A secondary impact crusher is an industrial machine designed for secondary crushing, reducing pre-crushed materials (50-300 mm) from primary crushers into smaller, homogeneous, and cubic-shaped aggregates (0-50 mm). It is optimized for medium-hard, non-abrasive materials (limestone, concrete, asphalt, sandstone, etc.) and plays a critical role in high-quality aggregate production, construction waste recycling, and mineral processing.

2. Purpose

  • Secondary Crushing: Reduces coarse materials from primary crushers into finer sizes.

  • Cubical Shaping: Enhances the angularity and uniformity of aggregates for higher concrete/asphalt strength.

  • Size Control: Adjustable screens/grates ensure precise output sizing.

  • Recycling: Converts waste concrete, asphalt, and bricks into reusable aggregates.

3. How Does It Work?

A. Key Components

  • Rotor: A high-speed (500-1000 rpm) steel disk with hammers (blow bars) transfers kinetic energy to the material.

  • Impact Plates: Fixed or hydraulically adjustable steel plates fracture the material upon impact.

  • Grinding Chamber: The gap between the rotor and plates allows repeated collisions for size reduction.

  • Adjustable Screen/Grate: Controls the final product size; oversized particles recirculate.

  • Drive System: Electric or diesel motors power the rotor.

B. Operational Stages

  1. Feeding: Pre-crushed material enters the grinding chamber via a feed hopper.

  2. Rotor Impact: Rotor hammers strike the material, propelling it toward the impact plates.

  3. Plate Collision: Material shatters upon hitting the plates, achieving cubical shaping.

  4. Grinding & Screening: Particles undergo repeated crushing; undersized material passes through the screen.

  5. Discharge & Recirculation: Final product is discharged via conveyors; oversized particles return for re-crushing.

4. Advantages

  • High Cubicity: Angular aggregates improve compaction and structural integrity.

  • Energy Efficiency: Lower energy consumption compared to primary crushers (≈30-50 kWh).

  • Adjustability: Hydraulic systems enable real-time adjustments to plate gaps and screen sizes.

  • Durability: Wear-resistant hammers (manganese steel) and plates (chrome alloy) ensure longevity.

5. Applications

  • Quarries: Aggregate production from limestone, granite, and basalt.

  • Recycling Plants: Processing construction waste (concrete, asphalt).

  • Cement Plants: Preparing raw materials for clinker production.

  • Mines: Secondary crushing of ores.