Modern Mining August 2016

PRODUCT News

Rapid turnaround on mill motor repair

they fitted 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,” states Megannon. Repair of the second motor was com- pleted at the end of March. In addition to the stator rewind with resin-rich windings, the rotor was overhauled and the quad- rants on a damaged damper winding of the rotor were replaced. Marthinusen & Coutts, tel (+27 11) 607-1700

Marthinusen & Coutts, a division of Actom, recently repaired two large mill motors for leading uranium producer Rössing Uranium in Namibia, a company celebrat- ing 40 years of production this year. Marthinusen & Coutts’field service team was requested by Rössing to inspect two brush mill motors on site. The team found that the starting cage winding on one of the motors hadmoved and rubbed 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. In view of the fact that no spare motor would be available to the mine in the event of a further breakdown while the two spare motors were being attended to by Marthinusen & Coutts in Johannesburg, the first of the two 1 586 kW, 3 300 V, 187,5 rpm brush motors to be repaired 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 were carried out as soon as it was received at our plant in October last year. The repairs were completed within three months and the motor was returned to the mine early in January this year,” says Craig Megannon, Marthinusen&Coutts’General Manager. The repairs carried out on the two motors consisted of rewinding the sta- tors incorporating use of a resin-rich winding system, overhaul of the rotors and complete replacement of the rotors’ electronic diode and synchro- nising hub. “Application of the resin-rich wind- ing 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 that

Alpheus Mtshali fromMarthinusen & Coutts is pic- tured with the 1 586 kW stator.

August 2016  MODERN MINING  75