The coal industry occupies a very important position in the national economy. According to the international EC standards and the provisions of my country's explosion-proof mark GB3836.1, coal mines and other mines with gas, because of the danger of gas explosion, must choose explosion-proof explosion-proof switch cabinets. Not only is the cabinet fully enclosed, but the incoming and outgoing lines are also closed. Explosion-proof electrical equipment is divided into two categories, namely category: electrical equipment for coal mines; Sichuan category: electrical equipment for other explosive gas environments except coal mines.
The explosion-proof type is to take specific safety measures for the structure of electrical equipment to prevent the ignition of the surrounding explosive mixture. As far as my country's existing mandatory national standards and technical conditions in recent years are concerned, its explosion-proof types are: flameproof type " d", increased safety type "", intrinsically safe type "", positive pressure shell type "p", oil-immersed type "o", sand-filled type "q", "n" type, potting type "", special type " s", mixed type (compound of the above types, for example d[b). The types commonly used in coal mines in my country are mainly flameproof, increased safety, intrinsically safe, special and mixed. Increased safety "" and intrinsically safe "standards and product standards, etc. 2. The basic environmental conditions of the mine.
1) Air composition
In the process of mining underground coal mines, the air contains methane, carbon dioxide, carbon monoxide, hydrogen sulfide, nitrogen dioxide, ammonia and other hydrocarbons, of which the methane content accounts for more than 85%. When the methane content in the air reaches 5~15%, the danger of gas explosion will occur when it encounters a high temperature above 1650°C or a spark with sufficient energy. During the excavation process, a large amount of coal dust will also be caused to fly. When the coal dust particle size is within 0.75~1m, and its concentration is within the range of 30~2000gm3, when encountering a large heat source above 10,700 ℃, there may be a danger of explosion. . These two kinds of explosions are associated, generally cause coal dust explosion after gas explosion, and the damage caused by coal dust explosion is more serious. Therefore, the "Coal Mine Safety Regulations" has made strict regulations on the air composition in the coal mine and the air flow speed in the tunnel. There are also corresponding regulations for excavation equipment. For example, in the comprehensive mechanized excavation working face, it is stipulated that the shearer and roadheader should be equipped with internal spray dust suppression devices; and other reprint sites are required to have external spray or water spray measures.
2) Ambient temperature
The temperature under the coal mine varies with the depth of the stratum and the changes of the four seasons. The annual average temperature of the same location is relatively stable, and the temperature difference between the upper and lower sides does not change much. GB3836.1 "General Requirements" stipulates that electrical equipment should be able to operate normally when the ambient temperature is between 120°C and 1040°C
The "Coal Mine Safety Regulations" stipulates that the mining face of the production mine shall not exceed 26 ℃, and the mechanical and electrical chamber shall not exceed 30 ℃. If individual locations exceed the specified temperature, cooling measures must be taken. The above regulations not only consider that the underground miners have a more suitable working environment, but also consider that the electrical equipment can basically prevent the difference in heat dissipation at high temperature and the thermal abrupt change at high and low temperature during operation. normal operation.
