Modern Quarrying July-August 2015

FACE TO FACE WITH ASPASA

Aspasa believes the time has come for the aggregate and sand industry to defineits own sector with rules designed to protect and promote companies and individuals within the smaller mining sector.”

(typically cone crushers) and on to tertiary crushers if finer materials are required. Quatenary crushing is sometimes used to make materials finer still.” He says that as a rule, it takes com- paratively little energy to break big lumps and considerably more for small stones each time the particle is reduced further. “That is precisely why plants need to be designed for efficiency to work out the correct pinch point to break the material quickly and efficiently. It is also impor- tant to keep running the plant efficiently thereafter.” Regular checks and clearing need to be done especially on feeders, screens and scalping screens. Even a 10% buildup of materials on a screen can have a big effect on efficiency as it will block 10% of the material; in addition, it will recircu-

a guaranteed method of boosting pro- duction with benefits that extend from the extraction of material to the stock- pile, and the sale of graded products. The workshop was addressed by none other than Metso’s crushing specialist Alan Fletcher. Depending on the type of material available at the quarry, the process of sizing and shaping stone and aggregate is usually undertaken with the use of a series of crushers to break rocks into man- ageable sizes until they confirm to the required specification. Bottlenecks at any of the steps along the process can have a dramatic effect on overall production and a negative effect on the profitability of the quarry. “The single most important aspect of rock processing is safety and training of all staff in the correct operation and pro- cedures when operating heavy process- ing equipment,” Fletcher says. “Thereafter it is important to understand the types of crushing processes required to manufac- ture the products needed and procure the right equipment to deliver the required tonnages. “Once we have established the type of product and tonnages, we can build the processing plant around those principals and work out what type and how many crushers are required. The typical plant will have primary crushers at the first stage (usually a jaw crusher), and then materials will go to secondary crushing

Specialist crushing guru Alan Fletcher.

late missed material and cause a buildup that will further com- pound the problem. Screen size and strati- fication also deter- mines the amount of material that is deliv- ered to the crusher and it is therefore important that the screen is correctly specified to deliver the correct tonnages. “Users must know that crushers need to

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MODERN QUARRYING July - August 2015