JPH0211793B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The disclosed technology belongs to the technical field of joint structure in which corrosion-resistant pipes such as oil country tubular goods are overlapped.

Therefore, the present invention provides a corrosion-resistant double-layered pipe such as a seed oil country pipe, in which the inner pipe is made of a corrosion-resistant pipe such as stainless steel, and the outer pipe is made of a carbon steel pipe, etc. This invention relates to a double pipe end structure in which corrosion-resistant short pipes are integrally joined by TIG welding etc., and in particular,
The invention relates to a corrosion-resistant double-pipe structure in which the corrosion-resistant short pipe joint part of the general part of the double-pipe pipe is formed to be thicker than the general part, similarly to the corrosion-resistant short pipe.

<Prior art> As is well known, various types of piping are used in many industries, such as transportation pipes, wiring protection pipes, document delivery pipes, etc. However, due to limitations in the capacity of manufacturing equipment installed in manufacturing plants, transportation Due to the above constraints, etc., the length of the unit pipes is determined by standards, and therefore, in order to achieve the set length, means are taken to connect the unit pipes to each other via pipe joints on site.

Welded joints, flange joints, and threaded joints are used as pipe joints depending on the purpose of use. For example, threaded joints are used for drilled pipes because they can be added and removed quickly, and have good sealing properties. Joints are widely used.

That is, as shown in FIG.
is threaded, and tapered female threads 5, 5 are threaded on the coupling ring 4 to be screwed and tightened together.

By the way, since the pipes for the flow of corrosive fluids, such as oil country tubular goods, need to be corrosion resistant as well as heat and pressure resistant, corrosion-resistant double pipes are used in which the inner pipe is made of stainless steel and the outer pipe is made of carbon steel. Although this type of corrosion-resistant double pipe has corrosion-resistant and pressure-resistant functions in general parts, the sealing performance and corrosion resistance are not always sufficient at the threaded joint pipe end. However, there are some problems that cannot be avoided, and various techniques have been devised to deal with these problems.

<Problems to be Solved by the Invention> To deal with this, for example, as shown in FIG. There is a type that is covered by the inner tube 6 and tightly abuts against the corrosion-resistant underhang part 9 of the coupling ring 4'.It has two metal surfaces and has excellent corrosion resistance and sufficient joint strength, but it is extremely expensive. It had the disadvantage of being expensive.

Furthermore, as shown in Fig. 3, the underhang part of the coupling ring 4' is omitted while maintaining the corrosion resistance of the pipe end, although the cost is low, but the seal part is one-sided. There was a drawback that the corrosive fluid was secondarily immersed, and the outer surface of the tube end 7, which was a carbon steel part, came into contact with the corrosive fluid and there was a risk of corrosion.

Furthermore, as shown in FIG. 4, in order to address the above-mentioned problem and ensure corrosion resistance, a single-layer corrosion-resistant short pipe 10 is formed by mechanical processing or the like after welding by friction welding on the pipe end of the corrosion-resistant double pipe 8. There is also a product that is screwed onto a corrosion-resistant coupler 4", but although it has excellent corrosion resistance, there is a problem that the strength of the joint and welded joint is insufficient, and there have been requests for even more strength. .

The purpose of the present invention is to solve the problems of corrosion resistance, sealing performance, and strength of the pipe end with respect to the joints of corrosion-resistant double pipes such as double pipes based on the above-mentioned prior art, and to It is an excellent product that satisfies all of corrosion resistance, sealing performance, and strength while making use of corrosion-resistant short pipe joining technology at the end, and also satisfies low cost, benefiting piping application fields in various industries. It is an object of the present invention to provide a corrosion-resistant double-pipe end structure.

<Means and operations for solving the problems> In order to solve the above-mentioned problems, the structure of the present invention, which is based on the above-mentioned claims, is to provide a double-walled pipe in which the inner pipe is a corrosion-resistant pipe. When welding the end of a threaded joint pipe as a single-layer corrosion-resistant short pipe, the thickness is increased from that of a typical double-ply pipe, and the joint position is set at the boundary of the increased thickness to improve the corrosion resistance of the joint. In addition to improving the strength of not only threaded joints but also welded joints, technical measures have been taken to enable them to be manufactured at low cost and to provide excellent sealing performance.

<Embodiment - Configuration> Next, an embodiment of the present invention will be described based on the screens shown in FIG. 5 and below. Furthermore, the first
The same reference numerals are given to the same parts as those in FIGS.

In the embodiment shown in FIG. 5, reference numeral 8 is a corrosion-resistant double tube, the general parts of which have the same wall thickness, the inner tube is a stainless steel tube 6, and the outer tube is a carbon steel tube 7. It is formed by the heat expansion method, etc., which is the claimed invention.

In particular, with the thermal expansion method, it is possible to relatively easily form a self-tightening double tube with increased thickness at the tube end.

10' is a stainless steel short tube serving as a corrosion-resistant short tube, the inner diameter of which is the same as that of the general portion of the corrosion-resistant double tube 8, and the outer diameter of which is thicker than the general portion. , is integrally connected to the pipe end of the corrosion-resistant double pipe 8, which is also thicker than the general part, via a weld joint 13 by means such as TIG welding or friction welding.

The front portion of the outer periphery of the corrosion-resistant short tube 10' is machined to form a tapered male thread 3 which is screwed into a tapered female thread 5 of the coupling ring 4.

Therefore, the mass of the stainless steel corrosion-resistant short pipe 10' is large, the length of the threaded portion can be made long, and the joint area of the welded joint 13 can be made large.

<Embodiment - Effect> In the above-described configuration, both the corrosion-resistant double pipes 8, 8 are connected by the coupling 4 through screw engagement,
When this is used as oil country tubular goods, as mentioned above, the threaded part is long, so the tightness is strong, there is also a labyrinth seal effect, and the metal contact between the corrosion-resistant materials is high, so the corrosion resistance is high. Similarly, the wall thickness of the short stainless steel pipe 10' is large, and therefore,
The strength of threaded joints is also high, so welded joints 1
The strength of No. 3 is also high, and it does not cause buckling and can sufficiently withstand the harsh use of oil country tubular goods.

Moreover, in this case, the stainless steel corrosion-resistant short pipe 10'
Since the wall thickness is large, it is easy to weld and screw, and therefore the cost is low.

And, because the thickness of the binding part is that large,
The tightening force is large, which allows for a more reliable connection, and is also easier to operate.

Next, the embodiment shown in FIG.
An underhang 9 is formed on the tube end side of the general portion 8', and an upset step portion 12 is formed on the tube end side of the general portion 8'.
Weld joint 13' in front of the upset step 12
Since the is tapered and oblique, the area of the joint portion 12 is also increased due to the increased thickness, and the strength of the welded joint is further increased.

In addition, since the stainless steel corrosion-resistant short pipe 10' is made into two-sided metal contact with the main body of the coupling 4' and the underhang part 9, not only the sealing performance but also the corrosion resistance is improved, and the strength of the joint is further increased.

<Other Embodiments> It goes without saying that the embodiments of the present invention are not limited to the above-mentioned embodiments. For example, a triple or more double-walled pipe may be used, and the upset portion may be formed in stages. Various embodiments can be adopted, such as forming it continuously or discontinuously.

Moreover, it goes without saying that the object is not limited to oil country tubular goods, and can be applied to various plant piping and heat exchangers.

<Effects of the Invention> As described above, according to the present invention, the wall thickness of the corrosion-resistant short pipe provided at the end of the corrosion-resistant double-layered pipe having the corrosion-resistant inner pipe is increased relative to the general part of the corrosion-resistant double-layered pipe. By forming the thread thicker, the joint thread forming area of the threaded joint can be increased, the thread length can be increased, and the corrosion resistance can be improved accordingly.

Further, since the thickness of the threaded joint is increased, the strength of the threaded joint is also increased, and an excellent effect of increasing the robustness is achieved.

By providing the upset part of the thickened part in the general part and providing a tube made of reinforcing material in the thickened part, in addition to the above effects, the welding area of the welded joint becomes larger, and the As a result, the excellent effect of improving the strength of the welded joint is achieved.

Moreover, such a structure can be formed without any particular difficulty when forming a tube body or a welded joint by a thermal expansion method, so there is an advantage that it does not increase costs or increase the number of work steps.

[Brief explanation of drawings]

Figures 1 to 4 are explanatory cross-sectional views of the end structure of a corrosion-resistant double pipe based on the prior art, Figure 5 and the following are explanatory views of embodiments of the present invention, and Figure 5 is a partial cross-sectional side view of one embodiment. FIG. 6 is a sectional view of another embodiment. 6...Inner pipe, 8...Double pipe, 10...Corrosion-resistant short pipe.

Claims (1)

[Claims] 1. In a corrosion-resistant double-pipe end structure in which a single-layer corrosion-resistant short pipe with the same inner diameter is integrally joined to a double-ply pipe end having a corrosion-resistant inner pipe that is non-metallurgically connected to an outer pipe, the corrosion-resistant short pipe portion is The wall thickness is increased relative to the general portion of the double pipe, and the joint portion of the general portion of the double pipe to the corrosion-resistant short pipe is also formed thicker than the general portion. Corrosion-resistant double-pipe end structure featuring