Eriez claims its trunnion magnet separators effectively remove up to 98% of grinding-media steel balls and ferrous chips from milled ore in SAG or ball mill operations. By eliminating these potentially destructive pieces, damage to downstream equipment is significantly reduced.

Positioned at the downstream end of the mill, the trunnion magnet consists of an arc of permanent magnets surrounding almost half of a blind trunnion extension. As the trunnion rotates, the magnetic circuit attracts and holds the steel balls to the inner surface of the trunnion. The steel balls are carried to the top of the trunnion where the magnetic arc terminates, thereby releasing the balls, which fall into a hopper and chute. Given mill capacity, ball size and other parameters, Eriez will select and specify the appropriate construction features for its trunnion magnet installations.