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Principle and design of explosion-proof lamps

Nov. 23, 2019

Principle

The principle of flameproof type is based on the explosion-proof concept and fire type of European Standard EN13463-1:2002 "Non-Electrical Equipment for Explosive Environments Part 1: Basic Methods and Requirements". Explosion-proof type is to take measures to allow internal explosion and prevent flame explosion. An explosion-proof type is the most commonly used type of explosion protection. Since the explosion-proof type of lamp housing is generally made of a metal material, the heat dissipation is good, the housing strength is high, and the durability is good, which is very popular among users. Moreover, many of the increased safety explosion-proof luminaire components, such as lamp holders, interlock switches, etc., also use a flameproof structure. An electrical device having a flameproof enclosure is referred to as an explosion-proof electrical apparatus. If the explosive gas mixture enters the flameproof enclosure and is ignited, the flameproof enclosure can withstand the explosive pressure of the internal explosive gas mixture and prevent the internal explosion from propagating to the explosive mixture surrounding the enclosure. This is a kind of gap explosion-proof principle, which is a structure designed by using the metal gap to prevent the propagation of the explosion flame and the temperature of the explosive product, to achieve the flame extinction and cooling, and to suppress the expansion of the explosion.

Design

When designing the structure of an explosion-proof luminaire, the manufacturer tends to focus on the shape and strength design of the flameproof enclosure, but often neglects the fasteners, the introduction device, the transparent member, the suspension device, the sign, explosion-proof wiring box, etc. which are integral with the outer casing. Design of other devices. In the following, according to the requirements of GB3838.2-2000 "Electrical Equipment for Explosive Gas Environments Part 1: Explosion-proof Type "d"", some problems that need attention should be analyzed in terms of structural design:

Explosion Proof Fluorescent Lamp

Explosion Proof Fluorescent Lamp

Shell fastener

There are two types of flameproof enclosures that are bolted: flat and dead. For flat structures, the bolts not only tighten the work, but also ensure the plane clearance. For the structure of the mouth, when the explosion-proof surface only considers the cylindrical part, the bolt only plays a fastening role; when the explosion-proof surface needs to consider the cylinder plus the plane, the bolt not only plays the fastening work, but also ensures the clearance of the plane part. When tapping directly on the outer casing, it must be noted that the fastener screw hole should not pass through the flameproof enclosure as much as possible. When passing through the outer casing, the bottom of the screw hole should have a margin of more than 3mm; use a light alloy material such as aluminum alloy as a partition. When the shell is exploded, because the strength of the aluminum alloy is low, when the explosion proof emergency light casing is often opened (such as replacing the light source and needs to be opened), the screw should not be directly tapped on the aluminum alloy casing, and the anti-loose should be pre-buried. Internal and external threaded steel sleeves to increase the strength of the screw hole and prevent failure due to thread rot; no need for the user to open the light source or open during maintenance, and the bolts installed at the factory can be directly tapped and fastened on the outer casing. Screw holes, but can not use fine thread, try to use coarse thread, and have enough number of engagement to meet the tightening requirements. In short, when designing the outer casing fastener, it should first distinguish its role in the flameproof enclosure, whether it is only for fastening, or to both tighten and ensure the plane clearance, and then determine the large axis of the bolt. Use the appropriate bolts for the load.