Quantifying SAG Mill Liner Survivability and Wear Life

2022

Amit, Saxena; Youqing, Yang

SAG mills are designed to run with up to 95% mill availability. This can only be achieved if unscheduled downtime due to any mill liner/bolting failures is eliminated and the time span between liner replacements (scheduled maintenance and downtime) is maximized. There are two essential mechanisms that may affect mill liner survivability and life: fatigue crack propagation in mill liners/bolts and wear resistance of steel alloys. In high cycle fatigue analysis, either stress life curve S-N or strain-life curve E-N of alloys are commonly used to predict cycles to failure. These curves are produced with constant alternative stress or strain cycles. Whereas in a SAG Mill, millions of particles (i.e., rocks and grinding media) are impacting the liners with varying magnitude and intensity. The authors are proposing the concept of damage rate index to measure the life span of a mill liner inside a SAG mill by combining it with the DEM simulations which calculates the frequency and impact forces on the liners. In a set of simulations, the analysis shows the damage risk is the highest at the beginning few months of campaign with speed ramp up. As the liners get worn off, the magnitude and frequency of impact substantially reduces. In another set of simulations, the effect of charge level (both Jb and Jc) is analyzed. In another set of simulations, DEM analysis is used to predict wear life of new designs of shell liners by benchmarking the wear tracking report data on existing shell liners with good accuracy.

Keywords: CIMBC22