September 11 - Johannesburg headquartered heavy lift specialist Vanguard used its heavy lift strand jacking system to install a conveyor gantry 30 m above ground level, in Namibia.
The initial request from the client was to complete the project using large cranes. Vanguard devised an alternative solution using strand jacks, explained Vanguard's Roger Rousseau: "While strand jacks have been in use globally for some time, their versatility and benefits are not well known in the field of steel construction in southern Africa and therefore are often unobserved."
Rousseau said the solution allowed the client to assemble each gantry section on the ground, improving the safety and speed of the works. "It was also more economical, as the cost of deploying large cranes for an extended period is very high and uncompromising in the face of any unforeseen delays in schedule," he added.
Three units weighing 115 tonnes each, plus a final 150-tonne piece, were safely installed using the Vanguard system. The individual gantry sections measured 50.4 m in length.
Each strand jack had a lifting capacity of 70 tonnes. In total, four jacks were used to lift each load. The conveyor gantry sections were lifted in turn using high-tensile steel cables, known as strands.
The four jacks operated in unison using IT software, working at a stroke distance of roughly 0.5 m.
Vanguard also constructed the lattice towers and header beams in which the strand jacks operated. Two platforms - each carrying two strand jacks -were individually placed on a pair of headers beams. This arrangement allowed for the lateral movement of the load to the required position.
"Lifting each section of the gantry required us to build our structure, conduct the lift, and break it down so that it could be moved to where the next gantry section needed to be lifted and placed," he said.
The strand jacking system was shipped from Vanguard's Johannesburg yard to the project site in Namibia.