EX-PROOF (Explosion-Proof) Classifications, Zones, Explosion Groups, Temperature Classes

Zones Areas containing potentially explosive atmospheres are classified into zones, and equipment to be deployed must likewise be classified into groups and categories. As noted in our "What is Exproof" article, the markings on the rating plate of certified equipment designate the specific zone in which the explosion-protected equipment may be installed. Equipment is divided into two distinct groups: Group I and Group II. Group I equipment relates to underground mining, whereas Group II equipment covers all other surface industries. As supplementary information in this context, the factors contributing to firedamp explosions in mines must be monitored with the utmost vigilance. Regrettably, hundreds of individuals worldwide suffer injury or fatal harm annually as a result of such explosions. To mitigate these explosion hazards, Sensidyne offers an instrument—supplied by NOVEL—that assesses the explosibility risk of coal dust. You may review this instrument, designated the CDEM-1000, via this link: Gilian CDEM-1000 Coal Dust Explosibility Meter Hazardous areas defined in mining operations are divided into two classifications designated M1 and M2. For further details regarding this category, reference may be made to the "Regulation on Occupational Health and Safety in Mining Workplaces" published in the Official Gazette on 19.09.2013. At NOVEL, we provide Occupational Health and Safety measuring instruments conforming to the M1 standard. Instruments complying with this standard enable measurements to be executed in underground mines in full compliance with statutory regulations. For further information, you can Contact contact us via the section.

Areas with potentially explosive atmospheres are divided into six zones depending on the likelihood, frequency, and duration of the presence of a potentially explosive atmosphere. A distinction is made between flammable gases, mists, vapours, and combustible dusts. For gases, mists, and vapours, Zones 0, 1, and 2 apply, where the constructional requirements for selected equipment increase progressively from Zone 2 to Zone 0. Stated simply, Zone 0 represents an area where the explosion risk is continuous or very high, Zone 1 entails lower risk, and Zone 2 represents significantly lower risk compared to Zones 0 and 1. In other terms: Zone Classification (for gases, vapours, and mists) Zone 0 = Signifies that explosive gases and/or vapours are present in high concentrations continuously or for prolonged periods in the designated area. For example, the interior of fuel storage tanks can be classified as Zone 0. Zone 1 = Signifies that explosive gases and/or vapours are unlikely to occur in high concentrations under normal operating conditions, but may be present due to maintenance and repair work, processing operations, or leaks. For example, the area surrounding a fuel dispenser at a filling station can be classified as Zone 1. Zone 2 = Signifies conditions where explosive gases and/or vapours occur only for very short periods, becoming hazardous solely as a result of potential incidents or unusual operational faults. For example, the perimeter surrounding a fuel filling station can be classified as Zone 2. As indicated in the graphic, areas classified as Zone 0 are tightly confined and present high hazard levels, whereas the boundaries expand progressively upon moving to Zone 1 and Zone 2. These standards are defined in NEC Article 505-9, CEC Section 19, EN 60079-10, and IEC 60079-10. In Turkey, the mandatory use of explosion-protected (ex-proof) materials in facilities presenting explosion hazards was adopted by the relevant Ministry and published in the Official Gazette No. 26392 dated 30.12.2006. (The initial standard was adopted by the Ministry of Industry and Trade under ATEX 94/9/EC in Official Gazette No. 24919 dated 27 October 2002, and republished in Official Gazette No. 25328 on 26 December 2003.)

Zone Classification (for Dusts and Fibres) A classification structure similar to that for gases exists to identify areas subject to explosion hazards caused by combustible dusts and fibres. Zone 20 = Signifies that combustible dusts and/or fibres are present in high concentrations continuously or for long periods in the designated area. Zone 21 = Signifies that combustible dusts and/or fibres are unlikely to occur in high concentrations under normal operating conditions, but may be present due to repair and maintenance activities or process releases. Zone 22 = Signifies conditions where combustible dusts and/or fibres occur only for very brief periods, becoming hazardous solely due to potential incidents or exceptional circumstances. Classification of Ex-proof Apparatus The equipment groups used determine the specific zones in which the equipment may be installed. There are 6 categories in total for this classification. In sequence, categories 1G, 2G, and 3G represent protection classifications against gas explosions (G = Gas). Consequently, equipment classified as 1G is suitable for deployment in Zones 0, 1, and 2. 2G equipment is suitable for use in Zones 1 and 2. 3G equipment is suitable for use solely in Zone 2. For explosion risks arising from dusts and fibres, categories 1D, 2D, and 3D designate protection classifications against dust explosions (D = Dust). Similarly to the gas section above, 1D equipment is suitable for installation in Zones 20, 21, and 22. 2D equipment is suitable for use in Zones 21 and 22. 3D equipment is suitable for use solely in Zone 22.

Reviewing the standards and practices applied in the United States, we addressed the differences between European and US standards under the heading "Who can test Explosion-Proof equipment and how?" in our "What is Exproof" article. Be sure to consult those publications as well. US practices are established in the NEC® standards as ANSI/NFPA 70. US standards divide hazardous locations into two divisions. Division 1: Locations where hazardous explosive atmospheres are likely to exist under normal operating conditions and where such hazards persist for extended durations fall under DIVISION 1. Division 2:Class I, Division 2 covers locations where flammable gases or vapours are normally confined within closed systems but may form ignitable concentrations following failure or abnormal operation. Ventilation failure or migration from an adjacent Division 1 location may also be relevant. Definitive area classification requires competent specialist assessment. NEC® also distinguishes CLASS categories by the type of combustible material, as follows:CLASS I: Flammable gases and vapours. CLASS II: Combustible dusts. (Example: Coal dust) CLASS III: Ignitible fibres and flyings normally coarser than dust. (Example: Cotton lint, textile fibres.) The critical point here is that these materials present a combustible and fire hazard rather than a primary explosion risk. The NEC® standard further delineates hazardous material groups, designated as Group A, Group B, Group C, Group D, and Groups E, F, and G. Each group encompasses specific gases, compounds, or dusts. A key aspect is that common gases used frequently both domestically and across industry, such as methane and propane, are classified under Group D. Explosion Groups While equipment groups and categories determine the zones in which equipment may be installed, explosion groups and temperature classes determine the specific atmospheric conditions within those zones for which the equipment is suitable. The type of protection applied is not a mark of product quality; rather, it is a constructive engineering solution that facilitates appropriate equipment selection for explosion protection. Explosion-protected equipment (Ex-proof) for gases, mists, and vapours is subdivided into three explosion groups (IIA, IIB, and IIC) according to the type of protection utilised. The explosion group serves as a metric to quantify the ignitibility of gases (potentially explosive atmospheres). Equipment construction requirements increase from IIA to IIC. That is, the requirements for apparatus classified as IIA are less stringent than those classified as IIB, whereas requirements for IIC apparatus exceed those for IIB and IIA. Expressed in order of increasing stringency: IIC > IIB > IIA Temperature Classes Explosion-proof (Ex-proof) equipment installed or used within a hazardous area is classified according to 6 temperature classes (T1 to T6). Temperature Class is often misunderstood. This class does not indicate the operating temperature range of the equipment; on any surface area of the equipment, it indicates the maximum permissible surface temperature relative to ambient temperature. The maximum surface temperature must always remain below the ignition temperature of the environment. Equipment design requirements increase from T1 to T6. Temperature classes are specified in the relevant standards according to IEC or EN NEC® 505-10. The NEC 500-3 and CEC 18-052 standards differ in temperature classes; however, they fundamentally incorporate the same parameters.

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