JPH02179382A - Method for repairing inside surface of pipe penetrating through vessel - Google Patents

Abstract

PURPOSE:To easily repair the defective part of a penetration pipe by expanding the wall of the penetration pipe mounted by welding into the piping penetration hole of the above-mentioned wall, inserting a metallic sleeve having the length to cover the range of the pipe expansion into the penetration pipe and then seal welding both ends thereof and the inside surface of the penetration pipe. CONSTITUTION:A closing plug 6 is mounted into the hole 3a of the penetration pipe 3 penetrating in the piping penetration hole 2 of the vessel wall 1. An air atmosphere is maintained in the hole 3a lower than the plug 6. Cooling water W is stored in the vessel. The pipe 3 is expanded by a roll method, etc., as shown by an arrow. The expanding range Y is taken slightly larger than the range of a weld zone 5. A rugged surface 7 is formed above and below from the weld zone 5 and distantly from the range Y. The metallic sleeve 8 of the length to cover the surface 7 from the inside is inserted into the pipe 3. The upper and lower parts of the sleeve are expanded. Both ends thereof and the inside surface of the pipe 3 are seal welded by TIG welding, etc. The defective part is easily repaired without exchanging the penetration pipe itself in this way.

Description

[Detailed description of the invention]

"Field of Industrial Application" The present invention relates to a method for repairing the inner surface of a container penetrating pipe. "Conventional technology and its issues" Nuclear power generation related plants, various energy related plants,
BACKGROUND OF THE INVENTION In chemical plants, thermal power plants, and the like, piping that penetrates a container, that is, a container penetrating pipe is used. For example, as shown in Fig. 2, the reactor pressure vessel (container) in a boiling water reactor has the following characteristics: ! (Lower mirror part)
Penetration pipe (piping) 3 via pipe penetration hole 2 drilled in l.
A stub tube 4 is erected at the inner bottom of the container wall 1 so as to extend the pipe penetration hole 2 upward, and the upper edge of the stub tube 4 and the penetration pipe 3
The through pipe 3 is integrated with the outer circumferential portion of the nuclear reactor by a welded portion 5, and the through pipe 3 performs, for example, signal transmission of various sensors for detecting the state of the nuclear reactor. Since such a penetration pipe 3 is attached to the container wall 1 and the stub tube 4, which have excellent mechanical strength, the influence of deformation force due to expansion, contraction, and bending of the penetration pipe 3 will affect the welded part 5 and its vicinity. It tends to appear on pipe walls, and it is required to ensure sufficient reliability. In addition, when forming the welded part 5, it is necessary to avoid the phenomenon that the through pipe 3, which has relatively low mechanical strength, is pulled outward due to the shrinkage of the molten weld metal as it solidifies, or the phenomenon that the through pipe 3, which has relatively low mechanical strength, is pulled outward. Since the heat capacity of the welded portion 5 is smaller than that of the nearby container wall l and the stub tube 4, the welded portion 5
The welding heat generated during formation tends to cause a phenomenon in which a part of the tube wall of the through tube 3 is heated. Therefore, it is desirable to inspect the condition of the welded portion 5 or the pipe wall in the vicinity during periodic inspections. Conventionally, if a defect occurred near the weld 5, it would be necessary to take measures such as dismantling the weld 5 and installing new piping by re-welding, depending on the condition of the defect. . However, the labor involved in replacing piping with new pipes is enormous, and in the case of the vessel wall 1 in the reactor pressure vessel mentioned above, replacement work after reactor operation requires a large amount of labor. It is also necessary to take sufficient measures to reduce radiation exposure, which requires an enormous amount of effort. The present invention has been made in view of the above circumstances, and is designed to protect the inner surface of piping from areas where defects may occur,
The defective part can be removed without dismantling the welded part etc.
The purpose is to ensure reliable repair. "Means for Solving the Problems" The present invention proposes three means for solving these problems. The first method is to expand the pipe wall of the penetration pipe attached to the pipe penetration hole in the container wall by a welded part in an area slightly larger than the area where the welded part is formed, and to create a length that covers the expanded area. A metal sleeve is inserted into a through-tube, and both ends of the metal sleeve are sealed and welded to the inner surface of the through-tube. The second method is to insert a metal sleeve with a length that covers the area where the weld is formed into the through pipe that is attached to the pipe through hole in the container wall by a weld, and to insert both ends of the metal sleeve into the through pipe. In a repair method that performs seal welding between surfaces, prior to inserting the metal sleeve, the metal sleeve is separated from the welding point in the longitudinal direction of the through-hole, and an uneven surface is formed on the inner surface of the through-hole or the outer surface of the metal sleeve at the position t; Then, the metal sleeve is inserted into the through tube, and the tube wall of the metal sleeve is expanded to bring both surfaces of the metal sleeve and the tube wall of the through tube into pressure contact in the area where the uneven surface is formed. Seal welding is performed.゛The third method is to expand the pipe wall of the penetration pipe that is attached to the pipe penetration hole in the container wall by a welded part in an area slightly larger than the area in which the welded part is formed, and to remove the penetration pipe from the welded part position. forming an uneven surface on the inner surface of the through-tube or on the outer surface of the metal sleeve at positions spaced apart in the longitudinal direction, and then inserting the metal sleeve into the through-tube and expanding the tube wall of the metal sleeve; After the surfaces of the metal sleeve and the tube wall of the through tube are brought into pressure contact in the area where the uneven surface is formed, seal welding is performed between both ends of the metal sleeve and the inner surface of the through tube. "Effect" In each of these means, when the wall of the through pipe is expanded,
The radially outward movement of the pipe wall due to pipe expansion is suppressed by the presence of the weld, and radially outward movement of the pipe wall at a location slightly away from the weld in the longitudinal direction of the through tube is allowed. As a result, the tube wall undergoes elastic deformation, and a portion of the tube wall begins to undergo plastic deformation beyond the range of tensile stress. When the external force for pipe expansion is released in a state where the diameter of the pipe wall has increased by the amount of plastic deformation, a phenomenon occurs in which the plastic deformation is reduced in the part of the pipe wall where no plastic deformation has occurred. A compressive residual stress is applied to the part. When the uneven surface between the penetrating pipe and the metal sleeve is brought into pressure contact by expanding the pipe after inserting the metal sleeve, a retaining part is formed between the surfaces due to elastic deformation of the uneven surface, etc., and the penetrating pipe The movement of the metal sleeve in the longitudinal direction is suppressed. Therefore, even if a force that causes misalignment is applied between the through pipe and the metal sleeve due to differences in thermal expansion, etc., mutual misalignment is prevented near the uneven surface portion, and the seal welded portion This prevents excessive force from being applied. In addition, the seal welded part of the metal sleeve inserted inside the penetrating pipe isolates the space between them, preventing direct contact with the internal fluid of the penetrating pipe, and causing new defects or growth of defects in that area. will be prevented. “Example” 1st r! ! J(A) to FIG. 1(, G) show one implementation in which the method for repairing the inner surface of a vessel penetrating pipe according to the present invention is applied to a penetrating pipe 2 of a vessel wall 1 in a reactor pressure vessel shown in FIG. This is an example. Hereinafter, the steps will be explained in order based on FIG. 1(A) to FIG. 1(G). [Study of the influence of welded part formation] When the penetrating pipe 3 is attached to the stub tube 4 by the welded part 5, due to the heat contraction phenomenon when the weld metal solidifies from a molten state, the penetrating pipe near the welded part 5 may 3 and the stub tube 4, a tensile residual stress is generated in the stub tube 4, as indicated by the 0 symbol in FIG. 1(A). For this reason, the penetration pipe 3 is pulled in the radial outward direction near the welded part 5, and as shown in FIG. It is assumed that a tensile residual stress indicated by the 0 sign is applied to the In addition, the penetration pipe 3 is a small-diameter pipe, and its pipe wall is thinner than that of the stub tube 4, so that its heat capacity is relatively small. It is assumed that a heat-affected zone X is generated in a part of the wall that has become sensitized by being heated, that is, in a range located at position 1 on both sides of the center position C of the welded part 5. On the other hand, generally speaking, in austenitic steel,
When corrosion factors and tensile residual stress exist at the same time, stress corrosion cracking and the like tend to progress. Therefore, if there is water as a corrosive fluid on the inner and outer surfaces of the penetrating pipe 3 and at the same time tensile residual stress is applied to the pipe wall, we will consider ways to improve this situation. For example, assuming that tensile residual stress is applied to the portion between position 1t+ and position 1t+ on the outer surface of the penetration pipe 3, the tensile residual stress shown in FIG. Improvements will be made by expanding a portion of the wall as described below. [Closure of container penetrating pipe] As shown in FIG. 1(C), a penetrating pipe (for example, made of 5US304 Piping) 3
A blockage stopper 6 is installed in the tube type 3 breather to divide the inside of the tube type 31 into upper and lower sections, and the tube type 31 below the blockage stopper 6 is made into an air atmosphere. In addition, the cooling water W is stored in the container, and the work is carried out while reducing the radiation exposure dose of the workers (the same applies to each of the following works). [Pipe Expansion of the Penetration Pipe] Insert appropriate equipment into the penetration pipe 3, and use the roll method, local internal pressure loading method, etc. to expand the pipe wall in the radial outward direction as shown by the arrows in Fig. 1(C). Expand the tube. In this case, the expansion range Y is set to be slightly larger than the range (height size range) of the welded part 5, for example, from 30 II m to 40 mm from the range of the welded part 5, and Set it to be larger than X. Note that if the tube expansion range Y has to be divided due to limitations of the tube expansion equipment or work, the ranges of the welded portions 5 are set to overlap. When the pipe wall is moved in the radial outward direction by pipe expansion, the movement of the pipe wall is blocked in the part where the welded part 5 is present, and on the other hand,
The pipe wall at locations vertically away from the welded part 5 is allowed to move in the radial outward direction, so the pipe wall deforms elastically, and some internal stress exceeds the yield point, resulting in plastic deformation. , as shown by the chain line in Figure 1 (D),
The diameter of the tube wall increases by the amount of plastic deformation. The amount of tube expansion in this case is affected by the material of the through tube 3 and the size of the welded portion 5, but the tube is expanded to an extent that the diameter increases by about 1 to 5%, for example. Next, when the force for expanding the tube is returned to the state in which it is removed, a force is generated that reduces the plastically deformed portion from the state shown by the chain line in FIG. 1(D) to the state shown by the solid line, and the plastically deformed portion
Regarding the surface indicated by the reference numeral in FIG. 1(B), it acts to shift the residual stress in that portion to a compressive residual stress. [Irregular surface machining 1 on the inner surface of the penetrating pipe 1 As shown in FIG.
An uneven surface 7 consisting of, for example, a plurality of circumferential grooves is formed on the inner surface of the tube wall in a portion that is deviated by about oam. When forming a circumferential groove, the depth is set to 0.1, for example.
Set m1 to 0.5 degrees.

[Insertion and expansion of metal sleeve]

A metal sleeve 8 having a dimension longer than the tube expansion range Y and having a length to cover the uneven surface 7 from inside is inserted into the through tube 3 to cover the uneven surface 7 from the inner side. In this case, the material of the metal sleeve 8 is 5US.
304 material, a material that is relatively softer than this, such as 5US304L material or 5US316L material.
Use materials. Then, the upper end portion and then the lower end portion of the metal sleeve 8 are expanded as shown in FIG.
At the same time, the pipe wall is slightly plastically deformed. That is, the outer diameter of the metal sleeve 8 is expanded to be larger, for example, by about 0.5 to 1% than the inner diameter of the tubular type 3&, so that the pressed state is maintained. However, in Figure 1 (F
) is shown with a seal welded portion 9, which will be described later, formed. In this way, when the through pipe 3 and the metal sleeve 8 are brought into pressure contact with each other with the uneven surface 7 interposed between them, the surface of the metal sleeve 8, which is soft in material, is locally elastically or plastically deformed. As a result, as shown in FIG. 1(G), a retaining portion is formed between both surfaces to prevent mutual movement in the longitudinal direction. [Seal Welding] Furthermore, seal welding is performed between both ends of the metal sleeve 8 and the inner surface of the through pipe 3 by TIG welding or YAG laser, etc., and by forming a seal weld 9, the area where the metal sleeve 8 is placed is sealed. Do this. In seal welding in this case, in order to reduce the influence of welding heat on the tube wall portion of the penetrating pipe 3, it is preferable to suppress the welding heat input to, for example, about 1 to 5 kg. [Condition after repair] After the seal weld 9 is formed, the metal sleeve 8 is integrated with the through pipe 3, but there is a difference in temperature, material difference, and heat between the through pipe 3 and the metal sleeve 8. If a deviation occurs due to dimensional differences due to differences in expansion, etc., in order to restrict movement in the longitudinal direction at the uneven surface 7, an excessive force or Addition of stress can be avoided. Furthermore, after the seal weld 9 is formed, the internal fluid of the through tube 3 does not come into direct contact with the inner surface of the tube wall in the vicinity of the weld 5. On the other hand, after the seal weld 9 is formed, the above-mentioned plug 6 is removed. Other Embodiments> The following configuration can be adopted instead of the embodiment described above. (b) Instead of being applied to the penetration pipe of the lower head of the reactor pressure vessel, it may be applied to the pipe in which 7 flanges are attached to the outer peripheral surface of the pipe by welding, or to a simple straight metal pipe. apply. (b) Forming the uneven surface 7 on the outer surface of the metal sleeve 8. (c) The uneven surface 7 is other than a circumferential groove, such as an embossed surface, a low-left surface, or a threaded surface. (d) The area in which the uneven surface 7 is formed is not limited to the vicinity of both ends of the metal sleeve 8, but is formed in the entire area or in a plurality of areas where the through pipe 3 and the metal sleeve 8 are fitted together. (E) The expansion range of the metal sleeve is not limited to the uneven surface 7, but is expanded to the entire range or multiple locations where the through pipe 3 and the metal sleeve 8 are fitted, and the expansion range is also integrated in the middle etc. What to aim for. (f) Forming a corrosion-resistant coating layer covering the inside of the penetrating pipe 3 at necessary locations on the inner surface, that is, in an appropriate range extending vertically from the position of the seal weld 9 (range of the heat affected zone due to seal welding). . (g) The corrosion-resistant coating layer is formed of metal plating such as Cr, Ti, etc. that has corrosion resistance, taking into account the internal fluid of the through pipe 3. (H) It is possible to replace the corrosion-resistant coating layer with a metal molten solidified layer. In this case, with powders of (r, Ti, etc.) adhered to the top and bottom of the seal weld 9, a laser beam is applied to Cr, Ti, etc. , T i is rapidly heated and melted, and then a metal molten solidified layer is formed on the inner surface of the through pipe 3 by cooling and solidification, and new corroded parts and defective parts are generated due to the corrosion resistance of the metal itself in the metal molten solidified layer. (1) Another method for forming a molten metal solidified layer is to use a laser or TIG welding torch and set it to have a small heat input to prevent the formation of the seal weld 9 described above. In addition to covering the range of the heat affected zone from the inside, the inner surface of the through pipe 3,
Modification of the re-solidified structure so that it contains delta ferrite by directly melting and solidifying the structure on the extreme surface. "Effects of the Invention" As explained above, the method for repairing the inner surface of a metal pipe according to the present invention includes: (i) inserting a new metal sleeve into the through pipe that is attached to the pipe through hole by a welded part; Since the pipe is sealed and welded to the inner surface of the through pipe, if a defect occurs or there is a possibility of a defect on the inner surface of the pipe wall near the weld, the through pipe itself should be replaced. This makes it easy to repair defective parts without any problems. (U) Defects or areas where defects may occur on the inner surface of the through pipe are covered with a metal sleeve and sealed by seal welding. It is possible to take measures to repair defective parts and prevent leakage without being affected by this. (iii) As a result of the above, there is no need to replace the penetrating pipe or dismantle the welded part, so in the case of a penetrating pipe of a reactor pressure vessel, the radiation exposure dose of repair workers can be reduced. (iv) By expanding the penetrating pipe, the pipe wall near the weld is guided in the direction of creating compressive residual stress, so it is possible to not only repair the inner surface of the penetrating pipe, but also to repair the residual stress on the outer surface near the weld. It is possible to improve stress, suppress the occurrence of defective parts themselves, and prevent the growth of defective parts if they have been generated. (v) Since the metal sleeve is expanded to bring the uneven surface into pressure contact, even if the through tube and the metal sleeve become misaligned in the longitudinal direction, they must be fixed by the uneven surface. Therefore, the displacement has little effect on the seal weld, and the area to be sealed can be reliably protected from the internal fluid and prevented from contacting it. It has excellent effects such as

[Brief explanation of the drawing]

1(A) to 1(G) are process explanatory diagrams showing one embodiment in which the method for repairing the inner surface of a vessel penetrating pipe according to the present invention is applied to a penetrating pipe of a vessel wall of a reactor pressure vessel; The figure is a front sectional view showing an example of piping that penetrates a vessel wall in a boiling water reactor. Figure 1 (A) l... Container! ! ! (Lower mirror part), 2...
Piping penetration hole, 3... Penetration pipe, 31... Pipe type, 4... Stub tube, 5... Welded part, 6... ...Occupation plug, 7...Uneven surface, 8...Metal sleeve, 9...Seal welded part, W...Cooling water, X... ...Heat-affected zone, Y...Pipe expansion range. Figure 1 (D) Figure 1 (F)

Claims (3)

[Claims] (1) Expand the pipe wall of the penetration pipe attached to the pipe penetration hole in the container wall by a weld to an area slightly larger than the area where the weld is formed, and install a metal sleeve long enough to cover the expansion range. A method for repairing the inner surface of a container penetrating pipe, the method comprising inserting the penetrating pipe into the pipe and sealing welding between both ends of the penetrating pipe and the inner surface of the penetrating pipe. (2) Insert a metal sleeve with a length that covers the area where the weld is formed into the through pipe that is attached to the pipe through hole in the container wall by a weld, and connect both ends of the sleeve to the inner surface of the through pipe. In the repair method of seal welding between
Prior to inserting the metal sleeve, an uneven surface is formed on the inner surface of the through-tube or on the outer surface of the metal sleeve at a position spaced apart from the welding point in the longitudinal direction of the through-tube, and then the metal sleeve is inserted into the through-tube. , after expanding the tube wall of the metal sleeve and bringing both surfaces of the metal sleeve and the tube wall of the through tube into pressure contact in the area where the uneven surface is formed,
A method for repairing an inner surface of a container penetrating pipe, the method comprising performing the seal welding described above. (3) Expand the pipe wall of the penetration pipe that is attached to the pipe penetration hole in the container wall by a weld to an area slightly larger than the area where the weld is formed, and extend the pipe wall from the weld location in the longitudinal direction of the penetration pipe. Forming an uneven surface on the inner surface of the through tube or the outer surface of the metal sleeve at a spaced apart position, and then inserting the metal sleeve into the through tube and expanding the tube wall of the metal sleeve to form the uneven surface. 1. A method for repairing an inner surface of a container penetrating tube, the method comprising: bringing both surfaces of the metal sleeve and the tube wall of the penetrating tube into a press-contact state, and then performing seal welding between both ends of the metal sleeve and the inner surface of the penetrating tube.