JP7600085B2 - Airtight construction - Google Patents

Description

The present invention relates to airtight structures for offshore structures.

A known example of a conventional offshore structure is the offshore wind turbine described in Patent Document 1 below. This type of wind turbine has a structure in which the wind turbine main body, including the nacelle and blades, is installed at the top end of a leg that extends from the seabed into the sky. A management facility for managing the operation of the wind turbine is provided in the hollow part of the cylindrical leg. Meanwhile, below the management facility, seawater has entered the hollow part of the leg up to the same height as the outside seawater level.

Patent No. 5993756

In the legs of such wind power generators, in order to prevent salt damage to the management equipment, it is possible to install an airtight structure that airtightly seals the area where seawater has infiltrated from the area of the management equipment. The airtight structure has, for example, a horizontal plate that divides the inside of the leg into upper and lower parts. If gas is generated below the horizontal plate, it is possible that the horizontal plate will block the rise of this gas and cause it to float and accumulate near the horizontal plate. In this case, a gas vent hole is provided in the horizontal plate, and the gas is vented above the horizontal plate through the gas vent hole, and ultimately disposed of by being discharged to the outside of the leg. On the other hand, it is also necessary to ensure the strength of the horizontal plate by a reinforcing structure, such as by installing a beam on the underside of the horizontal plate. In that case, there is a risk that this reinforcing structure will hinder the smooth movement of gas to the gas vent hole.

The present invention aims to smoothly exhaust gas generated in the area in contact with the seawater surface in an airtight structure that airtightly seals the area in contact with the seawater surface within the leg of an offshore structure from the area above.

The airtight structure of the present invention is an airtight structure that is provided in the internal space of the cylindrical legs of an offshore structure and airtightly seals the seawater environmental space that contacts the seawater level of the seawater that has entered the internal space from the normal environmental space above. It comprises a horizontal plate member that is provided horizontally above the seawater level and divides the internal space into upper and lower parts, a gas vent hole provided on the underside of the horizontal plate member for passing gas in the seawater environmental space and sending it upward, and a reinforcing section that has multiple beam members joined to the underside of the horizontal plate member and reinforces the horizontal plate member, and the reinforcing section is provided across the beam members and has a gas passageway that allows gas that floats and accumulates on the underside of the horizontal plate member to pass horizontally along the underside.

The beam may have a hollow structure, and the reinforcing portion may further include a lid that airtightly seals the hollow portion of the beam from the seawater environment space. The airtight structure of the present invention may be provided above an electrochemical protection device having an anticorrosion electrode immersed in seawater in the internal space. The airtight structure of the present invention may further include a ventilation pipe that passes through the normal environment space, connecting the gas vent hole and a gas exhaust port that is provided on the outer surface of the leg above the horizontal plate member and for exhausting gas to the outside of the leg.

According to the present invention, in an airtight structure in which the area in contact with the seawater surface within the leg of an offshore structure is airtightly sealed from the area above, gas generated in the area in contact with the seawater surface can be smoothly discharged.

1 is a front view of a wind power generator to which the airtight structure of the present embodiment is applied. FIG. 2 is an enlarged perspective view showing the vicinity of the platform of the wind power generator. FIG. 2 is a perspective view showing a part of a leg of the wind power generator, with a part cut away. FIG. 2A is a perspective view showing the airtight platform as viewed from below, and FIG. 2B is a bottom view of the airtight platform. 1A is a perspective view of a beam material, FIG. 1B is an enlarged side view showing the vicinity of the gas passage, and FIG. 1C is a perspective view thereof. 1A is an enlarged side view showing the vicinity of a gas passage according to a modified example, and FIG. 1B is an exploded perspective view of a beam material in which the gas passage is formed.

Below, an embodiment of the airtight structure according to the present invention will be described in detail with reference to the drawings. In the following description, identical or corresponding elements are given the same reference numerals in the drawings, and duplicated descriptions will be omitted as appropriate. In addition, the drawings may be simplified or exaggerated for ease of understanding, and the dimensional ratios, etc. are not limited to those shown in the drawings.

Figure 1 is a front view showing a wind power generator 1 as an example of an offshore structure to which the airtight structure of this embodiment is applied. As shown in the figure, the wind power generator 1 is installed, for example, on the seabed B, and generates offshore wind power. However, the wind power generator 1 is not limited to being installed on the ocean, and may be installed, for example, in a lake or river. The wind power generator 1 includes legs 41 that extend vertically from the seabed B and protrude above the seawater surface, and a generator body 42 attached to the upper end of the legs 41.

The generator body 42 includes a nacelle 5 and blades 6 attached to the nacelle 5. The nacelle 5 contains a generator, a speed increaser, and the like, and for example, a rotor shaft protrudes from the speed increaser to the outside of the nacelle 5. The blades 6 are fixed to the rotor shaft of the nacelle 5. The wind power generator 1 includes, for example, three blades 6. When the blades 6 rotate in response to the wind, this rotation is increased to a certain rotation speed by an amplifier inside the nacelle 5, and this rotational motion is converted into electricity by the generator inside the nacelle 5. For example, the nacelle 5 includes a wind vane and anemometer, and efficient power generation is achieved by controlling the orientation of the rotor and the angle of the blades 6 in response to the wind speed and direction.

The leg 41 comprises a foundation 2, which is a monopile driven into the seabed B, a transition piece 3 connected above the foundation 2, and a tower 4 connected further above the transition piece 3. The main bodies of the foundation 2, transition piece 3, and tower 4 have a roughly circular cross section and are arranged vertically coaxially with each other. Note that instead of a monopile foundation type, the foundation 2 may comprise a tripile-type offshore wind power foundation or a jacket-type offshore wind power foundation, and the type of foundation is not particularly limited.

The upper end of the foundation 2 is located below sea level and has a tapered shape. The lower end of the transition piece 3 has a conical inner surface that corresponds to the tapered shape of the upper end of the foundation 2, and the transition piece 3 is installed on the foundation 2 so that the lower end is placed over the upper end of the foundation 2. During construction, the verticality of the transition piece 3 is adjusted on the foundation 2, and grout is filled between the lower end of the transition piece 3 and the upper end of the foundation 2. The foundation 2 and the transition piece 3 are joined (grouted) via this grout, ensuring the verticality of the transition piece 3 and therefore the verticality of the wind turbine 1. The tower 4 is, for example, a vertical column made of concrete or steel, and is bolted to the upper end of the transition piece 3.

2 is an enlarged perspective view of the vicinity of the bolted joint between the transition piece 3 and the tower 4. As shown in FIG. 2, inside the transition piece 3, a multi-layered internal platform 9 for operating and managing the wind power generator 1 is provided. Between the internal platforms 9, workers can move via ladders or the like. Furthermore, at the upper end of the transition piece 3, an external platform 10 is provided that extends horizontally outward from the outer circumferential surface 3a. In addition, at the lower end of the tower 4 that is bolted to the transition piece 3, an entrance/exit 11 for entering and exiting the inside of the tower 4 is provided. A worker who operates and manages the wind power generator 1 moves to the external platform 10 via a ladder from a ship moored at the landing 51 (FIG. 1) near the sea surface. The worker then opens the door of the entrance/exit 11 to enter the inside of the tower 4, and can further access the internal platform 9 via an internal ladder or the like. The external platform 10 is used not only as an access route for workers as described above, but also for carrying in and out materials and temporarily storing them, and for example, a davit crane (not shown) is installed on the external platform 10.

As shown in FIG. 1, the cylindrical wall of the foundation 2 is provided with a cable hole 45 at a height close to the seabed B for drawing the cable on the seabed B into the internal space 43 of the leg 41, and a communication hole 47 is provided above the cable hole 45 for allowing seawater to enter and exit the internal space 43. Therefore, seawater enters the internal space 43 of the leg 41 through the cable hole 45 and the communication hole 47, and a seawater level W1 (FIG. 3) exists in the internal space 43 at the same height as the external seawater level W. All of the multiple internal platforms 9 (FIG. 2) as described above are located at a position higher than the above-mentioned seawater level W1. Note that "seawater level W" here means the mean sea level.

Figure 3 is a perspective view showing a part of the leg 41 with a part cut away. The multiple internal platforms 9 include a lower platform 53 and an airtight platform 55. The lower platform 53 is the internal platform 9 located at the lowest level among the multiple internal platforms 9, and the airtight platform 55 is the internal platform 9 located at the second level from the bottom. Note that the internal platform 9 above the airtight platform 55 includes a cable termination platform where electrical cables inside the leg 41 are processed, but illustrations and detailed descriptions of these are omitted.

The lower platform 53 is a platform for performing the work of installing the transition piece 3 on the foundation 2 while adjusting its verticality. For example, a plurality of height adjustment devices 53a are arranged in a circumferential direction on the outer peripheral edge of the lower platform 53. The height adjustment devices 53a are fixed to the transition piece 3, and adjust the height of each position of the transition piece 3 using a jack that receives a reaction force from the upper end surface of the foundation 2. After the verticality of the transition piece 3 is adjusted using these plurality of height adjustment devices 53a, grout is filled between the lower end of the transition piece 3 and the upper end of the foundation 2. In the internal space 43, the aforementioned seawater level W1 is present below the lower platform 53.

As mentioned above, seawater has entered the internal space 43, and below the seawater level W1, the inner wall surface 2b of the foundation 2 is in contact with seawater. Because the foundation 2 is constructed of a monopile made of circular steel pipes, it is necessary to prevent corrosion of the inner wall surface 2b of the foundation 2 due to seawater. For this reason, the lower platform 53 is provided with an electrochemical protection system 57 for protecting the inner wall surface 2b from corrosion. The electrochemical protection system 57 is equipped with a number of anticorrosion electrodes 59 suspended from the lower platform 53. As the anticorrosion electrodes 59, for example, platinum-plated electrodes or metal oxide-coated electrodes are used.

In the center of the lower platform 53 in a plan view, a circular opening 53b is provided for inserting cables. Each anticorrosion electrode 59 hangs down vertically from the lower platform 53 through the opening 53b under its own weight. The lower ends of the anticorrosion electrodes 59 reach below the seawater level W1 and are immersed in seawater. The lengths of the multiple anticorrosion electrodes 59 are adjusted so that their lower ends are located at different heights. Furthermore, the cathodic protection equipment 57 has a power supply device 58 that electrically connects the anticorrosion electrodes 59 and the inner wall surface 2b of the foundation 2 on the lower platform 53 and generates a potential difference between them. This forms a so-called external power supply type cathodic protection circuit, and current flows between the anticorrosion electrodes 59 and the inner wall surface 2b of the foundation 2 through seawater, suppressing corrosion of the inner wall surface 2b.

In this type of cathodic protection equipment 57, chlorine gas and hydrogen gas are generated from the anticorrosion electrode 59 and the inner wall surface 2b. Of these, chlorine gas is easily dissolved in water and therefore dissolves in seawater, or is heavier than air and therefore remains near the seawater level W1. On the other hand, hydrogen gas is lighter than air and therefore rises from the seawater level W1, passes through the lower platform 53, and continues to rise toward the airtight platform 55. The treatment of this hydrogen gas will be described later.

In addition, because seawater has entered the internal space 43 as described above, there is a problem in that even in the space above the seawater level W1 within the internal space 43, corrosion of metals and the like is likely to occur due to salt damage. Therefore, within the internal space 43, the space in contact with the seawater level W1 is airtight sealed from the space above the airtight platform 55 by the airtight platform 55. Hereinafter, the space within the internal space 43 that is below the airtight platform 55 and in contact with the seawater level W1 will be referred to as the "seawater environment space 43B," and the space above the airtight platform 55 will be referred to as the "normal environment space 43A."

Figure 4(a) is a perspective view showing the airtight platform 55 as viewed from below, and Figure 4(b) is a bottom view of the airtight platform 55. As shown in Figures 3 and 4, the airtight platform 55 has a circular flat horizontal plate 61 that divides the internal space 43 into a seawater environment space 43B and a normal environment space 43A in two parts, one above the other. The peripheral portion of the horizontal plate 61 is joined to the inner wall surface 3b of the transition piece 3 so that there is no gap. In this way, the horizontal plate 61 that crosses the cross section of the internal space 43 airtightly divides the seawater environment space 43B and the normal environment space 43A, suppressing salt damage in the normal environment space 43A.

As shown in FIG. 3, the airtight platform 55 has cable holes 62a for passing cables and opening/closing hatches 62b for workers to pass through, which are holes that penetrate the horizontal plate 61. However, these holes are airtight and do not impair the airtightness of the horizontal plate 61. In FIG. 4, the cable holes 62a and opening/closing hatches 62b are omitted to avoid complicating the illustration.

The lower surface 61b of the horizontal plate 61 is provided with a reinforcing portion 63 that reinforces the horizontal plate 61. The reinforcing portion 63 has a plurality of beams 65 arranged in a grid pattern and welded to the lower surface 61b of the horizontal plate 61. The beams 65 are made of steel material with a U-shaped cross section, and may be manufactured by dividing a square steel pipe into two as shown in FIG. 5(a). The portions of the airtight platform 55 that contact the seawater environment space 43B (the lower surface 61b of the horizontal plate, the surfaces of the beams 65, etc.) may be coated with an anticorrosive coating or the like.

The lower surface 61b of the horizontal plate 61 has a gas vent hole 67 near the inner wall surface 3b. A gas exhaust port 69 penetrating the outer wall of the transition piece 3 is formed near the gas vent hole 67 at a position above the horizontal plate 61. A ventilation pipe 68 is provided to connect the gas vent hole 67 and the gas exhaust port 69. The ventilation pipe 68 extends in an L-shape through the normal environment space 43A. The seawater environment space 43B is connected at its upper end to the outside of the leg 41 through the ventilation pipe 68. According to this structure, the rise of hydrogen gas generated in the cathodic protection equipment 57 is blocked by the horizontal plate 61 as described above, and the hydrogen gas floats and accumulates below the lower surface 61b, and then the hydrogen gas passes through the gas vent hole 67 and the ventilation pipe 68, and is discharged to the outside of the leg 41 through the gas exhaust port 69.

Here, there is a risk that the unevenness of the reinforcing portion 63 provided on the lower surface 61b of the horizontal plate 61 may hinder the smooth discharge of the hydrogen gas. That is, for example, if the beam material 65 of the reinforcing portion 63 had a complete lattice structure, some of the hydrogen gas would accumulate in a rectangular closed area completely surrounded on all sides by the beam material 65 in a plan view, and this hydrogen gas would not move smoothly to the gas vent hole 67. Therefore, the reinforcing portion 63 in this embodiment is configured so that such a closed area is not formed.

Specifically, as shown in FIG. 4, gas passages 71 are formed in the reinforcing portion 63 at necessary locations. As shown in FIG. 4(b), in the example of the arrangement of the beams 65 of the reinforcing portion 63, the two central regions 73 can be closed regions completely surrounded by the four beams 65. Therefore, a part of the beam 65A, which is one of the four beams 65, is cut out to form a gas passage 71 that crosses the beam 65A. At the location where the gas passage 71 is provided, the lower surface 61b of the horizontal plate 61 is exposed. With this configuration, hydrogen gas that floats and accumulates in the region 73 moves horizontally along the lower surface 61b to the adjacent region while passing through the gas passage 71. In other words, the gas passage 71 has the function of allowing gas that floats and accumulates on the lower surface 61b of the horizontal plate 61 to pass horizontally along the lower surface 61b.

5(b) is an enlarged side view of the gas passage 71 and FIG. 5(c) is a perspective view thereof. As shown in the figure, the gas passage 71 is formed by cutting and removing a portion of the beam 65A in the longitudinal direction. In this case, the cut end surface of the beam 65A at the gas passage 71 may be inclined with respect to the extension direction of the beam 65. In addition, a lid material 75 is provided on the cut end surface of the beam 65A to airtightly seal the hollow portion of the beam 65A from the seawater environment space 43B. The lid material 75 is, for example, a small rectangular steel plate piece, and is welded to the cut end surface and the lower surface 61b of the beam 65. The presence of such a lid material 75 makes it possible to omit anticorrosive coating or the like applied to the inside of the beam 65A.

Furthermore, as shown in FIG. 4(b), in the reinforcement portion 63, the beam 65 does not reach the surrounding wall surface (the inner wall surface 3b of the transition piece 3). Therefore, each gap between the outer peripheral end of the beam 65 and the inner wall surface 3b also functions as a gas passage 77. This gas passage 77 is also provided so as to cross the beam 65, and has the function of allowing hydrogen gas floating and accumulating on the lower surface 61b of the horizontal plate material 61 to pass horizontally along the lower surface 61b. In addition, the cut end surface of the beam 65 in this gas passage 77 is also provided with the above-mentioned lid material 75, so that the hollow portion of the beam 65A is airtightly sealed from the seawater environment space 43B.

In the reinforcement portion 63, the gas passages 71, 77 as described above are formed in necessary locations, so that, for example, in a plan view, there is no closed area that is completely surrounded on all four sides by the beam material 65 or the inner wall surface 3b. In other words, the gas passages 71, 77 continuously connect each area on the lower surface 61b side, and hydrogen gas in each area can smoothly move through the gas passages 71, 77 along the lower surface 61b to the gas vent hole 67. As a result, hydrogen gas that gathers near 61b of the horizontal plate material 61 is smoothly discharged to the outside of the leg portion 41 through the gas vent hole 67, the ventilation pipe 68, and the gas exhaust port 69.

In place of the gas passage 71, a gas passage 79 as shown in FIG. 6(a) may be provided. The gas passage 79 is formed by cutting out the upper edge of the beam 65A that contacts the lower surface 61b of the horizontal plate 61 in a semicircular shape. As shown in FIG. 6(b), semicircular cutouts 81, 81 are provided on the upper edge of the opposing vertical plate of the beam 65A, and a semicylindrical lid 83 is welded to bridge the cutouts 81, 81. The gas passage 79 is provided across the beam 65A, like the gas passage 71, and has the function of allowing gas floating and accumulating on the lower surface 61b of the horizontal plate 61 to pass horizontally along the lower surface 61b. In addition, the presence of the lid 83 hermetically seals the hollow portion of the beam 65A from the seawater environment space 43B, and anticorrosive coating or the like applied to the inside of the beam 65A can be omitted.

The present invention can be implemented in various forms, including the above-mentioned embodiment, with various modifications and improvements based on the knowledge of those skilled in the art. It is also possible to construct modified examples by utilizing the technical matters described in the above-mentioned embodiment. The configurations of each embodiment may be used in appropriate combination. For example, in the above-mentioned embodiment, the beam 65 of the reinforcing portion 63 has a U-shaped cross section and a hollow structure, but instead, a solid beam such as an H-shaped steel may be used for the reinforcing portion 63. The arrangement of the beam 65 is not limited to that shown in FIG. 4, and may be changed as appropriate. Even in this case, the gas passages 71, 77, and 79 may be formed at necessary locations so that there is no closed area completely surrounded on all sides by the beam 65 or the inner wall surface 3b in a plan view. In the above-mentioned embodiment, an example in which the airtight structure of the present invention is applied to the airtight platform 55 in the leg 41 of the offshore wind power generator 1 has been described, but the present invention can also be applied to other offshore structures.

1...offshore wind turbine (offshore structure), 41...legs, 43...internal space, 43B...seawater environment space, 43A...normal environment space, 55...airtight platform, 57...electrochemical protection equipment, 59...corrosion protection electrode, 61...horizontal plate material, 61b...underside, 63...reinforcement, 65, 65A...beam material, 67...gas vent hole, 69...gas exhaust port, 68...ventilation pipe, 71, 77, 79...gas passage, 75, 83...cover material, W1...seawater surface.

Claims (4)

An airtight structure that is provided in an internal space of a cylindrical leg of an offshore structure and airtightly seals a seawater environment space in contact with the seawater surface of the seawater that has entered the internal space from a normal environment space above,
A horizontal plate member that is provided horizontally above the sea level and divides the internal space into upper and lower parts;
A gas vent hole provided on the lower surface of the horizontal plate for passing gas in the seawater environment space and sending it upward;
a reinforcing portion having a plurality of beam members joined to the lower surface of the horizontal plate member and reinforcing the horizontal plate member;
The reinforcing portion is
An airtight structure having a gas passageway that is arranged across the beam material and allows gas that floats and accumulates on the underside of the horizontal plate material to pass horizontally along the underside. The airtight structure according to claim 1, wherein the beam has a hollow structure, and the reinforcing portion further includes a lid that airtightly seals the hollow portion of the beam from the seawater environment space. The airtight structure according to claim 1 or 2, which is provided above an electric protection device having an anticorrosion electrode immersed in seawater in the internal space. The airtight structure according to any one of claims 1 to 3 further comprises a ventilation pipe passing through the normal environment space, connecting the gas vent hole and a gas exhaust port provided on the outer surface of the leg above the horizontal plate member for exhausting the gas to the outside of the leg.

Images