Page 11 - Contractors World - International Vol 3 No 7

Page 11
Contractors World - InternationaVol 3 No 7
Our Terex AC 350/6 proved to be the ideal machine for
this lift,” says project manager, Steffen Zimpel. On one hand,
the crane’s performance characteristics were perfect for the
technical requirements related to the load’s weight and the
required reach; while, on the other, the company was already
familiar with the AC350/6’s manoeuvrability and flexibility.
These last two characteristics were needed in order for the
assignment to be cost effective, as the crane would have to change
locations four times at the site and would also have to be reconfigured three times.
Despite these inevitable complications, we were able to come up with a quote that was 40% more cost effective
than the alternative that was being considered, which was to use a helicopter.”
Tandem lifts with just the right touch
The company’s competitive quote also relied on the fact that the two cranes were able to travel by themselves to the site
accompanied by an escort vehicle, as well as the advantage that only two ballast trucks were required in addition to the
three trucks used to transport the required lattice sections.
Once on site, it took the four person Lange team six hours to set up the AC 350/6 and configure it for the assignment:
An extended main boom length of 22.7 meters and a 60 meter fly jib allowed the crane, which carried 116.7 tonnes of
counterweight, to reach the required working radius of 63 meters. Finally, in order to make it possible for the heavy
machines to travel and work on the unpaved ground at the site, all access roads and working areas were stabilized with
concrete slabs.
Once these preparations were done, the team was ready to take on the challenging lift. First, one of the team
members attached the AC350/6 slinging gear to the upper end of the lattice tower at a height of 32 meters. Next, crane
operator Michael Berger placed the tower under a slight pre load by lifting it with utmost precision while carefully
monitoring it with the load moment indicator. Once in
position, the mechanics used their cutting torches to separate
the tower from the foundation. “That was the most critical
moment: If the pre load had been too small or too big, the
tower could have slipped away or swung uncontrollably,
putting the mechanics’ lives at risk,” reports project manager
Zimpel.
There was also the risk that a sudden strong gust of wind
would have had dire consequences.
Once the tower was disconnected from the foundation,
the AC 350/6 lifted it and swung it at a radius of 63 m clearing
the tracks towards an open area on the opposite side of the
embankment, where the AC 80 was waiting – set up with a
full counterweight of 18 tonnes and a fully extended 50 meter
boom.
The Lange team members attached the lower end of the
lattice tower to the AC 80 so that the AC 350/6 would be able
to put it down, intact, in a horizontal position in tandem with
the AC 80. The team repeated the same process four times
and required less than two hours for each complete cycle.
This made it possible to successfully complete the entire
project in three and a half days despite a one day delay caused
by the unfavourable weather conditions on the first day.
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Once held in position, the mechanics used their cutting torches
to separate the tower from the foundation.