Marthinusen & Coutts (M&C) performed a significant rewind last year after being contracted by leading international hydro generation OEM Voith Hydro of Germany to wind the stator of Unit 1 at Eskom’s Drakensburg Hydro pump storage power station near Bergville in KwaZulu-Natal.
M&C technicians are seen working in the large area left inside the stator after removal of the rotor as they install some of several hundred stator bars as part of the complex stator winding operation.
The massive stator winding contract, performed by a winding team from M&C under the supervision of Voith, was the final stage in the refurbishment of three of the station’s four 250MW motor-generator units.
Eskom engaged Voith to refurbish Unit 1.
Richard Botton, M&C’s Divisional CEO, who project-managed the winding of the stator of the 281,5MVA reversible motor-generator, said: “We have worked with Voith over several years, during which time we have performed similar projects, such as a stator rewind at Eskom’s Ingula pumped storage scheme, among others. These have stood us in good stead and almost certainly played a key role in Voith’s decision to award us the contract for Unit 1.”
The contract was due to have commenced early last year, but only got under way in late-August as a result of COVID-19 occurring and the subsequent strict lockdowns.
“This left us with only three months to complete the rewind – half the original period allocated. We introduced two shifts per day with a 10-man team on each shift to ensure the work was completed on time,” Richard explained.
The 6,5m diameter stator was wound in situ under Voith’s supervision after removal of the rotor. Deploying a Voith-supplied winding kit, the winding teams were required to install a total of 720 heavy duty stator bars that had to be connected in an extremely complex bus arrangement.
“Our teams had to undergo special training by Voith technicians beforehand before getting started on it,” Richard pointed out.
The contract was completed on schedule in mid-November last year.
A further demonstration of the depth and variety of expertise M&C has on offer in its field came when M&C’s Engineering & Technical Executive Rob Melaia recommissioned the unit.
M&C’s Rob Melaia steps in to recommission Unit 1 of Drakensberg Hydro station
Rob Melaia.
When it was brought to Voith’s attention that the restrictions on travel between countries resulting from the COVID-19 pandemic prevented it from flying in one of its own senior engineers from Germany to recommission the unit, it asked Richard Botton, M&C’s Divisional CEO, if M&C could assist.
He had no hesitation recommending Rob to perform the recommissioning, as Rob has previously commissioned other power plants as part of repair and refurbishment contracts M&C has undertaken. These included the N’zilo hydro station in Katanga province, DRC, in 2013 and the SA Bureau of Standards’ National Electrical Test Facility’s High Power test laboratory in Gauteng last year.
Voith duly assigned the recommissioning to M&C after checking and approving Rob’s credentials.
Then followed hours of conference calls between Rob in his office at M&C’s main repair facility in Cleveland, Johannesburg, and senior technicians at Voith’s head office in Heidenheim, Germany, who provided detailed instructions on the required procedures.
Rob successfully performed the recommissioning of Unit 1 over a period of five days in March this year.
Commenting on it, he said: “By the time I got there I was thoroughly briefed about what I was required to do. The process was challenging and I had to give it all my attention. The one single thing that gave me the greatest confidence was knowing that M&C had done the winding of the stator; I wouldn’t have felt so confident if anyone else had done it.”
Richard commented: “It is a massive feather in our cap that M&C was able to offer to put the unit back into service. This is yet another set of skills we have in our division, further demonstrating M&C’s ability to partner with international OEM’s and proving that local competency is of a high standard.”
Mike Chamberlain, M&C’s Marketing & Commercial Executive, commented: “In this contract M&C have again demonstrated their ability to rewind complex large machines, including complying with the OEM’s stringent specifications. M&C also showed flexibility when encountering delays caused by circumstances outside their control by doing their utmost to ensure that the project was delivered on time.”
