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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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