What is explosion-proof electrical appliances?

Categories, levels and temperature groups of explosion-proof electrical equipment

1.1 Division of hazardous areas of explosive gas environments

Zone 0: Continuous or long-term occurrence of explosive gases Mixture environment.

Zone 1: An environment where explosive gas mixtures may occur during normal operation.

Zone 2: An environment in which explosive gas mixtures are unlikely to occur during normal operation or, even if they do occur, will only exist for a short period of time.

Zone 0 generally only exists in internal gas spaces such as closed containers and storage tanks. In the actual design process, zone 1 also rarely exists. Most cases belong to zone 2.

1.2. Explosion-proof electrical equipment is divided into two categories:

Class I electrical equipment for underground coal mines

Class II electrical equipment used in places other than mines< /p>

1.3. Class II electrical equipment is divided into three categories: IIA, IIB and IIC according to the maximum test safety gap or minimum ignition current ratio suitable for explosive gas mixtures; and is divided into T1~ according to its maximum surface temperature T6 six groups.

1.4. Explosive gas mixtures are grouped according to ignition temperature

2. Noun predicates

2.1. Flameproof electrical equipment

Electrical equipment with an electrical equipment enclosure that can withstand the explosion pressure of the internal explosive gas mixture and prevent the internal explosion from propagating to the explosive mixture around the enclosure is marked "d".

2.2. Increased safety electrical equipment

Under normal operating conditions, arcs, sparks or high temperatures that may ignite explosive mixtures will not occur. Structural measures should be taken to improve the safety margin to ensure Electrical equipment that avoids arcing, sparking or high humidity under normal and approved overload conditions is marked "e".

3. Explosion-proof principle

There are two reasons why electrical equipment ignites flammable gas mixtures: one is the sparks and arcs generated by the electrical equipment, and the other is the surface of the electrical equipment (that is, the surface of the electrical equipment). Surfaces in contact with flammable gas mixtures) generate heat. Explosion-proof purposes can be achieved by placing parts that can generate arcs and sparks during normal operation of the equipment in a flameproof enclosure, or by adopting other explosion-proof types such as cast-sealed type, sand-filled type, oil-filled type or positive pressure type. For increased safety electrical equipment, it is equipment that will not produce arcs, sparks and dangerous high temperatures during normal operation. If some protective measures are taken on its structure, try our best to ensure that the equipment will not produce arcs, sparks and dangerous high temperatures under normal operation or approved overload conditions. The occurrence of arcs, sparks and overheating can further improve the safety and reliability of the equipment. Therefore, this kind of equipment has no ignition source during normal operation and can be used in explosive hazardous environments.

4. Examples of explosion-proof signs

4.1. If the electrical equipment is Class IIB explosion-proof T3 group, the sign is ExdIIBT3.

4.2. If the electrical equipment is Class II increased safety, the temperature group is Group T2, and the mark is ExeIIT2.

4.3. If the electrical equipment adopts more than one composite type, the explosion-proof type of the main body shall be marked first, and then other explosion-proof types shall be marked. If the main body adopts the increased safety type with built-in Class IIC explosion-proof components, the temperature group The designation is T4 and the mark is ExedⅡCT4.

4.4. If the electrical equipment is dust explosion-proof and dust-proof type T11.

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