JPH01216191A - Multiple pipe structure - Google Patents

Abstract

PURPOSE:To apply compressive stress to an inner pipe to prevent stress corrosion cracking by making between the inner pipe and an outer pipe airtight and sealing in a fluid layer in high pressure state. CONSTITUTION:A multiple pipe is formed by a double-pipe comprising an outer pipe 2 and an inner pipe 4, wherein the outer pipe 2 has a lining layer 3 made by rubber or the like, which adheres to the inner surface of a pipe body made by carbon steel. The inner pipe 4 has a lining layer 5 made by rubber, which adheres to the outer surface of a pipe body made by stainless or the like. The outer pipe 2 and the inner pipe 4 are concentrically superposed relatively through an airtight gap 6, with the lining layers 3, 5 confronting with each other. In the gap 6, a fluid layer 6' of inert gas such as nitrogen gas or the like is charged in high pressure state. Further, in addition to the fluid layer 6', a lot of elastic bodies may be charged. Accordingly, there is no influence of heat and stress corrosion cracking or the like can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The disclosed technology belongs to the field of structural technology for multiple pipes such as double pipes used for piping.

Summary of the gist> The invention of this application is such that an inner tube and an outer tube, each having a circular cross section, are relatively heavily mounted, and a fluid such as an inert gas is injected into the ring-shaped cross section between the inner tube and the outer tube. This invention relates to a multi-tube structure in which layers are interposed and filled, and in particular, a gap such as a ring-shaped cross section is made airtight between the inner tube and the outer tube, so that a layer of fluid such as nitrogen gas is kept under high pressure. This invention relates to a multi-tube structure in which the fluid layer is sealed and further filled with an elastic material such as a foaming agent.

<Prior Art> As is well known, piping is widely used in all industries, and is not only used as a fluid layer as a resource, but also as a structural member and as a means of transmitting information.

Therefore, piping is required to have many functions such as pressure resistance, heat resistance, corrosion resistance, abrasion resistance, and constancy, depending on the operating conditions and balance with the surrounding environment during operation. No piping material has been developed that has these functions, especially the ability to satisfactorily meet multiple competing conditions.

Thus, for example, making the inner tube corrosion-resistant, wear-resistant,
Multiple pipes, such as double pipes, whose outer pipes are heat resistant and pressure resistant are increasingly being used.

And, although metal pipes are generally used for piping,
In the case of multiple pipes that are made of metals that are bonded together, special measures are required to bond the inner and outer tubes together, and in particular, it is extremely difficult to maintain uniform bonding force throughout the tube. There are problems such as cracks occurring in multiple pipes during manufacturing and operation.

<Problems to be solved by the invention> To deal with this, for example, there are double pipes such as clad pipes, but manufacturing them requires a lot of man-hours, and management control is extremely complicated, resulting in high costs. There are some inconveniences, such as being expensive.

<Object of the Invention> The object of the invention of this application is to solve the problem of the multiple tubes in which the inner tube and the outer tube are brought into close contact based on the above-mentioned prior art, and to solve the problem with a relatively simple structure. , the inner tube can be brought into a substantially tight state, albeit indirectly, with respect to the outer tube, and compressive stress is applied to the inner tube to prevent cracking during manufacturing or stress corrosion cracking during operation. The purpose of this invention is to provide an excellent multi-pipe structure that will benefit the field of piping technology used in various industries.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is summarized in the above-mentioned claims, is based on the above-mentioned object, in which the inner tube is uniform with respect to the outer tube. When 1q of multiple tubes are held tightly together, the inner tube and the outer tube are stacked relative to each other with a ring-shaped airtight gap in cross section, and a gas such as nitrogen gas is injected into the ring-shaped gap. The active gas is sealed in a high pressure state, the inner tube is held under pressure with respect to the outer tube, a uniform adhesion force is applied to the outer tube, and the inner tube is also provided with compressive stress. In addition, the fluid layer is filled with an elastic material such as a small-diameter balloon or a foaming agent to prevent stress corrosion cracking during operation, and the pressure behavior of the fluid layer during manufacturing or operation is improved. This technology takes technical measures to absorb the pressure and maintain a uniform pressure state.

<Example> Next, an example of the invention of this application will be described below based on the drawings.

In the embodiment shown in Fig. 1.2, numeral 1 indicates a multiple pipe which forms the center of the gist of the invention of this application, and 17 indicates a double pipe mode in the illustrated embodiment, and the outer pipe is made of carbon steel. A rubber lining layer 3 is attached to the inner surface of the tube 2, and a rubber lining layer 5 is attached to the outer surface of the inner tube 4 made of stainless steel. are stacked concentrically relative to each other with the rubber lining layers 3.5 facing each other through an airtight ring-shaped gap 5.

Further, the ring-shaped flanges 7 formed inward at both ends of the outer tube 2 and the inner tube 4 are integrally welded, and a rubber lining layer is attached to these parts as well.

When the inner tube 4 and the outer tube 2 are relatively stacked, a fluid layer 6' of an inert gas such as nitrogen gas is hermetically sealed in a ring-shaped gap 6 between them under a predetermined high pressure state. While holding the inner tube 4 against the outer tube 2, a tensile stress is applied to the outer tube 2, and a predetermined compressive stress is applied to the inner tube 4. A constant overall uniform tightening force is applied to the inner tube 4.

In the above configuration, when the double pipe of the multiple pipe 1 is put into operation and a predetermined corrosive fluid or the like is caused to flow into the inner pipe 4, the inner pipe 4 is indirectly but overall connected to the outer pipe 2. Since a uniform clamping force is applied by the nitrogen gas 6' in the fluid layer and compressive stress is applied, there is no risk of stress corrosion cracking occurring during operation, and the outer tube 2 is made of heat resistant material. Even though it is made of carbon steel, a kind of thermal insulation is maintained through the fluid layer 6', preventing high temperature transmission from the outside environment to the outer tube 4.

Also, pressure fluctuations from the outside environment are likewise absorbed by the fluid layer 6' and are not transmitted to the inner tube 4, so that the inner tube 4 remains stable during operation.

Next, in the embodiment of the multiple tube 1' shown in FIG. 3, a liquid such as water is sealed between the outer tube 2 and the inner tube 4 as a fluid layer, and a compressible This is an embodiment in which a predetermined number of small-diameter balloons filled with fluid air or the like are filled as elastic bodies 8, and the outer tube 2 and the inner tube 4 at the time of manufacture are
When it is difficult to adjust the pressure of water in the fluid layer between the inner tube 4 and the inner tube 4, or when internal and external pressure fluctuations occur during operation, the small diameter balloons 8.8... absorb the fluctuations and pressure.
This makes it possible to maintain a constant tightening force and compressive force at all times, so that the inner tube 4 can maintain an even more stable state during operation.

It is needless to say that the embodiment of the invention of this application is not limited to the above-mentioned embodiments. Various embodiments can be adopted, such as the possibility of interposing a foaming agent or the like in addition to a small-diameter balloon.

In addition, the applicable multiple pipes are not only double pipes, but also triple pipes,
Of course, it is possible to use a quadruple tube...etc.

<Effects of the Invention> As described above, according to the invention of this application, in a multi-tube structure in which a layer of fluid such as nitrogen gas is interposed in the airtight ring-shaped gap in cross section between the inner tube and the outer tube. Even if the temperature difference varies significantly due to the external environmental conditions of the multiple pipes during operation, the fluid layer can be interposed as a thermally relaxed vE layer, so there is no thermal influence on the fluid flowing inside the inner pipes. Not only is it effective, but as mentioned above, compressive stress is applied to the inner tube through the fluid layer during manufacturing, resulting in no stress corrosion cracking or the like occurring in the inner tube during operation. effect is produced.

Further, the fluid layer has a sound insulating effect and blocks noise from the outside due to cavitation noise of the liquid flowing in the inner tube.

A fluid layer such as an inert gas is sealed in the ring-shaped gap between the inner tube and the outer tube, and an elastic body such as a small diameter balloon or a foaming agent is delivered to the fluid layer. When the fluid layer is a liquid, it is extremely difficult to adjust the pressure during initial manufacturing, and even when the pressure difference between the inside and outside changes significantly during operation, the elastic body can function as a pressure buffer. , an excellent effect is achieved in that a constant clamping force is maintained on the inner tube.

In addition, since the structure is simple, consisting of an inner tube, an outer tube, and a fluid layer interposed in a ring-shaped gap between the two, initial manufacturing and assembly are easy, and maintenance and maintenance are easy. , the effect of excellent durability is exhibited.

Therefore, naturally, it can be manufactured at low cost,
The effect is that running costs can also be reduced.

In addition, since a fluid layer such as gas is interposed in the ring-shaped cross-sectional gap between the inner tube and the outer tube, mutual elasticity is maintained between the two, resulting in excellent cushioning properties during initial installation. It also has the advantage of being easy to construct and install, and easily preventing cracking due to impact during manufacturing.

Furthermore, since it is elastically held by the fluid layer, it not only absorbs the shock during initial installation, but also has the advantage of preventing cracks from occurring during operation.

[Brief explanation of the drawing]

The drawings are detailed explanatory diagrams of the invention of this application, and FIG. 1 is a cross-sectional view of one embodiment, FIG. 2 is a longitudinal sectional view of the same part, and FIG. 3 is a cross-sectional view of another embodiment. . 4...Inner tube, 2...Outer tube, 6...Fluid layer, 1...Multiple tube, 8...Elastic body

Claims (2)

[Claims] (1) In a multi-tube structure in which a fluid layer is interposed between an inner tube and an outer tube, the space between the inner tube and the outer tube is made airtight, and the fluid layer is sealed in a high pressure state. A multi-tube structure featuring (2) In a multi-tube structure in which a fluid layer is interposed between the inner tube and the outer tube, the space between the inner tube and the outer tube is made airtight, and the fluid layer is sealed under high pressure. A multi-tube structure characterized in that a large number of elastic bodies are filled in the fluid layer.