JPS6325240B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a support device for a spherical tank for liquefied gas, which supports the tank reliably and can easily cope with expansion or contraction of the tank due to temperature changes during use. be. (Prior Art) For example, Japanese Patent Publication No. 51-20797 (see FIG. 7) is known as an independent cargo tank system for ships for transporting liquefied gas. The support method for this tank is to support a spherical tank by a vertical cylindrical skirt b welded along its equatorial plane, and the entire skirt is reinforced by vertical stiffeners and horizontal ring girders. It consists of a cylindrical shell. The upper end of the skirt is welded to an equatorial ring a built into the equatorial portion of the spherical tank, and the lower end is welded directly to the hull. This equatorial ring has a groove c on its lower edge. Since the skirt b is composed of a cylindrical shell, that is, a cylindrical body plate, its ability to follow the thermal contraction of the tank is extremely poor, and depending on the temperature distribution inside the skirt b, the deformation of the skirt b and the equatorial ring a It has the disadvantage that the thermal stress in the vicinity changes greatly. The reason for this is that when a uniform axially symmetrical displacement is applied along a circular cross section of a cylindrical body plate cut perpendicular to the main axis, distortion in the circumferential direction occurs within the body plate at that cross section. This is because the deformation is restricted. Furthermore, when the tank is filled with liquefied gas, an opening occurs in the gap between the tank T and the skirt b at the lower edge groove c of the equatorial ring, and stress concentration occurs at the bottom of the groove. The result is that In order to keep this concentrated stress within an allowable stress value, it is necessary to appropriately control the temperature gradient within the skirt, which has the drawback of posing difficult problems in heat insulation construction. (Problems to be Solved by the Invention) The present invention solves the problems of the above-mentioned known support devices for spherical tanks, and even if there is a temperature change in the tank while the tank is in use, this invention can easily accommodate this temperature change with a simple structure. It is an object of the present invention to provide a strong support device that can be adapted to various situations and that does not have the problem of stress concentration. (Solution of the Invention) A large-capacity liquefied gas spherical tank welded along the equatorial plane of the spherical tank and fixed to the base by a continuous skirt extending downward from the equatorial plane, wherein the skirt is connected to the upper skirt. and a lower skirt, and the upper skirt is constituted by a vertical corrugated wall corrugated in the circumferential direction, and the upper part of the corrugated wall is directly connected to the tank surface along the corrugated line, that is, the contact line between the spherical surface and the corrugated. The lower skirt is welded, and the lower skirt is fixed to the lower end of the upper skirt through a horizontal ring-shaped shelf plate, and has a cylindrical vertical body plate fixed to the base at the lower end. By adopting a vertical corrugated wall whose radial cross section is corrugated in the circumferential direction on the cylindrical skirt that supports the spherical tank in this way, the tank wall can cope with expansion and contraction of the tank due to thermal load. This makes it possible to effectively absorb thermal stress caused by (Example) In FIG. 1, a spherical tank 1 is installed on an inner bottom 5 of a hull 4 via an upper skirt 2 and a lower skirt 3. The upper skirt 2 is welded to the equatorial plane 6 of the tank 1, and the lower skirt 3 is welded to the inner bottom 5 of the hull 4. As shown in Fig. 2, the upper skirt 2 has a corrugated shape in the circumferential direction, that is, a wavy shape in its horizontal cross section, and an outer arcuate shape concentric with the vertical main axis of the skirt. Consisting of a plate 7, an inner plate 8, and a swash plate 9 connecting them with suitable roundness, the entire upper skirt is constructed symmetrically about its vertical principal axis. The tank 1 is supported by the upper skirt 2, details of where the two join together are shown in FIGS. 3 and 4. In FIG. 3, the upper end of the upper skirt 2 is shaped like a corrugated line, ie, a contact line 10 between the corrugate and the spherical surface, and is directly welded to the tank wall 11 along the contact line. As shown in Figure 4, the vertically extending inner plate 8 of the upper skirt is welded 13 to the tank wall 11 at a distance below the tank equator line 12, and the outer plate 7 is welded 13 to the tank wall 11 at a distance below the tank equator line 12. It extends vertically to about line 12 and is welded 14 to the tank wall 11 which is curved above it as shown. Furthermore, the tank wall and the upper skirt 2 are welded together by means of a substantially horizontally arranged closing plate 15, a possible configuration of which is shown in FIG. A tank wall 11 and a T-shaped ring member consisting of a closing plate 15 and a corrugated flange plate 16 forming part of the upper skirt.
When the welding 17 with the upper skirt 2 is completed, the outer plate 7, the inner plate 8, and the swash plate 9 constituting the upper skirt 2 are butt welded 18 at the ends of the flange plate 16, respectively. The closing plate 15 is connected to the tank wall 11 and the inner plate 8 of the upper skirt 2 when the tank is filled with liquefied gas.
This is provided to prevent the gap 19 between the tank walls 1 and 1 from opening.
1 and the upper skirt 2 are directly connected to each other, it is possible to significantly reduce the thermal stresses occurring in the welded portion.
The installation position of this closing plate 15 is determined by thermal stress calculation taking into consideration the additional stress generated on the tank wall. In FIG. 5, a perspective view of the connecting portion between the upper skirt 2 and the lower skirt 3 is shown as seen from inside the skirt. The lower skirt 3 has a horizontal ring shelf 20,
It is composed of a vertical body plate 21, an outer cover plate 22, and an inner cover plate 23. The relatively thick vertical body plate 21 forms a cylindrical body centered on the vertical main axis of the skirt.
As shown in the figure, its upper end is a horizontal ring-shaped shelf board 20.
In addition, the lower end is welded and fixed to the inner bottom 5 of the hull. The outer plate 7, inner plate 8 and swash plate 9 of the upper skirt 2 are welded 24 to a horizontal ring-shaped shelf plate 20, as shown in FIG. The horizontal cross-sectional shape of the upper end of the plate where it contacts the horizontal ring-shaped shelf board 20 is the same as the horizontal cross-sectional shape of the upper skirt 2, and is aligned in the vertical direction as shown in FIG. The cover plates 22 and 23 are shaped like a contact line 25 shown in FIG.
Welded 27 to the horizontal ring shelf 20, and welded 26 to the horizontal ring shelf 20 as shown in FIG. By adopting a structural method in which this lower skirt 3 is provided, thermal stress within the skirt and additional stress generated on the tank wall can be reduced, compared to a structural method in which the upper skirt 2 is extended downward and directly fixed to the bottom 5 of the hull. Can be absorbed effectively. (Effects) With the above configuration, even if the tank is filled with cryogenic liquefied gas and the tank and skirt contract, the upper skirt 2 can easily accommodate the displacement in the radial direction. It can effectively absorb thermal stress generated on the wall. Incidentally, the following table shows the results of thermal stress analysis for a 21m radius aluminum alloy spherical tank supported by an aluminum alloy skirt, with the tank cooled to -190°C.

【table】
(Unit: Kg/ ^mm2 )
According to this, the structure of the present invention has a remarkable effect of reducing the stress at the lower end of the skirt by about 60%, contributing to improving the safety of the skirt structure and the tank as a whole. In addition, it can be seen that the stress at the junction between the tank and the skirt is reduced in all of the skirt, tank, and closing plate. Further, since the structure for connecting the tank and the skirt is simple, welding is very easy. Even if the temperature distribution of the skirt changes, the response is very insensitive and no significant change occurs in the thermal stress generated in the skirt and tank wall. Therefore, there is no need to place importance on heat insulation measures for the skirt near the equatorial ring. Although the above description has been made for use in ships, it can of course also be used in spherical tanks for use on land. Needless to say, in this case, a mounting base is required in place of the hull.

[Brief explanation of the drawing]

FIG. 1 is a side view of a spherical tank supported by the support device of the present invention. Figure 2 is a sectional view of Figure 1.
Figure 3 is an enlarged view of the joint between the upper skirt and the tank. FIG. 4 is a composite sectional view of the -section and -section of FIG. 3. FIG. 5 is a perspective view of the connection between the upper skirt and the lower skirt. Figure 6 is the same as Figure 5.
Composite cross-sectional view of cross-section and cross-section. Figure 7 shows Tokko Akira.
The joint structure of the equatorial ring, skirt, and tank in Publication No. 51-20797 is shown. In the figure: 1... Spherical tank, 2... Upper skirt, 3... Lower skirt, 4... Hull, 5... Inner bottom (of the hull), 6... Equatorial plane, 7... Outer plate, 8... Inner plate, 9... Swash plate. , 10... contact line, 11... tank wall,
12...equator line, 13, 14, 17, 18, 24,
26, 27... Welding, 15... Closing plate, 16... Flange plate, 19... Gap, 20... Horizontal ring-shaped shelf plate, 21... Vertical body plate, 22, 23... Covering plate, 25...
Contact line, a...equatorial ring, b...skirt, c...
Groove, T...tank.

Claims (1)

[Claims] 1. A large-capacity liquefied gas spherical tank that is welded along the equatorial plane of the spherical tank and fixed to the base by a continuous skirt that extends downward from the equatorial plane, the skirt consisting of an upper skirt and a lower skirt. , the upper skirt is constituted by a vertical corrugated wall corrugated in the circumferential direction, the upper part of the corrugated wall is directly welded to the tank surface along the contact line between the spherical surface and the corrugate, and the lower skirt is A support device for a spherical tank for liquefied gas, comprising a cylindrical vertical body plate that is fixed to the lower end of an upper skirt through a horizontal ring-shaped shelf board and fixed to a base at its lower end.