Floating offshore platform and its manufacture

Abstract

The present invention relates to a method for manufacturing a floating offshore platform using a template, the floating offshore platform comprising a central post, a plurality of peripheral posts circumferentially orbiting around the central post, and outboard floats extending radially from the central post connecting the peripheral posts to the central post. The template comprises an inner outboard float template, an outer outboard float template, a central post template, and a peripheral post template, and at a first position at a first temperature, a first pair pair is formed with the inner outboard float template and the central post template at the first position and under the first temperature, and at a second position at a second temperature, a second pair pair is formed with the outer outboard float template and the peripheral post template at the second position and under the second temperature. The central post, the peripheral posts, and the outboard floats are then formed using the template at different temperatures.

Description

[Technical field]

[0001] 2. Background of the Invention

[0002] The present invention relates to a method for manufacturing a floating offshore platform comprising a central pillar, a number of peripheral pillars extending circumferentially around the central pillar, and outriggers extending radially from the central pillar connecting the peripheral pillars to the central pillar.

[0003] Floating offshore platforms can be used, for example, to carry offshore wind turbines for generating electricity. Wind turbines are getting larger and larger, and economies of scale dictate that gigawatt-scale wind farms will use the largest wind turbines. To carry these very large wind turbines, floating offshore platforms are also getting larger. Summary of the Invention

[0004] Traditionally, floating offshore platforms are made of prefabricated components that are then finally welded at the final assembly site. The welding process requires adjustments to the length of the components, which can lead to eccentricities in the internal load transfer to the structural elements. This process is time-consuming due to the time required for final adjustments and welding, inspection, final repairs, and coating repairs around the welds.

[0005] Alternatively, floating offshore platforms would be made of prefabricated components and bolted together at the final assembly site. This process is similar to the current manufacturing and assembly method for wind turbines, which consist of tower sections, nacelles, and blades, all fitted with flange connections and bolted together at the final assembly site. Due to the geometry of floating offshore platforms, flanges need to be aligned very precisely to connect. The tolerances typically required are on the order of one millimeter, whereas traditional large steel structures are typically built with a tolerance of around five millimeters. Achieving the required high precision is very complex and costly, since the tighter tolerances required can only be achieved at increased cost using high-precision dimensional measuring tools that perform laser-based measurements. Furthermore, thermal expansion or contraction of parts can impair the ability to assemble, unless modifications are made to account for the thermal expansion or contraction estimated in the dimensional survey. This can introduce additional risks that parts will not fit together properly or that internal load transfer will be eccentric.

[0006] Floating offshore platforms are manufactured in large shipyards and then towed to the wind farm site. However, such large shipyards are few and far between and may be located far from the wind farm site. Transporting large floating offshore platforms long distances is very costly and time consuming. The offshore wind industry is increasingly looking for efficient manufacturing as floating offshore platforms get larger. Therefore, it may not be economical to develop very large wind farms using known strategies.

[0007] It is an object of the present invention to provide a method for manufacturing a floating offshore platform that maintains its efficiency as the size of the floating offshore platform increases depending on the size of the wind turbines mounted on it.

[0008] The present invention provides a method of manufacturing a floating offshore platform using a template, the method comprising the steps of: The floating offshore platform comprises a central column, a plurality of peripheral columns circumferentially orbiting around the central column, and outboard floats extending radially from the central column and connecting the peripheral columns to the central column; the central pillar includes a central pillar peripheral wall and an upper central pillar mounting portion and a lower central pillar mounting portion connected to the central pillar peripheral wall at a distance from each other, Each of the peripheral posts comprises a peripheral post circumferential wall and an upper peripheral post attachment portion and a lower peripheral post attachment portion connected to the peripheral post circumferential wall at spaced intervals; each of the outboard floats comprises an outboard float structure connected to an upper inboard outboard float attachment portion aligned with the upper central pole attachment portion, a lower inboard outboard float attachment portion aligned with the lower central pole attachment portion, an upper outer outboard float attachment portion aligned with the upper peripheral pole attachment portion, and a lower outer outboard float attachment portion aligned with the lower peripheral pole attachment portion; the templates include an inner outboard buoy template, an outer outboard buoy template, a central pillar template, and a peripheral pillar template; the inboard outboard buoy template comprises an upper inboard outboard buoy template interface and an inboard outboard template spacer connected to the interface and to the lower inboard outboard buoy template interface; the outer outboard buoy template comprises an outer outboard buoy template spacer connected to an upper outer outboard buoy template interface and a lower outer outboard buoy template interface; the center column template includes an upper center column template boundary surface and a center column template spacer connected to the boundary surface and the lower center column template boundary surface; the peripheral post template comprises a peripheral post template spacer connected to an upper peripheral post template interface and a lower peripheral post template interface; The method includes the following steps: forming a first pair of the inboard outboard float template and the central pole template at a first position and at a first temperature, wherein the upper inboard outboard float template interface is aligned with the upper central pole template interface and the lower inboard outboard float template interface is aligned with the lower central pole template interface; forming a second pair of the outer outboard float template and the peripheral post template at a second position and at a second temperature, the upper outer outboard float template interface being aligned with the upper peripheral post template interface and the lower outer outboard float template interface being aligned with the lower peripheral post template interface; a process step of manufacturing at least one of the outboard floats using the inner outboard float template and the outer outboard float template at a third position and at a third temperature, during which the upper inner outboard float template interface is aligned with the upper inner outboard float attachment portion, the lower inner outboard float template interface is aligned with the lower inner outboard float attachment portion, the upper outer outboard float template interface is aligned with the upper outer outboard float attachment portion, and the lower outer outboard float template interface interface is aligned with the lower outer outboard float attachment portion; a process step of fabricating at least one of the peripheral posts using the peripheral post template at a fourth position and at a fourth temperature, during which the upper peripheral post template interface is aligned with the upper peripheral post attachment portion and the lower peripheral post template interface is aligned with the lower peripheral post attachment portion; fabricating the central post using the central post template at a fifth position and at a fifth temperature, during which the upper central post template interface is aligned with the upper central post attachment portion and the lower central post template interface is aligned with the lower central post attachment portion; and assembling the floating offshore platform at a sixth temperature at a sixth location.

[0009] The method of the invention uses an inboard outboard float template and an outboard outboard float template to make outboard floats, a central pillar template to make central pillars, and a peripheral pillar template to make peripheral pillars. The inboard outboard float template and the central pillar template are pre-mated as a first mated pair at a first position and at a first temperature, and the outboard outboard float template and the peripheral pillar template are pre-mated as a second mated pair at a second position and at a second temperature. After mating, the templates are separated and used to make outboard floats at a third position and at a third temperature, and the central and peripheral pillars at a fourth position and at a fourth temperature, and at a fifth position and at a fifth temperature, respectively.

[0010] In the third, fourth and fifth positions, the outboard floats, the perimeter columns and the central column can be constructed according to the tolerances commonly used in the steel construction industry while using the mating template according to the invention. In the sixth position, the floating offshore platform is assembled at the sixth temperature. In the third position, any thermal expansion or contraction of the material has the same dimensional effect on the outer outboard float template and the inner outboard float template and the components of the outboard floats to be manufactured. In the fourth position, any thermal expansion or contraction of the steel has the same dimensional effect on the perimeter column template and the components of the perimeter column to be manufactured. In the fifth position, any thermal expansion or contraction of the steel has the same dimensional effect on the central column template and the components of the central column to be manufactured. In this way, it is ensured that the outboard floats are fully connected to the central column and the perimeter columns in the sixth position. This allows the central column, the perimeter columns and the outboard floats to be manufactured in separate yards and assembled in yet another yard. The yard can be selected such that the manufacturing is carried out efficiently.

[0011] The selected shipyard may use a variety of dimensional control tools. Templates must be used to ensure that the required tolerance levels are met at the final interface. To achieve tight tolerances, the shipyard may use templates as part of the manufacturing sequence to properly attach and weld the end connections to the columns or outriggers. Alternatively, or in addition, the shipyard may use templates only for the attachment and alignment of subassemblies and remove them especially for final welding. If deformations are expected to occur due to welding, such deformations must be taken into account in the attachment and welding process so that the template still matches the component after welding.

[0012] In one embodiment, the template interface is aligned with and abuts the mounting portion of the floating offshore platform.

[0013] In one embodiment, the template interface is aligned and attached to the mounting portion of the floating offshore platform, thereby ensuring proper location of the mounting portion of the floating offshore platform.

[0014] In one embodiment, the template interface and the mount comprise mount flanges that are bolted together.

[0015] In one embodiment, the template interfaces are aligned with mounting points on the floating offshore platform within a tolerance of less than one millimeter.

[0016] In one embodiment, at least one of the first temperature, the second temperature, the third temperature, the fourth temperature, the fifth temperature, and the sixth temperature is different from the other temperatures.

[0017] In one embodiment, at least one of the first location, the second location, the third location, the fourth location, the fifth location, and the sixth location is located more than 100 kilometers away from the other locations.

[0018] In one embodiment, the floating offshore platform comprises a spanning structural member spanning between each adjacent pair of adjacent perimeter columns, the method comprising and including the step of installing the structural member after attaching the outboard floats between the central and perimeter columns, the structural member being pre-tensioned.

[0019] The various aspects and features described and illustrated in this specification may, to the extent possible, be applied individually. These individual aspects and features, in particular those described in the accompanying dependent claims, may be the subject of divisional patent applications. [Brief description of the drawings]

[0020] The invention will now be explained on the basis of exemplary embodiments shown in the accompanying drawings. FIG. 1 is an isometric view of a floating offshore platform supporting a wind turbine. FIG. 2 is an isometric view showing only the relevant parts of a floating offshore platform to illustrate several steps in the manufacture of the floating offshore platform. 3A and 3B are isometric and top views of two stages in the fabrication of the outboard buoys of the floating offshore platform of FIG. 2 using an outboard buoy template. 4A and 4B are isometric views of two stages of manufacturing a perimeter post for the floating offshore platform of FIG. 2 using a perimeter post template. 5A and 5B are isometric views of two stages of manufacturing the center mast of the floating offshore platform of FIG. 2 using a center mast template. 6A and 6B show a mating pair of central post templates and corresponding mating outboard float templates, and a mating pair of peripheral post templates and corresponding mating outboard float templates, respectively.

[0021] FIG. 1 shows a floating offshore platform 1 supporting a wind turbine 300 in this example to form a floating wind turbine 5. The wind turbine 300 has a vertical tower 301 and a nacelle 302 at the top of the tower 301. The nacelle 302 has an internal generator driven by a wind turbine rotor 303. The wind turbine rotor 303 has a hub 304 connected to a generator and three blades 305 radiating from the hub 304 in this example. The wind turbine 300 can generate more than 1 MW of power, currently reaching about 10 MW to 12 MW. The diameter of the base of the tower 301 may be between 5 meters and 10 meters for a +10 MW wind turbine. The three blades 305 may each be more than 100 meters long. An example is the 12 MW HaliadeX turbine from General Electrics. Other turbine designs such as vertical axis wind turbines can also be supported by the floating offshore platform 1.

[0022] FIG. 2 shows the offshore platform 1 without the wind turbine 300, gangways, handrails and attached utilities, and illustrates several steps in the manufacture of its structural components.

[0023] As shown in Figures 2 and 5B, the offshore platform 1 comprises a central column 10 made of steel. The central column 10 has a vertical cylindrical upper peripheral wall section 11 closed by a top wall 17, which in this embodiment merges downwards through a flared wall section or a conically expanding central peripheral wall section 12 into a vertical cylindrical lower peripheral wall section 13. The bottom of the lower peripheral wall section 13 is closed by a bottom wall 14, which defines an internal chamber 16. The diameter of the upper peripheral wall section 11 of the central column 10 is approximately equal to the bottom diameter of the tower 301, and increases in diameter towards the bottom or keel of the central column 10 through the conically expanding central peripheral wall section 12. The central column 10 may be provided with a footing foundation (not shown) below the base wall section 13, which has a larger diameter (not shown) that provides additional volume. When the footing foundation is filled with air, it helps to support the weight of the wind turbine 300. When the scaffolding base is filled with water it helps to provide stability to the floating wind turbine 5.

[0024] The offshore platform 1 is comprised of three vertical cylindrical stabilizing or perimeter columns 30, in this example made of steel, which are radially arranged at 120 degree intervals around the central column 10. Each of the perimeter columns 30 is comprised of a vertical cylindrical peripheral wall 31 closed at the top by a top wall 32 and defining an internal chamber 34 which is open at the bottom. The perimeter columns 30 are comprised of a skirt 33 which extends horizontally around the lower ends of the cylindrical peripheral walls 31.

[0025] The offshore platform 1 comprises three outboard floats 50 extending radially between the central column 10 and the peripheral columns 30. The outboard floats 50 are made of steel and in this example consist of an upper tubular member 51 and a lower tubular member 52 extending parallel to each other and interconnected by diagonal struts 53. Alternatively, at least one of the upper tubular member 51 and the lower tubular member 52 may be diagonal to the other. Alternatively, the upper tubular member 51 and the lower tubular member 52 are separate pieces not interconnected by struts. As best shown in Figure 3B, the outboard float 50 comprises, at the end of the upper tubular member 51, an upper outer outboard float mounting portion 54 having an upper outer outboard float mounting flange 64, and an upper inner outboard float mounting portion 55 having an upper inner outboard float mounting flange 65, and, at the end of the lower tubular member 52, a lower outer outboard float mounting portion 56 having a lower outer outboard float mounting flange 66, and a lower inner outboard float mounting portion 57 having a lower inner outboard float mounting flange 67.

[0026] As shown in Figures 2 and 5B, the centre mast 10 comprises three upper centre mast attachments 20 and three lower centre mast attachments 25 for the outboard floats 50. The upper centre mast attachments 20 each comprise a tubular section 21 welded to the upper peripheral wall section 11 and a distal upper centre mast attachment flange 22. The lower centre mast attachments 25 each comprise a tubular section 26 welded to the lower peripheral wall section 13 and a distal lower centre mast attachment flange 27. The upper inner outboard float attachment flange 55 is bolted in line with the upper centre mast attachment flange 22 and the lower inner outboard float attachment flange 57 is bolted in line with the lower centre mast attachment flange 27.

[0027] As shown in Figures 2 and 4B, each of the perimeter columns 30 includes an upper perimeter column mounting portion 35 and a lower perimeter column mounting portion 38. The upper perimeter column mounting portion 35 includes a tubular portion 36 welded to the upper portion of the perimeter wall 31 and an upper perimeter column mounting flange 37 distally thereof. The lower perimeter column mounting portion 38 includes a tubular portion 39 welded to the lower portion of the perimeter wall 31 and a lower perimeter column mounting flange 40 distally thereof. The upper outer outboard float mounting flange 54 is bolted in line with the upper perimeter column mounting flange 37 and the lower outer outboard float mounting flange 56 is bolted in line with the lower perimeter column mounting flange 40.

[0028] The offshore platform 1 is composed of three pretensioned slender superstructural members or tendons 60 of equal length interconnecting the upper ends of the perimeter columns 30 and three pretensioned slender substructural members or tendons 65 of equal length interconnecting the lower ends of the perimeter columns 30 at the skirt 33. The tendons 60, 65 are embodied as steel tubes. Due to the pretensioning of the tendons 60, 65 and the resulting compressive forces in the outboard floats 50, the entire offshore platform 1 needs to be constructed with tight tolerances to prevent eccentricity of the internal load transfer.

[0029] The diameter of the base of the central pillar 10 is up to 20 meters. The combined height of the central pillar 10 and the peripheral pillars 30 is typically 20-30 meters, in this example approximately 24 meters. The diameter of the peripheral pillars 30 is 6-12 meters. The tendons 60, 65 each have a length of 60-90 meters, in this example approximately 73 meters.

[0030] 3A and 3B show two stages in the fabrication of the outboard buoys 50 of the offshore platform 1 using the outer outboard buoy template 120 and the inner outboard buoy template 140. FIG.

[0031] The outer outboard float template 120 is comprised of a steel spacer tube 121, an upper outer outboard float template interface 122 and a lower outer outboard float template interface 125. The upper outer outboard float template interface 122 is comprised of a tubular section 123 welded to the upper side of the spacer tube 121 and a distal upper outer outboard float template mounting flange 124. The lower outer outboard float template interface 125 is comprised of a tubular section 126 welded to the underside of the spacer tube 121 and a lower outer outboard float template mounting flange 127. The outer outboard buoy template 120 is comprised of a number of legs 130 on a spacer tube 121 and tubular sections 123, 126 which hold the upper outer outboard buoy template mounting flange 124 and the lower outer outboard buoy template mounting flange 127 at a well-defined position and height.

[0032] The inboard outboard buoy template 140 is comprised of a spacer tube 141, an upper inboard outboard buoy template interface 142, and a lower inboard outboard buoy template interface 145, which are made of steel. The upper inboard outboard buoy template interface 142 is comprised of a tubular section 143 welded to the upper side of the spacer tube 141 and a distal upper inboard outboard buoy template mounting flange 144. The lower inboard outboard buoy template interface 145 is comprised of a tubular section 146 welded to the underside of the spacer tube 141 and a lower inboard outboard buoy template mounting flange 147. The inboard outboard buoy template 140 is comprised of a number of legs 150 on the spacer tube 141 and the tubular sections 143, 146 that hold the upper inboard outboard buoy template mounting flange 144 and the lower inboard outboard buoy template mounting flange 147 at a well-defined position and height.

[0033] During manufacture of the outboard float 50, the upper outer outboard float mounting flange 64 is aligned and temporarily attached or bolted to the upper outer outboard float template mounting flange 124, the lower outer outboard float mounting flange 66 is aligned and temporarily attached or bolted to the lower outer outboard float template mounting flange 127, the upper inner outboard float mounting flange 65 is aligned and temporarily attached or bolted to the upper inner outboard float template mounting flange 144, and the lower inner outboard float mounting flange 67 is aligned and temporarily attached or bolted to the lower inner outboard float template mounting flange 147, all within tolerances of less than one millimeter. The outer outboard buoy template 120 and the inner outboard buoy template 140 are placed on each other according to the exact final positions of the outboard buoy attachment flanges 64, 65, 66, 67, and the upper tubular member 51, the lower tubular member 52 and the diagonal strut 53 are placed therebetween while being supported at an exact height with a tolerance of less than one millimeter by a number of tubular supports 131. Finally, the outboard buoy attachment flanges 64, 65, 66, 67 are welded to the ends of the tubular members 51, 52.

[0034] 4A and 4B show two stages of manufacturing the perimeter column 30 of the offshore platform 1 of FIG. 2 using a perimeter column template 160. The perimeter column template 160 is comprised of a spacer tube 161, an upper perimeter column template interface 162, and a lower perimeter column template interface 165. The upper perimeter column template interface 162 is comprised of a tubular section 163 welded to the upper part of the spacer tube 161 and a distal upper perimeter column template mounting flange 164. The lower perimeter column template interface 165 is comprised of a tubular section 166 welded to the lower part of the spacer tube 161 and a distal upper perimeter column template mounting flange 167. The perimeter column template 160 includes upper supports 170 and upper mounting portions 171, middle supports 178 and middle mounting portions 179, and lower supports 175 and lower mounting portions 176 at its ends.

[0035] During manufacture of the perimeter column 30, the skirt 33 is welded to the lower end of the perimeter wall 31. The upper perimeter column mounting flange 37 is aligned with the upper perimeter column template mounting flange 164 and temporarily attached or bolted, and the lower perimeter column mounting flange 40 is aligned with the lower perimeter column template mounting flange 167 and temporarily attached or bolted, and the lower perimeter column mounting flange 40 is aligned with the lower perimeter column template mounting flange 167 and temporarily attached or bolted, all within a tolerance of less than one millimeter. The perimeter column template 160 is positioned relative to the perimeter wall 31 and temporarily attached to the perimeter wall 31 by the upper mounting portion 171, the middle mounting portion 179 and the lower mounting portion 176, and the upper mounting portion 171 is coupled to the projection 41 on the perimeter wall 33 and the middle mounting portion 179 and the lower mounting portion 176 are bolted to the perimeter wall 33 within a tolerance of less than one millimeter. The tubular sections 36, 39 are positioned and their ends are welded to the upper circumferential column mounting flange 37 and the peripheral wall 33, and to the lower circumferential column mounting flange 40 and the peripheral wall 33, respectively.

[0036] Figures 5A and 5B show two stages of manufacturing the central column 10 of the offshore platform 1 of Figure 2 using a central column template 180. The central column template 180 includes a spacer tube 181, an upper central column template interface 182, and a lower central column template interface 185. The upper central column template interface 182 includes a tubular section 183 welded to the upper part of the spacer tube 181 and a distal upper central column template mounting flange 184. The lower central column template interface 185 includes a tubular section 186 welded to the lower part of the spacer tube 181 and a distal lower central column template mounting flange 187. The central column template 180 includes upper supports 190 and upper mounting portions 191, middle supports 198 and middle mounting portions 199, and lower supports 195 and lower mounting portions 196 at its ends.

[0037] During manufacture of the centre column 10, for each location of the three outboard floats 50 where the upper perimeter wall section portion 11 and the lower perimeter wall section portion 13 are welded to the intermediate perimeter wall section portion 12, the upper centre column mounting flange 22 is aligned with the upper centre column template mounting flange 184 and temporarily attached or bolted, and the lower centre column mounting flange 27 is aligned with the lower centre column template mounting flange 187 and temporarily attached or bolted, all within a tolerance of less than one millimeter. The centre column template 180 is positioned relative to the upper perimeter wall section 11 and the lower perimeter wall section 13 and temporarily attached to the upper perimeter wall section 11 and the lower perimeter wall section 13 by the upper mounting portion 191, the intermediate mounting portion 199 and the lower mounting portion 196, with the upper mounting portion 191 bonded to the respective lug 42 on the upper wall 17 and the intermediate mounting portion 199 and the lower mounting portion 196 bolted to the upper perimeter wall section 11 and the lower perimeter wall section 13 with a tolerance of less than one millimeter. The tubular sections 21, 26 are positioned and their ends are welded to the upper center column mounting flange 22 and the upper peripheral wall section 11, and to the lower center column mounting flange 27 and the lower peripheral wall section 11, respectively.

[0038] 6A shows a center post template 180 precisely mated with the inboard outboard buoy template 140 to form a first mating pair. The upper center post template mounting flange 184 is aligned with the upper inboard outboard buoy template mounting flange 144 and the lower center post template mounting flange 187 is aligned with the lower inboard outboard buoy template mounting flange 147, with the circumferentially abutting surfaces offset by a first offset D1 equal to the difference in length of the upper tubular member 51 and the lower tubular member 52 resulting from the conically expanding central peripheral wall section 12. A first distance H1 between the centerlines of the upper center post template mounting flange 184 and the lower center post template mounting flange 187 is equal to a second distance H2 between the centerlines of the upper inboard outboard buoy template mounting flange 144 and the lower inboard outboard buoy template mounting flange 147, all within a tolerance of less than 1 millimeter.

[0039] During manufacture of the center pillar template 180 and the inboard outboard float template 140, the upper center pillar template mounting flange 184 and the upper inboard outboard float template mounting flange 144 are aligned to each other and temporarily bolted or attached, temporary bolted or attached, and the lower center pillar template mounting flange 187 and the lower inboard outboard float template mounting flange 147 are aligned to each other and temporarily bolted or attached. The centerlines are positioned at equal first and second distances H1 and H2, the mating surfaces are parallel to each other and positioned at a first offset D1, and then the spacer tubes 141, 181 and tubular sections 143, 146, 183, 186 are positioned within an allowable error tolerance of less than one millimeter, and these parts are welded together.

[0040] 6B shows the perimeter post template 160 precisely mating with the outer outboard float template 120 to form a second mating pair. The upper outer outboard float template mounting flange 124 is aligned with the upper perimeter post template mounting flange 164 and the lower outer outboard float template mounting flange 127 is aligned with the lower perimeter post template mounting flange 167, with the circumferential abutting surfaces being in the same vertical plane V. A third distance H3 between the centerlines of the upper and lower outer outboard float template mounting flanges 124 and 127 is equal to a fourth distance H4 between the centerlines of the upper and lower perimeter post template mounting flanges 164 and 167 within an allowable error tolerance of less than 1 millimeter.

[0041] During manufacture of the perimeter column template 160 and the outer outboard float template 120, the upper outer outboard float template mounting flange 124 and the upper perimeter column template mounting flange 164 are aligned, temporarily bolted or attached, and temporary bolted or attached, and the lower outer outboard float template mounting flange 127 and the lower perimeter column template mounting flange 167 are aligned, temporarily bolted or attached, and temporary bolted or attached. The centerlines are positioned at equal third distances H3 and fourth distances H4, and the mating surfaces are positioned in the same vertical plane V, after which the spacer tubes 121, 161 and tubular sections 123, 126, 163, 166 are positioned within a tolerance of less than one millimeter, and these parts are welded together.

[0042] According to the present invention, at the first position L1 at the first temperature, the central pillar template 180 and the inner outboard float template 140 are manufactured as a first mating first pair, as shown in Figure 6A, before all the parts adopt the first temperature. At the second position L2 at the second temperature, the peripheral pillar template 160 and the outer outboard float template 120 are manufactured as a second mating second pair, as shown in Figure 6B, before all the parts adopt the second temperature. At the third position L3 at the third temperature, the outboard float 50 is manufactured by the outer outboard float template 120 and the inner outboard float template 140, before all the outboard float 50, the outer outboard float template 120 and the inner outboard float template 140 adopt the third temperature, as shown in Figures 3A and 3B. At the fourth location L4 at the fourth temperature, the peripheral columns 30 are fabricated by the peripheral column template 160, and each peripheral column 30 and the peripheral column template 160 have previously adopted the third temperature. At the fifth location L5 at the fifth temperature, the central columns 10 are fabricated by the central column template 180, and all the central columns 10 and the central column template 180 have previously adopted the fifth temperature. At the sixth location L6 at the sixth temperature, the offshore platform 1 is assembled, and all the components have previously adopted the sixth temperature. The third location L3, the fourth location L4, the fifth location L5 and the sixth location L6 may be located away from the first location L1 and the second location L2. The third temperature, the fourth temperature, the fifth temperature and the sixth temperature may be different from each other and from the first temperature and the second temperature.

[0043] In the third position L3, the thermal expansion or contraction of the steel has the same dimensional effect on the outer outboard float template 120 and the inner outboard float template 140 and the components of the outboard float 50 to be manufactured. In the fourth position L4, the thermal expansion or contraction of the steel has the same dimensional effect on the peripheral column template 160 and the components of the peripheral columns 30 to be manufactured. In the fifth position L5, the thermal expansion or contraction of the steel has the same dimensional effect on the central column template 180 and the components of the central column 10 to be manufactured. According to the invention, the templates 120, 140, 160, 180 are paired at a first temperature in the first position L1 and at a second temperature in the second position L2, respectively, which ensures that the outboard float 50 is fully connected to the central column 10 and the peripheral columns 30 in the sixth position L6.

[0044] In practice, the first location L1 and the second location L2 are in the same construction yard, but the third location L3, the fourth location L4, the fifth location L5 and the sixth location L6 are construction yards in different countries, at least one of which is more than 100 kilometers away from the other construction yards. The construction yards are selected based on production price and capacity, for example, the sixth location L6 is an assembly yard close to where the offshore location of the floating wind turbine 5 will be transported offshore and anchored.

[0045] It should be understood that the above description is included to illustrate the operation of the preferred embodiment and is not intended to limit the scope of the invention. Many variations within the scope of the invention will be apparent to those skilled in the art from the above description.

Claims

1. 1. A method of manufacturing a floating offshore platform using a template, comprising: The floating offshore platform comprises a central post, a plurality of peripheral posts circumferentially disposed about the central post, and outboard floats extending radially from the central post connecting the peripheral posts to the central post; the central pillar includes a central pillar peripheral wall, and an upper central pillar mounting portion and a lower central pillar mounting portion connected to the central pillar peripheral wall with a space between them; Each of the peripheral posts comprises a peripheral post circumferential wall and an upper peripheral post attachment portion and a lower peripheral post attachment portion connected to the peripheral post circumferential wall in spaced relation to each other; Each of the outboard floats comprises an outboard float structure connected to an upper inner outboard float attachment part aligned with the upper central pole attachment part, a lower inner outboard float attachment part aligned with the lower central pole attachment part, an upper outer outboard float attachment part aligned with the upper peripheral pole attachment part, and a lower outer outboard float attachment part aligned with the lower peripheral pole attachment part; The templates include an inner outboard buoy template, an outer outboard buoy template, a central pillar template, and a peripheral pillar template; the inner outboard buoy template comprises an inner outboard buoy template spacer connected to an upper inner outboard buoy template interface surface and a lower inner outboard buoy template interface surface; the outer outboard buoy template comprises an outer outboard buoy template spacer connected to an upper outer outboard buoy template interface surface and a lower outer outboard buoy template interface surface; the central pillar template includes a central pillar template spacer connected to an upper central pillar template boundary surface and a lower central pillar template boundary surface; the peripheral post template comprises a peripheral post template spacer connected to an upper peripheral post template interface and a lower peripheral post template interface; forming a first pair of the inboard outboard float template and the central pillar template at a first position and at a first temperature, wherein the upper inboard outboard float template interface is aligned with the upper central pillar template interface and the lower inboard outboard float template interface is aligned with the lower central pillar template interface; forming a second pair of the outer outboard float template and the peripheral post template at a second position and at a second temperature, the upper outer outboard float template interface surface being aligned with the upper peripheral post template interface surface and the lower outer outboard float template interface surface being aligned with the lower peripheral post template interface surface; manufacturing at least one of the outboard floats using the inboard outboard float template and the outboard outboard float template at a third position and at a third temperature, during which the upper inboard outboard float template interface is aligned with the upper inboard outboard float attachment portion, the lower inboard outboard float template interface is aligned with the lower inboard outboard float attachment portion, the upper outboard outboard float template interface is aligned with the upper outboard outboard float attachment portion, and the lower outboard outboard float template interface is aligned with the lower outboard outboard float attachment portion; fabricating at least one of the peripheral posts using the peripheral post template at a fourth location and at a fourth temperature, during which the upper peripheral post template interface is aligned with the upper peripheral post attachment portion and the lower peripheral post template interface is aligned with the lower peripheral post attachment portion; fabricating the central pillar using the central pillar template at a fifth position and at a fifth temperature, during which the upper central pillar template interface is aligned with the upper central pillar attachment portion and the lower central pillar template interface is aligned with the lower central pillar attachment portion; and assembling the floating offshore platform at a sixth position and at a sixth temperature.

2. The method of claim 1 , wherein the template interface is aligned with and abuts the mounting portion of the floating offshore platform.

3. The method of claim 1 or claim 2, wherein the template interface is aligned with and attached to the mounting portion of the floating offshore platform.

4. The method of claim 3 , wherein the template interface and the mounting portion comprise mounting flanges that are bolted together.

5. The method of claim 1 , wherein the template interface is aligned with the mounting portion of the floating offshore platform to within a tolerance of less than one millimeter.

6. 8. The method of claim 1, wherein at least one of the first temperature, the second temperature, the third temperature, the fourth temperature, the fifth temperature, and the sixth temperature is different from the other temperatures.

7. 7. The method of claim 1, wherein at least one of the first location, the second location, the third location, the fourth location, the fifth location, and the sixth location is located more than 100 kilometers away from the other locations.

8. the floating offshore platform comprising a structural member spanning between each adjacent pair of perimeter columns; installing the structural members after attaching the outboard floats between the central pole and the peripheral poles; The method of any of claims 1 to 7, wherein the structural member is pretensioned.

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