Industrial processes often need to be carried out in a hazardous atmosphere or when hazardous materials such as explosive gases, dust or flammable liquids are present. Such substances can be ignited by sufficient energy coming from sources like electrical sparks, open flames, and hot surfaces. The equipment installed in these areas must therefore be planned such that it does not represent an ignition source. In most countries around the world, national and/or local governments enact electrical construction standards intended to prevent accidents and enhance the safety of people and property. To ensure that installed components have been designed and tested according to regulations and offer sufficient protection, testing agencies are used. They certify that a particular device meets the specifications of the special standards for hazardous locations.
There are many types and categories of possible hazards in explosion hazard areas. How these areas are classified depends on in which country or region the equipment is being installed:
- In the European Union a harmonization scheme is used to eliminate technical trade barriers. The ATEX Directive 2014/34/EU is applied to devices and protection systems for proper use in explosion hazard areas. As part of a hazard assessment the operator divides the areas into zones and selects devices for the corresponding category.
- In the USA the NEC (National Electrical Code) uses two methods for classifying hazardous locations: these are based on both the class/division and the zone. Categorization into class/division is a long proven procedure in the USA. Division into zones is a newer alternate concept which is becoming more and more established. As soon as the decision is made as to which method will be used for certification, that method is consistently applied.
- Canada is similar to the US but follows the Canadian Standards Association (CSA) electrical codes.
- For the rest of the world various local regulations and standards apply. But more and more countries are turning to the uniform global standard IECEx (International Electrotechnical Commission Explosive). It is however possible that a country specifies IECEx as the basic standard while requiring additional national certifications to meet country-specific regulations.
For a comprehensive overview about the protection classes for electrical devices you may refer to following poster and brochure (including Balluff products for hazardous areas) that can be downloaded from the Balluff Homepage – or ask your Balluff sales representative for a printed version.