Thread Content
Explosion-proof electrical equipment is widely installed and used in industries such as coal, petroleum, chemicals, pharmaceuticals, textiles, and machinery manufacturing, in explosion-hazardous areas where dangerous substances such as explosive gases, vapors, combustible dusts, or fibers may occur and accumulate. According to surveys, 60%-80% of explosion and fire incidents are caused by improper installation or use of electrical equipment. Common misconceptions in the installation of explosion-proof electrical equipment include: Misconception 1: Using sealing compound instead of seals can meet explosion-proof requirements. For the sake of convenience during installation, many installers often discard the seals on the openings of explosion-proof electrical equipment and replace them with sealing compound, believing that this will prevent external explosive gases from entering the equipment, thereby ensuring its explosion-proof performance. In reality, if sealing compounds are used directly on the entry ports of flameproof explosion-proof electrical equipment, it will severely compromise the equipment’s explosion-proof performance. The sealing packing can achieve isolation sealing only when it is used correctly in conjunction with the corresponding isolation sealing box. Myth 2: Feeding the cable directly into the steel pipe can compress the sealing ring. The rubber sealing ring in the cable entry device of explosion-proof electrical equipment is an important component that helps maintain the explosion-proof properties of such equipment. However, during our inspection we found that many installation workers, in steel pipe wiring systems, directly screwed the explosion-proof electrical equipment’s inlet ports using the ridges on the outside of the steel pipes in order to compress the rubber seal, believing that this would ensure a tight fit for the seal. This is actually an extremely common mistake. GB50257-1996 \"Code for Construction and Acceptance of Electrical Installations in Explosive and Flammable Environments\" stipulates that in explosive gas environments of Zones 1 and 2, the number of effective thread engagements shall be: no less than 5 engagements for steel pipes with a diameter of 25 mm or less, and no less than 6 engagements for steel pipes with a diameter of 32 mm or more. The external threads on the steel pipe are created on-site by threading operations carried out by construction workers, and they are usually conical in shape; as a result, it is impossible to ensure that they can engage effectively with the straight internal threads at the power inlet of explosion-proof electrical equipment to meet the required number of connections. Once a spark is generated inside an explosion-proof electrical device of the flameproof type, it can ignite the explosive gases that may have entered the device through the flameproof joints, resulting in an explosion within the device. The unreinforced rubber seals may not be able to withstand the pressure generated by the explosion, allowing the flames produced by it to spread outside the device and thus leading to an even larger explosion, with consequences that could be disastrous. Therefore, in steel pipe wiring systems, while selecting appropriate single-hole or multi-hole rubber seals, an explosion-proof compression transition joint can be installed between the steel pipe and the equipment’s power inlet to serve the purpose of compressing the seal. Misconception 3: Explosion-proof electrical equipment remains explosion-proof as long as its enclosure isn’t replaced. During installation and construction, workers make arbitrary modifications to the structure, components, and internal wiring of explosion-proof electrical equipment. For example: Sealing ordinary instruments in increased safety type junction boxes for use in explosive hazard areas; modifying flameproof junction boxes arbitrarily to be used as explosion-proof electrical control boxes; creating holes in the housing of flameproof control boxes to allow wires to enter due to insufficient inlet ports, and so on. These construction workers mistakenly believed that not replacing the housing would not affect explosion-proof safety. On the contrary, these incorrect installations have severely compromised the original explosion-proof properties of the explosion-proof electrical equipment. Explosion-proof electrical equipment cannot be custom-made at will. For explosion-proof electrical equipment, its dimensions and volume must not be altered arbitrarily according to usage requirements. In accordance with the requirements of explosion-proof standards, after making local modifications, the revised drawings and relevant instructions must be submitted to the original testing agency. Only after re-examination and approval can they be put into use. Installation is an important step in ensuring the safe operation of explosion-proof electrical equipment. Before installation, it is necessary to check the following: whether the product’s markings are correct; that the enclosure is free of cracks or damage; that the surface of the flameproofing layer is clean and undamaged; that the gaskets are in good condition; that the electrical connections are secure; that there are no defects such as cracks in the materials used for sealing the enclosure; and that the intrinsically safe equipment corresponds to the specifications outlined in the relevant documents.