The superstructure of a Liebherr LTR 11200 crawler crane has been mounted on an offshore jack-up barge for wind farm work.
Danish based ship owner DBB Jack-Up Services A/S worked with Liebherr on the mounting of the 1,200 tonne capacity LTR 11200 superstructure to a pedestal on its self-propelled jack-up barge the Wind. The superstructure’s slew ring is mounted to a specially designed pedestal/column that is integrated into the structure of the ship.
DBB has used Liebherr mobile cranes for service work on its land based wind power installations for a number of years. So when it needed a crane to service its offshore contracts it turned to Liebherr Ehingen for a solution. The result is the largest telescopic crane ever mounted on a barge.
DBB says that the advantage of a telescopic crane is its smaller space requirements compared to lattice boom units and the lower centre of gravity of the crane thanks to the fact that the boom can be completely retracted. These advantages make it possible for a substantial hook height to be achieved from a relatively small barge.
The LTR 11200 has been subject to a number of modifications for working at sea, these include: An electric motor in place of the usual diesel power unit, which eliminates the need to store fuel on deck, marine standard paint and coatings and marine protection treatment for the cranes electrics.
It took just a week for the crane to be installed on the barge at the Orskov shipyard in Frederikshavn, with the barge going straight to work on the Dutch OWEZ offshore wind farm in June. DBB says that since then telescopic crane/jack up barge concept has proved to be outstandingly successful.
Aarhus, Denmark based DBB Jack-Up Services was established in January 2008 as a subsidiary of Dansk Bjergning og Bugsering (DBB – Danish Salvage and Towing Company).
The LTR/LTM 11200 superstructure is a highly sophisticated piece of equipment, with an ultra high tensile telescopic boom with sophisticated boom pinning electronics. Mounting it to a rugged crawler cranes chassis was already a step away from the easier life of being mounted to a wheeled chassis which is always jacked and levelled before the boom is extended.
Placing it on sea going barge takes it to an even greater extreme, although given the fact that it is a jack up barge it will, one assumes be levelled and removed from the effects of waves before the boom is extended.
Corrosion protection will of course have been a major concern, however assuming that these challenges have been thoroughly overcome, the benefits of a telescopic crane that can quickly retract and stow itself when bad weather approaches and then be equally fast to get back into service when it clears is a major benefit.
There will be a fair few offshore operators watching this unit closely to see how well it works out.