Electric Motors for Hazardous Locations
Electric motors for use in North American Hazardous (Classified) Locations generally fall into one of two categories:
Division 1 locations are environments where a hazard is present continuously or would be subject to fire or explosion if the hazard was present as a result of an accident or uncommon occurrence. Division 1 electric motors require special construction and are designed for use when the explosive material is present, self-containing any internal explosion.
Division 2 locations are environments where the threat of fire or explosion is not normally present but could potentially be present in the event of a system failure. Division 2 electric motor construction requirements are less stringent than Division 1 but do require Division 2 markings with the Class, Group and Temperature Code identified on the motor.
Hazardous (Classified) Locations are further defined by using Class and Group designations to identify the type of material present:
Class and Group information is broken down in the following way:
Class I (Flammable Gases, Vapors, Liquids)
Group A: Atmospheres containing acetylene.
Group B: Atmospheres containing butadiene, ethylene oxide, hydrogen, propylene oxide, or manufactured gases containing more than 30% hydrogen by volume.
Group C: Atmospheres containing ethyl ether, ethylene, or gases or vapors of equivalent hazard.
Group D: Atmospheres such as acetone, ammonia, benzene, butane, cyclopropane, ethanol, gasoline, hexane, methanol, methane, natural gas, naphtha, propane, or gases or vapors of equivalent hazard.
Class II (Combustible Dusts)
Group E: Atmospheres containing aluminum, magnesium and other metal dusts with similar characteristics.
Group F: Atmospheres containing carbonaceous dusts, including carbon black, charcoal, coal or coke dusts that have more than 8%total entrapped volatiles, or dusts that have been sensitized by other materials so that they present an explosion hazard.
Group G: Atmospheres containing combustible dusts not included in Group E or F, including flour, grain, wood, plastic, and chemicals.
Motors for hazardous locations in Europe must meet a different set of standards and require different markings than those of North America. The European Committee for Electrotechnical Standardization (CENELEC) sets the standards for equipment in hazardous locations and/or explosive atmospheres for motors used in Europe. These are often referred to as Zone 1 (flameproof) or Zone 2 (increased safety or non-sparking) motors and must comply with the ATEX Directive, which covers all electrical equipment for use in potentially explosive atmospheres.
Selecting an Electric Motor
The local Authority having Jurisdiction determines what is required at the site regarding:
- Temperature Code
Depending on the application and location, the authority having jurisdiction will determine if a severe duty electric motor or an explosion proof electric motor is required.
When operating in a harsh or severe duty environment, a severe duty electric motor will be required at minimum. Regal’s Severe duty motors are CSA Certified for Class I Division 2 hazardous locations. Industrial applications where severe duty motors are required include chemical plants, pulp and paper mills, refineries, mines, food processing, foundries, and other severe duty environments where long life and ultra-high efficiency are desired. Severe duty motors are premium efficiency electric motors on high cycle or long run applications.
The IEEE-841 standard was created by the Institute of Electrical and Electronics Engineers (IEEE) to address the requirements in the petroleum and chemical industries and improve efficiency, performance, and reliability of severe duty motors. The IEEE 841 motor, which includes an IP rated corrosion resistant enclosure, has become widely adopted in other industries as well.
Regal’s IEEE 841 severe duty electric motors are also CSA Certified for Class I Division 2 hazardous locations. They are used for extreme applications in the process industries such as chemical plants, pulp and paper mills, refineries, above-ground mines, food processing, foundries, and other severe duty environments where corrosion protection for long motor life and ultra-high efficiency are required. The IEEE 841 is the most robust severe duty motor that is not a Division I hazardous location.
NEMA defines an explosion-proof motor as “a totally-enclosed machine designed and constructed to withstand an explosion of a specified gas or vapor which may occur within it and to prevent ignition of specified gas or vapor surrounding the machine by sparks, flashes or explosions of the specified gas or vapor which may occur within the machine casing”. Explosion proof motors are required for Division I hazardous locations involving gases, liquids, or vapors including Class I Group D, Class I Groups C & D. Typical applications include petroleum and chemical plants or pipelines, gasoline pumps and natural gas compressors.
A dust-ignition-proof motor is “a totally enclosed machine whose enclosure is designed and constructed in a manner which will exclude ignitable amounts of dust or amounts which might affect performance or rating, and which will not permit arcs, sparks, or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specific dust on or in the vicinity of the enclosure. Successful operation of this type of machine requires avoidance of overheating from such causes as excessive overloads, stalling, or accumulation of excessive quantities of dust on the machine”. Dust ignition proof motors are required for Division 1 hazardous locations involving various types of dusts, such as Class II, Group F, or Class II, Group G. Typical applications include grain elevators, coal handling equipment, feed and cereal mills, sugar refineries and chemical plants.
Enclosures and Method of Cooling
Electric motors are available in various enclosures, and application conditions will determine the type of motor enclosure and method of cooling required. Electric motor enclosures include:
- Dripproof (DP) - Dripproof motors have open enclosures and are suitable for indoor use and in relatively clean atmospheres.
- Dripproof Force Ventilated (DPFV) - Dripproof motors have ventilating openings constructed so that drops of liquid or solid particles falling on the machine at an angle of not greater than 15 degrees from the vertical cannot enter the machine.
- Totally Enclosed Fan Cooled (TEFC) - Totally enclosed fan cooled motors are cooled by external means that are part of the motor but not in the internal workings of the motor.
- Totally Enclosed Non-Ventilated (TENV) - Totally enclosed non-ventilated motors are not cooled by external means but instead are self-cooled.
- Totally Enclosed (TEAO) - Totally enclosed air over motors are sufficiently cooled by external means, provided by the customer.
- Totally Enclosed Blower Cooled (TEBC) - Totally enclosed blower cooled motors have an external fan that blows outside air over the frame of the motor.
It’s important to remember that misapplication of a motor in hazardous environments can cause fire or an explosion and result in serious injury. Only the end user, local authority having jurisdiction, and/or insurance underwriter are qualified to identify the appropriate class(es), group(s), division(s), and temperature code(s) that apply in a hazardous environment.