Described is a method for taking up an elongate object from a ground surface using a hoisting yoke coupled to a lifting means. A beam-like support frame of the hoisting yoke extends in a longitudinal direction of the object and slings provided at end parts of the support frame take up the object. The object is taken up in a sling by holding a first outer end of a sling with a first holding means provided at an end part of the support frame and letting it hang down from the first holding means to a position in the vicinity of the object; paying out a messenger line from the end part using a messenger line winch, feeding it under the object and coupling it to a second outer end of the sling hanging from the first holding means; taking in the messenger line so that the sling is carried under the object and to the relevant end part; and coupling the second outer end of the sling to a second holding means provided at the end part, thus forming one of the slings for the object.

Assembling a jacket structure that includes two or more legs and crossing braces extending between the legs and forming cross joints. A first component of the jacket structure includes two or more legs and brace structures. Each brace structure includes a first brace and a second brace, sections of the first and second braces being at one end attached to the first leg at respective first and second leg-brace joints. The brace structure and the first leg form an A-frame. A second component of the jacket structure that includes a second set of brace structures and a second part of the brace cross node is further provided. The first component of the jacket structure is mounted to the second component of the jacket structure by joining the first and second parts of the brace cross nodes to form full brace cross nodes.

A cassette assembly is disclosed attachable to an end portion of a waterborne vessel and including a cassette section to bear against an external structure in use. The cassette section is movable relative to the vessel in a direction towards an opposite end of the vessel. A resilient buffer system counters movement of the cassette section when the vessel is moved towards the external structure, wherein the resilient buffer system includes a buffer including a plurality of resiliently compressible elements arranged in series. A waterborne vessel includes a receiving portion for receiving the cassette assembly, and can be used to service a water-accessible structure such as a wind turbine.

A cassette assembly is disclosed attachable to an end portion of a waterborne vessel including a cassette section to bear against an external structure in use. The cassette section is movable relative to the vessel in a direction towards an opposite end of the vessel. A resilient buffer system counters movement of the cassette section when the vessel is moved towards the external structure, wherein the resilient buffer system includes a fluid-operated buffer. A waterborne vessel includes a receiving portion for receiving the cassette assembly, and can be used to service a water-accessible structure such as a wind turbine.

Assembly of a suction pile and a pump system temporary connected by convenient means to the suction space of the suction pile, wherein the pump system bears onto the top of the upward extending suction pile. Between suction pile and pump system a quick connector is operative comprising a pin operated by actuator means of the pump system to move between a releasing retracted and locking extended position. It has one or more of: a pump interface remote from the protective frame; an auxiliary support frame; a hinged lift appliance; a level indicator; a docking cone designed to penetrate the suction pile interface means.

Device for erecting a wind turbine with a floating foundation, a tower arranged on the floating foundation and two booms extending from the tower, with an energy conversion unit that is arranged in each case at a free end of a boom and has a rotor, characterized by an auxiliary tower with a rope system, connected to a winch, for lifting the energy conversion units that are connected by the booms to the tower of the wind turbine.

A method of ballasting a vessel comprises positioning a vessel having a first draft adjacent to or underneath an offshore installation. The vessel has at least one ballasting tank and at least one port in fluid communication with the at least one ballasting tank. The at least one ballasting tank is arranged to selectively adjust the flow of ballast water in and out of the at least one ballasting tank. The method comprises pushing down from the offshore installation on the vessel to increase the draft of the vessel from the first draft to a second draft. The method further comprises opening the at least one port when the vessel is at the second draft and the at least one port is below a waterline. The method also comprises filling at least part of the at least one ballasting tank.

A wind turbine includes tower, a nacelle mounted at the top of the tower, a rotor mounted rotatable relatively to the nacelle about a rotation axis and includes at least one blade, wherein the blade, when rotating about the rotation axis, is configured to span a swept area, and a control device which is configured to control an actuator so as to move the swept area.

The invention relates to a method of installing rotor blades (5) on an offshore wind turbine (2). The method comprises arranging a tower (1) of the wind turbine at an offshore installation site. Then a first end (6) of a tensioner (7) is fastened to at least one of the tower (1), the nacelle (3), and the hub (4) at a distance above sea level. A second end (8) of the tensioner is fastened to a holding device (9,15) floating in the sea at a distance from the tower. Then a pulling force (F) is applied to the tensioner from the holding device at least part of the time while the rotor blades are being mounted to the hub, so that oscillations (M) of the tower due to external forces are dampened during installation of the rotor blades.

A sensor system for a floating wind turbine is provided. The sensor system includes a wind sensor configured to provide a wind sensor signal indicative of a wind flow; and a processing unit configured to receive the wind sensor signal and to determine, based on the wind sensor signal, information indicative of a spatial arrangement of a floating base of the floating wind turbine relative to an environment of the floating wind turbine. Furthermore, a corresponding floating wind turbine and method of operating a floating wind turbine are provided.