Crushers and their types

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.

Types of crushers:-

Crushers are divided into two main categories on the basis of crushing property.

• Primary crusher
• Secondary crushers

Primary Crushers:-

The primary crusher mainly refers to the jaw crusher and impact crusher. They reduce 1.5 meter feed to approximately 10-20 cm particles.In the designing of a crushing plant of any nature and size, to select the right type and size of primary gyratory crusher is of great significance. Generally speaking, this machine is the largest and most expensive single item in the plant; a mistake in the choice may lead to a full replacement. Therefore, you have to pay close attention when choosing primary crushers. The following tips may be helpful for the selection of primary crushers.

• The name, hardness, humidity of material
• Pay attention to the hourly, daily or yearly capacity
• The discharging granularity or the final particle size of the finished products
• Crushing machine type and size
• Feeding method

Secondary Crushers:-

Secondary crushers mainly handle rocks of smaller particle size that have already been impacted and crushed from their original size. They reduce feed in .5-2 cm particles.In recent years, with the rapid development of infrastructure projects, rock crushers have found more applications in various fields and industries, such as mining, chemical industry, road construction, metallurgy, construction etc.

 

Table Of Different Types Of Crushers:-

 

 

Jaw Crusher:-

A jaw or toggle crusher consists of a set of vertical jaws, one jaw being fixed and the other being moved back and forth relative to it by a cam or pitman mechanism. The jaws are farther apart at the top -than at the bottom, forming a tapered chute so that the material is crushed progressively smaller and smaller as it travels downward until it is small enough to escape from the bottom opening. The movement of the jaw can be quite small, since complete crushing is not performed in one stroke.

Gyratory Crusher:-

A gyratory crusher is similar in basic concept to a jaw crusher, consisting of a concave surface and a conical head;both surfaces are typically lined with manganese steel surfaces. The inner cone has a slight circular movement, but does not rotate; the movement is generated by an eccentric arrangement. As with the jaw crusher, material travels downward between the two surfaces being progressively crushed until it is small enough to fall out through the gap between the two surfaces.

 

 

Cone Crusher:-

 

A cone crusher is similar in operation to a gyratory crusher, with less steepness in the crushing chamber and more of a parallel zone between crushing zones. A cone crusher breaks rock by squeezing the rock between an eccentrically gyrating spindle, which is covered by a wear resistant mantle, and the enclosing concave hopper, covered by a manganese concave or a bowl liner. As rock enters the top of the cone crusher, it becomes wedged and squeezed between the mantle and the bowl liner or concave. Large pieces of ore are broken once, and then fall to a lower position (because they are now smaller) where they are broken again. This process continues until the pieces are small enough to fall through the narrow opening at the bottom of the crusher.

Impact Crusher:-

 

mpact crushers involve the use of impact rather than pressure to crush material. The material is contained within a cage, with openings on the bottom, end, or side of the desired size to allow pulverized material to escape. This type of crusher is usually used with so ft and non-abrasive material such as coal, seeds, limestone, gypsum or soft metallic ores. There are two types of impact crushers: horizontal shaft impactor and vertical shaft impactor.

Horizontal shaft impactor (HSI) / Hammer mill:-

The HSI crushers break rock by impacting the rock with hammers that fixed upon the outer edge of a spinning rotor. The practical use of HSI crushers is limited to soft mat erials and non abrasive materials, such as limestone, phosphate, gypsum, weathered shales.

Vertical shaft impactor (VSI):-

VSI crushers use a different approach involving a high speed rotor with wear resistant tips and a crushing chamber designed to 'throw' the rock against. The VSI crushers utilize velocity rather than surface force as the predominant force to break rock. In its natural state, rock has a jagged and uneven surface. Applying surface force (pressure) results in unpredictable and typically non-cubicle resulting particles. Utilizing velocity rather than surface force allows the breaking force to be applied evenly both across the surface of the rock as well as through the mass of the rock. Rock, regardless of size, has natural fissures (faults) throughout its structure. As rock is 'thrown' by a VSI Rotor against a solid anvil, it fractures and breaks along these fissures. Final particle size can be controlled by 1) the velocity at which the rock is thrown against the anvil and 2) the distance between the end of the rotor and the impact point on the anvil.

Mineral Sizers:-

The basic concept of the mineral Sizer, is the use of two rotors with large teeth, on small diameter shafts, driven at a low speed by a direct high torque drive system. This design produces three major principles which all interact when breaking materials using Sizer Technology. The unique principles are; The Three-Stage Breaking Action, The Rotating Screen Effect, and The Deep Scroll Tooth Pattern.

  

The Three-Stage Breaking Action: Initially, the material is gripped by the leading faces of opposed rotor teeth. These subject the rock to multiple point loading, inducing stress into the material to exploit any natural weaknesses. At the second stage, material is broken in tension by being subjected to a three point loading, applied between the front tooth faces on one rotor, and rear tooth faces on the other rotor. Any lumps of material that still remain oversize, are broken as the rotors chop through the fixed teeth of the breaker bar, thereby achieving a three dimensional controlled product size.

 

Reductoin ratio:-

It is ratio of maximum size of feed to the maximun size of product. The average number of pieces the raw feed rock is reduced into.

Reduction ratio= Maximum size of feed/Maximum size of product

Different reduction ratios are given;