JPS5857586A - Joint structure of double pipe - 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 belongs to the field of joint technology for connecting parts of corrosion-resistant double pipes, such as oil country tubular goods, between unit double pipes.

The present invention provides a unit for use when corrosive fluid transport pipes such as oil country tubular goods are made up of a unit pipe connection body consisting of a corrosion-resistant inner pipe and a pressure-resistant outer pipe to which the corrosion-resistant inner pipe is tightly connected. This relates to a structure in which the pipe joints between the pipes are of a box type and a pin type threaded connection, and in particular, there is a joint that is integral with the inner pipe on the abutting surface near the inner pipe on at least one of the box side and the bottle side. This relates to a double-pipe joint structure in which a corrosion-resistant material is attached and fixed to improve corrosion resistance.

As is well known, corrosive fluid transport pipes such as oil country tubular goods are made of corrosion-resistant double pipes in which a pressure-resistant and heat-resistant outer pipe is joined to a corrosion-resistant inner pipe, but the length of the unit pipe may vary depending on manufacturing, transportation, etc. conditions. It is generally limited to a predetermined value and joined and connected to a predetermined length in the field.

There are various types of such connections, but for example, in the above-mentioned oil country tubular goods, etc., coupling joints are widely used as shown in Figure 1 due to the quickness of connection and the reliability of connection. It is being

That is, for example, a unit tube 3.3 in which a stainless steel inner tube 1 is lined and tightened to a carbon steel outer tube 2 is provided with a tapered male thread 4, and a coupling 5 is attached to the unit tube 3.3.
They were screwed together tightly.

The inner surface of the carbon steel coupling IO is lined with a stainless steel end tube 7, as in the applicant's earlier invention, so that the inner corrosion-resistant liner is flush with the inner surface.

However, in this type of coupling joint, even if the unit pipe 3 is provided with a male thread, there are disadvantages in that it is extremely difficult to manufacture the coupling 5, and the cost is high, and the screw thread is insufficient to ensure sealing performance. There is a drawback that management is extremely complicated, and there is also a drawback that stress corrosion cracking may occur because there is no guarantee that compressive stress sufficient to reliably eliminate the tensile load due to the connection length will be applied to the joint joint.

The purpose of this invention is to omit the coupling as a box-type joint in view of the above-mentioned problems with the coupling joint 41 in the corrosion-resistant double pipe connection in the trench, and to provide corrosion-resistant material to the butt surface of the joint between the box side and the pin side. It is an object of the present invention to provide an excellent double-pipe joint structure in which the material is fixedly interposed to improve sealing performance, ensure complete corrosion resistance, and further apply axial compressive stress to the joint part.

The structure of the present invention, which achieves the above-mentioned purpose, is to insert the pin of the other unit tube into the box of one of the unit tubes that connects the corrosion-resistant inner tube to the pressure-resistant outer tube, and screw the male thread into the female thread of the former and tighten it. A corrosion-resistant material integrated into at least one of the inner tubes is provided at the abutting portion of the box and the pin, so that the inner tubes are tightened with a metal touch, ensuring a seal and ensuring that the inner tubes are axially connected to each other. The gist of this is that compressive stress is applied to prevent stress corrosion cracking during operation.

Next, an embodiment of the present invention will be described below with reference to the drawings from FIG. 2 onwards. Note that the same parts as in FIG. 1 will be described using the same reference numerals.

In the embodiment shown in FIGS. 2 to 5, one unit tube 3 has an outer tube 2 made of carbon steel, which is tightly joined to an inner tube l made of stainless steel by a predetermined method such as a heat expansion method. 2 is made of a material with a box 8, as shown in FIG. The corrosion-resistant material 10 is formed and fixed by overlay bath welding.

Next, as shown in Figure 4, the female thread 1 is made by thread processing as appropriate
1 is engraved, and an abutting surface 12 is formed on the corrosion-resistant material lO.

On the other hand, as shown in FIG. 5, the other unit pipe 3' having an outer pipe 2 to which the inner pipe l is joined is butted with a pin 15 formed with a male thread 14 and a stopper step surface 1.
6 is a butting surface 12 against the end surface of the one unit pipe 3.
．． It is designed to hit the rear side of the 13 metal touch.

Therefore, in the above configuration, when the male screw 14 is screwed onto the female screw 11 with the other pin 15 facing the box 8 of the unit pipe 3 and rotated and tightened, the pin 15 is tightened with a predetermined stroke. The end abutting surface 13 is brought into close contact with the abutting surface 12 of the corrosion-resistant material IO, and the stopper step surface 16 of the pin 15 is brought into close contact with the end surface of one of the unit tubes 3 while the screw is tightly connected.

Therefore, both unit pipes 3.3' have a butting surface 12.13
The inner tube 1 is tightly sealed and completely sealed. l
A strong compressive stress is applied in the axial direction, particularly in the vicinity of the abutment surfaces 12 and 13.

Therefore, even if they are connected to a predetermined length and installed vertically as oil country tubular goods, the axial tensile force is canceled out or relaxed, and stress corrosion cracking due to the corrosive crude oil transported does not occur, and the butt surface 12.
No leakage occurs from 13.

Also, as shown in FIG. 6, for the material unit pipe 3,
As shown in FIG. 7, a step 9 is formed and bored, and a stainless steel ring 10' having a predetermined thickness is welded and fixed as a corrosion-resistant material through electron beam welding 17 to form a butting surface 12. As shown in Figure 8, thread the female thread part 1.
．． 1' and similarly screwed to another unit pipe 3' as shown in FIG.

It should be noted that the embodiments of the present invention are of course not limited to the above-mentioned embodiments; for example, the corrosion-resistant material that is integrally joined to the inner tube may be fixed to the bottle side, or It is possible to adopt a variety of configurations, such as the possibility of providing it on both the bottle side and the box side.

In addition to the upset type, the lateral type can also be used, and in addition to oil country tubular goods, it can also be applied to transportation pipes, atomic couplet piping, etc.

As described above, according to the present invention, the joint portion of the double-pipe unit pipe consisting of the corrosion-resistant inner pipe and the pressure-resistant outer pipe joined thereto is a box thread and bottle thread joint, and furthermore, By fixing a corrosion-resistant material that is integrated with the inner tube on at least one side to the outer tube, it is basically a threaded connection, but there is no need to manufacture a compression ring, which makes manufacturing easier and lower costs. Not only does it have an excellent effect of making it easy to manage the screws, but the abutting surfaces are tightened and crimped during the screwing process, ensuring a sealing function.Moreover, an axial compressive force is applied to the inner tube. Additionally, the corrosion-resistant material has the advantage that it can be reliably formed by overlay welding, beam welding, or the like.

Since the bulging part of the box part has a block shape that is more rigid than that of the coupling joint, there is also the effect of guaranteeing the strength of the corrosion-resistant metal touch part.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of a threaded joint based on the prior art, Fig. 2 and the following are detailed explanatory diagrams of the present invention, and Figs.
6.7.8 and 5 are explanatory diagrams of the manufacturing and screwing processes of other embodiments. l...Inner tube, 2...Outer tube, 3.3'・
・Unit pipe, 8.15...Joint, 11...Box screw, 14...Bottle screw, 8...Box, 15゛pin 1O11O'...Corrosion-resistant material Applicant Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] In a structure in which a unit pipe connecting joint having an outer pipe that joins a corrosion-resistant inner pipe consists of a box screw of one unit pipe and a pin screw of the other unit, the step portions on the box side and the pin side near the inner pipe butt. A double pipe joint structure characterized in that a corrosion-resistant material is embedded and fixed integrally with the inner pipe on at least one of the box side and the bottle side.