Abstract: A method for installation of a transition piece on a monopile foundation of an offshore wind turbine along a common axis extending in a longitudinal direction is performed from a floating installation vessel. Buffer elements are arranged around an inner circumference of the transition piece and/or the monopile structure. The transition piece is lifted and lowered onto the monopile structure by use of a crane, and landed onto the monopile structure through the use of the buffer elements. A number of hydraulic cylinder jacks for circumferential alignment of bolt holes are provided in the transition piece and monopile, and alignment tools are used for alignment of the flanges provided on each of the transition piece and the monopile. The transition piece is lifted and the buffer elements are removed after which the transition piece is lowered onto the monopile, and bolts are tensioned fix the transition piece to the monopile.

Abstract: A method for offshore overboarding a structure on a vessel for subsequent lowering the structure to the sea floor, is using a crane (13) to lift the structure at its storage place on a deck of the vessel and move it by means of the crane to a position free of the vessel before lowering it into the sea. During at least a part of the overboarding movement of the structure (1), the structure (1) is forced to follow a track (2) along the deck of the vessel. Two apparatus for performing the method are also presented.

Abstract: A method for offshore overboarding a structure on a vessel for subsequent lowering the structure to the sea floor, is using a crane (13) to lift the structure at its storage place on a deck of the vessel and move it by means of the crane to a position free of the vessel before lowering it into the sea. During at least a part of the overboarding movement of the structure (1), the structure (1) is forced to follow a track (2) along the deck of the vessel. Two apparatus for performing the method are also presented.