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What is Explosion-Proof ?
What is “Explosion-Proof?”
Explosion Proof products are capable of containing an
explosion. It is able to withstand
an internal explosion without allowing the flames or gases to escape the
enclosure. If flames or gases would
be able to escape the enclosure, it could trigger an explosion in the
surrounding area.
Explosion-proof does not mean that the
enclosure is able to withstand an external explosion. They
are designed to withstand internal only.
The “explosion-proof” term is assigned to products certified
by national rating agencies such as Underwriters Laboratories and Factory Mutual
Research after meeting their specifications and passing their tests. Unless certified by one of these
agencies, the product does not meet the “explosion-proof” requirements of the
National Electrical Code.
Intrinsically
Safe products receive their
classification because their electrical power usage is below the level of power
required to set off an explosion within a given hazardous area. In addition,
"intrinsically safe'" products are incapable of storing large amounts of energy
which might spark an explosion when discharged.
What are Hazardous locations?
Hazardous locations are determined by the following
1. The possible presence of an explosive atmosphere such
as:
| Explosion
Proof Classification |
| Class |
| Class I |
Locations which are hazardous due to combustible
gas, vapors, or liquids |
| Class II |
Locations which are hazardous
due to
combustible durst |
| Class III |
Locations which are hazardous
due to
combustible fibers or flyings |
| Division |
| Division I |
Locations in which hazardous
concentrations in the air exist continuously, intermittently, or
periodically under normal operating conditions |
| Division II |
Locations in which hazardous
concentrations are handled, processed, or used but are normally within
closed containers or closed systems from which they can escape only in
case of accidental rupture or breakdown. |
| Group (Class I) |
| Group A |
Atmosphere contains acetylene |
| Group B |
Atmosphere contains hydrogen, or gases (or vapors)
of equivalent
hazard, such as manufactured gas |
| Group C |
Atmosphere contains ethyl-ether vapors,
ethylene, or
cyclo propane |
| Group D |
Atmosphere contains containing gasoline, hexane, naptha,
benzine, butane, alcohol, acetone, benzol, lacquer solvent vapors, or
natural gas |
| Group (Class II) |
Group
E |
Atmosphere contains metal dust, including aluminum,
magnesium and their commercial alloys and other metals of similarly
hazardous characteristics. |
Group
F |
Atmosphere contains carbon black, coal, or coke
dust. |
| Group G |
Atmosphere contains flour, starch, or grain
dust. |
2. The likelihood that the explosive atmosphere is present
when equipment is operating,
3. The
ignition-related properties of the explosive atmosphere that is present
Locations may also be labeled as
“hazardous” for other reasons, including, the use of electrical equipment in the
vicinity of water, the risk of personal injury from moving or falling parts, or
the presence of other biological hazards.
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