The Zest WEG Group has commissioned a range of equipment at Boteti Mining’s AK06 opencast diamond mining project in Botswana in record time, in execution of a contract awarded by EPCM contractor DRA. The electrical equipment was supplied in the form of a group package solution and was completed six weeks ahead of schedule on this fast-track diamond mining project located near the Orapa and Letlhakane mines.
Boteti Mining is 100% owned by Lucara Diamond Corp, a Canadian company. Lucara’s US$ 130 million Boteti AK06 project has seen the construction of a 2.5 Mtpa processing plant that will be upgraded to 4 Mtpa after four years.
“The integrated solutions we provided were custom designed for the project and our teams were closely involved in the application engineering process with DRA,” Zest WEG Group’s David Claassen says. “We harnessed the synergies between the technical products offered by the Zest WEG Group to craft a solution that guaranteed critical power to the plant at all times.”
The contract included the supply of a medium voltage (MV) mill package comprising a 4 MW 3.3 kV squirrel cage machine complete with phase shift transformer and 12 pulse MVW01 variable speed drive (VSD). Claassen comments that one of the main benefits of this application is the 99% efficiency on the VSD achieved by using high voltage IGBTs. The VSD technology is also very reliable and uses long life components. In addition, the user-friendly VSD technology allows for programming and operation by staff with noirmal electrical qualifications. Specialised knowledge is not a prerequisite. WEG also designed the system for ease of maintenance, since plant downtime is critical. A key design factor is the power arms which are easily removed and replaceable within five minutes.
WEG has developed a frozen charge protection specific to mill applications, where the torque and angular rotation of the mill is monitored, allowing for the detection of frozen charges in the mill. In this event, the mill trips and alerts the operator before any damage can occur.
“We delivered the entire mill package earlier than scheduled as a result of good project management, WEG, our Group’s holding company, also cleared manufacturing capacity to ensure the units were completed in good time,” comments Claassen.
The greater contract included supply of nine miniature substations incorporating Lucy Ring Main Units (RMUs), which are solely distributed by the Zest WEG Group. The mini-subs range from 200 to 1250 kVA, with voltages of 11 kV/550/420 VAC. Four fully extensible Lucy RMUs were also supplied as stand-alone outdoor units. The Lucy Sabre range comes standard in an IP54 configuration and is a very robust unit suitable for mining applications and outdoor use.
“Mini-subs have not been a part of our traditional scope of supply, but they were suitable in this application, owing to their synergy with the Lucy RMUs, the interchangeability of spare parts between the RMUs and the commonality of relays and programmes,” Claassen says.
The Zest WEG Group also supplied all low voltage (LV) electric motors and VSDs. All free-standing VSD panels were application designed, built, tested and commissioned by the Zest WEG Group, which also undertook and guaranteed the heating and ventilation calculations critical for the long term operational requirements. The LV motors were the latest generation three phase W22 IE2 units, which conform to the efficiency specification IEC 600343-30. As standard, these motors are IE2, IP66 with Class H installation. As with the MV drives, interfacing of the LV VSD’s was achieved using DeviceNet.
In addition, a standby power generator plant was supplied to AK06, including two 650 kVA containerised generators with full synchronisation to the mains, designed by Zest WEG Group company, IMS Cape. This was a non-standard and complex application whereby the generators were synchronised with two separate incomers and a bus coupler. This entire control system was designed and implemented by IMS cape.
“The supply of a combination of packages allowed us to offer our client the financial benefit of shared resources,” says Claassen, “but the main value lay in the technical assistance our team was able to provide as smaller, integrated team. Effectively, one company took responsibility for a host of commissioning and technical issues. This is a definite trend in the market that we’re pursuing and reflects our strategy to add value by integrating Zest WEG Group companies where products and services are complementary.”
The Boteti installation will be backed up from Zest WEG Group’s Rustenburg branch that covers the Botswana region and has a trained VSD technician on call 24/7. Further back-up is provided by a large compliment of technicians based at the Group’s headquarters in Johannesburg.
New developments While MV drive technology currently only goes up to 6 MW, Claassen says the release of higher power modules is planned. Research and development has also resulted in the launch of a brand new 2.2 – 6.6 kV soft starter with a current range from 180 – 360A.
“Another new product is the MVW01 medium voltage VSD, designed and built for synchronous machines, that includes excitation technology. Its present rating is 6 MW but the introduction of higher power ratings is planned.
The Zest WEG Group is an acknowledged leader in the supply of electric motors and drives, motor control panels, generator sets, energy solutions and ancillary products and services.
