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Intrinsic safety means that a piece of equipment under any conditions of use is incapable of releasing any electrical or thermal energy, to cause an ignition in any type of hazardous gaseous mixture surrounding it. Therefore, for a device that is being operated in areas with flammable gases, intrinsic safety is a requirement that ensures that there will be no danger of the gases catching fire due to the operation of the device. The device will be incapable of igniting these gases under any operating conditions. The definition of electrical safety of intrinsically safe equipment is given by the ISA-RP12-6.
Several modern manufacturing facilities include oil storage, paint manufacturing, textile mills and chemical plants. All these harbor environments with a preponderance of flammable liquids, gases and vapors. Operating electrical equipment in these hazardous environments require them to be incapable of producing any means for these gases and vapors to ignite. It is mandatory for the electrical equipment operating in this type of volatile environment to follow intrinsic safety normals for electrical safety. Evaluating intrinsic safety approval ratings could be daunting for even the most informed person. However, these intrinsically safe approvals are necessary even for the most up to date and rugged mobile computers, that operate in such hazardous conditions.
Obtaining an intrinsic safety or IS rating does not guarantee that the device can be operated in any hazardous environment. Each environment has its own specific certification requirement and any equipment operating in the environment must be IS certified for the level necessary for the specific environment. Certification of equipment for IS is carried out in Nationally Recognized Testing Laboratories or NRTLs. These laboratories carry out certifications under extremely stringent intrinsic safety standards, that vary according to the level of IS approval required. Therefore, an IS certified electrical equipment will carry a label specifying the exact IS level and rating, along with the name of the NRTL that tested it.
Intrinsic safety barriers are devices used to connect IS devices with other non-IS devices. This protection technique will limit the current, voltage and total energy delivered to a device situated in a hazardous area in order to prevent any explosion. Selecting intrinsic safety barriers requires an understanding and analysis of approvals and specifications. Among these specifications are important parameters such as operating temperatures, maximum voltages and currents, and the maximum number of input and output channels. Products can carry the UL mark (USA), CSA mark (Canada), CE mark (Europe), denoting the various national and international agencies that provide approvals for intrinsic safety barriers. Approvals are also provided by CENELEC or the European Committee for Electro-technical Standardization, and Factory Mutual Research, or the FM, as non-profit testing organizations.
IS approval ratings are not identical in all countries. It is imperative to understand the differences between the IS approval standards to get the product certified for use in the specified country. However, ATEX certification standardizes the IS certification process between the US and Europe and makes intrinsic safety certification a much easier process for electrical equipment meant to operate in both countries.
Excellent article. As a manufacturer of intrinsically safe Atex Certified Equipment, we know it is important to work with a specialist to help guide you through the options and pitfalls in order to confirm to the various health and safety directives globally.