The explosion-proof design of the LPG cylinder spot welding machine requires building a multi-layer protection system from three aspects: electrical safety, mechanical protection, and environmental control to ensure that the risk of ignition and explosion is eliminated during the welding process.
Explosion-proof electrical system: A flameproof control cabinet is used, and the enclosure protection level reaches IP65. The internal electrical components (such as contactors and transformers) must pass Ex d IIC T6 explosion-proof certification, and the cable interface is sealed with an explosion-proof gland to prevent spark leakage. The welding circuit adopts a double insulation design, the secondary cable withstand voltage is ≥3000V, and the loop grounding resistance is ≤4Ω to avoid electric sparks caused by leakage. At the same time, it is equipped with a spark suppression circuit. At the moment of electrode separation, the RC absorption network (capacitor 1-2μF, resistor 50-100Ω) is used to suppress the arc reignition, and the power-off spark energy is controlled below 0.2mJ, which is lower than the LPG explosion limit (0.28mJ).
Explosion-proof mechanical structure: The electrode arm uses flame-retardant reinforced nylon coated copper conductor, and the thickness of the insulation layer is ≥ 2mm to prevent sparks from metal friction; the work surface is paved with a 3-5mm thick explosion-proof rubber pad, which has both insulation and anti-static functions (surface resistance 10⁶-10⁹Ω ). The equipment has a built-in explosion-proof pressure relief device. When the gas is accidentally ignited inside, the pressure relief door plate (explosion pressure 0.1-0.2MPa ) automatically opens to release pressure to avoid explosion. In addition, the electrode head is made of beryllium copper alloy (hardness ≥ 180HB ) to avoid sparks caused by collision with the cylinder, and the electrode wear is checked regularly (allowable wear ≤ 0.5mm ) to prevent poor contact and heating.
Environmental safety control: A forced ventilation system is set up in the welding area, with an air volume of ≥3 times/h, to promptly discharge LPG gas that may leak during welding, so that the concentration of combustible gas in the air is kept below 1/4 of the lower explosion limit (1.5%). The equipment is linked to the installation of a combustible gas detector (detection accuracy 0.1% LEL). When the concentration exceeds the standard, the welding power supply is immediately cut off and the sound and light alarm is activated. The floor of the operation area is paved with conductive clay, with a grounding resistance of ≤100Ω, to eliminate the accumulation of static electricity on the human body and eliminate the source of detonation from the environmental level.
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