Company Announcement - Marthinusen & Coutts, a division of Actom, was awarded the contract to refurbish three winder motors at the Cullinan Diamond Mine. The contract was awarded by instrumentation and control specialist ABB, in consultation with Petra Diamonds. ABB is in the process of upgrading the mine’s winders to a thyristor drive control system. “We were requested to inspect the condition of the motors, one of them being 57 years old, and provide a report on any repairs or upgrades required to accommodate the new drives,” Craig Megannon, General Manager, Marthinusen & Coutts Cleveland, says.

“We inspected one of the running motors and a spare machine visually,” Megannon explains. Although well maintained, the 57-year-old running motor had a fine coating of abrasive stone dust over most of the field and armature windings. Despite this, the running surface of the commutator seemed to be in excellent condition, with the brush track wear exhibiting some depth and the carbon brushes retaining a 70% lifespan. The spare motor on the other hand had been cannibalised for spare parts and had not been prepared for long term storage, with the result that it had become contaminated with dust and other debris which had accumulated on it over the years. “ABB and Cullinan Mine were pleased with the report that we presented to them, and we were therefore awarded the contract for the necessary repairs. We initially thought that we would have to rewind both the armatures and the field frames, but on inspection in our works and after carrying out extensive electrical testing we reported that the field frames were in a good condition,” Megannon says. “We saved our customer a lot of money by not having to rewind the field frame coils, and only having the armatures rewound.”

Two of the three motors are in use while one is maintained as a spare unit. The plan was to inspect the spare and effect any necessary repairs, and then to swop it out with one of the other running motors during the annual shutdown period in December each year. “We have completed two of the motors to date while the third and final one will be swopped out in December this year,” Megannon confirms.

Commenting on the success of the project, Megannon concludes: “The project is a further demonstration of Marthinusen & Coutts’ ability to perform complicated repair work on large DC motors and ancillary equipment. This forms part of the long term strategy of Marthinusen & Coutts to become a preferred integrated electrical and mechanical services provider for the mining and industrial markets in Africa.”