EP-4739612-A1 - HEAVE COMPENSATOR FOR OFFSHORE CRANE, OFFSHORE CRANE, VESSEL AND HOISTING METHOD

EP4739612A1EP 4739612 A1EP4739612 A1EP 4739612A1EP-4739612-A1

Abstract

An offshore crane and a heave compensator (10) suspended in-line from a lower block, and to a method for hoisting an object. The heave compensator comprises a frame (11a, 11b) to be suspended in-line from the lower block, a vertical passive heave compensation system and a vertical active heave compensation system. The passive heave compensation system comprises a vertical passive cylinder (20) having a downward extending piston rod (21), medium-separators (25) and multiple pressurized gas tanks (26a-t). The vertical active heave compensation system comprises a vertical column (31) connected to the downward extending piston rod and extending vertically parallel to the passive cylinder, wherein the vertical column is vertically guided by the frame, and wherein a vertical rack (33) is mounted to the vertical column and one or more pinions (34) and associated electric motors (35) are supported by the frame.

Inventors

BOONTJES, Lucas
KROMDIJK, HARMEN JAN
WETERINGS, HENDRIKUS JACOBUS

Assignees

Itrec B.V.

Dates

Publication Date: 20260513
Application Date: 20240705

Claims (15)

1. Offshore crane for use on a vessel for handling an object (1), e.g. a wind turbine component, the crane comprising a hoist cable extending between a hoist winch and a lower block, wherein a heave compensator (10) is suspended in-line from the lower block, and wherein the object can be suspended from the heave compensator, e.g. via a spreader, the heave compensator comprising a frame, the heave compensator further comprising a vertical passive heave compensation system with: a vertical passive cylinder (20) having a cylinder body (22) supported by the frame (11a, 11b), a piston (23) and a vertically downwards extending piston rod (21), the piston delimiting a lower rod-side chamber (23a) and an upper piston-side chamber (23b) of the passive cylinder, one or more medium-separators (25) each having a hydraulic-side chamber (25a) and a gas-side chamber (25b), which hydraulic-side chamber is connected to the rod-side chamber (23a) of the passive cylinder, multiple pressurized gas tanks (26a-26t), each tank selectively connectable via a respective gas tank valve (26a’, 26b’) to the gas-side chamber (25b) of the medium-separator (25), the heave compensator further comprising a vertical active heave compensation system with: a vertical column (31) connected to the downward extending piston rod and extending vertically parallel to the passive cylinder (20), wherein the vertical column is vertically guided by the frame, and wherein a vertical rack is mounted to the vertical column, one or more pinions (34) and associated electric motors (35), supported by the frame, a battery (36) to provide power to the one or more electric motors (35).
2. Offshore crane according to claim 1 , wherein the heave compensator is configured: with the passive cylinder (20) vertically oriented at a central position, flanked by two opposite banks of vertically oriented pressurized gas tanks, e.g. each bank comprising a set of one of more pressurized gas tanks having the same pressure; and the one or more vertically oriented medium-separators between the banks of gas tanks at one side of the passive cylinder, and wherein the vertical column, rack and pinions of the active heave compensation system are provided between the banks of gas tanks at a side of the passive cylinder opposite the one or more medium-separators, and wherein the battery of the active heave compensation system is provided adjacent the one or more vertically oriented medium-separators.
3. Offshore crane according to one or more of the preceding claims, wherein distinct sets of pressurized gas tanks are provided, each set comprising one of more pressurized gas tanks having the same pressure.
4. Offshore crane according to one or more of the preceding claims, wherein the frame of the heave compensator comprises: a top frame (11 a) suspended in-line from the lower block, the top frame supporting the cylinder body of the passive cylinder and one or more pinions and associated electric motors, and preferably also upper column guides (32a); a landing frame (11 b) mounted to the cylinder body of the passive cylinder and preferably also comprising lower column guides (32b).
5. Offshore crane according to one or more of the preceding claims, the lower block is provided with a connector and the heave compensator comprises a connector guidance funnel (12).
6. Offshore crane according to one or more of the preceding claims, wherein a supercapacitor is provided to accept and deliver power from and to the electric motor when functioning as an electric generator.
7. Offshore crane according to one or more of the preceding claims, further comprising a spreader configured for lifting wind turbine parts such as monopiles, blades or nacelles, or for lifting freight containers, which spreader is connectable or connected to the heave compensator to suspend from the heave compensator.
8. Offshore crane according to one or more of the preceding claims, wherein a sensor and control system is provided using the information of the sensor to control the active heave compensation system, e.g. a position sensor to determine the distance between the object and the spreader, and wherein the information of the position sensor is used to operate the active heave compensation system so as to maintain a stable distance between the spreader and the object to facilitate the connection of the object to the spreader.
9. Vessel, e.g. for the installation of an object, e.g. a wind turbine component, comprising an offshore crane according to one or more of the preceding claims 1-8.
10. A heave compensator configured to be suspended in-line from a lower block of an offshore crane comprising a hoist cable extending between a hoist winch and the lower block, and wherein an object can be suspended from the heave compensator, e.g. via a spreader; the heave compensator comprising a frame; the heave compensator comprising a vertical passive heave compensation system with: a vertical passive cylinder having a cylinder body supported by the frame, a piston and a vertically downwards extending piston rod, the piston delimiting a lower rodside chamber and an upper piston-side chamber of the passive cylinder; one or more medium-separators each having a hydraulic-side chamber and a gasside chamber, which hydraulic-side chamber is connected to the rod-side chamber of the passive cylinder; multiple pressurized gas tanks, each tank selectively connectable via a respective gas tank valve to the gas-side chamber of the medium-separator; the heave compensator further comprising a vertical active heave compensation system with: a vertical column, connected to the downward extending piston rod and extending vertically parallel to the passive cylinder, wherein the vertical column is vertically guided by the frame, and wherein a vertical rack is mounted to the vertical column; one or more pinions and associated electric motors, supported by the frame; a battery to provide power to the one or more electric motors.
11. Offshore crane for use on a vessel for handling an object, e.g. a wind turbine component, the crane comprising a hoist cable extending between a hoist winch and a lower block, wherein a heave compensator is suspended in-line from the lower block, and wherein the object can be suspended from the heave compensator, e.g. via a spreader; the heave compensator comprising a frame; the heave compensator comprising a vertical passive heave compensation system with: a vertical passive cylinder having a cylinder body, a piston and a vertically downwards extending piston rod supported by the frame, the piston delimiting a lower rod-side chamber and an upper piston-side chamber of the passive cylinder; one or more medium-separators each having a hydraulic-side chamber and a gasside chamber, which hydraulic-side chamber is connected to the upper piston-side chamber of the passive cylinder; multiple pressurized gas tanks, each tank selectively connectable via a respective gas tank valve to the gas-side chamber of the medium-separator; the heave compensator further comprising a vertical active heave compensation system with: a vertical column connected to the cylinder body and extending vertically parallel to the passive cylinder, wherein the vertical column is vertically guided by the frame, and wherein a vertical rack is mounted to the vertical column; one or more pinions and associated electric motors, supported by the frame; a battery to provide power to the one or more electric motors.
12. Hoisting method for an object, e.g. a wind turbine component, wherein use is made of a vessel according to claim 9, comprising the steps of: a) providing the object on a vessel susceptible to heave; b) optionally connecting the heave compensator to the crane and providing the heave compensator of the offshore crane in the vicinity of the object; c) connecting the object to the heave compensator; d) operating the passive heave compensation system and optionally the active heave compensation system and hoisting the object.
13. Hoisting method according to claim 12, wherein prior to step c) the method furthermore comprises the steps of: connecting a spreader to the heave compensator to suspend from the heave compensator; providing a position sensor to determine the distance between the object and the spreader; using information from the position sensor to operate the active heave compensation system so as to maintain a stable distance between the spreader and the object to facilitate the connection of the object to the spreader.
14. Hoisting method according to claim 12 or 13, wherein distinct sets of pressurized gas tanks are provided, each set comprising one of more pressurized gas tanks having the same pressure, and wherein during step d) first one set of tanks is connected to the mediumseparator, followed by another set of tanks.
15. Hoisting method according to any one or more of claims 11 - 14, wherein prior to step d), the method comprises the step of providing a position sensor to determine the distance between the object and the spreader; and during step d) using information from the position sensor to operate the active heave compensation system as a brake mechanism for the upward motion of the piston rod of the passive cylinder, in particular when high-pressure tanks are connected to the gas-side chamber of the medium-separator to enable fast lifting.

Description

HEAVE COMPENSATOR FOR OFFSHORE CRANE, OFFSHORE CRANE, VESSEL AND HOISTING METHOD The present invention relates to an offshore crane with a heave compensator. In the field of installation of offshore wind turbines one approach envisages that a vessel is used both for transportation of the wind turbine, or components thereof, between an onshore location and the offshore location and for installation of the wind turbine, or components thereof, at the offshore location. So, for example, the vessel is loaded with monopiles, commonly stored horizontally on deck, at the onshore location and then sails to the offshore windfarm. There the crane of the vessel is used for upending the monopile and to install the monopile, e.g. further making use of a monopile gripper to accurately position the monopile. In another example, the foundation is already installed and the vessel is loaded with the mast, nacelle, and blades of the wind turbine. The vessel sails to the windfarm and then the crane is used to install the mast on the foundation, followed by installation of the nacelle, and then the installation of the blades. Alternative installation processes are known as well. Another approach in the field of installation of offshore wind turbines envisages that a dedicated installation vessel is positioned at the offshore location, the installation vessel having a crane configured for handling of the wind turbine and/or components thereof. A feeder vessel is then used for shuttling between an onshore location and the offshore location in order to supply wind turbine components. For example, a jack-up type or semi-submersible type installation vessel is positioned at the offshore location. The feeder vessel, e.g. self- propelled or a towed barge, is then used, for example, for supply of monopiles or other foundations. A drawback of the “feeder vessel approach” is the need for offloading the wind turbine components from the feeder vessel. Herein, commonly, the feeder vessel is floating and therefore subject to wave-induced heave motion. On the other hand, the crane on the installation vessel is not, in a jack-up vessel, or hardly, in a semi-submersible vessel or with a different response, subject to heave motion. In this approach, the relative motions in combination with the large weight of the object to be hoisted can be problematic. For example, offloading a monopile in horizontal orientation from the feeder vessel can be difficult, taking into account the enormous weight and dimensions, e.g. a length over 80 meters, a diameter of over 8 meters, e.g. up to 12 - 13 meters, and a weight of over 2000 tonnes. Proposals have been made to provide the feeder vessel with a heave motion compensated carrier that is configured to support the wind turbine component thereon that is to be offloaded by the crane. The carrier is supported on the hull of the feeder vessel by means of a heave motion compensating support system. Examples of these proposals are presented in WO2022/238152 and W02020/011679. The present invention aims to provide a solution, wherein a crane on the installation vessel is provided with a heave motion system. Such a crane can be used instead of, or in addition to a heave motion compensated carrier on a feeder vessel. For example, the carrier with the object is able to carry out rotations, while the heave compensator of the crane is provided to compensate for all types of heave. The first aspect of the invention provides an offshore crane according to claim 1 and 11 , a vessel according to claim 9, a heave compensator according to claim 10 and a method according to claim 12. The inventive offshore crane is suitable for use on a vessel for handling an object, e.g. a wind turbine component, e.g. an installation vessel for offloading objects such as wind turbine components from a feeder vessel, such as from a barge. Commonly, the objects such as monopiles or rotor blades are horizontally supported on the feeder vessel. The object can also be a monopile for forming a foundation, e.g. for a substation, drilling platform(s) or even as foundation for a viaduct or the like. For example, the feeder vessel is moved into reach of the inventive offshore crane, e.g. mounted on an installation vessel, which is already present at the offshore location where the wind turbine is to be installed. For example, monopile main design drivers such as turbines of up to 15 megawatts with rotor diameters of up to 230 metres, resistant to extreme wind loads, especially those driven by hurricanes or typhoons, operable in water depths of up to 65 metres and with wave loads in the Atlantic and Pacific Oceans lead to monopile design requirements with bottom diameters between 8 and 11 metres, lengths of up to 120 metres and wall thicknesses up to 150 millimetres. The final weight of such monopiles can reach up to 2500 tonnes, i.e. 2.500.000 kg. The crane comprises a hoist cable extending between a hoist winch and a lower block, suspended from the h