Marthinusen & Coutts recently performed a comprehensive on-site repair of a large DC winder motor at Konkola copper mine in Zambia. The 8,250 kW motor, which is one of the largest slow-speed DC motors in operation worldwide, was acquired by Konkola from a South African gold mine several years ago and was installed on the multi-rope winder at Konkola’s No.4 Shaft. “After successfully completing a four year shaft sinking program at Konkola, the motor indicated some overheating while the mine was in the process of converting the winder from shaft sinking to permanent duty operation,” Ian Solomon, M&C’s field services manager, says. “The repair job assigned to us had to be done on a breakdown basis to ensure that any disruption of the mine’s construction schedule was kept to a minimum.”M&C immediately sent a team to the mine to assess the condition of the motor under the supervision of sister company ACTOM Industry, the suppliers of the electrical winding system. They were closely followed by a team equipped to do all the repair work on site. The motor had to be fully dismantled. Careful preparation beforehand for mobilising of the materials and resources was an essential procedure, as most of these were unavailable locally. The repair work, performed 24 hours a day in about six days, involved cleaning, re-soldering and re-insulating all the compensating bars and compole connections on the field frame. “It also required continual testing of the components to ensure integrity of each progressive task. All work was carried out under the supervision of ACTOM Industry,” Solomon says. In addition, the commutator had to be skimmed and polished with special custom-made brush boxes fitted onto a portable lathe that was installed on the existing brush gear.Solomon says Adam Hughes, M&C’s resident engineer in Zambia, made an important contribution to the success of the project with his invaluable input of engineering expertise and provision of local resources. “The success of this project has further enhanced the good reputation M&C enjoys in Africa for repairing rotating electrical equipment in fast turnaround times,” he adds.“While planning is important, flexibility above all is a key requirement. You have to have the ability to adapt to changing circumstances and produce uncompromising quality in the face of often daunting time constraints and logistical problems, as applied in this case,” Solomon concludes.