Lifting at limit!

Demag AC 500-8 all terrain crane lifts chimney liner at Munich cogeneration plant

With this job, literally every centimeter counted: on behalf of Munich City Utilities, AKM Autokranvermietung lifted a chimney liner weighing 19 t into the existing chimney of a cogeneration plant in the Freimann district of Munich. With a required lifting height of 119 m, crane operator Klaus Kellner fully exploited the allowable capacity of his Demag AC 500-8 crane.

The decision in favor of the Demag AC 500-8 crane for this application was well-considered: “Of all the eight-axle cranes available, the Demag AC 500-8 is the only crane that can safely handle the required loads of up to 19 t at this height – otherwise we would have had to use a larger and thus more expensive 700 t or even 750 t crane,” explains Sven Bauer, General Manager of Technology at AKM.

But there was also another argument in favor of the AC 500-8: Due to its compact design – not only compared to a next-larger crane with nine axles, but also to other eight-axle cranes – it could cope much better with the cramped conditions on the construction site.

Every centimeter counts

For the task at hand, the AKM team had equipped the Demag crane with a 47-m main boom and a 72-m luffing jib in the SSL 60° configuration with 180 t of counterweight. This configuration was calculated from the factors lifting height and weight: “It was clear to us that we didn't have much room for manoeuver with the lifts. That's why we also placed bog mats under the outriggers of the AC 500-8 in order to raise the level of the crane and thus gain a little more height,” reports AKM crane operator Klaus Kellner. And it was also important not to give away a single centimeter when it came to the lifting tackle. For this reason, AKM had a customized spreader made of highly tempered steel built especially for this application, in which the holes to accommodate the load slings were precisely matched to the liner segments. “This ensured that we could really go to the maximum allowable hook height,” explains Sven Bauer.

Precision work at a height of 119 meters

In spite of all these measures and the meticulous preparation, lifting the chimney liner segments remained a difficult custom job that demanded the utmost precision from the crane operator and his equipment. “I was already aware that it would be very tight,” Klaus Kellner makes clear, and goes on to describe the lift with astonishing composure: “We hooked up the spreader, raised the liner to the required height of 119 m and then slewed it over the chimney.”

While lowering the liner segments, he was instructed by a colleague standing on the chimney because of lack of visibility. The challenge: The bulky liner segments had to be lifted over the railing at the top of the chimney without bumping into it – with just 20 cm clearance between load and railing. “However, I was able to rely one hundred percent on my signalman and the precise operability of the AC 500-8,” emphasizes Klaus Kellner, who then admits that this operation was something special: “You don't see a lift like that every day – especially at this height and with this weight. But with the AC 500-8 it was no problem. And yes: I was quite delighted about my crane once again,” he sums up with satisfaction.