A crusher is a machine that uses mechanical energy to break blocks of stone, concrete, or other building materials into smaller blocks of a specific grain size. They are particularly used in the mining industry to reduce the size of ore blocks and facilitate their processing. Crushers are designed to receive blocks of a maximum size. It may be necessary to go through several crushing steps to obtain the desired end product.
Crushers are classified according to the fineness with which they fragment the starting material. There are primary or secondary crushers (coarse finished products) and tertiary or quaternary crushers (fine particle finished products).
The abrasiveness and hardness factor. It is essential to know what material is going to be crushed, in particular its abrasiveness and hardness. You must evaluate the compressive strength or maximum force that the material can withstand before breaking.
The dimensions. You will need to consider the maximum dimensions you need to enter into the machine (length, width and thickness).
Granulometric requirement. It is necessary to define the desired result i.e. the grain size after crushing.
The capacity (throughput). You will need to determine the processing capacity (or throughput) necessary for your use. This is measured in tonnes/hour.
You can then look at the main technologies for crushers on the market:
Impact crushers, also known as hammer crushers
Why choose a jaw crusher?
It’s a primary crusher. The jaw crusher is a machine for crushing rocks and other hard and abrasive materials, such as granite, ores or recycled concrete, usually for industrial purposes. The crushing device consists of a fixed plate and a swing plate called jaws between which the rock is trapped and crushed. A motor and a belt transmit the movement to an eccentric shaft that drives the movable jaw by rotation. A spring returns this moving jaw to let the crushed materials gradually descend into the crusher. When the materials are small enough, they fall into the space between the crusher’s two jaws. The crusher breaks the rock into small stones that are used in particular for manufacturing concrete for construction and roads.
Jaw crushers use a rudimentary and reliable technology that does not require much maintenance or engineering knowledge. They are the most popular crushers in the world. Jaw crushers are particularly suitable when the main objective is to reduce large blocks into smaller pieces that can then be processed by other machines.
Low maintenance and operating costs because it has few moving parts
Reduces the raw material to about 150 mm
Not suitable for small material requirements (smaller than 150 mm). If a smaller grain size is required it can be used in combination with other crushers.
Not suitable for handling clay or metal mixed with rock.
Why choose a cone crusher?
Cone crushers, also known as conical crushers, break rock between an eccentric rotating head and a bowl. The rotating head is covered by a wear-resistant mantle. The large pieces are broken once between the two jaws, then they gradually descend into the crusher where they continue to be broken until the pieces are small enough to pass through the narrow opening at the bottom of the breaking space. A cone crusher can crush a variety of rocks, from medium to hard. The way a cone crusher operates is similar to how a gyratory crusher does, but in a cone crusher the slope in the breaking space is not as steep.
Although it is known for its ability to crush hard and abrasive ores and rocks, the cone crusher is better suited for secondary crushing. It is designed to crush pre-dimensioned materials, generally of 100 mm, 150 mm or 200 mm, and provide finished products of small dimensions.
Low operational costs This type of crusher is equipped with a spring release system that protects it against overloads and allows uncrushable materials to pass through the crushing space without damaging the crusher.
The cone crusher cannot take material of all sizes. The materials must be pre-dimensioned for the crusher (usually 200 mm or less).
The finished product is not homogeneous, which is an essential requirement for many material specifications.
Not suitable for handling clay or metal mixed with rock.
Why choose an impact crusher?
Impact crushers can be used as primary crushers, secondary crushers or tertiary crushers depending on the size and technology. They are equipped with beaters, also called hammers, and impact plates. They operate in the following way: they are fed from the upper part, then the stones are hit by the hammers and projected towards the plates. The stone breaks on the plate and bounces back towards the hammers. The process is repeated until the stone reaches the desired size. Impact crushers are ideal for mixed materials. They can crush clay, dirt or metal mixed with the feed material, for example reinforcing bars, wire mesh or anchors. They can crush hard materials, but are especially suitable for soft to medium rocks. Impact crushers, also called hammer crushers, can have a horizontal shaft or a vertical axis.
Horizontal-shaft: generates a uniform cubic product. It can accept all feed inputs and ensure maximum productivity, both in primary and secondary crushing.
The impact makes it possible to better control the size of the crushing result, for example better cubic gravel.
Operating costs can be higher.
It can have difficulty breaking small parts, as the crusher’s ability to break blocks is related to the energy accumulated by the stone upon impact with the hammer. This energy therefore depends on the speed of the hammer, but also on the mass of the stone.
Wear of the beaters depends on the matter being crushed.
Vertical-axis:can create quality sands. It crushes the gravel even more finely because it breaks the most persistent bonds of the aggregate. This results in a sand with optimal consistency and shape, especially for concrete. This machine combines rotational energy with impact energy for crushing.
High production capacity
High breakage rate
Low energy consumption
Uniform grain size
Can only be used to obtain fine finished products
What other characteristics are important to consider when choosing a crusher?
While stationary crushers have the advantage of being sturdy, it can be advantageous to choose a mobile crusher to get the crusher closer to where the it is going to be needed. Wheeled crushers can be moved to a construction site using a truck. These units are generally autonomous and therefore do not require an additional diesel engine to operate. Crawler crushers are designed to be moved around constantly. They are more compact and weigh less than mobile wheeled crushers.
Mobile crushers perform the same types of crushing as stationary ones. For reasons of autonomy, they also include a hopper and a conveyor to feed the crusher, as well as a second conveyor to evacuate the final product.