Tramp Steel of HPGR

Theoretically, the HPGR is equipped to handle tramp steel in that the bearing arrange- ment allows skewing of the floating roll and the hydraulic system is able to relieve exces- sive pressures. However, particularly with larger units, the inertia of the rolls and their very brief exposure to tramp metal in the compression zone generally results in damage to the roll surface instead of, or as well as, the relieving action of the floating roll.

Repair of roll damage can be expensive and operationally disruptive, and flowsheet design should endeavour to locate the HPGR in an intrinsically noncontaminated flow stream, or ensure that a comprehensive and practical tramp metal detection and removal system is included. Such a system should preferably be automatic, with contaminated ore bypassed around the HPGR or rejected from the circuit. It is important to minimise the need for operator intervention and process interruption.