JPH03168492A - Forming of pipe joint - Google Patents

Abstract

PURPOSE:To prevent crack by inserting a communicating pipe in a through hole in a mother pipe wall, and a backup ring in an annular clearance between the inner wall of the through hole and the outer wall of the communicating pipe, expanding the diameter of the outer edge of the communicating pipe for close contact, and welding a coupling to the backup ring. CONSTITUTION:A communicating pipe 13 is inserted in a through hole 12 in the pipe wall of a mother pipe 9, a backup ring 24 is inserted in an annular clearance 23 between the inner wall of the through hole 12 and the outer edge part of the communicating pipe 13. Next, the outer edge part of the communicating pipe 13 is plastic-deformed to fit it closely with the backup ring 24. Then a coupling 14 is disposed at the outside of the backup ring 24, the outer wall surface of the mother pipe 9, a part of surface of the backup ring 24, and the coupling 14 are welded 16 to form a jointing part. Thus, it is possible to prevent the communicating pipe 13 from being cracked by stress corrosion and reduce heat effect to the communicating pipe 13 since heat effect at the time of welding is transmitted indirectly.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to a method of forming a pipe joint, and in particular, to a method for forming a pipe joint, and in particular, a method for forming a welded joint when a connecting pipe and a coupling ring are attached by welding to a hole drilled in a main pipe wall. The present invention relates to technology for preventing the occurrence of defects in the vicinity.

"Conventional technology" Nuclear power generation related plants, various energy related plants,
BACKGROUND ART In chemical plants, thermal power plants, etc., sampling pipes, pressure detection pipes, signal extraction pipes, and the like may be connected in the middle of piping lines by pipe joints.

Taking the reactor containment vessel in a boiling water reactor as an example,
To explain based on FIG. 2, a reactor pressure vessel 3, a reactor pedestal 4, a reactor shielding wall 5, and a reactor pressure vessel 3, a reactor pedestal 4,
are stored respectively, and the diaphragm floor 6
According to the dry well 7 and subrecitan chamber 8
The main steam system piping 9 installed in the dry well 7 has a flow rate restriction for the purpose of limiting the maximum amount of steam in the event of a rupture accident in the piping route and detecting the steam flow rate. As shown in FIG. ) A through hole 12 and a connecting pipe 13 that communicate with the outside of the main pipe 9, and a coupling l4 located outside the connecting pipe 3 and attached to the outer wall of the main pipe 9 so as to extend the through hole l2 to the outside. It has a pipe joint structure in which the connecting pipe 13 and the coupling l4 are attached to the main pipe 9 by an internal welding hole L5 and an external welding part l6, and the coupling l4 further includes a flow rate. Detection tube 17
are connected and guided to the desired location.

``Problem to be Solved by the Invention'' With such a pipe joint structure, when forming both welded parts 15 and 16, it is difficult to Tensile residual stress tends to remain in the vicinity. For example, the main pipe 9, the connecting pipe l3, and the coupling l4 are each formed of austenitic steel such as SUS304 in many cases, but in particular,
In contrast to the main pipe 9 which has excellent mechanical strength, the connecting pipe l3 has a small diameter.
is attached, the main pipe 9 is thermally deformed and force is concentrated on the internal welding part l5 that fixes the connecting pipe l3. It is required to ensure sufficient reliability.

Therefore, during periodic inspections, etc., both welded parts l5 and 1
It is desirable to thoroughly inspect the condition of the pipe wall at or near the pipe wall.

Conventionally, if a defective part occurs near both welding holes l5 and l5, or if there is a concern about it, the pipe joint is
It is considered to take measures such as dismantling the pipe at part 6 and installing a new connecting pipe 13 and coupling 14 by re-welding.

However, even in that case, unless measures are taken to prevent the occurrence of defects near the internal welds 15, which are subject to particularly severe conditions, the pipe joint may have to be dismantled and repaired again. In the case of the above-mentioned main steam system piping 9, during replacement work after reactor operation, it is also necessary to take sufficient measures to reduce radiation exposure of workers, which requires a great deal of effort.

The present invention has been made in view of these circumstances, and it is possible to prevent the occurrence of defects near welds in pipe joints, and it can also be applied when repairing existing pipe joints.

"Means for Solving the Problem" In order to solve the problem, there is a step of inserting the outer end of the communicating tube into a through hole made in the wall of the main tube, and a step of inserting the outer end of the communicating tube into the through hole formed in the wall of the main pipe, and connecting the inner wall surface of the through hole with the communicating tube. A step of inserting a backup ring into the annular gap with the outer end, a step of expanding the diameter of the outer end of the communication pipe to cause plastic deformation and bringing the outer end into close contact with the backup ring, The method for forming a pipe joint combines the steps of arranging a coupling on the outside of the ring and welding the outer wall surface of the main pipe, the Ichiro surface of the backup ring, and the coupling.

"Effect" When the diameter of the outer end of the communication pipe is expanded to cause plastic deformation,
Due to the reaction force that elastically deforms the backup ring during diameter expansion, the outer end is compressed in proportion to the diameter expansion, resulting in a so-called fitted condition, which causes the outer end and the backup ring to tighten. A sealing property is created in the close contact portion, and movement of the connecting A-tube is prevented.

When welding between the outer wall surface of the main pipe, a part of the surface of the backup ring, and the coupling, the heat generated during the formation of the welded portion is less transmitted to the communicating pipe, and there is no thermal effect.

On the other hand, the backup ring part can be made of a material that is less likely to cause defects such as stress corrosion cracking. 4 shows an example of a process in which the method for forming a pipe joint according to the invention is applied to a pipe joint at the flow agitation restrictor IO shown in FIG. 3.

[Formation of main tube through hole] As shown in FIG. A welding seat 20 is integrally provided by a method such as buttering made of SOS30B and SOS3O9 materials so as to cover the outer surface of the pipe 9,
A large-diameter hole 2l is formed in the welding seat 20, concentrically connected to the through-hole l2, and having a larger diameter than the through-hole l2. The large diameter hole 21
The step portion 22 is formed by forming the step portion 22 . In addition, when applying the following method to an existing main pipe, the original through hole is enlarged in accordance with the above.

[Insertion of a communicating tube] A communicating tube 13 made of, for example, SUS304 material is inserted into the through hole 12 of the main tube 9 so as to face outward. By inserting the communicating tube t3, an annular gap 2 is created between the inner wall surface of the through hole l2 and the outer end (the upper end in FIG. 1) of the communicating tube l3.
3 is formed.

[Insertion of Backup Ring] A backup ring 24 is inserted into the annular gap 23 formed between the inner wall surface of the through hole l2 and the outer end of the communication pipe l3, as shown in FIG. 1(B). do.

The backup ring 24 has a large diameter hole 24a that can be inserted into the large diameter hole 2l and is locked to the step 22, and the upper end thereof is set to protrude outward from the welding seat 20.
For example, STJS, which is a low SCC material (stress corrosion cracking resistant material)
3 1 6L.

[Expanding the diameter of the communicating pipe] By expanding the range X shown in FIG. 1(C) in the radial outward direction using an Ifa device as appropriate, ) to elastically deform the inner wall of the through hole l2 and the backup ring 24, and at the same time cause plastic deformation to occur at the outer end of the communicating pipework 3, thereby bringing the plastically deformed portion into close contact with the backup ring 24. leave it in that state.

After expanding the diameter of the outer end of the communication pipe 13 to cause plastic deformation, if the diameter expansion force is removed, the through hole l will be removed when the diameter is expanded.
Due to the reaction force that elastically deforms the inner part 91 of 2 and the backup ring 24, the plastically deformed portion of the communication pipe l3 is compressed and contracted inward in accordance with the diameter expansion, resulting in a so-called fitted state. , a sealing property is generated at the close contact between the outer end of the communication pipe l3 and the backup ring 24, and the communication pipe l3 is in a fixed state, and henceforth, movement of the communication pipe {3 is prevented.

c Coupling Setting] As shown in FIG. 1(D), the coupling l4 is externally fitted onto the backup ring 24 protruding from the welding seat 2o. In this case, the backup ring 24 positions the coupling l4. The coupling 14 is made of, for example, SUS3 1 6L, which is a low scc material.
formed by

[Coupling Welding] As shown in FIG. 1(E), an external weld is formed between the welding seat 20, which is the outer wall surface of the main pipe 9, a part of the surface of the backup ring 24, and the coupling l4. 16 and integrate them.

“State of the pipe joint” The pipe joint formed in the state shown in Fig. 1 (E) is the state of the connecting pipe 13.
As a method of fixing the outer end to the main pipe 9, the diameter of the outer end is expanded together with the backup ring 24, and the reaction force caused by the elastic deformation at the time of diameter expansion causes the part whose diameter has increased due to plastic deformation to be connected. The outer end of the tube 13 is constantly compressed and supported, and compressive stress is applied to the outer end.
This prevents defects such as stress corrosion cracking from occurring in this part. Furthermore, since the welding heat when forming the external welded portion 16 passes through the welding seat 20, the main pipe 9, and the backup ring 24, the diameter expansion portion of the connecting pipe 13 may be affected by the heat. disappears.

On the other hand, when considering the influence of welding heat due to the shape of the external welding ring 16, the main pipe 9 forms a welding seat 20, and this welding seat 20, the coupling 14, and the backup ring 24 are made of stress corrosion cracking resistant material. You can respond by doing this.

[Other Embodiments] In the above embodiment, the main pipe 9 includes a connecting pipe l.
3 and the coupling L4, that is, the method of forming a new pipe joint, was taken as an example, but it can also be applied to the case of repairing a pipe joint.

To explain this application example, as mentioned above, the through hole l2 is re-drilled, a new welding seat 20 is provided, and the materials for the coupling 14 and backup ring 24 are carefully examined, and the process is carried out according to the process described above. A pipe joint can be formed by using the following steps.

"Effects of the Invention" As explained above, the method for forming a pipe joint according to the present invention is: (1) When attaching a connecting pipe to a main pipe, the diameter is expanded by interposing a backup ring; Compressive stress is applied to the expanded diameter portion of the connecting pipe,
The occurrence of stress corrosion cracking can be prevented.

■It is possible to omit welding of the fixed part of the connecting pipe, and the transfer of welding heat when forming the external weld is indirect via the backup ring and main pipe wall, reducing the thermal effect. can.

■Can be applied to existing pipe fittings by re-drilling the through holes and replacing the Ichiro material.
In particular, the effect of improving the connecting pipe attachment part is high.

It has excellent effects such as:

[Brief explanation of the drawing]

FIG. 1(A) to FIG. 1(E) are process explanatory diagrams in one embodiment of the method for forming a pipe joint according to the present invention, and FIG. 2 shows an example of a reactor containment vessel for a boiling water reactor. The front sectional view and FIG. 3 are enlarged sectional views taken along the chain line ■ in FIG. 9... Main steam system piping (main pipe), 10...
・Flow rate restrictor, 11... Throttle pipe, 12... Through hole, l3... Connecting pipe, l4... Coupling, 16... ...External welding part, 20...Weld seat, 21...Large diameter hole, 22...Step part, 23...Annular gap, 24... ...Backup ring, 24a...
...Large diameter part. Figure 2 Figure 3

Claims (1)

[Claims] inserting the outer end of the communicating pipe into a through hole drilled in the main pipe wall; inserting a backup ring into the annular gap between the inner wall surface of the through hole and the outer end of the communicating pipe; A step of enlarging the diameter of the outer end of the communication pipe to cause plastic deformation and bringing the outer end into close contact with the backup ring, and disposing a coupling on the outside of the backup ring and connecting it to the outer wall surface of the main pipe. 1. A method for forming a pipe joint, comprising the step of welding a part of the surface of a backup ring and a coupling.