Patent ID: 12209375

DETAILED DESCRIPTION OF THE INVENTION

In this description the same or similar parts will be referred to by the same or similar reference signs. Though different embodiments or parts thereof are shown also combinations of embodiments should be considered having been disclosed herein.

In this description an offshore structure should be understood as at least including any structure founded in or on the bottom of a body of water, including but not limited to the bottom of a sea or ocean. In this disclosure an offshore structure can for example be a wind mill, drilling rig, electrical unit such as a transformer, or the like, preferably supported at least partly above a water surface of the body of water where the structure is positioned.

In this description coating of a surface should be understood as at least encompassing providing a coating layer such as a coating substance or coating film covering at least part of said surface. In preferred embodiments the coating will form a substantially closed layer over at least overlapping areas of the pile and the relevant part of the offshore element, such as a mounting part of a platform or tower.

In this description a platform mounted or to be mounted on a pile as disclosed should be understood as meaning at least but not limited to a platform surrounding at least partly the pile and/or a lower portion of a tower or leg mounted on the pile. Such platform can be suitable for landing of a vessel for transferring people and/or products to and from the offshore structure, and/or for people to move around the pile and/or tower or leg mounted on the pile safely. In the present disclosure the platform is mounted prior to fixing the tower to the pile, such that personnel can enter onto the platform and assist in positioning and fixing, especially bolting the tower to the pile (wherein, in particular, the tower is not fixed to the pile by using a slip joint).

According to an embodiment, the platform can be substantially made from metal, for example steel. In an alternative embodiment, the platform can be substantially made of concrete, e.g. by casting. Such a substantially concrete platform can be stable and durable, in particular in offshore conditions, and can be easily manufactured. A platform can also be made of different materials, such as but not limited to metal, e.g. steel, plastics, e.g. reinforced plastics, or combinations of said materials. This description discloses the use of a coating provided on an outer surface portion of the pile and/or an inner surface portion of the platform, especially a mounting part thereof, mounted on or to be mounted on the pile. Such coating can be an anti-fouling coating and/or anti-corrosion coating. Such coating can have a surface roughness higher than the surface roughness of the surface portion on which the coating is to be provided. A coating according to the disclosure is advantageously provided as a foil, which can also be referred to for example as film, sheet or the like wording. The coating can for example be formed by a self-adhesive foil, for example a foil provided with a pressure sensitive adhesive, or by a foil that can be adhered to the relevant surface by an adhesive. Alternatively a coating can be provided as a coating layer for example sprayed, rolled, dipped or brushed onto said surface. During application the coating can be formed, for example by providing a resin or such carrier onto said surface and then providing fibers on and/or into said resin. The coating can be machined after application in order to for example increase the surface roughness.

In the embodiments shown as a tower, especially a tower of a windmill is provided on a pile. Alternatively the tower can also be a tower or leg of another offshore element, such as an oil rig, power station or the like.

In this description the expressions “bolt based mounting provision”, “bolting provision” and the-like are to be understood as deriving their mechanical strength mainly from one or more forces conferred, received and/or enacted by one or more bolts of the provision and/or from an act of bolting (i.e. actuating a bolt with respect to a suitable bolt receiving structure, e.g. a nut, and/or vice versa). It is well known and will be appreciated by the skilled person that a slip joint as such does not derive mechanical strength from any of such bolt based forces or from an act of bolting, so that a slip joint is per definition different from a bolt based mounting provision.

FIG.1-5show schematically steps of providing a foundation pile2and placing a platform16and a windmill1on the pile2placed offshore in a body of water3. The body of water3can for example be a sea or ocean. As shown inFIG.1the pile2is driven into the bottom4of the body of water3in a suitable manner, such that at least an upper portion5extends above the surface6of the water3. The pile can for example be hammered, vibrated, dug and/or sucked into the bottom, as known in the art. The surface6of water3is to be understood as regarded when the surface6is substantially flat, without waves.

As can be seen inFIGS.1and2, for example a vessel V1can be used for placing the pile2, for example using a crane C. After the pile2has been properly placed, the same or a different crane C or other suitable machine can be used for placing a platform16onto the upper end9of the pile2. To this end the platform16has a mounting part19, as will be described hereafter, which can form a slip joint with the upper end9of the pile.

FIG.3shows schematically how the platform is positioned on the upper end9of the pile2, such that a walking surface17of the platform16lies near the level of the upper end9of the pile2, for example between no more than about 2 meters below and no more than about 2 meters above said upper end9. Preferably the walking surface17lies at a level relative to the upper end9or at least bolting provisions B as will be described hereafter, provided at said end surface9A, such that average height personnel can reach said surface9A or bolting provisions B while resting, for example standing on said walking surface. An average height Hopoperator120should be understood as an operator having a standing height of between 1.6 and 2 meters.

FIG.4shows landing of a transfer vessel Vt onto the platform16, for allowing personnel to move onto the platform16. Such vessel Vt can for example be provided with a motion compensated transfer system200, such as but not limited to a system provided by Ampelmann BV, The Netherlands.

FIG.5shows schematically how a tower7of a windmill1has been lowered onto the upper end9of the pile2, to be bolted to said upper end9by a bolt based mounting provision, such as the bolting provisions B. Examples of such bolt based mounting provisions will be discussed.

The windmill1has a tower7which has a lower end8fitted onto the upper end9of the pile2. The pile2and a tower7mounted thereon have parallel, preferably collinear longitudinal axis X-X. The pile2has a substantially circular cross section, but can have a different cross section, such as but not limited to square, hexagonal, oblong, multi sided or the like.

In the embodiments shown the upper end5of the pile2has a substantially truncated cone shape. The lower end or mounting part19of the platform16has an opening10opening in axial direction, having an internal shape and configuration corresponding to at least part of the upper end5of the pile2. Thus the mounting part19of the platform16can be fitted with the opening10over said end5of the pile2to form a slip joint11. The slip joint11is preferably formed with a coating layer14between an inner surface area12of the opening10and an outer surface area13of the pile2.

A pile2can generally be made of metal, such as steel. However, it can also be made of different materials, such as but not limited to concrete, or combinations thereof. The longitudinal axis X-X extends substantially vertical, having said truncated upper end5. The upper end5has an outer surface area13sloping relative to the longitudinal axis X-X. The angle α between said surface13and the longitudinal axis can for example be between 1 and 45 degrees, such as for example between 2 and 40, such as for example between 2 and 35 degrees. A coating layer14can be provided on the said surface area13, in embodiments forming a substantially closed covering of said surface area13. In embodiments the coating layer14can have been applied as a foil, adhered to the said surface area13by an adhesive. The adhesive can be a pressure sensitive adhesive, for example as a layer of such adhesive provided at a back of said foil.

The coating layer14can in embodiments have a surface15at the side opposite the surface area13, which surface15can have a surface roughness higher than that of the surface area13. This will increase friction between the mounting part19and the pile2. In embodiments the coating layer can comprise a resin with fibers embedded therein. The resin can for example be an acrylic resin. The fibers can be plastic fibers, for example nylon fibers. The resin and fibers can be carried on a carrier, for example a plastic carrier, such as but not limited to a polyester carrier. Prior to adhering such coating14to the surface area13a tie coat can be provided on the surface area13, for example an epoxy or vinyl primer. The coating layer14can have a small thickness, for example between a few μm and a few mm, preferably about one mm or less. Thin coating layer has an advantage since it will limit or prevent the possibility of lateral or angular movement of the platform16, as will be discussed, relative to the pile2. A coating14as provided is free of toxic components such as organotin compounds.

In embodiments instead of or additional to providing a coating layer14on the surface area13of the pile2such coating layer can be provided on an inner surface area12of the opening10in the platform16.

In the present disclosure the coating14can be an antifouling foil as provided by the firm Micanti, The Netherlands.

In the present disclosure the slip joint11is formed substantially by force of gravity acting on the platform16, as can be seen in the figures.

Using a coating14as disclosed in a slip joint of a platform can have the advantage that the friction between the pile2and the platform16can be increased in a simple and effective manner, improving the connection between the pile2and said platform. Moreover in embodiments the coating can prevent or at least reduce corrosion of the surfaces12and/or13. The coating can additionally make release of the slip joint easier than when forming such slip joint between the surface areas12,13directly, without said coating14. It has been found that using such coating can provide for a firm connecting over the slip joint without the coating making release of the slip joint after a period of time, for example after several years, more difficult than when forming the slip joint traditionally between the surface areas12,13directly.

Without wanting to be bound to any theory, it is believed that the coating14prevents corrosion of the relevant surfaces and/or stick slip of the said surface areas when releasing the structure element from the pile and/or providing the possibility of creating small relative movement of the structure element relative to the pile in a direction other than in the axial direction prior to and/or during such release.

As can be seen the coating14can extend further along the surface13and12than the tower7, covering also part of said surface area13or the top5of the pile2below the lower end8of the tower2.

InFIG.6-7the mounting of the tower7onto the pile2is shown, using the platform16. The platform16is placed on the pile2, forming a slip joint11.

In this embodiment the platform16comprises a substantially ring shaped walking surface17, provided with a railing18and supported on a ring element19forming a mounting part. For structural strength supports20can be provided between the mounting part19and the platform surface17. The ring element or mounting part19in this embodiment is a substantially truncated cone shaped bushing or pipe, having an internal channel forming the opening10with a shape and dimension substantially complementary to part of the surface area13of the pile2, such that the ring element19can be slid onto the upper end5of the pile to a relatively low position on said pile2, as shown inFIG.6. Preferably the ring element19is in this position supported on the coating layer14.

As can be seen inFIGS.6and7, the walking surface17is provided at a height Hp just below the upper end9of the pile2, for example a height Hp of about 1 meter below said upper end9. In this embodiment a first flange130is connected to the upper end9of the pile2, or formed thereby. It may be welded to said end, or bolted, or mounted in any other suitable way, or may be integral with said pile2. Bolts131extend from said first flange130upward (in this case, in particular, the bolts131extend normally with respect to the flange). Bolts should be understood as having a broad meaning, including but not limited to any element provided with screw threads or such connecting provisions to cooperate with similar or at least complementary connecting provisions at a lower end8of the tower7. By way of example only screw threads are disclosed as such connecting provisions, such as provided by bolts and complementary nuts.

As follows from the drawings, in particular, a first (mounting) surface or mounting flange130of the pile can be or have a transversally extending flange surface, i.e. a surface that extends radially with respect to a longitudinal center axis of the pile (wherein that transversal flange surface preferably extends horizontally when the structure has been positioned offshore, e.g. in or on the bottom of a body of water, including but not limited to the bottom of a sea or ocean). The mounting surface or mounting flange130can mechanically contact and support the tower after joining therewith.

Similarly, the lower end of the tower can include a transversally extending mounting/support surface (e.g. a flange surface of a flange132) that mechanically contacts and is supported by the pile2after joining. It follows that said transversal support surface of the tower preferably extends horizontally when the structure has been positioned offshore.

Also, as follows from the drawings, it is preferred that bolts131are arranged such that their respective center lines extend substantially in parallel with center lines of the tower land pile2(the bolts131being oriented substantially vertically, i.e. having vertically arranged central bolt axes, after offshore placement of the structure).

As can be seen inFIG.7a person, e.g. personnel120, can be standing on said walking surface17and can reach the bolts131easily with appropriate tools, especially without the need of ladders, climbing gear or the like. The tower7can be placed onto the upper end9of the pile2, for example lowered by a crane C. Then the tower7can be secured to the pile2using the bolts131of the bolt based mounting provisions. To this end the lower end8of the tower7can for example be provided with a second flange132, having appropriately placed openings133to fit over the bolts131, such that nuts134can be screwed onto the bolts131. Such bolting provisions B as such are well known in the art and provide for a secure, simple and reliable mounting of the tower7to the pile2.

It should be noted that in an alternative embodiment (seeFIG.17), personnel120may be standing inside the tower7for reaching the bolts, in particular in case of application of an inwardly extending mounting flange132′ of the tower instead of the depicted outwardly extending flange132. For example, a lower section of the tower7can be provided with a passageway D, access, door or the like, allowing personnel120to enter an interior of the tower7from the platform's walking surface17.

The platform16can be provided with a mooring provision21, such as one or more mooring eyes, bollards, slings or the like. Moreover the platform16can be provided with a ladder22or such provision for persons to use to mount and/or dismount the platform16. Moreover the platform16and especially the walking surface17can be provided for allowing access to an entrance23to the offshore element such as the tower7and/or for example stairs or an elevator.

FIG.8-10show schematically each a part of a connection135between a pile2and a tower7, and part of a platform16mounted using a slip joint11.

InFIG.8a connection135is shown in which a first flange130is connected to the upper end9of the pile2. Bolts131have been fixed to the first flange130, for example by welding or press fit or any other suitable way. The flange130extends outward from the upper end9, i.e. has a larger outer diameter Dout(130)than the outer diameter Dout(9)of the upper end9of the pile2. The platform16is formed such that it can be lowered over the first flange130, to which end the opening10has a minimal inner diameter Din(10)larger than the said outer diameter Dout(130)of the flange130. This also provides that the walking surface17will end up the height Hp lower than the first flange130. The tower7has the second flange132provided with the openings133, through which the bolts131extend. Nuts134are screwed tight onto the ends of the bolts131, against the second flange132, or for example washers or rings or the like provided thereon, securing the tower7onto the pile2.

FIG.9shows a similar connection135, in which however the first flange130extends inward from the upper end9of the pile2. Here bolts and nuts131,134are used to bolt the two flanges130,132together.

InFIG.10an embodiment is shown in which bolts131are secured in the upper surface9A of an at least partly solid pile2, for example made of concrete. The tower7is provided with the flange132to be bolted onto the bolts in a known manner.

In stead of using a first and/or second flange130,132, bolts and/or nuts or the like could be provided for directly at the pile2and/or tower7, for example through, in and/or on the upper end9of the pile and/or the lower end8of the tower7.

In embodiments a filler30can be used in between the surface15of the coating14applied to a first of the surface areas12,13of the first of the pile2and platform16and the adjacent part of the surface area13,12of the other one of the platform16and pile2. It has been found that, due to at least the difference in surface roughness between the surface15and the said adjacent surface area12,13small channels are formed between the coating and the said adjacent surface area12,13. These channels will allow flow of fluid in between the mating surfaces15and12or13, for example free flow or flow by capillary action. In embodiments these channels are used to introduce a fluid, especially a curing fluid into at least part of said channels, filling said at least part of the channels, such that after curing said channels are blocked for fluid flow, such as flow of water or air. The curing fluid can for example be a two component curing composition, for example but not limited to a composition of a setting resin such as a thermosetting resin and a curing agent for said thermosetting resin, e.g., an unsaturated polyester resin, and a curing agent for the resin, or a curable resin composition comprising an epoxy acrylate resin composed mainly of an ester of an epoxy resin with at least one organic acid selected from the group consisting of acrylic acid and methacrylic acid, and a reactive monomer, said curing agent comprising an organic peroxide. Compositions used can for example be but are not limited to polyester, vinyl ester or epoxy resin based compositions, known in the art, which are after curing sea water resistant. The filler can also be formed by a single component curable for example by air, heat, moisture or any suitable manner.

In embodiments the curing composition or filler30is injected into the channels from an upper end31of the coating layer14, for example by pressure injection or by gravity and/or capillary action. For example as shown inFIG.11, not to scale, for a slip joint in which the coating is applied to the outer surface area13of the pile2, wherein the said adjacent surface area is the inner surface area12of the platform16. Obviously this could also be inversed or a coating14could be applied to both surface areas12,13. In this embodiment a curing composition or filler30has been poured or injected from the upper end31, as schematically indicated by the injector32. Any other suitable pouring method or injection method can be used, such as but not limited to pouring the composition onto the upper end31or injecting the composition directly into the channels33formed by at least the surface roughness of the surface15. Inside the channels33the filler30is then allowed to cure and/or set to fill the channels33at least partly. In embodiments the filler30may, at least after curing, adhere to the surface15and/or to the adjacent relevant surface area12,13. In embodiments the filler30may not adhere to either or both of said surfaces15and12or13, for example by specific choice of the coating14and filler30and/or by applying a coating onto the relevant surface or surfaces15, and12or13, preventing such adhering.

In the embodiment shown, the filler has formed a closed ring around at least part of the coating layer14, especially filling substantially all channels33at least in the overlapping area34between the mounting part19of the platform16and the pile2. Preferably, such that both at the upper end31and the lower end35of the slip joint11a closed ring of said filler30is formed, preventing air and/or (sea) water to enter into said slip joint11. This will further prevent corrosion of the relevant surface areas. Alternatively, the filler may be provided such that it will only fill part of the channels33, for example by ring injection from the lower end35or from the top end31or both, or by filling only a section of the cross section, such as for example strips of said filler extending in a substantially vertical direction, leaving channels open between the top and bottom ends31,35.

Using a filler as described filling at least ring-wise part of the channels of the slip joint11, may prevent spillage of fluids such as but not limited to oil, hydraulic fluids, gasoline products, lubricants and the like which might be spilled inside the tower and could otherwise spill into the water surrounding the pile by seeping through the slip joint11. The filler may moreover add to the mechanical strength and durability of the slip joint11.

A filler or filler composition30can be applied after forming the slip joint11, or can be provided during forming thereof, for example by coating a relevant surface area, for example area12or15with the filler or filler composition30prior, preferably directly prior to placing the platform16onto the pile2. This can be advantageous for example when the composition or filler30has a relatively high viscosity or cannot flow into the channels sufficiently by capillary action, for example because of chemical incompatibility.

FIGS.12-15show schematically a platform, mounted on a pile2placed offshore in a body of water3. The body of water3can for example be a sea or ocean. The platform16again has a mounting part19fitted over the upper end9of the pile2.

In the embodiments shown again the upper end5of the pile2has a substantially truncated cone shape. The mounting part19of the platform16has an opening10opening in axial direction, having an internal shape and configuration corresponding to at least part of the upper end5of the pile2. Thus the platform16can be fitted with the opening10over said end5of the pile2to form the slip joint11. In this embodiment the slip joint11is formed by at least two separate areas101,102of a substance14A, which may be similar to or different from a coating14as discussed, between the inner surface area12of the opening10and an outer surface area13of the pile2. Said surface areas12,13form surface areas sloping relative to the vertical axis X-X and/or relative to each other.

In this embodiment, in stead of a single area containing the coating14, at least two areas101,102comprising a substance14A are provided, separate from each other seen in a longitudinal direction of the pile2and tower7, i.e. in the direction of the axis X-X. In the embodiment shown, a first area101is disclosed on the pile2, spaced apart over a distance N101from an upper end9of the pile2and the second area102is disclosed within the mounting part19. The two areas101,102are positioned such that when the platform16is mounted onto the pile2in overlapping fashion as discussed before, the first area101is close to or next to the lower end of the mounting part19and the second area102is close to or next to the upper end of the mounting part, below the upper end9of the pile2. By way of example, the areas101and102can be provided such that they are in the assembled position enclosed between the upper end9of the pile2and the mounting part19of the platform16and between the lower end of the mounting part19and the pile2, separated over a length Ldsubstantially equal to the length Lo of overlap when joined, which length Lo can for example be in the order of between about 1 and 10 m, for example between 1 and 5 m.

In the embodiment disclosed inFIG.12-15the substance14A can be a coating14as disclosed previously. In the embodiment disclosed the substance14A can be an adhesive material, such as a self-adhesive material. In the embodiment disclosed the substance14A can be a viscoelastic material. Viscoelasticity is to be understood as at least meaning but not limited to the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. In embodiments the substance14A can be such that upon applying it to a relevant surface of the pile2or mounting part19it will enter at least in part of said surface, for example into pores or interstitial openings in such surface. In embodiments the substance14A can be a self-adhesive, visco-elastic material.

As can be seen in for exampleFIG.13, the substance14A, when applied to the relevant surface12,13, i.e. the areas101,102, can have a height Hs above the relevant surface12,13, i.e. a height measured in a direction substantially perpendicular to the said surface12,13, which is substantial, for example a height Hs of more than 1 mm, for example between 1 and 30 mm, such as for example between 1 and 10 mm. In embodiments, the height Hs can be between about 2 and 5 mm, such as between 2 and 4 mm on average. A substance14A can be applied with a length Ls measured parallel to said surface12,13which can be substantially longer than the height Hs. The length Ls can for example be more than 10 mm, when the height is less than 10 mm. The length Ls can for example be 30 mm when the height is less than 30 mm. The length Ls can for example be between 30 and 500 mm, for example between 30 and 300 mm, such as for example between 75 and 250 mm. In embodiments, the length Ls can be between 100 and 200 mm, for example about 150 mm. In embodiments, as for example shown inFIGS.12-15, the substance14A can be provided as substantially forming a ring103around the pile2and/or within the mounting part19of the platform16, on or forming the respective areas101,102. Such ring103can have the discussed height Hs and length Ls.

In embodiments the substance14A as discussed can be a sealing material. In embodiments the sealing material that is used can be a mouldable, self-adhesive and viscoelastic material. It preferably is watertight and gastight according to NEN 2768 qualifications. The sealing material can be such that it can be applied manually without the need of tools, primers or any pre-treatment of the surface. The material used can have a low surface tension and liquid-like behaviour to provide good impregnation of the surface on which it is applied, preferably such that excellent wetting is achieved on steel surfaces of a pile2and/or a tower7as well as on polymers like PE, PP and FBE. Preferably such material can have these properties persist until a −20 degrees C.). (C.°) environment without tearing, breaking or the build-up of internal stresses. In embodiments the material used as or for said substance can be Stopaq®, especially Stopaq® paste, provided by Stopaq BV, The Netherlands, or a similar sealant.

In embodiments more than one ring103can be provided on the pile2and/or within the mounting part19, spaced apart appropriately.

In embodiments the substance14A such as the sealing material can be applied onto the pile2and/or mounting part19when the relevant pile2and/or platform16are in a substantially horizontal position, i.e. having the longitudinal axis X-X extending horizontally, for example on shore, for example as shown inFIG.16. Then the pile2and platform16can be shipped to a location, where the pile2can be driven into the sea bed4or mounted in a different manner in a vertical position, as for example shown inFIGS.1and2. Then the platform16can be lifted and lowered onto the pile2, as discussed before. The platform16can be lowered easily, without the risk of damaging the substance14A of either surface area101,102. Only when the mounting part19has been lowered almost to an end position of maximal overlap Lo the lower end of the mounting part will slide over an outward facing surface105of the substance14A at the lower area101, coming into contact with an inner surface area of the platform, whereas an inward facing surface106of the substance14A on the second area102will be brought into contact with the outer surface of the pile2near the upper end9thereof. Sliding the mounting part19further down the substances14A in the said areas101,102will be compressed and party deformed, forming two spaced apart seals107,108between the mounting part19of the platform16and the pile2, forming a slip joint11.

As is schematically shown inFIG.15, the substances14A can be deformed such that part of the substance14A on the first area101will be pushed partly outside the lower end8of the tower7, effectively forming a water tight and gas tight first, lower seal107. Similarly preferably the substance in the second area102is partly pushed upward out onto the upper end9of the pile, effectively forming a water and gas tight second, upper seal108. Preferably the seals107,108are formed such that the tower7can be lifted back off the pile if needed.

In the embodiment shown the substance14A is provided as a closed ring103on the pile2and in the mounting part19. However, similarly the substance14A can be provided differently, for example as patches. In embodiments the substance14A can be provided for example as a strip of material having sufficient internal cohesion to be able to be draped onto the relevant surface area101,102. In embodiments the substance can be provided for example as a paste which can be delivered onto the relevant surface area101,102for example using an injector32as for example shown inFIG.11. In embodiments the substance14A can be sufficiently viscous to be applied to a relevant surface area using a brush or roller. In embodiments the substance can be viscoelastic such that it can be kneaded and can be applied by hand, for example having a paste or gum like consistency. Any other suitable method for applying the substance14A to the relevant areas101and102can be used.

A tower7can be mounted to a pile2using a method as discussed.

A pile2, a platform16and a tower7can be manufactured on shore, wherein the pile2and tower7can for example be supported in a substantially horizontal position, i.e. with the longitudinal axis X-X substantially horizontally, as for example shown inFIG.16. The platform16can e.g. stand on its mounting part19, the longitudinal axis X-X substantially vertical. Preferably in this position the substance14A is applied to at least one and preferably both areas101,102. When the pile2is in a horizontal position when applying the substance14A, the relevant areas can be reached by an operator120relatively easily, for example using a ladder or scaffolding. If applicable the opening10can be accessed by the operator120to apply any substance there. This enables easy and well controlled applying of the substance14A in a well controlled manner, especially when applying on shore, for example reducing possible influences of for example weather conditions.

After application of the substance14A to the areas101and102, at least the pile2and platform16can be loaded onto an appropriate vessel or vessels, to be shipped to a location for installing the pile2and platform, for example as discussed before. The tower7can then also be shipped, at the same time or later, to be mounted onto the pile2.

Since the first area101is provided on the pile2spaced well apart from the upper end9thereof, the pile can be lifted easily by engaging the upper end above said area101. Moreover, the pile can be driven into the bottom4as discussed before, for example by applying a force onto the upper end9of the pile2, without risk of damaging the substance14A provided on the first area101.

Since the second area102is provided inside the mounting part of the platform, the platform16can be manipulated easily without running the risk of damaging the substance14A applied to the second surface area102.

The platform16can be mounted onto the pile2by lifting it in a vertical position to a position above the upper end9of the pile2, and then lowering it onto the pile2, as discussed before, forming a slip joint11. Since the first area101is provided relatively far below the upper end9of the pile and the second area102is provided relatively high above the lower end8of the tower7, contact between the pile2and the substance14A on the second area102and contact between the platform mounting part19and the substance14A on the first area101is prevented until the platform16has been lowered onto the pile2over a substantial distance, for example at least half of the length Lo of the overlap of the slip joint11when completed, for example at least 75% of said length Lo. In embodiments such contact occurs only after lowering the platform over the pile over a distance substantially equal to said length Lo minus the length Ls of the substance14A applied onto at least one of the areas101,102.

When lowering the platform16further onto the pile2, contact will be established between the outer surface105of the substance14A on the first area and the inner surface of the platform mounting part19, and between the outer surface106of the substance in the second area102and the outer surface of the pile2. Due to the substantial conical shape of the relevant surfaces of the pile2and mounting part19, further lowering of the platform16will increase friction between said outer surfaces105and106and the surfaces mating therewith, such that the substance will be pushed further against the relevant opposing surfaces of the platform16and pile2, at the same time dragging at least part of the substance14A along said surfaces, thus forming the seals107,108as, by way of example, shown inFIG.15.

Preferably the substance14A will seal off the space109enclosed between said opposing surfaces of the platform mounting part19and pile2, between the upper and lower seals107,108. Preferably the seals107,108will cover at least part of the exposed end faces110,111of the upper end9of the pile2and the lower end of the mounting part19too. Preferably the substance14A forming the seals107,108will adhere to at least one of the said surfaces of the pile2and/or platform that the slip joint11can be disengaged relatively easily by pulling the tower7back upward, off the pile2.

It shall be clear that the substance14A can also be applied to the pile2and/or platform16off shore, for example on a transporting vessel or after the pile2has been placed in the bottom4.

In embodiments seals formed by the substance14A can be combined with a coating14, specially an anti fouling coating, for example such that said coating extends below the lower seal107, between the two seals107,108and/or above the upper seal108.

It shall be clear from the above description and the drawings that on the one hand a slip joint11is formed between the platform16and the pile2(which slip joint11in particular does not include any bolt based mounting provision), and on the other hand the tower7is mounted on the pile2using a bolt based mounting provision B, wherein such a bolt based mounting provision B is different from, and does not include, a slip joint, and wherein preferably the slip joint11is different from, and does not include, a bolt based mounting provision. The platform16and the tower7are thus each substantially separately mounted to the pile2, so that the mounting of the tower7to the pile2does not involve any formation of an actual slip joint between the tower7and the pile2.

The embodiments as disclosed are shown by way of example only and should not be construed as limiting the scope of the disclosure. Many variations are possible within the scope of the invention as defined by the claims. For example the offshore element mounted on the pile can be of a different structure and can for example be supported by a series of piles as disclosed. The coating can be formed and/or applied differently. For example the coating can be provided with a different resin or combination of resins. Different types of fibers can be used, for example made of a different material or different materials, or instead of or additional to fibers other materials and element can be provided on or embedded in a resin of the coating, such as for example pallets, flakes or the like, increasing for example surface roughness of the surface15of the coating14. Instead of or additional to a film or foil coating a coating layer14can be provided by spraying, rolling, dipping, brushing or the like, for example using a single or multiple component fluid or paste, which may be curable. The surface15of the coating layer14and/or the surface105,106of the substance14A can for example be processed, for example after application to the pile and/or tower, for example by machining or etching for manipulating the surface, especially the surface roughness or surface profile. For example dents or grooves can be provided in and/or on the surface15,105and/or106. A platform16can be provided in a different manner and can be formed differently, for example by mounting the walking surface directly on the ring element or integrating them into one artefact. The or each slip joint are shown as formed above the water surface. A slip joint according to the disclosure can however also be formed at or below said water surface.

These and other amendments, including but not limited to combinations of embodiments or parts thereof as disclosed are also considered to have been disclosed within the ambit of the claims.