WO2020043256A1

WO2020043256A1 - A method and system of installing a crane on a portion of an offshore wind turbine generator and a removeable crane adapter therefor

Info

Publication number: WO2020043256A1
Application number: PCT/DK2019/050252
Authority: WO
Inventors: Jens Andersen Gad; Frederik BUDDE; Peter FORNÉ; Allan Melgaard
Original assignee: Maersk Supply Service A/S
Priority date: 2018-08-31
Filing date: 2019-08-28
Publication date: 2020-03-05
Also published as: DK201800522A1

Abstract

A method of installing a crane (300) on a portion of an offshore wind turbine generator (102) from a vessel (100) comprises attaching a removable crane adapter (400) having a first coupling (702) to the portion of the offshore wind turbine generator. The method also comprises mounting a crane (300) having a second coupling (704) on the removable crane adapter, the second coupling being mechanically engageable with the first coupling wherein the crane adapter supports the weight of the crane on the portion of the offshore wind turbine.

Description

A method and system of installing a crane on a portion of an offshore wind turbine generator and a removeable crane adapter therefor

The present invention relates to a method and system of installing a crane on a portion of an offshore wind turbine generator and a removeable crane adapter therefor.

In order to reduce the dependence on limited fossil fuel resources around the world, there has been an increasing demand for renewable energy generation. One such source of renewable energy that has become increasingly reliable is wind energy generation.

Typically electricity is generated from the wind with wind turbine generators (WTG) installed in locations with a reliable prevailing wind. Some wind turbine generators have been installed on land in windy areas such as on hilltops. Wind turbine generators installed on land are also known as“onshore” wind turbine generators.

In recent times, the trend has been to install bigger and taller wind turbines. This increases the area that the blades of the wind turbine sweep through and increases the total potential energy production. In addition, by positioning the blades higher into the atmosphere, the wind blows more steadily, and the wind turbine blades are further from objects that may cause turbulent airflow.

The feasibility of the construction of onshore wind turbine generators can be affected by the local population objecting to the noise and other environmental impact. Accordingly, larger wind turbine generators can be installed in coastal waters. Wind turbine generators installed in coastal waters, the sea or deep ocean are also known as“offshore” wind turbine generators.

The complexity of installing offshore wind turbine generators is greatly increased with respect to installing onshore wind turbine generators. For example, the materials and structure of the offshore wind turbine generators must be transported to the installation site with a suitable vessel. Furthermore, the offshore wind turbine generator must be anchored securely in position.

In this way, offshore wind turbine generator installation is typically carried out in separate stages. One current method of installation is to anchor a foundation to the seabed using a monopile foundation. This is a steel and / or concrete tube which is fixed to and protrudes from the seabed. A transition piece (TP) is fixed to the monopile foundation and the transition piece projects out of the water. The offshore wind turbine generator is then fixed to the transition piece.

WO2014/070024 discloses a method of installing an offshore wind turbine generator is using a jack-up vessel. The jack-up vessel comprises legs that extend down to and engage with the seabed. The jack-up vessel comprises a crane sufficiently tall to receive and install pre-assembled offshore wind turbine generators to the transition piece. A problem with a jack-up vessel is that not all types of seabed are suitable for receiving the extended legs which means this vessel cannot be operated in all coastal waters. Furthermore, the jack-up vessel is very sensitive to adverse weather which means operation of the jack- up vessel is restricted to calm weather windows.

W02007/091042 discloses an alternative method of installing an offshore wind turbine generator using a crane mounted on a vessel. In order to install the largest wind turbine generators, the crane must be suitably massive. Similar to a jack-up vessel, a crane mounted vessel is also sensitive to adverse weather conditions during operation. Another problem is that the vessel must not collide with the foundation or transition piece and this means that the vessel must operate at a safe distance. This means the height of the crane is increased even further so that the crane has sufficient outreach whilst the vessel is positioned at a safe distance from the transition piece.

Another alternative method of offshore wind turbine generator installation is contemplated in WO2017/055598. This discloses installing separate parts of a wind turbine generator with a crane mounted to part of the tower. The crane is initially winched onto the tower from a barge. A problem with this arrangement is that the cable must be pre-attached to the tower in order for the crane to be winched onto the tower. This means that the vessel must be in close proximity to the foundation and transition piece because otherwise the crane will be immersed in water during the winching operation.

It is undesirable for the vessel to be in immediate proximity of the foundation piece for a protracted period of time because this increases the risk of collision of the vessel with the foundation and transition piece. Furthermore, during the final stage of the winching, swing against the foundation piece. The foundation can become damaged when the crane hits the tower. Alternatively, the impact can damage the eyes or the climbing mechanism which would render the crane inoperable. Indeed even when the crane is climbing the tower, the crane can scratch the paint of the tower which means that the wind turbine generator may need painting after installation.

Embodiments of the present invention aim to address the aforementioned problems.

According to an aspect of the present invention there is a method of installing a crane on a portion of an offshore wind turbine generator from a vessel comprising: attaching a removeable crane adapter having a first coupling to the portion of the offshore wind turbine generator; and mounting a crane having a second coupling on the removeable crane adapter, the second coupling being mechanically engageable with the first coupling wherein the crane adapter supports the weight of the crane on the portion of the offshore wind turbine.

According to an aspect of the present invention there is a method of installing a crane on a portion of an offshore wind turbine generator from a vessel comprising: hoisting a removeable crane adapter having a first coupling on to the portion of the offshore wind turbine generator; and mounting a crane having a second coupling on the removeable crane adapter, the second coupling being mechanically engageable with the first coupling wherein the crane adapter supports the weight of the crane on the portion of the offshore wind turbine. Optionally, the attaching the removeable crane adapter comprises removably fixing the removeable crane adapter to one or more protrusions on the portion of the offshore wind turbine generator.

Optionally, the one or more protrusions is a T-flange, a bracket, a pad eye, a hook, or loop fixed to the portion of the offshore wind turbine.

Optionally, the step of attaching comprises using bolts, straps, hooks, latch- catch mechanism the removeable crane adapter to the portion of the offshore wind turbine generator.

Optionally, the method comprises hoisting the removeable crane adapter on to the portion of the offshore wind turbine generator with the crane mounted on the vessel.

Optionally, the method comprises compensating for relative motion between the portion of the offshore wind turbine generator and the vessel such the crane and / or the removeable crane adapter is stable relative to the portion of the offshore wind turbine during the steps of attaching and / or mounting.

Optionally, the compensating comprises adjusting a moveable actuator coupled to a motion compensation platform and / or adjustable arms with respect to the vessel.

Optionally, the method comprises securing the crane to the portion of the offshore wind turbine.

Optionally, the securing comprises closing one or more moveable doors hinged on a body of the crane around the portion of the offshore wind turbine generator.

Optionally, the securing comprises engaging a coupling mounted on the crane with an external protrusion of the portion of the offshore wind turbine generator. Optionally, the securing comprises suspending the crane from cables from the portion of the offshore wind turbine generator.

Optionally, the step of mounting the crane comprises elevating the crane from a first position where the crane is adjacent to a deck of the vessel and to a second position wherein the crane is suspended above the deck of the vessel.

Optionally, the step of attaching the adapter comprises elevating the removeable crane adapter from a first position where the removeable crane adapter is adjacent to a deck of the vessel and to a second position wherein the removeable crane adapter is suspended above the deck of the vessel.

Optionally, the crane is fixed with respect to the removeable crane adapter after mounting and during operation of the crane.

Optionally, the crane is moveable with respect to the removeable crane adapter after mounting.

Optionally, the step of mounting comprises hoisting the crane with a winch mounted on the removeable crane adapter.

In another aspect of the invention there is a crane for lifting one or more a portions of an offshore wind turbine generator comprising: a crane body; and a first coupling mounted on the crane body, the first coupling being mechanically engageable with a second coupling mounted on a removeable crane adapter attached to the portion of the offshore wind turbine generator wherein the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.

In another aspect of the invention there is a crane for lifting one or more a portions of an offshore wind turbine generator comprising: a crane body; and a first coupling mounted on the crane body, the first coupling being mechanically engageable with a second coupling mounted on a removeable crane adapter hoisted to the portion of the offshore wind turbine generator wherein the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.

In yet another aspect of the invention there is a removeable crane adapter attachable to a portion of an offshore wind turbine generator comprising: an adapter body attachable to the portion of the offshore wind turbine generator; and a first coupling mounted on the adapter body, the first coupling being engageable with a second coupling mounted on a crane wherein the first and second couplings are engageable and the crane adapter supports the weight of the crane when the crane is mounted on the removeable crane adapter.

In another aspect of the invention there is a removeable crane adapter attachable to a portion of an offshore wind turbine generator comprising: an adapter body hoistable on to the portion of the offshore wind turbine generator; and a first coupling mounted on the adapter body, the first coupling being engageable with a second coupling mounted on a crane wherein the first and second couplings are engageable and the crane adapter supports the weight of the crane when the crane is mounted on the removeable crane adapter.

Optionally, the adapter body is circular and is arranged to surround the portion of the offshore wind turbine generator.

Optionally, the adapter body comprises a shoulder portion engageable with a flange of the portion of the offshore wind turbine generator.

Optionally, the first and second coupling comprises a loop and hook arrangement.

In yet another aspect of the invention there is a crane mounting system for installing on one or more portions of an offshore wind turbine generator comprising: a crane for lifting one or more a portions of an offshore wind turbine generator having: a crane body; and a first coupling mounted on the crane body, a removeable crane adapter attachable to a portion of an offshore wind turbine generator having: an adapter body attachable to the portion of the offshore wind turbine generator; and a second coupling mounted on the adapter body;

wherein the first coupling is mechanically engageable with the second coupling and the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.

In yet another aspect of the invention there is a crane mounting system for installing on one or more portions of an offshore wind turbine generator comprising: a crane for lifting one or more a portions of an offshore wind turbine generator having: a crane body; and a first coupling mounted on the crane body, a removeable crane adapter hoistable on to a portion of an offshore wind turbine generator having: an adapter body attachable to the portion of the offshore wind turbine generator; and a second coupling mounted on the adapter body; wherein the first coupling is mechanically engageable with the second coupling and the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.

Various other aspects and further embodiments are also described in the following detailed description and in the attached claims with reference to the accompanying drawings, in which:

Figure 1 shows a side view of a vessel in the proximity of a wind turbine generator;

Figure 2 shows a schematic perspective view of a vessel;

Figure 3 shows a side view of a vessel with a crane in a first position according to an embodiment;

Figure 4 shows a side view of a vessel with a crane in a first position according to an embodiment installing the removeable crane adapter;

Figure 5 shows a side view of a vessel with a crane in a second position according to an embodiment;

Figure 6 shows a close up perspective view of the adapter suspended by adjustable arms according to an embodiment; Figure 7 shows a schematic plan view a vessel with a crane according to an embodiment;

Figures 8a, 8b, 8c show a schematic side cross sectional views of the adapter attached to the wind turbine generator;

Figures 9a, 9b, 9c show a schematic side view of the adapter used with another crane according to an embodiment;

Figure 10 shows a schematic view of a vessel;

Figure 1 1 shows a flow diagram of a method of installing a crane on a portion of an offshore wind turbine generator;

Figure 12 shows a perspective view of a vessel with a crane according to an embodiment;

Figure 13 shows a perspective view of a vessel with a crane according to an embodiment; and

Figure 14 shows a perspective view of a vessel with a crane according to an embodiment; and

Figure 15 shows a perspective view of a crane mounted on a vessel according to an embodiment;

Figure 16 shows a perspective view of a crane mounted on a vessel according to an embodiment; and

Figure 17 shows a perspective view of a crane mounted on a portion of a wind turbine generator according to an embodiment.

Figure 1 shows a side view of a vessel 100 in the proximity of a wind turbine generator (WTG) 102. For the purposes of clarity, the WTG 102 is not drawn to scale and the broken portions of the WTG 102 represent missing portions of the WTG 102. The WTG 102 comprises a foundation 104 anchored to the seabed 106. The foundation 104 is a steel and / or concrete tube which is fixed to and protrudes from the seabed 106. Typically the foundation 104 engages with the seabed 106, but in some embodiments the foundation can be floating where the ocean is particularly deep. In other embodiments, other types of foundation 104 can be used including, but not limited to: monopile foundations, tripod foundations, jacket foundations, space-type foundations, floating foundations and / or gravity-based structure foundations. A transition piece (TP) 108 is fixed to the monopile foundation 104 and the transition piece 108 projects out from the surface of the water 1 10. The transition piece 108 comprises access ladders (not shown) for access to the WTG 102 from a boat. The transition piece 108 further comprises a platform 1 12 and a door 1 14 for internal access to the WTG 102.

The WTG 102 comprises a tower 1 16 which is fixed to the transition piece 108. The tower 1 16 can be a unitary element or can be constructed from a plurality of tower segments. A nacelle 1 18 is rotatably mounted on the top of the tower 1 16. The nacelle 1 18 can rotate about the vertical axis A-A of the tower 1 16. The nacelle 118 houses a generator (not shown) for converting the rotation of a hub 120 and blades 122 into electrical energy. There may a plurality of blades 122 connected to the hub. The generator is connected to an electrical substation via one or more cables (not shown). Access to the nacelle 1 18 can be achieved via an internal set of stairs (not shown).

Each of the elements of the WTG 102 is installed with the vessel 100, which will be described in further detail below.

The vessel 100 as shown in Figure 1 is a subsea supply vessel. In other embodiments the vessel is another type of vessel including but not limited to an anchor handling tug supply (AHTS) vessel, a platform supply vessel (PSV), multipurpose support vessel (MSV), a tug boat, a barge or any other suitable vessel for installing WTGs 102.

The vessel 100 can be used for various marine operations such as anchor handling, towing, supply of offshore installations, and fire-fighting. The vessel 100 comprises one or more winches (not shown) for handling towlines and anchors of offshore installations such as oil rigs. The vessel 100 comprises an open aft portion 124 for storing and managing anchors.

In some embodiments, the aft portion 124 is used for stowing one or more parts of the WTG 102. In some embodiments, the aft portion 124 can be used to store disassembled parts 302, 304, 306 of the tower 1 16 (as shown in Figure 3), the nacelle 1 18, the hub 120 and / or the blades 122. In other embodiments, disassembled parts of the WTG 102 can be stowed on a separate vessel (not shown) such as a barge which is positioned close to the vessel 100 when the WTG 102 is being installed.

Figure 1 shows that the open aft portion 124 is clear from anchors and towlines for the purposes of clarity. The open aft portion 124 may comprise one or more cranes (not shown) fixed to the structure of the vessel 100 for lifting and moving objects. The vessel 100 can use the winch together with a towline for towing the barge or other floating structures, if required. Alternatively, the towline can be attached to a capstan or bollard secured to the deck 334 of the vessel 100 when towing the barge. The method of towing barges with a towline and vessel is known and will not be discussed in any further detail.

The vessel 100 comprises a plurality of propulsors for moving the vessel through the water. In some embodiments, the propulsors are one or more of the following: a propeller, a thruster, or an azimuth thruster. The vessel 100 can have any number or configuration of propulsors. The vessel 100 as shown in Figure 1 comprises two propellers 1002 (schematically represented in Figure 10). The propellers 1002 are both coupled to a diesel two stoke engine 1000 (schematically shown in Figure 10) or each propeller 1002 is coupled to a separate diesel two stroke engine 1000. Alternatively, the two propellers 1002 can be driven by one or more diesel four stroke engines 1000. In other embodiments, the propulsors can be powered with a diesel electric engine with or without a direct coupling. Under normal sailing, the propellers 1002 are principally used for moving the vessel 100 in a direction towards the bow 126 of the vessel 100. When the propellers 1002 are reversed, the vessel 100 will move in a direction towards the stern 128. In some embodiments, the vessel 100 only has one propeller mounted along the centreline X-X (as shown in Figure 2) of the vessel 100.

A rudder 130 is positioned aftwards of each propeller 1002 for steering the vessel 100. The rudder 130 is used for directing a wash which is a mass of water moved by the propellers 1002. Each propeller 1002 can have a nozzle which is a hollow tube that surrounds each propeller 1002 for increasing the propulsive force of the respective propellers 1002.

The vessel 100 comprises plurality of bow thrusters 132, 134, 136 and a plurality of stern thrusters 138, 140, 142. Each of the bow thrusters 132, 134, 136 and the stern thrusters 138, 140, 142 are mounted in a tunnel 144. For the purposes of clarity, only one tunnel 144 has been labelled. The tunnel 144 is a hollow tube integral with the hull 146 of the vessel 100 and is open at both sides, e.g. port side and starboard side of the hull 146. This means a thrust force can be imparted at either side of the vessel 100. The tunnel 146 which is integral with the hull 146 of the vessel 100 maintains a compact form and reduces drag on the thrusters 132, 134, 136, 138, 140, 142 when the vessel 100 is moving forwards.

The bow thrusters 132, 134, 136 and the stern thrusters 138, 140, 142 provide a side force with respect to the vessel 100. In this way, the thrusters 132, 134, 136, 138, 140, 142 increase the manoeuvrability of the vessel 100. In some embodiments, the thrusters 132, 134, 136, 138, 140, 142 are driven by an electric motor 1004 (schematically shown in Figure 10). The electric motor 1004 is powered by a diesel engine which may be an auxiliary engine (not shown) in addition to the diesel engines 1000 driving the propellers 1002. Optionally, the electric motor 1004 can also drive the propellers 1002. Alternatively, the electric motors 1004 can be powered from the same engine 1000 which drives the propellers 1002. Additionally or alternatively, the electric motors 1004 of the thrusters 132, 134, 136, 138, 140, 142 are powered by a battery (not shown). In other embodiments, the thrusters 132, 134, 136, 138, 140, 142 are driven by a diesel engine 1000 and gearing and linkages (both not shown) couple the engine 1000 to the thrusters 132, 134, 136, 138, 140, 142. In operation, one or more thrusters 132, 134, 136, 138, 140, 142 can generate a thrust on a side of the vessel 100. All the thrusters 132, 134, 136, 138, 140, 142 can generate a thrust on the same side of the vessel 100 or on different sides of the vessel 100. In other embodiments, one or more of the propellers 1002 or the thrusters 132, 134, 136, 138, 140, 142 are replaced with azimuth thrusters 1006 (as shown in Figure 10). The azimuth thruster 1006 is housed in a pod and is also known as an“azipod”. The azipod 1006 is rotatable by an angle (azimuth) around a horizontal plane parallel with a main horizontal plane of the vessel 100. In this way, the azipod 1006 can direct thrust in any direction. Similar to the thrusters 132, 134, 136, 138, 140, 142, the azipods 1006 can be driven by an engine 1000 or an electric motor 1004.

Turning back to Figure 1 , control of the vessel 100 is achieved by manual controls 1008 such as joysticks, helm, wheel etc. (shown schematically in Figure 10) located in the bridge 148. The bridge 148 is usually located in position such that the crew members have good visibility of the vessel 100 and the surrounding sea. The bridge 148 as shown in Figure 1 has 360 degree visibility of the sea surrounding the vessel 100. This means that crew members operating the vessel 100 can safely and easily control the vessel 100 irrespective of whether the vessel 100 is moving forwards, backwards or side to side. In other embodiments, the vessel can be autonomously controlled with a dynamic positioning module 1010 and a vessel control module 1012 (as shown in Figure 10). Use of the dynamic positioning module 1010 will be discussed in further detail together with Figure 10 below.

Motion of the vessel 100 during operation will now be discussed in reference to Figure 2. Figure 2 shows a perspective schematic view of the vessel 100. The vessel 100 has three principle axis about which it can rotate, a longitudinal axis X-X, a transverse axis Y-Y, and a vertical axis Z-Z. Rotation about the longitudinal axis or centreline X-X of the vessel 100 is called roll. Rotation about the transverse axis Y-Y which is the perpendicular to the longitudinal axis X-X, is called pitch. Rotation about the vertical axis Z-Z is called yaw. In addition to rotational motion about the axes X-X, Y-Y and Z-Z, the vessel 100 can also experience translational motion along each of the axes. Translational motion about the longitudinal axis X-X, the transverse axis Y-Y and the vertical axis Z- Z is respectively known as surge, sway and heave. During operation of the vessel 100, motion compensation of the vessel 100 is carried out to compensate for one or more of roll, pitch, yaw, sway, surge, and heave. In order to compensate for the motion of the vessel 100, measurement of the motion of the vessel 100 is carried out by one or more sensors. Figure 2 schematically represents a pitch motion sensor, 200, a roll sensor 202, a yaw sensor 204, a surge sensor 206, a sway sensor 208 and a heave sensor 210.

In some embodiments, the sensors for detecting the motion of the vessel 100 can be accelerometers, gyroscopes, cameras, or any other suitable sensor for detecting motion of the vessel 100. In some embodiments, alternatively, or additionally the translation movement of the vessel 100 in a plane substantially parallel to the surface of the water is detected with a global positioning system (GPS) 1016 of the vessel 100. This means that the sway sensor 208 and the surge sensor 206 can optionally be omitted. The one or more sensors 200, 202, 204, 206, 208, 210 in some embodiments, can be one or more accelerometers for detecting motion in three perpendicular axes. In some embodiments, one or more sensors (not shown) can detect motion of the vessel 100 in all six degrees of freedom (roll, pitch, yaw, surge, sway, heave). The sensors 200, 202, 204, 206, 208, 210 are connected to a motion compensation module 1014. The motion compensation module 1014 determines the motion of the vessel 100 due to the wind and the waves based on the received sensor information. The compensating for the motion of the vessel 100 will be described in further detail below.

Turning to Figure 3, installation of the WTG 102 will be described in further detail. Figure 3 shows a side view of a vessel 100 with a crane 300 in a first position according to an embodiment. In the first position, the crane 300 is positioned at the aftmost part of the vessel 100. In the first position, the crane 300 is mounted on the deck 334 or positioned on a platform 324 mounted on the deck 334.

The crane 300 is mountable on a portion 308 of the WTG 102 via a removeable crane adapter 400 (as shown in Figure 4). The portion 308 of the WTG 102 is a first section 308 of the tower 1 16. The first section 308 has been installed and fixed to the transition piece 108 before the crane 300 is mounted on the WTG 102. In other embodiments, the crane 300 is mountable via the removeable crane adapter 400 on other parts of the WTG 102 such as the transition piece 108 or the foundation 104.

The crane 300 comprises a crane body 310 engageable with the tower 1 16 via removeable crane adapter 400. Briefly turning to Figure 9, the crane body 310 will be described in further detail. Figure 9 shows a plan view of the crane 300. As shown in Figure 9, in some embodiments the crane body 310 optionally comprises a first door 900, and a second door 902 pivotally hinged to the crane body 310. The first and second doors 900, 902 are arranged to move between a first position in which the doors 900, 902 in an open position and a second position in which the doors 900, 902 are in a closed position. In the open position, the crane body 310 can be positioned around the tower 1 16. In the closed position, the crane body 310 envelops the tower 1 16 and secures the crane body 310 to the tower 1 16. In some embodiments, as discussed below one or more other mechanisms for securing the crane body 310 to the tower 1 16 are additionally or alternatively used. In some other embodiments, the doors 900, 902 do not perform a securing function but instead when the doors 900, 902 are closed, the crane body 310 guides the vertical movement of the crane 300 on the WTG 102. The doors 900, 902 are actuated with hydraulic arms (not shown for clarity). The doors 900, 902 can be held together with a locking mechanism (not shown). The hydraulic arms can be connected to the vessel hydraulic system 1022. The crane body 310 is engageable with the removeable crane adapter 400, but this will be discussed in more detail later.

In some other embodiments, the crane body 310 comprises a single pivotally hinged door (not shown). In other embodiments, the doors 900, 902 slide against the crane body. In yet other embodiments, the crane body 310 does not have doors. Optionally there is a strap or other securing mechanism which secures around the tower 1 16 when there are no doors.

Optionally, the crane body 310 comprises one or more shock absorbers 904 for engaging with an external surface 906 of the tower 1 16. The shock absorbers 904 can be sprung mounted to absorb the impact of the crane body 310 abutting against the tower 1 16. In some embodiments, the shock absorbers 904 are sprung mounted wheels. The wheels reduce the friction between the inside surface 908 of the crane body 310 and the external surface 906 of the tower 1 16. Additionally or alternatively, the shock absorbers are resiliently deformable pads made from rubber or a similar material. The one or more shock absorbers 904 guide the vertical movement of the crane 300 on the WTG 102 and protect both the WTG 102 and the crane 300 from damage.

In some embodiments, when the crane body 310 surrounds the tower 1 16, a plurality of shock absorbers 904 engage the tower 1 16. Figure 9 shows three shock absorbers 904 surrounding the tower 1 16, however there can be any number of shock absorbers positioned on the inside surface 908 of the crane body 310. The position and orientation of the plurality of shock absorbers 904 can be in any suitable arrangement. In some embodiments, the shock absorbers 904 are arranged in a plurality of circles and each circle of shock absorbers 904 is positioned at a different height on the crane body 310.

Turning back to Figure 3, the crane 300 will be described in further detail. The crane 300 comprises a boom 312 which is pivotally coupled to the crane body 310 at pivot 314. The crane 300 comprises one or more cables 316 which is coupled to a winch 318. The cable 316 is connected to yoke 320 for engaging with a load, such as a tower segment 302, 304, 306 or the removeable crane adapter 400 to be lifted. The boom 312 projects laterally from the crane body 310 so that the load can be lifted clear from the crane body 310. In some embodiments, the boom 312 is optionally pivotally connected to an additional jib portion (not shown). The jib portion fixed to the boom 312 or is pivotally mounted to the boom 312 and increase the lateral reach of the crane 300.

In some embodiments, the crane 300 comprises a counterweight 322 positioned on the opposite side of the crane body 310 to the boom 312. In some embodiments, the counterweight 322 is a water filled container suspended from the crane body 310. In this way, the counterweight 322 is emptied of water when the crane 300 is being transferred from the vessel 100 to the WTG 102. This reduces the weight of the crane 300 during the lift operation.

As mentioned previously, the crane 300 as shown in Figure 3 is mounted in a first position on the aftmost portion of the vessel 100. The crane 300 is removably mounted on the stern 128 of the vessel 100. In some embodiments, the crane 300 is attached to the vessel 100 with quick release fixings. This means that the crane 300 can be fixed in place when the vessel 100 sails to the location of the WTG 102. Once the vessel 100 is in the proximity of the WTG 102, the crane 300 can be released from the vessel 100 and prepared for the transfer to the WTG 102. In some embodiments, the crane 300 is mounted on a moveable platform 324. The moveable platform 324 can be mounted on wheels or rails (not shown) on the deck 334 of the vessel 100. This means that the moveable platform 324 can undergo a translational movement on the deck 334 of the vessel 100. In this way, the crane 300 can be moved from a stowed position on the aft portion 124 of the vessel 100 to a transfer position at the aftmost part of the vessel 100 (as shown in Figure 3). The parts of the WTG stowed on the vessel 100 can also be mounted on moveable platforms (not shown) to move them from a stowed position to a position ready for transfer.

Figure 4 shows a side view of a vessel 100 with a crane 300 in a first position according to an embodiment wherein the crane 300 is hoisting the removeable crane adapter 400 on to the WTG 102. In some embodiments, the crane 300 is arranged to hoist the removeable crane adapter 400 on to the first portion 308 of the WTG 102. The crane 300 is configured to hoist the removeable crane adapter 400 on to the WTG 102 whilst the crane 300 is mounted on the vessel 100. In this way, the crane 300 is optionally configured to be operational whilst mounted on the vessel 100.

Referring back to Figure 3, in some embodiments, the platform 324 is rotatable with respect to the vessel 100 about an axis parallel with the Z-Z axis of the vessel 100. Indeed, the platform 324 comprises a rotatable bearing (not shown) mounted on the deck 334 of the vessel 100. I n this way, the crane 300 can slew about its vertical axis whilst mounted to the vessel 100. This means that the crane 300 can pick up the removeable crane adapter 400 stowed on the deck and hoist the removeable crane adapter 400 on to the WTG 102.

The removeable crane adapter 400 as shown in Figure 4 is attachable to the first portion 308. In other embodiments, the removeable crane adapter 400 is attachable to the transition piece 108 or the foundation 104. In other embodiments, the removeable crane adapter 400 is attachable to two or more portions 308, 306, 304, 302 of the WTG 102. The removeable crane adapter 400 is attachable between the transition of two portions 308, 306.

In some embodiments, the removeable crane adapter 400 is circular in cross section and circumferentially surrounds the tower 1 16. Accordingly, in some embodiments the crane 300 lifts the removeable crane adapter 400 above the installed first portion 308 and lowers the removeable crane adapter 400 so that the first portion 308 projects through the removeable crane adapter 400. The removeable crane adapter 400 is arranged to support the weight of the crane 300 when the crane 300 is installed on the WTG 102. The removeable crane adapter 400 can be any shape or size and need not be circular in cross section.

The removeable crane adapter 400 allows the crane 300 to be mounted on the WTG 102 without scratching the tower 1 16. This means that the WTG 102 will not need an additional coat of paint to treat scratches left by the installation and operation of the crane 300. The installation and attachment of the removeable crane adapter 400 will be discussed in further detail below.

Since the removeable crane adapter 400 can be removed after the crane 300 has been removed from the WTG 102, the removeable crane adapter 400 is reusable. This reduces the cost of the WTG 102 installation.

The crane 300 is releasably coupled to a support structure 332 arranged to suspend the crane 300 or the removeable crane adapter 400 above the deck 334 of the vessel 100 as shown in Figure 6. Figure 6 shows the removeable crane adapter 400, but the removeable crane adapter 400 can be replaced with the crane 300 as required. In this way, in some embodiments, the support structure 332 can be used to transfer the crane 300 and / or the removeable crane adapter 400. Accordingly, the removeable crane adapter 400 can be installed without the crane 300 being mounted and operable on the vessel 100 as previously mentioned.

The support structure 332 comprises a first adjustable arm 326 which is releasably engageable to a first side of the crane 300 and a second adjustable arm 500 (better viewed from Figure 6) releasably engageable to a second side of the crane 300.

The first and second adjustable arms 326, 500 (as shown in Figure 6) are moveably mountable to the platform 324. In other embodiments, the adjustable arm 326 is moveably mounted on the vessel 100. In some embodiments, the adjustable arms 326, 500 are each pivotally mountable with first and second orthogonal pivoting joints 508. In other embodiments, the adjustable arms 326, 500 are mounted in ball and socket joints. In yet other embodiments, the adjustable arms 326, 500 can be moveably mounted using any suitable mechanism for permitting multiple degrees of freedom.

The adjustable arms 326, 500 are configured to pivot with respect to the longitudinal axis X-X of the vessel 100. In this way, the adjustable arms 326, 500 can increase the outreach of the crane 300 as the adjustable arms 326, 500 tends towards the horizontal.

Similarly, the adjustable arms 326, 500 are configured to pivot with respect to the vertical axis Z-Z of the vessel 100. Accordingly, as the vessel 100 experiences roll or pitch in the X-X axis or Y axis respectively due to waves, the adjustable arms 326, 500 can be moved to remain upright.

Optionally, the crane body 310 and / or the removeable crane adapter body 600 comprises one or more body couplings 502. Figure 6 shows a first body coupling 502 mounted on a first side of the removeable crane adapter body 600. The opposite side of the removeable crane adapter body 600 comprises a second body coupling (not shown). The first and second body couplings 502 are configured to mount the crane 300 or the removeable crane adapter 400 to the support structure 332 during the transfer operation. In some embodiments, the first and second body couplings 502 permit relative movement between the crane 300 or the removeable crane adapter 400 and the support structure 332. In some embodiments, the body couplings 502 permit pivotal movement of the crane 300 or the removeable crane adapter 400 about the centre axis B-B of the body couplings 502. This means that as the angle between the adjustable arms 326, 500 and the longitudinal axis X-X varies as the adjustable arms extend, the crane 300 or adapter 400 pivots in the plane of the longitudinal axis X-X and the vertical axis Z-Z and the crane 300 or adapter 400 remains vertical. The difference in the angle between the adjustable arms 326 500 and the longitudinal axis X-X is visible between Figures 4 and 5.

In some embodiments, the first adjustable arm 326 and the second adjustable arm 500 are independently controllable. In this way, the first adjustable arm 326 can be moved with respect to the second adjustable arm 500. The relative movement between the first and second adjustable arms 326, 500 can be due to pivotal movement or extension of the telescopic arms. This means that the crane 300 can be tilted and rotated due to the relative movement between the first and second adjustable arms 326, 500. Where the first and second adjustable arms 326, 500 are independently controllable, the body couplings 502 permit movement in more than one degree of freedom. In this way, the body couplings 502 can be ball and socket joints or a plurality of orthogonal pivoting joints.

In some other embodiments, the body couplings 502 only permit pivoting movement along the X-X axis. Accordingly, the relative movement of crane 300 with respect to the adjustable arms 326, 500 is constrained. Instead, the support structure 332 is mounted on a motion compensated platform 324. This means that the roll, pitch and heave can of the vessel is compensated by the platform 324. In this way, the pivoting movement of the crane 300 about axis B-B is to compensate for the change in angle of the adjustable arms 326, 500 as the adjustable arms 326, 500 extend from the first position to the second position. Discussion of the method installing the crane 300 and the removeable crane adapter 400 on the WTG 102 will now be discussed in reference to Figures 4, 6, 10 and 1 1 . Figure 10 is a schematic view of the components and control systems of the vessel 100. Figure 1 1 is a flow diagram of the method installing the crane 300 on the WTG 102.

In order to transfer the crane 300 to the WTG 102, the removeable crane adapter 400 is either hoisted on to the WTG 102 by the crane 300 or suspended in the support structure 332 and transferred to the WTG 102. The removeable crane adapter 400 is then attached to the first portion 308 of the WTG 102 as shown in step 1100 of Figure 1 1

The removeable crane adapter 400 is suspended in the support structure 332. The support structure 332 will be further described in reference to Figure 5. Figure 5 is the same as the arrangement shown in Figures 3 and 4, except that the adjustable arms 326 are extended.

The adjustable arms 326 are telescopic and have extended from the first, transfer position as shown in Figure 3 to a second position in which the removeable crane adapter 400 is in a suspended position in Figure 5. As the adjustable arms 326, 500 extend, the removeable crane adapter 400 is moved closer to the tower 116. In some embodiments, the telescopic arms are hydraulically actuated. In other embodiments, the extension of the telescopic arms 326, 500 is carried out with a rack and pinion mechanism (not shown) or any other suitable mechanism. In some embodiments, the extension of the telescopic arms is controllable via a hydraulic system 1022 (as shown in Figure 10). The adjustable arms 326, 500 extend along their longitudinal axis. Optionally, the adjustable arms 326, 500 can also pivot with respect to the vessel 100.

In the suspended position, the removeable crane adapter 400 is ready to be attached to the WTG 102 as shown in step 1100. As mentioned, previously, the crane 300 is mounted on the removeable crane adapter 400 using the adjustable arms 326, 500 in the same way as for the removeable crane adapter 400. As shown in Figure 5, the crane body 310 is surrounding the tower 1 16. The crane 300 is then mounted to the removeable crane adapter 400 as shown in step 1 102.

When the crane 300 or the removeable crane adapter 400 is being suspended from the support structure 332, movement of the vessel 100 from the wind and the waves are exaggerated.

When the crane 300 is mounted on the removeable crane adapter 400, optionally, the boom 312 is in a horizontal position. Placing the boom 312 in a horizontal position can protect the crane 300 during the transfer of the crane 300 from the vessel 100 to the WTG 102. Accordingly, the doors 900, 902 of the crane body 310 have been closed and secured together. Accordingly, the motion of the vessel 100 is compensated in order to keep the suspended crane stable relative to the tower 1 16. This means that the movement of the vessel due to the waves and wind does not affect the position of the crane 300 with respect to the tower 1 16. Instead, translational movement of the crane 300 with respect to the tower 1 16 is due to transferring the crane 300 from the vessel 100 to the tower 1 16. In this way, the translational movement of the crane 300 is with respect to the tower 1 16 is due to the extension of the support structure 332 or from a controlled thrust of the vessel itself required to move the crane 300 closer to the tower 116.

Optionally compensation for relative motion between the portion of the offshore wind turbine generator 102 and the vessel 100 is carried out when the crane 300 is mounted on the removeable crane adapter 400 in step 1 102 or when the removeable crane adapter 400 is attached to the WTG 102 in step 1100. Discussion of compensating the motion of the vessel 100 will now be discussed in reference to Figures 6 and 10.

Turning to Figure 10, the vessel 100 comprises a plurality of different modules for controlling one or more aspects of the vessel 100. The modules may be implemented on hardware, firmware or software operating on one or more processors or computers. A single processor can operate the different module functionalities or separate individual processors, or separate groups of processors can operate each module functionality.

The vessel 100 further comprises modules for determining parameter information relating the vessel 100. Figure 10 is a non-exhaustive list of the different control modules of a vessel 100. The vessel 100 comprises a vessel control module 1012 for controlling the movement, positioning and orientation of the vessel 100 by sending instructions to the propulsors e.g. the propellers 1002, the thrusters 132, 134, 136, 138, 140, 142 and / or azipods 1006. The vessel control module 1012 can control one or more other aspects of the vessel 100 such as the motion compensation module 1014.

The vessel control module 1012 receives position information from a dynamic positioning module 1010. The dynamic position module 1010 receives positioning information from one or more inputs such as a global positioning system (GPS) 1016, global navigation satellite system (GLONASS) 1018, and a compass 1020 for determining the current position and heading of the vessel 100. The dynamic positioning module 1010 can receive additional positioning input information from other input sources, if required such as a WTG distance module 1026. The dynamic position module 1010 sends target position information to vessel control module 1012. The target position information received from the dynamic positioning module 1010 is position information for moving the vessel 100 from a current position to a desired target position of the vessel 100. For example, the target position information can be position information for maintaining the vessel 100 in a static position for the vessel 100 or a maintaining the vessel on a course or heading.

Additionally or alternatively, at least one beacon or 402 is placed on a surface of the WTG 102 for measuring the distance between the WTG 102 and the vessel 100 by the WTG distance module 1026. The beacon 402 can be passive and provide a surface which is better for reflecting the measurement signals e.g. light, radio waves, sound waves. In this way the beacon 402 can be made from a reflective material such as foil. In alternative embodiments, the beacon 402 can be active and send a signal to a distance sensor 1024 for measuring the distance. The distance sensor 1024 can be a laser range finder, LIDAR, a camera, radar, sonar or any other suitable sensor for measuring distance between the vessel 100 and the WTG 102. For example, the active beacon 402 can comprises a GPS detector for determining position of the WTG 102 which is sent to the distance sensor 1024. In some embodiments, the beacon 402 can be launched from the vessel 100 to the WTG 102 using a drone, cannon or any other suitable means for delivering the beacon 402 to the WTG 102.

In some embodiments, the WTG distance module 1026 sends target position information based on the measured distance between the WTG 102 and the vessel 100. Based on the measured distance, the WTG distance module 1026 issues a command to the dynamic positioning system to move the vessel 100 to a safe operating distance. In this way, the WTG distance sensor 1024 can provide accurate distance information to the dynamic positioning module 1010 which the dynamic positioning module 1010 may not be able to determine using only information from the GPS sensor 1016.

Accordingly, the dynamic positioning module 1010 can compensate for vessel motion due to drift from the wind and the waves. That is the sway, surge and yaw motion of the vessel 100 can be compensated with use of the thrusters and propellers.

As mentioned above, the vessel 100 can also experience motion due to roll, pitch and heave from the waves. The motion compensation module 1014 moves the support structure 332 in order to compensate for the roll, pitch and heave of the vessel 100 whilst attaching the removeable crane adapter 400 or mounting the crane 300 on the removeable crane adapter 400. The support structure 332 will be discussed in more detail with reference to Figure 6. Figure 6 shows a close up perspective view of the removeable crane adapter 400 mounted on the support structure 332 fixed to the vessel 100. Only the aft portion of the vessel 100 is shown for the purposes of clarity.

The support structure 332 is suspending the crane 300 above the deck 334 of the vessel 100. Indeed, the first and second adjustable arms 326, 500 are in the extended, second position.

In some embodiments, the support structure 332 comprises at least one actuator for moving the suspended crane 300 with respect to the vessel 100. In the embodiment shown in Figure 6, there is a first actuator 328 and a second actuator 330 for moving the first adjustable arm 326. Similarly the second adjustable arm 500 comprises first and second actuators 504, 506 for moving the second adjustable arm 500. The actuators 328, 330, 504, 506 are configured to move the adjustable arms 326, 500 to compensate for the motion of the vessel. In some embodiments, there are any number of actuators for moving the support structure 332. The actuators 328, 330, 504, 506 are hydraulically actuated extendable pistons and are coupled to the hydraulic system 1022. In some embodiments, the actuators 328, 330, 504, 506 moved by linkages and gearing or any other suitable mechanism.

The pitch, roll and heave motion of the vessel 100 is detected using the pitch motion sensor, 200, the roll sensor 202, and the heave sensor 210. The motion compensation module 1014 receives the sensor data relating to the detected motion of the vessel 100. The motion compensation module 1014 determines the deviation of the crane 300 due to the detected motion of the vessel from a stable crane position.

The stable crane position is a position whereby the movement of the vessel 100 due to the waves and wind does not affect the position of the crane 300 with respect to the tower 1 16. Instead, translational movement of the crane 300 with respect to the tower 1 16 is due to transferring the crane 300 from the vessel 100 to the removeable crane adapter 400 attached to the tower 1 16. In this way, the translational movement of the crane 300 is with respect to the tower 1 16 is due to the extension of the support structure 332 or from a controlled thrust of the vessel 100 itself required to move the crane 300 closer to the tower 1 16.

In some embodiments, the motion compensation module 1014 calculates the deviation from a position of the crane suspended above the vessel at a height corresponding to the position on the WTG 102 where the crane 300 is to be transferred to. On detection of deviation from a stable crane position, the motion compensation module 1014 then sends one or more instructions to the actuators 328, 330, 504, 506 to move the crane 300 back to a stable position. In this way, the motion compensation module 1014 controls the actuators 328, 330, 504, 506 to keep the crane 300 fixed at a height with respect to the WTG 102.

Additionally or alternatively, in some embodiments, the motion compensation module 1014 generates a model of the motion of the vessel 100 over a period time based on observed vessel motion. Accordingly, the generated model is a prediction of the motion of the vessel 100 based on recent motion on the vessel. The motion compensation model sends control instructions to the actuators 328, 330, 504, 506 based on the vessel motion model.

Additionally or alternatively, the platform 324 is coupled to actuators connected to the motion compensation module 1014. Accordingly, the platform 324 can be used for loading the crane 300 and / or parts 302, 304, 306 of the WTG 102 and stabilized. The same motion compensation method is used for attaching the removeable crane adapter 400 to the tower 1 16.

Once the crane 300 is in a stable position and in a suspended position, the crane 300 can be mounted on the removeable crane adapter as shown in step 1 102 of Figure 1 1 . During the mounting step 1 102, the crane 300 is positioned such that it is orientated around the tower 1 16 as shown in Figure 5 and in engagement with the removeable crane adapter 400. Accordingly the crane 300 can be transferred and secured to the WTG 102 via the removeable crane adapter 400. The crane 300 can be secured to any portion of the offshore wind turbine 102 to which the removeable crane adapter 400 is attached. In some embodiments, as mentioned above the securing comprises abutting shock absorbers 904 against the outer surface 906 of the WTG 102.

The removeable crane adapter 400 will now be discussed in more detail with reference to Figures 7 and 8a, 8b, 8c. Figure 7 shows a schematic plan view a vessel with a crane 300 according to an embodiment. Figures 8a, 8b, 8c show a schematic side cross sectional views of the adapter attached to the wind turbine generator.

The removeable crane adapter 400 is attached to the exterior surface 906 of the tower 1 16 such that the tower 1 16 supports the removeable crane adapter 400 and the crane 300. As shown in Figure 7, removeable crane adapter 400 comprises tightening bolts 700 for tightening the removeable crane adapter 400 on the exterior surface 906 of the tower 1 16. The removeable crane adapter 400 as shown in Figure 7 is a unitary element. However in other embodiments, the removeable crane adapter 400 can be formed from a two hinged parts which are bolted together with the tightening bolts 700. In this way, the removeable crane adapter 400 is fixed with respect to the exterior surface 906 of the tower 1 16 due to frictional engagement between the removeable crane adapter 400 and the tower 1 16. In other embodiments the removeable crane adapter 400 is fixed to the tower 1 16 with bolts, hooks, cables, brackets, clamps, eyes, welding, or any other suitable fastening.

The removeable crane adapter 400 comprises a first adapter coupling 702 mounted on the removeable crane adapter body 600. The crane 300 comprises a second adapter coupling 704 mounted on the crane body 310. The first and second adapter couplings 702, 704 are arranged to mechanically engage such that the removeable crane adapter 400 supports the weight of the crane 300 when the crane 300 is mounted on the removeable crane adapter 400 as shown in step 1 104.

Whilst Figure 7 shows a single set of first and second adapter couplings 702, 704, there can be a plurality of sets of first and second adapter couplings 702, 704 to increase the mechanical engagement between the removeable crane adapter 400 and the crane 300. For example, Figure 6 shows a plurality of protruding loops 702a 702b mounted on the removeable crane adapter body 600.

In Figure 7 the first adapter coupling 702 is an integral loop on the removeable crane adapter body 600. The second adapter coupling 704 is reciprocal hook configured to project through the loop 702 to provide mechanical engagement between the first and second adapter couplings 702, 704.

In other embodiments the first adapter coupling 702 is a flange, eye, bracket, bolts, hooks, clamps, or any other suitable protrusion on the outer surface of the removeable crane adapter 400. The second adapter coupling 704 can be a reciprocal projection such as a hook for engaging the flange, eye, bracket or any other suitable protrusion. In other embodiments, the first adapter coupling 702 mounted on the removeable crane adapter 400 is a hook and the second adapter coupling 704 mounted on the crane 300 is eye, bracket or any other suitable protrusion.

Optionally, the first or second adapter couplings 702, 704 move between a retracted and a deployed position when the crane 300 is being secured. The adapter coupling engages with a flange, eye, bracket or any other suitable protrusion on the outer surface the removeable crane adapter 400. The first and second adapter couplings 702, 704 can comprise a locking mechanism for providing and maintaining positive mechanical engagement.

Turning to Figures 8a, 8b, 8c, different embodiments of the removeable crane adapter 400 and the crane 300 will be discussed. As mentioned the removeable crane adapter 400 is attached to a portion of the WTG 102. The removeable crane adapter 400 comprises a first adapter coupling 800 for engaging a second adapter coupling 802 of the crane 300. Figure 8a shows only part of the crane 300 for the purposes of clarity. A projecting leg 806 of the crane 300 extends downwardly from the crane body 310. The projecting leg 806 comprises a free end 802 which slots into a reciprocal recess 800 in the removeable crane adapter boy 600. Optionally, the free end 802 can pivot when it is in mechanical engagement with the reciprocal recess 800.

The arrangement as shown in Figure 8a means that the crane 300 can move out of engagement with the removeable crane adapter 400. For example, additionally or alternatively, the crane 300 is secured to the WTG 102 by suspending the crane 300 from cables 316 from the portion of the offshore wind turbine generator. In some embodiments, the cables 316 are attached to the top of the tower 1 16 or the nacelle 1 18. In this way, the crane 300 can move vertically on the tower 1 16. The cables 316 support the weight of the crane 300 once the crane 300 is no longer in mechanical engagement with the removeable crane adapter 400. In this way, the removeable crane adapter 400 is only used for initially transferring the crane 300 from the vessel to the WTG 102.

Once the crane 300 is secured to the WTG 102, the vessel 100 can move away from the WTG 102. The crane 300 can then hoist parts 302, 304, 306 of the WT G 102 to be installed from the vessel 100 or another vessel such as a barge (not shown). This means that the crane 300 can be transferred to the WTG 102 without endangering the vessel 100 or damaging the WTG 102 or the crane 300.

In other embodiments, the crane 300 is fixed with respect to the removeable crane adapter 400. For example, turning to Figure 8b, the removeable crane adapter 400 comprises two loops 808, 810 and the crane body 310 comprises two reciprocal hooks 812, 814 for mechanical engagement. Accordingly, the hooks 812, 814 hang from the loops 808, 810 and the removeable crane adapter 400 supports the weight of the crane 300. Figures 8a, 8b show arrangements whereby the removeable crane adapter 400 is in frictional engagement with the exterior surface 906 of the tower 1 16. Additionally or alternatively, the removeable crane adapter 400 comprises an overhang 816 which couples to the underside surface of a T-flange 818 where two portions 308, 306 of the WTG 102 join.

In the arrangements as shown in Figures 8b, 8c, the hooks 812, 814 mounted to the crane body 310 of the crane are lowered into engagement with the loops 808, 810 when mounting the crane 300 on the removeable crane adapter 400 as shown in step 1 102.

Turning to Figures 9a, 9b and 9c another embodiment will be described. Figures 9a, 9b, 9c show a schematic side view of removeable crane adapter 400 used with another crane 910. Figures 9a, 9b and 9c respectively show sequential steps of the crane 910 initially being mounted on the vessel 100, being transferred and mounted on the removeable crane adapter 400, and being increased in size.

The removeable crane adapter 400 as shown in Figures 9a, 9b, 9c is the same as the removeable crane adapter 400 discussed in previous embodiments with reference to Figure 7 and Figures 8a, 8b, 8c.

The crane 910 as shown in Figure 9a is a tower crane with a tower portion 912 and a horizontal boom portion 914. The crane 910 can be initially mounted to the vessel 100. Whilst the crane 910 is mounted to the vessel 100, the crane 910 can hoist and transfer the removeable crane adapter 400 similar to the methods previously discussed. The tower portion 912 is constructed from a plurality of tower modules 922a, 922b, 922c each of which are coupled together. Each tower module 922a, 922b, 922c can be separated and transported separately. The crane 910 further comprises a moveable crane body 916 on which hooks 812, 814 are mounted. The hooks 812, 814 are arranged to mechanically engage the reciprocal loops 808, 810 mounted on the removeable crane adapter 400. The moveable crane body 916 is moveable with respect to the tower portion 912. The moveable crane body 916 comprises a frame which surrounds the tower portion 912. The tower portion 912 guides the movement of the moveable crane body 916 along the tower portion 912.

The moveable crane body 916 comprises one or more pinions 920 for engagement with a rack 918 on the tower portion 912. Accordingly the moveable crane body 916 can climb the tower portion 912 by travelling along the rack. In other embodiments, other mechanisms can be used for driving the movement of the moveable crane body 916 with respect to the tower portion 912. The moveable crane body 916 moves vertically up the tower portion 912 when the vessel 100 is in position.

The moveable crane body 916 has climbed up the tower portion 912 and is mounted to the removeable crane adapter 400 as shown in Figure 9b. The engagement between the hooks 812, 814 on the moveable crane body 916 and the loops 808, 810 mounted to the removeable crane adapter 400 is the same as discussed in reference to previous embodiments. The tower portion 912 is mounted on the platform 324 (not shown in Figure 9 for the purposes of clarity). The platform 324 moves the crane 910 vertically and laterally with respect to the WTG 102 and the removeable crane adapter 400. This means that movement of the platform 324 can position the hooks 814, 812 within the loops 808, 810.

Once the moveable crane body 916 is mounted on the removeable crane adapter 400, the moveable crane body 916 is fixed with respect to the removeable crane adapter 400. In some embodiments the removeable crane adapter 400 is bolted or locked to the moveable crane body 916 to prevent relative movement therebetween.

In Figure 9c the moveable crane body 916 engages the tower portion 912 and the pinions 920 engage the rack 918. Accordingly, the moveable crane body 916 raises the tower portion 912 vertically. Additional tower modules 924 are then raised from the platform 324 on the vessel 100 into the moveable crane body 916 until the pinion 920 engages the rack 918 of the additional tower module 924. At this point, the additional tower module 924 is raised by the pinion 924 and rack 918 mechanism until it is positioned underneath the tower portion 912 of the crane 912.

The additional tower module 924 is fastened to the bottom end of the existing tower portion 912. The additional tower module 924 can be bolted or fastened with any suitable means to the bottom of the tower portion 912. Any number of additional tower modules 924 can be fed into the moveable crane body 924 to construct a tower portion 912 of suitable height for installing subsequent portions 306, 304, 302 of the WTG 102.

An embodiment will now be discussed in reference to Figure 12. Figure 12 shows a perspective view of a vessel 100 with a crane 1200 mounted on the deck. The parts of only one WTG 102 are shown in Figure 12, however the vessel 100 is capable of transporting more WTGs 102. The crane 1200 as shown in Figure 12 is arranged to transfer one or more portions of the crane 1200 such as a crane adapter 226 or one or more portions of the WTG 102 when mounted on the vessel.

The crane 1200 is shown in a first position according to an embodiment. In the first position, the crane 1200 is positioned at the aftmost part of the vessel 100. In the first position, the crane 1200 is mounted on the deck or optionally positioned on a motion compensation platform 324 mounted on the deck. The motion compensation platform 324 will be discussed in further detail below.

The crane 1200 is removably mounted on the stern 128 of the vessel 100. In some embodiments, the crane 1200 is attached to the vessel 100 or to the motion compensation platform 324 with quick release fixings (not shown).

The crane 1200 is an erectable tower crane 1200 which comprises a plurality of connectable tower segments 1204, 1206, 1208 when erected. Whilst Figure 12 shows three additional connectable tower segments 1204, 1206, 1208, the erected tower crane 1200 can comprise any number of connectable tower segments. This means that the height of the tower crane 1200 is variable.

The tower crane 1200 as shown in Figure 12 is similar to the tower crane 910 as shown in Figure 9. However there are differences, which will be discussed below. In particular, the tower crane 1200 as shown in Figure 12 is a luffing tower crane 1200 whereby the boom 1214 is pivotally moveable. In contrast, the boom 914 of the tower crane 910 as shown in Figure 9 remains horizontal.

The connectable tower segments 1204, 1206, 1208 comprise a hollow lattice structure. Advantageously, this reduces the weight of the components of the tower crane 1200 and can make installation of the tower crane 1200 on the transition piece 108 easier.

The tower crane 1200 comprises a slewing hoisting unit 1210 mounted on a first tower segment 1212. The slewing hoisting unit 1210 is rotatably mounted on the first tower segment 1212 and is rotatable about a central longitudinal axis W-W of the tower crane 1200. This means that the tower crane 1200 can hoist loads in a circular working area about the axis W-W.

The tower crane 1200 comprises the boom 1214 which is pivotally coupled to the hoisting unit body 1218 at pivot 1216. The tower crane 1200 comprises one or more cables 1220 which are coupled to a winch 1222 mounted in the hoisting unit body 1218. The cable 1220 is connected to yoke 1224 for engaging with a load, such as a WTG tower or any other suitable load.

As shown in Figure 12, the hoisting unit 1210 is raising a removeable crane adapter 1226. In some embodiments, the tower crane 1200 is arranged to hoist the removeable crane adapter 1226 on to the transition piece 108 of the WTG 102 whilst the tower crane 1200 is mounted on the vessel 100. Alternatively, or additionally whilst the tower crane 1200 is mounted on the vessel 100, the tower crane 1200 can hoist one or more portions of the offshore wind turbine generator 102 on to the transition piece 108. In this way, the tower crane 1200 is configured to be operational whilst mounted on the vessel 100. The boom 1214 projects laterally from the hoisting unit body 1218 so that the load can be lifted clear from the hoisting unit body 1218. In some embodiments, the boom 1214 is optionally pivotally connected to an additional jib portion (not shown). The jib portion fixed to the boom 1214 or is pivotally mounted to the boom 1214 and increases the lateral reach of the tower crane 1200.

In some embodiments, the tower crane 1200 comprises a counterweight (not shown) positioned on the opposite side of the hoisting unit body 1218 to the boom 1214 for limiting the turning moment about the tower crane structure 1228. The tower crane structure 1228 is formed from the first tower segment 1212 and / or the connectable tower segments 1204, 1206, 1208.

Figure 12 shows a tower crane 1200 with a slewing hoisting unit 1210 with a pivoting boom 1214 such that the angle that the boom 1214 makes with the longitudinal axis W-W can be varied. This means that the lateral reach of the tower crane 1200 can be varied by changing the angle the boom 1214 makes with the longitudinal axis W-W. This can be advantageous to avoid the boom 1214 colliding with nearby tall objects such as the WTG tower 1 10 on the vessel 100.

The tower crane 1200 is mountable on a portion of the WTG 102 via the removeable crane adapter 1226 as shown in step 1 102 of Figure 1 1 . The portion of the WTG 102 as shown in Figure 12 is the transition piece 108 of the WTG 102. In other embodiments, the tower crane 1200 is mountable via the removeable crane adapter 1226 on other parts of the WTG 102 such as the foundation 104, a part of the WTG tower 1 10 or the entire WTG tower 110.

The tower crane 1200 comprises a moveable crane body 1230. The moveable crane body 1230 comprises different functionality and attach the tower crane 1200 to the transition piece 108 and also lift the tower crane structure 1228 to for introducing the new connectable tower segments 1204, 1206, 1208. The moveable crane body 1230 comprises a tower segment receiving unit 1230. The tower segment receiving unit 1230 is mountable on the removeable crane adapter 1226 mounted on the WTG 102. For the purposes of clarity, the term tower segment receiving unit 1230 will be used, but this will also refer to the moveable crane body 1230.

When the tower segment receiving unit 1230 engages the adapter 1226, the tower segment receiving unit 1230 supports the weight of the tower crane structure 1228 as shown in step 1 104 of Figure 11 . This means that the foundation 104 of the WTG 102 supports the weight of both the tower crane 1200 and the WTG 102.

The tower segment receiving unit 1230 is arranged to receive new connectable tower segments 1204, 1206, 1208 to couple to the existing crane tower structure 1228 to increase the height of the tower crane 1200. Installation of the tower crane 1200 will be described in further detail below.

The tower segment receiving unit 1230 comprises a frame 1234 which surrounds a portion of the tower crane structure 1228. The frame 1234 as shown in Figure 12 comprises solid walls, but in other embodiments the frame 1234 can comprise a lattice structure similar to the connectable tower segments 1204, 1206, 1208. The frame 1234 is in mechanical engagement with the tower crane structure 1228. This means that the tower segment receiving unit 1230 can be fixed in position with respect to the tower crane structure 1228. However, the tower segment receiving unit 1230 is moveable with respect to the tower crane structure 1228. This means that the tower segment receiving unit 1230 can be fixed with respect to the WTG 102 and the tower crane structure 1228 can move with respect to the WTG 102 and the tower segment receiving unit 1230. Movement of the tower segment receiving unit 1230 will be discussed later on.

The tower segment receiving unit 1230 as shown in Figure 12 is in a lowered position adjacent to the motion compensation platform 324 on the deck 118 of the vessel 100. As mentioned previously, the tower crane 1200 as shown in Figure 12 is mounted on the motion compensation platform 324. The motion compensation platform 324 is coupled to at least one actuator 1232 connected to a motion compensation module 1014 for controlling actuation of the at least one actuator 232. In some embodiments, there are a plurality of actuators 1232 for moving the motion compensation platform 324 in multiple degrees of freedom. Accordingly, the motion compensation platform 324 can be used for stabilizing the tower crane 1200 whilst transferring the tower crane 1200 to the WTG 102 and / or during operation of the tower crane 1200 when mounted on the vessel 100.

Indeed, the motion compensation platform 324 method is used for attaching the removeable crane adapter 1226 to the transition piece 108 as shown in Figure 12. Accordingly, the movement of the vessel 100 due to the vessel 100 does not affect movement of the removeable crane adapter 1226 when hoisted and transferred to the transition piece 108. The method of motion compensation is the similar to the previously discussed embodiments.

In some embodiments, the pitch, roll and heave motion of the vessel 100 is detected using sensors (not shown) for determining pitch, roll, and / or heave. The motion compensation module 1014 receives the sensor data relating to the detected motion of the vessel 100. The motion compensation module 1014 determines the deviation of the tower crane 1200 mounted on the motion compensation platform 324 due to the detected motion of the vessel 100 from a stable crane position.

The stable crane position can be a predetermined position whereby the movement of the vessel 100 due to the waves and wind does not affect the position of the tower crane 1200 with respect to the transition piece 108. Whilst the tower crane 1200 is mounted on the activated motion compensation platform 324, any translational movement of the tower crane 1200 with respect to the WTG 102 may due to a controlled thrust of the vessel 100. The controlled thrust of the vessel 100 may be required to move the tower crane 1200 closer to the WTG 102 for transfer. In some embodiments, the motion compensation module 1014 calculates the deviation of a portion of the tower crane 1200 from the predetermined stable crane position. The predetermined stable crane position is a height of the portion of the tower crane 1200 above the vessel 100 required during transferred of the tower crane 1200 to the WTG 102. On detection of deviation from a stable crane position, the motion compensation module 1014 then sends one or more instructions to the actuators 232, to move the motion compensation platform 324. In this way, the motion compensation module 1014 controls the 232 to keep the tower crane 1200 fixed at a height with respect to the WTG 102.

The removeable crane adapter 1226 as shown in Figure 12 is attachable to the to the transition piece 108 or the foundation 104 or another part of the WTG 102. In some embodiments, the removeable crane adapter 1226 is circular in cross section and circumferentially surrounds the transition piece 108. Accordingly, in some embodiments the tower crane 1200 lifts the removeable crane adapter 1226 above the transition piece 108 and lowers the removeable crane adapter 1226 so that the transition piece 108 projects through the removeable crane adapter 1226 according to step 1 100 as show in Figure 1 1 . The removeable crane adapter 1226 comprising a first coupling to the transition piece 108. In some embodiments the first coupling is bolts threaded and fastened between the crane adapter 1226 and the transition piece 108.

However, in other embodiments the removeable crane adapter 1226 clamps onto a flange at the top of the transition piece 108. Additionally or alternatively, the removeable crane adapter 1226 can use hooks, loops, brackets, clamps, clips, welds or any other suitable fastening device for fixing the removeable crane adapter 1226 to the transition piece 108. Indeed, any of the couplings discussed with respect to the previous embodiments can be used with the crane adapter 1226.

The removeable crane adapter 1226 is arranged to support the weight of the tower crane 1200 when the tower crane 1200 is installed on the WTG 102. The removeable crane adapter 1226 can be any shape or size and need not be circular in cross section.

The removeable crane adapter 1226 allows the tower crane 1200 to be mounted on the WTG 102 without scratching the WTG tower 1 10 or the transition piece 108. This means that the WTG 102 will not need an additional coat of paint to treat scratches left by the installation and operation of the tower crane 1200.

Since the removeable crane adapter 1226 can be removed after the tower crane 1200 has been removed from the WTG 102, the removeable crane adapter 1226 is reusable. This reduces the cost of the WTG 102 installation. In some embodiments, the removeable crane adapter 1226 is preinstalled on the transition piece 108.

Discussion of the method installing the tower crane 1200 on the WTG 102 will now be discussed in further detail in reference to Figures 13 and 15. Figures 13 and 15 show a perspective view of a crane according to an embodiment.

Turning to Figure 13, the removeable crane adapter 1226 has been attached on the transition piece 108 as shown in step 1 100 as shown in Figure 1 1. The removeable crane adapter 1226 is ready to receive the tower segment receiving unit 1230.

The tower segment receiving unit 1230 has been raised with respect to the tower crane structure 1228 such that it is aligned slightly above a fixing position on the WTG 102. In this way, the tower segment receiving unit 1230 has been raised such that it is at the same height as the removeable crane adapter 1226 mounted on the transition piece 108. Accordingly one portion, e.g. the tower segment receiving unit 1230 is suspended above the deck of the vessel 100.

In this way, the tower crane structure 1228 is a support structure 1228 which suspends at least one portion of the crane 1200 above the vessel. The tower segment receiving unit 1230 optionally comprises a drive mechanism (not shown) mounted in the frame 1234 for lifting the tower segment receiving unit 1230 up the tower crane structure 1228.

The drive mechanism comprises a drive pinion coupled to a drive shaft of a motor (not shown). The drive pinion engages with one or more racks on one or more surfaces of the first tower segment 1212 and also the new tower segments 1204, 1206, 1208. As the drive pinions engage the rack and rotate, the rack moves with respect to the drive pinions. Accordingly, the tower segment receiving unit 1230 moves with respect to the first tower segment 1212. This means that the tower segment receiving unit 1230 can climb the tower structure 1228 and move from the lowered position as shown in Figure 12 to the raised suspend position as shown in Figure 13. Indeed in some embodiments, the drive mechanism is similar to the rack and pinion mechanism 918, 920 described in Figure 9.

Optionally, the tower segment receiving unit 1230 does not move from the lowered position to the raised suspended position. Instead, the tower segment receiving unit 1230 is transported on the vessel 100 to the transition piece 102 of the WTG 102 in the raised suspended position.

Optionally, the motion compensation platform 324 comprises a lifting platform for raising the first tower segment 1212 or new connectable tower segments 1204, 1206, 1208 relative to the WTG 102. The lifting platform can comprise hydraulic actuators (not shown) coupled to a scissor linkage for changing the height of the lifting platform.

Returning to Figure 13, the tower segment receiving unit 1230 comprises a first coupling arm 1300 and a second coupling arm 1302. The first and second coupling arms 1300, 1302 are arranged to be positioned either side of the transition piece 108. The first coupling arm 1300 comprises at least one first notch 1304 which is engageable with at least one first protruding peg 1306 on the removeable crane adapter 1226. The second coupling arm 1302 comprises at least one second notch 1308 which is engageable with at least one second protruding peg 1310 on the removeable crane adapter 1226. Figure 13 shows that the first and second coupling arms 1300, 1302 each comprise two notches 1304, 1308 which engage with respective pegs 1306, 1310. In this way the moveable crane body comprises couplings 1304, 1308 which are mechanically engageable with couplings 1306, 1310 mounted on a removeable crane adapter 1226.

Once the tower segment receiving unit 1230 has been moved to the raised position as shown in Figure 13, the vessel 100 is moved towards the transition piece 108 and relative movement between the vessel 100 and the WTG 102 is compensated.

Figure 14 shows the tower segment receiving unit 1230 mounted on the removeable crane adapter 1226 according to step 1 102 as shown in Figure 1 1 . Accordingly, the suspended tower segment receiving unit 1230 and the tower crane structure 228 are transferred between the vessel 100 and the WTG 102 as shown in step 1 102 in Figure 1 1.

In this way, the transition piece 108 and the foundation 104 are entirely supporting the weight of the tower crane 1200 since the tower segment receiving unit 1230 is fixed to the transition piece 108 via the removeable crane adapter 1226 according to step 1104 as show in Figure 1 1. At the same time the support structure 1228 provides a dual purpose. Firstly, the support structure 1228 allows the tower segment receiving unit 1230 to be suspended above the vessel 100. Secondly, the support structure 1228 is the tower crane structure 1228 for providing the vertical height of the tower crane 1200.

In some embodiments, the vessel 100 is optionally tethered to the transition piece 108 by a tether 1400. The tether 1400 can be used to limit the movement of the vessel 100 with respect to the transition piece 108 in one or more directions. The tether 1400 as shown in Figure 14 is a strap wrapped around the transition piece 108, but the tether 1400 can be a mooring line attached at one end to the transition piece 108 and to the vessel 100 at the other end. In other embodiments, the tether 1400 can be any number of straps, lines or ropes or any other suitable means for attaching the vessel 100 to the transition piece 108. By tethering the vessel 100 to the transition piece 108, the relative movement of the vessel 100 with respect to the transition piece 108 of WTG 102 can be limited. This can make the motion compensation when transferring the tower crane 1200 easier because there will be fewer degrees of relative movement between the vessel 100 and the transition piece 108. Additionally or alternatively, the vessel 100 can use dynamic positioning to fix the position of the vessel 100 with respect to the transition piece 108 as mentioned above.

The tower segment receiving unit 1230 is then lowered on to the removeable crane adapter 1226 so that the coupling arms 1300, 1302 engage the pegs 306, 310 of the crane adapter 1226. Once the first and second coupling arms 1300, 1302 are in engagement with the removeable crane adapter 1226, the first and second coupling arms can optionally be further secured to the transition piece 108. The first and second coupling arms 1300, 1302 can be bolted, clipped or clamped to the removeable crane adapter 1226 to prevent the tower crane 1200 from moving with respect to the transition piece 108.

Additionally or alternatively, the removeable crane adapter comprises a locking mechanism 1406 for actively securing the coupling arms 1300, 1302 to the adapter 1226. The locking mechanism 1406 comprises a first latch 1402 and a second latch 1404 arranged to move between a released position and a locked position. When in the locked position, the first and second latches 1402, 1404 physically engage the first and second coupling arms 1300, 1302 and counteract any turning moment the tower crane 1200 is creating about the removeable crane adapter 1226. In some embodiments, the locking mechanism 1406 is hydraulically actuated.

The tower crane structure 1228, as shown in Figure 14, has also moved with respect to the tower segment receiving unit 1230 and the transition piece 108. The driving mechanism which is used by the tower segment receiving unit 1230 to climb the tower crane structure 1228 is optionally also a lifting mechanism to lift the tower crane structure 1228 to an operational position. The arrow as shown in Figure 14 indicates the direction that the tower crane structure 1228 is lifted by the tower segment receiving unit 1230.

Another embodiment will now be described in reference to Figures 15 to 17. Figures 15 to 17 show a perspective view of the tower crane 1200 mounted on the vessel 100 or the transition piece 108.

The tower crane 1200 as shown in Figures 15 to 17 is the same as described in reference to the previous embodiments shown in Figures 12 to 14 and the installation of the tower crane structure 228 is the same. However, the embodiment differs in that a crane adapter 1500 mounts differently on the tower segment receiving unit 1230.

The crane adapter 1500 is mountable on the tower crane receiving unit 1230 during transportation of the tower crane 1200 to the WTG 102 installation site. Accordingly, the crane adapter 1500 takes up less space on the vessel 100.

In contrast to the preceding embodiments, the crane adapter 1500 comprises first and second coupling arms 1508, 1510 each comprising a notch 1512, 1514 which engage with a projecting peg 1306, 1310 on the transition piece 108. The coupling arms 1508, 1510 engage with the transition piece 108 in a similar way to the previous embodiments.

In addition, the crane adapter 1500 comprises a first and second stabilizing arm 1502, 1504 for engagement with a first and a second projecting stop elements 1506 mounted on the transition piece 108. The stabilizing arms 1502, 1504, engage with the first and second stop elements 1506 and prevent the tower crane 1200 and the adapter 1500 tilting with respect to the transition piece 108. In other embodiments, the first and second stabilising arms 1502, 1504 are the same as the first and second coupling arms 1508, 1510 and similarly notches for engagement with additional projecting studs (not shown) from the transition piece 108.

Figure 16 shows the first stabilizing arm 1502 engaged with the first projecting stop element 1506. The stabilizing arms as shown in Figures 15 to 17 can be used in combination with the coupling arms as described in any of the preceding embodiments.

Figure 16 shows the crane adapter 1500 mounted on the transition piece 108. The tower crane 1200 has hoisted the crane adapter 1500 on to the transition piece 108 similar to the process as described in reference to the previous embodiments.

The crane adapter 1500 comprises a first winch 1600 and a second winch 1602 arranged to hoist the tower crane 1200 up to the crane adapter 1500 mounted on the transition piece 108. In other embodiments, the crane adapter 1500 can have a single winch. The tower segment receiving unit 1230 comprises one or more brackets 1604 for coupling to cables 1606 from the first and second winches 1602, 1604. This means that there are only cable connections between the crane adapter 1500 and the tower crane 1200 when the tower crane 1200 is transferred to the transition piece 108. This can make the transfer simpler and require less motion compensation. In some embodiments, the cables 1606 are always connected between the crane adapter 1500 and the tower segment receiving unit 1230. This means that time can be saved installing the tower crane 1200 on the crane adapter 1500.

The crane adapter 1500 comprises a notch 1608 for receiving a projecting stud 1610 on each side of the tower segment receiving unit 1230. When the tower crane 1200 is hoisted by the first and second winches 1600, 1602, the stud 1610 engages an inclined surface 1612 on the underside of the crane adapter 1500 as the tower segment receiving unit 1230 approaches the crane adapter 1500. The inclined surface 1612 guides the stud 1610 into the notch 1608. Accordingly, the first and second winches only need to hoist the tower crane 1200 from the vessel 100 in a vertical direction and the underside of the crane adapter 1500 is shaped to guide the tower crane 1200 into engagement with the crane adapter 1500.

Figure 17 shows the tower crane 1200 in mechanical engagement with the crane adapter 1500. Once the inclined surface 1612 abuts a reciprocally inclined surface 1702 of the tower segment receiving unit 1230, the tower crane 1200 is secured to the crane adapter 1500.

In some embodiments, the crane adapter 1500 comprises a locking mechanism 1700 for securing the stud 1610 in position in the notch 1608. The locking mechanism comprises a bar which is moveable between an unlocked position and a locked, secured position. In the locked, secured position, the bar 1700 is below the projecting stud 1610 and prevents the stud 1610 from being removed from the notch 1608. In this way, the crane adapter comprises a first coupling with the transition piece 108 and a second coupling with the tower crane 120.

When the tower crane 1200 is hoisted into the position as shown in Figure 17 with respect to the crane adapter 1500, the locking mechanism is moved to the secure position and the tower crane 1200 is secured to the crane adapter 1500. In some embodiments, the locking mechanism is hydraulically actuated. Once the locking mechanism 1700 has been actuated, the first and second winches 1600, 1602 can be disengaged. In other embodiments, any other suitable securing mechanism can be used to securely fix the crane adapter 1500 to the tower crane 1200 such as bolts, moveable pins, clamps, etc. In other embodiments, the locking mechanism is not required and the first and second winches 1600, 1602 positively hold the tower crane 1200 against the crane adapter 1500. In some embodiments, the first and second winches 1600, 1602 comprise brakes for holding the winches 1600, 1602 with the cables 1606 a fully retracted state. Accordingly, the first and second winches 1600, 1602 are a redundancy for keeping the tower crane 1200 fixed with respect to the crane adapter 1500 and the WTG 102. In order to uninstall the tower crane 120, the reverse steps are taken to the installation described herein.

In another embodiment two or more embodiments are combined. Features of one embodiment can be combined with features of other embodiments.

Embodiments of the present invention have been discussed with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the invention.

Claims

1 . A method of installing a crane on a portion of an offshore wind turbine generator from a vessel comprising:

hoisting a removeable crane adapter having a first coupling on to the portion of the offshore wind turbine generator; and

mounting a crane having a second coupling on the removeable crane adapter, the second coupling being mechanically engageable with the first coupling wherein the crane adapter supports the weight of the crane on the portion of the offshore wind turbine.

2. A method according to claim 1 wherein the attaching the removeable crane adapter comprises removably fixing the removeable crane adapter to one or more protrusions on the portion of the offshore wind turbine generator.

3. A method according to claim 2 wherein the one or more protrusions is a T-flange, a bracket, a pad eye, a hook, or loop fixed to the portion of the offshore wind turbine.

4. A method according to any of claims 1 to 3 wherein the step of attaching comprises using bolts, straps, hooks, latch-catch mechanism the removeable crane adapter to the portion of the offshore wind turbine generator.

5. A method according to any of the preceding claims wherein the method comprises hoisting the removeable crane adapter on to the portion of the offshore wind turbine generator with the crane mounted on the vessel.

6. A method according to any of the preceding claims wherein the method comprises compensating for relative motion between the portion of the offshore wind turbine generator and the vessel such the crane and / or the removeable crane adapter is stable relative to the portion of the offshore wind turbine during the steps of attaching and / or mounting.

7. A method according to claim 6 wherein the compensating comprises adjusting a moveable actuator coupled to a motion compensation platform and / or adjustable arms with respect to the vessel.

8. A method according to any of the preceding claims wherein the method comprises securing the crane to the portion of the offshore wind turbine.

9. A method according to claim 8 wherein the securing comprises closing one or more moveable doors hinged on a body of the crane around the portion of the offshore wind turbine generator.

10. A method according to any of claims 8 or 9 wherein the securing comprises engaging a coupling mounted on the crane with an external protrusion of the portion of the offshore wind turbine generator.

11. A method according to any of claims 8 to 10 wherein the securing comprises suspending the crane from cables from the portion of the offshore wind turbine generator.

12. A method according to any of the preceding claims wherein the step of mounting the crane comprises elevating the crane from a first position where the crane is adjacent to a deck of the vessel and to a second position wherein the crane is suspended above the deck of the vessel.

13. A method according to any of the preceding claims wherein the step of attaching the adapter comprises elevating the removeable crane adapter from a first position where the removeable crane adapter is adjacent to a deck of the vessel and to a second position wherein the removeable crane adapter is suspended above the deck of the vessel.

14. A method according to any of the preceding claims wherein the crane is fixed with respect to the removeable crane adapter after mounting and during operation of the crane.

15. A method according to any of the preceding claims wherein the crane is moveable with respect to the removeable crane adapter after mounting.

16. A method according to any of the preceding claims wherein the step of mounting comprises hoisting the crane with a winch mounted on the removeable crane adapter.

17. A crane for lifting one or more a portions of an offshore wind turbine generator comprising:

a crane body; and

a first coupling mounted on the crane body, the first coupling being mechanically engageable with a second coupling mounted on a removeable crane adapter hoisted to the portion of the offshore wind turbine generator wherein the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.

18. A removeable crane adapter attachable to a portion of an offshore wind turbine generator comprising:

an adapter body hoistable on to the portion of the offshore wind turbine generator; and

a first coupling mounted on the adapter body, the first coupling being engageable with a second coupling mounted on a crane wherein the first and second couplings are engageable and the crane adapter supports the weight of the crane when the crane is mounted on the removeable crane adapter.

19. A removeable crane adapter according to claim 18 wherein the adapter body is circular and is arranged to surround the portion of the offshore wind turbine generator.

20. A removeable crane adapter according to claims 18 or 19 wherein the adapter body comprises a shoulder portion engageable with a flange of the portion of the offshore wind turbine generator.

21. A removeable crane adapter according to claims 18 to 20 wherein the first and second coupling comprises a loop and hook arrangement.

22. A crane mounting system for installing on one or more portions of an offshore wind turbine generator comprising:

a crane for lifting one or more a portions of an offshore wind turbine generator having:

a crane body; and

a first coupling mounted on the crane body,

a removeable crane adapter hoistable on to a portion of an offshore wind turbine generator having:

an adapter body attachable to the portion of the offshore wind turbine generator; and

a second coupling mounted on the adapter body; wherein the first coupling is mechanically engageable with the second coupling and the removeable crane adapter supports the weight of the crane when the crane is mounted to the removeable crane adapter.