Type EE vs. Type EX
Type EE equipment is authorized for use in Division 2 designated hazardous areas, while Type EX equipment is authorized for use in both Division 1 and Division 2. Under normal conditions in a Division 1 area, hazardous concentrations of flammable gases, vapors or dusts can exist all of the time. In Division 2 areas, hazardous concentrations are not likely to exist and are normally prevented by keeping flammable liquids, gases, or dusts in closed containers.
EE equipment is used in Division 2 areas where flammable or explosive materials are stored in sealed containers. However, if a sealed container or drum is pierced by a fork or dropped, the resulting leak or rupture makes the Division 2 area immediately volatile and creates an instantaneous Division 1 environment. Under these circumstances, the use of EE equipment is no longer safe and could result in fire or explosion.
Type Designation EE
“An electrically powered unit that, in addition to meeting all the requirements for Type E and ES units, has its electrical motors and all other electrical equipment completely enclosed.” NFPA 505(2002)188.8.131.52
In Type EE construction, motors and switches should be enclosed to prevent sparks from escaping, and flexible leads should be in non-metallic looming or tubing. Type EE equipment is authorized for use in some Division 2 designated hazardous areas.
Type EE equipment rating does not protect against explosive mixtures of gases or dusts in the atmosphere. The EE rating does not protect against: static discharges in atmosphere, auto ignition temperatures generated during normal forklift operation or electrical system failures. Type EE equipment cannot be used in any Division 1 designated hazardous area.
Type Designation EX
“An electrically powered unit in which the electrical fittings and equipment are so designed, constructed and assembled that the unit can be used in atmosphere containing specifically named flammable vapors, dusts, and under certain conditions, fibers.” NFPA505(2002)184.108.40.206
Type EX equipment must meet the fire and shock hazard requirements of UL583. In addition, EX equipment must have Explosion Proof enclosures (for Class 1, Division 1) and dust-ignition proof enclosures (for Class II, Division 1), in accordance with UL1203. EX equipment (for Classes I and II, Division 2 and Class III) must meet UL1604 requirements in which the circuits and components are incapable of causing ignition of the flammable gases or vapors in the environment. Articles 500-504 of the National Electric Code define and set forth the rigid requirements for EX equipment labeled for use in Class I, Divisions 1, 2, Groups C,D and Class II, Divisions 1, 2, Group G.
Misunderstanding of EE Rating
There is a very dangerous misunderstanding that EE rated machines are safe for use in hazardous locations. These EE machines have minimal spark protection and do not comply with the strict electrical requirements of NFPA 70 (NEC) for hazardous environments.
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