JPS6124889A - Piping having double pipe structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Conventional technology]

In general, 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, under the fire service law, etc., the technical standards for piping lines for petroleum, etc. require that all tanks be equipped with measures to prevent leakage and diffusion when piping is installed in urban areas, over rivers, over shaded roads, on roads, and other locations specified by public notice. (Article 28-22 of the Fire Service Act), and especially when crossing rivers or roads, piping with a double pipe structure is 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, the inner pipe was constructed with steel plate glue or rubber material attached to it to prevent direct contact between the inner pipe and the outer pipe, and the construction was carried out at appropriate locations near bent pipes and straight pipes. It was common practice to weld steel rib plates to the inner and outer tubes to fix the inner and outer tubes together.

However, in such double-tube structure piping, the inner and outer tubes are connected and fixed by steel, which limits the expansion and contraction caused by the temperature difference between the inner and outer tubes, and the piping at the rib and lip welds. There was a risk that excessive stress (thermal stress) would occur and 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 occurrence of the above-mentioned thermal stress (Japanese Patent Laid-Open No. 48-6911
5).

[Problem that the invention seeks to solve]

Piping has a straight section and a bent section, and the curved section prevents the generation of concentrated stress at the bent section due to expansion and contraction of the straight section, and prevents direct contact between the inner and outer pipes at the bent section. In order to avoid this, and 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 absorbing part is provided in the outer pipe, it is necessary to provide an expansion absorbing part before and after the fixed part of the curved part for each bent part, and there is a risk of stress due to thermal protection at the bent part. The occurrence of this is unavoidable, and it also poses difficulties in manufacturing the double pipe.

Furthermore, since the expansion and absorption part frequently expands and contracts and advances and retreats,
There is also a possibility that the airtightness in preventing leakage in this expansion/absorbing portion may be impaired.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide piping with a double-pipe structure that can more effectively handle the difference in the amount of expansion and contraction between the inner and outer tubes in response to temperature changes at low cost. purpose.

[Means for solving problems]

According to the present invention, in a pipe having a double pipe structure having a bent part, spacers smaller than the inner diameter of the outer pipe are fixed to the inner pipe at appropriate intervals to the extent that there is play between the inner pipe and the outer pipe, and The inner tube is inserted loosely into the outer tube without providing any fixing points, and the outer tube is provided with a telescopic joint.

〔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 piping is the inner pipe 1
It has a double pipe structure made of metal and an outer pipe 2, and is laid in a crank-like shape consisting of four bent parts 3a to 3d and five straight pipe parts 4a to 4C. In addition, straight pipe parts 4m, 4c
, 4s are laid horizontally, and the straight pipe portions 4b, 4d corresponding to the crank-shaped crank arms are laid vertically.

In addition, the inner tube 1 is provided with spacers 5 (5', 5
″) is attached, and this spacer allows the outer tube 2
The inner and outer tubes are loosely inserted into the outer tube without being in direct contact with each other, and the inner and outer tubes are not fixed at the bends 3a to 3d. On the other hand, the outer tube 2 is provided with an expansion joint portion 6.

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 furthermore, a heat insulating material 7 is placed on the outside so that the heat insulating material 7 does not come into direct contact with the outer pipe 2. is installed. The heat insulating material 7 is made of a molded product such as calcium silicate or a urethane foam material, 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. Although 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, it is preferably about 2 to 5 tyn. If the gap is larger than this, the outer tube size will be thicker and economical, but if it is smaller than this, there will be little absorption of the difference in expansion and contraction between the inner and outer tubes, and the expansion joint 6 of the outer tube 2 will always act.
The durability of the joint deteriorates, and the workability also deteriorates.

It should be noted that the spacer 5 is preferably made of a non-conductive material such as glass, rubber, or ceramics.
As for the spacer 5' that is placed on the vertical straight pipe sections 4b and 4d in the figure, a pushing force is applied to the outer tube 2'1 due to expansion and contraction force, and the spacer 5'' is connected to the pipe weight of the vertical straight pipe sections 4b and 4d. Therefore, it is necessary to consider the amount of expansion and contraction and piping size, and consider using a steel plate.However, in the case of a steel plate, at least the part that contacts the inner wall of the outer tube should be insulated with a non-conductive or conductive material. By using this spacer, it is possible to prevent the current that is normally applied to the inner tube for cathodic protection from flowing to the outer tube.The shape of the spacer can be arbitrary, such as rib-like, gear-like, or cage-like. The shape is fine.

On the other hand, the spacer installation interval is determined after 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.
Therefore, it is preferable to install them at relatively short intervals in locations where large forces are applied.

FIG. 3 is a partial sectional view of the straight pipe section 4C shown in FIG. 1, particularly showing the structure of the expansion joint section 6 of the outer tube 2. In the figure, a sleeve 6a that completely 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. There is.

Therefore, when a longitudinal force acts between the two outer tubes that sandwich the expansion joint 6, the seal member 6b and the outer tube circumferential surface with which it comes into contact act as a sliding surface, causing the two outer tubes to move. , to absorb the longitudinal force, ie the movement between the two outer tubes.

In addition, the vicinity of both ends of the expansion joint 6 are supported by pipe supports 8 so that the expansion joint 6 can expand and contract in the axial direction correctly, and U & It is attached to the piping support stand 8 with silt.

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

In the horizontal straight pipe parts 4a, 4e, and 4e (Fig. 1), the difference in expansion and contraction in the longitudinal direction of the inner and outer pipes is the vertical straight pipe part 4b.

4d, the difference in expansion and contraction is the vertical straight pipe part 4,
h, 4 d cover? It is sequentially absorbed by the gap between s' and the inner wall of the outer tube.

If the expansion/contraction difference exceeds the amount of absorption by the gap (Z), the cover 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 Since the expanded Mg arm portion 6 of the outer tube expands and contracts, its pressing force, that is, the difference in expansion and contraction that exceeds the amount absorbed by the upper gap B is secondarily absorbed here.

On the other hand, if there is a difference in expansion and contraction in the longitudinal direction of the inner and outer tubes in the straight pipe parts 4b and 4d VC perpendicular to , to 4e,! ', -rrr Sue? - It is absorbed by the gap between the sensor and the inner wall of the outer tube. In addition, in relatively short portions such as the vertical i-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 in the outer tube.

This piping with a double pipe structure can absorb the difference in expansion and contraction both in the gap between the pipe and the inner wall of the outer pipe and in the expansion joint.

In this example, we have explained an example of installation when crossing a river, but in any place such as when crossing a road, inside a premises that requires a double pipe structure, horizontal piping above ground or underground, etc.
The present invention is applicable to any case. 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 a single L-shaped bend of about 90", or a pipe with an obtuse angle (square) bend. Piping having one part,
It also includes any type of piping made of a combination of these. FIGS. 4(a), 4(b), and 4(C) show other examples of piping including the above-mentioned bow-shaped and rectangular bent portions, respectively. Note that the X-7 plane indicates a horizontal plane. FIG. 4(,) shows a pipe consisting of a combination of two L-shaped bends.

Of course, either one may be used for a Ku-shaped object. Figure 4(b) shows a pipe consisting of a combination of one L-shaped bent part and two box-shaped bent parts, and Figure 4(c) shows a piping system consisting of a combination of three L-shaped bent parts. This is the piping.

In addition, expansion joints should be limited to sleeve types such as the one used in my case, such as lath, universal, bellows, etc., as long as they are expandable and sufficiently watertight to prevent leakage and diffusion. Various types can be used, but the sleeve type is preferable because the reaction force during operation is small and it is relatively inexpensive.Also, the location and number of expansion joints are limited to those in this example. Furthermore, the end of the inner pipe is connected to a ponder, tank, etc., but the end of the outer pipe may be shaped like a cylinder to prevent leakage and diffusion. fluid't
:a, j It can also be made into a closed type.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to more effectively absorb into the expansion/contraction difference between the inner and outer tubes, the gap between the cover and the inner wall of the outer tube, and the expansion/contraction grip of the outer tube. ′+/
ζ, If the above expansion It can be prevented. Furthermore, it is not necessary to fix the inner and outer tubes to each other.
The construction is 1) 11 strands, and the spun fixing points are very effective at preventing heat dissipation from the fixing point and providing cathodic protection.2) It is easy to insulate.

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

[Brief explanation of the drawing]

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 part, and is a diagram of piping of another shape to which the piping of the double pipe structure 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 part, 7... Heat insulating material, 8...
...Piping support stand, 9...U Zelt. Baa\
〆1\Oj)

Claims (4)

[Claims] (1) In piping with a double pipe structure consisting of an inner pipe and an outer pipe and having a bent part, spacers smaller than the inner diameter of the outer pipe are fixed to the inner pipe at appropriate intervals to allow play between the outer pipe and the outer pipe. The pipe has a double pipe structure, in which the inner pipe is loosely inserted into the outer pipe without providing a fixing point near the bent part, and the outer pipe is provided with an expansion joint. (2) The double pipe structure piping according to claim (1), wherein the spacer electrically insulates at least the inner pipe and the outer pipe. (3) The outer diameter of the spacer is 2 to 5 cm larger than the inner diameter of the outer tube.
A pipe having a double pipe structure according to claim (1). (4) The double pipe structure piping according to claim (1), wherein the spacers are installed at intervals of about 2 to 5 m, and are relatively short in the vicinity of the bend.