Heave compensation device

Abstract

A heave compensation device (1) for controlling the vertical position of a load (35), comprising a first frame, a second frame for connection to the load (35), the second frame arranged to move decoupled with respect to the first frame, and a configurable (gas- or) hydro-pneumatic spring (401), which includes at least one pressure vessel (405) that has a fiber layer (61).

Description

HEAVE COMPENSATION DEVICEBACKGROUND

[0001] The invention relates to controlling the vertical position of a load (by decoupling, stabilizing, balancing or moving the load). The invention relates to a heave compensation device for decoupling a load to be lifted by a hoisting device. The heave compensation device is to be connected to a hook of the hoisting device. The invention further relates to a hoisting system, preferably controlling the vertical position of the load during heaving motions, more preferably a spring balanced hoisting system. The invention also relates to a method of heave compensated hoisting.

[0002] By controlling the vertical position of a load (by decoupling, stabilizing, balancing or moving the load), the load can be transferred from a heaving object to a fixed object, from a fixed object to a heaving object, or between two heaving objects. In the prior art, especially, prior art relating to offshore applications, springs have been used to decouple a vertical movement of the load from the hoisting device, which could be a crane on a ship. In prior art, the spring is coupled linearly to the load.

[0003] A spring-balanced decoupling device is known from EP 3 653 561, the content of which is fully incorporated here. EP 3 653 561 discloses examples of balanced heave compensation devices.

[0004] Other examples of heave compensation devices comprise passive heave compensation devices (with or without active components), which comprise a spring placed in line with a load path.

[0005] Heave compensation devices that are coupled to the hook or a hoisting wire of an existing hoisting system can be very heavy, as a result of the combination of components, which include structural framing, hydraulic systems, and connective elements. These parts are typically made of high-strength materials, such as steel. Gas cylinders, for example, containing gas volumes and medium separators according to the prior art are made of steel. Steel is known to be heavy, but according to the prior art it is the only material with properties suitable for heave compensation.

[0006] Recently, developments in regular lifting operations have introduced more demanding requirements for heave compensation devices. For higher loads and more violent heaving motions, a larger gas volume with higher flow rates is beneficial to control the load. Onemethod of meeting these demands involves increasing the number or the size of gas cylinders to raise total gas volume, though this adds weight and may overcomplicate the system. Alternatively, parameters of the hydraulic system can be modified, such as the fluid volumes or valve configurations.

[0007] By virtue of the weight of the heave compensation device, the net load that can be suspended by the hoisting wire is decreased. It is thus a goal to decrease the weight of such heave compensation devices while also meeting performance requirements, allowing the operation in harsh conditions. It is an object of the invention to provide sufficient gas volume suitable for heavy duty heave compensation.SUMMARY OF THE INVENTION

[0008] According to an aspect of the invention a heave compensation device is provided for decoupling a load. A heave compensation device with reduced weight is provided. The heave compensation device has a first frame and a second frame that can be coupled to the load. The first frame and the second frame can move with respect to each other, resulting in the decoupling of the load. In embodiments, the heave compensation device comprises a preferably configurable (gas- or) hydro-pneumatic spring system, preferably coupled to first and second frame. To configure the (gas- or) hydro-pneumatic spring system, at least one pressure vessel is provided. That vessel has a fiber layer for weight reduction, while retaining high strength and other properties required for heave compensation. The fiber layer provides strength and has little wear even though the vessel is at least partially filled and emptied at high frequencies, such as every 6-12 seconds, and with a high number of cycles, such as >300.000 and preferably >1.000.000 and more preferably > 5 Mio cycles during its service life.

[0009] Surprisingly, the inventors found a significant weight reduction of the heave compensation device can be found in providing a fiber layer for the pressure vessel, while meeting performance requirements for heave compensation devices. It is noted that fluid pressure vessels for storage and transport purposes are typically designed for a limited number of full pressure cycles, often less than lO.OOOcycles. These vessels are generally intended for infrequent filling and discharge, and are not suited for high-frequency cycling in heave compensation.

[0010] In embodiments, a gas spring is provided that comprises a gas volume acting on a cylinder directly. In embodiments, a hydro-pneumatic spring comprises a medium separator in between the cylinder and the gas: an oil volume acts on the cylinder and the gas acts on a pistonbetween the gas and the oil volume. (Gas- or) hydro-pneumatic springs can be configured. A (gas- or) hydro-pneumatic spring can comprise a configuration set up to increase or reduce the volume and / or the filling amount of the oil and / or the gas volume of the spring, thereby configuring the spring and adapting its spring behavior.

[0011] Preferably the heave compensation device is arranged to be deployed in a hoisting device. The heave compensation device has on the first frame a connection unit for connection to a hoisting device. The heave compensation device has on the second frame a carrying or support unit that can be coupled to the load.

[0012] In embodiments a transmission is provided between the first and second frame, which guides first and second frames and which provides a force transmission between the two frames. The configurable (gas- or) hydro-pneumatic spring is preferably part of the force transmission. The transmission is arranged to at least partially, preferably fully, decouple movement of the load connected to the second frame from movement of the first frame.

[0013] In embodiments, the pressure vessel with fiber layer is a fiber overlayed pressure vessel. The fiber layer is an outer layer of the vessel. This results in a highly reinforced structure able to resist high pressures by the gas in the vessel. In some embodiments, the fiber layer is the only layer of vessel. The fiber layer is then resistant to gas penetration, preferably resistant to N2.

[0014] In embodiments, the pressure vessel comprises an inner liner, which is partially, substantially or fully covered by a fiber layer or more preferably a layer of fiber composite. The inner liner provides the gas-penetration prevention. The inventors found the combination of a fiber layer combined with an inner liner provides a relevant weight reduction when compared with full steel pressure vessel. Compared to embodiments with an only-fiber layer, a combination of inner liner with fiber layer for the pressure vessel provides a further weight reduction.

[0015] In embodiments, the inner liner of the pressure vessel consists of one or multiple layers of metal, preferably aluminum or steel and / or plastic, preferably HDPE or Polyamide, more preferably PAI 1.

[0016] In embodiments, the inner liner of the pressure vessel is made of metal with a thickness of at least 2 mm. In further embodiments, the inner liner is made of plastic with a thickness of at least 1 mm.

[0017] In embodiments, the fiber composite of the pressure vessel comprises or consists of carbon fiber.

[0018] In embodiments, the pressure vessel has an access point. The access point can be neck of the pressure vessel. The access point comprises a channel allowing the gas to enter and exit the pressure vessel. The channel or a port opening can be 1 inch BSP or larger, or 1 / i inch BSP or larger.

[0019] In an embodiment, the pressure vessel will have a central axis extending in the length direction of the pressure vessel. Preferably the access point is at an end of the pressure vessel in that length direction. In embodiments, the pressure vessel has a length of at least 1200mm. In embodiments, the pressure vessel has a circular cross-section across the central axis. In embodiments, the pressure vessel has a radius of at least 300mm. In embodiments, the channel or port opening of the pressure vessel will have a circular cross-section across the central axis. In embodiments, the ratio of the cross-sectional area of the channel / port opening of the at least one access point with respect to a cross-sectional area of the pressure vessel across its length axis is at least 0.003, preferably at least 0.004. The ratio is >0.004 for a pressure vessel with 1.5 inch access channel and a 60cm diameter pressure vessel (0.0041).

[0020] In embodiments, the pressure vessel has a water volume of at least 250 liters, preferably at least 315 liters. In embodiments, the pressure vessel has a port opening of at least 1 / i inch, preferably at least 1 % inch, and more preferably at least 2”. In embodiments the ratio of port opening (inch, in BSP) to water volume (liters) is at least 0.002 (inch / liters), preferably at least 0.025, and more preferably at least 0.003. At a ratio of 0.002 it was found that the heave compensator could operate. However, at a ratio of 0.0025 or higher any restraints in operations, such a reduced frequency or reduced strokes, could be lifted and full operation was possible.

[0021] In embodiments, the pressure vessel has a working pressure of at least 200 bars.

[0022] In embodiments, the pressure vessel is suitable for over 30.000 pressure cycles, preferably over 1 Mio and more preferably over 5 Mio cycles between working pressure and 20% of working pressure.

[0023] In embodiments, the fiber layer has a thickness of at least 6mm, preferably 8mm, and more preferably at least 10mm.

[0024] In embodiments, the pressure vessel has a water volume of at least 100 liters.

[0025] In embodiments, the pressure vessel has an access point and a connection for connecting the pressure vessel to a piston type accumulator of the (gas- or) hydro-pneumatic spring system.

[0026] In embodiments, the transmission comprises at least one pivoting arm, with the (gas- or) hydro-pneumatic spring system coupled to the pivoting arm, wherein the transmission is preferably arranged as a spring-balanced system.

[0027] According to a further aspect a hoisting device is provided with the heave compensation device as disclosed herein. The connection unit of the heave compensation device is connected to a hoisting wire of the hoisting device.

[0028] According to a further aspect a ship is provided comprising a hoisting device as disclosed herein.BRIEF DESCRIPTION OF DRAWINGS

[0029] Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:FIG. 1 is a schematic diagram showing a detailed embodiment of a heave compensation device comprising a fiber overlayed pressure vessel;FIG. 2 is a schematic diagram showing an embodiment of a linear heave compensator comprising a fiber overlayed pressure vessel;FIGs. 3a+b are schematic diagram showing a fiber overlayed pressure vessel in detail; and FIG. 4 is a schematic diagram showing a composition of fiber overlayed pressure vesselsDESCRIPTION OF EMBODIMENTS

[0030] Hereinafter, certain embodiments will be described in further detail. It should be appreciated, however, that these embodiments may not be construed as limiting the scope of protection for the present disclosure. Although this application is illustrated with examples relating to hoisting and / or heaving, the application is not limited to such application. The vessel according to the invention can be used in any weight balancing system. An embodiment disclosed here is a device comprising a first frame and second frame moveable with respect to the first frame and a configurable (gas- or) hydro-pneumatic spring, which includes at least one pressure vessel that has a fiber layer. This embodiment can have any of the other features disclosed herein.

[0031] FIG. l is a schematic diagram showing a detailed embodiment of a hook-based heave compensation device 1. Such a heave compensation device can be arranged in a hoisting device. The heave compensation device comprises a fiber overlayed pressure vessel 405. The pressure vessel is shown in more detail in FIG. 3.

[0032] The heave compensation device 1 can be used in an existing non-motion compensated crane. The heave compensation device 1 will convert the existing non-motion compensatedcrane into a crane that operates with the load decoupled, e.g. using balanced heave compensation. The heave compensation device 1 of this embodiment allows to add the decoupling feature to existing high-load cranes without having to make costly adaptations to the existing crane equipment. The heave compensation devices according to the invention are suitable for offshore transfers of large loads. Transfers can include feeder barge operations for transferring loads such as wind-turbine components between a heaving vessel and a fixed of floating crane vessel. Transfers can also include floating installation, wherein loads are transferred from a floating crane vessel to a fixed or floating landing target.

[0033] The heave compensation device 1 could also be easily connected and disconnected to any type of mechanical support or suspension system which is mounted on the ground or for example onto an off-shore platform. The heave compensation device 1 is suitable for deployment below the hook of a crane on a floating or fixed (jacked up) offshore crane vessel. The heave compensation device is lifted by a hook connected to a hoisting wire, the hook engaging connection unit 22. In embodiments, the heave compensation device 1 is lifted by a crane with a wire and hook. Although in this application a crane is used to illustrate the invention, clearly any kind of support structure can be used. The crane or support structure could be placed on a floating vessel. The vessel can be a heaving ship or platform.

[0034] In this application a heave compensation device 1 can be a device that decouples, preferably balances, a load 35 at different positions or can be a device that generally balances the load, preferably by spring loaded means. Embodiments of the heave compensation device comprise balancing a load at different positions of the heave compensation device, the balancing force being provided for the most part by spring loaded means, preferably (gas- or) hydro-pneumatic spring systems. Preferably loads of over 10 tons, preferably over 20 tons, and more preferably over 30 tons are supported and balanced using a heave compensation device 1.

[0035] The heave compensation device 1 comprises a first frame 2 having the connection unit 22. The connection unit 22 is a ring, which, in this embodiment, forms an integral part of a first frame 2.

[0036] The heave compensation device 1 further comprises a second frame 3 having a carrying unit 32 for suspending a load 35. In other embodiments, a load 35 can be supported by carrying unit 32.

[0037] The first frame 2 and second frame 3 can move with respect to each other. The connection unit 22 and carrying unit 32 move with respect to each other along a linear guideline 209. Preferably the connection unit 22 and / or the carrying unit 32 are positioned on theguideline 209. Preferably, in operation, the guideline 209 is generally parallel to the gravitational force, although in some embodiments, as result of heaving and other movements of a ship offshore, this can change.

[0038] A transmission couples the moving frame parts 2,3. In the embodiment, the transmission allows moving connection unit 22 with respect to carrying unit 32, resulting in an increase or reduction of the distance between the two suspension points 22,32. In balanced operation the suspension points are oriented along the vertical line, here the guide line 209, thereby thus controlling the vertical position of the load.

[0039] A linear guide is provided in the heave compensation device 1, which guides the moving frame parts 2,3 with respect to each other. The linear guide is part of the transmission. The linear guide is arranged such that the connection unit 22 and carrying unit 32 move along the straight guideline 209.

[0040] Preferably the transmission comprises one or more arms or beams 6,7 for transferring forces between the suspension points, the arm being positioned non-parallel, preferably at an angle between 2-178 degrees, with respect to the guideline 209 / the direction of the guide. In use the arms are at an angle with the vertical direction. Preferably one or more arms are pivotable with respect to a first frame 2 or second frame 3.

[0041] In the shown embodiment, the transmission comprises one or more beams 6,7 connected via one or more pivot connections 21,31,41. The beams and pivot connections transfer forces between the first and second frame.

[0042] In this embodiment, the transmission comprises two leverage units in the form of arms assemblies 50, 51 positioned on opposite sides of the linear guideline 209. As a result of their positioning, not aligned with the guideline 209, the arm assemblies allow providing a force at arm length, corresponding to a lever. Arm assemblies 50,51 work simultaneously and identically. The mechanical parts are labelled only on the left-hand side. Left-hand arm assembly 50 comprises an arm part 7 and a balancer arm 6. Arms 6,7 are connected to each other via a pivot point 41 that can comprise a bearing. Arm 6 is connected to the second frame 3 via pivot point 31. Arm 7 is connected to the first frame 2 via pivot point 21.

[0043] The second frame 3 has pivot points. Pivot point 31 is connected to the balancer arm 6 of arm assembly 50. Balancer arm 6 can pivot with respect to pivot point 31. Arms 6 and 7, part of the transmission, are connected at pivot point 41.

[0044] The transmission comprises force application points 41,42. At least one force application point 41 is positioned away from the linear guideline 209. The force application points are preferably arranged symmetrically around the guideline. Force application points arepreferably arranged so the carrying / supporting / suspension forces are guided symmetrically around the guideline. Preferably forces transmitted through said one or more force application points are not in line with, that is non-parallel to, the guideline 209.

[0045] In embodiments, the transmission comprises a (gas- or) hydro-pneumatic spring system 4. In embodiments the application points of the transmission are such that the orientation of the (hydro-) pneumatic spring changes and that a direction of said forces changes when frames 2 and 3 move with respect to each other and / or when the distance between the connection unit and the carrying unit changes. This will allow using the (gas- or) hydropneumatic springs as a spring in a spring-balanced system.

[0046] In this embodiment, pivot point 41 also forms a point of force application for (gas- or) hydro-pneumatic spring system 4. The (gas- or) hydro-pneumatic spring system 4 is arranged as a pulling device. The spring force is applied between application points 41 and 42. The (gas- or) hydro-pneumatic spring system comprises cylinder 401 that is connected to first frame 2 via pivoting connection point 42 and to beams 6,7 in pivot point 41. As point 41 is on arm 7 at a distance from pivot point 21, the distance between the two points 21,31 acts as a lever.

[0047] The (gas- or) hydro-pneumatic spring system 4 comprises cylinder 401, a first hydraulic connection 402, a second hydraulic connection 403, a piston type accumulator 404 and pressure vessel 405. The (gas- or) hydro-pneumatic spring system 4 allows setting the spring force of the (gas- or) hydro-pneumatic cylinder 401. One chamber of cylinder 401 is connected to the piston type accumulator 404 and will have a relatively high pressure. The other chamber 43, on the opposite side of the piston of cylinder 401, may have a limited, relatively low pressure at minimum compression of the spring. When compressed, the gas pressure in chamber 43 increases. This helps to prevent the heave compensation device to suddenly reach the end of the stroke and it allows for better balance given the non-linear and adiabatic characteristics of a gas spring.

[0048] The heave compensation device can comprise an actuator. In embodiments, the actuator can be part of the (gas- or) hydro-pneumatic spring. Such an actuator is arranged to move the spring. In embodiments, the actuator can be part of the transmission between first and second frames 2,3. The actuator can be used to move the first with respect to the second frame / move the connection unit 22 with respect to carrying unit 32.

[0049] In an embodiment, the actuator is connected between the first and second frames 2,3 directly via a toothed gear 82 on one frame and a toothed track 81 on the other frame. The actuator can comprise a drive that drives the gear wheel 82.

[0050] In other embodiments the actuator acts on the piston of the (gas- or) hydro-pneumatic spring. In other embodiments, the actuator is coupled to a leverage unit, preferably the same leverage unit as the pneumatic spring. The actuator can provide an additional force to compensate for non-ideal spring balance behavior of the spring balance arrangement. The actuator can further be used to drive the system, e.g. lift or lower the load.

[0051] FIG. 1 is an example embodiment of a heave compensation device 1 suspended by a hoisting device to carry or suspend a load. The combination of connection unit and carrying unit allows to hoist the heave compensation device by existing hoisting devices and pick up and drop off loads while in operation.

[0052] The heave compensation device of FIG. 1 allows decoupling, preferably complete decoupling, of that load suspended by a hoisting device. The invention is not limited to 100%, e.g. spring-balanced, decoupling. A significant decoupling, e.g. of at least 40% of the weight, preferably at least 50%, more preferably at least 60%, and even more preferably at least 80% decoupling of the weight.

[0053] FIG.l shows an example of a heave compensation device 1 that comprises a transmission. In the shown embodiment, the transmission comprises a pivoting arm loaded by a configurable spring, such as a gas- or hydro-pneumatic spring. The transmission comprises a spring force balancing arrangement. The spring does not have to be a (perfect) linear spring. Additional decoupling can be provided by an actuator.

[0054] By providing the heave compensation device between load and hoisting line, further weight is added to be hoisted by the hoisting device. A goal is to reduce the weight of the heave compensation device.

[0055] FIG. 2 shows an embodiment of a passive heave compensation (PHC) device 4. The PHC 4 decouples at least partially the load 35. The PHC 4 can be connected to a hoisting device via a connection unit 22. PHC 4 also comprises a support or carrying unit 32, that can suspend or support the load 35. Both the connection unit 22 as the carrying unit 32 are shown schematically as rings. Other connections units are possible too.

[0056] Connection unit 22 is connected to a first frame formed by the body of cylinder 400. Carrying unit 32 is connected to the rod of cylinder 400, which forms a second frame. The first and second frames can move with respect to each other along a guideline, preferably a vertical line in operation. Moving the first and second frames allows decoupling of the load 35. In this embodiment the cylinder 400 is the guide for guiding the movement. The cylinder is in this arrangement in line with the guideline and vertical direction in use.

[0057] The PHC 4 comprises a hydro-pneumatic spring system 401 that comprises one or more cylinders. A hydraulic connection 402 connects the cylinder 400 to a piston type accumulator (PTA) 404. A pneumatic connection 403 connects the PTA 404 to a pressure vessel 405.

[0058] PTA 404 is in fluid communication with the rod side chamber 45 of cylinder 400. During heaving, when the piston rod 36 strokes outward, fluid from the cylinder 400 is transported into the hydraulic fluid side of PTA 404. The fluid can be a mineral oil or a gly col- water fluid, but not limited only thereto. As the fluid moves into the PTA 404, the PTA piston 406 therein displaces (in FIG. 2) upwards and compresses the gas in the chamber (in FIG. 2) above the PTA piston 406. The gas can normally be nitrogen or air, but not limited only thereto. The compression of gas in chamber creates an effective spring.

[0059] Pressure vessel 405 is used as a gas reservoir. Gas from the pressure vessel 405 is used to increase or decrease pressure inside chamber through the pneumatic connection 403.

[0060] According to the invention, the heave compensation device of FIG. 1 or FIG. 2, or any other heave compensation device for at least partially decoupling a load in a hoisting device, has one or more fiber overlayed pressure vessels 405, which will be discussed in more detail with reference to FIG. 3.

[0061] FIG. 3A and FIG. 3B show respectively a schematic drawing of a cross-sectional (A) and non-cross-sectional (B) view of a fiber overlayed pressure vessel 405. The vessel comprises a liner 60 that is fully or partially covered by a fiber composite 61.

[0062] The inner aluminium liner 60 acts as a gas barrier, preventing any unwanted escaping of gas from the pressure vessel to the outside of the vessel. The liner 60 can consist of a metal, preferably aluminum or steel, and / or a plastic, preferably HDPE or Polyamide, more preferably PAI 1, or another material that can act as a sufficient gas barrier. The liner 60 may consist of one or multiple layers of the aforementioned materials, including a combination of layers of different materials. The liner 60 can be cylindrical. The liner can comprise a top and bottom part. The cylinder can have rounded edges near the top and bottom ends. In embodiments, the liner 60 and vessel 405 are ball-shaped or cubic.

[0063] The liner 60 of vessel 405 comprises one or several access points 407. In cylindrical vessels, the access point can be part of a bottleneck of the vessel. Access point 407 allows filling and emptying of the pressure vessel. The access point can have a sealed opening with a removable cover. The access point can have a flanged or threaded connection or other type of closure mechanism that ensures a leak proof seal when the vessel is pressurized.

[0064] The access points 407 can include a port opening or channel. The port opening is a channel or passage that provides for the filling and emptying of the pressure vessel 405. The size of the port opening refers to its cross-sectional area. It was found that for pressure vessels in heave compensation devices, the ratio between the size of the port opening (in this application measured in inches according to the widely adopted standard BSP (British standard Pipe)) of the access point 407 and the water volume (in this application measured in liters) of the pressure vessel 405 is 0.002 or higher. It was found that lower ratios result in a restriction of the rate of filling and emptying of the pressure vessel 405, leading to relevantly increased friction and / or temperature changes. A larger ratio results in a less restrictive flow path and higher rate of filling and emptying. A smaller ratio indicates a restrictive flow path and a lower rate of filling and emptying.

[0065] In the embodiments, the pressure vessel has a 325 liters water volume and a 1 ’A inch BSP channel or port opening, resulting in a 0.0045 ratio. A larger port opening can increase the rate at which the pressure vessel 405 can be filled or emptied, without resulting in relevantly increased friction and / or temperature changes, while a smaller port opening can restrict the rate of filling and emptying of the pressure vessel 405, leading to relevantly increased friction and / or temperature changes.

[0066] In embodiments, the ratio of the port opening of the access point 407 (in inches BSP) and the water volume (in liters) of the pressure vessel 405 is at least 0.003 (inches / litres).

[0067] In one preferred embodiment, at least one of the access points 407 of each vessel 405 of the balanced heave compensator of FIG. 1 or the passive heave compensator of FIG.2 is connected to the cylinder 401 through connection 403, which enables the increase and / or decrease of the pressure inside the cylinder, increasing / decreasing the pulling force. Also, the pressure in the cylinder 401 can be changed using the vessel 405 and the PTA 404 to set / configure / operate the (gas- or) hydro-pneumatic spring dependent on the weight of the load that is to be decoupled.

[0068] The pneumatic connection between vessel 405 and PTA 404 also provides a driving force for moving first frame 2 with respect to second frame 3 and thus allows using the (gas- or) hydro-pneumatic spring system 4 as an actuator for the heave compensation device 1. In a combined modus of spring-balance and actuator, the settings for the actuating function can be super-positioned over the settings for the spring balance function of the (gas- or) hydropneumatic spring system 4.

[0069] In any of the scenarios, the pressure in the vessel 405 varies significantly and repeatedly, often at high frequencies and at very high repetitions over its service life. This results in high stress and can create wear.

[0070] To reduce the weight of the vessel 405 and thereby of the heave compensation device 1 while providing high stress resistance and resistance to wear / fatigue, the liner 60 is covered by a fiber composite 61. By fully or partially covering the liner 60, strength, corrosion resistance and fatigue resistance to the pressure vessel is increased. The fiber composite 61 may consist of one or multiple layers of fiber material, preferably carbon.

[0071] A pressure vessel consisting of only a fiber composite material 61 can also be envisioned. In this case the fiber composite material acts as both the gas barrier as well as the load bearing structure.

[0072] FIG.4 shows another embodiment. In a heave compensation device that has several pressure vessels, the vessels can be interconnected via their access points 407 through interconnections 408, wherein at least one access point 407 of at least one of these vessels is connected to the PTA 404 through connection 403. It can also be envisioned that the pressure vessel is directly connected to the cylinder by connection 403.

[0073] One way of manufacturing fiber overlayed pressure vessels is through a process called filament winding (FW). During FW, tensioned bands of fibers are wound around a rotating mandrel. In embodiments the mandrel is formed by the liner. Fibers are wound until the desired thickness of the composite layer is reached. After curing the composite material, part of the mandrel can be removed. In embodiments, the mandrel is removed, while the liner remains.

[0074] The benefit of the current invention over heavier state of the art vessels made of steel only, is not only the reduction of weight, but also the superior properties of the fiber overlayed pressure vessels. The strength of the fiber allows for a higher gravimetric storage density for overlayed pressure vessels compared to all metal vessels. Overlayed pressure vessels furthermore show an increased fatigue performance and corrosion resistance. For the application in heave compensation devices, a high frequency and high repetition of emptying and filling of the vessels is required and increased fatigue performance reduces long-term costs. The overlayed pressure vessels weigh significantly less than the vessels employed in the state of the art. Since the pressure vessels are present in line on hook, this reduction in weight allows suspending a higher load from the crane. Vice vera, for heave compensation devices suitable for larger loads and increasing heaving motions, overlayed pressure vessels can provide a much larger gas volume at the same weight when compared to steel pressure vessels according to the prior art.

Claims

CLAIMS1. A heave compensation device (1) for controlling the vertical position of a load (35), comprising a first frame , a second frame for connection to the load (35), the second frame arranged to move decoupled with respect to the first frame, and a configurable (gas- or) hydropneumatic spring (401), which includes at least one pressure vessel (405) that has a fiber layer (61).

2. The heave compensation device according to claim 1, wherein the pressure vessel (405) comprises an inner liner (60), preferably an aluminium liner.

3. The heave compensation device according to claim 2, wherein the inner liner (60), is partially, substantially or fully covered by the fiber layer (61) comprising of a fiber composite.

4. The heave compensation device according to claim 3, wherein preferably the inner liner (60) of the pressure vessel comprises one or multiple layers of metal and / or plastic, preferably aluminium and / or steel, and / or preferably HDPE or Polyamide, more preferably PAI L5. The heave compensation device according to any of the claims 2-4, wherein the inner liner (60) is made of metal with a thickness of at least 2mm, and / or wherein the inner liner (60) is made of a plastic with a thickness of at least 1mm.

6. The heave compensation device according to any of the preceding claims, is a carbon overlay pressure vessel, wherein the fiber layer (61) of the pressure vessel (405) comprises or consists of carbon fiber.

7. The heave compensation device according to any of the previous claims, wherein the pressure vessel (405) has at least one access point (407) and a connection (403) for connecting the pressure vessel (405) to a piston type accumulator (404) and / or a cylinder (43) and / or another pressure vessel (405) of the (gas- or) hydro-pneumatic spring (401).

8. The heave compensation device according to any of the preceding claims, wherein the access point (407) has a port opening of 1 / i inch or larger.

9. The heave compensation device according to any of the preceding claims, wherein the ratio of the port opening (inch, in BSP) of the at least one access point (407) and a water volume of the pressure vessel (405) is at least 0.002, preferably at least 0.025, and more preferably at least 0.003.

10. The heave compensation device according to any of the preceding claims, wherein the pressure vessel (405) has a working pressure of at least 200 bars.

11. The heave compensation device according to any of the preceding claims, wherein the pressure vessel (405) is suitable for over 30.000 pressure cycles between working pressure and 20% of working pressure.

12. The heave compensation device according to any of the preceding claims, wherein the fiber layer (61) has a thickness of at least 10mm and / or wherein the pressure vessel (405) has a length of at least 1500mm, and / or a diameter of at least 300mm, and / or a water volume of at least 100 liters.

13. The heave compensation device according to any one of the preceding claims, wherein the first frame comprises a connection unit (22) to be connected to a hoisting device, and wherein the second frame has a carrying or support unit (32) for supporting the load, and a transmission coupling the first frame to the second frame comprising the configurable (gas- or) hydro-pneumatic spring (401), wherein preferably the transmission comprises at least one pivoting arm (50), with the (gas- or) hydro-pneumatic spring system coupled to the pivoting arm, preferably arranged as a spring-balanced system, wherein preferably the heave compensation device, more preferably the transmission, comprises an actuator.

14. Hoisting device comprising a heave compensation device according to any of the previous claims, the connection unit (22) of the heave compensation device is connected to a hoisting wire of the hoisting device.

15. Ship or offshore structure comprising a hoisting device according to the previous claim.

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