Roll crusher circuit design. Roll crushers are generally not used as primary crushers for hard ores. Even for softer ores, such as chalcocite and chalcopyrite, they have been used as secondary crushers. Choke feeding is not advisable as it tends to produce particles of irregular size.
Gyratory Circuit Design. Large units are rarely installed underground. Charge is fed by trucks, tipwagons, side dump cars, and conveyor belts. Feed enters from a hopper and passes through a grizzly screen to remove oversize; Gyratory crushers are operated in open circuit. The feed is limited to 1 to meters in size.