Introduction
Crushers are essential pieces of equipment in almost any material processing application, responsible for reducing large rocks and ores into smaller, manageable sizes, often for conveying and/or further processing. Whether the goal is to produce aggregates, liberate valuable minerals, or prepare material for further crushing or grinding, selecting the right crusher is critical to achieving operational efficiency, minimizing wear and optimizing throughput. With a wide range of crusher types available, each suited to specific material properties and crushing stages, informed selection is key to long-term success.
What Are Crushers Used For?
Crushers are used to break down raw materials, such as ore, rock, mineral deposits and aggregates, into smaller particles suitable for downstream processing. This includes:
- Preparing feed for secondary and tertiary crushing
- Producing aggregate for construction
- Facilitating mineral liberation in metallurgical processes
- Reducing waste material for easier handling or disposal
The crushing process can be mechanical (compression, impact, shear) and is typically conducted in multiple stages to achieve the desired particle size and shape.
Types of Crushers and Their Applications
1. Jaw Crushers
Jaw crushers use compressive force between a fixed and moving jaw plate to crush hard, abrasive material. They are ideal for primary crushing of large feed sizes and are commonly used in mining operations involving granite, basalt and gold ore. Jaw crushers are typically used for hard and abrasive materials with minimal clay in the feed.
2. Gyratory Crushers
Gyratory crushers operate with a rotating spindle inside a concave shell. They offer high capacity and are suited for continuous primary crushing in large-scale operations, especially with hard and abrasive materials.
3. Cone Crushers
Cone crushers compress material between a rotating mantle and a stationary bowl. Commonly used in secondary and tertiary stages, they are effective for medium to hard materials and provide excellent control over particle shape and size.
4. Impact Crushers
Impact crushers use high-speed impact forces to fracture material. Best suited for softer, less abrasive rocks like limestone and coal, they produce a cubical product and are often used in recycling and aggregate production.
5. Hammer Crushers
Hammer crushers break material by striking it with rotating hammers. They are simple and cost-effective for soft, brittle material such as clay, shale and limestone, but are not recommended for hard rock.
6. Roll Crushers
Roll crushers apply compressive and shear forces between two rotating rolls. They are used for fine crushing of softer materials and are common in coal production and clay processing.
7. VSI Crushers (Vertical Shaft Impactors)
VSI crushers use rock-on-rock or rock-on-metal impact to produce fine, well-shaped particles. They are ideal for final stage crushing in the production of manufactured sand and high-quality aggregates.
8. Sizers
Sizers use rotating shafts with teeth or blades to crush soft to medium-hard materials. They are effective for wet, sticky or friable ores and are often used in coal, nickel, bauxite and potash operations.
9. Rotary Breakers
Rotary breakers are cylindrical drums that tumble and break material using gravity and impact. Commonly used in coal processing, they separate rock from coal and reduce oversize material.
10. Feeder-Breakers
Feeder-breakers combine feeding and crushing in one unit. They are used in both surface and underground mining to reduce run-of-mine material to a manageable size while regulating flow to the conveyor system.
Stages of Crushing
Crushing is typically carried out in multiple stages to progressively reduce the size of mined material and prepare it for downstream processing. Each stage serves a distinct purpose and requires specific types of crushers suited to the material characteristics and desired output.
Primary
Primary Crushing is the first step in the process, where large run-of-mine (ROM) material is reduced to a size suitable for transport or further processing. This stage is focused on handling high volumes of coarse, unprocessed rock and ore. Crushers used in this phase must be robust and capable of accepting large feed sizes, often exceeding one meter in diameter.
Common equipment:
- Jaw Crushers
- Gyratory Crushers
- Primary Sizers
- Feeder-Breakers (in underground or soft rock applications)
Key considerations:
- High throughput capacity
- Ability to handle hard and abrasive materials
- Reliability and ease of maintenance
- Ability to handle wet and sticky material
Secondary
Secondary crushing follows primary crushing and further reduces the material size to facilitate mineral liberation or prepare feed for grinding mills. This stage focuses on refining particle size and improving product uniformity. Crushers used here are generally more precise and offer better control over output specifications.
Common equipment:
- Cone Crushers
- Impact Crushers
- Roll Crushers
- Sizers (for soft or stick materials)
Key considerations:
- Consistent particle size distribution
- Material hardness and abrasiveness
- Desired shape and quality of the product
- Material moisture content
Tertiary and Quaternary Crushing
In some operations, particularly in aggregate production or mineral beneficiation, additional crushing stages are employed to achieve finer particle sizes or specific product shapes. These stages are not always necessary but can be critical for high-spec applications such as manufactured sand or mineral liberation in complex ores.
Common equipment:
- VSI Crushers (for shaping and fine crushing)
- Cone Crushers (in closed-circuit configurations)
- High-pressure grinding rolls (HPGRs) in some mineral applications
Key considerations:
- Particle shape and surface texture
- Minimizing fines generation
- Energy efficiency and wear management
Matching Crusher Type to Material Characteristics
Selecting the appropriate crusher requires a thorough understanding of the physical properties of the material being processed. Key factors include hardness, abrasiveness, moisture content, friability and the desired particle size and shape. For example, hard and abrasive materials such as granite, basalt or iron ore are best handled by jaw crushers, gyratory crushers or cone crushers, which are designed to withstand high compressive forces and minimize wear. Medium-hard materials like copper ore or quartz may also be suitable for cone crushers or impact crushers depending on the required output specifications.
Softer and more brittle materials, such as limestone, clay or shale, are more efficiently processed using sizers, impact crushers, hammer crushers or roll crushers, which offer high reduction ratios and produce a more cubical product. For wet, sticky or friable materials, such as coal, potash or phosphate, specialized equipment like sizers are often preferred as these machines are designed to prevent clogging and maintain consistent throughput.
In applications where fine shaping or precise particle control is essential, such as in the production of manufactured sand or concrete aggregates, VSI (vertical shaft impactor) crushers are commonly used. These machines produce well-graded, cubical particles through rock-on-rock or rock-on-metal impact mechanisms.
Ultimately, matching crusher type to material characteristics ensures optimal performance, reduces wear and maintenance costs and supports consistent product quality across the crushing circuit.