The Vulcan plant, which began cold commissioning last year, is expected to improve the Tharisa mine’s chrome recoveries from about 62% to around 80%. An important aspect of achieving this outcome will be the performance and reliability of its electrical equipment, the majority of which comes from Zest WEG.
“This was an exciting project for us, where we were able to demonstrate our broad offering of electrical solutions,” says Dillon Govender, sector specialist in business development at Zest WEG. The order included low voltage WEG motors and variable speed drives (VSDs), as well as soft starters, transformers, generators, motor control centres and distribution boards.
Indicating the scale of the project, some 120 WEG W22 motors of 525 V capacity were supplied. In line with Zest WEG’s commitment to sustainability goals through energy efficiency, these motors are IE3-rated premium efficiency motors.
“We keep extensive stock of these motors in South Africa, so there was no lead time for manufacturing or transportation for the client,” says Govender. “Also, we were able to supply these directly to the project’s pump vendor, where the motors were to be fitted. This was a service we offered to the client, to help streamline the project and reduce their logistics.”
A competitive advantage of WEG motors from 132 to 500 kW, he says, is the standard provision of an insulated end shield. This allows the motor to run with a VSD, without the need to add insulated bearings. This makes maintenance easier, as it can be fitted with a normal bearing.
With an ingress protection rating of IP66, combined with Class H temperature rise capacity, the motors are designed for long life and efficient power consumption. In fact, he adds, Zest WEG offers a five year warranty on these motors. Further enhancing the motors’ efficiency was the supply of 115 WEG low voltage VSDs. Four of WEG’s latest SSW900 heavy duty 185kW soft starters were also supplied, complete with a three-year warranty.
“Most motors are VSD-driven, using our heavy duty CFW11 mining-spec system drive,” he says. “Supplied standard with a safety stop relay function, these motors are rated SIL2 for low statistical risk of failure.”
There were three MCCs in the order – with two back-to-back and one front-and-rear configuration. Zest WEG locally manufactured these according to the IEC standards 61641 and 61439 – for internal arc protection. The company also built separate free-standing panels for the VSDs from 250 to 500kW, to facilitate better heat dissipation. For the same reason, the four soft starters were also supplied in their own panels.
Ten distribution boards were locally manufactured for the project, built according to SANS10142. These supply 230 to 400 V currents to lighting and small power applications at the plant.
“Another aspect of our supply package was three 2000 kVA transformers, to step power down from 11 kV to 550 V,” says Govender. “These copper wound, oil cooled units were also manufactured by Zest WEG locally, to SANS780 specifications. We also built a smaller transformer for lighting and small power.”
An important component of the plant was the emergency backup diesel generator, also designed and engineered by Zest WEG. This 550 V containerised unit is prime rated at 1250 kVA, and was delivered with a 12 000 litre diesel storage tank.
“The confidence of our design and engineering expertise allows us to offer this generator with a 12 month warranty – or 250 hours – from the factory acceptance test,” he says.
He emphasises the value to the customer of having easy access to the sales and technical support in Zest WEG’s Rustenburg branch. The branch, he says, is staffed to respond to queries on the full range of the company’s equipment – drawing on the skills of specialists within Zest WEG wherever necessary.
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