The ignition source, as a heat source providing combustion reaction, is the direct cause of inducing dust explosion accidents. In industrial production, there are various types of ignition sources around each process equipment or accessory component. According to incomplete statistics, the ignition methods that cause dust explosions mainly include impact or friction, electrostatic sparks, welding or melting sparks, spontaneous combustion sparks, open flames, metal overheating, and electrical sparks according to the frequency of accidents. Overall, the common ignition sources in explosive dust environments are:
flame
Open flames are important ignition sources for industrial fire and explosion accidents, and smoking, industrial hot work (such as gas cutting and welding), heating furnaces, etc. are all effective ignition sources for explosive hazardous environments. Usually, in safety management, enterprises should absolutely prohibit the existence of open flame ignition sources in explosive hazardous areas, and establish a sound system for hot work operations. If open flame operations are necessary, they should be strictly carried out in accordance with the hot work operation system.
High temperature objects
The hot surface of high-temperature objects is a potential ignition source for explosive hazardous environments, which can be divided into two categories: electrical equipment hot surfaces and non electrical equipment hot surfaces. In industrial production, heating equipment, heating devices, motors/lamps, etc. are prone to become high-temperature objects and should be explosion-proof treated in accordance with the relevant requirements of GB3836 and GB12476 series standards. Mechanical equipment such as internal combustion engines, gearboxes, bearings and other mechanical components or assemblies are also prone to forming high-temperature hot surfaces under normal or fault conditions. In industrial safety production, ignition hazard assessment and detection should be carried out in accordance with GB25286 and related series standards.
Electrical spark
Electrical spark is a potential ignition source carried by electrical equipment itself, which is a breakdown discharge between electrodes. It is usually generated when the electrical circuit is disconnected or short circuited, the electrical equipment starts braking, or the electrical equipment runs overloaded.
electrostatic discharge
According to the forms of static electricity generation, static electricity can be divided into various forms of electrification, such as contact friction separation electrification, electrostatic induction electrification, and electromagnetic induction electrification; According to the properties of charged bodies, they can be divided into solids, liquids, gases, powders, and human body charges. In explosive dust environments, various non-metallic components or their non-metallic parts are prone to generate frictional static electricity, while various electromagnetic inductions make metal components prone to inducing static electricity. As an important participant in explosive dust environments, the human body itself is an important source of static electricity generation. Therefore, various types of static electricity are widely present in dust explosion hazardous environments, and effective measures should be taken to avoid them.
Impact and Friction
The impact and friction between mechanical equipment or components are also important ignition sources in combustible dust environments. During the process of impact and friction between metal components, metal sparks or friction on high-temperature surfaces are easily generated, which can ignite explosive hazardous environments. Therefore, all types of mechanical equipment or components used in explosive hazardous areas should undergo an assessment of their ignition hazard, analyze the risk of the equipment itself becoming an effective ignition source, and take measures to avoid it, ensuring the safe use of mechanical equipment in explosive hazardous environments.
chemical reaction
Chemical reactions, especially self heating reactions, are potential ignition sources in explosive hazardous environments, such as aluminum iron reactions, oxidative combustion, etc. A large amount of freely accumulated dust, such as coal mines, flour and corn starch grain warehouses, often self ignite and catch fire due to the accumulation of dust.
thunder
Lightning is one of the biggest threats to explosive dust environments in nature. The huge discharge current generated during lightning discharge has great destructive power and is also prone to dust explosion accidents. Therefore, the factory buildings (structures) in workplaces with dust explosion hazards must be equipped with lightning protection systems in accordance with the "Code for Design of Lightning Protection of Buildings" (GB50057-2010) and can be grounded.
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