New heavy-lift offshore crane

Paul Boughton

The new Liebherr offshore crane, type MTC 78000, marks the Liebherr group of companies' entry into a new market segment of heavy-lift cranes for offshore applications.

The MTC 78000 is one of the biggest offshore slewing cranes world-wide and was designed using conventional anti-friction bearing technology.

Featuring a maximum dynamic moment of 78 000 mt the MTC 78000 is the most powerful machine within the extensive range of cranes and material handling machines offered by the Liebherr group of companies. Four units of the new heavy-lift crane have already been ordered to date.

The MTC 78000 achieves a maximum lifting capacity of 1600 t at up to 35 m radius. This corresponds to a maximum dynamic moment of 78 000 mt, the crane still being able to slew over 360°. At a maximum radius of 74 m for the main hoist the crane achieves a lifting capacity of almost 530 t. The boom length of the cranes currently ordered is 87 m. In addition to the main hoist, the MTC 78000 offers two auxiliary hoists with lifting capacities of up to 500 t and 50 t respectively.

The dead weight of the new heavy-lift crane is 1420 t without the base column which weighs approximately another 300 t - depending on its design.

The size of the MTC 78000, which is derived from customer requirements, represents a new dimension in product development for Liebherr. Thereby, the crane's design is characterized by state-of-the-art drive technology. The drive concept is based on an electro-hydraulic drive with 8 x 500 kW or 4 MW power. The two main winches offer a line pull of 500 kN (50 t) with a rope diameter of 48 mm.

As the crane is mainly intended for application on mobile installations, the minimization of its dead weight was one of the main design requirements. In order to fulfil this requirement the supporting steel structure is made exclusively of high-strength fine grained steel with a yield strength of 690 N/mm2.

High safety standards are among the most important criteria to be fulfilled during the development of the new offshore crane. The standard equipment of the MTC 78000 features the proven Litronic control system with integrated display of load and radius as well as automatic load moment limitation. This is completed by special overload protections which are either activated electronically (AOPS "automatic overload protection system") or manually (MOPS "manual overload protection system"). The crane's auxiliary hoist is fitted with a constant tension system exerting a tensile force on the hoist rope in case of significant wave height, thus ensuring that the hook follows the moving load.

Two of the ordered MTC 78000 units will be used as heavy-lift cranes for the overhaul and/or renewal of existing offshore platforms. Their main field of application is the assembly and disassembly of main components such as drilling derrick, accommodation module or various production modules. The cranes are also used for converting platforms from oil to gas production or vice versa and, therefore, they are mounted on a crane ship specially designed for these jobs. Approximately 300 of these ships specially designed for crane applications are in operation throughout the world. The design of the ships fulfils the requirements derived from the crane specification.

Liebherr shall deliver the remaining two MTC 78000 units currently on order for applications on jack-up barges for assembly of wind power stations of the 5 megawatt class. The heavy-lift applications include the installation of Tripod foundations weighing up to 1,400 t as well as the assembly of single components with a dead weight of up to 500 t up to a height of 120 m above sea level or 106 m above deck.

Liebherr-Werk Nenzing GmbH is based in Nenzing, Austria.

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