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DefinitionAndPrincipleOfFlameproofTypeElectricalEquipment|TechnicalSpecifications

Technical Specifications

Definition And Principle Of Flameproof Type Electrical Equipment

Definition:

Explosion-proof electrical equipment, denoted by the symbol “d,” is a classic form of explosion-proof equipment. For decades, the flameproof structure has been the primary choice in the development and application of explosion-proof electrical devices. Such flameproof electrical devices are reliable in explosion safety, have mature manufacturing technology, and enjoy a long service life. They are widely used in hazardous locations with various combustible gas-air mixtures. However, due to the flameproof structure, these devices are somewhat heavy and bulky.

flameproof type electrical equipment

Principle of Explosion Protection:

The safety and explosion-proof performance of this type of electrical equipment are ensured by a casing known as the “flameproof enclosure.”

A “flameproof enclosure” allows combustible gas-air mixtures to combust and explode inside the casing but prevents the explosion products from rupturing the casing or escaping through any passages to the exterior that could ignite the surrounding explosive mixtures. As long as the maximum surface temperature of the enclosure does not exceed the temperature class for its intended group, the device will not become an ignition source for the surrounding explosive gas-air mixture.

This is how flameproof electrical equipment operates.

Understanding this principle, we can deduce that the casing of flameproof electrical equipment must have sufficient mechanical strength to withstand the explosion pressure generated inside without undergoing significant deformation or damage. The gaps between components of a flameproof enclosure, which form channels from the inside to the outside, must have appropriate mechanical dimensions that can reduce or even prevent the escape of explosion products. This way, ignition of the explosive gas-air mixtures around the equipment is prevented. The explosion protection levels for flameproof electrical equipment are classified into three grades: IIA, IIB, and IIC. The protection levels of the equipment can also be categorized into three grades: a, b, and c, commonly represented in practice as: Equipment of Group I, Ma and Mb; Equipment of Group II, Ga, Gb, and Gc.

The enclosure of explosion-proof electrical equipment should be made from materials with good mechanical strength, such as steel plate, cast iron, aluminum alloy, copper alloy, stainless steel, and engineering plastics. The strength and gap dimensions must comply with the relevant requirements of GB3836.2—2010 Explosive Atmospheres Part 2: Equipment protected by flameproof enclosures.

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