Method for connecting two blocks of an offshore structure

Abstract

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 comprising forming a thickened portion (26) at the respective ends of the two blocks to be connected, mounting a junction plate (22) against the end to be connected of a first block (B-1), the junction plate having a radially inwardly and outwardly projecting frame (24) bearing against the ends of the flat panels, bringing the end of the second block (B-2) to bear against the junction plate, and welding the ends of the two blocks to each other.

Description

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 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. Prior art

[0002] An offshore wind turbine uses 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 to which the present invention relates comprise a turbine generally formed by a motor with several rotating blades on a horizontal axis and an electric generator coupled to the motor, the motor and 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 the "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" in English), "SPAR" type floats (for "Single Point Anchor Reservoir"), semi-submersible "barge" type floats, etc. For example, we can refer to the publication WO 2019 / 106283 which describes a floating support structure whose The main structure has a toroidal or polygonal shape. As for the 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 a unit power of several megawatts.

[0006] In floating offshore wind farm development projects, the floater delivery schedule is a key parameter for the successful delivery of large offshore wind farms within tight installation windows. Furthermore, the ability to secure local floater production is of utmost importance, but land space available for floater assembly is usually a major obstacle.

[0007] Patent application FR 23 02023 filed on March 3, 2023 discloses a method for mass-producing floats for offshore wind turbines, each consisting of the assembly of at least two different unit blocks of floats. This method is remarkable in that it allows floats for offshore wind turbines to be manufactured in series on a very limited land area.

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

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

[0010] According to the invention, this aim is achieved by means of a method of 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; - mounting 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, projecting radially inwards and outwards; - the support 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 extra thickness, which in particular makes it possible to stiffen them. Associated with the junction plate, these extra thicknesses also make it possible to increase the offset tolerances between these ends when the two blocks are docked. In other words, the method according to the invention makes it possible to accept 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 planar panels.

[0013] In another embodiment, the offshore structure is a fixed foundation or a V-shaped semi-submersible float, and the blocks comprise: tubular members, and at least one central tubular member.

[0014] The end of the second block coming to bear against the junction plate of the first block is advantageously chamfered.

[0015] In addition, the ends of two blocks are welded together preferably by automatic welding.

[0016] The invention also relates to a method for mass production of semi-submersible floats for offshore wind turbines, each consisting of the assembly of at least two different unit blocks, a first block comprising a central column, an outer column and a lower pontoon, and a 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 in different storage areas of a production area of a plurality of different blocks of floats, the same blocks of floats being stored in the same storage area of the production area; - the production line manufacturing of floats comprising successively for each float, a step of preparing the blocks, a step of assembling and primary welding the float blocks together at an assembly and primary welding zone separate from the storage zones and adjacent to them, followed by a step of final welding of the blocks together at a final welding zone separate from the other zones of the production area, followed by a step of completing the float at a completion zone separate from the other zones of the production area; - the float blocks and floats being manufactured being moved on the production surface between the different zones thereof mainly according to translational movements; and - the step of assembly and primary welding of the float blocks together being carried out using the process as defined previously. Brief description of the drawings

[0017] [Fig. 1] Figure 1 shows an example of different unit blocks of a semi-submersible float to which the connection method according to the invention is applied.

[0018] [Fig. 2] Figure 2 is a schematic and perspective view of an example of an installation for implementing the connection method according to the invention.

[0019] [Fig. 3] Figure 3 is a perspective view of a first float block of an offshore wind turbine to be connected.

[0020] [Fig. 4] Figure 4 is a perspective view of a second float block for connection to the first block of Figure 2.

[0021] [Fig. 5] Figure 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] Figure 6 shows an example of compensating for the alignment differences of the two blocks connected to each other using the method according to the invention.

[0023] [Fig. 7] Figure 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] Figure 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 embodiments

[0025] The invention relates to the general field of mass 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 unit 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 Figure 1, four columns including a central column 4 which is intended to receive a wind turbine mast and three external columns 6 which are connected to the central column by lower pontoons 8.

[0028] In practice, such floats 2 can each be formed by assembling three blocks: a first block B1 comprising the central column 4, an outer column 6 and a lower pontoon 8, and two second identical 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 having to be formed by the assembly of at least two different unit blocks of floats.

[0030] Furthermore, at least the lower pontoons 8 of each block B1, B-2 are formed by an assembly of flat panels. For example, as shown in Figures 3 and 4, these lower pontoons are each formed by the assembly of four flat panels 8i to 84 forming a rectangular parallelepiped (only the flat panels 81 and 84 are visible in Figures 3 and 4).

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

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

[0033] As shown in Figure 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 blocks B-1 are stored, a second storage zone Z-2 on which the blocks B-2 are stored, an assembly and primary welding zone Z-3 on which the different blocks B1, B-2 constituting the same float are assembled together and subjected to a primary weld, a final weld zone Z-4 on which the various constituent blocks of the float undergo a new weld 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' presenting manufacturing defects can be withdrawn for repair.

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

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

[0037] At the primary assembly and welding area Z-3, the blocks Bl, B-2 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 figure 3, this is the block Bl).

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

[0040] The attachment of the junction 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 without a junction plate (see figure 4).

[0042] As shown in particular in Figures 5 and 6, the method according to the invention also provides for forming an excess thickness 26 at the end to be connected of the flat panels forming the pontoons of the two blocks B1, B-2.

[0043] For example, these excess 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 extra thicknesses 26 makes it possible in particular to stiffen the ends to be connected to the pontoons of the two blocks. Associated with the junction plate, it also makes it possible to increase the offset tolerances between these ends when they are docked.

[0045] The next step of the method according to the invention consists of placing the ends of the flat panels forming the second block B-2 in support against the junction plate 22 of the first block B-1. This placing in support (or docking) is carried out 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 junction plate 22 (and more precisely to the overflow frame 24 thereof), preferably by an automatic 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 indicated, the junction plate 22 makes it possible to accept misalignments between the respective panels of the two blocks B1, B-2.

[0048] Thus, as shown in Figure 6, it is possible that the docking of the two blocks B1, B-2 results in an offset ô (typically of the order of 10 to 20 mm) between the ends of the flat panels forming the pontoons of the two blocks. Thanks to the fact that the overhanging frame 24 of the junction plate projects radially inwards and outwards, the welding of the end of the flat panels forming the pontoon of the second block B-2 can be carried out despite the presence of such an offset ô.

[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 compensate for this offset by leaving the end 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 figure 7 (relating to the manufacture of fixed foundations for offshore wind turbines), each foundation 2' comprises 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 mounting and fixing a junction plate 32 on the end to be connected of each external tubular element 28 (or of the central tubular element at the level of its connection with the external tubular elements).

[0053] This junction plate 32 comprises an overflow frame (not shown in FIG. 7) which projects (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 excess thickness (not shown in FIG. 7) at the ends to be connected of the outer tubular elements 28 and the central tubular element 30.

[0055] The remainder of the method 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 Figure 8, the invention applies to the manufacture of semi-submersible V-shaped floats with tubular branches.

[0057] As shown in this figure 8, such a float 2" comprises 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 of 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 overflow frame which projects (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 excess 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 method according to the invention for this embodiment is identical to that described previously in connection with figures 1 to 6.

Claims

Claims

1. Method for connecting two blocks of an offshore structure (2; 2'; 2"), the structure being constituted by the assembly of at least two different unit blocks (Bl, B-2; 28, 30; 34, 36), the method comprising: - the formation of an excess thickness (26) at the level of the respective ends of the two blocks to be connected; - mounting a junction plate (22; 32; 42) against the end to be connected of a first block (Bl; 28), said junction plate having an overhanging frame (24) bearing perpendicularly against the end of the first block, projecting radially inwards and outwards; - the support of the end of the second block (B-2; 30) against the junction plate of the first block; and - welding 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 planar panels (8i to 84).

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

4. Method according to any one of claims 1 to 3, in which the end of the second block (B-2; 30) bearing against the junction plate (22; 32; 42) of the first block (B1; 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 mass production of semi-submersible floats (2) for offshore wind turbines each consisting of the assembly of at least two different unit blocks (Bl, B-2) including a first block (Bl) comprising a central column (4), an outer column (6) and a lower pontoon (8), and a second block (B-2) comprising 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 method comprising: - the routing and storage on different storage areas (Zl, Z-2) of a production surface (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 surface; - the chain manufacturing of floats comprising successively for each float, a step of preparing the blocks, a step of assembling and primary welding the float blocks together at an assembly and primary welding zone (Z-3) separate from the storage zones and adjacent to them, followed by a step of final welding of the blocks together at a final welding zone (Z-4) separate from the other zones of the production area, followed by a step of completing the float at a completion zone (Z-5) separate from the other zones of the production area; - the float blocks and floats being manufactured being moved on the production surface between the different zones thereof mainly according to translational movements, and - the step of assembling and primary welding the float blocks together being carried out using the method according to claim 2.

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