Dust-Explosion Protection in Mine Shafts

means for the prevention and localization of coal-dust explosions. Methods used to combat explosions are based on the use of inert dust (rock dusting) or water (watering method).

Rock dusting involves settling dust in excavations with powdered rock and installing rock barriers. Dusting with powdered rock is done to neutralize the explosiveness of precipitated coal dust. In this treatment, inert dust is applied manually or by means of a mechanical rock duster; limestone, dolomite, and coquina are used nowadays, but argillaceous schist was usually used in the past. The inert dust is treated with hydrophobic additives to prevent consolidation. Rock-dust barriers are used for localizing dust explosions; they consist of shelves laden with rock dust and loosely arranged on brackets across the excavation near the roof. A barrier is at least 20 m long. When the wave of an explosion trips the shelves, the inert dust is scattered and the flame is extinguished. Roadheads, which are located 40-150 m from the working faces, are isolated by primary rock barriers with forced triggering.

Watering involves whitewashing and wetting the excavation and binding the settled coal dust with wetting-binding solutions, paste, and dispersed mist-sprayed curtains. Engineers install primary and other water barriers, which consist of a series of overturning containers, each with a maximum capacity of 80 liters, set below the roof across the excavation. The barrier is no less than 30 m long.

The watering method is required in areas of intense dust deposition and in flooded excavations, where rock-dusting is not effective.

The frequency of rock dusting or watering depends on the degree of dust deposition and the lower explosive limit of the dust. In the USSR, the lower explosive limit of dust and the rock-dusting standard for each mine seam in coal basins is established in accordance with the Catalog of Mine Seams According to Explosive Properties of Coal Dust.