At global diversified miner Vedanta Resources’ Gamsberg mine, in the Northern Cape, motor and controls manufacturer Zest WEG Group is working closely with lead contractor ELB Engineering Services as a preferred supplier to standardise its range of transformers and motors across a number of on-site applications.
The Gamsberg project is currently South Africa’s largest greenfield mining project and will exploit one of the world’s largest zinc deposits. It is being developed at a capital cost of $400-million and is expected to produce 250 000 t/y of zinc metal in concentrate.
“This is a very exciting project for South Africa, especially as we haven’t seen a new mine being developed in the country for many years,” says ELB Engineering Services chief executive Dr Stephen Meijers. “Vedanta Resources has shown real intent in terms of investment in South Africa, not only in this project but also in others, and we are proud to be building Gamsberg.”
ELB Engineering Services’ first package of work was to connect the process plant to water supply from the Orange river through a pipeline of about 40 km and an upgraded pumpstation. The second package is to supply the mine with power from the existing switching yard belonging to State-owned power utility Eskom using overhead lines, while the third package involves the process plant and covers all aspects from run-of-mine tip through to final product, including process dams and balance of plant.
“First product is expected through the plant by mid-2018, with the civil works being largely completed by the end of the second quarter last year,” says Meijers. “Structural and mechanical construction on the plant is now starting to become the focus of work, and the pace will continue to be intense until the middle of this year.”
Extreme temperatures on site – down to –10 ºC at night in winter and up to between 45 ºC and 50 ºC in summer during the day – have affected the design and the construction methodology, he says. This has meant making optimal use of the cooler hours in summer, even premanufacturing as much as possible at night before placing during daylight hours.
Meijers is a strong believer in partnerships, with much of the project technology being applied through exclusive partnerships with preferred suppliers.
“We’ve worked with Zest WEG Group for many years and appreciate their professionalism, high-quality service and reliable scheduling,” he says. “We have, therefore, placed a number of the contracts for this important and fast-tracked venture through Zest WEG Group companies.”
As a group of specialist electrical companies, Zest WEG Group’s scope of supply covers two main spheres – the water-related package, which focuses on the upgrading of the municipal supply station providing water to the Gamsberg site, and the package for the mine’s zinc concentration plant and related processes.
In this process, Zest WEG Group supplied several nonstandard products – providing the mechanical and design engineering necessary to ensure that the nonstandard specifications could be met, including the redundancy requirements to ensure optimal plant uptime.
“The Gamsberg plant is a showcase for WEG motors and includes four different medium-voltage (MV) motor ranges that were fit-for-purpose in their different applications,” says Zest WEG Group company Shaw Controls MV business manager Kirk Moss. “These included our new W50 line, the HGF line, large slip-ring motors from our M line and our W22 line of low-voltage (LV) IE3 motors; meeting the range of requirements demonstrated Zest WEG Group’s versatility in terms of the multiple MV and LV motor offering.”
Energy efficiency is a key driver in the project design, with high efficiency W22 WEG IE3 motors being specified across the site. To streamline and facilitate the implementation of this focus, Zest WEG Group was tasked by ELB Engineering Services to coordinate with all the original-equipment manufacturers that would use motors to drive their equipment. This is to ensure that the principle of energy efficiency is fully applied across all aspects of the project scope.
“Importantly, we are supplying all the LV motors for the plant, ensuring the project will save considerably on its energy costs by complying with the IE3 energy efficiency standard,” says Moss. “These motors are also IP66-rated with Class H insulation, which enhances the IE3 specification by providing higher ingress protection and accommodating a higher temperature rise.”
According to Shaw Controls business development manager Tyrone Willemse, the MV mill package being supplied for the plant comprises two large 6.5 MW WEG motors – MAF 11 kV slip ring units – specified for the ball and semi-autogenous mills.
“The jaw crushers will be fitted with proven, robust 11 kV, 400 kW motors from WEG’s HGF line,” says Willemse. “We were also requested to supply the distribution transformers on the plant.
Zest WEG Group’s contribution to the water supply facility upgrade involved the provision of eight 3.3 kV, 550 kW MV motors and its locally designed and manufactured transformers to provide power to the pumpstation.
“This included two 2.5 MVA transformers (reducing 11 kV down to 3.3 kV), as well as four 315 KVA (reducing 3.3 kV to 400 V) units,” says Willemse. “Once again, these were not standard transformer designs but were prepared specifically to suit the specifications of the client.”
The package also includes the new WEG W50 motor, which features a compact size and design; through the application of the latest computational analysis techniques, both the scale and the cooling efficiency have been improved – delivering optimised airflow that enhances the unit’s expected lifespan.
“This means that the performance and temperature rise of these motors is not compromised in any way by its smaller dimensions,” says Moss.
Connected to these motors are WEG MVW01 3.3 kV variable-speed drives (VSDs), further enhancing energy efficiencies. These are also compact – just 2 315 mm high, 2 600 mm wide and 980 mm deep, including the integral phase-shift transformer – together helping reduce the footprint of the substation.
The VSDs also boast a low component count – imperative in terms of reliability – of just three power arms that can be changed in two or three minutes, allowing for quick maintenance and low downtime in the case of replacement.
“Helping to meet the short lead times demanded by this project, Zest WEG Group was able to leverage the global WEG group’s multiple manufacturing facilities around the world, giving us flexibility in terms of where we build and how quickly we can source product,” says Moss.