3854 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
From the speed histograms, the Ball Mills and SAG
Mills are typically operated at a higher speed than the
original design speed. The variable speed drives provide the
flexibility to operate at a higher speed without the require-
ment to change the pinions on any mill. The change in the
speeds, allows for more efficient grinding, and allows for
optimizations in the grinding circuit, and can be used to
compensate for variations in the ore that is fed to the mills.
Additionally, the Ball Mills can be seen to operate at very
low speeds, where there is no grinding at all. This situation
can arise when there is no ore feed to the Ball Mills. This
negates the need to grind out and stop the Ball mill and
allows the Ball Mills to continue operating until the feed
is restored, following which the speed can be ramped up
quickly minimizing the length of any potential downtime.
MAINTENANCE AND OPERATION
OPTIMIZATION
Maintenance Schedule and Procedures
Following the ABB recommended maintenance schedule
has proven crucial to maximizing the drive system reli-
ability and utilization. The maintenance schedule takes
a very pro-active approach to maintenance activities and
includes primarily predictive and preventative maintenance
practices.
(a)
(b)
Figure 9. Current drawn from the network by Ball Mill 2 during a transient event
Figure 10. Mill speeds during a network transient event
From the speed histograms, the Ball Mills and SAG
Mills are typically operated at a higher speed than the
original design speed. The variable speed drives provide the
flexibility to operate at a higher speed without the require-
ment to change the pinions on any mill. The change in the
speeds, allows for more efficient grinding, and allows for
optimizations in the grinding circuit, and can be used to
compensate for variations in the ore that is fed to the mills.
Additionally, the Ball Mills can be seen to operate at very
low speeds, where there is no grinding at all. This situation
can arise when there is no ore feed to the Ball Mills. This
negates the need to grind out and stop the Ball mill and
allows the Ball Mills to continue operating until the feed
is restored, following which the speed can be ramped up
quickly minimizing the length of any potential downtime.
MAINTENANCE AND OPERATION
OPTIMIZATION
Maintenance Schedule and Procedures
Following the ABB recommended maintenance schedule
has proven crucial to maximizing the drive system reli-
ability and utilization. The maintenance schedule takes
a very pro-active approach to maintenance activities and
includes primarily predictive and preventative maintenance
practices.
(a)
(b)
Figure 9. Current drawn from the network by Ball Mill 2 during a transient event
Figure 10. Mill speeds during a network transient event