When Voith Hydro invited Marthinusen & Coutts (M&C) earlier this year to quote for the manufacture of four new replacement field coils and poles for a 25MVA generator at a hydroelectric power station in Cameroon, the division soon discovered upon investigation that the project was beset with seemingly insurmountable difficulties.
“We are often called upon to manufacture items by applying reverse engineering procedures when the OEM’s design drawings for the equipment are unavailable, but usually we’re able to gain access to the original component itself to work from,” said Craig Smorenburg, M&C’s Works Executive.
“However, in this instance the original coils and poles had been stolen out of a 24 600kVA 36-pole generator in the power station. We were provided with rough dimensions, which were sufficient for our quotation, but not accurate enough to work from.”
M&C sent two senior technical staff-members to the 264MW Edéa power station on the Sanaga River near the town of Edéa in Cameroon to try and obtain more accurate dimensions and any other information they could gather. What they got included useful photographic evidence, along with the more reliable dimensions.
“These were invaluable, but could not alone have enabled us to perform the task were we not able to draw on the pooled knowledge and experience of the experts that made up M&C’s team. A crucial part of the whole process was the design and manufacture of the tooling and jigs required for the manufacture of the coils and poles,” Craig commented.
The field coils were of a complex design that consisted of a double-bank series coil with a unique method of connection between the north and south poles.
“Another unusual feature was that the copper dimensions required on-edge bending to wind a continuous coil,” Craig pointed out.
M&C manufactured the required items on the customised coil press at its Power Generation & Large Motor facility in Benoni, having prepared the necessary designs mainly on the strength of the photographs they’d been provided with.
The contract was completed on schedule at the end of September.
