WO2005082747A1

WO2005082747A1 - Low-temperature pc tank and method for constructing and operating low-temperature pc tank

Info

Publication number: WO2005082747A1
Application number: PCT/JP2005/002871
Authority: WO
Inventors: Fumio Kamada; Takeyoshi Nishizaki; Tomoki Ushida
Original assignee: Obayashi Corporation; Osaka Gas Co., Ltd.
Priority date: 2004-03-01
Filing date: 2005-02-23
Publication date: 2005-09-09
Also published as: JP2005247324A

Abstract

Disclosed is a low-temperature PC tank (10) for storing a low-temperature liquid (21) wherein a bottom plate (14) and a side wall (16) are constructed integrally and the bottom plate (14) is provided with a heating means (26). The low-temperature PC tank (10) also comprises a PC steel member (30) for applying prestress to the bottom plate (14) and a temperature-setting unit (28) for regulating the temperature to which the bottom plate (14) is heated by the heating means (26) lower than the ambient temperature.

Description

Specification

Low-temperature PC tank, construction and operation method of low-temperature PC tank

Technical field

The present invention relates to a low-temperature PC tank for storing a low-temperature substance such as liquefied natural gas or liquefied petroleum gas, which has a configuration in which a bottom plate and a side wall are integrally connected, and a construction and operation method of the low-temperature PC tank.

Background art

[0002] As a cylindrical tank for storing low-temperature liquids such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG), a PC (Pre-stressed Concrete) tank with an integrated bottom plate and side walls is used. Can be In this PC tank, PC steel (tendon) is used to introduce prestress in the circumferential direction and vertical direction of the side wall, and this prestress can ensure resistance to loads such as pressure of liquid stored in the tank. Like that. By the way, the stress generated on the side wall due to the pressure of the liquid inside the tank is greatest at the lower part of the side wall, and the lower part of the side wall is the most important part in the tank structure. However, when the bottom plate and the side wall of the PC tank are integrated, it is difficult to introduce sufficient prestress to the bottom of the side wall because the bottom of the side wall is restrained by the bottom plate.

[0003] Therefore, conventionally, for example, as disclosed in Japanese Patent Publication No. 3-20548, an annular opening is provided near the outer peripheral edge of the bottom plate to divide the bottom plate into an outer peripheral portion and an inner peripheral portion. A configuration has been proposed. According to the strong structure, the degree of restraint of the side wall by the bottom plate is greatly reduced as compared with the case where the bottom plate is formed as an integral structure, and sufficient prestress can be applied to the lower portion of the side wall.

Disclosure of the invention

Problems to be solved by the invention

[0004] However, in the configuration described in Japanese Patent Publication No. 3-20548, the bottom plate must be divided into an outer peripheral portion and an inner peripheral portion, and the side wall is prestressed. Later, it is necessary to cast concrete into the annular opening of the bottom slab and connect the divided outer and inner perimeters, which is extremely labor-intensive. [0005] The present invention has been made in view of the above points, and a low-temperature PC tank and a low-temperature PC tank capable of introducing a sufficient prestress into a lower portion of a side wall without requiring laborious work such as division of a bottom plate. The purpose is to provide a construction operation method.

Means for solving the problem

[0006] In order to achieve the above object, the present invention provides a low-temperature PC tank for storing low-temperature substances, wherein a bottom plate and a side wall are integrally formed, and a heating means is provided in the bottom plate.

A prestressing means for introducing a prestress to the bottom plate,

Temperature setting means for setting a heating temperature of the bottom plate by the heating means to be lower than an environmental temperature at the time of construction.

[0007] According to the present invention, by setting the temperature of the bottom plate of the PC tank to a temperature lower than the environmental temperature at the time of construction to contract the volume of the bottom plate, prestress can be effectively introduced to the lower portion of the side wall. . Also, since prestress is introduced into the bottom slab, cracking of concrete due to shrinkage can be prevented. The “environmental temperature at the time of construction” means the environmental temperature from the completion of the PC tank until the injection of low-temperature substances to be stored. It is preferable that the set temperature of the bottom slab be as low as possible in terms of management (however, not less than o ° c).

[0008] In the present invention, the bottom plate preferably has a substantially constant thickness. In this way, a large load can be transmitted to the side wall by the shrinkage of the bottom slab, so that prestress can be effectively introduced into the lower part of the side wall.

[0009] The present invention also relates to a method of constructing and operating a low-temperature PC tank for storing low-temperature substances, wherein a bottom plate and a side wall are integrally formed and provided with a heating means inside the bottom plate, wherein the bottom plate is operated. After the completion of the low-temperature PC tank, the heating means is used to store the low-temperature material after the completion of the low-temperature PC tank. Is set to a temperature lower than the environmental temperature at the time of construction.

[0010] <Cross reference with related documents>

This application claims the priority based on Japanese Patent Application No. 2004-55885 filed on March 1, 2004. This document is incorporated herein by reference.

Brief Description of Drawings

FIG. 1 is a front view of a PC tank according to one embodiment of the present invention. Indicated by

FIG. 2 is an enlarged vertical sectional view showing a side wall portion of a PC tank.

FIG. 3 is a perspective view showing a structure for introducing prestress into a bottom plate of a PC tank.

FIG. 4 is a diagram schematically showing stress acting on the side wall due to the internal pressure of the low-temperature liquid stored in the PC tank, pre-stress introduced into the side wall by tendons, and prestress introduced into the side wall due to shrinkage of the bottom plate. is there.

Explanation of symbols

[0012] 10 PC tank 12 Ground

14 Bottom plate 16 Side wall

18 Foundation pile 19, 20 tendon

21 Cryogenic liquid 22, 24 Coolant

26 Heating means 28 Temperature setting section

30 PC steel

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a front view of a PC tank 10 according to one embodiment of the present invention, and the left side in the figure is shown in a vertical cross section. FIG. 2 is an enlarged vertical sectional view showing the side wall of the PC tank 10. As shown in FIG. The PC tank 10 is, for example, a low-temperature PC tank that stores a low-temperature liquid 21 such as LNG or LPG.

[0014] The PC tank 10 is made of concrete in which the bottom slab 14 and the side wall 16 are joined together. The bottom plate 14 is supported on the ground 12 by a foundation structure, for example, a foundation pile 18.

As shown in FIG. 2, tendons 19 and 20 are arranged on a side wall 16 of the PC tank 10 in a vertical direction and a circumferential direction. These tendons 19 and 20 introduce vertical and circumferential prestress into the side wall 16, which causes the pressure of the low-temperature liquid 21 (LNG or LPG) stored inside the PC tank 10, etc. It is possible to secure the resistance to the load. Cooling materials 22 and 24 are provided on the upper surface of the bottom plate 14 and the inner wall surface of the side wall 16, and the low-temperature liquid 21 is accommodated inside them. The upper part of the PC tank 10 is covered with a roof 25. [0016] The bottom plate 14 is provided with a heating means 26. The heating means 26 may be, for example, an electric heater such as a heating wire or a hot water pipe through which a heated antifreeze flows. The temperature setting section 28 controls the heating temperature of the bottom plate 14 by the heating means 26. More specifically, the bottom plate 14 is provided with a temperature sensor (not shown), and the temperature setting unit 28 specifies the heating temperature of the bottom plate 14 by the heating means 26 based on the temperature detected by this temperature sensor. Control to temperature.

The heating means 26 has a role of preventing the tank from being adversely affected by the freezing of the ground under the bottom plate 14 due to the cold heat of the stored liquid when the low-temperature liquid 21 is stored in the PC tank 10. That is, after the construction of the PC tank 10, when the low-temperature liquid 21 is injected into the PC tank 10, the heating means 26 heats the bottom plate 14 so that the temperature of the bottom plate 14 decreases from the temperature at the time of construction. This prevents cracks, cracks, the formation of lenticular or layered ice on the upper surface of the bottom slab due to the lowering of the upper surface force of the bottom slab, and the freezing of the ground under the lower slab. The heating means 26 is intended to prevent the cracks caused by the temperature drop of the bottom plate 14 by heating the bottom plate 14 so as to keep the temperature of the bottom plate 14 substantially equal to the temperature at the time of construction (that is, the environmental temperature). In the PC tank 10, as described below, the heating temperature of the bottom plate 14 is set to a temperature sufficiently lower than the environmental temperature by the temperature setting unit 28, and the prestress is introduced into the bottom plate 14 by the PC steel material 30. In addition, while preventing the bottom plate 14 from being cracked, the pre-stress can be smoothly introduced into the side wall 16 by effectively utilizing the change in volume.

FIG. 3 is a perspective view showing a structure for introducing prestress into bottom plate 14. As shown in the figure, inside the bottom plate 14, PC steel materials 30 are arranged in two plane directions. Tension is applied to these PC steel materials 30, and the end of each PC steel material 30 is fixed to the outer peripheral surface of the bottom plate 14, so that in-plane prestress is introduced into the bottom plate 14.

When constructing the PC tank 10 of the present embodiment, a foundation such as a foundation pile 18 is constructed on the ground, and concrete of the bottom slab 14 is embedded thereon, and the PC steel material 30 and the heating means 26 are embedded therein. It is cast so that it is done. Furthermore, the concrete on the side wall 16 is cast into the bottom slab 14 integrally from the bottom so that the tendons 19 and 20 are embedded, and tension is applied to the tendons 19 and 20 to fix the prestress on the side wall 16. Introduce. The bottom plate is made of PC steel 30 The prestress is introduced at 14 at an arbitrary force S, preferably at the timing when the concrete at the bottom of the side wall 16 is cast. The reason is that after the concrete is placed on the side wall 16, heat is generated and then shrinks in the cooling process, so that the side wall 16 is apt to crack. This is because the degree of restraint of the side wall 16 is reduced by the shrinkage of the bottom plate 14 that restrains shrinkage, and an effect of suppressing cracking of the side wall 16 can be expected.

[0020] After the concrete of the side wall 16 is cast in this way, the roof 25 and the cold insulators 22 and 24 are constructed, and the PC tank 10 is completed. Then, the inside of the completed PC tank 10 is cooled, and then the cryogenic liquid 21 to be stored is poured. At this time, the bottom plate 14 is heated by the heating means 26 carried on the bottom plate 14 to suppress a temperature drop of the bottom plate 14.

In the present embodiment, the heating temperature of the bottom plate 14 by the heating means 26 is set to a temperature lower than the ambient temperature (for example, 20 ° C.) (but higher than 0 ° C.) by the temperature setting unit 28; For example, it is set to 5 ° C-15 ° C). By lowering the bottom plate 14 to a temperature lower than the ambient temperature, the bottom plate 14 is contracted, whereby the lower portion of the side wall 16 is drawn toward the center of the tank, thereby prestressing the side wall 16. Is introduced.

FIG. 4 shows the stress generated on the side wall 16 due to the internal pressure of the low-temperature liquid stored in the PC tank 10, the prestress introduced into the side wall 16 by the tendons 19 and 20, and the shrinkage of the bottom plate 14. 16 schematically illustrates the pre-stress introduced into 16. As shown in the figure, since the lower end of the side wall 16 is constrained by the bottom slab 14, it is difficult to introduce sufficient prestress into the lower part of the side wall using only the tendons 19 and 20, but the hatching is shown in the figure. As shown, if a prestress due to the contraction of the bottom plate 14 is introduced, a sufficient prestress that can resist the internal pressure of the liquid can be secured also at the lower part of the side wall 16. In other words, the amount of prestress to be introduced at the tendons 19 and 20 can be reduced by the prestress introduced by the contraction of the bottom slab 14, so that the work of introducing the prestress to the side wall 16 can be simplified.

[0023] In addition, although a tensile force is generated in the bottom plate 14 due to shrinkage of the bottom plate 14, in the present embodiment, cracks are generated in the bottom plate 14 by introducing prestress into the bottom plate 14 with the PC steel material 30. Can be prevented. As described above, according to the present embodiment, prestress is introduced into the bottom plate 14 without dividing the bottom plate 14 to perform troublesome work, and the temperature of the bottom plate 14 during operation of the tank is reduced. By setting, sufficient prestress can be introduced into the lower part of the side wall 16 while preventing the bottom plate 14 from cracking.

Further, in the present embodiment, since the temperature of the bottom plate 14 is set lower than in the past, the amount of energy required for heating the bottom plate 14 can be reduced. Therefore, since the size of the heating means 26 can be small, the construction cost can be reduced, and the energy consumption is reduced, so that the operation cost can be reduced.

[0026] Further, by setting the temperature of the bottom plate 14 to be lower, the amount of heat input to the low-temperature liquid 21 stored in the tank from the bottom of the tank is also reduced, so that the cooling performance of the PC tank 10 is improved. For this reason, it is possible to reduce the volume of the vaporized gas processing equipment by reducing the amount of generated vaporized gas, and to reduce the thickness of the cold insulator 22 at the bottom and to lower the performance of the heat insulating material. It is also possible to reduce equipment costs.

[0027] Conventionally, the bottom plate of the PC tank generally has a configuration in which only the outer peripheral portion to which the side wall is connected is thickened and the inner peripheral portion is thinned. By making the value substantially constant, it is possible to effectively introduce prestress into the side wall 16 by contraction of the bottom plate 14.

[0028] In addition, when constructing the bottom slab 14, if the entire concrete is cast at once, it may be difficult to cast the whole at once due to factors such as the force of the concrete and the capacity of the concrete manufacturing equipment. The prestress may be introduced by dividing the bottom slab into sectors, rectangles, or rings, etc. In such a case, by introducing prestress into the surface of the bottom slab, it is easy and reliable to secure the liquid tightness and the waterproofness at the joint of the divided and poured concrete.

Industrial potential

According to the present invention, it is possible to introduce a sufficient prestress to the lower portion of the side wall without requiring a troublesome work such as dividing the bottom plate.

Claims

The scope of the claims

[1] A low-temperature PC tank for storing a low-temperature substance, wherein a bottom plate and a side wall are integrally formed and provided with heating means in the bottom plate,

A prestressing means for introducing a prestress to the bottom plate,

A low-temperature PC tank comprising: a temperature setting unit that sets a heating temperature of the bottom plate by the heating unit to be lower than an environmental temperature at the time of construction.

2. The low-temperature PC tank according to claim 1, wherein the bottom plate has a substantially constant thickness.

[3] A method of constructing and operating a low-temperature PC tank for storing a low-temperature substance, wherein a bottom plate and a side wall are integrally formed and provided with a heating means in the bottom plate, wherein the bottom plate is constructed and pressed. A tress is introduced, a side wall is constructed integrally with the bottom plate, and a prestress is introduced into the side wall. After completion of the low-temperature PC tank, the low-temperature material is stored by the heating means when the low-temperature material is stored. A method of building and operating a low-temperature PC tank, which is set at a temperature lower than the temperature.