Liebherr Delivers New Subsea Crane

On the premises of Liebherr in Rostock a single lift of the new RL-K 7500 subsea crane has taken place in the course of its loading for shipment to Asia. The lift was executed by four Liebherr cranes.

In the beginning of September, two LHM 600 mobile harbour cranes and two LG 1750 lattice boom mobile cranes lifted the subsea crane onto a transportation device. Since it was the first time that four cranes were involved in a single lift at the test stand in Rostock a lot of planning and preparation work was required. Only the assembly of the mobile cranes took approximately two days. Besides the crane’s dead weight of 665 tonnes a further challenge of the approximately 90 minutes lasting lift was the loosening of about 100 bolts on the slewing ring.

“With the RL-K 7500 Liebherr offers an innovative crane concept for subsea applications. The RL-K 7500 can be rated both as general purpose offshore crane and as heavy lift crane, being able to hoist loads weighing up to 300 t. It can thus be installed on board drill vessels and heavy lift vessels. The knuckle boom is designed for use in hazardous areas. The crane can additionally be equipped with an Arctic temperature package allowing for operation at temperatures down to -40 degrees Celsius,” the company said.

Liebherr thinks that the new subsea crane with knuckle boom represents a convenient solution for subsea operations. Together with the crane’s prototype the above mentioned RL-K 7500 is already the fourth model to be completed. It features impressive technical figures, being able to lift up to 300 t in the air and handle loads down to a water depth of 3,600 m. The maximum rope diameter is 82 mm, the maximum overturning moment of the crane is 75.000 kNm. Depending on customers’ specifications, the boom configuration allows for working radii of up to 50 m.

One vital advantage of the crane’s knuckle boom is that loads can be lowered to the water surface with a short rope length between crane boom head and water line. Furthermore, the crane is equipped with a number of hydraulic, electric and electronic features and functions, some of which were submitted for patent by Liebherr, e.g. Heavetronic, Pactronic and the innovative winch system.

The RL-K 7500 was scheduled for delivery mid-November from the pier of the Liebherr factory in Rostock. The RL-K 4200, another model of Liebherr’s series of knuckle boom cranes, will be delivered to Daewoo Shipbuilding & Marine Engineering Co. LTd. (DSME) together with the RL-K 7500. DSME plans to equip several of its ships with a set of Liebherr cranes consisting of one RL-K 7500 and three RL-K 4200.