CN114096840B - Method for inspecting plant equipment and method for repairing plant equipment - Google Patents
Method for inspecting plant equipment and method for repairing plant equipment Download PDFInfo
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- CN114096840B CN114096840B CN202080045079.3A CN202080045079A CN114096840B CN 114096840 B CN114096840 B CN 114096840B CN 202080045079 A CN202080045079 A CN 202080045079A CN 114096840 B CN114096840 B CN 114096840B
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- 238000000034 method Methods 0.000 title claims abstract description 318
- 238000007689 inspection Methods 0.000 claims abstract description 312
- 238000001514 detection method Methods 0.000 claims abstract description 107
- 239000000463 material Substances 0.000 claims abstract description 27
- 230000003014 reinforcing effect Effects 0.000 claims description 47
- 238000007789 sealing Methods 0.000 claims description 36
- 238000003466 welding Methods 0.000 claims description 30
- 230000002093 peripheral effect Effects 0.000 claims description 28
- 229910001220 stainless steel Inorganic materials 0.000 claims description 6
- 239000006247 magnetic powder Substances 0.000 claims description 5
- 230000035515 penetration Effects 0.000 claims description 4
- 238000012546 transfer Methods 0.000 claims description 4
- 238000011156 evaluation Methods 0.000 description 237
- 238000005259 measurement Methods 0.000 description 105
- 230000035882 stress Effects 0.000 description 35
- 230000008439 repair process Effects 0.000 description 26
- 230000008569 process Effects 0.000 description 20
- 238000012545 processing Methods 0.000 description 20
- 239000002344 surface layer Substances 0.000 description 16
- 238000012423 maintenance Methods 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 9
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- 238000013459 approach Methods 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
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- 230000008646 thermal stress Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/043—Analysing solids in the interior, e.g. by shear waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/023—Solids
- G01N2291/0234—Metals, e.g. steel
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Abstract
An inspection method of a plant according to an embodiment is an inspection method of a plant including a stem and a parent pipe having a stem hole for mounting the stem, the inspection method including: a step of selecting an inspection site from among one or more inspection candidate sites including a region offset from an inner wall surface of the stem hole toward an inside of a base material of the base pipe in an axial direction of the base pipe; and performing flaw detection on the inspected portion.
Description
Technical Field
The present disclosure relates to a method of inspecting and repairing plant equipment.
Background
In pipes used for a long time under high temperature and high pressure, for example, in boilers, cracks are generated due to creep damage at welded parts such as pipes. Since the progress of cracks due to creep damage is advanced, it is necessary to evaluate the remaining life based on the presence or absence of cracks and the length of the cracks (the height of the cracks) in the thickness direction of the welded portion, and repair the welded portion in time. Accordingly, a technique for measuring the presence or absence of cracks in the welded portion and the length of the cracks and evaluating the remaining life has been developed.
For example, in the method for evaluating the remaining life disclosed in patent document 1, the inside of the welded portion is inspected by ultrasonic inspection by a phased array method, and the remaining life is evaluated based on the inspection result (see patent document 1).
Prior art literature
Patent document 1: japanese patent application laid-open No. 2017-151107
As described above, for example, it is known that cracks are easily generated due to creep damage at welded portions such as pipes in pipes of a boiler, and therefore, for example, the pipes of the boiler are mainly maintained and managed at the welded portions.
In addition, it has recently been found that cracks may occur in the base material of the pipe, not in the welded portion. However, in a plant having a relatively large scale such as a power generation plant or a chemical plant, the number of pipes used is large. Therefore, in the case where the inspection period is limited, for example, a regular inspection performed by stopping the operation of the plant equipment, it is difficult to inspect all of the base material portions of the pipes.
Disclosure of Invention
In view of the foregoing, it is an object of at least one embodiment of the present disclosure to provide an efficient inspection method for plant equipment.
(1) The inspection method of the plant equipment of at least one embodiment of the present disclosure is an inspection method of a plant equipment including a stem and a parent pipe formed with a stem hole to which the stem is mounted,
The method for inspecting the plant equipment comprises the following steps:
A step of selecting an inspection site from among one or more inspection candidate sites including a region offset from an inner wall surface of the stem hole in an axial direction of the parent material of the parent pipe; and
And performing flaw detection on the detection part.
(2) The repair method of the plant equipment of at least one embodiment of the present disclosure is a repair method of a plant equipment including a stem and a parent pipe to which the stem is attached,
The repair method of the factory equipment comprises the following steps:
Removing the tube seat installed on the main tube;
A step of removing a region, to which the stem is attached, from the parent pipe to form a recess, while leaving a region of a part of the inner peripheral surface side of the parent pipe;
A step of disposing a sealing plate in the partial region to a stem hole that communicates the inner space of the main pipe with the outside of the main pipe; and
And a step of refilling the concave portion by welding after the step of disposing the sealing plate.
Effects of the invention
According to at least one embodiment of the present disclosure, it is possible to efficiently inspect plant equipment.
Drawings
Fig. 1 is a diagram showing steps in a method for inspecting plant equipment according to several embodiments.
Fig. 2 is a table showing the locations where the welded portions exist, and the relationship between the thickness of the locations and the locations where cracks are likely to occur.
Fig. 3 is a diagram showing a storage device storing a database and a terminal device accessing the storage device.
Fig. 4 is a flowchart showing a flow of processing to be performed in step S3 of performing the inspection of the evaluation target portion.
Fig. 5 is a graph in which the horizontal axis represents stress acting on the evaluation target portion and the vertical axis represents the ratio of the size of damage to the plate thickness at the maintenance target portion.
Fig. 6 is a flowchart showing a flow of processing to be performed in step S3 of performing the inspection of the evaluation target portion.
Fig. 7 is a flowchart showing a flow of processing to be performed in step S3 of checking the evaluation target portion.
Fig. 8 is a cross-sectional view of a pipe including a base pipe having a base hole formed therein for mounting the base pipe.
Fig. 9 is a schematic diagram showing a structure of a flaw detector used in ultrasonic inspection by a phased array method in the step of inspecting an evaluation target portion.
Fig. 10 is a view for explaining the refractive angle in the flaw detector shown in fig. 9.
Fig. 11 is a flowchart showing a procedure of processing performed in a step of repairing a portion to be evaluated in the piping shown in fig. 8.
Fig. 12 is a sectional view of the pipe after the stem is removed from the parent pipe in the step of removing the stem.
Fig. 13 is a cross-sectional view of a pipe in which a concave portion is formed.
Fig. 14 is a view of a pipe in which a concave portion is formed, as seen from the radially outer side of the main pipe.
Fig. 15 is a view showing an example of a case where the plurality of sockets are arranged in a state of being adjacent to each other along the axial direction of the main pipe.
Fig. 16 is a view for explaining a step of disposing a sealing plate in a stem hole.
Fig. 17 is a cross-sectional view of the pipe after the backfilling step is performed.
Fig. 18 is a flowchart showing a procedure of processing performed in a step of repairing a portion to be evaluated in the piping shown in fig. 8.
Fig. 19 is a perspective view of the reinforcing plate.
Fig. 20 is a view of the two dividing plates arranged as seen from the radially outer side of the main pipe.
Fig. 21 is a cross-sectional view of the pipe 5 after the reinforcing plate is welded to the parent pipe in the step of welding the reinforcing plate to the parent pipe.
Detailed Description
Several embodiments of the present invention are described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements of the components and the like described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.
For example, the expression "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" and the like means not only such an arrangement but also a state in which angles or distances having tolerances or the degree of obtaining the same function are relatively displaced.
For example, the expressions "identical", "equal" and "homogeneous" and the like mean that the expressions of the things being equal are not only strictly equal but also a state having a tolerance or a difference in the degree to which the same function can be obtained.
For example, the expression of the shape such as a square shape or a cylindrical shape indicates not only the shape such as a square shape or a cylindrical shape in a geometrically strict sense, but also the shape including a concave-convex portion, a chamfer portion, or the like within a range where the same effect can be obtained.
On the other hand, the expression "provided with", "having", "including" or "containing" a component is not an exclusive expression excluding the presence of other components.
(Outline of inspection method for plant equipment)
First, an outline of an inspection method of plant equipment according to several embodiments will be described with reference to fig. 1.
Fig. 1 is a diagram showing steps in a method for inspecting plant equipment according to several embodiments. The method for inspecting the plant equipment according to several embodiments includes a step S1 of selecting the evaluation target portion, a step S2 of selecting the inspection method and adding the measurement item, a step S3 of inspecting the evaluation target portion, and a step S4 of evaluating the remaining lifetime of the evaluation target portion. The method for inspecting the plant equipment according to the several embodiments may include step S5 of repairing the evaluation target portion.
The inspection method of the plant according to the several embodiments is applied to an inspection method of a metal member used for a long time under an environment where a large stress is applied at a high temperature, and is applied to an inspection of a welded portion of a steam pipe or the like connecting a boiler and a steam turbine and an inspection of a base material of a pipe or the like in a thermal power plant, for example.
The outline of each step in the inspection method of the plant equipment according to several embodiments will be described below.
(Outline of step S1 of selecting evaluation target portion)
The step S1 of selecting the evaluation target portion is a step of selecting the evaluation target portion to be subjected to the flaw detection and the remaining life evaluation based on the result of the flaw detection from among a plurality of steam pipes or the like existing in the plant. That is, the step S1 of selecting the evaluation target portion according to several embodiments is a step of selecting the inspection portion from one or more inspection candidate portions.
Fig. 8 is a cross-sectional view of a pipe including a base pipe having a base hole formed therein for mounting the base pipe. In fig. 8, the connection portion 7 between the parent pipe 10 and the stem 20 is shown in a cross section along the axis AXa of the parent pipe 10 and the axis AXb of the stem 20. The pipe 5 shown in fig. 8 includes a main pipe 10 and a stem 20 connected to the main pipe 10 by welding. The main pipe 10 has a pipe socket hole 13 for mounting the pipe socket 20. The stem hole 13 includes a wall surface that is a boundary between the main pipe 10 and the stem 20, i.e., a branch pipe, a plug, a tube, and the like, in addition to the hole 13a that communicates the hole 23 extending in the axial direction AXb of the stem 20 with the inside of the main pipe 10 in the stem 20.
In the pipe 5 shown in fig. 8, the stem 20 is welded to the main pipe 10 by the stem weld portion 30. In the pipe 5 shown in fig. 8, the stem weld portion 30 includes a weld metal 31 and a heat affected zone (HAZ portion) 33 generated by welding.
As a result of intensive studies, the inventors have found that, in the pipe 5 including the stem 20 and the base pipe 10 formed with the stem hole 13 to which the stem 20 is attached, there is a possibility that the crack 41 may occur in the region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial line AXa direction of the base pipe 10. In fig. 8, the region 19 is, for example, a region surrounded by a broken line. In fig. 8, the crack 41 is a cross-hatched area in the region 19.
The mechanism of such cracks 41 will be briefly described. In a pipe having a thick cylindrical shape and functioning with a relatively high internal pressure, such as a pipe in a boiler, for example, the circumferential stress is usually greatest in the radially innermost region of the base material of the pipe. That is, in the case of the pipe 5 shown in fig. 8, the circumferential stress is usually the largest at the inner circumferential surface 10a of the main pipe 10.
In general, when a through hole for connecting the inside of the pipe to the outside is formed in a side surface of the pipe, a circumferential stress due to an internal pressure of the pipe is greatest at a position along a center in a circumferential direction of the pipe in a wall surface where the through hole is formed. That is, in the case of the pipe 5 shown in fig. 8, the pipe is usually maximum at a position along the center of the circumferential direction of the parent pipe 10 in the inner wall surface 15 of the stem hole 13.
However, as a result of intensive studies, the inventors have found that in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, particularly in a pipe made of high-chromium steel, there is a tendency that the position where the circumferential stress due to the internal pressure of the pipe is greatest moves from the above-described position due to deformation caused by creep.
Specifically, it was found that in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, the position where the circumferential stress due to the internal pressure of the pipe is greatest moves to a position radially outside the innermost region in the radial direction in the base material of the pipe due to deformation caused by creep. In addition, it was found that in a pipe used in a high-temperature and high-pressure environment such as a pipe in a boiler, when a through hole for connecting the inside of the pipe to the outside is formed in a side surface of the pipe at a position where a circumferential stress due to an internal pressure of the pipe is maximum due to deformation caused by creep, the pipe moves from a wall surface where the through hole is formed to a region offset toward the inside of a base material of the pipe in an axial direction of the pipe.
That is, it is found that, in the case of the pipe 5 shown in fig. 8, the position where the circumferential stress due to the internal pressure of the pipe 5 is greatest moves toward the region 19 which is offset toward the inside of the base material 11 of the parent pipe 10 in the axial line AXa direction of the parent pipe 10 by deformation due to creep.
Therefore, the inspection method of the plant according to several embodiments includes the above-described region 19 as an inspection candidate.
The details of step S1 for selecting the evaluation target portion according to several embodiments will be described later.
(Outline of step S2 of selecting inspection method and adding measurement item)
The step S2 of selecting the inspection method and adding the measurement item is a step of selecting the inspection method and adding the measurement item for flaw detection of the evaluation target portion selected in the step S1 of selecting the evaluation target portion.
In step S2 of selecting the inspection method and adding the measurement item, an inspection method suitable for flaw detection of the evaluation target portion selected in step S1 of selecting the evaluation target portion is selected.
Here, the inspection method selected in step S2 of selecting the inspection method and adding the measurement item is an inspection method set for each combination of the type of the evaluation target portion including at least one of the circumferential weld portion or the longitudinal weld portion of the pipe and the stem weld portion and the thickness of the evaluation target portion, as will be described later. The inspection method selected in step S2 of selecting the inspection method and adding the measurement item is an inspection method in which, as will be described later, the type of the portion to be evaluated and the combination of the index including the outer diameter of the parent pipe and the thickness of the parent pipe as parameters are set for the piping including the parent pipe and the parent pipe on which the pipe socket is formed.
The welded portion includes: weld metal, heat-affected zone (HAZ zone) produced by welding, and inner surface slit described later.
In step S2 of selecting the inspection method and the additional measurement item, an additional measurement item appropriate for the selected inspection method is selected.
Here, the additional measurement is performed to obtain parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target portion based on the inspection result of the evaluation target portion by the selected inspection method. That is, in step S3 of inspecting the evaluation target portion, which will be described later, flaw detection of the evaluation target portion is performed by the selected inspection method, and an inspection result is obtained. Based on the obtained inspection result, in step S4 of evaluating the remaining life of the evaluation target portion, which will be described later, the remaining life of the evaluation target portion is evaluated. In the evaluation of the remaining life of the evaluation target portion, several parameters are required in addition to the inspection result of the flaw detection. In the additional measurement, parameters required to improve the accuracy of the remaining lifetime evaluation among these parameters are acquired.
In the following description, the measurement item to be additionally measured is also simply referred to as an additional measurement item.
Details of step S2 of selecting the inspection method and adding the measurement item will be described later.
(Outline of step S3 of checking evaluation target portion)
The step S3 of inspecting the evaluation target portion is a step of performing flaw detection on the evaluation target portion selected in the step S1 of selecting the evaluation target portion by using the inspection method selected in the step S2 of selecting the inspection method and adding the measurement item. That is, the step S3 of inspecting the evaluation target portion is a step of performing flaw detection on the evaluation target portion selected in the step S1 of selecting the evaluation target portion.
In step S3 of inspecting the evaluation target portion, additional measurement is performed as needed with respect to the additional measurement item selected in step S2 of selecting the inspection method and the additional measurement item.
Details of step S3 for performing the inspection of the evaluation target portion will be described later.
(Outline of step S4 of evaluating residual Life of evaluation target portion)
The step S4 of evaluating the remaining life of the evaluation target portion is a step of evaluating the remaining life of the evaluation target portion based on the result of the inspection of the evaluation target portion performed in the step S3 of inspecting the evaluation target portion.
In step S4 of evaluating the remaining lifetime of the evaluation target portion, if additional measurement is performed for the additional measurement item in step S3 of checking the evaluation target portion, the remaining lifetime of the evaluation target portion is also evaluated using the parameter obtained by the additional measurement.
For example, crack progression calculation, FEM, evaluation of damage mechanics, void simulation, tissue simulation, and the like can be used for evaluation of remaining life.
(Outline of step S5 of repairing evaluation target portion)
The step S5 of repairing the evaluation target portion is a step of repairing the evaluation target portion as needed based on the result of the inspection of the evaluation target portion performed in the step S3 of inspecting the evaluation target portion or the result of the remaining life evaluation of the evaluation target portion performed in the step S4 of evaluating the remaining life of the evaluation target portion.
Details of step S5 for repairing the evaluation target portion will be described later.
As described above, the method for inspecting plant equipment according to several embodiments includes: a step S1 of selecting a part to be evaluated, a step S2 of selecting an inspection method and adding a measurement item, and a step S3 of inspecting the part to be evaluated.
That is, the inspection method of the plant according to several embodiments includes a step S1 of selecting an inspection site, that is, a target site to be evaluated, from among one or more inspection candidate sites including a region 19 that is offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the parent pipe 10 in the axial line AXa direction of the parent pipe 10. The inspection method of the plant equipment according to several embodiments includes a step S3 of inspecting the evaluation target portion including at least one of the circumferential weld portion, the longitudinal weld portion, and the stem weld portion of the pipe, which is a step of inspecting the evaluation target portion by an inspection method set for each combination of the type of the evaluation target portion and the thickness of the evaluation target portion. The inspection method of the plant equipment according to several embodiments includes a step S3 of inspecting the evaluation target portion, which is a step of inspecting the evaluation target portion by an inspection method set for each combination of the type and index of the evaluation target portion for a pipe including a stem and a main pipe having a stem hole formed for mounting the stem, the index including, as parameters, an outer diameter of the main pipe and a plate thickness of the main pipe.
Therefore, according to the inspection method of the plant equipment of several embodiments, since the step S1 of selecting the evaluation target portion and the step S3 of inspecting the evaluation target portion, which is the step of performing the flaw detection on the inspection portion selected in the step S1, are provided, the presence of the crack 41 generated in the area 19 can be confirmed even during the limited inspection period. Therefore, the plant equipment can be efficiently inspected.
The inspection method of the plant equipment according to the several embodiments further includes a step S2 of selecting an inspection method and an additional measurement item, which are measurement items for obtaining additional measurement of parameters required to improve the accuracy of the remaining life evaluation of the evaluation target portion based on the inspection result of the evaluation target portion by the inspection method. Therefore, according to the inspection method of the plant equipment of the several embodiments, the inspection method of the evaluation target portion is appropriate according to the combination of the type of the evaluation target portion and the thickness of the evaluation target portion, and the accuracy of the inspection result of the evaluation target portion is improved. Further, the measurement item for additional measurement for improving the accuracy of the remaining lifetime evaluation is appropriate depending on the method of inspecting the evaluation target portion. By this, the accuracy of the remaining lifetime evaluation of the evaluation target portion based on the inspection result of the evaluation target portion is improved.
(Details of step S1 regarding the selected evaluation target portion)
Details of step S1 of selecting the evaluation target portion will be described. In the following description, a case will be described in which the pipe is the pipe 5 including the parent pipe 10 to which the supply pipe base 20 is attached, as shown in fig. 8.
As described above, in the pipe 5 of the type shown in fig. 8, it is found that the crack 41 may occur in the region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial line AXa direction of the base pipe 10. In addition, in the pipe 5 shown in fig. 8, it is known that cracks are likely to occur in the stem weld 30 as will be described later.
Accordingly, as a result of intensive studies, the inventors have found that in the piping 5 shown in fig. 8, the outside diameter D and the plate thickness T of the main pipe 10 are included as parameters, and that if the index indicating the relative thickness of the plate thickness T is equal to or smaller than a predetermined value, that is, if the plate thickness T of the main pipe 10 is relatively thin, the above-mentioned region 19 is liable to generate cracks before the pipe seat welded portion 30. On the other hand, if the index exceeds the predetermined value, that is, if the plate thickness T of the parent pipe 10 is relatively large, it is determined that the header weld 30 is likely to crack before the region 19.
Therefore, in several embodiments, in step S1 of selecting the evaluation target portion, if the index is equal to or smaller than the predetermined value, the region 19 is selected as the inspection portion (evaluation target portion). In several embodiments, in step S1 of selecting the evaluation target portion, if the index exceeds the predetermined value, the stem weld 30 is selected as the inspection portion (evaluation target portion).
Here, the index may be, for example, a ratio (T/D) of the plate thickness T of the parent pipe 10 divided by the outer diameter D of the parent pipe 10.
That is, in several embodiments, in step S1 of selecting the evaluation target portion, if the parent pipe thickness/outer diameter ratio (T/D) is equal to or smaller than the predetermined value Th, the above-described region 19 is selected as the inspection portion (evaluation target portion). In several embodiments, in step S1 of selecting the evaluation target portion, if the ratio (T/D) of the outer diameter of the base pipe plate thickness exceeds the predetermined value Th, the socket weld 30 is selected as the inspection portion (evaluation target portion).
In the case where the outside diameter/thickness ratio (D/T) of the parent pipe 10, which is the inverse of the parent pipe thickness/outside diameter ratio (T/D), is divided by the thickness T of the parent pipe 10, as the index, the region 19 may be selected as the inspection region (evaluation target region) if the parent pipe outside diameter/thickness ratio (D/T) is equal to or greater than the predetermined value Th in the step S1 of selecting the evaluation target region. If the ratio (D/T) of the outer diameter to the plate thickness of the parent pipe is smaller than the predetermined value Th, the socket weld 30 may be selected as the inspection site (the site to be evaluated).
The predetermined value Th is different depending on the value of an index including, for example, the outer diameter d and the thickness t of the pipe of the connected socket 20 as parameters. That is, in several embodiments, the predetermined value Th is present for each of the connection portions 7 connected to the respective stem 20 in respect of the plurality of pipes 5 shown in fig. 8 present in the plant.
In several embodiments, information about the positions of the connection portions 7 connected to the respective stem 20 and the predetermined value Th existing for each connection portion 7 is stored in advance as a database in a storage device (see fig. 3).
Fig. 3 is a diagram showing a storage device storing the database and a terminal device accessing the storage device. As described above, in the storage device 1, the positions of the connection portions 7 connected to the respective stem 20 in the plurality of pipes 5, the predetermined value Th existing for each connection portion 7, the information on the outer diameter D and the plate thickness T of the parent pipe 10, and the like are stored as databases.
As will be described later, the storage device 1 stores information about the relation between the portion where the welded portion exists, the thickness of the portion, and the position where the greatest damage is likely to occur as a database. The terminal device 2 is a terminal device such as a personal computer, for example, and can read information of a database stored in the storage device 1 from the storage device 1 and present the information to an operator of the terminal device 2. The storage device 1 may be disposed in a different place from the terminal device 2 or may be disposed in the terminal device 2. The terminal device 2 includes: an arithmetic device 3 for executing various arithmetic processes, an input device 4 for receiving an input operation from an inspector, an operator, or the like, and a display unit 2a for displaying an arithmetic result or the like of the arithmetic device 3.
In several embodiments, in step S1 of selecting the evaluation target portion, when an instruction is input from the input device 4 to select the evaluation target portion, the computing device 3 reads out information stored in the database of the storage device 1 from the storage device 1 and selects the evaluation target portion.
For example, in several embodiments, in step S1 of selecting the evaluation target portion, the arithmetic device 3 reads information on the predetermined value Th, the outer diameter D of the parent pipe 10, and the plate thickness T from the storage device 1 for the pipe 5 to which the stem 20 is connected as shown in fig. 8. The computing device 3 calculates the ratio (T/D) of the outer diameter of the main pipe plate based on the read information. The computing device 3 compares the calculated plate thickness/outer diameter ratio (T/D) of the parent pipe with the read predetermined value Th.
When the ratio (T/D) of the outer diameter to the plate thickness of the parent pipe is equal to or smaller than the predetermined value Th, the arithmetic unit 3 selects the above-mentioned region 19 as the inspection site (evaluation target site). If the ratio (T/D) of the outer diameters of the thicknesses of the parent pipes exceeds the predetermined value Th, the computing device 3 selects the socket weld 30 as the inspection site (the site to be evaluated).
Note that the ratio (T/D) of the outer diameters of the thicknesses of the parent pipe of the plurality of pipes 5 may be stored in the storage device 1. In this case, the arithmetic unit 3 may read the plate thickness/outer diameter ratio (T/D) of the parent pipe from the storage device 1 instead of reading the information on the outer diameter D and the plate thickness T of the parent pipe 10.
After the evaluation target portion is selected, the arithmetic device 3 performs the processing described below in step S2 of selecting the inspection method and adding the measurement item.
(Details of step S2 of selecting a test method and adding a measurement item)
The details of step S2 of selecting the inspection method and adding the measurement item will be described below.
For example, in a thermal power plant, there are many types of welded parts in a steam pipe connecting a boiler and a steam turbine. For example, steam pipes include a circumferential weld portion connecting pipes to each other and a stem weld portion connecting pipes to a branch pipe. In addition, when the pipe is made of a plate-like member, there is a longitudinal welded portion extending in the pipe axis direction in order to connect the end portions of the plates to each other.
As is clear from the findings of the inventors, when the welded portion is present at a different location, the position where the crack is likely to occur is different. In addition, according to the findings of the inventors, even in the same kind of welded portion, the position where the crack is likely to occur is different depending on the thickness of the portion.
Fig. 2 is a table showing the relationship between the portion where the welded portion exists, the thickness of the portion, and the position where the crack is likely to occur, as found by the inventors of the present invention.
The inventors have found that even in the same type of welded portion, the positions where cracks are likely to occur are different from each other with a thickness of about 20mm as a boundary. In the table shown in FIG. 2, thin walls indicate a thickness of 20mm or less, and thick walls indicate a thickness exceeding 20mm. The same applies to the following description.
For example, in a longitudinal welded portion in a straight pipe of a pipe, cracks are likely to occur in the thick portion of the longitudinal welded portion, and the greatest damage is likely to occur. This is because the creep speed of the Heat Affected Zone (HAZ) due to welding is faster than the creep speeds of the base metal and the weld metal, and the multiaxial degree of stress in the plate thickness in the HAZ is increased.
For example, in a longitudinal welded portion in a bend of a pipe, cracks are likely to occur in the thick portion of the longitudinal welded portion, and the greatest damage is likely to occur. The reason for this is the same as the longitudinal welded portion in the straight pipe described above.
For example, in a circumferential welded portion of a pipe, cracks are likely to occur on the outer surface of the circumferential welded portion at a thick portion, and the greatest damage is likely to occur. This is because the maximum position of the bending stress acting on the welded portion due to the pipe system stress, that is, the stress caused by external forces or the like received from, for example, the support structure of the pipe and other pipes connected thereto, and the thermal stress generated by limiting the thermal expansion of the pipe system stress itself is the outer surface. In addition, for example, in a circumferential welded portion of a pipe, cracks are easily generated in the thickness of the circumferential welded portion at a thin portion, and the most damage is easily generated. The reason for this is that, although the thin portion is also affected by the piping stress as well as the thick portion, the distribution of bending stress in the plate thickness direction is small because the plate thickness is small, and the influence of the multi-axis degree due to the creep speed difference is larger.
In the case of the pipe 5 shown in fig. 8, for example, as described above, if the ratio (T/D) of the outer diameter of the plate thickness of the parent pipe is equal to or smaller than the predetermined value Th, the region 19 is likely to be cracked. Conversely, if the ratio (T/D) of the plate thickness and the outer diameter of the parent pipe exceeds the predetermined value Th, the header weld 30 is liable to crack.
For example, in the stem weld 30, both the thin portion and the thick portion are likely to crack and the greatest damage is likely to occur at the outer surface and the inner surface of the stem weld 30 at the slit peripheral portions. The reason why the outer surface is easily damaged is that hoop stress (hoop stress) of the pipe is greatest at the outer surface. On the other hand, the reason why the inner surface slit is easily damaged is that stress concentration occurs at the crack-like tip portion of the slit. The slit in the inner surface of the stem welding portion 30 is a boundary between the pipe (parent pipe 10) and the stem 20 (branch pipe, plug, tube, etc.), and the boundary is a portion left as a slit because the weld metal is not sufficiently fused at the time of welding.
In most of the current factory facilities, the thin-walled straight pipe and the thin-walled elbow used in the high-temperature and high-pressure environment are hardly welded, and therefore, the longitudinal welded portion in the thin-walled straight pipe and the thin-walled elbow is not described.
Such information about the relation between the portion where the welded portion exists, the thickness of the portion, and the position where the greatest damage is likely to occur is stored in advance as data in the storage device 1 shown in fig. 3.
As described above, the storage device 1 stores information about the relation between the portion where the welded portion exists, the thickness of the portion, and the position where the greatest damage is likely to occur as a database.
(Inspection method suitable for flaw detection in the interior of sheet thickness)
Examples of inspection methods suitable for inspection of the inside of a sheet thickness include ultrasonic inspection by a conventional UT method, ultrasonic inspection by a TOFD method, ultrasonic inspection by a phased array method, ultrasonic inspection by an open-composite method, ultrasonic inspection by a high-frequency UT method, and ultrasonic inspection by an ultrasonic noise method.
Parameters required to improve the accuracy of the remaining life evaluation of the evaluation target portion based on the inspection results of the inspection method based on the flaw detection suitable for the inside of the plate thickness are, for example, the size, shape, temperature, and material characteristics of the evaluation target portion.
Examples of the measurement items for additional measurement for obtaining the size and shape of the evaluation target portion include the outer diameter of the pipe, the plate thickness of the pipe, the flatness of the pipe, the shape of the cross section of the weld line when viewed in the longitudinal direction, and the shape of the heat affected zone (HAZ zone) generated by welding. By obtaining the size and shape of the evaluation target portion, the stress acting on the welded portion can be calculated with high accuracy in the residual life evaluation. In particular, the outer diameter, the flatness, and the cross-sectional shape of the piping are effective measurement items for precisely calculating stress (bending and stretching) acting in the circumferential direction, which is important in the longitudinal welded portion.
Examples of the measurement items for additional measurement for obtaining the temperature of the evaluation target portion include the formation state of the steam oxide scale, the formation state of the precipitate, and the tissue change of the evaluation target portion, and the temperature of the evaluation target portion can be estimated from these measurement results. The temperature in this case means a past temperature history or a highest temperature that has been applied in the past. By acquiring the temperature of the evaluation target portion, the temperature condition can be set with high accuracy in the remaining lifetime evaluation.
Examples of the measurement items for additional measurement for obtaining the material properties of the evaluation target portion include hardness of the evaluation target portion. In addition, a small amount of sample may be collected from the evaluation target portion, and a creep test or the like may be performed on the sample, thereby obtaining the material characteristics of the evaluation target portion. By obtaining the material characteristics of the evaluation target portion, the strength of the welded portion can be set with high accuracy in the evaluation of the remaining life.
In the storage device 1, each of the inspection methods is stored as a database as an inspection method suitable for flaw detection in the inside of the sheet thickness. In the storage device 1, the additional measurement items are stored in a database in association with an inspection method suitable for flaw detection in the inside of the sheet thickness. In the storage device 1, information of the flow of the process to be performed in step S3 of checking the evaluation target portion including the process of determining whether to measure the additional measurement item is stored as a database. The flow of this process will be described later.
In the ultrasonic inspection, the area near the surface (for example, a distance of a few mm from the surface) of the evaluation target portion is a dead zone, and therefore flaw detection is impossible. Therefore, for example, if it is determined that the flaw in the plate thickness is present in the vicinity of the dead zone as a result of the flaw detection in the plate thickness, in step S3 of performing the inspection of the evaluation target portion, a dead zone reduction countermeasure for reducing the influence of the dead zone is performed.
As a countermeasure for the dead zone reduction, for example, inspection of the outer surface is cited. Examples of the method for inspecting the outer surface include magnetic powder inspection, penetration inspection, inspection by MT transfer, and eddy current inspection. If the presence of the damage to the outer surface can be confirmed by these checks, it can be determined that the damage existing in the vicinity of the dead zone inside the plate thickness is continuous with the damage to the outer surface, and if the presence of the damage to the outer surface cannot be confirmed, it can be determined that the damage existing in the vicinity of the dead zone inside the plate thickness does not reach at least the outer surface.
In addition, as a countermeasure for the dead zone reduction, the pile height of the welded portion may be removed. By removing the pile height of the welded portion, magnetic powder inspection and the like become easy. In addition, by removing the pile height of the welded portion, the flaw detector for ultrasonic flaw detection can be brought into contact with the surface after the pile height of the welded portion is removed, and the flaw detection range can be enlarged. In addition, by removing the pile height of the welded portion, there is a case where a visually observable damage occurs on the surface after the pile height of the welded portion is removed. Further, by removing the pile height of the welded portion, damage existing only in the vicinity of the surface of the pile height can be removed.
In the storage device 1, the dead zone reduction measures associated with the inspection method suitable for the flaw detection in the plate thickness are stored as a database.
(Inspection method suitable for flaw detection of outer surface)
Examples of inspection methods suitable for inspection of the outer surface include magnetic powder inspection, penetration inspection, inspection by MT transfer, and eddy current inspection.
Parameters required for improving the accuracy of the remaining lifetime evaluation of the evaluation target portion based on the inspection results of the inspection method based on the inspection suitable for the outer surface inspection are, for example, the size, shape, temperature, and material characteristics of the evaluation target portion.
The measurement items for additional measurement for obtaining the size and shape of the evaluation target portion, the measurement items for additional measurement for obtaining the temperature of the evaluation target portion, and the measurement items for additional measurement for obtaining the material property of the evaluation target portion are as described above.
As described later, when the maximum damage is likely to occur on the outer surface, in addition to the flaw detection by the inspection method suitable for the flaw detection of the outer surface, a nondestructive inspection for obtaining, for example, a local life consumption rate in the outer surface, which is a local life consumption rate of 100% of the time when a crack is visually observable, may be performed. Examples of the nondestructive inspection method include a nondestructive inspection method such as a void number density method, a void area ratio method, a texture contrast method, a precipitate inter-grain distance method, an a-parameter method, a crystal grain deformation method, a void grain boundary length method, and a carbide composition measurement method.
As will be described later, when the local life consumption rate of the outer surface obtained based on the inspection result of the nondestructive inspection exceeds a predetermined value or when there is damage to the outer surface, flaw detection is performed in the interior of the evaluation target portion in the vicinity of the outer surface.
Examples of the inspection method suitable for the flaw detection inspection of the interior of the evaluation target portion in the vicinity of the outer surface include ultrasonic inspection by a conventional UT method, ultrasonic inspection by a TOFD method, ultrasonic inspection by a phased array method, ultrasonic inspection by an open synthesis method, ultrasonic inspection by a high-frequency UT method, ultrasonic inspection by an ultrasonic noise method, and the like.
In the storage device 1, as inspection methods suitable for flaw detection of the outer surface, the inspection methods are stored as databases. In the storage device 1, the additional measurement items are stored in association with an inspection method suitable for flaw detection of the outer surface as a database. In the storage device 1, as a nondestructive inspection method for determining a local lifetime consumption rate in the outer surface, the nondestructive inspection method is stored as a database. In the storage device 1, as inspection methods suitable for flaw detection in the interior of the evaluation target portion in the vicinity of the outer surface, the inspection methods are stored as databases. In the storage device 1, information of the flow of the process to be performed in step S3 of checking the evaluation target portion including the process of determining whether to measure the additional measurement item is stored as a database. The flow of this process will be described later.
(Inspection method suitable for flaw detection of peripheral portion of slit on inner surface)
In flaw detection of the peripheral portion of the inner surface slit, although the inner surface slit exists from the beginning in the flaw detection range, the existence range of the inner surface slit changes depending on the state of welding. Therefore, in flaw detection of the peripheral portion of the inner surface slit, it is difficult to distinguish the inner surface slit from the flaw. Therefore, in the flaw detection of the peripheral portion of the inner surface slit, the crack that can be observed by visual observation such as a macro crack is detected, and the detected crack is not distinguished from the inner surface slit, and is treated as the crack that can be observed by visual observation such as a macro crack.
Examples of the inspection method suitable for flaw detection of the peripheral portion of the inner surface slit include ultrasonic inspection by a conventional UT method, ultrasonic inspection by a TOFD method, ultrasonic inspection by a phased array method, ultrasonic inspection by an open synthesis method, ultrasonic inspection by a high-frequency UT method, ultrasonic inspection by an ultrasonic noise method, and the like.
Parameters required to improve the accuracy of the remaining lifetime evaluation of the evaluation target portion based on the inspection results of the inspection method applied to the flaw detection of the peripheral portion of the inner surface slit are, for example, the size, shape, temperature, and material characteristics of the evaluation target portion.
Examples of the measurement items for additional measurement for obtaining the size and shape of the evaluation target portion include the shape of the heat affected zone (HAZ portion) generated by welding, the surface shape of the weld metal, the outer diameter of the pipe (parent pipe) in the base, and the wall thickness of the parent pipe.
The measurement items for additional measurement for obtaining the temperature of the evaluation target portion and the measurement items for additional measurement for obtaining the material property of the evaluation target portion are the same as those described above.
In the storage device 1, as inspection methods suitable for flaw detection of the peripheral portion of the inner surface slit, the above-described inspection methods are stored as a database. In the storage device 1, the additional measurement items are stored in a database in association with an inspection method suitable for flaw detection of the peripheral portion of the inner surface slit. In the storage device 1, information of the flow of the process to be performed in step S3 of checking the evaluation target portion including the process of determining whether to measure the additional measurement item is stored as a database. The flow of this process will be described later.
In step S2 of selecting the inspection method and the additional measurement item, when the inspector operates the terminal device 2 to input the type of the evaluation target portion and the thickness of the evaluation target portion, the terminal device 2 reads out an inspection method suitable for flaw detection of the evaluation target portion and the additional measurement item for improving the accuracy of remaining life evaluation of the evaluation target portion based on the inspection result of the inspection method from the database of the storage device 1. The terminal device 2 displays the read inspection method and the additional measurement item on, for example, the display unit 2a of the terminal device 2.
The terminal device 2 reads information of the flow of the processing to be performed in step S3 of checking the evaluation target portion from the database of the storage device 1. The terminal device 2 displays the read information of the flow of the processing to be performed in step S3 of checking the evaluation target portion on, for example, the display unit 2a of the terminal device 2.
In the case where the read inspection method is an inspection method suitable for flaw detection of the outer surface, for example, a nondestructive inspection method for obtaining a local life consumption rate and an inspection method suitable for flaw detection of the inside of the evaluation target portion in the vicinity of the outer surface are displayed on the display unit 2a of the terminal device 2.
That is, step S2 of selecting the inspection method and the additional measurement item is a step of selecting the inspection method and the measurement item by using a database of predetermined inspection methods and additional measurement items for each combination of the type of the evaluation target portion and the thickness of the evaluation target portion.
As described above, according to the inspection method of the plant equipment of the several embodiments, since the step S2 of selecting the inspection method and adding the measurement item is provided, the inspection method and the measurement item to be executed in the step S3 of inspecting the evaluation target portion can be rapidly selected.
(Details of step S3 for inspecting the evaluation target portion)
In step S3 of inspecting the evaluation target portion, flaw detection is performed on the evaluation target portion as follows.
(1) The evaluation target portion is a portion in which the maximum damage is likely to occur in the plate thickness
For example, when the evaluation target portion is a portion where the maximum damage is likely to occur in the plate thickness, the flow chart shown in fig. 4 is presented in step S2 in which the inspection method and the additional measurement item are selected.
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 maximum damage is likely to occur in the plate thickness. In step S3 of inspecting the evaluation target portion, the inspector performs flaw detection of the evaluation target portion, determines whether to measure an additional measurement item, and performs additional measurement as needed, according to the flowchart shown in fig. 4.
In step S301, the inspector performs a flaw detection inspection of the inside of the plate thickness of the evaluation target portion, and detects the position and the size of the flaw in the inside of the plate thickness.
In step S301, flaw detection of the inside of the sheet thickness is performed by any one of the inspection methods of ultrasonic inspection by a conventional UT method, ultrasonic inspection by a TOFD method, ultrasonic inspection by a phased array method, ultrasonic inspection by an open synthesis method, ultrasonic inspection by a high-frequency UT method, ultrasonic inspection by an ultrasonic noise method, and the like. As described above, each inspection method is presented to the inspector in step S2 of selecting an inspection method and adding a measurement item.
Next, in step S302, the inspector determines whether or not there is an intrinsic damage, that is, whether or not there is a damage in the plate thickness of the evaluation target portion, based on the result of the flaw detection performed in step S301. When it is determined in step S302 that there is no damage, the present process is ended.
When it is determined in step S302 that there is a damage, the flow proceeds to step S303, where an inspector determines whether or not the detected damage exists in the vicinity of the dead zone of the inspection method performed in step S301.
If the detected damage does not exist in the vicinity of the dead zone, the process proceeds to step S306, which will be described later. If the detected damage exists in the vicinity of the dead zone, the flow proceeds to step S304, where the inspector performs the dead zone reduction countermeasure described above. The dead zone reduction countermeasure is presented to the inspector in step S2 of selecting the inspection method and adding the measurement item.
As described above, in the case of performing the dead zone reduction countermeasure, for example, inspection of the outer surface and removal of the pile height of the welded portion are performed. In addition, in the case of performing the dead zone reduction countermeasure, the outer surface inspection and the flaw detection of the inside of the plate thickness of the evaluation target portion may be performed after the stack height of the welded portion is removed.
In this way, in the inspection method of the plant equipment according to the several embodiments, step S304 is a step of further performing an inspection based on an inspection method of inspecting the outer surface of the evaluation target portion or performing an inspection of the interior of the evaluation target portion after the removal of the pile of the welded portion at the evaluation target portion, in a case where the interior of the evaluation target portion is inspected and the damage is detected within a predetermined distance from the outer surface side of the evaluation target portion to the insensitive area of the inspection method. Therefore, the influence of the dead zone of the inspection method can be suppressed.
After the dead zone reduction countermeasure is performed in step S304, in step S305, the inspector determines whether or not the damage existing in the vicinity of the dead zone inside the plate thickness is continuous with the damage of the outer surface.
If it is determined in step S305 that the damage existing in the vicinity of the dead zone in the plate thickness interior is not continuous with the damage of the outer surface, the inspector obtains the size of the damage in the plate thickness interior from the result of the flaw detection in step S301 without considering the damage of the outer surface in step S306.
If it is determined in step S305 that the damage existing in the vicinity of the dead zone inside the sheet thickness is continuous with the damage of the outer surface, in step S309, the inspector obtains the size of the damage inside the sheet thickness from the result of the flaw detection in step S301 so as to include the damage of the outer surface.
In step S307, when the inspector performs the remaining life evaluation in step S4 of performing the remaining life evaluation of the evaluation target portion according to the size of the damage acquired in step S306 or step S309, it is determined whether or not it is necessary to improve the accuracy of the remaining life evaluation. Specifically, it is determined whether or not the accuracy of the remaining life evaluation needs to be improved by referring to the size of the damage acquired in step S306 and the simple determination coordinate diagram shown in fig. 5.
Fig. 5 is a graph showing the ratio of the magnitude of damage to the plate thickness at the site to be maintained, along the horizontal axis, and the stress acting on the site to be evaluated along the vertical axis. Lines L1 to L7 in the graph of fig. 5 represent cases where the remaining life until the detected damage penetrates the evaluation target portion is 20000 hours. The difference between the straight lines L1 to L7 is the difference in temperature at each of the maintenance target portions, and the temperature at the maintenance target portion increases as the line is located on the left side in fig. 5. That is, the straight line L1 is a straight line indicating the highest temperature, and the straight line L7 is a straight line indicating the lowest temperature. The 20000 hours are, for example, about 17000 hours plus a margin of about 3000 hours, which is the time until the next periodic inspection after two years.
The inspector obtains the ratio of the size of the damage to the plate thickness at the maintenance target portion from the size of the damage and the plate thickness of the maintenance target portion obtained in step S306, and obtains the stress and temperature acting on the evaluation target portion during the operation of the plant from, for example, the operation condition of the plant. Further, it was confirmed that the position corresponding to the obtained ratio and stress is the positional relationship between any one of the straight lines L1 to L7 corresponding to the obtained temperature and the position in the graph shown in fig. 5.
If the point corresponding to the determined ratio and stress is located in the left region of any of the straight lines L1 to L7 corresponding to the determined temperature and is distant from the straight line to a certain extent, it can be determined that the remaining life until the detected damage penetrates the evaluation target portion exceeds 20000 hours. In this case, in step S307, when the inspector performs the remaining life evaluation in step S4 of performing the remaining life evaluation of the evaluation target portion, it is determined that it is not necessary to improve the accuracy of the remaining life evaluation, and the process in step S3 of performing the inspection of the evaluation target portion is ended.
If the point corresponding to the obtained ratio and stress is located in the left region of any of the straight lines L1 to L7 corresponding to the obtained temperature but is close to the straight line or is located in the region on the right side of the straight line, it can be determined that the remaining life until the detected damage penetrates the evaluation target portion may be less than 20000 hours. In this case, in step S307, when the inspector performs the remaining life evaluation in step S4 of performing the remaining life evaluation of the evaluation target portion, it is determined that the accuracy of the remaining life evaluation needs to be improved, and the flow proceeds to step S308.
In step S308, the inspector performs additional measurement of the additional measurement item. As described above, the additional measurement item is presented to the inspector in step S2 of selecting the inspection method and the additional measurement item. After performing the additional measurement, the inspector ends the process in step S3 of inspecting the evaluation target portion.
In this way, in the inspection method of the plant equipment according to the several embodiments, step S307 is a step of determining whether additional measurement is necessary based on the damage length obtained from the inspection result of the evaluation target portion. In the inspection method of the plant equipment according to the several embodiments, since the step of determining whether additional measurement is necessary or not is provided based on the damage length obtained from the inspection result of the evaluation target portion, it is possible to easily determine whether additional measurement is necessary or not based on the damage length. Further, if it is determined that additional measurement is not necessary, additional measurement is not required, and therefore, the system is efficient.
In the inspection method of the plant equipment according to several embodiments, it is determined whether additional measurement is necessary or not based on the size of the damage acquired in step S306 and the simple determination coordinate diagram shown in fig. 5. That is, the threshold value of the damage length used for determining whether or not the additional measurement is necessary is determined based on at least one of the temperature condition and the stress condition of the evaluation target portion during the operation of the plant. Therefore, the threshold value of the damage length used for determining whether additional measurement is necessary or not reflects at least one of the temperature condition and the stress condition of the evaluation target portion during the operation of the plant equipment, and therefore, the accuracy of whether additional measurement is necessary or not can be improved.
(2) The evaluation target portion is a portion where the outer surface is likely to be damaged most
For example, when the evaluation target portion is a portion where the external surface is likely to be damaged most, the flow chart shown in fig. 6 is presented in step S2 of selecting the inspection method and adding the measurement item.
Fig. 6 is a flowchart showing a flow of processing to be performed in step S3 of inspecting the evaluation target portion when the evaluation target portion is a portion where the greatest damage is likely to occur on the outer surface. In step S3 of inspecting the evaluation target portion, the inspector performs flaw detection of the evaluation target portion, determines whether to measure an additional measurement item, and performs additional measurement as needed, according to the flowchart shown in fig. 6.
In step S321, the inspector performs inspection of the outer surface of the evaluation target portion to detect damage to the outer surface.
In step S321, flaw detection of the outer surface is performed by any one of inspection methods such as magnetic powder flaw detection, penetration flaw detection, inspection by MT transfer method, eddy current flaw detection, and the like. As described above, each inspection method is presented to the inspector in step S2 of selecting an inspection method and adding a measurement item.
Next, in step S322, the inspector determines whether or not there is damage to the outer surface based on the result of the inspection performed in step S321. If it is determined in step S322 that there is no damage, the process proceeds to step S326, which will be described later.
When it is determined in step S322 that there is a flaw, the flow proceeds to step S323, and the inspector performs flaw detection in the interior of the evaluation target portion in the vicinity of the outer surface in order to inspect how much the flaw of the outer surface has passed into the interior of the evaluation target portion. In step S323, the inspector performs inspection of the inside of the evaluation target portion in the vicinity of the outer surface by any one of an ultrasonic inspection by a normal UT method, an ultrasonic inspection by a TOFD method, an ultrasonic inspection by a phased array method, an ultrasonic inspection by an open synthesis method, an ultrasonic inspection by a high-frequency UT method, an ultrasonic inspection by an ultrasonic noise method, and the like. The above-mentioned inspection methods are presented to the inspector in step S2 of selecting an inspection method and adding a measurement item.
In step S324, the inspector obtains the depth (size) of the damage occurring on the outer surface based on the inspection result of the flaw detection performed in step S323, and proceeds to step S307. The processing in step S307 and step S308 in fig. 6 is the same as the processing in step S307 and step S308 shown in fig. 4, and therefore, the description thereof is omitted.
In step S326, if there is no replica of the evaluation target portion, the inspector ends the process in step S3 of inspecting the evaluation target portion, and if there is a replica of the evaluation target portion, the flow proceeds to step S327.
In step S327, the inspector performs a nondestructive inspection (NED) based on the replica of the evaluation target portion, and calculates the local life consumption rate of the outer surface. In step S327, the inspector calculates the local life consumption rate in the outer surface based on any one of inspection methods such as a void number density method, a void area ratio method, a texture comparison method, a precipitate inter-grain distance method, an a parameter method, a crystal grain deformation method, a void grain boundary length method, and a carbide composition measurement method. The above-mentioned inspection methods are presented to the inspector in step S2 of selecting an inspection method and adding a measurement item.
In step S328, the inspector determines whether or not the local life consumption rate of the outer surface calculated in step S327 exceeds a predetermined value. Here, when the time when the crack is visually observable is set to 100%, for example, 90% is used as the predetermined value, but the predetermined value is not limited to 90%.
If the local life consumption rate of the outer surface calculated in step S327 exceeds 90%, the routine proceeds to step S323, and the inspector performs the above-described processing of step S323.
When the local lifetime consumption rate of the outer surface calculated in step S327 is 90% or less, the inspector ends the process of step S3 of inspecting the evaluation target portion.
As described above, the inspection method of the plant equipment according to the several embodiments includes step S327 of inspecting the outer surface of the evaluation target portion and calculating the local life consumption rate, which is set to 100% of the time when the crack that can be visually observed is generated. In addition, the inspection method of the plant according to the several embodiments includes a step S323 of performing an inspection based on an inspection method of inspecting the inside of the evaluation target portion when the calculated life consumption rate exceeds a predetermined value. Therefore, it is possible to check how far the damage progresses from the outer surface of the evaluation target portion toward the inside.
(3) The evaluation target portion is a portion in which the peripheral portion of the inner surface slit is likely to be damaged most
For example, when the evaluation target portion is a portion where the maximum damage is likely to occur in the peripheral portion of the inner surface slit, the flowchart shown in fig. 7 is presented in step S2 in which the inspection method and the additional measurement item are selected.
Fig. 7 is a flowchart showing a flow of processing to be performed in step S3 of inspecting the evaluation target portion when the evaluation target portion is a portion where the greatest damage is likely to occur in the peripheral portion of the inner surface slit. In step S3 of inspecting the evaluation target portion, the inspector performs flaw detection of the evaluation target portion, determines whether to measure an additional measurement item, and performs additional measurement as needed, according to the flowchart shown in fig. 7.
In step S341, the inspector performs inspection of the peripheral portion of the inner surface slit at the evaluation target portion to detect the position and the size of the damage of the peripheral portion of the inner surface slit.
In step S341, flaw detection of the peripheral portion of the inner surface slit is performed by any one of the inspection methods of ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the open synthesis method, ultrasonic inspection by the high-frequency UT method, ultrasonic inspection by the ultrasonic noise method, and the like. As described above, each inspection method is presented to the inspector in step S2 of selecting an inspection method and adding a measurement item.
Next, in step S342, the inspector determines whether or not there is damage to the peripheral portion of the inner surface slit based on the result of the flaw detection performed in step S341. When it is determined in step S342 that there is no damage, the present process is ended.
When it is determined in step S342 that there is a flaw, the flow proceeds to step S343, and the inspector obtains the size of the flaw in the peripheral portion of the inner surface slit from the result of the flaw detection in step S341, and proceeds to step S307. The processing in step S307 and step S308 in fig. 7 is the same as the processing in step S307 and step S308 shown in fig. 4, and therefore, the description thereof is omitted.
In this way, in the inspection method of the plant equipment according to the several embodiments, if the maintenance target portion is a thick longitudinal welded portion in a straight pipe or a bent pipe, for example, the greatest damage is likely to occur in the plate thickness of the longitudinal welded portion. Accordingly, the inspector performs flaw detection of the evaluation target portion by using the inspection method suitable for flaw detection inside the plate thickness according to the flowchart shown in fig. 4 as described in (1) above, determines whether to measure the additional measurement item, and performs additional measurement as needed.
That is, the inspection method set for the longitudinal welded portion having the wall thickness exceeding the predetermined 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 prescribed value.
In the inspection method of the plant equipment according to the several embodiments, if the maintenance target portion is a longitudinal welded portion having a wall thickness exceeding a predetermined value, an inspection method suitable for flaw detection inside the plate thickness is selected, and therefore, the additional measurement item is selected to include the cross-sectional shape of the pipe, that is, the cross-sectional shape of the pipe when viewed in the pipe axis direction. Therefore, a measurement item suitable for a longitudinal welded portion having a wall thickness exceeding a predetermined value can be selected.
In the inspection method of the plant equipment according to the several embodiments, if the maintenance target portion is, for example, a thick cylindrical welded portion, the greatest damage is likely to occur on the outer surface of the cylindrical welded portion. Accordingly, the inspector performs flaw detection of the evaluation target portion by using an inspection method suitable for flaw detection of the outer surface, makes a determination as to whether to measure an additional measurement item, and performs additional measurement as needed, according to the flowchart shown in fig. 6, as described in (2) above.
That is, the inspection method set for the circumferential weld having a wall thickness exceeding a predetermined value is an inspection method for inspecting the outer surface of the circumferential weld that is the evaluation target portion. Therefore, the inspection method is suitable for circumferential welds having a wall thickness exceeding a prescribed value.
In the inspection method of the plant equipment according to the several embodiments, if the maintenance target portion is, for example, a thin cylindrical welded portion, the greatest damage is likely to occur in the plate thickness of the cylindrical welded portion. Accordingly, the inspector performs flaw detection of the evaluation target portion by using the inspection method suitable for flaw detection inside the plate thickness according to the flowchart shown in fig. 4 as described in (1) above, determines whether to measure the additional measurement item, and performs additional measurement as needed.
That is, the inspection method set for the circumferential weld having a wall thickness equal to or smaller than a predetermined value is an inspection method for inspecting the inside of the circumferential weld as the evaluation target portion. Therefore, the inspection method is suitable for circumferential weld portions having a wall thickness of a predetermined value or less.
In the inspection method of the plant equipment according to the several embodiments, if the maintenance target portion is, for example, a stem welded portion, the greatest damage is likely to occur in the peripheral portions of the outer surface and the inner surface slit of the stem welded portion. Accordingly, the inspector performs flaw detection of the evaluation target portion by using an inspection method suitable for flaw detection of the outer surface according to the flowchart shown in fig. 6 as described in (2) above, determines whether to measure an additional measurement item, and performs additional measurement as needed. Further, the inspector performs flaw detection of the evaluation target portion by using an inspection method suitable for flaw detection of the peripheral portion of the inner surface slit according to the flowchart shown in fig. 7 as described in (3) above, determines whether to measure additional measurement items, and performs additional measurement as needed.
That is, the inspection method set for the stem weld is an inspection method for inspecting the outer surface of the stem weld and the peripheral portion of the internal slit, which are the evaluation target portions. Therefore, the inspection method is suitable for the stem weld.
(Regarding flaw detectors used in ultrasonic inspection based on phased array method)
Fig. 9 is a schematic diagram showing a structure of a flaw detector used in performing ultrasonic inspection by a phased array method in step S3 of inspecting an evaluation target portion.
The flaw detector 50 shown in fig. 9 includes a transmitting element 51 including a plurality of piezoelectric elements, a receiving element 53 including at least one piezoelectric element and different from the transmitting element 51, and a wedge member 55 in one housing 57. In the flaw detector 50 shown in fig. 9, the transmitting element 51 is disposed on one surface 55b of two surfaces 55b, 55c of the wedge member 55 adjacent to each other with the ridge line 55a interposed therebetween so that the arrangement direction ad of the plurality of piezoelectric elements is the same as the extending direction of the ridge line 55a, and the receiving element 52 is disposed on the other surface 55 c.
As a result of intensive studies, the inventors have found that, when ultrasonic flaw detection by the phased array method is performed, the transmitting element 51 and the receiving element 52 are separated elements and are disposed on the single wedge member 55 as described above, and thus, a region closer to the surface layer of the inspection object and a region farther from the surface layer can be inspected by the single flaw detector 50. As a result of intensive studies, the inventors have found that the above-described configuration of the flaw detector 50 can suppress the dead zone in the vicinity of the surface layer of the inspection object and can suppress the noise level in the vicinity of the surface layer of the inspection object.
Therefore, according to the flaw detector 50 shown in fig. 9, it is possible to inspect a region relatively close to the surface layer of the inspection object and a region relatively far from the surface layer 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 near the surface layer of the inspection object and the noise level near the surface layer of the inspection object are suppressed.
Fig. 10 is a view for explaining the refractive angle in the flaw detector 50 shown in fig. 9.
As shown in fig. 10, the flaw detector 50 shown in fig. 9 is configured such that the scanning range of the refraction angle θ includes at least a range of 35 degrees or more and 75 degrees or less.
The conventional phased array method generally has a scanning range of refraction angles of about 40 degrees to 70 degrees. Therefore, according to the flaw detector 50 shown in fig. 9, a larger range can be inspected.
The flaw detector 50 shown in fig. 9 is configured to be capable of performing ultrasonic flaw detection by a phased array method using ultrasonic waves having a frequency of 10MHz or more and 15MHz or less.
In the ultrasonic flaw detection, the shorter the wavelength, that is, the higher the frequency of ultrasonic waves used in general flaw detection, the smaller the defect size as a detection limit.
In the conventional ultrasonic flaw detection using the phased array method, the frequency of ultrasonic waves is often about 5 MHz. Therefore, according to the flaw detector 50 shown in fig. 9, since inspection is performed by using ultrasonic waves having a higher frequency than that of the conventional ultrasonic flaw detection by the phased array method, it is possible to detect a smaller crack.
(Details of step S5 of repairing the evaluation target portion)
Details of step S5 for repairing the evaluation target portion will be described. In the following description, a case where the crack 41 is generated in the region 19 will be described.
In the case where it is found that the crack 41 is generated in the region 19 in the pipe 5 shown in fig. 8, it is conceivable that the life of the pipe 5 is prolonged by repairing.
(Repair method according to one embodiment)
Fig. 11 is a flowchart showing the procedure of the process performed in step S5 of repairing the evaluation target portion when the crack 41 is generated in the region 19 in the pipe 5 shown in fig. 8.
Fig. 11 shows a repair method according to an embodiment of the processing sequence, which includes: step S51 of removing the stem 20, step S53 of forming the recess, step S55 of disposing the sealing plate 60 to the stem hole 13, and step S57 of backfilling.
(Step S51 of removing socket 20)
Step S51 of removing the stem 20 is a step of removing the stem 20 from the parent tube 10. Fig. 12 is a cross-sectional view of the pipe 5 after the stem 20 is removed from the parent pipe 10 in step S51 of removing the stem 20. In step S51 of removing the stem 20, the stem 20 is removed from the parent tube 10.
(Step S53 of forming a concave portion)
The step S53 of forming the concave portion is a step of forming the concave portion 71 by removing the region 11a, to which the stem 20 has been attached, from the parent tube 10 while leaving a part of the region 10c on the inner peripheral surface 10a side of the parent tube 10. 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 concave portion 71 is formed, when viewed from the radial outside of the main pipe 10, that is, when viewed from the axial line AXb of the stem 20.
In step S53 of forming the recess, the recess 71 is formed by removing a range larger than the diameter of the stem hole 13 except for the region 10c of a part of the inner peripheral surface 10a side of the parent tube 10 when viewed from the axial line AXb direction of the stem 20. 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, a region 10c of a part of the inner peripheral surface 10a side of the parent pipe 10 is reserved as a joint of the weld metal when the recess 71 is filled back and forth by welding in the backfilling step S57.
Fig. 15 is a schematic view of the pipe 5 in which the concave portion 71 is formed, as viewed from the outside in the radial direction of the parent pipe 10, and shows an example of the case where the concave portion 71 is provided when the plurality of tube holders 20 are arranged in a state of being close to each other along the axis AXa direction of the parent pipe 10.
As shown in fig. 15, when the plurality of sockets 20 are arranged in a state of approaching along the axis AXa direction of the parent pipe 10, the concave portion 71 may have a long hole shape along the axis AXa direction of the parent pipe 10. That is, after removing the plurality of sockets 20 that are adjacent in the direction of the axis AXa of the parent pipe 10, each region 11a to which the plurality of sockets 20 are attached may be removed from the parent pipe 10, thereby forming one concave portion 71.
In the case where the plurality of sockets 20 are arranged so as to approach each other along the axis AXa of the parent pipe 10 as in the case shown in fig. 15, the plurality of socket holes 13 may be connected to form long holes when the concave portion 71 is formed. In this case, in step S55 of disposing the sealing plate 60 to the stem hole 13, the sealing plate 60 formed so as to block the long hole may be disposed.
(Step S55 of disposing sealing plate 60 in socket hole 13)
Step S55 of disposing the sealing plate 60 in the stem hole 13 is a step of disposing the sealing plate 60 in the stem hole 13 formed in the above-described partial region 10 c.
Fig. 16 is a view for explaining step S55 of disposing sealing plate 60 in stem hole 13. As shown in fig. 16, in step S55 of disposing the sealing plate 60 to the stem hole 13, the small diameter portion 61 of the sealing plate 60 having the small diameter portion 61 smaller than the inner diameter of the stem hole 13 and the large diameter portion 63 larger than the inner diameter of the stem hole 13 is fitted to the stem hole 13 when disposing the sealing plate 60. That is, in several embodiments, the sealing plate 60 has a shape in which the large diameter portion 63 having a plate shape larger than the inner diameter of the stem hole 13 and the small diameter portion 61 having a plate shape smaller than the inner diameter of the stem hole 13 overlap in the plate thickness direction. Therefore, when the sealing plate 60 is disposed in the stem hole 13, the large diameter portion 63 is in contact with the surrounding area of the stem hole 13, and the sealing plate 60 can be prevented from accidentally penetrating into the interior of the parent pipe 10 from the stem hole 13. Further, when the sealing plate 60 is disposed in the stem hole 13, the small diameter portion 61 can be fitted in the stem hole 13, and thus, the disposed sealing plate 60 can be prevented from being accidentally displaced from the stem hole 13.
By closing the stem hole 13 with the sealing plate 60 having such a shape, it is possible to suppress the weld metal from accidentally penetrating into the interior of the parent pipe 10 from the stem hole 13 when the recess 71 is backfilled with welding in the backfilling step S57 as will be described later.
(Backfilling step S57)
The backfilling step S57 is a step of filling the recess 71 back and forth by welding after the step S55 of disposing the sealing plate 60 to the stem hole 13.
Fig. 17 is a cross-sectional view of the pipe 5 after the backfilling step S57 is performed. In step S57 of backfilling, the recess 71 is backfilled with the weld metal 73.
As described above, according to the repair method in the sequence of the processing shown in fig. 11, when the crack 41 is generated in the region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial line AXa direction of the base pipe 10, the repair can be performed appropriately.
(Repair methods according to other embodiments)
When the crack 41 generated in the region 19 is relatively small, the evaluation target portion can be repaired by the following repair method.
Fig. 18 is a flowchart showing the procedure of the process performed in step S5 of repairing the evaluation target portion when the relatively small crack 41 is generated in the region 19 in the pipe 5 shown in fig. 8.
The repair method according to another embodiment of the sequence of the processing shown in fig. 18 includes a step S151 of disposing the reinforcing plate and a step S153 of welding the reinforcing plate to the parent pipe. That is, the repair method according to the other embodiment of the sequence of the processing shown in fig. 18 is a repair method in which the mother pipe 10 is reinforced by attaching a reinforcing plate to the outer peripheral surface 10d of the mother pipe 10.
(Step S151 of disposing reinforcing plate)
The step S151 of disposing the reinforcing plate is a step of disposing the reinforcing plate 80 so as to surround the periphery of the stem 20 from the radially outer side of the stem 20 at the connection portion 7 of the parent pipe 10 to be connected to the stem 20.
Fig. 19 is a perspective view of the reinforcing plate 80. The reinforcing plate 80 according to one embodiment is a plate member having a wall thickness formed along the outer peripheral surface 10d of the parent pipe 10. In the reinforcing plate 80 of the embodiment, a hole 83 penetrating in the plate thickness direction is formed so as to surround the periphery of the stem 20 from the radially outer side. Accordingly, the inner diameter of the hole 83 is larger than the outer shape of the stem 20. The reinforcing plate 80 of one embodiment includes two dividing plates 81 divided into two along the radial direction of the hole 83.
In step S151 of disposing the reinforcing plate, the dividing plate 81, which is one part of the reinforcing plate 80 divided into two parts, and the dividing plate 81, which is the other part thereof, are disposed so as to face each other along the axis AXa direction of the parent pipe 10 with the stem 20 interposed therebetween.
Fig. 20 is a schematic view of a state in which the two dividing plates 8 are arranged so as to face each other along the axis AXa direction of the parent pipe 10 with the stem 20 interposed therebetween, as viewed from the outside in the radial direction of the parent pipe 10, that is, as viewed along the axis AXb of the stem 20.
As described above, the crack 41 generated in the region 19 is generated by the circumferential stress acting on the parent pipe 10. Therefore, when one of the partition plates 81 and the other partition plate 81 of the reinforcing plate 80 to be divided into two parts are disposed so as to face each other along the axis AXa direction of the parent pipe 10 with the stem 20 interposed therebetween, the partition plates 81 extend in the circumferential direction of the parent pipe 10, respectively. Therefore, by welding the dividing plates 81 to the parent pipe 10, the hoop stress acting on the parent pipe 10 can be effectively reduced by the dividing plates 81. Further, by using the reinforcing plate 80 divided into two parts, even if the other end of the two ends of the stem 20 opposite to the one end connected to the main pipe 10 is connected to another pipe or the like, the respective dividing plates 81 can be easily arranged.
If the other end of the two ends of the stem 20 opposite to the one end connected to the main pipe 10 is not connected to another pipe or the like, a reinforcing plate 80 that is not divided into two parts can be used.
(Step S153 of welding reinforcing plate to parent pipe)
The step S153 of welding the reinforcing plate to the parent pipe is a step of welding the reinforcing plate 80 disposed in the step S151 of disposing the reinforcing plate to the parent pipe 10.
Fig. 21 is a cross-sectional view of the pipe 5 after the reinforcing plate 80 is welded to the parent pipe 10 in step S153 of welding the reinforcing plate to the parent pipe. In step S153 of welding the reinforcing plate to the parent pipe, the reinforcing plate 80 may be welded not only to the parent pipe 10 but also to the stem 20. That is, in the example shown in fig. 21, the reinforcing plate 80 is welded to the parent pipe 10 by, for example, a welded portion 85, and is welded to the stem 20 by, for example, a welded portion 86.
If the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 is welded to the parent pipe 10 as described above, whereby the reinforcing plate 80 can reduce the hoop stress acting on the parent pipe 10. This reduces the progress rate of the crack 41, thereby extending the life. In addition, since the repair can be performed by a relatively simple method such as welding the reinforcing plate 80, the time and cost required for the repair can be suppressed.
The present invention is not limited to the above-described embodiments, and includes a modified embodiment and a combination of these embodiments as appropriate.
For example, in the above-described embodiments, the evaluation target portion is a welded portion of a steam pipe of a plurality of systems connecting a boiler and a steam turbine in a thermal power plant, but the welded portion to be evaluated is not limited to a part of the boiler, and the inspection method of the plant of the present invention can be applied to various welded portions exposed to high temperature and high pressure and to portions other than the welded portion.
The contents described in the above embodiments are grasped as follows, for example.
(1) The inspection method of the plant equipment according to at least one embodiment of the present disclosure is an inspection method of the plant equipment including a stem (for example, the stem 20 according to several embodiments) and a parent pipe (for example, the parent pipe 10 according to several embodiments) having a stem hole (for example, the stem hole 13 according to several embodiments) to which the stem 20 is attached.
The inspection method includes a step of selecting an inspection site from one or more inspection candidate sites (for example, a step S1 of selecting an evaluation target site in several embodiments), the one or more inspection candidate sites including a region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial line AXa direction of the base pipe 10.
The inspection method includes a step of performing flaw detection on the inspection site (for example, a step S3 of performing inspection of the evaluation target site in several embodiments).
As a result of intensive studies, the inventors have found that, in the pipe 5 including the stem 20 and the base pipe 10 formed with the stem hole 13 to which the stem 20 is attached, there is a possibility that the crack 41 may occur in the region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial line AXa direction of the base pipe 10.
Therefore, according to the method of (1) above, since the step S1 of selecting the evaluation target portion and the step S3 of inspecting the evaluation target portion are provided, the presence of the crack 41 generated in the region 19 can be confirmed even during the limited inspection period. Therefore, the plant equipment can be efficiently inspected.
(2) In several embodiments, in addition to the method (1) described above, in step S1 of selecting the evaluation target portion, if the index (for example, the mother pipe thickness outer diameter ratio (T/D) of several embodiments) including the outer diameter D and the thickness T of the mother pipe 10 as parameters and indicating the relative thickness of the thickness T is equal to or smaller than a predetermined value (for example, the predetermined value Th of several embodiments), the region 19 is selected as the inspection portion.
As described above, the inventors have earnestly studied and determined that: when the outer diameter D and the plate thickness T of the parent pipe 10 are included as parameters and the index indicating the relative thickness of the plate thickness T is equal to or smaller than a predetermined value, cracks 41 are likely to occur in the region 19.
Therefore, according to the method of the above (2), if the index (for example, the ratio of the outer diameter of the mother pipe plate (T/D) in several embodiments) is equal to or smaller than a predetermined value (for example, the predetermined value Th in several embodiments), the region 19 is selected as the inspection site, and therefore, when the crack 41 is likely to occur in the region 19, the region 19 can be selected as the inspection site, and the plant equipment can be inspected efficiently.
(3) In several embodiments, in addition to the method (2) described above, in step S3 of performing inspection of the evaluation target portion, ultrasonic flaw detection can be performed on the inspection portion.
According to the method of (3), the region can be inspected by an inspection method suitable for detecting the crack 41 in the region 19.
(4) In several embodiments, in addition to the method (2) described above, in step S1 of selecting the evaluation target portion, if the index (for example, the ratio (T/D) of the outer diameter of the thickness of the parent pipe in several embodiments)) exceeds the predetermined value (for example, the predetermined value Th in several embodiments), the welded portion (for example, the tube seat welded portion 30 in several embodiments) connecting the parent pipe 10 and the tube seat 20 is selected as the inspection portion.
The results of intensive studies by the inventors revealed that: if the index (for example, the ratio of the plate thickness and the outer diameter (T/D) of the parent pipe in several embodiments) exceeds the predetermined value (for example, the predetermined value Th in several embodiments), the crack 41 is more likely to occur in the welded portion (for example, the tube seat welded portion 30 in several embodiments) connecting the parent pipe 10 and the tube seat 20 than in the region 19.
Therefore, according to the method of (4), if the index exceeds the predetermined value, the welded portion (stem welded portion 30) connecting the parent pipe 10 and the stem 20 is selected as the inspection portion, and therefore, when the crack 41 is likely to occur in the welded portion (stem welded portion 30), the welded portion (stem welded portion 30) can be selected as the inspection portion, and the plant equipment can be inspected efficiently.
(5) In several embodiments, the parent pipe 10 is formed of high chromium steel in addition to the methods of any one of (1) to (4) above.
The method (5) is applicable to the inspection of a pipe (for example, pipe 5 of several embodiments) made of high-chromium steel.
(6) In several embodiments, the method according to any one of (1) to (5) above includes a step S51 of removing the stem 20 and a step S53 of forming the recess. In several embodiments, the method according to any one of (1) to (5) above further includes step S55 of disposing the sealing plate 60 in the stem hole 13 and step S57 of backfilling.
According to the method (6) described above, when the crack 41 is generated in the region 19 offset from the inner wall surface 15 of the stem hole 13 toward the inside of the base material 11 of the base pipe 10 in the axial AXa direction of the base pipe 10, the repair can be appropriately performed.
(7) In several embodiments, in addition to the method of (6) above, in step S55 of disposing the sealing plate 60 to the stem hole 13, the small diameter portion 61 of the sealing plate 60 having the small diameter portion 61 smaller than the inner diameter of the stem hole 13 and the large diameter portion 63 larger than the inner diameter of the stem hole 13 is fitted to the stem hole 13 when disposing the sealing plate (for example, the sealing plate 60 of several embodiments).
According to the method of (7) above, when the sealing plate 60 is disposed in the stem hole 13, the large diameter portion 63 is in contact with the surrounding area of the stem hole 13, and it is possible to prevent the sealing plate 60 from accidentally penetrating into the interior of the parent pipe 10 from the stem hole 13. Further, when the sealing plate 60 is disposed in the stem hole 13, the small diameter portion 61 can be fitted in the stem hole 13, so that the disposed sealing plate 60 can be prevented from being accidentally displaced from the stem hole 13.
(8) In several embodiments, the method according to any one of (1) to (5) above further includes a step S151 of disposing the reinforcing plate and a step S153 of welding the reinforcing plate to the parent pipe.
If the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 can reduce the circumferential stress acting on the parent pipe 10 by welding and attaching the reinforcing plate 80 to the parent pipe as in the method (8). This reduces the progress rate of the crack 41, thereby extending the life. In addition, since the repair can be performed by a relatively simple method such as the method (8), the time and cost required for the repair can be reduced.
(9) In several embodiments, in addition to the method (8) described above, in step S151 of disposing the reinforcing plate, the dividing plate 81, which is one part of the reinforcing plate 80 divided into two parts, and the dividing plate 81, which is the other part thereof, are disposed so as to face each other along the axis AXa direction of the parent pipe 10 with the stem 20 interposed therebetween.
As described above, the inventors have found that the crack 41 generated in the region 19 is generated by the circumferential stress acting on the parent pipe 10 as a result of intensive studies.
Therefore, when the two dividing plates 81 are arranged so as to face each other along the axial line AXa of the parent pipe 10 with the stem 20 interposed therebetween as in the method (9), the dividing plates 81 extend along the circumferential direction of the parent pipe 10. Therefore, by welding and attaching the dividing plates 81 to the parent pipe 10, the circumferential stress acting on the parent pipe 10 can be effectively reduced by each dividing plate 81. In addition, according to the method of (9) above, even if the other end of the both ends of the stem 20 opposite to the one end connected to the parent pipe 10 is connected to another pipe or the like, the reinforcing plate 80 can be easily disposed.
(10) In several embodiments, in addition to the methods of any one of the above (1) to (9), in the step of performing the ultrasonic flaw detection (for example, the step S3 of performing the inspection of the evaluation target portion of several embodiments), the ultrasonic flaw detection by the phased array method is performed using the flaw detector 50, the flaw detector 50 includes the transmitting element 51 including a plurality of piezoelectric elements, the receiving element 53 including at least one piezoelectric element and being different from the transmitting element 51, and the wedge member 55 in one case 57, the transmitting element 51 is disposed on one surface 55b of two surfaces 55b and 55c adjacent to each other across the ridge line 55a in the wedge member 55 so that the arrangement direction of the plurality of piezoelectric elements is the same as the extending direction of the ridge line 55a, and the receiving element 53 is disposed on the other surface 55 c.
As described above, the inventors have studied intensively, and as a result, have found that when ultrasonic flaw detection by the phased array method is performed, the transmitting element 51 and the receiving element 53 are separated elements and are disposed on the single wedge member 55 as described above, and thus, the area closer to the surface layer of the inspection object and the area farther from the surface layer can be inspected by the single flaw detector 50. As a result of intensive studies, the inventors have found that by configuring the flaw detector 50 as described above, the dead zone near the surface layer of the inspection object can be suppressed, and the noise level near the surface layer of the inspection object can be suppressed.
Therefore, according to the method (10), the area closer to the surface layer of the inspection object and the area farther from the surface layer can be inspected by one flaw detector 50. Further, according to the method of (10), it is possible to obtain an inspection result in which the dead zone near the surface layer of the inspection object and the noise level near the surface layer of the inspection object are suppressed.
(11) In several embodiments, in addition to the methods (1) to (10) described above, in the step of performing ultrasonic flaw detection (for example, in the step S3 of performing inspection of the evaluation target portion in several embodiments), ultrasonic flaw detection by the phased array method is performed using the flaw detector 50 in which the scanning range of the refraction angle includes at least a range of 35 degrees to 75 degrees.
The conventional phased array method generally has a scanning range of refraction angles of about 40 degrees to 70 degrees. Therefore, according to the method of (11) above, a larger range can be inspected.
(12) In several embodiments, in addition to the methods (1) to (11) above, in the step of performing ultrasonic flaw detection (for example, in the step S3 of performing inspection of the evaluation target portion in several embodiments), ultrasonic flaw detection by the phased array method is performed using ultrasonic waves having a frequency of 10MHz to 15 MHz.
In the ultrasonic flaw detection, the shorter the wavelength of ultrasonic waves used in general flaw detection, that is, the higher the frequency, the smaller the defect size as a detection limit.
In the conventional ultrasonic flaw detection using the phased array method, the frequency of ultrasonic waves is often about 5 MHz. Therefore, according to the method (12), since the inspection is performed by using ultrasonic waves having a higher frequency than that of the conventional ultrasonic flaw detection inspection by the phased array method, it is possible to detect a smaller crack.
(13) The repair method of the plant equipment according to at least one embodiment of the present disclosure is a repair method of the plant equipment including a stem (for example, the stem 20 according to several embodiments) and a parent pipe (for example, the parent pipe 10 according to several embodiments) to which the stem is attached.
The repairing method includes a step S51 of removing the stem 20 and a step S53 of forming a recess.
The repairing method further includes step S55 of disposing the sealing plate 60 in the stem hole 13 and step S57 of backfilling.
According to the method of (13), when the crack 41 is generated in the region 19, the repair can be performed appropriately.
(14) The repair method of the plant equipment according to at least one embodiment of the present disclosure is a repair method of the plant equipment including a stem (for example, the stem 20 according to several embodiments) and a parent pipe (for example, the parent pipe 10 according to several embodiments) to which the stem is attached.
The repair method includes a step S151 of disposing a reinforcing plate and a step S153 of welding the reinforcing plate to a parent pipe.
As described above, when the crack 41 is generated in the region 19, if the crack 41 is relatively small, the reinforcing plate 80 can reduce the hoop stress acting on the parent pipe 10 by welding and attaching the reinforcing plate 80 to the parent pipe 10 as in the method (14) described above. This reduces the progress rate of the crack 41, thereby extending the life. Further, since the repair can be performed by a relatively simple method such as the method (14), the time and cost required for the repair can be reduced.
Description of the reference numerals
1 Storage device
2 Terminal device
2A display part
3 Arithmetic device
4 Input device
5 Piping
7 Connecting part
10 Main pipe
11 Base material
13 Tube socket hole
19 Area
20 Tube seat
30 Tube seat welding part
50 Flaw detector
51 Transmitting element
53 Receiving element
55 Wedge-shaped component
57 Shell
60 Sealing plate
61 Small diameter portion
63 Large diameter portion
71 Concave portion
80 Reinforcing plate
81 Dividing the plate.
Claims (13)
1. A method for inspecting a plant including a stem and a parent tube having a stem hole for mounting the stem,
The method for inspecting the plant equipment comprises the following steps:
A step of selecting an inspection site from one or more inspection candidate sites including a region offset from an inner wall surface of the stem hole toward an inside of a base material of the base pipe in an axial direction of the base pipe; and
A step of performing flaw detection on the inspection site,
In the step of performing the flaw detection,
When performing a flaw detection inspection of the inside of the plate thickness of the inspection portion or a flaw detection inspection of the peripheral portion of the slit on the inner surface of the inspection portion, performing an ultrasonic flaw detection inspection,
When performing the flaw detection of the outer surface of the inspection site, any one of the magnetic powder flaw detection, the penetration flaw detection, the inspection by MT transfer method, and the eddy current flaw detection is performed.
2. The method for inspecting plant according to claim 1, wherein,
In the step of selecting the inspection site, the outer diameter and the plate thickness of the parent pipe are included as parameters, and if an index indicating the relative thickness of the plate thickness is equal to or less than a predetermined value, the region is selected as the inspection site.
3. The method for inspecting plant according to claim 2, wherein,
In the step of selecting the inspection site, if the index exceeds the predetermined value, a welded portion connecting the main pipe and the stem is selected as the inspection site.
4. The method for inspecting plant according to claim 1, wherein,
The main pipe is formed of high chromium steel.
5. The method for inspecting plant according to claim 2, wherein,
The main pipe is formed of high chromium steel.
6. The method for inspecting plant according to claim 3, wherein,
The main pipe is formed of high chromium steel.
7. The method for inspecting plant according to any one of claims 1 to 6, wherein,
The method for inspecting the plant equipment further comprises the following steps:
A step of removing the stem from the parent pipe;
A step of removing a region, to which the stem is attached, from the parent pipe while leaving a part of the region on the inner peripheral surface side of the parent pipe, thereby forming a recess;
A step of disposing a sealing plate to the stem hole formed in the partial region; and
And backfilling the recess by welding after the step of disposing the sealing plate.
8. The method for inspecting plant according to claim 7, wherein,
In the step of disposing the sealing plate, the small diameter portion and the large diameter portion of the sealing plate having the small diameter portion smaller than the inner diameter of the stem hole and the large diameter portion larger than the inner diameter of the stem hole are fitted into the stem hole when the sealing plate is disposed.
9. The method for inspecting plant according to any one of claims 1 to 6, wherein,
The method for inspecting the plant equipment further comprises the following steps:
a step of disposing a reinforcing plate on a connection portion of the main pipe connected to the stem so as to surround the periphery of the stem from the radially outer side of the stem; and
And welding the reinforcing plate disposed in the step of disposing the reinforcing plate to the parent pipe.
10. The method for inspecting plant according to claim 9, wherein,
In the step of disposing the reinforcing plate, one part and the other part of the reinforcing plate divided into two parts are disposed so as to face each other along the axial direction of the main pipe with the stem interposed therebetween.
11. The method for inspecting plant according to any one of claims 1 to 6, wherein,
In the step of performing the ultrasonic flaw detection, the ultrasonic flaw detection by the phased array method is performed using a flaw detector including a transmitting element including a plurality of piezoelectric elements, a receiving element including a piezoelectric element and different from the transmitting element, and a wedge member in which the transmitting element is disposed on one of two surfaces adjacent to each other with a ridge interposed therebetween so that an arrangement direction of the plurality of piezoelectric elements is the same as an extending direction of the ridge, and the receiving element is disposed on the other surface.
12. The method for inspecting plant according to any one of claims 1 to 6, wherein,
In the step of performing the ultrasonic flaw detection, the ultrasonic flaw detection by the phased array method is performed using a flaw detector in which a scanning range of the refraction angle is at least a range of 35 degrees or more and 75 degrees or less.
13. The method for inspecting plant according to any one of claims 1 to 6, wherein,
In the step of performing the ultrasonic flaw detection, ultrasonic flaw detection by a phased array method is performed using ultrasonic waves having a frequency of 10MHz or more and 15MHz or less.
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| JP2019121199A JP7277286B2 (en) | 2019-06-28 | 2019-06-28 | Plant inspection method |
| JP2019-121199 | 2019-06-28 | ||
| PCT/JP2020/024565 WO2020262364A1 (en) | 2019-06-28 | 2020-06-23 | Plant inspection method and plant repairing method |
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| WO2020262364A1 (en) | 2020-12-30 |
| JP2021006801A (en) | 2021-01-21 |
| JP7277286B2 (en) | 2023-05-18 |
| CN114096840A (en) | 2022-02-25 |
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