Figure 4 – Severe peening on shell liner lifter, pegging on FE liners and cracks on DE intermediate liners 2.2 Historical Liner Failure Modes Historically, Clarabelle SAG mill has been experiencing several failure modes including intermediate discharge-end liner cracking, frequent failure of the discharge deflector cone bolts and undesirable shell liner packing—cemented rock-charge adhered within the space between the shell lifters (Royston, 2012). As well, severe peening—an impact induced deformation and work-hardening—on liners caused by frequent hammering from grinding media and ore are conditions that increase liner wear and may lead to breakage (Powel, 2006). Lastly, chronic presence of pegging—oversized particles and balls getting stuck between lifter bars, posed a safety risk for SAG entry during maintenance. Original Hi-Hi Shell Liner Failure Modes Figure 5 shows the original 60-3 row Hi-Hi liner with 7° face angle design and trajectory simulation at 10.8 max rpm (with no packing) with harmful media to liner impacts above charge toe. Also, this liner was designed to start-up and operate at max speed (10.8 rpm). This liner set was prone to significant packing which also depends on several factors such as ore types, slurry characteristics, liner design and wear profiles (Royston, 2012). Though packing benefits are to protect the liner plate from wear, it also affects the ore breakage mechanism and changes the trajectory of the grinding media and therefore reduces grinding efficiency. For liner inspections, to ensure safe SAG entry, extensive liner washing was commonly required to remove the packing which increased entry timeline. Figure 5 – Hi-Hi with 7° face angle, Bradken’s MILLSIM charge trajectory simulation at 10.8rpm, 30% mill charge and severe packing on shell liners.
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