Offshore structure offshore impact absorption device for absorbing external impact loads
Patent Information
- Authority / Receiving Office
- US · United States
- Patent Type
- Applications(United States)
- Current Assignee / Owner
- Filing Date
- 2024-02-02
- Publication Date
- 2026-08-13
AI Technical Summary
The workability of a jack-up vessel is greatly limited by its ability of lowering and lifting its legs to or from the seabed.
Smart Images
Figure US20260234887A1-D00000_ABST
Abstract
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an offshore structure offshore impact absorption device for absorbing external impact loads.BACKGROUND OF THE INVENTION
[0002] Jack-up vessels, also called self-elevating platforms, are widely used in the industry for e.g. drilling, production, well services and construction. The jack-up vessel can float on water with its legs retracted from the seabed. When operating, a body of the vessel is fully raised out of water while its legs stand on the seabed. This minimizes the wave load effect on the jack-up vessel and improves the vessel's workability. Nowadays, in the fast-growing offshore wind energy industry, jack-up vessels are a predominant type of vessels used for wind turbine installation and maintenance, due to their superior motion stability comparing with other types of mobile offshore units.
[0003] Most jack-up vessels need to be relocated frequently from one working site to another. For wind turbine installation the frequency is around one day per turbine site. When a jack-up arrives on its working site, it would lower its legs to the seabed, jack up its body out of water, preload the legs to improve seabed stability, and then raise to the operating height.
[0004] The workability of a jack-up vessel is greatly limited by its ability of lowering and lifting its legs to or from the seabed. Due to the roll and pitch motions of the vessel, touchdown of the leg onto the seabed starts always from one leg only, and this would cause a large impact load on that leg. To avoid possible damages to the leg and jacking system, the allowable seastate for jack-up leg handling is reduced accordingly. Seastate refers to the short-term weather conditions of the sea, including wave height, period, direction, and wind speed. The allowable seastate for jack-up vessel installation depends on various factors, including the design and capabilities of the vessel, the equipment and crew on board, site-specific seabed condition, and etc. For most modern jack-up vessels, this seastate is limited to a significant wave height of 1~1.5 m. If the significant wave height is higher than the limit, the jack-up vessel waits for calmer weather before lowering its legs. This will increase the operation costs of the vessel.
[0005] Currently, known devices are unfortunately insufficiently capable of handling the large impact and side loads during touchdown of the leg on the seabed. GB2247038A discloses a shock absorber mechanism for use on the leg structure of a jack-up offshore drilling vessel. The shock absorber mechanism is mounted on the bottom of each of the jack-up vessel legs. The mechanism comprises a pointed piston member which is positioned on the bottom of the leg structure and projects downwardly through the footing of the vessel leg. A resilient tension member is provided to hold the piston member in place. During the impact of the leg with the soil of the ocean floor, the resilient members allow the pistons to bounce to a limited degree, thus absorbing the shock of the impact and preventing serious damage to the leg structure and to the lowering mechanism itself.
[0006] It has been found that a disadvantage of the known mechanism is that, due to the piston projecting downwardly through the footing, the mechanism is not able to withstand sideloads, i.e. loads in a direction away from the longitudinal direction of the piston, during touchdown. Moreover, due to the magnitude of the impact load and the sideload on the footing, the piston needs to be very strong and can hardly be made in practice. Another disadvantage thereof is that maintenance will often be required to keep the mechanism working optimally. When the mechanism is installed into the seabed, soil and dirt will end up in all parts of the mechanism, which can cause accelerated wear and malfunctioning of the mechanism, in particular the resilient member.
[0007] Another piston mechanism having similar disadvantages is disclosed in U.S. Pat. No. 4,195,950A, which sloped surface of the piston opening has been found to be especially prone to sand ingression and corrosion. A corrosion-limiting coating on the piston or opening would be easily damaged, e.g. due to abrasion. It has been found that the diameter of the contact area of movable parts is relatively large, which causes the required tolerances for the bearing and sealing surfaces to be relatively difficult to manufacture and maintain.
[0008] KR20140123773A discloses a spud can that is installed at the lower part of a jack-up vessel leg. The spud can comprise a hydraulic damper connected to the lower part of the jack-up vessel leg and the spud can. When the jack-up vessel leg touches the seabed, the hydraulic dampers are compressed to dampen the impact loads on the jack-up vessel leg and therewith prevent damage to the jack-up vessel and other equipment.
[0009] A disadvantage of the spud can from KR20140123773 is that the hydraulic dampers are provided axially with respect to the jack-up vessel leg and are therefore only able to absorb the axial loads during touchdown of the legs on the seabed. Hence, the side loads exerted on the spud can cannot be absorbed. Moreover, the tilting of the spud can after landing on the seabed may cause damage to both the hydraulic dampers as well as the jack-up vessel leg.
[0010] KR20160067465A discloses another example of a spudcan comprising a hydraulic cylinder that is provided axially with respect to the jack-up vessel leg. The bearing surfaces between the fixed and movable parts have a relatively large diameter. Further, it has been found that the spud can be prone to sand ingression and corrosion in between the movable parts, thereby causing entrapment of sand, mud, corrosion therebetween, which can hamper movement and may even result in improper lifting or closure. Side loads on the spudcan will induce a contact stress that, especially when further aggravated by a combination of the disadvantages mentioned above, can seriously affect the durability of the vertical bearing surfaces of spudcan.OBJECT OF THE INVENTION
[0011] The present invention aims to overcome those disadvantages at least partly or to provide a usable alternative. In particular the present invention aims to provide offshore impact absorption device that can handle loads from multiple directions, for example from all possible touchdown directions.
[0012] Moreover, the present invention aims to provide an offshore impact absorption device that allows jack-up vessels to be installed at higher seastates.DESCRIPTION OF THE INVENTION
[0013] In a first aspect, the present invention provides an offshore impact absorption device for absorbing external impact loads on an offshore structure according to claim 1. The offshore impact absorption device comprises:
[0014] a mounting body configured to be provided on the offshore structure;
[0015] an impact element arranged at a distance from the mounting body, wherein the impact element is movably connected to the mounting body; and
[0016] an impact absorption system configured to absorb impact loads between the mounting body and the support element.
[0017] The impact absorption system comprises:
[0018] a damper that extends from a first end to a second end and that is arranged to dampen movement between the first end and the second end;
[0019] a base connected to one of the mounting body or the impact element;
[0020] a guide connected to another one of the mounting body or the impact element, and arranged to guide the second end of the damper in a longitudinal direction; and
[0021] a load transmitting element that extends between the base and the guide, and that is rotatably connected to the base and the second end of the damper, wherein the impact element is rotatably mounted to the mounting body, such that the second end of the damper is moved in the longitudinal direction by rotation of the load transmitting element upon application of an external load to the impact element.
[0022] The offshore impact absorption device is able to absorb relatively large impact loads, including side loads, on offshore structures as forces exerted on the impact element are damped by the impact absorption system. The offshore impact absorption device is configured to be provided on an offshore structure, e.g. a jack-up vessel, such as on the bottom of a jack-up vessel leg, to absorb impact loads during touchdown of the leg on the seabed, or on the sides of the jack-up vessel or jack-up vessel leg, to function as ship impact protection device. Alternatively, the offshore impact absorption device may also be provided on a ship, such as on the hull of a ship.
[0023] The mounting body of the offshore impact absorption device is movably connected to the impact element via the impact absorption system. A single impact absorption system may be provided, but alternatively, multiple impact absorption systems may be provided that are preferably arranged spatially apart.
[0024] When the offshore impact device is in use, external impact loads will be applied on the impact element when the impact element comes in contact with an external object, e.g. the seabed or another vessel. These impact loads on the impact element are at least partially absorbed by the impact absorption system. The impact absorption system comprises a base, which is connected to one of the mounting body or the impact element. The guide is connected to the other one of the mounting body or the impact element. The load transmitting element is rotatably connected to said base, for example via pivot hinge. The load transmitting element can therefore rotate around a first rotation axis, e.g. a rotation axis parallel to the impact element. Alternatively a ball hinge may be used to allow the load transmitting element to rotate in a second rotation direction perpendicular to the first rotation direction. The rotation in the second rotation direction may avoid over-constraints of the load transmitting element and allow a certain relative rotation between the impact element and the mounting body. The load transmitting element extends between the base and the guide and may be arranged at an inclination with respect to the longitudinal direction of the guide. The load transmitting element may e.g. be a load transmitting bar, which can be a cost-effective element that is able to transfer large loads. Optionally, multiple load transmitting elements, such as two load transmitting elements, are provided in the impact absorption system. The multiple load transmitting elements are rotatably mounted at a common base and extend towards the guide, or alternatively, to respective guides that are arranged parallel. The multiple load transmitting elements may be connected to the second end of the damper. Thus advantageously, during impact, the impact load may be spread over the multiple load transmitting elements.
[0025] The load transmitting element is connected to the damper, in particular to the second end of the damper. The second end of the damper is arranged to be guided by the guide. Hence, when the load transmitting element rotates at the base, the load transmitting element is guided in the longitudinal direction by the guide, thereby simultaneously moving the second end of the damper in the longitudinal direction. Thus, impact loads exerted on the impact element are not transferred directly to the damper, but are, via the load transmitting element and the guide, guided in the longitudinal direction. This way, non-longitudinal load of the damper is significantly reduced compared to the prior art, and the impact absorption device is able to handle impact loads from multiple directions, and / or may potentially be used to dampen impacts in higher seastates compared to the prior art.
[0026] The longitudinal direction may be substantially transverse to the offshore structure on which the offshore impact absorption device is mounted, such as the jack up vessel leg. The longitudinal direction may for example be perpendicular to the offshore structure.
[0027] When the offshore impact absorption device is in use, large (side) loads are applied to the impact element. For example, movement of the offshore structure due to waves may cause contact between the impact element and external objects, such as the seabed. This is especially the case when lowering the legs of the offshore structure, or when another vessel or another offshore structure is approaching the offshore structure.
[0028] The loads may be unevenly distributed over the impact element, which may result in translation and / or rotation of the impact element with respect to the mounting body.
[0029] These loads are transferred to the load transmitting element, which, as a consequence of the impact loads, rotates with respect to the base around a first rotation axis. The first rotation axis may be arranged in a plane substantially parallel to a longitudinal axis of the impact element or the mounting body to which the base is mounted. In use, the first rotation axis may be arranged in a plane substantially parallel to the external object. The load transmitting element may also rotate around a second rotation axis perpendicular to the first rotation axis. The second rotation axis may be arranged in the same plane. Additionally or alternatively, the load transmitting element may rotate around a third rotation axis perpendicular to the first and the second rotation axis. It is for example possible to use a ring-shaped bearing with a spherical outer-face on a pin-hole connection. The rotation capacity of the impact absorption element around the first, second, and third rotation axis may differ from each other. A rotation capacity around the second and / or third rotation axes may be smaller than a rotation capacity around the first rotation axis. For example, the rotation capacity around the second rotation and / or third rotation axis may be around 15°.
[0030] The load transmitting element may be a rigid element.
[0031] Due to the rotation of the load transmitting element, the opposite second end of the load transmitting element is moved in the longitudinal direction by the guide, causing the second end of the damper to move simultaneously in the longitudinal direction. During the movement of the second end of the damper the impact loads applied to the impact element (and transferred to the load transmitting element) are absorbed by the damper, thus causing the dampening effect during impacts on the impact element.
[0032] Due to the configuration of the impact absorption system, and in particular the rotatably mounted load transmitting element which extends towards the guide, the impact element may rotate relative to the mounting body. The impact element may additionally or alternatively translate towards the mounting body. In an embodiment, the guide is arranged at an inclination with respect to the mounting body. The impact absorption system advantageously guides these movements of the impact element into the longitudinal direction which can be absorbed by the damper.
[0033] The offshore impact absorption device may for example comprise a single impact absorption system. The impact element and the mounting body may for example be connected to each other by means of a hinge and the impact absorption system.
[0034] In an embodiment, the offshore impact absorption device comprises multiple impact absorption systems connected with their respective base and / or guide to the impact element at a distance from each other. An offshore impact absorption device may for example comprise two, three, four, five, six or more impact absorption systems. Having multiple absorption systems allows a better distribution of the impact loads over the offshore impact absorption device, thereby increasing the stability of the device. For increased stability the offshore impact absorption device may comprise at least three impact absorption systems. It can furthermore be advantageous that the impact absorption systems are equally spaced relative to each other.
[0035] Optionally, the impact absorption systems are arranged on the impact element at an angle with respect to each other. For example, the angle may be such that the first rotation axes of the respective bases are at an angle with respect to each other.
[0036] This further improves to load absorption effect of the offshore impact absorption device and provides dampening in different directions. Due to the impact absorption systems being arranged at an angle with respect to each other, the impact element may rotate in multiple directions relative to the mounting body, especially around the first and / or second axis.
[0037] The angle between respective impact absorption systems may vary, or alternatively, may be equal between each impact absorption system. This may allow the greatest freedom of rotation of the impact element relative to the mounting body, and thus the best absorption of side loads on said impact element.
[0038] In an embodiment, the mounting body and / or the impact element comprises a watertight compartment, and at least the damper is provided in the watertight compartment. For example, the watertight compartment may be arranged surrounding the damper only, or the mounting body and / or the impact element may entirely be sealed off from water to form the watertight compartment, wherein at least the damper is provided in the watertight compartment. Another option is that the entire offshore impact absorption device is free of water, e.g. both the impact element, the mounting body and the space between the impact element and the mounting body together form a watertight compartment.
[0039] An advantage of the watertight compartment is that the durability of the impact absorption system, and in particular the durability of the damper, is improved. For example, marine growth on the impact absorption system may be avoided this way. Moreover, the watertight compartment can be easily made accessible for maintenance.
[0040] In an embodiment, a link is provided between the load transmitting element and the second end of the damper. This allows to provide the load transmission element and the second at a distance from each other. For example, the guide may be arranged directly at the second end of the damper, e.g. in the watertight compartment, or at a distance from the second end, whereby the link spaces the second end from the guide and wherein the link is guided by the guide, e.g. wherein the guide is arranged outside of the watertight compartment.
[0041] When having a watertight compartment, wherein the watertight compartment may be provided with an opening, wherein the link is arranged through the opening. The link, e.g. a link bar, allow for easy arrangement of a water protection seal at the opening.
[0042] In an embodiment, a seal is provided for protecting the damper from environmental influences. The seal may be provided around the link, around the cylinder piston and / or at another location. The seal may for example be a ring-type seal, such as an o-ring, or a bellow which is provided at the opening and optionally around the link. As such, water is prevented from entering the watertight compartment. Optionally, multiple seals may be used to assure no water leaks into the watertight compartment. This allows maintenance and / or replacement of one of the seals while maintaining water tightness with another seal, such that the offshore structure does not need to be moved to a dry dock.
[0043] In addition and / or as alternative to a seal, one or more filters, e.g. a soil filter, may be provided. An additional shield or filter may be provided for additional sealing and / or filtering when the impact element and the mounting body move close to each other, e.g. during damping or in a stationary position.
[0044] In an embodiment, each damper comprises a hydraulic piston-cylinder system, optionally with associated accumulators and / or pumps. The power-to-weight and power-to-size ratios of these hydraulic piston-cylinder assemblies are very efficient to allow relatively large damping in a relatively limited space. The use of hydraulic piston-cylinder assemblies is especially advantageous when the damper is required to handle extremely large loads, e.g. when requiring to absorb the impact of jack-up leg touchdowns. In these conditions, mechanical springs can usually not be used as damper as these are not able to resist such large loads without use a relatively large space.
[0045] A pump may be operatively connected, for example hydraulically connected to the hydraulic piston. This way, movement of the piston and / or a damping ratio may be controllable with the pump.
[0046] In an embodiment, the impact absorption system comprises a linkage mechanism connecting the second end of the damper with the load transmitting element. The linkage mechanism may for example be a multi-bar linkage mechanism, such as a four-bar mechanism. When using a four-bar mechanism, the four bars are rotatably connected to each other in a quadrilateral shape having four pivot points. A first pivot point may for example be fixed with respect to the guide, a third pivot point opposite to the first pivot point may be connected to the second end of the load transmitting element, and a second and fourth pivot point are connected to the first end and the second end of the damper, respectively.
[0047] This way, when the second end of the load transmitting element moves within the guide, the third pivot point moves in the longitudinal direction relative to the first pivot point.
[0048] As a result, the second pivot point and fourth pivot point simultaneously move with the first end and second end of the damper, thereby absorbing the impact loads and causing the dampening effect at both ends of the damper.
[0049] For example, when the lengths of the linkage bars are equal to half length of the corresponding load transmitting element, and the initial inclination angles of the linkage bars are equal to the inclination of the load transmitting element, the force exerted on the damper and damper stroke may be equal to the vertical force and movement at the lower end of the corresponding load transmitting element, e.g. at the base due to movement of the impact element. The linkage mechanism may increase efficiency of the damper to reduce space and / or costs thereof. Other shapes or dimensions for the linkage mechanism are also possible.
[0050] When using a four-bar mechanism, it may be advantageous to use a hydraulic double-acting piston-cylinder system, having a hydraulic cylinder and pistons extending from each end of the cylinder. Alternatively, two hydraulic single-piston cylinder systems that move in opposite directions may be used.
[0051] In addition or alternative to a hydraulic cylinder, the damper may comprise a rope-sheeve connected dead weight. Optionally, the rope-sheeve connected dead weight may include a relatively small active drive, like a winch or cylinder. The costs of producing an offshore impact absorption device may be reduced this way.
[0052] In an embodiment, the impact absorption system comprises a second load transmitting element that extends between the base and the guide, wherein the second load transmitting element is rotatably connected to the base and to the first end of the damper. An advantage thereof is that the lateral stiffness of the load transmitting elements is increased. The load transmitting element may for example form a V-shape.
[0053] In this embodiment, the second end of the damper may be configured for moving in the longitudinal direction during impact on the impact element, and the first end of the damper is configured for moving in an opposite direction of the longitudinal direction.
[0054] In an embodiment, the impact absorption system comprises two load transmitting elements, wherein one load transmitting element is connected to the first end and another one of the load transmitting elements is connected to the second end of the damper. Each impact absorption system may comprise two load transmitting elements. The two load transmitting elements may be connected to the same base.
[0055] In a further embodiment, both the first pivot point and the third pivot point of the four-bar mechanism are connected to a respective load transmitting element, such that the first and third pivot points move in opposite longitudinal directions during impact. The linkage mechanism may also be a three-bar mechanism, forming a Y-shape in which each bar is with a first end connected to a pivot point, and two bars are with their opposite ends connected to their respective load transmitting element.
[0056] The second end of the damper may be movably arranged in the guide. The second end may for example be slidable or rollable on or in the guide.
[0057] In an embodiment, the guide comprises a sliding mechanism or rolling mechanism, e.g. a wheel-rail mechanism. For example, the guide may comprise wheels connected to the load transmitting element. A wheel-rail mechanism allows the impact absorption element to move relatively fast and agile within the guide and may be more durable in case small particles (e.g. sand) would come in contact with the guide, for example when leaked into the space where the guide is installed. Counter wheels or sliding joints may be needed for the wheels, due to tensile forces on the load transmitting elements in certain circumstances.
[0058] As an addition or alternative, the sliding mechanism, e.g. using low-friction materials on the contact surfaces with relative motion, may be used for allowing the load transmitting element to slide within the guide. It has been found that a sliding mechanism may be relatively compact in dimensions and easy (cheaper) to manufacture.
[0059] In an embodiment, the sliding mechanism is achieved by using sliding pads. The sliding pads may be provided on the slide, on the track, and / or on other contact surfaces of sliding. The sliding surface contacted with the sliding pad may be coated, profiled and / or comprise a material for reducing the friction coefficient. The sliding pads may be made of bronze or plastic, for example nylon. It has been found that a plastic pad may be advantageous as it may be strong, durable, economic and non-corrosive.
[0060] In an embodiment, the offshore impact absorption device further comprises one or more support bodies provided between the mounting body and impact element. The support body may be rigidly arranged on the impact element and / or the mounting body and the support body may extend perpendicular to the respective impact element and / or mounting body.
[0061] In an embodiment, the mounting body and the impact element are movable with respect to each other between a support position, in which the mounting body is supported by the impact element via the support bodies, and an impact-damping position, in which the mounting body and impact element are located further away from each other. The one or more support bodies may advantageously protect the impact absorption systems from overload. Furthermore, the support bodies may be configured to support the offshore structure, for example, to allow maintenance of the impact absorption system, or at the jack-up leg preloading condition.
[0062] The support body may for example be provided at either the impact element or the mounting body. The support body may e.g. be a single body, or alternatively, a series of discrete support bodies provided at the circumference of one of the impact element or the mounting body. Alternatively, a continued (ring-shaped) support body may be arranged between the mounting element and impact element, e.g. at the circumference of one of the impact element or the mounting body.
[0063] Optionally, one or more support bodies comprise at least one load measuring sensor configured for emitting a sensor signal representative for a contact load between the impact element and the mounting body when the impact element and the mounting body are in the support position. This allows the measurement of the eccentric load distribution between the impact element and the mounting body. Measuring the eccentric load distribution is especially advantageous when the impact absorption device is arranged on a bottom of a jack-up leg to determine loads exerted thereon. This may for example be advantageous in reducing rack phase difference of a jack-up vessel's jacking system during the jacking and leg preloading condition. The rack phase difference should be as close to 0 as possible to ensure optimal performance of the jacking system and ensure stability of the vessel during the jacking operation. Measuring this rack phase difference during jacking operations can give an early indication of possible leg over-stresses and may indicate that the jack-up vessel leg should be replaced to another position on the seabed.
[0064] In an embodiment, the damper has a controllable damping, further comprising a controller operatively connected to the damper and configured to control the damping of the damper. The controllable damping advantageously achieves a desirable displacement-load curve and automatic overload protection. This is especially useful in applications where control of impact element positioning relative to the mounting body is required.
[0065] In an embodiment, the impact absorption system comprises a tuneable damper and / or a pump operatively connected to the damper and the controller to control the damping.
[0066] In an embodiment, the offshore impact absorption device comprises one or more dirt shields provided at a circumferential edge of the absorption device. The one or more dirt shields advantageously allow dirt, e.g. soil, from entering an inner space between the mounting body and impact element when the offshore impact absorption device is installed, such as when jack-up vessel legs touchdown onto the seabed.
[0067] The one or more dirt shields may be arranged such that there is some space between the dirt shields and the mounting body to allow rotation and lateral movement of the impact element relative to the mounting body.
[0068] Optionally, the dirt shield comprises multiple segments that are configured to telescopically slide over each other, for example wherein a first segment is connected to the mounting body and wherein a second segment is connected to the impact element. Preferably, the second segment of the impact element is configured to slide over the first segment, or vice versa. Additionally or alternatively, flexible shields, such as bellow type-shields may be used for the one or more dirt shields.
[0069] The one or more dirt shields may also be used for providing the watertight compartment within the offshore impact absorption device, e.g. by arranging the one or more dirt shields to prevent water from entering the space between the impact element and mounting body.
[0070] In an embodiment, the offshore impact absorption device comprises a soil filter configured for filtering particles, e.g. sand, sediment and / or other foreign matter, from the water that flows through the offshore impact absorption device. Sand, sediment and / or other foreign matter may cause damage to the parts and equipment in the offshore impact absorption device. By filtering out the soil particles, the risk of abrasion and wear on equipment is reduced, leading to longer lifespans and lower maintenance costs. In addition, filtering can help to prevent clogging of the offshore impact absorption device and its parts. The filter may be relatively fluid-permeable.
[0071] The filter may be provided at some or several places at the offshore impact device, such as at the spacing between the mounting body and the impact element, at the dirt shield, and / or at the guides. The filters may for example surrounding at least the guides.
[0072] Several types of filters may be used, such as brush filters for blocking larger soil particles and / or fabric or screen type filters that use woven or non-woven materials that may block smaller soil particles. Preferably, at least fabric or screen type filters are provided surrounding at least the guides to prevent any soil particles from reaching the guides which may contribute to an advantageously long lifespan.
[0073] Multiple filters may be used in conjunction, for example having an increasingly fine filtration. For example, a relatively course brush type sand filter may be provided at the dirt shield, and a finer screen-type sand stopper may be provided around the guides.
[0074] In an embodiment, flow access passages may be provided in the offshore impact absorption device. The flow access passages may be arranged to fluidly connect inner parts to the outer environment. For example, the flow access passages may be configured for allowing water flow in the space between the mounting body and the impact element to be in fluid communication with the body of water surrounding the offshore impact absorption device. When the impact element collides with an external object or structure, the impact element moves towards the mounting body, which may cause a substantial volume of water to be moved and / or expelled from the space between the mounting body and the impact element.
[0075] Advantageously, the flow access passages facilitate improved water drainage. This way, the influence of water pressure on movement of the impact element may be reduced. For example, excessive pressure on the components within the device may be prevented. Said flow access passages may be provided in the impact element and / or in the mounting body. Preferably, one or more flow access passages are provided in the impact element and / or a central flow access passage is provided in the mounting body.
[0076] In an embodiment, the impact element comprises a removable portion. The removable portion has several advantages, as will be explained below with respect to another aspect of the invention.
[0077] It has been found that several aspects mentioned in embodiments hereinabove, such as the filter, the flow access passage, the removable portion and / or the sliding mechanism, may also be used in an offshore impact device not according to the present invention while still providing similar advantages.
[0078] Another aspect of the invention relates to an offshore impact device, such as a spudcan, for absorbing external impact loads on an offshore structure, comprising: a mounting body configured to be provided on the offshore structure; and an impact element connected to the mounting body, wherein the impact element comprises a removable portion.
[0079] In an embodiment, the impact element comprises an impact surface configured to during use impact an external object, e.g. the seabed, and the impact surface comprises the removable portion. The impact surface may be arranged such that, when the mounting body is arranged on the offshore structure, the impact surface faces substantially downwards. For example, the impact surface may be arranged opposite of said mounting body.
[0080] In an embodiment, the removable portion determines the shape of at least a part of the impact surface of the impact element. The removable portion may form the entire impact surface and / or a portion of the impact surface.
[0081] The impact surface of the impact element of an offshore impact device is during operation usually the first point of the impact device to come into contact with an external object, mainly the seabed. Different types of soil of the seabed may require a different shape for the impact surface. Some type of soils, e.g. soft clay type soils, may benefit from a sharp protrusion at the impact surface, as this would cause the impact device to be more easily positioned relative to the ground. A smoother rounded shape in contrast would be more beneficial for hard, rock type soils. The removable portion may be removed and replaced by another removable portion that provides a different shape to the impact surface of the impact device. By providing a different shape to the impact surface of the spudcan, the impact device may be easily adapted to the type of seabed on which the jack-up rig's leg needs to land. By being able to remove and replace the removable portion to provide at different shape at the impact surface, the spudcan does not have to be replaced in its entirety when the legs of the jack-up rig will touch down on a different type of soil.
[0082] Additionally and / or alternatively, the external object may be another object, such as an offshore vessel, which may cause wear on the impact element. By having a removable portion, maintenance can be performed more efficiently.
[0083] Preferably, the removable portion is provided at the centre of the impact surface. Spudcans often have a tapered or pointed impact surface, such that the centre of the impact surface is often provided furthest away from the mounting section. This centre is therefore usually the first part of the impact surface to come into contact with the external object. As such, providing the removable portion at the centre of the impact surface advantageously allows this centre of the impact surface to be easily removed and replaced.
[0084] Said removable portion may be provided in any type of conventional spudcan, but may also advantageously be provided in the offshore impact device according the first aspect of the invention. Conventional spudcans may for example have an impact element that forms an integral part with the mounting body.
[0085] The impact element may for example have an indentation at the impact surface of the impact element or it may have an opening, in which the removable portion is provided. The indentation or opening may extend through the entire impact element. The indentation or the opening is preferably provided centrally in the impact element.
[0086] The removable portion may be removably connectable to the mounting body and / or the impact element by means of a shape lock, e.g. by having a complementary shape and / or a force lock, e.g. by clamping. A fastener, e.g. a pin or a bolt, may be provided.
[0087] In an embodiment, the removeable portion is laterally restricted in the impact element of the offshore impact device. The removable portion for example has inwardly slanted abutment surfaces that abut against complementary outwardly slanted abutment surfaces at the impact element of the offshore impact device. Alternatively, the removable portion may have abutment surfaces that have another shape and are complementary to the abutment surfaces of the impact surface, such that the removable portion is blocked laterally outwards when the spudcan is displaced.
[0088] Alternative connections between the removable portion and the impact surface may also be envisaged, such as a threaded connection or a snap-fit connection between the impact surface of a spudcan and the removable portion.
[0089] In an embodiment, the removable portion is configured for floating in water. The advantage of such a floatable removable portion is that the removable portion has an inherent upward force, causing it to consistently have the tendency to float upward, thereby enhancing fixation of the removable portion, e.g. when a jack-up rig leg ascends. Hence, less force is required to raise a firmly embedded removable portion from the seabed or to dislodge it if it were to become detached. Moreover, fewer heavy fasteners are needed to secure the removable portion to the impact surface of the spudcan. This reduces costs and facilitates the removal and replacement of the removable portion.
[0090] In an embodiment, the removable portion is made of plastic, metals (such as aluminum or titanium), and / or rubber. Preferably, the material is chosen to make the removable portion configured for floating in water. Additionally or alternatively, the buoyancy may be adjusted by having air pockets or other low-density material filled pockets to improve the floatability of the removable portion.
[0091] The offshore impact absorption device may be provided on a variety of offshore structures, such as a jack-up vessel, e.g. the legs of the jack-up vessel or ships. The device may also be used as seismic isolator or motion compensation support.
[0092] In another aspect, the invention provides a spud can having an offshore impact absorption device according to the invention. The offshore impact absorption device may be integrated in commonly used spud cans. The offshore impact absorption device may not necessarily change the overall shape of common spud cans, but may increase the height.
[0093] In another aspect, the invention relates to a jack-up vessel having a jack-up vessel leg provided with an offshore impact absorption device according to the invention, or with a spud can according to the invention, for absorbing external impact loads during touchdown of the respective leg or spud can on a seabed.
[0094] The offshore impact absorption device may be arranged to damp impacts exerted on the vessel leg. The mounting body may be provided underneath the vessel leg. The impact element may be configured to come in contact with the seabed. Alternatively, the impact element may be mounted between the vessel leg and an existing spud can.
[0095] By providing an impact absorption device or spud can according to the invention on the bottom of jack-up vessel legs, the maximum touchdown load may be controlled. As such, the jack-up installation seastate may be increased, such that the vessel may be used more efficiently, potentially allowing installation of the jack-up vessel to be done much more frequently.
[0096] Moreover, the impact absorption device may function as a seismic isolator during earthquakes when the jack-up vessel is in a (semi) jacked up condition by absorbing vibrations and movements of the ground. This way, the risk of earthquake damages to the legs may thus be reduced.
[0097] In another aspect, the present invention relates to a ship impact protection system comprising an offshore impact absorption device according to the invention. The mounting body may for example be mounted to the side of a vessel, for example to the side of a jack-up vessel leg.
[0098] The mounting body may be configured to be slidably mounted to the offshore structure, for example to be slidably mounted to the side of a vessel, e.g. to the side of a jack-up vessel leg. The offshore impact absorption device may be configured to float on the water. The impact element and the mounting body are preferably both afloat on the water surface, while the mounting body is connected to a jack-up vessel (leg) or a ship. This way, impacts may be damped at a location where it is most desired.
[0099] In another aspect, the present invention relates to a method for absorbing external impact loads when installing a jack-up vessel, comprising the steps of:
[0100] positioning the jack-up vessel at a working site;
[0101] lowering a leg of the jack-up vessel towards the seabed;
[0102] touching the seabed with the impact element, causing the second end of the damper to move in the longitudinal direction, such that the load applied on the impact surface by the seabed is dampened by the damper.
[0103] In an embodiment, the step of touching the seabed with the impact element is performed at a non-perpendicular angle between the seabed and the impact element, causing the second end to be moved in the longitudinal direction only.
[0104] In an embodiment, the method is performed using an offshore impact absorption device according to any of the embodiments disclosed herein.
[0105] In another aspect, the present invention relates to a method for providing offshore impact absorption on an offshore structure, comprising the steps of:
[0106] providing the offshore structure to be protected;
[0107] optionally, removing an existing spud can from the offshore structure, for example from a jack-up vessel leg; and
[0108] attaching the mounting body of the offshore impact absorption device according to the invention to the offshore structure, for example to the jack-up vessel leg.This way, an offshore impact absorption device according to any of the embodiments disclosed herein may advantageously be provided on an existing offshore structure.
[0109] The offshore impact absorption device may also be provided on other structures, such as a quay or mooring structure, by mounting the mounting body to the structure.BRIEF DESCRIPTION OF THE DRAWINGS
[0110] Further characteristics of the invention will be explained below, with reference to embodiments, which are displayed in the appended drawings, in which:
[0111] FIG. 1 schematically shows an embodiment of an offshore impact absorption device in a spud can according to an embodiment of the invention;
[0112] FIG. 2 schematically shows an embodiment of an impact absorption system according to the present invention;
[0113] FIG. 3 schematically shows another embodiment of an impact absorption system with a linkage mechanism according to the present invention;
[0114] FIG. 4 shows a three-dimensional view of an offshore impact absorption device according to the present invention;
[0115] FIG. 5 shows a three-dimensional view of another embodiment of an offshore impact absorption device having two load transmitting elements in each impact absorption system;
[0116] FIG. 6 shows three-dimensional view of an embodiment of an offshore impact absorption device having two load transmitting elements that are connected to the second end of the damper;
[0117] FIG. 7 shows another embodiment of an offshore impact absorption device in a spud can according to an embodiment of the invention;
[0118] FIG. 8 schematically shows another embodiment of an impact absorption system with a three-bar linkage mechanism according to the present invention;
[0119] FIG. 9 shows a ship impact protection system having an offshore impact absorption device according to the present invention.
[0120] FIG. 10a schematically shows another embodiment of the impact absorption system according to the invention having a removable portion;
[0121] FIG. 10b shows an enlarged view of the removable portion according to FIG. 10a;
[0122] FIG. 11 shows an embodiment of the impact absorption device according to the invention having dirt filters and flow access passages.
[0123] Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.DETAILED DESCRIPTION OF THE DRAWINGS
[0124] FIG. 1 schematically shows an embodiment of a spud can with an offshore impact absorption device according to the invention, which is in its entirety denoted by reference numeral 2. The spud can is generally present on the leg 4 of a jack-up vessel. The offshore impact absorption device 2 comprises an impact element 6. The impact element 6 in this embodiment has a first face 8 which faces the jack-up vessel leg, and a second face 10 on the opposite side of the first face 8. The second face 10 in this embodiment is conically shaped, but may have a variety of other shapes as well, such as conical, curved or trapezoidal. Furthermore, a sharp protrusion 12 is provided on a centre part of the second face 10. The conical shape and sharp protrusion 12 provide sliding and bearing resistance to the jack-up vessel leg when deployed into the sea bed. The offshore impact absorption device 2 furthermore comprises a mounting body 14. The mounting body is provided at a distance from the impact element 6. The mounting body comprises a first face 16 at which the mounting body 14 is mounted to the offshore structure, in this embodiment thus a jack-up vessel leg, and a second face 20 opposite of the first face which faces the impact element 6.
[0125] A number of impact absorption system 22 moveably connect the impact element 6 with the mounting body 14. In this embodiment, two impact absorption systems 22 are shown, but more impact absorption systems 22 may be provided as well, such as three, four, five or six impact absorption systems, or even more. Each impact absorption system 22 comprises a damper 24 that extends from a first end 26 to a second end 28. The damper 24 is arranged to dampen movement between the first end 26 and the second end 28. In this embodiment, the first end 26 of the damper 24 is stationary. The impact absorption element in this embodiment is a hydraulic piston-cylinder system. Optionally, the damper 24 comprises a link 40, such as a link bar, between the load transmitting element and the second end of the damper. This may be especially advantages when the damper 24 is provided in a watertight compartment in the mounting body 14. The watertight compartment then comprises an opening, wherein the link is arranged through the opening. A seal, such as a ring type seal 41a or a bellow 41b may be provided between the watertight compartment and the impact absorption system to ensure the compartment is watertight, for example around the link 40 as depicted in FIG. 11. Additionally or alternatively, a filter 66, such as a fluid-permeable soil filter may be provided, or the seal may be provided at another location, e.g. the location of the filter 66 in FIG. 11.
[0126] The impact absorption system further comprises a base 30 which is connected to the impact element 6 and a guide 32 that is connected to the mounting body. The guide 32 is arranged to guide the second end in a longitudinal direction.
[0127] The impact absorption system 22 further comprises a load transmitting element 34. This load transmitting element 34 may e.g. be a bar. The load transmitting element comprises a first end 36 and a second end 38, of which the first end 36 is rotatably connected to the base 30 and the second end 38 is connected to the second end 28 of the damper 24. The load transmitting element 34 is provided at an inclination relative to the guide 32.
[0128] When the offshore impact absorption device 2 is in use, e.g. when a jack-up vessel leg with an offshore impact absorption device 2 mounted to the bottom of the leg touches the seabed, large external perpendicular and side loads will be applied to the impact element 6, which is partly due to the unevenness of the seabed. Under these impact loads, the force transmitting element 34 rotates at the base 30. Due to the rotation at the base, the second end 38 of the force transmitting element 34 moves within the guide in the longitudinal direction, causing the second end 28 of the damper 24 to move simultaneously in the longitudinal direction which causes a dampening effect.
[0129] The degree to which each individual element moves within the guide depends on the direction and magnitude of the external impact loads on the impact element 6. This is beneficial because the system thus has a balancing function, preventing the jack-up vessel from tipping over.
[0130] The offshore impact absorption device 2 optionally further comprises dirt shields 42 provided at a circumferential edge of the device 2. These dirt shields 42 prevent dirt from entering an inner space between the mounting body 14 and impact element 6 when the offshore impact absorption device 2 is installed into the ground, such as when the jack-up vessel legs 4 touchdown onto the seabed.
[0131] Optionally, support bodies 43, such as footings, are provided between the impact element 4 and mounting body 6. Hence, when the impact element and the mounting body move close to each other, e.g. during damping wherein the support bodies 43 prevent complete contact of the impact element and mounting body to protect the impact absorption system from overload, or in a stationary position wherein the offshore structure may rest on the seabed via the support bodies 43, to protect the impact absorption system from continuous load (this is especially useful in case of malfunction of the impact absorption system).
[0132] FIG. 2 schematically shows an embodiment of the impact absorption system 22 in more detail. The impact absorption system 22 comprises a load transmitting element 34 that is rotatably mounted to the base 30 at the first end 36 of the load transmitting element 34.
[0133] The second end of the load transmitting element extends towards the guide 32 and is connected to the second end of the damper 28. The load transmitting elements 34 are provided at an inclination. The second end 38 of the load transmitting element 34 is connected to the second end 28 of the damper 24, which in this embodiment comprises a hydraulic piston-cylinder system and a link bar. The second end 38 of the load transmitting element 34 is provided in the guide 32. When an external load is applied to the impact element 6, the load is transferred to the load transmitting element 34 which will rotate at the base 30. Consequently, when the load transmitting element 34 rotates, the second end 38 of the load transmitting elements 34 will move within the guide, thereby moving the second end 28 of the damper 24 simultaneously and causing the dampening effect. In this embodiment, the first end 26 of the damper 24 remains stationary as it is fixed to a fixing element 18.
[0134] Movement of the second end 38 of the load transmitting element 34 within the guide 32 is in this embodiment achieved by sliding with a sliding mechanism 33. Other mechanisms may be used as well, such as a rolling mechanism, e.g. a wheel-rail system.
[0135] FIG. 3 schematically shows an alternative embodiment of an offshore impact absorption device 2 according to the invention, comprising a linkage mechanism 44 which connects the damper 24 with the load transmitting element 34. The linkage mechanism 44 in this embodiment is a linkage mechanism, having four bars equal in length that are connected to each other into a diamond shape having four pivot points 46a, 46b, 46c, 46d. A first pivot point 46a is fixed to a fixing element 18 and remains stationary with respect to the guide 24. A third pivot point 46c, opposite to the first pivot point, is connected to the second end of the load transmitting element 34. A second pivot point 46b and fourth pivot point 46d are connected to the first end 26 and the second end 28 of the damper 24, respectively. In this embodiment, the damper 24 is a hydraulic double-acting piston-cylinder system, having pistons extending from both ends of the hydraulic cylinder. Alternatively, two hydraulic single-piston cylinder systems that move in opposite directions may be used as well. When using the linkage mechanism 44, the hydraulic cylinder can also be replaced by a rope-sheeve connected dead weight plus a small active drive, like a winch or cylinder.
[0136] When the second end 38 of the load transmitting element 34 moves within the guide 32, the third pivot point 46c moves in the longitudinal direction of the guide 32 with respect to the first pivot point 46a. As a result, the second pivot point 46b and fourth pivot point 46d makes the first end 26 and second end 28 of the damper 24 move simultaneously, causing the dampening effect. When the lengths of the linkage mechanism 44 bars equal to half length of the corresponding load transmitting element 34, and the initial inclination angles of the linkage bars are equal to the inclination of the load transmitting element 34, the cylinder force and stroke will be always equal to the vertical force and movement at the lower end of the corresponding load transmitting element 34. The linkage mechanism 44 may be used to rectify the actuator force-stoke relationship and reduce the cost of damper 24. Therefore other shapes or dimensions for the linkage mechanism 44 are possible depending on the rectifying requirements.
[0137] FIGS. 4 and 5 show a three-dimensional view of embodiments of the offshore impact absorption device 2 according to the invention. The offshore impact absorption devices 2 each have three impact absorption systems 22 which are provided at equal angles from each other. In FIG. 4, each impact absorption system 22 has one load transmitting element 34. The load transmitting element is connected to the damper 24 at the second end 28 of the damper 24, while the first end 26 of the damper 24 is fixed. In FIG. 5 each impact absorption system 22 comprises two guides 32 connected to respective ends 26, 28 of the damper 24. The impact absorption system 22 of FIG. 5 furthermore comprises two load transmitting elements 34 that have a common base 30. Each load transmitting element 34 is connected to a different end 26, 28 of the damper 24. Consequently, when an external load is applied to the impact element 6 and the load transmitting elements 34 rotate at their base, both the second end 38 of each load transmitting element 34 moves in the respective guide, and hence moves the respective end in the longitudinal direction. As a result, the damper 24 extends in both directions.
[0138] FIG. 6 shows a three-dimensional view of an alternative embodiment of the offshore impact absorption device 2 according to the invention in which the impact absorption system 22 comprises two load transmitting elements 34 that are rotatably mounted to a common base 30 and extend towards respective guides 32. The two load transmitting elements 34 are both connected to the second end 28 of the damper 24 and move simultaneously during impact, thus allowing the impact load to be spread over the two guides 32 and respective two load transmitting elements 34.
[0139] FIG. 7 shows another embodiment of a spud can having an offshore impact absorption device 2 according to the invention. The offshore impact absorption device 2 comprises two impact absorption systems 22 with a four-bar diamond shaped linkage mechanism 44.
[0140] Furthermore, a dirt shield 42 is provided at the circumference of the spud can. The dirt shield 42 comprises a first segment 48 that is connected to the impact element 6 and a second segment 50 that is connected to the mounting body 14. The first segment 48 and the second segment 50 are telescopically arranged. Hence, when the impact element and the mounting body move close to each other during damping, the first segment 48 telescopically slides over the second segment 50 telescopically to prevent dirt from entering the inner space between the mounting body 14 and impact element 6.
[0141] FIG. 8 shows an embodiment of an impact absorption system 22 with two load transmitting elements 34 that have a common base 30. The impact absorption system 22 comprises a multi-bar linkage mechanism 52 with three bars 54a, 54b, 54c. The three bars form a Y-shape in which each bar is with a first end connected to a pivot point 56, and two bars 54a, 54b are with their opposite ends connected to their respective load transmitting element 34.
[0142] FIG. 9 shows an embodiment of an offshore impact absorption device 2 as a ship impact protection system. The ship impact protection system in this embodiment comprises two impact absorption systems 22. The ship impact protection system is afloat on the water with the mounting body 14 afloat but attached to the offshore structure, like a jack-up leg, which is to be protected. The mounting body 14 can also be provided on a ship which is potentially the source of impact.
[0143] FIG. 10a shows an embodiment an offshore impact device, here a spudcan, for absorbing external impact loads on an offshore structure, comprising a mounting body 14 configured to be provided on the offshore structure and an impact element 6 connected thereto, wherein the impact element 6 comprises a removable portion 58. FIG. 10b shows an enlarged view of said removable portion 58. The impact element 6 comprises an impact surface 10 arranged opposite of the mounting body 14, configured to during use impact an external object, e.g. the seabed, and that comprises the removable portion 60 which forms a portion of the impact surface 10. When the mounting body 14 is arranged on the offshore structure, the impact surface 6 faces substantially downwards. The removable portion 58 determines the shape of the centre of the impact surface 10 of the impact element 6. In this example, the centre of the impact surface has a rounded shape that is suitable for use in hard rocky seabed, and extends all the way through the impact element from the first face 8 that faces the jack-up vessel leg to the impact surface 10 that touches the seabed upon impact. The removable portion is removably connectable via a fastener, e.g. bolt 63 and nut 64, and additionally has inwardly slanted abutment surfaces 60 that abut against complementary outwardly slanted abutment surfaces 62 of the impact element. This causes the removeable portion 58 to be clamped and laterally restricted in the impact element. The removable portion 58 is furthermore configured for being able to float in water. As such, the removable portion 58 has an inherent upward force, causing it to consistently have the tendency to float upward when a jack-up rig leg ascends. As a result, fewer fasteners 63, 64 are needed to secure the removable portion in the impact element.
[0144] FIG. 11 shows an offshore impact absorption device 2 that is provided with soil filters 66, 68, in conjunction. A fabric type soil filter 66 is provided surrounding the guide 32. The fabric type soil filter 66 is configured for filtering out both small and larger soil particles to prevent as much of the soil particles from reaching the guide 32. A coarser brush type filter 68 is provided at the dirt shields 42, near the outer edges of the impact absorption device. These brush type soil filters 68 filter out coarser soil particles. An additional shield or filter 67 is provided for additional sealing and / or filtering when the when the impact element 6 and the mounting body 14 move close to each other, e.g. during damping or in a stationary position.
[0145] The offshore impact absorption device 2 is provided with a sliding mechanism 33 provided on a track 32. The low friction sliding pads, in this embodiment made of plastic, such as nylon, are used in the sliding mechanism 33. The track may comprise other materials, be coated and / or be profiled.
[0146] FIG. 11 furthermore shows examples of flow access passage 72 and dirt drainage 70. In the Figure, two of these dirt drainage 70 are provided in the impact element 6, and one flow access passage 72 is provided in the mounting body 14. In case of excessive dirt or sand accumulated above the load impact element 6, pressurized water may be used to flush away the sediment through the drainage 70. The flow access passages 70 facilitate improved water drainage from the impact device during impact, such that excessive pressure on the components within the device is prevented
Claims
1-22. (canceled)23. Offshore impact absorption device for absorbing external impact loads on an offshore structure, comprising:a mounting body configured to be provided on the offshore structure;an impact element arranged at a distance from the mounting body, wherein the impact element is movably connected to the mounting body; andan impact absorption system configured to absorb impact loads between the mounting body and the impact element,wherein the impact absorption system comprises:a damper that extends from a first end to a second end and that is arranged to dampen movement between the first end and the second end;a base connected to, respectively, the impact element or the mounting body;a guide connected to the mounting body or the impact element, respectively, and arranged to guide the second end of the damper in a longitudinal direction,a load transmitting element that extends between the base and the guide, and that is rotatably connected to the base and the second end of the damper; andwherein the impact element is rotatably mounted to the mounting body, such that the second end of the damper is moved in the longitudinal direction by rotation of the load transmitting element upon application of an external load to the impact element.
24. Offshore impact absorption device according to claim 23, comprising multiple impact absorption systems arranged spatially apart and connected with their respective base to the impact element or the mounting body.
25. Offshore impact absorption device according to claim 24, wherein the impact absorption systems are connected to the impact element at an angle with respect to each other.
26. Offshore impact absorption device according to claim 23, wherein the mounting body and / or the impact element comprises a watertight compartment and wherein at least the damper is provided in the watertight compartment.
27. Offshore impact absorption device according to claim 23, wherein a link is provided between the load transmitting element and the second end of the damper, wherein the watertight compartment is provided with an opening, and wherein the link is arranged through the opening.
28. Offshore impact absorption device according to claim 23, wherein damper comprises a linkage mechanism comprising four bars that are rotatably connected to each other in a quadrilateral shape having four pivot points, wherein a first pivot point is fixed with respect to the guide, a third pivot point opposite to the first pivot point is connected to the second end of the load transmitting element, and a second and fourth pivot point are connected to the first end and the second end of the damper, respectively.
29. Offshore impact absorption device according to claim 23, wherein each damper comprises a hydraulic piston-cylinder system.
30. Offshore impact absorption device according to claim 23, wherein the guide comprises a sliding mechanism or rolling mechanism, for example, a wheel-rail mechanism wherein the guide comprises wheels connected to the load transmitting element.
31. Offshore impact absorption device according to claim 23, wherein the impact element comprises an impact surface that is configured to during use impact an external object, wherein the impact surface comprises a removable portion.
32. Offshore impact absorption device according to claim 23, wherein impact absorption system comprises a second load transmitting element that extends between the base and the guide, wherein the second load transmitting element is rotatably connected to the base and to the first end of the damper.
33. Offshore impact absorption device according to claim 23, further comprising one or more support bodies provided between the mounting body and impact element, wherein the mounting body and the impact element are movable with respect to each other between a support position, in which the mounting body is supported by the impact element via the support bodies, and an impact-damping position, in which the mounting body and impact element are located further away from each other.
34. Offshore impact absorption device according to claim 33, wherein the one or more support bodies comprise at least one load measuring sensor configured for emitting a sensor signal representative for contact load between the impact element and the mounting body when the impact element and the mounting body are in the support position.
35. Offshore impact absorption device according to claim 23, wherein the damper has a controllable damping, further comprising a controller operatively connected to the damper and configured to control the damping of the damper.
36. Offshore impact absorption device according to claim 23, further comprising a dirt shield provided at a circumferential edge of the offshore impact absorption device.
37. Spud can comprising an offshore impact absorption device according to claim 23.
38. Jack-up vessel having a jack-up vessel leg provided with an offshore impact absorption device according to claim 23 for absorbing external impact loads during touchdown of the respective leg or spud can on a seabed.
39. Ship impact protection system comprising an offshore impact absorption device according to claim 23.
40. Method for absorbing external impact loads when installing a jack-up vessel according to claim 38, comprising the steps of:positioning the jack-up vessel at a working site;lowering the legs of the jack-up vessel according to claim 18 towards the seabed;touching the seabed with the impact element, causing the second end of the damper to move in the longitudinal direction, such that the load applied on the impact surface by the seabed is dampened by the damper.
41. Method according to claim 40, wherein the step of touching the seabed with the impact element is performed at a non-perpendicular angle between the seabed and the impact element, causing the second end to be moved in the longitudinal direction only.
42. Method for providing an offshore impact absorption device according to claim 23 on an offshore structure, comprising the steps of:providing the offshore structure to be protected;optionally, removing an existing spud can from the offshore structure, for example from a jack-up vessel leg; andattaching the mounting body of the offshore impact absorption device to the offshore structure, for example to the jack-up vessel leg.