Regular Check-ups

Operations in the mining industry cannot make a move without mobile equipment. But traditional maintenance approaches sometimes stalls productivity in its tracks.

Mobile equipment represents one of the largest capital expenditures in a mine, and can account for up to 70% of the total maintenance budget. Contributing to this high cost is the industry's long-time reliance on time-based maintenance, where equipment is removed from service for inspection and maintenance whether it needs it or not.

The resulting downtime and unavailability of equipment curbs productivity. In addition, time-based maintenance is unprepared to detect premature or "random" failures and may even cause problems down the road due to improper or inappropriate service procedures.

All the pitfalls associated with time-based (basically preventive) maintenance strategies have long been viewed as problems in search of solutions. The light at the end of the tunnel: Advanced condition monitoring systems — onboard and on-line — engineered specifically for mobile mining equipment.

Unearthing applications

These systems elevate "fault detection" to new heights. The technology (hardware and software) enables the condition of mechanical components to be monitored while equipment is actually in operation, when data can then be communicated for analysis and, if appropriate, remedial action.

This proactive approach to maintenance eliminates the detouring of equipment for time-based inspections, thereby increasing its availability. Vehicle reliability is enhanced, too, because suspected problems can be identified in real time for prompt, corrective action before a catastrophic failure can occur.

The numbers tell a compelling "capital" story that drills down to core bottom-line benefits:

Using on-line fault detection systems, it has been estimated that predictive maintenance can increase equipment availability up to 3%. The increased availability, in turn, can help reduce fleet size, because redundant vehicles need not be dedicated to pinch-hit. With a purchase price for a new truck in the range of $1.5 million to $3 million, the potential savings drive home.

For mining operations well under way with periodic monitoring procedures using permanently installed sensors and hand-held data collectors, an on-line system can transport the process to higher ground. Measurement accuracy improves and random events can be caught in time.

Mining operations can readily apply on-line condition monitoring to a wide range of mobile equipment components. Among them:

• Large haul trucks, miners, loaders, dozers, and excavators: Engine, transmission, cardan shaft, differential, alternator and final drive
• Shovels: Hoist, crowd, swing and propel mechanisms
• Bucket wheel excavators and stacker/reclaimers: Conveyors and bucket supports
• Draglines: Hoist, drag and swing mechanisms
• Drills: Drillhead
• Auxiliaries: Motors, pumps, fans, blowers and compressors

Inherent challenges

These systems monitor key operating parameters such as vibration, temperature, speed and load conditions. For equipment "on the move," though, systems must be equipped to deal with a variety of inherent challenges.

For one, mining vehicles travel or operate at varying speeds. This means that a meaningful condition monitoring system should incorporate software with conditional "gating" (or measurement logic) capabilities to capture data under varying conditions. Using a "time window," the gating can govern when measurements would best be collected under specific conditions (such as speed and load) for enhanced accuracy and reliability.

Example: When a vibration measurement is to be collected, the system should be engineered to determine whether the speed signal is within the interval preset for this measurement. Then, only if the speed condition falls within the appropriate window will the measurement be collected for best interpretation.