United States Hazardous Location Device Testing and Certification|
Article- November 2012 By Larson Electronics.com
Larson Electronics Hazardous Area Fluorescent Light Fixture
Equipment designed for use in hazardous locations must be of a much more robust and complex construction in order to meet the demanding requirements of hazardous location regulations. Unlike electrical devices intended for use in typical commercial or household applications, equipment used in hazardous locations must prevent, prohibit, or otherwise mitigate the dangers posed by flammable gases, vapors and materials that can create an explosive atmosphere. In order for there to be a clear manner of ensuring the minimum amount of protection a device provides, it has been necessary for federal, state and local agencies to enact regulations and form standards by which the ability of this equipment to provide protection is measured and approved.
In North America, the dominant form of hazardous location standards are based on the National Electrical Code (NEC) which is published by the National Fire Protection Association (NFPA). These standards apply in the United States and to an extent are compatible Canadian standards as well. Canadian hazardous location certification revolves around the Canadian Electrical Code and differences exist between NEC and CEC and CSA standards, thus operators in North America are responsible for ensuring that equipment compliance between these two regions is acceptable when applying equipment approved under one of these two systems. The US and Canada also incorporate the old European zone system of classification to an extent, however, again compatibility is not uniform.
European standards are determined under CENLEC and the European Committee for Electrotechnical Standardization ATEX Directive. The EU is currently also incorporating the IECex conformity Scheme developed by The International Electrotechnical Commission (IEC) which is intended to provide a single mark of conformity that can be accepted worldwide in order to facilitate trade and reduce certification procedures and costs.
Regardless of the region or standards, the overriding feature here is that all equipment intended for use in hazardous locations must be tested and approved according to the standards relevant to the region. In order for this to happen, it is necessary for equipment to be tested by independent laboratories that have been approved by that regions regulating agencies under conditions defined by the relevant standards. In the United States for example, Underwriters Laboratories is an approved testing lab which tests equipment according to standards set forth by the NEC. Once the equipment has met the minimum requirements of testing, it receives certification according to the standards it has met. There are several approved laboratories of which UL is only one. The process is very similar within Canada and the EU, and every piece of equipment to be used in hazardous locations is required to carry certification that it has undergone and passed such independent testing.
In North America, equipment is certified according to a Class and Division system.
Classes note the type of hazardous environment according to the nature of the materials present. Thus, a Class 1 certification denotes that the equipment meets standards for use in locations where flammable vapors and gases are or may be present, a Class 2 certification denotes locations where combustible or conductive dusts are or may be present, and a Class three certification denotes flammable fibers and flyings such as wood chips.
Divisions note the probability of the hazard. Thus, a Division 1 certification denotes compliance for locations where the hazard is present on a continual basis or as a normal part of operations, in essence signifying compliance for areas where the threat is always present. Division 2 certification denotes compliance for locations where the hazardous condition may exist only under intermittent or abnormal conditions, such as in the presence of a leaking storage container or a spill. Under Division 2 certification, the condition is only expected to be present under unusual conditions and not a normal part of operations.
There is no 3rd Division, however, US certification also takes into account the types of materials expected to be encountered and applies approval through a Grouping systems. This system consists of seven groups designated with alphabetical letters.
Group A refers only to Acetylene which has an extremely high explosion pressure.
Group B refers to Hydrogen, gases with more than 30% hydrogen by volume, butadiene, and other gases with similar explosive properties.
Group C refers to ether, ethyl, and ethylene gases, and other gases of a similar potential.
Group D refers to gasoline, acetone, ammonia, benzene, butane, methanol, propane and other more commonly encountered compounds.
Finally, equipment must also carry a temperature rating. This temperature rating denotes the maximum safe surface operating temperature of the device. This rating is based on the ignition temperatures of various flammable gases and materials. The device in question must be rated below the ignition temperature of the materials it is expected to encounter. This temperature code is listed as a letter and numbering system, with lower numbers typically denoting higher operating temperatures. A typical temperature rating may appear as “T3C”, which would denote suitability for locations where Methane may be encountered.
In the United States, equipment must carry certification somewhere on its structure that proves its suitability for use in a given hazardous environment. This is usually a stamped metal tag affixed to the body of the device, but can also take the form of printed labels and the like. Unless the device carries this labeling, it cannot be considered compliant and thus poses a potential risk of fire or explosion as well as violation of compliance regulations if utilized in a hazardous location.
The testing and certification of electrical devices for use in hazardous locations can be a complex process and requires that operators familiarize themselves with their local standards and operating conditions in order to ensure compliance. Failure to utilize equipment with the proper certification can result not only in the potential for fatalities, injuries, and expensive damages, but costly citations and fines from regulating bodies such as OSHA. It is the responsibility of the operators and owners to ensure that equipment complies with all applicable standards and regulations, and by utilizing equipment with the correct certification provided by only by approved testing laboratories, operators ensure the safest possible work place possible.