We often stress the importance of optimizing blast parameters to reduce the cost of comminution and cut back on energy use, but effective blasting can also reduce the likelihood of crusher obstructions. Most unplanned plant downtime is crusher related and primarily due to blockages caused by oversized feed. These events can cause mines to incur significant financial losses due to unplanned downtime, a decrease in throughput, or an increase in energy use.
When boulders are larger than the opening of the primary jaw crusher, they can build up in and eventually block or obstruct the crusher. In this case, production must be temporarily stopped to break down or remove the boulder. But even boulders that are small enough to be processed by the primary jaw crusher can cause problems – breaking down large rocks requires a great deal of energy and can result in power spikes, slower production rates, and wear and tear of the crusher liner.
Traditional approaches to mitigation
Mines have traditionally taken a reactive approach to mitigating the problems associated with oversized material. A boulder obstruction is typically identified by monitoring trends in crusher throughput – a falling trend indicates that material is not able to pass through the crusher. At this point, the blockage or obstruction has already occurred. Mine personnel must halt production to dig out the boulders or use rock breakers to clear the obstruction, creating a bottleneck and further decreasing production.
Boulders that cannot pass through the grizzly must be broken down by rock breaking equipment.
A common misconception is that a grizzly can eliminate the problem of oversized material. It is true that, with a grizzly in place, boulders are less likely to enter the primary crusher. However, a grizzly is still susceptible to blockages – mine personnel need to remove oversized material or schedule rock breaking.
A proactive alternative
The best way to manage oversized material is to avoid the situation entirely but, failing that, mines should aim to mitigate problems caused by boulders as early in the process as possible. We developed TruckMetrics™ to prevent oversized material from reaching your processing plant in the first place.
Mounted on a gantry above the mine road, TruckMetrics scans each passing haul truck to detect boulders and analyze particle size in real time – without interrupting production. Using artificial intelligence and stereo imaging, the system scans the truck bed, segments each visible rock, and identifies any oversized material. If a boulder is detected, the system automatically alerts dispatch so that trucks can be diverted.
Haul trucks do not need to slow down when passing under the TruckMetrics system.
TruckMetrics therefore provides a two-pronged approach to mitigating problems caused by oversized material. Firstly, it helps dispatch keep boulders out of the crusher by identifying trucks that contain oversized material and diverting them before they reach the plant. Secondly, the particle size data TruckMetrics captures can be used to optimize blasting parameters so that fewer boulders are produced in the first place.
A comprehensive strategy for reducing risk
Boulders are not the only object worth keeping out of your processing plant – disengaged shovel and loader teeth can also travel downstream and obstruct crushers. We developed ShovelMetrics™ and LoaderMetrics™ to alert equipment operators to missing or broken teeth before they are transported downstream in the excavated ore. These computer vision solutions use artificial intelligence and a rugged camera to continually monitor the shovel or loader bucket for missing teeth.
Removing a shovel or loader tooth from an obstructed crusher is highly dangerous due to the tremendous amount of stored kinetic energy. While there are no comprehensive Canadian statistics, American researchers at the National Institute for Occupational Safety and Health found that incidents involving crushers are the second most common cause of fatalities caused by stationary machinery at mines in the United States. To learn more about this process, read this article about the danger and unpredictability of crusher obstructions caused by missing teeth.
Support at each stage of comminution
Although TruckMetrics, ShovelMetrics, and LoaderMetrics require minimal training for operators to use confidently, mine management may appreciate an additional set of eyes on their equipment. With a service and support agreement in place, Motion Metrics can remotely monitor each installed system to verify that they are functioning as expected and alert mine personnel to any issues. To learn more about our service and support agreements, please contact us.