South African crushing and screening equipment supplier IMS Engineering highlights the importance for quarries to produce sand from aggregate sizes of which there is an overabundance, since natural sand is declared a nonrenewable resource. “Construction and infrastructure development industries are becoming limited in using natural sand, enabling quarries to generate income from products that would otherwise be waste or stockpiled indefinitely until demand for this material can be realised,” Hazemag crushing and material preparation division marketing and sales manager Shannon McEwan tells Mining Weekly. He adds that quarries require Hazemag sand impactors to perform this process, with the material typically produced by secondary crushers, such as Hazemag’s hard-rock impactor, being used as feed for the sand impactor. According to McEwan, Hazemag impactors are being used in several quarries in South Africa and abroad, providing the opportunity to produce materials ranging from specification stone to sand. These hard-rock series impactors are designed to process a variety of abrasive materials, including gravel, granite, tillite, dolorite, basalt, gneiss, glass, fireclay, as well as less-abrasive materials such as dolomite and norite. The hard-rock impactor, a secondary impactor, has the ability to produce a cubical, fissure- and stress-free product, with a size distribution that can be tuned to conform to customers’ specific requirements, such as crusher run gradings. “The cubical shape of the product allows it to compact well, and ensures excellent particle strength, which is important in applications such as roads construction,” says McEwan. He adds that the secondary impactor produces a high reduction ratio in comparison to other crushers, with reduction ratios achieved in the order of 10:1 to 20:1, at relatively low power consumption. The secondary impactor also offers great versatility, which is obtained by varying the rotor speed, impact-apron gap settings and grinding-path gap setting, allowing the production of a variety of product sizes. In addition, the crusher is lined with high wear-resistant chrome molybdenum materials providing economical operation. “The crusher is able to reduce the size of relatively large rocks, from –150 mm to –300 mm, depending on crusher size, to stones smaller than 40 mm in size. “These stones can then be screened into usable aggregate fractions or used to produce sand,” says McEwan. He adds that the sand impactor is designed to reduce material of less than 40 mm directly to sand fractions in the order of 60% less than 3 mm in open circuit. “One of the special features of this tertiary crusher is that with its high rotor speed, it is able to reduce materials with a single impact, avoiding wear-intensive friction or attrition, and thus reducing wear and energy costs. “The efficiency of the high-energy transfer on impact with the rotor’s crushing implements, or blow bars, results in very effective particle reduction, producing a large amount of sand in a single pass through the crusher,” says McEwan. He adds that the sand impactor is ideal for quarries with heaps of unsaleable product, which could be used to generate income and compete in the sand market.

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• Hazemag USA

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