1、 The basic requirements for the shell are (1) non explosive performance (explosion-proof performance). The explosion-proof type of shell is mainly designed based on the principle of gap explosion-proof. In actual products, the shell and door structures can be roughly divided into two types, namely quick opening doors and bolt fastening, with gaps in their joint surfaces. Therefore, it is required that the gap between the explosion-proof joint surfaces is within the range specified by the standard. For example, for quick opening structures, the gap is usually required to be around 0.25mm. The average roughness of the explosion-proof joint surface does not exceed 6.3um (3.2um on the shaft), which fully meets the explosion-proof requirements. The explosion-proof joint surface must be processed by circular turning, vertical turning, and vertical milling, and the surface is composed of circular blade patterns. The surface roughness of the machined parts is relatively high, with small peaks and valleys, and micro geometric features composed of small spacing, such as building barriers, which help the flame spread from place to place

The flame channel sprays out, indicating that the smoother the explosion-proof joint surface, the better. When machining flange surfaces, lathes and boring machines are generally used. On the premise of ensuring the accuracy of the machine tool, rough machining should be carried out first, and then the chuck claw should be loosened once to eliminate internal stress during rough machining. Then, it should be tightened, and the clamping force should be slightly reduced before precision machining. The cutting amount is generally 0.1-0.3 Im, The flatness should be ≤ 0.06 mrs. In addition, attention should also be paid to increasing the front and rear angles of the tool, reducing the radius of the cutting edge arc, increasing the cutting speed, appropriately reducing the feed rate, and taking cooling and lubrication measures. These will all reduce the stress on the explosion-proof surface. (2) Structural strength (explosion resistance)

The main function of an explosion-proof shell is to limit the internal explosion within the shell, so the shell must have sufficient structural strength to withstand the explosion pressure generated during the explosion.

For mining products, the main component of explosive gas mixtures is methane (CH4), and the explosion pressure is usually around 0.8Mpa. When designing, 1MPa is usually taken

Products with explosion-proof structures, such as explosion-proof, increased safety, or both, account for the vast majority of explosion-proof electrical products. Proper waterproof and dustproof performance is one of the essential functions that products must possess. In the process of design, production, inspection, and maintenance, how to ensure that products have this function and are effective is an important issue.