Mechanical Technology August 2016

⎪ Proactive maintenance ⎪

M arthinusen & 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 had moved 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, 3.3 kV, 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,” Craig Megannon, Marthinusen & Coutts’ general manager, says. Repairs carried out on the two motors consisted of rewinding the stators with the use of a resin-rich winding system; overhaul of the rotors and complete replacement of 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 ensur- ing that the dimensions of the cells were 100% correct so that they could fit exactly into the core slots. A coil reset jig also had to be made to enable us to manufacture the coils to the correct shapes,” Megannon says. Repair of the second motor was completed at the end of March. 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. q Marthinusen & Coutts, a division of Actom, recently repaired two large mill motors for leading uranium producer, Rössing Uranium in Namibia; a company celebrating 40 years of production this year. Rapid mill motor repair for Rössing Uranium

Alpheus Mtshali, from Marthinusen & Coutts, is pictured with the 1 586 kW 187.5 rpm, 3.3 kV, 278 A stator.

Mechanical Technology — August 2016

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