Renewal at the wind farm - with one of the largest cranes in the world

From Markus van Appeldorn

The blue crane stretching up into the sky on the fields on the outskirts of Oberseifersdorf in the wind farm is a real monster. It measures 180 meters up to the top of its boom. A larger crane has probably never been used here before. But that's the kind of equipment you need when you're repowering, as is the case here in Oberseifersdorf. at the end of which there will be three new wind turbinesalmost twice as high as the existing ones here - up to 247 meters.

The blue engineering marvel bears the simple name "LR 11000" - where "L" stands for the manufacturer Liebherr and "R" for "crawler crane". This is because the machine does not stand on wheels, but on crawler tracks like a lignite excavator - two meters wide. Finally, the number "1000" at the back stands for the maximum weight that the crane can lift: 1,000 tons. For comparison: This is equivalent to the weight of ten large detached houses. It also weighs a good 1,000 tons. A simple description for a superlative piece of equipment. "It's one of the biggest of its kind in the world," says crane operator Paul. Only the crane also built by World market leader Liebherr LR 13000" for lifting loads of up to 3,000 tons.

"We have three such cranes," says Steffen Lehmann, head of the large crane department at Maxikraft, the company responsible for erecting the three new wind turbines, and: "There are no more than ten of them in Germany."

Transportation with 70 semitrailers

However, the loads that the "LR 11000" has to deal with at the Oberseifersdorf-Eckartsberg wind farm are child's play for the giant, a flyweight. "A rotor blade weighs 21 tons, the heaviest part is the rotor head at 81 tons," says crane operator Paul. But this is about something else - the hub height of the new wind turbines is 160 meters. Hardly any mobile crane in the world can manage that.

The delivery of the mega crane alone is a logistical feat - it is transported in individual parts on 70 articulated trucks. "We arrived here in the last week of April and spent about a week setting it up on the first new wind turbine mast," says the crane operator. And because there are three of the new giants in the wind farm, the team will have assembled and dismantled the blue giant three times by the end of the project. The first new wind giant has already been completed. The rotor head of the second is now waiting to be lifted into the air. There is a break on this day - it is too windy. "We can only work up to a maximum wind speed of nine meters per second," says the crane operator.

A gentle giant for the ground despite its weight

"The crane could, of course, travel from one wind turbine mast to the next on its crawlers," explains the crane operator - at walking speed. In reality, however, it is becoming increasingly rare for a crane to cover these distances at construction sites "on its own wheels". "You often need permission from the farmer who owns the land," says Paul. And as there may even be several of them, dismantling and reassembly are often faster than preparing for the crawler drive.

As with the first new wind turbine, a large area of gravel has been piled up in front of the second - this serves to cushion it. The crane itself then travels on its crawlers on two additional tracks made of wooden planks, on which it finally rests for its work. Once set up, the crane hardly needs any manpower. Paul takes turns with a colleague to operate it. The crane operator, who sits just a few meters above the ground, is instructed by radio by a team that positions itself at hub height to assemble the rotor head and finally the rotor blades.

Despite its enormous weight, the crawler crane exerts surprisingly little pressure on the ground - because its weight is distributed over a huge area. "A colleague once drove it through a corn field on a construction site after consulting with the farmer - after two weeks, the stalks were upright again," says Paul. And heavy crane manager Steffen Lehmann also knows: "When a crane like this drives over a field, it sinks less than a tractor." This would be completely different for a mobile crane, which usually has an axle load of twelve tons. Its weight would act on the ground via the comparatively tiny contact surface of the wheels.