JP7502776B2 - Pipe connection structure and pipe connection method - Google Patents

Description

This application relates to a pipe connection structure and a pipe connection method.

Valve devices such as drain traps have been known for some time. A pipe is connected to the outlet of the valve device by plug welding. As disclosed in Patent Document 1, for example, plug welding is performed with a predetermined plug gap between the pipe and the object to be plugged, i.e., with the pipe and the object to be plugged apart, so that the weld does not become distorted due to the expansion of the pipe caused by welding heat.

JP 2010-69595 A

However, in the above-mentioned valve device, some insertion gap may remain between the outlet and the piping. If this happens, erosion may easily occur at the end of the piping at the outlet.

The technology disclosed in this application has been developed in light of these circumstances, and its purpose is to provide a pipe connection structure and a pipe connection method that can suppress the effects of welding heat while suppressing the occurrence of erosion caused by remaining insertion gaps.

The technology disclosed in this application is a piping connection structure that includes a cylindrically formed fluid outlet and a pipe that is connected to the outlet by plug welding. The outlet has a large diameter portion into which the pipe is inserted, and a small diameter portion that is formed continuous with the large diameter portion and has an inner diameter smaller than that of the large diameter portion. The pipe has a pipe body that is inserted into the large diameter portion, and an expansion absorption portion that is provided at the inner end of the pipe body and contacts a step portion formed at the boundary between the large diameter portion and the small diameter portion at the outlet, and absorbs expansion of the pipe body in the pipe axial direction caused by welding heat.

Another technology disclosed in the present application is a piping connection method for connecting a pipe to a fluid outlet formed in a cylindrical shape and having a step on its inner circumferential surface by insertion welding. The piping connection method includes the steps of inserting the pipe into the outlet so that a predetermined insertion gap exists between the step and the outlet, welding the end face of the outlet and the outer circumferential surface of the pipe, and causing the end of the pipe to come into contact with the step due to the expansion of the pipe caused by the welding heat during the welding, thereby reducing the insertion gap to zero, and deforming the end of the pipe that comes into contact with the step to absorb further expansion of the pipe caused by the welding heat during the welding.

The technology disclosed in this application makes it possible to suppress the effects of welding heat while also suppressing the occurrence of erosion caused by the insertion gap.

FIG. 1 is a cross-sectional view showing a schematic configuration of a pipe connection structure according to a first embodiment. FIG. 2 is a cross-sectional view showing one state when piping is connected according to the first embodiment. FIG. 3 is a cross-sectional view showing one state when piping is connected according to the first embodiment. FIG. 4 is a cross-sectional view showing one state when piping is connected according to the first embodiment. FIG. 5 is a cross-sectional view showing a schematic configuration of a pipe connection structure according to the second embodiment. FIG. 6 is a cross-sectional view showing one state when piping is connected according to the second embodiment. FIG. 7 is a cross-sectional view showing one state when piping is connected according to the second embodiment. FIG. 8 is a cross-sectional view showing one state when piping is connected according to the second embodiment.

The following describes embodiments of the present application with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the technology disclosed in the present application, its applications, or its uses.

(Embodiment 1)
A first embodiment of the present invention will be described with reference to Figures 1 to 4. A pipe connection structure 100 of this embodiment includes an outlet port 10 for a fluid and a pipe 20.

The outlet 10 is, for example, the outlet of the drain trap 1. The drain trap 1 is installed in a steam system or the like, and allows drain to flow out when drain flows in, but prevents steam from flowing out when steam flows in. In other words, the drain trap 1 allows only drain that flows in from the inlet to flow out from the outlet. The drain trap 1 is an example of a fluid device, and drain is an example of a fluid.

As shown in FIG. 1, the outlet 10 is formed in a tubular shape (more specifically, a cylindrical shape). The outlet 10 has a large diameter section 11 and a small diameter section 12. The large diameter section 11 is provided at one end side (downstream end side) of the outlet 10, and is the section into which the piping 20 is inserted. The small diameter section 12 is provided on the upstream side of the large diameter section 11 at the outlet 10. The small diameter section 12 is formed continuous with the large diameter section 11. The inner diameter d2 of the small diameter section 12 is smaller than the inner diameter d1 of the large diameter section 11.

The inner peripheral surface of the outlet 10 configured as described above is provided with a step portion 14. That is, the step portion 14 is formed at the boundary between the large diameter portion 11 and the small diameter portion 12 in the outlet 10. The step portion 14 has a surface that extends in the radial direction of the outlet 10, i.e., a surface that is perpendicular to the axis of the outlet 10 (coaxial with the tube axis X described below). In the outlet 10, the fluid flows from the small diameter portion 12 to the large diameter portion 11, as shown by the outline arrow in FIG. 1.

The pipe 20 is connected to the outlet 10 by plug welding. The pipe 20 has a pipe body 21 and an expansion absorption section 22.

The pipe body 21 is formed in a cylindrical shape. The outer diameter D of the pipe body 21 is approximately the same as the inner diameter d1 of the large diameter portion 11 of the outlet 10. The inner diameter d3 of the pipe body 21 is approximately the same as the inner diameter d2 of the small diameter portion 12 of the outlet 10. The pipe body 21 is inserted into the large diameter portion 11 of the outlet 10.

The expansion absorption section 22 is provided at the inner end of the pipe body 21 and is provided integrally with the pipe body 21. The inner end of the pipe body 21 refers to the end of the pipe body 21 that is inserted into the large diameter section 11 of the outlet 10. The expansion absorption section 22 is located at the end of the piping 20. The tip 23 of the expansion absorption section 22 is in contact with the step section 14 of the outlet 10.

The expansion absorbing section 22 absorbs the expansion of the pipe body 21 in the pipe axis X direction caused by the welding heat during plug welding. More specifically, the expansion absorbing section 22 is configured to absorb the expansion of the pipe body 21 by shortening in the pipe axis X direction.

Specifically, the cross-sectional shape of the expansion absorption section 22 is formed in a zigzag shape. This configuration allows the expansion absorption section 22 to be shortened in the pipe axis X direction. The zigzag shape is a straight line that is bent multiple times in a Z shape, and is also called a lightning bolt shape. The pipe 20 is inserted and welded with the pipe body 21 and the expansion absorption section 22 inserted into the outlet 10. In other words, the end face 13 of the outlet 10 and the outer circumferential surface of the pipe body 21 are welded together (see welded part W shown in Figure 1).

During insertion welding, the pipe 20 expands due to the welding heat. That is, during insertion welding, the portion of the pipe body 21 near the welded portion W expands toward the step portion 14 (left side in FIG. 1). This expansion of the pipe body 21 causes the expansion absorbing portion 22 to shorten toward the step portion 14. In this way, the expansion of the pipe body 21 (piping 20) due to the welding heat is absorbed by the expansion absorbing portion 22. This makes the insertion gap zero while absorbing the expansion of the pipe 20 due to the welding heat. Note that the tip 23 of the expansion absorbing portion 22 does not protrude radially inward from the step portion 14.

<Pipe connection method>
The pipe connection method of this embodiment will be described with reference to Figures 2 to 4. This pipe connection method is a method for connecting the pipe 20 to the outlet 10 by plug welding, and includes an "insertion step", a "first expansion absorption step" and a "second expansion absorption step" in this order.

First, the "insertion process" is carried out. As shown in FIG. 2, the "insertion process" is a process in which the pipe 20 is inserted into the outlet 10 so that a predetermined insertion gap G exists between the stepped portion 14 and the pipe 20. Specifically, in this "insertion process", a part of the pipe body 21 and the expansion absorption portion 22 are inserted into the large diameter portion 11 of the outlet 10. At that time, a predetermined insertion gap G is secured between the tip 23 of the expansion absorption portion 22 and the stepped portion 14.

The specified insertion gap G is set to a gap amount that ensures that the tip 23 of the expansion absorbing section 22 comes into contact with the step section 14 when the pipe 20 expands due to the welding heat during insertion welding. More specifically, the specified insertion gap G is set to an amount that is smaller than the amount of expansion of the pipe 20 that may occur due to the welding heat.

Then, the "first expansion absorption process" is performed. As shown in FIG. 3, the "first expansion absorption process" is a process in which the end face 13 of the outlet 10 and the outer peripheral surface of the pipe 20 (pipe body 21) are welded together, and the end of the pipe 20 (expansion absorption section 22) comes into contact with the step section 14 due to the expansion of the pipe 20 (pipe body 21) caused by the welding heat during the welding process, thereby reducing the insertion gap G to zero.

Specifically, in the "first expansion absorption process", the end face 13 of the outlet 10 and the outer circumferential surface of the pipe body 21 are welded together. At this time, the portion of the pipe body 21 near the welded portion W expands toward the step 14 due to the welding heat (see the dashed arrow in Figure 3). As a result, the expansion absorption section 22 is displaced toward the step 14, and the tip 23 of the expansion absorption section 22 comes into contact with the step 14. This makes the insertion gap G zero. Thus, in the "first expansion absorption process", the expansion of the pipe 20 due to the welding heat is absorbed by the insertion gap G provided in the "insertion process".

Then, the "second expansion absorption process" is carried out. As shown in FIG. 4, the "second expansion absorption process" is a process in which the end of the pipe 20 in contact with the step portion 14 (expansion absorption portion 22) deforms so as to absorb further expansion of the pipe 20 (pipe body 21) caused by the welding heat during welding.

Specifically, in the "second expansion absorption process", the portion of the pipe body 21 near the welded portion W further expands toward the step portion 14 due to the welding heat (see the dashed arrow in FIG. 4). Accordingly, the expansion absorption portion 22 shortens toward the step portion 14 (see the solid arrow in FIG. 4). In this way, in the "second expansion absorption process", the further expansion of the pipe 20 due to the welding heat is absorbed by the expansion absorption portion 22. In other words, the expansion of the pipe 20 that was not fully expanded in the "first expansion absorption process" is absorbed by the expansion absorption portion 22. In this way, the expansion of the pipe 20 due to the welding heat is absorbed while the insertion gap is made zero.

As described above, the piping connection structure 100 of the above embodiment includes a cylindrically formed fluid outlet 10 and a pipe 20 connected to the outlet 10 by plug welding. The outlet 10 has a large diameter section 11 into which the pipe 20 is inserted, and a small diameter section 12 formed continuous with the large diameter section 11 and having an inner diameter smaller than that of the large diameter section 11. The pipe 20 has a pipe body 21 inserted into the large diameter section 11, and an expansion absorption section 22 provided at the inner end of the pipe body 21, contacting a step section 14 formed at the boundary between the large diameter section 11 and the small diameter section 12 at the outlet 10, and absorbing the expansion of the pipe body 21 in the pipe axis X direction caused by welding heat.

The pipe connection method of the above embodiment also includes a step of inserting the pipe 20 into the outlet 10 so that a predetermined insertion gap exists between the outlet 10 and the step 14 (insertion step), a step of welding the end face 13 of the outlet 10 to the outer circumferential surface of the pipe 20 together, and a step of bringing the end of the pipe 20 into contact with the step 14 due to the expansion of the pipe 20 caused by the welding heat during welding, thereby reducing the insertion gap to zero (first expansion absorption step), and a step of deforming the end of the pipe 20 in contact with the step 14 to absorb further expansion of the pipe 20 caused by the welding heat during welding (second expansion absorption step).

These configurations make it possible to absorb the expansion of the pipe 20 due to the welding heat while keeping the insertion gap to zero. That is, in the above embodiment, a portion of the expansion of the pipe 20 caused by the welding heat is absorbed by a predetermined insertion gap, and the remaining expansion is absorbed by the expansion absorption section 22. Therefore, it is possible to suppress the occurrence of erosion caused by the remaining insertion gap, while suppressing the effects of the welding heat (e.g., distortion and cracks in the welded portion W).

In addition, in the pipe connection structure 100 of the above embodiment, the expansion absorption section 22 is configured to absorb the expansion of the pipe body 21 by shortening in the pipe axis X direction. Specifically, the vertical cross-sectional shape of the expansion absorption section 22 is formed in a zigzag shape.

The above configuration allows the expansion of the pipe 20 to be absorbed with a relatively simple configuration. In the pipe connection structure 100 of the above embodiment, the cross-sectional shape of the expansion absorption section 22 may be formed into a corrugated shape instead of a zigzag shape. The corrugated shape is obtained by making the corners of the zigzag shape described above into gentle curves.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to Figures 5 to 8. The pipe connection structure 100 of this embodiment is obtained by modifying the configuration of the expansion absorption section of the pipe in the first embodiment. Here, differences from the first embodiment will be described.

As shown in FIG. 5, the piping 30 of this embodiment is connected to the outlet 10 by plug welding, as in the first embodiment, and includes a pipe body 31 and an expansion absorbing section 32. The pipe body 31 is formed cylindrically and is inserted into the large diameter section 11 of the outlet 10. The expansion absorbing section 32 is provided at the inner end of the pipe body 31 and is integral with the pipe body 31. The expansion absorbing section 32 absorbs the expansion of the pipe body 31 in the pipe axis X direction caused by the welding heat during plug welding.

More specifically, the expansion absorbing section 32 is formed thinner than the pipe body 31, and the tip 33 is bent radially inward to contact the step 14. The expansion absorbing section 32 is configured to absorb the expansion of the pipe body 31 by displacing the tip 33 radially inward along the step 14. As a result, similar to the first embodiment, the insertion gap is made zero and the expansion of the pipe 30 due to welding heat is absorbed. Note that the tip 33 of the expansion absorbing section 32 does not protrude radially inward from the step 14.

<Pipe connection method>
The pipe connection method of this embodiment will be described with reference to Figures 6 to 8. This pipe connection method, like the first embodiment, is a method of connecting the pipe 30 to the outlet 10 by insertion welding, and includes an "insertion step", a "first expansion absorption step", and a "second expansion absorption step" in this order.

First, the "insertion process" is performed. As shown in FIG. 6, the "insertion process" is a process in which the piping 30 is inserted into the outlet 10 so that a predetermined insertion gap G exists between the stepped portion 14 and the piping 30. Specifically, in this "insertion process", a part of the pipe body 31 and the expansion absorption portion 32 are inserted into the large diameter portion 11 of the outlet 10. At that time, a predetermined insertion gap G is secured between the tip 33 of the expansion absorption portion 32 and the stepped portion 14.

In this embodiment, the predetermined insertion gap G is set to a gap amount that ensures that the tip 33 of the expansion absorbing section 32 contacts the step section 14 when the pipe 30 expands due to the welding heat during insertion welding. More specifically, the predetermined insertion gap G is set to an amount that is smaller than the amount of expansion of the pipe 30 that may occur due to the welding heat.

Then, the "first expansion absorption process" is performed. As shown in FIG. 7, the "first expansion absorption process" is a process in which the end face 13 of the outlet 10 and the outer peripheral surface of the pipe 30 (pipe body 31) are welded together, and the end of the pipe 30 (expansion absorption section 32) comes into contact with the step section 14 due to the expansion of the pipe 30 (pipe body 31) caused by the welding heat during the welding process, thereby making the insertion gap G zero.

Specifically, in the "first expansion absorption process", the end face 13 of the outlet 10 and the outer circumferential surface of the pipe body 31 are welded together. At this time, the portion of the pipe body 31 near the welded portion W expands toward the step 14 due to the welding heat (see the dashed arrow in Figure 7). As a result, the expansion absorption section 32 is displaced toward the step 14, and the tip 33 of the expansion absorption section 32 comes into contact with the step 14. This makes the insertion gap G zero. Thus, in the "first expansion absorption process", the expansion of the pipe 30 due to the welding heat is absorbed by the insertion gap G provided in the "insertion process".

Then, the "second expansion absorption process" is carried out. As shown in FIG. 8, the "second expansion absorption process" is a process in which the end of the pipe 30 in contact with the step portion 14 (expansion absorption portion 32) is deformed so as to absorb further expansion of the pipe 30 (pipe body 31) due to the welding heat during welding.

Specifically, in the "second expansion absorption process", the portion of the pipe body 31 near the welded portion W further expands toward the step portion 14 due to the welding heat (see the dashed arrow in FIG. 8). Accordingly, the expansion absorption portion 32 shortens toward the step portion 14 (see the solid arrow in FIG. 8). In this way, in the "second expansion absorption process", the further expansion of the pipe 20 due to the welding heat is absorbed by the expansion absorption portion 32. In other words, the expansion of the pipe 30 that was not fully expanded in the "first expansion absorption process" is absorbed by the expansion absorption portion 32. In this way, the expansion of the pipe 30 due to the welding heat is absorbed while the insertion gap is made zero.

As described above, according to the pipe connection structure 100 and pipe connection method of this embodiment, as in the first embodiment, the insertion gap can be made zero while absorbing the expansion of the pipe 20 due to the welding heat. Therefore, it is possible to suppress the occurrence of erosion caused by the remaining insertion gap while suppressing the effects of the welding heat.

The technology disclosed in this application is useful for a pipe connection structure and a pipe connection method that connects a pipe to a fluid outlet by plug welding.

Reference Signs List 100 Pipe connection structure 10 Outlet 11 Large diameter portion 12 Small diameter portion 13 End surface 14 Step portion 20 Pipe 21 Pipe body 22 Expansion absorbing portion 30 Pipe 31 Pipe body 32 Expansion absorbing portion 33 Tip X Pipe axis G Insertion gap

Claims (2)

A piping connection structure including a tubular fluid outlet and a piping connected to the outlet by plug welding,
the outlet has a large diameter portion into which the pipe is inserted, and a small diameter portion formed continuously with the large diameter portion and having an inner diameter smaller than that of the large diameter portion,
the piping includes a pipe body inserted into the large diameter portion, and an expansion absorbing portion provided at an inner end of the pipe body, contacting a step portion formed at a boundary between the large diameter portion and the small diameter portion at the outlet, and absorbing expansion of the pipe body in the pipe axis direction caused by welding heat ;
The expansion absorbing portion is configured to absorb the expansion of the pipe main body by shortening in the pipe axial direction,
The longitudinal cross-sectional shape of the expansion absorbing portion is formed in a zigzag or wave shape.
A piping connection structure characterized by: A pipe connection method for connecting a pipe to a fluid outlet that is formed in a cylindrical shape and has a step portion on an inner peripheral surface by socket welding, comprising:
inserting the pipe into the outlet port so that a predetermined insertion gap exists between the pipe and the step portion;
a step of welding an end face of the outlet and an outer peripheral surface of the pipe together, and causing the end of the pipe to come into contact with the step portion due to expansion of the pipe caused by welding heat during the welding, thereby reducing the insertion gap to zero;
and a step of deforming the end of the pipe in contact with the step portion so as to absorb further expansion of the pipe due to welding heat during the welding joint.

Images