[0001]The present disclosure relates to a plant inspection method and a plant repair method.
Background technology
[0002]
　In boiler pipes that are used for a long time in a high temperature and high pressure environment, for example, cracks occur due to creep damage in welded parts such as pipes. Since cracks due to creep damage grow, it is necessary to evaluate the remaining life according to the presence or absence of cracks and the length of the crack in the thickness direction of the weld (crack height), and repair the weld in a timely manner. be. Therefore, a technique for evaluating the remaining life by measuring the presence or absence of cracks in the weld and the length of the cracks is being developed.
　For example, in the method for evaluating the remaining life disclosed in Patent Document 1, the inside of the welded portion is detected by ultrasonic flaw detection by the phased array method, and the remaining life is evaluated based on the flaw detection result (see Patent Document 1).
Prior art literature
Patent documents
[0003]
Patent Document 1: Japanese Unexamined Patent Publication No. 2017-151107
Outline of the invention
Problems to be solved by the invention
[0004]
　As described above, for example, in boiler piping, it has been known that cracks are likely to occur due to creep damage in welded parts such as pipes to each other. Therefore, for example, boiler piping is mainly maintained and managed by welded parts. I came.
　By the way, recently, it has become clear that cracks may occur not in the welded part but in the base material of the pipe. However, in relatively large-scale plants such as power plants and chemical plants, the number of pipes used is large. Therefore, when the inspection period is limited, such as periodic inspections performed by stopping the operation of the plant, it is difficult to inspect all the base metal parts of the pipes.
[0005]
　In view of the above circumstances, at least one embodiment of the present disclosure is intended to provide an efficient inspection method for a plant.
Means to solve problems
[0006]
(1) The plant inspection method according to at least one embodiment of the present disclosure is a plant inspection method including a
　pipe base and a mother pipe having a pipe base hole to which the pipe base is attached, and the pipe base hole
　. A step of selecting an inspection site from one or more inspection candidate sites including a region displaced from the inner wall surface of the mother tube to the inside of the base material of the mother tube in the axial direction of the mother tube, and a
　step of performing a flaw detection inspection on the inspection site. And
.
[0007]
(2) The method for repairing a plant according to at least one embodiment of the present disclosure is a method for
　repairing a plant including a pipe base and a
　mother pipe to which the pipe base is attached, and removes the pipe base attached to the mother pipe. A step of
　removing the area to which the tube stand was attached from the mother tube to form a recess, and a part of the area, leaving a part of the area on the inner peripheral surface side of the mother tube
　. In, a step of arranging a seal plate in a tube base hole communicating the internal space of the mother pipe and the outside of the mother pipe, a step of
　arranging the seal plate, and then a step of backfilling the recess by welding.
To prepare for.
Effect of the invention
[0008]
　According to at least one embodiment of the present disclosure, the plant can be inspected efficiently.
A brief description of the drawing
[0009]
[Fig. 1] Fig. 1 is a diagram showing each process in a plant inspection method according to some embodiments.
[Fig. 2] Fig. 2 is a table showing the relationship between a portion where a welded portion is present, the thickness of the portion, and a location where cracks are likely to occur.
FIG. 3 is a diagram showing a storage device that stores a database and a terminal device that accesses the storage device.
FIG. 4 is a flowchart showing a flow of processing to be performed in step S3 for inspecting an evaluation target portion.
[Fig. 5] The horizontal axis is the stress acting on the evaluation target site, and the vertical axis is the ratio of the size of the flaw to the plate thickness at the maintenance target site.
FIG. 6 is a flowchart showing a flow of processing to be performed in step S3 for inspecting an evaluation target portion.
FIG. 7 is a flowchart showing a flow of processing to be performed in step S3 for inspecting an evaluation target portion.
FIG. 8 is a cross-sectional view of a pipe including a pipe base and a mother pipe having a pipe base hole to which the pipe base is attached.
[Fig. 9] Fig. 9 is a schematic diagram showing the structure of a flaw detector used when performing ultrasonic inspection by the phased array method in the step of inspecting the evaluation target site.
10 is a diagram for explaining a refraction angle in the flaw detector shown in FIG. 9. FIG.
FIG. 11 is a flowchart showing a procedure of processing performed in a step of repairing an evaluation target portion in the piping shown in FIG. 8.
FIG. 12 is a cross-sectional view of a pipe after removing the pipe base from the mother pipe in the step of removing the pipe base.
FIG. 13 is a cross-sectional view of a pipe in which a recess is formed.
[Fig. 14] Fig. 14 is a view of a pipe having a recess formed from the radial outside of the mother pipe.
[Fig. 15] Fig. 15 is a diagram showing an example of a case where a recess is provided when a plurality of pipe bases are arranged in a state of being close to each other along the axial direction of the mother pipe.
[Fig. 16] Fig. 16 is a diagram for explaining a step of arranging a seal plate in a tube base hole.
[Fig. 17] Fig. 17 is a cross-sectional view of a pipe after performing a backfilling step.
FIG. 18 is a flowchart showing a procedure of processing performed in a step of repairing an evaluation target portion in the piping shown in FIG. 8.
FIG. 19 is a perspective view of a reinforcing plate.
FIG. 20 is a view of a state in which two dividing plates are arranged as viewed from the radial outside of the mother tube.
FIG. 21 is a cross-sectional view of a pipe 5 after the reinforcing plate is welded to the mother pipe in the step of welding the reinforcing plate to the mother pipe.
Embodiment for carrying out the invention
[0010]
　Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure to this, and are merely explanatory examples. do not have.
　For example, expressions that represent relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" are exact. Not only does it represent such an arrangement, but it also represents a tolerance or a state of relative displacement at an angle or distance to the extent that the same function can be obtained.
　For example, expressions such as "same", "equal", and "homogeneous" that indicate that things are in the same state not only represent exactly the same state, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
　For example, an expression representing a shape such as a square shape or a cylindrical shape not only represents a shape such as a square shape or a cylindrical shape in a geometrically strict sense, but also an uneven portion or a chamfering within a range where the same effect can be obtained. It shall also represent the shape including the part and the like.
　On the other hand, the expressions "to have", "to have", "to have", "to include", or "to have" one component are not exclusive expressions that exclude the existence of other components.
[0011]
(Overview of Plant Inspection Method)
　First, with reference to FIG. 1, an outline of a plant inspection method according to some embodiments will be described.
　FIG. 1 is a diagram showing each step in the plant inspection method according to some embodiments. The plant inspection methods according to some embodiments include step S1 for selecting the evaluation target site, step S2 for selecting the inspection method and additional measurement items, step S3 for inspecting the evaluation target site, and evaluation target site. Includes step S4 for evaluating the remaining life of the above. The plant inspection method according to some embodiments may include step S5 for repairing the evaluation target portion.
　The plant inspection method according to some embodiments is an inspection method applied to the inspection of metal members used for a long time in an environment where a large temperature is applied and a large stress is applied, for example, with a boiler in a thermal power generation facility. It is applied to the inspection of welded parts such as steam pipes connecting to the steam turbine and the inspection of base materials such as pipes.
　Hereinafter, the outline of each step in the plant inspection method according to some embodiments will be described.
[0012]
(Outline of step S1 for selecting the
　evaluation target part) In step S1 for selecting the evaluation target part, a flaw detection inspection is performed and the remaining life is evaluated based on the results of the flaw detection inspection from among a plurality of steam pipes and the like existing in the plant. This is the step of selecting the evaluation target site. That is, the step S1 for selecting the evaluation target site according to some embodiments is a step of selecting the test site from one or more test candidate sites.
[0013]
　FIG. 8 is a cross-sectional view of a pipe including a pipe base and a mother pipe having a pipe base hole to which the pipe base is attached. In FIG. 8, the connection portion 7 between the mother pipe 10 and the pipe base 20 is represented by a cross section along the axis AXa of the mother pipe 10 and the axis AXb direction of the pipe base 20. The pipe 5 shown in FIG. 8 includes a mother pipe 10 and a pipe base 20 connected to the mother pipe 10 by welding. The mother pipe 10 is formed with a pipe base hole 13 to which the pipe base 20 is attached. The tube base hole 13 includes a hole portion 13a that communicates between the hole portion 23 extending in the axis AXb direction of the tube base 20 and the inside of the mother tube 10 in the tube base 20, as well as the mother tube 10 and the tube base 20. It shall include the wall surface that is the boundary with the branch pipe, plug, cylinder, etc.
[0014]
　In the pipe 5 shown in FIG. 8, the pipe base 20 is attached to the mother pipe 10 by being welded by the pipe base welded portion 30. In the pipe 5 shown in FIG. 8, the pedestal welded portion 30 includes a weld metal 31 and a heat-affected zone (HAZ portion) 33 due to welding.
[0015]
　As a result of diligent studies by the inventors, in the pipe 5 including the pipe base 20 and the mother pipe 10 in which the pipe base hole 13 to which the pipe base 20 is attached is formed, the inner wall surface 15 of the pipe base hole 13 to the mother pipe 10 It has been found that a crack 41 may occur in a region 19 displaced inside the base material 11 of the mother pipe 10 in the axis AXa direction. In FIG. 8, the region 19 is, for example, a region surrounded by a broken line. Further, in FIG. 8, the crack 41 is a hatched region that intersects in the region 19.
[0016]
　The mechanism by which such a crack 41 is generated will be briefly described. In a pipe having a thick cylindrical shape and a relatively high internal pressure, such as a pipe in a boiler, the circumferential stress is generally maximum in the innermost region of the pipe base in the radial direction. Become. That is, in the case of the pipe 5 shown in FIG. 8, the circumferential stress is generally maximum on the inner peripheral surface 10a of the mother pipe 10.
　In general, when a through hole that communicates the inside and the outside of the pipe is opened on the side surface of the pipe, the circumferential stress generated by the internal pressure of the pipe is the circumferential direction of the pipe among the wall surfaces forming the through hole. Maximum at the center position along. That is, in the case of the pipe 5 shown in FIG. 8, it is generally the maximum at the center position of the inner wall surface 15 of the pipe base hole 13 along the circumferential direction of the mother pipe 10.
[0017]
　However, as a result of diligent studies by the inventors, pipes used in high temperature and high pressure environments, especially pipes made of high chrome steel, such as pipes in boilers, are deformed by creep due to the internal pressure of the pipes. It was found that the position where the generated circumferential stress is maximum tends to move from the above-mentioned position.
　Specifically, in a pipe used in a high temperature and high pressure environment such as a pipe in a boiler, the position where the circumferential stress generated by the internal pressure of the pipe due to the deformation due to creep is maximized is in the base material of the pipe. It was found to move to a position outside the radial direction from the innermost region in the radial direction. Further, in a pipe used in a high temperature and high pressure environment such as a pipe in a boiler, the position where the circumferential stress generated by the internal pressure of the pipe due to the deformation due to creep is maximized is located on the side surface of the pipe and inside the pipe. It was found that when the through hole communicating with the outside was opened, the wall surface forming the through hole moved to a region shifted to the inside of the base material of the pipe in the axial direction of the pipe.
　That is, in the case of the pipe 5 shown in FIG. 8, the position where the circumferential stress generated by the internal pressure of the pipe 5 due to the deformation due to creep is maximized is inside the base material 11 of the mother pipe 10 in the axis AXa direction of the mother pipe 10. It turned out to move to the area 19 shifted to.
[0018]
　Therefore, in the plant inspection method according to some embodiments, the above-mentioned region 19 is included as an inspection candidate site.
　The details of step S1 for selecting the evaluation target site according to some embodiments will be described later.
[0019]
(Outline of step S2 for selecting the
　inspection method and additional measurement items) Step S2 for selecting the inspection method and additional measurement items is the inspection method and addition of the flaw detection inspection for the evaluation target site selected in step S1 for selecting the evaluation target site. This is the step of selecting the measurement items for measurement.
　In step S2 for selecting the inspection method and additional measurement items, an appropriate flaw detection inspection inspection method is selected for the evaluation target site selected in step S1 for selecting the evaluation target site.
　Here, the inspection method and the inspection method selected in step S2 for selecting additional measurement items include at least one of the circumferential welded portion or the longitudinal welded portion of the pipe, or the pedestal welded portion, as will be described later. It is an inspection method set for each combination of the type of the evaluation target part and the thickness of the evaluation target part. Further, as described later, the inspection method and the inspection method selected in step S2 for selecting additional measurement items evaluate the pipe base and the pipe including the master pipe having the pipe base hole to which the pipe base is attached. It is an inspection method set for each combination of the type of the target part and the index including the outer diameter of the mother tube and the plate thickness of the mother tube as parameters.
　The welded portion includes a weld metal, a heat-affected zone (HAZ portion) due to welding, and an inner surface slit described later.
[0020]
　Further, in step S2 for selecting an inspection method and additional measurement items, measurement items for additional measurement appropriate for the selected inspection method are selected.
　Here, the additional measurement is a measurement performed to acquire the parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part, which is performed based on the inspection result of the evaluation target part by the selected inspection method. .. That is, in step S3 in which the evaluation target portion is inspected, which will be described later, the evaluation target portion is subjected to the flaw detection inspection by the selected inspection method, and the inspection result is obtained. Then, based on the obtained inspection result, the remaining life of the evaluation target site is evaluated in step S4 for evaluating the remaining life of the evaluation target site, which will be described later. When evaluating the remaining life of the evaluation target site, some parameters are required in addition to the inspection results of the flaw detection inspection. In the additional measurement, among these parameters, the parameters necessary for improving the accuracy of the remaining life evaluation are acquired.
　In the following description, the measurement item of the additional measurement is also simply referred to as the additional measurement item.
　The details of step S2 for selecting the inspection method and additional measurement items will be described later.
[0021]
(Outline of step S3 for
　inspecting the evaluation target part) In step S3 for inspecting the evaluation target part, the inspection method and additional measurement items are selected for the evaluation target part selected in step S1 for selecting the evaluation target part. This is a step of performing a flaw detection inspection by the inspection method selected in step S2. That is, the step S3 for inspecting the evaluation target portion is a step for performing a flaw detection inspection on the evaluation target portion selected in the step S1 for selecting the evaluation target portion.
　Further, in step S3 for inspecting the evaluation target portion, additional measurement is performed for the additional measurement items selected in step S2 for selecting the inspection method and additional measurement items, if necessary.
　The details of step S3 for inspecting the evaluation target site will be described later.
[0022]
(Outline of step S4 for evaluating
　the remaining life of the evaluation target part) Step S4 for evaluating the remaining life of the evaluation target part is based on the inspection result of the evaluation target part performed in step S3 for inspecting the evaluation target part. This is a step to evaluate the remaining life of the evaluation target site.
　In step S4 for evaluating the remaining life of the evaluation target part, if additional measurement is performed for the additional measurement item in step S3 for inspecting the evaluation target part, the parameter acquired by the additional measurement is also used for the evaluation target. Evaluate the remaining life of the part.
　For the evaluation of the remaining life, for example, crack growth calculation, FEM, damage mechanical evaluation, void simulation method, microstructure simulation method and the like can be used.
[0023]
(Outline of step S5 for
　repairing the evaluation target part) Step S5 for repairing the evaluation target part is the inspection result of the evaluation target part performed in step S3 for inspecting the evaluation target part, or the evaluation target part. This is a step of repairing the evaluation target part as necessary based on the result of the remaining life evaluation of the evaluation target part performed in step S4 of performing the remaining life evaluation.
　The details of step S5 for repairing the evaluation target portion will be described later.
[0024]
　As described above, in the plant inspection method according to some embodiments, the step S1 for selecting the evaluation target part, the step S2 for selecting the inspection method and additional measurement items, and the step S3 for inspecting the evaluation target part. To prepare for.
　That is, the plant inspection method according to some embodiments includes one or more regions 19 including a region 19 displaced from the inner wall surface 15 of the tube base hole 13 to the inside of the base material 11 of the mother pipe 10 in the axis AXa direction of the mother pipe 10. A step of selecting an inspection site from inspection candidate sites, that is, a step S1 of selecting an evaluation target site is provided. The plant inspection method according to some embodiments is the type of the evaluation target portion including at least one of the circumferential welded portion or the longitudinal welded portion of the pipe, or the pedestal welded portion, and the thickness of the evaluation target portion. A step of inspecting the evaluation target site, that is, a step S3 of inspecting the evaluation target site is provided by the inspection method set for each of the combinations of. In the inspection method of the plant according to some embodiments, the type of the evaluation target part, the outer diameter of the mother pipe, and the mother pipe are used for the pipe including the pipe base and the mother pipe having the pipe base hole to which the pipe base is attached. A step of inspecting the evaluation target portion, that is, a step S3 of inspecting the evaluation target portion is provided by the inspection method set for each of the combinations with the index including the plate thickness of the pipe as a parameter.
[0025]
　Therefore, according to the inspection method of the plant according to some embodiments, the evaluation target part is a step of selecting the evaluation target part and a step of performing a flaw detection inspection on the inspection part selected in the step S1. Since the inspection step S3 is provided, the presence of the crack 41 generated in the region 19 can be confirmed even for a limited inspection period. Therefore, the plant can be inspected efficiently.
[0026]
　Further, in the plant inspection method according to some embodiments, in order to acquire the parameters necessary for improving the accuracy of the inspection result of the evaluation target part by the above inspection method and the remaining life evaluation of the evaluation target part performed based on the inspection result. The step S2 for selecting the measurement item of the additional measurement, that is, the inspection method and the additional measurement item is provided. Therefore, according to the inspection method of the plant according to some embodiments, the inspection method of the evaluation target part becomes appropriate according to the combination of the type of the evaluation target part and the thickness of the evaluation target part, and the evaluation target part of the evaluation target part. The accuracy of inspection results is improved. Further, the measurement items of the additional measurement for improving the accuracy of the remaining life evaluation become appropriate according to the inspection method of the evaluation target site. As a result, the accuracy of the remaining life evaluation of the evaluation target site, which is performed based on the inspection result of the evaluation target site, is improved.
[0027]
(Details of Step S1 for Selecting an Evaluation Target Site) Details of step S1 for
　selecting an evaluation target site will be described. In the following description, as shown in FIG. 8, a case where the pipe is a pipe 5 including a mother pipe 10 to which the pipe base 20 is attached will be described.
　As described above, in the pipe 5 as shown in FIG. 8, a crack 41 is generated in the region 19 displaced from the inner wall surface 15 of the tube base hole 13 to the inside of the base material 11 of the mother pipe 10 in the axis AXa direction of the mother pipe 10. It turned out that there was a risk. It is also known that in the pipe 5 as shown in FIG. 8, cracks are likely to occur in the pipe base welded portion 30 as described later.
　Therefore, as a result of diligent studies by the inventors, in the pipe 5 as shown in FIG. 8, an index showing the relative thickness of the plate thickness T including the outer diameter D and the plate thickness T of the mother pipe 10 as parameters is defined. It was found that if it is equal to or less than the value, that is, if the plate thickness T of the mother pipe 10 is relatively thin, cracks are likely to occur in the above-mentioned region 19 prior to the pipe base welded portion 30. On the contrary, if the index exceeds the specified value, that is, if the plate thickness T of the mother pipe 10 is relatively thick, cracks are likely to occur in the pipe base welded portion 30 before the above-mentioned region 19. It has been found.
[0028]
　Therefore, in some embodiments, if the index is equal to or less than the specified value in step S1 for selecting the evaluation target site, the above-mentioned region 19 is selected as the inspection site (evaluation target site). Further, in some embodiments, if the index exceeds the above-mentioned specified value in step S1 for selecting the evaluation target portion, the pipe base welded portion 30 is selected as the inspection portion (evaluation target portion).
　Here, the index may be, for example, a mother tube thickness outer diameter ratio (T / D) obtained by dividing the plate thickness T of the mother tube 10 by the outer diameter D of the mother tube 10.
　That is, in some embodiments, if the mother tube plate thickness outer diameter ratio (T / D) is equal to or less than the specified value Th in step S1 for selecting the evaluation target site, the above-mentioned region 19 is the inspection site (evaluation target). Select as part). Further, in some embodiments, if the mother tube plate thickness outer diameter ratio (T / D) exceeds the specified value Th in step S1 for selecting the evaluation target portion, the tube base welded portion 30 is inspected (inspected portion). Select as the evaluation target site).
[0029]
　As the above index, the mother tube outer diameter plate thickness ratio (D /) obtained by dividing the outer diameter D of the mother tube 10, which is the inverse of the mother tube plate thickness outer diameter ratio (T / D), by the plate thickness T of the mother tube 10. When T) is adopted, if the mother tube outer diameter plate thickness ratio (D / T) is the specified value Th or more in step S1 for selecting the evaluation target site, the above-mentioned region 19 is the inspection site (evaluation target site). It may be selected as. Then, if the outer diameter plate thickness ratio (D / T) of the mother pipe is less than the specified value Th, the pipe base welded portion 30 may be selected as the inspection site (evaluation target site).
[0030]
　なお、上記規定値Ｔｈは、例えば接続されている管台２０の管の外径ｄ及び板厚ｔをパラメータとして含む指標の値等によって異なる値を取る。すなわち、幾つかの実施形態では、プラントにおいて複数存在する図８に示すような配管５のそれぞれについて、各々の管台２０との接続部７毎に上記規定値Ｔｈが存在する。
　幾つかの実施形態では、各々の管台２０との接続部７の位置や該接続部７毎に存在する上記規定値Ｔｈについての情報は、データベースとして記憶装置（図３参照）に予め格納されている。
　図３は、このデータベースを格納する記憶装置と、該記憶装置にアクセスする端末装置とを示す図である。上述したように、記憶装置１には、複数の配管５における各々の管台２０との接続部７の位置や該接続部７毎に存在する上記規定値Ｔｈ、母管１０の外径Ｄや板厚Ｔについての情報等がデータベースとして格納されている。
　また、後述するように、記憶装置１には、溶接部が存在する部位と、その部位の厚さと、最も大きな損傷が発生し易い場所との関係についての情報がデータベースとして格納されている。端末装置２は、例えばパーソナルコンピュータ等の端末装置であり、記憶装置１に格納されたデータベースの情報を記憶装置１から読み出して、端末装置２の操作者に提示することができる。なお、記憶装置１は、端末装置２と異なる場所に配置されていてもよく、端末装置２内に設けられていてもよい。端末装置２は、各種の演算処理を実行する演算装置３と、検査員や作業員などからの入力操作を受け付ける入力装置４と、演算装置３による演算結果などを表示するための表示部２ａとを有している。
[0031]
　幾つかの実施形態では、評価対象部位を選定するステップＳ１において、演算装置３は、評価対象部位を選定するように指示が入力装置４から入力されると、記憶装置１に格納されたデータベースの情報を記憶装置１から読み出して、評価対象部位を選定する。
　例えば、幾つかの実施形態では、評価対象部位を選定するステップＳ１において、演算装置３は、図８に示すような管台２０が接続されている配管５については、記憶装置１から上記規定値Ｔｈ、母管１０の外径Ｄや板厚Ｔについての情報を読み出す。そして、演算装置３は、読み出した情報に基づいて、母管板厚外径比（Ｔ／Ｄ）を算出する。そして、演算装置３は、算出した母管板厚外径比（Ｔ／Ｄ）と読み出した規定値Ｔｈとを比較する。
　母管板厚外径比（Ｔ／Ｄ）が規定値Ｔｈ以下であれば、演算装置３は、上述した領域１９を検査部位（評価対象部位）として選定する。また、母管板厚外径比（Ｔ／Ｄ）が規定値Ｔｈを超えていれば、演算装置３は、管台溶接部３０を検査部位（評価対象部位）として選定する。
[0032]
　なお、記憶装置１には、複数の配管５における母管板厚外径比（Ｔ／Ｄ）が予め格納されていてもよい。この場合、演算装置３は母管１０の外径Ｄや板厚Ｔの情報を読み出すことに代えて、記憶装置１から母管板厚外径比（Ｔ／Ｄ）を読み出してもよい。
[0033]
　演算装置３は、評価対象部位を選定した後、検査方法及び追加計測項目を選定するステップＳ２において、以下で述べる処理を実施する。
[0034]
（検査方法及び追加計測項目を選定するステップＳ２の詳細について）
　以下、検査方法及び追加計測項目を選定するステップＳ２の詳細について説明する。
　例えば、火力発電設備におけるボイラと蒸気タービンとの間を接続する蒸気配管には、複数の種類の溶接個所が存在する。例えば、蒸気配管には、配管同士を接続する円周溶接部や、配管と分岐管とを接続する管台溶接部が存在する。また、配管が板状部材から製造されている場合には、板の端部同士を接続するために管軸方向に延在する長手溶接部が存在する。
　溶接部が存在する部位が異なると、亀裂が生じ易い場所が異なることが発明者らの知見によって分かってきた。また、同種類の溶接部であっても、その部位の厚さによって亀裂が生じ易い場所が異なることが発明者らの知見によって分かってきた。
[0035]
　図２は、発明者らが鋭意検討した結果判明した、溶接部が存在する部位と、その部位の厚さと、亀裂が生じ易い場所との関係を示す表である。
　同種類の溶接部であっても、おおよそ厚さ２０ｍｍを境にして亀裂が生じ易い場所が異なることが発明者らの知見によって分かった。図２に示した表において、薄肉とは、厚さが２０ｍｍ以下であることを表し、厚肉とは、厚さが２０ｍｍを超えていることを示している。以下の説明においても同様である。
[0036]
　例えば配管の直管における長手溶接部において、厚肉の部分では、長手溶接部の板厚内部に亀裂が生じ易く、最も大きな損傷が発生し易い。なぜなら、溶接による熱影響部（ＨＡＺ部）のクリープ速度が母材や溶接金属のそれより早いことで、ＨＡＺ部における板厚内部の応力の多軸度が大きくなるためである。
　例えば配管のエルボにおける長手溶接部において、厚肉の部分では、長手溶接部の板厚内部に亀裂が生じ易く、最も大きな損傷が発生し易い。その理由は、上述の直管における長手溶接部と同じである。
[0037]
　例えば配管の円周溶接部において、厚肉の部分では、円周溶接部の外表面に亀裂が生じ易く、最も大きな損傷が発生し易い。なぜなら、配管システム応力、すなわち、例えば配管の支持構造物や接続されている他の配管等から受ける外力等に起因する応力や、自身の熱膨張が拘束されることで生じる熱応力等の影響で溶接部に作用する曲げ応力の最大位置が外表面であるためである。また、例えば配管の円周溶接部において、薄肉の部分では、円周溶接部の板厚内部に亀裂が生じ易く、最も大きな損傷が発生し易い。その理由として、薄肉の部分も厚肉と同様に配管システム応力の影響を受けるが、板厚が小さいため板厚方向における曲げ応力の分布は小さく、上述したクリープ速度差に起因する多軸度の影響の方が大きいためである。
[0038]
　例えば図８に示すような配管５の場合、上述したように、母管板厚外径比（Ｔ／Ｄ）が規定値Ｔｈ以下であれば、上述した領域１９に亀裂が発生し易い。逆に、母管板厚外径比（Ｔ／Ｄ）が規定値Ｔｈを超えていれば、管台溶接部３０に亀裂が生じ易い。
[0039]
　例えば管台溶接部３０では、薄肉の部分及び厚肉の部分の双方とも、管台溶接部３０の外表面及び内面スリット周辺部位に亀裂が生じ易く、最も大きな損傷が発生し易い。外表面で損傷が発生し易い理由は、配管のフープ応力（周方向応力）が外表面で最大となるためである。一方、内面スリット周辺部位でも損傷が発生し易い理由は、スリットのような亀裂状の先端部では応力集中が起こるためである。なお、管台溶接部３０の内面スリットとは、配管（母管１０）と管台２０（分岐管やプラグ、筒等）との境目であって、溶接の際に溶接金属の溶け込みが不十分で、該境目がスリットとして残った部分のことである。
　なお、現在のプラントの多くでは、高温高圧の環境下で使用される薄肉の直管及び薄肉のエルボに電縫管を用いることがほとんどないため、薄肉の直管及び薄肉のエルボにおける長手溶接部については、説明を省略する。
[0040]
　このような、溶接部が存在する部位と、その部位の厚さと、最も大きな損傷が発生し易い場所との関係についての情報は、図３に示した記憶装置１に予めにデータベースとして格納されている。
　上述したように、記憶装置１には、溶接部が存在する部位と、その部位の厚さと、最も大きな損傷が発生し易い場所との関係についての情報がデータベースとして格納されている。
[0041]
（板厚内部の探傷検査に適した検査方法）
　例えば板厚内部の探傷検査に適した検査方法として、コンベンショナルＵＴ法による超音波検査、ＴＯＦＤ法による超音波検査、フェーズドアレイ法による超音波検査、開口合成法による超音波検査、高周波ＵＴ法による超音波検査、超音波ノイズ法による超音波検査等を挙げることができる。
　また、これら板厚内部の探傷検査に適した検査方法による検査結果に基づいて行われる評価対象部位の余寿命評価の精度向上に必要なパラメータは、例えば、評価対象部位に係る寸法、形状、温度、材料特性である。
[0042]
　評価対象部位に係る寸法や形状を取得するための追加計測の計測項目は、例えば、配管の外径、配管の板厚、配管の扁平率、溶接線を長手方向から見たときの断面の形状、溶接による熱影響部（ＨＡＺ部）の形状を挙げることができる。評価対象部位に係る寸法や形状を取得することで、余寿命評価の際に溶接部に作用している応力を精度よく算定できる。特に配管の外径、扁平率、断面の形状は、長手溶接部で重要となる円周方向に作用している応力（曲げ、引っ張り）を精度よく算定する際に有効な計測項目となる。
　評価対象部位に係る温度を取得するための追加計測の計測項目は、例えば、水蒸気酸化スケールの形成状態や、析出物の形成状態、評価対象部位の組織変化を挙げることができ、これらの計測結果から評価対象部位に係る温度を推定することができる。この場合の温度とは、過去の温度履歴や、過去に作用した最高温度のことを指す。評価対象部位に係る温度を取得することで、余寿命評価の際に温度条件を精度よく設定できる。
　評価対象部位に係る材料特性を取得するための追加計測の計測項目は、例えば、評価対象部位の硬さを挙げることができる。また、評価対象部位から少量のサンプルを採取し、このサンプルに対してクリープ試験等を実施することで評価対象部位に係る材料特性を取得してもよい。評価対象部位に係る材料特性を取得することで、余寿命評価の際に溶接部の強度を精度よく設定できる。
[0043]
　なお、上述した記憶装置１には、板厚内部の探傷検査に適した検査方法として上述した各検査方法がデータベースとして格納されている。また、上述した記憶装置１には、板厚内部の探傷検査に適した検査方法と紐づけられて上記の追加計測項目がデータベースとして格納されている。さらに、上述した記憶装置１には、上記の追加計測項目を計測するか否かの判断を行うための処理を含む、評価対象部位の検査を行うステップＳ３で実施すべき処理の流れの情報がデータベースとして格納されている。なお、該処理の流れについては、後で説明する。
[0044]
　なお、上述した超音波検査では、評価対象部位のうち表面近傍（例えば表面から数ｍｍ）の範囲は不感帯となるため、探傷ができない。そこで、例えば板厚内部の探傷検査の結果、板厚内部のきずが不感帯の近傍に存在すると判断される場合には、評価対象部位の検査を行うステップＳ３において、不感帯の影響を低減するための不感帯低減策を行うこととしている。
[0045]
　不感帯低減策として、例えば外表面を検査することが挙げられる。外表面の検査方法としては、例えば、磁粉探傷検査、浸透探傷検査、ＭＴ転写法による検査、渦電流探傷検査等がある。これらの検査によって外表面のきずの存在が確認できれば、板厚内部で不感帯の近傍に存在するきずが、外表面のきずと連続していると判断することができ、外表面のきずの存在が確認できなければ、板厚内部で不感帯の近傍に存在するきずが、少なくとも外表面には達していないと判断できる。
[0046]
　Further, as a measure for reducing the dead zone, the surplus of the welded portion may be removed. By removing the excess of the welded part, it becomes easier to perform magnetic particle inspection. Further, by removing the surplus of the welded portion, the flaw detector of the ultrasonic flaw detector can be brought into contact with the surface after the surplus of the welded portion is removed, and the flaw detection range can be expanded. Further, by removing the surplus of the welded portion, visually observable scratches may appear on the surface after the surplus of the welded portion is removed. Further, by removing the surplus of the welded portion, it is possible to remove the flaws existing only in the vicinity of the surface of the surplus.
　In the storage device 1 described above, a dead zone reduction measure associated with an inspection method suitable for a flaw detection inspection inside the plate thickness is stored as a database.
[0047]
(Inspection method suitable for flaw detection inspection of
　outer surface) For example, as an inspection method suitable for flaw detection inspection of outer surface, magnetic particle flaw detection inspection, penetrant inspection, inspection by MT transfer method, eddy current flaw detection inspection and the like can be mentioned.
　The parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part, which is performed based on the inspection results by the inspection method suitable for the flaw detection inspection of the outer surface, are, for example, the dimensions, shape, temperature, and material characteristics of the evaluation target part. Is.
[0048]
　Measurement items for additional measurement to acquire the dimensions and shape of the part to be evaluated, measurement items for additional measurement to acquire the temperature for the part to be evaluated, and material properties for the part to be evaluated. The measurement items of the additional measurement are as described above.
[0049]
　As will be described later, when the outer surface is most likely to be damaged, in addition to the above-mentioned flaw detection inspection by an inspection method suitable for the outer surface flaw detection inspection, for example, the local life consumption rate on the outer surface. In some cases, a non-destructive inspection is performed to obtain a local life consumption rate with the time point at which a visually observable crack occurs as 100%. As this non-destructive inspection method, a void number density method, a void area ratio method, a structure contrast method, a precipitate grain distance method, an A parameter method, a crystal grain deformation method, a void grain boundary length method, a carbide composition measuring method, etc. Non-destructive inspection methods can be mentioned.
　In addition, as will be described later, when the local life consumption rate on the outer surface obtained based on the inspection result of the non-destructive inspection exceeds a predetermined value, or when there are scratches on the outer surface. , The inside of the evaluation target site near the outer surface is inspected for flaw detection.
　As inspection methods suitable for flaw detection inspection of the inside of the evaluation target site near the outer surface, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the aperture synthesis method, Examples thereof include ultrasonic inspection by the high frequency UT method and ultrasonic inspection by the ultrasonic noise method.
[0050]
　In the storage device 1 described above, each inspection method described above is stored as a database as an inspection method suitable for flaw detection inspection of the outer surface. Further, in the storage device 1 described above, the additional measurement items described above are stored as a database in association with an inspection method suitable for flaw detection inspection of the outer surface. The above-mentioned storage device 1 stores the above-mentioned non-destructive inspection method as a database as a non-destructive inspection method for obtaining a local life consumption rate on the outer surface. In the storage device 1 described above, each of the inspection methods described above is stored as a database as an inspection method suitable for the flaw detection inspection inside the evaluation target portion near the outer surface. Further, the storage device 1 described above contains information on the flow of processing to be performed in step S3 for inspecting the evaluation target site, including processing for determining whether or not to measure the additional measurement items. It is stored as a database. The flow of the process will be described later.
[0051]
(Inspection method suitable for flaw detection inspection of the
　area around the inner surface slit) In the flaw detection inspection of the area around the inner surface slit, the inner surface slit exists in the flaw detection range from the beginning, but the existence range of the inner surface slit changes depending on the welding state. Therefore, it is difficult to distinguish between the inner slit and the flaw in the flaw detection inspection of the portion around the inner slit. Therefore, in the flaw detection inspection of the area around the inner surface slit, cracks that can be observed by visual observation such as microscopic cracks are targeted for detection, and all the detected cracks are visually observed like microscopic cracks without distinguishing them from the inner surface slits. It will be treated as an observable crack.
[0052]
　For example, as an inspection method suitable for flaw detection inspection of the area around the inner surface slit, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the aperture synthesis method, and high frequency UT method are used. Examples include ultrasonic inspection and ultrasonic inspection by the ultrasonic noise method.
　In addition, the parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part, which is performed based on the inspection result by the inspection method suitable for the flaw detection inspection of the part around the inner surface slit, are, for example, the dimensions and shape of the evaluation target part. Temperature and material properties.
[0053]
　The measurement items of the additional measurement for acquiring the dimensions and shape related to the evaluation target part are, for example, the shape of the heat-affected zone (HAZ part) due to welding, the surface shape of the weld metal, and the outside of the pipe (master pipe) in the pipe stand. The diameter, the wall thickness of the mother tube, etc. can be mentioned.
　The measurement items of the additional measurement for acquiring the temperature of the evaluation target part and the measurement items of the additional measurement for acquiring the material properties of the evaluation target part are as described above.
[0054]
　The above-mentioned storage device 1 stores each of the above-mentioned inspection methods as a database as an inspection method suitable for the flaw detection inspection of the portion around the inner surface slit. Further, in the above-mentioned storage device 1, the above-mentioned additional measurement items are stored as a database in association with an inspection method suitable for a flaw detection inspection of a portion around an inner surface slit. Further, the storage device 1 described above contains information on the flow of processing to be performed in step S3 for inspecting the evaluation target site, including processing for determining whether or not to measure the additional measurement items. It is stored as a database. The flow of the process will be described later.
[0055]
　In step S2 for selecting the inspection method and additional measurement items, the inspector operates the terminal device 2 to input the type of the evaluation target part and the thickness of the evaluation target part, and the terminal device 2 detects the damage of the evaluation target part. The inspection method suitable for the inspection and the additional measurement items for improving the accuracy of the remaining life evaluation of the evaluation target part performed based on the inspection result by the inspection method are read from the database of the storage device 1. Then, the terminal device 2 displays the read out inspection method and the additional measurement item on, for example, the display unit 2a of the terminal device 2.
　Further, the terminal device 2 reads information on the flow of processing to be performed in step S3 of inspecting the evaluation target portion from the database of the storage device 1. Then, the terminal device 2 displays, for example, information on the flow of processing to be performed in step S3, which is read out and inspects the evaluation target portion, on the display unit 2a of the terminal device 2.
　When the read inspection method is an inspection method suitable for flaw detection inspection of the outer surface, for example, the display unit 2a of the terminal device 2 has a non-destructive inspection method for obtaining a local life consumption rate and a non-destructive inspection method. An inspection method suitable for flaw detection inspection inside the evaluation target site near the outer surface is also displayed.
[0056]
　That is, in step S2 for selecting the inspection method and additional measurement items, each combination of the type of the evaluation target site and the thickness of the evaluation target site is inspected using a database that defines the inspection method and the additional measurement items. This is a step to select the method and measurement items.
　As described above, according to the plant inspection method according to some embodiments, the inspection method and the step S2 for selecting the additional measurement item are provided. Measurement items can be selected quickly.
[0057]
(Details of Step S3 for Inspecting the Evaluation Target Site) In step S3
　for inspecting the evaluation target site, a flaw detection inspection is performed on the evaluation target site as follows.
[0058]
(1) When the part to be evaluated is the part where the largest damage is likely to occur
　inside the plate thickness For example, when the part to be evaluated is the part where the largest damage is likely to occur inside the plate thickness, the inspection method and addition In step S2 for selecting the measurement item, the flowchart shown in FIG. 4 is presented.
　FIG. 4 is a flowchart showing a flow of processing to be performed in step S3 for inspecting the evaluation target portion when the evaluation target portion is a portion where the largest damage is likely to occur inside the plate thickness. In step S3 of inspecting the evaluation target site, the inspector performs a flaw detection inspection of the evaluation target site according to the flowchart shown in FIG. 4, determines whether or not to measure additional measurement items, and if necessary. And make additional measurements.
[0059]
　In step S301, the inspector performs a flaw detection inspection inside the plate thickness of the evaluation target portion to detect the position and size of the flaw inside the plate thickness.
　In step S301, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the aperture synthesis method, ultrasonic inspection by the high frequency UT method, and ultrasonic noise method. A flaw detection inspection inside the plate thickness is performed by one of the inspection methods such as ultrasonic inspection. As described above, each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
[0060]
　次いで、ステップＳ３０２において、検査員は、ステップＳ３０１で実施した探傷検査の結果から、内在きず、すなわち評価対象部位の板厚内部のきずの有無を判断する。ステップＳ３０２において、きずが存在しなかったと判断されると本処理を終了する。
　ステップＳ３０２において、きずが存在したと判断されるとステップＳ３０３へ進み、検査員は、検出されたきずがステップＳ３０１で実施した検査方法における不感帯の近傍に存在したか否かを判断する。
　検出されたきずが不感帯の近傍に存在していなければ、後述するステップＳ３０６へ進む。検出されたきずが不感帯の近傍に存在している場合、ステップＳ３０４へ進み、検査員は、上述した不感帯低減策を実施する。なお、不感帯低減策は、検査方法及び追加計測項目を選定するステップＳ２において検査員に提示されている。
　上述したように、不感帯低減策の実施にあたっては、例えば外表面の検査や溶接部分の余盛りの除去が行われる。また、不感帯低減策の実施にあたっては、溶接部分の余盛りの除去後に外表面検査や評価対象部位の板厚内部の探傷検査を実施してもよい。
[0061]
　このように、幾つかの実施形態に係るプラントの検査方法では、ステップＳ３０４は、評価対象部位の内部を検査して、評価対象部位の外表面側において検査方法の不感帯から所定距離内の内部にきずが検出された場合、評価対象部位の外表面を検査する検査方法による検査をさらに実施するか、又は、評価対象部位における溶接部の余盛りの削除を行った後、再び評価対象部位の内部を検査するステップである。したがって、検査方法に係る不感帯の影響を抑制できる。
[0062]
　ステップＳ３０４で不感帯低減策を実施した後、ステップＳ３０５において、検査員は、板厚内部で不感帯の近傍に存在するきずが、外表面のきずと連続しているか否かを判断する。
[0063]
　ステップＳ３０５で、板厚内部で不感帯の近傍に存在するきずが外表面のきずと連続していないと判断されれば、ステップＳ３０６において、検査員は、外表面の傷を考慮せずに板厚内部のきずの大きさをステップＳ３０１における探傷検査の結果から取得する。
　ステップＳ３０５で、板厚内部で不感帯の近傍に存在するきずが外表面のきずと連続していると判断されれば、ステップＳ３０９において、検査員は、外表面のきずを含めて板厚内部のきずの大きさをステップＳ３０１における探傷検査の結果から取得する。
[0064]
　In step S307, the inspector improves the accuracy of the remaining life evaluation when performing the remaining life evaluation in step S4, which evaluates the remaining life of the evaluation target site from the size of the flaw acquired in step S306 or step S309. Determine if it is necessary. Specifically, it is determined whether or not it is necessary to improve the accuracy of the remaining life evaluation by referring to the size of the flaw acquired in step S306 and the simple determination graph shown in FIG.
　In addition, FIG. 5 is a graph in which the stress acting on the evaluation target portion is taken on the horizontal axis, and the ratio between the size of the flaw and the plate thickness at the maintenance target portion is taken on the vertical axis. The straight lines L1 to L7 in the graph of FIG. 5 show a case where the remaining life until the detected flaw penetrates the evaluation target site is 20,000 hours. The difference between the straight lines L1 to L7 is the difference in temperature at the maintenance target site, and the temperature at the maintenance target site is higher toward the left side in FIG. That is, the straight line L1 is a straight line representing the case where the temperature is the highest, and the straight line L7 is a straight line representing the case where the temperature is the lowest. The above 20,000 hours is, for example, about 17,000 hours, which is the time until the next periodic inspection two years later, with a margin of about 3,000 hours.
[0065]
　The inspector obtains the ratio of the size of the flaw acquired in step S306, the plate thickness of the part to be maintained, and the size of the flaw to the plate thickness at the part to be maintained, and evaluates during the operation of the plant, for example, from the operation status of the plant. Find the stress and temperature acting on the target site. Then, it is confirmed which position in the graph shown in FIG. 5 the point corresponding to the obtained ratio and stress is, and the positional relationship with any of the straight lines L1 to L7 corresponding to the obtained temperature.
[0066]
　The point corresponding to the obtained ratio and stress is within the region on the left side of any of the straight lines L1 to L7 corresponding to the obtained temperature, and if it is separated from the straight line to some extent, the detected flaw penetrates the evaluation target site. It can be determined that the remaining life until the end is over 20,000 hours. In this case, in step S307, the inspector determines that it is not necessary to improve the accuracy of the remaining life evaluation when performing the remaining life evaluation in step S4 for evaluating the remaining life of the evaluation target site, and determines that it is not necessary to improve the accuracy of the remaining life evaluation. The process in step S3 for inspecting the above is completed.
[0067]
　Further, 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, but is close to the straight line, or is on the straight line or on the right side of the straight line. Within the region of, it can be determined that the remaining life until the detected flaw penetrates the evaluation target site may be less than 20,000 hours. In this case, in step S307, the inspector determines that it is necessary to improve the accuracy of the remaining life evaluation when performing the remaining life evaluation in step S4 for evaluating the remaining life of the evaluation target site, and proceeds to step S308. ..
[0068]
　In step S308, the inspector carries out additional measurement of the additional measurement item. As described above, the additional measurement items are presented to the inspector in step S2 for selecting the inspection method and the additional measurement items. After performing the additional measurement, the inspector ends the process in step S3 in which the evaluation target site is inspected.
[0069]
　As described above, in the plant inspection method according to some embodiments, step S307 is a step of determining the necessity of additional measurement based on the flaw length obtained from the inspection result of the evaluation target portion. Since the plant inspection method according to some embodiments includes a step of determining the necessity of additional measurement based on the flaw length obtained from the inspection result of the evaluation target site, the necessity of additional measurement is determined. It can be easily judged based on the length. Moreover, if it is determined that additional measurement is not necessary, it is not necessary to perform additional measurement, which is efficient.
[0070]
　Further, in the plant inspection method according to some embodiments, the necessity of additional measurement is determined based on the size of the flaw acquired in step S306 and the simple determination graph shown in FIG. That is, the threshold value of the flaw length used for determining the necessity of additional measurement is determined according to at least one of the temperature condition and the stress condition of the evaluation target portion during the operation of the plant. Therefore, since at least one of the temperature condition and the stress condition of the evaluation target part during the operation of the plant is reflected in the threshold value of the flaw length used for determining the necessity of the additional measurement, the accuracy of the necessity of the additional measurement can be improved.
[0071]
(2) When the evaluation target part is the part where the largest damage is likely to occur on the
　outer surface For example, when the evaluation target part is the part where the largest damage is likely to occur on the outer surface, the inspection method and additional measurement items In step S2 for selecting the above, the flowchart shown in FIG. 6 is presented.
　FIG. 6 is a flowchart showing a flow of processing to be performed in step S3 for inspecting the evaluation target portion when the evaluation target portion is a portion where the largest damage is likely to occur on the outer surface. In step S3 of inspecting the evaluation target site, the inspector performs a flaw detection inspection of the evaluation target site according to the flowchart shown in FIG. 6, determines whether or not to measure additional measurement items, and if necessary. And make additional measurements.
[0072]
　In step S321, the inspector inspects the outer surface of the evaluation target site and detects a flaw on the outer surface.
　In step S321, the outer surface flaw detection inspection is performed by any of the inspection methods such as magnetic particle flaw detection inspection, penetrant flaw detection inspection, inspection by MT transfer method, and eddy current flaw detection inspection. As described above, each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
[0073]
　Next, in step S322, the inspector determines the presence or absence of scratches on the outer surface from the results of the inspection performed in step S321. If it is determined in step S322 that no flaw is present, the process proceeds to step S326 described later.
　In step S322, if it is determined that a flaw is present, the process proceeds to step S323, and the inspector evaluates the vicinity of the outer surface in order to inspect to what extent the flaw on the outer surface extends to the inside of the evaluation target site. Inspect the inside of the target area for flaw detection. In step S323, the inspector performs ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the aperture synthesis method, ultrasonic inspection by the high frequency UT method, and ultrasonic noise. Among the ultrasonic inspections by the method, the inside of the evaluation target part near the outer surface is inspected by any inspection method. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
[0074]
　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 inspection carried out in step S323, and proceeds to step S307. Since the processing in step S307 and step S308 in FIG. 6 is the same as the processing in step S307 and step S308 shown in FIG. 4, the description thereof will be omitted.
[0075]
　In step S326, the inspector ends the process in step S3 for inspecting the evaluation target site if the replica of the evaluation target site does not exist, and proceeds to step S327 if the replica of the evaluation target site exists.
　In step S327, the inspector performs a non-destructive inspection (NED) based on the replica of the site to be evaluated to calculate the local lifetime consumption rate on the outer surface. In step S327, the inspector uses the void number density method, the void area ratio method, the structure contrast method, the precipitate grain distance method, the A parameter method, the crystal grain deformation method, the void grain boundary length method, and the carbide composition measurement. The local life consumption rate on the outer surface is calculated based on one of the inspection methods among the methods. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
[0076]
　In step S328, the inspector determines whether or not the local life consumption rate on the outer surface calculated in step S327 exceeds a predetermined value. Here, assuming that the time point at which a visually observable crack occurs is 100%, for example, 90% is adopted as the predetermined value, but the predetermined value is not limited to 90%.
　If the local life consumption rate on the outer surface calculated in step S327 exceeds 90%, the process proceeds to step S323, and the inspector carries out the process of step S323 described above.
　If the local life consumption rate on the outer surface calculated in step S327 is 90% or less, the inspector ends the process in step S3 for inspecting the evaluation target portion.
[0077]
　このように、幾つかの実施形態に係るプラントの検査方法では、評価対象部位の外表面を検査し、局部的な寿命消費率であって目視観察可能な亀裂が発生した時点を１００％とする局部的な寿命消費率を算出するステップＳ３２７を備える。また、幾つかの実施形態に係るプラントの検査方法では、算出した上記の寿命消費率が所定値を超えている場合には、評価対象部位の内部を検査する検査方法による検査を実施するステップＳ３２３を備える。したがって、評価対象部位の外表面から内部にかけてどの程度まできずが進展しているのかを検査できる。
[0078]
（３）評価対象部位が内面スリット周辺部位に最も大きな損傷が発生し易い部位であった場合
　例えば、評価対象部位が内面スリット周辺部位に最も大きな損傷が発生し易い部位であった場合、検査方法及び追加計測項目を選定するステップＳ２では、図７に示すフローチャートが提示される。
　図７は、評価対象部位が内面スリット周辺部位に最も大きな損傷が発生し易い部位である場合に、評価対象部位の検査を行うステップＳ３で実施すべき処理の流れを示すフローチャートである。検査員は、評価対象部位の検査を行うステップＳ３において、図７に示したフローチャートに従って、評価対象部位の探傷検査を実施し、追加計測項目を計測するか否かの判断を行い、必要に応じて追加計測を行う。
[0079]
　In step S341, the inspector inspects the portion around the inner surface slit in the evaluation target portion to detect the position and size of the flaw in the portion around the inner surface slit.
　In step S341, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the aperture synthesis method, ultrasonic inspection by the high frequency UT method, and ultrasonic noise method. A flaw detection inspection is performed on the area around the inner slit by any of the inspection methods such as ultrasonic inspection. As described above, each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
[0080] [0080]
　Next, in step S342, the inspector determines the presence or absence of a flaw in the portion around the inner surface slit from the result of the flaw detection inspection performed in step S341. If it is determined in step S342 that no scratches have existed, this process ends.
　If it is determined in step S342 that a flaw is present, the process proceeds to step S343, and the inspector acquires the size of the flaw in the portion around the inner surface slit from the result of the flaw detection inspection in step S341 and proceeds to step S307. Since the processing in step S307 and step S308 in FIG. 7 is the same as the processing in step S307 and step S308 shown in FIG. 4, the description thereof will be omitted.
[0081]
　As described above, in the plant inspection method according to some embodiments, if the maintenance target part is, for example, a straight pipe of a pipe or a thick longitudinal welded portion in an elbow, the largest portion is inside the plate thickness of the longitudinal welded portion. Prone to damage. Therefore, as explained in (1) above, the inspector carries out a flaw detection inspection of the evaluation target site by an inspection method suitable for a flaw detection inspection inside the plate thickness according to the flowchart shown in FIG. 4, and adds additional measurement items. Judge whether to measure or not, and make additional measurements as needed.
　That is, the inspection method set for the longitudinal welded portion having a wall thickness exceeding the specified value is an inspection method for inspecting the inside of the longitudinal welded portion as the evaluation target portion. Therefore, the inspection method is suitable for a longitudinal welded portion having a wall thickness exceeding a specified value.
　Further, in the plant inspection method according to some embodiments, if the maintenance target part is a longitudinal welded portion having a wall thickness exceeding a specified value, an inspection method suitable for flaw detection inspection inside the plate thickness is selected. Therefore, an item including the pipe cross-sectional shape of the pipe, that is, the cross-sectional shape when the pipe is viewed from the pipe axis direction is selected as the measurement item of the additional measurement. Therefore, a measurement item suitable for a longitudinal welded portion having a wall thickness exceeding a specified value is selected.
[0082]
　Further, in the plant inspection method according to some embodiments, if the maintenance target portion is, for example, a thick-walled cylindrical welded portion, the largest damage is likely to occur on the outer surface of the cylindrical welded portion. Therefore, as explained in (2) above, the inspector carries out a flaw detection inspection of the evaluation target site by an inspection method suitable for the flaw detection inspection of the outer surface according to the flowchart shown in FIG. 6, and measures additional measurement items. Determine whether or not to do so, and make additional measurements as needed.
　That is, the inspection method set for the circumferential welded portion having a wall thickness exceeding the specified value is an inspection method for inspecting the outer surface of the circumferential welded portion as the evaluation target portion. Therefore, the inspection method is suitable for a circumferential welded portion having a wall thickness exceeding a specified value.
[0083]
　Further, in the plant inspection method according to some embodiments, if the maintenance target portion is, for example, a thin-walled cylindrical welded portion, the largest damage is likely to occur inside the plate thickness of the cylindrical welded portion. Therefore, as explained in (1) above, the inspector carries out a flaw detection inspection of the evaluation target site by an inspection method suitable for a flaw detection inspection inside the plate thickness according to the flowchart shown in FIG. 4, and adds additional measurement items. Judge whether to measure or not, and make additional measurements as needed.
　That is, the inspection method set for the circumferential welded portion having a wall thickness equal to or less than the specified 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 the circumferential welded portion having a wall thickness of the specified value or less.
[0084]
　Further, in the plant inspection method according to some embodiments, if the maintenance target portion is, for example, a pipe base welded portion, the largest damage is likely to occur on the outer surface and the inner surface slit peripheral portion of the pipe base welded portion. Therefore, as described in (2) above, the inspector will detect the damage on the outer surface of the evaluation target site by an inspection method suitable for the flaw detection inspection of the outer surface according to the flowchart shown in FIG. Perform inspections, determine whether to measure additional measurement items, and make additional measurements as needed. Further, the inspector evaluates the damage generated around the inner slit by an inspection method suitable for the flaw detection inspection of the portion around the inner slit according to the flowchart shown in FIG. 7, as described in (3) above. Perform a flaw detection inspection of the site, determine whether to measure additional measurement items, and perform additional measurement as necessary.
　That is, the inspection method set for the pedestal welded portion is an inspection method for inspecting the outer surface and the inner slit peripheral portion of the pedestal welded portion as the evaluation target portion. Therefore, the inspection method is suitable for the welded portion of the tube base.
[0085]
(Regarding the flaw detector used in the ultrasonic inspection by the phased array method)
　FIG. 9 is a schematic diagram showing the structure of the flaw detector used in the ultrasonic inspection by the phased array method in step S3 in which the inspection target site is inspected. Is.
　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. It is included in the housing 57. In the flaw detector 50 shown in FIG. 9, in the wedge member 55, the arrangement direction ad of the plurality of piezoelectric elements and the extending direction of the ridge line 55a are the same on one surface 55b of the two surfaces 55b and 55c adjacent to each other with the ridge line 55a interposed therebetween. The transmitting element 51 is arranged so as to be, and the receiving element 52 is arranged on the other surface 55c.
[0086]
　As a result of diligent studies by the inventors, in performing ultrasonic flaw detection by the phased array method, the transmitting element 51 and the receiving element 52 are set as separate elements and arranged as described above for one wedge member 55. As a result, it was found that a region relatively close to the surface layer and a region relatively far from the surface layer of the inspection target can be inspected by one flaw detector 50. Further, as a result of diligent studies by the inventors, by configuring the flaw detector 50 as described above, it is possible to suppress the dead zone in the vicinity of the surface layer of the inspection target and to suppress the noise level in the vicinity of the surface layer of the inspection target. There was found.
　Therefore, according to the flaw detector 50 shown in FIG. 9, a region relatively close to the surface layer and a region relatively far from the surface layer of the inspection target 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 target and the noise level in the vicinity of the surface layer of the inspection target are suppressed.
[0087]
　FIG. 10 is a diagram for explaining the refraction angle in the flaw detector 50 shown in FIG.
　As shown in FIG. 10, the flaw detector 50 shown in FIG. 9 is configured so that the scanning range of the refraction angle θ includes a range of at least 35 degrees or more and 75 degrees or less.
　The scanning range of the refraction angle by the conventional phased array method is often 40 degrees or more and 70 degrees or less. Therefore, according to the flaw detector 50 shown in FIG. 9, a wider area can be inspected.
[0088]
　Further, the flaw detector 50 shown in FIG. 9 is configured to be capable of performing an ultrasonic flaw detection inspection by a phased array method using ultrasonic waves having a frequency of 10 MHz or more and 15 MHz or less.
　In ultrasonic flaw detection inspection, the defect size, which is generally the detection limit, becomes smaller as the wavelength of the ultrasonic wave used for flaw detection is shorter, that is, as the frequency is higher.
　In the ultrasonic flaw detection inspection by the conventional phased array method, the frequency of the ultrasonic wave is often about 5 MHz. Therefore, according to the flaw detector 50 shown in FIG. 9, since the inspection is performed with ultrasonic waves having a higher frequency than the ultrasonic flaw detection inspection by the conventional phased array method, smaller cracks can be detected.
[0089]
(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, the case where the crack 41 is generated in the above-mentioned region 19 will be described.
　When it is found that the crack 41 is generated in the above-mentioned region 19 in the pipe 5 shown in FIG. 8, it is conceivable to extend the life of the pipe 5 by repairing the pipe 5.
[0090]
(Regarding the repair method according to one embodiment)
　FIG. 11 shows the process performed in step S5 for repairing the evaluation target portion when the crack 41 is generated in the above-mentioned region 19 in the pipe 5 shown in FIG. It is a flowchart which shows the procedure of.
　The repair method according to the embodiment showing the processing procedure in FIG. 11 includes a step S51 for removing the tube base 20, a step S53 for forming a recess, and a step S55 for arranging the seal plate 60 in the tube base hole 13. A step S57 for backfilling is provided.
[0091]
(Step S51 for removing the
　tube base 20) Step S51 for removing the tube base 20 is a step for removing the tube base 20 from the mother tube 10. FIG. 12 is a cross-sectional view of the pipe 5 after the pipe base 20 is removed from the mother pipe 10 in the step S51 for removing the pipe base 20. In step S51 for removing the tube base 20, the tube base 20 is removed from the mother tube 10.
[0092]
(Step S53 for Forming the Recession) In step S53
　for forming the recess, the region 11a to which the tube base 20 was attached is removed from the mother pipe 10 by leaving a part of the area 10c on the inner peripheral surface 10a side of the mother pipe 10. This is a step of removing and forming the recess 71. FIG. 13 is a cross-sectional view of the pipe 5 in which the recess 71 is formed. FIG. 14 is a schematic view of the pipe 5 in which the recess 71 is formed when viewed from the radial outside of the mother pipe 10, that is, when viewed from the axis AXb direction of the pipe base 20.
　In step S53 for forming the recess, when viewed from the axis AXb direction of the tube base 20, a range larger than the diameter of the tube base hole 13 is provided except for a part of the region 10c on the inner peripheral surface 10a side of the mother tube 10. By removing it, the recess 71 is formed. When forming the recess 71, the region 19 where the crack 41 is generated is removed as much as possible. As will be described later, in the backfilling step S57, a part of the region 10c on the inner peripheral surface 10a side of the mother pipe 10 is left as a connection destination of the weld metal when the recess 71 is backfilled by welding.
[0093]
　FIG. 15 is a diagram showing an example of the case where the recess 71 is provided when the plurality of tube bases 20 are arranged in a state of being close to each other along the axis AXa direction of the mother tube 10, and the recess 71 is formed. It is a schematic diagram which looked at the pipe 5 from the radial outside of a mother pipe 10.
　As shown in FIG. 15, when a plurality of tube bases 20 are arranged in a state of being close to each other along the axis AXa direction of the mother tube 10, the recess 71 is a long hole along the axis AXa direction of the mother tube 10. It may have a shape. That is, after removing a plurality of tube bases 20 that are close to each other along the axis AXa direction of the mother tube 10, each region 11a to which the plurality of tube bases 20 are attached is removed from the mother tube 10. The recess 71 may be formed.
　When a plurality of pipe bases 20 are arranged in a state of being close to each other along the axis AXa direction of the mother pipe 10 as shown in FIG. 15, when the recess 71 is formed, the plurality of pipes are formed. An elongated hole may be formed by connecting the base holes 13. In this case, in step S55 for arranging the seal plate 60 in the tube base hole 13, it is preferable to arrange the seal plate 60 formed so as to close the elongated hole.
[0094]
(Step S55 for arranging the seal plate 60 in the
　tube base hole 13) In step S55 for arranging the seal plate 60 in the tube base hole 13, the seal plate 60 is formed in the tube base hole 13 formed in a part of the above-mentioned area 10c. It is a step to place.
　FIG. 16 is a diagram for explaining step S55 in which the seal plate 60 is arranged in the tube base hole 13. As shown in FIG. 16, in step S55 in which the seal plate 60 is arranged in the tube base hole 13, when the seal plate 60 is arranged, the small diameter portion 61 smaller than the inner diameter of the tube base hole 13 and the inner diameter of the tube base hole 13 are smaller. The small diameter portion 61 of the seal plate 60 having the large diameter portion 63 is fitted into the tube base hole 13. That is, in some embodiments, the seal plate 60 has a large diameter portion 63 having a plate shape larger than the inner diameter of the base hole 13 and a small diameter portion 61 having a plate shape smaller than the inner diameter of the base hole 13. It has a shape that seems to be overlapped in the plate thickness direction. Therefore, when the seal plate 60 is arranged in the tube base hole 13, the large diameter portion 63 abuts on the area around the tube base hole 13, and the seal plate 60 is intended from the tube base hole 13 to the inside of the mother tube 10. It is possible to avoid invading without doing so. Further, when the seal plate 60 is arranged in the tube base hole 13, the small diameter portion 61 can be fitted into the tube base hole 13, so that the arranged seal plate 60 is unintentionally displaced from the tube base hole 13. Can be suppressed.
　By closing the pipe base hole 13 with the seal plate 60 having such a shape, as will be described later, when the recess 71 is backfilled by welding in the backfilling step S57, the weld metal is transferred from the pipe base hole 13 to the mother pipe 10. It is possible to prevent unintentional intrusion into the inside.
[0095]
(Backfilling Step S57)
　The backfilling step S57 is a step of backfilling the recess 71 by welding after the step S55 for arranging the seal plate 60 in the tube base hole 13.
　FIG. 17 is a cross-sectional view of the pipe 5 after performing the backfilling step S57. In the backfilling step S57, the recess 71 is backfilled with the weld metal 73.
　As described above, according to the repair method shown in FIG. 11, the crack is formed in the region 19 displaced from the inner wall surface 15 of the tube base hole 13 to the inside of the base material 11 of the mother pipe 10 in the axis AXa direction of the mother pipe 10. When 41 occurs, it can be repaired appropriately.
[0096]
(Regarding the repair method according to another 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 a procedure of processing performed in step S5 for repairing the evaluation target portion when a relatively small crack 41 is generated in the above-mentioned region 19 in the pipe 5 shown in FIG. ..
　A repair method according to another embodiment showing a processing procedure in FIG. 18 includes a step S151 for arranging the reinforcing plate and a step S153 for welding the reinforcing plate to the mother pipe. That is, the repair method according to another embodiment showing the processing procedure in FIG. 18 is a repair method for reinforcing the mother pipe 10 by attaching a reinforcing plate to the outer peripheral surface 10d of the mother pipe 10.
[0097]
(Step S151 for arranging the
　reinforcing plate) In step S151 for arranging the reinforcing plate, the reinforcing plate is formed so as to surround the circumference of the pipe base 20 from the radial outside of the pipe base 20 at the connection portion 7 with the pipe base 20 in the mother pipe 10. It is a step of arranging 80.
　FIG. 19 is a perspective view of the reinforcing plate 80. The reinforcing plate 80 according to one embodiment is a thick plate member formed along the outer peripheral surface 10d of the mother pipe 10. The reinforcing plate 80 according to the embodiment is formed with a hole 83 penetrating along the plate thickness direction so as to surround the periphery of the tube base 20 from the outside in the radial direction. Therefore, the inner diameter of the hole 83 is larger than the outer diameter of the tube base 20. The reinforcing plate 80 according to one embodiment includes two divided plates 81 divided into two along the radial direction of the hole 83.
[0098]
　In step S151 in which the reinforcing plate is arranged, the divided plate 81, which is one of the two divided reinforcing plates 80, and the divided plate 81, which is the other, face each other along the axis AXa direction of the mother pipe 10 with the tube base 20 interposed therebetween. Let and place.
　FIG. 20 shows a state in which the two dividing plates 81 are arranged so as to face each other along the axis AXa direction of the mother pipe 10 with the pipe base 20 sandwiched between them, as viewed from the radial outside of the mother pipe 10, that is, the pipe base 20. It is a schematic diagram seen along the axis AXb.
[0099]
　As described above, the crack 41 generated in the region 19 is generated by the circumferential stress acting on the mother tube 10. Therefore, when one split plate 81 of the reinforcing plate 80 divided into two and the other split plate 81 are arranged so as to face each other along the axis AXa direction of the mother pipe 10 with the tube base 20 interposed therebetween, the split plate 81 is arranged. Each extends along the circumferential direction of the mother tube 10. Therefore, by welding and attaching each of the dividing plates 81 to the mother pipe 10, the circumferential stress acting on the mother pipe 10 by each of the dividing plates 81 can be effectively reduced. Further, by using the reinforcing plate 80 divided into two, even if the other end of the two ends of the tube base 20 opposite to the one end connected to the mother pipe 10 is connected to another pipe or the like. Each of the dividing plates 81 can be easily arranged.
　If the other end of the pipe base 20 opposite to the one end connected to the mother pipe 10 is not connected to another pipe or the like, the reinforcing plate 80 not divided into two can be used. can.
[0100]
(Step S153 for welding the
　reinforcing plate to the mother pipe) Step S153 for welding the reinforcing plate to the mother pipe is a step for welding the reinforcing plate 80 arranged in step S151 for arranging the reinforcing plate to the mother pipe 10.
　FIG. 21 is a cross-sectional view of the pipe 5 after the reinforcing plate 80 is welded to the mother pipe 10 in step S153 in which the reinforcing plate is welded to the mother pipe. In step S153 in which the reinforcing plate is welded to the mother pipe, the reinforcing plate 80 may be welded not only to the mother pipe 10 but also to the tube base 20. That is, in the example shown in FIG. 21, the reinforcing plate 80 is welded to the mother pipe 10 at, for example, the welded portion 85, and is welded to the tube base 20 at, for example, the welded portion 86.
[0101]
　When a crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 is attached to the mother pipe 10 by welding the reinforcing plate 80 to the mother pipe 10 as described above. The acting circumferential stress can be reduced. As a result, the growth speed of the crack 41 can be reduced, and the life can be extended. Further, since the reinforcing plate 80 can be repaired by a relatively simple method of welding, the time and cost required for the repair can be suppressed.
[0102]
　The present invention is not limited to the above-described embodiment, and includes a modification of the above-mentioned embodiment and a combination of these embodiments as appropriate.
　For example, in some of the above-described embodiments, the evaluation target portion is a welded portion in a plurality of steam pipes connecting between a boiler and a steam turbine in a thermal power generation facility, but the welded portion to be evaluated is a boiler. The method for inspecting a plant according to the present invention is not limited to a part of the above, and can be applied to various welded parts exposed to high temperature and high pressure and parts other than the welded parts.
[0103]
　The contents described in each of the above embodiments are grasped as follows, for example.
(1) The method for inspecting a plant according to at least one embodiment of the present disclosure is a tube stand (for example, a tube base 20 according to some embodiments) and a tube base hole (for example, some embodiments) to which the tube base 20 is attached. It is an inspection method of a plant including a master pipe (for example, the master pipe 10 according to some embodiments) in which the tube base hole 13) according to the embodiment is formed.
　This inspection method is a step of selecting an inspection site from one or more inspection candidate sites including a region 19 displaced from the inner wall surface 15 of the tube base hole 13 to the inside of the base material 11 of the mother tube 10 in the axis AXa direction of the mother tube 10. (For example, step S1 for selecting an evaluation target site according to some embodiments) is provided.
　Further, this inspection method includes a step of performing a flaw detection inspection on the inspection site (for example, step S3 of inspecting the evaluation target site according to some embodiments).
[0104]
　As a result of diligent studies by the inventors, in the pipe 5 including the pipe base 20 and the mother pipe 10 in which the pipe base hole 13 to which the pipe base 20 is attached is formed, the inner wall surface 15 of the pipe base hole 13 to the mother pipe 10 It has been found that a crack 41 may occur in a region 19 displaced inside the base material 11 of the mother pipe 10 in the axis AXa direction.
　Therefore, according to the method (1) above, since the step S1 for selecting the evaluation target site and the step S3 for inspecting the evaluation target site are provided, the above-mentioned area 19 is provided even for a limited inspection period. The existence of the crack 41 generated in the above can be confirmed. Therefore, the plant can be inspected efficiently.
[0105]
(2) In some embodiments, in the method of (1) above, the step S1 for selecting the evaluation target site includes the outer diameter D and the plate thickness T of the mother tube 10 as parameters and is relative to the plate thickness T. If the index indicating the thickness (for example, the mother tube plate thickness outer diameter ratio (T / D) according to some embodiments) is equal to or less than the specified value (for example, the specified value Th according to some embodiments), the region 19 is selected as the inspection site.
[0106]
　As described above, as a result of diligent studies by the inventors, if the index indicating the relative thickness of the plate thickness T including the outer diameter D and the plate thickness T of the mother tube 10 as parameters is equal to or less than the specified value, the above It was found that the crack 41 was likely to occur in the region 19.
　Therefore, according to the method (2) above, the index (for example, the thickness outer diameter ratio (T / D) of the mother tube plate according to some embodiments) is a specified value (for example, a specified value according to some embodiments). If Th) or less, the region 19 is selected as the inspection site, so that the region 19 can be selected as the inspection site when cracks 41 are likely to occur in the region 19, and the plant can be efficiently inspected.
[0107]
(3) In some embodiments, in the method of (2) above, in step S3 for inspecting the evaluation target site, ultrasonic flaw detection inspection can be performed on the inspection site.
[0108]
　According to the method (3), the region can be inspected by an inspection method suitable for detecting the crack 41 in the region 19.
[0109]
(4) In some embodiments, in the method of (2) above, step S1 for selecting an evaluation target site is an index (for example, a mother tube plate thickness outer diameter ratio (T / D) according to some embodiments). )) Exceeds the above-mentioned specified value (for example, the specified value Th according to some embodiments), the welded portion connecting the mother pipe 10 and the pipe base 20 (for example, the pipe base welding according to some embodiments). Part 30) is selected as the inspection site.
[0110]
　As a result of diligent studies by the inventors, the above index (for example, the outer diameter ratio (T / D) of the mother tube plate thickness according to some embodiments) is the above-mentioned specified value (for example, the specified value Th according to some embodiments). If it exceeds, it is found that the crack 41 is more likely to occur in the welded portion connecting the mother pipe 10 and the tube base 20 (for example, the pipe base welded portion 30 according to some embodiments) than in the above region 19. ..
　Therefore, according to the method (4) above, if the index exceeds the specified value, the welded portion (tube base welded portion 30) connecting the mother pipe 10 and the tube base 20 is selected as the inspection site. Therefore, when a crack 41 is likely to occur in the welded portion (tube base welded portion 30), the welded portion (tube base welded portion 30) can be selected as an inspection site, and the plant can be inspected efficiently.
[0111]
(5) In some embodiments, in any of the above methods (1) to (4), the mother tube 10 is made of high chromium steel.
[0112]
　The method (5) above is suitable for inspecting a pipe made of high chrome steel (for example, a pipe 5 according to some embodiments).
[0113]
(6) In some embodiments, in any of the above methods (1) to (5), a step S51 for removing the tube base 20 and a step S53 for forming a recess are provided. In some embodiments, in any of the above methods (1) to (5), further, a step S55 for arranging the seal plate 60 in the tube base hole 13 and a step S57 for backfilling are provided.
[0114]
　According to the method (6) above, it is appropriate when a crack 41 occurs in a region 19 displaced from the inner wall surface 15 of the tube base hole 13 to the inside of the base material 11 of the mother pipe 10 in the axis AXa direction of the mother pipe 10. Can be repaired.
[0115]
(7) In some embodiments, in the method of (6) above, in step S55 for arranging the seal plate 60 in the tube base hole 13, the seal plate (for example, the seal plate 60 according to some embodiments) is arranged. The small diameter portion 61 of the seal plate 60 having a small diameter portion 61 smaller than the inner diameter of the tube base hole 13 and a large diameter portion 63 larger than the inner diameter of the tube base hole 13 is fitted into the tube base hole 13.
[0116]
　According to the method (7) above, when the seal plate 60 is arranged in the tube base hole 13, the large diameter portion 63 comes into contact with the area around the tube base hole 13, and the seal plate 60 comes into contact with the tube base hole 13. It is possible to avoid unintentionally invading the inside of the mother tube 10 from the above. Further, when the seal plate 60 is arranged in the tube base hole 13, the small diameter portion 61 can be fitted into the tube base hole 13, so that the arranged seal plate 60 is unintentionally displaced from the tube base hole 13. Can be suppressed.
[0117]
(8) In some embodiments, in any of the above methods (1) to (5), a step S151 for arranging the reinforcing plate and a step S153 for welding the reinforcing plate to the mother pipe are further provided.
[0118]
　When a crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 is welded to the mother pipe and attached as in the method (8) above. The circumferential stress exerted by the 80 on the mother tube 10 can be reduced. As a result, the growth speed of the crack 41 can be reduced, and the life can be extended. Further, since the repair can be performed by a relatively simple method such as the method (8) above, the time and cost required for the repair can be suppressed.
[0119]
(9) In some embodiments, in the method of (8) above, in step S151 in which the reinforcing plate is arranged, the divided plate 81, which is one of the two divided reinforcing plates 80, and the divided plate 81, which is the other, are provided. , The tube base 20 is sandwiched between them and arranged so as to face each other along the axis AXa direction of the mother tube 10.
[0120]
　As described above, as a result of diligent studies by the inventors, it was found that the crack 41 generated in the region 19 is caused by the circumferential stress acting on the mother tube 10.
　Therefore, when the two dividing plates 81 are arranged so as to face each other along the axis AXa direction of the mother pipe 10 with the tube base 20 interposed therebetween as in the method (9) above, each of the dividing plates 81 is a mother pipe. It will extend along the circumferential direction of 10. Therefore, by welding and attaching each of the dividing plates 81 to the mother pipe 10, the circumferential stress acting on the mother pipe 10 by each of the dividing plates 81 can be effectively reduced. Further, according to the method (9) above, even if the other end of the pipe base 20 opposite to the one end connected to the mother pipe 10 is connected to another pipe or the like, the reinforcing plate is used. 80 can be easily arranged.
[0121]
(10) In some embodiments, in any of the above methods (1) to (9), a step of performing the ultrasonic flaw detection inspection (for example, a step of inspecting an evaluation target site according to some embodiments). In S3), a transmission element 51 including a plurality of piezoelectric elements, a reception element 53 including at least one piezoelectric element and different from the transmission element 51, and a wedge member 55 are included in one housing 57. In the wedge member 55, the transmission element 51 is provided on one of the two surfaces 55b and 55c adjacent to each other with the ridge line 55a in between so that the arrangement direction of the plurality of piezoelectric elements and the extending direction of the ridge line 55a are the same. An ultrasonic flaw detection inspection by the phased array method is performed using the flaw detector 50 which is arranged and the receiving element 53 is arranged on the other surface 55c.
[0122]
　As described above, as a result of diligent studies by the inventors, in performing ultrasonic flaw detection by the phased array method, the transmitting element 51 and the receiving element 53 are set as separate elements, and the above-mentioned one wedge member 55 is described above. It was found that the region relatively close to the surface layer and the region relatively far from the surface layer of the inspection target can be inspected by one flaw detector 50 by arranging them as described above. Further, as a result of diligent studies by the inventors, by configuring the flaw detector 50 as described above, it is possible to suppress the dead zone in the vicinity of the surface layer of the inspection target and to suppress the noise level in the vicinity of the surface layer of the inspection target. There was found.
　Therefore, according to the method (10) above, a region relatively close to the surface layer and a region relatively far from the surface layer of the inspection target can be inspected by one flaw detector 50. Further, according to the method (10) above, an inspection result in which the dead zone in the vicinity of the surface layer of the inspection target and the noise level in the vicinity of the surface layer of the inspection target are suppressed can be obtained.
[0123]
(11) In some embodiments, in any of the above methods (1) to (10), a step of performing an ultrasonic flaw detection inspection (for example, a step S3 of inspecting an evaluation target site according to some embodiments). ) Performs an ultrasonic flaw detection inspection by a phased array method using a probe 50 including a scanning range of a refraction angle of at least 35 degrees or more and 75 degrees or less.
[0124]
　The scanning range of the refraction angle by the conventional phased array method is often 40 degrees or more and 70 degrees or less. Therefore, according to the method (11) above, a wider area can be inspected.
[0125]
(12) In some embodiments, in any of the above methods (1) to (11), a step of performing an ultrasonic flaw detection inspection (for example, a step S3 of inspecting an evaluation target site according to some embodiments). ) Performs an ultrasonic flaw detection inspection by a phased array method using ultrasonic waves having a frequency of 10 MHz or more and 15 MHz or less.
[0126]
　In ultrasonic flaw detection inspection, the defect size, which is generally the detection limit, becomes smaller as the wavelength of the ultrasonic wave used for flaw detection is shorter, that is, as the frequency is higher.
　In the ultrasonic flaw detection inspection by the conventional phased array method, the frequency of the ultrasonic wave is often about 5 MHz. Therefore, according to the method (12) above, since the inspection is performed with ultrasonic waves having a higher frequency than the ultrasonic flaw detection inspection by the conventional phased array method, smaller cracks can be detected.
[0127]
(13) The method for repairing a plant according to at least one embodiment of the present disclosure includes a pipe base (for example, a pipe base 20 according to some embodiments) and a mother pipe to which the pipe base is attached (for example, some embodiments). This is a method for repairing a plant including the mother pipe 10).
　This repair method includes a step S51 for removing the tube base 20 and a step S53 for forming a recess.
　Further, this repair method includes a step S55 for arranging the seal plate 60 in the tube base hole 13 and a step S57 for backfilling.
[0128]
　According to the method (13), when a crack 41 is generated in the region 19, it can be appropriately repaired.
[0129]
(14) The method for repairing a plant according to at least one embodiment of the present disclosure includes a pipe base (for example, a pipe base 20 according to some embodiments) and a mother pipe to which the pipe base is attached (for example, some embodiments). This is a method for repairing a plant including the mother pipe 10).
　This repair method includes a step S151 for arranging the reinforcing plate and a step S153 for welding the reinforcing plate to the mother pipe.
[0130]
　As described above, when a crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 is welded to the mother pipe 10 as in the method of (14) above. By attaching the reinforcing plate 80 to the mother pipe 10, the circumferential stress acting on the mother pipe 10 can be reduced. As a result, the growth speed of the crack 41 can be reduced, and the life can be extended. Further, since the repair can be performed by a relatively simple method such as the method (14) above, the time and cost required for the repair can be suppressed.
Code description
[0131]
1 Storage device
2 Terminal device
2a Display unit
3 Arithmetic device
4 Input device
5 Piping
7 Connection part
10 Mother tube
11 Base material
13 Tube base hole
19 Area
20 Tube base
30 Tube base welded part
50 Scratch detector
51 Transmission element
53 For reception Element
55 Wedge member
57 Housing
60 Seal plate
61 Small diameter part
63 Large diameter part
71 Recession
80 Reinforcing plate
81 Dividing plate

WE CLAIMS

This is a method for inspecting a plant including a pipe base 　and a mother pipe in which a pipe base hole to which the pipe base is attached is formed. A plant inspection method comprising a step of selecting an inspection site from one or more inspection candidate sites including a region deviated from the
　above, and a step of performing a flaw detection inspection on the inspection site .
[Claim 2]
　In the step of selecting the inspection site, if the outer diameter and the plate thickness of the mother tube are included as parameters and the index indicating the relative thickness of the plate thickness is equal to or less than the specified value, the region is selected as the inspection site. The plant inspection method according to
claim 1.
[Claim 3]

The plant inspection method according to claim 2 　, wherein the step of performing the flaw detection inspection is to perform an ultrasonic flaw detection inspection on the inspection site .
[Claim 4]

The plant inspection according to claim 2 　, wherein in the step of selecting the inspection site, if the index exceeds the specified value, the welded portion connecting the mother pipe and the tube base is selected as the inspection site . Method.
[Claim 5]

The plant inspection method according to any one of claims 1 to 4, 　wherein the mother pipe is made of high chrome steel .
[Claim 6]
　The step of removing the tube stand from the mother tube and
　the area to which the tube stand was attached are removed from the mother tube to form a recess, leaving a part of the area on the inner peripheral surface side of the mother tube. Further , a step
　of arranging a seal plate in the tube base hole formed in the partial region, a step of arranging the seal plate, and
　a step of backfilling the recess by welding.
The plant inspection method according to any one of claims 1 to 5.
[Claim 7]
　The step of arranging the seal plate is the small diameter of the seal plate having a small diameter portion smaller than the inner diameter of the pedestal hole and a large diameter portion larger than the inner diameter of the pedestal hole when arranging the seal plate.
The plant inspection method according to claim 6, wherein the portion is fitted into the tube base hole .
[Claim 8]
　A step of arranging a reinforcing plate so as to surround the circumference of the pedestal from the radial outside of the pedestal at a connection portion of the mother pipe with the pedestal, and a
　step of arranging the reinforcing plate in the step of arranging the pedestal are the mother.
The plant inspection method according to any one of claims 1 to 5, further comprising a step of welding to a pipe .
[Claim 9]

The plant according to claim 8, 　wherein the step of arranging the reinforcing plate is to arrange one of the two divided reinforcing plates and the other so as to face each other along the axial direction of the mother pipe with the tube stand interposed therebetween . Inspection methods.
[Claim 10]
　The step of performing the ultrasonic flaw detection inspection includes a transmitting element including a plurality of piezoelectric elements, a receiving element including a piezoelectric element different from the transmitting element, and a wedge member in one housing. The transmitting element is arranged on one of two adjacent surfaces of the wedge member with the ridge line sandwiched therein so that the arrangement direction of the plurality of piezoelectric elements and the extending direction of the ridge line are the same, and the receiving element is arranged on the other side.
The plant inspection method according to any one of claims 1 to 9, wherein an ultrasonic flaw detection inspection by a phased array method is performed using a flaw detector in which an element is arranged .
[Claim 11]
　The step of performing the ultrasonic flaw detection inspection is
any one of claims 1 to 10 in which the ultrasonic flaw detection inspection by the phased array method is performed using a probe having a scanning range of a refraction angle of at least 35 degrees or more and 75 degrees or less. The plant inspection method described in item 1.
[Claim 12]

The plant inspection method according to any one of claims 1 to 11, 　wherein the step of performing the ultrasonic flaw detection inspection is to perform an ultrasonic flaw detection inspection by a phased array method using ultrasonic waves having a frequency of 10 MHz or more and 15 MHz or less .
[Claim 13]
　A method of repairing a plant including a pipe base and a
　mother pipe to which the pipe base is attached, in which a step of removing the pipe base attached to the mother pipe and
　a part of the area on the inner peripheral surface side of the mother pipe are covered. A pipe that
　connects the internal space of the mother pipe and the outside of the mother pipe in the part of the region and the step of removing the area to which the tube stand was attached from the mother pipe to form a recess. A method for repairing a plant including a step of arranging a seal plate in a table hole, a step of arranging the
　seal plate, and then a step of backfilling the recess by welding .
[Claim 14]
　It is a repair method of a plant including a pipe base and a mother pipe to which the pipe base is attached
　so as to surround the circumference of the pipe base from the radial outside of the pipe base at a connection portion with the pipe base in the mother pipe. A method for repairing a plant including a step of arranging a reinforcing plate and a step of welding the reinforcing plate arranged in the arranging step
　to the mother pipe .