3. Hazardous AREA
Industrial processes involving Flammable materials, form
explosive atmospheres termed as :
The presence of Methane , coal-dust & other gases generate an extremely explosive
atmosphere inside the Coal Mines. Also termed as :
Hazardous AREA
Above Surface
Below Surface
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4. Flammable materials exist in the form of:
•GAS or Vapours
•Liquids
• powders
• Dust
•Flyings or fluff
Explosive atmosphere is created by :
•Methane
•Coal dust
•A combination of all, known as FIRE DAMP
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5. For the Flammable materials which exist in the form of:
•GAS or Vapours
•Liquids
• powders
• Dust
•Flyings or fluff
In order to understand & carry out :
Qualitative analysis &
Quantitative analysis of the flammable materials
Selection of electrical Equipments
The idea of GROUPS is employed.
The above-surface groups are GROUP II & GROUP III
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In order to understand & carry out :
Qualitative analysis &
Quantitative analysis of the flammable materials
Selection of electrical Equipments
The idea of GROUPS is employed.
The below-surface group is GROUP I
6. GROUP II & GROUP III
Thus the above-surface explosive atmosphere belongs to GROUP II
If it is an EXPLOSIVE Gas ATMOSPHERE
And the above-surface explosive atmosphere belongs to GROUP III
If it is an EXPLOSIVE DUST ATMOSPHERE
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GROUP I
The below-surface explosive atmosphere belongs to GROUP I……
If it is an EXPLOSIVE ATMOSPHERE created by the presence of
FIREDAMP
7. GROUP II
GROUP II is further divided into following 3 levels according to the nature of the explosive GAS
involved as manifested through Maximum Experimental Safe Gap (MESG) & Minimum Ignition
Current (MIC)
1. Group II A
2. Group II B
3. Group II C
GROUP III
GROUP III is further divided into following 3 levels according to the nature of the explosive DUST
involved:-
1. Group III A
2. Group III B
3. Group III C
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GROUP I
This group is further divided in to following two levels of operation:
1. M1 (Equipment Protection Level) Ma
2. M2 (Equipment Protection Level) Mb
8. GROUP II
1. Group II A Representative Gas is PROPANE
2. Group II B Representative Gas is Ethylene
3. Group II C Representative Gas is Hydrogen
GROUP III
1. Group III A Combustible Flyings belong to group IIIA
2. Group III B Combustible but non-conductive dust belongs to IIIB
3. Group III C Combustible & conductive dust belongs to IIIC
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GROUP I
This group is further divided in to following two levels of operation:
1. M1 (Equipment Protection Level) Ma
2. M2 (Equipment Protection Level) Mb
9. Ex-pert Electrical Technologies
GROUP I
This group is further divided in to following two levels of operation:
1. M1 (Equipment Protection Level) Ma
2. M2 (Equipment Protection Level) Mb
Group IIC is the most explosive and the group IIA is the least
10. Ex-pert Electrical Technologies
GROUP I
This group is further divided in to following two levels of operation:
1. M1 (Equipment Protection Level) Ma
2. M2 (Equipment Protection Level) Mb
GROUP III
1. Group III A Combustible Flyings belong to group IIIA
2. Group III B Combustible but non-conductive dust belongs to IIIB
3. Group III C Combustible & conductive dust belongs to IIIC
It is obvious that combustible flyings & dust represent twofold danger:-
1. Danger of FIRE as per nature of the material
2. Fire-spread Danger , due to the layer of the material which usually gets deposited in
the area.
11. Ex-pert Electrical Technologies
Once the concept of GROUPS is understood then it becomes easy to select
the proper Electrical Equipment for Gas or Dust Explosive Atmosphere.
The Gas Group of the Area Of Installation should Match with the gas Group
of the Equipment which is being selected.
The equipment selection becomes a bit easy.
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