Crushers play an important role in the material handling process for underground mine operations. There are two possible locations for an underground crusher: near the shaft and under the ore body. The location is mainly determined by the steepness and shape of the ore body, the depth of the ore body and the production schedule of the mine. For underground crushing, three stages of material handling are defined: pre-crushing, crushing, and post-crushing. The pre-crushing stage prepares the material for the crusher, the crushing stage reduces the size of the material, the post-crushing stage transports the material to surface for further processing. The main types of crushers are the gyratory crusher, the jaw crusher and the impact crusher. Each of these types uses a different technique to reduce the size of the material. The costs for crushers are divided in the capital costs and the operating costs. The capital costs include the crusher cost, the installation cost and a couple of other costs like the cost of the motor. Crushers produce fine material that will become airborne when air movement is present. Dust can be a health and safety hazard and therefore needs to be controlled. Two ways of dust control are wet dust suppression and airborne dust capture.
Location of the Crusher In an Underground Mine
The location of the crusher in an underground mine operation has a great impact on the design and development of the mine. The reason for this great impact is the role of the crusher on the design of material handling and skipping. Two possible locations for an underground crusher exist: near the shaft and under the orebody. Factors that determine the location of the shaft are the steepness of the orebody, the production schedule of the mine and the ground stress. It will take approximately six to twelve months to excavate, install and commission an underground crusher station (de la Vergne, 2003).
Near the Shaft
In classic mine design, the crusher is located near the shaft. This has the advantage that the material can go directly from the crusher to the skip. For mine operations that use truck haulage, the extra travel distance for the trucks is compensated by the advantages of more rapid access for excavation of the crusher and the expenses involved in moving the crusher (de la Vergne, 2003).
Under the Orebody
By mining rule of thumb, production shaft should be positioned in the footwall side of the orebody in the host rock from its stability point of view. For the same reason ore handling and hoisting equipment including the underground primary crusher will also be located in the footwall side of the ore body.