JPH0214720Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to an inner tank support structure for a double-shell tank, and in particular, the invention aims to reduce stress concentration as much as possible at the inner tank attachment part, and to This invention relates to an inner tank support structure that allows the tank skirt to be made as short as possible.

[Prior Art] Generally, as a device for storing low-temperature liquid such as liquefied natural gas, there is a double-shell tank consisting of an inner tank that essentially accommodates the low-temperature storage liquid, and an outer tank that surrounds the inner tank with a heat insulating layer interposed therebetween. is already known.

The inner tank support method in this double shell tank includes:
Two methods are known: one in which the inner tank is suspended and supported by a number of hangers attached to the inner wall of the outer tank, and the other in which an annular inner tank skirt is attached to the bottom inner wall of the outer tank to directly support the inner tank. However, in view of the simplicity of the structure and the ease of installation, structures in which the inner tank is supported by the inner tank skirt as described above have recently been widely adopted.

This conventional inner tank support structure will be explained based on FIG. It is covered with an outer tank 2 through a layer. A cylindrical outer tank skirt 3 extending downward is attached to the lower part of the outer tank 2, and is attached to a base (not shown) to support the entire tank body.

Further, an annular inner tank skirt 4 extending downward is attached to the lower part of the inner tank 1.
By welding and fixing the lower end of this inner tank skirt 4 to the bottom inner wall surface 5 of the outer tank 2, the inner tank 1 is supported and fixed to the outer tank 2 side.

[Problems to be solved by the invention] By the way, in this type of conventional inner tank support structure, the lower end of the inner tank skirt 4 is directly welded and fixed to the bottom inner wall surface 5 of the outer tank 2. As a result, bending and shearing forces due to external forces such as earthquakes are applied directly to the bottom of the outer tank, and the stress concentration applied here becomes extremely large, which is not desirable from a safety standpoint.

Further, as mentioned above, in order to cope with excessive stress concentration, the amount of weld fillet must be increased, and the installation work of the inner tank 1 is also time-consuming.

Furthermore, in order to prevent frost from forming on the outer wall surface of the bottom of the outer tank 2, the length of the inner tank skirt 4 must be sufficiently removed to increase the distance l between the bottom of the outer tank 2 and the bottom of the inner tank 1. As a result, the tank had to be made larger in relation to its capacity.

Particularly in today's world where tanks are required to be larger as storage capacity increases, an immediate solution to the above-mentioned problems is desired.

[Purpose of the invention] The present invention has been devised to focus on the above-mentioned problems and to effectively solve them.

The purpose of this invention is to attach a reinforcing ring to the inner wall surface of the bottom of the outer tank, and to weld and fix the inner tank skirt to this ring, to disperse the stress applied to the outer tank, thereby increasing the durability of the device itself. An object of the present invention is to provide an inner tank support structure for a double-shell tank, which can improve the temperature of the tank and shorten the distance between the bottom of the inner tank and the bottom of the outer tank by providing a heating means along the reinforcing ring.

[Summary of the invention] The structure of the invention that achieves the above object is to form an annular reinforcing ring along the circumferential direction on the bottom inner wall surface of the outer tank, and weld the lower end of the inner tank skirt onto this reinforcing ring. By fixing the inner tank to distribute the load on the outer tank and providing a heating means along the reinforcing ring, the bottom of the inner tank and the bottom of the outer tank can be brought close to each other without causing frosting. The main point is that it has been made possible.

[Example] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

Figure 1 shows 2 having an inner tank support structure according to the present invention.
FIG. 2 is a longitudinal cross-sectional view showing the heavy shell tank, FIG. 2 is a cross-sectional view along the line taken along the line in FIG. 1, and FIG. 3 is an enlarged cross-sectional view showing the inner tank support structure according to the present invention.

As shown in the figure, reference numeral 1 denotes a bottomed cylindrical inner tank that substantially contains a low-temperature liquid such as liquefied natural gas, and the inner tank mirror plate 7 that constitutes the ceiling 6 and bottom of this inner tank 1 is dome-shaped. It is molded to protrude vertically. The entire inner tank 1 is covered with an outer tank 2 via a cold insulation layer 8 of a predetermined thickness on the outside.
The tank as a whole has a double shell structure.

A cylindrical outer tank skirt 3 extending downward is attached to the outer tank end plate 9 that constitutes the bottom of the outer tank 2, and the entire tank is supported by attaching the lower end of this to a base (not shown). are doing.
Further, a large number of reinforcing ribs 10 are attached radially to the outside of the outer tank skirt 3 to reinforce the strength of the skirt.

In addition, an inner tank end plate 7 constituting the bottom of the inner tank 1
An annular inner tank skirt 11 extending downward is attached to the lower part of the tank, and the inner tank 1 is fixed by supporting the inner tank skirt 11 on the outer tank 2 side. Specifically, the bottom inner wall surface 12 of the outer tank 2, which is a portion located vertically below the inner tank skirt 11, that is, the inner wall surface of the outer tank head plate 9, has the feature of the present invention along its circumferential direction. An annular reinforcing ring 13 is attached and fixed.
This reinforcing ring 13 is made of, for example, an L-shaped steel 14 having an L-shaped cross section, and is welded and fixed in the circumferential direction along the bottom of the outer tank 2 while maintaining one side of this L-shaped steel in a horizontal state. It is made up of. especially,
In this embodiment, the L-shaped steel 14 is used to use the space s defined by the L-shaped steel 14 and the bottom inner wall surface 12 of the outer tank 2 as part of the heating means described later.
4 are liquid-tightly welded and fixed to the bottom inner wall surface 12 of the outer tank 2, and the space s formed here is an airtight space. Then, the lower end 11a of the annular inner tank skirt 11 is welded and fixed along the upper side surface 13a of the annular reinforcing ring 13, that is, along the horizontal plane of one side of the L-shaped steel 14, so that the inner tank 1 is supported on the outer tank 2 side. That is, by applying the load of the inner tank 1 to the outer tank 2 side via the reinforcing ring 13 provided at the lower part, the load of the inner tank 1 is distributed and transmitted to the end plate 9 side at the bottom of the outer tank 2. ing.

Further, a heating means 15, which is a feature of the present invention, is further formed along the reinforcing ring 13, and the heat supplied from this heat source heats the bottom mirror plate 9 of the outer tank 2 to prevent frost formation thereon. Preventing this from occurring. Specifically, this heating means 15 includes a heating medium passage 16 constituted by a ring-shaped sealed space s defined by the L-shaped steel 14 and the bottom inner wall surface 12 of the outer tank 2, and this passage. A heating medium supply pipe 17 penetrates through the outer tank 2 and has its supply port 17a facing the inside of the heating medium passage 16 in order to supply a heating medium from the outside into the outer tank. Mainly, the heating medium is discharged from the passage 16 to the outside by a heating medium discharge pipe 18 whose discharge port 18a is located inside the passage 16 and whose discharge side penetrates the wall of the outer tank 2 and extends outside the tank. The supply pipe 17 and the discharge pipe 18 are provided with on-off valves 19 and 20, respectively, to adjust the flow rate of the heating medium. As a result, the outer tank end plate 9 can be heated by introducing the heating medium supplied from the heating medium supply pipe 17 into the heating medium passage 16 serving as the closed space s below the inner tank, and the heating medium whose temperature has decreased due to heating. The medium can be discharged from the heating medium discharge pipe 18.

Here, it is preferable to use a heated gas such as nitrogen gas or air as the heating medium.

As described above, by providing the heating means 15, even if the outer tank head plate 9 and the inner tank head plate 7 are brought closer to each other, frost formation does not occur on the outer tank head plate 9. Therefore, the length of the inner tank skirt 11, which has the function of separating the outer tank head plate 9 and the inner tank head plate 7, is set shorter in this embodiment than in the conventional example.

In the above embodiment, L-shaped steel is used as the reinforcing ring 13, but the reinforcing ring 13 is not limited to this, and for example, T-shaped steel may be used.

With the above configuration, the entire load of the inner tank 1 including the weight of the stored liquid L is transmitted to the reinforcing ring 13 via the inner tank skirt 11 attached to the lower part of the inner tank 1. The signal is transmitted to the bottom mirror plate 9 of the outer tank 2 and finally to the base plate via the outer tank skirt 3. Here, inner tank skirt 1
Since the reinforcing ring 13 is interposed between the lower end 11a of the outer tank 1 and the bottom end plate 9 of the outer tank 2, the inner tank 1
The load is distributed and transmitted to the bottom mirror plate 9 of the outer tank 2 without being concentrated. That is, the load of the inner tank 1 is
Since the load is transmitted via the welded portion between the bottom head plate 9 of the outer tank 2 and the bottom head plate 9 of the outer tank 2, the load of the inner tank can be distributed and transmitted to the bottom end plate 9 of the outer tank 2, unlike the conventional example.

Therefore, even if an external force such as an earthquake is applied to the inner tank 1, it is possible to reduce the stress concentration such as bending and shear force applied to the bottom end plate 9 of the outer tank 2 as much as possible. The strength of the outer tank head plate 9 can be improved accordingly.

In addition, when welding the lower end 11a of the inner tank skirt 11, it is attached to the horizontal surface of the reinforcing ring 13, so unlike the conventional case where it is attached directly to the curved bottom plate of the outer tank, 1. Installation welding work can be easily performed.

Furthermore, since the skirt 11 of the inner tank 1 is welded onto the horizontal surface portion of the reinforcing ring 13, which is maintained at the same horizontal level in advance, it becomes possible to easily ensure the horizontal level of the inner tank 1.

Further, since no large stress concentration is applied to the welded portion between the reinforcing ring 13 and the bottom end plate 9 of the outer tank, the amount of fillet in this portion can be reduced and the welding work can be simplified.

In addition, in this embodiment, by shortening the length of the inner tank skirt 11, the distance between the inner tank head plate 7 and the outer tank head plate 9 is shortened compared to the conventional example, so that low-temperature storage liquid can be maintained. Cold heat tends to be easily conducted to the outer tank head plate 9, and frost tends to form here. However, since the heating means 15 is provided in this area, the outer tank head plate 9 is heated using this as a heat source. frost does not form here. That is,
Since the outer tank end plate 9 is heated by a heating medium such as heated nitrogen gas supplied into the heating medium passage 16 from the heating medium supply pipe 17, the distance between the end plates 7 and 9 of the inner and outer tank is smaller than in the conventional example. Even though they are close to each other, frost formation on the outer tank end plate 9 can be prevented. In this manner, by providing the heating means 15 on the outer tank end plate 9, the distance between the end plates 7 and 9 of the inner and outer tanks can be reduced without causing frosting, and the overall size of the tank can be reduced.

In particular, in this embodiment, the closed space s formed by the L-shaped steel 14 forming the reinforcing ring 13 and the bottom inner wall surface 12 of the outer tank 2 is used as the heating medium passage 16 forming the heating means 15. , the heating means 15 can be formed without using any special equipment.

[Effects of the invention] In summary, according to the present invention, the following excellent effects can be achieved.

(1) Since the inner tank is supported and fixed to the bottom of the outer tank via a reinforcing ring, the load on the inner tank can be distributed and stress concentration can be alleviated.

(2) Therefore, the strength of the bottom end plate of the outer tank can be improved by that amount, and the durability and safety of the tank can be improved as much as possible.

(3) Since the inner tank is mounted on the reinforcing ring which is in a horizontal state in advance, the horizontal level of the inner tank can be easily ensured.

(4) By providing a heating means on the bottom end plate of the outer tank, the distance between this end plate and the inner tank end plate can be shortened without causing frost formation on the outer tank end plate, thus making the tank itself more compact. It is possible to achieve this and reduce material costs.

(5) Since the reinforcing ring component (L-shaped steel) constitutes the heating medium passage, which is a component of the heating means, the heating means can be installed while suppressing cost increase.

[Brief explanation of the drawing]

Figure 1 shows 2 having an inner tank support structure according to the present invention.
FIG. 2 is a longitudinal cross-sectional view showing a heavy shell tank, FIG. 2 is a cross-sectional view along the line taken along the line in FIG. 1, FIG. 3 is an enlarged cross-sectional view showing the inner tank support structure according to the present invention, and FIG. 4 is a conventional inner tank. FIG. 2 is a longitudinal cross-sectional view showing a double shell tank having a support structure. In the figure, 1 is an inner tank, 2 is an outer tank, 9 is a head plate as the bottom of the outer tank, 11 is an inner tank skirt, 12 is a bottom inner wall surface, 13 is a reinforcing ring, 15 is a heating means,
16 is a heating medium passage, 17 is a heating medium supply pipe, 1
8 is a heating medium discharge pipe.

Claims (1)

[Scope of utility model registration request] An inner tank that is housed in the outer tank and substantially contains a low-temperature storage liquid is supported on the bottom side of the outer tank via an annular inner tank skirt that extends downward from the lower part of the inner tank. In the inner tank support structure of the double shell tank, an annular reinforcing ring is formed on the bottom inner wall surface of the outer tank along its circumferential direction in order to disperse the inner tank load, and the inner tank skirt is attached to the reinforcing ring. An inner tank support structure for a double shell tank, characterized in that a lower end is attached and a heating means is formed along the reinforcing ring to heat the bottom of the outer tank.