For many modern open-pit mines, shovels are one of the most critical components in the production process. These multi-million-dollar machines are the first to handle the material before transporting and processing begins. Because of this, the shovel must be closely monitored to avoid any unnecessary downtime and to ensure it is in peak operating condition. Any unnecessary downtime can cost a mine thousands of dollars per hour in lost production time.
One of the common causes of shovel downtime for many mines is worn or missing shovel teeth or adaptors. Operating with worn teeth reduces the performance of the shovel, resulting in increased energy usage, slower operation and an increased likelihood of missing teeth or adaptors.
Replacing the worn teeth must be carefully planned as an unplanned change-out can result in up to two hours of unexpected downtime. When factoring in the opportunity cost of lost production, a 2009 case study of an American copper mine determined that the total cost of an unplanned change-out is US$41,368 — compared to US$3,000 for a planned change-out.
In hard-rock mining, such as iron or copper ore mining, it is not uncommon for the shovel teeth to go missing in normal operation. During the digging cycle, the extreme forces can cause the teeth to break off completely and become mixed with the loaded material. Big problems occur when a load with a shovel tooth accidentally makes its way to the crusher. Because the shovel teeth are made of a very durable metal, when a tooth enters the crusher, it jams the crusher and can disable it for hours or even days at a time. If the mine has no other primary crushers or has little or no stockpile of crushed ore to feed the next stages of production at the time, the mine production could be put to a complete halt, which can result in millions of dollars in lost production time for every occurrence.
To address issues with worn or missing shovel teeth or adaptors, a Canadian company, Motion Metrics International Corp., has developed two innovative tooth monitoring solutions: ToothMetrics and WearMetrics. The ToothMetrics system constantly monitors the shovel teeth with advanced image processing techniques and artificial intelligence algorithms, and alerts the shovel operator when a shovel tooth or adaptor is missing. Once detected, the tooth or adaptor can be located and prevented from reaching the crusher. The WearMetrics system automatically monitors the shovel tooth-wear and provides the status of each shovel tooth by displaying the remaining length of the tooth expressed as a percentage of the original length. This assists the mine engineers in planning teeth replacements, and helps avoid any unplanned change-outs. Both solutions share the same rugged embedded CPU platform and hardware components, reducing the total cost of ownership for any mine.
The system works by installing a rugged camera mounted on the boom of an electric rope shovel or on the stick of a hydraulic face shovel. The high-sensitivity, monochrome camera provides a clear view of the shovel teeth directly to the embedded CPU, which is installed in the shovel operator’s cab. Due to intense shock and vibration experienced by the shovel during operation, Motion Metrics has designed shock-absorbing camera brackets specifically for each different type of shovel, including P&H and Bucyrus/CAT electric rope shovels, as well as Komatsu, Liebherr, Terex/CAT, Hitachi and other makes of hydraulic shovels.
The open-pit mining environment is also subject to a number of environmental conditions such as dirt, dust and varying lighting conditions, a key challenge for any mining system to deliver consistent results. To counter lighting variations, a heavy-duty, high-intensity LED light is installed alongside the camera to illuminate the shovel teeth during night operations. Advanced artificial intelligence algorithms continuously monitor the incoming video to exclude images when the view of the teeth is blocked by dirt, dust or shadows and select only optimal images for tooth analysis.
Building on this successful shovel-monitoring platform, Motion Metrics has added the optional safety and collision avoidance components: ViewMetrics and RadarMetrics. Due to the sheer size and vast blind spots of mining shovels, the frequent and swift swinging action of the shovel is a common concern for open-pit shovel operations as there is always a risk of collision with other equipment or personnel working in close proximity.
The ViewMetrics addition provides the shovel operator with three additional wide-angle surveillance views around the shovel blind spots in the left, right, and rear of the shovel for greater visibility. RadarMetrics enhances the operator’s awareness even more by providing intelligent proximity sensing and active feedback to the operator. This addition seamlessly combines a strategically placed array of heavy-duty pulsed radar sensors with the three surveillance views from ViewMetrics to provide visual and audible alerts to the operator when an object enters the shovel’s swing radius. Optional warning lights can also be installed around the shovel to extend the warning to any nearby equipment or personnel, providing an extra level of safety. This unique patent-pending approach, according to Motion Metrics, is the “only collision avoidance system for mining shovels [that] takes into account the swing radius of the shovel when alerting the shovel operator.” This additional level of intelligence helps eliminate unnecessary alarms that would otherwise be distracting to the operator.
As real estate in the operator’s cab is limited, the company has managed to integrate all five of the shovel monitoring solutions mentioned above into a single embedded CPU platform and a 12-inch touchscreen display installed in the cab.
The operator-oriented interface displays the shovel bucket camera view from the ToothMetrics and WearMetrics systems, along with the three surveillance views from the ViewMetrics systems. As an object enters the shovel’s swing radius, RadarMetrics displays a graphical bird’s-eye view of the shovel to indicate the direction and proximity of the object, and also makes an audible alarm to grab the shovel operator’s attention.
Motion Metrics is also a provider of payload monitoring systems for large hydraulic mining shovels, such as the Terex/CAT RH340/400 and the Komatsu PC8000. Many mines only have weighing systems on their haul trucks, but this makes it difficult for the shovel operator to know when a truck is being overloaded, since the weight will not be known before the load is in the truck. Furthermore, many truck scales require the truck to be in motion before the weighing system is able to provide an accurate measurement. To prevent voiding the manufacturer’s warranty, overloaded trucks must dump their load immediately, resulting in a significant loss of productivity, as the same load will need to be reworked and loaded a second time. On the other hand, underloaded trucks requires the truck to make more trips, thereby increasing the mine’s haulage cost per ton.
One of the key features of the LoadMetrics system is to provide the bucket-by-bucket payload information directly to the shovel operator, allowing the operator to determine whether dumping the current load will overload or underload the haul truck. The system also provides helpful warnings to the operator when the shovel is reaching its cylinder extension or retraction limits. Repeated over-extending or retracting of the shovel’s hydraulic cylinders can cause the cylinders to burst, thus requiring premature replacements.
As a crucial element in open-pit mining operations, shovels should be closely monitored to maximize productivity and minimize downtime. The cost of any unnecessary downtime can easily cost the mine thousands or millions of dollars in lost production time. To address many of these challenges, Motion Metrics has developed a unique collection of shovel monitoring solutions. Their proven systems have been installed in various combinations in over 150 mining shovels and in over 30 mines around the world since 2003.
Enoch Chow is the marketing manager with Motion Metrics International Corp. For more information, visit www.motionmetrics.com.