WO2022239682A1

WO2022239682A1 - Plug, pipe structure, and plug installation method

Info

Publication number: WO2022239682A1
Application number: PCT/JP2022/019375
Authority: WO
Inventors: 純之下田; 巧時吉; 紘希片渕; 直子藤原
Original assignee: 三菱重工業株式会社; 三菱パワー株式会社
Priority date: 2021-05-14
Filing date: 2022-04-28
Publication date: 2022-11-17
Also published as: JP2022175715A

Abstract

Provided are a plug, a pipe structure, and a plug installation method that make it possible to seal back-shielding gas using the plug itself. The plug (1) blocks, from the outer circumferential surface side of a pipe (50), a through-hole (51) formed in the pipe (50), and comprises: a columnar pipe base portion (20) that extends in the axial (X) direction; and a sealing portion (30) that is connected to the pipe base portion (20) and defines a retention space (S) in which gas is retained between the sealing portion (30) and the pipe base portion (20) inside the through-hole (51). In addition, the sealing portion (30) has: a shaft (31) that has a smaller diameter than the inner diameter of the through-hole (51) and has the base end thereof connected to the pipe base portion (20); and a circular plate portion (32) that corresponds to the internal shape of the through-hole (51) and is connected to the tip of the shaft (31).

Description

Plugs, piping structures and plug installation methods

The present disclosure relates to plugs, piping structures, and plug installation methods.

A large boiler used in a power plant or the like has a hollow furnace that is installed vertically, and multiple combustion burners are arranged along the circumference of the furnace wall. In the boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is arranged in the flue. Then, the combustion burner injects a mixture of fuel and air (oxidizing gas) into the furnace to form a flame and generate combustion gas that flows into the flue. A heat exchanger is installed in a region where the combustion gas flows, and superheated steam is generated by heating water or steam flowing inside the heat transfer tubes constituting the heat exchanger.

A steam system used in a power plant with a boiler is constructed by connecting multiple pipes by welding. In this case, a radiographic examination may be performed in order to confirm the soundness (presence or absence of defects) of the joint. For this reason, a through hole for inserting a radiation test device (radiation source) is drilled in the pipe in the vicinity of the joint. A radiographic test is normally performed only once after welding, and the drilled through hole must be closed after the radiographic test is completed.

As a method of closing a through hole, Patent Document 1, for example, discloses a closing plug. The closing plug of Patent Document 1 is fixed to the pipe by welding.

JP 2013-158823 A

When welding a plug to a pipe, a back shield is sometimes used to suppress oxidation of the inner surface of the weld and improve the quality of the weld. Here, as a method of back shielding, a method of using a balloon to prevent the diffusion of back shield gas (for example, an inert gas such as nitrogen or argon) inside the pipe is exemplified. However, since this method takes time to attach and remove the balloon, it is preferable to seal the gas for the back shield by the simplest possible method.

The present disclosure has been made in view of such circumstances, and aims to provide a plug, a piping structure, and a plug installation method that can seal the back shield gas with the plug itself.

In order to solve the above problems, the plug, piping structure, and plug installation method of the present disclosure employ the following means.
That is, a plug according to an aspect of the present disclosure is a plug that closes a through hole formed in a pipe from the outer peripheral surface side of the pipe, and includes a columnar nozzle portion extending in an axial direction; and a sealing portion that defines a retention space in which gas is retained between the through hole and the nozzle portion.

Further, a piping structure according to an aspect of the present disclosure includes a piping having a through hole and a steam plug, and the plug has the sealing portion inserted into the through hole.

Further, a plug installation method according to an aspect of the present disclosure is a plug that closes a through hole formed in a pipe from the outer peripheral surface side of the pipe, the plug including a columnar nozzle extending in the axial direction; and a sealing portion that is connected to the nozzle portion and defines a retention space for retaining gas between the through hole and the nozzle portion in the through hole, the plug installation method comprising: A step of supplying a gas used for shielding to the residence space is included.

According to the present disclosure, the plug itself can seal the gas for the back shield.

1 is a schematic diagram showing steam, condensate, and feedwater systems in a boiler power plant; FIG. [0014] Fig. 4 is a side view of a plug according to an embodiment of the present disclosure; 1 is a longitudinal cross-sectional view of a plug according to an embodiment of the present disclosure; FIG. 1 is a plan view of a plug according to one embodiment of the present disclosure; FIG. [0014] Fig. 4A is a bottom view of a plug according to an embodiment of the present disclosure; 1 is a longitudinal and circumferential cross-sectional view of a pipe with a plug installed according to an embodiment of the present disclosure; FIG. FIG. 7 is a cross-sectional view along the section line VII-VII shown in FIG. 6; 1 is a longitudinal and circumferential cross-sectional view of a pipe with a welded plug according to an embodiment of the present disclosure; FIG. It is a reference drawing showing the concept of a stress concentration part. FIG. 4 is a partial enlarged view of the vicinity of a welded portion; It is the figure which showed each relationship between the damage degree Dc in a stress concentration part and a weld toe, and the welding leg length Lw which overhangs. It is the figure which showed each relationship between the damage degree Dc in a stress concentration part and a weld toe, and the weld toe radius Rw.

[About the boiler power plant]
First, a boiler power plant in which a plug according to an embodiment of the present disclosure is installed will be described using FIG.

FIG. 1 is a schematic diagram representing steam, condensate, and feed water systems in a boiler power plant.
The boiler power plant includes

boiler heat exchangers

102, 103, and 104, a steam turbine 110 that is driven to rotate by steam generated by the boiler, and is connected to the steam turbine 110 to generate power according to the rotation of the steam turbine 110. and a generator 115 .

The steam turbine 110 includes, for example, a high-pressure turbine 111, an intermediate-pressure turbine 112, and a low-pressure turbine 113. 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. do.

A condenser 114 is connected to the low-pressure turbine 113, and the steam that rotationally drives the low-pressure turbine 113 is cooled by cooling water (eg, seawater) in the condenser 114 to become condensed water. Condenser 114 is connected to economizer 107 via water supply system L1.

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 124.

A part of the steam that drives the steam turbine 110 is extracted by the low-pressure feed water heater 122 and the high-pressure feed water heater 124, and supplied as a heat source to the high-pressure feed water heater 124 and the low-pressure feed water heater 122 via an extraction system (not shown). The feedwater supplied to the coalger 107 is heated.

A case where the boiler is a once-through boiler will be described below as an example.
An economizer 107 is connected to each evaporator tube of the furnace wall 101 . The feed water heated by the economizer 107 is heated by radiation from the flames in the furnace when passing through the evaporator tube of the furnace wall 101 and is led to the steam separator 126 . The steam separated by the steam separator 126 is supplied to the

superheaters

102, 103, and 104, and the drain water separated by the steam separator 126 is sent to the condenser 114 via the drain water system L2. be guided.

When the combustion gas flows through the combustion gas passage (flue) 13, the heat of the combustion gas is recovered by the

superheaters

102, 103, 104, the

reheaters

105, 106, and the economizer 107. On the other hand, the feed water supplied from the boiler feed water pump (BFP) 123 is preheated by the economizer 107 and then heated to steam when passing through each evaporator tube of the furnace wall 101 and introduced to the steam separator 126. be killed.

The steam separated by the steam separator 126 is introduced into the

superheaters

102, 103, 104 and superheated by the combustion gas.

The superheated steam generated by the

superheaters

102, 103, 104 is supplied to the high pressure turbine 111 via the steam system L3, and drives the high pressure turbine 111 to rotate.

The steam discharged from the high-pressure turbine 111 is introduced into the

reheaters

105 and 106 via the steam system L4 and reheated. The re-superheated steam is supplied to the low-pressure turbine 113 through the intermediate-pressure turbine 112 via the steam system L5, and drives the intermediate-pressure turbine 112 and the low-pressure turbine 113 to rotate.

The rotating shaft of each

steam turbine

111 , 112 , 113 is connected to a generator 115 . Rotation of the rotating shafts of the

steam turbines

111, 112, and 113 drives the generator 115 to generate power. The steam discharged from the low-pressure turbine 113 is cooled by the condenser 114 to become condensate, and is sent to the economizer 107 again through the water supply system L1.

Plugs 1 are installed at a plurality of locations in the pipes 50 constituting each steam system of the boiler power plant as described above to block through holes 51 drilled for inserting radiation sources. For example, it is installed at a point P on each steam system in the figure. Note that the location P in the figure is an example, and does not indicate all installation locations.

[About the plug]
Next, a plug 1 according to an embodiment of the present disclosure will be described using FIGS. 2 to 5. FIG.
FIG. 2 is a side view of the plug 1. FIG. FIG. 3 is a longitudinal sectional view of the plug 1. FIG. FIG. 4 is a plan view of the plug 1. FIG. FIG. 5 is a bottom view of the plug 1. FIG.

The plug 1 is a member made of metal.
Examples of metals forming the plug 1 include chromium-containing alloy steels such as 12Cr steel, 9Cr steel, and 2Cr steel.
Here, considering ease of welding, it is preferable that the material of the metal forming the plug 1 is the same as or similar to the material of the metal forming the pipe 50, which will be described later.

As shown in FIGS. 2 to 5, the plug 1 includes a nozzle portion 20, a sealing portion 30 and a groove portion 40.

The nozzle portion 20 is a columnar portion extending along the direction of the axis X. As shown in FIG.
The nozzle portion 20 has a bottom surface 22 . The bottom surface 22 faces the pipe 50 (more specifically, the through hole 51) when the plug 1 is installed in the pipe 50 (see FIG. 6). A sealing portion 30 and a groove portion 40 are connected to the bottom surface 22 .
The diameter of the nozzle portion 20 is larger than the inner diameter of a through hole 51 formed in the pipe 50 (see FIG. 6), for example, about φ100 mm to φ130 mm. Note that the diameter of the nozzle portion 20 is also the maximum outer diameter of the plug 1 .

The sealing portion 30 is a portion formed to extend from the bottom surface 22 of the nozzle portion 20 .
The sealing portion 30 is inserted into a through-hole 51 formed in the pipe 50 described later (see FIG. 6) when the plug 1 is installed in the pipe 50 described later.
The sealing portion 30 has a shaft portion 31 and a disc portion 32 .

The shaft portion 31 is a columnar portion extending along the direction of the axis X, and has a base end connected to the bottom surface 22 of the nozzle portion 20 and integrated with the nozzle portion 20 . In consideration of ease of manufacture, it is preferable that the shaft portion 31 has a columnar shape.
The diameter of the shaft portion 31 is smaller than the inner diameter of a through hole 51 formed in a pipe 50 (see FIG. 6). For example, if the inner diameter of the through hole 51 is approximately φ50 mm, the diameter of the shaft portion 31 is approximately φ20 mm.

The disc portion 32 is a plate-like portion, connected to the tip of the shaft portion 31 and integrated with the shaft portion 31 .
The disk portion 32 defines a space (retention space S) with the nozzle portion 20 when the sealing portion 30 is inserted into the through hole 51 (see FIG. 6).
The disk portion 32 has a shape corresponding to the cross-sectional shape of the through hole 51 perpendicular to the axis X (see FIG. 6). Note that the corresponding shape does not mean a completely identical shape, but means a shape with a gap that allows smooth insertion of the disk portion 32 into the through hole 51 . For example, if the inner diameter of the through-hole 51 is approximately φ50 mm, the diameter of the disc portion 32 is approximately φ49.8 mm. That is, a gap of 0.1 mm is provided on both sides in the radial direction between the disk portion 32 and the through hole 51 .
Although this gap is not limited to 0.1 mm, if it is excessively large, gas for a back shield, which will be described later, is likely to leak, and steam flowing inside the pipe 50 and foreign matter contained in the steam are likely to enter. . Therefore, it is necessary to set the dimensions of the disk portion 32 so that the gap is not excessively large. Specifically, in order to suppress the entry of steam and foreign substances contained in the steam, it is preferable that the gaps on both sides in the radial direction be 0.4 mm or less, and the closer to 0.1 mm, the more preferable.

The groove portion 40 is a portion formed so as to protrude from the bottom surface 22 of the nozzle portion 20 on the tip 11 side of the plug 1 .
The groove portion 40 has a groove surface 41 and a straight surface 42 .

The groove surface 41 is an inclined surface whose diameter is reduced from the outer peripheral surface of the nozzle portion 20 toward the axis X in the direction from the proximal end 12 to the distal end 11 of the plug 1 .
The groove surface 41 is formed in an annular shape in the circumferential direction about the axis X. As shown in FIG.

The straight surface 42 is a surface connected to the tip (the end near the axis X) of the groove surface 41 near the bottom surface 22 of the plug 1, and extends along the axis from the tip 11 of the plug 1 toward the base end 12. It extends along the X direction.
The straight surface 42 is parallel or substantially parallel to the axis X. As shown in FIG.
The straight surface 42 is formed in an annular shape in the circumferential direction about the axis X, like the groove surface 41 .
The straight surface 42 preferably has a length dimension in the direction of the axis X of 10 mm or more and 14 mm or less. If the length dimension is 9 mm or less, poor welding may occur. Moreover, if the length dimension is 15 mm or more, it may be difficult to process the straight surface 42 .

The base end of the straight surface 42 , the tip of which is connected to the groove surface 41 , is connected to the bottom surface 22 via a quarter arc-shaped round surface 44 .
The round surface 44 has, for example, an outer diameter of the plug 1 (that is, a diameter of the nozzle portion 20) of 110 mm and a thickness dimension (thickness in the radial direction from the straight surface 42 to the outermost peripheral surface of the nozzle portion 20) of 30 mm. If so, it is preferable that the radius is 4 mm or less. The numerical value of 4 mm is the minimum value within the range of dimensions that can ensure the length of the straight surface 42 for eliminating defects during welding and also satisfies the service life (for example, 240,000 hours). The radius of the round surface 44 is determined within the above dimensions so that the straight surface 42 is located radially outside the inner diameter of a through hole 51 formed in the pipe 50, which will be described later.

With the groove surface 41 and the straight surface 42 formed as described above, the groove portion 40 projecting sharply in a V shape is formed in the lower portion of the plug 1 .
The groove portion 40 is formed in an annular shape in the circumferential direction about the axis X, like the groove surface 41 and the straight surface 42 .
The groove portion 40 is formed so as to protrude toward the pipe 50 when the plug 1 is installed in the pipe 50 described later. As a result, it is possible to improve the melt penetration of the molten metal during welding with the pipe 50, and to suppress the occurrence of unwelded portions in the portions to be welded.
A root surface 43 may be formed between the groove surface 41 and the straight surface 42 at the tip of the groove portion 40 .

[About piping structures]
Next, the structure of the pipe 50 in which the plug 1 is installed will be described with reference to FIGS. 6 to 9. FIG.
FIG. 6 is a cross-sectional view of the pipe 50 in which the plug 1 is installed in the longitudinal direction (the right side of the axis X in the drawing) and the circumferential direction (the left side of the axis X in the drawing). FIG. 7 is a cross-sectional view along section line VII-VII shown in FIG. FIG. 8 is a longitudinal and circumferential sectional view of a pipe 50 to which the plug 1 is fixed by welding. FIG. 9 is a reference diagram showing the concept of the stress concentrated portion.
Although the piping 50 shown in FIGS. 6 and 8 is a cross-sectional view, it is drawn without hatching.

The pipe 50 is a pipe that constitutes the steam system (L3, L5 in FIG. 1), and high-temperature and high-pressure steam flows inside.
The thickness of the pipe 50 is, for example, approximately 25 mm to 130 mm.
A through-hole 51 for inserting a radiation source for radiographic examination is formed in the pipe 50 . The through-hole 51 is a straight tubular hole that penetrates the pipe wall of the pipe 50 in its thickness direction, and communicates the outside and the inside of the pipe 50 .

A radiographic examination is performed in the vicinity of joints between pipes 50 . For this reason, the through holes 51 are preferably formed in the vicinity of joints between the pipes 50 .
Note that the through hole 51 may be formed with a gap between the joints between the pipes 50 as long as the radiation source inserted into the through hole 51 can be appropriately inspected.

As shown in FIG. 6 , the plug 1 is installed in the pipe 50 such that at least a portion of the sealing portion 30 is inserted into the through hole 51 and the groove portion 40 abuts against the outer peripheral surface of the pipe 50 . be. At this time, the axis X of the plug 1 substantially coincides with the axis of the through hole 51 .

At this time, the through hole 51 into which the sealing portion 30 is inserted includes the bottom surface 22 of the nozzle portion 20, the shaft portion 31, the disc portion 32, the straight surface 42 and the round surface 44 of the groove portion 40, and the through hole 51. A retention space S is defined by the inner peripheral surface of the . As shown in FIG. 7, the retention space S has an annular shape around the axis X. As shown in FIG.

The retention space S is a space for retaining back shield gas when connecting the plug 1 to the pipe 50 by welding.
Back shielding is to replace the oxygen-containing gas such as air in the space in contact with the back surface of the first layer bead with an inert gas during the first layer welding. As a result, it is possible to suppress the oxidation of the back surface of the first-layer bead and the occurrence of defects such as pores and cracks due to the oxidation.
If the space in contact with the back surface of the first-layer bead is an open space, the inert gas diffuses into the space, and the oxidation suppressing effect is lost. Therefore, as described above, it is generally necessary to use a sealing member such as a balloon to define a space in which the inert gas is retained.
Examples of the back shield gas include inert gases such as nitrogen and argon.

Here, the disk portion 32 inserted into the through hole 51 is set so that the lower surface 32 a is substantially flush with the inner peripheral surface of the pipe 50 . As a result, the step between the lower surface 32a and the inner peripheral surface of the pipe 50 is reduced, making it difficult for foreign matter contained in the steam to adhere. In addition, it is possible to prevent the disk portion 32 from obstructing the flow of steam flowing inside the pipe 50 . Furthermore, by not obstructing the flow of steam, turbulence of the steam flow in the vicinity of the disk portion 32 is suppressed. And the amount of foreign matter contained in steam can be reduced. In addition, since the disc portion 32 is brought closer to the inner peripheral surface side of the pipe 50, the volume of the retention space S can be secured as large as possible.
Note that the lower surface 32a is the surface of the disk portion 32 facing the inside of the pipe 50 (steam flow path).

A groove for welding is formed between the groove portion 40 and the outer peripheral surface of the pipe 50 by abutting the groove portion 40 against the outer peripheral surface of the pipe 50 . Here, between the groove portion 40 and the outer peripheral surface of the pipe 50, a predetermined gap (root gap) is secured and held. The root spacing is, for example, 2 mm to 7 mm.

At this time, since the straight surface 42 is located radially outside the inner diameter of the through hole 51 with respect to the direction of the axis X, the outer peripheral surface of the pipe 50 is radially inside the tip of the groove portion 40. (part A surrounded by a dotted square in FIG. 6).
The outer peripheral surface of the pipe 50 from the tip of the groove portion 40 to the through hole 51 functions as a receiving portion for molten metal flowing out from the gap between the tip of the groove portion 40 and the outer peripheral surface of the pipe 50 when welding is started. In addition, by welding the groove portion 40 against the outer peripheral surface of the pipe 50, the melt penetration at the start of welding can be improved. As a result, it is possible to suppress the occurrence of an unwelded portion in the portion to be welded, thereby suppressing the occurrence of a discontinuous weld penetration shape.

At the start of welding, the groove surface 41 of the groove portion 40 or the outer peripheral surface of the nozzle portion 20 and the outer peripheral surface of the pipe 50 are placed so as to cover the initial layer welding region between the groove portion 40 and the outer peripheral surface of the pipe 50. A heat-resistant seal is affixed between and and the gas for the back shield is supplied to the retention space S through the cut of the seal. The air originally present in the retention space S is discharged from the gap between the disk portion 32 and the inner peripheral surface of the through hole 51 as the gas for the back shield is supplied. When the air is discharged from the retention space S and the retention space S is filled with gas for the back shield, welding is started.

Specifically, first, first layer welding is performed over the entire circumference of the groove portion 40 while peeling off the seal, and then, as shown in FIG. The plug 1 and the pipe 50 are connected by forming a welded portion 60 by depositing molten metal. Thereby, the through hole 51 can be closed with the plug 1 .

In forming the welded portion 60, the position of the weld toe 61 is positioned farther from the axis X than the outer peripheral surface of the nozzle portion 20, that is, positioned radially outside the outer peripheral surface of the nozzle portion 20. It is preferable to keep With this configuration, the weld toe 61 can be kept away from the stress concentration portion 53 generated inside the pipe 50 (inside the pipe wall).
The weld toe 61 is the end of the portion of the welded portion 60 in contact with the pipe 50, and is the end located radially outward.

The stress concentration portion 53 will be described below with reference to FIG.
It is assumed that a tensile stress σf is applied to the long side of a flat plate 70 formed with a through hole 71 and extending in the longitudinal direction. At this time, as is known, the stress σy acting on the center line of the flat plate 70 produces a maximum stress σmax near the through-hole 71 in the longitudinal direction (so-called stress concentration). Note that the maximum stress σmax is about three times the stress generated at the through-hole point 72 .

A hoop stress acts on the pipe 50 in the circumferential direction of the through hole 51 due to the pressure of the steam flowing inside. Here, when the phenomenon of stress concentration described above is applied to the pipe 50, as shown in FIG. A stress concentrated portion 53 is generated in the vicinity.

In this embodiment, part of the stress of the stress concentration portion 53 generated by the hoop stress can be borne by the nozzle portion 20, and the weld toe 61 is the stress concentration portion generated inside the pipe 50. Since it is located radially outside of 53 with respect to the direction of the axis X, stress concentration due to hoop stress can be alleviated, and the service life of weld toe 61 and pipe 50 can be extended.

[Details of weld toe]
Specifically, the position of the weld toe 61 of the weld 60 is preferably determined as follows.

As shown in FIG. 10, the weld leg length of the welded portion 60 projecting radially from the outer peripheral surface of the nozzle portion 20 of the plug 1 is Lw. That is, the distance along the radial direction (the radial direction of the plug 1) from the outer peripheral surface of the plug 1 to the weld toe 61 is defined as Lw.

At this time, the relationship between the weld leg length Lw and the damage degree Dc at the stress concentrated portion 53 and the relationship between the weld leg length Lw and the damage degree Dc at the weld toe 61 are as shown in the graph of FIG. That is, the degree of damage Dc at the stress concentration portion 53 decreases as the weld leg length Lw increases. Further, as the weld leg length Lw increases, the degree of damage Dc at the weld toe 61, particularly at the weld toe 61 (see FIG. 8) in the circumferential direction of the pipe 50 increases. For this reason, it is preferable to determine the range of the weld leg length Lw in which the degree of damage to both the stress concentration portion 53 and the weld toe 61 does not easily exceed a predetermined amount that affects material performance.
Here, the degree of damage Dc indicates the influence of the damage on the metal structure, and indicates the degree of influence on the deterioration factor of material performance such as mechanical strength.

Also, as shown in FIG. 10, the welded portion 60 near the weld toe 61 is preferably formed into a rounded shape that is smoothly curved. Thereby, stress concentration at the weld toe 61 can be suppressed.

Here, the radius of the weld toe 61 formed in a round shape is defined as Rw. At this time, the relationship between the radius Rw and the degree of damage Dc at the stress concentration portion 53 and the relationship between the radius Rw and the degree of damage Dc at the weld toe 61 are as shown in the graph of FIG. That is, the degree of damage Dc at the stress concentrated portion 53 and the degree of damage Dc at the weld toe 61 decrease as the radius Rw increases. Therefore, it is preferable to set the radius Rw large.

However, due to the property that the through hole 51 is formed near the joint between the pipes 50, when the position of the through hole 51 is fixed, the larger the radius Rw is set, the more the weld toe 61 becomes the joint between the pipes 50. will approach. In this case, the thermal influence of forming the welded portion 60 may reach the joints between the pipes 50, which is not preferable.
On the other hand, when the position of the weld toe 61 is fixed, the larger the radius Rw is set, the farther the position of the through-hole 51 is from the weld joint between the pipes 50 . In this case, the through-hole 51 is separated from the welded joint between the pipes 50, and there is a possibility that the operation of inserting the radiation source through the through-hole 51 for the radiographic examination may be hindered, which is not preferable.
From the above, the radius Rw of the welded portion 60 is a range that does not exert a thermal effect on the joints of the pipes 50 during welding, and the work of inserting the radiation source for the radiographic test from the through hole 51 is hindered. It is preferable to set the value as large as possible within a range in which no For example, it is desirable to set the radius Rw of the welded portion 60 within a range of 10 mm to 30 mm.

According to this embodiment, the following effects are obtained.
A columnar nozzle portion 20 extending in the direction of the axis X, and a sealing portion 30 connected to the nozzle portion 20 and defining a retention space S in which gas is retained between the nozzle portion 20 and the through hole 51 . and , the back shield gas can be retained in the retention space S when the plug 1 is welded to the pipe 50 . As a result, it is possible to seal the gas for the back shield by a simple operation of using the plug 1, and to reduce ancillary work associated with welding the plug 1 and the pipe 50 together.

The sealing portion 30 includes a shaft portion 31 connected to the nozzle portion 20 at its proximal end and having a smaller diameter than the inner diameter of the through hole 51, and a through hole connected to the distal end of the shaft portion 31 and perpendicular to the axis X. 51 and the disk portion 32 having a shape corresponding to the cross-sectional shape of the disk 51 . Intrusion of foreign matter into the through hole 51 can be suppressed by the portion 32 .
In addition, since the disk portion 32 functions as a guide for the through hole 51, positioning when inserting the sealing portion 30 into the through hole 51 can be easily performed.

In addition, since the lower surface 32a of the disc portion 32 is configured to be substantially flush with the inner peripheral surface of the pipe 50, there is no step between the surface of the disc portion 32 and the inner peripheral surface of the pipe 50. It becomes difficult for foreign matter to adhere. In addition, it is possible to prevent the disk portion 32 from obstructing the flow of steam flowing inside the pipe 50 . Furthermore, since the flow of steam is not hindered, the turbulence of the steam flow in the vicinity of the disk portion 32 is suppressed. Quantity and the amount of contaminants contained in the steam can be reduced.
Moreover, since the disc portion 32 is brought as close to the inner peripheral surface side of the pipe 50 as possible, the volume of the retention space S in which a sufficient amount of gas can be retained can be secured.

In addition, since the groove portion 40 is formed so as to protrude from the nozzle portion 20 and abut against the outer peripheral surface of the pipe 50 , the plug 1 can be connected to the pipe 50 by welding using the groove portion 40 .

In addition, since the groove portion 40 has a groove surface 41 and a straight surface 42, the formed groove portion 40 is butted against the outer peripheral surface of the pipe 50 and welded, so that when welding is started, It is possible to improve melt penetration.
Further, when the groove portion 40 is butted against the pipe 50, the outer peripheral surface of the pipe 50 exists by the distance from the tip of the groove portion 40 formed by the straight surface 42 and the groove surface 41 to the through hole 51. It will be. As a result, the outer peripheral surface of the pipe 50 from the tip of the protruding groove portion 40 to the through hole 51 is a receiving portion for molten metal flowing out from between the tip of the groove portion 40 and the outer peripheral surface of the pipe 50 at the start of welding. , the melting of molten metal can be further improved, and the occurrence of unwelded portions can be suppressed. By improving the penetration of the molten metal in this way, the occurrence of a discontinuous weld penetration shape in which there is an unwelded part in the part to be welded is suppressed. As a result, when a load is applied, it is possible to reduce the possibility that stress will concentrate on the welded portion 60 and cause cracks.

In addition, since the straight surface 42 is located radially outside the through hole 51 when the groove portion 40 abuts against the pipe 50 , the groove formed by the straight surface 42 and the groove surface 41 The outer peripheral surface of the pipe 50 exists by the distance from the tip of the portion 40 to the through hole 51 . The outer peripheral surface of the pipe 50 from the tip of the groove portion 40 to the through hole 51 functions as a receiving portion for the molten metal flowing out from between the tip of the groove portion 40 and the outer peripheral surface of the pipe 50 at the start of welding. The penetration of molten metal can be further improved, and the occurrence of a discontinuous weld penetration shape such as an unwelded portion in the portion to be welded can be suppressed.

In addition, since the plug 1 has the sealing portion 30 inserted into the through hole 51, the back shield gas can be retained in the retention space S when the plug 1 is welded to the pipe 50. As a result, it is possible to seal the gas for a good back shield by a simple operation of using the plug 1, and to reduce the burden of incidental work involved in welding the plug 1 and the pipe 50 together.

In addition, the plug 1 is connected to the pipe 50 by forming a welded portion 60 between the groove surface 41 of the groove portion 40 and the outer peripheral surface of the pipe 50, with the groove portion 40 abutting against the outer peripheral surface of the pipe 50. Therefore, the entire welded portion 60 can be formed on the outer peripheral surface of the pipe 50 . As a result, the presence or absence of defects in the welded portion 60 can be inspected by a non-destructive method, so that the inspection of the welded portion 60 can be easily performed. In addition, since all the welded portions 60 to be inspected are formed on the outer peripheral surface of the pipe 50, the accuracy of inspection is improved.

In addition, since the weld toe 61 is further away from the axis X than the outer peripheral surface of the nozzle portion 20, the welded portion 60 is more stress concentrated than the stress concentrated portion generated inside the pipe material of the pipe 50 and near the through hole 51. A weld toe 61 can be positioned radially outward. As a result, the nozzle portion 20 can bear part of the stress generated in the stress concentration portion. Therefore, the proof stress of the pipe 50 can be improved. In addition, stress concentration generated in the welded portion 60 can be alleviated, and the strength of the welded portion 60 can be secured and the service life of the welded portion 60 can be extended.
The “stress concentration portion” referred to here means a peak portion of stress generated in the vicinity of the through-hole 51 by the hoop stress acting on the pipe 50 and its vicinity.

In addition, since the position of the weld toe 61 is determined by comparing the degree of damage of the stress concentration portion and the degree of damage of the weld toe 61, both the stress concentration portion and the weld toe 61 are damaged. The weld toe 61 can be set at a difficult position.

In addition, since the welded portion 60 is formed in a round shape that curves concavely with respect to the outer peripheral surface of the pipe 50, concentration of stress on the weld toe 61 can be suppressed. As a result, even if the nozzle portion 20 bears part of the stress generated in the stress concentration portion of the pipe 50 , it is possible to suppress damage to the welded portion 60 due to the stress.

Each embodiment described above can be understood as follows, for example.
That is, a plug (1) according to one aspect of the present disclosure is a plug (1) that closes a through hole (51) formed in a pipe (50) from the outer peripheral surface side of the pipe (50), A columnar nozzle portion (20) extending in the (X) direction is connected to the nozzle portion (20) and retains gas between the nozzle portion (20) and the through hole (51). a sealing portion (30) defining a retention space (S) for allowing

According to the plug (1) according to this aspect, the columnar nozzle portion (20) extending in the direction of the axis (X) is connected to the nozzle portion (20), and the nozzle portion is inserted into the through hole (51). (20) and a sealing portion (30) defining a retention space (S) for retaining gas. The back shield gas can be retained in the retention space (S). As a result, the gas for the back shield can be effectively sealed by a simple operation of using the plug (1), and the burden of incidental work associated with welding the plug 1 and the pipe 50 can be reduced.

Further, in the plug (1) according to one aspect of the present disclosure, the sealing portion (30) has a smaller diameter than the inner diameter of the through hole (51), and a proximal end thereof is connected to the nozzle portion (20). and a disk portion (32) connected to the tip of the shaft portion (31) corresponding to the inner shape of the through hole (51).

According to the plug (1) according to this aspect, the sealing part (30) has a diameter smaller than the inner diameter of the through hole (51), and the base end of the shaft part (31) is connected to the nozzle part (20). and a disc portion (32) connected to the tip of the shaft portion (31) corresponding to the inner shape of the through hole (51). 31), the disk portion (32) and the through hole (51) define the retention space (S), and the disk portion (32) can prevent foreign matter from entering the through hole (51).
In addition, since the disk portion (32) functions as a guide for the through hole (51), it is possible to easily position the sealing portion (30) when inserting it into the through hole (51).

Further, in the plug (1) according to one aspect of the present disclosure, the surface (32a) of the disk portion (32) facing the inner side of the pipe (50) is substantially flush with the inner peripheral surface of the pipe (50). is configured to be

According to the plug (1) according to this aspect, the surface (32a) of the disk portion (32) facing the inside of the pipe (50) is configured to be substantially flush with the inner peripheral surface of the pipe (50). As a result, there is no level difference between the surface of the disk portion (32) and the inner peripheral surface of the pipe (50), making it difficult for foreign matter to adhere. In addition, it is possible to prevent the disk portion (32) from obstructing the flow of steam flowing inside the pipe (50). Furthermore, by not obstructing the steam flow, turbulence of the steam flow in the vicinity of the disk portion (32) is suppressed, so that the retention space ( S) It is possible to reduce the amount of steam entering the interior and the amount of foreign matter contained in the steam.
In addition, since the disk portion (32) is brought as close to the inner peripheral surface of the pipe (50) as possible, the volume of the retention space (S) in which a sufficient amount of gas can be retained can be secured.

Further, the plug (1) according to one aspect of the present disclosure includes a groove (40) that is formed to protrude from the nozzle (20) and that abuts against the outer peripheral surface of the pipe (50). ing.

According to the plug (1) of this aspect, the groove (40) is formed so as to protrude from the nozzle (20) and is abutted against the outer peripheral surface of the pipe (50). The plug (1) can be connected to the pipe (50) by welding using the part (40).

Further, in the plug (1) according to one aspect of the present disclosure, the groove portion (40) has a radial outer circumference perpendicular to the axis (X) direction in the direction from the proximal end (12) to the distal end (11). A groove surface (41) contracting from the side, and from the end of the groove surface (41), from the tip (11) side toward the base end (12) along the axis (X) direction. and a straight surface (42) extending along the rim.

According to the plug (1) according to this aspect, the groove portion (40) is contracted from the outer peripheral side in the radial direction orthogonal to the axis (X) direction in the direction from the proximal end (12) to the distal end (11). and a straight surface (42) extending along the axis (X) from the end of the groove surface (41) toward the base end (12) from the tip (11) side. , so that the formed groove portion (40) is butt-welded against the outer peripheral surface of the pipe (50), thereby making it possible to improve the penetration of molten metal at the start of welding.
Also, when the groove (40) is butted against the pipe (50), the distance from the groove (40) formed by the straight surface (42) and the groove surface (41) to the through hole (51) The outer peripheral surface of the pipe (50) is present for the amount of . As a result, the outer peripheral surface of the pipe (50) from the tip of the protruding groove (40) to the through hole (51) is the same as the tip of the groove (40) and the outer peripheral surface of the pipe (50) at the start of welding. Since it functions as a receiving portion for the molten metal flowing out from between, it is possible to further improve the melting of the molten metal and suppress the occurrence of unwelded portions. By improving the penetration of the molten metal in this way, the occurrence of a discontinuous weld penetration shape in which there is an unwelded part in the part to be welded is suppressed. As a result, when a load is applied, it is possible to reduce the possibility that stress will concentrate on the welded portion (60) and cause cracks.

Further, in the plug (1) according to one aspect of the present disclosure, the straight surface (42) is configured such that, when the groove portion (40) abuts against the outer peripheral surface of the pipe (50), the straight surface (42) extends in the radial direction. It is positioned outside the through hole (51).

According to the plug (1) of this aspect, the straight surface (42) is located radially outside the through hole (51) when the groove (40) is butted against the pipe (50). Therefore, the outer peripheral surface of the pipe (50) exists by the distance from the tip of the groove (40) formed by the straight surface (42) and the groove surface (41) to the through hole (51). It will be. The outer peripheral surface of the pipe (50) from the tip of the groove (40) to the through hole (51) flows out from between the tip of the groove (40) and the outer peripheral surface of the pipe (50) at the start of welding. Since it functions as a receiving part for molten metal, it is possible to further improve the penetration of molten metal, and it is possible to prevent the occurrence of a discontinuous weld penetration shape in which there is an unwelded part in the part to be welded. can be suppressed.

Further, a piping structure according to an aspect of the present disclosure includes a piping (50) having a through hole (51) formed therein, and the plug (1), wherein the plug (1) is the sealing portion (30) is inserted into the through hole (51).

According to the piping structure according to this aspect, since the plug (1) has the sealing part (30) inserted into the through hole (51), the plug (1) is welded to the piping (50). Occasionally, the back shield gas can be retained in the retention space (S). As a result, the gas for the back shield can be effectively sealed by a simple operation of using the plug (1), and the burden of incidental work associated with welding the plug 1 and the pipe 50 can be reduced.

Further, a piping structure according to an aspect of the present disclosure includes a piping (50) having a through hole (51) formed therein, and the above-described plug (1), wherein the plug (1) includes the groove portion (40) is abutted against the outer peripheral surface of the pipe (50), and a welded portion (60) is formed between the groove portion (40) and the outer peripheral surface of the pipe (50) to form the pipe ( 50).

According to the piping structure according to this aspect, the plug (1) has the groove portion (40) butted against the outer peripheral surface of the pipe (50), and the groove portion (40) and the outer peripheral surface of the pipe (50) are aligned. Since the weld (60) is formed between and connected to the pipe (50), the entire weld (60) can be formed on the outer peripheral surface of the pipe (50). As a result, the presence or absence of defects in the weld (60) can be inspected by a non-destructive method, so the inspection of the weld (60) can be easily carried out. In addition, since all the welded portions (60) to be inspected are formed on the outer peripheral surface of the pipe (50), the accuracy of inspection is improved.

Further, in the piping structure according to one aspect of the present disclosure, the welded portion (60) is such that the end portion (61) of the portion in contact with the pipe (50) is closer to the axis ( X).

According to the pipe structure according to this aspect, the end (61) of the welded part (60) in contact with the pipe (50) is further away from the axis (X) than the outer peripheral surface of the nozzle part (20). Therefore, the end (61) of the welded portion (60) can be positioned radially outside the stress concentration portion generated inside the pipe material of the pipe (50) and near the through hole (51). . As a result, part of the stress generated in the stress concentrated portion can be borne by the nozzle portion (20). Therefore, the proof stress of the pipe (50) can be improved. In addition, the stress concentration generated in the welded portion (60) can be alleviated, and the strength of the welded portion (60) can be secured and the service life of the welded portion (60) can be extended.
In addition, the "stress concentration portion" referred to here means a peak portion of stress generated in the vicinity of the through hole (51) due to the hoop stress acting on the pipe (50) and its vicinity.

Further, in the piping structure according to one aspect of the present disclosure, the position of the end (61) of the weld (60) depends on the degree of damage of the stress concentration portion and the end (61) of the weld (60). ) is determined by comparing the degree of damage of

According to the piping structure according to this aspect, the position of the end (61) of the weld (60) depends on the degree of damage of the stress concentrated portion, the degree of damage of the end (61) of the weld (60), , the end (61) of the welded portion (60) can be set at a position where both the stress concentration portion and the end (61) of the welded portion (60) are unlikely to be damaged.

In addition, in the piping structure according to one aspect of the present disclosure, the welded portion (60) is formed in a round shape concavely curved with respect to the outer peripheral surface of the pipe (50).

According to the pipe structure according to this aspect, the welded portion (60) is formed in a round shape that curves concavely with respect to the outer peripheral surface of the pipe (50). 61) can be suppressed from stress concentration. As a result, even if the nozzle part (20) bears part of the stress generated in the stress concentration part of the pipe (50), the weld part (60) can be prevented from being damaged by the stress.

Further, a method for installing a plug (1) according to an aspect of the present disclosure is a plug (1) that closes a through hole (51) formed in a pipe (50) from the outer peripheral surface side of the pipe (50), , a columnar nozzle portion (20) extending in the direction of the axis (X), and a nozzle portion (20) connected to the nozzle portion (20) to provide a gas flow between the nozzle portion (20) and the through hole (51). and a sealing part (30) defining a retention space (S) for retaining a gas used for a back shield during welding, the gas being used for the retention space (S). including the step of supplying to

1 Plug 11 Tip 12 Base end 20 Nozzle part 22 Bottom surface 30 Sealing part 31 Shaft part 32 Disk part 32a Bottom surface 40 Groove part 41 Groove surface 42 Straight surface 43 Root surface 44 Round surface 50 Piping 51 Through hole 53 Stress Concentrated portion 60 Welded portion 61 Weld toe 70 Flat plate 71 Through hole 72 Through hole point 101 Furnace wall (heat transfer tube)
102 first superheater (heat exchanger)
103 second superheater (heat exchanger)
104 third superheater (heat exchanger)
105 first reheater (heat exchanger)
106 second reheater (heat exchanger)
107 Economizer (heat exchanger)
111 High-pressure turbine 112 Intermediate-pressure turbine 113 Low-pressure turbine 114 Condenser 121 Condensate pump (CP)
122 Low-pressure feed water heater 123 Boiler feed pump (BFP)
124 High-pressure water supply heater 126 Steam separator L1 Water supply system L2 Drain water system L3-L5 Steam system

Claims

A plug that closes a through hole formed in a pipe from the outer peripheral surface side of the pipe,
a columnar nozzle extending in the axial direction;
a sealing portion that is connected to the nozzle portion and that defines a retention space in which gas is retained between the through hole and the nozzle portion;
Plugs with.
The sealing portion is
a shaft portion having a smaller diameter than the inner diameter of the through hole and having a proximal end connected to the nozzle;
a disc portion connected to the tip of the shaft portion corresponding to the inner shape of the through hole;
2. The plug of claim 1, comprising:
The plug according to claim 2, wherein the surface of the disk portion facing the inner side of the pipe is configured to be substantially flush with the inner peripheral surface of the pipe.
The plug according to any one of claims 1 to 3, comprising a groove portion that is formed to protrude from the nozzle portion and that abuts against the outer peripheral surface of the pipe.
The groove portion is
a groove surface that contracts from the outer peripheral side in a radial direction orthogonal to the axial direction in the direction from the base end to the tip;
a straight surface extending from the end of the groove surface along the axial direction from the distal end side toward the proximal end side;
5. The plug of claim 4, comprising:
The plug according to claim 5, wherein the straight surface is positioned outside the through-hole in the radial direction when the groove portion abuts against the outer peripheral surface of the pipe.
a pipe in which a through hole is formed; a plug according to any one of claims 1 to 6;
with
The plug is a piping structure in which the sealing portion is inserted into the through hole.
a pipe in which a through hole is formed; a plug according to any one of claims 4 to 6;
with
The plug is a piping structure in which the groove portion is abutted against the outer peripheral surface of the pipe, and a weld portion is formed between the groove portion and the outer peripheral surface of the pipe to be connected to the pipe. .
The pipe structure according to claim 8, wherein the end portion of the welded portion that contacts the pipe is further away from the axis than the outer peripheral surface of the nozzle portion.
The piping structure according to claim 9, wherein the position of the end portion of the welded portion is determined by comparing the degree of damage of the stress concentration portion and the degree of damage of the end portion of the welded portion.
The pipe structure according to claim 9 or 10, wherein the welded portion is formed in a round shape concavely curved with respect to the outer peripheral surface of the pipe.
A plug that closes a through hole formed in a pipe from the outer peripheral surface side of the pipe,
a columnar nozzle extending in the axial direction;
a sealing portion that is connected to the nozzle portion and that defines a retention space in which gas is retained between the through hole and the nozzle portion;
A method of installing a plug comprising:
A method for installing a plug, including a step of supplying a gas used for a back shield during welding to the retention space.