In the production process of coal mines, there are explosive substances such as gas and coal dust. In order to ensure safe production and prevent explosion accidents caused by gas and coal dust, on the one hand, the content of gas and coal dust in the air underground should be controlled; on the other hand, all ignition sources and high-temperature heat sources that can ignite gas and coal dust in mines should be eliminated.
Mine electrical equipment is divided into two categories, namely general mine electrical equipment and mine explosion-proof electrical equipment.
Mine general electrical equipment is a non-explosion-proof electrical equipment used in coal mines. It can only be used in places where there is no danger of gas and coal dust explosion underground. The basic requirements for it are: the shell is strong and closed, which can prevent direct contact with the live parts from the outside; it has good drip, splash and moisture-proof performance; there is a cable entry device, and it can prevent the cable from twisting, pulling out and damage; there is a locking device between the switch handle and the door cover, etc.
- . Types of explosion-proof electrical equipment for mining
According to different explosion-proof requirements, explosion-proof electrical equipment for mining is mainly divided into explosion-proof type for mining, increased safety type for mining, intrinsic safety type for mining, positive pressure type for mining, sand-filled type for mining, cast-in-place type for mining and gas-tight type for mining.
- Explosion-proof electrical equipment for mining
The so-called explosion-proof means placing the live parts of the electrical equipment in a special shell. The shell has the function of isolating the sparks and arcs generated by the electrical parts in the shell from the explosive mixture outside the shell, and can withstand the explosion pressure generated when the explosive mixture entering the shell is detonated by the sparks and arcs of the electrical equipment in the shell, while the shell is not destroyed, and at the same time, it can prevent the explosion products in the shell from spreading to the explosive mixture outside the shell. This special shell is called a flameproof shell. Electrical equipment with a flameproof shell is called a flameproof electrical equipment.
- Increased safety electrical equipment for mining
The explosion-proof principle of increased safety electrical equipment is: for those mining electrical equipment that will not generate arcs, sparks and dangerous temperatures under normal operating conditions, in order to improve their safety, a series of measures are taken in the structure, manufacturing process and technical conditions of the equipment, so as to avoid the equipment from generating sparks, arcs and dangerous temperatures under operation and overload conditions, and achieve electrical explosion-proof. Increased safety electrical equipment is to take certain measures to improve its safety level based on the original technical conditions of the electrical equipment, but it does not mean that this type of electrical equipment has better explosion-proof performance than other types of electrical equipment. The degree of safety performance of increased safety electrical equipment depends not only on the structural form of the equipment itself, but also on the maintenance of the equipment's use environment. Only those electrical equipment that do not generate arcs, sparks and overheating during normal operation, such as transformers, motors, lighting fixtures, etc., can be made into increased safety electrical equipment.
- Intrinsically safe electrical equipment for mining
The explosion-proof principle of intrinsically safe electrical equipment is: by limiting various parameters of the electrical equipment circuit, or taking protective measures to limit the spark discharge energy and heat energy of the circuit, the electric sparks and thermal effects generated in normal operation and specified fault conditions cannot ignite the explosive mixture in the surrounding environment, thereby achieving electrical explosion-proof. The circuit of this kind of electrical equipment itself has explosion-proof performance, that is, it is "essentially" safe, so it is called intrinsically safe (hereinafter referred to as intrinsically safe). Electrical equipment using intrinsically safe circuits is called intrinsically safe electrical equipment.
- Positive pressure electrical equipment
The explosion-proof principle of positive pressure electrical equipment is: the electrical equipment is placed in an outer shell, and there is no source of flammable gas release in the shell; the shell is filled with protective gas, and the pressure of the protective gas in the shell is higher than the pressure of the surrounding explosive environment, so as to prevent the external explosive mixture from entering the shell and realize the explosion-proof of the electrical equipment.
The symbol of positive pressure electrical equipment is "p", and the full name of the symbol is "Expl".
- Sand-filled electrical equipment for mining
The explosion-proof principle of sand-filled electrical equipment is: fill the outer shell of the electrical equipment with quartz sand, bury the conductive parts or live parts of the equipment under the quartz sand explosion-proof filler layer, so that under specified conditions, the arc generated in the shell, the propagated flame, the overheating temperature of the outer shell wall or the surface of the quartz sand material cannot ignite the surrounding explosive mixture. Sand-filled electrical equipment is used for electrical equipment with a rated voltage not exceeding 6kV, whose moving parts do not directly contact the filler when in use.