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:

Presenza di gas Gas

Color

Zones

Presence of gas

0 Continuously present
(during long periods)
1 Not likely to be present
(regular service)
2 Accidentally present
(short-time-service - never in regular service)
 
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.
Presenza di polveri Dusts

Color

Zones

Presence of dusts

20 Continuously present
(during long periods)
21 Not likely to be present
(regular service)
22 Accidentally present
(short-time-service - never in regular service)
 
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.

Types of protection for gas electric equipment (G)

Protection symbol Zones Description Symbolic drawing
  0 1 2  
"d"   zone zone 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.

Explosion proof casing in accordance to EN 50018
" e "
  zone zone 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.

Enanched safety in accordance to EN 50019
"i"
" ia "
zone zone zone 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).

Intrinsic safety in accordance to EN 50020
" ib "
  zone zone
"m"   zone zone 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.

Encapsuling in accordance to EN 50028
" o "   zone zone Immersion in accordance to EN 50015

Refers to electrical apparatus immersed in oil.

"p"   zone zone Pressurization in accordance to EN 50016

Pressurization is maintained against atmosphere by means of a neutral inert gas.

Pressurization in accordance to EN 50016
"q"   zone zone Filling in accordance to EN 50017

Refers to a casing containing powder filling.

 


Temperature classes

Group I

Temperatures < 150°C or < 450°C depending on the possibility of coal dust accumulation on equipment

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
Ignition temperature for dusts

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.