Method for connecting two blocks of an offshore structure

Abstract

Method for connecting two blocks of an offshore structure. The invention relates to a method for connecting two blocks of an offshore structure consisting of the assembly of at least two different unit blocks (B-1, B-2). The method comprises forming an overthickness (26) at the respective ends of the two blocks to be connected, mounting a joining plate (22) against the end to be connected of a first block (B-1), said joining plate having an overhanging frame (24) bearing against the ends of the flat panels and extending radially inwards and outwards, resting the end of the second block (B-2) against the joining plate, and welding the ends of the two blocks together. Figure for the abstract: Fig. 6.

Description

Title of the invention: Method for connecting two blocks of an offshore structure technical field

[0001] The invention relates to the general field of the mass production of offshore structures, and in particular of fixed and floating foundations for offshore wind turbines. More specifically, it relates to a method of connecting two blocks (or elements) forming such structures. Previous technique

[0002] An offshore wind turbine aims to harness wind energy to generate electricity using a turbine and an electric generator. There are two main types of offshore wind turbines: fixed wind turbines, which are installed on the seabed (at shallow depths typically less than 100m), and floating wind turbines, which offer the advantage of being able to be built on land and installed in areas where the seabed depth typically exceeds 100m.

[0003] The wind turbines which are concerned by the present invention comprise a turbine generally formed by a motor with several rotating horizontally axis blades and an electric generator coupled to the motor, the motor and the generator being fixed to an upper end of a vertical mast (or pylon).

[0004] The lower end of the mast is mounted on a support structure (called a "foundation"). For floating foundations, there are different types of floats, namely semi-submersible floats (with or without a pendulum counterweight), submerged floats with tensioned cables (or "TLP" platforms for "Tension-Leg Platform"), "SPAR" type floats (for "Single Point Anchor Reservoir"), semi-submersible "barge" type floats, etc. Reference may be made, for example, to publication WO 2019 / 106283, which describes a floating support structure whose main structure has a toroidal or polygonal shape. As for fixed foundations, they can be made of steel, concrete, or a combination of these two materials.

[0005] Offshore wind turbines are most often grouped together in a “wind park” or “wind farm” generally comprising between 20 and 100 wind turbines with several megawatts of unit power.

[0006] In floating offshore wind farm development projects, the delivery schedule for the floats is a key parameter for the successful delivery of large offshore wind farms within tight installation windows. Furthermore, the ability to guarantee local production of the floats is of paramount importance. but the land areas available for assembling the floats generally constitute a major obstacle.

[0007] French patent application FR 23 02023, filed on March 3, 2023, discloses a method for the mass production of floats for offshore wind turbines, each float consisting of at least two different unit blocks of floats. This method is remarkable in that it allows for the mass production of floats for offshore wind turbines on a very limited land area.

[0008] The implementation of such a production process poses a number of technical problems, in particular that of having to connect the float blocks while controlling the berthing tolerances between the blocks. Description of the invention

[0009] The invention therefore aims to provide a method for connecting blocks of an offshore structure (such as a semi-submersible float) to address this problem.

[0010] In accordance with the invention, this objective is achieved by means of a method for connecting two blocks of an offshore structure, the float being constituted by the assembly of at least two different unit blocks, the method comprising: - the formation of an excess thickness at the respective ends of the two blocks to be connected; - the mounting of a junction plate against the end to be connected of a first block, said junction plate having an overhanging frame bearing perpendicularly against the end of the first block, extending radially inwards and outwards; - the bracing of the end of the second block against the junction plate of the first block; and - welding the ends of the two blocks together.

[0011] The method according to the invention is remarkable in that the ends of the two blocks are provided with an additional thickness, which notably makes them more rigid. Combined with the joining plate, this additional thickness also increases the offset tolerances between these ends when the two blocks are joined. In other words, the method according to the invention allows for misalignments between the respective ends of the two blocks to be connected.

[0012] In one embodiment, the offshore structure is a semi-submersible float, and the blocks comprise: a first block comprising a central column, an outer column and a lower pontoon of the float, and a second block comprising an outer column and a lower pontoon of the float, the lower pontoons each being formed by an assembly of flat panels.

[0013]

[0014]

[0015]

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[0018]

[0019] In another embodiment, the offshore structure is a fixed foundation or a semi-submersible V-shaped float, and the blocks include: tubular elements, and at least one central tubular element. The end of the second block that rests against the junction plate of the first block is advantageously chamfered. Furthermore, the ends of the two blocks are welded together preferably by automatic welding. The invention also relates to a method for the mass production of semi-submersible floats for offshore wind turbines, each consisting of the assembly of at least two different unit blocks, the first block comprising a central column, an outer column and a lower pontoon, and the second block comprising an outer column and a lower pontoon, the lower pontoons each being formed by an assembly of flat panels, the method comprising: - the transport and storage on different storage areas of a production surface of a plurality of different blocks of floats, the same blocks of floats being stored on the same storage area of ​​the production surface; - the assembly line manufacturing of floats comprising successively for each float, a step of preparation of the blocks, a step of assembly and primary welding of the float blocks together at the level of an assembly and primary welding area separate from the storage areas and adjacent to them, followed by a step of final welding of the blocks together at the level of a final welding area separate from the other areas of the production surface, followed by a step of completion of the float at the level of a completion area separate from the other areas of the production surface; - the float blocks and the floats being manufactured are moved across the production surface between its different zones, primarily through translational movements; and - the assembly and primary welding stage of the float blocks together being carried out using the process as defined above. Brief description of the drawings [Fig.1] Fig.1 shows an example of different unit blocks of a semi-submersible float to which the connection method according to the invention is applied. [Fig.2] Fig.2 is a schematic and perspective view of an example installation for implementing the connection method according to the invention. [Fig.3] The [Fig.3] is a perspective view of a first floating block of an offshore wind turbine to be connected.

[0020] [Fig.4] The [Fig.4] is a perspective view of a second float block to be connected to the first block of the [Fig.2].

[0021] [Fig.5] The [Fig.5] is a cross-sectional view of the first and second blocks connected to each other using the method according to the invention.

[0022] [Fig.6] Fig.6 shows an example of compensating for differences in alignment of the two blocks connected to each other using the method according to the invention.

[0023] [Fig.7] Fig.7 shows an example of a fixed foundation for an offshore wind turbine to which the connection method according to the invention also applies.

[0024] [Fig.8] Fig.8 shows another example of a submersible V-shaped float for an offshore wind turbine to which the connection method according to the invention also applies. Description of the implementation methods

[0025] The invention relates to the general field of series production and the chain of offshore structures, and in particular of fixed or floating foundations for offshore wind turbines, and more particularly of semi-submersible type floats.

[0026] The offshore structures to which the present invention applies in particular have the particularity of being able to be manufactured by assembling a plurality of different unitary blocks (or elements).

[0027] In the embodiment described below in connection with figures 1 to 6 (relating to the manufacture of semi-submersible floats), each float 2 comprises, as shown in [Fig.1], four columns including a central column 4 which is intended to receive a wind turbine mast and three outer columns 6 which are connected to the central column by lower pontoons 8.

[0028] In practice, such floats 2 can each be formed by the assembly of three blocks: a first block Bl comprising the central column 4, an outer column 6 and a lower pontoon 8, and two identical second blocks B-2 each comprising an outer column 6 and a lower pontoon 8.

[0029] Of course, the invention applies to other types and other forms of semi-submersible floats, the latter being formed by the assembly of at least two different unit blocks of floats.

[0030] Furthermore, at least the lower pontoons 8 of each block Bl, B-2 are formed by an assembly of flat panels. For example, as shown in Figures 3 and 4, these lower pontoons are each made up of the assembly of four flat panels 8i to 84 forming a rectangular parallelepiped (only the flat panels 8i and 84 are visible in Figures 3 and 4).

[0031] Furthermore, the lower pontoons 8 of each block of the float can be reinforced by internal longitudinal stiffeners 9a and / or internal transverse stiffeners 9b (see [Fig.4]).

[0032] Reference may be made to patent application FR 23 01328 filed on February 13, 2023, which describes an example of a flat-panel float structure.

[0033] As shown in [Fig.2], these floats 2 can be manufactured on a relatively compact production land surface 10 capable of accommodating the various elements and equipment necessary for the manufacture of the floats.

[0034] This production area 10 is divided into different zones Z1 to Z6, namely: a first storage zone Z1 on which the Bl blocks are stored, a second storage zone Z-2 on which the B-2 blocks are stored, an assembly and primary welding zone Z-3 on which the different Bl, B-2 blocks constituting the same float are assembled together and subjected to primary welding, a final welding zone Z-4 ​​on which the different constituent blocks of the float undergo a new welding pass, a completion zone Z-5 on which the float is inspected and equipped with various equipment, and a buffer zone Z-6 on which a float 2' with manufacturing defects can be withdrawn for repair.

[0035] A transport barge 20 is moored at the loading quay of the production area. The float 2 located in completion area Z-5 is then loaded onto the transport barge by means of transport.

[0036] It should be noted that the float blocks and the floats being manufactured are moved between the different areas of the construction surface by multi-wheeled transport vehicles or by skidding, that is to say mainly by following translational movements.

[0037] At the primary assembly and welding zone Z-3, the Bl, B-2 blocks of each float being manufactured are assembled using a connection method according to the invention.

[0038] According to this connection method, it is planned to mount and fix a junction plate 22 on the end to be connected of the pontoon 8 of a first block (in [Fig.3], this is block Bl).

[0039] The joining plate 22 has an overhanging frame 24 which, when mounted against the ends of the flat panels forming the pontoon 8, overhangs (i.e., protrudes radially) outwards and inwards relative to the flat panels. In other words, the overhanging frame 24 of the joining plate has dimensions slightly larger than those of the straight section of the pontoon.

[0040] The fixing of the joining plate 22 against the end of the pontoon is obtained for example by welding the overhanging frame 24 onto the ends of the flat panels forming the pontoon.

[0041] As for the end of pontoon 8 of the second block 8-1 to be connected to the first block Bl, it is devoid of a junction plate (see [Fig.4]).

[0042] As shown in particular in figures 5 and 6, the method according to the invention also provides for forming an extra thickness 26 at the end to be connected of the flat panels forming the pontoons of the two blocks Bl, B-2.

[0043] For example, these extra thicknesses 26 can extend longitudinally from the end to be connected of the flat panels to the first transverse stiffener 9b.

[0044] The presence of these additional thicknesses 26 makes it possible, in particular, to stiffen the connecting ends of the pontoons of the two blocks. Combined with the joining plate, it also makes it possible to increase the offset tolerances between these ends during their docking.

[0045] The next step of the method according to the invention consists of supporting the ends of the flat panels forming the second block B-2 against the joining plate 22 of the first block BL. This support (or docking) is achieved by vertical translation of the blocks towards each other.

[0046] The ends of the flat panels forming the second block B-2 are then welded to the joining plate 22 (and more specifically to its overhanging frame 24), preferably by an automated welding process. For this purpose, the ends of the flat panels forming the second block B-2 can be chamfered to facilitate welding.

[0047] As previously stated, the junction plate 22 allows for misalignments between the respective panels of the two blocks Bl, B-2.

[0048] Thus, as shown in [Fig. 6], the joining of the two blocks B1, B-2 may result in a misalignment θ (typically on the order of 10 to 20 mm) between the ends of the flat panels forming the pontoons of the two blocks. Because the overlapping frame 24 of the joining plate extends radially inwards and outwards, the welding of the ends of the flat panels forming the pontoon of the second block B-2 can be carried out despite the presence of such a misalignment θ.

[0049] It should be noted that this same offset ô also affects the alignment of the longitudinal reinforcements 9a formed inside the lower pontoons of the two blocks to be assembled.

[0050] Here, it is possible to correct this misalignment by leaving the ends of the longitudinal reinforcements of the second block B-2 free (i.e., not attached to the panel on which they are mounted) so that they can be realigned with the longitudinal reinforcements of the first block BL

[0051] In the other embodiment described below in connection with [Fig.7] (relating to the manufacture of fixed foundations for offshore wind turbines), each foundation 2' includes in particular three first external tubular elements 28 forming feet which are connected to a central tubular element 30 forming the support of the wind turbine mast.

[0052] In this embodiment, the connection method according to the invention provides for mount and fix a junction plate 32 on the end to be connected of each external tubular element 28 (or of the central tubular element at the point where it connects with the external tubular elements).

[0053] This junction plate 32 includes an overhanging frame (not shown in [Fig.7]) which overhangs (i.e. protrudes radially) outwards and inwards relative to the ends of the tubular elements.

[0054] The method according to the invention also provides for forming an extra thickness (not shown in [Fig.7]) at the ends to be connected of the external tubular elements 28 and the central tubular element 30.

[0055] The remainder of the process according to the invention for this embodiment is identical to that described previously in connection with Figures 1 to 6.

[0056] In yet another embodiment described in connection with [Fig.8], the invention applies to the manufacture of semi-submersible V-shaped floats with tubular arms.

[0057] As shown in this [Fig.8], such a float 2” includes in particular two horizontal tubular branches 34, two diagonal tubular branches 36, a connecting tube 38, and a central tubular branch 40 forming the support for the wind turbine mast.

[0058] In this embodiment, the connection method according to the invention provides for mounting and fixing a junction plate 42 on the end to be connected of each tubular branch 34, 36, 38 (or of the central tubular branch at the level of its connection with the horizontal and diagonal tubular branches).

[0059] These junction plates 42 each comprise an overhanging frame which overhangs (i.e. protrudes radially) outwards and inwards relative to the ends of the tubular branches.

[0060] The method according to the invention also provides for forming an extra thickness (not shown in [Fig.8]) at the ends to be connected of the tubular branches 34, 36, 38 and of the central tubular branch 30.

[0061] The remainder of the process according to the invention for this embodiment is identical to that described previously in connection with Figures 1 to 6.

Claims

Demands

1. Method for connecting two blocks of an offshore structure (2; 2'; 2"), the structure being made up by the assembly of at least two different unit blocks (B1, B-2; 28, 30; 34, 36), the method comprising: - the formation of an overthickness (26) at the respective ends of the two blocks to be connected; - the mounting of a joining plate (22; 32; 42) against the end to be connected of a first block (B1; 28), said joining plate having an overhanging frame (24) bearing perpendicularly against the end of the first block, extending radially inwards and outwards; - the bearing of the end of the second block (B-2; 30) against the joining plate of the first block; and - the welding of the ends of the two blocks together.

2. A method according to claim 1, wherein the offshore structure is a semi-submersible float (2), and wherein the blocks comprise a first block (B1) comprising a central column (4), an outer column (6) and a lower pontoon (8) of the float, and a second block (B-2) comprising an outer column (6) and a lower pontoon (8) of the float, the lower pontoons each being formed by an assembly of flat panels (81 to 84).

3. A method according to claim 1, wherein the offshore structure is a fixed foundation (2') or a semi-submersible V-shaped float (2"), and wherein the blocks comprise tubular elements (28; 34, 36, 38), and at least one central tubular element (30; 40).

4. A method according to any one of claims 1 to 3, wherein the end of the second block (B-2; 30) bearing against the joining plate (22; 32; 42) of the first block (Bl; 28) is chamfered.

5. A method according to any one of claims 1 to 4, wherein the ends of two blocks are welded together by automatic welding.

6. Method for the mass production of semi-submersible floats (2) for offshore wind turbines, each consisting of the assembly of at least two different unit blocks (B-1, B-2) of which a first block (B-1) comprises a central column (4), an outer column (6) and a lower pontoon (8), and a second block (B-2) comprises an outer column (6) and a lower pontoon (8), the lower pontoons each being formed by an assembly of flat panels (8i to 84), the process comprising: - the transport and storage on different storage areas (Zl, Z-2) of a production area (10) of a plurality of different blocks (Bl, B-2) of floats, the same blocks of floats being stored on the same storage area of ​​the production area; - the assembly line manufacturing of floats comprising successively for each float, a step of preparation of the blocks, a step of assembly and primary welding of the float blocks together at the level of an assembly and primary welding area (Z-3) separate from the storage areas and adjacent to them, followed by a step of final welding of the blocks together at the level of a final welding area (Z-4) separate from the other areas of the production surface, followed by a step of completion of the float at the level of a completion area (Z-5) separate from the other areas of the production surface; - the float blocks and the floats being manufactured are moved across the production surface between its different zones, primarily through translational movements, and - the assembly and primary welding stage of the float blocks together being carried out using the method according to claim 2.

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