CN114096840A

CN114096840A - Method for inspecting plant equipment and method for repairing plant equipment

Info

Publication number: CN114096840A
Application number: CN202080045079.3A
Authority: CN
Inventors: 时吉巧; 驹井伸好; 本田雅干; 浦田干康; 片渕纮希; 本田尊士; 富永公彦; 下田纯之
Original assignee: Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Heavy Industries Ltd
Priority date: 2019-06-28
Filing date: 2020-06-23
Publication date: 2022-02-25
Also published as: JP2021006801A; WO2020262364A1; JP7277286B2

Abstract

A method for inspecting a plant facility according to an embodiment is a method for inspecting a plant facility including a stem and a mother pipe having a stem hole to which the stem is attached, the method including the steps of: selecting an inspection portion from one or more inspection candidate portions including a region that is offset from an inner wall surface of the socket hole toward an inside of a parent material of the parent tube in an axial direction of the parent tube; and a step of performing flaw detection on the inspection site.

Description

Method for inspecting plant equipment and method for repairing plant equipment

Technical Field

The present disclosure relates to a method for inspecting a plant and a method for repairing a plant.

Background

In pipes for boilers, for example, which are used for a long time in a high-temperature and high-pressure environment, cracks are generated in welded portions of the pipes, for example, due to creep damage. Since cracks caused by creep damage progress, it is necessary to evaluate the residual life depending on the presence or absence of cracks and the length of cracks in the thickness direction of the welded portion (height of cracks) and to repair the welded portion in time. Therefore, a technique for measuring the presence or absence of cracks in the welded portion and the length of the cracks and evaluating the remaining life has been developed.

For example, in the method for evaluating the remaining life disclosed in patent document 1, the inside of a welded portion is inspected by ultrasonic inspection by a phased array method, and the remaining life is evaluated based on the inspection result (see patent document 1).

Prior art documents

Patent document 1: japanese patent laid-open publication No. 2017-151107

As described above, it is known that cracks are likely to be generated by creep damage in a welded portion such as a piping portion of a piping of a boiler, for example, and therefore, maintenance and management are performed mainly on the welded portion of the piping of the boiler, for example.

Further, it has recently been found that instead of the welded portion, a crack may be generated in the base material of the pipe. However, in a relatively large-scale plant such as a power plant or a chemical plant, a large number of pipes are used. Therefore, when the inspection period is limited, for example, by a periodic inspection performed by stopping the operation of the plant equipment, it is difficult to inspect the base material portion of all the pipes.

Disclosure of Invention

In view of the above, an object of at least one embodiment of the present disclosure is to provide an efficient inspection method for plant equipment.

(1) A method for inspecting a plant equipment according to at least one embodiment of the present disclosure is a method for inspecting a plant equipment including a stem and a mother pipe having a stem hole for mounting the stem,

the method for inspecting the plant equipment includes the steps of:

selecting an inspection site from one or more inspection candidate sites including a region that is offset from an inner wall surface of the socket hole toward an inside of the parent material of the parent pipe in an axial direction of the parent pipe; and

and performing flaw detection on the inspection part.

(2) A method for repairing a plant equipment according to at least one embodiment of the present disclosure is a method for repairing a plant equipment including a socket and a mother pipe to which the socket is attached,

the method for repairing the plant equipment comprises the following steps:

removing a tube seat arranged on the main tube;

a step of forming a recess by removing a region where the stem is mounted from the mother pipe, leaving a part of a region on the inner peripheral surface side of the mother pipe;

disposing a sealing plate in the partial region in a socket hole that communicates an inner space of the main pipe with an outside of the main pipe; and

and a step of backfilling the recess by welding after the step of disposing the sealing plate.

Effects of the invention

According to at least one embodiment of the present disclosure, plant equipment can be efficiently inspected.

Drawings

Fig. 1 is a diagram showing each step in a method for inspecting plant equipment according to some embodiments.

Fig. 2 is a table showing a portion where a welded portion exists and a relationship between the thickness of the portion and a position where a crack is likely to occur.

Fig. 3 is a diagram showing a storage device for storing a database and a terminal device for accessing the storage device.

Fig. 4 is a flowchart showing a flow of processing to be performed in step S3 for performing an examination of a region to be evaluated.

Fig. 5 is a graph in which the horizontal axis represents stress acting on the evaluation target portion and the vertical axis represents the ratio of the size of damage to the thickness of the sheet at the maintenance target portion.

Fig. 6 is a flowchart showing the flow of processing to be performed in step S3 for performing an examination of a region to be evaluated.

Fig. 7 is a flowchart showing a flow of processing to be performed in step S3 for performing an examination of a region to be evaluated.

Fig. 8 is a cross-sectional view of a pipe including a stem and a female pipe having a stem hole for mounting the stem.

Fig. 9 is a schematic diagram showing the structure of a flaw detector used when ultrasonic inspection is performed by a phased array method in a step of performing inspection of a region to be evaluated.

Fig. 10 is a view for explaining a refraction angle in the flaw detector shown in fig. 9.

Fig. 11 is a flowchart showing a procedure of processing performed in a step of repairing a portion to be evaluated in the pipe shown in fig. 8.

Fig. 12 is a sectional view of the pipe after the stem is removed from the mother pipe in the stem removing step.

Fig. 13 is a sectional view of the pipe with the recess formed.

Fig. 14 is a view of the pipe in which the concave portion is formed, as viewed from the outside in the radial direction of the main pipe.

Fig. 15 is a view showing an example of a case where the concave portion is provided when the plurality of sockets are arranged in a state of being close to each other along the axial direction of the mother pipe.

Fig. 16 is a diagram for explaining a step of disposing a sealing plate in a stem hole.

Fig. 17 is a cross-sectional view of the pipe after the step of backfilling is performed.

Fig. 18 is a flowchart showing a procedure of processing performed in a step of repairing a portion to be evaluated in the pipe shown in fig. 8.

Fig. 19 is a perspective view of the reinforcing plate.

Fig. 20 is a view of the state where two split plates are arranged as viewed from the radially outer side of the mother pipe.

Fig. 21 is a sectional view of the pipe 5 after the reinforcing plate is welded to the mother pipe in the step of welding the reinforcing plate to the mother pipe.

Detailed Description

Hereinafter, several embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements of the components described as the embodiments or shown in the drawings, and the like are not intended to limit the scope of the present invention, but are merely illustrative examples.

For example, expressions indicating relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "central", "concentric", or "coaxial" indicate not only such arrangements as they are strictly, but also states of being relatively displaced by an angle or distance to the extent of tolerance or obtaining the same function.

For example, expressions indicating states in which objects are equal, such as "identical", "equal", and "homogeneous", indicate not only states in which the objects are exactly equal but also states in which there are tolerances or differences to the extent that the same function can be obtained.

For example, the expression "square-shaped" or "cylindrical" as used herein means not only a shape having a geometrically strict meaning, such as a square shape or a cylindrical shape, but also a shape including a concave-convex portion or a chamfered portion as long as the same effect can be obtained.

On the other hand, expressions such as "set", "have", "include", or "contain" a constituent element are not exclusive expressions which exclude the presence of other constituent elements.

(outline of inspection method of plant Equipment)

First, an outline of a method for inspecting plant equipment according to some embodiments will be described with reference to fig. 1.

Fig. 1 is a diagram showing each step in a method for inspecting plant equipment according to some embodiments. The method for inspecting a plant according to some embodiments includes a step S1 of selecting a site to be evaluated, a step S2 of selecting an inspection method and adding measurement items, a step S3 of inspecting the site to be evaluated, and a step S4 of evaluating the remaining life of the site to be evaluated. The method for inspecting a plant facility according to some embodiments may include step S5 of repairing the evaluation target site.

The inspection method of the plant equipment according to some embodiments is applied to inspection of a metal component used for a long time in an environment where a high temperature and a large stress are applied, and is applied to inspection of a welded portion such as a steam pipe connecting a boiler and a steam turbine in thermal power generation plant equipment, and inspection of a base material such as a pipe.

Hereinafter, the outline of each step in the inspection method for plant equipment according to some embodiments will be described.

(outline of step S1 for selecting evaluation target site)

Step S1 of selecting an evaluation target site is a step of selecting an evaluation target site for performing a flaw detection test and for performing a remaining life evaluation based on the result of the flaw detection test from among a plurality of steam pipes and the like existing in the plant equipment. That is, step S1 of selecting an evaluation target site in some embodiments is a step of selecting an examination site from one or more examination candidate sites.

Fig. 8 is a cross-sectional view of a pipe including a stem and a female pipe having a stem hole for mounting the stem. In fig. 8, a connection portion 7 between the female pipe 10 and the socket 20 is shown in a cross section along the axis AXa of the female pipe 10 and the axis AXb of the socket 20. The pipe 5 shown in fig. 8 includes a mother pipe 10 and a stem 20 connected to the mother pipe 10 by welding. The female pipe 10 is formed with a socket hole 13 to which the socket 20 is mounted. The socket hole 13 includes a hole portion 13a communicating the hole portion 23 extending in the direction of the axis AXb of the socket 20 with the interior of the female pipe 10 in the socket 20, and also includes a wall surface serving as a boundary between the female pipe 10 and the socket 20, that is, a branch pipe, a plug, a cylinder, and the like.

In the pipe 5 shown in fig. 8, the socket 20 is welded and attached to the mother pipe 10 by the socket welding portion 30. In the pipe 5 shown in fig. 8, the stem welded portion 30 includes a weld metal 31 and a Heat Affected Zone (HAZ) 33 by welding.

As a result of diligent research, the inventors have found that in the pipe 5 including the socket 20 and the mother pipe 10 having the socket hole 13 formed therein, in which the socket 20 is to be mounted, a crack 41 may be generated in the region 19 that is displaced from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the mother pipe 10 in the direction of the axis AXa of the mother pipe 10. In fig. 8, the region 19 is a region surrounded by a broken line, for example. In fig. 8, the crack 41 is a region in which cross hatching is added to the region 19.

The mechanism of the crack 41 is briefly described. In a pipe having a thick cylindrical shape and having a relatively high internal pressure, such as a pipe in a boiler, for example, the circumferential stress is usually greatest in the radially innermost region of the base material of the pipe. That is, in the pipe 5 shown in fig. 8, the circumferential stress is usually the largest at the inner circumferential surface 10a of the parent pipe 10.

In general, when a through hole for communicating the inside and the outside of the pipe is opened in a side surface of the pipe, a circumferential stress generated by an internal pressure of the pipe is largest at a position along a center of a wall surface forming the through hole in a circumferential direction of the pipe. That is, in the pipe 5 shown in fig. 8, the maximum is usually at the position along the center of the main pipe 10 in the circumferential direction in the inner wall surface 15 of the pipe seat hole 13.

However, as a result of earnest study, the inventors have found that, in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, particularly a pipe formed of high-chromium steel, a position where a circumferential stress due to an internal pressure of the pipe is the largest tends to move from the above-described position due to deformation caused by creep.

Specifically, it was found that, in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, for example, a position where a circumferential stress due to an internal pressure of the pipe is the largest moves to a position radially outward of a radially innermost region in a base material of the pipe due to a deformation caused by a creep. Further, it was found that, in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, for example, when a through hole for communicating the inside of the pipe with the outside is opened in a side surface of the pipe at a position where a circumferential stress due to an internal pressure of the pipe is the largest due to deformation caused by creep, the pipe moves from a wall surface where the through hole is formed to a region displaced toward the inside of a base material of the pipe in an axial direction of the pipe.

That is, it was found that in the case of the pipe 5 shown in fig. 8, the position where the circumferential stress due to the internal pressure of the pipe 5 is the largest is moved to the region 19 shifted to the inside of the base material 11 of the parent pipe 10 in the direction of the axis AXa of the parent pipe 10 by the deformation due to the creep.

Therefore, in the inspection method of the plant equipment according to some embodiments, the area 19 is included as the inspection candidate portion.

The details of step S1 for selecting an evaluation target site according to some embodiments will be described later.

(outline of step S2 for selecting inspection method and adding measurement items)

Step S2 of selecting an inspection method and adding measurement items is a step of selecting an inspection method for flaw detection of the evaluation target site selected in step S1 of selecting an evaluation target site and adding measurement items for measurement.

In step S2 of selecting an inspection method and adding measurement items, an inspection method for flaw detection suitable for the evaluation target site selected in step S1 of selecting an evaluation target site is selected.

The inspection method selected in step S2 of selecting the inspection method and adding the measurement items is an inspection method that is set for each combination of the type of the evaluation target site including at least one of the circumferential welded portion, the longitudinal welded portion, and the stem welded portion of the pipe and the thickness of the evaluation target site, as will be described later. The inspection method selected in step S2 of selecting the inspection method and adding the measurement items is an inspection method in which, as described later, for a pipe including a stem and a mother pipe having a stem hole into which the stem is fitted, the type of the portion to be evaluated and an index including, as parameters, the outer diameter of the mother pipe and the plate thickness of the mother pipe are set.

The welded portion includes: weld metal, a heat affected zone (HAZ zone) by welding, and an inner surface slit described later.

In step S2 of selecting the inspection method and adding the measurement items, the measurement items to be additionally measured appropriate for the selected inspection method are selected.

Here, the additional measurement is performed to obtain a parameter required to improve the accuracy of the evaluation of the remaining life of the part to be evaluated based on the result of the inspection of the part to be evaluated by the selected inspection method. That is, in step S3 of performing an inspection of the evaluation target site, which will be described later, a flaw detection inspection of the evaluation target site is performed by the selected inspection method, and an inspection result is obtained. Then, based on the obtained inspection result, the remaining life of the evaluation target site is evaluated in step S4, which will be described later, of evaluating the remaining life of the evaluation target site. When evaluating the remaining life of the part to be evaluated, several parameters are required in addition to the inspection result of the flaw detection inspection. In the additional measurement, a parameter required to improve the accuracy of the remaining life evaluation is acquired from among these parameters.

In the following description, the measurement item to be additionally measured is simply referred to as an additional measurement item.

Details of step S2 for selecting the inspection method and adding the measurement items will be described later.

(outline of step S3 for examining the site to be evaluated)

Step S3 of performing the inspection of the site to be evaluated is a step of performing a flaw detection inspection on the site to be evaluated selected in step S1 of selecting the site to be evaluated by the inspection method selected in step S2 of selecting the inspection method and adding the measurement items. That is, step S3 of performing the inspection of the evaluation target site is a step of performing the flaw detection inspection on the evaluation target site selected in step S1 of selecting the evaluation target site.

In step S3 of performing the examination of the site to be evaluated, additional measurement is performed as needed in relation to the additional measurement item selected in step S2 of selecting the examination method and the additional measurement item.

Details of step S3 for performing the examination of the evaluation target site will be described later.

(outline of step S4 for evaluating remaining Life of evaluation target site)

Step S4 of performing the remaining life evaluation of the evaluation target site is a step of performing the remaining life evaluation of the evaluation target site based on the result of the examination of the evaluation target site performed in step S3 of performing the examination of the evaluation target site.

In step S4 of evaluating the remaining life of the part to be evaluated, if additional measurement is performed for the additional measurement item in step S3 of inspecting the part to be evaluated, the remaining life of the part to be evaluated is also evaluated using the parameters obtained by the additional measurement.

For example, crack progression calculation, FEM, damage mechanics evaluation, void simulation, and texture simulation can be used for evaluation of the residual life.

(outline of step S5 of repairing the evaluation target site)

The step S5 of repairing the site to be evaluated is a step of repairing the site to be evaluated as needed based on the result of the examination of the site to be evaluated performed in the step S3 of examining the site to be evaluated or the result of the evaluation of the remaining life of the site to be evaluated performed in the step S4 of evaluating the remaining life of the site to be evaluated.

Details of step S5 for repairing the evaluation target site will be described later.

As described above, the method for inspecting a plant according to some embodiments includes: step S1 of selecting a site to be evaluated, step S2 of selecting an inspection method and adding measurement items, and step S3 of inspecting a site to be evaluated.

That is, the method of inspecting plant equipment according to some embodiments includes a step S1 of selecting an evaluation target portion, which is a step of selecting an inspection portion from one or more inspection candidate portions including the region 19 shifted from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the parent pipe 10 in the direction of the axis AXa of the parent pipe 10. The method for inspecting a plant according to some embodiments includes a step S3 of inspecting an evaluation target site including at least one of a circumferential weld portion, a longitudinal weld portion, and a socket weld portion of a pipe, which is a step of inspecting the evaluation target site by an inspection method set for each combination of a type of the evaluation target site and a thickness of the evaluation target site. The method for inspecting a plant according to some embodiments includes a step S3 of inspecting an evaluation target site, which is a step of inspecting the evaluation target site by an inspection method that is set for each combination of a type of the evaluation target site and an index as parameters, the index including an outer diameter of a mother pipe and a plate thickness of the mother pipe, the pipe including a pipe socket and the mother pipe having a pipe socket hole to which the pipe socket is attached.

Therefore, according to the inspection method of the plant equipment of the several embodiments, since the step S1 of selecting the site to be evaluated and the step S3 of performing the inspection of the site to be evaluated, which is the step of performing the flaw detection inspection of the site to be inspected selected in the step S1, the presence of the crack 41 generated in the area 19 can be confirmed even in a limited inspection period. Therefore, the plant equipment can be efficiently inspected.

The method for inspecting plant equipment according to some embodiments includes step S2 of selecting an inspection method and additional measurement items, which are steps of selecting additional measurement items for obtaining parameters necessary for improving the accuracy of the evaluation of the remaining life of the part to be evaluated based on the inspection result of the part to be evaluated by the inspection method. Therefore, according to the inspection method for a plant facility of the several embodiments, the inspection method for the evaluation target portion is appropriate depending on the combination of the type of the evaluation target portion and the thickness of the evaluation target portion, and the accuracy of the inspection result of the evaluation target portion is improved. Further, the measurement items for additional measurement for improving the accuracy of the remaining life evaluation are appropriate depending on the method of inspecting the part to be evaluated. By doing so, the accuracy of the evaluation of the remaining lifetime of the evaluation target site based on the inspection result of the evaluation target site is improved.

(details of step S1 for selecting evaluation target site)

Details of step S1 for selecting the evaluation target site will be described. In the following description, a case will be described where the pipe is a pipe 5 including a mother pipe 10 to which a stem 20 is attached as shown in fig. 8.

As described above, it was found that in the pipe 5 of fig. 8, the crack 41 may be generated in the region 19 shifted from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the parent pipe 10 in the direction of the axis AXa of the parent pipe 10. Further, it is also known that cracks are likely to occur in the pipe 5 of the type shown in fig. 8 at the stem welding portion 30 as will be described later.

Accordingly, the inventors have earnestly studied and found that in the pipe 5 of the type shown in fig. 8, the outer diameter D and the plate thickness T of the mother pipe 10 are included as parameters, and when an index indicating the relative thickness of the plate thickness T is equal to or less than a predetermined value, that is, when the plate thickness T of the mother pipe 10 is relatively thin, the above-mentioned region 19 is likely to cause cracks before the pipe seat welding portion 30. On the other hand, it was found that if the index exceeds the predetermined value, that is, if the thickness T of the mother pipe 10 is relatively thick, the stem welded portion 30 is likely to crack before the region 19.

Therefore, in some embodiments, in step S1 of selecting an evaluation target site, if the index is equal to or less than the predetermined value, the region 19 is selected as an examination site (evaluation target site). In some embodiments, in step S1 of selecting the portion to be evaluated, if the index exceeds the predetermined value, the stem welding portion 30 is selected as the inspection portion (the portion to be evaluated).

Here, the index may be, for example, a thickness-to-outside diameter ratio (T/D) of the mother pipe obtained by dividing the thickness T of the mother pipe 10 by the outside diameter D of the mother pipe 10.

That is, in some embodiments, in step S1 of selecting a site to be evaluated, when the mother pipe plate thickness/outer diameter ratio (T/D) is equal to or less than the predetermined value Th, the above-described region 19 is selected as an inspection site (site to be evaluated). In some embodiments, in step S1 of selecting the portion to be evaluated, if the mother pipe thickness-to-outer diameter ratio (T/D) exceeds the predetermined value Th, the stem weld portion 30 is selected as the inspection portion (portion to be evaluated).

In the case where the mother pipe outer diameter plate thickness ratio (D/T) obtained by dividing the outer diameter D of the mother pipe 10, which is the reciprocal of the mother pipe plate thickness outer diameter ratio (T/D), by the plate thickness T of the mother pipe 10 is used as the index, the above-mentioned region 19 may be selected as the inspection site (evaluation target site) when the mother pipe outer diameter plate thickness ratio (D/T) is equal to or greater than the predetermined value Th in the step S1 of selecting the evaluation target site. When the mother pipe outer diameter/thickness ratio (D/T) is smaller than the predetermined value Th, the stem welded portion 30 can be selected as an inspection portion (evaluation target portion).

The predetermined value Th is set to a value different from each other depending on parameters including, for example, the index of the outer diameter d and the plate thickness t of the pipe of the connected stem 20. That is, in some embodiments, the predetermined value Th is present for each of the connection portions 7 connected to the respective sockets 20 in the plurality of pipes 5 shown in fig. 8 which are present in the plant facility.

In some embodiments, information on the position of the connection portion 7 connected to each header 20 and the predetermined value Th existing for each connection portion 7 is stored in advance in a storage device as a database (see fig. 3).

Fig. 3 is a diagram showing a storage device for storing the database and a terminal device for accessing the storage device. As described above, the storage device 1 stores, as a database, information on the positions of the connection portions 7 connected to the respective sockets 20 in the plurality of pipes 5, the predetermined value Th existing for each of the connection portions 7, the outer diameter D of the mother pipe 10, the plate thickness T, and the like.

As will be described later, the storage device 1 stores information on a portion where a welded portion exists, a relationship between the thickness of the portion and a position where the maximum damage is likely to occur, as a database. The terminal device 2 is a terminal device such as a personal computer, for example, and can read information of a database stored in the storage device 1 from the storage device 1 and present the information to an operator of the terminal device 2. The storage device 1 may be disposed at a different place from the terminal device 2, or may be disposed in the terminal device 2. The terminal device 2 includes: an arithmetic device 3 for executing various arithmetic processes, an input device 4 for receiving an input operation from an inspector, an operator, or the like, and a display unit 2a for displaying an arithmetic result or the like of the arithmetic device 3.

In some embodiments, in step S1 in which the evaluation target site is selected, when an instruction is input from the input device 4 to select the evaluation target site, the arithmetic device 3 reads information stored in the database of the storage device 1 from the storage device 1 and selects the evaluation target site.

For example, in some embodiments, in step S1 in which the evaluation target portion is selected, the arithmetic device 3 reads information on the predetermined value Th, the outer diameter D of the mother pipe 10, and the plate thickness T from the storage device 1 for the pipe 5 to which the stem 20 is connected, as shown in fig. 8. The arithmetic device 3 then calculates the mother pipe plate thickness-to-outer diameter ratio (T/D) based on the read information. The arithmetic device 3 compares the calculated thickness-to-outer diameter ratio (T/D) of the mother pipe with the read predetermined value Th.

When the mother tube plate thickness/outer diameter ratio (T/D) is equal to or less than the predetermined value Th, the arithmetic device 3 selects the above-described region 19 as an examination site (evaluation target site). When the mother pipe thickness-to-outer diameter ratio (T/D) exceeds a predetermined value Th, the arithmetic device 3 selects the stem weld portion 30 as an inspection portion (evaluation target portion).

In the storage device 1, the mother pipe plate thickness/outer diameter ratio (T/D) of the plurality of pipes 5 may be stored in advance. In this case, the arithmetic device 3 may read out the thickness/outside diameter ratio (T/D) of the mother pipe from the storage device 1 instead of reading out the information on the outside diameter D and the thickness T of the mother pipe 10.

After the evaluation target site is selected, the arithmetic unit 3 performs the processing described below in step S2 of selecting the inspection method and adding the measurement items.

(details of step S2 for selecting inspection method and adding measurement items)

The details of step S2 for selecting the inspection method and adding the measurement items will be described below.

For example, steam pipes connecting a boiler and a steam turbine in a thermal power plant facility have a plurality of types of welded portions. For example, steam pipes include circumferential weld portions for connecting pipes to each other and pipe seat weld portions for connecting pipes to branch pipes. In addition, when the pipe is manufactured from a plate-shaped member, there is a vertical welded portion extending in the pipe axial direction in order to connect the ends of the plates to each other.

According to the findings of the inventors, it is found that when the portions where the welded portions exist are different, the positions where cracks are likely to occur are different. Further, according to the findings of the inventors, even in the same type of welded portion, the position where the crack is likely to occur differs depending on the thickness of the portion.

Fig. 2 is a table showing a portion where a welded portion exists, a relationship between the thickness of the portion and a position where cracks are likely to occur, which has been found by the inventors as a result of earnest study.

According to the findings of the inventors, even in the same type of welded portion, the positions where cracks are likely to occur differ in the range of about 20mm in thickness. In the table shown in FIG. 2, the thin wall means a thickness of 20mm or less, and the thick wall means a thickness exceeding 20 mm. The same applies to the following description.

In a vertical welded portion in a straight pipe of a piping, for example, cracks are likely to occur in a thick portion in the thickness of the vertical welded portion, and the largest damage is likely to occur. This is because the creep speed of the Heat Affected Zone (HAZ) by welding is higher than the creep speed of the base material and the weld metal, and the multiaxial degree of stress in the inside of the plate thickness in the HAZ increases.

In a vertical welded portion in an elbow of a pipe, for example, cracks are likely to occur in a thick portion in the thickness of the vertical welded portion, and the largest damage is likely to occur. The reason is the same as that of the longitudinal weld in the straight pipe described above.

For example, in a circumferential welded portion of a pipe, cracks are likely to occur in the outer surface of the circumferential welded portion in a thick portion, and the largest damage is likely to occur. This is because the maximum position of the bending stress acting on the welded portion is the outer surface under the influence of the piping system stress, that is, the stress caused by external force or the like received from, for example, a support structure of the piping and other piping connected thereto, and the thermal stress generated by the restriction of the thermal expansion of the pipe itself. In addition, for example, in a circumferential welded portion of a pipe, cracks are likely to occur in a thin portion in the thickness of the circumferential welded portion, and the largest damage is likely to occur. The reason for this is that, although the thin portion is also affected by the pipe system stress as with the thick portion, the distribution of the bending stress in the thickness direction is small because of the small thickness, and the influence of the multiaxial velocity due to the creep velocity difference is larger.

For example, in the case of the pipe 5 shown in fig. 8, as described above, when the mother pipe thickness-to-outer diameter ratio (T/D) is equal to or less than the predetermined value Th, cracks are likely to occur in the region 19. On the other hand, if the mother pipe thickness-to-outer diameter ratio (T/D) exceeds the predetermined value Th, the stem weld portion 30 is likely to be cracked.

For example, in the case of the socket welding portion 30, both the thin portion and the thick portion are likely to crack at the outer surface and the inner surface of the socket welding portion 30 around the slit, and are likely to be damaged most. The reason why damage is easily generated on the outer surface is because hoop stress (circumferential stress) of the pipe is largest at the outer surface. On the other hand, the reason why the inner surface is easily damaged in the slit periphery is that stress concentration occurs in the crack-like tip portion of the slit. The inner surface slit of the stem welding portion 30 is a boundary between the pipe (the main pipe 10) and the stem 20 (the branch pipe, the plug, the cylinder, and the like), and the welding metal is not sufficiently melted in the welding, and the boundary is a portion remaining as the slit.

In most of the current plant facilities, the longitudinal welded portions in the thin-walled straight pipes and the thin-walled elbows are not described because the thin-walled straight pipes and the thin-walled elbows used in the high-temperature and high-pressure environment are almost free from the use of the electric welding pipes.

Such information on the portion where the welded portion exists, the relationship between the thickness of the portion and the position where the largest damage is likely to occur is stored in advance as a database in the storage device 1 shown in fig. 3.

As described above, the storage device 1 stores information on a portion where a welded portion exists, a relationship between the thickness of the portion and a position where the largest damage is likely to occur, as a database.

(inspection method suitable for flaw detection in the thickness of the plate)

Examples of inspection methods suitable for flaw detection in the inside of the sheet thickness include ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the open-end synthesis method, ultrasonic inspection by the high-frequency UT method, and ultrasonic inspection by the ultrasonic noise method.

Parameters required for improving the accuracy of the evaluation of the remaining life of the evaluation target portion based on the inspection results of the inspection methods suitable for flaw detection inspection in the sheet thickness interior are, for example, the size, shape, temperature, and material properties of the evaluation target portion.

The measurement items for additional measurement for obtaining the size and shape of the evaluation target site include, for example, the outer diameter of the pipe, the plate thickness of the pipe, the flattening ratio of the pipe, the shape of the cross section of the weld line when viewed from the longitudinal direction, and the shape of the Heat Affected Zone (HAZ) by welding. By obtaining the size and shape of the evaluation target portion, the stress acting on the welded portion can be calculated with high accuracy at the time of the remaining life evaluation. In particular, the outer diameter, the aspect ratio, and the cross-sectional shape of the pipe are effective measurement items for calculating with high accuracy the stress (bending, stretching) acting in the circumferential direction, which is important in the longitudinal welded portion.

The measurement items for additional measurement for obtaining the temperature of the evaluation target site include, for example, the formation state of water vapor scale, the formation state of precipitates, and the structural change of the evaluation target site, and the temperature of the evaluation target site can be estimated from the measurement results. The temperature in this case refers to the past temperature history or the highest temperature of the past operation. By acquiring the temperature of the evaluation target portion, the temperature condition can be set with high accuracy at the time of the remaining life evaluation.

The measurement items for additional measurement for obtaining the material properties of the evaluation target site include, for example, the hardness of the evaluation target site. Further, a small amount of sample may be collected from the site to be evaluated, and the material properties of the site to be evaluated may be obtained by performing a creep test or the like on the sample. By obtaining the material characteristics of the evaluation target portion, the strength of the welded portion can be set with high accuracy in the residual life evaluation.

In the storage device 1, the inspection methods described above are stored as a database as inspection methods suitable for flaw detection inspection in the sheet thickness interior. In the storage device 1, the additional measurement items are stored as a database in association with an inspection method suitable for flaw detection inspection in the sheet thickness interior. The storage device 1 stores, as a database, information of a flow of processing to be performed in step S3 for performing the examination of the site to be evaluated including processing for determining whether or not to measure the additional measurement item. The flow of this process will be described later.

In the ultrasonic inspection, the range near the surface (for example, several mm from the surface) in the evaluation target region is a dead zone, and thus flaw detection is impossible. Therefore, for example, as a result of the flaw detection inspection in the sheet thickness, when it is determined that the damage in the sheet thickness exists in the vicinity of the dead zone, in step S3 in which the part to be evaluated is inspected, a dead zone reduction measure for reducing the influence of the dead zone is performed.

As a measure for reducing the dead zone, for example, an outer surface is inspected. Examples of the inspection method for the outer surface include magnetic particle inspection, penetrant inspection, inspection by MT transfer, eddy current inspection, and the like. If the presence of the damage to the outer surface can be confirmed by these inspections, it can be determined that the damage present in the vicinity of the dead zone inside the sheet thickness and the damage to the outer surface are continuous, and if the presence of the damage to the outer surface cannot be confirmed, it can be determined that the damage present in the vicinity of the dead zone inside the sheet thickness does not reach at least the outer surface.

In addition, as a dead zone reduction measure, the stack height of the welded portion may be removed. By removing the pile height of the welded portion, magnetic powder inspection and the like become easy to perform. Further, by removing the pile of the welded portion, a flaw detector for ultrasonic flaw detection can be brought into contact with the surface from which the pile of the welded portion has been removed, and the flaw detection range can be expanded. Further, by removing the pile of the welded portion, a damage that can be observed visually or the like may appear on the surface after the pile of the welded portion is removed. Further, by removing the pile height of the welded portion, it is possible to remove the damage existing only in the vicinity of the surface of the pile height.

In the storage device 1, the insensitive area reduction measures associated with the inspection method suitable for the flaw detection inspection in the sheet thickness interior are stored as a database.

(inspection method suitable for inspection of flaw detection of outer surface)

Examples of inspection methods suitable for inspection of the outer surface include magnetic particle inspection, penetrant inspection, inspection by MT transfer, eddy current inspection, and the like.

Parameters required to improve the accuracy of the remaining life evaluation of the evaluation target site by the inspection results of the inspection methods suitable for the flaw detection inspection of the outer surface are, for example, the size, shape, temperature, and material properties of the evaluation target site.

The measurement items for additional measurement for obtaining the size and shape of the evaluation target site, the measurement items for additional measurement for obtaining the temperature of the evaluation target site, and the measurement items for additional measurement for obtaining the material properties of the evaluation target site are as described above.

When the maximum damage is likely to occur on the outer surface as described later, in addition to the flaw detection by the above-described inspection method suitable for the flaw detection inspection of the outer surface, for example, a nondestructive inspection for obtaining a local life consumption rate of the outer surface, which is a local life consumption rate of 100% at the time of occurrence of a crack that can be visually observed, may be performed. Examples of the nondestructive inspection method include a nondestructive inspection method such as a void number density method, a void area ratio method, a texture contrast method, a precipitate inter-granular distance method, an a parameter method, a crystal grain deformation method, a void grain boundary length method, and a carbide composition measurement method.

As will be described later, when the local life consumption rate of the outer surface obtained based on the inspection result of the nondestructive inspection exceeds a predetermined value or when the outer surface is damaged, the inspection is performed on the inside of the evaluation target portion in the vicinity of the outer surface.

Examples of inspection methods suitable for the inspection of the internal flaw of the evaluation target site in the vicinity of the outer surface include ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the open pore synthesis method, ultrasonic inspection by the high-frequency UT method, and ultrasonic inspection by the ultrasonic noise method.

The storage device 1 stores the above-described inspection methods as a database as inspection methods suitable for the flaw detection inspection of the outer surface. In the storage device 1, the additional measurement items are stored as a database in association with an inspection method suitable for the flaw detection inspection of the outer surface. In the storage device 1, the nondestructive inspection method is stored as a database as a nondestructive inspection method for obtaining the local life consumption rate of the outer surface. The storage device 1 stores the above-described inspection methods as a database as inspection methods suitable for flaw detection inspection of the inside of the evaluation target region near the outer surface. The storage device 1 stores, as a database, information of a flow of processing to be performed in step S3 for performing the examination of the site to be evaluated including processing for determining whether or not to measure the additional measurement item. The flow of this process will be described later.

(inspection method suitable for flaw detection of portion around slit on inner surface)

In the flaw detection of the portion around the inner surface slit, the inner surface slit exists from the beginning within the flaw detection range, but the existence range of the inner surface slit changes depending on the state of welding. Therefore, in the flaw detection of the portion around the inner surface slit, it is difficult to distinguish the inner surface slit from the flaw. Therefore, in the flaw detection of the portion around the inner surface slit, a crack which can be observed visually as a macro crack is a detection target, and the detected crack is not distinguished from the inner surface slit, and all of the cracks are treated as a crack which can be observed visually as a macro crack.

Examples of inspection methods suitable for flaw detection of a portion around an inner surface slit include ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the open seam synthesis method, ultrasonic inspection by the high-frequency UT method, and ultrasonic inspection by the ultrasonic noise method.

The parameters required for improving the accuracy of the evaluation of the remaining life of the evaluation target site based on the inspection results of the inspection methods applied to the flaw detection inspection of the internal surface slit periphery are, for example, the size, shape, temperature, and material properties of the evaluation target site.

The measurement items for additional measurement for obtaining the size and shape of the evaluation target site include, for example, the shape of a Heat Affected Zone (HAZ) by welding, the surface shape of the weld metal, the outer diameter of a pipe (mother pipe) in the stem, and the thickness of the mother pipe.

The measurement items for additional measurement for obtaining the temperature of the evaluation target site and the measurement items for additional measurement for obtaining the material properties of the evaluation target site are the same as described above.

In the storage device 1, the inspection methods described above are stored as a database as inspection methods suitable for flaw detection of the portion around the inner surface slit. The storage device 1 stores the additional measurement items in association with an inspection method suitable for flaw detection of a portion around the inner surface slit as a database. In the storage device 1, information of the flow of the process to be performed in step S3 for performing the examination of the site to be evaluated including the process for determining whether or not to measure the additional measurement item is stored as a database. The flow of this process will be described later.

In step S2 in which the inspection method and the additional measurement items are selected, when the inspector operates the terminal device 2 and inputs the type of the part to be evaluated and the thickness of the part to be evaluated, the terminal device 2 reads out, from the database of the storage device 1, the inspection method suitable for the flaw detection of the part to be evaluated and the additional measurement items for improving the accuracy of the evaluation of the remaining life of the part to be evaluated based on the inspection result of the inspection method. The terminal device 2 then displays the read-out inspection method and the additional measurement item on, for example, a display unit 2a of the terminal device 2.

The terminal device 2 reads out information on the flow of the process to be performed in step S3 of performing the examination of the site to be evaluated from the database of the storage device 1. The terminal device 2 then displays the read information of the flow of the process to be performed in step S3 of performing the examination of the evaluation target site on, for example, the display unit 2a of the terminal device 2.

In the case where the read-out inspection method is an inspection method suitable for flaw detection of the outer surface, for example, a nondestructive inspection method for obtaining a local life consumption rate and an inspection method suitable for flaw detection in the interior of the evaluation target portion in the vicinity of the outer surface are also displayed on the display unit 2a of the terminal device 2.

That is, step S2 of selecting the inspection method and the additional measurement items is a step of selecting the inspection method and the measurement items using a database of predetermined inspection methods and additional measurement items for each combination of the type of the part to be evaluated and the thickness of the part to be evaluated.

As described above, according to the inspection method for plant equipment according to some embodiments, since the step S2 of selecting an inspection method and adding measurement items is provided, the inspection method and the measurement items to be performed in the step S3 of inspecting the site to be evaluated can be quickly selected.

(details of step S3 for examining the part to be evaluated)

In step S3, in which the evaluation target site is inspected, a flaw detection inspection is performed on the evaluation target site as follows.

(1) In the case where the evaluation target portion is a portion where the largest damage is likely to occur in the sheet thickness

For example, when the evaluation target portion is a portion in which the largest damage is likely to occur in the sheet thickness, the flowchart shown in fig. 4 is presented in step S2 in which the inspection method is selected and the measurement items are added.

Fig. 4 is a flowchart showing a flow of processing to be performed in step S3 for inspecting the evaluation target site when the evaluation target site is a site in which the largest damage is likely to occur in the sheet thickness. In step S3, in which the inspector performs the inspection of the evaluation target site, the inspection of the evaluation target site is performed according to the flowchart shown in fig. 4, and whether or not to measure the additional measurement item is determined, and additional measurement is performed as needed.

In step S301, the inspector performs a flaw detection inspection of the inside of the sheet thickness of the evaluation target portion, and detects the position and size of the flaw in the sheet thickness.

In step S301, flaw detection inspection of the inside of the sheet thickness is performed by any one of an ultrasonic inspection method by the conventional UT method, an ultrasonic inspection method by the TOFD method, an ultrasonic inspection method by the phased array method, an ultrasonic inspection method by the open aperture synthesis method, an ultrasonic inspection method by the high-frequency UT method, an ultrasonic inspection method by the ultrasonic noise method, and the like. As described above, each of the inspection methods is presented to the inspector in step S2 in which the inspection method is selected and the measurement item is added.

Next, in step S302, the inspector determines the presence or absence of internal damage, that is, the presence or absence of damage within the sheet thickness of the evaluation target site, based on the results of the flaw detection performed in step S301. When it is determined in step S302 that there is no damage, the present process is ended.

When it is determined in step S302 that there is a damage, the process proceeds to step S303, and the inspector determines whether or not the detected damage exists in the vicinity of the dead zone of the inspection method performed in step S301.

If the detected damage is not present in the vicinity of the dead zone, the process proceeds to step S306, which will be described later. If the detected damage is present in the vicinity of the dead zone, the process proceeds to step S304, and the inspector takes the above-described dead zone reduction measures. The insensitive area reduction measure is presented to the inspector in step S2 of selecting the inspection method and adding the measurement items.

As described above, when the dead zone reduction measure is implemented, for example, the outer surface is inspected and the height of the welded portion is removed. In addition, when taking measures for reducing the dead zone, the outer surface inspection and the flaw detection inspection in the board thickness interior of the evaluation target portion may be performed after removing the pile height of the welded portion.

As described above, in the inspection method of the plant facility according to some embodiments, step S304 is a step of performing an inspection based on the inspection method of inspecting the outer surface of the evaluation target site or performing an inspection based on the inside of the evaluation target site after deleting the stack height of the welded portion at the evaluation target site when the inside of the evaluation target site is inspected and the damage is detected in the inside of the outer surface side of the evaluation target site within a predetermined distance from the dead zone of the inspection method. Therefore, the influence of the dead zone of the inspection method can be suppressed.

After the dead zone reduction measure is implemented in step S304, the inspector determines whether or not the damage existing in the vicinity of the dead zone in the sheet thickness is continuous with the damage of the outer surface in step S305.

If it is determined in step S305 that the flaw present in the vicinity of the dead zone in the plate thickness does not continue with the flaw on the outer surface, the inspector obtains the magnitude of the flaw in the plate thickness from the result of the flaw detection in step S301 without considering the flaw on the outer surface in step S306.

If it is determined in step S305 that the flaw present in the vicinity of the dead zone in the plate thickness is continuous with the flaw on the outer surface, the inspector obtains the magnitude of the flaw in the plate thickness from the result of the flaw detection in step S301, including the flaw on the outer surface, in step S309.

In step S307, the inspector determines whether or not it is necessary to improve the accuracy of the remaining life evaluation when the remaining life evaluation is performed in step S4 in which the evaluation of the remaining life of the evaluation target site is performed based on the magnitude of the damage acquired in step S306 or step S309. Specifically, it is determined whether or not it is necessary to improve the accuracy of the remaining lifetime evaluation with reference to the magnitude of the damage acquired in step S306 and the simple determination coordinate graph shown in fig. 5.

Fig. 5 is a graph in which the horizontal axis represents stress acting on the evaluation target portion and the vertical axis represents the ratio of the size of damage to the thickness of the sheet at the maintenance target portion. Straight lines L1 to L7 in the graph of fig. 5 indicate the case where the remaining life until the detected damage penetrates the evaluation target site is 20000 hours. The difference between the straight lines L1 to L7 is the temperature difference at each part to be maintained, and the temperature at the part to be maintained is higher as it gets closer to the left side in fig. 5. That is, the straight line L1 represents the case where the temperature is the highest, and the straight line L7 represents the case where the temperature is the lowest. The aforementioned 20000 hours is a time required for the next periodic inspection two years later, i.e., about 17000 hours plus a margin of about 3000 hours.

The inspector obtains the ratio of the size of the damage to the plate thickness of the part to be maintained from the size of the damage and the plate thickness of the part to be maintained acquired in step S306, and obtains the stress and temperature acting on the part to be evaluated during the operation of the plant equipment from, for example, the operating conditions of the plant equipment. Then, it was confirmed what position in the coordinate graph shown in fig. 5 the point corresponding to the obtained ratio and stress is and the positional relationship between any one of the straight lines L1 to L7 corresponding to the obtained temperature.

If the point corresponding to the obtained ratio and stress is in the region on the left side of any of the straight lines L1 to L7 corresponding to the obtained temperature and is far from the straight line to some extent, it can be determined that the residual life until the detected damage penetrates the evaluation target site exceeds 20000 hours. In this case, when the inspector performs the remaining life evaluation in step S4 of evaluating the remaining life of the part to be evaluated in step S307, the inspector determines that it is not necessary to improve the accuracy of the remaining life evaluation and ends the process in step S3 of inspecting the part to be evaluated.

Further, if the point corresponding to the obtained ratio and stress is in the region on the left side of any one of the straight lines L1 to L7 corresponding to the obtained temperature but is close to the straight line or is in the region on the straight line or on the right side of the straight line, it can be determined that the remaining life until the detected damage penetrates the evaluation target site may be less than 20000 hours. In this case, when the inspector performs the remaining life evaluation in step S4 of evaluating the remaining life of the part to be evaluated in step S307, the inspector determines that the accuracy of the remaining life evaluation needs to be improved, and proceeds to step S308.

In step S308, the inspector performs additional measurement of additional measurement items. As described above, the additional measurement items are presented to the inspector in step S2 of selecting the inspection method and the additional measurement items. After performing the additional measurement, the examiner terminates the process in step S3 of performing the examination of the evaluation target site.

As described above, in the method for inspecting plant equipment according to some embodiments, step S307 is a step of determining whether or not additional measurement is necessary based on the damage length obtained from the inspection result of the site to be evaluated. In the method for inspecting a plant according to some embodiments, since the step of determining whether additional measurement is necessary based on the damage length obtained from the inspection result of the portion to be evaluated is provided, it is possible to easily determine whether additional measurement is necessary based on the damage length. Further, if it is determined that additional measurement is not necessary, additional measurement is not required, and therefore, it is efficient.

In the method for inspecting plant equipment according to some embodiments, it is determined whether additional measurement is necessary based on the size of the damage acquired in step S306 and the simple determination coordinate diagram shown in fig. 5. That is, the threshold value of the damage length used for the necessity/unnecessity determination of the additional measurement is determined based on at least one of the temperature condition and the stress condition of the evaluation target site during the operation of the plant. Therefore, the threshold value of the damage length used for the necessity/unnecessity determination of the additional measurement reflects at least one of the temperature condition and the stress condition of the evaluation target portion during the operation of the plant, and therefore, the accuracy of the necessity/unnecessity of the additional measurement can be improved.

(2) In the case where the evaluation target site is a site where the largest damage is likely to occur on the outer surface

For example, when the evaluation target site is a site where the largest damage is likely to occur on the outer surface, the flowchart shown in fig. 6 is presented in step S2 in which the inspection method is selected and the measurement items are added.

Fig. 6 is a flowchart showing a flow of processing to be performed in step S3 for performing an examination of the evaluation target site when the evaluation target site is a site where the largest damage is likely to occur on the outer surface. In step S3, in which the inspector performs the inspection of the evaluation target site, the inspection of the evaluation target site is performed according to the flowchart shown in fig. 6, and whether or not to measure the additional measurement item is determined, and additional measurement is performed as needed.

In step S321, the inspector performs an inspection of the outer surface of the evaluation target portion to detect damage of the outer surface.

In step S321, the flaw detection inspection of the outer surface is performed by any one of the magnetic particle inspection, the penetrant inspection, the inspection by the MT transfer method, the eddy current inspection, and the like. As described above, each of the inspection methods is presented to the inspector in step S2 in which the inspection method is selected and the measurement item is added.

Next, in step S322, the inspector determines whether or not there is damage on the outer surface based on the result of the inspection performed in step S321. If it is determined in step S322 that there is no damage, the process proceeds to step S326, which will be described later.

When it is determined in step S322 that there is a flaw, the process proceeds to step S323, and the inspector performs a flaw detection inspection on the inside of the evaluation target site near the outer surface in order to inspect how far the flaw on the outer surface has spread to the inside of the evaluation target site. In step S323, the inspector performs the flaw detection inspection of the inside of the evaluation target portion in the vicinity of the outer surface by any one of the ultrasonic inspection by the conventional UT method, the ultrasonic inspection by the TOFD method, the ultrasonic inspection by the phased array method, the ultrasonic inspection by the aperture synthesis method, the ultrasonic inspection by the high-frequency UT method, the ultrasonic inspection by the ultrasonic noise method, and the like. Each of the inspection methods is presented to the inspector in step S2 in which the inspection method is selected and the measurement items are added.

In step S324, the inspector acquires the depth (size) of the flaw appearing on the outer surface based on the inspection result of the flaw detection performed in step S323, and the process proceeds to step S307. The processing in step S307 and step S308 in fig. 6 is the same as the processing in step S307 and step S308 in fig. 4, and therefore, the description thereof is omitted.

In step S326, if there is no duplicate of the part to be evaluated, the examiner ends the process in step S3 of performing the examination of the part to be evaluated, and if there is a duplicate of the part to be evaluated, the process proceeds to step S327.

In step S327, the inspector performs a nondestructive inspection (NED) based on the replica of the portion to be evaluated, and calculates a local life consumption rate of the outer surface. In step S327, the inspector calculates the local lifetime consumption rate of the outer surface based on any one of the inspection methods such as the void number density method, the void area ratio method, the texture contrast method, the precipitate inter-granular distance method, the a parameter method, the crystal grain deformation method, the void grain boundary length method, and the carbide composition measurement method. Each of the inspection methods is presented to the inspector in step S2 in which the inspection method is selected and the measurement items are added.

In step S328, the inspector determines whether or not the local life consumption rate of the outer surface calculated in step S327 exceeds a predetermined value. Here, when the time at which the visually observable crack occurs is 100%, the predetermined value is, for example, 90%, but the predetermined value is not limited to 90%.

When the local life consumption rate of the outer surface calculated in step S327 exceeds 90%, the process proceeds to step S323, and the inspector performs the process of step S323 described above.

When the local life consumption rate of the outer surface calculated in step S327 is 90% or less, the inspector terminates the process of step S3 in which the evaluation target site is inspected.

As described above, the method for inspecting plant equipment according to some embodiments includes step S327 of inspecting the outer surface of the evaluation target portion and calculating the local life consumption rate, which is 100% of the time when the crack that can be visually observed occurs. Further, the method for inspecting plant equipment according to some embodiments includes step S323 of performing an inspection based on an inspection method for inspecting the inside of the evaluation target site when the calculated life consumption rate exceeds a predetermined value. Therefore, it is possible to examine how far the damage has progressed from the outer surface to the inner surface of the evaluation target portion.

(3) In the case where the evaluation target portion is a portion where the largest damage is likely to occur in the portion around the inner surface slit

For example, when the evaluation target site is a site where the largest damage is likely to occur in the vicinity of the inner surface slit, the flowchart shown in fig. 7 is presented in step S2 in which the inspection method is selected and the measurement items are added.

Fig. 7 is a flowchart showing a flow of processing to be performed in step S3 for inspecting the evaluation target site when the evaluation target site is a site where the largest damage is likely to occur in the vicinity of the inner surface slit. In step S3, in which the inspector performs the inspection of the evaluation target site, the inspection of the evaluation target site is performed according to the flowchart shown in fig. 7, and whether or not to measure the additional measurement item is determined, and additional measurement is performed as needed.

In step S341, the inspector performs an inspection of the portion around the inner surface slit at the evaluation target portion to detect the position and size of the damage of the portion around the inner surface slit.

In step S341, flaw detection of the portion around the inner surface slit is performed by any one of an ultrasonic inspection method such as an ultrasonic inspection by the conventional UT method, an ultrasonic inspection by the TOFD method, an ultrasonic inspection by the phased array method, an ultrasonic inspection by the aperture synthesis method, an ultrasonic inspection by the high-frequency UT method, and an ultrasonic inspection by the ultrasonic noise method. As described above, each of the inspection methods is presented to the inspector in step S2 in which the inspection method is selected and the measurement item is added.

Next, in step S342, the inspector determines whether or not there is no damage in the portion around the inner surface slit based on the result of the flaw detection performed in step S341. When it is determined in step S342 that there is no damage, the present process is ended.

When it is determined in step S342 that there is a flaw, the process proceeds to step S343, and the inspector obtains the size of the flaw in the portion around the inner surface slit from the result of the flaw detection in step S341 and proceeds to step S307. The processing in step S307 and step S308 in fig. 7 is the same as the processing in step S307 and step S308 in fig. 4, and therefore, the description thereof is omitted.

As described above, in the inspection method for plant equipment according to some embodiments, if the site to be maintained is, for example, a thick vertical welded portion in a straight pipe or an elbow of a pipe, the largest damage is likely to occur in the plate thickness of the vertical welded portion. Therefore, as described in (1) above, the inspector performs the flaw detection inspection of the evaluation target portion by the inspection method suitable for the flaw detection inspection in the sheet thickness interior, determines whether to measure the additional measurement item, and performs the additional measurement as needed, according to the flowchart shown in fig. 4.

That is, the inspection method set for the vertical welded portion having a thickness exceeding the predetermined value is an inspection method for inspecting the inside of the vertical welded portion as the evaluation target portion. Therefore, the inspection method is suitable for a longitudinal weld portion having a wall thickness exceeding a prescribed value.

In the inspection method for plant equipment according to some embodiments, when the site to be maintained is a vertical welded portion having a thickness exceeding a predetermined value, an inspection method suitable for flaw detection inspection in the inside of the plate thickness is selected, and therefore, the measurement items to be additionally measured are selected to include the pipe cross-sectional shape of the pipe, that is, the shape of the cross section of the pipe when viewed from the pipe axial direction. Therefore, the measurement items suitable for the vertical welded portion having a thickness exceeding the predetermined value can be selected.

In the method for inspecting plant equipment according to some embodiments, for example, if the site to be maintained is a thick cylindrical welded portion, the outer surface of the cylindrical welded portion is likely to be damaged most. Therefore, as described in (2) above, the inspector performs the flaw detection of the evaluation target site by the inspection method suitable for the flaw detection of the outer surface according to the flowchart shown in fig. 6, determines whether or not to measure the additional measurement item, and performs the additional measurement as needed.

That is, the inspection method set for the circumferential weld portion having a thickness exceeding the predetermined value is an inspection method for inspecting the outer surface of the circumferential weld portion as the evaluation target portion. Therefore, the inspection method is suitable for circumferential welds having a wall thickness exceeding a prescribed value.

In the method for inspecting plant equipment according to some embodiments, when the site to be maintained is, for example, a thin-walled cylindrical welded portion, the largest damage is likely to occur in the plate thickness of the cylindrical welded portion. Therefore, as described in (1) above, the inspector performs the flaw detection inspection of the evaluation target portion by the inspection method suitable for the flaw detection inspection in the sheet thickness interior, determines whether to measure the additional measurement item, and performs the additional measurement as needed, according to the flowchart shown in fig. 4.

That is, the inspection method set for the circumferential welded portion having a thickness equal to or less than a predetermined value is an inspection method for inspecting the inside of the circumferential welded portion as the evaluation target portion. Therefore, the inspection method is suitable for circumferential welds having a thickness of a predetermined value or less.

In the method for inspecting a plant facility according to some embodiments, when the site to be maintained is, for example, the socket welded portion, the maximum damage is likely to occur in the outer surface and the inner surface of the socket welded portion around the slit. Therefore, the inspector performs the flaw detection inspection of the evaluation target site by the inspection method suitable for the flaw detection inspection of the outer surface with respect to the flaw generated on the outer surface according to the flowchart shown in fig. 6 as described in (2) above, determines whether or not to measure the additional measurement item, and performs the additional measurement as necessary. As described in (3) above, the inspector performs the flaw detection of the portion to be evaluated by the inspection method suitable for the flaw detection of the portion around the inner surface slit in accordance with the flowchart shown in fig. 7 with respect to the flaw generated around the inner surface slit, determines whether or not to measure the additional measurement item, and performs the additional measurement as needed.

That is, the inspection method set for the socket welded portion is an inspection method for inspecting the outer surface and the inner slit peripheral portion of the socket welded portion as the evaluation target portion. Therefore, the inspection method is suitable for the socket weld.

(regarding flaw detector used for ultrasonic inspection by phased array method)

Fig. 9 is a schematic diagram showing the structure of a flaw detector used when ultrasonic inspection by the phased array method is performed in step S3 in which an evaluation target portion is inspected.

The flaw detector 50 shown in fig. 9 includes a transmitting element 51 including a plurality of piezoelectric elements, a receiving element 53 including at least one piezoelectric element and different from the transmitting element 51, and a wedge member 55 in one case 57. In the flaw detector 50 shown in fig. 9, the transmission element 51 is disposed on one surface 55b of two

surfaces

55b and 55c of the wedge-shaped member 55 adjacent to each other with the ridge line 55a interposed therebetween, such that the arrangement direction ad of the plurality of piezoelectric elements is the same as the extending direction of the ridge line 55a, and the reception element 52 is disposed on the other surface 55 c.

As a result of diligent research, the inventors have found that when ultrasonic testing is performed by the phased array method, a region closer to the surface layer of the test object and a region farther from the surface layer can be inspected by one flaw detector 50 by arranging the transmission element 51 and the reception element 52 as separate elements in one wedge-shaped member 55 as described above. As a result of diligent research, the inventors have found that by configuring the flaw detector 50 as described above, the dead zone in the vicinity of the surface layer of the inspection target can be suppressed, and the noise level in the vicinity of the surface layer of the inspection target can be suppressed.

Therefore, according to the flaw detector 50 shown in fig. 9, a region relatively close to the surface layer of the inspection object and a region relatively far from the surface layer can be inspected by one flaw detector 50. Further, according to the flaw detector 50 shown in fig. 9, it is possible to obtain an inspection result in which the dead zone in the vicinity of the surface layer of the inspection object and the noise level in the vicinity of the surface layer of the inspection object are suppressed.

Fig. 10 is a view for explaining a refraction angle in the flaw detector 50 shown in fig. 9.

As shown in fig. 10, the flaw detector 50 shown in fig. 9 is configured such that the scanning range of the refraction angle θ includes at least a range of 35 degrees or more and 75 degrees or less.

The scanning range of the refraction angle by the conventional phased array method is generally about 40 degrees or more and 70 degrees or less. Therefore, according to the flaw detector 50 shown in fig. 9, a wider range can be inspected.

The flaw detector 50 shown in fig. 9 is configured to be able to perform ultrasonic flaw detection by the phased array method using ultrasonic waves having a frequency of 10MHz to 15 MHz.

In ultrasonic flaw detection, generally, the shorter the wavelength of the ultrasonic wave used for flaw detection, that is, the higher the frequency, the smaller the size of the flaw which is a detection limit.

In a conventional ultrasonic flaw detection by a phased array method, the frequency of ultrasonic waves is usually about 5 MHz. Therefore, according to the flaw detector 50 shown in fig. 9, since the ultrasonic inspection is performed using the ultrasonic waves having the higher frequency than the conventional ultrasonic inspection by the phased array method, a smaller crack can be detected.

(details of step S5 for repairing the evaluation target site)

Details of step S5 for repairing the evaluation target site will be described. In the following description, a case where the crack 41 is generated in the region 19 will be described.

In the case where it is found that the crack 41 is generated in the region 19 in the pipe 5 shown in fig. 8, it is conceivable that the life of the pipe 5 is extended by performing the repair.

(repairing method of one embodiment)

Fig. 11 is a flowchart showing the procedure of the process performed in step S5 of repairing the evaluation target site when the crack 41 has occurred in the region 19 in the pipe 5 shown in fig. 8.

The repair method according to an embodiment of the processing procedure shown in fig. 11 includes: step S51 of removing the stem 20, step S53 of forming the recess, step S55 of disposing the sealing plate 60 in the stem hole 13, and step S57 of backfilling.

(step S51 of removing socket 20)

The step S51 of removing the socket 20 is a step of removing the socket 20 from the mother tube 10. Fig. 12 is a sectional view of the pipe 5 after the socket 20 is removed from the mother pipe 10 in step S51 of removing the socket 20. In step S51 of removing the socket 20, the socket 20 is removed from the mother tube 10.

(step S53 of Forming concave portion)

Step S53 of forming the recessed portion is a step of forming the recessed portion 71 by removing the region 11a to which the stem 20 has been attached from the mother pipe 10, leaving the region 10c on the inner peripheral surface 10a side of the mother pipe 10. Fig. 13 is a sectional view of the pipe 5 with the recess 71 formed. Fig. 14 is a schematic view of the pipe 5 having the recess 71 formed thereon, as viewed from the outside in the radial direction of the mother pipe 10, that is, as viewed from the direction of the axis AXb of the stem 20.

In step S53 of forming the recess, when viewed from the axis AXb direction of the socket 20, the recess 71 is formed by removing a region larger than the diameter of the socket hole 13 except for a region 10c of a part of the female pipe 10 on the inner peripheral surface 10a side. When the recess 71 is formed, the region 19 where the crack 41 is generated is removed as much as possible. As will be described later, a region 10c on the inner peripheral surface 10a side of the mother pipe 10 is reserved as a joint of the weld metal when the recess 71 is filled back and forth by welding in step S57 of back filling.

Fig. 15 is a view showing an example of a case where the recess 71 is provided when the plurality of sockets 20 are arranged in a state of being close to each other along the axis AXa direction of the mother pipe 10, and is a schematic view of the pipe 5 in which the recess 71 is formed, as viewed from the outside in the radial direction of the mother pipe 10.

As shown in fig. 15, when the plurality of sockets 20 are arranged in a state of being close to each other along the axis AXa direction of the mother pipe 10, the recess 71 may have a long hole shape along the axis AXa direction of the mother pipe 10. That is, after removing the plurality of sockets 20 that approach along the axis AXa direction of the mother pipe 10, each region 11a to which the plurality of sockets 20 are once attached may be removed from the mother pipe 10, thereby forming one recess 71.

In the case where the plurality of sockets 20 are arranged in a state of being close to each other along the axis AXa of the mother pipe 10 as in the case shown in fig. 15, the plurality of socket holes 13 may be connected to each other to form a long hole when the recess 71 is formed. In this case, in step S55 of disposing the seal plate 60 in the stem hole 13, the seal plate 60 formed so as to close the long hole may be disposed.

(step S55 of disposing sealing plate 60 in socket hole 13)

Step S55 of disposing the sealing plate 60 in the stem hole 13 is a step of disposing the sealing plate 60 in the stem hole 13 formed in the partial region 10c described above.

Fig. 16 is a diagram for explaining step S55 of disposing the sealing plate 60 in the stem hole 13. As shown in fig. 16, in step S55 of disposing the seal plate 60 in the stem hole 13, the small diameter portion 61 of the seal plate 60 having the small diameter portion 61 smaller than the inner diameter of the stem hole 13 and the large diameter portion 63 larger than the inner diameter of the stem hole 13 is fitted to the stem hole 13 when the seal plate 60 is disposed. That is, in some embodiments, the seal plate 60 has a shape in which a large diameter portion 63 having a plate shape larger than the inner diameter of the stem hole 13 and a small diameter portion 61 having a plate shape smaller than the inner diameter of the stem hole 13 overlap each other in the plate thickness direction. Therefore, when the seal plate 60 is disposed in the socket hole 13, the large diameter portion 63 abuts against the area around the socket hole 13, and the seal plate 60 can be prevented from accidentally entering the interior of the mother pipe 10 from the socket hole 13. Further, when the seal plate 60 is disposed in the stem hole 13, the small diameter portion 61 can be fitted in the stem hole 13, and thus the disposed seal plate 60 can be prevented from being accidentally displaced from the stem hole 13.

By closing the socket hole 13 with the seal plate 60 having such a shape, it is possible to suppress the welding metal from accidentally entering the interior of the mother pipe 10 from the socket hole 13 when the recess 71 is filled back and forth by welding in step S57 of back filling, as will be described later.

(step of backfilling S57)

The step S57 of backfilling is a step of backfilling the recess 71 by welding after the step S55 of disposing the sealing plate 60 in the stem hole 13.

Fig. 17 is a sectional view of the pipe 5 after the back filling step S57 is performed. In the backfilling step S57, the recess 71 is backfilled with the weld metal 73.

Thus, according to the repairing method of the procedure shown in fig. 11, when the crack 41 is generated in the region 19 shifted from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the parent pipe 10 in the direction of the axis AXa of the parent pipe 10, the repair can be performed appropriately.

(repairing method according to other embodiment)

When the crack 41 generated in the region 19 is relatively small, the evaluation target portion can be repaired by the following repair method.

Fig. 18 is a flowchart showing the procedure of the process performed in step S5 of repairing the evaluation target site when a relatively small crack 41 is generated in the region 19 in the pipe 5 shown in fig. 8.

The repairing method according to another embodiment of the process sequence shown in fig. 18 includes step S151 of arranging the reinforcing plate and step S153 of welding the reinforcing plate to the mother pipe. That is, the repairing method of another embodiment showing the procedure of the process in fig. 18 is a repairing method of reinforcing the mother pipe 10 by attaching a reinforcing plate to the outer circumferential surface 10d of the mother pipe 10.

(step S151 of disposing reinforcing plate)

The reinforcing plate disposing step S151 is a step of disposing the reinforcing plate 80 so as to surround the periphery of the stem 20 from the radially outer side of the stem 20 at the connecting portion 7 connected to the stem 20 in the mother tube 10.

Fig. 19 is a perspective view of the reinforcing plate 80. The reinforcing plate 80 of one embodiment is a thick plate member formed along the outer peripheral surface 10d of the mother pipe 10. In the reinforcing plate 80 of the embodiment, a hole 83 penetrating in the plate thickness direction is formed so as to surround the circumference of the stem 20 from the outside in the radial direction. Therefore, the inner diameter of the hole 83 is larger than the outer shape of the stem 20. The reinforcing plate 80 of one embodiment includes two dividing plates 81 divided into two parts in the radial direction of the hole 83.

In step S151 of arranging the reinforcing plates, the split plate 81 as one of the reinforcing plates 80 split into two parts and the split plate 81 as the other part are arranged so as to face each other along the axis AXa direction of the mother tube 10 with the stem 20 interposed therebetween.

Fig. 20 is a schematic view of a state in which two split plates 8 are arranged so as to face each other in the direction of the axis AXa of the mother pipe 10 with the stem 20 interposed therebetween, as viewed from the outside of the mother pipe 10 in the radial direction, that is, along the axis AXb of the stem 20.

As described above, the crack 41 generated in the region 19 is generated by the circumferential stress acting on the parent pipe 10. Therefore, when one split plate 81 and the other split plate 81 of the reinforcing plate 80 split into two parts are arranged to face each other in the direction of the axis AXa of the mother pipe 10 with the stem 20 interposed therebetween, the split plates 81 extend in the circumferential direction of the mother pipe 10. Therefore, by welding the split plates 81 to the mother pipe 10, the stress acting on the mother pipe 10 in the circumferential direction can be effectively reduced by the split plates 81. Further, by using the reinforcing plate 80 divided into two parts, even when the other end of the both ends of the stem 20 opposite to the one end connected to the mother pipe 10 is connected to another pipe or the like, the respective divided plates 81 can be easily arranged.

In addition, if the other end of the opposite ends of the stem 20 to the one end connected to the mother tube 10 is not connected to another pipe or the like, the reinforcing plate 80 that is not divided into two parts can be used.

(step S153 of welding the reinforcing plate to the mother pipe)

The step S153 of welding the reinforcing plates to the mother pipe is a step of welding the reinforcing plates 80 arranged in the step S151 of arranging the reinforcing plates to the mother pipe 10.

Fig. 21 is a sectional view of the pipe 5 after the reinforcing plate 80 is welded to the mother pipe 10 in step S153 of welding the reinforcing plate to the mother pipe. In step S153 of welding the reinforcing plate to the female pipe, the reinforcing plate 80 may be welded not only to the female pipe 10 but also to the stem 20. That is, in the example shown in fig. 21, the reinforcing plate 80 is welded to the mother pipe 10 by a weld portion 85, for example, and is welded to the stem 20 by a weld portion 86, for example.

When the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 is welded and attached to the mother pipe 10 as described above, and thereby the reinforcing plate 80 can reduce the circumferential stress applied to the mother pipe 10. This reduces the rate of progress of the crack 41, thereby extending the life. Further, since the repair can be performed by a relatively simple method such as welding the reinforcing plate 80, the time and cost required for the repair can be reduced.

The present invention is not limited to the above-described embodiments, and includes a mode in which the above-described embodiments are modified and a mode in which these modes are appropriately combined.

For example, in the above-described embodiments, the evaluation target portion is the welded portion of the steam pipes of a plurality of systems connecting the boiler and the steam turbine in the thermal power generation plant, but the welded portion to be evaluated is not limited to a part of the boiler, and the inspection method of the plant of the present invention can be applied to various welded portions exposed to high temperature and high pressure and portions other than the welded portion.

The contents described in the above embodiments are grasped as follows, for example.

(1) The method for inspecting a plant facility according to at least one embodiment of the present disclosure is a method for inspecting a plant facility including a socket (for example, the socket 20 according to some embodiments) and a main pipe (for example, the main pipe 10 according to some embodiments) having a socket hole (for example, the socket hole 13 according to some embodiments) formed therein, to which the socket 20 is attached.

The inspection method includes a step of selecting an inspection site from one or more inspection candidate sites (for example, step S1 of selecting an evaluation target site according to some embodiments), the one or more inspection candidate sites including a region 19 that is offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the parent pipe 10 in the direction of the axis AXa of the parent pipe 10.

The inspection method further includes a step of performing a flaw detection inspection on the inspection site (for example, step S3 of performing an inspection of the evaluation target site according to some embodiments).

As a result of diligent research, the inventors have found that in the pipe 5 including the socket 20 and the mother pipe 10 having the socket hole 13 formed therein, in which the socket 20 is to be mounted, a crack 41 may be generated in the region 19 that is displaced from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the mother pipe 10 in the direction of the axis AXa of the mother pipe 10.

Therefore, according to the method of the above (1), since the step S1 of selecting the evaluation target site and the step S3 of performing the inspection of the evaluation target site are provided, the presence of the crack 41 generated in the region 19 can be confirmed even in a limited inspection period. Therefore, the plant equipment can be efficiently inspected.

(2) In some embodiments, in addition to the method of the above (1), in step S1 of selecting an evaluation target site, when an index indicating the relative thickness of the plate thickness T (for example, the plate thickness/outer diameter ratio (T/D) of the mother pipe in some embodiments) including the outer diameter D and the plate thickness T of the mother pipe 10 as parameters is equal to or less than a predetermined value (for example, the predetermined value Th in some embodiments), the region 19 is selected as an inspection site.

As described above, the inventors have earnestly studied and, as a result, have found that: if an index indicating the relative thickness of the plate thickness T is equal to or less than a predetermined value, including the outer diameter D and the plate thickness T of the mother pipe 10 as parameters, a crack 41 is likely to be generated in the region 19.

Therefore, according to the method (2), since the region 19 is selected as the inspection site when the index (for example, the mother pipe thickness-to-outer diameter ratio (T/D) in some embodiments) is equal to or less than a predetermined value (for example, the predetermined value Th in some embodiments), the region 19 can be selected as the inspection site when the crack 41 is easily generated in the region 19, and the plant equipment can be efficiently inspected.

(3) In some embodiments, in addition to the method of the above (2), in step S3 of performing the inspection of the evaluation target site, the ultrasonic flaw detection inspection can be performed on the inspection site.

According to the method of the above (3), the region can be inspected by an inspection method suitable for detecting the crack 41 in the region 19.

(4) In some embodiments, in the method of the above (2), in step S1 of selecting the evaluation target site, if the index (for example, the mother pipe plate thickness/outer diameter ratio (T/D) of some embodiments) exceeds the predetermined value (for example, the predetermined value Th of some embodiments), the welded portion (for example, the stem welded portion 30 of some embodiments) connecting the mother pipe 10 and the stem 20 is selected as the inspection site.

The inventors have earnestly studied and found that: if the index (for example, the mother pipe thickness-to-outer diameter ratio (T/D) of some embodiments) exceeds the predetermined value (for example, the predetermined value Th of some embodiments), the crack 41 is more likely to be generated in the welded portion (for example, the stem welded portion 30 of some embodiments) connecting the mother pipe 10 and the stem 20 than in the region 19.

Therefore, according to the method of the above (4), since the welded portion (the socket welded portion 30) connecting the parent pipe 10 and the socket 20 is selected as the inspection portion when the index exceeds the predetermined value, the welded portion (the socket welded portion 30) can be selected as the inspection portion when the crack 41 is easily generated in the welded portion (the socket welded portion 30), and the plant equipment can be efficiently inspected.

(5) In some embodiments, in addition to the method of any one of the above (1) to (4), the mother pipe 10 is formed of high chromium steel.

The method (5) is suitable for inspecting a pipe made of high-chromium steel (for example, the pipe 5 according to some embodiments).

(6) In some embodiments, the method of any one of the above (1) to (5) further includes a step S51 of removing the stem 20 and a step S53 of forming the recess. In some embodiments, the method of any one of (1) to (5) further includes step S55 of disposing the sealing plate 60 in the stem hole 13 and step S57 of backfilling.

According to the method of the above (6), when the crack 41 is generated in the region 19 shifted from the inner wall surface 15 of the socket hole 13 toward the inside of the base material 11 of the mother pipe 10 in the direction of the axis AXa of the mother pipe 10, the repair can be appropriately performed.

(7) In some embodiments, in addition to the method (6), in step S55 of disposing the seal plate 60 in the stem hole 13, the small diameter portion 61 of the seal plate 60 having the small diameter portion 61 smaller than the inner diameter of the stem hole 13 and the large diameter portion 63 larger than the inner diameter of the stem hole 13 is fitted to the stem hole 13 when disposing the seal plate (for example, the seal plate 60 of some embodiments).

According to the method of the above (7), when the seal plate 60 is disposed in the socket hole 13, the large diameter portion 63 abuts on the area around the socket hole 13, and the seal plate 60 can be prevented from accidentally entering the interior of the mother pipe 10 from the socket hole 13. Further, when the seal plate 60 is disposed in the stem hole 13, the small diameter portion 61 can be fitted in the stem hole 13, and thus the disposed seal plate 60 can be prevented from being accidentally displaced from the stem hole 13.

(8) In some embodiments, the method of any one of (1) to (5) further includes a step S151 of arranging the reinforcing plate and a step S153 of welding the reinforcing plate to the mother pipe.

When the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 can reduce the circumferential stress acting on the mother pipe 10 by welding and attaching the reinforcing plate 80 to the mother pipe as in the method (8). This reduces the rate of progress of the crack 41, thereby extending the life. Further, since the repair can be performed by a relatively simple method such as the method (8), the time and cost required for the repair can be reduced.

(9) In some embodiments, in addition to the method of the above (8), in the step S151 of arranging the reinforcing plates, the split plate 81 as one part and the split plate 81 as the other part of the reinforcing plates 80 split into two parts are arranged so as to face each other in the direction of the axis AXa of the mother pipe 10 with the stem 20 interposed therebetween.

As described above, the inventors have earnestly studied and found that the crack 41 generated in the region 19 is generated by the circumferential stress acting on the parent pipe 10.

Therefore, when the two split plates 81 are arranged to face each other along the axis AXa direction of the mother pipe 10 with the stem 20 interposed therebetween as in the method (9), the split plates 81 extend in the circumferential direction of the mother pipe 10. Therefore, by welding and attaching the split plates 81 to the mother pipe 10, the stress acting on the mother pipe 10 in the circumferential direction can be effectively reduced by the split plates 81. Further, according to the method of the above (9), even when the other end of the both ends of the stem 20 opposite to the one end connected to the mother tube 10 is connected to another pipe or the like, the reinforcing plate 80 can be easily disposed.

(10) In some embodiments, in addition to the method of any one of the above (1) to (9), in the step of performing the ultrasonic flaw detection inspection (for example, step S3 of performing the inspection of the evaluation target site of some embodiments), the ultrasonic flaw detection inspection by the phased array method is performed using the flaw detector 50, in which the flaw detector 50 includes the transmission element 51 including a plurality of piezoelectric elements, the reception element 53 including at least one piezoelectric element and being different from the transmission element 51, and the wedge member 55 in one case 57, the transmission element 51 is disposed on one surface 55b of two

surfaces

55b, 55c adjacent to each other with the ridge line 55a interposed therebetween in the wedge member 55 such that the arrangement direction of the plurality of piezoelectric elements is the same as the extending direction of the ridge line 55a, and the reception element 53 is disposed on the other surface 55 c.

As described above, the inventors have earnestly studied and found that, when ultrasonic testing by the phased array method is performed, by arranging the transmission element 51 and the reception element 53 as separate elements in the single wedge-shaped member 55 as described above, a region relatively close to the surface layer of the test object and a region relatively far from the surface layer can be inspected by the single flaw detector 50. As a result of diligent research, the inventors have found that by configuring the flaw detector 50 as described above, the dead zone in the vicinity of the surface layer of the inspection target can be suppressed, and the noise level in the vicinity of the surface layer of the inspection target can be suppressed.

Therefore, according to the method of the above (10), the region relatively close to the surface layer of the inspection object and the region relatively far from the surface layer can be inspected by one flaw detector 50. Further, according to the method of the above (10), the dead zone in the vicinity of the surface layer of the inspection object and the inspection result in which the noise level in the vicinity of the surface layer of the inspection object is suppressed can be obtained.

(11) In some embodiments, in addition to any of the methods (1) to (10) described above, in the step of performing an ultrasonic flaw detection test (for example, in step S3 of performing a test of a part to be evaluated in some embodiments), an ultrasonic flaw detection test by a phased array method is performed using the flaw detector 50 in which the scanning range of the refraction angle at least includes a range of 35 degrees or more and 75 degrees or less.

The scanning range of the refraction angle by the conventional phased array method is usually about 40 degrees or more and 70 degrees or less. Therefore, according to the method of (11) above, a wider range can be examined.

(12) In some embodiments, in addition to any of the methods (1) to (11) described above, in the step of performing an ultrasonic flaw detection test (for example, in step S3 of performing a test of a part to be evaluated in some embodiments), an ultrasonic flaw detection test by a phased array method is performed using ultrasonic waves having a frequency of 10MHz or more and 15MHz or less.

In ultrasonic flaw detection, generally, the shorter the wavelength, that is, the higher the frequency of the ultrasonic wave used for flaw detection, the smaller the size of the flaw as a detection limit.

In a conventional ultrasonic flaw detection by a phased array method, the frequency of ultrasonic waves is usually about 5 MHz. Therefore, according to the method of (12), since the inspection is performed using ultrasonic waves having a higher frequency than that of the conventional ultrasonic flaw detection by the phased array method, a smaller crack can be detected.

(13) A method for repairing a plant facility according to at least one embodiment of the present disclosure is a method for repairing a plant facility including a socket (for example, the socket 20 according to some embodiments) and a mother pipe (for example, the mother pipe 10 according to some embodiments) to which the socket is attached.

The repairing method includes a step S51 of removing the stem 20 and a step S53 of forming the recess.

The repairing method further includes a step S55 of disposing the sealing plate 60 in the stem hole 13 and a step S57 of refilling.

According to the method of (13), when the crack 41 is generated in the region 19, the repair can be appropriately performed.

(14) A method for repairing a plant facility according to at least one embodiment of the present disclosure is a method for repairing a plant facility including a socket (for example, the socket 20 according to some embodiments) and a mother pipe (for example, the mother pipe 10 according to some embodiments) to which the socket is attached.

The repairing method includes a step S151 of arranging a reinforcing plate and a step S153 of welding the reinforcing plate to the mother pipe.

As described above, when the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 can reduce the circumferential stress acting on the mother pipe 10 by welding and attaching the reinforcing plate 80 to the mother pipe 10 as in the method (14). This reduces the rate of progress of the crack 41, thereby extending the life. Further, since the repair can be performed by a relatively simple method such as the method (14), the time and cost required for the repair can be reduced.

Description of the reference numerals

1 storage device

2 terminal device

2a display part

3 arithmetic device

4 input device

5 piping

7 connecting part

10 female pipe

11 base material

13 socket hole

19 region

20 tube holder

30-tube seat welding part

50 flaw detector

51 transmitting element

53 receiving element

55 wedge-shaped component

57 casing

60 sealing plate

61 minor diameter portion

63 major diameter part

71 concave part

80 reinforcing plate

And (81) dividing the plate.

Claims

1. A method of inspecting a plant equipment including a socket and a female pipe formed with a socket hole for fitting the socket,

the method for inspecting the plant equipment comprises the following steps:

selecting an inspection site from one or more inspection candidate sites including a region that is offset from an inner wall surface of the socket hole toward an inside of a parent material of the parent pipe in an axial direction of the parent pipe; and

and performing flaw detection on the inspection part.

2. The method of inspecting a plant according to claim 1,

the step of selecting the inspection portion includes an outer diameter and a plate thickness of the mother pipe as parameters, and the region is selected as the inspection portion when an index indicating a relative thickness of the plate thickness is equal to or less than a predetermined value.

3. The method of inspecting a plant according to claim 2,

in the step of performing the flaw detection, an ultrasonic flaw detection is performed on the inspection site.

4. The method of inspecting a plant according to claim 2,

in the step of selecting the inspection portion, if the index exceeds the predetermined value, a welded portion connecting the parent pipe and the stem is selected as the inspection portion.

5. The method for inspecting a plant according to any one of claims 1 to 4,

the parent tube is formed from high chromium steel.

6. The method for inspecting a plant according to any one of claims 1 to 5,

the method for inspecting plant equipment further includes the steps of:

removing the tube seat from the mother tube;

disposing a sealing plate in the stem hole formed in the partial region; and

a step of backfilling the recess by welding after the step of disposing the sealing plate.

7. The method of inspecting a plant according to claim 6,

in the step of disposing the seal plate, the small diameter portion of the seal plate having a small diameter portion smaller than an inner diameter of the socket hole and a large diameter portion larger than the inner diameter of the socket hole is fitted to the socket hole when the seal plate is disposed.

8. The method for inspecting a plant according to any one of claims 1 to 5,

the method for inspecting plant equipment further includes the steps of:

disposing a reinforcing plate at a connecting portion of the female pipe to the stem so as to surround a periphery of the stem from a radially outer side of the stem; and

a step of welding the reinforcing plate configured in the step of configuring the reinforcing plate to the mother pipe.

9. The method of inspecting a plant according to claim 8,

in the step of disposing the reinforcing plate, one and the other of the reinforcing plates divided into two parts are disposed so as to face each other along the axial direction of the female pipe with the stem interposed therebetween.

10. The method for inspecting a plant according to any one of claims 1 to 9,

in the step of performing the ultrasonic testing, the ultrasonic testing by the phased array method is performed using a flaw detector including a transmission element including a plurality of piezoelectric elements, a reception element including a piezoelectric element and being different from the transmission element, and a wedge member in one case, wherein the transmission element is disposed on one of two faces adjacent to each other with a ridge line interposed therebetween such that an arrangement direction of the plurality of piezoelectric elements is the same as an extension direction of the ridge line, and the reception element is disposed on the other face.

11. The method for inspecting a plant according to any one of claims 1 to 10,

in the step of performing the ultrasonic testing, ultrasonic testing by a phased array method is performed using a flaw detector in which a scanning range of a refraction angle includes at least a range of 35 degrees or more and 75 degrees or less.

12. The method for inspecting a plant according to any one of claims 1 to 11,

in the step of performing the ultrasonic flaw detection, ultrasonic flaw detection by a phased array method is performed using ultrasonic waves having a frequency of 10MHz to 15MHz inclusive.

13. A method for repairing a plant equipment including a socket and a mother pipe on which the socket is mounted,

the method for repairing the factory equipment comprises the following steps:

removing a tube seat arranged on the main tube;

14. A method for repairing a plant equipment including a socket and a mother pipe on which the socket is mounted,

the method for repairing the factory equipment comprises the following steps: