TOP PART OF A BASE CONSTRUCTION

Abstract

 Described is a device for arranging an add-on construction with internal cavity around a top part of a base construction. The device comprises a first and a second part which are coupled displaceably relative to each other along a common axis, extending in a longitudinal direction of both parts, between two positions in which the parts can be secured to each other. The first part can be connected to the add-on construction with first coupling means, while the second part can be connected to the base construction with second coupling means. The second part can be received in the cavity of the add-on construction for the purpose of supporting the add-on construction. Also described is a corresponding method. The device and method are particularly suitable for accurate mounting of an add-on construction on a monopile foundation of an offshore wind turbine.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a device for arranging an add-on construction with internal cavity around a top part of a base construction. The invention likewise relates to a method for accurate arrangement with the device of the add-on construction on the base construction. The method relates particularly to a device and method for arranging a work platform on a monopile foundation of an offshore wind turbine.

[0002] The invention will be elucidated hereinbelow with reference to an offshore wind turbine, for which the invention is particularly suitable. The reference to a wind turbine does not imply that the invention is limited to the use in the context of such a wind turbine, and the device and corresponding method can likewise be applied for any other combination of add-on construction for arranging on a base construction.

BACKGROUND OF THE INVENTION

[0003] An offshore wind turbine is generally placed on a support structure anchored to a seabed. For offshore wind turbines which are placed in relatively shallow water the support structure can comprise a monopile arranged in the seabed and extending above the water surface. A lattice structure or jacket can, if desired, be applied for deeper water. Reference will be made hereinbelow to a monopile, although this can also be understood to mean a jacket. In order to connect the wind turbine mast to a monopile use is in the prior art made of a transition piece. The transition piece is connected on a lower side thereof to the monopile and on an upper side thereof to the wind turbine mast. The transition piece can, if desired, be provided with add-on constructions such as a work platform, a jetty and other useful applications.

[0004] In a known method for mounting an add-on construction on a monopile the auxiliary construction is lifted from a jack-up platform or other floating device with a crane and mutually aligned with the monopile for the purpose of coupling the add-on construction to the monopile. During the mutual alignment use is for instance made of auxiliary cables or tugger lines operated with winches. For connection, an internal cavity of the add-on construction must be arranged around a top part of the monopile. With the known method the risk of damage to the add-on construction or the monopile is considerable, especially when work has to be carried out in relatively severe weather.

SUMMARY OF THE INVENTION

[0005] The invention has for its object, among others, to provide a device and corresponding method which at least partially obviates the above stated prior art drawbacks.

[0006] According to the invention, this object is achieved by providing a device according to claim 1. According to the invention, the device for arranging an add-on structure with internal cavity around a top part of a base structure comprises a first and a second part which are coupled displaceably relative to each other along a common axis, extending in a longitudinal direction of both parts, between two positions in which the parts can be secured to each other; wherein the first part can be connected to the add-on structure with first coupling means; wherein the second part can be connected to the base structure with second coupling means and wherein the second part can be received in the cavity of the add-on structure for the purpose of supporting the add-on structure.

[0007] With the invented device it is possible to align an add-on structure with internal cavity around a top part of a base structure in accurate and safe manner for the purpose of coupling these structures. With the invented device it is particularly possible to arrange an add-on structure, for instance a work platform, on an upper side of a monopile in accurate and safe manner.

[0008] Provided for this purpose according to the invention is a method which includes the steps of:

• providing a device according to any one of the foregoing claims;
• connecting the first part to the add-on structure with the first coupling means;
• displacing the second part relative to the first part until the second part has been received in the cavity of the add-on structure for the purpose of supporting it;
• hoisting the thus coupled first and second parts and the add-on structure onto the base structure;
• connecting the second part to the base structure with the second coupling means;
• displacing the first part and the add-on structure coupled thereto relative to the second part, wherein the internal cavity of the add-on structure is arranged around the top part of the base structure.

[0009] An embodiment of the invention relates to a device wherein the second part is elongate and is received over at least a part of its length in the first part. In this embodiment the first part can be displaced over at least a portion of the second elongate part between two positions in which the two parts can be mutually coupled. An add-on structure connected to the first part will then be able to co-displace over at least a portion of the second elongate part.

[0010] A suitable embodiment according to the invention provides a device wherein the second part can be displaced in the cavity of the add-on structure along a common axis extending in a longitudinal direction of the second part and the add-on structure. When the second part is situated substantially in the cavity of the add-on structure, then the add-on structure is supported by the second part. During lowering of the add-on structure around the top part of the base structure the second part can be gradually removed by displacement from the cavity of the add-on structure, wherein the supporting function is taken on by the top part of the base structure itself.

[0011] According to the invention, the first part can be connected to the add-on structure with first coupling means. Because the add-on structure is configured to be arranged around a top part of the base structure, it is advantageous to provide a device wherein the first coupling means are configured for connection to an upper side of the add-on structure. In this embodiment the add-on structure is suspended from the first part during use, and the internal cavity is accessible to the top part.

[0012] Another embodiment of the device is characterized in that the second coupling means are configured for connection to an upper side of the base structure. In this embodiment the second part is connected to an upper side of the base structure, which allows an add-on structure connected to the second part to be lowered relatively freely along the first part and over the top part of the base structure.

[0013] The first and second coupling means can be embodied in any suitable manner. An embodiment wherein the first and/or second coupling means comprise a pin connection, preferably a hydraulic pin connection, is particularly suitable. In an embodiment with a pin connection, preferably a hydraulic pin connection, the first and second parts can also be secured to each other in the two positions in which they are fixedly connected to each other. Relative displacement of the two parts is in principle not possible in these positions.

[0014] According to an embodiment, the device comprises a hydraulic circuit which can be remotely controlled and which comprises at least the above described coupling means. In this embodiment the device can be controlled from a position above water, for instance from a jack-up platform or other floating device.

[0015] According to an embodiment of the invention, the first and/or second part form a lattice of mutually connected stiffening elements such as bars. Such an embodiment imparts sufficient stiffness and strength to the parts at a relatively low weight.

[0016] According to another embodiment of the device, a lower edge part of at least the second part comprises an inner surface with a conical progression in the longitudinal direction. This makes it easier to align the second part with the base structure, for instance when connecting the second part to the base structure.

[0017] According to the invention, the first and the second part are coupled displaceably relative to each other along a common axis extending in a longitudinal direction of both parts. In order to facilitate the displacement, in an embodiment the first and/or second part is provided with sliding surfaces for the purpose of displacing the parts relative to each other. The sliding surfaces can for instance comprise a low-friction plastic, such as a polyolefin.

[0018] Particularly suitable embodiments comprise devices wherein the base construction is stationary and the add-on construction is placed on or partially over the base construction, more particularly wherein the base construction comprises a monopile or jacket, particularly of an offshore wind turbine, and the add-on construction comprises a work platform, a cage construction, a mooring construction and/or a J-tube construction, particularly of an offshore wind turbine.

[0019] Another aspect of the invention relates to a method for arranging an add-on construction with internal cavity around a top part of a base construction, wherein use is made of the described device. Preferred methods have already been described above in the light of preferred embodiments of the device.

[0020] Suitable embodiments of the method comprise, among others, methods in which the second part is elongate and is received over at least a part of its length in the first part; wherein the second part is displaced in the cavity of the add-on construction along a common axis extending in a longitudinal direction of the second part and the add-on construction; wherein an upper side of the add-on construction is connected to the first part with the first coupling means; wherein an upper side of the base construction is connected to the second part with the second coupling means; wherein the first and/or second coupling means comprise a pin connection, preferably a hydraulic pin connection; wherein the first and second parts are secured to each other with a pin connection, preferably a hydraulic pin connection; wherein the first and/or second part form a lattice; wherein a lower edge part of the second part comprises an inner surface with a conical progression in the longitudinal direction; wherein the first and/or second part is provided with sliding surfaces for the purpose of displacing the parts relative to each other; wherein, among others, the coupling means are remotely controlled by a hydraulic circuit; wherein the base construction comprises a foundation pile or transition piece of an offshore wind turbine; and wherein the add-on construction comprises a work platform, a cage construction, a mooring construction and/or a J-tube construction.

[0021] Finally, it is stated that the embodiments of the invention described in this patent application can be combined in any possible combination of these embodiments, and that each embodiment can individually form the subject-matter of a divisional patent application.

BRIEF DESCRIPTION OF THE FIGURES

[0022] The invention will now be further elucidated on the basis of the following figures and description of a preferred embodiment, without the invention otherwise being limited thereto. In the figures:

Fig. 1 is a schematic perspective view of an offshore wind turbine on a monopile foundation, with a detail of a transition piece;

Fig. 2 is a schematic view of an embodiment of a work platform of the wind turbine connected to the transition piece of the monopile;

Fig. 3 is a schematic perspective view of a work platform of the wind turbine connected to a monopile without interposing of a transition piece;

Fig. 4A and 4B are schematic views of a device according to an embodiment of the invention in coupled situation and connected to a work platform for arranging;

Fig. 5 is a schematic perspective view of a second part of the device according to the embodiment of the invention shown in figure 4;

Fig. 6 is a schematic perspective view of a first part of the device according to the embodiment of the invention shown in figure 4; and

Fig. 7A-7N are schematic views of different steps of an embodiment of the method according to the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0023] Referring to figure 1, an offshore wind turbine 2 is shown. Turbine 2 comprises a turbine mast 20 which is provided on an upper side with a nacelle 21 and a number of rotor blades 22. As also shown in figure 2, such a wind turbine 2 is placed on a support structure in the form of a monopile 4 anchored to a seabed 3. Monopile 4 forms a tubular element and can extend from the seabed 3 to a position above the water surface 5, but can also be situated with an upper edge 40 under water, as shown in figure 2. To connect wind turbine mast 20 to a monopile 4 use can be made of a transition piece 6. Transition piece 6 likewise forms a tubular element and extends from a bottom part 60 to a top part 61. According to the detail drawing of figure 1, transition piece 6 can be provided with a skirt part 64 which is moved over a top part of monopile 4, wherein an intermediate space 65 is created between an inner surface of the transition piece (6, 64) and an outer surface of monopile 4. The height of intermediate space 65 can, if desired, be determined by providing an inner surface of the transition piece (6, 64) with protrusions 66 which find support on an upper edge 40 of monopile 4. Space 65 can then be filled with a curing substance such as grouting mortar or grout. After curing, a connection is in this way obtained between transition piece 6 and monopile 4.

[0024] If desired, transition piece 6 (or monopile 4) can be provided with a work platform 7 with for instance boat ladder 70. An add-on structure to be placed over a monopile 4 and provided with a work platform 7 is shown in detail in figure 3 and comprises a work deck 72 surrounded by a railing 71. Work platform 7 further comprises a cage construction 73 constructed from a number of peripheral rings 74 connected to longitudinal rods 76 running in a longitudinal direction 75. Peripheral rings 74 and longitudinal rods 76 together define an internal cavity 79 which is arranged around a top part 41 of monopile 4. To connect work platform 7 to top part 41 of monopile 4 work platform 7 is provided on an underside of work deck 72 with a number of dovetail plates 78 which co-act with yokes 62 provided on the top part 41 of monopile 4. The upper side of monopile 4 can also be provided with an internal cover plate 63, which closes an internal space between the water surface and cover plate 63 in order to prevent corrosion.

[0025] Because the intermediate space between the external peripheral surface of monopile 4 and the internal peripheral surface of cage construction 73 of work platform 7 is relatively small, damage to work platform 7 and/or to monopile 4, for instance damage to the rust-preventing protective layers, may result during placing of work platform 7 on monopile 4. Device 1 according to the invention makes it possible to arrange work platform 7 over the top part 41 of monopile 4 and secure it thereto in accurate, rapid and safe manner.

[0026] The embodiment of the invented device 1 shown in assembled situation in figures 4A and 4B comprises a first part 10 and a second part 30 which is coupled to first part 10 for displacement relative to first part 10. Both parts (10, 30) are embodied as a lattice of longitudinal and transverse bars. The displacement is possible along a common axis 13, extending in a longitudinal direction (11, 31) of both parts (10, 30), between two positions (A, B) in which the parts (10, 30) can be secured to each other. Second part 30 is elongate and is received over at least a part of its length in first part 10. In the position A of first part 10 shown in figure 4A the first part 10 is situated at the height of an upper side of the second part, and second part 30 extends largely under first part 10. In the position B of first part 10 shown in figure 4B the first part 10 is situated at the height of a lower side of second part 30, and second part 30 extends largely above first part 10.

[0027] During use first part 10 is connected to an upper side of the add-on construction, particularly work platform 7, with first coupling means 19. Work platform 7 is provided for this purpose with a number of connecting plates 77 which co-act with first coupling means 19. Work platform 7 thus co-displaces with first part 10 when first part 10 displaces relative to second part 30 between position A and position B. In position A, in which second part 30 protrudes under first part 10, second part 30 is received at least partially in cavity 79 of work platform 7 for the purpose of supporting work platform 7. The second part 30 can here be displaced in the cavity 79 of work platform 7 along an axis extending in the longitudinal direction 31 of second part 30 and a longitudinal direction 80 of work platform 7, which axis coincides with common axis 13. The position A is taken up inter alia when the assembly (10, 30) of first and second part and the work platform 7 coupled to first part 10 is hoisted.

[0028] During use the second part 30 is connected with second coupling means 38 to the base construction, particularly monopile 4, as shown in figure 4A. In the situation in which second part 30 is connected to monopile 4, work platform 7 will co-displace when first part 10 is displaced from position A to position B, wherein cavity 79 of the work platform is moved over top part 41 of monopile 4 and second part 30 is simultaneously removed from cavity 79 until the situation of figure 4B is achieved. In this situation work platform 7 is secured to monopile 4, second part 30 is detached from monopile 4 and the assembly (10, 30) of the first and second part is removed.

[0029] In the above described method add-on structure 7 is lifted from a jack-up work platform (not shown) with a crane (not shown) and add-on structure 7 and monopile 4 are mutually aligned to a certain extent along a common axis 45, extending in a longitudinal direction of both elements, for the purpose of coupling add-on structure 7 and monopile 4. The alignment of add-on structure 7 relative to monopile 4 is for instance performed by auxiliary cables or tugger lines operated with winches. Add-on structure 7 is hereby kept under control and aligned with monopile 4 to a certain extent.

[0030] Referring to figure 5, the second part 30 is shown in more detail. Second part 30 comprises a lattice of mutually connected longitudinal bars 32 and transverse bars 33, reinforced with crosswise torsion bars 34, which is elongate in longitudinal direction 31. Transverse bars 33 form a number of levels which are mutually connected by means of ladders 35.

[0031] An upper surface of second part 30 is provided at corner points with lifting eyes 36 with which part 30 can be attached to a lifting crane (not shown) and lifted, and with two hydraulic connecting pins 37. A lower surface of the second part is provided with second coupling means in the form of hydraulic clamps 38 which are configured for connection to an upper side of monopile 4, and with four hoisting guides 39. A lower edge part of second part 30 is further provided with guide plates 42 having an inner surface with a conical progression in the longitudinal direction 31. Stoppers 40 ensure that first part 10 is held in the position B when first part 10 is displaced downward along second part 30. An internal monopile cover plate 63 can likewise form part of the lower surface of second part 30. If desired, second part 30 can also be provided with a ladder 41 which can be lowered from the lower surface.

[0032] Referring to figure 6, the first part 10 is shown in more detail. First part 10 also comprises a lattice of mutually connected longitudinal bars 12 and transverse bars 13, reinforced with crosswise torsion bars 14. In the situation in which first part 10 is coupled to second part 30 a longitudinal direction 11 of first part 10 runs parallel to the longitudinal direction 31 of second part 30. Transverse bars 13 form an open upper surface 15a and an open lower surface 15b. If desired, lower surface 15b is provided with a ladder 16. The connecting plates between transverse bars 13 can, if desired, also be provided with sliding surfaces 13a for the purpose of displacing the parts (10, 30) relative to each other.

[0033] At the position of upper surface 15a first part 10 is provided along transverse bars 13 with lifting plates 17 with which part 10 can be attached to a lifting crane (not shown) and lifted, and with connecting pins 18 which can be manually operated in the shown embodiment. Connecting pins 18 are provided with a locking pin 18a. Connecting pins 18 are mounted with transverse plates 18b on a transverse bar 13 of lower surface 15b. Connecting pins 18 of first part 10 and hydraulic connecting pins 37 of second part 30 function as temporary coupling means configured for connection of first part 10 to second part 30. Guides 19 for work platform 7 which are held at some distance from transverse bars 13 of lower surface 15b are also provided with connecting pins 19a for work platform 7.

[0034] The hydraulic pin connections are remotely controlled by a hydraulic circuit (not shown).

[0035] With the described device 1 an add-on construction with internal cavity, for instance work platform 7, can be arranged around a top part 41 of monopile 4. A suitable method is elucidated with reference to figure 7.

[0036] In step A a hoisting yoke 50 is first attached with hoisting cables 51 to lifting eyes 36 of second part 30. First part 10 is coupled to second part 30 by having connecting pins 18 engage on second part 30.

[0037] In step B the assembly (10, 30) of the coupled first and second part which is suspended from hoisting yoke 50 is lifted with a lifting crane (not shown) and carried to an upper side of work platform 7.

[0038] In step C a connection is then made between first part 10 and an upper surface of work platform 7 by connecting pins 19, 19a engaging on connecting plates of work platform 7. The coupling between first part 10 and second part 30 is then broken by releasing connecting pins 18.

[0039] In step D second part 30 is then moved downward so that this part 30 is received in the cavity 79 of work platform 7 and the stoppers 40 of second part 30 come into contact with first part 10.

[0040] In a subsequent step E second part 30 is once again coupled to first part 10 by activation of hydraulic connecting pins 37.

[0041] Hoisting yoke 50 is then uncoupled from second part 30 and hoisting cables 51 are attached to the lifting plates 17 of the first part (step F).

[0042] In step G the internal work platform plate 63 is then arranged in the guides 42 of the second part and connected to second part 30.

[0043] In a subsequent step H the assembly (30, 10, 7, 63) of first and second part, work platform 7 and plate 63 which is suspended from hoisting yoke 50 is then collectively lifted with a lifting crane (not shown) and carried to an upper side of monopile 4.

[0044] Step I comprises of connecting second part 30 to an upper side of monopile 4 by activating hydraulic clamps 38. The connection between the first and second part is simultaneously broken by retraction of hydraulic connecting pins 37.

[0045] In step J first part 10 with work platform 7 coupled thereto is lowered over the top part of monopile 4, wherein first part 10 displaces from position A to position B along the second part 30 fastened to monopile 4.

[0046] In step K the internal work platform plate 63 is then lowered with a hoisting installation suspended in second part 30 to a position in the upper surface of monopile 4 and there fastened to monopile 4.

[0047] In step L hoisting yoke 50 is detached from first part 10 and attached with cables 51 to the lifting eyes 36 of second part 30. First part 10 is then once again coupled to second part 30 by having connecting pins 18 engage on second part 30. Work platform 7 is then uncoupled from first part 10 by removing connecting pins 19a.

[0048] In step M hydraulic clamps 38 are then opened, whereby the connection of second part 30 to monopile 4 is broken.

[0049] In a final step N the assembly (10, 30) of the first and second part which is suspended from hoisting yoke 50 is collectively lifted with a lifting crane (not shown) and carried away to a storage location or optionally carried to an upper side of a second work platform 7 for placing, after which the method is repeated from step C.

Claims

1. Device for arranging an add-on construction with internal cavity around a top part of a base construction, comprising:

- a first and a second part which are coupled displaceably relative to each other along a common axis, extending in a longitudinal direction of both parts, between two positions in which the parts can be secured to each other;

- wherein the first part can be connected to the add-on construction with first coupling means;

- wherein the second part can be connected to the base construction with second coupling means; and

- wherein the second part can be received in the cavity of the add-on construction for the purpose of supporting the add-on construction.

2. Device according to claim 1, wherein the second part is elongate and is received over at least a part of its length in the first part.

3. Device according to claim 1 or 2, wherein the second part can be displaced in the cavity of the add-on construction along a common axis extending in a longitudinal direction of the second part and the add-on construction.

4. Device according to any one of the foregoing claims, wherein the first coupling means are configured for connection to an upper side of the add-on construction.

5. Device according to any one of the foregoing claims, wherein the second coupling means are configured for connection to an upper side of the base construction.

6. Device according to any one of the foregoing claims, wherein the first and/or second coupling means comprise a pin connection, preferably a hydraulic pin connection.

7. Device according to any one of the foregoing claims, comprising a pin connection, preferably a hydraulic pin connection, for securing the parts to each other in the two positions.

8. Device according to any one of the foregoing claims, wherein the first and/or second part form a lattice.

9. Device according to any one of the foregoing claims, wherein a lower edge part of the second part comprises an inner surface with a conical progression in the longitudinal direction.

10. Device according to any one of the foregoing claims, wherein the first and/or second part is provided with sliding surfaces for the purpose of displacing the parts relative to each other.

11. Device according to any one of the foregoing claims, comprising a hydraulic circuit which can be remotely controlled.

12. Device according to any one of the foregoing claims, wherein the base construction comprises a foundation pile or transition piece of an offshore wind turbine.

13. Device according to any one of the foregoing claims, wherein the add-on construction comprises a cage construction, a mooring construction and/or a J-tube construction.

14. Method for arranging an add-on construction with internal cavity around a top part of a base construction, comprising of:

- providing a device according to any one of the foregoing claims;

- connecting the first part to the add-on construction with the first coupling means;

- displacing the second part relative to the first part until the second part has been received in the cavity of the add-on construction for the purpose of supporting it;

- hoisting the thus coupled first and second parts and the add-on construction onto the base construction;

- connecting the second part to the base construction with the second coupling means;

- displacing the first part and the add-on construction coupled thereto relative to the second part, wherein the internal cavity of the add-on construction is arranged around the top part of the base construction.

Drawing