German crane contractor Ley-Krane chose a 90 tonne capacity Liebherr LTM 1090-4.1 wheeled mobile telescopic crane for a project to install a sluice gate on a dam near Cologne.
The installation posed a number of challenges. First, the gate had to be reinstalled underwater, at a depth of 20 metres – around half the height of the dam. Second, the gross load of around 11 tonnes had to be handled with half the available outrigger spread due to the narrow area available on top of the dam. Third, there was a clearance of just two millimetres between the sluice gate and the vertical rails mounted on the dam wall.
Despite these challenges, however, the sluice gate (measuring more than four metres) was positioned on the dam wall without any problems and let down into the water. The job demanded a high level of precision from the crane and its operator and the underwater installation work was monitored by divers.
The Aggertal dam is 50 km east of Cologne and the work follows removal of the submersible sluice gate a year ago and its subsequent refurbishment.