Flameproof electrical equipment

Introduction of non-flameproof electrical equipment into restricted area Mechanical isolation, e.g. conveyors, lifts Confined space entry Radioactive areas... 

Use of non-flameproof electrical equipment where flammable liquids/vapours/ dusts may arise... 

Removal of potentially contaminated equipment to workshop for maintenance, introduction of non-flameproof electrical equipment into a classified area. 

Entry into confined spaces (e.g. vat, vessel, flue, sewer, boiler or similar) Use of non-flameproof electrical equipment where flammable liquids/ vapours/dusts may arise... 

As a general rule, the use of organic solvents in chromatographic processes should be minimized, because of the requirement for specialized flameproof equipment which can be extremely costly compared with the equivalent item for a safe area. Where unavoidable, a separate flameproof room for handling solvent-based materials is recommended, with the appropriate specification for mechanical and electrical equipment, controls and room fittings including lights, switches, and telephone systems. 

So, cutting edge-shaped joints do prevent flame transmission to the external atmosphere. For the purpose of manufacturing electrical equipment, this fact may be unimportant, but it is very helpful towards an explanation of the working principle of a flameproof joint. 

Dielectric strength of flames in flameproof electrical equipment... 

Flame Transmission Caused by Arcing in Flameproof Electrical Equipment... 

Much electrical equipment, although flameproof, will attain surface temperatures over 160 °C when in use and careful inspection of the certification of such equipment must be made before diethyl ether is handled in a plant not specifically built for the purpose. 

One of the main hazards of air-entrainment sublimation is the risk of fire many substances that are considered to be quite safe in their normal state can produce explosive mixtures with air. All electrical equipment should be flameproof, and all parts of the plant should be earthed (grounded) efficiently to avoid the build-up of static electricity. Vacuum operation after nitrogen purging can provide a much safer processing enviromnent. 

In zone 1 all electrical equipment must be flameproof, as shown in Fig. 3.71, and marked Ex d to indicate a flameproof enclosure. 

Ordinary electrical equipment cannot be installed in zone 0, even when it is flameproof protected. However, many chemical and oil-processing plants are entirely dependent upon instrumentation and data transmission for their safe operation. Therefore, very low-power instrumentation and data-transmission circuits can be used in special circumstances, but the equipment must be intrinsically safe, and used in conjunction with a safety barrier installed outside the hazardous area. Intrinsically safe equipment must be marked Ex ia or Ex s , specially certified for use in zone 0. 

Electricity is particularly dangerous because it cannot be seen only an electrician should ever interfere with any electrical device, starter motor, connection box, or cable. Water should be kept away from all electrical equipment and any damage to electrical equipment must be put right by a skilled electrician before it is used. Special flameproof electrical equipment is provided in areas where flammable solvents are handled. 

Dust is created, not only when solid material is worked on, but also whenever materials are moved or handled. A dust presents a higher fire risk than the solid because of its greater contact area with air with resultant lower ignition characteristics. A dust cloud has many of the fire characteristics of a gas. Accumulations of dust should be removed as quickly as possible by techniques which do not generate a dust cloud, i.e. damp sweeping or vacuum cleaning. The electrical equipment in areas where flammable solids and powders are handled or occur must be designed and maintained to the appropriate flameproof standard. 

EN 13 463-3 2005. (2005a) Non-Electrical Equipment for Use in Potentially Explosive Atmospheres - Part 3 Protection by Flameproof Enclosure "d". 

Originally the classification of materials was derived from tests of proprietary explosion-proof (flameproof) enclosures. There were no published criteria. Equipment was approved relative to the lowest ignition temperature of any material in the group (Magison 1987). In about 1965 the U.S. Coast Guard asked the National Academy of Sciences (NAS) to form a panel to classify 200 materials of commerce. The Electrical Hazards Panel of the Committee on Hazardous Materials was formed by the NAS. The Panel studied many ways to estimate the hazard classification of materials. The Panel finally reported to die U.S. Coast Guard in 1970 that no workable, predicdve scheme could be defined, and it then proceeded to assign tentative classifications to the 200 materials. 

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