Explanation of Hazardous Locations – Class II Div. 1, Groups E, F and G

Per the National Electrical Code (NEC) there are (3) classifications for areas that are defined as hazardous.  They are Class I (gases & vapors), Class II (flammable dusts) & Class III (fibers), the focus of today’s Blog is on Class II locations.

Class II locations are those that are hazardous because of the presence of combustible dust. Note that the dust must be present in sufficient quantities for a fire or explosion hazard to exist. The fact that there is some combustible dust present does not mean a Class II hazardous location exists. Dust is defined as a combustible material that must exist as a finely divided solid of 420 microns (0.420 mm) or less. This will allow the dust to pass through a No. 40 sieve.  Just as in Class I, Division 1 and 2, the subdivision of Class II into Divisions 1 and 2 identifies the likelihood that there is an explosion hazard.

Division 1 locations are defined as an area where the amount of combustible dust is either suspended in the air or accumulated on surfaces in a sufficient concentration to allow for ignition.  The ignition could be caused by a failure or malfunction of the equipment in the classified area.  Group E & F dust (see chart below) are considered conductive and could penetrate into electrical equipment such as electric motors, control panels, electrical panels, etc.. and cause an electrical failure.

Chart1

Group E dusts are metal dusts, such as aluminum and magnesium. In addition to being highly abrasive, and likely to cause overheating of motor bearings if it gets into them. Group E dusts are also electrically conductive and if they are allowed to enter an enclosure can cause an electrical failure.

Chart2

Group F dusts are carbonaceous, the primary dust in this group is coal dust. Coal dust has a lower ignition temperatures than those in Group E.  While Group F dust has a higher thermal insulating value than the layer of Group E.  Therefore Group F requires more control of the temperature on the surfaces that the dust settles on. Group E dusts are semi-conductive, however if the voltages are 600 volts or less it is not generally considered a factor.

Chart3

Group G dusts include plastic dusts, most chemical dusts and food-grain dusts. They are not electrically conductive. Generally these dusts have the highest thermal insulating characteristics and the lowest ignition temperatures. Therefore the equipment used in Group G areas must have the lowest surface temperatures to prevent ignition of a layer.

Chart4

Lastly, equipment rated for use in Classified Environments have a rating called the Temperature Code or “T-Code”.  This is the temperature or temperature range that the rated device will operate normally and/or in a failed or failing state.  Consider something as common as a light fixture, electric motors, etc.. as they could become hot enough to cause ignition depending on the type of dust in the area.  So be sure to check the “T-Codes” for every piece of equipment that will be used within a Classified Environments.

Chart5

When you are looking for expert advice on Hazardous Location Cabinet Coolers or safe, quiet and efficient point of use compressed air products give us a call.   We would enjoy hearing from you.

Steve Harrison
Application Engineer
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Standards, Compliance, And You. And EXAIR.

I’m pretty impressed with the number of safety features my car has. Aside from the literal lifesaving functions like seat belts and air bags, it’s got anti-lock brakes…if you’ve ever had to counter-steer out of a skid on an icy road, you will appreciate the value of this for sure.  Those are just some of the ones I’m keenly aware of – the Federal Motor Vehicle Safety Standards comprise dozens of regulations in three categories: crash avoidance, crashworthiness, and post-crash survivability.  None of these prevent me from operating my vehicle at an unsafe rate of speed…an expensive reality that an Ohio State Highway Patrolman dutifully reminded me of last Sunday afternoon.

Likewise, there are many regulations to ensure safety and prevent hazards of all kinds in industry, administered by a host of agencies that are either subordinates of, or accountable to, the federal government.  When you manufacture products that are used with high energy sources (compressed air or high voltage electricity,) a strong commitment to safety is not negotiable.  So, at EXAIR, we commit considerable resources towards the best engineering and manufacturing practices to make our products as safe as possible.  That includes compliance with a number of standards and certifications:

The Occupational Safety and Health Administration (OSHA) is an agency of the U.S. Department of Labor.  Their mission is to “assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance.”  They are a regulatory body in the truest sense, in that they don’t offer certification or approval of products, processes, etc.; they publish guidelines and standards for manufacturers and users to comply with.  OSHA Standard 1910.242(b), for instance, limits the downstream pressure of a compressed air operated device used for cleaning purposes to 30psi. Now, you can regulate the supply pressure to meet this, but that also limits the effectiveness of the air flow generated.  EXAIR Intelligent Compressed Air Products are all designed and manufactured to be in compliance with this standard, at any supply pressure.  Take, for example, our Super Air Nozzles:

Because none of our products can be dead-ended, there’s always a relief path preventing the downstream pressure from exceeding that level.

OSHA also has Standard 1910.95(a), that sets limits for maximum allowable noise exposure.  All EXAIR Intelligent Compressed Air Products, with the exception of some our largest and most power Super Air Nozzles (which aren’t normally used in areas that don’t already require hearing protection anyway) meet the 8-hour exposure limits of this standard.

Hearing loss is the best known, but not the only, ill effect of harmful noise exposure. It can also cause physical and psychological stress, impair concentration, and contribute to workplace accidents or injuries.

CE marking indicates conformity with health, safety, and environmental protection standards for products sold withing the European Economic Area.  Unlike OSHA standards, responsibility for CE marking falls solely with the seller of the product – a CE marked product has been tested and certified to have been made in such a way to meet safety & quality benchmarks specified for that type of product.  All EXAIR products that are defined under applicable directives have been tested according to these standards, and carry the CE mark.

The Restriction of Hazardous Substances Directive, or RoHS, is another standard borne from the European Union, and is geared towards public & workplace safety by restricting the use of hazardous materials in the manufacture of electronic & electrical equipment.  Since its inception in 2006, similar standards have been vigorously adopted around the globe.  Electrical portions of EXAIR’s Static Eliminators, EFC Electronic Flow Controls, ETC Electronic Temperature Controls, Digital Flowmeters, Solenoid Valves, and Thermostats all comply with the RoHS Directive.

Section 1502 of the Dodd-Frank Wall Street Reform and Consumer Protection Act doesn’t address a concern for product users, but rather a particularly troubling human rights issue – Conflict Minerals.  For almost two decades, trade in tin, tantalum, tungsten and gold in the Democratic Republic of the Congo (DRC) has been used by some very bad people to finance violent campaigns against their neighbors.  EXAIR thoroughly and systematically documents our supply chain compliance with this act.  We are proudly committed to our support for this effort to the world a better place for everyone…especially those in desperate circumstances beyond their control.

EXAIR Intelligent Compressed Air Products have been successfully implemented into a variety of uses where application- or industry-specific standards are in force.  We’re happy to work with you to determine if our products meet those standards…or can be made to meet them.  If you’ve got such an application, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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