JPS5934089A - Corrosion-resistant double pipe joint 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] The disclosed technology improves the durability of threaded joints for corrosion-resistant double pipes such as oil country tubular goods!
It belongs to the technical field of IT structure.

Accordingly, in this invention, at least the unit pipes of the corrosion-resistant double-ply pipes whose corrosive fluid flow inner pipes are made of a corrosion-resistant material such as stainless steel are connected via threaded joints, and the pipe end portions of the threaded portions are connected to each other through a threaded joint. This invention relates to a joint structure that is integrally joined with a corrosion-resistant material and has a corrosion-resistant sealing property.In particular, a multi-layered corrosion-resistant short pipe is integrally joined metallurgically from the threaded surface of the pipe end to the inner surface, and the thread is machined. This invention relates to a processed corrosion-resistant double pipe joint structure.

As is well known, the pipe bodies used for transporting corrosive fluids, such as oil country tubular goods, are made of corrosion-resistant double pipes, which are made by layering a stainless steel inner pipe over a pressure- and heat-resistant carbon steel outer pipe to provide corrosion resistance. It is used.

Therefore, the length of the unit pipe for nuclide corrosion-resistant double pipe is determined by the standard due to the size conditions from the manufacturing equipment, transportation restrictions to the site, etc. Therefore, when installing the pipe on site, it is connected to the set length via a joint. It's like that.

Although various types of joints have been adopted, threaded joints are widely used because of their advantages such as ease of disassembly and connection, and good sealing performance.

However, in order to provide the same corrosion resistance as that of the tube-crotch section, it is necessary to perform corrosion-resistant processing on the tube end at the connecting section such as the tube end thread and the coupling thread.

For example, as shown in FIG. 1, the tube end 4 of a corrosion-resistant double tube 3 in which a stainless steel inner tube 2 is clad on a carbon steel outer tube 1 is removed by mechanically cutting and removing the outer tube 1 as shown in FIG. 5, and then, as shown in FIG.
vC stainless steel overlay bath contact 6 setting length same < 1 color,
Finally, as shown in FIG. 4, the threaded portion 7 was formed by la-casting processing.

However, the nuclide technology required a lot of man-hours and the work was complicated.

The purpose of this invention is to solve the problem of the corrosion-resistant pipe end of the corrosion-resistant double pipe threaded joint based on the prior art as described above, and to ensure good sealing performance and sufficient corrosion resistance. It is an object of the present invention to provide an excellent corrosion-resistant double pipe joint structure that is easy to manufacture and is useful for piping applications in various industries.

The structure of the present invention, which achieves the above-mentioned purpose, is to form a single-layer short pipe of a predetermined length made of a corrosion-resistant material at the pipe end of a pre-made corrosion-resistant double-walled pipe with a threaded portion formed in advance, and to metallurgically form it integrally. , or
After integration, the threaded parts were machined and the unit corrosion-resistant double pipes were connected by threading, ensuring sealing at the threaded parts, guaranteeing corrosion resistance, and preventing stress corrosion cracking at the core. The gist is that technical measures have been taken.

Next, one embodiment of the present invention will be explained based on FIG. 5 for the following reasons. The same parts as those shown in FIGS. 1 to 4 will be described using the same reference numerals.

In the embodiment shown in FIG. 5, the corrosion-resistant double tube 3' of the unit tube is made up of a carbon steel outer tube l and a stainless steel inner tube 2, and the tube 14i4 is connected to a stainless steel short tube 8' having a set length. is a single layer in which a male thread 7 has been carved in advance, and is integrally metallurgically connected via friction welding 10 from the front side by internal contact, so that the entire area of the coupling 9 is undercovered.

Therefore, the short pipe 8 in this embodiment has a sufficiently longer axial length than the overlay shown in FIG. , there is no tensile residual stress, etc.

In the above structure, when the unit corrosion-resistant double pipes 3', 3' are fastened and connected by the coupling 9 and operated in the illustrated manner, since the pipe end is a single-layer corrosion-resistant pipe, the corrosive fluid flowing through the unit is Even if there is a leak in the fastening seal part, it exhibits sufficient corrosion resistance, and as mentioned above, there is no tensile residual stress, so stress corrosion cracking does not occur.

Of course, /-rule 1/1: is fully guaranteed.

It should be noted that the embodiments of the present invention are not limited to the above-mentioned embodiments (for example, the outer V of the coupling joint
It can also be used for C-box joints (various forms of Φ can be adopted).

In addition, (corrosion-resistant double-walled pipes) can include triple-backed pipes and quadruple-backed pipes in addition to triple-walled pipes, and it goes without saying that low-joint pipes other than clad pipes can also be applied as part of the 77J model.

As described in MiJ, according to this invention, a multi-functional corrosion-resistant double pipe threaded joint unit is provided with an integral single-layer corrosion-resistant 44 short pipe at both ends of the corrosion-resistant pipes from the external threaded part to the internal surface where corrosive fluid flows. Since they are metallurgically connected and the threaded parts are machined, there is no repeated welding on the pipe ends, so there is no change in material quality, and corrosion resistance and physical properties do not deteriorate.
Since no tensile stress is generated, an excellent effect is achieved in that stress corrosion cracking does not occur.

Further, since the corrosion-resistant material is provided in a single layer, excellent effects such as improved reliability due to uniformity of sealing performance and constant accuracy of the joint portion are produced.

Furthermore, there are fewer steps during manufacturing, which increases precision, makes management easier, and reduces costs.

Historically, single-layer short pipes with metallurgically bonded pipe ends have a degree of freedom in design regarding their length, which also has the advantage of being flexible in designing designs that improve the sealing performance and corrosion resistance of the joint.

[Brief Description of the Drawings] Fig. 1.2.3.4 is a partial sectional view illustrating the process of forming a pipe end joint of a corrosion-resistant double pipe based on the prior art, and Fig. 5 is a partial sectional view of an embodiment of the present invention. It is a diagram.

Claims (1)

[Claims] [Corrosion-resistant double pipe joint in which the ends of the A and J parts of a joint of a double pipe whose inner pipe is made of at least corrosion-resistant A2 are integrally joined with a corrosion-resistant material] In the 1 degree construction, the double pipe is A corrosion-resistant double pipe joint structure characterized in that the end of the threaded part is machined by metallurgically joining a single layer of corrosion-resistant short pipe from the inner surface to the outer surface.