9
consistent in collecting the data. Powell et al, [17]
recommends selecting three rows of liners and taking
5 to 6 profiles along each row is sufficient to track
liner wear. Scheduling routine liner inspections dur-
ing mill maintenance downtime is good practice to
ensure sufficient measurements are taken.
Grinding Media
Challenge—Poor Quality or Incorrect Composition
Poor-quality grinding media can be a significant source
of SAG mill instability. A high degree of fracturing, spall-
ing, and chipping due to high internal stresses, leads to the
media being discharged from the mill, making controlling
the media addition difficult. Continuous operation at low
milling filling levels and high mill speeds can also increase
wear rates and fracturing of media.
Incorrect grinding media composition and hardness
profiles can lead to media deformation. Deformed media
can either pass through the grates prematurely, leading to
poor grinding efficiency, or can get lodged into the dis-
charge grate slot reducing the grate capacity and nega-
tively impacting throughput. An example of a deformed
SAG mill ball and the resulting blinded grates are shown in
Figure 14 and Figure 15.
• Accounting for liner wear
“As with most processes, optimization does not come
without measurement” [17]. To develop ramp up
profiles and previously discussed mill load mod-
els, the liner wear must be measured and tracked
in detail. The use of 3D scanners and ultrasonic
thickness gauge can provide a high level of detail
on wear rates and patterns. A pin gauge is a simple
tool that allows for quick measurements of the liner
profile, shown in Figure 13. Irrespective of the tool
used to obtain the measurements, it is critical to be
Figure 12. Example of a bi-(top) and unidirectional (bottom) shell lifter design [11]
Figure 13. Pin gauge for measuring liner profiles [17]
consistent in collecting the data. Powell et al, [17]
recommends selecting three rows of liners and taking
5 to 6 profiles along each row is sufficient to track
liner wear. Scheduling routine liner inspections dur-
ing mill maintenance downtime is good practice to
ensure sufficient measurements are taken.
Grinding Media
Challenge—Poor Quality or Incorrect Composition
Poor-quality grinding media can be a significant source
of SAG mill instability. A high degree of fracturing, spall-
ing, and chipping due to high internal stresses, leads to the
media being discharged from the mill, making controlling
the media addition difficult. Continuous operation at low
milling filling levels and high mill speeds can also increase
wear rates and fracturing of media.
Incorrect grinding media composition and hardness
profiles can lead to media deformation. Deformed media
can either pass through the grates prematurely, leading to
poor grinding efficiency, or can get lodged into the dis-
charge grate slot reducing the grate capacity and nega-
tively impacting throughput. An example of a deformed
SAG mill ball and the resulting blinded grates are shown in
Figure 14 and Figure 15.
• Accounting for liner wear
“As with most processes, optimization does not come
without measurement” [17]. To develop ramp up
profiles and previously discussed mill load mod-
els, the liner wear must be measured and tracked
in detail. The use of 3D scanners and ultrasonic
thickness gauge can provide a high level of detail
on wear rates and patterns. A pin gauge is a simple
tool that allows for quick measurements of the liner
profile, shown in Figure 13. Irrespective of the tool
used to obtain the measurements, it is critical to be
Figure 12. Example of a bi-(top) and unidirectional (bottom) shell lifter design [11]
Figure 13. Pin gauge for measuring liner profiles [17]