JP6901950B2 - Marine tank cover and ships equipped with it - Google Patents

Description

The present invention relates to a marine tank cover that covers a tank in which liquefied gas such as liquefied natural gas is stored, and a ship provided with the marine tank cover.

Conventionally, a spherical liquefied gas tank independent of the hull has been known as a tank mounted on a ship for storing liquefied gas such as liquefied natural gas. The conventional liquefied gas tank has a spherical shape, but in recent years, the shape of the liquefied gas tank has been improved in order to improve the volumetric efficiency while enjoying the advantages of this type of liquefied gas tank.

For example, Patent Document 1 discloses a liquefied gas carrier equipped with a plurality of non-spherical liquefied gas tanks. Each non-spherical tank of this liquefied gas carrier has a shape that bulges diagonally upward and downward from the center of the tank as compared with the spherical tank. Therefore, a liquefied gas tank having improved volumetric efficiency as compared with a true sphere tank having the same width has been realized.

Each of the above-mentioned non-true sphere tanks protrudes above the upper deck of the hull, and the protruding portion is covered with a tank cover supported by the upper deck of the hull. The tank cover is arranged at a predetermined distance from the non-true sphere tank, and plays a role of protecting the non-true sphere tank from external damage and suppressing a temperature rise around the non-true sphere tank. This tank cover has the same shape as a non-spherical tank.

Japanese Unexamined Patent Publication No. 2016-199092

However, as described above, the non-spherical tank has an advantage of improving volumetric efficiency, but the non-spherical tank cover has an advantage in manufacturing difficulty, but does not have such an advantage.

In order to facilitate the manufacture of the tank cover, it is conceivable to adopt a tank cover having a true spherical shape, which has been used for covering the conventional true spherical tank, as the tank cover for covering the non-spherical tank. However, in this case as well, another problem arises as follows.

FIG. 7 is a cross-sectional view of the non-spherical tank 100 and the tank cover 110 when a conventional tank cover 110 having a true spherical shape is adopted as the tank cover for covering the non-spherical tank 100. Generally, the conventional spherical tank cover 110 has a cylindrical portion 112 supported by an upper deck 111, a top plate portion 113 extending horizontally above the tank 100, and an upper end portion of the cylindrical portion 112. A spherical portion 114 is provided to connect the peripheral portion of the top plate portion 113 with the spherical portion 114.

It is necessary to secure a certain amount of space between the tank 100 and the tank cover 110 for construction work on the outer surface of the tank 100, maintenance of the tank 100, and the like. As shown in FIG. 7, when a conventional tank cover 110 having a true spherical shape is adopted for the non-true sphere tank 100, the space between the non-true sphere tank 100 and the tank cover 110 is the non-true sphere tank 100. It becomes narrower at the portion 101 that bulges diagonally upward in. In order to secure this space above a certain level, it is necessary to raise the cylindrical portion 112 and widen the top plate portion 113, which increases the weight of the entire tank cover 110.

Therefore, the present invention is a marine tank cover that covers a non-spherical tank having a shape that bulges diagonally upward as compared with a spherical tank, and a space between the non-spherical tank and the non-spherical tank while suppressing the overall weight. It is an object of the present invention to provide a marine tank cover and a ship equipped with the marine tank cover, which can easily manufacture a marine tank cover configured to secure a certain amount or more.

In order to solve the above problems, the marine tank cover according to one aspect of the present invention protrudes upward from the upper deck of the hull in a non-spherical tank having a shape that bulges diagonally upward as compared with the spherical tank. A marine tank cover that covers the vertical central axis and is symmetrical around the vertical central axis, and has a cylindrical portion supported by the upper deck and a circular peripheral edge that extends horizontally above the top of the non-spherical tank. It includes a top plate portion having a portion and a curved surface portion extending from the upper end portion of the cylindrical portion along the outer surface of the non-spherical tank and connecting to the peripheral edge portion of the top plate portion, and the curved surface portion is on the lower side. The center of curvature of the first spherical surface portion includes the first spherical surface portion and the upper second spherical surface portion of the above, and is located above the center of curvature of the second spherical surface portion.

According to the above-mentioned marine tank cover, the center of curvature of the lower first spherical surface portion is located above the center of curvature of the upper second spherical surface portion, so that the curved surface portions are the first spherical surface portion and the second spherical surface portion. The shape is such that it protrudes outward at the boundary of the part. For this reason, while suppressing the height of the cylindrical portion and the width of the top plate portion to reduce the weight of the entire tank cover, a certain amount of space or more is secured between the portion of the non-spherical tank that bulges diagonally upward and the tank cover. can do. Further, since the first spherical surface portion and the second spherical surface portion of the curved surface portion each have a constant radius of curvature in any direction, they can be easily manufactured as compared with the case of manufacturing a tank cover having a non-spherical shape. can do.

Further, the marine tank cover according to another aspect of the present invention is a vertical center that covers a portion of a non-spherical tank having a shape that bulges diagonally upward as compared with a spherical tank and that protrudes upward from the upper deck of the hull. A marine tank cover that is symmetrical around the axis, with a cylindrical portion supported by the upper deck and a top plate portion that extends horizontally above the top of the non-spherical tank and has a circular peripheral edge. A curved surface portion extending from the upper end portion of the cylindrical portion along the outer surface of the non-true sphere tank and connecting to the peripheral edge portion of the top plate portion, and having a vertical cross-sectional shape passing through the vertical central axis of the curved surface portion. One of them coincides with a circle centered on a point distant from the vertical central axis toward the one.

According to the above-mentioned marine tank cover, the circle having one of the vertical cross-sectional shapes passing through the vertical central axis in the curved surface is centered on the point away from the vertical central axis toward the one, so that the radius of curvature is large. Even if the size is small, it is possible to secure a certain space between the non-spherical tank and the tank cover. Further, by reducing the radius of curvature of the circle whose vertical cross-sectional shape matches the curved surface portion, the height of the cylindrical portion and the width of the top plate portion can be suppressed, and the weight of the entire tank cover can be suppressed. Further, since the curved surface portion has a structure having a constant radius of curvature in the direction along the curve from the lower end portion to the upper end portion, for example, the radius of curvature changes as the curved surface portion moves from the lower end portion to the upper end portion. It can be easily manufactured as compared with the case of manufacturing a tank cover having a non-spherical shape.

Further, the ship according to one aspect of the present invention is a non-true shape that bulges diagonally upward with respect to the hull and a spherical tank supported by the hull so as to protrude upward from the upper deck of the hull. A ball tank and any of the above marine tank covers that cover a portion of the non-true ball tank that protrudes above the upper deck are provided.

According to the present invention, it is a marine tank cover that covers a non-spherical tank having a shape that bulges diagonally upward as compared with a spherical tank, and a space between the non-spherical tank and the non-spherical tank while suppressing the overall weight. Provided are a marine tank cover and a ship equipped with the same, which can easily manufacture a tank cover configured to secure a certain amount or more.

It is a side view of the ship provided with the marine tank cover which concerns on 1st Embodiment of this invention. It is a top view of the ship shown in FIG. It is sectional drawing of the ship shown in FIG. 1 as seen from the arrow III-III. It is a figure explaining the structure of the marine liquefied gas tank shown in FIG. FIG. 3 is an enlarged cross-sectional view showing an enlarged view of the marine tank cover in FIG. FIG. 5 is an enlarged cross-sectional view showing an enlarged view of a marine tank cover according to a second embodiment of the present invention. It is an enlarged cross-sectional view which shows the relationship between the non-spherical tank and the conventional marine tank cover when the conventional spherical marine tank cover is adopted as a non-spherical tank.

[First Embodiment]
Hereinafter, a ship provided with a marine tank cover according to the first embodiment will be described with reference to the drawings.

(Ship composition)
1 and 2 are a side view and a top view of the ship 1 according to the first embodiment. Vessel 1 is equipped with a tank 10 in which liquefied gas is stored. Vessel 1 is, for example, a liquefied gas carrier or a floating storage / regasification facility. The liquefied gas stored in the tank 10 is, for example, liquefied natural gas (LNG) or liquid hydrogen. In the present embodiment, the ship 1 is provided on the hull 20 so that a plurality of (four in this example) tanks 10 are arranged in the captain direction.

Further, the ship 1 of the present embodiment is provided with a bridge 21 at the rear portion (left side in FIG. 1), which is a place for maneuvering the ship during the voyage. As shown by the broken line in FIG. 1, the upper part of the tank 10 projects upward from the upper deck 22 of the hull 20. Further, the upper deck 22 is provided with a plurality of marine tank covers (hereinafter, simply referred to as “tank covers”) 50 that cover the upper portions of the plurality of tanks 10 protruding above the upper deck 22 of the hull 20. .. A tank dome 11 protruding from the tank cover 50 is provided on the top of each tank 10. The tank dome 11 is covered with a dome cover (not shown).

FIG. 3 is a cross-sectional view taken along the line III-III of the ship shown in FIG. FIG. 3 shows a tank 10 mounted on a ship 1 and a structure for supporting the tank 10. The pipe tower and the like for accommodating the cargo handling pipes and the like arranged in the tank 10 are omitted in FIGS. 3 to 7 for the sake of simplicity.

In the present embodiment, the tank 10 is a liquefied gas tank symmetrical about the vertical central axis C. The outer surface of the tank 10 is covered with a heat insulating material (not shown). The tank 10 in the present embodiment has a shape that bulges diagonally upward and downward as compared with a spherical tank having the same width. The configuration of the non-spherical tank 10 will be described in detail later.

A pair of vertical bulkheads 25 are provided on both sides of the hull 20 in the beam width direction within a predetermined distance from the pair of ship-side outer plates 24. The pair of longitudinal bulkheads 25 extend in the captain direction along the ship side skin 24. A tank 10 is arranged between the pair of longitudinal partition walls 25, and a foundation deck 26 that supports the tank 10 via a skirt 27 is provided around the tank 10.

The foundation deck 26 is provided at a predetermined height position below the upper deck 22 on the hull 20 so as to connect the ship-side outer plates 24 to each other in the ship width direction, and the above-mentioned longitudinal passage is provided on the upper surface of the foundation deck 26. The lower end of the partition wall 25 is connected. At the position where the tank 10 is provided on the foundation deck 26, a circular opening having a size substantially the same as the diameter of the skirt 27 is provided. The skirt 27 has a cylindrical shape, the lower end of the skirt 27 is connected to the upper surface of the foundation deck 26, and the upper end of the skirt 27 is connected to the outer peripheral surface of the tank 10.

Further, below the tank 10, an inner bottom plate 28 extending in the captain direction along the ship bottom outer plate 23 is provided above the ship bottom outer plate 23 by a predetermined distance. Further, a pair of bilge hopper plates 29 are provided between both ends of the inner bottom plate 28 in the ship width direction and the foundation deck 26. The bilge hopper plate 29 is provided so as to extend in the direction of the captain. The pair of bilge hopper plates 29 are inclined outward from both ends of the inner bottom plate 28 in the width direction of the ship.

(Composition of non-true sphere tank)
Next, the configuration of the tank 10 will be described with reference to FIG. FIG. 4 schematically shows a vertical cross-sectional shape passing through the vertical central axis C of the tank 10. In FIG. 4, for comparison with the non-spherical tank 10, the spherical tank 90 having the same width as the tank 10 is shown by a three-dot chain line.

The tank 10 is a pressure vessel symmetrical about the vertical central axis C. The tank 10 has a lower tank body 12 that forms a lower portion of the tank 10 and opens upward, and an upper tank body 13 that forms an upper portion of the tank 10 and opens downward. In the present embodiment, the lower tank body 12 and the upper tank body 13 are directly connected by the upper end portion 12a of the lower tank body 12 and the lower end portion 13a of the upper tank body 13. The outer surfaces of the lower tank body 12 and the upper tank body 13 are each covered with a heat insulating material (not shown).

First, the lower tank body 12 will be described. The lower tank body 12 has a true sphere portion 31 having a shape forming a part of a true sphere and a non-true sphere portion 32 having a shape forming a part of a non-true sphere. The true sphere 31 and the non-true sphere 32 are connected, and in FIG. 4, the boundary between the true sphere 31 and the non-true sphere 32 in the lower tank body 12 is shown by a two-dot chain line.

The true sphere 31 is formed so as to extend from the vertical central axis C so as to form the vicinity of the vertical central axis C in the lower tank body 12. The true sphere 31 has a circular shape when viewed from the vertical direction, and has an annular outer edge 33.

Lower tank body 12, in vertical cross-section through a vertical center axis C, the center of curvature c ₁ of the true sphere portion 31 is a vertically above the central axis C, and above the upper end 12a of lower tank 12 positioned. In the present embodiment, the lower tank body 12, in vertical cross-section through a vertical center axis C, and is formed such that in the space center of curvature c ₁ of the true sphere portion 31 is surrounded by the upper tank 13 ..

The non-true sphere 32 is formed around the true sphere 31 so as to form a portion distal to the vertical central axis C in the lower tank body 12. The non-true sphere 32 is annular when viewed in the vertical direction, and has a central edge 34 and a peripheral edge 35. The central edge 34 is an edge proximal to the vertical central axis C in the non-true sphere 32 and is connected to the outer edge 33 of the true sphere 31. The peripheral edge 35 is the edge distal to the vertical central axis C in the non-true sphere 32. That is, the peripheral side edge 35 constitutes the upper end portion 12a of the lower tank body 12.

The non-true sphere portion 32 has a minimum radius of curvature portion 36 having a minimum radius of curvature between the central side edge 34 and the peripheral side edge 35 in a vertical cross-sectional shape passing through the vertical central axis C. .. Further, in the vertical cross-sectional shape of the non-true sphere portion 32 passing through the vertical central axis C, the radius of curvature continuously decreases from the central side edge 34 to the minimum radius of curvature portion 36, and from the minimum radius of curvature portion 36. It is formed so that the radius of curvature continuously increases toward the peripheral edge 35. That is, the non-true sphere portion 32 is formed so as to bulge diagonally downward.

To explain the shape of the non-true sphere 32 in more detail, the non-true sphere 32 is formed so that the vertical cross-sectional shape passing through the vertical central axis C matches the locus represented by the following equation (1). ing.
| X / r ₁ | ⁿ + | y / r ₂ | ⁿ = 1 ... (1)

The x and y of the above equation (1) are the x-coordinate and the y-coordinate when the straight line orthogonal to the vertical central axis C is the x-axis and the straight line corresponding to the vertical central axis C is the y-axis. In the present embodiment, a straight line orthogonal to the vertical central axis C and on a horizontal plane passing through the peripheral edge 35 of the non-true sphere 32 is set as the x-axis.

_{R 1} and r _{2 in} the above equation (1) are constants satisfying 0.5 ≦ r ₂ / r ₁ ≦ 2. In order to secure the strength of the lower tank body 12 without making the change in the curvature of the locus of the equation (1) extremely large, r ₁ and r ₂ are set to 0.9 ≤ r ₂ / r ₁ ≤ 1. It is more preferable that the constant satisfies 1. In the present embodiment, r ₁ is the length from the vertical central axis C to the peripheral side edge 35, and r ₂ is from the peripheral side edge 35 in the vertical central axis C direction to the lower end of the lower tank body 12. It is a little up to the upper side.

N in the above equation (1) is a constant satisfying 2 <n <3, preferably a constant satisfying 2.3 ≦ n <3. In this embodiment, the value of n in the formula (1) is 2.5. Since the value of n in the formula (1) is larger than 2, the lower tank body 12 has a shape that bulges diagonally downward from the center of the tank 10 as compared with the spherical tank 90.

_{In the present embodiment, the angle α formed by the straight line l 1} connecting the origin O and the minimum radius of curvature portion 36 set by the coordinates related to the above equation (1) with the vertical central axis C is 45 °.

The lower tank body 12 is formed so that the true sphere 31 and the non-true sphere 32 are smoothly connected. For example, in the present embodiment, the tangent line at the outer edge 33 of the true sphere 31 and the tangent line at the central end edge 34 of the non-true sphere 32 in the vertical cross-sectional shape passing through the vertical central axis C coincide with each other. However, it suffices that the tangent line at the outer edge 33 and the tangent line at the central edge 34 substantially coincide with each other.

_{The straight line l 2} connecting the point where the true sphere 31 and the non-true sphere 32 are connected (that is, the outer edge 33 and the central edge 34) and the origin O set by the coordinates related to the above equation (1) is the vertical center. The angle β formed with the axis C is preferably 45 ° or less, and more preferably 20 ° to 30 °. In this embodiment, the angle β is 25 °.

In the present embodiment, the upper tank body 13 has the same configuration as the lower tank body 12 described above. That is, the upper tank body 13 has a true sphere 41 that forms a part of the true sphere and a non-true sphere 42 that forms a part of the non-true sphere, similarly to the lower tank body 12. Have. The true sphere 41 and the non-true sphere 42 are connected to each other, and in FIG. 4, the boundary between the true sphere 41 and the non-true sphere 42 in the upper tank body 13 is shown by a two-dot chain line.

Further, in the present embodiment, the upper tank body 13 has a shape symmetrical to the lower tank body 12 with respect to a plane perpendicular to the vertical central axis C passing through the lower end portion 13a (that is, the peripheral side edge 45). Have. That is, the non-true sphere 42 of the upper tank body 13 has a vertical cross-sectional shape passing through the vertical central axis C, between the central edge 44 connected to the outer edge 43 of the true sphere 41 and the peripheral edge 45. It has a minimum radius of curvature portion 46 that minimizes the radius of curvature, and the radius of curvature continuously decreases from the central side edge 44 to the minimum radius of curvature 46, from the minimum radius of curvature 46 to the peripheral edge 45. It is formed so that the radius of curvature increases continuously as it goes.

Further, the non-true sphere 42 of the upper tank body 13 is also formed so that the vertical cross-sectional shape passing through the vertical central axis C matches the locus represented by the above equation (1). In the present embodiment, the setting position of the x-axis and y-axis in the case of the upper tank body, setting the value of the constant r _1, r ₂ and n is also the same as the case of the lower tank body 12. Other configurations of the upper tank body 13 will be omitted because they overlap with the description of the lower tank body 12 having the same shape. For example, the center of curvature c ₁ of the lower tank body 12 is read as the _{center of curvature c 2} of the upper tank body 13. The peripheral edge 35 of the lower tank body 12 and the peripheral edge 45 of the upper tank body 13 do not have to coincide with each other.

(Composition of tank cover)
Next, the configuration of the tank cover 50 will be described with reference to FIG. FIG. 5 is an enlarged cross-sectional view showing the tank cover 50 in FIG. 3 in an enlarged manner. The tank cover 50 is symmetrical about the vertical central axis C. The tank cover 50 is supported by the upper deck 22. The tank cover 50 has a cylindrical portion 51, a curved surface portion 52, and a top plate portion 53 in this order from bottom to top.

The cylindrical portion 51 extends in the vertical direction, and the tank 10 and the central axis C coincide with each other. The lower end portion 51a of the cylindrical portion 51 is connected to the upper deck 22 and is supported by the upper deck 22.

The top plate portion 53 extends in the horizontal direction above the top of the tank 10. The top plate portion 53 has a circular peripheral edge portion 53a. The top plate portion 53 is arranged so that the vertical central axis C of the tank 10 passes through the center of the circular peripheral edge portion 53a.

An opening 53b for projecting the tank dome 11 from below is formed in the center of the top plate portion 53. An expansion rubber portion (not shown) for connecting the tank dome 11 and the tank cover 50 is provided around the opening 53b of the top plate portion 53. The expansion rubber portion is configured to be expandable and contractible so as to absorb the displacement of the tank dome 11 with respect to the tank cover 50 caused by the heat shrinkage of the tank 10. Therefore, the top plate portion 53 is not supported by the expansion rubber portion, but is supported by the curved surface portion 52 connected to the top plate portion 53.

The curved surface portion 52 extends from the upper end portion 51b of the cylindrical portion 51 along the outer surface of the tank 10 and connects to the peripheral edge portion 53a of the top plate portion 53. In the present embodiment, the curved surface portion 52 is composed of a lower first spherical surface portion 61 and an upper second spherical surface portion 62 adjacent to each other in the vertical direction. The first spherical surface portion 61 and the second spherical surface portion 62 each have a shape forming an upper part of a true sphere having different radii. That is, the first spherical portion 61 has a constant radius of curvature R _1, the second spherical surface portion 62 has a constant radius of curvature R _2.

The first spherical surface portion 61 is annular when viewed in the vertical direction, the lower end portion 61a of the first spherical surface portion 61 opens downward, and the upper end portion 61b of the first spherical surface portion 61 opens upward. To do. The second spherical surface portion 62 is annular when viewed in the vertical direction, the lower end portion 62a of the second spherical surface portion 62 opens downward, and the upper end portion 62b of the second spherical surface portion 62 opens upward. To do.

The lower end portion 61a of the first spherical surface portion 61 is connected to the upper end portion 51b of the cylindrical portion 51. Further, the upper end portion 61b of the first spherical surface portion 61 is connected to the lower end portion 62a of the second spherical surface portion 62. Further, the upper end portion 62b of the second spherical surface portion 62 is connected to the peripheral edge portion 53a of the top plate portion 53. In FIG. 5, the boundary between the cylindrical portion 51 and the first spherical surface portion 61 and the boundary between the first spherical surface portion 61 and the second spherical surface portion 62 are shown by a two-dot chain line.

_{The center of curvature d 1} of the first spherical surface portion 61 and the center of curvature d ₂ of the second spherical surface portion 62 are located on the central axis C. Further, the center of curvature d ₁ of the first spherical surface portion 61 is located above the _{center of curvature d 2} of the second spherical surface portion 62. Further, the center of curvature _{d 1} is located below the upper end portion 51b of the cylindrical portion 51. However, the center of curvature d ₁ may be located at the same height as the upper end portion 51b of the cylindrical portion 51.

As described above, the tank cover 50 according to the present embodiment, the center of curvature d ₁ of the first spherical surface portion 61 of the lower, located above the center of curvature d ₂ of the upper side of the second spherical part 62. Therefore, the curved surface portion 52 has a shape that protrudes outward (that is, in a direction away from the non-spherical tank 10) at the boundary between the first spherical surface portion 61 and the second spherical surface portion 62. Therefore, while suppressing the height of the cylindrical portion 51 and the width of the top plate portion 53 to suppress the weight of the entire tank cover 50, the space between the portion of the non-spherical tank 10 that bulges diagonally upward and the tank cover 50. Can be secured above a certain level.

Further, in the present embodiment, the first spherical portion 61 and the second spherical part 62 in the curved portion 52 is configured to have a constant radius of curvature R _1, R ₂ in any respective direction. Therefore, the tank cover 50 of the present embodiment can be easily manufactured as compared with the case of manufacturing a non-spherical tank cover.

[Second Embodiment]
Next, the configuration of the tank cover 70 according to the second embodiment will be described with reference to FIG. FIG. 6 is an enlarged cross-sectional view showing an enlarged view of the tank cover 70 according to the second embodiment. In the present embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and duplicate description will be omitted.

The tank cover 70 of the present embodiment has a curved surface portion 72 having a different shape from that of the first embodiment, but other configurations are the same as those of the first embodiment. That is, the tank cover 70 is symmetrical around the vertical central axis C, and has a cylindrical portion 51, a curved surface portion 72, and a top plate portion 53 in this order from bottom to top. Then, the curved surface portion 72 extends from the upper end portion 51b of the cylindrical portion 51 along the outer surface of the tank 10 and is connected to the peripheral edge portion 53a of the top plate portion 53. Then, the lower end portion 72a of the curved surface portion 72 is connected to the upper end portion 51b of the cylindrical portion 51, and the upper end portion 72b of the curved surface portion 72 is connected to the peripheral edge portion 53a of the top plate portion 53. In FIG. 6, the boundary between the cylindrical portion 51 and the curved surface portion 72 is indicated by a two-dot chain line.

In the present embodiment, the vertical cross-sectional shape of the curved surface portion 72 passing through the vertical central axis C is two curves symmetrical to the vertical central axis C. In this embodiment, these two curves is a vertical cross-section of the curved portion 72, matches the e ₁ point away from each vertical central axis C in a circle centered.

Specifically, one of these two curves, which is the vertical cross-sectional shape of the curved surface portion 72, is _{a predetermined distance from a predetermined point e 0} on the vertical central axis C toward the one in a direction orthogonal to the vertical central axis C. meets the circle centered only e ₁ that is displaced D. That is, the curve having the vertical cross-sectional shape of the curved surface portion 72 is an arc centered on _{the point e 1 displaced from the predetermined point e 0} on the vertical central axis C by a predetermined distance D toward the curve. Therefore, the curved portion 72 has a constant radius of curvature R ₃ in the direction along the curve toward the upper end portion 72b from its lower end 72a.

In the present embodiment, the point e ₀ on the vertical central axis C is located below the upper end portion 51b of the cylindrical portion 51. Further, the distance D from the point e ₀ to the point e ₁ is shorter than the distance from the vertical central axis C to the circular peripheral edge portion 53a of the top plate portion 53. In other words, the point e ₁ is located at a position overlapping the top plate portion 53 when viewed from the vertical direction. The point e ₀ may be located at the same height as the upper end portion 51b of the cylindrical portion 51, and the distance D is the distance from the vertical central axis C to the circular peripheral portion 53a of the top plate portion 53. May match.

In the tank cover 70 of the present embodiment, the circle in which one of the vertical cross-sectional shapes passing through the vertical central axis C in the curved surface portion 72 matches is centered on _{the point e1 which is separated from the vertical central axis C toward the one.} to reason, even with a small radius of curvature R ₃ than circle centered on the point on the vertical central axis C, is the space between the non-sphericity tank 10 and the tank cover 70 can be fixed secured. Further, by the vertical cross section of the curved portion 72 to reduce the radius of curvature R ₃ of the circle that matches, it is possible to suppress the total weight of the tank cover 70 with reduced height and width of the top plate portion 53 of the cylindrical portion 51 it can.

Further, in the present embodiment, the curved portion 72 is configured to have a constant radius of curvature R ₃ in the direction along the curve toward the upper portion from the lower end. Therefore, the tank cover 70 of the present embodiment is easier than the case of manufacturing a tank cover having a non-spherical shape in which the radius of curvature changes as the curved surface portion moves from the lower end portion to the upper end portion, for example. Can be manufactured.

[Other Embodiments]
It should be considered that the above embodiments are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

For example, the non-spherical tank covered with the tank cover according to the present invention is not limited to the shape of the tank 10 described in the first and second embodiments described above, and bulges diagonally upward as compared with the spherical tank. Any shape may be used as long as it has a shape.

For example, in the first and second embodiments described above, as the non-true sphere tank 10, the upper tank body and the lower tank body each have a true sphere portion and a non-true sphere portion, respectively. Is not limited to such a configuration. For example, the non-true sphere tank does not have to have a true sphere portion, and the entire vertical cross-sectional shape passing through the vertical central axis C is formed so as to match the locus represented by the above equation (1). You may.

Further, in the first and second embodiments described above, the lower tank body 12 and the upper tank body 13 in the non-true sphere tank 10 have a shape symmetrical with respect to the plane perpendicular to the vertical central axis C. However, the lower tank body 12 and the upper tank body 13 may have different shapes. For example, the upper tank body 13 in the non-spherical tank may bulge diagonally upward, and the lower tank body 12 may exhibit a true sphere that does not bulge diagonally downward. Further, the shape of the non-spherical portion also matches the locus represented by an equation other than the above equation (1) if the non-spherical tank has a shape that bulges diagonally upward as compared with the spherical tank. It may be formed as follows. Further, the non-true sphere tank may have a cylindrical body extending in the vertical direction connecting the upper tank body 13 and the lower tank body 12 between the upper tank body 13 and the lower tank body 12.

Further, in the first embodiment described above, the curved surface portion 52 is composed of two spherical portions 61 and 62 adjacent to each other in the vertical direction, but the curved surface portion may be composed of three or more spherical portions. Good. In this case, among the three or more spherical portions, the center of curvature of the spherical portion located on the lower side is located above the center of curvature of the spherical portion located on the upper side. Further, the lower spherical surface portion and the upper spherical surface portion may be connected via a truncated cone-shaped connecting member. In other words, the lower spherical portion and the upper spherical portion are connected via a connecting member whose vertical cross-sectional shape linearly connects the upper end portion of the lower spherical portion and the lower end portion of the upper spherical portion. May be good.

1: Ship 10: Non-spherical tank 20: Hull 22: Upper deck 50, 70: Tank cover 51: Cylindrical part 52, 72: Curved surface part 53: Top plate part 61: First spherical part 62: Second spherical part

Claims (3)

A marine tank cover that is symmetrical around the vertical central axis and covers the part of the non-spherical tank that bulges diagonally upward compared to the spherical tank and that protrudes above the upper deck of the hull.
The cylindrical part supported by the upper deck and
A top plate portion that extends horizontally above the top of the non-spherical tank and has a circular peripheral edge, and a top plate portion.
A curved surface portion extending from the upper end portion of the cylindrical portion along the outer surface of the non-spherical tank and connecting to the peripheral edge portion of the top plate portion is provided.
The curved surface portion includes a lower first spherical surface portion and an upper second spherical surface portion.
The center of curvature of the first spherical surface portion is a marine tank cover located above the center of curvature of the second spherical surface portion. A marine tank cover that is symmetrical around the vertical central axis and covers the part of the non-spherical tank that bulges diagonally upward compared to the spherical tank and that protrudes above the upper deck of the hull.
The cylindrical part supported by the upper deck and
A top plate portion that extends horizontally above the top of the non-spherical tank and has a circular peripheral edge, and a top plate portion.
A curved surface portion extending from the upper end portion of the cylindrical portion along the outer surface of the non-spherical tank and connecting to the peripheral edge portion of the top plate portion is provided.
One of the vertical cross-sectional shapes of the curved surface portion passing through the vertical central axis is a marine tank cover that matches a circle centered on a point distant from the vertical central axis toward the one. With the hull
A non-spherical tank that is supported by the hull so as to protrude upward from the upper deck of the hull and has a shape that bulges diagonally upward compared to the spherical tank.
A ship comprising the marine tank cover according to claim 1 or 2, which covers a portion of the non-spherical tank protruding above the upper deck.

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