Early in 2020 a copper mine in Zambia – a longstanding customer of Marthinusen & Coutts (M&C) – after notifying M&C’s workshop in Kitwe that one of its large 1846kW submersible pump motors used to dewater the mine was faulty and sent it through to the workshop for assessment and repair.
Armature Winder Shepard Thigwa is shown pulling new conductors through the slots of the rotor of one of the large submersible pump motors repaired recently at M&C’s Benoni facility.
The workshop established an earth fault to be the likely cause of the malfunction, but not being equipped itself to repair such a large motor, it arranged for it to be sent through to M&C’s Power Generation and Large Motor Repair facility in Benoni, Gauteng, which is fully equipped to assess, test and repair very large machines and has a substantial amount of factory floor space to accommodate them.
After long use extending over decades, the motor suffered from extensive wear and tear of the rotating mechanical parts and there was water ingress into the motor which damaged some of its internal components, resulting in the earth fault.
“To fix it we had to do a rewind of the stator. For this we had to arrange for the OEM in Germany to provide a specialised rewind kit consisting of all the materials required for the purpose,” explained Rudi Els, General Manager of the Power Generation facility.
The stator is about 2.5m long, with an external diameter of 900mm. “Due to the specialised winding and construction of the submersible pump motor, M&C designed and manufactured specialised tooling to perform these rewinds,” Rudi said.
Upon the successful completion of the rewind the motor was returned for reinstallation in the mine in August last year.
Within a month of delivery of this motor M&C was contracted by another longstanding customer to repair an almost identical submersible pump motor manufactured by the same German OEM as the first. “In addition, the stator of this motor also required a rewind, so again we procured the specialised rewind kit from the OEM as before and were able to use the same specialised tooling we had made for the first one,” Rudi remarked.
Although more powerful than the earlier unit, at 2595kW, the later motor and its stator were the same size as the Zambian motor. “All these favourable factors, including the experience we’d gained doing the first rewind, enabled us to perform this rewind more speedily than before,” he said.
The repaired motor was delivered to the customer within only two months of M&C commencing the work. The customer in this instance was a Johannesburg-based company that extracts acidic water from local gold mines and purifies it before releasing it into rivers and streams.
“M&C have successfully shown that they are very capable to rewind submersible pump motors,” commented Mike Chamberlain, the division’s Marketing & Commercial Executive.
“They have also shown once again that they are flexible to assist customers to carry out complex electrical and mechanical refurbishments of rotating machines.”
M&C has subsequently received more dewatering pump motors to repair from other customers.
