Modern Quarrying Q1 2019

CRUSHING

The VSI is a critical part in obtaining high specification road stone, or as a pre-milling crusher to increase mill throughput in mining applications.

A jaw crusher is universally applicable in primary crushing applications and is used to reduce large material to a more manageable size.

Trio jaw crushers for use in primary crushing.

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 sec- ondary 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 reduc- primary gyratory crushers (similar in operating principal to a cone crusher), cone crushers are generally used as secondary or tertiary crushers (with some exceptions such as in coal applications). “Cone crushers are also compression crushers and offer a greater ability to adjust your final product size and shape than a jaw crusher and operate at a lower cost per tonne than an impact crusher in tion ratios,” says Singleton. Scherf says while there are

Right crusher for the right application

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

It is important to deploy the right crusher for the right application. There are different types of crushers available in the market, ranging from jaws to cone and impact crushers. Scherf says for the long-term profit- ability of any operation, it’s impera- tive 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, 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

18

MODERN QUARRYING QUARTER 1 - 2019