basic mining process/terminology


associated functions





Good quality air has to be provided for personnel to breath, to dilute both natural and introduced (e.g. diesel exhaust) gases, to dilute or carry away dust and to provide cooling for personnel and machinery. A small quantity of air may flow through mine workings naturally but this would be insufficient and uncontrolled and therefore it is necessary to provide a mechanical means of ventilating the mine.

To do this at least two connections between seam and surface are required and large fans are connected to one of these. These are primarily exhaust fans which suck air into the mine from the surface via the other connection(s), through the roadways to where mining operations are being carried out and back to the surface through the exhausting fan(s). A few mines do use intake or "forcing" fans, particularly in the US where exhaust adits are mined to outcrops. The roadways underground are divided into 2 groups, those carrying fresh air into the workings ("intake airways") and those carrying used air back out ("return airways"). Adjoining intake and return airways are separated by the coal pillars or by installing "stoppings" (most commonly in the form of a wall of some kind) in any interconnecting roadways to prevent air short-circuiting between the roadways. Sometime doors are used in place of stoppings to allow passage of equipment or personnel where required. Where air routes have to cross, a section of roof or floor is removed and an artificial tunnel constructed to carry return air over (most commonly) or under the intake air. These structures are known as "overcasts".

Where there is more than one location where mining is being carried out, legislative requirements (and good mining practice) require that no air used to ventilate one working location can be used to ventilate another. This requires a number of separate circuits off the main roadways known as ventilation "splits".

Other control devices are required to ensure adequate flow to all parts of the mine (if not controlled, air will take the path of least resistance back to the fans). Flow to different areas of the mine is regulated by constructing artificial restrictions in airways in the form of a stopping or doors with an opening usually of an adjustable size (by the use of adjustable louvers, sliding doors, etc), such restrictions being known as "regulators".

All installations such as stoppings, overcasts, doors, regulators, etc are known collectively as "ventilation control devices or VCD's".

With all the above taken into account, what appears a simple process can become very complex.

Because mine fans operate continuously and require considerable power to do so, ventilation efficiency is an important consideration and fan specification and ventilation circuit maintenance become important cost considerations.

At the point where roadways are being driven in advance of the ventilation circuit other measures are required to enable air to travel into the advancing roadways. These measures include using a temporary "wall" of flexible, air tight material (known as "brattice") to create a ventilation circuit in the advancing roadways(s), or by using ventilation ducting combined with a relatively small fan (an "auxiliary fan") to cause air to flow into the advancing roadway(s).

The state of the mine ventilation needs to be monitored to ensure that the quantity of air is maintained consistently and that emitted gas levels are maintained below safe threshold levels. Monitoring is done both manually and by the use of continuously operating monitors that may indicate remotely, often to the surface.