Method for assembling a tubular floating structure and its use

Abstract

A method for assembling a tubular floating structure and its use. First and second tubular members (11, 12) are welded to opposite sides of a stiffening ring (10) to obtain a double segment (12 / 11). Additional segments (13, 14) can be added to form a tubular multi-segment with a stiffening ring (10) between three adjacent tubular members (11, 12, 13). The resulting multi-segment (12 / 11 / 13) is used as a tubular buoyancy module for a floating offshore structure.

Description

Technical Field

[0001] The present invention relates to a method of assembling a tubular floating body structure for an offshore support, for example, a tubular floating body structure for an offshore wind turbine.

Background Art

[0002] For example, an offshore wind turbine support platform disclosed in US Patent Application Publication No. 2020 / 269960, and other types of support platforms in the marine industry for floating fish farms, for example, disclosed in International Publication No. 2021 / 053361, include buoyancy tanks moored to the seabed to maintain the structure in place.

[0003] For large platforms, the buoyancy tanks become correspondingly large and can be difficult to manufacture. Typically, the buoyancy tanks are manually assembled and welded using curved steel plates supported by reinforcing rings and stringers in a very labor-intensive process similar to shipbuilding. In a more industrial process, the buoyancy tanks can be manufactured by assembling fully fabricated tubular elements and continuously welding the edges together to form a tank with the desired tubular length. To maintain its tubular shape underwater, the reinforcing rings are inserted into the tubular members and welded to the inner surface of the tubular members as a countermeasure against hydrostatic and dynamic pressures when installed under marine conditions.

[0004] Reinforcement rings are heavy, expensive, and time-consuming to install. Therefore, it is desirable to reduce the number of reinforcement rings to facilitate production and shorten production time. Furthermore, inserting reinforcement rings requires that the inner circle of the tubular member coincide with the outer circle of the reinforcement ring, which has a small tolerance. However, due to the large size of the tubular member, there is a risk of its diameter changing, or the segment shape deviating slightly from circular, becoming elliptical. This can occur, for example, during the handling and transportation of the segment. Such deviations in diameter and deviations from circular can cause difficulties when inserting circular reinforcement rings. This is particularly problematic when the central axis of the segment is horizontal. Therefore, it is appropriate to insert the ring when the axis of the segment is vertical. However, in this case, when welding is performed along both edges of the ring, a single weld from below the ring is required, which increases the difficulty of the welding process. Each method has its own disadvantages.

[0005] Therefore, it would be desirable to discover improvements to the assembly method that overcome these disadvantages.

[0006] In other technical fields, the assembly of tubular members into elongated tanks is a standard practice, for example, when assembling silos in agriculture. In some silo structures, segments are provided with internal rings used for assembly with bolts. Another example is found in French patent application publication No. 2395903, in which segments are provided with rings at their opposite ends, and adjacent rings are then stacked one by one and welded to each other by welding from the side. However, side welding of such rings is difficult, especially when the welds need to be watertight. Thus, the methods known from silo manufacturing do not seem to be well applicable to the production of large buoyancy tanks for floating offshore structures.

[0007] As a result, other improved assembly principles will be needed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent Application Publication No. 2020 / 269960 [Patent Document 2] International Publication No. 2021 / 053361 [Patent Document 3] French Patent Application Publication No. 2395903 Specification [Overview of the Initiative]

[0009] Therefore, an object of the present invention is to provide improvements in the art. Specifically, the object is to provide an assembly method for buoyancy tanks of offshore structures, in particular for offshore wind turbines. This object and further advantages are described below and realized by the assembly method and its use as described in the claims.

[0010] In short, two tubular members are welded to opposite sides of a reinforcing ring to obtain a double segment. Additional segments can be added to form a tubular multi-segment with a reinforcing ring, which is a structural stabilizing ring between adjacent tubular members. The resulting multi-segment is used as a tubular buoyancy module in a floating offshore structure.

[0011] In the following, the term "tank" will be used together with the term "tubular buoyancy module" to conform to technical terminology. Similarly, segments for tubular buoyancy modules may also be called tank segments, or simply segments.

[0012] The assembly method involves the following two main steps:

[0013] 1. Manufacturing of tank segments 2. Assembling the tank segments to form a complete tank.

[0014] The tank segment comprises a cylindrical tubular member and a reinforcing ring. The tubular member forms the segment and the wall of the final, complete tank. Both parts are made of steel. The tubular member has a first edge and an opposing second edge at opposite ends. The reinforcing ring has a first surface and an opposing second surface on opposite sides. The reinforcing ring also has an outer circumference that is larger than the outer circumference of the first edge of the tubular member and an inner circumference that is smaller than the inner circumference of the first edge of the tubular member. In this way, a certain degree of tolerance is ensured when positioning the tubular member against the reinforcing ring.

[0015] In the manufacturing of the tank segment, the reinforcing ring is installed horizontally and flat with a vertical central axis, having an upward-facing first surface and resting on a second surface. Next, the tubular member is installed on the reinforcing ring from above, and the vertical axis of the tubular member is concentric or nearly concentric with the vertical central axis of the reinforcing ring. Because the vertical axes of the tubular member and the reinforcing ring are concentric, the tubular member rests on the first surface of the reinforcing ring. In this position, the outer circumference of the first edge of the tubular member is within the outer circumference of the first surface of the reinforcing ring, and the inner circumference of the first edge of the tubular member is outside the inner circumference of the first surface of the reinforcing ring. In this position, the tubular member and the reinforcing ring are joined by welding, and the weld forms a waterproof seam.

[0016] Since the outer circumference of the first edge of the tubular member lies within the outer circumference of the first surface of the reinforcing ring, and the inner circumference of the first edge of the tubular member lies outside the inner circumference of the first surface of the reinforcing ring, the welding is of the fillet weld type, which can be performed with or without full penetration. Due to the orientation of the vertical axes of the tubular member and the reinforcing ring, the welding is performed in a horizontal position, which is very convenient to carry out.

[0017] After the tank segment is manufactured, if the tubular member and reinforcing ring are joined, the tank segment rotates 180 degrees around the horizontal axis. While the reinforcing ring is positioned beneath the tubular member during the segment's manufacture, the reinforcing ring is positioned on the tubular member after the rotation. Here, the segment rests on the downward second edge of the tubular member, where the second surface of the reinforcing ring forms the top surface of the tank segment.

[0018] The tank segment is assembled by placing the second segment on top of the first segment. The second segment is installed from above, and its vertical axis is concentric or nearly concentric with the vertical axis of the second segment, and the second edge of its tubular member rests on the second surface of the reinforcing ring of the first segment. Because the vertical axes are concentric, the second segment is installed in the following position: In this position, the outer circumference of the second edge of the second tubular member of the second segment is within the outer circumference of the second surface of the reinforcing ring of the first segment, and the inner circumference of the second edge of the tubular member of the second segment is outside the inner circumference of the second surface of the reinforcing ring of the first segment. In this position, the tubular member of the second segment and the reinforcing ring of the first segment are joined by welding, and the weld forms a waterproof seam.

[0019] Since the outer circumference of the second edge of the tubular member of the first segment lies within the outer circumference of the second surface of the reinforcing ring of the second segment, and the inner circumference of the second edge of the tubular member of the first segment lies outside the inner circumference of the second surface of the reinforcing ring of the second segment, the welding is of the fillet weld type, which can be performed with or without full penetration. Due to the orientation of the vertical axes of the tubular member and the reinforcing ring, the welding is performed in a horizontal position, which is very convenient to carry out.

[0020] This method of manufacturing and assembling the tank segments offers several advantages over conventional techniques.

[0021] Instead of the rings being inserted into the segments, welding is performed on the segments of each reinforcing ring, saving time and making manufacturing considerably easier because the tolerance requirements between the tubular member and the reinforcing ring are less.

[0022] Similarly, by installing the tubular member on top of the reinforcing ring during the manufacture of the segments, the tolerance requirements between individual tubular members are considerably reduced. In the conventional manufacturing method, the tubular members are installed directly on top of each other, but the diameters and roundness of two adjacent tubular members need to be the same in order to obtain a joint without stress concentration resulting from the mismatch between the tubular members. In the manufacturing method according to the present invention, certain variations in the diameters and circularity of two adjacent tubular members are acceptable. This is because the stress concentration resulting from the mismatch between the tubular members is considerably reduced by the reinforcing ring inserted between the tubular members.

[0023] Generally, the method provides an improvement in the assembly of buoyancy elements for offshore structures when used, for example, to assemble the buoyancy modules of a tubular floating wind turbine offshore structure.

[0024] In some specific embodiments, a first welding station is provided, the first welding station comprising a plurality of rollers arranged in a circular configuration and configured to rotatably support a first reinforcing ring on the rollers in a horizontal orientation during welding between a first tubular member and the first reinforcing ring. As will become apparent below, this first station is used to weld subsequent tubular members onto each ring in order to provide additional segments for assembling a multi-segment tube. In the first welding station, one or more welding machines are provided for welding.

[0025] In some embodiments, one or more welding machines are installed on both the outside and inside of the tubular member, thereby facilitating welding simultaneously on both sides of the weld seam.

[0026] The welding machine is preferably provided at a fixed location of the first welding station, and the welding of the tubular member to the reinforcing ring is performed while rotating the combination of the tubular member and the reinforcing ring about its vertical central axis, instead of moving the head along the edge.

[0027] This practical embodiment is advantageous in that when the movement of the head is large, accuracy can become an issue, so the stationary welding machine requires only minimal and simple mechanical support compared to a welding machine that moves around the ring. This is especially true when the segment has a diameter in the range of 5 to 15 meters.

[0028] In an advantageous embodiment, a second welding station with a plurality of rollers is provided, the plurality of rollers being arranged in a circular configuration and configured to rotatably support a first segment with a second edge without a second ring when each first reinforcing ring is upward and horizontal.

[0029] In fact, to provide the first segment, after welding the first tubular member to the first reinforcing ring at the first welding station, the resulting first segment is turned upside down, so that the first reinforcing ring is upward and the first segment is lifted onto the second welding station, and the rollers rotatably support the second edge of the first segment.

[0030] Optionally, a support ring or support plate is provided between the downward edge and the rollers to protect the rollers from potentially sharp downward edges.

[0031] After welding the second tubular member to the second reinforcing ring at the first welding station, the resulting second segment is turned upside down, so that the second ring is upward. The second segment is lifted onto the first ring of the first segment at the second welding station, and a double segment is formed.

[0032] Advantageously, as described for the first welding station, one or more welding machines are installed on both the outside and inside of the tubular member, thereby facilitating simultaneous welding on both sides of the weld seam. The welding machines are advantageously located at the fixed location of the second welding station, and welding of the segments to the ring is performed by rotating the two segments around their vertical central axis, rather than moving the head along the edge.

[0033] Optionally, the height of the welding head of a welding machine can be adjusted, for example, by mounting it on the arm of a welding robot. This allows the welding head height to be adjusted to match the height of a single segment. However, if all segments have a single standard height, head height adjustment is not necessary.

[0034] To further extend the length of a multi-segment structure, as is typically done to construct a buoyancy module of a desired height, additional segments can be manufactured and joined to segments that are already joined by welding.

[0035] In a preferred embodiment, the additional segment is manufactured using the same method as that used to manufacture the first segment. After manufacturing, the additional segment is rotated upside down and lifted onto a second welding station. A pre-assembled structure comprising two or more segments is then placed from above on top of the additional segment, with its vertical axis concentric or nearly concentric with the vertical axis of the additional segment. In this position, the tubular member of the first segment and the reinforcing ring of the second segment are joined by welding, the weld forming a waterproof seam.

[0036] This method can be repeated as many times as there are relevant segments to achieve the desired height.

[0037] Here, we would like to point out that the method of lifting a multi-segment already combined with two or more segments onto an additional segment may seem counterintuitive compared to lifting single segments one after another onto an already welded multi-segment. However, as explained below, this arrangement has a valid reason because it does not require lifting the welding head upwards with each additional segment. Instead, by first lifting the already welded multi-segment to a storage station and then, always, turning only a single segment for the next weld, it is not necessary to lift the welding head higher than the height of a single segment, which is typically in the range of 2 to 10 meters.

[0038] As mentioned above, to protect the roller, the second welding station optionally includes a support ring or support plate between the roller and the second downward edge of the single segment, and the single segment is lifted from the first welding station toward the second welding station. This becomes more important as the weight increases proportionally with the number of segments welded together into the elongated tube.

[0039] Advantageously, one welding station, or rather both welding stations, are equipped not only with a first roller that supports the segment and ring combination from below, but also with a second roller that contacts the combination laterally to precisely position and guide the ring and tubular member during welding, which is performed simultaneously with rotation.

[0040] The present invention will be described in more detail with reference to the drawings. [Brief explanation of the drawing]

[0041] [Figure 1] This shows the arrangement of the rotating support for the welding station. [Figure 2] Three welding stations are shown. [Figure 3A] The first assembly step is shown in a perspective view. [Figure 3B] The first assembly step is shown in a side view. [Figure 4] The following shows the subsequent steps for assembling the double segment. [Figure 5] The following shows the subsequent steps for assembling the double segment. [Figure 6] The following shows the subsequent steps for assembling the double segment. [Figure 7] The following shows the subsequent steps for assembling the double segment. [Figure 8] The following shows the subsequent steps for assembling the double segment. [Figure 9] The following shows the subsequent steps for assembling the double segment. [Figure 10A] An additional assembly step using the third segment is shown in the side view. [Figure 10B] An additional assembly step using the third segment, which is being prepared, is shown in a perspective view. [Figure 11A] The assembly of the triple segment is shown in a side view. [Figure 11B] The assembly of the triple segment is shown in a perspective view. [Figure 12] A side view illustrating the movement of the triple segments of the storage station is shown. [Figure 13] A side view of the triple-segment storage station is shown. [Figure 14] A perspective view is shown illustrating the triple segment of the storage station and the preparation of the fourth segment at the first welding station. [Figure 15A] The welding machines at the first and second welding stations are shown in perspective views. [Figure 15B] This shows an enlarged cross-section of the welding machine at the first welding station. [Modes for carrying out the invention]

[0042] Figure 1 shows the arrangement of a rotating support for welding station 1. Welding station 1 comprises a plurality of first rollers 5 on a corresponding first frame 4 to rotatably support a circular tubular segment from below for welding. The first frame 4 and the first rollers 5 are arranged in a circular configuration to support the corresponding circular structure. Welding station 1 also comprises a second roller 6 on a corresponding second frame 7 to contact such a circular tubular structure from the side, and to properly guide the circular tubular structure in a rotational motion about a vertical central axis.

[0043] Optionally, the second roller 6 is movable radially inward and outward in the horizontal direction. This is also useful for easily fitting ring-shaped segments to the roller station 1 when the segment diameter changes or when they deviate slightly from a circle.

[0044] Figure 2 shows three welding stations. The first welding station 1 and the second welding station 1' are provided in addition to a third station, which is a storage station 1'', and the storage station 1'' is equipped with a fixed support ring 9'. The support ring 9 is provided in the second welding station 1', for example, as is the support ring 9' of the storage station 1''. Furthermore, referring to Figure 1, the support ring 9 is supported by a first roller 5 and fixed by a second roller 6 to guide it into a circle. Instead of the support ring 9, a support plate is optionally used in the second welding station 1'.

[0045] Figures 3A (perspective view) and 3B (side view) show the first assembly step using the first welding station 1 and the second welding station 1'. The reinforcing ring 10 is placed on the support roller 5 of the first welding station 1 and guided by the second roller 6 which abuts its outer periphery, in order to rotate about a vertical axis X.

[0046] Figure 4 shows the arrangement of the first tubular member 11 on the reinforcing ring 10, with the first edge 11A of the first tubular member 11 in contact with the upper surface of the reinforcing ring 10. Advantageously, the first edge 11A has a smaller diameter than the reinforcing ring 10, which is intended to ensure that even if the first edge 11A deviates slightly from its circular shape due to deformation during transport and handling, for example, the entire first edge 11A rests on the reinforcing ring 10, leaving sufficient space for fillet welding. The orientation of the first tubular member 11 positioned on top of the reinforcing ring 10 offers advantages, particularly in that welding can be performed from above more easily than welding from below due to the melting of the metal during welding.

[0047] Figure 5A shows the rotation and motion of the first segment, which is manufactured by welding the tubular member 11 and the reinforcing ring 10 from the first welding station 1 to the second welding station 1'. The final result of the first segment rotating on the second welding station 1' is shown in Figure 5B. Arrow 8 indicates the orientation of the segment relative to the vertical direction in Figure 5A, where arrow 8 is downward. While the first edge 11A of the first tubular member 11 is welded to the first reinforcing ring 10, the second edge 11B of the first tubular member 11 rests on the support ring 9, but is not fixed to the support ring 9. This is because the support ring 9 remains on the roller 5 of the second support station 1' to support various segments, and then the segment's downward edge is placed on the support ring 9.

[0048] Figure 6 shows the preparation of the second segment, where the first edge 12A of the second tubular member 12 is welded to the second reinforcing ring 10 at the first welding station 1. In the example of the present invention, the second reinforcing ring 10 is similar in dimensions to the first reinforcing ring 10, but this is not absolutely necessary. The procedure is shown in Figure 4 and is identical to the procedure for the first segment described above.

[0049] As shown in Figure 7A, once welding is complete at the first welding station 1, the second segment rotates and is lifted towards the top of the first segment at the second welding station 1'. As a result, the downward second edge 12B of the second segment 12 abuts against the first reinforcing ring 10 of the first segment 11 for welding, as shown in Figure 7B. By welding at the second welding station 1', the two segments form a double segment 12 / 11, with the two tubular segments 11, 12 fixed to each other and the first reinforcing ring 10 positioned as a single ring between the two mutually adjacent tubular members 11, 12, with the second reinforcing ring 10 on top. The second edge 11B of the first segment 11 rests on the support ring 9.

[0050] In the procedure shown, the first segment is lifted onto the second welding station 1', and the second segment is lifted onto the top of the first segment. Alternatively, the first segment is lifted from the first welding station 1 onto the storage station 1'', and after welding, the second segment is lifted from the first welding station 1 onto the second welding station 1', and then the first segment is lifted from the storage station 1'' onto the second segment at the second welding station 1'. This is possible but undesirable because it requires an additional lifting motion. Given that the segment size is typically quite large, with a diameter of 5-10 meters, the number of motions can be advantageously minimized.

[0051] Next, the double segment 12 / 11 is lifted from the second welding station 1' and stored in the storage station 1'' with the downward second edge 11B of the first tubular member 11 resting on the support ring 9' of the storage station 1'', as shown in Figure 8.

[0052] Figure 9 shows the welding of the third tubular member 13 to the third reinforcing ring 10. As shown in Figure 10A, the resulting third segment is lifted and rotated away from the first welding station 1, and as shown in Figure 10B, the downward second edge 13B of the third tubular member 13 is positioned on the upper surface of the support ring 9 of the second welding station 1', and the reinforcing ring 10 is lifted so that it faces upward.

[0053] As shown in Figure 11A, the double segment 12 / 11 is then lifted from the storage station 1'', and the downward second edge 11B of the first tubular member 11 is positioned on the third support reinforcing ring 10 at the top of the third tubular member 13, resulting in the configuration shown in Figure 11B. At the second welding station 1', the downward second edge 11B of the first tubular member 11 is welded on the third support reinforcing ring 10 at the top of the third tubular member 13 to form the triple segment 12 / 11 / 13.

[0054] As shown in Figure 12, the triple segments 12 / 11 / 13 are lifted from the second welding station 1' and stored in the storage station 1'' as shown in Figure 13. As shown in Figure 14, the fourth segment is generated at the first welding station 1 by using an additional tubular member 14 and an additional reinforcing ring 10, and the procedure described is repeated for the number of segments desired to form the final buoyancy structure.

[0055] Although an additional lifting step is required, the procedure shown offers several advantages compared to the following alternative. In that alternative, the double segment 12 / 11 is not lifted from the second welding station 1', but the third segment 13 is lifted onto the top of the double segment 12 / 11, and the fourth segment 14 is lifted onto the top of the triple segment. By lifting and moving the double segment 12 / 11 and its corresponding triple segment 12 / 11 / 13 twice, i.e., by moving them from the second welding station 1' to the storage station 1'' and then returning them to the second welding station 1' when the additional single segment is placed on top of the second welding station 1', it is always the case that the bottom segment is welded at the second welding station 1'. Therefore, by adding segments, it is not necessary to lift the welding head of the second welding station 1' upward. Since the tubular members 11, 12, 13, and 14 of the segments are usually at the same height, there is no need to move the welding head to assemble all the added rings upward. Specifically, this allows lifting and welding to be performed simultaneously at two stations 1 and 1', minimizing structural and operational complexity and increasing speed.

[0056] The welding machine 15 is shown in Figure 15A and in an enlarged view in Figure 15B. As shown in Figure 15A, the welding of the third tubular member 13 onto the corresponding reinforcing ring 10 can be performed simultaneously with the welding of the second tubular member 12 onto the reinforcing ring 10 which has already been welded to the first tubular member 11 of the first segment.

[0057] As shown in Figure 15B, the welding machine 15 has a fixed base 16 and welds the third tubular member 13 onto the third reinforcing ring 10 from above. The welding machine 15 has a connecting arm 17 or a welding head 18 that moves to the welding location. The distance of the welding head 18 from the fixed base 16 is adjustable to accommodate slight variations in welding position and angle, but the welding machine 15 is not configured to reach the upper edge 13B of the third tubular member 13. This was explained above for the purpose of simplifying the welding station 15. However, as explained in detail above, it is necessary to move long multi-segments onto the storage station 1'' and then from the storage station 1'' towards the top of the reinforcing ring 10 with segments consisting only of single tubular members. This is necessary when additional single segments are manufactured at the first welding station 1 and are being moved to the second welding station 1'.

Claims

1. A method for assembling a buoyancy module of a tubular floating offshore structure, the method comprising providing a first tubular member (11) and a first reinforcing ring (10) for a first segment, and a second tubular member (12) and a second reinforcing ring (10) for a second segment, wherein each of the first and second tubular members (11, 12) comprises a first edge (11A, 12A) and an opposing second edge (11B, 12B), The method further includes, for each of the first and second segments, providing the corresponding reinforcing ring (10) which is laid flat and has an outer circumference larger than the circumference of the corresponding tubular members (11, 12) of the first edges (11A, 12A); placing the tubular members (11, 12) with the first edges (11A, 12A) on the reinforcing ring (10) within the outer circumference; and welding the first edges (11A, 12A) to the reinforcing ring (10) from above. A method comprising: inverting both the first and second segments so that the corresponding reinforcing ring (10) faces upward; lifting one of the segments, with the second edge (11B, 12B) of the tubular member (11, 12), toward the reinforcing ring (10) of the other segment; welding the second edge (11B, 12B) of one of the segments to the reinforcing ring (10) of the other segment from above; and forming a double segment (12 / 11) including two segments, each having one of the reinforcing rings (10) at the top and a downward-facing second edge (11B, 12B) at the bottom without a reinforcing ring (10).

2. The method further includes: providing a third reinforcing ring (10) which is laid flat and has a third outer circumference larger than the circumference of the first edge (13A) of the third tubular member (13); placing the third tubular member (13) with the first edge (13A) on the third reinforcing ring (10) within the third outer circumference; and welding the first edge (13A) of the third tubular member (13) to the third reinforcing ring (10) to provide a third segment. The method according to claim 1, further comprising: inverting the third segment so that the third reinforcing ring (10) faces upward; lifting the double segment (12 / 11) with the second edges (11B, 12B) on the lower side of the segment toward the third reinforcing ring (10); and welding the second edges (11B, 12B) to the third reinforcing ring (10) from above to provide a triple segment (12 / 11 / 13).

3. The method according to claim 1, comprising providing a first welding station (1) having a plurality of rollers (5, 6), the plurality of rollers (5, 6) arranged in a circular configuration during welding between the first tubular member (11) and the first reinforcing ring (10), and configured to support the first reinforcing ring (10) on the rollers (5, 6) so as to be rotatable horizontally, the method comprising maintaining a first welding machine (15) for welding at a fixed location of the first welding station (1), and welding the first tubular member (11) to the first reinforcing ring (10) while rotating the first reinforcing ring (10) about a vertical central axis (X).

4. The method comprises providing a second welding station (1') comprising a plurality of other rollers (5, 6), the plurality of other rollers (5, 6) arranged in a circular configuration and configured to rotatably support the first tubular member (11) with a downward-facing second edge (11B) when each of the first reinforcing rings (10) is facing upward, and the method comprises, - To provide the first segment, after welding the first tubular member (11) to the first reinforcing ring (10) at the first welding station (1), the first segment is lifted from the first welding station (1) and the first segment is turned upside down so that the first reinforcing ring (10) faces upward, - To provide the second segment, after welding the second tubular member (12) to the second reinforcing ring (10) at the first welding station (1), the second segment is lifted from the first welding station (1) and the second segment is turned upside down so that the second reinforcing ring (10) faces upward, - After inverting them, the first and second segments are lifted onto the second welding station (1') so that they overlap each other vertically, and with the rollers (5, 6) rotatably supporting the second edge (11B, 12B) associated with the lower segment of the two segments, the second edge (11B, 12B) associated with the upper segment of the two segments is welded to the reinforcing ring (10) of the lower segment of the two segments at the second welding station (1') to form a double segment (12 / 11) with the upper and lower segments, - Maintain the second welding station (15) at the fixed location of the second welding station (1'), and while rotating the double segment (12 / 11) around the vertical central axis, weld the lower side of the two reinforcing rings (10) from above. The method according to claim 3, including the method described in claim 3.

5. - Lifting the double segment (12 / 11) from the second welding station (1') towards the storage station (1''), - To provide the third segment, after welding the third tubular member (13) to the third reinforcing ring (10) at the first welding station (1), the third segment is inverted so that the third reinforcing ring (10) is facing upward, and then the third segment is lifted up toward the second welding station (1'), Next, the double segment (12 / 11) is lifted from the storage station (1'') toward the third reinforcing ring (10) of the second welding station (1'), and the lower second edges (11B, 12B) of the tubular members (11, 12) of the double segment (12 / 11) are welded toward the third reinforcing ring (10) to form a triple segment (12 / 11 / 13) of the first segment, second segment, and third segment. - Lifting the formed triple segment (12 / 11 / 13) from the second welding station (1'), The method according to claim 4, which is dependent on claim 2, including the following:

6. The method according to claim 4, wherein the second welding station (1') includes a support ring (9) or support plate between the rollers (5, 6) and the second edge (11B) of the first tubular member (11), and the method comprises lifting the first segment from the first welding station (1), turning the first segment upside down, and lifting the first segment onto the support ring (9) or support plate of the second welding station (1') before welding the double segment (12 / 11) at the second welding station (1').

7. The method according to claim 3, wherein at least one of the first and second welding stations (1, 1') comprises a first roller (5) that supports a combination of tubular members (11, 12, 13, 14) and a reinforcing ring (10) from below, and a second roller (6) that contacts the combination laterally, the method comprising guiding the combination with the second roller (6) during welding which is performed simultaneously with rotation.

8. Use of the method according to any one of claims 1 to 7 for assembling a buoyancy module for an offshore structure of a tubular floating wind turbine.

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