JPH0235193B2 - TAISHOKUFUKUJUKANTSUGITEBUKOZO - Google Patents

Description

[Detailed Description of the Invention] <Technical Classification/Field> The disclosed technology belongs to the technical field of joint structures between unit pipes of corrosion-resistant duplex pipes in which corrosion-resistant pipes such as oil country tubular goods are made into double pipes.

<Explanation of the gist> The invention of this application is based on the invention in which a joint formed at the pipe end of a corrosion-resistant double pipe, such as a corrosion-resistant double pipe used for oil country tubular goods, etc., is located outside the inner diameter of the pipe end. This invention relates to a corrosion-resistant double-pipe joint structure in which a welded joint is formed on the end face of a thickened part whose diameter part is made large, and in particular, the invention relates to a corrosion-resistant double-pipe joint structure in which a thickened part is formed at the end of a general part of the corrosion-resistant double-pipe pipe. is formed, and at the pipe end of the thickened part, the corrosion-resistant pipe for the pressure-resistant pipe of the corrosion-resistant double pipe is replaced by overlay welding with a corrosion-resistant material from the pipe end of the corrosion-resistant pipe to the pipe end of the pressure pipe, so that the corrosion-resistant pipe is integrated. The ends of these corrosion-resistant pipes and pressure-resistant pipes are integrally connected by welding, or non-metallurgical methods are used in which corrosion-resistant materials for joints are welded and connected by screws, etc. This invention relates to a corrosion-resistant double pipe joint structure based on joining.

<Prior Art> As is well known, piping is used in all industries, but it is particularly widely used as transportation pipes.

Among these transport pipes, for example, oil country tubular goods, etc., pressure resistance and corrosion resistance are important, and it is impossible to make a pipe that satisfies all conditions with a single material.
To deal with this, various corrosion-resistant double pipes have been adopted, such as double pipes in which the outer pipe is made of carbon steel and the inner pipe is made of stainless steel, etc., and the two are integrated by various means. There is.

In the general part of these corrosion-resistant double pipes,
Considerable progress has been made in developing the pressure resistance, corrosion resistance, and tightness of both materials, and excellent products have emerged.

However, due to various restrictions such as equipment conditions during factory production and transportation to the site, this kind of corrosion-resistant double pipe can only be manufactured into unit pipes of a specified length at the factory.
Therefore, in order to achieve the set length, it is necessary to connect via a joint during on-site installation.

However, unlike ordinary single pipes, corrosion-resistant double pipes have problems such as corrosion-resistant seals in general parts and joints, and various countermeasures have been taken.

For example, threaded joints such as pin-knot springs are widely used because they are easy to connect and disconnect at installation sites, but corrosion resistance is extremely important, so corrosion-resistant materials are used in the joints. There are many.

Therefore, based on FIG. 1, the joint structure of the conventional corrosion-resistant double-layered pipe 1 will be briefly explained. On the other hand, for example, they are connected via a screw thread 4 of a coupling 3 made of a corrosion-resistant material for a joint, and in that case, since the joint is made of a corrosion-resistant material for a joint, its pressure resistance is reduced. In order to improve the corrosion resistance, an increased thickness part 7 is formed with a step part 6 interposed between the general part of the double pipe and the corrosion resistance.

The pin 2 is connected to the general portion 5 in the following manner.

That is, the corrosion-resistant tube 9 made of stainless steel is integrated with the pressure-resistant tube 8 made of carbon steel from the inside, and corrosion is prevented from entering the joint interface between the pressure tube 8 and the corrosion-resistant tube 9 from the tube end. In order to avoid this problem, seal welding 10 is performed on the tube end as shown in FIG. 2 to deal with this problem.

Thereafter, a predetermined machining process is performed on the tube end to form a groove, and the pin 2 is integrally joined via welding 11.

<Problems to be Solved by the Invention> However, in the joint structure using the above-mentioned joining means, as shown in FIG. Since there is a heat-affected zone 14 due to end welding and an overlapping portion 15 of both heat-affected zones, there is a drawback that the strength decreases due to the overlap of the heat-affected zones.In particular, as shown in FIG. 1, the pin 2 If there is a welded joint to the general part 5 in the general part, the strength decrease is extremely serious.

To deal with this, a stepped portion 6 is formed at the tube end of the general portion 5, and an increased thickness portion 7 is formed at the tube end.
There is also a joint structure in which pin 2 is joined by welding, but in order to avoid a decrease in strength at the overlapping part of the heat-affected zone mentioned above, the third
4, cut the pipe end of the corrosion-resistant double pipe 1 in the circumferential direction, leave the non-metallurgical joint 16 of the pressure-resistant pipe 8 and the corrosion-resistant pipe 9 as is, and attach the pin 2 to the corrosion-resistant double pipe 1.
When directly welded to the pipe end of the corrosion-resistant double pipe 1, there was a problem that blowholes 17 and cracks were likely to occur at the pipe end of the corrosion-resistant double pipe 1.

In either case, the non-metallurgical joint 16 is located in the vicinity of the welded joint, making it difficult to perform non-destructive inspection using X-rays or the like.

<Object of the Invention> The object of the invention of this application is to solve the problems related to unit pipe joints in the joint structure of corrosion-resistant double pipes based on the above-mentioned technology, to improve joint strength, and to improve pressure resistance. It is an excellent corrosion-resistant multi-layer product that reliably maintains the pipes and ensures corrosion resistance, and also facilitates post-inspection and allows pipe installation to be carried out as designed, benefiting piping technology applications in various industries. It is intended to provide a pipe joint structure.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the invention of this application, which is based on the scope of the above-mentioned patent claims, is to solve the above-mentioned problem. At the end of the pipe, a thickened part with a larger outer diameter is formed with the inner surface facing the general part of the pipe and the stepped part, and the end of the corrosion-resistant pipe is aligned in the longitudinal direction with respect to that of the pressure-resistant pipe. Then, only the short part is replaced with corrosion-resistant overlay welding at the pipe end to be integrally joined to the pressure-resistant pipe, and then the pipe end of the corrosion-resistant double pipe is machined. to form a bevel and connect the ends of each unit pipe by welding, or by welding a corrosion-resistant material for a joint to the end surface of the end of the corrosion-resistant double pipe to connect the unit pipes to each other. This ensures strength at the end of the corrosion-resistant double pipe, ensures corrosion resistance, and facilitates non-destructive testing using corrosion-resistant pipes. Technical measures have been taken to ensure that a sound welded joint structure is obtained without any welding.

<Example> Next, an example of the invention of this application will be described below based on the drawings from FIG. 5 onwards.

Note that the same parts as in FIGS. 1 to 4 will be described using the same reference numerals.

In the embodiment shown in FIGS. 5 to 7, when making a corrosion-resistant double pipe 1'', at the end of the pipe, the outer diameter part is larger than the inner diameter part through the general part 5 and the stepped part 6. The end portion of the corrosion-resistant tube 9, which is lined and integrated with the pressure-resistant tube 8 on which the thickened portion 7 has been formed, is cut out by a predetermined mechanical means or the like over the entire circumference of the predetermined length in the length direction. Form.

Then, as shown in FIG. 6, overlay welding 19 with a corrosion-resistant material such as stainless steel is applied to the missing portion 18.
is applied to make it an extension of the corrosion-resistant tube 9 and integrated with the end of the pressure-resistant tube 8, thereby sealing the ends of the pressure-resistant tube 8 and the corrosion-resistant tube 9.

In this case, instead of cutting off the end of the corrosion-resistant tube 9, which has been formed to the same length as the pressure-resistant tube 8,
Of course, the length of the corrosion-resistant tube 9 may be shortened in advance by an appropriate means, and then the corrosion-resistant material may be welded overlay 19 to the end of the tube.

As shown in FIG. 7, after the overlay welding 19 is performed, a groove is suitably machined on the end face of the corrosion-resistant double pipe 1'', and the groove is prepared in advance. A welded joint is formed by welding 20 with the inner pin end face of the pin 2 as a corrosion-resistant material for the joint.

In this case, the welded joint thus formed is formed in the thickened portion 7, as shown in FIG. 7, and is therefore sufficiently excellent not only in corrosion resistance but also in pressure resistance.

In addition, since the overlay weld 19 made of a corrosion-resistant material is also formed on the thickened portion 7, its strength is of course high, and therefore, there is no non-metallurgical joint in the welded connection portion of the pin 2. Because they are far apart, welding defects such as blowholes and cracks do not occur.

Further, it is easy to carry out non-destructive inspection using X-rays later.

Next, in the embodiment shown in FIGS. 8 to 10, similar to the process explained in FIGS. At the end of the pipe 9, welding 1 is also performed.
9, which have been integrally joined, are connected by direct welding, with the joining surfaces of the thickened parts 7 and 7 facing each other, as shown in FIG. 10. In this case, the same effects as described above can be obtained.

It goes without saying that the embodiments of the invention of this application are not limited to the above-mentioned embodiments, and other main embodiments can be adopted, such as being applicable to corrosion-resistant double pipes such as pin box joints and flange joints. be.

<Effects of the Invention> According to the invention of this application, basically, in the pipe end portion of the corrosion-resistant double-layer pipe in which the thickened portion is formed at the pipe end,
The corrosion-resistant pipe is integrally joined to the pressure-resistant pipe at its pipe end through overlay welding using a corrosion-resistant material from the pipe end of the corrosion-resistant pipe to the pipe end of the pressure-resistant pipe. When forming a welded joint,
The increased thickness not only ensures sufficient strength but also has the excellent effect of ensuring corrosion resistance.

Also, as long as the build-up weld can be made large enough for the thickened section and the non-metallurgical joint of the corrosion-resistant pipe to the pressure-resistant pipe is kept at a sufficient distance from the weld joint, then the weld The excellent effect is that welding defects such as blowholes and cracks are not formed in the joint, and a sound joint weld is formed.

Further, since there is the thickened portion, there is an effect that the corrosion resistance of the built-up portion due to penetration of the pressure tube does not deteriorate during build-up welding.

Furthermore, since there are no non-metallurgical joints in close proximity to the welded joint, non-destructive inspection using X-rays is easy and the inspection can be performed reliably, which is an excellent effect.

In addition, when forming welded joints at the installation site, even if pre-prepared corrosion-resistant double pipes are piled up in the open, the ends of the corrosion-resistant double pipes are not corrosive to the pressure pipes. Since the pipe is overlay welded, an excellent effect is achieved in that corrosion does not invade the interface between the pressure-resistant pipe and the corrosion-resistant pipe.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the position of a welded joint based on the prior art, Fig. 2 is a partially enlarged sectional view of Fig. 1, Fig. 3 is a sectional view of a welded joint based on the prior art, and Fig. 4 is a sectional view of the welded joint based on the prior art. Fig. 5 is a partially enlarged sectional view, Fig. 5 and the following are explanatory views of embodiments of the invention of this application, Fig. 5 is a sectional view of a corrosion-resistant double pipe before welding of one embodiment, and Fig. 6 is a map of overlay welding. 7 is a cross-sectional view of the structure of the joint, FIGS. 8 and 9 are opposing cross-sectional views of units of corrosion-resistant double pipes of other embodiments, and FIG. 10 is a cross-sectional view of the joint structure. 1″, 1...corrosion-resistant double pipe, 7...thickened part, 9
...Corrosion resistant pipe, 8...Pressure resistant pipe, 19...Overlay welding.

Claims (1)

[Claims] 1. In a joint structure in which a welded joint is formed at the end of a corrosion-resistant double pipe by non-metallurgical joining, the outside diameter of the end of the pressure pipe is larger than the inside diameter. The longitudinal end of the inner corrosion-resistant pipe in the thickened part of the pipe end is welded in advance with a corrosion-resistant material to the end of the pressure pipe. A corrosion-resistant double pipe joint structure characterized in that the thickened parts of the pipe ends are welded and connected to each other. 2. In a joint structure in which a welded joint is formed at the pipe end of a corrosion-resistant double pipe by non-metallurgical joining, the pipe end of the pressure-resistant pipe is thickened so that the outer diameter part is larger than the inner diameter part. , the longitudinal end of the inner corrosion-resistant tube of the tube end thickened section is integrated with the outer pressure-resistant tube from the tube end of the corrosion-resistant tube to the tube end of the pressure-resistant tube in advance through overlay welding with a corrosion-resistant material, and A corrosion-resistant double pipe joint structure characterized in that a corrosion-resistant material for the joint is integrally welded to the thickened part of the pipe end.