3952 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Automatic Mill Speed Adjustment for Liner Wear
Compensation
The following case describes a 32-foot SAG mill where the
impact angle (IA) is controlled and maintained around
135° for the entire liner wear cycle. The target IA value is
controlled by adjusting mill motor speed until a point is
reached where IA can no longer be held at the optimal value
due to the limitation of reaching maximum motor speed.
When motor speed hits the maximum limit, the control-
ler can no longer maintain the desired IA target. Instead,
IA begins increasing to 150° at the end of the liner cycle
campaign. This can be seen in Figure 7, where the blue sig-
nal is Motor RPM and in red the IA. During the first 17
weeks of operation, the speed is slowly increased to flatten
out or maintain an IA value of ~135°. In week 18, the mill
begins to reach the upper limit of motor RPMs. By week
20, significant wear on the liners has occurred, and with the
limitation of reaching maximum motor speed, the control-
ler no longer can maintain the optimal Impact Angle, and
Figure 5. New (green)/Worn (red) Liner Impact Angle (IA) Measurements versus Speed—36 ft. SAG Mill
Figure 6. Liner Wear/Impact Angle for Feed, Middle and Discharge Regions of a 30ft AG Mill
Automatic Mill Speed Adjustment for Liner Wear
Compensation
The following case describes a 32-foot SAG mill where the
impact angle (IA) is controlled and maintained around
135° for the entire liner wear cycle. The target IA value is
controlled by adjusting mill motor speed until a point is
reached where IA can no longer be held at the optimal value
due to the limitation of reaching maximum motor speed.
When motor speed hits the maximum limit, the control-
ler can no longer maintain the desired IA target. Instead,
IA begins increasing to 150° at the end of the liner cycle
campaign. This can be seen in Figure 7, where the blue sig-
nal is Motor RPM and in red the IA. During the first 17
weeks of operation, the speed is slowly increased to flatten
out or maintain an IA value of ~135°. In week 18, the mill
begins to reach the upper limit of motor RPMs. By week
20, significant wear on the liners has occurred, and with the
limitation of reaching maximum motor speed, the control-
ler no longer can maintain the optimal Impact Angle, and
Figure 5. New (green)/Worn (red) Liner Impact Angle (IA) Measurements versus Speed—36 ft. SAG Mill
Figure 6. Liner Wear/Impact Angle for Feed, Middle and Discharge Regions of a 30ft AG Mill