Views:551 Author:Site Editor Publish Time: 2021-01-13 Origin:Site
Hazardous locations are defined as premises, buildings, or parts thereof where fire or explosion hazards may exist due to the presence of flammable gases or vapors, flammable liquids, combustible dust, or easily ignitable fibers or flyings.
Although flammable gases, vapors, and combustible dust exist almost everywhere, fortunately, they are present only in minute quantities. Simply because flammable gasses or vapors, or combustible dust are present, there is not necessarily a hazardous location. The quantities or concentrations must be sufficient to present a potential explosion hazard.
The electrical codes that deal with these types of hazardous locations areas do not deal with materials such as high explosives, such as dynamite, munitions, or fireworks. Other rules and regulations deal with areas involving these materials.
Understanding “Global” Hazardous Location Requirements
The evolution of hazardous location electrical codes and standards throughout the world has taken two distinct paths. In North America, a “Class, Division” System has been used for decades as the basis for area classification of hazardous (classified) locations. Because the hazards and methods of protecting electrical equipment against these hazards differ for different materials, hazardous locations are divided into three Classes, and two Divisions.
The Classes are based on the type of hazard and the explosive characteristics of the material with the Divisions being based on the occurrence or risk of fire or explosion that the material presents. While the United States and Canada have some differences in acceptable wiring methods and product standards, their systems are very similar. In other parts of the world, areas containing potentially explosive atmospheres are dealt with using a “Zone System”. Zones are based predominantly on the International Electrotechnical Commission (IEC) and European Committee for Electrotechnical Standardization (CENELEC) standards.
Whereas North America deals with multiple types of hazardous atmospheres, the North American Zone System presently addresses only flammable gases and vapors which is the equivalent to North America’s Class I locations. The most significant difference in the Zone system is that the level of hazard probability is divided into three Zones as oppose to two Divisions.
While specific requirements differ, the Unites States and Canada have incorporated the Zone System for Class I, hazardous locations into their recent electrical code updates. Both systems provide effective solutions for electrical equipment used in hazardous locations and both have excellent safety records.
HAZARDOUS LOCATION BASICS
In North America, hazardous locations are separated into three “Classes” or types based on the explosive characteristics of the materials. The Classes or type of material is further separated into “Divisions” or “Zones” based on the risk of fire or explosion that the material poses. The Zone system has three levels of hazard versus the Division System’s two levels.
➀ The United States and Canada have adopted Zones for Gasses and Vapors
➁ Zones for Dust are not yet developed for North America