DRA Technical Services, the specialist South African winder engineering company, has handed over two refurbished winders to the Great Basin Gold’s Burnstone gold mine near Balfour. The project not only reduced the amount of capex the client required for the winders but also enabled it to bring the project to an earlier completion date.
The project saw the units, an 1,800kW 4,27m double-drum man-winder and a 4,88m double-drum rock winder driven by two 1343kW motors, undergo a full mechanical refurbishment, replacing all wear components as well as providing modern brakes and hydraulics. All of the rotating machines including motors and generators were completely rebuilt, being rewound to class F insulation standards in the process and new, state-of-the-art electronic speed control and protection equipment was supplied and installed.
The man-winder will hoist a 5,25t payload, in a 7t cage on a depth-of-wind of 500m. The rock-winder features a 12,5t payload, a skip mass of 9,38t and a depth-of-wind of 490m. One of the unique features of the project is the incorporation of a fibre-optic bell signalling system. Designed and built by DRA Technical Services, the system is the first for the mining industry anywhere in the world.
Graham du Plessis, managing director of DRA Technical Services, says: “It made economic sense to the client to refurbish the winder units rather than opt for new ones. From a cost perspective, in this particular case, the refurbished winders offered a 50% saving compared to the cost of new winders, while at the same time providing a delivery period of about half that of new machines. This project took about nine months to complete from contract signing to completion of winder refurbishment.”
“In their refurbished state, the winders will operate as new and according to the mining industry’s strict safety requirements. This despite the man-winder tracing its origins back to the 1930s where it operated at the now defunct Okiep Copper mine. The rock-winder was sourced from Zambia and was originally built in 1954. The refurbishment and modernisation of these units will extend their operating lifespans another 30 years.” According to du Plessis, while the electrical equipment in a winder has a finite lifespan, due to eventual obsolescence, overall, a winder can be used almost indefinitely. He cites the example of the oldest continuously operating winder in South Africa, at the Hercules shaft at ERPM in Boksburg, which was in use at its original location for 91 years until the mine was closed.
“It has been a policy of many local mining companies to re-use second hand-winders wherever possible,” adds du Plessis. “DRA Technical Services is fully equipped to handle any type of winder project whether it be for new units or refurbished ones and has handled some of the biggest winder installations in Africa.”