Motion compensated crane for use on a ship at sea

Abstract

Motion compensated crane (10) for use on a sea-going vessel (1) having a hull (2) with a designed waterline, the crane comprising a rotatable superstructure (12), a main jib (14) mounted to the superstructure and connected at an inner end to the superstructure, the main jib having a distal end remote from the inner end, a main jib luffing assembly (15) adapted to set an angle of the main jib relative to the superstructure within a main jib working angle range, a rigid boom frame (20) pivotally connected to the distal end (14b) of the main jib, and a horizontal setting assembly (22) adapted to set the rigid boom frame in a levelled position at an angle within the main jib working angle range. The rigid boom frame is provided with parallel X-direction rails (25) which are horizontal in the levelled position of the rigid boom frame. The crane has a movable carrier (27) supported by the X-direction rails and moved by a motor-driven X-direction motion displacement actuator assembly.

Description

[0001] This application is a divisional application of the invention patent application with application number 201880035848.4, application date April 20, 2018, and invention name “Motion-compensated crane for use on offshore vessels”. Technical Field

[0002] The present invention relates to the field of offshore vessel cranes.

[0003] In a particularly attractive embodiment, the crane of the present invention is contemplated for use on a floating vessel, whereby the crane is operable while the vessel is subject to wave-induced motion. As explained herein, aspects of the present invention are also applicable to vessels having a crane that is operated while the vessel is not afloat, for example, a jack-up vessel having the crane described herein. Background Art

[0004] In the field of offshore wind turbines, there is a need to increase efficiency and reduce costs, for example in view of the increasing time and expense required for maintenance work on the mounting base of offshore wind turbines, such as in the North Sea, the Baltic Sea, US coastal waters, etc.

[0005] Maintenance work may, for example, comprise handling of components of the offshore wind turbine located “at nacelle height” by a high crane, which comprises, for example, handling the nacelle itself and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades.

[0006] Current offshore wind turbine designs propose or already place the nacelle at altitudes exceeding 100 meters above sea level, for example, at 120 meters or higher. Consequently, handling these components requires very tall cranes. Similarly, the mass of these components can be substantial, ranging from 5 to 150 tons, with components such as the generator and gearbox at the upper end of this range.

[0007] The wind turbine may be of the type mounted on the seabed, for example by means of a monopile or jacket foundation etc. In another design, the wind turbine is implemented on a floating structure, whereby the wind turbine is also fully exposed to and moves due to wave action.

[0008] In a typical approach, the vessel, which is a jack-up vessel, is positioned close to the wind turbine and the leg members are then extended, causing the vessel to be at least partially, but substantially fully, lifted to provide a stable situation for crane operation.

[0009] The process of jacking up and later down of a jack-up crane vessel is time consuming and the jacked-up position is very limited in terms of wave height, so the vessel must be well placed in a floating condition before the weather actually changes when in rough weather. This reduces the effective operational window for such vessels for offshore wind turbine related activities. Also, the sailing speed is typically less than for ordinary vessels. SUMMARY

[0010] It should be noted that the present invention is primarily envisaged for use in the field of offshore wind turbines, thus for maintenance, and also for installation and / or removal of wind turbines. However, the present invention can also be used in other offshore applications, such as oil and gas related work, civil engineering operations, etc.

[0011] It is an object of the present invention to provide an improved crane for use on an offshore vessel, or at least an alternative to existing cranes for such use.

[0012] A first aspect of the present invention provides a motion compensated crane for use on an offshore vessel in a floating condition, the offshore vessel having a hull with a designed waterline, such as for use in handling one or more offshore wind turbine components of an offshore wind turbine, such as handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or a blade, such as for installation and / or maintenance of the offshore wind turbine.

[0013] A first aspect of the present invention also provides a motion compensated crane for use on an offshore vessel, the offshore vessel having a hull with a designed waterline, such as for use in handling one or more offshore wind turbine components of an offshore wind turbine, such as handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or a blade, such as for installation and / or maintenance of the offshore wind turbine.

[0014] In one embodiment, the motor-driven X-direction motion displacement actuator assembly, the motor-driven Y-direction motion displacement actuator assembly and the Z-direction heave motion compensation device are configured to each provide independent control of X-direction motion of the movable load carrier, Y-direction motion of the movable boom hoist cable suspension member and Z-direction heave motion compensation of the object suspension device, respectively.

[0015] In one embodiment, a motor driven X-direction motion displacement actuator assembly includes an X-direction capstan and cable assembly including at least one X-direction cable and associated capstan connected to a movable carrier to move the movable carrier in the X-direction relative to an X-direction guide rail.

[0016] In one embodiment, the X-direction winch and cable assembly includes a first X-direction cable and a second X-direction cable, wherein the first X-direction cable is attached to the movable carrier at its first attachment point near the first X-direction guide rail of the rigid boom frame, and the second X-direction cable is attached to the movable carrier at its second attachment point near the second X-direction guide rail of the rigid boom frame, wherein the X-direction winch and cable assembly includes a motor-driven X-direction winch, the motor-driven X-direction winch having a rotatable winch drum, the rotatable winch drum having a first drum section, a second drum section, a third drum section and a fourth drum section, wherein the first end of the first X-direction cable is wound onto the first drum section, wherein the second end of the first direction cable is wound onto the second drum section in an opposite direction to the winding of the first end of the first X-direction cable, and wherein the first end of the second X-direction cable is wound onto the third section, and wherein the second end of the second X-direction cable is wound onto the fourth section in an opposite direction to the winding of the first end of the second X-direction cable.

[0017] In one embodiment, the motor-driven Y-direction motion displacement actuator assembly includes a Y-direction winch and cable assembly, wherein the Y-direction winch and cable assembly includes at least one Y-direction cable, and the at least one Y-direction cable is connected to the movable lifting cable suspension member and the associated winch to enable the movable lifting cable suspension member to move in the Y direction relative to the one or more Y-direction guide rails.

[0018] In one embodiment, the Y-direction winch and cable assembly has a single Y-direction cable, which is attached to the movable lift cable suspension member and an associated motor-driven Y-direction winch, and the associated motor-driven Y-direction winch has a rotatable winch drum, and the rotatable winch drum has a first drum section and a second drum section, wherein the first end of the single Y-direction cable is wound onto the first drum section and the second end of the single Y-direction cable is wound onto the second drum section in a direction opposite to the winding of the first end of the Y-direction cable.

[0019] In one embodiment, the movable boom lifting cable suspension component includes a first top pulley, a second top pulley, a third top pulley and a fourth top pulley, wherein, viewed along the Y direction, the movable carrier is provided with a first cable guide pulley and a second cable guide pulley at relative positions thereof. The boom lifting cable passes from its first end in the positive X direction to the first cable guide pulley on the movable carrier, then passes from the first cable guide pulley on the movable carrier to the first top pulley, passes via the first bottom pulley to the second top pulley, and passes from the second top pulley to the second cable guide pulley on the movable carrier, wherein the rigid boom frame is provided with a third cable guide pulley and a fourth cable guide pulley, each of the third cable guide pulley and the fourth cable guide pulley being near the end of the corresponding second X-direction guide rail and the first X-direction guide rail of the rigid boom frame, and wherein the boom lifting cable extends from the second cable guide pulley on the movable carrier in the positive X direction, and from the third cable guide pulley to the fourth cable guide pulley. The movable carrier is further provided with a fifth cable guide pulley and a sixth cable guide pulley, the fifth cable guide pulley being adjacent to the first cable guide pulley, and the sixth cable guide pulley being adjacent to the second cable guide pulley.

[0020] The boom hoist cable extends from the fourth cable guide pulley on the rigid boom frame in the negative X-direction to the fifth cable guide pulley on the movable carrier, passes from the fifth cable guide pulley to the third top pulley, passes downward to the second bottom pulley and upward to the fourth top pulley, and from the fourth top pulley to the sixth cable guide pulley, from which the boom hoist cable extends in the negative X-direction to the second end of the hoist cable. At least one of the first and second ends of the boom hoist cable is connected to a hoisting winch.

[0021] In one embodiment, a first boom lifting winch is connected to the first end, for example the first boom lifting winch has a drum, and the first end is wound onto the drum, wherein a second boom lifting winch is connected to the second end, for example the second boom lifting winch has a drum, and the second end is wound onto the drum, wherein the movable boom lifting cable suspension member comprises a third top pulley and a fourth top pulley with horizontal pulley axes, wherein the object suspension member comprises a second bottom pulley, wherein the boom lifting cable extends in a two-reel arrangement between the third and fourth top pulleys and the second bottom pulley, and thus in a four-reel arrangement between the movable boom lifting cable suspension member and the object connection member.

[0022] In one embodiment, at least one boom hoist winch is an active motion compensating winch (AHC winch).

[0023] In one embodiment, the motor-driven X-direction motion displacement actuator assembly and / or the motor-driven Y-direction motion displacement actuator assembly includes a rack-and-pinion drive or a linear cylinder drive, for example having one or more hydraulic cylinders.

[0024] In one embodiment, the one or more X-direction guide rails are implemented to provide an X-direction motion range of the movable carrier of at least 3 meters (eg, at least 4 meters, such as between 5 meters and 8 meters, such as approximately 6 meters).

[0025] In one embodiment, the one or more Y-direction guide rails are implemented to provide a Y-direction range of motion of the movable lift cable suspension member of at least 2 meters (eg, at least 3 meters, eg, between 3 meters and 5 meters, eg, approximately 4 meters).

[0026] In one embodiment, the rigid boom has an inner end pivotally secured to the distal end of the main boom and an outer end distal to the distal end.

[0027] In one embodiment, the rigid boom frame has a first X-direction frame beam and a parallel second X-direction frame beam, wherein the first X-direction frame beam is provided with the first X-direction guide rail, and the second X-direction frame beam is provided with the second X-direction guide rail. For example, the first X-direction frame beam and the second X-direction frame beam are both implemented as hollow box beams with the corresponding X-direction guide rails provided on the outside.

[0028] In one embodiment, the rigid boom frame is provided with an inner transverse frame beam extending in the Y direction and interconnecting respective inner ends of the first X-direction frame beam and the second X-direction frame beam,

[0029] In one embodiment, the rigid boom frame is provided with an outer transverse frame beam extending in the Y direction and interconnecting respective outer ends of the first and second X-direction frame beams.

[0030] In one embodiment, the rigid boom frame is provided with one or more diagonal bracing members, for example, the rigid boom frame has a first X-direction beam member and a second X-direction beam member and at least one of an inner transverse beam member and an outer transverse beam member, the inner transverse beam member and the outer transverse beam member interconnecting the first X-direction beam member and the second X-direction beam member at their inner and outer ends, respectively, for example forming corners of a substantially rectangular frame portion, for example, the rigid frame has two diagonal bracing members extending between opposite corners on a diagonal of the rectangular frame portion.

[0031] In one embodiment, the end of the main boom is provided with a first hinge member and a second hinge member, and the first hinge member and the second hinge member are spaced apart in the Y direction, for example, the first hinge member is located near the inner end of the first X-direction frame beam of the rigid boom frame, for example, at the inner end of the first X-direction frame member, and the second hinge member is located near the inner end of the second X-direction frame beam of the rigid boom frame, for example, at the inner end of the second X-direction frame member.

[0032] In one embodiment, the distal end of the main boom is provided with a torsionally stable platform.

[0033] In one embodiment, the crane is provided with:

[0034] a boom frame strut structure having an inner end portion pivotally connected to the rigid boom frame near a pivot axis of the rigid boom frame, and the boom frame strut structure having an outer end portion,

[0035] - at least one front tie rod member extending from said outer end of the boom frame strut structure to an attachment point on the rigid boom frame remote from its pivot axis,

[0036] - a main boom strut structure, the inner end of which is connected to the main boom near the end of the main boom,

[0037] - a main boom rear tie rod extending between the outer end of the main boom support structure and the lower part of the main boom,

[0038] - a variable length tie rod mechanism provided between the main boom support structure and the boom support structure, wherein the variable length tie rod mechanism forms the level setting assembly and is adapted to set the rigid boom frame in a levelled position when the main boom is at any angle within the main boom operating angle range.

[0039] In one embodiment, the two front tie rod members extend between the boom frame strut structure and corresponding attachment points on the rigid boom frame, and / or the two rear tie rod members extend between the main boom strut structure and the lower portion of the main boom.

[0040] In one embodiment, the main cantilever is a single truss-type main cantilever.

[0041] In one embodiment, the main boom has a length of at least 75 meters, such as between 75 meters and 160 meters.

[0042] In one embodiment, the main boom has a longitudinal section or consists of two parallel main boom leg members, preferably truss arm leg members, along its length.

[0043] In another embodiment, the main cantilever is of A-frame type.

[0044] In one embodiment of the crane, the main boom is an A-frame type boom, the inner end of which is pivotally connected to a base structure fixed to the vessel's hull. In this design, the main boom is always controlled by the vessel's heading, which is a constraint compared to designs with a rotatable superstructure. However, this design can allow for a very high stability of the main boom of a desired length or height, for example, achieving very high stability with a relatively reduced main boom mass, thus presenting its own advantages.

[0045] In one embodiment, the rigid boom frame has a single boom-type X-frame beam, which is provided with at least one X-direction guide rail. This design can reduce weight and is therefore beneficial for the dynamic characteristics of the crane.

[0046] In one embodiment, at least the top of the main boom is implemented as a hollow box-shaped top, as this provides enhanced rigidity at a relatively reduced weight.The rest of the main boom can then be made, for example, into a truss-type design.

[0047] In one embodiment, the lifting capacity of the boom lift system is at least 150 mt at a radius of between 30 and 50 meters from the vertical axis of the rotatable superstructure.

[0048] In one embodiment, the main boom is provided with one or more traction winches, for example near the end of the main boom and / or on the boom frame, each traction winch being provided with a traction cable which can be attached to the object and / or to an object suspension device suspended from the boom lifting cable.

[0049] In one embodiment, an active motion damping mechanism is mounted to a boom frame or to a main boom near its distal end. The active motion damping mechanism includes a solid motion damping ballast and a damping ballast drive and control system. The solid motion damping ballast is movable in a motion damping direction relative to the distal end of the boom frame or tower. The damping ballast drive and control system is configured to induce and control movement of the solid motion damping ballast, for example, in response to output from a motion detection sensor. For example, a first solid motion damping ballast is configured to move in an X-direction and / or a second solid motion damping ballast is configured to move in a Y-direction.

[0050] In one embodiment, it is envisaged that the active motion damping mechanism operates during the relatively short time periods of picking up and loading and unloading loads (eg, loads of components, removing components from or placing components in the nacelle).

[0051] For example, the active motion damping mechanism may be releasably mounted to the boom frame or to the main boom near the end of the main boom, for example, so that the effective lifting capacity can be increased by removing the active motion damping mechanism when heavier loads need to be handled.

[0052] In one embodiment, the crane has a main hoist system comprising a top pulley assembly arranged near the end of a main boom, a main hoist unit having a plurality of pulleys, a main hoist cable, and a main hoist winch, wherein the main hoist unit is suspended from the top pulley assembly by the main hoist cables in a multi-reel arrangement.

[0053] In one embodiment, the main lifting unit is an elongated lifting unit with opposite ends, wherein the main lifting system includes a left top pulley block and a right top pulley block, and the left top pulley block and the right top pulley block are spaced apart on the end of the main cantilever in the Y direction, wherein the elongated lifting unit is provided with a left bottom pulley block and a right bottom pulley block, and the left bottom pulley block and the right bottom pulley block are suspended from the left top pulley assembly and the right top pulley assembly respectively in a multi-reel arrangement, the elongated lifting unit extends in the Y direction, and wherein the object connection member (such as a hook) is centrally arranged below the elongated lifting unit.

[0054] In one embodiment, the main lifting system of the crane has a lifting capacity of at least 400 mt at a radius of between 30 and 50 meters from the vertical axis of the rotatable superstructure.

[0055] In one embodiment, the base structure comprises a cylindrical tub or base extending upwardly from the deck of the vessel, and wherein the rotation support is mounted on a top end of the cylindrical tub or base. The base may have a square or rectangular cross section.

[0056] In one embodiment, the superstructure includes a crane housing and a gantry structure, the gantry structure being erected on and supported by the crane housing, wherein the crane housing is mounted on a base structure via a rotating support, wherein a main cantilever luffing assembly of the crane includes a main cantilever luffing cable and a winch system, wherein the winch system includes a luffing cable, wherein the luffing cable extends between the gantry structure and the main cantilever, is suitable for pivoting the cantilever up and down by means of a luffing winch, and is suitable for setting the main cantilever to one or more desired angles within the working angle.

[0057] In one embodiment, the crane housing includes one or more main boom supports on a front side of the crane housing, wherein the gantry structure includes a substantially vertical rear gantry frame member connected at a lower end thereof to the rear side of the crane housing, and wherein the gantry structure includes a front gantry frame member attached at an upper end thereof to the rear gantry frame member and extending obliquely forward to an attachment on the crane housing proximate to the one or more main boom supports.

[0058] In one embodiment, the crane housing includes a left main boom support and a right main boom support spaced apart from each other in the Y direction.

[0059] In one embodiment, the crane is provided with one or more boom cable orientation sensors, such as one or more cameras or tilt sensors, adapted to sense the actual orientation of one or more sheaves of the boom hoist cable relative to the boom frame, e.g., to take into account wind deflecting objects and / or object connector members from a position vertically below the movable boom hoist cable suspension member.

[0060] In one embodiment, the crane is provided with one or more nacelle position detectors adapted to sense the actual position of the nacelle and / or one or more components in or on the nacelle relative to the boom frame, e.g., wherein the nacelle position detectors comprise one or more radar devices.

[0061] In one embodiment, the crane is provided with one or more sensors adapted to sense the actual deflection of the main boom, such as one or more strain gauges mounted on the main boom.

[0062] In one embodiment, an inertial measurement device is mounted at the end of the main boom or the boom frame, and the inertial measurement device provides one or more reference signals, based on which control signals are calculated and provided for the motor-driven X-direction motion displacement actuator assembly, the motor-driven Y-direction motion displacement actuator assembly and the Z-direction heave motion compensation device, each of these control signals being configured to independently control the X-direction motion of the movable carrier, the Y-direction motion of the movable boom lifting cable suspension member and the Z-direction heave motion compensation of the object suspension device.

[0063] In one embodiment, the motion-compensated support device controller is connected to a satellite positioning system, such as a GPS system, which provides coordinates based on satellite signals. For example, corresponding receivers are mounted on the end of the boom and / or the boom frame and / or on the suspension member to provide position information of various parts of the crane, which can be used to control the motion-compensated support device. Due to the differential GPS system, which provides enhanced accuracy for position determination, beacons or fixed references can be installed on the wind turbine, such as on the nacelle.

[0064] In one embodiment, at least three boom hoist cables each extend from a respective boom hoist winch to the load connector, the cables extending to define an inverted pyramid emanating upwardly from the load connector.

[0065] In one embodiment, the load connector comprises an upper portion suspended from one or more boom hoist cables and a rotatable lower portion (e.g. a hook), the upper portion being configured to be connected to the load and being rotatable relative to the upper portion of the load connector. This allows for rotation of the object load about the vertical axis of the load connector, wherein preferably the rotation of the lower portion relative to the upper portion is controlled by a control device, such as a motorized rotary drive, if present, thereby controlling the rotation and thereby the actual angular position of the load in its horizontal plane.

[0066] A first aspect of the invention also relates to a vessel provided with such a crane, and also to a method of handling a load, such as a load as described herein, using said crane and / or vessel.

[0067] A second aspect of the invention relates to a motion-compensated crane for use on an offshore vessel having a hull with a design waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0068] - a main boom having an inner end portion pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end portion,

[0069] - a main boom luffing assembly adapted to set the angle of the main boom within a main boom working angle range,

[0070] wherein the main boom preferably has a length and a main boom working angle range such that the distal end of the main boom is positionable at a position at least 100 meters above the designed waterline of the hull of the vessel,

[0071] - a movable hoisting cable suspension member,

[0072] - a hoisting winch and a hoisting cable driven by said hoisting winch, the hoisting cable being suspended from said movable hoisting cable suspension member, wherein the object suspension arrangement is suspended from said hoisting cable,

[0073] wherein the movable hoisting cable suspension member is supported by a motion compensated support arrangement, the motion compensated support arrangement being fitted to the distal end of the main boom, the motion compensated support arrangement comprising a motor driven motion displacement actuator assembly and a motion compensated support arrangement controller, the motion compensated support arrangement being configured to provide motion compensation in at least two directions, e.g. along mutually orthogonal X-Y directions,

[0074] characterized in that the crane is provided with an active motion damping mechanism, which is mounted to the motion compensated support arrangement, e.g. the boom frame as discussed herein, or to the main boom in the vicinity of the distal end of the main boom, the active motion damping mechanism comprising motion damping ballast and damping ballast drive and control system, the motion damping ballast being movable in a motion damping direction relative to the motion compensated support arrangement or the main boom, the damping ballast drive and control system being configured to cause and control motion of the motion damping ballast, e.g. in response to output of a motion detection sensor. For example, a first motion damping ballast is configured to move in the X direction and / or a second motion damping ballast is configured to move in the Y direction.

[0075] The motion compensated support arrangement fitted to the distal end of the main boom can be implemented as discussed with reference to the first aspect of the invention. In an alternative design, the motion compensated support arrangement can comprise a scissor mechanism, which is operable in a horizontal plane and levelled by a horizontal levelling mechanism.

[0076] Instead of mobility in the X direction and the Y direction, the motion compensated support arrangement of the crane fitted to the distal end of the main boom of the crane can be configured to provide rotation about a vertical axis and linear extension and retraction in a radial direction relative to said vertical axis. This can be identified as a phi, R mechanism, i.e. a rotational and radial direction.

[0077] In one embodiment, reference is made herein to co-pending applications NL2017937 and PCT / NL2017 / 050812, which are incorporated herein by reference.

[0078] For example, as shown in said document, the crane comprises:

[0079] - a base structure suitable for installation on board a vessel;

[0080] - a rotatable superstructure adapted to rotate relative to the base structure about a substantially vertical axis of rotation;

[0081] - a cantilever structure mounted to the superstructure and pivotally connected at a first end thereof for pivoting relative to the superstructure about a substantially horizontal cantilever pivot axis;

[0082] - a motion compensating support device mounted to the end portion of the cantilever structure;

[0083] a lifting winch, a lifting cable and an object suspension device suspended from said lifting cable, wherein the lifting winch is mounted on a rotatable superstructure or on a cantilever structure, and wherein the lifting cable extends from the lifting winch to said portion of the cantilever structure and then along the motion-compensating support device to the object suspension device;

[0084] - optionally, a heave compensation device acting on the hoisting cable, wherein the heave compensation device is integrated in the hoisting winch and / or is arranged to act on the hoisting cable intermediate the hoisting winch and said portion of the boom structure; and

[0085] - control unit,

[0086] Wherein, the motion compensation support device includes:

[0087] o a base member movably (e.g., pivotally) connected to the portion of the cantilever structure, e.g., so as to pivot about a substantially horizontal base member pivot axis parallel to a substantially horizontal cantilever pivot axis;

[0088] o a level setting device, which is arranged between the cantilever structure and the base member and is adapted to set the base member in a horizontal position;

[0089] o a boom beam mounted to a base member, wherein the boom beam is rotatable relative to the base member about a substantially vertical axis of rotation, wherein the boom beam (55) extends in a substantially horizontal direction away from the substantially vertical axis of rotation, wherein a lifting cable extends between a lifting position on the boom beam and an object suspension device at a distance from the substantially vertical axis of rotation, and wherein the distance is adjustable,

[0090] The boom beam carries a pulley arrangement having a front pulley located at the front of the boom beam, a rear pulley remote from the front pulley, and a first guide pulley, wherein the lifting cable extends from the front pulley to the pulley of the object suspension device, the first guide pulley being arranged such that the lifting cable extends from the pulley of the object suspension device via the first guide pulley to the boom beam supporting member and its terminal end is connected thereto,

[0091] wherein the boom beam support member carries a second guide pulley, and the hoisting cable extends from the second guide pulley to a rear pulley on the boom beam,

[0092] wherein preferably, the first guide pulley and the second guide pulley are arranged such that the length of the hoisting cable between the second guide pulley and the terminal portion on the boom beam support member is substantially constant regardless of the linear position of the boom beam relative to the boom beam support member,

[0093] wherein the control unit provides a wave-induced motion compensation mode in which the boom beam is rotated and the distance is adjusted to maintain a predetermined XY position of the object suspension means,

[0094] And wherein, optionally, provision is made that, where present, the heave compensation arrangement is operable to compensate for wave-induced Z-direction movement of the object suspension arrangement.

[0095] Exemplary embodiments of such a crane are shown in the aforementioned NL2017937 and PCT / NL2017 / 050812.

[0096] For example, as shown in said document, the crane comprises:

[0097] - a base structure suitable for mounting to a vessel;

[0098] - a superstructure arranged to rotate relative to the base structure about a substantially vertical axis of rotation;

[0099] - a cantilever structure having a first end pivotally mounted to said superstructure for pivoting relative to the superstructure about a substantially horizontal cantilever pivot axis;

[0100] - a motion compensating support device mounted to an end portion of the cantilever structure opposite said first end;

[0101] - a lifting winch, a lifting cable and an object suspension device suspended from the lifting cable, wherein the lifting cable extends at least along the motion-compensating support device to the object suspension device;

[0102] - a heave compensation device acting on said hoisting cables; and

[0103] - control unit,

[0104] Wherein, the motion compensation support device includes:

[0105] o a base member mounted to an end portion of the cantilever structure;

[0106] o a boom beam mounted to the base member, wherein the boom beam is rotatable relative to the base member about a substantially vertical axis of rotation, wherein the boom beam extends in a substantially horizontal direction away from the substantially vertical axis of rotation, wherein a lift cable extends between a lift location on the boom beam and an object suspension device at a distance from the substantially vertical axis of rotation, and wherein the distance is adjustable,

[0107] Therein, the control unit provides a wave induced motion compensation mode, wherein the boom beam is rotated and the distance is adjustable so as to maintain a predetermined XY position of the object suspension means.

[0108] And wherein the heave compensation device is operable to compensate for wave-induced Z-direction movement of the object suspension device.

[0109] Exemplary embodiments of such a crane are shown in the aforementioned NL2017937 and PCT / NL2017 / 050812.

[0110] For example, one or more solid ballast members (e.g., blocks or plates of steel or other rigid material (e.g., concrete)) are mounted on a carrier or multiple carriers that are movable along linear tracks, such as those mounted on beams of a rigid boom frame, such as those extending in the X or Y directions. For example, the one or more solid ballast members are moved by a winch and cable arrangement, thereby periodically reciprocating in a manner that provides active motion compensation.

[0111] In one embodiment, it is envisaged that the active motion damping mechanism operates during the relatively short time periods of picking up and loading and unloading loads (eg, loads of components, removing components from or placing components in the nacelle).

[0112] The motion damping ballast may be a solid motion damping ballast, such as one or more ballast members made of steel, such as steel plates, concrete, etc. In another example, the ballast may include one or more movable tanks filled with a liquid, such as water or mud.

[0113] For example, the active motion damping mechanism may be releasably mounted, eg the solid motion damping ballast may be removable, eg so that when heavier loads need to be handled the effective lifting capacity may be increased by removing the active motion damping mechanism.

[0114] The motion damping ballast may be movable in a linear path, for example on one or more ballast guide rails as are preferred. Alternatively, the motion damping ballast may be made rotatable about an axis of rotation, for example using a solid damping ballast having a centre of gravity eccentric to the axis of rotation.

[0115] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel on which the crane is arranged is used and wherein an active motion damping mechanism is operated.

[0116] The active motion damping mechanism can compensate for sea-induced motions when the vessel's crane is operated while the vessel is afloat (and thus subject to sea motions). The active motion damping mechanism can also be advantageous in embodiments where the vessel's crane is operated while the vessel is non-floating, such as a jack-up vessel equipped with a crane.

[0117] The provision of an active motion damping mechanism and its operation are considered advantageous when handling one or more offshore wind turbine components of an offshore wind turbine, for example, handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub, and / or blades, for example, during installation and / or maintenance of the offshore wind turbine. As explained, this requires a significant height of the crane and, therefore, a long main boom, which exhibits motion at the distal end even when the crane is mounted on a vessel, such as a jack-up vessel, due to, for example, wind forces acting on the crane, vibrations in the main boom, etc.

[0118] A second aspect of the invention also relates to a vessel provided with such a crane, and also to a method of handling a load using said crane and / or vessel, for example as described herein.

[0119] A third aspect of the present invention relates to a motion-compensated crane adapted for installation or mounting on an offshore vessel having a hull with a design waterline, the crane being configured for handling one or more offshore wind turbine components of an offshore wind turbine, such as handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example for installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0120] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0121] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0122] The main boom has a length and a main boom operating angle range so that its end is positioned at a position at least 100 meters above the design waterline of the vessel's hull.

[0123] - movable lifting cable suspension members,

[0124] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0125] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising one or more motor-driven motion displacement actuator assemblies and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least one direction, such as in at least two directions (e.g., in orthogonal XY directions),

[0126] Characterized in that the crane is provided with one or more nacelle position detectors configured to sense the actual position and / or movement of the nacelle and / or one or more components in or on the nacelle, and wherein the one or more nacelle position detectors are associated to the motion-compensated support device controller.

[0127] In one embodiment, one or more nacelle position detectors are mounted near the end of the main boom and / or on the motion compensating support arrangement.

[0128] In one embodiment, the one or more cabin position detectors include one or more of the following:

[0129] - radar detectors,

[0130] - Laser ranging detectors, such as LiDAR technology,

[0131] Camera. Based on suitable image processing software running on a computer, the camera images can be processed and the position and / or movement of the cabin detected therefrom.

[0132] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel provided with a crane is used and wherein one or more nacelle position detectors are operated.

[0133] Where the vessel's crane is operated while the vessel is afloat (and thus subject to sea motion), provision of one or more nacelle position detectors may be advantageous. Provision of one or more nacelle position detectors may also be advantageous in embodiments where the vessel's crane is operated while the vessel is non-floating (e.g., a jack-up vessel equipped with a crane).

[0134] A third aspect of the invention also relates to a vessel provided with such a crane, and also to a method of handling a load using said crane and / or vessel, for example as described herein.

[0135] A fourth aspect of the invention relates to a motion-compensated crane for use on an offshore vessel having a hull with a design waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0136] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0137] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0138] The main boom preferably has a length and a main boom operating angle range such that the end of the main boom can be positioned at a position at which the end is at least 100 meters above the design waterline of the vessel's hull.

[0139] - movable lifting cable suspension members,

[0140] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0141] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising one or more motor-driven motion displacement actuator assemblies and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least one direction, such as in at least two directions (e.g., in orthogonal XY directions),

[0142] Characterized in that the crane is provided with a first lifting winch, which is connected to a first end of the lifting cable, for example, the first boom lifting winch has a drum, the first end is wound around the drum, and the second lifting winch is connected to a second end of the lifting cable, for example, the second lifting winch has a drum, the second end is wound around the drum.

[0143] This arrangement provides redundancy and allows a wide range of effective speeds for lowering and lifting loads, which is advantageous, for example, in the rapid picking and unloading of components belonging to a nacelle or a wind turbine blade.

[0144] In one embodiment, the first lifting winch and the second lifting winch are configured for independent control of each of the first lifting winch and the second lifting winch.

[0145] In one embodiment, the movable lift cable suspension member includes a first top pulley, a second top pulley, a third top pulley, and a fourth top pulley, each having a horizontal pulley axis, wherein the object suspension member includes a first bottom pulley and a second bottom pulley, wherein the lift cable extends between the first and second top pulleys and the first bottom pulley in a two-reel arrangement, and between the third and fourth top pulleys and the second bottom pulley in a two-reel arrangement, thereby extending in a four-reel arrangement between the movable lift cable suspension member and the object connection member.

[0146] A fourth aspect of the invention also relates to a vessel provided with such a crane, and also to a method of handling a load using the crane and / or vessel, for example as described herein.

[0147] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel on which a crane is provided is used.

[0148] The fourth aspect of the invention is advantageous in operating the vessel's crane when the vessel is afloat (and therefore subject to sea motion), but is also advantageous in embodiments in which the vessel's crane is operated when the vessel is non-floating, such as a jack-up vessel equipped with a crane.

[0149] A fifth aspect of the invention relates to a motion-compensated crane for use on an offshore vessel having a hull with a designed waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0150] a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end,

[0151] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0152] wherein the main boom has a length and a main boom operating angle range such that the end of the main boom is positioned at a position at least 100 meters above the design waterline of the vessel's hull,

[0153] - movable lifting cable suspension members,

[0154] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0155] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising a motor-driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, for example, in orthogonal XY directions,

[0156] Characterized in that one or more motor driven motion displacement actuator assemblies are provided with a clutch arrangement configured to provide a free floating mode of the motion compensating support arrangement in the event of a power outage.

[0157] A fifth aspect of the invention also relates to a vessel provided with such a crane and a method of operating said crane, wherein the clutch arrangement provides, preferably automatically provides, a free floating mode of the motion compensated support arrangement in case of a power outage.

[0158] A fifth aspect of the invention also relates to a motion-compensated crane for use on an offshore vessel having a hull with a designed waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or a blade, during, for example, installation and / or maintenance of an offshore wind turbine, wherein the crane comprises:

[0159] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0160] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0161] The main boom has a length and a main boom operating angle range, so that the end of the main boom is positioned at a certain position, at which the end is at least 100 meters above the design waterline of the ship's hull,

[0162] - movable lifting cable suspension members,

[0163] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0164] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising an electric motor driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, such as in orthogonal XY directions,

[0165] It is characterized in that the crane is provided with one or more backup energy storage devices, which are configured to provide power to at least the electric motor-driven motion displacement actuator assembly in the event of a power outage on board the ship, for example, the one or more backup energy storage devices include:

[0166] - backup batteries,

[0167] -supercapacitor devices,

[0168] - a flywheel coupled to a generator,

[0169] -Backup fuel-powered generators.

[0170] A fifth aspect of the invention also relates to a motion-compensated crane for use on an offshore vessel having a hull with a designed waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or a blade, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0171] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0172] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0173] The main boom has a length and a main boom operating angle range, so that the end of the main boom is positioned at a certain position, at which the end is at least 100 meters above the design waterline of the ship's hull,

[0174] - movable lifting cable suspension members,

[0175] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0176] wherein the movable lifting cable suspension member is supported by a motion compensating support device, the motion compensating support device being mounted to the end of the main boom, the motion compensating support device including a hydraulic motor driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, for example, in orthogonal XY directions,

[0177] The crane is characterized in that one or more backup energy storage devices are provided, which are configured to provide hydraulic power to at least the motion displacement actuator assembly driven by the hydraulic motor in the event of a power outage on board the ship, and the one or more backup energy storage devices include, for example:

[0178] - hydraulic accumulators,

[0179] - A set of compressed gas (e.g. nitrogen) storage containers connected to gas pressurized hydraulic actuating cylinders, the hydraulic chambers of which are connected to the motion displacement actuator assembly driven by the hydraulic motor.

[0180] A fifth aspect of the invention also relates to a vessel provided with such a crane.

[0181] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel on which a crane is provided is used.

[0182] A sixth aspect of the invention relates to a motion-compensated crane for use on an offshore vessel having a hull with a design waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0183] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0184] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0185] The main boom has a length and a main boom operating angle range, so that the end of the main boom is positioned at a certain position, at which the end is at least 100 meters above the design waterline of the ship's hull,

[0186] - movable lifting cable suspension members,

[0187] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0188] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising one or more motor-driven motion displacement actuator assemblies and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least one direction, such as in at least two directions (e.g., in orthogonal XY directions),

[0189] characterised in that the crane is provided with an inertial measurement unit which is mounted near the end of the main boom and / or on the hull of the vessel or on a component rigidly connected to the hull of the vessel, such as the base structure of the crane,

[0190] And wherein the one or more inertial measurement devices provide one or more reference signals, and based on the one or more reference signals, a control signal for the motor-driven motion displacement actuator assembly is calculated and provided to a motion compensation support device controller.

[0191] A sixth aspect of the invention also relates to a vessel provided with such a crane.

[0192] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel on which a crane is provided is used.

[0193] A sixth aspect of the invention further relates to a method for handling one or more offshore wind turbine components, for example a nacelle of an offshore wind turbine and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or a blade, by means of a crane, the handling being for example installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0194] - movable lifting cable suspension members,

[0195] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0196] wherein the moveable hoisting cable suspended member is supported by a motion compensated support arrangement comprising one or more motor driven motion displacement actuator assemblies and a motion compensated support arrangement controller, the motion compensated support arrangement being configured to provide motion compensation in one or more (at least two) directions, for example in orthogonal X-Y directions,

[0197] characterized in that a first inertial measurement device is mounted on or near the nacelle and configured to provide one or more first reference signals indicative of the actual motion of the wind turbine nacelle or in the vicinity thereof, and a second inertial measurement device is mounted on the crane, for example near the end of the main boom of the crane, said second inertial measurement device being configured to provide one or more second reference signals indicative of the actual motion of the crane,

[0198] wherein the motion compensated support arrangement controller is associated to said first and said second inertial measurement devices and configured to calculate and provide control signals for said one or more motor driven motion displacement actuator assemblies based on said first and said second reference signals.

[0199] This arrangement allows for an effective compensation of the motion of the nacelle and / or the top end of the tower of the wind turbine itself, for example caused by wind and / or waves.

[0200] In one embodiment, the first reference signals are wirelessly transmitted to the motion compensated support arrangement controller.

[0201] A seventh aspect of the present invention relates to a motion compensated crane for use on a sea going vessel having a hull with a designed water line, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, for example a gear box, a generator, a hub and / or a blade, for example installation and / or maintenance of an offshore wind turbine, wherein the crane comprises:

[0202] - a main boom having an inner end portion pivotally connected about a substantially horizontal boom pivot axis, the main boom having a distal end portion distal to the inner end portion;

[0203] - a main boom luffing assembly adapted to set an angle of the main boom within a main boom working angle range,

[0204] wherein the main boom has a length and a main boom working angle range such that the distal end portion of the main boom is positioned at a location where the distal end portion is at least 100 meters above the designed water line of the hull of the vessel,

[0205] - a moveable hoisting cable suspended member,

[0206] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0207] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising a motor-driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, such as in orthogonal XY directions,

[0208] Characterized in that the lifting winch is an active heave compensating winch (AHC winch), and the crane and / or the vessel (on which the crane is installed or to be installed) is provided with one or more sensors, such as radar, laser ranging device, camera vision system, inertial measurement device, wherein the one or more sensors provide one or more reference signals, and control signals for the active heave compensating winch are provided based on the one or more reference signals.

[0209] A seventh aspect of the invention also relates to a vessel provided with such a crane, and also to a method of handling a load using said crane and / or vessel, for example as described herein.

[0210] An eighth aspect of the invention relates to a motion-compensated crane for use on an offshore vessel having a hull with a design waterline, for example for use in handling one or more offshore wind turbine components of an offshore wind turbine, for example handling a nacelle and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades, for example during installation and / or maintenance of the offshore wind turbine, wherein the crane comprises:

[0211] - a main boom, the inner end of which is pivotally connected about a substantially horizontal boom pivot axis, said main boom having a distal end remote from said inner end;

[0212] - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range,

[0213] The main boom has a length and a main boom operating angle range, so that the end of the main boom is positioned at a certain position, at which the end is at least 100 meters above the design waterline of the ship's hull,

[0214] - movable lifting cable suspension members,

[0215] a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable,

[0216] wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising at least one motor-driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least one direction, such as in at least two directions (e.g., in orthogonal XY directions),

[0217] It is characterized in that the main cantilever is provided with one or more force sensors, which are configured to provide a reference signal representing the actual load on the main cantilever, wherein the motion compensation support device controller is associated with the one or more force sensors and is configured to calculate and provide a control signal for the one or more motor-driven motion displacement actuator assemblies based on the reference signals of the one or more force sensors.

[0218] For example, fiber Bragg grating force sensors are used.

[0219] In this regard it is contemplated that the force sensor may indicate actual deflection and / or dynamic motion within the main boom, which may then be taken into account by the motion-compensated support device controller when controlling one or more motor-driven motion displacement actuator assemblies.

[0220] An eighth aspect of the present invention also relates to a vessel provided with such a crane.

[0221] The invention further relates to a method for lifting a load, wherein a crane and / or a vessel on which a crane is provided is used.

[0222] It will be appreciated that any measure according to any aspect described herein, including those described herein as optional, preferred, etc., in the context of one aspect, may be readily combined with any other aspect described herein.

[0223] The invention also relates to a marine vessel according to any aspect or combination of aspects of the invention provided with a crane as described herein.

[0224] In one embodiment, the vessel has a semi-submersible hull having two parallel submersible or submersible buoys, support columns extending upwardly from the buoys, and a deck box structure supported on the columns.

[0225] It should be understood that the various aspects of the invention described herein are applicable to vessels operating in a floating state when handling loads via cranes, and also to vessels configured for crane operation in a non-floating state, such as jack-up crane vessels. As explained, even when a crane is mounted on a jack-up vessel and operated with the vessel elevated, thereby acting as a floating vessel unaffected by sea conditions, taller cranes required to handle, for example, components to be placed in a nacelle, are subject to motion. Similarly, even when the crane is relatively stationary, tall wind turbines can exhibit motion due to wind and / or sea conditions.

[0226] The crane may be a jack-up leg member crane, wherein the supports supporting the superstructure are mounted to extend around the jack-up leg members of the jack-up vessel.

[0227] The invention further relates to a method for handling components of an offshore wind turbine, using a crane as described herein, e.g. components "at the height of the nacelle", which comprises e.g. handling the nacelle itself and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator, a hub and / or blades. BRIEF DESCRIPTION OF THE DRAWINGS

[0228] Various aspects of the present invention will now be discussed with reference to the accompanying drawings. In the drawings:

[0229] Figure 1 Schematically shows an example of an offshore crane vessel provided with a crane according to the invention during processing of components being installed in or removed from a nacelle of an offshore wind turbine,

[0230] Figure 2 Shown Figure 1 The plan of the ship during transportation,

[0231] Figure 3 shows a close-up of the cantilever tip in different positions,

[0232] Figure 4 Shown Figure 1 Schematic diagram of the X-, Y-, and Z-direction compensation systems of a crane.

[0233] Figure 5 Shown Figure 1 Schematic diagram of the crane compensation in the X direction,

[0234] Figure 6 Shown Figure 1 Schematic diagram of the crane compensation in the Y direction,

[0235] Figure 7 Shown Figure 1Schematic diagram of the crane compensation in the Z direction,

[0236] Figure 8 shows a setup of one or more sensors,

[0237] Figure 9 shows the setup of the active damping mechanism,

[0238] Figure 10 shows a vessel and a crane in which one or more aspects of the invention may be implemented,

[0239] Figure 11 An alternative arrangement of the boom raising and lowering winches and cables is shown. DETAILED DESCRIPTION

[0240] Figure 1 and Figure 2 An offshore vessel 1 is shown having a motion-compensated crane 10 for use on an offshore vessel. The vessel has a hull 2 ​​with a designed waterline. The vessel is configured, for example, to handle one or more offshore wind turbine components, such as a nacelle 3 and / or one or more components housed in and / or mounted on the nacelle, such as a gearbox, a generator 4, a hub, and / or blades 5 of an offshore wind turbine 6. These activities may involve the installation and / or maintenance of the offshore wind turbine 6.

[0241] As will be understood by those skilled in the art, the vessel 1 shown is a semi-submersible vessel having two parallel submersible pontoons, columns extending upwardly from each of these pontoons, and a deck box structure supported by the columns, the deck box structure having a deck to which a base structure is secured.

[0242] As will be understood by those skilled in the art, the vessel 1 is shown having a crew and bridge superstructure 90 at the bow of the vessel. Aft of the crew and bridge superstructure 90 the vessel has a deck 2a.

[0243] Here, a crane 10 is installed at the stern of the ship 1 .

[0244] As shown, the crew and bridge superstructure is asymmetrically arranged at the bow of the ship, e.g. towards the port side of the ship, while the crane 10 is asymmetrically arranged at the stern of the ship, opposite from the centerline of the ship relative to the crew and bridge superstructure, e.g. towards the starboard side of the ship.

[0245] The crane 10 comprises:

[0246] - a base structure 11 adapted to be fixed to the hull 2 ​​of the ship, here to the deck of the ship;

[0247] - a rotatable superstructure 12 mounted on the base structure 11 and adapted to rotate relative to the base structure about a substantially vertical axis of rotation;

[0248] - a rotary drive adapted to rotate the superstructure, such as a rack and pinion drive;

[0249] a main boom 14 mounted to the rotatable superstructure 12 and pivotally connected at its inner end to the rotatable superstructure 12 about a substantially horizontal boom pivot axis 14a, the main boom having a distal end 14b remote from the inner end;

[0250] - A main boom luffing assembly 15 adapted to set the angle of the main boom relative to the superstructure within a main boom operating angle range.

[0251] The upper structure includes a crane housing 12a and a gantry structure 12b, wherein the gantry structure 12b is erected on and supported by the crane housing 12a. The crane housing 12a is mounted on the base structure 11 via a rotating support.

[0252] The main boom luffing assembly 15 of the crane comprises main boom luffing cables 15a and a winch system 15b. The luffing cables extend between the gantry structure 12b and the main boom 14, allowing the boom 14 to be pivoted up and down via the luffing winches 15b, and allowing the main boom to be set to one or more desired angles within its operating range.

[0253] The crane housing 12a includes one or more main cantilever supports at the front side of the crane housing.

[0254] The gantry structure 12b includes a generally vertical rear gantry frame member connected at its lower end to the rear side of the crane housing, and a front gantry frame member attached at its upper end to the rear gantry frame member and extending obliquely forward to an attachment member located on the crane housing adjacent to one or more main boom supports.

[0255] In one embodiment, the crane housing includes a left main boom support member and a right main boom support member spaced apart from each other in the Y direction. For example, the main boom is a double-leg member main boom, each leg member being pivotally fixed to a corresponding main boom support member.

[0256] Specifically, considering that the vessel 1 is deployed in an offshore wind farm, the main boom 14 (e.g., lattice arm 14) has a length and a main boom working angle range so that its end can be positioned at a certain position in which the end is at least 100 meters above the design waterline of the vessel's hull.

[0257] The crane further comprises:

[0258] a rigid boom frame 20 pivotally connected to the end of the main boom 14 about a substantially horizontal boom frame pivot axis 21 ,

[0259] - a level setting assembly 22 adapted to set the rigid boom frame 20 in a leveled position when the main boom 14 is at any angle within said main boom operating angle range.

[0260] As shown, the rigid boom frame 20 is provided with a set of parallel X-direction guide rails 25 which extend perpendicular to the horizontal boom frame pivot axis 21 and are substantially horizontal in the leveled position of the rigid boom frame 20 .

[0261] As shown in the figure, the rigid boom frame 20 includes a first X-direction frame beam and a parallel second X-direction frame beam. The first X-direction frame beam is provided with the first X-direction guide rail 25a, and the parallel second X-direction frame beam is provided with the second X-direction guide rail 25b. For example, the first X-direction frame beam and the second X-direction frame beam are both implemented as hollow box beams, each of which is provided with the corresponding X-direction guide rail on the outside.

[0262] like Figure 2 As shown, the rigid boom frame 20 is provided with an outer transverse frame beam 20a extending in the Y direction and interconnected with the outer ends of the first X-direction frame beam and the second X-direction frame beam, respectively. An inner transverse frame beam may also be provided, extending in the Y direction and interconnected with the corresponding inner ends of the first X-direction frame beam and the second X-direction frame beam, respectively.

[0263] Figure 2 The rigid boom frame is further shown provided with one or more diagonal bracing members 20b, for example, the rigid boom frame having a first X-direction beam member 25a and a second X-direction beam member 25b and having at least one of an inner transverse beam member 20a and an outer transverse beam member 20a, the inner transverse beam member 20a and the outer transverse beam member 20a interconnecting the inner and outer ends of the first and second X-direction beam members, respectively, to form corners of a substantially rectangular frame portion.

[0264] In more detail, the crane 10 is provided with:

[0265] a boom frame strut structure 60 having an inner end 61 and an outer end 62 , the inner end 61 being pivotally connected to the rigid boom frame about its pivot axis 21 ,

[0266] at least one front tie rod member 63 extending from the outer end 62 of the boom frame strut structure 60 to an attachment point on the rigid boom frame 20 remote from its pivot axis 21 ,

[0267] a main boom strut structure 65 , the inner end 66 of which is connected to the main boom 14 near its distal end 14 b ,

[0268] A main boom backstay 67 extending between the outer end 68 of the main boom strut structure 65 and the lower portion of the main boom 14 .

[0269] - a variable-length strut mechanism 69, which is arranged between the main boom strut structure 66 and the boom strut structure 60. This variable-length strut mechanism 69 here forms the level setting assembly 22 and is suitable for setting the rigid boom frame 20 in a leveled position, while the main boom 14 has any angle within the main boom operating angle range.

[0270] In one embodiment, two front tie rod members 63 extend between the boom frame strut structure 60 and corresponding attachment points on the rigid boom frame 20, for example, each attachment point is fixed at the end of an X-rail 25a, 25b.

[0271] In one embodiment, two back tie rod members extend between the main boom strut structure and the lower portion of the main boom.

[0272] The crane 10 further comprises:

[0273] a movable carrier 27 supported by the parallel X-direction guide rails 25 and movable in the X-direction relative to the X-direction guide rails 25,

[0274] -Motor driven X-direction motion displacement actuator assembly (see Figure 5 ), which is suitable for moving the movable carrier 27 in the X direction relative to the X-direction guide rail 25,

[0275] The movable carrier 27 is provided with one or more parallel Y-direction guide rails 28 , which extend perpendicularly to the X-direction guide rails 25 .

[0276] The crane 10 further comprises:

[0277] a movable boom lifting cable suspension member 30 supported by one or more Y-direction guide rails 28 and movable in the Y-direction relative to the Y-direction guide rails 28,

[0278] -Motor driven Y direction motion displacement actuator assembly (see Figure 6 ), which is adapted to move the movable boom lifting cable suspension member 30 in the Y direction relative to one or more Y-direction guide rails 28,

[0279] The crane 10 further comprises boom hoisting winches 32, 33 and boom hoisting cables 34 driven by the hoisting winches 32, 33, the boom hoisting cables 34 being suspended from the movable boom hoisting cable suspension member 30. From the boom hoisting cables 34 an object suspension device 35 is suspended.

[0280] The crane 10 further includes a Z-direction heave motion compensation device (herein Figure 7 3 (embodied in an AHT (active heave compensation) winch 32, 33 in the embodiment of the present invention) which acts on a boom hoist cable 34 and is integrated in the boom hoist winch and / or comprises a boom hoist cable engaging member arranged and adapted to act on the boom hoist cable intermediate a hoist winch object suspension arrangement suspended from the boom hoist cable.

[0281] Figure 5 An X-direction winch and cable assembly is shown that includes a first X-direction cable 40 attached to the movable carrier 27 at a first attachment point 41 thereof near the first X-direction rail 25a of the rigid boom frame 20. A second X-direction cable 45 is attached to the movable carrier 27 at a second attachment point 46 thereof near the second X-direction rail 25b of the rigid boom frame 20.

[0282] The X-direction winch and cable assembly includes a motor-driven X-direction winch 48 having a rotatable winch drum 49, which has a first drum section, a second drum section, a third drum section, and a fourth drum section. Here, the first end 40a of the first X-direction cable 40 is wound onto the first drum section. The second end 40b of the first X-direction cable 40 is wound onto the second drum section in a direction opposite to the winding direction of the first end 40a of the first X-direction cable. The first end 45a of the second X-direction cable 45 is wound onto the third drum section, and the second end 45b of the second X-direction cable 45 is wound onto the fourth drum section in a direction opposite to the winding direction of the first end 45a of the second X-direction cable.

[0283] Figure 6 A Y-direction winch and cable assembly is shown having a single Y-direction cable 50 attached to a movable lift cable suspension member 30 and an associated motor-driven Y-direction winch 55 having a rotatable winch drum 56 having a first drum section and a second drum section. Here, a first end 50a of the single Y-direction cable is wound onto the first drum section, while a second end 50b of the single Y-direction cable is wound onto the second drum section in an opposite direction to the winding of the first end 50a of the Y-direction cable.

[0284] In one embodiment, one or more motor-driven motion displacement actuator assemblies, such as capstans associated with the X-direction and / or the Y-direction, are provided with clutch devices on capstans 48, 49 and 55, 56, configured to provide a free-floating mode for the motion-compensating support assembly in the event of a power outage. Unfortunately, power outages do occur on offshore vessels for a variety of reasons. By providing one or more clutches, for example, between the capstan drive motors and the drums, the clutches automatically switch to free-floating mode in the event of a power outage, thereby avoiding undue forces on the load 4 suspended from the cable 34. For example, if the load is a gearbox still within the nacelle 3, the suspension member 30 will remain substantially centered above the gearbox when free-floating mode is enabled in both the X-direction and the Y-direction. Of course, it is conceivable that the capstan controlling the Z-direction does not switch to free-floating mode.

[0285] In view of the occurrence of power outages, the crane 10 may be provided with one or more backup energy storage devices configured to provide power to at least the electric motor-driven motion displacement actuator assembly (here, winches 48, 59 and 55, 56 as well as 32, 33) (in the event of a power outage on board). For example, the one or more backup energy storage devices include:

[0286] - Backup batteries,

[0287] -supercapacitor devices,

[0288] - a flywheel coupled to a generator,

[0289] -Backup fuel-powered generators.

[0290] The crane 10 may be provided with one or more backup energy storage devices configured to provide hydraulic power to at least the hydraulic motor driven motion displacement actuator assembly in the event of a power outage on board. These one or more backup energy storage devices may include, for example:

[0291] - hydraulic accumulators,

[0292] - A set of compressed gas (e.g. nitrogen) storage containers connected to gas pressurized hydraulic actuating cylinders, the hydraulic chambers of which are connected to the motion displacement actuator assembly driven by the hydraulic motor.

[0293] Figure 7 The boom hoist cable 34 is shown having a first end 34a and a second end 34b.The movable boom hoist cable suspension member 30 comprises first and second top pulleys, here four top pulleys 30a-30d, each having a horizontal pulley axis.

[0294] The object suspension member 35 comprises a first bottom pulley, here two bottom pulleys 35a, 35b. The boom hoist cable 34 extends in a double sheave arrangement between the four top pulleys 30a-30d and the two bottom pulleys 35a, 35b.

[0295] As shown, the movable boom hoist cable suspension member 30 includes a first top pulley 30a, a second top pulley 30b, a third top pulley 30c, and a fourth top pulley 30d to implement a four-reel arrangement of the hoist cables 34. If more reels are required, one or more additional pairs of top pulleys may be provided, and additional bottom pulleys may be provided for each pair of top pulleys.

[0296] The movable carrier 27 is provided with a first cable guide pulley 70 and a second cable guide pulley 71 at opposite positions thereof as viewed in the Y direction.

[0297] The boom hoist cable 34 passes from its first end 34a in the positive X direction, for example, away from the axis 21, to a first cable guide pulley 70 on the movable carrier 28, then from the first cable guide pulley 70 on the movable carrier to the first top pulley 30a, via the first bottom pulley 35a to the second top pulley 30b, and from the second top pulley 30b to the second cable guide pulley 71 on the movable carrier 27.

[0298] The rigid boom frame is provided with a third cable guide pulley 72 and a fourth cable guide pulley 73 near the ends of the respective second X-direction guide rail 25b and first X-direction guide rail 25a of the rigid boom frame.

[0299] The boom hoisting cable 34 extends in the positive X direction from the second cable guide pulley 71 on the movable carrier to the third cable guide pulley 72 on the rigid boom frame and from the third cable guide pulley 72 to the fourth cable guide pulley 73 .

[0300] The movable carrier 27 is further provided with a fifth cable guide pulley 74 and a sixth cable guide pulley 75. The fifth cable guide pulley 74 is arranged in the vicinity of the first cable guide pulley 70, while the sixth cable guide pulley 75 is in the vicinity of the second cable guide pulley 71.

[0301] The boom hoist cable 34 extends from the fourth cable guide pulley 73 on the rigid boom frame in the negative X direction to the fifth cable guide pulley 74 on the movable carrier 27, and from the fifth cable guide pulley 74 passes to the third top pulley 30c, passes downward to the second bottom pulley 35b and passes upward to the fourth top pulley 30d, and from the fourth top pulley 30d passes to the sixth cable guide pulley 75,

[0302] The boom hoisting cable extends from the sixth cable guide pulley in the negative X-direction to said second end 34b of the hoisting cable.

[0303] At least one of said first and second ends of the boom hoisting cable is connected to a hoisting winch 32, 33. If only one winch is provided for one end, the other end may be implemented as an anchoring point.

[0304] In one embodiment, a first boom lifting winch 32 is connected to the first end 34a, for example, the first boom lifting winch has a drum, and the first end is wound on the drum, and a second boom lifting winch 33 is connected to the second end 34b, for example, the second boom lifting winch has a drum, and the second end is wound on the drum.

[0305] Figure 8 The crane 10 is schematically shown provided with one or more boom cable orientation sensors, such as one or more cameras 110, 111, or with a tilt sensor, which is suitable for sensing the actual orientation of one or more pulleys of the boom hoist cable 34 relative to the boom frame 20, for example, taking into account wind deflection of the object 4 and / or the object connector member 35 from a position vertically below the movable boom hoist cable suspension member 30.

[0306] Figure 8 It is schematically shown that the crane 10 is provided with one or more nacelle position detectors 120, 121, which are adapted to sense the actual position of the nacelle 3 or parts of the nacelle 3 and / or one or more components in or on the nacelle relative to the boom frame 20, wherein the nacelle position detectors include, for example, one or more radar devices, LiDAR sensor systems and / or one or more cameras.

[0307] Figure 8 The crane 10 is schematically shown provided with one or more sensors adapted to sense the actual deflection of the main boom 14, for example one or more force sensors, such as strain gauges 130 mounted on the main boom.

[0308] In one embodiment, the main boom is provided with one or more force sensors 130 configured to provide a reference signal representing the actual load on the main boom 14, wherein a motion compensation support device controller (here controlling winches 48, 49, 55, 56) is associated with the one or more force sensors 130 and configured to operate and provide a control signal for the one or more motor-driven motion displacement actuator assemblies based on the reference signal of the one or more force sensors 130.

[0309] For example, a fiber Bragg grating force sensor is used.

[0310] The force sensors may indicate actual deflections and / or dynamic motions within the main boom 14, which are then taken into account by the motion-compensated support device controller when controlling one or more motor-driven motion displacement actuator assemblies.

[0311] Figure 8 The crane 10 (e.g., the main boom 14) is schematically shown to be provided with one or more traction winches, for example near the end of the main boom and / or on the boom frame. Each traction winch is provided with a traction cable 140 that can be attached to the object 4 and / or to the object suspension device 35 suspended from the boom hoist cable 34.

[0312] Figure 9 The crane 10 is schematically shown provided with an active motion damping mechanism 150 mounted to the boom frame 20. In the alternative, such a mechanism could be mounted to the main boom 14, for example near the distal end 14b thereof.

[0313] The active motion damping mechanism 150, for example, comprises a solid motion damping ballast, here one or more solid motion damping ballasts, for example a plurality of interconnected ballast members 151, 152, 153, each ballast member being movable on a ballast guide rail on a wheeled carriage, the ballast being movable relative to the boom frame 20 in a motion damping direction. A damping ballast drive and control system, for example having one or more winches 154, 155 and one or more cables connected to the solid ballast, is configured to induce and control the movement of the solid damping ballasts 151, 152, 153. This can be done in response to the output of a motion detection sensor 170, for example an inertial measurement device mounted on the boom frame and / or near the top of the main boom 14.

[0314] Shown here is a motion damping ballast mechanism 150 configured to counteract undue motion of the boom frame 20 in the X direction. In another embodiment, or in addition, a second motion damping mechanism having a movable solid ballast may be arranged and configured to operate in the Y direction.

[0315] In one embodiment, it is contemplated that the active motion damping mechanism 150 operates in a relatively short period of time to pick up a load and to load and unload a load (eg, a load of a component 4, removing the component 4 from the nacelle or placing the component 4 in the nacelle 3).

[0316] For example, the active motion damping mechanism 150 may be releasably mounted to the boom frame 20 or to the main boom near the end thereof, such that effective lifting capacity is increased by removing the active motion damping mechanism when heavier loads need to be handled.

[0317] In one embodiment, an inertial measurement device 170 is mounted at the end of the main boom or on the boom frame. The inertial measurement device can provide one or more reference signals based on which control signals are calculated and provided for at least one of a motor-driven X-direction motion displacement actuator assembly, a motor-driven Y-direction motion displacement actuator assembly, and a Z-direction heave motion compensation device, each of which is configured to independently control the X-direction motion of the movable load, the Y-direction motion of the movable boom hoist cable suspension member, and the Z-direction heave motion compensation of the object suspension device. As described appropriately, this arrangement allows compensation for motion of the boom frame and / or the main boom, such as wind-induced motion, sea-induced motion, vibration in the main boom (e.g., due to displacement of a load suspended from the crane relative to the main boom), deflection of the main boom, etc. As explained, the device 170 can also or alternatively be configured to provide control signals for the active motion damping mechanism 150.

[0318] Instead of or in combination with the inertial measurement device 170 , a GPS receiver may be provided, for example, at the end of the main boom and / or on the boom frame.

[0319] Figure 9 The crane 10 is schematically shown as being provided with a main lifting system comprising a top pulley assembly 160 arranged near the end 14b of the main boom 14, a main lifting unit 161 having a plurality of pulleys, a main lifting cable 162, and a main lifting winch (e.g., on the housing 12a). The main lifting unit 161 is suspended from the top pulley assembly 160 by the main lifting cable in a multi-reel arrangement.

[0320] Figure 10 A vessel 1 and a crane 200 are shown in which one or more aspects of the invention, such as the second, third, fourth, fifth, sixth, seventh and / or eighth aspects (or any combination thereof) may be implemented. The crane is described in detail in co-pending application PCT / NL2017 / 050812, which is incorporated herein by reference.

[0321] The vessel has a hull 2 ​​with a deck 2a.

[0322] The crane has a base 201, a rotatable superstructure 202, a main jib 203, a main jib luffing assembly 205. A motion compensated support arrangement 220 with a horizontally set base is mounted at the end of the main jib 203. Its boom 221 is rotatable about a vertical axis and extendable and retractable in radial direction relative to said vertical axis. A boom hoist cable 222 extends to a load connector 223 which can be used to hoist a load, e.g. a component to be placed in the nacelle of the described offshore wind turbine.

[0323] Figure 11 Alternative arrangements of boom hoist winches and boom hoist cables are shown, e.g. as Figure 4 and Figure 7 alternative to the arrangements shown.

[0324] Here, at least three boom hoist cables 34a, 34b, 34c each extend from a respective boom hoist winch 32a, 32b, 32c to the load connector 35, the cables 34a, 34b, 34c extending to define an inverted pyramid diverging upwardly from the load connector 35. This provides stability of the position of the load connector relative to the structure 30, and can also be achieved with four boom hoist cables and winches in an arrangement with the four boom hoist cables in an inverted pyramid. The respective boom hoist winches 32a, 32b, 32c can be mounted on the structure 30 itself or at other locations, e.g. on the frame 20 or on the main jib 14. The boom hoist winches 32a, 32b, 32c are for example implemented as AHC (active heave compensation) winches, or as shown, a heave compensation mechanism comprising a heave compensation actuation cylinder 145 is configured to act on each boom hoist cable 34a, 34b, 34c.

[0325] In one embodiment, as shown here, the load connector 35 comprises an upper part 35a suspended from one or more boom hoist cables 34a, 34b, 34c and a rotatable lower part 35b, e.g. a hook, configured to be connected to a load and rotatable about a vertical axis 155 relative to the upper part of the load connector. This allows the object load to be rotated about the vertical axis of the load connector. The rotation of the lower part relative to the upper part is controlled by a control device, e.g. a motorized rotation drive 35c, if present, thereby controlling said rotation and thereby the actual angular position of the load 4 in its horizontal plane. It will be appreciated that the rotation of the lower part 35a can be controlled by means of one or more sensors, cameras, etc. as described herein.

Claims

1. A method for handling one or more offshore wind turbine components by means of a crane, the one or more offshore wind turbine components being accommodated in and / or mounted on a nacelle of an offshore wind turbine, wherein the crane comprises: - movable lifting cable suspension members, a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable, wherein the movable lift cable suspension member is supported by a motion compensating support device, the motion compensating support device comprising one or more motor-driven motion displacement actuator assemblies and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in one or more directions, The invention is characterized in that a first inertial measurement device is mounted on or near the nacelle and is configured to provide one or more first reference signals representing the actual motion of the nacelle or the vicinity of the wind turbine, and a second inertial measurement device is mounted on the crane, and the second inertial measurement device is configured to provide one or more second reference signals representing the actual motion of the crane. The motion-compensated support device controller is associated with the first inertial measurement device and the second inertial measurement device and is configured to calculate and provide control signals for the one or more motor-driven motion displacement actuator assemblies based on the first reference signal and the second reference signal.

2. A motion compensated crane for use on an offshore vessel having a hull with a design waterline for use in handling one or more offshore wind turbine components, the one or more offshore wind turbine components being housed in and / or mounted on a nacelle of the offshore wind turbine, wherein the crane comprises: a main boom, the inner end of which is pivotally connected about a horizontal boom pivot axis, said main boom having a distal end remote from said inner end, - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range, - movable lifting cable suspension members, a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable, wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising a motor-driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, The main boom has a length and a main boom operating angle range, so that the end of the main boom can be positioned in a certain position, in which the end is at least 100 meters above the design waterline of the ship's hull, One or more motor driven motion displacement actuator assemblies are provided with a clutch arrangement configured to provide a free floating mode of the motion compensating support arrangement in the event of a power outage.

3. A ship provided with a motion-compensated crane according to claim 2.

4. A method for lifting an offshore wind turbine component, the offshore wind turbine component being housed in and / or mounted on a nacelle of an offshore wind turbine, wherein a motion compensated crane according to claim 2 is used and the clutch device provides a free-floating mode of the motion compensated support device in a power outage situation.

5. A motion compensated crane for use on an offshore vessel having a hull with a design waterline for use in handling one or more offshore wind turbine components housed in and / or mounted on a nacelle of the offshore wind turbine, wherein the crane comprises: a main boom, the inner end of which is pivotally connected about a horizontal boom pivot axis, said main boom having a distal end remote from said inner end, - a main boom luffing assembly adapted to set the angle of the main boom within the main boom operating angle range, - movable lifting cable suspension members, a lifting winch and a lifting cable driven by said lifting winch, the lifting cable being suspended from said movable lifting cable suspension member, wherein an object suspension device is suspended from said lifting cable, wherein the movable lift cable suspension member is supported by a motion compensating support device mounted to a distal end of the main boom, the motion compensating support device comprising a motor-driven motion displacement actuator assembly and a motion compensating support device controller, the motion compensating support device being configured to provide motion compensation in at least two directions, It is characterized in that the crane is provided with an active motion damping mechanism, which is installed to the motion compensating support device, or to the main cantilever near the end of the main cantilever, and the active motion damping mechanism includes a motion damping ballast and a damping ballast drive and control system. The motion damping ballast is movable in a motion damping direction relative to the motion compensating support device or the main cantilever, and the damping ballast drive and control system is configured to cause and control the movement of the motion damping ballast.

6. The motion compensating crane of claim 5, wherein the first motion damping ballast is configured to move in an X direction and the second motion damping ballast is configured to move in a Y direction, wherein the X direction and the Y direction are orthogonal to each other.

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