Baldor CMG Western Rotor WEG


In electrical engineering, hazardous locations (sometimes abbreviated to HazLoc, pronounced Haz·Lōk) are defined as places where fire or explosion hazards may exist due to flammable gases, flammable liquid–produced vapors, combustible liquid–produced vapors, combustible dusts, or ignitable fibers/flyings present in the air in quantities sufficient to produce explosive or ignitable mixtures.[1] Electrical equipment that must be installed in such classified locations should be specially designed and tested to ensure it does not initiate an explosion, due to arcing contacts or high surface temperature of equipment.

The introduction of electrical apparatus for signaling or lighting in coal mines was accompanied by electrically-initiated explosions of flammable gas and dust. Technical standards were developed to identify the features of electrical apparatus that would prevent electrical initiation of explosions due to energy or thermal effects. Several physical methods of protection are used. The apparatus may be designed to prevent entry of flammable gas or dust into the interior. The apparatus may be strong enough to contain and cool any combustion gases produced internally. Or, electrical devices may be designed so that they cannot produce a spark strong enough or temperatures high enough to ignite a specified hazardous gas.

Typical gas hazards are from hydrocarbon compounds, but hydrogen and ammonia are common industrial gases that are flammable.

Class I, Division 1 classified locations
An area where ignitable concentrations of flammable gases, vapors or liquids can exist all of the time or some of the time under normal operating conditions. A Class I, Division 1 area encompasses the combination of Zone 0 and Zone 1 areas.
Zone 0 classified locations
An area where ignitable concentrations of flammable gases, vapors or liquids are present continuously or for long periods of time under normal operating conditions. An example of this would be the vapor space above the liquid in the top of a tank or drum. The ANSI/NEC classification method consider this environment a Class I, Division 1 area. As a guide for Zone 0, this can be defined as over 1000 hours/year or >10% of the time.[4]
Zone 1 classified location
An area where ignitable concentrations of flammable gases, vapors or liquids are likely to exist under normal operating conditions. As a guide for Zone 1, this can be defined as 10–1000 hours/year or 0.1–10% of the time.[4]
Class I, Division 2 or Zone 2 classified locations
An area where ignitable concentrations of flammable gases, vapors or liquids are not likely to exist under normal operating conditions. In this area the gas, vapor or liquids would only be present under abnormal conditions (most often leaks under abnormal conditions).
As a general guide for Zone 2, unwanted substances should only be present under 10 hours/year or 0–0.1% of the time.[4]
Unclassified locations
Also known as non-hazardous or ordinary locations, these locations are determined to be neither Class I, Division 1 or Division 2; Zone 0, Zone 1 or Zone 2; or any combination thereof. Such areas include a residence or office where the only risk of a release of explosive or flammable gas would be such things as the propellant in an aerosol spray. The only explosive or flammable liquid would be paint and brush cleaner. These are designated as very low risk of causing an explosion and are more of a fire risk (although gas explosions in residential buildings do occur). Unclassified locations on chemical and other plant are present where it is absolutely certain that the hazardous gas is diluted to a concentration below 25% of its lower flammability limit (or lower explosive limit (LEL)).
Class II, Division 1 classified locations
An area where ignitable concentrations of combustible dust can exist all of the time or some of the time under normal operating conditions.
Class II, Division 2 classified locations
An area where ignitable concentrations of combustible dust are not likely to exist under normal operating conditions.
Class III, Division 1 classified locations
An area where easily ignitable fibers or materials producing combustible flyings are handled, manufactured or used.
Class III, Division 2 classified locations
An area where easily ignitable fibers are stored or handled.
Zone 20 classified locations
An area where ignitable concentrations of combustible dust or ignitable fibers/flyings are present continuously or for long periods of time under normal operating conditions.
Zone 21 classified location
An area where ignitable concentrations of combustible dust or ignitable fibers/flyings are likely to exist under normal operating conditions.
Zone 22 classified locations
An area where ignitable concentrations of combustible dust or ignitable fibers/flyings are not likely to exist under normal operating conditions.
Unclassified locations
Also known as non-hazardous or ordinary locations, these locations are determined to be neither Class II, Division 1 or Division 2; Class III, Division 1 or Division 2; Zone 20, Zone 21 or Zone 22; or any combination thereof.

 

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