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Mechanical Technology — August 2016
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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.
Alpheus Mtshali, from Marthinusen & Coutts, is pictured with the
1 586 kW 187.5 rpm, 3.3 kV, 278 A stator.
Rapid mill motor repair
for Rössing Uranium
⎪
Proactive maintenance
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