Branching piping and method for manufacturing branching piping

Abstract

This branching piping 1 comprises: a main pipe 2 that has a main pipe inner layer part 21, and a main pipe outer layer part 22 surrounding the main pipe inner layer part 21, and that is provided with a main pipe branching hole 2H which penetrates the main pipe inner layer part 21 and the main pipe outer layer part 22 and in which the diameter of an outer-layer-side opening 22h formed on an outer layer outer circumferential surface 22a is larger than the diameter of an inner-layer-side opening 21H formed on an inner layer inner circumferential surface 21a; a branch pipe 3 that extends in a direction intersecting with that of an axis X21 of the main pipe 2; and a joining part 4 that joins a branch pipe lower end surface 3a of the branch pipe 3 to the main pipe branching hole 2H of the main pipe 2. The joining part 4 has: a main-pipe-side joining weld part 42 that covers a location 2d3 where the edge of the main pipe outer layer part 22 and the edge of the main pipe inner layer part 21 exposed in the main pipe branching hole 2H contact each other; and a branch-pipe-side joining weld part 43 that is provided between the main-pipe-side joining weld part 42 and the branch pipe lower end surface 3a and that joins the branch pipe 3 and the main pipe 2. The main pipe outer layer part 22 is formed from a different material than the main pipe inner layer part 21.

Description

Branch pipe and method of manufacturing branch pipe

[0001] The present invention relates to a branch pipe and a method for manufacturing the branch pipe.

[0002] Plants where oil processing or gas processing is carried out include areas where corrosive fluids such as hydrogen sulfide or chlorides (hereinafter referred to as "corrosive fluids") flow. So-called clad pipes are sometimes used in areas where corrosive fluids flow, such as towers, tanks, equipment, and piping. Clad pipes are composite materials made by joining dissimilar metals. Clad pipes have a laminated structure consisting of, for example, a base material made of carbon steel and a composite material made of a nickel alloy or the like. By appropriately selecting the material of the composite material, corrosion resistance to corrosive fluids can be achieved.

[0003] In oil processing plants, gas processing plants, and the like, fluids are often branched or merged. To achieve this, a branch section is provided in the clad pipe. For example, Patent Document 1 describes a method for connecting a branch pipe to a corrosion-resistant alloy composite pipe.

[0004] Chinese Patent Application Publication No. 112439979

[0005] When a branch section is provided in a clad pipe, a through-hole is provided in the clad pipe. Because the clad pipe is made of different materials laminated together, the area where the different materials are bonded is exposed on the inner surface of the through-hole. When a fluid comes into contact with the area where the different materials are bonded together, corrosion of the material with a relatively higher ionization tendency is accelerated. This phenomenon is called galvanic corrosion. Therefore, when forming a branch pipe including a clad pipe, measures to suppress the occurrence of galvanic corrosion are required.

[0006] Therefore, the present invention provides a branch pipe capable of suppressing the occurrence of galvanic corrosion and a method for manufacturing the branch pipe.

[0007] A branch pipe according to one embodiment of the present invention comprises: a main pipe having a main pipe inner layer portion and a main pipe outer layer portion surrounding the main pipe inner layer portion, the main pipe having a main pipe branch hole penetrating the main pipe inner layer portion and having an opening formed in the outer layer outer surface, which is the outer surface of the main pipe outer layer portion, the diameter of the opening formed in the inner layer inner surface, which is the inner surface of the main pipe inner layer portion, larger than the diameter of the opening formed in the inner layer inner surface, which is the inner surface of the main pipe inner layer portion; a branch pipe extending in a direction intersecting the axial direction of the main pipe; and a connecting portion connecting an end of the branch pipe to the outer layer outer surface of the main pipe. The connecting portion has a main pipe-side connecting weld where the main pipe inner layer portion and the main pipe outer layer portion contact each other and covers the main pipe contact portion exposed at the main pipe branch hole, and a branch pipe-side connecting weld provided between the main pipe-side connecting weld and the end of the branch pipe to connect the branch pipe to the main pipe, the main pipe outer layer portion being made of a different material from the main pipe inner layer portion.

[0008] In this branch pipe, the diameter of the opening formed in the outer peripheral surface of the outer layer is larger than the diameter of the opening formed in the inner peripheral surface of the inner layer. With this configuration of the main pipe branch hole, it is easy to insert a welding rod from the opening formed in the outer peripheral surface of the outer layer toward the opening formed in the inner peripheral surface of the inner layer, making it easy to form a main pipe side connecting weld at the location where the main pipe inner layer and the main pipe outer layer contact each other. Therefore, since the fluid does not come into contact with the location where the main pipe inner layer and the main pipe outer layer contact each other, the occurrence of galvanic corrosion can be suppressed.

[0009] In one embodiment of the branch pipe, the main pipe side connection weld may have an inner buildup exposed surface exposed from the inner circumferential surface of the inner layer. With this configuration, the inner buildup exposed surface is exposed from the inner circumferential surface of the inner layer of the main pipe. As a result, the main pipe side connection weld covers the area from the point where the inner layer portion of the main pipe and the outer layer portion of the main pipe contact each other to the opening formed in the inner circumferential surface of the inner layer. This makes it difficult for fluid to reach the point where the inner layer portion of the main pipe and the outer layer portion of the main pipe contact each other, further suppressing the occurrence of galvanic corrosion.

[0010] In one embodiment of the branch pipe, the area of ​​the main pipe connection weld along the outer peripheral surface of the outer layer may be larger than the area of ​​the exposed inner buildup surface. This configuration ensures a large contact area between the main pipe connection weld and the branch pipe connection weld. As a result, the main pipe connection weld can be satisfactorily connected to the branch pipe connection weld.

[0011] In one embodiment, the connecting portion further includes a ring member disposed in the main pipe branch hole, and the main pipe side connecting weld may include a buildup outer peripheral surface that contacts the branch hole inner peripheral surface, which is the inner peripheral surface of the main pipe branch hole, and covers the main pipe contact portion, and a buildup inner peripheral surface that contacts the ring outer peripheral surface, which is the outer peripheral surface of the ring member. With this configuration, the inner peripheral surface of the ring member disposed in the main pipe branch hole defines the flow path. As a result, the flow path can be configured as desired.

[0012] In one embodiment of the branch piping, the flow path formed by the main pipe, branch pipe, and connecting portion is defined by the inner layer inner circumferential surface, the inner overlay exposed surface, the ring inner circumferential surface which is the inner circumferential surface of the ring member, the connecting weld inner circumferential surface which is the inner circumferential surface of the branch pipe side connecting weld, and the branch pipe inner circumferential surface which is the inner circumferential surface of the branch pipe, and the main pipe inner layer portion, main pipe side connecting weld, ring member, branch pipe side connecting weld, and branch pipe may be made of materials having equivalent corrosion resistance. With this configuration, a flow path for a corrosive fluid can be formed using materials having equivalent corrosion resistance.

[0013] In one embodiment of the branch pipe, the outer peripheral edge of the branch pipe may be located outside the outer peripheral edge of the main pipe-side connection weld as viewed from the axial direction of the branch pipe. This configuration allows for the connection of relatively thick branch pipes.

[0014] In one embodiment of the branch pipe, the outer peripheral edge of the branch pipe may be located inside the outer peripheral edge of the main pipe-side connection weld as viewed from the axial direction of the branch pipe. This configuration allows for the connection of relatively thin branch pipes.

[0015] In one embodiment of the branch pipe, the inner peripheral edge of the branch pipe may be located inside the inner peripheral edge of the main pipe-side connection weld as viewed from the axial direction of the branch pipe. With this configuration, a step is provided between the inner peripheral surface of the branch pipe and the inner peripheral surface of the main pipe-side connection weld. A ring member can be placed at this step.

[0016] A method for manufacturing branch piping, which is another embodiment of the present invention, includes the steps of: forming a main pipe branch hole in a main pipe having an inner layer portion of the main pipe and an outer layer portion of the main pipe surrounding the inner layer portion and made of a different material from the inner layer portion; the main pipe branch hole penetrating the inner layer portion and the outer layer portion and having an opening formed in the outer layer outer surface, which is the outer surface of the outer layer portion, that has a diameter larger than the opening formed in the inner layer inner surface, which is the inner surface of the main pipe inner layer portion; forming a main pipe side connection weld where the main pipe inner layer portion and the main pipe outer layer portion come into contact with each other and cover the main pipe contact portion exposed in the main pipe branch hole; and forming a branch pipe side connection weld that connects the branch pipe to the main pipe between the main pipe side connection weld and an end of the branch pipe that extends in a direction intersecting the axial direction of the main pipe and is positioned so as to face the main pipe side connection weld.

[0017] In this method of manufacturing branch pipes, a main pipe branch hole is provided with an opening formed in the outer peripheral surface of the outer layer that has a larger diameter than the opening formed in the inner peripheral surface of the inner layer. This main pipe branch hole configuration facilitates inserting a welding rod from the opening formed in the outer peripheral surface of the outer layer toward the opening formed in the inner peripheral surface of the inner layer, facilitating the formation of a main pipe-side connecting weld at the contact point between the inner and outer layers of the main pipe. This prevents fluid from coming into contact with the contact point between the inner and outer layers, thereby suppressing the occurrence of galvanic corrosion.

[0018] Another embodiment of the branch pipe manufacturing method may further include a step of providing a ring member in the main pipe branch hole after the step of forming the main pipe branch hole. In the step of forming the main pipe side connection weld, the main pipe side connection weld may be formed between the branch hole inner circumferential surface, which is the inner circumferential surface of the main pipe branch hole, and the ring outer circumferential surface, which is the outer circumferential surface of the ring member. This step allows the fluid flow path to be defined by the inner circumferential surface of the ring member placed in the main pipe branch hole. As a result, the flow path can be configured as desired.

[0019] According to the branch pipe and the method for manufacturing the branch pipe of the present invention, the occurrence of galvanic corrosion can be suppressed.

[0020] FIG. 1 is a perspective view of a branch pipe, partly shown in cross section. FIG. 2 is a partially enlarged view of FIG. 1. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 4(a) is a cross-sectional perspective view showing an enlarged view of a branch pipe of a branch pipe according to a modified example and a main pipe side connection weld. FIG. 4(b) is a cross-sectional perspective view showing an enlarged view of a branch pipe of a branch pipe according to another modified example and a main pipe side connection weld. FIG. 5 is a flowchart of a method for manufacturing a branch pipe. FIG. 6 is a perspective view showing a main pipe base material. FIG. 7 is a view showing a process of forming a temporary through hole in the main pipe base material. FIG. 8 is a view showing a process of forming a main pipe branch hole. FIG. 9 is a view showing a process of temporarily fastening a ring base material to a main pipe. FIG. 10 is a view showing a process of forming a main pipe side connection weld. FIG. 11 is a view showing a process of forming a ring member. FIG. 12 is a view showing a process of connecting branch pipes.

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0022] The branch pipe 1 shown in Fig. 1 is a pipe through which a corrosive fluid flows. Examples of the corrosive fluid include fluids containing hydrogen sulfide and chlorides. In a plant where oil processing or gas processing is performed, the branch pipe 1 is used to branch or merge the corrosive fluid flowing therethrough.

[0023] The branch pipe 1 includes a main pipe 2, a branch pipe 3, and a connecting portion 4. A corrosive fluid flows inside the main pipe 2. A portion of the corrosive fluid flowing inside the main pipe 2 branches off, and a portion of the corrosive fluid flows inside the branch pipe 3.

[0024] The main pipe 2 is a so-called clad pipe. The main pipe 2 has a cylindrical shape. The main pipe 2 has an axis X21. The branch pipe 3 also has a cylindrical shape. The axis X3 of the branch pipe 3 intersects with the axis X21. In this embodiment, the axis X3 is perpendicular to the axis X21. The axis X3 does not have to be perpendicular to the axis X21. For example, the axis X3 may be inclined at 45° with respect to the axis X21. The inner diameter of the branch pipe 3 may be smaller than the inner diameter of the main pipe 2. The outer diameter of the branch pipe 3 may be smaller than the outer diameter of the main pipe 2. The connecting portion 4 is provided between the outer peripheral surface of the main pipe 2 and the end of the branch pipe 3, and connects the branch pipe 3 to the main pipe 2.

[0025] FIG. 2 is an enlarged cross-sectional perspective view of the branch pipe 3 and the connecting portion 4. The main pipe 2 has a main pipe inner layer portion 21 and a main pipe outer layer portion 22. The main pipe inner layer portion 21 of the main pipe 2 constitutes the inside portion of the main pipe 2. The main pipe inner layer portion 21 has an inner layer inner circumferential surface 21a that constitutes the inner circumferential surface of the main pipe 2. The inner layer inner circumferential surface 21a comes into contact with a corrosive fluid. The main pipe inner layer portion 21 is made of a corrosion-resistant material. In this specification, "corrosion resistance" refers to the property of being less susceptible to corrosion by a corrosive fluid. The branch pipe 1 of this embodiment focuses on corrosion resistance. The materials constituting the branch pipe 1 to ensure corrosion resistance will be described in detail later.

[0026] The main pipe outer layer portion 22 is a portion that surrounds the main pipe inner layer portion 21. The main pipe outer layer portion 22 has an outer layer outer surface 22a that forms the outer surface of the main pipe 2. The main pipe outer layer portion 22 is made of a different material from the main pipe inner layer portion 21. The main pipe outer layer portion 22 is made of a material that improves the strength of the main pipe 2.

[0027] The main pipe 2 is provided with a main pipe branch hole 2H. The main pipe branch hole 2H has an axis X22 that overlaps with the axis X3 of the branch pipe 3, and penetrates the main pipe inner layer portion 21 and the main pipe outer layer portion 22. The main pipe branch hole 2H has an inner layer side opening 21h and an outer layer side opening 22h. The inner layer side opening 21h is formed on the inner layer inner circumferential surface 21a. The outer layer side opening 22h is formed on the outer layer outer circumferential surface 22a. The inner diameter of the outer layer side opening 22h is larger than the inner layer side opening 21h. In other words, the main pipe branch hole 2H has a truncated cone shape. More specifically, the inner diameter of the main pipe branch hole 2H increases as it moves away from the axis X21.

[0028] The branch pipe 3 has a branch pipe lower end surface 3a, a branch pipe upper end surface 3b, a branch pipe inner circumferential surface 3c, and a branch pipe outer circumferential surface 3d. The branch pipe lower end surface 3a faces the main pipe 2 via a connecting portion 4. The branch pipe upper end surface 3b is the end surface opposite the branch pipe lower end surface 3a and is connected to another pipe (not shown). The branch pipe inner circumferential surface 3c is the inner circumferential surface of the branch pipe 3 and comes into contact with the corrosive fluid. The branch pipe outer circumferential surface 3d is the outer circumferential surface of the branch pipe 3 and is a visible surface.

[0029] The connecting portion 4 connects the branch hole inner circumferential surface 2S, which defines the main pipe branch hole 2H, to the branch pipe lower end surface 3a. More specifically, the branch hole inner circumferential surface 2S has an exposed inner layer surface 21s, where a portion of the main pipe inner layer 21 is exposed, and an exposed outer layer surface 22s, where a portion of the main pipe outer layer 22 is exposed. The connecting portion 4 covers both the exposed inner layer surface 21s and the exposed outer layer surface 22s. The branch pipe lower end surface 3a includes a flat lower end surface 3a1 and a sloped lower end surface 3a2. The connecting portion 4 covers both the flat lower end surface 3a1 and the sloped lower end surface 3a2.

[0030] The connecting portion 4 will be described in more detail with reference to Fig. 3. As shown in Fig. 3, the connecting portion 4 has a ring member 41, a main pipe side connecting weld portion 42, and a branch pipe side connecting weld portion 43.

[0031] The ring member 41 is a member that defines a flow path through which the corrosive fluid flows. The ring member 41 is made of a corrosion-resistant material. The ring member 41 may be formed, for example, of the same material as the branch pipe 3. The ring member 41 has a cylindrical shape. The ring member 41 is disposed in the main pipe branch hole 2H. The ring member 41 has an axis that overlaps with the axis X3. The ring member 41 has a ring lower end surface 41a and a ring upper end surface 41b. The ring lower end surface 41a is the end surface of the ring member 41 in the direction along the axis X3 that is closer to the axis X21. The ring lower end surface 41a is the end surface located opposite the ring upper end surface 41b. The ring upper end surface 41b is spaced from the branch pipe lower end surface 3a, and a portion of the branch pipe side connection weld 43 is sandwiched between the ring upper end surface 41b and the branch pipe lower end surface 3a. The ring upper end surface 41b is substantially flush with the outer layer outer peripheral surface 22a in the radial direction centered on the axis X21.

[0032] The ring member 41 has a ring inner peripheral surface 41c and a ring outer peripheral surface 41d. The ring inner peripheral surface 41c is the inner peripheral surface of the ring member 41. The corrosive fluid comes into contact with the ring inner peripheral surface 41c. In the example shown in Figure 2, when the branch pipe 3 is viewed from the direction of the axis X3 using the ring inner peripheral surface 41c as a reference, the branch pipe inner peripheral surface 3c of the branch pipe 3 roughly coincides with the ring inner peripheral surface 41c. The ring outer peripheral surface 41d is the outer peripheral surface of the ring member 41. The ring outer peripheral surface 41d is spaced from the branch hole inner peripheral surface 2S of the main pipe 2, and the main pipe side connection weld 42 is sandwiched between the ring outer peripheral surface 41d and the branch hole inner peripheral surface 2S.

[0033] The main pipe side connection weld 42 connects the ring member 41 to the main pipe 2. The main pipe side connection weld 42 is provided to fill the gap between the ring outer surface 41d and the branch hole inner surface 2S. In other words, the main pipe side connection weld 42 covers the branch hole inner surface 2S. More specifically, the main pipe side connection weld 42 covers the main pipe contact portion 2C included in the branch hole inner surface 2S. The main pipe contact portion 2C is the portion where the edge 21s1 of the inner layer exposed surface 21s and the edge 22s1 of the outer layer exposed surface 22s, both exposed in the main pipe branch hole 2H, meet. Because the branch hole inner surface 2S includes the inner layer exposed surface 21s and the outer layer exposed surface 22s, neither the inner layer exposed surface 21s nor the outer layer exposed surface 22s is exposed to the flow path through which the corrosive fluid flows. Furthermore, the main pipe contact portion 2C is also not exposed to the flow path through which the corrosive fluid flows.

[0034] The main pipe side connection weld 42 is made of a corrosion-resistant material and has an inner weld exposure surface 42 a, an outer weld exposure surface 42 b, an inner weld exposure surface 42 c, and an outer weld exposure surface 42 d.

[0035] The inner overlay exposed surface 42a intersects with a radial direction centered on the axis X21. When viewed from the internal space of the main pipe 2, the inner overlay exposed surface 42a is located between the inner layer inner circumferential surface 21a and the ring lower end surface 41a. The inner overlay exposed surface 42a may be flush with the inner layer inner circumferential surface 21a. The inner overlay exposed surface 42a may be flush with the ring lower end surface 41a.

[0036] The outer overlay exposed surface 42b intersects with a radial direction centered on the axis X21. When viewed from the external space of the main pipe 2, the outer overlay exposed surface 42b is located between the outer layer outer peripheral surface 22a and the ring upper end surface 41b. The outer overlay exposed surface 42b may be flush with the outer layer outer peripheral surface 22a. The outer overlay exposed surface 42b may be flush with the ring upper end surface 41b.

[0037] The outer peripheral edge of the outer weld build-up exposed surface 42b constitutes the weld build-up outer peripheral edge 42ba of the main pipe side connection weld 42. When the branch pipe 3 is viewed from the direction of the axis X3 using the weld build-up outer peripheral edge 42ba as a reference, the branch pipe outer peripheral surface 3d of the branch pipe 3 generally coincides with the weld build-up outer peripheral edge 42ba.

[0038] The relationship between the branch pipe outer peripheral surface 3d of the branch pipe 3 and the padding outer peripheral edge 42ba when viewed from the axis X3 may be as shown in Figures 4(a) and 4(b). In the example shown in Figure 4(a), when the branch pipe 3 is viewed from the direction of the axis X3, the branch pipe outer peripheral surface 3d of the branch pipe 3 is located outside the padding outer peripheral edge 42ba. In the example shown in Figure 4(b), when the branch pipe 3 is viewed from the direction of the axis X3, the branch pipe outer peripheral surface 3d of the branch pipe 3 is located inside the padding outer peripheral edge 42ba.

[0039] When the ring member 41 and the main pipe side connection weld 42 melt and become integrated, a weld line 42s (weld line) is formed due to welding. The inner circumferential buildup surface 42c shares the weld line 42s with the outer circumferential ring surface 41d. The weld line 42s shown in FIG. 3 is linear. However, the weld line 42s is not limited to being linear. In the example shown in FIG. 3, when the branch pipe 3 is viewed from the direction of the axis X3 using the inner circumferential buildup surface 42c as a reference, the inner circumferential buildup surface 3c of the branch pipe 3 is located inside the inner circumferential buildup surface 42c. The outer circumferential buildup surface 42d contacts the inner circumferential surface 2S of the branch hole. Because the inner circumferential surface 2S of the branch hole is inclined, the outer circumferential buildup surface 42d is also inclined.

[0040] The branch pipe side connection weld 43 connects the branch pipe 3 to the ring member 41 and the main pipe side connection weld 42. The branch pipe side connection weld 43 is made of a corrosion-resistant material.

[0041] The branch pipe side connection weld 43 has a connection weld lower end surface 43a, a connection weld upper end surface 43b, a connection weld inner peripheral surface 43c, and a connection weld outer peripheral surface 43d.

[0042] Furthermore, the branch pipe side connection weld 43 is provided to fill the gap between the main pipe side connection weld 42 and the branch pipe 3. Specifically, the branch pipe side connection weld 43 is provided between the ring member 41 and the branch pipe lower end surface 3a, and between the main pipe side connection weld 42 and the lower end slope 3a2. The branch pipe side connection weld 43 has a thin-walled connection portion 431 and a thick-walled connection portion 432. The thin-walled connection portion 431 is located between the ring member 41 and the branch pipe lower end surface 3a. The thick-walled connection portion 432 is located between the main pipe side connection weld 42 and the lower end slope 3a2. The thin-walled connection portion 431 has a constant thickness. The thick-walled connection portion 432 has a thickness that increases with increasing distance from the thin-walled connection portion 431. The branch pipe side connecting weld 43 connects the branch pipe 3 to the ring member 41 via a part of the connecting thick portion 432 and the connecting thin portion 431. The branch pipe side connecting weld 43 connects the branch pipe 3 to the main pipe side connecting weld 42 via the connecting thick portion 432.

[0043] The branch pipe side connection weld 43 has a connection weld inner circumferential surface 43c, which is the inner circumferential surface of the branch pipe side connection weld 43, and a connection weld outer circumferential surface 43d, which is the outer circumferential surface of the branch pipe side connection weld 43. The connection weld inner circumferential surface 43c comes into contact with the corrosive fluid. The connection weld outer circumferential surface 43d is located outside the branch pipe outer circumferential surface 3d.

[0044] <Materials of Main Pipe, Branch Pipe, and Connecting Portion> The branch pipe 1 of this embodiment constitutes a flow path through which a corrosive fluid flows. Therefore, all parts that come into contact with the corrosive fluid are made of corrosion-resistant materials.

[0045] Examples of corrosion-resistant materials include nickel-chromium-iron alloys and high-nickel iron-based alloys. An example of a nickel-chromium-iron alloy is Inconel®, which is primarily nickel with additives such as iron, chromium, niobium, and molybdenum. One specific example of Inconel is Inconel 625 (ALLOY 625). Other specific examples of Inconel are ALLOY 82 and ALLOY 182. ALLOY 82 and ALLOY 182 have excellent corrosion resistance, similar to ALLOY 625. According to the specifications established by the American Welding Society (AWS), the specifications for ALLOY 625 are ENiCrMo-3 or ERNiCrMo-3. The specifications for ALLOY 82 are ERNiCr-3. The specifications for ALLOY 182 are ENiCrFe-3. An example of a high nickel iron-base alloy is Incoloy, an austenitic nickel-iron-chromium alloy containing titanium, copper, and molybdenum additives. One specific example of Incoloy is Incoloy 825.

[0046] Another example of a corrosion-resistant material is austenitic stainless steel. Specific examples of austenitic stainless steel include SUS316L and SUS309LMo. SUS309LMo is also used as a material for welding rods, so it can be used as the material for the connecting portion 4 formed by welding.

[0047] The metallic materials exemplified above are generally known to have high corrosion resistance. In this embodiment, "materials having equivalent corrosion resistance" refers to materials included in the metallic materials exemplified above. In other words, examples of materials having equivalent corrosion resistance include Inconel 625 (ALLOY 625), Incoloy 825 (ALLOY 825), SUS316L, and SUS309LMo. Furthermore, other materials belonging to nickel-chromium-iron alloys, high-nickel iron-based alloys, and austenitic stainless steels may also be included in materials having equivalent corrosion resistance.

[0048] Specific combinations of materials are shown below. However, the branch pipe 1 of this embodiment is not limited to the following combinations of materials. For example, if the main pipe inner layer 21 is formed by forging, the main pipe inner layer 21 and the ring member 41 may be formed from the same material. If the main pipe inner layer 21 is formed by build-up welding, the main pipe inner layer 21, the main pipe side connecting weld 42, and the branch pipe side connecting weld 43 may be formed from the same material.

[0049] A first example is as follows: Main pipe inner layer 21: Stainless steel (SUS316L) Main pipe outer layer 22: Carbon steel Branch pipe 3: Stainless steel (SUS316L) Ring member 41: Stainless steel (SUS316L) Main pipe side connection weld 42 and branch pipe side connection weld 43: Stainless steel (SUS309LMo)

[0050] A second example is as follows: Main pipe inner layer 21: Alloy 625 (nickel-chromium-iron alloy) Main pipe outer layer 22: carbon steel Branch pipe 3: Alloy 825 (high-nickel-iron-based alloy) Ring member 41: Alloy 825 (high-nickel-iron-based alloy) Main pipe side connection weld 42 and branch pipe side connection weld 43: Alloy 625 (nickel-chromium-iron alloy)

[0051] For example, in the first example, the main pipe 2 includes a contact area between carbon steel and stainless steel. Comparing the standard electrode potentials of the respective materials, the standard electrode potential of stainless steel is relatively high, while the standard electrode potential of carbon steel is relatively low. In other words, stainless steel is difficult to ionize, while carbon steel is easy to ionize. This difference in ionization tendency can cause so-called galvanic corrosion. However, in the branch pipe 1 of this embodiment, the contact area between the main pipe inner layer 21 made of stainless steel and the main pipe outer layer 22 made of carbon steel is covered by the main pipe-side connection weld 42. Therefore, the contact area between the dissimilar metals is not exposed to a corrosive fluid, thereby suppressing the occurrence of galvanic corrosion.

[0052] Furthermore, the main pipe inner layer 21, branch pipe 3, main pipe side connection weld 42, and branch pipe side connection weld 43, which are the parts exposed to the corrosive fluid, are all made of austenitic stainless steel or nickel alloy. These materials have similar standard electrode potentials even if their specific composition ratios differ, so galvanic corrosion does not generally occur.

[0053] In other words, the branch pipe 1 of this embodiment ensures corrosion resistance against corrosive fluids for two reasons: first, the outer circumferential surface of the buildup has a configuration that prevents the areas where dissimilar metals come into contact from being exposed to corrosive fluids, and second, the areas exposed to corrosive fluids are made of materials that are highly corrosion-resistant and have standard electrode potentials that are close to each other.

[0054] Next, a flow path of a corrosive fluid in the branch pipe 1 when it flows from the main pipe 2 to the branch pipe 3 will be described. When the corrosive fluid flows from the main pipe 2 to the branch pipe 3, the corrosive fluid first flows in the area defined by the inner layer inner circumferential surface 21a of the main pipe inner layer 21 of the main pipe 2. Next, the corrosive fluid flowing toward the main pipe branch hole 2H flows along the inner buildup exposed surface 42a of the main pipe side connection weld 42, the ring lower end surface 41a of the ring member 41, and the ring inner circumferential surface 41c of the ring member 41. Next, the corrosive fluid flows along the connection weld inner circumferential surface 43c of the branch pipe side connection weld 43 and the branch pipe inner circumferential surface 3c of the branch pipe 3. Therefore, the flow path formed by the main pipe 2, branch pipe 3 and connecting portion 4 is defined by the inner layer inner surface 21a, the inner buildup exposed surface 42a, the ring lower end surface 41a, the ring inner surface 41c, the connecting weld inner surface 43c, and the branch pipe inner surface 3c.

[0055] Next, a method for manufacturing the branch pipe 1 of this embodiment will be described with reference to FIGS. 5 to 12. FIG. 5 is a flowchart of the method for manufacturing the branch pipe 1. FIG. 6 is a perspective view showing the main pipe base material M2. FIG. 7 is a diagram showing a process for forming a temporary through hole M2H in the main pipe base material M2. FIG. 8 is a diagram showing a process for forming a main pipe branch hole 2H. FIG. 9 is a diagram showing a process for temporarily fastening the ring base material M41 to the main pipe 2. FIG. 10 is a diagram showing a process for forming a main pipe side connection weld 42. FIG. 11 is a diagram showing a process for forming a ring member 41. FIG. 12 is a diagram showing a process for connecting the branch pipe 3.

[0056] First, as shown in Fig. 6, a main pipe substrate M2 is prepared (S1). The main pipe substrate M2 differs from the main pipe 2 mainly in that the main pipe branch hole 2H is not formed in the main pipe substrate M2. Next, as shown in Fig. 7, temporary through holes M2H are formed in the main pipe substrate M2 (S2). The diameter of the temporary through holes M2H is a fixed size.

[0057] Next, as shown in Fig. 8, a main pipe branch hole 2H is formed (S3). The main pipe branch hole 2H is formed by cutting the inner peripheral surface of the temporary through hole M2H. By forming the main pipe branch hole 2H, the main pipe 2 is obtained.

[0058] Next, as shown in Fig. 9, a ring substrate M41 is temporarily fastened to the main pipe 2 (S4). The ring substrate M41 is a component that will become the ring member 41. The ring substrate M41 has a cylindrical shape. The length of the ring substrate M41 is longer than that of the ring member 41. In a subsequent step (S6), the ring substrate M41 is cut to form the ring member 41 having a predetermined length.

[0059] The outer peripheral surface M41d of the ring base material M41 does not contact the branch hole inner peripheral surface 2S of the main pipe 2. The lower end surface of the ring base material M41 roughly coincides with the inner layer inner peripheral surface 21a of the main pipe 2. The ring base material M41 is fixed to the main pipe 2 by tack welded portions M5. The tack welded portions M5 have a curved shape that curves away from the ring base material M41. One end of the tack welded portions M5 is connected to the outer layer outer peripheral surface 22a. The other end of the tack welded portions M5 is connected to the outer peripheral surface M41d of the ring base material M41. Two tack welded portions M5 are shown in Figure 9. The number of tack welded portions M5 used to temporarily fix the ring base material M41 is arbitrary.

[0060] Next, as shown in Figure 10, a main pipe side connection weld 42 is formed (S5). The main pipe side connection weld 42 is formed, for example, by gas tungsten arc welding (GTAW welding). For example, a welding rod for arc welding is inserted from the outer layer side opening 22h of the main pipe branch hole 2H toward the inner layer side opening 21h. Then, the main pipe side connection weld 42 is formed between the outer peripheral surface M41d of the ring base material M41 and the branch hole inner peripheral surface 2S, from the inner layer side opening 21h toward the outer layer side opening 22h. The main pipe side connection weld 42 is formed until it coincides with the position of the outer layer outer peripheral surface 22a or protrudes beyond the outer layer outer peripheral surface 22a.

[0061] Note that if the wall thickness of the main pipe 2 is thick, the main pipe side connection weld 42 may be formed by a different type of welding. For example, the main pipe side connection weld 42 includes a lower weld layer 42r including a portion in contact with the exposed inner layer surface 21s and an inner overlay exposed surface 42a, and an upper weld layer 42p including a portion in contact with the exposed outer layer surface 22s and an outer overlay exposed surface 42b. As described above, both the lower weld layer 42r and the upper weld layer 42p may be formed by gas tungsten arc welding. Alternatively, the lower weld layer 42r may also be formed by gas tungsten arc welding, and the upper weld layer 42p may be formed by shielded metal arc welding (SMAW welding) or flux-cored arc welding (FCAW welding).

[0062] Next, as shown in FIG. 11 , a ring member 41 is formed (S6). More specifically, a portion of the ring base material M41 protruding from the main pipe branch hole 2H is cut. The ring base material M41 is cut in a direction perpendicular to the direction along the axis X22. The ring upper end surface 41b of the ring member 41 obtained as a result of cutting may be flush with the outer layer outer peripheral surface 22a. In this case, the ring upper end surface 41b is curved along the outer layer outer peripheral surface 22a. Alternatively, the ring upper end surface 41b may protrude from the outer layer outer peripheral surface 22a. In this case, the ring upper end surface 41b is a plane perpendicular to the axis X3. Note that in this step S6, a portion of the main pipe side connection weld portion 42 may be removed. As a result of such cutting or grinding, an outer buildup exposed surface 42b may be formed. In this case, the outer build-up exposed surface 42b may be flush with the outer layer outer peripheral surface 22a and may be curved along the outer layer outer peripheral surface 22a.

[0063] 12, the branch pipe 3 is positioned (S7). Specifically, the branch pipe 3 is positioned so as to be spaced apart from the ring member 41 in the direction along the axis X3 and to face the main pipe side connection welded portion 42.

[0064] Then, branch pipe side connection welds 43 are formed between the branch pipe 3 and the ring member 41, and between the branch pipe 3 and the main pipe side connection welds 42 (S8). A welding rod is inserted between the branch pipe 3 and the main pipe side connection welds 42 from the branch pipe outer peripheral surface 3d side of the branch pipe 3, and the tip of the welding rod is positioned between the branch pipe 3 and the ring member 41. The tip of the welding rod is then moved outward while being rotated about axis X3, thereby forming the branch pipe side connection welds 43. As a result, the branch pipe 3 is connected to the ring member 41 and the main pipe side connection welds 42.

[0065] <Action and Effect> The branch pipe 1 includes a main pipe 2 having a main pipe inner layer portion 21 and a main pipe outer layer portion 22 surrounding the main pipe inner layer portion 21, and having a main pipe branch hole 2H penetrating the main pipe inner layer portion 21 and the main pipe outer layer portion 22 and having an opening formed in an outer layer outer surface 22a, which is the outer surface of the main pipe outer layer portion 22, with the diameter of the opening formed in the inner layer inner surface 21a, which is the inner surface of the main pipe inner layer portion 21; a branch pipe 3 extending in a direction intersecting the direction of the axis X21 of the main pipe 2; and a connecting portion 4 connecting an end of the branch pipe 3 to the outer layer outer surface 22a of the main pipe 2. The connecting portion 4 has a main pipe side connecting weld 42 where the main pipe inner layer 21 and the main pipe outer layer 22 come into contact with each other and cover the main pipe contact portion 2C exposed in the main pipe branch hole 2H, and a branch pipe side connecting weld 43 provided between the main pipe side connecting weld 42 and the end of the branch pipe 3 to connect the branch pipe 3 to the main pipe 2. The main pipe outer layer 22 is made of a different material from the main pipe inner layer 21.

[0066] The diameter of the opening formed in the outer layer outer peripheral surface 22a is larger than the diameter of the opening formed in the inner layer inner peripheral surface 21a. With this configuration of the main pipe branch hole 2H, it is easy to insert a welding rod from the opening formed in the outer layer outer peripheral surface 22a toward the opening formed in the inner layer inner peripheral surface 21a, making it easy to form a main pipe side connecting weld 42 at the location where the main pipe inner layer portion 21 and the main pipe outer layer portion 22 contact each other. Therefore, the fluid does not come into contact with the location where the main pipe inner layer portion 21 and the main pipe outer layer portion 22 contact each other, thereby suppressing the occurrence of galvanic corrosion.

[0067] The main pipe side connection weld 42 has an inner buildup exposed surface 42a exposed from the inner layer inner circumferential surface 21a. With this configuration, the inner buildup exposed surface 42a is exposed from the inner layer inner circumferential surface 21a of the main pipe 2. As a result, the main pipe side connection weld 42 covers the area from the contact point between the main pipe inner layer portion 21 and the main pipe outer layer portion 22 to the opening formed in the inner layer inner circumferential surface 21a. This makes it difficult for fluid to reach the contact point between the main pipe inner layer portion 21 and the main pipe outer layer portion 22, further suppressing the occurrence of galvanic corrosion.

[0068] The area of ​​the outer overlay exposed surface 42b along the outer layer outer peripheral surface 22a is larger than the area of ​​the inner overlay exposed surface 42a. This configuration ensures a large contact area between the main pipe connection weld 42 and the branch pipe connection weld 43. As a result, the main pipe connection weld 42 can be well connected to the branch pipe connection weld 43.

[0069] The connecting portion 4 further includes a ring member 41 disposed in the main pipe branch hole 2H. The main pipe side connecting weld 42 includes a build-up outer peripheral surface 42d that contacts the branch hole inner peripheral surface 2S, which is the inner peripheral surface of the main pipe branch hole 2H, and covers the main pipe contact portion 2C, and a build-up inner peripheral surface 42c that contacts the ring outer peripheral surface 41d, which is the outer peripheral surface of the ring member 41. With this configuration, the inner peripheral surface of the ring member 41 disposed in the main pipe branch hole 2H defines the flow path. As a result, the flow path can be configured as desired.

[0070] The flow path formed by the main pipe 2, branch pipe 3, and connecting portion 4 is defined by the inner layer inner circumferential surface 21a, the inner overlay exposed surface 42a, the ring inner circumferential surface 41c which is the inner circumferential surface of the ring member 41, the connecting weld inner circumferential surface 43c which is the inner circumferential surface of the branch pipe side connecting weld 43, and the branch pipe inner circumferential surface 3c which is the inner circumferential surface of the branch pipe 3. The main pipe inner layer 21, the main pipe side connecting weld 42, the ring member 41, the branch pipe side connecting weld 43, and the branch pipe 3 are made of materials that are equivalent to each other in corrosion resistance. With this configuration, a flow path for the flow of corrosive fluid can be formed using materials that are equivalent to each other in corrosion resistance.

[0071] When viewed from the direction of the axis X3 of the branch pipe 3, the outer peripheral edge of the branch pipe 3 may be located outside the outer peripheral edge of the main pipe side connection weld 42 (see FIG. 4(a)). This configuration allows for the connection of relatively thick branch pipes 3.

[0072] In one embodiment of the branch pipe 1, the outer peripheral edge of the branch pipe 3 may be located inside the outer peripheral edge of the main pipe side connection weld 42 when viewed from the direction of the axis X3 of the branch pipe 3 (see FIG. 4(b)). This configuration allows for the connection of relatively thin branch pipes 3.

[0073] In one embodiment of the branch pipe 1, when viewed from the direction of the axis X3 of the branch pipe 3, the position of the inner peripheral edge of the branch pipe 3 is located inside the position of the inner peripheral edge of the main pipe side connection weld 42. With this configuration, a step is provided between the inner peripheral surface of the branch pipe 3 and the inner peripheral surface of the main pipe side connection weld 42. A ring member 41 can be placed at this step.

[0074] The method for manufacturing the branch pipe 1 includes a step (S2) of forming a main pipe branch hole 2H in a main pipe 2 having a main pipe inner layer portion 21 and a main pipe outer layer portion 22 that surrounds the main pipe inner layer portion 21 and is made of a material different from that of the main pipe inner layer portion 21. The main pipe branch hole 2H penetrates the main pipe inner layer portion 21 and the main pipe outer layer portion 22, and has an opening formed in an outer layer outer surface 22a, which is the outer surface of the main pipe outer layer portion 22, with a diameter larger than the diameter of the opening formed in an inner layer inner surface 21a, which is the inner surface of the main pipe inner layer portion 21. and a step (S8) of forming a branch pipe side connection weld 43 that connects the branch pipe 3 to the main pipe 2 between the main pipe side connection weld 42 and the end of the branch pipe 3 that extends in a direction intersecting the direction of the axis X21 of the main pipe 2 and is positioned so as to face the main pipe side connection weld 42.

[0075] In the method for manufacturing the branch pipe 1, a main pipe branch hole 2H is provided in which the diameter of the opening formed in the outer layer outer peripheral surface 22a is larger than the diameter of the opening formed in the inner layer inner peripheral surface 21a (S2, S3). With the main pipe branch hole 2H configured in this manner, in step S5, it is easy to insert a welding rod from the opening formed in the outer layer outer peripheral surface 22a toward the opening formed in the inner layer inner peripheral surface 21a, making it easy to form a main pipe side connection weld 42 at the contact point between the main pipe inner layer portion 21 and the main pipe outer layer portion 22. Therefore, fluid does not come into contact with the contact point between the main pipe inner layer portion 21 and the main pipe outer layer portion 22, thereby suppressing the occurrence of galvanic corrosion.

[0076] After the steps (S2, S3) of forming the main pipe branch hole 2H, the method further includes steps (S4, S6) of providing a ring member 41 in the main pipe branch hole 2H. In the step (S5) of forming a main pipe side connection weld 42, the main pipe side connection weld 42 is formed between the branch hole inner circumferential surface 2S, which is the inner circumferential surface of the main pipe branch hole 2H, and the ring outer circumferential surface 41d, which is the outer circumferential surface of the ring member 41. This step allows the fluid flow path to be defined by the inner circumferential surface of the ring member 41 placed in the main pipe branch hole 2H. As a result, the flow path can be configured as desired.

[0077] Although several embodiments of the present invention have been described above, the branch pipe and the method for manufacturing the branch pipe of the present invention are not limited to the aspects described in the above embodiments.

[0078] In the above embodiment, it is not specified whether the branch pipe 3 is a clad pipe or not. The branch pipe 3 may or may not be a clad pipe. When a clad pipe is used as the branch pipe 3 (Olet), the material of the branch pipe inner layer of the branch pipe 3 may be the same as the material of the main pipe side connection weld 42 and the branch pipe side connection weld 43. When a pipe material that is not a clad pipe is used as the branch pipe 3, the material of the branch pipe 3 may be the same as the material of the ring member 41.

[0079] 1...branch piping, 2...main pipe, 2C...main pipe contact portion, 2H...main pipe branch hole, 2S...branch hole inner surface, 3...branch pipe, 3c...branch pipe inner surface, 4...connecting portion, 21...main pipe inner layer portion, 21a...inner layer inner surface, 22...main pipe outer layer portion, 22a...outer layer outer surface, 41...ring member, 41c...ring inner surface, 41d...ring outer surface, 42...main pipe side connection weld portion, 42a...inner buildup exposed surface, 42c...buildup inner surface, 42d...buildup outer surface, 43...branch pipe side connection weld portion, M41d...outer surface.

Claims

1. A branch piping comprising: a main pipe having a main pipe inner layer portion and a main pipe outer layer portion surrounding the main pipe inner layer portion, the main pipe being provided with a main pipe branch hole which penetrates the main pipe inner layer portion and the main pipe outer layer portion and has an opening diameter formed in an outer layer outer peripheral surface which is the outer peripheral surface of the main pipe outer layer portion greater than the opening diameter formed in an inner layer inner peripheral surface which is the inner peripheral surface of the main pipe inner layer portion; a branch pipe extending in a direction intersecting the axial direction of the main pipe; and a connecting portion connecting an end of the branch pipe to the outer layer outer peripheral surface of the main pipe, the connecting portion having: a main pipe side connection weld portion where the main pipe inner layer portion and the main pipe outer layer portion come into contact with each other and which covers a main pipe contact portion exposed at the main pipe branch hole; and a branch pipe side connection weld portion provided between the main pipe side connection weld portion and the end of the branch pipe and connecting the branch pipe to the main pipe, the main pipe outer layer portion being made of a material different from that of the main pipe inner layer portion.

2. The branch pipe according to claim 1, wherein the main pipe side connecting weld has an inner buildup exposed surface exposed from the inner layer inner circumferential surface.

3. The branch pipe according to claim 2, wherein the area of ​​the main pipe side connecting weld along the outer peripheral surface of the outer layer is larger than the area of ​​the inner buildup exposed surface.

4. A branch piping as described in claim 2 or claim 3, wherein the connecting portion further has a ring member arranged in the main pipe branch hole, and the main pipe side connection weld portion includes a build-up outer peripheral surface that contacts the branch hole inner peripheral surface, which is the inner peripheral surface of the main pipe branch hole, and covers the main pipe contact portion, and a build-up inner peripheral surface that contacts the ring outer peripheral surface, which is the outer peripheral surface of the ring member.

5. The branch piping described in claim 4, wherein a flow path formed by the main pipe, the branch pipe and the connecting portion is defined by the inner layer inner surface, a ring inner surface which is the inner surface of the inner buildup exposed surface and the ring member, a connecting weld inner surface which is the inner surface of the branch pipe side connecting weld, and a branch pipe inner surface which is the inner surface of the branch pipe, and the main pipe inner layer portion, the main pipe side connecting weld, the ring member, the branch pipe side connecting weld and the branch pipe are each composed of materials having equivalent corrosion resistance.

6. A branch pipe as claimed in any one of claims 1 to 5, wherein, when viewed in the axial direction of the branch pipe, the position of the outer circumferential edge of the branch pipe is located outside the position of the outer circumferential edge of the main pipe side connecting weld.

7. A branch pipe as claimed in any one of claims 1 to 5, wherein, when viewed in the axial direction of the branch pipe, the position of the outer circumferential edge of the branch pipe is located inside the position of the outer circumferential edge of the main pipe side connecting weld.

8. A branch pipe as claimed in any one of claims 1 to 5, wherein, when viewed in the axial direction of the branch pipe, the position of the inner periphery of the branch pipe is located inside the position of the inner periphery of the main pipe side connecting weld.

9. A method for manufacturing branch piping, comprising the steps of: forming a main pipe branch hole in a main pipe having a main pipe inner layer portion and a main pipe outer layer portion surrounding the main pipe inner layer portion and made of a material different from the main pipe inner layer portion, the main pipe branch hole penetrating the main pipe inner layer portion and the main pipe outer layer portion and having a diameter of an opening formed in an outer layer outer surface that is the outer surface of the main pipe outer layer portion greater than a diameter of an opening formed in an inner layer inner surface that is the inner surface of the main pipe inner layer portion; forming a main pipe side connection weld where the main pipe inner layer portion and the main pipe outer layer portion come into contact with each other and cover a main pipe contact portion exposed in the main pipe branch hole; and forming a branch pipe side connection weld between an end of a branch pipe that extends in a direction intersecting the axial direction of the main pipe and is arranged so as to face the main pipe side connection weld and the main pipe side connection weld, connecting the branch pipe to the main pipe.

10. A method for manufacturing branch piping as described in claim 9, further comprising a step of providing a ring member in the main pipe branch hole after the step of forming the main pipe branch hole, and in the step of forming the main pipe side connection weld, the main pipe side connection weld is formed between a branch hole inner surface, which is the inner surface of the main pipe branch hole, and a ring outer surface, which is the outer surface of the ring member.

Images