ON THE GROUND
documentation, temp import load (concrete beams), and we knew their from Rustenburg to Keetmanshoop,
taxes, temp export documentation, size and weight. In the simulation, we specifically for this project. This crane
documentation for the crane, then attached the load (scale replicate) was used to dismantle an 80m-high
documentation for the trucks, and to the hook of the crane and told the tower crane and re-erect it on top of
correct and detailed description of the software what we wanted to do — how the dam wall. Smith explains that the
load on each truck. This is a process high we want to lift the load and how far tower crane was placed on the river
that can take anywhere from one hour away we wanted to place it,” he adds. side of the dam wall and had supported
to a couple of days. By making use of
construction work on both the wet side
clearing agents, they tend to overcome software would then consider all most of these obstacles — they possible configurations to provide assist with doing pre-clearances and the user with suitable options. From dismantling: “As the building of the
preparing the border control staff for there, it is up to the user to select wall progressed, the usability of the
the arrival of the machine.
and on top of the dam wall.
Smith describes the process of
the most suitable solution from those crane reduced proportionally, and it
The crane’s main function was to presented. Further considerations are had to be lifted higher. We dismantled
install trash racks and roof beams for things like congestion on the site, the the crane on the river bed, and then
the inlet tower facing the water side ability to travel on site and manoeuvre re-erected it on top of the 60m-high
of the dam. Water enters the inlet the crane, the ability to build the crane dam wall. The 550t crane was used to
tower through the dam wall into the on site, all the while ensuring that the remove the parts and then place them
turbine room, where it generates client receives the most cost-effective on the dam wall. We had a second,
hydroelectricity. solution. Smith asserts that the aim is smaller crane on the wall, which was
The trash racks are essentially giant always to choose the simplest solution used to assemble the tower crane in its
filters placed in front of the water inlets with the fewest number of accessories. new position.”
to prevent any debris from entering the “The simple solution is easier to build system. These had to be installed by on site and is a big time-saver,” adds for dismantling the conveyor-belt
the crane that was perched on top of Smith. “Also, the fewer accessories you systems supplying concrete from
the dam wall. The trash racks eventually use, the fewer the trucks required to the batching plant to the dam wall.
stacked up to 60m in height. transport them, and this saving can be “These conveyer belts transported
passed directly to the client,” he says. wet concrete from the batching plant
While still inside the partially
The 550t crane was also responsible
completed inlet tower, complex rigging The 220t crane was then relocated to and lifting were required to position the the river or ‘dry’ side of the dam, where 22t concrete roof beams for the tower. it was used to dismantle two tower as well as their supporting tower,”
With the final four beams directly on cranes that had been deployed over explains Smith.
top of the crane, the crane had to be the four-year construction period. Smith re-positioned outside the tower, on a explains that removing a tower crane installed by means of two big cranes
narrow dam wall, and the beams lifted is a two- to three-day process. “In this operating in tandem so as to share the
up and over the tower walls to place case, these cranes had been stationary load, we opted to supply one big crane
the remaining four beams. for almost four years, thus the pins to carry out the dismantling, based
were rusted and corroded and difficult on the computerised rigging studies
were carried out to ensure a safe and to remove — which took extra time. that simulated the lift. The study was
successful lift of every beam. The You also need to be very careful which submitted to Salini Impregilo engineers
studies were personally performed by sections you loosen first, and how you and their safety department. The single-
Smith, using computer software that is remove it. The designer of the tower crane solution was cost-effective, with
purpose-built for the application. “The cranes gives very detailed procedures a significant cost saving for the client,”
software contains detailed models of on how to dismantle and how to build. comments Smith.
the cranes in our fleet. Apart from the If this procedure is not followed, then physical dimensions, it also contains the risk of the tower crane tipping over successful lifting solution, intensive
a vast database of the capacities and grows exponentially — the result is planning had to be carried out to
capabilities of the crane; in other words, normally a catastrophic failure of the overcome the logistical challenges
how high, how far, and how heavy the tower crane,” warns Smith. on site. Construction roads and steep
Several computerised rigging studies
crane can lift,” explains Smith. “For this
specific project we had details on the
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Smith further explains that the
FEBRUARY 2019
In addition, a 550t Terex Demag
AC500-2 mobile crane was transported
to the dam wall for use. In total, three
conveyer belt system were removed,
“Although these systems were
In conjunction with providing a
inclines can prove difficult for moving
equipment around — and vehicles 20m
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