3954 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
LDL event, the Trunnion Vibration Difference migrates
(blue arrow) to a high limit (20). This indicates the imbal-
ance between the feed and the mill’s discharge due to
the pegging event confirmed by inspections, as shown in
Figure 9 with vertical dotted lines. The pegging affected the
throughput severely, mainly when the second inspection
(major pegging event, 75%) was observed.
High and Low Ball Charge (Jb/Jc) Ratios
One of the most essential variables for optimizing the per-
formance of a grinding mill is the relationship between
the ball filling level (Jb) and the total charge (Jc), which
includes both the grinding media and slurry. Maintaining
a good Jb/Jc ratio is important for the following reasons: 1)
Reducing damage, wear and tear on the mechanical parts of
both the mill and grinding media. 2) Controlling and con-
serving energy consumption. 3) Optimizing mill through-
put. 4) Maximizing grinding efficiency.
Figure 10 shows the Jb/Jc ratio from a 22-foot SAG mill
where the baseline grinding media charge is approximately
12–13%. Under regular process operating conditions, the
Jb/Jc ratio is usually ~0.75 (high impact condition) as
shown initially in Figure 10. In the middle of the figure,
the Jb/Jc ratio increases to over 0.85 (very high impact
condition). During this period, the plant increased the Jb
(grinding media level) to approximately 15%, and the ore
volume (feed) was slightly decreased to compensate for the
increased power draw to stay within mill motor limitations.
In this case, the ore portion of the total charge was too
low for the existing ball charge. On the right-hand side of
the figure, we then observe the opposite case where the ball
(Jb) drops to ~10%. The ore volume was then increased
to maintain regular motor power draw operation. In this
case, the ore portion of the total charge was too high for the
existing ball charge. The Jb/Jc ratio dropped to ~0.5 (very
low impact condition).
Figure 9. High liner damage levels and pegging detection using trunnion sensor vibration differences
Figure 10. Detection of High and Low Grinding Media Operation through Jb/Jc Measurements
LDL event, the Trunnion Vibration Difference migrates
(blue arrow) to a high limit (20). This indicates the imbal-
ance between the feed and the mill’s discharge due to
the pegging event confirmed by inspections, as shown in
Figure 9 with vertical dotted lines. The pegging affected the
throughput severely, mainly when the second inspection
(major pegging event, 75%) was observed.
High and Low Ball Charge (Jb/Jc) Ratios
One of the most essential variables for optimizing the per-
formance of a grinding mill is the relationship between
the ball filling level (Jb) and the total charge (Jc), which
includes both the grinding media and slurry. Maintaining
a good Jb/Jc ratio is important for the following reasons: 1)
Reducing damage, wear and tear on the mechanical parts of
both the mill and grinding media. 2) Controlling and con-
serving energy consumption. 3) Optimizing mill through-
put. 4) Maximizing grinding efficiency.
Figure 10 shows the Jb/Jc ratio from a 22-foot SAG mill
where the baseline grinding media charge is approximately
12–13%. Under regular process operating conditions, the
Jb/Jc ratio is usually ~0.75 (high impact condition) as
shown initially in Figure 10. In the middle of the figure,
the Jb/Jc ratio increases to over 0.85 (very high impact
condition). During this period, the plant increased the Jb
(grinding media level) to approximately 15%, and the ore
volume (feed) was slightly decreased to compensate for the
increased power draw to stay within mill motor limitations.
In this case, the ore portion of the total charge was too
low for the existing ball charge. On the right-hand side of
the figure, we then observe the opposite case where the ball
(Jb) drops to ~10%. The ore volume was then increased
to maintain regular motor power draw operation. In this
case, the ore portion of the total charge was too high for the
existing ball charge. The Jb/Jc ratio dropped to ~0.5 (very
low impact condition).
Figure 9. High liner damage levels and pegging detection using trunnion sensor vibration differences
Figure 10. Detection of High and Low Grinding Media Operation through Jb/Jc Measurements