Through Wilbert’s own rental business, the company always has an open ear for its customers’ requirements. Thanks to a flat management organisation and a leadership that has a life-long association with the tower crane business, trends of the changing market are discovered at an early stage and quickly transposed into new products.

Franz RudolfWilbert, manager, says: “When riding the economic storms it is not the time to decline fabrication cost by selling an old fashioned technique. It is more than ever a time to develop a new market by pushing the limits of tower crane design and application and, of course, you must be fast in catching the market chance with the new products you may have just as an idea in your head.”

Recent projects and new crane types on the drawing board are a good example of how innovative crane designs developed at the new Wilbert plant in Waldlaubersheim, Germany change tower crane application.

Light recovery crane
As a crane rental specialist for high-rise construction projects, Wilbert collected fundamental experiences in bringing down cranes from a topped-out high building. Up to now, for this kind of work the A30 recovery crane, originally manufactured by Wolffkran in 1995 for a Singapore project, has been used. The lightweight roof-mounted crane can handle 6t up to 5m and 1.25t at 25m radius. Besides other unique self-rigging devices, the boom can be extended by inserting additional boom sections when it is raised in a steep position. The heaviest module of the crane is the 220kg central element with slewing ring.

The hoisting winch can store 600m of rope. Thanks to the cruciform pedestal, the A30 can be attached to any support beam spreading its load on the roof or coupled with standard tower sections in order to gain extra height.

Wilbert has now redesigned this crane to give greater hoisting speed and allow different crane movements at the same time. The original electro-hydraulic drive has been replaced by frequency regulated drives. This has the additional benefit of eliminating any risk of hydraulic oil leak.

Multi-purpose luffer
For bringing down a tower crane in the 400t class, this equipment is simply too small. Wilbert is working on closing the missing link between the capabilities of the A30 and the demands of dismantling larger capacity tower cranes by developing theWT175L e.tronic. Wilbert says that this crane is the first in Europe in this completely new multi-functional recovery crane class.

Although this luffing jib crane is still on the drawing board, its main design criteria has already been unveiled by Günter Kronewitter, authorised officer of theWilbert sales department: “This medium sized luffer will be the first tower crane adapting many features of modern mobile cranes, especially the intensive use of high-strength fine grained steel, reducing the deadweight not only of the movable boom but as well of the complete structure.

“TheWT175L e.tronic can be stripped down to modules not exceeding 1.5t, adequate to be handled easily by our A30 recovery crane. With a 24m-long boom 15t can be lifted at a radius of 10m. On a comparable conventional luffing jib tower crane the heaviest erection unit weights would be at least 7t to10t,” says Kronewitter.

TheWT175L upper can be used as either a roof-mounted pedestal crane or be installed on a standard 2 x 2m Wilbert tower system. Adding 6m sections can extend the jib. Wilbert is targeting not only extremely high building sites, but also construction sites where there is limited access for mobile cranes during erection.

The compact machinery deck of the WT175L e.tronic will provide a counterweight radius of just 4m. To allow for different rigging conditions, the steel plate counterweights can be installed piece-by-piece, or the hoisting winch can be used to raise the complete filled ballast frame of 18.6t in a single lift by the crane itself. The A-frame and boom are manufactured from ultra-high strength steel tubes, leading to a significant weight reduction. Boom intersections, for example, weigh just 480kg.

Cooling tower specialist
At the high capacity end, Wilbert is changing the crane philosophy of power station construction by introducing its modular Heavy Lifter line. Since September 2009, the prototype has been working successfully at a coal power plant in Hamm, Germany. The new crane was configured as aWT 905L e.tronic, with a 90m free standing tower and 60m boom. The maximum lifting capacity in three fall operation mode is 48t. A second unit will be erected at the site in mid-2010.

A much bigger version of the Heavy Lifter line was undergoing testing as this article was written, and is due to be rigged in Karlsruhe, Germany for the construction of a new 912MW coal power plant. In this case, the lifting capacity will be increased to 128t by using an eight fall line. At 42m outreach, the crane can lift 56t. The luffing jib tower crane is rigged as an 80.4m free travelling unit on a 12m wide and 7.98m high portal. It can cover a large erection area while construction material can be delivered to the cramped site under the crane’s portal.

Thanks to the modular design of the Heavy Lifter product line, the all new Wilbert WT 2405L e.tronic can use many components of the proven WT 905L e.tronic.

To raise the load moment, the counterweight radius is extended from 12m to 13.20m by adding an intersection unit to the machinery platform. This gives space for a second hoisting winch. By reeving one hoisting rope on both winches the drum capacity and hoisting speed is doubled, in order to allow multiple fall operation up to eight lines. With a shortened 42m heavy lift boom, 128t can be handled at 19m radius.

Wilbert says the new crane is unique to the European top-slewing luffing jib tower crane market. The firm believes it is competitive to crawler cranes for the main steel rigging work of boiler scaffolding in the 1,000MW size class. By combining two of itsWT 2405L e.tronic giants, as proposed for the new 900MW Mannheim power plant, it will be possible to raise the complete boiler house without large crawler cranes, which would not find enough space under the very restricted site conditions.

While each crane can lift the K-frames, columns and roof beams of the boiler scaffolding in front of itself, the remaining two sides, which need more outreach, will be served in a tandem lifting operation.

Besides the extension of the counterjib, the pendulum ballast of the WT 2405L e.tronic will be increased from 152t of theWT 905L e.tronic to 161t. The already massive A-frame will be raised by 4m thanks to the addition of an intersection unit.

Wider tower
Although the WT 2405L can be rigged in the same way as the WT 905L e.tronic on the Wilbert E33 standard mono-block tower system, above 70m free standing height a newly designed stronger tower system must be used.

The new E66 rigid tower system measures 6 x 6 x 11.9m. It can be split into web members and mast chords for easy transport. As on the E33, the tower sections will be connected by the proven method of using two large screws at each corner.

Wilbert is developing a jacking unit that will be installed at the inner side of the mast chords in order to jack the upper crane, supported by the 3.3 x 3.3 x 5m E33 mono-block tower system.

Günter Kronewitter says the E66 was not just developed with the Heavy Lifter product line in mind. “We are also seriously thinking of changing application conditions for tall free standing standard cranes. Expecting raising wind conditions due to global climatic changes will be essential to provide a strong tower system.”

Wilbert’s engineering department is working on a project where one of the new Heavy Lifter range will need to be erected to a free standing height of 130m. For such heights a combination of internal and external climbing systems will substantially reduce assist crane costs.

The conventional method of combining different tower sizes is to use adaptor frames. This means rigging crews have to work at extreme heights to install the upper crane. In the system proposed by Wilbert, the tower crane will be rigged on standard mast sections and raised by the climbing frame to the maximum free standing height. The E66 outer tower, surrounding the standard tower, will be installed by the crane itself. Then the crane will climb inside the outer tower, in the same way that an internally climbing tower climbs the lift shaft of a building under construction.

The E66 tower system, in the non-climbing version, will be used for the first time by the WT 2405L e.tronic at the Karlsruhe power station in order to boost the free travelling tower height.

On rails
At Karlsruhe, a massive new travelling portal will be installed for the first time. The weight of the fully loaded crane and the ground bearing mean that four bogies need to be used at each portal corner. To speed up erection, many of the portal components are connected by slug bolts. During rigging, each bogie support pair will be connected by special adjustable frames with two E33 tower sections spreading the rail gauge. The tower sections keep the bogies in a safe upright position while the portal side framework is fitted. Once this is done, the top beams stabilise the structure.

Cooling towers are a big challenge on power station sites, due to their height, their size and, worst of all, the hyperbolic shape of the concrete shell. It is always a problem to find a way to climb a tall tower crane down through the narrowest section of the structure after topping-out.

Wilbert’s engineering department worked out a sophisticated crane concept in close cooperation with its customers. The crane would need to be erected to a free standing height of 170–180m. This could only be realized by using a combination of a standard tower system with special large base tower sections, like the all-new E66.

Instead of a truly free standing tower, a conventional rope guy system could be used, leading vertically from the crane tower to the foundation of the cooling tower. However the guy ropes, which have to be ordered for every single project to cope with the individual site conditions, are expensive as well.

Together with the construction company of the 179m-high cooling tower at the new 1,100MW Datteln coal power plant in Germany, Wilbert decided to use two sets of four anchor cables, each made up of strands leading to a cross frame inserted in the standard

TV20.4 tower system on two levels, one at 110m and one at 155m, to reach the required 195m under hook height. At the foundation the strands were pulled taut by hydraulic jacks.

Thanks to the combination of 2.4 x 2.4m and 2 x 2m tower systems in the initial construction phase, the chosen WilbertWT300 e.tronic was used free standing up to 100m under hook height. The flat top design turned out to be a benefit for the necessary boom length change during the construction period. At an under hook height of 63m, the 70m boom required for the construction of the cooling tower basement was shortened to 60m with the assistance of a truck crane.

After topping-out, a self-dismantling device was used in order to shorten the boom to just 25m so that the crane could climb down inside the cooling tower. At the crane’s hook, a balanced three armed lever cradle was lifted under the trolley. The cradle raised itself up as a kind of derrick over the boom section that had to be dismantled. As soon as the boom section was fixed with four slings it could be unbolted from the remaining boom.

When the hook is lowered the cradle will swing downwards into a well balanced position due to the counterweight at the rear of the cradle. Then the boom section hanging at the cradle is safely lowered by the crane’s own hoist rope. As there is no complex reeving of erection ropes and the topless crane design is missing pendants holding the boom, the system works very fast.

In just two days the saddle boom had been shortened from 60m to 25m and all counterweight had been removed to keep the tower crane in balance. Wilbert will use the same crane concept for two further cooling towers under construction.