View source for Rock Crushers

[[Category:Particle Size Reduction]]{{Knoppen}}  
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[[File:Impact_Crusher.jpg|thumb|right|Impact Crusher]] 
[[File:Kaakbreker_stationaire.jpg |thumb|right|Stationary Jaw Crusher]] 
[[File:VSI_Crusher_mobile.jpg|thumb|right|Mobile Vertical Shaft Impact Crusher]]



A '''crusher''' is a machine designed to reduce large rocks into smaller rocks, gravel, or rock dust. Crushers may be used to reduce the size, or change the form, of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in rock ore), so that pieces of different composition can be differentiated. Crushing is the process of transferring a force amplified by mechanical advantage through a material made of molecules that bond together more strongly, and resist deformation more, than those in the material being crushed do. Crushing devices hold material between two parallel or tangent solid surfaces, and apply sufficient force to bring the surfaces together to generate enough energy within the material being crushed so that its molecules separate from (fracturing), or change alignment in relation to (deformation), each other. The earliest crushers were hand-held stones, where the weight of the stone provided a boost to muscle power, used against a stone anvil. Querns and mortar and mortars are types of these crushing devices.




==Industrial use==
In  the industry, crushers are machines which use a metal surface to break  or compress materials. Mining operations use crushers, commonly  classified by the degree to which they fragment the starting material,  with [[Primary Stage Crushers| primary]] and [[Secondary Stage Crushers|  secondary]] crushers handling coarse materials, and [[Tertiary Stage  Crushers |tertiary]] and [[Quaternary Crushers|quaternary]] crushers  reducing ore particles to finer gradations. Each crusher is designed to  work with a certain maximum size of raw material, and often delivers its  output to a [[Screeners|screening]] machine which sorts and directs the  product for further processing. Typically, crushing stages are followed  by milling stages if the materials need to be further reduced. Crushers  are used to reduce particle size enough so that the material can be  processed into finer particles in a [[Grinders|grinder]]. A typical  circuit at a mine might consist of a crusher followed by a grinder SAG  mill followed by a grinder [[Ball Mills|Ball mill]]. In this context,  the SAG mill and [[Ball Mills|Ball mill]] are considered [[Grinders]]  rather than crushers.

Crushers can be categorized in the way they are used in the industry (Continuous or per batch). 
*[[Batch Crushers]] 
*[[Continuous Roller Crushers]]

And used for smaller places or for crushers with more mobility or agility there are 
*[[Compact Crushers]]
*[[Portable Crushers]]

==Stages==

For  the purpose of mineral extraction when ore is excavated from earth  the  size of run of-mine ore can vary a lot between fines powders to big   boulders of 1.5 m across. Moreover the feed can also be intermittent   type in the form of dumpers feeding the crushing plant. The crusher at  this stage is called [[Primary Stage Crushers|primary crusher]]  the  main purpose of which is to give continuous feed to the plant down  the  line in a size convenient for further handling in the process plant. In  the next stage further crushing may be required so as to ensure proper  releasing of mineral from gangue. The crusher in this stage is called 
[[Secondary Stage Crushers|secondary crusher]].


There  can be also another stage of crushing called [[Tertiary Stage  Crushers|tertiary crushing]] depending on the initial size of the run of  mine ore and the final product size requirement.  Different stages are  required as total size reduction in one single crusher is not possible  efficiently. Moreover smaller sizes of material  tend to jam the flow of  ore in the crusher and unless there is  sufficient space for the  crushed ore to expand in volume there will be  choking of the crusher.  Hence [[Screeners|vibrating screens]] are deployed in between  different  stages of the crushers so that only those oversize ore can be  fed to  the crusher whose sizes need to be reduced. This also helps in  reducing  the capacity requirement of the crusher as total run of mine  ore need  not be fed to the crusher. Also there will be closed circuit  operation  in case of secondary and tertiary crushers so as to avoid passing of any  oversize material to the final stage. Primary crushing is done in open  circuit only. 


Some [[Mobile  Crushers|crushers are mobile]] and can crush rocks (as large as 60  inches). Primarily used in-pit at the mine face these units are able to  move with the large infeed machines (mainly shovels)to increase the  tonnage produced.  In a mobile road operation, these crushed rocks are  directly combined with concrete and asphalt which are then deposited on  to a road surface.  This removes the need for hauling over-sized  material to a stationary crusher and then back to the road surface.

*[[Primary Stage Crushers]]
*[[Secondary Stage Crushers]]
*[[Tertiary Stage Crushers]]
*[[Quaternary Crushers]]


==Technology==

For  the most part advances in crusher design have moved slowly. Jaw   crushers have remained virtually unchanged for sixty years. More   reliability and higher production have been added to basic [[Cone  Crushers|cone crusher]] designs that have also remained largely  unchanged. Increases in rotating  speed, have provided the largest  variation. For instance, a 48 inch  (120 cm) cone crusher manufactured  in 1960 may be able to produce 170  tons/h of crushed rock, whereas the  same size cone manufactured today  may produce 300 tons/h. These  production improvements come from speed  increases and better crushing  chamber designs.



==Types of Crushers==

Crushers can be divided in three groups: Attrition, Shear and Compression. 


*[[Attrition Crushers]]
**[[Hammer Crushers]]
***[[Cone Crushers]]
**[[Gyratory Crushers]]
****[[Gyradisc Crushers]] 
****[[Rhodax crushers]]

*[[Shear Crushers]]
**[[Roll Crushers]]
***[[Single Roller Crushers]]
***[[Double Roller Crushers]]

*[[Compression Crushers]]
**[[Jaw Crushers]]
***[[Clinker Crushers]]
**[[Hammer Crushers]]

*[[Impact Crushers]]
**[[Vertical Shaft Impact Crushers]]
**[[Horizontal Impact Crushers]]

Misc. 
**[[Disc Crushers]]
**[[Cam Crushers]]
**[[Pin Crushers]]


==Common materials crushed==
Ash,  Bauxite, Bricks, CarbonAnode, Ceramic, Tile, Clay, Coal, Culm, Waste,  Diatomite, Dolomite, Fertilizer, Filter Cake, Fullers Earth, Glass, Gob  Waste, Graphite, Gypsum, Iron, Lime, Limestone, Met. Coke, Oil Shale,  Petro Coke, Phosphate, Potash, Salt, Sand, Sand Cores, Slag, Silicon,  Sinter, Sulphur, Tar Sands, Trona Ore, Vermiculite.