Refurb of mill drive for Platinum mine

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Team expertise key to successful maintenance of mill drive motors

Meticulous planning underpinned the successful completion by Marthinusen & Coutts of the servicing and pole changes on two of the largest mill motors operating in Africa, at a South African platinum mine.  These are ABB gearless mill drives (GMDs) with 17.5MW 60 pole synchronous motors.


According to Owen Kilian,  M&C’s National Technical Sales and Service Manager, the business’ experience ensured the work was done efficiently while planning for any eventuality. The GMDs require regular inspection and maintenance, and the mine gave Owen’s team just 120 hours – the five days of the quarterly shutdown period – to complete the work.


“As the preferred service partner in Africa, we deployed 16 people on this contract, allowing us to keep working through the day and night shift,” he said. “Time was of the essence, as we couldn’t delay the resumption of plant operations at the end of the shutdown.”


The seasoned team for this work included two site managers and two supervisors – one for each shift – as well as mechanical fitters and armature winders with their assistants. Preparation began well before the team arrived on site, with various medical fitness tests and inductions being required to comply with the mine’s strict health, safety and other requirements.


“Before the shutdown, we also conducted an inspection and risk assessment. By doing this, we identified any aspect of the job that might take more time than normal, and planned for that by stocking all relevant tools, equipment and spares,” he said. “We even took back-up tools and testing equipment to keep all functions running smoothly, and to make the best use of the available time.”


The work itself followed a strict and optimal sequence, noted Owen, from the lifting of connection plates and stator covers to the removal and replacement of the damaged rotor poles. This sequence kept the process efficient and allowed the team to work in close collaboration with the mine’s riggers, who conducted the heavy lifting duties.


“While we were changing the rotor poles, we were also able to clean the motor inside – removing dust and wiping the walls with an electrical solvent,” he said. “For efficient operation, these motors need to be kept as clean as possible.”


He emphasised that confidence in his team’s expertise was the key to successful project completion, with each member trained and prepared for their tasks. “This experience is what makes us leaders in the repair of both rotating electrical and mechanical machines,” said Owen.