Hazardous Areas Classification - Europe
European hazardous areas classifications in zones, protection types,
temperature codes and codes
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Hazardous areas outside North America are classified by gas groups and
zones.
·
Zones are used to define the probability of the presence of
flammable materials.
·
Groups classify the exact flammable nature of the material.
Protection Types are used to denote the level of
safety for the device. Equipment approved receives a temperature code
indicating the maximum surface temperature of the equipment.
Zones
The zone defines the probability of hazardous material
being present in an ignitable concentration in the surrounding atmosphere.
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Zone 0
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Area in which an
explosive gas-air mixture is continuously present or present for long
periods.
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Zone 1
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Combustible or
conductive dusts are present. Area in which an explosive gas-air mixture is
likely to occur for short periods in normal operation.
|
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Zone 2
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Area in which an
explosive gas-air mixture is not likely to occur, and if it occurs it will
only exist for a very short time due to an abnormal condition.
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Protection Types
Different protection techniques are used to address the
hazardous zones.
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|
Zone
|
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Ex d
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Flameproof
(Explosion proof) Enclosure
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1,2
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Ex e
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Increased Safety
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1,2
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Ex ia
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Intrinsically Safe
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0,1,2
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Ex ib
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Intrinsically Safe
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1,2
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Ex o
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Oil Immersion
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2
|
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Ex p
|
Pressurized
Apparatus (Purged Apparatus)
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1,2
|
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Ex q
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Powder Filling (Sand
Filling)
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2
|
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Ex m
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Encapsulation
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1,2
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Ex n or Ex N
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Non incentive or/and
normally no sparking circuits
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2
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Flameproof (Explosion proof) Enclosure
All electrical circuits are enclosed in a house strong
enough to contain any explosion or fire that may take place on the inside.
Increased Safety
Electrical circuits incorporates special measures to reduce
the probability of excessive temperatures and the occurrence of arcs and sparks
in normal service.
Intrinsically Safety
The electrical energy available in circuits and equipment,
is limited to a level to low to ignite the most easily ignitable mixtures in a
hazardous area.
Intrinsically safe barriers, as Zener, are installed in the
circuit to limit current and voltage in the hazardous areas to avoid sparks or
hot spots under fault conditions.
Temperature Codes
A mixture of air and hazardous gases may ignite by coming
in contact with a hot surface. An ignition depends on surface area, temperature
and the concentration of the gas.
Certified equipment are tested for maximum temperature
ratings by approval agencies. Equipment for Group II receives a temperature
code indicating the maximum surface temperature.
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Temperature Code
|
oF
|
oC
|
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T1
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842
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450
|
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T2
|
572
|
300
|
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T3
|
392
|
200
|
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T4
|
275
|
135
|
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T5
|
212
|
100
|
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T6
|
185
|
85
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The coding is based on a 104 oF (40 oC)
ambient temperature.
The automatic ignition temperature can be found in IEC
79-4.
Groups
Electrical equipment are divided into two groups where
Group I covers equipment used in mines and Group II covers all other
applications. Group II is subdivided into three subgroups where the specific
hazardous materials within each group can be found in CENELEC
EN 50014.
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Group I
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For application in
below ground installations (mines) where methane (firedamp) and coal dust may
be present.
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Group IIA
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For application in
above ground installation where hazards due to propane may exist.
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Group IIB
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For application in
above ground installations where hazards due to ethylene may exist.
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Group IIC
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For application in
above ground installations where hazards due to hydrogen or acetylene may
exist.
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