Demag used at cogeneration plant

With a required lifting height of 119m, crane operator Klaus Kellner fully exploited the allowable capacity of his Demag AC 500-8 crane.

“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 19t at this height—otherwise we would have had to use a larger and thus more expensive 700t or even 750t crane,” said Sven Bauer, general manager of technology at AKM. Its compact design was another reason behind the choice of this machine.

For the task at hand, the AKM team equipped the Demag crane with a 47m main boom and a 72m luffing jib in the SSL 60° configuration with 180t 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 manoeuvre 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,” said Kellner.

It was also important not to give away a single centimetre when it came to the lifting tackle. For this reason, AKM had a customised 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,” said Bauer.

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,” said Kellner. “We hooked up the spreader, raised the liner to the required height of 119m 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 20cm 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,” Kellner said.