When you enter a hazardous location, you will only find certain types of electrical enclosures. The manufacturer must design the enclosure specially for that environment, adjusting the design and materials to ensure that the perils presented by the setting do not harm the enclosure or the equipment contained within. We recently discussed two types of enclosures made for hazardous locations – NEMA type 7 and type 8 – and today we’re exploring two more. NEMA type 9 and type 10 are not as versatile as many other types of enclosures, but they do perfectly suit several sorts of hazardous locations.
NEMA Type 9 and Type 10
Before we dig in to discussing NEMA types 9 and 10, we need to review NFPA 70. More commonly known as the National Electrical Code (NEC), NFPA 70 is a standard used to ensure safe electrical design, installation, and inspection in order to protect both people and property from electrical hazards. The NEC defines many hazardous locations in which NEMA type 9 and type 10 come in handy.
Protections Offered by a NEMA Type 9 Enclosure
Type 9 enclosures prove immensely useful in environments where the ignition of combustible dust is a concern. In fact, the enclosure is specifically designed to prevent that dangerous situation from occurring. Manufacturers construct this type of enclosure for use in hazardous locations classified as Class II, Division 1, Groups E, F, or G, as defined in NFPA 70.
In order for an area to meet the conditions of a Class II, Division I location, it must contain one of the following situations (source):
- Under normal operating conditions, combustible dust is present in the air in such an amount as to produce explosive or ignitable mixtures. This situation can occur continuously, intermittently, or periodically.
- If a mechanical failure or abnormal machinery operation occurs, it could produce an ignitable and/or explosive mixture.
- Electrically conductive dusts are present in hazardous concentrations.
Hazardous groups are defined as follows (source):
- Group E: Group E atmospheres contain combustible metal dusts. These can include aluminum and magnesium, as well as their commercial alloys. It can also include combustible dusts that present similar hazards in the use of electrical equipment due to their particular size, abrasiveness, or conductivity.
- Group F: Group F atmospheres contain combustible carbonaceous dusts with more than 8% total entrapped volatiles. Or, they could have been sensitized by other materials, creating an explosion hazard. Examples include coal, carbon black, charcoal, and coke dusts.
- Group G: Group G atmospheres contain combustible dusts that are not included in Group E or Group F, such as flour, grain, wood, plastic, and chemicals.
Protections Offered by a NEMA Type 10 Enclosure
As the National Electrical Manufacturers Association (NEMA) explains, “In hazardous locations, when completely and properly installed and maintained,” type 10 enclosures (along with type 7 enclosures) are designed to effectively contain an internal explosion without provoking an external hazard. In addition, NEMA type 10 enclosures meet the requirements of the Mine Safety and Health Administration (MSHA), 30 CFR, Part 18.
Ready to Purchase an Enclosure?
If you need an enclosure for use in a hazardous location, a NEMA type 9 or type 10 enclosure might be just the ticket. However, it is important to review all of your options to ensure that you select the best enclosure for your specific situation. To view all of the NEMA enclosure types, please visit the NEMA website.
Finally, if you’re on the hunt for a company that can manufacture premium metal enclosures on your behalf, check out American Products Contract Manufacturing. Our high-quality, innovative enclosures enable our customers to assist the telecommunications industry in expanding and improving their network services. We offer NEMA type 1, type 2, type 3, type 3-R, type 3X, type 4, and type 4X metal enclosures. Plus, we manufacture these enclosures from aluminum, galvanized steel, carbon steel, and stainless steel to create a rugged and reliable structure and to meet your environment conditions. Give us a call at 1-877-960-3703 to learn more, or request a free quote online.
