Explosive atmospheres - Part 10-1: Classification of areas - Explosive gas atmospheres

IEC 60079-10-1:2020 is concerned with the classification of areas where flammable gas or vapour hazards may arise and may then be used as a basis to support the proper design, construction, operation and maintenance of equipment for use in hazardous areas.
It is intended to be applied where there may be an ignition hazard due to the presence of flammable gas or vapour, mixed with air, but it does not apply to:
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) catastrophic failures or rare malfunctions which are beyond the concept of normality dealt with in this standard;
d) rooms used for medical purposes;
e) domestic premises;
f) where a hazard may arise due to the presence of combustible dusts or combustible flyings but the principles may be used in assessment of a hybrid mixture.
Flammable mists may form or be present at the same time as flammable vapour. In such case the strict application of the details in this document may not be appropriate. Flammable mists may also form when liquids not considered to be a hazard due to the high flash point are released under pressure. In these cases the classifications and details given in this document do not apply.
For the purpose of this document, an area is a three-dimensional region or space.
Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar) and 20 °C (293 K), provided that the variations have a negligible effect on the explosion properties of the flammable substances.
In any site, irrespective of size, there may be numerous sources of ignition apart from those associated with equipment. Appropriate precautions will be necessary to ensure safety in this context. This standard is applicable with judgement for other ignition sources but in some applications other safeguards may also need to be considered. E.g. larger distances may apply for naked flames when considering hot work permits.
This document does not take into account the consequences of ignition of an explosive atmosphere except where a zone is so small that if ignition did occur it would have negligible consequences.
This third edition of IEC 60079-10-1 cancels and replaces the second edition, published in 2015, and constitutes a technical revision, see foreword for further details.

Atmosphères explosives - Partie 10-1: Classification des emplacements - Atmosphères explosives gazeuses

l'IEC 60079-10-1:2020 concerne la classification des emplacements dans lesquels des phénomènes dangereux dus à des gaz ou vapeurs inflammables peuvent apparaître, et peut ainsi constituer une base pour la conception, l'exploitation et la maintenance correctes du matériel utilisé dans de tels emplacements.
Elle est destinée à être appliquée là où il peut exister un danger d'inflammation du fait de la présence de gaz ou vapeurs inflammables, en mélange avec l'air, mais elle ne s'applique pas:
a) aux mines grisouteuses;
b) au traitement et à la fabrication des explosifs;
c) aux défaillances catastrophiques ou rares dysfonctionnements, qui dépassent le concept de normalité traité dans la présente norme;
d) aux locaux utilisés à des fins médicales;
e) aux locaux à usage domestique;
f) lorsqu’un danger peut apparaître compte tenu de la présence de poussières combustibles ou de particules combustibles en suspension dans l'air, mais les principes définis peuvent toutefois être appliqués dans l’évaluation d’un mélange hybride. Des brouillards inflammables peuvent se former ou être présents en même temps que les vapeurs inflammables. Dans ce type de cas, l’application stricte des détails du présent document peut ne pas être appropriée. Les brouillards inflammables peuvent également se former lorsque les liquides qui ne sont pas considérés comme dangereux en raison du point d’éclair élevé sortent sous pression. Dans ces cas, les classifications et détails donnés dans le présent document ne s’appliquent pas. Des informations relatives aux brouillards inflammables sont données à l’Annexe G.
Pour les besoins du présent document, un emplacement est une région ou un espace tridimensionnel.
Les conditions atmosphériques englobent les écarts au-dessus et au-dessous des niveaux de référence de 101,3 kPa (1 013 mbar) et 20 °C (293 K) à condition que cela ait un effet négligeable sur les propriétés explosives des substances inflammables.
Dans tout site quelle que soit son importance, il peut y avoir de nombreuses sources d'inflammation en dehors de celles qui sont associées au matériel. Il est nécessaire dès lors de prendre les précautions appropriées pour garantir la sécurité. La présente norme est applicable avec prudence pour ces autres sources d'inflammation mais d'autres applications peuvent nécessiter de prendre en considération d’autres mesures de protection. Par exemple, de plus grandes distances peuvent s'appliquer aux flammes nues lorsqu’il s’agit de permis de travaux à chaud.
Le présent document ne tient pas compte des conséquences de l'inflammation d'une atmosphère explosive, sauf dans une zone si petite que si une inflammation se produit, ses conséquences sont négligeables.
Cette troisième édition de l'IEC 60079-10-1 annule et remplace la deuxième édition parue en 2015. Cette édition constitue une révision technique.

General Information

Status
Published
Publication Date
17-Dec-2020
Current Stage
PPUB - Publication issued
Completion Date
18-Dec-2020
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IEC 60079-10-1
Edition 3.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres
Atmosphères explosives –
Partie 10-1: Classification des emplacements – Atmosphères explosives
gazeuses
IEC 60079-10-1:2020-12(en-fr)
---------------------- Page: 1 ----------------------
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IEC 60079-10-1
Edition 3.0 2020-12
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Explosive atmospheres –
Part 10-1: Classification of areas – Explosive gas atmospheres
Atmosphères explosives –
Partie 10-1: Classification des emplacements – Atmosphères explosives
gazeuses
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.260.20 ISBN 978-2-8322-8890-0

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® Registered trademark of the International Electrotechnical Commission
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---------------------- Page: 3 ----------------------
– 2 – IEC 60079-10-1:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 6

INTRODUCTION ................................................................................................................... 10

1 Scope ............................................................................................................................ 11

2 Normative references .................................................................................................... 11

3 Terms and definitions .................................................................................................... 12

4 General ......................................................................................................................... 16

4.1 Safety principles ................................................................................................... 16

4.2 Hazardous area classification objectives ............................................................... 17

4.3 Interior of equipment containing flammable materials ............................................ 18

4.4 Explosion risk assessment .................................................................................... 18

4.4.1 General ......................................................................................................... 18

4.4.2 Zone of negligible extent................................................................................ 18

4.5 Catastrophic failures ............................................................................................. 19

4.6 Competence of personnel ..................................................................................... 19

5 Hazardous area classification methodology ................................................................... 19

5.1 General ................................................................................................................. 19

5.2 Classification by sources of release method .......................................................... 20

5.3 Use of industry codes and national standards ....................................................... 21

5.3.1 General ......................................................................................................... 21

5.3.2 Fuel gas installations ..................................................................................... 21

5.4 Simplified methods................................................................................................ 21

5.5 Combination of methods ....................................................................................... 21

6 Release of flammable substance ................................................................................... 22

6.1 General ................................................................................................................. 22

6.2 Sources of release ................................................................................................ 22

6.3 Forms of release ................................................................................................... 23

6.3.1 General ......................................................................................................... 23

6.3.2 Gaseous release ........................................................................................... 24

6.3.3 Liquefied under pressure release ................................................................... 24

6.3.4 Liquefied by refrigeration release ................................................................... 24

6.3.5 Flammable mists release ............................................................................... 25

6.3.6 Vapours release ............................................................................................ 25

6.3.7 Liquid release ................................................................................................ 25

7 Ventilation (or air movement) and dilution ...................................................................... 26

7.1 General ................................................................................................................. 26

7.2 Main types of ventilation ....................................................................................... 27

7.2.1 General ......................................................................................................... 27

7.2.2 Natural ventilation .......................................................................................... 27

7.2.3 Artificial ventilation ........................................................................................ 27

7.2.4 Degree of dilution .......................................................................................... 29

8 Type of zone ................................................................................................................. 30

8.1 General ................................................................................................................. 30

8.2 Influence of grade of the source of release ........................................................... 30

8.3 Influence of dilution ............................................................................................... 30

8.4 Influence of availability of ventilation ..................................................................... 30

9 Extent of zone ............................................................................................................... 31

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IEC 60079-10-1:2020 © IEC 2020 – 3 –

10 Documentation .............................................................................................................. 31

10.1 General ................................................................................................................. 31

10.2 Drawings, data sheets and tables ......................................................................... 32

Annex A (informative) Suggested presentation of hazardous areas ...................................... 33

A.1 Hazardous area – Preferred symbols for zones ..................................................... 33

A.2 Hazardous area suggested shapes ....................................................................... 36

Annex B (informative) Estimation of sources of release ........................................................ 38

B.1 Symbols ................................................................................................................ 38

B.2 Examples of grade of release ................................................................................ 38

B.2.1 General ......................................................................................................... 38

B.2.2 Sources giving a continuous grade of release ................................................ 39

B.2.3 Sources giving a primary grade of release ..................................................... 39

B.2.4 Sources giving a secondary grade of release ................................................. 39

B.3 Assessment of grades of release .......................................................................... 39

B.4 Summation of releases ......................................................................................... 40

B.5 Hole size and source radius .................................................................................. 41

B.6 Forms of release ................................................................................................... 43

B.7 Release rate ......................................................................................................... 44

B.7.1 General ......................................................................................................... 44

B.7.2 Estimation of release rate .............................................................................. 45

B.7.3 Release rate of evaporative pools .................................................................. 47

B.8 Release from openings in buildings ....................................................................... 49

B.8.1 General ......................................................................................................... 49

B.8.2 Openings as possible sources of release ....................................................... 50

B.8.3 Openings classification .................................................................................. 50

Annex C (informative) Ventilation guidance .......................................................................... 52

C.1 Symbols ................................................................................................................ 52

C.2 General ................................................................................................................. 53

C.3 Assessment of ventilation and dilution and its influence on hazardous area .......... 53

C.3.1 General ......................................................................................................... 53

C.3.2 Effectiveness of ventilation ............................................................................ 54

C.3.3 Criteria for dilution ......................................................................................... 54

C.3.4 Assessment of ventilation velocity ................................................................. 55

C.3.5 Assessment of the degree of dilution ............................................................. 56

C.3.6 Dilution in a room .......................................................................................... 58

C.3.7 Criteria for availability of ventilation ............................................................... 59

C.4 Examples of ventilation arrangements and assessments ....................................... 60

C.4.1 Introduction ................................................................................................... 60

C.4.2 Jet release in a large building ........................................................................ 61

C.4.3 Jet release in a small naturally ventilated building ......................................... 62

C.4.4 Jet release in a small artificially ventilated building ........................................ 62

C.4.5 Release with low velocity ............................................................................... 63

C.4.6 Fugitive emissions ......................................................................................... 63

C.4.7 Local ventilation-extraction ............................................................................ 64

C.5 Natural Ventilation in buildings .............................................................................. 64

C.5.1 General ......................................................................................................... 64

C.5.2 Wind induced ventilation ................................................................................ 64

C.5.3 Buoyancy induced ventilation ......................................................................... 65

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– 4 – IEC 60079-10-1:2020 © IEC 2020

C.5.4 Combination of the natural ventilation induced by wind and buoyancy ........... 67

Annex D (informative) Estimation of hazardous areas .......................................................... 69

D.1 General ................................................................................................................. 69

D.2 Estimating types of the zones ............................................................................... 69

D.3 Estimating the extent of the hazardous area ......................................................... 70

Annex E (informative) Examples of hazardous area classification ........................................ 72

E.1 General ................................................................................................................. 72

E.2 Examples .............................................................................................................. 72

E.3 Example case study for hazardous area classification ........................................... 86

Annex F (informative) Schematic approach to classification of hazardous areas .................. 96

F.1 Schematic approach to classification of hazardous areas ...................................... 96

F.2 Schematic approach to classification of hazardous areas ...................................... 97

F.3 Schematic approach to classification of hazardous areas ...................................... 98

F.4 Schematic approach to classification of hazardous areas ...................................... 99

Annex G (informative) Flammable mists ............................................................................. 100

Annex H (informative) Hydrogen ........................................................................................ 103

Annex I (informative) Hybrid mixtures ................................................................................ 105

I.1 General ............................................................................................................... 105

I.2 Use of ventilation ................................................................................................ 105

I.3 Concentration limits ............................................................................................ 105

I.4 Chemical reactions ............................................................................................. 105

I.5 Energy/temperature limits ................................................................................... 105

I.6 Zoning requirements ........................................................................................... 105

Annex J (informative) Useful equations in support to hazardous area classification .......... 106

J.1 General ............................................................................................................... 106

J.2 Dilution with air of a flammable substance release .............................................. 106

J.3 Estimate of the time required to dilute a flammable substance release ................ 106

Annex K (informative) Industry codes and national standards ............................................ 108

K.1 General ............................................................................................................... 108

Bibliography ........................................................................................................................ 112

Figure 1 – Dilution Volume .................................................................................................... 29

Figure A.1 – Preferred symbols for zones ............................................................................. 33

Figure A.2 – Gas or vapour at low pressure (or at high pressure in case of

unpredictable release direction) ............................................................................................ 36

Figure A.3 – Gas or vapour at high pressure ......................................................................... 36

Figure A.4 – Liquefied gas .................................................................................................... 37

Figure A.5 – Flammable liquid (non boiling evaporative pool) ................................................ 37

Figure B.1 – Forms of release ............................................................................................... 43

Figure B.2 – Specific volumetric evaporation rate of liquids .................................................. 49

Figure C.1 – Chart for assessing the degree of dilution ......................................................... 57

Figure C.2 – Self diffusion of an unimpeded high velocity jet release .................................... 61

Figure C.3 – Supply only ventilation ...................................................................................... 62

Figure C.4 – Supply and extraction ventilation ...................................................................... 63

Figure C.5 – Local extraction ventilation ............................................................................... 64

Figure C.6 – Specific volumetric flow rate of fresh air of equivalent effective opening area .. 67

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IEC 60079-10-1:2020 © IEC 2020 – 5 –

Figure C.7 – Example of opposing ventilation driving forces.................................................. 68

Figure D.1 – Chart for estimating hazardous area distances ................................................. 71

Figure E.1 – Degree of dilution (Example No. 1) ................................................................... 73

Figure E.2 – Hazardous distance (Example No. 1) ................................................................ 74

Figure E.3 – Zone classification (Example No. 1) .................................................................. 74

Figure E.4 – Degree of dilution (Example No. 2) ................................................................... 76

Figure E.5 – Degree of dilution (Example No. 3) ................................................................... 78

Figure E.6 – Hazardous distance (Example No. 3) ................................................................ 79

Figure E.7 – Zones classification (Example No. 3) ................................................................ 79

Figure E.8 – Degree of dilution (Example No. 4) ................................................................... 81

Figure E.9 – Hazardous distance (Example No. 4) ................................................................ 82

Figure E.10 – Zones classification (Example No. 4) .............................................................. 83

Figure E.11 – Degree of dilution (Example No. 5) ................................................................. 85

Figure E.12 – Hazardous distance (Example No. 5) .............................................................. 86

Figure E.13 – Enclosed compressor handling natural gas ..................................................... 88

Figure E.14 – Example of hazardous area classification for a compressor facility

handling natural gas (elevation) ............................................................................................ 94

Figure E.15 – Example of hazardous area classification for a compressor facility

handling natural gas (plan) ................................................................................................... 95

Figure F.1 – Schematic approach to classification................................................................. 96

Figure F.2 – Schematic approach to classification for continuous grade releases .................. 97

Figure F.3 – Schematic approach to classification for primary grade releases ....................... 98

Figure F.4 – Schematic approach to classification for secondary grade releases .................. 99

Table A.1 – Hazardous area classification data sheet – Part I: Flammable substance

list and characteristics .......................................................................................................... 34

Table A.2 – Hazardous area classification data sheet – Part II: List of sources of

release ................................................................................................................................. 35

Table B.1 – Suggested hole cross sections for secondary grade of releases ......................... 42

Table B.2 – Effect of zones on openings as possible sources of release ............................... 51

Table C.1 – Indicative outdoor ventilation velocities (u ) ...................................................... 56

Table D.1 – Zones for grade of release and effectiveness of ventilation ................................ 69

Table E.1 – Compressor facility handling natural gas ............................................................ 88

Table E.2 – Hazardous area classification data sheet – Part I: Flammable substance

list and characteristics .......................................................................................................... 91

Table E.3 – Hazardous area classification data sheet – Part II: List of sources of

release ................................................................................................................................. 92

Table K.1 – Examples of codes and standards .................................................................... 109

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– 6 – IEC 60079-10-1:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
EXPLOSIVE ATMOSPHERES –
Part 10-1: Classification of areas –
Explosive gas atmospheres
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