Cradle to grave
Modification
of mill motor
cuts costs
Marthinusen & Coutts recently
refurbished the largest AC electric
motor operating in Zimbabwe.
R
ebecca gold mine in Zimbabwe recently refurbished the AC synchronous
electric motor that drives the reduction mill of its processing plant.
The main hub of the electrical rotor component on the 2 150kW
motor, which is about 30 years old, broke down due to metal fatigue.
Marthinusen & Coutts, a division of Actom was called to site by the
mine to investigate further and to provide a long-term solution. A full
assessment undertaken by the Marthinusen & Coutts team resulted in
the motor being brought back to the division’s facility in South Africa.
It was decided, following negotiations with the mine, to do a
design modification instead of replacing the hub. Richard Botton,
divisional CEO of Marthinusen & Coutts, explains that this
option was chosen as it would save costs and reduce the lead time
without sacrificing the performance of the refurbished motor.
“Our team’s extensive experience and understanding of large rotating
machinery enabled us to offer an alternative to the mine that ensures
optimum reliability going forward. One of the solutions is to use the existing
rotor superstructure with a bolt-on hub on the motor,” says Botton.
In addition, 18 main pole coils were replaced; these were
manufactured by Marthinusen & Coutts in South Africa.
A complete rewind of the stator was necessary due to the extensive
damage caused during the failure at the mine. Fortunately, the mine
store had a spare set of coils, manufactured 20 years ago, and these
were rewound at Marthinusen & Coutts in South Africa.
A compete upgrade and modification to the sleeve bearings
also brought these back to OEM specifications.
“The ability to implement enhancements during the repair of critical
electrical rotating machinery such as this motor is a major advantage
to the mine, as it allows for the latest technology and enhancements
to be included in the final product solution,” Botton says.
The scope of work included the on-site commissioning of the motor which
was facilitated by the Marthinusen & Coutts Zimbabwe operation with
technical support from the division’s centre of excellence in Johannesburg.
JANUARY 2018 MINING MIRROR
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