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| Understanding Hazardous Area classifications is critical. |
Hazardous areas refer to locations with a possible risk of explosion or fire due to dangerous atmosphere. The hazards can be associated with flammable vapors or gases, ignitable fibers, and combustible dusts.
Different hazardous area classifications exist in the North America and Europe. Generally, the National Electric Code (NEC) classifications govern hazardous areas in the US. While in Europe, hazardous area classification has been specified by the International Electrotechnical Commission (IEC).
CLASS
|
NATURE
OF HAZARDOUS MATERIAL
|
CLASS I
|
Hazardous area due the presence of flammable vapors or gases
in sufficient quantities to produce ignitable mixtures and cause
an explosion.
Examples include
natural gas and liquified petroleum.
|
CLASS II
|
Hazardous area due the presence of conductive or combustible
dusts in sufficient quantities to produce ignitable mixtures
and cause an explosion.
Examples include
aluminum and magnesium powders.
|
CLASS III
|
Hazardous area due the presence of flammable fibers
or other flying debris that collect around lighting fixtures,
machinery, and other areas in sufficient quantities to produce
ignitable mixtures and cause an explosion.
Examples include
sawdust and flyings
|
Division groups hazardous areas based on the chances of an explosion due to the presence of flammable materials in the area.
DIVISION
|
LIKELIHOOD
OF HAZARDOUS MATERIAL
|
DIVISION 1
|
Areas where there is
a high chance of an explosion due to hazardous material that is
present periodically, intermittently, or continuously under normal
operation.
|
DIVISION 2
|
Areas where there is
a low chance of an explosion under normal operation.
|
Group categorizes areas based on the type of flammable or ignitable materials in the environment. As per NEC guidelines, Groups A to D classify gasses while Groups E to G classify dust and flying debris.
GROUP
|
TYPE
OF HAZARDOUS MATERIAL IN THE AREA
|
GROUP A
|
Acetylene.
|
GROUP B
|
Area contains flammable gas, liquid, or liquid produced vapor with
any of the following characteristics:
Examples include hydrogen, ethylene oxide, acrolein, propylene
oxide.
|
GROUP C
|
Area contains flammable gas, liquid, or liquid produced vapor with
any of the following characteristics:
Examples include carbon monoxide, hydrogen sulphide, ether,
cyclopropane, morphline, acetaldehyde, isoprene, and ethylene.
|
GROUP D
|
Area contains flammable gas, liquid, or liquid produced vapor with
any of the following characteristics:
Examples include ammonia, gasoline, butane, benzene, hexane,
ethanol, methane, methanol, natural gas, propane, naphtha, and
vinyl chloride.
|
GROUP E
|
Area contains metal dusts such as magnesium, aluminum, chromium,
bronze, titanium, zinc, and other combustible dusts whose
abrasiveness, size, and conductivity present a hazard.
|
GROUP F
|
Area contains
carbonaceous dusts such as charcoal, coal black, carbon black,
coke dusts and others that present an explosion hazard.
|
GROUP G
|
Area contains combustible dusts not classified in Groups E and F.
Examples include
starch, grain, flour, wood, plastic, sugar, and chemicals.
|
NOTE: This post serves only as a guide to acquaint the reader with hazardous area classifications in the USA. It is imperative to discuss your instrumentation, valve, or process equipment requirement with a qualified applications expert prior to installing any electrical device inside of any hazardous area.
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