Dam job for Fanger
By Alex Dahm13 July 2021
Working high up in the Swiss Alps it is challenge enough just to get there, let alone being able to then get the job done when you arrive.
Adding the fact that the crane had to work from the top of a concrete dam that from some angles looked barely wider than its wheel track, further added to the challenge. Swiss construction, crane and transport company Fanger chose its 160 tonne capacity Demag AC 160-5 for the high altitude task.
To get up to the Zervreila dam jobsite in the Swiss canton of Grisons, the five axle crane had to negotiate narrow twisting roads and tunnels where even in a car it demands your full attention not to put a wheel wrong.
Josef Waser, Fanger head of cranes and transport, explained, “That’s why we decided to use our Demag AC 160-5 for this job. With its extremely compact design and outstanding manoeuvrability, it was perfectly suited for the mission – both in terms of getting to the dam and of taking care of the corresponding work.”
The crane’s job was to lower construction materials 130 metres down the face of the concrete dam.
For a start, however, the crane had to be prepared for its ascent into the mountains. Its weight had to be reduced to less than 60 tonnes by removing the counterweight baseplate. That was loaded along with the required counterweight slabs and accessories onto two trucks that travelled with the crane to the jobsite. A signalperson was employed to ensure the convoy’s smooth passage.
Tight turns and tunnels along the way demanded absolute precision, “Sometimes we only had a few centimetres between the crane and the tunnel walls, meaning that our operator was threading the machine through the eye of the needle, so to speak,” explained Josef Waser.
The crane was set up in the centre of the dam where there was six metres between the guardrails. Waser commented, “We couldn’t extend the outriggers all the way to the edge of the dam due to safety reasons, so we were limited to an actual width of 5.4 metres after consulting with the responsible engineer.”
Fanger’s AC 160-5 was fitted with the IC‑1 Plus control system which allowed the outrigger spread to be maximised in the available space. Its minimum spread is 5.3 metres. Once set up the crane lowered the construction materials and equipment 130 metres down the face of the dam using its 9.9 tonne line pull main hoist winch carrying 330 metres of rope.
Items lowered included components of a suction excavator, a pontoon, pipes, plus other material, in loads weighing up to 7.8 tonnes. the crane was set with 32.9 metre main boom and 46 tonnes of counterweight. Waser commented, “Due to the dam’s convex contour, we had to work with a radius of up to 27.5 meters. However, that wasn’t a problem whatsoever for our Demag AC 160-5.”
The crane operator completed all the required lifts by himself on one day, Demag said.
The concrete dam on the Zervreilasee in the Swiss Alps is 150 metres high and was built in 1957. Fanger’s Demag AC 160-5 lowered construction materials 130 metres from the top of the dam in the middle.