JP2002181235A - Buried pipe device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compactify size as the whole to reduce a construction cost, when an LNG of a low temperature is transported by piping buried in the ground. SOLUTION: When the LNG is transported by a pipe 11 made of Invar, thermal stress is reduced since a linear expansion coefficient is small, and a sheath pipe 14 of relatively small diameter is allowed to be buried underground since a loop shape is not required therein. A periphery of the Invar-made pipe 11 is coated with an urethane-made cold insulator 12, and an outer tube 13 is used in order to prevent deformation when inserted into the sheath pipe 14. A clearance part 16 is formed between the cold insulator 12 and the outer tube 13 by an urethane-made protrusion 15. Heated air or the like is made to flow in the clearance part 16 to prevent an influence of the low temperature of the LNG from reaching to the sheath pipe 14, so as to prevent lowering in strength of the sheath pipe 14 and freezing of a peripheral soil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burying a pipe for transporting a fluid having a large temperature difference from the surrounding ground, for example, liquefied natural gas at a very low temperature (hereinafter abbreviated as "LNG"). Buried piping equipment.

[0002]

2. Description of the Related Art Conventionally, for example, in an LNG base for producing city gas from LNG as a raw material, a transportation pipe 1 is provided on the ground as shown in FIG. Piping 1
For example, when made of a metal such as stainless steel or the like, and a very low temperature fluid such as LNG at about −160 ° C. flows through such a metal pipe 1, thermal stress is generated. If the pipe 1 is long, thermal stress may be superimposed, resulting in an excessive force.
The pipe 1 through which a fluid having a large temperature difference from the surroundings has a loop shape 2 in order to absorb the generated thermal stress. Even if thermal stress is generated in the pipe 1, an excessive force is not applied to the entire pipe 1 because the thermal stress is relieved at the loop shape 2. The pipe 1 has an inner diameter of, for example, 300 mm, and is formed with a loop shape 2 protruding laterally by about 3 m at intervals of about 50 m.

In some cases, it is necessary to pass a pipe 1 for transporting LNG or the like through a tunnel 3 that crosses the lower part of the sea, river, road, or mountain. Even in the tunnel 3, it is necessary to form the loop shape 2.

[0004]

The tunnel 3 as shown in FIG. 5 needs to pass through the pipe 1 having the loop shape 2 and therefore has a large sectional area. For example, when the loop shape 2 projects about 3 m in the lateral direction as described above, the inside diameter of the tunnel 3 needs to be about 4 m. Installing the tunnel 3 having a diameter of about 4 m in order to pass the pipe 1 having an inner diameter of about 300 mm causes an increase in the installation cost of the pipe 1.

[0005] An object of the present invention is to provide a buried piping device capable of reducing the cross-sectional area when buried in the ground and reducing the installation cost.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a buried piping apparatus for transporting a fluid buried underground and having a large temperature difference from the ground, and is used for transporting a fluid and having a low coefficient of linear expansion. With the pipe made of and heat insulation material surrounding the pipe,
A buried piping device comprising: a sheath tube for accommodating a pipe covered with a heat insulating material with a gap; and a temperature difference reducing means for reducing a temperature difference at a gap between the sheath tube and the heat insulating material. .

According to the present invention, the buried piping device transports a fluid buried in the ground and having a large temperature difference from the ground by piping. The piping for fluid transport is made of a material having a low coefficient of linear expansion. The periphery of the pipe is covered with a heat insulating material. The sheath covered by the heat insulating material is stored with a gap between the sheaths. The temperature difference reducing means reduces the temperature difference at the gap between the sheath and the heat insulating material. Since the pipe is made of a material having a low coefficient of linear expansion, a large thermal stress is not generated even when a fluid having a large temperature difference from the ground is transported. The periphery of the pipe is covered with a heat insulating material, and the pipe covered with the heat insulating material is stored with a gap in the sheath. The gap between the sheath and the heat insulating material is provided with a temperature difference mitigation means to reduce the temperature difference, so the effect of the temperature of the fluid transported through the piping extends only to the gap between the sheath and the heat insulating material. And it does not reach the ground outside the sheath. Since a material having a low coefficient of linear expansion is used for the pipe, it is not necessary to provide a loop shape or the like for relaxing thermal stress in the pipe, and the inner diameter of the sheath can be reduced. Since the diameter of the sheath tube can be reduced, the installation cost of the sheath tube can be reduced.

Further, in the present invention, the pipe is characterized by transporting a fluid having a temperature of 0 ° C. or less.

According to the present invention, even if a fluid having a temperature of 0 ° C. or less is transported through a pipe, the influence of a low temperature can be prevented from reaching the sheath.

In the present invention, the temperature difference mitigation means is characterized in that a temperature difference mitigation fluid is caused to flow through a gap between the sheath and the heat insulating material.

According to the present invention, the fluid for reducing the temperature difference flows through the gap between the sheath and the heat insulating material. Therefore, even if the influence of the temperature of the fluid transported from the pipe to the heat insulating material is transmitted, the temperature difference can be reduced. The effect of the temperature is reduced by the fluid, and the fluid can be hardly transmitted to the sheath.

Further, in the present invention, the temperature difference reducing means circulates the fluid for reducing the temperature difference.

According to the present invention, it is possible to reduce the energy required for reducing the temperature difference by circulating the fluid for reducing the temperature difference.

Further, in the present invention, the temperature difference reducing means includes an electric heater disposed between the sheath and the heat insulating material or in the heat insulating material.

According to the present invention, the electric heater is provided between the sheath and the heat insulating material or in the heat insulating material. Water can be prevented from freezing.

In the present invention, the material for manufacturing the pipe is as follows:
It is characterized by being an invar. According to the present invention, since invar is used as the material of the pipe for transporting the fluid, even if the temperature difference between the fluid and the surroundings is large, thermal stress can be prevented from being generated.

[0017]

FIG. 1 shows a schematic cross-sectional structure of a buried piping device 10 as one embodiment of the present invention. Invar piping 11 is used for transporting LNG. The periphery of the Invar pipe 11 is covered with a urethane cold insulator 12 as a heat insulating material. The urethane cold insulator 12 is housed in the outer tube 13 for preventing the collapse of the mold. The outer tube 13 is further housed in a steel sheath tube 14.
A gap 16 is provided between the inner peripheral surface of the outer tube 13 and the outer peripheral surface of the urethane cold insulator 12.
A urethane projection 15 protrudes from an outer peripheral surface of the outer tube 13, and a tip of the urethane projection 15 contacts an inner peripheral surface of the outer tube 13,
The gap 16 is maintained.

In the pipe 11 made of Invar, LNG at about -160 ° C. flows. When such a cryogenic fluid flows through the metal tube, the metal tube tends to shrink, generating thermal stress. The linear expansion coefficient of Invar is 1.7 × 10 ⁻⁶ / ° C.,
It is about 1/10 the size of stainless steel. For this reason, even if LNG passes, excessive thermal stress does not occur in the pipe 11 made of Invar, so that it is not necessary to provide the loop shape 2 as shown in FIG.

In order to prevent LNG from boiling due to heat input from the outside, a urethane cold insulator 1 is provided around the Invar pipe 11.
Cover with 2. When the inner diameter of the Invar pipe 11 is about 300 mm, the outer diameter of the urethane cold insulator 12 is 500 mm.
It is about. The urethane projection 15 further projects by about 100 mm from the outer peripheral surface of the urethane cold insulator 12. The sheath tube 14 has an inner diameter of about 700 to 800 mm. Since it is not necessary to provide the loop shape 2 shown in FIG. 5 in the pipe 11 made of Invar, the diameter of the sheath 14 can be made smaller than the diameter of the tunnel 3 shown in FIG.

The material of the sheath tube 14 is, for example, steel. The steel sheath tube 14 becomes brittle if it gets too cold. If the sheath 14 is cooled and the surrounding ground freezes over a wide area, the sheath 14 may be crushed by earth pressure and collapsed. The urethane cold insulator 12 also serves to prevent the steel sheath 14 from being overcooled.

FIG. 2 shows the buried piping device 10 shown in FIG.
The schematic cross section of the ground when passing through the seabed is shown. LNG
The base is located on the shore and may need to route the LNG piping 11 to the bottom of the sea 17. Buried piping equipment 10
Is installed to pass through the viscosity and mud layers at the bottom of the sea 17. As a construction order of the buried piping device 10, first, construction for installing the sheath 14 is performed. As a construction method, it can be pushed into the ground 18 at the bottom of the sea 17 by a propulsion method. In some cases, the ground 18 to be buried can be cut from the ground instead of the bottom of the sea 17 or the like, and the buried piping device 10 can be buried. In the propulsion method, a pipe smaller in diameter than the sheath pipe 14 is used.
It is pushed into the ground 18 from one side, and when it reaches the other side, it is pulled back and a larger pipe is pulled from the other side to the one side at the tip. When the leading end of the tube drawn from the other side reaches one side, it is drawn back to the other side again, at which time a tube with a larger diameter is drawn from one side. By such repetition, the sheath tube 14 can be installed in the ground 18 without cutting.

When the sheath 14 is installed in the ground 18,
Invar pipe 11 and urethane cold insulator 1 shown in FIG.
2. The outer tube 13 and the urethane projection 15 are integrally manufactured on the ground, and inserted into the sheath tube 14. If the outer tube 13 is not used, the urethane cold insulator 12 and the urethane protrusion 1
4 comes into direct contact with the inner peripheral surface of the sheath 14 and has a relatively low strength due to frictional resistance.
There is a possibility that the projections 2 and the urethane projections 15 will lose their shape. By covering the urethane cold insulator 12 and the urethane projections 15 with the outer tube 13, the role of preventing the mold from being lost is fulfilled. Although not shown, a roller or the like is attached around the outer tube 13 to further reduce frictional resistance,
Insertion into the sheath 14 can also be performed smoothly.

As described above, the sheath tube 14 serves to protect the internal structure against the earth pressure from the ground 18.
If the surrounding ground 18 freezes extensively, the sheath 14
The earth pressure acting on the air becomes very large. Therefore, it is necessary to make the temperature of the sheath tube 14 equal to or higher than 0 ° C. so that the water in the surrounding ground 18 does not freeze. However, even if the heat conduction is reduced by the urethane cold insulator 12, if the static state continues, the temperature in the sheath 14 decreases. In order to prevent this, a blower 19 and the like are installed with the gap 16 formed by the urethane cold insulator 12, the outer tube 13 and the urethane projection 15 as a flow path, and a temperature difference of air or heated air or the like is set. By flowing the relaxing fluid, it is possible to prevent the sheath tube 14 from being excessively cooled. If the gaps 16 divided by the urethane projections 15 are alternately circulated so that fluids in different directions flow, the energy required for humidification can be saved.

FIG. 3 shows a configuration in which the joint portion is double-covered with a urethane cold insulator 12 covering the periphery of the Invar pipe 11. The urethane cold insulator 12 has a thickness of, for example, about 100 mm as described above. The urethane cold insulator 12 having such a thickness is generally formed by winding a rectangular shape around the periphery of the Invar pipe 11. Therefore, at the joint of the ends of the urethane cold insulator 12 to be wound,
Gaps may be created. Therefore, another layer of the urethane cold insulator 12 is provided on the joint.

FIG. 4 shows a schematic sectional configuration of a buried piping device 20 as another embodiment of the present invention. In the present embodiment, portions corresponding to the embodiment of FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, like the embodiment of FIG.
Pass LNG at 0 ° C. Around the Invar pipe 11,
The electric heaters 21a, 21b, 21c, 21d are arranged. The electric heaters 21a to 21d are made of urethane cold insulator 2.
Embed in 2. The urethane cold insulator 22 is filled between the outer peripheral side of the Invar pipe 11 and the inner peripheral side of the outer pipe 13.

In this embodiment, the sheath tube 14 can be prevented from being excessively cooled by heating with the electric heaters 21a to 21d embedded near the outer periphery of the urethane cold insulator 22. The urethane cold insulator 22 of the present embodiment also has the urethane projections 15 with the urethane protrusions 15 such that the gaps 16 are formed as shown in FIG.
In this case, the electric heaters 21a to 21d may be embedded in the inside, and a fluid such as air may flow through the gap portion 16. The electric heaters 21a to 21d are not embedded in the urethane cold insulators 12 and 22,
It can also be placed on the surface.

In each of the embodiments described above, LNG is transported in the pipe 11 made of Invar. However, a low-temperature fluid such as ethylene at about -100 ° C. or liquefied nitrogen at about −190 ° C. It can also be applied to the transport of high-temperature steam or the like. However, when a high-temperature fluid is used, the fluid for reducing the temperature difference may be flowed by using the structure shown in FIG. 1 without using the electric heaters 21a to 21d as shown in FIG. The fluid for reducing the temperature difference can be circulated as described above.
By circulating the fluid, thermal energy for heating can be saved, especially when transporting cryogenic fluids.

Further, if the inside of the sheath tube 14 is made in a high vacuum state, the heat insulation performance can be further improved. If the type of fluid to be transported is different, a material whose linear expansion coefficient decreases in accordance with the temperature of the fluid may be used instead of the Invar pipe 11. Other materials include an Fe-Pd alloy and super Invar having a smaller linear expansion coefficient. Further, instead of the urethane cold insulators 12 and 22 and the urethane projections 15, for example, glass foam or glass wool may be used.
Other insulation can be used.

[0029]

As described above, according to the present invention, a pipe for transporting a fluid having a large temperature difference from the ground is made of a material having a low linear expansion coefficient. Even without the provision of the heat sink, the generation of thermal stress can be reduced, the diameter of the sheath to be buried in the ground can be reduced, and the cost required for installation can be reduced.

Further, according to the present invention, even when a fluid at a temperature of 0 ° C. or less is transported, the underground sheath is not affected by the low temperature, and a situation in which the sheath around the sheath freezes can be avoided. .

According to the present invention, the fluid for reducing the temperature difference flows in the gap between the sheath and the heat insulating material covering the circumference of the pipe, so that the influence of the fluid in the pipe through the heat insulating material is reduced. By not transmitting to the pipe side, it is possible to keep the temperature of the sheath pipe from largely changing from the temperature of the surrounding ground.

Further, according to the present invention, it is possible to circulate the fluid to save heat energy.

Further, according to the present invention, even if a low-temperature liquefied gas or the like flows in the pipe, the pipe is heated by the electric heater, so that the influence of the low temperature does not appear on the surface of the pipe, and the moisture in the ground, etc. Can be prevented from freezing.

Further, according to the present invention, since the pipe is manufactured by using Invar, the generation of thermal stress can be sufficiently reduced.

[Brief description of the drawings]

FIG. 1 shows a buried piping device 1 according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of a zero.

FIG. 2 is a sectional view showing a state in which the buried piping device 10 of the embodiment of FIG.

FIG. 3 is a partial cross-sectional view showing a heat insulating structure at a joint of a urethane cold insulator 12 in the buried piping device 10 of FIG.

FIG. 4 is a sectional view showing a schematic configuration of a buried piping device 20 as another embodiment of the present invention.

FIG. 5 is a perspective view showing a schematic configuration of a conventional pipe 1 in which a loop shape 2 is formed.

[Explanation of symbols]

 10, 20 Buried piping device 11 Invar piping 12, 22 Urethane cold insulator 13 Outer pipe 14 Sheath pipe 15 Urethane projection 16 Gap 17 Sea 18 Ground 19 Blowers 21a-21d Electric heater

Claims (6)

[Claims] 1. A buried piping device for transporting a fluid buried in the ground and having a large temperature difference from the ground, the piping being made of a material having a low linear expansion coefficient for fluid transport, Including a heat insulating material covering the periphery of the pipe, a sheath tube for housing the pipe covered by the heat insulating material with a gap, and a temperature difference mitigation means for reducing a temperature difference in a gap between the sheath tube and the heat insulating material. A buried piping device characterized by the following. 2. The buried piping device according to claim 1, wherein the piping transports a fluid having a temperature of 0 ° C. or less. 3. The burying device according to claim 1, wherein the temperature difference reducing unit flows a fluid for reducing a temperature difference through a gap between the sheath and the heat insulating material. Plumbing equipment. 4. The buried piping device according to claim 1, wherein the temperature difference reducing means circulates the temperature difference reducing fluid. 5. The apparatus according to claim 1, wherein the temperature difference reducing unit includes an electric heater disposed between the sheath and the heat insulating material or in the heat insulating material. Buried piping equipment. 6. The buried piping device according to claim 1, wherein the material for forming the piping is invar.