JP7675641B2 - Piping joining method - Google Patents

Description

The present invention relates to a pipe joining method.

Many pipes run through structures such as power plants and factories. Two pipes are connected by overlapping and joining their ends.

FIG. 8 is a diagram showing an example of a conventional pipe joining method.
In one example of a conventional pipe joining method shown in Fig. 8, first, the flange 20A of the first pipe 10A and the flange 20B of the second pipe 10B are overlapped. Then, the flange 20A of the first pipe 10A and the flange 20B of the second pipe 10B are fastened and fixed using bolts 30 and nuts 40. Furthermore, a plurality of bolts 30 and nuts 40 are provided along the circumferential direction of the flanges 20A and 20B.

In one example of a conventional pipe joining method, an O-ring 50 is used as a sealing member. To fit this O-ring 50, a seal groove 60 is formed in the flange 20A of the first pipe 10A and the flange 20B of the second pipe 10B. Then, by tightening the bolt 30 and the nut 40, the joining surfaces of the flange 20A of the first pipe 10A and the flange 20B of the second pipe 10B are brought closer together. This causes the O-ring 50 installed in the seal groove 60 to come into strong contact with the inner surface of the seal groove 60, realizing a seal between the first pipe 10A and the second pipe 10B.

FIG. 9 is a diagram showing another example of a conventional pipe joining method.
In the pipe joining method shown in FIG. 9, end faces of a first pipe 90A and a second pipe 90B are overlapped with each other, and the end faces of the pipes 90A and 90B are joined by a weld metal 80.

Another example of a conventional pipe joining method is an ultrasonic joining method in which parts are brought into strong contact with each other and ultrasonic waves are introduced from the outside to vibrate the two contacting surfaces relatively in the in-plane direction (see Patent Document 1). In the ultrasonic joining method, the vibrations cause plastic deformation in a surface coating such as an oxide coating, and a new surface appears directly below the coating. The pipes are joined by metallic bonding between these new surfaces.

JP 2007-253164 A

However, when fastening using bolts and nuts, as shown in FIG. 8, if the bolt 30 loosens during operation of the equipment, the tightening of the flanges 20A, 20B weakens and the O-ring 50 no longer makes strong contact with the inner surface of the seal groove 60. This can cause leakage due to the path 70 formed between the two flanges 20A, 20B. Furthermore, if the O-ring 50 deteriorates over time due to creep or other factors, a path 70 will similarly form between the two flanges 20A, 20B, causing leakage.

Furthermore, the pipe joining method shown in Figure 8 had the problem that if the tightening force of the multiple bolts 30 and nuts 40 became uneven, the surface pressure of the two flanges 20A, 20B became uneven, causing leaks in areas where the surface pressure was weak.

In addition, in the joining method using welding shown in FIG. 9, unwelded parts K1 were generated at the interface between the base material pipes 90A, 90B and the weld metal 80. Furthermore, tensile stress P1 was generated in the metal of the welded part due to the influence of heat input during welding. Therefore, in the joining method using welding, there was a possibility that cracks would be generated starting from the unwelded parts K1 and breakage would occur due to vibrations being applied to the pipes 90A, 90B during equipment operation.

In addition, ultrasonic joining methods require plastic deformation of the surface coating due to ultrasonic vibrations and subsequent metallic bonding between the newly formed surfaces, and therefore have been used for relatively soft metals such as copper, aluminum, and alloys of these metals. However, for piping in power plants and factories such as nuclear power plants, carbon steel and low alloy steel, which have a higher yield stress and are harder than copper or aluminum, are used. And for components such as piping made of these steel materials, the surface coating is less likely to plastically deform, and new surfaces do not appear, even when ultrasonic waves are introduced while the joining surfaces are strongly contacted. For this reason, it was difficult to reliably join two pipes using conventional ultrasonic joining methods such as those shown in Patent Document 1.

The objective of this study is to provide a pipe joining method that takes the above problems into consideration, suppresses the occurrence of leaks and breaks, and improves safety.

In order to solve the above problems and achieve the object, a pipe joining method includes the following steps (1) to (4).
(1) A step of forming a convex portion on the joint surface of two pipes and a flow channel surrounding the convex portion and through which the chemical polishing liquid can pass.
(2) The process of overlapping the joint surfaces of the two pipes.
(3) A step of introducing a chemical polishing solution into the flow channel of the piping.
(4) A process of ultrasonically bonding the joint surfaces of the two pipes using an ultrasonic vibrator.

The above-described pipe joining method can reduce the occurrence of leaks and breaks, improving safety.

1A to 1C are schematic diagrams showing a pipe joining method according to a first embodiment; 1 is a front view showing a joint surface of a pipe in a pipe joining method according to a first embodiment; 4 is an explanatory diagram showing an enlarged view of a state in which the joining surfaces of two pipes are brought into contact in the pipe joining method according to the first embodiment; FIG. 1 is a diagram showing the relationship between the gap width at the joint surfaces of two pipes and the penetration length of a chemical polishing liquid. 11A to 11C are diagrams showing modified examples of a protrusion in the pipe connecting method according to the first embodiment. 5A to 5C are schematic diagrams showing a pipe joining method according to a second embodiment; FIG. 11 is a front view showing a joint surface of a pipe in a pipe joining method according to a second embodiment. FIG. 11 is a cross-sectional view showing a conventional pipe joining method. FIG. 13 is a schematic diagram showing a conventional pipe joining method.

Below, an embodiment of the pipe joining method will be described with reference to Figs. 1 to 7. Note that common members in each figure are given the same reference numerals.

1. First embodiment 1-1. Configuration example of pipe connecting method First, an example of a structure in which a pipe connecting method according to a first embodiment (hereinafter, referred to as "this example") is installed will be described with reference to FIG.
FIG. 1 is a schematic diagram showing an example of a structure.

The pipe joining method of this example is applied to pipes connected to the reactor pressure vessel of a nuclear power plant, for example. This pipe carries reactor coolant and is equipped with an isolation valve. By directly connecting the isolation valve to the reactor pressure vessel, even if a pipe such as the main steam pipe breaks, the loss of reactor coolant in the reactor pressure vessel can be avoided by closing the isolation valve.

As shown in FIG. 1, the pipe joining method of this example is a method of joining a first pipe 110A and a second pipe 110B. A flange 120A is provided at the end of the first pipe 110A, which is the joining point, and a flange 120B is provided at the end of the second pipe 110B, which is the joining point. The flanges 120A and 120B protrude in a direction perpendicular to the axial direction of the pipes 110A and 110B. The flange 120A of the first pipe 110A and the flange 120B of the second pipe 110B are fixed by a plurality of jigs 160 such as vices with the joining surfaces 130, which are the opposing surfaces, in contact with each other.

The jig 160 has a pressing bolt 162 that contacts the flanges 120A and 120B, and a nut 161 that screws onto the pressing bolt 162. Then, by tightening the nut 161, the pressing bolt 162 presses the flanges 120A and 120B in a direction in which they come into contact with each other. In addition, an ultrasonic vibrator 230 used for ultrasonic bonding comes into contact with the flanges 120A and 120B.

FIG. 2 is a front view showing the joining surface 130 of the flanges 120A, 120B.
2, the flanges 120A and 120B are formed in a substantially disk shape so as to surround the cylindrical holes 111 of the pipes 110A and 110B. Note that the shape of the flanges 120A and 120B is not limited to a disk shape, and may be various other shapes such as a square or a hexagon.

A labyrinth structure 133 consisting of multiple convex portions 131 and multiple flow grooves 132 is formed on the joining surface 130 of the flanges 120A and 120B. The multiple convex portions 131 protrude from the joining surface 130. This forms multiple flow grooves 132 between the multiple convex portions 131. The multiple convex portions 131 are formed on concentric circles of the cylindrical hole 111. Similarly to the convex portions 131, the multiple flow grooves 132 are also formed on concentric circles of the cylindrical hole 111.

The convex portion 131 has a communication groove 132b formed therein, which communicates the two flow grooves 132, 132 with the convex portion 131 in between. Therefore, the multiple flow grooves 132 are all connected via the communication groove 132b. Note that the communication groove 132b is not formed in the innermost convex portion 131a, which is located at the innermost portion in the radial direction of the joining surface 130 of the multiple convex portions 131, and the outermost convex portion 131b, which is located at the outermost portion.

The innermost protrusion 131a is formed continuously in the circumferential direction of the cylindrical hole 111 of the pipes 110A and 110B and surrounds the cylindrical hole 111. This makes it possible for the innermost protrusion 131a to prevent the fluid passing through the cylindrical hole 111 of the pipes 110A and 110B from leaking out of the pipes 110A and 110B via the flow channel 132.

In addition, an introduction hole 180 that communicates with the flow groove 132 is formed in the outermost convex portion 131b during the pipe joining operation. The introduction hole 180 is a through hole that penetrates the outermost convex portion 131b in the radial direction, and is formed on the side surface of the flanges 120A and 120B. An introduction pipe 190 is connected to this introduction hole 180. Then, the chemical polishing liquid M1 (see FIG. 3) is introduced into the flow groove 132 through the introduction pipe 190 and the introduction hole 180. As described above, by not providing a communication groove 132b in the outermost convex portion 131b, it is possible to prevent the liquid introduced into the flow groove 132 during the pipe joining operation from leaking out to the outside.

Furthermore, the multiple convex portions 131 formed on the joint surface 130 of the flange 120A of the first pipe 110A and the multiple convex portions 131 formed on the joint surface 130 of the flange 120B of the second pipe 110B are formed in the same position and shape. This allows the convex portions 131 formed on each joint surface 130 to face each other and be close to each other when the joint surfaces 130 of the flanges 120A and 120B are overlapped.

In this example, the convex portion 131 and the flow channel 132 are formed on concentric circles, but this is not limited to the above. For example, the convex portion 131 and the flow channel 132 may be formed radially along the radial direction of the joining surface 130, or may have any other shape.

1-2. Pipe Joining Method Next, the pipe joining method will be described with reference to FIGS.
First, as shown in Fig. 1, the joint surface 130 of the flange 120A of the first pipe 110A and the joint surface 130 of the flange 120B of the second pipe 110B are overlapped. Then, the flanges 120A, 120B are fixed using a plurality of jigs 160. In addition, abutment plates 170 are installed between the flanges 120A, 120B and the pressing bolts 162 of the jigs 160. This allows the load from the plurality of jigs 160 to be applied to the flanges 120A, 120B so as to be uniformly distributed.

When the joining surfaces 130 of the two flanges 120A and 120B are brought into contact, the projections 131 of the labyrinth structure 133 formed on the joining surfaces 130 are aligned so that they come into contact with each other.

As shown in FIG. 2, after the two flanges 120A and 120B are fixed to the jig 160, an inlet hole 180 is formed on the side of the flanges 120A and 120B, i.e., in the outermost convex portion 131b. The inlet hole 180 is also threaded to connect the inlet pipe 190.

The introduction holes 180 may be formed before the flanges 120A and 120B are fixed with the jig 160. The positions and number of the introduction holes 180 may be set arbitrarily.

Next, an inlet pipe 190 is connected to the inlet hole 180. Then, the chemical polishing liquid M1 is introduced into the flow grooves 132 of the labyrinth structure 133 via the inlet pipe 190, and the multiple flow grooves 132 are filled with the chemical polishing liquid M1.

The chemical polishing liquid M1 may be introduced from at least one of the multiple inlet pipes 190, and the chemical polishing liquid M1 may be discharged to the outside from at least one of the multiple inlet pipes 190. Then, even after the flow channel 132 is filled with the chemical polishing liquid M1, the introduction and discharge of the chemical polishing liquid M1 from the inlet pipes 190 continues. This allows the chemical polishing liquid M1 to circulate within the flow channel 132 of the labyrinth structure 133.

An example of the chemical polishing solution M1 is hydrogen peroxide solution heated from room temperature to about 50°C.

FIG. 3 is an explanatory diagram showing an enlarged view of the state where joint surfaces 130 of two pipes 110A and 110B are in contact with each other.
It is difficult to form the joining surface 130 into a completely smooth surface. Therefore, even if the joining surfaces 130 of the two flanges 120A and 120B are brought into contact with each other, a gap 220 of, for example, about 0.1 mm to 0.5 mm is formed between the two joining surfaces 130, 130 as shown in FIG. 3. Therefore, the chemical polishing liquid M1 introduced into the flow groove 132 of the labyrinth structure 133 is also introduced into the gap 220 formed between the two joining surfaces 130, 130 by capillary action. As a result, not only the side portion of the convex portion 131 on the flow groove 132 side, but also the opposing surfaces of the two joining surfaces 130, 130 can be wetted with the chemical polishing liquid M1.

By introducing the chemical polishing liquid M1, the oxide film 136 formed on the surface of the joining surface 130 is removed by the chemical polishing liquid M1. This allows the metal surfaces of the convex portions 131 formed on the two flanges 120A, 120B to come into strong contact with each other. When minute plastic deformation occurs on the metal surface, it makes it easier for the new metal surface 137 present directly below the metal surface film to appear on the surface.

In addition, by removing the oxide film 136 with the chemical polishing solution M1, the surface roughness of the metal after removal is reduced compared to before removal. This makes it possible to increase the contact area of the convex portions 131 of the labyrinth structure 133 when the convex portions 131 of the joining surfaces 130 of the flanges 120A and 120B are brought into contact with each other after chemical polishing. As a result, strong contact of the metal surfaces occurs over the entire contact surface, and the appearance of new metal surfaces 137 due to the occurrence of plastic deformation also occurs over the entire expanded contact surface.

FIG. 4 is a diagram showing the relationship between the width H1 of the gap 220 and the penetration length of the chemical polishing liquid M1 into the gap 220. As shown in FIG.
4, even when the width H1 of gap 220 is relatively large at 0.5 mm, it is understood that chemical polishing liquid M1 penetrates about 3 cm into gap 220. As a result, even when joint surfaces 130 of two pipes 110A, 110B are in contact with each other, chemical polishing liquid M1 can be spread throughout convex portion 131 of labyrinth structure 133, and the oxide film 136 can be reliably removed.

The chemical polishing liquid M1 penetrates the convex portion 131 located between the innermost convex portion 131a and the outermost convex portion 131b from both radial sides through the two flow grooves 132, 132. Therefore, the thickness of the convex portion 131 located between the innermost convex portion 131a and the outermost convex portion 131b, i.e., the radial length, of the convex portion 131 may be set to twice the thickness of the innermost convex portion 131a or the outermost convex portion 131b. This increases the contact area of the joining surface 130 and increases the joining strength of the two flanges 120A, 120B.

In addition, the joining surface 130 has an innermost convex portion 131a and an outermost convex portion 131b, and the chemical polishing liquid M1 seeps out from the gap 220 onto the inner surface on the innermost side and the outer surface on the outermost side of the flanges 120A and 120B. This allows the chemical polishing liquid M1 to block outside air from entering the joining surface 130, preventing the oxide film 136 from forming again on the joining surface 130.

Next, after a predetermined time has elapsed since the introduction of the chemical polishing liquid M1, as shown in FIG. 1, the ultrasonic vibrator 230 is brought into contact with the flanges 120A, 120B via the contact plate 170. Then, the ultrasonic vibrator 230 is driven to apply ultrasonic vibrations to the flanges 120A, 120B. The application of ultrasonic vibrations increases the wettability of the metal surface in the gap 220 formed between the convex portions 131 of the joining surfaces 130. This makes it easier for the chemical polishing liquid M1 to penetrate between the convex portions 131 of the two joining surfaces 130, 130.

After a predetermined time has elapsed since the ultrasonic vibrator 230 was driven, the introduction of the chemical polishing liquid M1 is stopped, and the drive of the ultrasonic vibrator 230 is also stopped. When the introduction of the chemical polishing liquid M1 is stopped, the chemical polishing liquid M1 is not discharged from the flow channel 132 of the labyrinth structure 133, and the introduction pipe 190 is left connected to the introduction hole 180.

Next, the jig 160 is tightened to bring the joint surfaces 130 of the two pipes 110A and 110B closer together. The tightening operation increases the surface pressure of the two joint surfaces 130, and the chemical polishing liquid M1 present on the surface of the convex portion 131 is discharged into the flow channel 132.

FIG. 5 is a diagram showing a modified example of the convex portion of the labyrinth structure.
The convex portion 135 of the labyrinth structure shown in Fig. 5 is formed in a mountain shape. That is, the center of one surface of the convex portion 135 that faces the convex portion 135 of the other joint surface 130 bulges toward the convex portion 135 of the other joint surface 130. According to the convex portion 135 shown in Fig. 5, the force applied to the center of one surface of the convex portion 135 during the retightening operation is stronger than that applied to other portions. This allows the chemical polishing liquid M1 to be smoothly discharged from one surface of the convex portion 135 to the flow channel 132 side.

When the tightening of the jig 160, i.e., the discharge of the chemical polishing liquid M1 present on the surface of the convex portion 131, is completed, the operation of the ultrasonic vibrator 230 is resumed. At this point, the flow channel 132 is filled with the chemical polishing liquid M1. Therefore, the chemical polishing liquid M1 filling the flow channel 132 acts as an airtight material, preventing air from entering the surface of the convex portion 131.

When ultrasonic vibrations are applied to the protrusions 131 provided on the joining surfaces 130 of the two flanges 120A, 120B in contact with each other, plastic deformation occurs on the metal surfaces of the protrusions 131. This causes new surfaces 137 directly below the oxide film 136 to appear on the surface. As a result, the new surfaces 137 can be brought into contact with each other, and the pipes 110A, 110B can be reliably ultrasonically joined even if the pipes 110A, 110B are made of steel materials such as carbon steel or low alloy steel, which have a higher yield stress and are harder than copper or aluminum.

After completing the ultrasonic bonding of the flanges 120A, 120B of the pipes 110A, 110B, the inlet pipe 190 is made negative pressure and the chemical polishing liquid M1 remaining in the flow channel 132 is discharged. Then, the inlet pipe 190 is removed from the inlet hole 180, and the inlet hole 180 is blocked. By carrying out the above-mentioned steps, the first pipe 110A and the second pipe 110B are bonded.

In addition, since the joining surfaces 130 of the flanges 210A and 120B are ultrasonically joined, no load is applied to the introduction hole 180. Therefore, the sealing member that blocks the introduction hole 180 will not be damaged during operation of the device.

In this way, according to the pipe joining method of this example, by introducing chemical polishing liquid M1 into the labyrinth structure 133 formed on the joining surface 130 before ultrasonic joining, the oxide film 136 can be removed and a new surface 137 can appear on the surface of the joining surface 130. This makes it possible to perform ultrasonic joining on pipes made of steel materials such as carbon steel and low alloy steel, which have a higher yield stress and are harder than copper or aluminum, such as pipes used in nuclear power plants. As a result, the pipes can be joined reliably, the occurrence of leaks and breaks can be suppressed, and safety can be improved.

2. Second Embodiment Next, a pipe joining method according to a second embodiment will be described with reference to FIGS.
6 is a schematic diagram showing a pipe joining method according to a second embodiment. It is a front view showing a joining surface of a pipe in the pipe joining method according to the second embodiment. Note that the same reference numerals are used for the parts common to the pipe joining method according to the first embodiment, and the duplicated explanation is omitted.

As shown in FIG. 6, a mating protrusion 251 is formed on the joint surface 130 of the first pipe 110A. A mating recess 250 into which the mating protrusion 251 fits is formed on the joint surface 130 of the second pipe 110B. The mating protrusion 251 is formed so as to surround the cylindrical hole 111 on the radial center side of the joint surface 130. The mating protrusion 251 protrudes from the joint surface 130 toward the joint surface 130 of the second pipe 110B.

As shown in Figures 6 and 7, the fitting recess 250 is formed so as to surround the cylindrical hole 111 on the radial center side of the joining surface 130. The fitting recess 250 is formed in a tapered shape that is inclined from the joining surface 130 toward the end of the cylindrical hole 111.

As shown in FIG. 7, the innermost convex portion 131a of the multiple convex portions 131 constituting the labyrinth structure 133 formed on the joining surface 130 of the second pipe 110B is disposed radially outward of the mating recess 250. That is, the innermost convex portion 131a is formed radially outward of the arrow B shown in FIG. 6. Here, the tightening force of the jig 160 is applied to the region indicated by the dashed line C on the joining surface 130. Therefore, even if the convex portion 131 is not provided radially inward of the arrow B, the ultrasonic joining is not affected.

By fitting the mating protrusion 251 and the mating recess 250 together, the positioning of the joint surface 130 of the flange 120A of the first pipe 110A and the joint surface 130 of the flange 120B of the second pipe 110B can be easily performed. This allows the surfaces of the protrusions 131 formed on each joint surface 130 to be reliably in contact with each other.

Other configurations are the same as those of the pipe joining method according to the first embodiment, so their explanation will be omitted. With a pipe joining method having such a configuration, it is possible to obtain the same effects as those of the pipe joining method according to the first embodiment described above.

The above describes an embodiment of the pipe joining method, including its effects. However, the pipe joining method is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention described in the claims.

In the above-mentioned embodiment, the labyrinth structure 133 is formed with multiple convex portions 131 and flow grooves 132, but the present invention is not limited to this. For example, the convex portion 131 may have at least the innermost convex portion 131a, and at least one flow groove 132 may be formed to surround the innermost convex portion 131a in order to allow the chemical polishing liquid M1 to penetrate into the innermost convex portion 131a. In addition, by forming multiple convex portions 131 as in the above-mentioned embodiment, the joining area of the two pipes 110A and 110B can be increased, and the joining strength can be increased. This allows the two pipes 110A and 110B to be firmly joined.

In this specification, the words "parallel" and "orthogonal" are used, but these do not mean only "parallel" and "orthogonal" in the strict sense, but also include "parallel" and "orthogonal" and may also mean a "nearly parallel" or "nearly orthogonal" state within a range in which the functions can be exerted.

110A, 110B...piping, 111...tube hole, 120A, 120B...flange, 130...joint surface, 131, 135...convex portion, 131a...innermost convex portion, 131b...outermost convex portion, 132...flow channel, 132b...communicating groove, 133...labyrinth structure, 136...oxide coating, 137...new surface, 160...jig, 180...inlet hole, 190...inlet pipe, 220...gap, 230...ultrasonic transducer, 250...fitting recess, 251...fitting convex portion, H1...gap, K1...unwelded portion, M1...chemical polishing liquid, P1...tensile stress

Claims (8)

forming a convex portion on the joint surface of the two pipes and a flow channel surrounding the convex portion and through which the chemical polishing liquid can pass;
overlapping the joint surfaces of the two pipes;
introducing a chemical polishing liquid into the flow channel of the piping;
ultrasonically bonding the joining surfaces of the two pipes by an ultrasonic vibrator;
A pipe joining method comprising: The pipe connecting method according to claim 1 , wherein a plurality of the protrusions and the flow grooves are formed on the connecting surface. the protrusion has an innermost protrusion disposed on an innermost periphery of the joining surface,
The pipe connecting method according to claim 1 , wherein the innermost protrusion is formed continuously in a circumferential direction of the cylindrical hole of the pipe and surrounds the cylindrical hole. A fitting protrusion is formed on the joint surface of one of the two pipes,
The pipe connecting method according to claim 3 , wherein the other of the two pipes has a fitting recess formed on the connecting surface thereof, the fitting recess being fitted into the fitting protrusion. The fitting recess is formed to surround the periphery of the cylindrical hole,
The pipe connecting method according to claim 4 , wherein the innermost convex portion is formed outside the fitting concave portion. The pipe connecting method according to claim 1 , wherein a center portion of the protrusion bulges toward the protrusion of the pipe to be connected. an outermost protrusion disposed on the outermost periphery of the joint surface among the plurality of protrusions has an introduction hole formed therein and communicating with the flow channel;
The pipe connecting method according to claim 2 , wherein the chemical polishing liquid is introduced into the flow channel through the introduction hole. The pipe joining method according to claim 1 , wherein the step of ultrasonic joining using the ultrasonic vibrator is performed in a state where the flow channel is filled with the chemical polishing liquid.

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