This document discusses hazardous area classification. It defines hazardous areas as areas where flammable gases or vapors may be present. Areas are classified into zones based on the likelihood and duration of an explosive atmosphere occurring. Zone 0 areas have explosive atmospheres present continuously, Zone 1 areas have them likely to occur occasionally, and Zone 2 areas are not likely but possible for short periods. Selection of electrical equipment depends on the area classification and gas properties. Standards provide guidelines for equipment certification to ensure safe operation in hazardous environments.

1. HAZARDOUS AREA CLASSIFICATION
Debabrata Das
Indian Oil Corporation Limited

2. Objective
1
Understand concept of
Hazardous area Classification
2
Understand the selection of
Equipments for Hazardous Area

3. Agenda
 Basic concept of Hazardous area
 Classification of Hazardous area
 Statutory requirements
 Selection of Equipments

4. Why Classify an Area as Hazardous?
Potential for explosion Safety of personnel Property Damage
Blast in a refinery due to non-classification of Cooling
Tower as Hazardous Area

5. What is Hazardous Area Classification?
 A method of analyzing and classifying the environment
 Proper selection of electrical apparatus
 Enable electrical apparatus to be operated safely
IS 5572
An area in which an explosive gas atmosphere is present,
or likely to be present, in quantities such as to require
special precautions for the construction, installation and
use of electrical apparatus.

6. Hazardous Areas-Definitions
Petroleum Rule 1976
An area shall be deemed to be a hazardous area, where
(i) Petroleum liquid having flash point below 65°C or any
flammable gas or vapour in a concentration capable of
ignition is likely to be present.
(ii) Petroleum or any flammable liquid having flash point
above 65°C is likely to be refined, blended, handled or
stored at or above its flash point.

7. Flash Point
The minimum temperature at which the liquid gives so
much vapour that this vapour, when mixed with air, forms
an ignitable mixture and gives a momentary flash on
application of a small pilot flame under specified
conditions of test.
Flammable Liquids classification
Class A: Flash point below 23°C
Class B: Flash point 23°C and above but below 65°C
Class C: Flash point 65°C and above but below 93°C
Classification of Flammable Liquids

8. Explosive Limit
 Lower Explosive Limit (LEL) – below which an explosive gas
atmosphere will not be formed.
 Upper Explosive Limit (UEL) –above which an explosive gas
atmosphere will not be formed.
Explosive Atmosphere
Explosive Gas Atmosphere
 A mixture with air of flammable materials
 In the form of gas, vapour, or mist
 After ignition, combustion spreads throughout the mixture
Measured with Explosive Meter at out Locations

9. Agenda
 Basic concept of Hazardous area
 Classification of Hazardous area
 Statutory requirements
 Selection of Equipments

10. Classification of Hazardous Area
Class I
Typical Environment
• Oil Refinery
• Terminal
• Bottling Plant
Class II
Typical Environment
• Coal Mine
• Grain Silo
• Hay Storage
Areas where flammable
gaes/vapours may be
present
Areas where
combustible dust be
may present
Class III
Areas where
combustible dust be
may present
Typical Environment
• Textile Mill
• Paper Mill
• Wook factory

11. Classification of Hazardous Area
 Zone 0- explosive atmosphere is present continuously or for long
periods or frequently
 Zone 1- explosive atmosphere is likely to occur in normal operation
occasionally
 Zone 2- explosive atmosphere is not likely to occur in normal
operation but, if it does occur, will persist for a short period
only
Classified in 03 zones based upon the Frequency of the appearance and
duration of an explosive gas atmosphere
NEC Classification: Div 1( Zone 0+ Zone 1) & Div 2( Zone 2)

12. Zone 0 -Typical areas
 Vapour space above
closed process vessels
 Storage tanks
 Closed containers
 Areas containing open
tanks of volatile,
flammable liquid
An area in which an explosive atmosphere is present
continuously or for long periods or frequently

13. Zone 1 Typical Area
 Flammable gas or vapour
concentration is likely to exist in the air
under normal operating conditions
 Is likely to occur frequently because of
maintenance, repairs or leakage
 Piping system (containing valves,
meters, or screwed or flanged fittings)
is in an inadequately ventilated area
 The area below the surrounding
elevation or grade is such vapours may
accumulate therein
 Failure of equipment is likely to cause
an electrical system failure
simultaneously with the release of
flammable gas
 Imperfectly fitting peripheral seals on
floating roof tanks
 Inadequately ventilated pump rooms
for flammable gas /liquid
 Oily waste water sewer / basins
 Loading / unloading gantries
 Interiors of Sample Retention Room
 Areas in the immediate vicinity of
vents and filling hatches
An area in which an explosive atmosphere is not likely to occur in
normal operation but, if it does occur, will persist for a short period only
Examples

14. Zone 2 Typical Area
The system handling flammable liquid /vapour is in an adequately
ventilated area
Release of flammable liquid/gas in abnormal conditions such as accidental
release of a gasket or packing
The flammable vapours can be conducted to the location as through
trenches, pipes or ducts
Locations adjacent to Zone 1 areas
Pressurized rooms where flammable gas / vapour can enter in the case of
failure of positive mechanical ventilation
An area in which an explosive atmosphere is likely to occur in
normal operation occasionally.

15. Areas Not Classified
 Piping system without valves,
fittings, flanges
 Flammable material are
transported only in suitable
containers or vessels.
Areas where permanent ignition-
flare tips, flare pits, other open
flames and hot surfaces.
 Diesel Generator room / shed
having adequate ventilation.
 Oil/gas fired boilers installation
 Enclosed premises in which
purging stream from safe
atmosphere maintained
A protected fired vessel is not considered a source
of ignition and the surrounding area is classified the
same as for a hydrocarbon pressure vessel.

16. Properties of Flammable Substance
Relative density- The lighter vapour will rise in a comparatively still
atmosphere and heavier vapour will tend to sink, and may thereby spread
over some distance horizontally at a lower level.
Flammable limits- The lower the “LEL” the larger will be the extent of the
hazardous area.
Flash point- The lower the flash point, the larger may be the extent of the
hazardous area.
Volatility- The more volatile a liquid and the lower will be its boiling point
Ignition temperature & Energy - affect the design of electrical apparatus
for hazardous areas so that these do not present an ignition risk.

17. Factors Affecting Extent of Hazard
•Increasing temperature
of process liquid
•The lower the IBP
results in greater
concentration of vapour
at the release source
•Rate of release of
flammable material
Temp Air
•A very mild breeze may
serve to extend the area
in those directions to
which vapours might
normally be carried.
•A stronger breeze may
so accelerate the
dispersion of vapours
that the extent of
potentially hazardous
area would be greatly
reduced.
Ventilation
•Increased rate of
ventilation, the extent of
hazardous area may be
reduced
•Obstacles e.g. dykes,
walls may impede the
ventilation and thus may
enlarge the extent.
• On the other hand,
they may limit the
movement of a cloud of
an explosive gas
atmosphere and thus
may reduce the extent.
Elevated or depressed sources of release will alter the areas of potential hazards.

18. Grouping Of Industrial Gas
Categorized into Group-I and Group-II gases(IS-9570)
Group-I : Found in the coal mining
industry(Methane)
Group-II: Subgroups in the increasing order of
their explosiveness.
 Group-IIA: Acetone, ammonia, ethyl
alcohol, gasoline, LGP/ Propane.
 Group-IIB: Ethylene, acetaldehyde.
Group-IIC: Acetylene, hydrogen

19. To classify a flammable gas or vapour by its ability to get ignited by a hot
surface.
The temperature class defines the maximum surface temperature an electrical
apparatus is allowed to operate at.
The maximum surface temperature of the apparatus must always be lower than
the ignition temperature of the surrounding gases.
Apparatus, that are certified suitable for use in a hazardous area, should be
marked with their temperature class.
Temperature Class
Temperature Class Max Surface Temperature of
Apparatus in C
Ignition Temperature of the
Flammable Substance in C
T1 450 >450
T2 300 >300<=450
T3 200 >200<=300
T4 135 >135<=200
T5 100 >100<=135
T6 85 >85<=100

20. Gas group-Ignition Energy
GAS GROUP REPRESENATATIVE GAS IGNITION ENERGY
(mj)
I METHANE 280
II A PROPANE 260
II B ETHYLENE 95
II C HYDROGEN 18

21. VARIOUS GASES/VAPOURS (IS 13408 Part I)
Flammable limitS No Name of the
chemical
Minimum
Ignition
Current
(MIC) mA
Flash point
Deg. Cen.
Iignition
temperatur
e
(Deg C)
LEL UEL
1 Methane I,
T1
85 - 595 5% 15%
2 Ammonia
II A T1
- - 630 105 mg/l 200 mg/l
3 Ethylene
II B T2
45 - 425 2.7% 34%
4 Propane
II A T1
70 - 470 2% 9.5%
5 Acetylene
II C T2
24 - 305 1.5 % 100%

22. Case-1

23. Case-2

24. Case-3

25. Case-4

26. Case-5

27. Case-6

28. Case-7

29. Case-8

30. Case-9

31. Agenda
 Basic concept of Hazardous area
 Classification of Hazardous area
 Regulations, Guidelines
 Selection of Equipments

32. Various Standards

33. Certifying Agencies
Factory Mutual Underwriters Laboratories
CMRI
Dhanbad

34. Statutory Regulations
• Petroleum Act, 1884
– Petroleum Rules, 1976
• Explosive Act, 1934
– Explosive Rules, 1983
– Gas Cylinder Rules, 1981
– Static & Mobile pressure Vessel (Unfired) Rules, 1981
CCoE, Department of Explosives is entrusted with the
responsibility of administration of the above statutory rules
in India

35. Agenda
 Basic concept of Hazardous area
 Classification of Hazardous area
 Statutory requirements
 Selection of Equipments

36. How to select equipment for various zones?
Area Classification Div/Zone
Gas Group
Temp Class
Protection concept IP Codes

37. FLAMMABLE
MIXTURE, EXPLOSION

38. Protection concepts
 No Arcs, sparks, or hot surface-
Increased Safety, Non-incendive
 Containing the explosion and extinguishing the flame-
Explosion proof, flame proof, power filled
 Limiting energy – Intrinsically Safe
Keeping Flammable material Out
Pressurized, encapsulated, oil emersion,

39. Type of Protection
Type Ex-
Code
Description Location Use
Flameproof d A method of protection where the
enclosure of apparatus will
withstand an internal explosion of
the inflammable gas which may
enter it without causing damage
and without communicating the
internal inflammation to the
external flammable gas. he escaping
(hot) gases must sufficiently cool
down along the escape path that by
the time they reach the outside of
the enclosure not to be a source of
ignition of the outside, potentially
ignitable surroundings.
Zone 1 if gas
group &
temp. class
correct
Motors,
lighting,
junction
boxes,
electronics

40. Type of Protection
Type Ex-
Code
Description Location Use
Intrinsically
safe
i A protection technique based upon
based on restriction of electrical
energy within apparatus and in the
interconnecting wiring, exposed to
potentially explosive atmosphere, to
a level below that which can cause
ignition by either sparking or
heating effects. Because of the
method by which intrinsic safety is
achieved it is necessary that not
only the electrical apparatus
exposed to the potentially explosive
atmosphere but also other electrical
apparatus with which it is
interconnected is suitably
constructed
'ia‘ : Zone 0
'ib‘: Zone1
'ic : Zone 2
Instrumentation,
measurement,
control

41. Type of Protection
Type Ex-
Code
Description Location Use
Pressurized/
purged
p Equipment is pressurized to a
positive pressure relative to the
surrounding atmosphere with air or
an inert gas, thus the surrounding
ignitable atmosphere can not come
in contact with energized parts of
the apparatus. The overpressure is
monitored, maintained and
controlled.
Zone 1 (px
or py), or
zone 2 (pz)
Analyzers,
motors, control
boxes,
computers
Oil
immersed
o A method of protection where
electrical apparatus is made safe by
oil immersion in the sense that
flammable gasses or vapors above
the oil or outside the enclosure will
not be ignited
Zone 2 or
Zone 1
switchgear

42. Type of Protection
Non
Incendive
n A type of protection applied to an
electrical apparatus such that in
normal operation, it is not capable
of igniting a surrounding explosive
atmosphere, and a fault capable of
causing ignition is not likely to occur
Zone 2
Motors, lighting,
junction boxes,
electronic
equipment
Special
Protection
s A concept for those type of
electrical apparatus that, by their
nature do not comply with the
constructional or other
requirements specified for
apparatus with established types of
protection, but which nevertheless
can be shown, where necessary by
test, to be suitable for use in
hazardous areas in prescribed zones
Zone
depending
upon
Manufactur
ers
Certificatio
n.
As its
certification
states

43. Type of Protection
Increased
Safety
e A method of protection by which
additional measures are applied to
an electrical apparatus to give
increased security against the
possibility of excessive
temperatures and of the
occurrences of arcs and sparks
during service life of the apparatus.
It applies only to an electrical
apparatus, no part of which produce
arcs or sparks or exceed the limiting
temperature in normal service
Zone 2 or
Zone 1
Motors, lighting,
junction boxes
Sand filled q A method of protection where the
enclosure of the electrical apparatus
is filled with a mass of powdery
material such that, if an arc occurs,
the arc will not be liable to ignite
the outer flammable atmosphere
Zone 2 or
Zone 1
Electronics,
telephones,
chokes

44. IP Types and Protection Details
FIRST NUMERAL
0 No protection
1 Objects greater than 50 mm
2 Objects greater than 12 mm
3 Objects greater than 2.5 mm
4 Objects greater than 1.0 mm
5 Dust - protected
6 Dust tight
SECOND NUMERAL
0 No protection
1 Vertically dripping
2 Angular dripping
3 Sprayed water
4 Splashed water
5 Water jets
6 Heavy seas
7 Effects of immersion
8 Indefinite immersion
IP XY
Degree of Solid ingress Ingress of Liquid

45. Recommended Protection in Zone-0
No electrical equipment should be allowed. When
this is not practicable, Ex ‘ i ‘ (ia or ib) apparatus or
circuits to be used
• No transformers, motors, lights, switch gear or
control gear

46. Recommended Protection in Zone-1
Motors- Ex d, Ex p
Transformers & Capacitors - Ex d
Control & Instrument Transformers - Ex i
Lighting Fitting - Ex d
Switch Gear & Control Gear - Ex d
Communication/ Telephone equipment/Meters - Ex i
Portable Hand Lamps- Ex i
*Ex o, Ex q type equipment are also allowed for use
as per IS 5571

47. Recommended Protection in Zone-2
Motors- Ex d, Ex p, Ex n, Ex e,
Transformers & Capacitors - Ex d, Ex p (auxiliary devices to be
located in pressurized room/hermetically sealed /
intrinsically safe)
Control & Instrument Transformers - Ex i
Lighting Fitting - Ex d, Ex e, Ex n
Switch Gear & Control Gear - Ex d, Ex o, Ex
Communication/ Telephone equipment/Meters - Ex i
Portable Hand Lamps- Ex i
* Minimum IP 55 (for UN-insulated parts) and IP 44 (for
insulated parts) if Ex e protection is used for outdoor
applications