Among the different meanings of the word “Classified”, my favorite example is from the movie “Top Gun”. Maverick (the hot shot fighter pilot) tells Charlie (the aviation expert and his soon-to-be love interest) that he can’t disclose the location of his encounter with an enemy plane: “That’s classified. I could tell you, but I’d have to kill you.”
That’s not the “classified” I’m writing about today, although this definition is near and dear to my heart as well: “Areas with possible fire or explosion risks due to explosive atmospheres and/or mixtures” are known in industry as “classified” or “hazardous”. Operations in such areas are strictly regulated…depending on the nature & severity of the hazard, the use of non-sparking tools (commonly made of brass) may be required, for example. Equipment installed in these areas must likewise be designed to eliminate risks of fire or explosion…like EXAIR HazLoc Cabinet Cooler Systems. These are engineered and approved for use in certain classified areas. In the United States, the National Electrical Code (NEC) defines these areas in a system of Classes, Divisions, and Groups, depending on the nature of the material that presents the hazard (Class), whether it normally exists or if it’s just possible in abnormal situations (Division), and the specific type of the subject material (Group).
Among the classified areas we can specify a HazLoc Cabinet Cooler System in, I’ve previously covered Class I Div 1 here, and Class III has been covered here. Class II areas are where the material presenting the hazard is dust, and that’s the subject of today’s blog.
Typical Class II environments are, well, dusty places. One example would be a coal burning power plant. Specific areas of may be classified as Class II Div 1, if sufficient concentration of the dust exists during normal operation. These plants have a machine called a pulverizer, which is aptly named…it turns lump coal into dust, which is way more efficient to burn than lump coal. Areas adjacent to the pulverizer may be Class I Div 1, but the rest of the boiler room itself may be considered a Class II Div 2 environment. As long as the pulverizer is working properly (e.g., sending all the coal dust into the boiler instead of the boiler room), there’s a low probability of a explosive or ignitable mixture of coal dust in the air.
Class II areas are further separated into Groups, defined by the type of dust that merits the Class II designation:
- Group E: Atmosphere containing combustible metal dusts, including aluminum, magnesium, bronze, chromium, titanium, zinc and their commercial alloys or other combustible dusts whose particle size, abrasiveness and conductivity present similar hazards in connection with electrical equipment.
- Group F: Atmosphere containing carbonaceous dusts, carbon black, coal black, charcoal, coal or coke dusts that have more than 8% total entrapped volatiles or dusts that have been sesitized by other materials so they present an explosion hazard.
- Group G: Atmosphere containing combustible dust not included in Group E & F – such as flour, grain, starch, sugar, wood, plastics and chemicals.
EXAIR HazLoc Cabinet Cooler Systems carry the UL Classified Mark, and as such, can be used safely in classified areas on purged electrical enclosures. It’s important to note that, to maintain Class I Div 1, Class II Div 1, or Class III integrity, they must be used in conjunction with such a purge & pressurized control system – they don’t take the place of such a system. We stock them in cooling capacities from 1,000 to 5,600 Btu/hr, in NEMA 4 or NEMA 4X (IP66) ratings.
EXAIR is committed to safety, and that, of course, includes the proper specification and use of our products. If you’d like to find out which of our Cabinet Cooler Systems…or any of our engineered compressed air products…are suitable for use in a particular environment, give me a call.
Russ Bowman, CCASS