Capital Equipment News August 2018

CRUSHING – PART 1

TALKING POINTS

to the softest of sedimentary, the jaw crusher is a compression crusher that takes large primary material and reduces it to a manageable size for further crushing. In some cases, granulator jaw crushers can be used in secondary applications,” says Scherf. Van Rensburg says each customer’s application will be specific, so it is crucial to design and manufacture crushing plants with appropriately sized and staged equipment, as well as the right screening and other infrastructure, to suit the purpose. “This requires understanding a range of factors that might affect the crushing circuit; at B&E International, we are therefore able to work closely with customers not only on designing and building the plant but with a number of related services,” says Van Rensburg. “For instance, we can help find and approve a quarry site, and test the stone available. By assisting with blast design and practices we help gather the information required to arrive at the correct crushing plant application,” says Van Rensburg, adding that blasting techniques and fragmentation achieved together with throughput requirements will determine the size of the jaw crusher required. Pruewasser reasons that generally jaw crushers are provided for abrasive to very abrasive materials as primary crushers. Cone crushers are mainly used for abrasive to very abrasive materials as secondary crushers. Ravenscroft agrees, saying that a jaw is predominantly classified as a primary crusher, by virtue of being the first stage in the crushing process. “It caters for large feed size and a high production output, with a crushing ratio of 4/5:1,” says Ravenscroft. Secondary and tertiary crushing Singleton says jaw crushers are typically used in a primary crushing station – to take the run of mine (ROM) and produce a feed to the secondary cone crushers. “Cone crushers are used in secondary and tertiary crushing stages. The reduction per stage is typically between 3:1 and 4:1, depending on the application. A cone crusher can produce any aggregate size fraction you require, provided you stay within the required reduction ratios,” says Singleton. Scherf says while there are primary gyratory crushers (similar in operating principle to a cone crusher), cone crushers re generally used as secondary or tertiary crushers (with some exceptions such as in coal applications). “Cone crushers are also compression crushers and offer a

“Knowing the silica content or abrasion index of the feed material is critical in selecting not only the correct crusher, but also the correct wearing materials to ensure a profitable operation.”

Sandro Scherf, CEO of Pilot Crushtec International

“Knowing the geology of the material assists in specifying the correct crusher for the specific rock application. Further to this, knowing the product size distribution of the ROM allows the crusher to be spec’d correctly. Should there be a high fraction of fines in the feed ROM, pre-screens can be fitted to the jaw, cone and impact crushers.”

Tyron Ravenscroft, Finlay product manager at Bell Equipment

“Cone crushers are used in secondary and tertiary crushing stages. The reduction per stage is typically between 3:1 and 4:1, depending on the application. A cone crusher can produce any aggregate size fraction you require, provided you stay within the required reduction ratios.”

JD Singleton, process director at Weir Minerals Africa

volume of output in a specific timeframe. On the strength of these considerations, it can be decided whether the process must be single-stage or multi-stage, and the screening aspects can be designed aligned with this,” explains Van Rensburg. Tyron Ravenscroft, Finlay product manager at Bell Equipment, says without crushing, very little aggregate would be produced from purely using explosives to blast the natural rock. “Therefore, the crushing stage is a vital necessity to be able to produce high quality aggregates. However, screening the crushed material is just as important to be able to produce the different aggregate sizes, which then become a valuable and sellable product,” says Ravenscroft.

extremely high because the crushing stage influences the overall quality of the final product. He adds that the costs of processing are mainly dependent on the crushing system and the energy demand. Right crusher for the right application It is important to deploy the right crusher for the right application. There are different types of crushers available in the market, ranging from jaw to cone and impact crushers. Scherf says for the long- term profitability of any operation, it’s imperative to have the correct type and size of crusher in a correct application. He reasons that a jaw crusher is universally applicable in primary crushing applications and is used to reduce large material to a more manageable size. “From the hardest of granite or basalt,

Johann Pruewasser, engineer at Keestrack, says the importance is

CAPITAL EQUIPMENT NEWS AUGUST 2018 10