JPH0214591B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to piping with a double-pipe structure, and in particular to a pipe that absorbs the difference in expansion and contraction caused by the temperature difference between the inner pipe and the outer pipe that make up the double pipe. This invention relates to piping with a double pipe structure.

[Conventional technology]

Generally, piping with a double pipe structure is used for the jacket method and for the purpose of protecting heat and cold insulation materials in buried areas. Furthermore, in recent years, technical standards for pipelines for petroleum, etc. under the Fire Service Act require measures to be taken to prevent leakage and diffusion when installing pipes in urban areas, rivers, tunnels, roads, and other locations specified by public notice. (Article 28 of the Fire Service Act)
22), especially when crossing rivers or roads, pipes with a double pipe structure are used.

Such double-tube structure piping requires treatment to absorb the difference in expansion and contraction caused by the temperature difference between the inner tube and the outer tube.

Therefore, in the past, steel plate ribs or rubber spacers were attached to the inner pipe to prevent direct contact between the inner and outer pipes, and steel plate ribs were installed at appropriate positions near the curved pipe or on the straight pipe. It has been common practice to weld plates to the inner and outer tubes to secure the inner and outer tubes together.

However, in such double-tube structure piping, the inner and outer tubes are connected and fixed by steel materials, which limits the expansion and contraction caused by the temperature difference between the inner and outer tubes, and the ribs and rib welds. Excessive stress (thermal stress) was generated in the piping, and there was a risk that the piping would be destroyed.

Therefore, conventionally, an expansion absorbing portion is provided in the outer tube before and after the fixed portion of the outer tube and the inner tube in the longitudinal direction to prevent the generation of the above-mentioned thermal stress (Japanese Patent Laid-Open No. 48-69115).

[Problem that the invention seeks to solve]

Piping has a straight section and a bent section, and at this bent section, measures are taken to prevent concentrated stress from occurring at the bent section due to expansion and contraction of the straight section, and to avoid direct contact between the inner and outer pipes at the bent section. In order to make the expansion absorbing portion of the outer tube work effectively, it is common to fix the inner and outer tubes.

Therefore, in conventional piping in which an expansion absorption part is provided in the outer pipe, it is necessary to provide an expansion absorption part before and after the fixed part of each bend at each bent part, and the generation of thermal stress at the bend can be avoided. This is difficult, and there are also difficulties in manufacturing the double pipe. Furthermore, since the expansion/absorption section frequently expands/contracts and moves back and forth, there is a risk that the airtightness of the expansion/absorption section for preventing leakage may be impaired.

The present invention has been made in view of the above circumstances, and can suitably be applied to piping for rivers, roads, etc.
It is an object of the present invention to provide piping with a double pipe structure that can inexpensively and effectively absorb the difference in the amount of expansion and contraction between inner and outer pipes due to temperature changes.

[Means for solving problems]

According to the present invention, in piping having a double pipe structure consisting of a combination of a straight pipe and a curved pipe, in which spacers small enough to allow play between the inner pipe and the outer pipe are fixed to the inner pipe at appropriate intervals, A substantially crank-shaped crank part spaced from the ground surface is provided in a part of the pipe, and a sleeve-type expansion joint is provided in the straight pipe part of the outer pipe.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of piping having a double pipe structure according to the present invention, and shows an example of laying a heated fluid transport line when crossing a river. In the same figure, this pipe has a double pipe structure consisting of an inner pipe 1 and an outer pipe 2, and has a crank-like shape consisting of four bent parts 3a to 3d and five straight pipe parts 4a to 4e. It is laid down. In addition, the straight pipe parts 4a, 4c, 4
The pipe e is laid horizontally, and the straight pipe parts 4b and 4d, which correspond to the above-mentioned crank-shaped crank arms, are laid vertically.

In addition, the inner tube 1 is provided with spacers 5, 5', at appropriate intervals.
5'' is attached, and is loosely inserted into the outer tube without directly contacting the outer tube 2 with this spacer, and the inner and outer tubes are not fixed at the bends 3a to 3d.On the other hand, the outer tube 2 has a An expansion joint section 6 is provided.

FIG. 2 is a cross-sectional view of this double-pipe structure, and particularly shows the straight pipe section laid horizontally.
In the figure, a heat insulating material 7 is stretched on the outside of the inner pipe 1 in consideration of the temperature drop of the transport fluid, and a spacer 5 is attached to the outside of the heat insulating material 7 to prevent it from coming into direct contact with the outer pipe 2. ing. The heat insulating material 7 is made of a molded product such as calcium silicate or a urethane foaming agent, and can be applied not only to the outside of the inner tube 1 but also to the outside of the outer tube 2.

Also, what should be noted here is that, as is clear from FIG. 2, a gap is intentionally provided between the spacer 5 and the inner wall of the outer tube. This gap varies depending on the thickness of the heat insulating material 7, the elongation rate of the pipe, the height of the spacer 5, and the method of assembling the double pipe, but is preferably about 2 to 5 cm. If the gap is larger than this, the outer pipe size will become thicker, which is uneconomical. On the other hand, if the gap is smaller than this, there will be little absorption of the difference in expansion and contraction between the inner and outer pipes, and the expansion joint part 6 of the outer pipe 2 will always work, so the same joint The durability of the material deteriorates, and the workability also deteriorates.

Note that the spacer 5 is preferably made of a non-conductive material such as plastic, rubber, or ceramics, but especially for the spacer 5' in the vertical straight pipe portions 4b and 4d in FIG. Since a pushing force acts on the spacer 5'' and the weight of the vertical straight pipe sections 4b and 4d acts on the spacer 5'', it is necessary to consider the amount of expansion/contraction and the size of the pipes and consider making the spacer 5'' made of steel plate. In this case, at least the inner wall of the outer tube is insulated with a non-conductive material to prevent the current that normally flows through the inner tube for cathodic protection from flowing into the outer tube. Further, the shape of the spacer may be any shape such as a rib shape, a gear shape, or a getter shape.

On the other hand, the mounting gap for the spacer is determined by taking into account the diameter of the pipe, the contents of the inner pipe, the strength of the heat insulating material, the strength of the spacer, etc., and is generally about 2 to 5 m, but for the same reason as above. It is preferable to attach them at relatively short intervals in locations where large forces are applied.

FIG. 3 is a partial cross-sectional view of the straight pipe section 4c in FIG.
In particular, the structure of the expansion joint 6 of the outer tube 2 is shown. In the figure, a sleeve 6a that surrounds the end of the other outer tube is attached to the end of one of the separated outer tubes. A sealing member 6b is disposed in the gap between the tip of the sleeve 6a and the outer tube, and the sealing member 6b is held at the tip of the sleeve by a stopper 6c fixed to the tip of the sleeve. It's summery.

Therefore, when a longitudinal force acts between the two outer tubes sandwiching the expansion joint 6, the seal member 6b and the outer tube circumferential surface with which it comes into contact become a sliding surface, causing the two outer tubes to move between each other. It will move and absorb said longitudinal forces, ie the movement between the two outer tubes.

The vicinity of both ends of the expansion joint 6 is supported by a pipe support stand 8 so that the expansion joint 6 can expand and contract in the axial direction correctly, and U-bolts are installed to prevent the pipe from falling from the pipe bridge during an earthquake. It is attached to the piping support stand 8 by 9.

Next, the action of this double pipe structure piping will be explained.

In the horizontal straight pipe parts 4a, 4c, 4e (first
), when the difference in expansion and contraction in the longitudinal direction of the inner and outer tubes acts on the vertical straight tube sections 4b and 4d, the expansion and contraction difference is due to the gap between the spacer 5' and the inner wall of the outer tube in the vertical straight tube sections 4b and 4d. Absorbed primarily.

If the expansion/contraction difference exceeds the amount absorbed by the gap, the spacer 5' will come into contact with the inner wall of the outer tube and press the outer tube, but this pressing force will cause the expansion joint 6 of the outer tube to Since it expands and contracts, the pressing force, that is, the amount of expansion and contraction that exceeds the amount absorbed by the gap is secondarily absorbed here.

On the other hand, if a difference in expansion/contraction occurs in the longitudinal direction of the inner and outer tubes in the vertical straight pipe parts 4b, 4d, the difference in expansion/contraction occurs in the horizontal straight pipe parts 4a, 4c, 4d, as described above.
It is absorbed by the gap between the spacer and the inner wall of the outer tube at point e. In addition, in relatively short portions such as the vertical straight pipe portions 4b and 4d, the difference in expansion and contraction is small and the above-mentioned gap can sufficiently absorb the difference, so there is no need to further provide an expansion joint portion in the outer tube.

In this way, this double-tube structure piping can absorb the difference in expansion and contraction both at the gap between the spacer and the inner wall of the outer tube and at the expansion joint.

In this embodiment, an example of laying pipes when crossing a river has been described, but the present invention can be applied to crossing a road or any other place where three-dimensional pipes are required. In addition, the shape of the piping is not limited to the crank shape of this example, but various shapes can be considered, such as piping with one approximately 90° L-shaped bend, or one obtuse-angled (rectangular) bend. This includes any type of piping that has one or a combination of these. FIGS. 4a and 4b show other examples of piping including the above-mentioned L-shaped and rectangular bent portions, respectively. Note that the xy plane indicates a horizontal plane.
Of course, you can use a variant of either one. Figure 4a shows a pipe consisting of a combination of one L-shaped bend and two dog-shaped bends,
FIG. 4b shows a pipe consisting of a combination of three L-shaped bends.

Further, the expansion joint may be of any type as long as it is expandable and contractible and sufficiently watertight to prevent leakage and diffusion, but a sleeve type is preferred because the reaction force during operation is small and it is relatively inexpensive. Furthermore, the location and number of expansion joints are not limited to those in this embodiment. Furthermore, the end of the inner pipe is connected to a pump, tank, etc., but the end of the outer pipe may be left open to prevent leakage and diffusion, or it may be used to connect various fluids between it and the inner pipe. It can also be of a closed type for passage.

〔Effect of the invention〕

As explained above, according to the present invention, a crank portion spaced apart from the ground surface is provided in a part of the piping having a double pipe structure in which spacers are interposed between the inner pipe and the outer pipe at appropriate intervals. Therefore, it can be suitably applied to three-dimensionally shaped pipes, such as those that cross rivers and roads, regardless of location conditions. Further, a sleeve-type expansion joint is provided in the straight pipe part of the outer pipe,
Since the expansion and contraction of the piping is simply absorbed in the axial direction of the piping, the design becomes easier and the equipment cost can be reduced. Furthermore, there is no need to fix the inner and outer pipes to each other, which simplifies construction.
Furthermore, since there are no fixed points around the perimeter, it is easy to prevent heat dissipation from fixed points and to insulate against cathodic protection.

Therefore, it can be advantageously applied to the installation of double pipes for preventing leakage and diffusion, pipes for transporting various high-temperature or low-temperature fluids, and the like.

[Brief explanation of drawings]

Fig. 1 is an overall conceptual diagram showing an embodiment of piping with a double pipe structure according to the present invention, Fig. 2 is a sectional view showing the double pipe structure of Fig. 1, and Fig. 3 is an expansion/contraction diagram of Fig. 1. FIG. 4 is a partial cross-sectional view showing the structure of the joint portion, and is a diagram of another piping shape to which the double pipe structure piping according to the present invention is applied. 1...Inner pipe, 2...Outer pipe, 3a to 3d...Bent part, 4a to 4e...Straight pipe part, 5, 5', 5''...
Spacer, 6... Expandable joint, 7... Insulating material, 8
...Piping support stand, 9...U bolt.

Claims (1)

[Scope of Claims] 1. In a pipe with a double pipe structure consisting of a combination of a straight pipe and a curved pipe, in which spacers small enough to allow play between the inner pipe and the outer pipe are fixed to the inner pipe at appropriate intervals. A double-pipe structure piping comprising: a substantially crank-shaped crank part spaced from the ground surface in a part of the piping; and a sleeve-type expansion joint in the straight pipe part of the outer pipe. 2. The double pipe structure piping according to claim 1, wherein the sleeve type expansion joint is provided in a straight pipe section of the crank section.