A Guide to Secondary Crusher Types and Sizes

Secondary crushing is a critical stage in the aggregate production and mineral processing circuit. Its primary function is to take the coarse material from the primary crusher and further reduce it in size, shaping it into a more uniform, cubical product suitable for final use or further processing. Selecting the correct type and size of secondary crusher is paramount for achieving optimal efficiency, product quality, and overall operational cost-effectiveness. This article provides a detailed overview of the common types of secondary crushers and the key factors that determine their appropriate sizing.

Common Types of Secondary Crushers

Several crusher designs are well-suited for secondary crushing applications, each with unique operating principles and ideal use cases. The most prevalent types are cone crushers, impact crushers, and roll crushers.

Cone crushers are among the most widely used secondary crushers. They operate by compressing rock between a gyrating spindle and a stationary concave liner. This compression action makes them exceptionally efficient for processing hard and abrasive materials like granite, basalt, and iron ore. Modern cone crushers often feature hydraulic systems for adjusting the closed-side setting (CSS), which controls the product size, and for clearing the chamber in case of a blockage.

Impact crushers, available in horizontal shaft (HSI) and vertical shaft (VSI) configurations, utilize a different principle. They fracture rock through high-speed impact rather than compression. HSI crushers are excellent for processing softer, less abrasive materials such as limestone and recycled concrete, producing a well-shaped product. VSI crushers are specialized for producing highly cubical aggregates and manufactured sand by accelerating rock against a stationary anvil or within a rock-lined rotor.

Roll crushers provide a solution through compression as well, but with two counter-rotating cylinders. The material is drawn between the rolls and crushed. They are particularly effective for crushing medium-hard to hard materials with a low silica content and are known for producing a minimal amount of fines. The choice between these types depends heavily on the material’s characteristics, the required product shape, and the desired production capacity.

Key Factors Influencing Crusher Sizing

Selecting the correct size of a secondary crusher is not about simply picking the largest available model. It involves a careful analysis of several interconnected operational parameters to ensure the machine matches the plant’s needs.

The most fundamental factor is the required production capacity, typically measured in tons per hour. The crusher must be sized to handle the peak output from the primary crushing stage without becoming a bottleneck. Closely related to this is the feed size; the crusher’s inlet dimensions must be large enough to accept the largest rocks expected from the primary circuit.

The desired final product size is another critical driver. A machine capable of achieving a finer end product often requires more power and may have a lower throughput than one set for a coarser output. Furthermore, material characteristics play a huge role in sizing decisions. Harder, more abrasive rocks demand robustly built crushers with more power to achieve the same tonnage as softer materials.

Finally, site-specific conditions must be considered. This includes available space for installation, electrical power constraints that may limit motor size, and transportation logistics that could dictate maximum equipment dimensions.

Matching Crusher Type to Material Characteristics

The success of a secondary crushing stage hinges on aligning the crusher’s operating principle with the physical properties of the feed material.

For hard and highly abrasive rocks like granite or quartzite, cone crushers are typically unrivaled due to their robust construction and efficient compression-breaking action which minimizes wear part consumption compared to other methods.

Conversely, when processing softer, non-abrasive materials like limestone or asphalt debris from demolition sites impact crushers often present significant advantages including excellent reduction ratios allowing single-stage secondary crushing where applicable superior particle shape control resulting in cubical products desirable for concrete mixes asphalt mixes etc also they generally offer higher throughput capacities compared similarly sized cone models handling soft materials

For friable or sticky materials containing clay or moisture roll crushers can be an effective choice their low-headroom design continuous compression action helps squeeze material through while minimizing clogging issues common other designs however they generally offer lower capacities require more frequent maintenance rolls

Operational Considerations Beyond Initial Selection

Once an appropriate type model has been selected ongoing operational considerations become crucial maintaining performance profitability these include regular maintenance schedules wear part replacement strategies overall energy consumption monitoring

Wear parts liners mantles blow bars rolls represent significant recurring cost operation monitoring replacing timely manner essential preventing damage core components maintaining consistent product quality modern designs often feature hydraulic adjustment tramp release systems protect machine uncrushable objects facilitate quick settings changes optimize output furthermore energy efficiency increasingly important factor different models vary their power draw per ton processed making crucial evaluate long-term operating costs alongside initial investment many factors influence final investment including specific configuration chosen required production targets local market conditions