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Maintenance: Rapid response creates long-term value

Limiting downtime and reducing maintenance costs have become paramount in a world where volatile markets are the norm

Fluctuations in commodity prices have become more frequent as demand has become more and more unpredictable. This has forced many mining companies to adapt their current business models and to focus more on cost reduction and increased productivity. Paul Mitchell, global mining and metals advisory leader at EY, says that during the mining boom, miners witnessed costs escalating significantly — in some cases by more than 200%. “Initially, higher commodity prices masked these resultant costs, but as prices have fallen, these embedded higher costs have been impacting bottom lines. As prices declined, miners started eliminating costs from all areas of the business, including reducing capital expenditure and labour. There are, however, still many opportunities for removing costs from the business, and miners need to maintain a focus on building a long-term sustainable cost base,” says Mitchell.

“It is important that every activity in the business is challenged, as the ‘long tail’ of smaller costs is often overlooked in traditional cost-cutting approaches,” says Mitchell. Even small costs should be pursued because – combined – they are often significant in number. Maintenance costs and expenses associated with breakdowns play a pivotal role in any mining company’s operations. Shutting down for maintenance should be avoided, if not managed, so that it has the minimum impact on the mine’s operations. In addition, unplanned breakdowns should be repaired immediately.

When two large mill motors at Rössing Uranium’s plant near Swakopmund in Namibia had to be repaired recently, it was done as quickly as possible, saving costs in the process. Johannesburg-based Marthinusen & Coutts, a division of Actom, was requested by the mine to inspect two brush mill motors on site. The team discovered that the starting cage winding on one of the motors had shifted and was rubbing against the stator winding, while an insulation test conducted on the second motor indicated that the stator winding was down to earth. This necessitated having both motors repaired at Marthinusen & Coutts’ facility in Cleveland, South Africa.

Because no spare motor would be available to the mine in the event of a further breakdown while Marthinusen & Coutts were repairing the two spare motors in Johannesburg, the first brush motor was treated with the greatest urgency to ensure that it was returned to the mine as quickly as possible.

“We therefore designated it as being ‘a breakdown’ and the repairs on it commenced as soon as it was received at our plant. The repairs were completed within three months and the motor was returned to the mine,” says Craig Megannon, general manager at Marthinusen & Coutts.

The repair team had to rewind the stators using a resin-rich winding system; overhaul the rotors; and replace the rotors’ electronic diode and synchronising hub.

“Application of the resin-rich winding system for the stator rewinds necessitated having to manufacture special customised press boxes for curing the cells. A critical part of this was ensuring that the dimensions of the cells were 100% correct so they fit into the core slots exactly. A coil reset jig also had to be made to enable us to manufacture the coils to the correct shapes,” says Megannon.

Repair of the second motor was completed two months later. In addition to the stator rewind with resin-rich windings, the rotor was overhauled and the quadrants on a damaged damper winding of the rotor were replaced. Because of the rapid turnaround, Rössing’s production figures were not affected severely.

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