The disadvantage of standards with example installations, is that a huge safety factor is incorporated and thus relative large hazardous area are defined. Sources
Iso Container 2: For Group IIIC combustible dusts or metal combustible fibers/flyings, there shall only be Zone 20 or 21 locations. >> For Gas/Vapor this would be Zone 2. Quick Tips #124.1. April 2021 In the United States, the NEC uses 2 different classifications: Classification of locations, testing and listing of equipment, and inspection of installation, is typically overseen by governmental bodies. This rapid expansion of volume is caused by the combustion of a fuel, like e.g. * Zone 1 a location in which explosive gas atmospheres are likely to occur during normal operation, or which is adjacent to a Zone 0 location. A list must be drawn up of every explosive material that is on the refinery or chemical complex and included in the site plan of the classified areas. SEWAGE TREATMENT For explosion hazards caused by flammable liquids or gases, the following zones are defined: So a zone 0 is the most hazardous zone and a zone 2 is a less hazardous zone. 2: Where gas detection, Informational Note No. Such properties include flame temperature, minimum ignition energy, upper and lower explosive limits, and molecular weight. Reefer Container area in which an explosive gas atmosphere is not likely to occur in normal operation, but, if it does occur, will exist for a short period only (less than 0,1% of the time), Window breakage, cracks plaster, light damage to buildings, Collapse of wood or asbestos siding of homes, Collapse of walls made of concrete blocks, Reinforced concrete structures severely damaged, Flames and hot gases (including hot particles), Mechanically generated impact, friction and abrasion, Stray electric currents, cathodic corrosion protection, Radio frequency (RF) electromagnetic waves from 10, Exothermic reactions, including self-ignition of dusts, EI 15 Energy Institute 15, mostly for on- and offshore oil and gas applications. October 2022 Zone type (0/1/2/ 20/21/ 22) Zone extent. It is obvious to use those standards within these industries. An area where combustible dusts or ignitable fibers and flyings are not likely to occur under normal operating conditions and do so only for a short period of time. This temperature is used for classification for industry and technology applications.[6]. The Zone system for classifying hazardous locations used in NFPA 70 NEC, IEC 60079, and the Canadian Electrical Code indicates the level of probability that a flammable concentration of a hazardous substance may be present. 2) MIC (Minimum Igniting Current) Ratio - The ratio of the minimum current required from an inductive spark discharge to ignite the most easily ignitable mixture of a gas or vapor, divided by the minimum current required from an inductive spark discharge to ignite methane under the same test conditions. Temperature classification, except for intrinsically safe apparatus. NFPA 70 NEC uses the familiar Class/Division system and has added an Americanized version of the International Electrochemical Commissions (IEC) IEC Zone system which maintains the NEC wiring methods and protection techniques. Whenever you are filling up your tank you are standing in a Zone 1 hazardous area. .14 . No other aspect of safety receives more attention in the form of codes and standards. So, it is good to know that when a flammable substance concentration exceeds the LEL, it will not automatically lead to an explosion with the highest Pmax. This is exactly defined as the limiting concentration of oxygen below which combustion is not possible, independent of the concentration of fuel. As world trade becomes more globalized, international standards are slowly converging, so that a wider range of acceptable techniques can be approved by national regulatory agencies. 0. Electrical equipment installed in such locations can provide an ignition source, due to electrical arcing, or high temperatures. The classification process requires the participation of operations, maintenance, safety, electrical and instrumentation professionals; and the use of process diagrams, material flows, safety data sheets, and other pertinent documents. Equipment that is safe for the location shall be of a type and design that the employer demonstrates will provide protection from the hazards arising from the combustibility and flammability of vapors, liquids, gases, dusts, or fibers involved. Beside the Lower Explosion Limit, each substance also has an Upper Explosion Limit (UEL). Group II is for explosive gases (Zone 0, 1 and 2) and Group III is for explosive dusts (Zone 20, 21 and 22). NFPA 70, the National Electrical Code (NEC), defines area classification and installation principles. . When the concentration of gas or vapor is above the UEL the gas mixture is too rich to burn. Identifying Zone 0, Zone 1, and Zone 2 Hazardous Areas. The relation between that system and de zone classification system is clarified within the following table (only for gases and liquids are displayed, not for dusts and fibers). As mentioned, the first important step of achieving a safe work environment in relation to explosion safety is to identify and classify those areas, where a concentration of flammable gases or vapors within the flammable range can be present. A60 For dusts: Zone 20, Zone 21 and Zone 22. Ways to ensure this level of safety are non-arcing design and limitation of the temperature of the equipment. coal and charcoal), Group G Nonconductive dusts (eg. Examples are: production facilities in the food industry, chemical plants, oil & gas, and the pharmaceutical industry etc. These areas only become hazardous in case of an accident or some unusual operating condition. In the United States, the hazardous location classification system is defined by the National Fire Protection Association (NFPA) 70, National Electric Code(NEC). The term equipment is applied both for fixed equipment and mobile equipment that are operated in such area. according to ISO standard 80079 series. The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. Class I, Zone 0 = Area Classification, AEx = Symbol for equipment built to American specifications, ia = Type of protection designations, IIC = Gas classification group (as required), T6 = Temperature Classification, [46 FR 4056, Jan. 16, 1981; 46 FR 40185, Aug. 7, 1981; 72 FR 7210, Feb. 14, 2007], Occupational Safety & Health Administration. 9: For additional information concerning the installation of, Informational Note No. Marking "EEx d" in Accordance with EN 50 0 14 and 50 018 . Explosions can cause significant damage along with severe injury or worse loss of life. | For Dust this would be Zone 22. This paper will discuss and review the current approaches and solutions of dealing with these HSE concerns, especially with the involvement of hazardous and potentially flammable and explosive chemicals. Category 2 equipment may be used in zone 1 or zone 2 areas. Atmosphere containing flammable gas, flammable liquid produced vapor, or combustible liquid produced vapor mixed with air that may burn or explode, having either a MESG value greater than 0.75 mm or a MIC ratio greater than 0.80 - such as gasoline, acetone, ammonia, benzene, butane, ethanol, hexane, methanol, methane, vinyl chloride, natural gas, naphtha, propane or gases of equivalent hazard. The Occupational Safety and Health Administration (OSHA) has adopted these hazardous classifications and all except Groups are defined in 29 Code of Federal Register (CFR) 1910.399. Zone 1 is an area in which an explosive atmosphere is likely to occur occasionally in normal operation. Ignition sources can be divided in 13 categories (acc. 6: For further information on electrical systems for hazardous (classified), Informational Note No. Analysers, motors, control boxes, computers, Any arcs or sparks in this equipment has insufficient energy (heat) to ignite a vapour. Comparisons between the two systems are not easily accomplished. Vertical. Note to paragraph (c)(2)(i) of this section: NFPA 70, the National Electrical Code, lists or defines hazardous gases, vapors, and dusts by "Groups" characterized by their ignitable or combustible properties. Offshore Accommodation Module Shown below is a summary of the applicable NEC Articles to reference to ensure the proper requirements are applied. The above groups are formed in order of how explosive the material would be if it was ignited, with IIC being the most explosive zone system gas group and IIA being the least. These areas only become hazardous in case of an accident or some unusual operating condition. Hazardous areas are classified into 3 zones based upon the frequency of the occurrence and duration of an explosive gas atmosphere, as follows: Zone 0 Area in which an explosive gas atmosphere is present continuously or for long periods or frequently. This page was last edited on 20 January 2023, at 22:32. A: When comparing Divisions and Zones, Division 2 is equivalent to Zone 2, but Division 1 is equivalent to either Zone 0 or 1. 3: Text that is followed by a reference in brackets has been extracted from NFPA 497-2017, All other applicable rules contained in this, Where the term "Class I" is used with respect to, Informational Note: The term "Class I" was originally included as a prefix to, All areas in industrial occupancies designated as hazardous (classified). The first thing to understand is that much like the metric vs imperial measuring systems, the United States uses its own methodology which differs from much of the world. Area classification documentations are reviewed and updated to reflect process changes. But every hazardous area is different and each has specific requirements depending on the nature of the atmosphere and the elements that are present. The flash-point is the temperature at which the material will generate sufficient quantity of vapor to form an ignitable mixture. Is intended for us in Zone 2 (gases) or Zone 22 (dusts). Hazardous areas are defined as: " Zones " under worldwide IEC standards (and their local versions, such as ATEX in Europe) " Divisions " under North American NEC standards. Equipment construction is such that it can withstand an internal explosion and provide relief of the external pressure via flamegap(s) such as the labyrinth created by threaded fittings or machined flanges. [4], Flammability of combustible liquids are defined by their flash-point. You will find these zones at the manifold of a tank truck or the interior of a silo. Zone 1 - Explosive atmospheres are likely to occur. a headlamp, rather than a dedicated fixed luminaire. Terminology for both hazards and protective measures can vary. What is an Explosion Protection Document? When comparing Divisions and Zones, Division 2 is equivalent to Zone 2, but Division 1 is equivalent to either Zone 0 or 1. October 2019 This means that the electrical equipment is safe for use within these area by applying special protection strategies. >> NEC: Class II, Division 1, Group F. | IEC: Zone 20, Group IIC. Definition of hazardous area zones (AS/NZS 60079.10): Zone 0 1994-2020, W.W. Grainger, Inc. All Rights Reserved. Specific types of protection being used will also be marked. The two general approaches are: Several techniques of flame-proofing exist, and they are often used in combination: Equipment has flameproof gaps (max 0.006" (150m) propane/ethylene, 0.004" (100m) acetylene/hydrogen), Equipment can be installed in ANY housing provided to IP54.A 'Zener Barrier', opto-isolator or galvanic unit may be used to assist with certification.