Difference between revisions of "Crushers"

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Crushers (view source)

Revision as of 07:42, 31 January 2012

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In operation, the raw material (of various sizes) is usually delivered to the primary crusher's hopper by dump trucks, excavators or wheeled front-end loaders. A feeder device such as an apron feeder, conveyor or vibrating grid controls the rate at which this material enters the crusher, and often contains a preliminary screening device which allows smaller material to bypass the crusher itself, thus improving efficiency. Primary crushing reduces the large pieces to a size which can be handled by the downstream machinery.
==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 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 crusher.
 
 
There can be also another stage of crushing called 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 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.  




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