Operating and maintaining critical mining machinery can be extremely difficult. The challenge comes not only from the size of the equipment, but from the inaccessibility of its components. Nevertheless, it is critical to maintain and strive for superior performance if one is to be profitable in this highly-competitive market.
Cargill Crop Nutrition was eager to improve the reliability of its draglines in a phosphate mine in South Fort Meade, Fla., so it turned to Timken to benefit from its expertise in the operation of rotating mining equipment.
“Cargill continues to be proactive in troubleshooting their mining equipment,” said Trip Kern, global market manager for mining at The Timken Company. “They continually look for ways to improve their operations and anticipate problems before they occur. Having worked with Cargill for many years, we are happy to provide them with the solutions they need to take them to the next level of operational efficiency.”
A New Monitoring Technique
Working with Timken, Cargill has implemented a unique monitoring system that provides them with a continuous assessment of bearing conditions in the most critical positions on their draglines. The technique assesses the interaction between the roller and race surfaces in the bearings. Two transducers, the size of a pack of Lifesavers®, are mounted on the boom point sheaves and relay information regarding the health of the bearings to mine operations and maintenance personnel. This provides them with the ability to plan their maintenance activity more effectively by notifying them when these bearings need to be repaired or replaced.
Planning Equals Profit
The operation of a mine requires intensive planning to maximize operational efficiency and profitability. The nature of mining is such that large quantities of material must be extracted from the ground to yield a relatively small amount of finished product. Therefore, the equipment focus at a mine is to maximize up-time to achieve the most profitability possible.
Draglines are at the heart of the extraction process. They must operate continuously for weeks at a time, and when maintenance is required it must be performed as quickly and efficiently as possible. This demands effective planning to insure that the required resources are available to replace or repair components when they have reached their service life. Furthermore, because the equipment is so massive and the mine locations are so remote, performing this work can be very cost-intensive. Just bringing down the 300-foot-long boom on a dragline costs tens of thousands of dollars and incurs days of downtime. Reducing the number of times this must be done positively impacts the profitability of the mine. This makes effective maintenance planning critical. The mine’s worst fear is that an unexpected failure occurs in a critical piece of equipment, resulting in expensive repairs, excessive downtime and the potential for collateral damage to other components.
For companies to maximize profitability in a highly-competitive industrial environment, they should consider the concepts of Reliability Centered Maintenance (RCM) to keep their equipment running most effectively. RCM mandates that proactive techniques be used to plan maintenance on equipment that may fail unpredictably. By monitoring the condition of equipment rather than either replacing it at timed intervals or allowing it to run to failure, the typical industrial facility can avoid unnecessary replacements, unplanned outages and excessive repair costs.
A System Suited to Draglines
The new monitoring system installed at Cargill provides the needed window of observation into the operation of the dragline bearings. The system includes proven sensing equipment, proprietary signal-conditioning software and expert interpretation of the bearing condition. The transducers mounted on the bearing support structure are wired to a data acquisition system on the dragline and send their signals back to the plant using a wireless data transfer system. The raw sensor signals are conditioned and analyzed to provide a direct indication of bearing condition. Tracking the system output will assure the mine of smooth operation when the bearings are healthy, and allow them to determine when to replace the bearings as they approach the end of their service life.
This proprietary new Timken technology is uniquely suited to dragline bearing applications. The location of these bearings makes them difficult to access, either buried deep within the machinery spaces or hovering 200 feet in the air. This makes monitoring the bearings manually both difficult and dangerous. Furthermore, the speed of these bearings varies as the dragline bucket is raised and lowered, making it difficult to apply standard vibration analysis.
High Frequency Is The Key
The system Timken has devised is different from standard vibration analysis. It uses a special high-frequency sensing technique that detects bearing damage while tuning out the ambient vibrations from equipment operation. Furthermore, the signal that is delivered to the mine is easier to store and trend than the complex output of a typical vibration-based system.
The signals generated by metal-to-metal contact in the bearings are no less complex than a standard vibration signal. However, dedicated conditioning electronics mounted near the bearings convert these signals into a simple parameter that varies with only two factors: bearing condition and rotational speed. Since the bearing speed varies continuously with dragline operation, the output of the signal conditioner is still not simple to interpret, as shown below:
However, Timken experts eliminate the variation caused by speed changes in a secondary analysis performed in the plant’s data management system. This results in an output that can be easily trended and interpreted by the mine, since it is a simple parameter that varies with bearing condition alone:
Bearing Condition No Longer a Mystery
This system was first installed on one Cargill dragline in the fall of 2002. In the summer of 2003, they replaced the bearings being monitored and noted the changes in the system output after the new bearings were installed.
These are the readings taken over the course of one shift before the bearings were replaced. Note the average level and amount of variation in the readings. This is typical of damaged components:
After the new bearings were installed, the readings leveled out and became more consistent:
In this way, the system provides a clear indication of the bearing condition. But it doesn’t end there. To better plan bearing replacements and coordinate them with other maintenance actions, Timken is assisting the mine in developing a knowledge base to make the assessment of bearing condition a routine activity.
More Than a Product
Through this Reliability Solutions initiative, Timken is helping customers operate their rotating equipment more efficiently to maximize the profitability of their enterprise. This includes a wide range of products and services to increase the effectiveness of their maintenance and operations. The hardware described here provides a window into system operation that enables the mine to assess the bearing condition simply by watching the trend of the bearing condition parameter. But the hardware alone will not accomplish this objective. The system still needs to be trained to qualify this assessment.
This is where Timken’s intimate knowledge of bearings comes in. By tapping into the expertise of its seasoned field service engineering force, Timken analyzes bearings that have been removed from service, correlates their condition with the output of the monitoring system, and sets qualified thresholds corresponding to specific bearing condition. Timken’s service engineers are uniquely qualified to provide this essential step to complete the bearing assessment. But while they are performing these inspections, they also have an opportunity to recommend actions that will help the mine improve the performance and increase the life of their bearings in the future. This will further reduce the cost of maintenance and increase the profitability of Cargill’s mining operation.
Additionally, service engineers will help Cargill implement the state-of-the-art monitoring tools that Timken is bringing to industry today, including:
- intelligent monitoring platforms that integrate all of the critical sensed parameters – vibration, temperature, load and wear debris – into a single analysis to diagnose problems and predict future bearing performance
- wireless transmission of sensor output to eliminate the cost and nuisance of wiring new monitoring systems
- software tools to institute the most advanced maintenance practices in industry today
“Cargill is excited by the reduced maintenance costs and increased uptime they will gain from Timken’s full suite of reliability solutions,” added Kern. “They are looking forward to growing with us to benefit from the continued value we can add to their operation. ”
"Teaming with Timken has allowed us to increase our machine reliability,” said Karen Mikkola, engineering manager - mining operations for Cargill Crop Nutrition. “It gives us greater peace of mind today, and allows us to capitalize on opportunities to reduce emergency maintenance and decrease costs. "