 0. del: Oprema - Splošne zahteveExplosionsgefährdete Bereiche - Teil 0: Betriebsmittel - Allgemeine AnforderungenAtmosphères explosives - Partie 0: Matériel - Exigences généralesExplosive atmospheres - Part 0: Equipment - General requirements29.260.20Electrical apparatus for explosive atmospheresICS:Ta slovenski standard je istoveten z:IEC 60079-0 Ed. 7.0oSIST IEC 60079-0:2018en,fr,de01-april-2018oSIST IEC 60079-0:2018SLOVENSKI
STANDARD
IEC 60079-0 Edition 7.0 2017-12 INTERNATIONAL STANDARD NORME INTERNATIONALE Explosive atmospheres –
Part 0: Equipment – General requirements
Atmosphères explosives –
Partie 0: Matériel – Exigences générales INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE
ICS 29.260.20
ISBN 978-2-8322-5065-5
– 2 – IEC 60079-0:2017  IEC 2017 CONTENTS FOREWORD . 8 1 Scope . 15 2 Normative references . 16 3 Terms and definitions . 18 4 Equipment grouping . 36 4.1 General . 36 4.2 Group I . 36 4.3 Group II . 36 4.4 Group III . 36 4.5 Equipment for a particular explosive gas atmosphere . 37 5 Temperatures . 37 5.1 Environmental influences . 37 5.1.1 Ambient temperature . 37 5.1.2 External source of heating or cooling . 37 5.2 Service temperature . 37 5.3 Maximum surface temperature . 38 5.3.1 Determination of maximum surface temperature . 38 5.3.2 Limitation of maximum surface temperature . 38 5.3.3 Small component temperature for Group I or Group II electrical equipment. 39 5.3.4 Component temperature of smooth surfaces for Group I or Group II electrical equipment . 40 6 Requirements for all equipment . 41 6.1 General . 41 6.2 Mechanical strength of equipment . 41 6.3 Opening times . 41 6.4 Circulating currents in enclosures (e.g. of large electric machines) . 42 6.5 Gasket retention . 42 6.6 Electromagnetic and ultrasonic energy radiating equipment . 42 6.6.1 General . 42 6.6.2 Radio frequency sources . 42 6.6.3 Ultrasonic sources . 43 6.6.4 Lasers, luminaires, and other non-divergent continuous wave optical sources. 44 7 Non-metallic enclosures and non-metallic parts of enclosures . 44 7.1 General . 44 7.1.1 Applicability . 44 7.1.2 Specification of materials . 44 7.2 Thermal endurance . 45 7.2.1 Tests for thermal endurance . 45 7.2.2 Material selection . 46 7.2.3 Alternative qualification of elastomeric sealing O-rings . 46 7.3 Resistance to ultraviolet light . 46 7.4 Electrostatic charges on external non-metallic materials . 47 7.4.1 Applicability . 47 7.4.2 Avoidance of a build-up of electrostatic charge for Group I or Group II . 47 oSIST IEC 60079-0:2018

7.4.3 Avoidance of a build-up of electrostatic charge for Group III . 49 7.5 Attached external conductive parts . 50 8 Metallic enclosures and metallic parts of enclosures . 51 8.1 Material composition . 51 8.2 Group I . 51 8.3 Group II . 51 8.4 Group III . 52 8.5 Copper Alloys . 52 9 Fasteners . 52 9.1 General . 52 9.2 Special fasteners . 53 9.3 Holes for special fasteners . 53 9.3.1 Thread engagement . 53 9.3.2 Tolerance and clearance . 53 9.4 Hexagon socket set screws . 54 10 Interlocking devices . 54 11 Bushings . 54 12 (Reserved for future use) . 54 13 Ex Components . 54 13.1 General . 54 13.2 Mounting . 55 13.3 Internal mounting . 55 13.4 External mounting . 55 13.5 Ex Component certificate . 55 14 Connection facilities . 55 14.1 General . 55 14.2 Type of protection . 56 14.3 Creepage and clearance . 56 15 Connection facilities for earthing or bonding conductors . 56 15.1 Equipment requiring earthing or bonding . 56 15.1.1 Internal earthing . 56 15.1.2 External bonding. 56 15.2 Equipment not requiring earthing . 56 15.3 Size of protective earthing conductor connection . 56 15.4 Size of equipotential bonding conductor connection . 57 15.5 Protection against corrosion . 57 15.6 Secureness of electrical connections . 57 15.7 Internal earth continuity plate . 57 16 Entries into enclosures . 57 16.1 General . 57 16.2 Identification of entries . 57 16.3 Cable glands . 58 16.4 Blanking elements. 58 16.5 Thread adapters . 58 16.6 Temperature at branching point and entry point . 59 16.7 Electrostatic charges of cable sheaths . 59 17 Supplementary requirements for electric machines . 60 17.1 General . 60 oSIST IEC 60079-0:2018

– 4 – IEC 60079-0:2017  IEC 2017 17.2 Ventilation. 60 17.2.1 Ventilation openings . 60 17.2.2 Materials for external fans . 60 17.2.3 Cooling fans of rotating electric machines . 60 17.2.4 Auxiliary motor cooling fans . 61 17.2.5 Room ventilating fans . 61 17.3 Bearings . 62 18 Supplementary requirements for switchgear . 62 18.1 Flammable dielectric . 62 18.2 Disconnectors . 62 18.3 Group I – Provisions for locking . 63 18.4 Doors and covers . 63 19 Reserved for future use . 63 20 Supplementary requirements for external plugs, socket outlets and connectors for field wiring connection . 63 20.1 General . 63 20.2 Explosive gas atmospheres . 64 20.3 Explosive dust atmospheres . 64 20.4 Energized plugs . 64 21 Supplementary requirements for luminaires . 64 21.1 General . 64 21.2 Covers for luminaires of EPL Mb, EPL Gb, or EPL Db . 64 21.3 Covers for luminaires of EPL Gc or EPL Dc . 65 21.4 Sodium lamps . 65 22 Supplementary requirements for caplights and handlights . 65 22.1 Group I caplights . 65 22.2 Group II and Group III caplights and handlights
................................................... 65 23 Equipment incorporating cells and batteries ................................................................... 66 23.1 General ................................................................................................................. 66 23.2 Interconnection of cells to form batteries ............................................................... 66 23.3 Cell types .............................................................................................................. 66 23.4 Cells in a battery ................................................................................................... 69 23.5 Ratings of batteries ............................................................................................... 69 23.6 Interchangeability ................................................................................................. 69 23.7 Charging of primary batteries ................................................................................ 69 23.8 Leakage ................................................................................................................ 69 23.9 Connections .......................................................................................................... 69 23.10 Orientation ............................................................................................................ 69 23.11 Replacement of cells or batteries .......................................................................... 69 23.12 Replaceable battery pack ...................................................................................... 70 24 Documentation .............................................................................................................. 70 25 Compliance of prototype or sample with documents ....................................................... 70 26 Type tests ..................................................................................................................... 70 26.1 General ................................................................................................................. 70 26.2 Test configuration ................................................................................................. 70 26.3 Tests in explosive test mixtures ............................................................................ 70 26.4 Tests of enclosures ............................................................................................... 71 26.4.1 Order of tests ................................................................................................ 71 oSIST IEC 60079-0:2018

26.4.2 Resistance to impact . 73 26.4.3 Drop test . 74 26.4.4 Acceptance criteria . 75 26.4.5 Degree of protection (IP) by enclosures . 75 26.5 Thermal tests . 76 26.5.1 Temperature measurement . 76 26.5.2 Thermal shock test . 78 26.5.3 Small component ignition test (Group I and Group II) . 78 26.6 Torque test for bushings . 79 26.6.1 Test procedure . 79 26.6.2 Acceptance criteria . 80 26.7 Non-metallic enclosures or non-metallic parts of enclosures . 80 26.7.1 General . 80 26.7.2 Test temperatures . 80 26.8 Thermal endurance to heat . 80 26.9 Thermal endurance to cold . 81 26.10 Resistance to UV light . 81 26.10.1 General . 81 26.10.2 Light exposure . 82 26.10.3 Acceptance criteria . 82 26.11 Resistance to chemical agents for Group I equipment . 82 26.12 Earth continuity . 83 26.13 Surface resistance test of parts of enclosures of non-metallic materials . 84 26.14 Measurement of capacitance . 85 26.14.1 General . 85 26.14.2 Test procedure . 85 26.15 Verification of ratings of ventilating fans . 86 26.16 Alternative qualification of elastomeric sealing O-rings . 86 26.17 Transferred charge test . 86 26.17.1 Test equipment . 86 26.17.2 Test sample . 87 26.17.3 Test procedure . 87 27 Routine tests . 88 28 Manufacturer's responsibility . 88 28.1 Conformity with the documentation . 88 28.2 Certificate . 89 28.3 Responsibility for marking . 89 29 Marking . 89 29.1 Applicability . 89 29.2 Location . 89 29.3 General . 89 29.4 Ex marking for explosive gas atmospheres . 90 29.5 Ex marking for explosive dust atmospheres . 92 29.6 Combined types (or levels) of protection . 95 29.7 Multiple types of protection . 95 29.8 Ga equipment using two independent Gb types (or levels) of protection . 95 29.9 Boundary wall . 95 29.10 Ex Components . 95 29.11 Small Ex Equipment and small Ex Components . 96 oSIST IEC 60079-0:2018

– 6 – IEC 60079-0:2017  IEC 2017 29.12 Extremely small Ex Equipment and extremely small Ex Components . 96 29.13 Warning markings . 96 29.14 Cells and batteries . 97 29.15 Electric machines operated with a converter . 97 29.16 Examples of marking . 98 30 Instructions . 101 30.1 General . 101 30.2 Cells and batteries . 102 30.3 Electric machines . 103 30.4 Ventilating fans . 103 30.5 Cable glands . 104 Annex A (normative)
Supplementary requirements for cable glands . 105 A.1 General . 105 A.2 Constructional requirements . 105 A.2.1 Cable sealing . 105 A.2.2 Filling compounds . 106 A.2.3 Clamping . 106 A.2.4 Lead-in of cable . 106 A.2.5 Release by a tool . 107 A.2.6 Fixing . 107 A.2.7 Degree of protection . 107 A.3 Type tests . 107 A.3.1 Tests of clamping of non-armoured and braided cables . 107 A.3.2 Tests of clamping of armoured cables . 110 A.3.3 Type test for resistance to impact . 111 A.3.4 Test for degree of protection (IP) of cable glands . 112 A.4 Marking . 113 A.4.1 Marking of cable glands . 113 A.4.2 Identification of cable-sealing rings . 113 A.5 Instructions . 113 Annex B (normative)
Requirements for Ex Components . 115 Annex C (informative)
Example of rig for resistance to impact test . 118 Annex D (informative)
Electric machines connected to converters . 119 Annex E (informative)
Temperature evaluation of electric machines . 120 Annex F (informative)
Guidance flowchart for tests of non-metallic enclosures or
non-metallic parts of enclosures (26.4) . 123 Annex G (informative)
Guidance flowchart for tests of cable glands . 124 Annex H (informative)
Shaft voltages resulting in motor bearing or shaft brush sparking Discharge energy calculation . 125 H.1 General . 125 H.2 Assessment of the risk of ignition using ignition energy calculation . 125 H.3 Shaft voltage determination for a rotating machine . 126 H.4 Capacitance “C” calculation for a rotating machine . 126 H.5 Energy “E” calculation for a rotating machine . 129 H.6 Assessment using reference curves . 129 Bibliography . 131
Figure 1 – Typical battery examples . 20 oSIST IEC 60079-0:2018

Figure 2 – Typical battery compartment . 21 Figure 3 – Typical replaceable battery pack . 22 Figure 4 – Tolerances and clearance for threaded fasteners . 53 Figure 5 – Contact surface under head of fastener with a reduced shank . 54 Figure 6 – Cable gland . 59 Figure 7 – Conduit entry . 59 Figure 8 – Assembly of test sample for earth-continuity test . 84 Figure 9 – Test piece with painted electrodes . 85 Figure 10 – Compression set of an O-ring . 86 Figure A.1 – Illustration of the terms used for cable glands . 106 Figure A.2 – Rounded edge of the point of entry of the flexible cable . 107 Figure A.3 – Example of rig for resistance to impact test . 112 Figure C.1 – Example of rig for resistance to impact test . 118 Figure F.1 – Non-metallic enclosures or non-metallic parts of enclosures . 123 Figure H.1 – Capacitance stored in bearing clearance of sleeve bearing Between journal and outer bearing housing . 128 Figure H.2 – Air-gap between stator and rotor . 128 Figure H.3 – Typical surfaces that form capacitors from the motor shaft to ground . 129 Figure H.4 – Capacitive ignition curves . 130
Table 1 – Ambient temperatures in service and additional marking . 37 Table 2 – Classification of maximum surface temperatures
for Group II electrical equipment . 38 Table 3 – Assessment of temperature classification according to component size . 40 Table 4 – Assessment of temperature classification Component surface area ≥ 2M mm2. 40 Table 5 – Threshold power . 43 Table 6 – Threshold energy . 43 Table 7 – Limitation of surface areas . 48 Table 8 – Maximum diameter or width . 49 Table 9 – Limitation of thickness of non-metallic layer . 49 Table 10 – Maximum acceptable transferred charge . 49 Table 11 – Maximum capacitance of unearthed conductive parts . 51 Table 12 – Minimum cross-sectional area of PE conductors . 57 Table 13 – Primary cells . 66 Table 14 – Secondary cells . 68 Table 15 – Tests for resistance to impact . 74 Table 16 – Torque to be applied to the stem of bushing used for connection facilities . 79 Table 17 – Thermal endurance test . 80 Table 18 – Text of warning markings . 97 Table 19 – Example of type-test converter parameters . 103 Table B.1 – Applicability of clauses to Ex Components . 115 Table H.1 – Maximum permitted energy . 126
– 8 – IEC 60079-0:2017  IEC 2017 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
EXPLOSIVE ATMOSPHERES –
Part 0: Equipment – General requirements
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 60079-0 has been prepared by IEC technical committee 31: Equipment for explosive atmospheres. This seventh edition cancels and replaces the sixth edition, published in 2011. This edition constitutes a technical revision.
The significance of the changes between IEC Standard, IEC 60079-0, Edition 6 (2011) and IEC 60079-0, Edition 7 (2017) are as listed below:
Type Explanation of the significance of the changes Clause Minor and editorial changes Extension Major technical changes Throughout document, “electrical equipment” replaced by “equipment” where appropriate. Multiple X
Scope List of “Type of “Protection” and “Product” standards combined into one list. 1 X
Definitions used in multiple sub-parts added. Definitions harmonized across sub-parts and added to 60079-0 where appropriate. Battery definitions updated 3 X
Clarification of the way that information on process temperature influences can be expressed. 5.1.2 X
Clarification regarding the determination of service temperatures when dust layers are present 5.2 X
Clarification on the need to provide service temperature information for Ex Components in the Schedule of Limitations 5.2 X
Relocation of EPL Da dust layer requirements from IEC 60079-18 & IEC 60079-31 5.3.2.3.1 A1
Clarified that for EPL Db, a maximum specified dust layer of greater than 200 mm is not permitted as thicker layers have no additional effect on maximum surface temperature. b) X
Added for EPL Db, a dust layer in a specified orientation, marked as TL c)
X
Clarified that for EPL Dc, no dust layer tests are required. 5.3.2.3.3 X
Clarified that the “temperature” is the temperature of the air surrounding the component 5.3.3 X
Subdivided section dealing with higher permitted surface temperatures for “smooth” surfaces. Corrected area from 1 000 mm2 to 10 000 mm2. 5.3.4 X
Clarified that the “Ex” requirements of IEC 60079 supplement those of the relevant industrial standards. 6.1 X
Added requirement that where an adhesive is used to secure a gasket, it shall be used within its COT and shall comply with the requirements for cements. 6.5
C1 Requirements relocated to IEC 60079-28 former 6.6.2 A2
Ultrasonic requirements updated based on latest research work 6.6.3
X
Added reference to IEC 60079-28 6.6.4 A2
Material identification parameters have been revised to reflect reasonably obtainable information 7.1.2.2 X
“RTI-mechanical” has been clarified to include “RTI-mechanical strength” and “RTI-mechanical impact” 7.1.2.2 X
Material identification parameters have been revised to reflect reasonably obtainable information 7.1.2.3 X
Relocated information on “cements” from Clause 12. 7.1.2.4 X
“RTI-mechanical” has been clarified to include “RTI-mechanical strength” and “RTI-mechanical impact”. Requirements for cements aligned with the requirements for elastomers.
7.2.2 X
– 10 – IEC 60079-0:2017  IEC 2017
Type Explanation of the significance of the changes Clause Minor and editorial changes Extension Major technical changes Relocation of 10 K margin for EPL Gc or Dc from IEC 60079-15, IEC 60079-18 & IEC 60079-31 7.2.2 A3
Added clarification with respect to gaskets and seals where only the outer edge is potentially exposed to light. 7.3 X
Clarification added that one or more of the described techniques may be used 7.4.2 X
Added additional relaxation for the case where a surface is in contact with an earthed surface on only two of four sides. 7.4.2 b)
X
Added reference to IEC 60243-1 and IEC 60243-2 for test method to require a 4 kV DC test. 7.4.2.c)
C2 Additional guidance added with respect to the possible Specific Conditions of Use 7.4.2 e) X
New option added for portable, mains-powered equipment with earth-connected guard 7.4.2 f)
X
Added option for determination of maximum transferred charge. 7.4.2 g) Table 10
X
Added missing limits (same as 7.4.2) 7.4.3 a) X
Clarified that it is a dc test that is conducted 7.4.3 b) X
Clarified that this requirement is not applied to personal or portable equipment 7.5 X
Clarified Group I limits 8.2 X
Clarified Group II, EPL Ga limits 8.3 X
Added limitation for external surfaces of >65% copper 8.5
C3 Added clarification as to what is considered a tool 9.1 X
Clarified that the tolerance class of the set screw is not critical, only that it not protrude from the threaded hole after tightening. 9.4 X
Information on cements transferred to Clause 7 12 X
Required that Ex Component Certificates require a Schedule of Limitations in all cases 13.5
X
Revised to clarified that all connection facilities may not be a “Compartment”. 14 X
Sub-clause split to separate the requirements for protective earthing and equipotential bonding into separate sections 15.3 15.4 X
Section split to separate secureness of electrical connections from the internal earth continuity plate. 15.6 15.7 X
Non-threaded Group I cable glands are no longer required to be Ex Components. 16.3
X
Non-threaded Group I blanking elements are no longer required to be Ex Components. 16.4
X
Scope of Clause 17 clarified to define applicability 17 X
Additional guidance notes added to address bearings 17.3 X
Clarified applicability to disconnectors, interlocks, and maintenance switches. 18.2 X
Fuse requirements deleted as they are addressed in the individual sub-parts 19 X
Added requirements for EPL Gc and Dc 20.1
C4 oSIST IEC 60079-0:2018
Type Explanation of the significance of the changes Clause Minor and editorial changes Extension Major technical changes The test circuit requirements for a flameproof connection have been removed as they are more completely specified in IEC 60079-1. 20.2 X
The impact test requirements for luminaires are relocated to Table 15 21.1 Table 15 X
Clarified interlock switch operation for flameproof luminaires 21.2 X
Clarified that some Types of Protection permit connection of cells in parallel 23.2 X
New cell types and data added based on latest available data Table 13
X
New cell types and data added based on latest available data Table 14
C5 Clarification of what documentation is to be prepared regarding the explosion safety aspects of the equipment 24 X
Clarification that the type tests are to take into consideration the installation instructions 26.2 X
Clarification that the “glass” requirements also apply to “ceramic” parts 26.4.1.1 X
Added a permission to interchange the order of tests at the “lower test temperature” and the “upper test temperature”. 26.4.1.2.2 26.4.1.2.3 X
Clarified the construction of the impact test fixture 26.4.2 X
Clarified the impact tests for glass parts 26.4.2 X
Added clarification to deal with the new IPX9 ratings 26.4.5.1
X
Clarified the test voltage for maximum surface temperature 26.5.1.3 X
Relocation of EPL Da dust layer requirements from IEC 60079-18 & IEC 60079-31 26.5.1.3 A1
Relocation of EPL Db specified dust layer requirements from IEC 60079-31 26.5.1.3 A4
Added for EPL Db, a dust layer in a specified orientation, marked as TL 26.5.1.3
B1
Clarified that for EPL Dc, the testing is conduc
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