January 19 - South African heavy lift and relocation specialist, Vanguard, has recently completed the installation of a semi-autogenous grinding (SAG) and ball mill for a renowned copper mine in the Democratic Republic of Congo.
Despite on-site challenges, including operational limitations, remote location and lack of on-site equipment, the job was completed in a minimum of two weeks with only four people on-site, says the company.
"The mills float on oil during production and sit on copper brass bushings. These bushings are particularly vulnerable to damage, thus requiring extreme caution during the installation process, especially as a replacement bushing would take months to arrive on-site," says Dane Zijlstra, project manager, Vanguard.
Vanguard decided to use two of its 70 tonne strand jacks with a 140 tonne lattice gantry system to position the SAG and ball mills, weighing 70 and 35 tonnes respectively. "The strand jacks afforded us the precision we required for the job. It allowed us to move the equipment almost a millimetre at a time, enabling us to correct any misalignments immediately," explains Zijlstra. The mills were lifted to a height of 10 metres and moved 25 metres forward into position.
"We positioned our rails before assembling the tower legs and beams. With the legs and beams constructed, we built the gantry system above the ball mill foundation. We then lifted the mill before moving it forward and placing it in its final position," says Zijlstra. As the same positioning procedure was followed for the SAG mill, Vanguard disassembled the lattice gantry and rebuilt it over the SAG mill foundation before completing the installation.
In contrast to large mobile cranes that are normally used for heavy installation projects such as this, the strand jacks feature two holding points, making them more stable in external conditions like wind and minimising any swaying movements. The strand jack and gantry system is also easily manoeuvrable. "Another benefit of the system was that it could be brought on-site in just three containers, which made the transportation arrangements for the client easier to handle," notes Zijlstra.