Plug structure, piping structure, and piping inspection method

Abstract

To appropriately prevent a problem caused by entry of particles together with fluid into a cylindrical nozzle stub part installed so as to surround a through hole formed in a pipe through which the fluid flows.SOLUTION: A plug structure 200 blocks a through hole 52 formed in a pipe through which fluid flows, and the plug structure 200 comprises: a cylindrical nozzle stub part 210 arranged so as to surround the through hole 52, and having a base end part 211 joined to an outer peripheral surface of a pipe 50; and a plug 220 inserted into the nozzle stub part 210, and joined to a tip part 212 of the nozzle stub part 210. The plug 220 comprises a sealing part 222 sealing the through hole so that an internal space IS1 of the pipe 50 and an internal space IS2 of the nozzle stub part 210 do not communicate with each other.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a plug structure, a piping structure, and a piping inspection method. [Background technology]

[0002] Large boilers used in power plants and the like have a hollow furnace installed vertically, with multiple combustion burners arranged circumferentially around the furnace wall. The boiler also has a flue connected vertically above the furnace, with a heat exchanger for generating steam disposed in the flue. The combustion burner injects a mixture of fuel and air (oxidizing gas) into the furnace, forming a flame, generating combustion gas that flows down the flue. A heat exchanger is installed in the area where the combustion gas flows, and water or steam flowing through the heat transfer tubes that make up the heat exchanger is heated to generate superheated steam.

[0003] Steam systems used in power plants with boilers are constructed by welding multiple pipes together. In this case, radiographic testing may be performed to check the integrity of the joints (presence or absence of defects). For this purpose, through-holes are drilled near the joints to allow the insertion of radiological testing equipment (radiation sources) into the inside of the pipes. Radiographic testing is usually performed only once after welding, and the drilled through-holes must be sealed after the radiographic testing is complete.

[0004] As a method for closing a through hole, for example, Patent Document 1 discloses a closing plug. The closing plug in Patent Document 1 is fixed to the piping by welding. Furthermore, Patent Document 2 discloses welding an inspection tube to an inspection hole in a header and welding a cover to the inspection tube. Patent Document 2 also discloses lining the inner surface of the inspection tube with ceramics or a composite material containing ceramics to prevent the inner surface of the inspection tube from being thinned by vortex flows of condensed condensate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-158823 [Patent Document 2] Japanese Utility Model Application Publication No. 5-25109 Summary of the Invention [Problem to be solved by the invention]

[0006] As in Patent Document 2, when one end of an inspection tube is connected to a header so as to surround the inspection hole, the internal space of the inspection tube and the internal space of the header are in communication. If particles (e.g., oxides of the metal material forming the header) contained in the fluid (steam, etc.) flowing through the internal space of the header enter and remain in the internal space of the inspection tube, they may wear away the inner circumferential surface and welded joints of the inspection tube. In particular, when an inspection hole is formed in a header that bends at a predetermined curvature or in a nearby piping, the fluid is likely to enter the internal space of the inspection tube and form a swirling flow, resulting in significant wear on the inner circumferential surface and welded joints of the inspection tube. Wear on the inner circumferential surface and welded joints of the inspection tube may result in fluid leaking from the piping.

[0007] Patent Document 2 discloses lining the inner surface of the inspection tube with ceramics or the like to prevent thinning due to vortexes in the drainage water resulting from condensed steam, but does not disclose any measures to prevent particles contained in the fluid. Furthermore, lining the inner surface of the inspection tube with ceramics or the like increases construction costs. Furthermore, the lining of the inspection tube may peel off depending on the conditions of use, and if the lining peels off, wear caused by particles contained in the fluid will progress.

[0008] The present disclosure has been made in consideration of the above circumstances, and aims to provide a plug structure, a piping structure, and a piping inspection method that can appropriately prevent malfunctions caused by particles entering, along with the fluid, into a cylindrical pipe base portion that is installed so as to surround a through-hole formed in a pipe through which a fluid flows. [Means for solving the problem]

[0009] In order to solve the above problems, the present disclosure employs the following means. A plug structure according to one aspect of the present disclosure is a plug structure for blocking a through hole formed in a pipe through which a fluid flows, and includes a cylindrical nozzle portion arranged to surround the through hole and having a base end joined to the outer peripheral surface of the pipe, and a plug inserted into the nozzle portion and joined to the tip end of the nozzle portion, and the plug has a sealing portion that seals a first internal space of the pipe from communicating with a second internal space of the nozzle portion.

[0010] A piping inspection method according to one embodiment of the present disclosure is a piping inspection method for inspecting a welded joint where a first pipe and a second pipe, through which a fluid flows, are welded, and includes the steps of inserting an inspection tool into a through hole formed in the first pipe, inspecting the welded joint with the inspection tool, removing the inspection tool from the through hole, and inserting a plug into a nozzle section that is arranged to surround the through hole and has a base end joined to the outer peripheral surface of the first pipe, and joining the plug to a tip end of the nozzle section, wherein the plug has a sealing section that seals so that a first internal space of the first pipe and a second internal space of the nozzle section do not communicate with each other. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a plug structure, a piping structure, and a piping inspection method that can appropriately prevent malfunctions caused by particles entering along with the fluid into a cylindrical pipe base portion that is installed to surround a through hole formed in a pipe through which a fluid flows. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram showing a steam, condensate, and feedwater system in a boiler power plant. [Figure 2] FIG. 1 is a perspective view showing an example of piping constituting a steam system of a boiler power plant. [Figure 3] FIG. 3 is a partial enlarged view of part A of the piping shown in FIG. 2. [Figure 4] FIG. 3 is a partial enlarged view of part B of the piping shown in FIG. [Figure 5] FIG. 1 is a cross-sectional view showing a plug structure for closing a through-hole in a pipe. [Figure 6] FIG. 6 is an exploded view of the plug structure shown in FIG. 5. [Figure 7] 1 is a flowchart illustrating a piping inspection method according to an embodiment of the present disclosure. [Figure 8] FIG. 10 is a cross-sectional view showing a state in which an inspection tool is inserted into a through-hole of a pipe. DETAILED DESCRIPTION OF THE INVENTION

[0013] A boiler power plant in which a plug according to an embodiment of the present disclosure is installed will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the steam, condensate, and feedwater systems in the boiler power plant. The boiler power plant includes boiler superheaters (heat exchangers) 102, 103, and 104, a steam turbine 110 that is rotationally driven by steam generated by the boiler, and a generator 115 that is connected to the steam turbine 110 and generates electricity by the rotation of the steam turbine 110.

[0014] The steam turbine 110 is composed of, for example, a high-pressure turbine 111, an intermediate-pressure turbine 112, and a low-pressure turbine 113, and steam from reheaters 105 and 106, which will be described later, flows into the intermediate-pressure turbine 112 and then into the low-pressure turbine 113.

[0015] A condenser 114 is connected to the low-pressure turbine 113, and the steam that rotates and drives the low-pressure turbine 113 is cooled by cooling water (e.g., seawater) in this condenser 114 to become condensed water. The condenser 114 is connected to the economizer 107 via a water supply system L1.

[0016] The water supply system L1 is provided with, for example, a condensate pump (CP) 121, a low-pressure water supply heater 122, a boiler water supply pump (BFP) 123, and a high-pressure water supply heater .

[0017] A portion of the steam that drives the steam turbine 110 is extracted and supplied to the low-pressure feedwater heater 122 and the high-pressure feedwater heater 124 as a heat source via an extraction system not shown, thereby heating the feedwater supplied to the coal economizer 107.

[0018] The following description will be given taking as an example a case where the boiler is a once-through boiler. The economizer 107 is connected to each evaporation tube of the furnace wall 101. The feedwater heated by the economizer 107 is heated by radiation from the flame inside the furnace as it passes through the evaporation tubes of the furnace wall 101, and is then led to the steam separator 126. The steam separated in the steam separator 126 is supplied to the superheaters 102, 103, and 104, and the drain water separated in the steam separator 126 is led to the condenser 114 via a drain water system L2.

[0019] When the combustion gas flows through the combustion gas passage (flue) 13, heat of this combustion gas is recovered by the superheaters 102, 103, 104, the reheaters 105, 106, and the economizer 107. On the other hand, the boiler feed water is preheated by the economizer 107, and then heated to become steam as it passes through each evaporator tube of the furnace wall 101. The steam is then led to the steam separator 126.

[0020] The steam separated in the steam separator 126 is introduced into the superheaters 102, 103, and 104, where it is superheated by the combustion gas. The superheated steam generated in the superheaters 102, 103, and 104 is supplied to the high-pressure turbine 111 via the steam line L3, and drives the high-pressure turbine 111 to rotate.

[0021] The steam discharged from the high-pressure turbine 111 is introduced into the reheaters 105 and 106 via the steam line L4 and is superheated again. The re-superheated steam is supplied to the low-pressure turbine 113 via the intermediate-pressure turbine 112 via the steam line L5, and drives the intermediate-pressure turbine 112 and the low-pressure turbine 113 to rotate.

[0022] The rotating shafts of the high-pressure turbine 111, the intermediate-pressure turbine 112, and the low-pressure turbine 113 are connected to a generator 115. The rotation of the rotating shafts of the high-pressure turbine 111, the intermediate-pressure turbine 112, and the low-pressure turbine 113 drives the generator 115 to generate electricity. The steam discharged from the low-pressure turbine 113 is cooled in the condenser 114 to become condensed water, which is sent again to the economizer 107 via the water supply system L1.

[0023] In the piping 50 constituting each steam system of the boiler power plant as described above, plug structures 200 for closing through holes 52 drilled for inserting a radiation source are installed at multiple locations. For example, in the figure, they are installed at location P on each steam system. Note that location P in the figure is an example and does not represent all installation locations.

[0024] Fig. 2 is a perspective view showing an example of piping 50 constituting a steam system of a boiler power plant. Fig. 3 is a partially enlarged view of part A of the piping shown in Fig. 2. Fig. 4 is a partially enlarged view of part B of the piping shown in Fig. 2. In Figs. 2 to 4, arrows indicate the flow direction of steam (fluid). In Figs. 2 to 4, the plug structure 200 that closes the through hole 52 is not shown.

[0025] As shown in FIG. 2, the piping 50 is a cylindrical member with a circular cross section through which steam flows in the order of piping 50a, 50b, 50c, 50d, 50e, 50f, 50g, 50h, 50i, 50j, 50k, 50l, and 50m. The piping 50a, 50b, 50e, 50g, 50i, 50k, and 50m are linear members formed to extend along a straight line. The piping 50c, 50d, 50f, 50h, 50j, and 50l are piping formed to bend at a predetermined curvature. The piping 50c, 50d, 50f, 50j, and 50l change the flow direction of steam by, for example, 90 degrees.

[0026] As shown in Fig. 2, welded portions 51 are formed at the portions where each of the pipes 50a to 50m is connected to an adjacent pipe. Welded portions 51 are portions where a pair of adjacent pipes are joined by welding. When a new boiler power plant is constructed, it is necessary to inspect the welding condition of welded portions 51 using an inspection tool (not shown) that uses a radiation source. For this reason, a through-hole 52 is formed in the pipe near welded portion 51 to allow the inspection tool to be inserted into the pipe.

[0027] 3, through-hole 52A for inspecting welded portion 51 connecting straight pipe 50e and curved pipe 50f is formed in curved pipe 50f. Near a point where the steam flow line changes from a straight line to a curved line, such as near through-hole 52A formed in curved pipe 50f, a swirling flow is likely to be formed inside the pipe.

[0028] 3, through-hole 52B for inspecting welded portion 51 connecting curved pipe 50f and straight pipe 50g is formed in straight pipe 50g. Near a point where the steam flow line changes from a curve to a straight line, such as near through-hole 52B formed in straight pipe 50g, a swirling flow is unlikely to form inside the pipe.

[0029] 4, through-hole 52C for inspecting welded portion 51 connecting straight pipe 50i and curved pipe 50j is formed in straight pipe 50i. Near a point where the steam flow line changes from a straight line to a curve, such as near through-hole 52C formed in straight pipe 50i, a swirling flow is likely to be formed inside the pipe.

[0030] 4, through-hole 52D for inspecting weld 51 connecting curved pipe 50j and straight pipe 50k is formed in straight pipe 50k. Near through-hole 52D formed in straight pipe 50k, a swirling flow is unlikely to be formed in the pipe near the point where the steam flow line changes from a curve to a straight line.

[0031] As described above, in the piping 50 of this embodiment, one pipe (first pipe) and the other pipe (second pipe) that are arranged adjacent to each other are welded to each other to form the welded portion 51. At least one of the one pipe and the other pipe is formed into a shape that is bent with a predetermined curvature. The through hole 52 is formed in either one of the one pipe or the other pipe that are arranged adjacent to each other, and is provided in the vicinity of the welded portion 51.

[0032] Next, a plug structure 200 for closing a through hole 52 formed in a pipe 50 through which steam flows will be described with reference to the drawings. Fig. 5 is a cross-sectional view showing a plug structure for closing a through hole in a pipe. Fig. 6 is an exploded view of the plug structure 200 shown in Fig. 5. As shown in Figs. 5 and 6, the plug structure 200 includes a nozzle portion 210 and a plug 220. The plug structure 200 is made of a metal material.

[0033] The nozzle stub portion 210 is a tubular (cylindrical) member joined by welding to the outer peripheral surface 50A of the pipe 50 so as to surround the through-hole 52. The nozzle stub portion 210 is formed to extend along an axis X that is perpendicular to a central axis (not shown) of the pipe 50. The base end portion 211 of the nozzle stub portion 210 is welded to the outer peripheral surface 50A of the pipe 50 at each portion of its entire circumference around the axis X to form a welded portion 211a. The tip end portion 212 of the nozzle stub portion 210 is welded to the joint surface 221a of the plug 220 at each portion of its entire circumference around the axis X to form a joint surface 221b.

[0034] 5 and 6, the outer diameter OD1 of the nozzle stub portion 210 is larger than the inner diameter ID1 of the through hole 52. The inner diameter of the nozzle stub portion 210 is equal to the inner diameter ID1 of the through hole 52. Note that the inner diameter of the nozzle stub portion 210 may be different from the inner diameter ID1 of the through hole 52.

[0035] The plug 220 is an axial member that is inserted into the nozzle stub portion 210 that is joined to the outer peripheral surface 50A of the pipe 50, and is joined to the tip portion 212 of the nozzle stub portion 210. The plug 220 has a main body portion 221, a sealing portion 222, and a connecting portion 223. The main body portion 221, the sealing portion 222, and the connecting portion 223 are integrally formed from a metal material.

[0036] The main body portion 221 is a portion that is joined by welding to the tip portion 212 of the nozzle stub portion 210. The main body portion 221 has a joining surface 221a that is disposed opposite the tip portion 212 of the nozzle stub portion 210 when the plug 220 is inserted into the nozzle stub portion 210.

[0037] The sealing portion 222 is a member that seals the internal space (first internal space) IS1 of the pipe 50 so as not to communicate with the internal space (second internal space) IS2 of the nozzle portion 210. The sealing portion 222 is formed in a cylindrical shape extending along the axis X.

[0038] The shape of the outer peripheral surface of the sealing portion 222 corresponds to the shape of the inner peripheral surface of the through hole 52. Note that a corresponding shape does not mean an exact same shape, but rather a shape with a gap that allows the sealing portion 222 to be smoothly inserted into the through hole 52. Furthermore, the length L1 of the sealing portion 222 along the axis X is set to a length sufficient to prevent communication between the internal spaces IS1 and IS2. The state in which the internal spaces IS1 and IS2 do not communicate means a state in which no, or almost no, steam flows from the internal space IS1 to the internal space IS2.

[0039] The tip surface 222a of the sealing portion 222 facing the internal space IS1 is disposed so as to coincide with the position of the inner circumferential surface 50B of the pipe 50. Alternatively, the tip surface 222a may be disposed near the position of the inner circumferential surface 50B of the pipe 50.

[0040] The position where the tip surface 222a is disposed may not coincide with the position where the inner circumferential surface 50B of the pipe 50 is disposed. The position where the tip surface 222a is disposed may be any position where the internal space IS1 and the internal space IS2 are not in communication with each other. For example, the position where the tip surface 222a is disposed may be another position inside the through hole 52.

[0041] The connecting portion 223 is a portion that connects the main body portion 221 and the sealing portion 222. The connecting portion 223 is a cylindrical member that extends along the axis X. The outer diameter OD2 of the connecting portion 223 is smaller than the inner diameter ID1, which is the inner diameter of the nozzle stub portion 210 and the through hole 52. The connecting portion 223 is disposed coaxially with the nozzle stub portion 210, and forms an annular gap CL with the inner peripheral surface of the nozzle stub portion 210.

[0042] Next, a piping inspection method of this embodiment will be described with reference to the drawings. Fig. 7 is a flowchart showing the piping inspection method of this embodiment. Fig. 8 is a cross-sectional view showing a state in which inspection tool 300 is inserted into through hole 52 of piping 50. The piping inspection method of this embodiment is used to inspect the welding state of welded portion 51 using inspection tool 300 that uses a radiation source when a boiler power plant is newly constructed.

[0043] In step S101, guide tube 301 of inspection tool 300 is inserted into through hole 52 formed in pipe (first pipe) 50g, and radiation source 302 is placed at the position of welded portion 51. Penetrometer 303 is placed on the outer periphery of welded portion 51 of pipe 50g, and protective film 304 that prevents radiation from passing through is placed on the outer periphery of penetrometer 303.

[0044] In step S102, welded portion 51 is inspected using inspection tool 300. Specifically, radiation is irradiated onto welded portion 51 from radiation source 302, and radiation that has passed through welded portion 51 is detected using transmittance meter 303. By detecting the radiation using transmittance meter 303, it is possible to inspect welded portion 51 for the presence or absence of welding defects, such as the presence of voids, and the extent of such defects.

[0045] In step S103, the guide tube 301 of the inspection tool 300 is removed from the through-hole 52 formed in the pipe 50g.

[0046] In step S104, the nozzle stub portion 210 is arranged to surround the through hole 52, and the base end portion 211 of the nozzle stub portion 210 is joined by welding to the outer peripheral surface of the piping 50g. Note that step S104 is performed after the welded portion 51 is inspected in step S102, but other aspects are also possible. For example, step S104 may be performed before the inspection tool 300 is inserted into the through hole 52 in step S101, and the nozzle stub portion 210 may be joined around the through hole 52 of the piping 50g before inspection by the inspection tool 300.

[0047] In step S105, the plug 220 is inserted into the nozzle stub portion 210, the joint surface 221a of the plug 220 is butted against the tip end 212 of the nozzle stub portion 210, and the joint surface 221a is joined to the tip end 212 by welding. When the plug 220 is joined to the nozzle stub portion 210, the state shown in Fig. 5 is achieved, and the internal space IS1 of the piping 50 and the internal space IS2 of the nozzle stub portion 210 are sealed by the sealing portion 222 so as not to communicate with each other.

[0048] The plug structure 200 of this embodiment described above provides the following functions and effects. According to the plug structure 200 of this embodiment, a base end 211 of a cylindrical nozzle portion 210 is joined to an outer peripheral surface 50A of the pipe 50 so as to surround a through hole 52 formed in the pipe 50, and a plug 220 inserted into the nozzle portion 210 is joined to a tip end 212 of the nozzle portion 210. A sealing portion 222 of the plug 220 seals an internal space IS1 of the pipe 50 from an internal space IS2 of the nozzle portion 210 so as not to communicate with each other.

[0049] According to the plug structure 200 of this embodiment, the internal space IS1 of the pipe 50 and the internal space IS2 of the nozzle stub portion 210 are not in communication with each other, so that particles (including, for example, oxides of the metal material forming the pipe 50 that have been detached from the base material of the pipe 50, i.e., rust on the inner surface of the pipe 50) contained in the fluid (steam, etc.) do not invade and remain in the internal space IS2 of the nozzle stub portion 210. Therefore, it is possible to appropriately prevent problems caused by particles invading together with the fluid into the cylindrical nozzle stub portion 210 that is installed so as to surround the through-hole 52 formed in the pipe 50 through which the fluid flows.

[0050] According to the plug structure 200 of this embodiment, the tip surface 222a of the sealing portion 222 facing the internal space IS1 of the pipe 50 is located near the position where the inner circumferential surface 50B of the pipe 50 is located. This makes it possible to reliably prevent particles contained in the fluid from entering the internal space IS2 of the nozzle portion 210. Furthermore, it is possible to reliably prevent the flow of the fluid flowing through the internal space IS1 of the pipe 50 from being disturbed.

[0051] According to the plug structure 200 of this embodiment, an annular gap CL is formed between the connecting portion 223 and the inner circumferential surface of the nozzle stub portion 210, and therefore, when joining the main body portion 221 of the plug 220 to the tip end portion 212 of the nozzle stub portion 210, the connecting portion 223 is kept spaced apart, thereby making it possible to achieve a full penetration weld at the welded portion. Furthermore, it is possible to prevent a notch, which would cause stress to concentrate, from being formed on the inner circumferential surface of the welded portion where the nozzle stub portion 210 and the plug 220 are joined.

[0052] According to the piping structure of this embodiment, at least one of the first pipe and the second pipe is formed in a shape that is bent at a predetermined curvature, and a through hole is formed in the first pipe. Since the through hole is disposed near a portion where the flow direction of the fluid is switched, if the first internal space of the pipe and the second internal space of the nozzle portion are connected to each other, there is a risk that the nozzle portion will be worn by particles.

[0053] According to the piping structure according to one aspect of the present disclosure, the sealing portion 222 prevents communication between the internal space IS1 of the piping 50 and the internal space IS2 of the nozzle stub portion 210, thereby appropriately preventing problems caused by particles entering the nozzle stub portion 210 along with the fluid. Furthermore, since the through hole 52 is provided near the welded portion 51, the welded portion 51 can be easily inspected.

[0054] The plug structure described in the above-described embodiment can be understood, for example, as follows. A plug structure (200) according to one embodiment of the present disclosure is a plug structure for blocking a through hole (52) formed in a pipe through which a fluid flows, and comprises a cylindrical pipe support portion (210) arranged to surround the through hole and having a base end portion (211) joined to the outer peripheral surface of the pipe, and a plug (220) inserted into the pipe support portion and joined to a tip end portion (212) of the pipe support portion, and the plug has a sealing portion (222) that seals a first internal space (IS1) of the pipe from communicating with a second internal space (IS2) of the pipe support.

[0055] According to one aspect of the present disclosure, a base end of a cylindrical nozzle section is joined to an outer peripheral surface of the pipe so as to surround a through-hole formed in the pipe, and a plug inserted into the nozzle section is joined to a tip end of the nozzle section. A sealing section of the plug seals the first internal space of the pipe from communicating with the second internal space of the nozzle section.

[0056] According to a plug structure according to one aspect of the present disclosure, the first internal space of the pipe and the second internal space of the nozzle section are not in communication with each other, so particles (e.g., oxides of the metal material forming the pipe) contained in the fluid (steam, etc.) do not enter and remain in the second internal space of the nozzle section. This makes it possible to appropriately prevent problems caused by particles entering the cylindrical nozzle section, which is installed so as to surround a through-hole formed in the pipe through which the fluid flows.

[0057] In the plug structure according to one aspect of the present disclosure, a tip surface of the sealing portion facing the first internal space may be configured to be located near a position where an inner circumferential surface of the pipe is located. The plug structure of this configuration can reliably prevent particles contained in the fluid from entering the second internal space of the nozzle section, and can also reliably suppress turbulence of the fluid flowing through the first internal space of the piping.

[0058] In a plug structure according to one aspect of the present disclosure, the plug has a main body portion joined to the tip portion of the nozzle stub portion, and a connecting portion connecting the main body portion and the sealing portion, and the connecting portion may be configured to be arranged coaxially with the nozzle stub portion and to form an annular gap between itself and the inner surface of the nozzle stub portion.

[0059] With this plug structure, an annular gap is formed between the connecting portion and the inner peripheral surface of the nozzle, so that when joining the main body of the plug to the tip of the nozzle, the connecting portion can be kept spaced apart to achieve a full penetration weld. Also, it is possible to prevent the formation of a notch, which would cause stress to concentrate, on the inner peripheral surface of the weld where the nozzle and plug are joined.

[0060] A piping structure according to one embodiment of the present disclosure includes any of the plug structures described above, a first pipe having a through hole through which a fluid flows and which is blocked by the plug structure, and a second pipe welded to the first pipe, wherein at least one of the first pipe and the second pipe is formed in a shape that is bent with a predetermined curvature, and the through hole is provided near a weld where the first pipe and the second pipe are welded.

[0061] According to a piping structure of one aspect of the present disclosure, the through hole is disposed near the portion where the fluid flow direction is switched, and therefore, if the first internal space of the piping and the second internal space of the nozzle portion are in communication with each other, the nozzle portion may be worn by particles. According to a piping structure of one aspect of the present disclosure, the sealing member prevents communication between the first internal space of the piping and the second internal space of the nozzle portion, thereby appropriately preventing defects caused by particles entering the nozzle portion along with the fluid. Furthermore, because the through hole is disposed near the weld where the first pipe and the second pipe are welded, inspection of the weld can be easily performed.

[0062] In the piping structure having the above configuration, one of the first piping and the second piping may be formed in a shape that bends at the specified curvature, and the other of the first piping and the second piping may be formed in a shape that extends along a straight line.

[0063] According to the piping structure of this embodiment, the through hole is located near the portion where the fluid flow direction is switched, so if the first internal space of the piping and the second internal space of the nozzle portion are connected, there is a risk that the nozzle portion will be worn by particles. According to the piping structure of this embodiment, the sealing member prevents the first internal space of the piping from being connected to the second internal space of the nozzle portion, so defects caused by particles entering the nozzle portion along with the fluid can be appropriately prevented. Furthermore, because the through hole is located near the weld where the first pipe and the second pipe are welded, inspection of the weld can be easily performed.

[0064] A piping inspection method according to one embodiment of the present disclosure is an inspection method for inspecting a welded portion where a first pipe and a second pipe, through which a fluid flows, are welded, and includes the steps of: inserting an inspection tool (300) into a through hole formed in the first pipe (S101); inspecting the welded portion using the inspection tool (S102); removing the inspection tool from the through hole (S103); and inserting a plug into a pipe stub that is arranged to surround the through hole and has a base end joined to the outer peripheral surface of the first pipe, and joining the plug to the tip end of the pipe stub (S105). The plug has a sealing portion that seals the first internal space of the first pipe from communicating with the second internal space of the pipe stub.

[0065] According to a piping inspection method according to one aspect of the present disclosure, an inspection tool is inserted into a through hole formed in a first pipe, and the welded portion is inspected using the inspection tool. After the welded portion has been inspected, the inspection tool is removed from the through hole. A plug is inserted into a nozzle section whose base end is joined to the outer peripheral surface of the pipe so as to surround the through hole. A sealing portion of the plug seals the first internal space of the pipe from communicating with a second internal space of the nozzle section.

[0066] According to a piping inspection method according to one aspect of the present disclosure, the first internal space of the piping and the second internal space of the nozzle section are not in communication with each other, so particles (e.g., oxides of the metal material forming the piping) contained in the fluid (steam, etc.) do not enter and remain in the second internal space of the nozzle section. Therefore, it is possible to appropriately prevent problems caused by particles entering together with the fluid into the cylindrical nozzle section that is installed so as to surround a through-hole formed in the piping through which the fluid flows. [Explanation of symbols]

[0067] 50 Piping 50A outer surface 50B Inner surface 50a, 50b, 50c, 50d, 50e, 50f, 50g, 50h, 50i, 50j, 50k, 50l, 50m piping 51 Welded section 52,52A,52B,52C,52D through hole 101 Furnace wall 102,103,104 Superheater 105,106 Reheater 107 Economizer 110 Steam Turbine 111 High-pressure turbine 112 Intermediate Pressure Turbine 113 Low-pressure turbine 114 Condenser 115 Generator 122 Low pressure water heater 124 High-pressure water heater 126 Brackish water separator 200 plug structure 210 Pipe support 211 Proximal end 211a Welded section 212 Tip 220 plug 221 Main body 221a,221b joint surface 222 Sealing part 222a Tip surface 223 Connecting part 300 Inspection Tools 301 Guide tube 302 Radiation source 303 Penetration meter 304 Protective Film CL Gap ID1 Inner diameter IS1 interior space IS2 interior space X axis

Claims

1. A plug structure for closing a through-hole formed in a pipe through which a fluid flows, a cylindrical pipe base portion that is arranged to surround the through hole and has a base end portion joined to an outer peripheral surface of the pipe; a plug that is inserted into the nozzle portion and joined to a tip end portion of the nozzle portion, The plug is a sealing portion that seals the first internal space of the piping and the second internal space of the nozzle portion so that they do not communicate with each other; a main body portion joined to the tip end portion of the nozzle portion; a connecting portion that connects the main body portion and the sealing portion, the sealing portion, the main body portion, and the connecting portion are integrally formed from a metal material, The connecting portion has a plug structure that is arranged coaxially with the nozzle portion and forms an annular gap between itself and the inner peripheral surface of the nozzle portion.

2. The plug structure according to claim 1 , wherein a tip end surface of the sealing portion facing the first internal space is located near a position where an inner circumferential surface of the pipe is located.

3. The pipe base portion is formed to extend along an axis, the connecting portion is formed in a cylindrical shape so as to extend along the axis and has an outer diameter smaller than an inner diameter of the through hole, 3. The plug structure according to claim 1, wherein the gap is formed along the axis from the base end of the nozzle portion to the tip end of the nozzle portion.

4. The plug structure according to any one of claims 1 to 3; a first pipe having a through hole through which a fluid flows and which is closed by the plug structure; a second pipe welded to the first pipe, At least one of the first pipe and the second pipe is formed into a shape that is bent at a predetermined curvature, The through hole is provided in the vicinity of a welded portion where the first pipe and the second pipe are welded.

5. one of the first pipe and the second pipe is formed in a shape that is bent at the predetermined curvature, The piping structure according to claim 4 , wherein the other of the first pipe and the second pipe is formed in a shape extending along a straight line.

6. A piping inspection method for inspecting a welded portion at which a first pipe and a second pipe, through which a fluid flows, are welded, comprising: inserting an inspection tool into a through hole formed in the first pipe; inspecting the welded portion with the inspection tool; removing the inspection tool from the through hole; and inserting a plug into a nozzle section that is arranged to surround the through hole and has a base end joined to the outer circumferential surface of the first pipe, and joining the plug to a tip end of the nozzle section, The plug is a sealing portion that seals the first internal space of the first piping so that the first internal space and the second internal space of the nozzle portion do not communicate with each other; a main body portion joined to the tip end portion of the nozzle portion; a connecting portion that connects the main body portion and the sealing portion, the sealing portion, the main body portion, and the connecting portion are integrally formed from a metal material, A piping inspection method in which the connecting portion is arranged coaxially with the nozzle portion and forms an annular gap between the connecting portion and an inner surface of the nozzle portion.

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