The local fan must cooperate with a special air duct to send fresh air to the working surface, and exhaust gas. According to the arrangement of the local fan and the air cylinder, it can be divided into press-in type, pull-out type and hybrid type.
The press-in type is shown in Figure 1. The local fan is arranged in the fresh air flow roadway, and the fresh air flow is pressed into the working surface by the air cylinder to discharge the dirty air. This method is called press-in type.
Figure 1 Press-in wind diagram
The fan is installed in the fresh airflow roadway, and the wind is taken out by the air duct. This method is called pull-out ventilation, as shown in Figure 2.
Figure 2 Diagram of the extraction ventilation
Press-in ventilation is easy to discharge the gun smoke and dust from the working face because the wind is emitted by the air cylinder. However, the sewage is discharged for a long time and is generally used for tunneling within 200m in length.
The draw-out ventilation air duct can extend into the smoke area after the explosion. The cannon smoke discharge speed is fast, the fresh air flow in the roadway is good, and the working conditions are good, but the extraction ventilation requires the exhaust air outlet to be close to the working surface. When blasting, the air duct is easy to be broken, and the farther away from the working surface, the smoke exhaust The more difficult it is. Therefore, it is generally rare to use single extraction ventilation.
Mixed ventilation is shown in Figure 3. It takes full advantage of push-in ventilation and extractive ventilation. As long as it is used properly, ventilation is better.
Figure 3 Schematic diagram of hybrid ventilation
Installation of local fan ventilation must pay attention to:
First, overcome the leakage of wind. Due to factors such as blasting and collision of the mining car, it is easy to cause damage to the air cylinder, resulting in air leakage, which deteriorates the ventilation effect. Air leakage from the air duct should be discovered in time and trapped on the spot.
Second, overcome the serial flow of the working surface. When the circulation mode is arranged, the series air flow between the working faces should be avoided, and the waste wind of each working face is directly discharged to the return air passage.
Third, overcome the circulating wind. When the ventilation distance is too long, the local fans need to work in tandem. In order to avoid circulating airflow, the distance between the two local fans is preferably one-third of the total length of the air duct, and the working air volume of the local fan must be less than 70% of the air volume of the installed local roadway.
4. The air cylinder of the press-in type air outlet should be straight to overcome the waste air circulation of the working surface.
5. The fan of the bureau is continuously activated to ensure that the concentration of gunpowder, mineral dust and other harmful gases on the working surface meets the sanitary standards.
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