hazardous area classification

1. ElEctrical MaintEnancE in
Hazardous arEa
-Bhagawan Prasad
amieclub@gmail.com

2. Objective of Area classification
 It is a method of:
-Analyzing & classifying the environment
where Explosive atmosphere may
occur during.
a) Normal Conditions
b) Abnormal Conditions.
 Advantage:
-Classification Provides a basis for the
selection of suitable electrical
apparatus for safe operation

3. Why is this Important?
 Prevent Electrical Hazards from Starting Fires
and Explosions.
 These can be Devastating Loss of Life Loss of
Facilities Preventable by Following Guidelines
Established Cost of Installing
 Wrong Type of New & Replacement Electrical
Equipment

4. Fire Explosion Triangle
These oxidation
reactions normally
involves the
release of heat &
pressure, which is
the major criteria
of an explosion.

5. Important Termology
Hazard: Risk of presence of flammable gas and air mixture.
-Hazardous atmosphere: An atmosphere/ environment containing
any hazard in a concentration capable of ignition.
-Hazardous area: An area/ surrounding where, hazardous
atmosphere is likely to occur during normal/ abnormal operation.
-Ignition temperature: The lowest temp at which ignition occurs in
vapour air mixture.

6. Flammable substances
Flammable substances may be gaseous, liquid or solid
- Flammable gas: Are often hydrocarbons & require very little energy
to react with atmospheric oxygen.
Ex : Methane, Ethane, Hydrogen
- Flammable Liquids: Which evaporates at room temperature in
sufficient quantities to form flammable atmosphere. Ex: Lighter fuel
(MS, Naphtha ….)
- Flammable Solids: Flammable Dust & fibers which react with
atmospheric air to cause explosions in the presence of source of
ignition. Ex: (Wood,Coal Dust, metals…..)

7. Concentration: Explosive Limits
-LEL Lower explosive limit:
Lower or Minimum level of concentration of flammable
vapour/gas in atmosphere which can ignite by
arc/spark
-HEL/UEL:
Upper or maximum level of concentration of flammable
vapour/gas in atmosphere which can ignite by
arc/spark
-Explosive/Flammability Range:
Range between LEL to HEL

8. Concentration: Explosive Limits

9. Area Classification
There are two major classifications prevalent world
wide:
•NEC (National Electrical Code) of USA
•BIS/IEC (Bureau of Indian standard/International
Electro technical Commission)

10. NEC CODE
Classifies combustible media as:
•Class I (Flammable gases, vapour & liquid)
•Class II (Combustible dusts)
•Class III (Ignitable Fibers)
Groups under different class:
Class 1 Class 2 Class 3
Group-A (acetylene) Group-E (Combustible metal dust) No Group (Ignitable fibers)
Group-B (Hydrogen) Group-F (Combustible dust having volatile material like: charcoal, coke
dust)
Group-C (Ethylene)
Group-D (Propane)
Extent of Hazard:
•Division 1: Hazardous media can exist under normal
operating condition
•Division 2: Hazardous media can exist under
abnormal operating condition

11. IEC CODE
Classifies combustible media as:
•Group I: Mining (Methane)
•Group II: Other than mining (Gases & Vapors)
Gas Group:
Group-A : Propane
Group-B : Ethylene
Group-C : Acetylene, Hydrogen & carbon Di Sulphide.
Extent of Hazard is defined by Zone:
•Zone 0: Hazardous media is continuously present or
likely to be present for longer period.
•Zone 1: Hazardous media can exist under normal
operating condition.
•Zone 2: Hazardous media can exist under abnormal
operating condition & for a short duration.

12. Examples
- Zone-0:
- Area like vapour space above storage tank, process tank,
container having flammable material open or close.
- Zone-1:
- Inadequately ventilated pump house handling flammable
material.
- Area around imperfectly fitted rim seal of floating roof
tank.
- Loading of rail Waggon & TT, dispensing stations
- Normal start up & shut down of refinery.
- Zone-2:
- All other area where handling of flammable product is
being done in ventilated area & system is designed that
vapours are confined within the system,& cannot escape
except during abnormal condition.

13. Zone presentation

14. Gas group
 Group Representative Gases
 I All Underground Coal Mining. Firedamp
(methane)
 IIA Industrial methane, propane, petrol
and
the majority of industrial
 IIB Ethylene, coke oven gas and other
industrial gases
 IIC Hydrogen, acetylene, carbon
disulphide

15. Temperature class

16. IP (Ingress Protection)
1st(Protection against solid) 2nd(Protectionagainst
liquid)
0 No protection 0 No protection
1 Solids size > 50 mm 1 Vertically following
drops
2 Solids size > 12 mm 2 15 deg from vertical
3 Solids size > 2.5 mm 3 60 deg from vertical
4 Solids size > 1.0 mm 4 Water from all direction
5 Against dust 5 Water jet from all
direction
6 Complete against dust 6 Water jet with force
7 Immersion

17. Type of Protections
Various method of protection is prevalent & is
suitable for use in hazardous location depending
on the extent of hazard. They are:
- Explosion proof or flame proof (Ex d)
- Increased safety (Ex e)
- Intrinsically safe (Ex i)
- Purge protected (Ex p)
- Non sparking (Ex n)
-Oil filled (Ex o)

18. Electrical gadgets

19. Electrical gadgets zone wise
Likelihood of Hazardous Likelihood of Common Protection
gas/vapour (Above Area Rating Ignition Source Basis for Electrical
LEL) Equipment
Certain Zone -0 Extremely rare Intrinsic Safety Exi
Likely Zone-1 Rare Flame Proof Ex d
Pressurization Ex p
Un likely Zone-2 Un likely Increase Safety- Ex e
Non Sparking – Ex n
Most Un likely Non Possible Normal Electrical
Hazardous Equipment

20. FLAME PROOF EX D
Performance Requirements:
It is a method of protection, where the equipment is
enclosed in an enclosure, which
-Will withstand the internal explosion of flammable gases
that enter it, without damage.
- Do not allow the internal explosion to permeate to the
surroundings through any joints.
Constructional Features:
Flame path (length & clearances) is ensured as per code.
•
Suitability:
For use in Zone-1 & Zone-2.
•

21. INCREASED SAFETY EX E
Performance Requirements:
It is a method of protection,
-Wherein additional precautions are taken to provide
additional safety against excessive temperature,
occurrence of arc & spark.
-These are not capable of withstanding explosion inside
enclosure.
Constructional Features:
•No arcing devices such as fuse & switchgears are used.
•Ignition is prevented by use of non sparking components.
•Clearances & creep age distances are maintained as per
code.
Suitability:
For use in Zone-2.
•

22. INTRINSICALLY SAFE EX I
Performance Requirements:
It is a method of protection,
-Explosion is prevented by ensuring that sufficient energy
for ignition of flammable gases is not available.
-The Surface temperature does not exceeds auto ignition
temperature of surrounding flammable gases.
Constructional Features:
These equipments are primarily low energy electronic device.
•
Operates at lower voltage & amp.(28V,93mA,0.65W)
Suitability:
For use in Zone-0 (ia) & Zone-1 (ib).
•

23. INTRINSICALLY SAFE EX P
Performance Requirements:
It is a method of protection,
-Explosion is prevented by purging flammable media &
ensuring non-ingress of flammable media by keeping
positive pressure.
•The Surface temperature does not exceeds auto
ignition temperature of surrounding flammable gases.
Constructional Features:
Components & devices are installed inside a purge panel.
•
A positive pressure of uncontaminated air or other
neutral gas is maintained inside the panel.
Suitability:
For use in Zone-1.
•

24. NON SPARKING SAFE EX N
CONCEPT SHARES SIMILARITIES WITH EX E PHILOSOPHY
Performance Requirements:
It is a method of protection,
-Wherein in normal condition, it is not capable of
igniting the surrounding explosive atmosphere.
-Fault capable of causing the ignition is not likely to
occur.
Constructional Features:
•Components selected are non arcing, non sparking
•Enclosed break-Incendive components.
•Restricted breathing by sealing & gasketing.
Suitability:
For use in Zone-2.
•

25. MATERIAL OF CONSTRUCTION
Following material is generally specified:
For enclosure:
Casting: Al Alloy, CI & CS
•
Sheet fabrication: Al Alloy, SS & MS
•

26. Leveling

27. Labeling
The letters "CE" stand for "Conformité Européenne"
("European Conformity"). The Product confirmas to
all requièrent of Heath, Safety & Environnent.
Once certified, the equipment is marked by the ‘CE’ (meaning
it complies with ATEX and all other relevant directives) and
‘Ex’ symbol to identify it as approved under the ATEX
directive.

28. Labeling
The letters "CE" stand for "Conformité Européenne"
("European Conformity"). The Product confirmas to
all requièrent of Heath, Safety & Environnent.
Once certified, the equipment is marked by the ‘CE’ (meaning
it complies with ATEX and all other relevant directives) and
‘Ex’ symbol to identify it as approved under the ATEX
directive.

29. DO’S IN HAZARDOUS AREA
 Use brass made tools
 Ensure gasket/seal is not missing
 Use recommended 3 pin top/socket only
 Care for glass/fragile items
 Stop working if too much smell is there
 Ensure earth connection in switch board/DB box
 Ensure no glass or sharp item is in working area
 Use dustbin for cotton waste/CRC/ used bottle
 Ensure all wiring is neatly tied or dressed
 Area is not dry grassy
 Carry recommended torch at night
 Carry panel key, tool box with you

30. Don’ts IN HAZARDOUS AREA
 Don’t overload wire /MCB
 Don’t use so many jig jag connection or tops
 Don’t leave the cover open
 Don’t stand/rest under tank
 Don’t discharge the capacitor in side LPG/tank
area
 Don’t use rusted or strained nut bolt
 Don’t use un-sleeved pliers /screw driver
 Don’t hit metal part with hammer
 Don’t disconnect the earth bonding

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