During the construction of the massive 950MW brown coal power plant at Niederaussem near Cologne, the crane rental company Franz Bracht and the Leichlingen depot of industrial rigging specialist Scholpp Montage joined forces to install three 90t cooling vessels up to 26m long and 4.5m diameter under tricky site conditions.

The two companies cooperated closely on the planning and execution of the project. With little space to manoeuvre on site, everything had to be phased in precisely with the overall construction programme. The vessels had to be lifted up to a height of 38m and then shifted sideways, up to a maximum 80m, to reach their final installation point inside the concrete structure of the new power station.

The simple solution of lifting the vessels through roof openings was not available because the building was enclosed by a roof mounted Wolff 320B tower crane moving on top. Furthermore, it would take a crane with a load moment of at least 8,100tm, so it was not going to be an economically sound solution. The only answer was to lift the vessels through a wall opening and a skid it inside the building.

To cope with the low head room and the strict floor load restrictions of 1t/m2, project manager Helmut Börnert of Scholpp Montage decided to install a Scholpp TG 360 hydraulic gantry on a purpose built 80m-long track runway. The gantry had to be disassembled and stripped down into parts small enough to be handled inside the building by a low-weight forklift with a lifting boom. It took Scholpp three days to install all the required equipment, assisted by a 60t capacity Liebherr LTM 1060/2 all-terrain, on hire from Bracht, and a forklift.

The plan called for the vessels to be laid in slings so that they could be installed by two pairs of hydraulic lift towers at just the right height within the overall structure. Each of the pair of TG 360 towers was connected by a lifting beam which in turn was connected by additional ropes at the bases over a distance of 20m to ensure parallel movement of all four legs. Furthermore, special measuring devices were used during the operation to supervise the synchronised movement.

To minimise generated ground pressure, Bracht’s project manager Heinz-Gert Kessel decided to use two telescopic boom cranes in the 500t to 600t capacity class, rigged on 2.5m by 5m pontoons under each outrigger pad.

Restricted space, crossing underground installations and a cellar just in front of the wall opening where the vessel had to be lifted made crane installation anything but a straight forward job. In a CAD examination carried out by Bracht a solution was found: the 50m-long low bed transport unit delivering each vessel could move between both cranes lifting the load in a tandem operation at 17.5m radius and 15m radius, still guaranteeing the required safety factor of 10% extra capacity for each crane, as per German DIN regulations.

The lift planners had to take into account a change in the centre of gravity when the load transferred from the cranes to the jacking system. Bracht’s engineering department used its computer simulation programme to calculate the optimum point for slinging the vessel, corresponding to the changing capacity of the cranes during the different lifting stages.

On the day that the cooling vesses were delivered to the site, Bracht brought in a Demag AC 650 rigged with 120t ballast and 60m main boom and a Demag AC 1600 rigged with 98t ballast, 50m main boom, and 8m jib extension, standing on the opposite side. All three vessels were safely installed and fixed on foundations within a day and a half, to the full satisfaction of the customer.

Kessel says that for Bracht, jobs like this one with a high engineering input are becoming more and more important to the company, as are strategic alliances between specialised service providers. In this way the company extends its business from not only supplying cranes and other lifting equipment but also offering bare engineering consultancy services such as feasibility studies and risk management.