2. INTRODUCTION
• A hazardous location is any location
where a potential hazard, either a fire or
an explosion can exist due to the presence
of flammable, combustible, or ignitable
materials.
• These materials can consist of gases,
vapors, liquids, dusts, fibers, etc.
3. HAZARDOUS LOCATION
TYPES
• Class I Locations:
An area where flammable gases or vapors are
or can be present in the air in quantities
sufficient to produce explosive or ignitable
mixtures. For Example
* Petroleum Refineries, Gasoline storage and
dispensing areas, Dry cleaning plants, Spray
Finishing areas, utility gas plants.
4. Continued
• Class II Locations:
An area where presence of combustible
dust present a fire or explosion hazard.
For example:
Grain elevators, flour and feed mills, Use
or store of magnesium or aluminum
powders, producers of plastics, fireworks.
5. Continued
• Class III Locations:
An area made hazardous due to the
presence of easily ignitable fibers or
flyings. For example:
Textile mills, cotton gins, cotton seed
mills, plants that shape or cut wood and
create sawdust or flyings.
6. Hazardous Location Conditions
• In addition to the types of hazardous
locations, the kind of conditions under
which these hazards are present are very
important : Normal Conditions,
Abnormal Conditions.
• Division 1: Normal Conditions
• Division 2 : Abnormal Conditions
7. Continued
• Class I, Class II, and Class III hazardous
locations can be either Division 1 or
Division 2
• Good examples of Class I, Division 1
locations: areas near open dome loading
facilities or adjacent to relief valves in a
petroleum refinery, because the
hazardous material would be present
during normal plant operations.
8. Continued
• Closed storage drums containing
flammable liquids in an inside storage
room would not normally allow
hazardous vapors to escape into the
atmosphere but, what happens if one of
the containers is leaking? You have got a
Division 2 – Abnormal – condition … A
Class I, Division 2 hazardous location.
12. Nature of Hazardous Substances
• The gases and vapors of class I locations
are broken into four groups : A, B, C, and
D. These materials are grouped
according to the ignition temperature of
the substance, its explosion pressure, and
other flammable characteristics.
13. Group A
• Group A is an atmosphere containing
acetylene.
• Equipment with rating up to 536º F
(280ºC) can be utilized.
14. Group B
• Group B is an atmosphere containing
hydrogen, or gases or vapors with a
hazard equal to hydrogen. Butadiene,
and ethylene and propylene oxide are
included in this group.
15. Group C
• Group C is an atmosphere containing
cyclo-propane, ethyl ether, or ethylene or
gases or vapors with hazard equal to
these gases.
16. Group D
• Group D is an atmosphere containing
acetone, alcohol, benzene, butane,
gasoline, propane, natural gases or gases
with vapors with a hazard equal to these
gases.
17. Nature of Hazardous
Substances
• In Class II - dust locations – we find the
hazardous materials in Groups: E, F, G.
These groups are classified according to
the ignition temperature and the
conductivity of the hazardous substance.
• Conductivity is an important
consideration in Class II locations,
especially with metal dusts.
18. Group E
• Group E is an atmosphere containing
metallic dusts or other dusts with a
similar hazard that is equivalent, such as
Aluminum and Magnesium dusts.
19. Group F
• Group F is an atmosphere containing
Carbon Black, Charcoal Coal, or Coke
dusts with 8% or less total volatile
material.
20. Group G
• Group G is an atmosphere containing
grain dusts, flour , starch, cocoa, and
similar types of materials.
22. Equipment for Hazardous
Locations
• Equipment for Class I locations:
The equipment used in Class I locations
are housed in enclosures designed to
contain any explosion that might occur if
hazardous vapors were to enter the
enclosure and ignite.
Also it is designed to cool and vent the
products of this explosion.
23.
24.
25. Equipment for Class II
Locations
• Class II locations make use of equipment
designed to seal out dust. The enclosures are
not intended to contain an internal
explosion, but rather to eliminate the source
of ignition so no explosion can occur within
the enclosure.
26. Equipment for Class III
Locations
• Equipment used in class III locations need
to be designed to prevent fibers and flyings
from entering the housing. It also needs to
be constructed in such a way as to prevent
the escape of sparks or burning materials.
• It must also operate below the point of
combustion.
27. Types of Protection
1. Flameproof Enclosures “d”
2. Intrinsic Safety “i”
3. Increased Safety “e”
4. Powder/Sand Filled “q”
5. Pressurized Apparatus “p”
6. Oil Immersion “o”
7. Special Protection “s”
8. Encapsulation “m”
9. Type of protection N “N”
28. Flameproof Enclosures “d”
Type of protection, for which
the parts which can ignite an
explosive atmosphere are
inside an enclosure which will
Withstand the pressure of the
Explosion within the enclosure.
Prevent the transmission of the
Explosion to an explosive
Atmosphere surrounding the
Enclosure.
29. Intrinsic Safety “i”
• Type of protection, for which the
energy in the electrical circuit is held
so low that sparks, arcs or
temperatures capable of causing
ignition cannot occur.
• Includes sub-division into the
categories ia & ib
• Ia must not produce any ignition when
any combination of two faults is
present.
• Ib must not produce any ignition, in
normal operation, when one fault is
present.
30. Increased Safety “e”
• Type of protection, for
which measures are taken to
prevent the possibility of
non-permissible high
temperatures and the
formation of sparks or arcs
on inner or outer parts of
electrical apparatus, on
which these do not occur in
normal operation, with an
increased level of safety.
31. Powder/Sand Filled “q”
• The electrical apparatus
enclosure is filled with
powder or sand.
• An arc occurring in the
enclosure does not ignite
an explosive
atmospheres
surrounding the
enclosure.
32. Pressurized Apparatus “p”
• Preventing the entry of
surrounding atmosphere
into the enclosure by
holding an ignition-
protection gas (air, inert
gas) under over-pressure
in relation to the
surrounding atmosphere
33. Oil Immersion “o”
• Electrical apparatus or
parts thereof are made
safe by immersion in oil
such that potentially
explosive atmosphere
above the surface of the
oil or outside the
enclosure will not be
ignited.
34. EEx ib IIB T4
• E: European Standards
• Ex ib: Intrinsically safe to category ib
• II: Certification for use in apparatus group II
(in other industries) (I is for mines)
• B: Explosion classes
• T4: The ignition temperature of any gas or
vapor with which this device will be used is not
less than 135 degree C
35. Division into Groups
Protection from Firedamp and
Explosion
• Group I:
• Contains equipment
intended for operation
underground in mines
endangered by
firedamp.
• Group II:
• Contains equipment
intended for operation
in all explosive gas
atmospheres other than
those to be found in
mines.
36. Temperature Classes Ignition
Groups
Temp. Class Highest
Permissible
Surface Temp. in
Degree C
Ignition Temp of
Flammable
Substance in
Degree C
T1 450 < 450
T2 300 < 300
T3 200 < 200
T4 135 < 135
T5 100 < 100
T6 85 < 85
37. Explosion Classes
Apparatus group
for flameproof
enclosure “d”
Limiting Gap
Width
Minimum Ignition
Current for Intrinsically
Safe Circuits “i”
Ratio in relation to
Methane
A > 0.9 mm > 0.8
B > Or = 0.5 to
0.9 mm
> Or = 0.45 to 0.8
C < 0.5 mm < 0.45
38. Dust and Water Protection IP
The first number refers to protection against the ingress
of solid & the second refers to protection against the
ingress of liquids
1st Number Degree of Protection 2nd Number Degree of Protection
1 Protection against large-
sized foreign bodies
(hands)
1 Drops of condensed
water
2 Medium-sized foreign
bodies (finger)
2 Drops of liquid, with
the equipment tilted at
any angle up to 15°
from the vertical
3 Protection against the
ingress of foreign bodies
greater than 2.5 mm
thick
3 Against rain falling at
an angle of 60° or less
from the vertical
4 Greater than 1 mm thick 4 Protection against
water splashed from
any direction
39. 5 Protection against the
ingress of dust
5 Protection against jets of
water
6 Complete protection from
the ingress of dust
6 Protection against water
from heavy seas
7 Protection against
immersion in water under
stated conditions of
pressure and time
8 Protection against
immersion in water under
specified pressure for an
indefinite period of time.
