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EXPLOSIONPROOF MOTOR ENCLOSURE FORMAT DEFINITION

EXPLOSIONPROOF MOTOR ENCLOSURE FORMAT DEFINITION
How to group explosionproof motor according to its format?

The explosionproof motor is a totally enclosed machine and is designed to withstand an explosion of specified gas or vapor inside the motor casing and prevent the ignition outside the motor by sparks, flashing or explosion. These motors are designed for specific hazardous purposes, such as atmospheres containing gases or hazardous dusts. For safe operation, the maximum motor operating temperature must be below the
ignition temperature of surrounding gases or vapors. Explosionproof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories.

Hazardous location motor applications are classified by the type of hazardous environment present, the characteristics of the specific material creating the hazard, the probability of exposure to the environment, and the maximum temperature level that is considered safe for the substance creating the hazard. The format used to define this information is a class, group, division and temperature code structure.

Class I (Gas or Vapor)
    Group:
        A - Acetylene
        B - Hydrogen and Manufactured Gases
        C - Ethyl-Ether, Ethylene and Cyclopropane
       D - Gasoline, Hexane, Naphtha, Benzine, Butane, Propane, Alcohol Lacquer Solvent Vapors and  Natural Gas
    Division II:
Hazard of fire or explosion is present only as a result of an accident. Motors may be dripproof or TEFC.

Class II (Dusts)
    Group:
        E - Metal Dust (Special Seals)
        F - Carbon Black, Coal or Coke Dust
        G - Flour, Starch or Grain Dust
    Division I:
Hazard is always present due to normal conditions. (Dust suspended in the atmosphere.) Motors must be explosionproof construction with Underwriter’s label.
    Division II:
Motors may be TEFC or externally ventilated:

(A) Where dust deposits on electrical equipment prevent safe heat dissipation.
(B) Where deposit or dust might be ignited by arcs or burning material.

Class III (Fibers)
Fibers those are easily ignitable but not apt to be suspended in the air to produce mixtures. Examples include rayon, nylon, cotton, saw dust, and wood chips.

Division II:
Location in which easily ignitable fibers are stored or handled TEFC enclosure can be used if there is a minimal amount of fibers or flying in the air.

source: 2010 IIEE Technical Manuals
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