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Jun 22, 2017

Laser scanning for liner management improves safety and profit

Grinding mills are often the largest capital item to be purchased for a minerals processing plant. Consequently, there is a strong industry impetus to maximise grinding mill production as a means to maximise profitability and return on investment. Investigations indicate that comminution consumes more than half of all power generated on mine sites globally and grinding mills typically represent the majority of that energy consumption. Consequently optimising energy use in a grinding circuit is often also what’s best for the bottom line.
Laser scanning for liner management
Figure 1: 3D laser scan data cloud of a SAG Mill lining system (left) and false-colour version to show liner and lifter surfaces (right)

Safety continues to be a major issue in mining and minerals processing. Grinding mills and the mill relining process in particular represent several hazards including the presence of MV power, pinch points, confined spaces, elevated loads and manual handling. Laser scanning condition monitoring allows 100% inspection of exposed liners in a fraction of the time required for conventional inspections and can eliminate the need for confined space entry.

The data acquired through 3D laser scanning can be processed in many ways. Basic outputs might be liner life prediction and lifter profile tracking. However this analysis can become very powerful when it is correlated with metallurgical performance of the mill or circuit in question.

Liner Management for Grinding Mill Performance

Grinding mill liners are the interface where energy is transferred to the grinding media and ore. Therefore an understanding of liner wear characteristics and profiles is crucial to the overall management of Grinding Mill performance, availability, reliability and plant profitability.

During the service life of a liner system, the metallurgical performance of the mill can vary as the liner profile and thickness changes due to wear. Typical behaviour is for throughput to increase over life, with peak performance coming just before a reline. However the opposite is also possible, with lifter wear adversely affecting throughput. Every mill and every plant is different, so while the path to optimisation usually includes maximising liner life and minimising reline, re-torque and other shutdowns, in some cases the optimum regime is to use thinner liners to optimise throughput and accept a shorter reline interval.

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Liner Management in Brazil Leads to Significant Increase in Profit

We have been providing in liner management and other services to an operation in Brazil for several years. Due to a variety of process conditions, the service life of the SAG mill lining system varied during early operation. However a pattern of reduced throughput during longer reline intervals became apparent. Using a combination of liner mapping and trajectory modelling, we identified that the reduction in throughput at the end of the liner life was caused by reduced lifter height and lifter face angle late in the wear cycle. By redesigning liner and lifter profiles and managing reline intervals, we were able to increase annual throughput, with a resulting increase in annual profit of approximately 5 million USD.

Liner management graph 3
Figure 4: Reduced capacity of a SAG Mill due to loss of lifter height and angle

Summary

Grinding mills typically represent a large portion of capital outlay as well as operating cost and are therefore a key driver for concentrator profitability. We are the global leader in mill liner optimisation by 3D Laser scanning, and the advanced analysis and monitoring of mill performance by Outotec MillMapper can provide significant operational and bottom line benefits.

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