Modern Quarrying Q1 2019

break it down. Similar to a racing car, using different gear ratios depending on the race track, efficient and economical operation of a plant requires fine tuning to take the material properties into account,” he says. Van Rensburg says a good host rock is vital for production of a quality product, and the geology of the host rock is relevant right from the blasting stages of aggregate production. This tends to affect the size of the material that will report to the crushers, and hence will determine the size of the jaw crusher required at primary stage. “The hardness of the material will also affect the primary crusher selection and may well impact the throughput that can be achieved through the crushing circuit. Silica levels and other abrasiveness factors will influence wear levels, so operators need to be aware that maintenance interventions may be more frequent under these conditions,” concludes Van Rensburg. l

CRUSHING

Impact crushers are used mainly for less abrasive materials as primary and secondary crushers.

manage customer expectations and operating costs, we generally send rock samples to the Metso Lab for abrasion and crushability tests, we can then simulate the plant and provide accurate estimates of the operating cost and ensure we have the correct configuration,” adds Scherf. Scherf also reasons that harder material will have an impact on the number of crushing stages. “The harder the rock the more energy required to

correct crusher, but also the correct wearing materials to ensure a profitable operation,” says Scherf. He adds that rock properties, even on the same rock types, vary considerably as they are produced in a natural and varying environment, not a controlled lab. “Not all granites are the same, a fine grain granite is significantly harder than a coarse grain granite; some will have a higher silica (SiO2) content than others. In order to

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MODERN QUARRYING QUARTER 1 - 2019