Ventilation, Shaft

the creation of normal atmospheric conditions in underground mine shafts by eliminating poisonous gases and high or low temperatures, which have a harmful effect on man, and by preventing the formation of dangerous accumulations of harmful gases.

A shaft is ventilated by means of continuously operating fans installed on the surface to supply the shaft with clean atmospheric air. In exceptional cases, underground auxiliary fans are used to ventilate individual groups of excavations (panels). All shafts should be ventilated by a draft created by a common ventilator.

A distinction is made between central (Figure 1,a), side (Figure 1,b), and combined designs for shaft ventilation. The combined system includes several variants of the central and side designs.

Figure 1. Shaft ventilation: (a) central, (b) side; (1) ventilator, (2) working face

The ventilation of a shaft is characterized by the amount of air supplied to the shaft and by the magnitude of the draft created by the ventilator. The amount of air required depends in part on the amount needed to lower to permissible levels the quantities of methane, carbon dioxide, and gases formed in explosive operations. In addition, an adequate amount of clean air must be supplied to those working in the mine, and the amount of dust in excavations must be reduced to nonharmful levels. Because of these needs, the greatest possible amount of air is introduced, with allowance made for leaks through sealed installations, the excavated space, and ventilation dividers, such as crossings and connectors.

The amount of air, which is calculated on the basis of these factors, is checked relative to the minimum and maximum permissible air flow rates. Air flow rates are checked to ensure the necessary temperature conditions in the mines, to allow for the removal of harmful gases and dust from the excavations, and to prevent dust formation.

Blind mining excavations can be ventilated in a number of ways. In the forced ventilation method, local ventilators draw clean air to the area near the working face through an air vent. In the suction method, impure air is drawn from the area near the working face. A combination of these two methods may also be used.

Ventilation is improved by reducing the aerodynamic resistance of mine excavations that is caused by enlarged cross sections. This is done by streamlining profiles and eliminating sharp narrowings and turns in the excavations. Ventilation is also improved by introducing more efficient and reliable methods to ventilate shafts and panels, reducing the amount of dangerous gases released into excavations (methane drainage), and reducing the temperature in excavations through air conditioning and insulation of the rock surrounding the excavation.