Groups & zones
Groups
| Equipment for mines - Group I | ||
|---|---|---|
| Protection level | VERY HIGH (powered also in presence of esplosive atmosphere) |
HIGH (to be switched off in presence of esplosive atmosphere) |
| Category of equipment which may be used following 94/9/CE directive | M1 | M2 |
| Equipment for surface installations - Group II | ||||||
|---|---|---|---|---|---|---|
| Zones | 0 | 20 | 1 | 21 | 2 | 22 |
| Nature of atmosphere | G gas |
D dust |
G gas |
D dust |
G gas |
D dust |
| Protection level | VERY HIGH | HIGH | NORMALE | |||
| Category of equipment which may be used following 94/9/CE directive |
1 | 2 | 3 | |||
Zones
Hazardous areas for Group II are further divided in zones, these zones relate to the predicted occurrence of when an explosive atmosphere may be present in the area. These zones are defined as being:
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Gas
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| Nota: Drawing and colors are just an example and should not be used for an actual plant, the design of which is the chief architect's responsability. |
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Dusts
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| Nota: Drawing and colors are just an example and should not be used for an actual plant, the design of which is the chief architect's responsability. |
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Types of protection for gas electric equipment (G)
| Protection symbol | Zones | Description | Symbolic drawing | |||
|---|---|---|---|---|---|---|
| 0 | 1 | 2 | ||||
| "d" |  |
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Explosion proof casing in accordance to EN 50018
Refers to an electrical apparatus whose explosive parts are enclosed in an explosion proof casing. This casing will resist the pressure generated by the internal explosion of an explosive mixture and will prevent the explosion from penetrating to the ambient explosive atmosphere. |
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" e " |
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Enanched safety in accordance to EN 50019
Refers to an electrical apparatus with a high safety coefficient. Such an apparatus is free from excessively high temperatures and, like under normal service conditions, cannot develop inside and outside electric arcs and sparks. |
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"i" |
" ia " |
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Intrinsic safety in accordance to EN 50020
Refers to a circuit in which neither sparks nor temperature can ignite an explosive atmosphere, if generated under the service conditions specified by the standard regulations (normal and faulty operating conditions). |
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" ib " |
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| "m" | |
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Encapsuling in accordance to EN 50028
Refers to a special casing in which the parts, of an electrical apparatus which could ignite an explosive atmosphere by either sparking or heating, are encapsulated in a compound in such a way that this explosive atmosphere cannot be ignited. |
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| " o " | |
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Immersion in accordance to EN 50015
Refers to electrical apparatus immersed in oil. |
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| "p" | |
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Pressurization in accordance to EN 50016
Pressurization is maintained against atmosphere by means of a neutral inert gas. |
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| "q" | |
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Filling in accordance to EN 50017
Refers to a casing containing powder filling. |
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Temperature classes
| Group I | |
|---|---|
Temperatures < 150°C or < 450°C depending on the possibility of coal dust accumulation on equipment |
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| Group II | |
| Temperature class for gas (G) | Permissible surface temperature of electrical equipment |
| T1 T2 T3 T4 T5 T6 |
450°C 300°C 200°C 135°C 100°C 85°C |
The dust ignition temperature depends on the its consistency and its nature. The ignition temperatures for various types of dust are available from reference tables. Examples:
| Dusts | Ignition temperature | |
|---|---|---|
| Cloud | Layer | |
| Aluminium | 560°C | > 450°C |
| Coal dust (lignite) | 380°C | 225°C |
| Grain dust | 510°C | 300°C |
| Methyl cellulose | 420°C | 320°C |
| Phenolic resin | 530°C | > 450°C |
| Polythene | 420°C | ( melts ) |
| PVC | 700°C | >450°C |
| Soot | 810°C | 570°C |
| Starch | 460°C | 435 |
| Sugar | 490°C | 460°C |
Nota : these temperature information are given as examples and cannot be used as reference table.
All the information about groups, protection type and temperature classes have to be mentioned on the product marking.