Killark Full Catalog

I NTRODUCT I ON HAZARDOUS LOCATION DATA

Zone System – Material (Dust) Groups (IIA, IIB, IIC) Zone Dust Groups General information

bearings, and if allowed to enter an enclosure, metal dusts are likely to cause an electrical fault in the equipment. Since Group IIIC dusts have the potential to be the source of the equipment failure, source of ignition and fuel for an explosion simultaneously, any accumulation is normally considered to be Zone 0. Group IIB Non-conductive dust with electrical resistivity greater than 103 Ω ·m Group IIIB includes all non-conductive dust. This equates to most of the dusts identified as Class II Groups F and G. Group IIA Easily ignited fibers and flyings. Essentially this is “big” dust and includes all the materials identified as Class III. Group IIIA materials are not likely to be suspended in the air in sufficient quantities to produce an ignitable mixture. Group IIIA materials do not present an explosion hazard but they can support a flash fire.

The Zone explosive dust groups are based on the IEC and prefixed by “III”. Underground mining uses the same Dust Groups.

Note: the NEC does not deal with mining; references to “I” are excluded.

Group IIIC Combustible dust with electrical resistivity equal to or less than 103 Ω ·m NOTE: Metal dust is treated as conductive dust because it is assumed that surface oxidation cannot be depended upon to always ensure electrical resistivity greater than 1 × 103 Ω ·m. Group III includes metal dusts, such as aluminums and magnesium. These dusts are highly abrasive and can cause overheating in equipment such as motor

Hazardous Location – Area Classification for Easily Ignitable Fibers or Flyings

Class III, Division 1 Locations Typical locations include facilities with equipment that produces ignitable fibers or flyings (textile mill machinery, for example) or where the material is collected and packaged (for example, where the material is placed into bags). Class III, Division 2 Locations Typical locations include facilities where easily ignitable fibers are stored or handled, that are separate from the manufacturing process. Class III Material Groups There are no Material Groups identified in the Class III System.

Class III locations address the presence of easily ignitable fibers or flyings, but in which the fibers or flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures. While easily ignitable fibers and flyings do not present an explosion hazard, their presence increases the risk of a “flash fire” which can progress at near explosive speed. A typical example of this type of material is the cotton lint that accumulates in the lint trap of clothes dryers. Listed clothes dryers are designed so that even if the lint ignites, the fire will be contained within the dryer enclosure. NOTE: Applies only to the Class/Division System. The equivalent to “Class III” locations are identified as a “Group IIIA” Explosive Dust Atmospheres in the Zone system

www.hubbell.com/killark

H15