Last month, electric motor repair company Marthinusen & Coutts Zambia was requested by a copper smelter based in the Copperbelt region of Zambia to provide an in-country repair solution to two of their critical 4.5 MW compressor motors.

Marthinusen & Coutts was given only three weeks in which to overhaul and commission the motors.

The scope of work involved the dismantling, cleaning and assessing of all motor parts, as well as the dynamic balancing of rotors at operating speed using Marthinusen & Coutts Zambia’s own 12 t balancing machine.

As part of the project, Marthinusen & Coutts was also required to supply new bearing assembly parts, assemble the motors and conduct no-load tests, and laser align the motors on site.

“Upon dismantling both motors, we identified that the stator coils indicated partial discharge and the stator wedges had deteriorated significantly over time,” says Marthinusen & Coutts Zambia GM Eugene Lottering.

Consequently, the Zambian branch requested Marthinusen & Coutts’ workshop in Cleveland, Johannesburg, to supply partial discharge treatment of the stator coils and to manufacture the stator wedges that needed to be replaced, he says.

To ensure that all its on-site work complied with international standards, Marthinusen & Coutts also sent a senior technician from Johannesburg to assist the Zambian team on fulfilling the contract.

“Our team is well experienced in how to approach and action various stages throughout the overhaul of these motors,” says Lottering, adding “we successfully completed various medium voltage overhauls up to 4 650 kW”.

The motors were tested under no load at 11 kV with “exceptionally good” results being recorded, with Marthinusen & Coutts reporting that the customer consequently provided approval to commission the motors.

“Installing them on site turned out to be a complicated procedure, especially [regarding] the alignment of the motors to the compressors,” he added.

The motors were finally tested on load, recording satisfactory vibration levels of below 1.34 mm a second.

“The motors were successfully installed and commissioned three days before the scheduled deadline for completion,” Lottering concludes.

Marthinusen & Coutts offers a wide array of services including 24/7 onsite engineering; the servicing of generators, alternators, turbines, transformers and flameproof motors; the servicing of high, medium and low voltage alternating current (ac) motors, and ac and direct current traction motors; and coil manufacturing. The company also possesses capability in testing, lathe tasks, designing and insulation systems.