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hazardous location classification

hazardous location classification

Hazardous Locations consist of areas where there is the potential for a fire or explosion due to electrical equipment that is in operation in this area with a reaction to flammable or ignitable gases, liquids, vapors, combustible dusts, fibers or flyings. The need for Explosion-Proof equipment then arises due to this potential for fire or explosion.

The National Electrical Code (NEC) along with the National Fire Protection Association (NFPA) and Underwriters Laboratories (UL) have published a guide along with codes that classify hazardous areas into classes, divisions and zones.

The Combustion or Fire Triangle is used to classify Hazardous Locations in the Explosion-Proof industry. A source of fuel (explosive gases,liquids, or vapors), source of ignition (fire, spark, or explosion) and oxygen must be present in the appropriate consistencies for an explosion to occur. Our Explosion-Proof Enclosures & Systems operate to prevent these three criteria from mixing in such a way that would generate an explosion and be hazardous to the surrounding environment.

Class I locations consist of areas where gases, vapors or liquids may exist that have the potential to become flammable or ignitable. There are two different divisions that exist in Class I, Division 1 and Division 2, along with three Zones; Zone 0, 1 & 2. Locations that would be considered to be Class I include Petroleum Refineries, Gasoline Storage Areas, Dry Cleaning Plants, Spray Finishing Areas, Fuel Servicing Areas, etc.

Class II locations consist of locations where combustible dusts may exist that have the potential to become flammable or ignitable. Locations that would be considered to be Class II include Grain elevators, Flour and feed mills, Metal powder manufacturers, and Coal plants, etc.

Class III locations consist of locations where fibers and flyings may exist that have the potential to become flammable or ignitable. Locations that would be considered to be Class III include Cotton Gins, Cotton Seed Mills, Sawdust or flyings plants, or Textile mills.

TYPE 4 - Type 4 enclosures are intended for indoor or outdoor use primarily to provide a degree of protection against windblown rain, dust, splashing water, hose directed water, and external ice formation

TYPE 4X - Type 4X enclosures are intended for indoor and outdoor use primarily to provide a degree of protection against corrosion, windblown dust and rain, splashing water, hose directed water and external ice formation.

Explosion-Proof Enclosure: An enclosure which can withstand the pressures resulting from an internal explosion of specified gases, and contain such an explosion sufficiently to prevent the ignition of the explosive atmosphere surrounding the enclosure (for Class I, II and III).

Oil Immersion: The electrical apparatus are arranged such that the arcing contacts, connections, etc., are immersed in oil. Arcing is confined under the oil such that it will not ignite an explosive mixture of specified gases above the oil or in the atmosphere surrounding the enclosure (for Class I, II and III).

Purged & Pressurized Enclosures: The accumulation of ignitable gases or vapors in the enclosure is prevented by maintaining, inside the enclosure, sufficient flow of clean air or inert gas (for Class I, II and III).

Intrinsically Safe Equipment: Wiring that is incapable of releasing sufficient electrical or thermal energy, under normal and abnormal conditions, to cause ignition of a specific hazardous atmospheric mixture in its most easily ignitable concentration (for Class I, II and III).

Dust Ignition-Proof: The enclosure prevents the entrance of dust, and external surfaces shall not reach temperatures capable of igniting or discoloring dust on the enclosure or igniting dust-air mixtures in the surrounding atmospheres (for Class II).

Type d (Exd): Explosionproof/Flameproof Enclosure. An enclosure that can withstand the pressure developed during an internal explosion of specified gases and which prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure (for Zones 1 and 2).

Type o (Exo): Oil immersion. The electrical apparatus is immersed in oil in such a way that an explosive atmosphere, which may be above the oil or outside the enclosure cannot be ignited (for Zone 1).

Type p (Exp): Pressurized enclosure. The entry of a surrounding atmosphere into the enclosure is prevented by maintaining inside the enclosure a protective gas at a higher pressure than that of the surrounding atmosphere (for Zones 1 and 2).

Type i (Exi): Intrinsically Safe Systems are incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause and ignition of a given explosive atmosphere (for all Zones, 0, 1 and 2).

Type e (Exe): Increased Safety. Measures are taken to prevent, with a minor degree of security, the possibility of excessive temperatures and the occurrence of arcs or sparks in the interior and on the external parts of the electrical apparatus which do not occur in normal service (for Zones 1 and 2).

Type q (Exq): Powder filled. The enclosure is filled with finely granulated material such that, in the intended service conditions, any arc occurring within the enclosure of an electrical apparatus will not ignite the surrounding atmosphere. No ignition shall be caused by flame or excessive temperature of the surfaces of the enclosure (for Zone 1).

Type N (Exn): Not CENELEC recognized. Measures are applied to the electrical apparatus such that, in normal operation, it is not capable of igniting a surrounding explosive atmosphere and a fault capable of causing ignition is not likely to occur (for Zone 2).

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