Crushing means reducing the size of large boulders and consists of the following steps.
1) Primary Crushing Process
It is also called rough crushing or large crushing. It can be considered as reducing the sizes of rocks having 0.5-1.5 m radius at a rate of 1/3 to 1/7. At this stage, the choice of the type of crushing machine depends directly on the physical characteristics of the rock. Jaw and conical crushers are generally used for hard and abrasive rocks. As for the soft and medium-hard quarries with low pollution rate, impact crushers are used for primary crushing purposes as a more economical solution.
2) Secondary Crushing Process
If the size of the fed material is around 300-400 mm, then the crushers used are called secondary crushers, while the aim is to obtain the final product [(0-60 mm) or 40 mm or 0-25 mm]. Once again, the physical characteristics of the material at this stage determine the crusher type.
3) Tertiary Crushing Process
This process is considered as a third crushing stage where the oversize materials resulting from screening final products obtained from the secondary crushing process are not returned to the secondary crushing stage. The aim here is to obtain more fine materials or shape the products. The sizes and distribution features of products to be crushed vary at this stage based on the types of machines used.
4) Quaternary Crushing Process
An additional crushing process may be planned as a quaternary crushing subsequent to the third stage in order to obtain special-purpose very fine product groups. The aim at this stage is to make crushing so as to obtain products smaller than 1 mm. High-speed or pressurized special crushing machines and screens come into play at this stage.
One or more than one crushers used in these crushing stages that we mentioned briefly are included in full plant designs based on the required capacity, products, product distributions, and the characteristics of the land on which the plant to be installed, so that they are transformed into plants involving most convenient and economical solutions to produce products suitable for customer demands thanks to 60-year experience of NACE.