73 / 76
PRODUCT News
August 2016
MODERN MINING
75
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
Rapid turnaround on mill motor repair
Alpheus Mtshali fromMarthinusen & Coutts is pic-
tured with the 1 586 kW stator.
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