When a gold and copper mine in rural Australia had repeated failures on the mill motors that drove production in its grinding plant, a lot was at risk. The company processes the ore on site, grinding it to a slurry to prepare it for the recovery of gold and copper. When a mill motor fails, the loss of production and the cost of repair have a considerable negative impact on revenue.
The mill motors were flashing over and arcing on their sliprings and brush gear, putting the safety of employees at risk from flying debris and causing expensive emergency shutdowns. The mine operators had performed limited maintenance, but the work wasn’t documented and the problems continued. Each critical mill motor failure could cost the company more than $500,000 in lost production and another $100,000 to overhaul the failed machine. The company needed a solution that would stop the repeated mill motor failures once and for all.
The mine operators wanted to understand the cause of the problems so they could prevent future occurrences. They began to look for a strategic partner with a reputation for problem-solving and extensive experience in machine asset management.
Slipring motors are robust, but brush systems are sensitive to a few fundamentals: correct brush grade, correct dimensions and seating, proper spring pressure, clean and smooth ring surfaces, and consistent operating load. If any of these drift, localized heating and poor current sharing can lead to arcing, carbon tracking, and flashover. Without documented practices, the same failure mechanisms tend to reappear after personnel or load changes.
To eliminate repeat failures, the site adopted a process-based approach that standardizes inspection, replacement, and verification. The following checklist captures the principles operators agreed to institutionalize:
To prevent regression, the mine implemented standard work: a single, version-controlled procedure; acceptance criteria with sign-off; calibrated tools; and a kitted set of approved brushes, springs, and hardware. The procedure includes a brief supervisor review after any planned load change. These controls make the correct actions the default, even as personnel rotate.
Brush maintenance addresses the slipring failure mode. For broader motor health—especially stator insulation and mechanical risks—continuous or periodic condition monitoring can provide early warning signals that support planning and reduce emergency stops:
Where in-house bandwidth is limited, our Xpert Services can handle monitoring, data diagnosis, and health assessments on your behalf, and help operationalize findings into maintenance actions.
The mine formalized three elements: (1) a brush system standard (approved grades, inspection intervals, and acceptance criteria); (2) a single maintenance checklist with measured values; and (3) a basic data flow—retaining records so trends are visible at turnover. With those in place, emergency stops due to brush flashover were eliminated.
The cost basis was straightforward. Each critical mill motor failure could exceed $500K in lost production, plus about $100K to overhaul the machine. Avoiding even two such failures per year yields savings on the order of $1.2M annually (production + repair). The process-based brush program is low-cost to maintain; its value is realized by preventing a handful of high-impact events.
To keep results durable, the mine tied the checklist to work orders, required photo evidence of brush seating and ring condition, and set quarterly audits of spring pressure and ring finish. When operating changes were planned (duty cycle, throughput), engineering reviewed brush current density and cooling before implementation. The result is a stable mill motor fleet and a repeatable way to train new staff.