ANS:A - rod mills

Size reduction does not occur due to compression in smooth roll crushers. Here's why:

1. Compression Crushing:
   • Compression crushing involves squeezing the material between two surfaces, where the forces applied compress the material to break it into smaller pieces.
   • This method is characteristic of machines like jaw crushers, gyratory crushers, and some types of cone crushers, where the material is crushed by applying compressive forces.
2. Smooth Roll Crushers:
   • Smooth roll crushers primarily use impact and shear forces to break down the material.
   • Material is fed between the rotating rolls, which crushes the material primarily by impact and shearing action rather than by compressive forces.
   • The rolls rotate at different speeds, creating a pulling action on the material, which causes it to be drawn down into the crushing zone where it is crushed by the rolls.

Therefore, while compression is a significant mechanism in machines like jaw crushers, gyratory crushers, and rod mills, it is not the primary mechanism in smooth roll crushers. Smooth roll crushers rely more on impact and shear forces for size reduction.