Rehabilitation methods for existing pipes

Abstract

To prevent breakage caused by twisting of a pulling wire during pipe fabrication, and prevent damage and the like of a connection portion between wires caused by tensile load at the time of pulling, in a method of rehabilitating an existing pipe through an expansion pipe fabrication method.SOLUTION: A belt-like member 10 is spirally wound, and adjacent edge portions are joined together. A spiral pipe shaped rehabilitation pipe 3 is fabricated into a smaller diameter than an existing pipe 1 and screwed into the existing pipe. At the beginning of a pipe fabricating process, a connection end portion 22e of a pulling wire 22 is connected to an extension end portion 21e of a cutting wire 21 that extends from a pipe end 3e of the rehabilitation pipe 3. After a pipe fabrication process of the rehabilitation pipe 3, a rotary joint 30 is removed, and the connection end portion 22e and the extension end portion 21e are connected together. Thereafter, by pulling the pulling wire 22, a part of a joined portion 15 between neighboring edge portions is cut off, to weaken a binding force of the joined portion 15 from a second side toward a first side in order. Concurrently, a circumferential length of the weakened portion of the rehabilitation pipe 3 is expanded.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for rehabilitating existing pipes such as aging sewer pipes. In particular, after manufacturing a spiral-shaped rehabilitation pipe made of a strip member (profile) along the inner circumference of an existing pipe to have a diameter smaller than the inner diameter of the existing pipe, the present invention relates to a method for rehabilitating an existing pipe by an expansion pipe manufacturing (expand pipe manufacturing) method that expands the circumference of the rehabilitation pipe.

Background Art

[0002] A method for rehabilitating an existing pipe by constructing a spiral-shaped rehabilitation pipe made of a strip member (profile) along the inner circumference of an existing pipe such as an aging sewer pipe is known (see Patent Document 1, etc.).

[0003] For example, Patent Document 1 discloses a method for rehabilitating an existing pipe by a so-called expand pipe manufacturing method. Specifically, a mandrel-type pipe manufacturing machine is installed in the manhole on the launching side. By winding a strip member in a spiral shape and joining adjacent edge portions thereof by concave-convex fitting, while manufacturing a spiral-shaped rehabilitation pipe to have a diameter smaller than the inner diameter of the existing pipe, the rehabilitation pipe is sequentially pushed into the existing pipe. During pipe manufacturing, a cutting wire is interposed between adjacent edge portions of the strip member. When the tip portion in the pushing direction of the rehabilitation pipe reaches the pipe mouth on the reaching side, the tip portion (the end portion on the reaching side) in the pushing direction is fixed. Then, by pulling out the cutting wire, a part of the joint portion between the adjacent edge portions is sequentially cut along the winding direction to weaken the joining force. In parallel, by supplying the strip member to the rehabilitation pipe by the pipe manufacturing machine, the end portion on the launching side of the rehabilitation pipe is twisted and rotated. As a result, the adjacent edge portions of the joint portion whose joining force has been weakened by the cutting slide, and the circumference of the rehabilitation pipe is sequentially expanded (diameter-expanded) from the reaching side toward the launching side and is attached to the inner peripheral surface of the existing pipe.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] In the expanded pipe manufacturing method, for example, a pull-up wire is passed from the starting side (first side) to the receiving side (second side) within the rehabilitated pipe during the initial stage of pipe manufacturing, and connected to the end of a cutting wire extending from the receiving side (second side) of the rehabilitated pipe. Subsequently, as the rehabilitated pipe is extended during manufacturing, the cutting wire and the pull-up wire are each fed out from the starting side (first side).

[0006] On the other hand, when a pipe is being manufactured using a push-type pipe manufacturing machine, the rehabilitated pipe is pushed toward the receiving side (second side) while being rotated. Therefore, if the cutting wire and the pull-up wire were connected in a way that could transmit rotational force, there is a risk that the pull-up wire would be continuously twisted and break during the pipe manufacturing process. To avoid this, it is conceivable to install a swivel joint between the cutting wire and the pull-up wire to isolate them from the rotational force.

[0007] However, rotary joints cannot be expected to have high strength against tensile loads. Therefore, when pulling up a wire to cut a portion of the joint between adjacent edges of a rehabilitation pipe, a tensile load exceeding the tensile strength of the rotary joint may be applied, potentially damaging the rotary joint and, consequently, the connection between the wires. In particular, if the portion to be cut is thick-walled, or if the rigidity of the strip-shaped member is high and it is difficult to pull out the cutting wire, a considerably large tensile load will be required, making the rotary joint more susceptible to damage. Furthermore, the rotary joint may also be damaged by contact with pull-up guides such as pulleys along the pull-up path. In view of these circumstances, the present invention aims to prevent breakage due to twisting of the pull-up wire during pipe manufacturing and to prevent damage to the connection between wires due to tensile load during pull-up in an existing pipe rehabilitation method using expanded pipe construction. [Means for solving the problem]

[0008] To solve the aforementioned problems, the present invention provides a method for rehabilitating an existing pipe, comprising: a pipe manufacturing step in which a spiral-shaped rehabilitated pipe is formed by spirally winding a strip-shaped member and joining adjacent edge portions that are offset by one rotation, is manufactured to a diameter smaller than the inner diameter of the existing pipe and is twisted into the existing pipe from the first side to the second side in the pipe axis direction; a restraint weakening step in which the restraint force between the adjacent edge portions of the rehabilitated pipe is sequentially weakened from the second side to the first side; and an expansion step in which the pipe end on the first side of the rehabilitated pipe is twisted to expand the circumference of the weakened portion of the rehabilitated pipe. In the aforementioned pipe manufacturing process, during the joining process, a wire interposition step is performed in which a cutting wire is interposed between the adjacent edge portions, In the initial stage of the pipe manufacturing process, the connecting end of the pull-up wire is passed through the rehabilitation pipe from the first side to the second side, and a rotatable coupling step is performed to connect it to the extended end of the cutting wire extending from the second pipe end of the rehabilitation pipe so that it can rotate relative to the pull-up wire via a rotary joint. After the pipe manufacturing process and before the start of the restraint weakening process, a high-tensile strength connecting process is performed, in which the rotary joint is removed and the connecting end and the extended end are connected via a connecting means having higher tensile strength than the rotary joint. The device is characterized in that, from the beginning to the middle of the restraint weakening process, the pull-in wire is pulled towards the first side, and thereafter the cutting wire is pulled, thereby cutting a portion of the joint between adjacent edge portions with the cutting wire.

[0009] According to this rehabilitation method, even if the extended end of the cutting wire rotates in conjunction with the rotation of the rehabilitated pipe during the pipe manufacturing process after the rotatable joint process, the rotational force is cut off by the rotary joint, preventing the pull-up wire from rotating. Therefore, it is possible to prevent the pull-up wire from being excessively twisted and broken. Furthermore, by reconnecting the pull-up wire and the cutting wire with a high-tensile-strength connecting means prior to the restraint weakening process and the expansion process, it is possible to prevent the connection between the pull-up wire and the cutting wire from breaking due to the tensile load when the pull-up wire is pulled to take up the cutting wire. In particular, even if a considerably large connection is required because the portion to be cut at the joint between adjacent edges of the rehabilitation pipe is thick-walled, or because the rigidity of the strip-shaped member is high and it is difficult to pull out the cutting wire, it is possible to reliably prevent the connection between the wires from breaking. Furthermore, the rotary coupling will not be damaged by contact with pulleys or other pull-up guides along the pull-up path.

[0010] Preferably, in the high-tensile strength connection step, the connecting end and the extension end are connected via a crimping fitting that is crimped to these ends. The crimping fitting constitutes a connection means with higher tensile strength than the rotary joint. Preferably, the crimping fitting is cylindrical in which the connecting end and the extension end can be inserted. [Effects of the Invention]

[0011] According to the present invention, in a method for rehabilitating existing pipes using the expanded pipe construction method, it is possible to prevent breakage due to twisting of the pull-up wire during pipe construction. Furthermore, it is possible to prevent damage to the connection points between wires due to tensile load during pull-up. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a front cross-sectional view showing an existing pipe undergoing rehabilitation work using the expanded pipe manufacturing method according to the first embodiment of the present invention, at the initial stage of the pipe manufacturing process. [Figure 2] Figure 2(a) is a cross-sectional view of the strip-shaped member along the line IIa-IIa in Figure 1. Figure 2(b) is a cross-sectional view of the rehabilitated pipe during the pipe manufacturing process, showing an enlarged view of the circular section IIb in Figure 1. Figure 2(c) is a cross-sectional view of the rehabilitated pipe during the restraint weakening process, showing an enlarged view of the circular section IIc in Figure 5. [Figure 3]FIG. 3 is a front view of a wire connection part including a rotary joint in the pipe manufacturing process. [Figure 4] FIG. 4(a) is a front view showing a wire connection part including a crimp joint in the restraint weakening process and the expansion process in a state before crimping. FIG. 4(b) is a front view of a wire connection part including a crimped crimp joint. [Figure 5] FIG. 5 is a front cross-sectional view showing an existing pipe during the rehabilitation construction in the restraint weakening process and the expansion process. [Figure 6] FIG. 6 is a cross-sectional view showing a wire connection part including a crimp joint according to the second embodiment of the present invention in a cross-section perpendicular to the axis of the crimp joint. [Figure 7] FIG. 7 is a cross-sectional view showing a wire connection part including a crimp joint according to the third embodiment of the present invention in a cross-section perpendicular to the wire. [Figure 8] FIG. 8 is a front view of a wire connection part including a crimp joint according to the fourth embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. <First Embodiment> As shown in FIG. 1, the existing pipe 1 is rehabilitated by lining the rehabilitation pipe 3 on the inner circumference of the aged existing pipe 1. The existing pipe 1 to be rehabilitated is, for example, a sewer pipe buried underground, but the present invention is not limited to this, and it may be a water supply pipe, an agricultural water pipe, a gas pipe, a hydraulic power generation water conduit, a tunnel, or the like.

[0014] As shown in FIG. 2(a), the rehabilitation pipe 3 is composed of a strip member 10 (profile). The strip member 10 is made of a synthetic resin such as polyvinyl chloride (PVC) and is formed in a certain cross-sectional shape. In this embodiment, the strip member 10 has a plurality of hollow and rectangular cross-sectional ribs 12. On both edge portions in the width direction of the strip member 10, two male and female fitting portions 13 and 14 are provided.

[0015] The existing pipe 1 is rehabilitated as follows. <Pipe manufacturing process> As shown in FIG. 1, a push-type pipe manufacturing machine 8 is prepared and installed in the starting-side manhole 4 connected to the pipe end 1d on the starting side (first side) of the existing pipe 1. The strip-shaped member 10 is sequentially fed out from the drum 7 on the ground and supplied to the pipe manufacturing machine 8. In the pipe manufacturing machine 8, the strip-shaped member 10 is wound in a spiral shape, and the fitting portions 13 and 14 of the adjacent edge portions that are shifted by one turn are joined by concave-convex fitting (FIG. 2(b)), and the spiral-shaped rehabilitated pipe 3 is sequentially manufactured. The concave-convex fitting portions 13 and 14 form a spiral joint portion 15. In the joint portion 15, the adjacent edge portions are constrained. The rehabilitated pipe 3 in the pipe manufacturing process is manufactured to have a smaller diameter than the inner diameter of the existing pipe

[0016] Preferably, as shown in FIG. 2(b), among the two groove-shaped fitting grooves 13a and 13b of the female fitting portion 13, for example, a moisture-curing adhesive 16 is filled in the fitting groove 13a. A hot-melt adhesive 17 is filled in the fitting groove 13b. Among the two ridges 14a and 14b of the male fitting portion 14, the ridge 14a is slidably fitted into the fitting groove 13a. The ridge 14b is fitted into the fitting groove 13b and adhered.

[0017] <Wire intervention process> In parallel with the pipe manufacturing process, the cutting wire 21 is introduced from the pay-off roll 23 to the pipe manufacturing machine 8 and interposed between the fitting portions 13 and 14 (adjacent edge portions) during joining (FIG. 2(b)). Specifically, the cutting wire 21 is disposed between the two ridges 14a and 14b and sandwiched by covering the fitting portion 13. The end portion 21e of the cutting wire 21 is extended from the vicinity of the tip of the rehabilitated pipe 3, that is, the pipe end 3e on the arrival side (second side), to the inside of the rehabilitated pipe 3.

[0018] <Rotatable connection process> As shown in Figure 1, in the early stages of the pipe manufacturing process, for example, when the number of turns in the spiral of the rehabilitated pipe 3 is several, the connecting end 22e of the pull-up wire 22 is passed from the starting side (first side) to the receiving side (second side) inside the rehabilitated pipe 3. Then, the extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22 are connected via a swivel joint 30.

[0019] As shown in Figure 3, the rotary coupling 30 includes a pair of connecting parts 31 and a rotary connecting part 32 between these connecting parts 31. The connecting parts 31 on both sides are connected via the rotary connecting part 32 so as to be rotatable relative to each other. The rotary connecting part 32 may have bearings.

[0020] The extended end 21e of the cutting wire 21 is connected to one of the connecting sections 31, for example, in the shape of a loop, and the connecting end 22e of the pull-up wire 22 is connected to the other connecting section 31, for example, in the shape of a loop. Thus, the cutting wire 21 and the pull-up wire 22 are connected via the rotary joint 30 so as to be able to rotate relative to each other.

[0021] In the pipe manufacturing process described above, the rehabilitated pipes 3 manufactured by the push-type pipe manufacturing machine 8 are sequentially twisted into the existing pipe 1. That is, as shown by the white arrow a in Figure 1, the rehabilitated pipes 3 are pushed in while being rotated. As a result, the rehabilitated pipes 3 are sequentially extended toward the receiving side (second side) in the pipe axis direction of the existing pipe 1. As the rehabilitated pipes 3 are extended, the cutting wires 21 are sequentially fed out from the feed roll 23 and embedded in the joint 15 of the rehabilitated pipes 3, and are wound spirally along the joint 15, while the pull-up wires 22 are sequentially fed out from the pull-up winch 24, which is in a free-rotating state, and stretched throughout the inside of the rehabilitated pipes 3. The connecting portion 25 between the wires 21 and 22, including the rotating joint 30, is rotated along the circumferential direction of the pipe end 3e of the rehabilitated pipes 3 and moves toward the receiving side (second side) end 1e. On the other hand, since the rotation of the cutting wire 21 and the pull-up wire 22 is separated by the rotary joint 30, the rotation of the cutting wire 21 is not converted into twisting of the pull-up wire 22. Therefore, the pull-up wire 22 is not continuously twisted during pipe making, and the pull-up wire 22 is not excessively twisted and broken.

[0022] As shown by the dashed line in Figure 1, the pipe manufacturing process is completed when the pipe end 3e of the rehabilitated pipe 3 reaches the pipe end 1e on the receiving side (second side) of the existing pipe 1. Next, the pipe end 3e of the rehabilitated pipe 3 is secured against the pipe end 1e of the existing pipe 1 to prevent rotation.

[0023] <High-tensile strength joining process> Around the same time as the aforementioned anti-rotation mechanism is activated, the rotary joint 30 is removed to temporarily separate the extended end 21e of the cutting wire 21 from the connecting end 22e of the pull-up wire 22. Next, as shown in Figure 4, the extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22 are connected via a crimping fitting 40 (connecting means). The crimping fitting 40 has a higher tensile strength than the rotary joint 30. The crimping fitting 40 is crimped to the extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22, respectively.

[0024] More specifically, as shown in Figure 4(a), the crimping fitting 40 has a cylindrical shape before crimping. The extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22 are inserted into the crimping fitting 40 from opposite directions, and then the crimping fitting 40 is crimped. As shown in Figure 4(b), a recessed crimping mark 40d is formed on the crimping fitting 40. Preferably, multiple locations in the cylindrical axis direction of the crimping fitting 40 (two locations in Figure 4(b)) are crushed from multiple directions (directions shifted by approximately 90° in Figure 4(b)).

[0025] More preferably, the connecting means is made up of multiple (three in Figure 4) crimping fittings 40. These crimping fittings 40 are lined up in a row, and the ends 21e and 22e of the wires 21 and 22 are inserted through them and crimped. This forms a wire connecting section 25A consisting of multiple crimping fittings 40 and wire ends 21e and 22e, which has higher tensile strength than during the pipe manufacturing process.

[0026] <Restraint weakening process> Next, as shown in Figure 5, the pull-up winch 24 is rotated in the pull-up direction to pull the pull-up wire 22 towards the starting side (first side). As a result, as shown in Figure 2(c), the portion 21c of the cutting wire 21 that has been pulled out from inside the joint 15 to the inside of the rehabilitation pipe 3 is strongly pulled towards the starting side (left side in Figure 5). The base portion 14c (part of the joint 15) of the protrusion 14b is cut by this pulled-out portion 21c. By continuing the pull-up operation of the pull-up wire 22, the pulled-out portion 21c moves spirally toward the starting side (first side) along the winding direction of the rehabilitation pipe 3, and the base portions 14c are sequentially cut. As a result, the restraining force between the fitting portions 13 and 14 (adjacent edge portions) of the rehabilitation pipe 3 is sequentially weakened from the receiving side (second side) toward the starting side (first side).

[0027] <Expansion Process> As shown in Figure 5, the push-type pipe-making machine 8 is driven in parallel with the drive of the pull-up winch 24 to further supply the strip-shaped member 10 to the rehabilitated pipe 3. As a result, as indicated by the white arrow b in Figure 5, the starting end 3d of the rehabilitated pipe 3 is twisted, and the small-diameter unexpanded pipe section 3a from the starting end (first side) 3d to the pull-out section 21c of the rehabilitated pipe 3 is rotated. In the portion 3c of the rehabilitated pipe 3 on the receiving side (right side in Figure 5) of the pull-out section 21c, where the joining force is weakened, the fitting portions 13 and 14 of the joint 15 slide relative to each other in the winding direction, and the circumference is sequentially expanded (increased in diameter). As a result, the rehabilitated pipe 3, after passing through the cone section 3c, becomes the large-diameter expanded pipe section 3b, and is attached to the inner surface of the existing pipe 1. At this point, the moisture-curing adhesive 16 is not yet cured, and sliding of the mating parts 13 and 14 is permitted.

[0028] In the aforementioned restraint weakening process, a large tensile load is applied to the pull-up wire 22 and the cutting wire 21. Consequently, a large tensile load is applied to the connecting portion 25A between these wires 21 and 22. On the other hand, when the restraint weakening process is performed, the wire connecting means of the connecting portion 25A is replaced with a high-tensile-strength crimp fitting 40 instead of a rotary joint 30, so that the connecting portion 25A can sufficiently withstand the large tensile load. In particular, in this embodiment, as shown in Figure 2, the portion 14c to be cut is thick-walled, and the strip-shaped member 10 is not easily elastically deformed, making it difficult to pull the cutting wire 21 out from between the fitting portions 13 and 14. As a result, a tensile force greater than usual is required, and the connecting portion 25A can withstand this tensile load, preventing damage to the connecting portion 25A.

[0029] From the beginning to partway through the restraint weakening process, the pull-up wire 22 is pulled up and wound onto the pull-up winch 24. As shown in Figure 5, the connecting section 25A is brought out from inside the rehabilitation pipe 3 through the launch side manhole 4 to the ground. A pulley 26 (pull-up guide) is positioned along its pull-up path. When the connecting section 25A passes through the pulley 26, the crimping fitting 40 comes into contact with the pulley 26, but this does not cause damage to the crimping fitting 40. Eventually, the connecting section 25A is wound onto the retrieval winch 24. After that, the cutting wire 21 is directly retrieved by the retrieval winch 24.

[0030] In this way, the entire length of the rehabilitation pipe 3, from end 3e to end 3d, is expanded and attached to the inner surface of the existing pipe 1. Subsequently, the moisture-curing adhesive 16 (Figure 2(b)) hardens, and the mating parts 13 and 14 are bonded and fixed together.

[0031] Next, other embodiments of the present invention will be described. In the following embodiments, components that overlap with those described above are denoted by the same reference numerals in the drawings and their descriptions are omitted. <Second Embodiment (Figure 6)> As shown in Figure 6, the crimping fitting 41 of the second embodiment is a modified example of the cylindrical crimping fitting 40 (Figure 4) of the first embodiment, and is formed in a cylindrical shape with an elliptical or oblong cross-section.

[0032] <Third Embodiment (Figure 7)> As shown in Figure 7, the crimping fitting 50 (connecting means) of the third embodiment has a generally U-shaped body 51, a U-shaped pressing member 52, and a pair of tightening screws 53. After passing the extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22 through the insertion hole 54 formed by the body 51 and the pressing member 52, the tightening screws 53 are tightened. As a result, the wires 21 and 22 are firmly clamped and crimped between the body 51 and the pressing member 52.

[0033] <Fourth Embodiment (Figure 8)> As shown in Figure 8, the crimping fitting 60 (connecting means) of the fourth embodiment has a cylindrical body 61 and a plurality (two in the figure) of tightening screws 63 provided on the side of the body 61. After passing the extended end 21e of the cutting wire 21 and the connecting end 22e of the pull-up wire 22 through the insertion hole 64 of the body 61, the tightening screws 63 are tightened. As a result, the wires 21 and 22 are firmly clamped and crimped between the inner circumferential surface of the insertion hole 64 of the body 51 and the tightening screws 63.

[0034] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from its spirit. For example, in the high-tensile strength joining process, the connecting means for connecting the pull-up wire 22 and the cutting wire 21 only needs to have a higher tensile strength than the rotary joint 30, and is not limited to using a separate component from the wires 21 and 22, such as a crimping fitting, but may also be a knot formed by directly connecting the pull-up wire 22 and the cutting wire 22. The cross-sectional shape of the strip-shaped member is not limited to that of the embodiment described above. Various shapes can be adopted, such as replacing the hollow rectangular cross-section of the rib 12 with a T-shaped cross-section. [Industrial applicability]

[0035] This invention can be applied, for example, to a technology for rehabilitating existing pipes such as aging sewer pipes. [Explanation of Symbols]

[0036] 1 Existing pipe 1d End of the pipe on the starting side (first side) 1e End of the receiving side (second side) 3 Rehabilitation pipe 3a Small diameter unexpanded pipe section 3b Large diameter expanded pipe section 3c Cone section (part where the bonding strength is weakened) 3d End of the pipe on the starting side (first side) 3e The end of the pipe on the receiving side (second side) 8. Push-type pipe making machine 10 Strip-shaped member 12 Ribs 13,14 Fitting portion (adjacent edge portion) 14c Base (part of the joint) 15 Joint 21 Cutting wire 21c Drawer section 21e Extended end 22. Pickup wire 22e Connection end 23 Feed Roll 24. Pickup winch 25 Rotatable wire connector 25A High tensile strength wire connector 26 Pulley (Pickup Guide) 30 Rotary joint 31 A pair of connecting parts 32 Rotating connecting part 40 Crimping fasteners (connecting means) 41 Crimping fasteners (connecting means) 50 Crimping fasteners (connecting means) 60 Crimping fasteners (connecting means)

Claims

1. A method for rehabilitating an existing pipe, comprising: a pipe manufacturing step in which a spiral-shaped rehabilitation pipe is formed by winding a strip-shaped member in a spiral shape and joining adjacent edges that are offset by one full turn, is manufactured to a diameter smaller than the inner diameter of the existing pipe and is twisted into the existing pipe from the first side in the axial direction to the second side; a restraint weakening step in which the restraint force between the adjacent edges of the rehabilitation pipe is gradually weakened from the second side to the first side; and an expansion step in which the pipe end on the first side of the rehabilitation pipe is twisted to expand the circumference of the weakened portion of the rehabilitation pipe, In the aforementioned pipe manufacturing process, during the joining process, a wire interposition step is performed in which a cutting wire is interposed between the adjacent edge portions, In the initial stage of the pipe manufacturing process, the connecting end of the pull-up wire is passed through the rehabilitation pipe from the first side to the second side, and a rotatable coupling step is performed to connect it to the extended end of the cutting wire extending from the second pipe end of the rehabilitation pipe so that it can rotate relative to the pull-up wire via a rotary joint. After the pipe manufacturing process and before the start of the restraint weakening process, a high-tensile strength connecting process is performed, in which the rotary joint is removed and the connecting end and the extended end are connected via a connecting means having higher tensile strength than the rotary joint. A method for rehabilitating an existing pipe, comprising the following: pulling the pull-out wire toward the first side from the beginning to the middle of the restraint weakening process, and thereafter pulling the cutting wire, thereby cutting a part of the joint between adjacent edge portions with the cutting wire.

2. The method for rehabilitating an existing pipe according to claim 1, wherein in the high-tensile strength connection step, the connecting end and the extended end are connected via crimping fittings that are crimped to these ends.

3. The method for rehabilitating an existing pipe according to claim 2, wherein the crimping fitting is cylindrical in which the connecting end and the extended end can be inserted.

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