Jaw crushers for mining environments
Jaw crushers are mainly used as primary crushers. Their main purpose is to produce material that can be transported by belt conveyors to the next crushing stages. The crushing takes place between a fixed and moving jaw which is mounted on a pitman, and its motion it set up by the movement produced by the eccentric shaft at the top of the pitman.
A toggle plate located at the bottom of the moving jaw is a wear plate that takes the momentum of the moving jaw. Material to be broken enters through the inlet opening and, under gravity, moves between the jaws, gets compressed and finally fractures as the material, now also receiving additional pressure from fresh boulders above, is forced through an ever-reducing gap. The closed side setting at the very bottom of moving and fixed jaw dies will determine the size of end product leaving the crusher outlet.
Impact crushing jaw crushers
Impactors are characterised by a high-reduction ratio and cubically shaped products. The feed material, usually supplied from a primary jaw crusher, is crushed by highly intensive impacts originating as rocks come into contact with fast-revoluting hammers.
These hammers are fixed to a rotor that forces the rocks to collide with internal wear plates on the swing beams. These particles are further crushed as rock-on-rock collisions happen, resulting in a fine, high-quality, shaped end product. The closed side setting is the distance between the lowest point of the lower swing beam and the hammers. This gap will determine the size of the end material being produced.
Cone crushing for mining materials
Cone crushing works on the principle of an oscillating shaft. The material is crushed in a crushing cavity between an external fixed element (cone) and an internal moving element (mantle) mounted on the oscillating shaft assembly. The fragmentation of the material takes place as the material is compressed between the wear parts around the crusher chamber.
Crushing also occurs as the material compresses against itself. With very abrasive materials, cone crushes offer lower wear costs when compared to impact crushers.
Mining material screening
Screening principles for vibrating screens are basically the same for any application. Material to be screened is fed onto a screening surface (either meshes, bofar plates or fingers). Aas the material loses its vertical velocity it is submitted to a change in direction of travel.
Through vibration, the bed of material assumes a fluid motion. The larger fractions rise to the top of this bed and the smaller fractions filter through the gaps. These smaller-sized particles reach the mesh elements and either fall through because they are smaller than the mesh apertures or stay moving because they are bigger than the mesh openings. In two-deck screeners the material falling through the top mesh repeats the process on the bottom mesh.
The above article is extracted from Mining Technology.