M&C refurbish massive mill motor for Zimbabwe gold mine
January 2018
News
The largest AC electric motor operating in Zimbabwe drives a reduction mill, and this synchronous motor was recently refurbished by leading rotating machinery repairer, Marthinusen & Coutts.
Estimated to be around 30 years old, the 2150 kW motor, in operation at Freda Rebecca Gold Mine, suffered a catastrophic failure caused by age related metal fatigue. The main hub of the electrical rotor component had sheared off.
Following preliminary repair work undertaken by the mine, Marthinusen & Coutts was called to site to investigate further and provide a permanent solution. A full assessment undertaken by the 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 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 would ensure optimum reliability going forward,” he explains. “One of the solutions was to use the existing rotor superstructure with a bolt-on hub on the motor.”
In addition, 18 main pole coils were replaced. These were manufactured by Marthinusen & Coutts at its ISO 9001 accredited facility in Gauteng.
A complete rewind of the stator was necessary due to the extensive damage caused during the failure. Fortunately, the mine store had a spare set of coils, manufactured 20 years ago, and these were rewound in South Africa.
A complete upgrade and modification to the sleeve bearings also brought these back to OEM specifications.
“The ability to implement enhancements during the repair of 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,” concludes Botton.
The scope of work included the onsite commissioning of the motor which was facilitated by the Zimbabwe operation with technical support from the division’s centre of excellence in Johannesburg.
For more information contact Richard Botton, Marthinusen & Coutts, +27 (0)11 607 1700, [email protected], www.mandc.co.za
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