JP7125266B2 - Plant inspection method - Google Patents

Description

The present disclosure relates to plant inspection methods.

Cracks occur due to creep damage at welded portions, such as boiler pipes, which are used for a long time in a high-temperature and high-pressure environment. Since cracks grow due to creep damage, it is necessary to evaluate the remaining life according to the presence or absence of cracks and the length of cracks in the thickness direction of the weld (crack height), and to repair the welds in a timely manner. be. Therefore, techniques for evaluating the remaining life by measuring the presence or absence of cracks in the weld and the length of the cracks are being developed.

For example, in a method for evaluating remaining life disclosed in Patent Document 1, the inside of a welded portion is detected by ultrasonic flaw detection using a phased array method, and the remaining life is evaluated based on the results of the flaw detection.
Further, for example, in the method for diagnosing creep damage disclosed in Patent Document 2, the creep damage of the welded portion is diagnosed by performing the life diagnosis by the void area ratio method and the life diagnosis by the ultrasonic flaw detection method.

JP 2017-151107 A JP-A-2002-31632

The findings of the inventors have revealed that the places where cracks are likely to occur are different when the sites where the welded parts are present are different. Therefore, further measures are required to improve the accuracy of remaining life evaluation. However, simply increasing the number of inspection items cannot improve the accuracy of life expectancy evaluation, and may rather reduce the accuracy of life expectancy evaluation.

In view of the circumstances described above, at least one embodiment of the present invention aims to improve the accuracy of remaining life evaluation of an evaluation target part in a plant.

(1) A plant inspection method according to at least one embodiment of the present invention includes:
A plant inspection method comprising:
By the inspection method set for each combination of the type of evaluation target part including at least one of the circumferential welded part or longitudinal welded part of the pipe, or the nozzle welded part, and the thickness of the evaluation target part, a step of inspecting the site to be evaluated;
and selecting a measurement item for additional measurement for obtaining 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 inspection method.

According to the above method (1), the inspection method of the evaluation target region becomes appropriate according to the combination of the type of the evaluation target region and the thickness of the evaluation target region, and the accuracy of the inspection result of the evaluation target region is improved. . Furthermore, measurement items for additional measurement for improving the accuracy of remaining life evaluation are appropriate according to the inspection method of the evaluation target portion. As a result, the accuracy of the remaining life evaluation of the evaluation target portion, which is performed based on the inspection result of the evaluation target portion, is improved.

(2) In some embodiments, in the method of (1) above, the inspection method and additional measurement items are performed for each of the combinations of the type of the evaluation target site and the thickness of the evaluation target site. A step of selecting the inspection method and the measurement items using a defined database is provided.

According to the method (2) above, the inspection method and measurement items can be quickly selected.

(3) In some embodiments, in the method (1) or (2) above, the necessity of the additional measurement is determined based on the flaw length obtained from the inspection result of the evaluation target site by the inspection method. A step of determining is provided.

According to the method (3) above, it is possible to easily determine whether or not additional measurement is necessary based on the length of the flaw. Moreover, if it is determined that additional measurement is not necessary, additional measurement is not required, which is efficient.

(4) In some embodiments, in the method of (3) above, the threshold value of the flaw length used for determining the necessity of the additional measurement is the temperature condition or stress of the evaluation target portion during operation of the plant. determined according to at least one of the conditions.

According to the method (4) above, since at least one of the temperature condition and stress condition of the evaluation target part during plant operation is reflected in the flaw length threshold used for determining the necessity of additional measurement, additional measurement is performed. The accuracy of necessity can be improved.

(5) In some embodiments, in any one of the methods (1) to (4), the inspection method set for the longitudinal weld portion having a thickness exceeding a specified value includes the evaluation target portion It is an inspection method for inspecting the inside of the longitudinal weld as.

The findings of the inventors have revealed that damage is likely to occur inside the longitudinal welds of plant piping having a wall thickness exceeding a specified value.
Therefore, according to the above method (5), the inspection method is suitable for longitudinal welds having a wall thickness exceeding the specified value.

(6) In some embodiments, in any one of the methods (1) to (5) above, the inspection method set for the circumferential weld having a thickness exceeding a specified value is the evaluation object It is an inspection method for inspecting the outer surface of the circumferential weld as a part.

The inventors have found that damage to the outer surface of the circumferential welded portion, which has a wall thickness exceeding a specified value, is likely to occur in plant piping.
Therefore, according to the above method (6), the inspection method is suitable for circumferential welds having a wall thickness exceeding the specified value.

(7) In some embodiments, in any one of the methods (1) to (6) above, the inspection method set for the circumferential weld having a wall thickness equal to or less than the specified value includes the evaluation It is an inspection method for inspecting the inside of the circumferential welded portion as a target portion.

The inventors of the present invention have found that damage is likely to occur inside the circumferential welded portion of plant piping having a wall thickness equal to or less than a specified value.
Therefore, according to the above method (7), the inspection method is suitable for circumferential welds having a wall thickness equal to or less than the specified value.

(8) In some embodiments, in the method according to any one of (1) to (7) above, the inspection method set for the nozzle welded portion is the nozzle welded portion as the evaluation target portion. This is an inspection method for inspecting the outer surface of and the internal slit peripheral part.

The findings of the inventors have revealed that damage is likely to occur on the outer surface of the welded nozzle stub and the area around the internal slit in the welded nozzle stub.
Therefore, according to the above method (8), the inspection method is suitable for the nozzle welded portion.

(9) In some embodiments, in the method of (8) above, the inspection method set for the nozzle weld is ultrasonic inspection by a conventional UT method, ultrasonic inspection by a TOFD method, magnetic particle inspection. , penetrant inspection, MT transfer method inspection, and eddy current inspection.

(10) In some embodiments, in the method according to any one of (1) to (9) above, the longitudinal welded portion in which the portion to be evaluated inspected by the inspection method has a thickness exceeding the prescribed value. Then, the pipe cross-sectional shape of the pipe is selected as the measurement item.

According to the method (10) above, a measurement item suitable for a longitudinal welded portion having a wall thickness exceeding a prescribed value is selected.

(11) In some embodiments, in the method according to any one of (1) to (10) above, the measurement items include the pipe outer diameter, plate thickness, pipe cross-sectional shape, and weld metal shape at the evaluation target site. , the shape of a heat-affected zone due to the heat of welding, the temperature of the evaluation target portion during operation of the plant, and the hardness of the evaluation target portion.
According to the method (11) above, measurement items suitable for the basic parameters necessary for improving the accuracy of the remaining life evaluation of the weld are selected.

(12) In some embodiments, in any one of the above methods (1) to (11), the interior of the evaluation target site is inspected, and the dead zone of the inspection method is inspected on the outer surface side of the evaluation target site. If a flaw is detected inside a predetermined distance from the evaluation target portion, an inspection is further performed by an inspection method for inspecting the outer surface of the evaluation target portion, or the weld surplus at the evaluation target portion is deleted. After that, the step of inspecting the inside of the evaluation target region is further provided.

According to the method (12) above, it is possible to suppress the influence of the dead zone related to the inspection method.

(13) In some embodiments, in any of the methods (1) to (12) above,
a step of inspecting the outer surface of the evaluation target part and calculating a local life consumption rate, which is a local life consumption rate and takes the point of time when visually observable cracks occur as 100%;
The method further comprises the step of performing an inspection by an inspection method for inspecting the interior of the evaluation target portion when the calculated life consumption rate exceeds a predetermined value.

According to the method (13) above, it is possible to inspect how far the flaw has progressed from the outer surface to the inside of the site to be evaluated.

According to at least one embodiment of the present invention, it is possible to improve the accuracy of remaining life evaluation of an evaluation target part in a plant.

It is a figure which shows each process in the inspection method of the plant which concerns on some embodiment. FIG. 10 is a table showing the relationship between a portion where a welded portion exists, the thickness of that portion, and a location where cracks are likely to occur; FIG. 1 is a diagram showing a storage device that stores a database and a terminal device that accesses the storage device; FIG. 4 is a flow chart showing the flow of processing to be performed in step S3 of inspecting an evaluation target region; It is a graph in which the horizontal axis represents the stress acting on the portion to be evaluated, and the vertical axis represents the ratio between the size of the flaw and the thickness of the portion to be maintained. 4 is a flow chart showing the flow of processing to be performed in step S3 of inspecting an evaluation target region; 4 is a flow chart showing the flow of processing to be performed in step S3 of inspecting an evaluation target region;

Several embodiments of the present invention will now be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, and are merely illustrative examples. do not have.
For example, expressions denoting relative or absolute arrangements such as "in a direction", "along a direction", "parallel", "perpendicular", "center", "concentric" or "coaxial" are strictly not only represents such an arrangement, but also represents a state of relative displacement with a tolerance or an angle or distance to the extent that the same function can be obtained.
For example, expressions such as "identical", "equal", and "homogeneous", which express that things are in the same state, not only express the state of being strictly equal, but also have tolerances or differences to the extent that the same function can be obtained. It shall also represent the existing state.
For example, expressions that express shapes such as squares and cylinders do not only represent shapes such as squares and cylinders in a geometrically strict sense, but also include irregularities and chamfers to the extent that the same effect can be obtained. The shape including the part etc. shall also be represented.
On the other hand, the expressions "comprising", "comprising", "having", "including", or "having" one component are not exclusive expressions excluding the presence of other components.

(Overview of plant inspection methods)
First, with reference to FIG. 1, an outline of a plant inspection method according to some embodiments will be described.
FIG. 1 is a diagram showing each step in a plant inspection method according to some embodiments. A plant inspection method according to some embodiments includes a step S1 of selecting a portion to be evaluated, a step S2 of selecting an inspection method and additional measurement items, a step S3 of inspecting the portion to be evaluated, and a step S3 of inspecting the portion to be evaluated. and a step S4 of performing a remaining life evaluation.
The plant inspection method according to some embodiments is an inspection method that is applied to inspection of metal members that are used for a long time in an environment where high temperature and large stress is applied. It is applied to the inspection of welded parts such as steam pipes connecting between steam turbines.
Hereinafter, the outline of each process in the plant inspection method according to some embodiments will be described.

(Outline of step S1 for selecting evaluation target parts)
The step S1 of selecting a part to be evaluated is a step of selecting a part to be evaluated from among a plurality of welded parts such as steam pipes that exist in a plant by conducting a flaw detection inspection and performing a remaining life evaluation based on the results of the flaw detection inspection. .

(Outline of step S2 for selecting an inspection method and additional measurement items)
The step S2 of selecting an inspection method and additional measurement items is a step of selecting an inspection method and additional measurement items for the flaw detection inspection for the evaluation target portion selected in the step S1 of selecting the evaluation target portion.
In step S2 of selecting an inspection method and additional measurement items, an appropriate inspection method for flaw detection inspection is selected for the evaluation target portion selected in step S1 of selecting the evaluation target portion.
Here, the inspection method selected in step S2 for selecting the inspection method and additional measurement items includes at least one of the circumferential welded portion, the longitudinal welded portion, or the nozzle welded portion of the pipe, as will be described later. It is an inspection method set for each combination of the type of evaluation target site and the thickness of the evaluation target site.
Note that the weld zone includes the weld metal, the heat affected zone (HAZ zone) due to welding, and the inner surface slit described later.

Further, in step S2 of selecting the inspection method and additional measurement items, appropriate measurement items for additional measurement are selected for the selected inspection method.
Here, the additional measurement is a measurement performed to acquire the parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part based on the inspection result of the evaluation target part by the selected inspection method. . That is, in step S3 for inspecting the evaluation target portion, which will be described later, the evaluation target portion is subjected to flaw detection inspection by the selected inspection method, and the inspection result is obtained. Then, based on the obtained inspection result, the remaining life evaluation of the evaluation target portion is performed in step S4 for evaluating the remaining life of the evaluation target portion described later. Several parameters are required in addition to the inspection results of the flaw detection inspection when performing the remaining life assessment of the evaluation target portion. In the additional measurement, among these parameters, the parameters necessary for improving the accuracy of remaining life evaluation are acquired.
Note that, in the following description, the measurement item of the additional measurement is also simply referred to as the additional measurement item.
The details of step S2 for selecting the inspection method and additional measurement items will be described later.

(Outline of Step S3 for Inspecting Evaluation Target Site)
In step S3 of inspecting the evaluation target portion, the evaluation target portion selected in step S1 of selecting the evaluation target portion is inspected by the inspection method selected in step S2 of selecting the inspection method and additional measurement items. This is the step to take.
Further, in step S3 of inspecting the site to be evaluated, additional measurement of the additional measurement items selected in step S2 of selecting the inspection method and additional measurement items is performed as necessary.
The details of step S3 for inspecting the evaluation target site will be described later.

(Outline of step S4 for evaluating the remaining life of the portion to be evaluated)
The step S4 of evaluating the remaining life of the evaluation target portion is a step of performing the remaining life evaluation of the evaluation target portion based on the inspection result of the evaluation target portion performed in the step S3 of inspecting the evaluation target portion.
In addition, in step S4 for evaluating the remaining life of the evaluation target part, if additional measurement is performed for the additional measurement items in step S3 for inspecting the evaluation target part, the parameters obtained by the additional measurement are also used for evaluation. Assess the remaining life of the part.
For the evaluation of remaining life, for example, crack growth calculation, FEM, damage mechanics evaluation, void simulation method, structure simulation method, or the like can be used.

As described above, the plant inspection method according to some embodiments includes step S2 of selecting an inspection method and additional measurement items, and step S3 of inspecting an evaluation target portion.
That is, a plant inspection method according to some embodiments includes a type of an evaluation target portion including at least one of a circumferential welded portion, a longitudinal welded portion, or a nozzle welded portion of a pipe, and the type of the evaluation target portion. A step of inspecting the evaluation target region by an inspection method set for each combination with the thickness, that is, a step S3 of inspecting the evaluation target region.
In addition, the plant inspection method according to some embodiments acquires the parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part performed based on the inspection result of the evaluation target part by the above inspection method. , that is, a step S2 of selecting an inspection method and additional measurement items. Therefore, according to the plant inspection method according to some embodiments, the inspection method of the evaluation target portion becomes appropriate according to the combination of the type of the evaluation target portion and the thickness of the evaluation target portion. Accuracy of test results is improved. Furthermore, measurement items for additional measurement for improving the accuracy of remaining life evaluation are appropriate according to the inspection method of the evaluation target portion. As a result, the accuracy of the remaining life evaluation of the evaluation target portion, which is performed based on the inspection result of the evaluation target portion, is improved.

(Details of step S2 for selecting inspection methods and additional measurement items)
Details of step S2 for selecting an inspection method and additional measurement items will be described below.
For example, steam pipes connecting boilers and steam turbines in thermal power plants have multiple types of welds. For example, steam pipes have circumferential welds that connect pipes together and nozzle welds that connect pipes and branch pipes. Further, when the pipe is manufactured from a plate-like member, there is a longitudinal weld extending in the pipe axial direction for connecting the ends of the plate.
The findings of the inventors have revealed that the places where cracks are likely to occur differ when the sites where the welded parts are present differ. Furthermore, the inventors have found that even if the same type of welded portion is used, the location where cracks are likely to occur differs depending on the thickness of the portion.

FIG. 2 is a table showing the relationship between the site where the welded portion exists, the thickness of the site, and the location where cracks are likely to occur, which was found as a result of the inventors' intensive studies.
The inventors have found that even if the same type of welded portion is used, the locations where cracks are likely to occur differ at a thickness of about 20 mm. In the table shown in FIG. 2, "thin" indicates that the thickness is 20 mm or less, and "thick" indicates that the thickness exceeds 20 mm. The same applies to the following description.

For example, in a longitudinal welded portion of a straight pipe of piping, cracks are likely to occur inside the plate thickness of the longitudinal welded portion in thick-walled portions, 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 that of the base metal and the weld metal, so the multiaxiality of the stress inside the thickness of the HAZ increases.
For example, in a longitudinal welded portion of an elbow of a pipe, cracks are likely to occur inside the plate thickness of the longitudinal welded portion in thick-walled portions, and the greatest damage is likely to occur. The reason is the same as for the longitudinal welds in the straight pipe described above.
For example, in a circumferentially welded portion of a pipe, cracks are likely to occur on the outer surface of the circumferentially welded portion at thick portions, and the greatest damage is likely to occur. This is because of the effects of piping system stress, that is, stress caused by external forces received from, for example, the support structure of the piping and other connected piping, etc., and thermal stress generated by restraining the thermal expansion of the piping itself. This is because the maximum position of the bending stress acting on the weld is on the outer surface. In addition, for example, in a circumferential welded portion of a pipe, cracks are likely to occur inside the plate thickness of the circumferentially welded portion at thin portions, and the greatest damage is likely to occur. The reason for this is that although the thin-walled portion is also affected by the piping system stress in the same way as the thick-walled portion, the bending stress distribution in the plate thickness direction is small because the plate thickness is small. This is because the impact is greater.
For example, in nozzle welds, both thin-walled portions and thick-walled portions are prone to cracks on the outer surface and inner surface of the nozzle welded portion around slits, and are most likely to be damaged. The reason that damage is likely to occur on the outer surface is that the hoop stress of the pipe is greatest on the outer surface. On the other hand, the reason why damage is likely to occur around the slit on the inner surface is that stress concentration occurs at the tip of the crack like the slit. In addition, the inner surface slit of the welded part of the nozzle is the boundary between the pipe and the branch pipe, plug, cylinder, etc., and the weld metal is not sufficiently penetrated during welding, and the boundary remains as a slit. That is.
In addition, in many of the current plants, since ERW pipes are rarely used for thin straight pipes and thin elbows used in high temperature and high pressure environments, longitudinal welds in thin straight pipes and thin elbows The description of is omitted.

Information about the relationship between the site where the weld exists, the thickness of the site, and the location where the greatest damage is likely to occur is stored in advance as a database in a storage device. FIG. 3 is a diagram showing a storage device that stores this database and a terminal device that accesses the storage device.
As described above, the storage device 1 stores, as a database, information on the relationship between the site where the welded portion exists, the thickness of the site, and the location where the greatest damage is likely to occur. The terminal device 2 is a terminal device such as a personal computer, for example, and can read out information from a database stored in the storage device 1 from the storage device 1 and present it to the operator of the terminal device 2 . Note that the storage device 1 may be arranged at a location different from that of the terminal device 2 or may be provided within the terminal device 2 .

(Inspection method suitable for flaw detection inspection inside plate thickness)
For example, as inspection methods suitable for flaw detection inspection inside the plate thickness, ultrasonic inspection by conventional UT method, ultrasonic inspection by TOFD method, ultrasonic inspection by phased array method, ultrasonic inspection by synthetic aperture method, ultrasonic inspection by high frequency UT method A sonic inspection, an ultrasonic inspection by an ultrasonic noise method, and the like can be mentioned.
In addition, the parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target part based on the inspection results by the inspection method suitable for the flaw detection inspection inside the plate thickness are, for example, the dimensions, shape, temperature, etc. of the evaluation target part. , are the material properties.

Additional measurement items to acquire the dimensions and shape of the part to be evaluated include, for example, the outer diameter of the pipe, the plate thickness of the pipe, the oblateness of the pipe, and the shape of the cross section when the weld line is viewed from the longitudinal direction. , the shape of the heat affected zone (HAZ) due to welding. By acquiring the dimensions and shape of the part to be evaluated, it is possible to accurately calculate the stress acting on the weld zone during the remaining life evaluation. In particular, the outer diameter, oblateness, and cross-sectional shape of the pipe are effective measurement items for accurately calculating the stress (bending, tension) acting in the circumferential direction, which is important in longitudinal welds.
Additional measurement items for obtaining the temperature of the evaluation target site include, for example, the formation state of steam oxidation scale, the formation state of precipitates, and the structural change of the evaluation target site. can be used to estimate the temperature of the evaluation target site. The temperature in this case refers to the past temperature history or the highest temperature that has worked in the past. By obtaining the temperature of the evaluation target portion, it is possible to set the temperature conditions with high accuracy when evaluating the remaining life.
A measurement item of the additional measurement for acquiring the material properties related to the evaluation target region can be, for example, the hardness of the evaluation target region. Alternatively, a small amount of sample is collected from the evaluation target site, and a creep test or the like may be performed on this sample to obtain the material properties of the evaluation target site. By acquiring the material properties related to the part to be evaluated, it is possible to accurately set the strength of the weld zone when evaluating the remaining life.

In addition, in the storage device 1 described above, each inspection method described above as an inspection method suitable for flaw detection inspection inside the plate thickness is stored as a database. Further, in the storage device 1 described above, the additional measurement items described above are stored as a database in association with the inspection method suitable for the flaw detection inspection inside the plate thickness. Further, in the above-described storage device 1, there is information on the flow of processing to be performed in step S3 for inspecting the evaluation target region, including the processing for determining whether or not to measure the additional measurement items. Stored as a database. The flow of the processing will be explained later.

In the above-described ultrasonic inspection, a range near the surface (for example, several millimeters from the surface) of the portion to be evaluated is a dead zone, so flaw detection cannot be performed. Therefore, for example, as a result of the flaw detection inspection inside the plate thickness, if it is determined that the flaw inside the plate thickness exists in the vicinity of the dead zone, in step S3 of inspecting the evaluation target part, the effect of the dead zone is reduced. We are planning to take measures to reduce the dead zone.

As a measure to reduce the dead zone, for example, inspection of the outer surface can be mentioned. Examples of methods for inspecting the outer surface include magnetic particle testing, penetrant testing, MT transfer method testing, and eddy current testing. If the existence of flaws on the outer surface can be confirmed by these inspections, it can be judged that the flaws existing near the dead zone within the plate thickness are continuous with the flaws on the outer surface, and the existence of flaws on the outer surface can be determined. If it cannot be confirmed, it can be determined that the flaws existing in the vicinity of the dead zone inside the plate thickness have not reached at least the outer surface.

Moreover, as a measure to reduce the dead zone, the surplus of the welded portion may be removed. By removing the surplus from the welded portion, it becomes easier to perform a magnetic particle inspection or the like. Further, by removing the excess buildup of the welded portion, it becomes possible to bring the ultrasonic flaw detector into contact with the surface after the excess buildup of the welded portion has been removed, thereby expanding the flaw detection range. In addition, by removing the excess buildup of the welded portion, there are cases where visually observable flaws appear on the surface after the excess buildup of the welded portion is removed. In addition, by removing the excess buildup of the welded portion, it is possible to remove the flaws existing only in the vicinity of the surface of the excess buildup.
The storage device 1 described above stores, as a database, countermeasures for reducing dead zones linked to inspection methods suitable for flaw detection inspection inside the plate thickness.

(Inspection method suitable for flaw detection inspection of outer surface)
For example, inspection methods suitable for the inspection of the outer surface include magnetic particle inspection, penetrant inspection, inspection by MT transfer method, eddy current inspection, and the like.
The parameters necessary for improving the accuracy of the remaining life evaluation of the part to be evaluated based on the inspection results of the inspection method suitable for the flaw detection inspection of the outer surface are, for example, the dimensions, shape, temperature, material properties of the part to be evaluated. is.

Measurement items for additional measurement to acquire the dimensions and shape of the part to be evaluated, measurement items for additional measurement to acquire the temperature of the part to be evaluated, and material properties for the part to be evaluated The measurement items of the additional measurement are as described above.

As will be described later, when the outer surface is most likely to be damaged, in addition to the flaw detection inspection by the inspection method suitable for the flaw detection inspection of the outer surface described above, for example, the local life consumption rate on the outer surface A non-destructive test may be performed to determine the local life consumption rate, where 100% is the point at which visually observable cracks occur. As this non-destructive inspection method, void number density method, void area ratio method, structure contrast method, precipitate intergranular distance method, A parameter method, grain deformation method, void grain boundary length method, carbide composition measurement method, etc. Non-destructive inspection methods can be mentioned.
In addition, as will be described later, when the local life consumption rate on the outer surface obtained based on the inspection result of the non-destructive inspection exceeds a predetermined value, or when there is a flaw on the outer surface , the inside of the portion to be evaluated in the vicinity of the outer surface is inspected.
As inspection methods suitable for flaw detection inside the evaluation target site near the outer surface, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the synthetic aperture method, An ultrasonic inspection by a high frequency UT method, an ultrasonic inspection by an ultrasonic noise method, and the like can be mentioned.

In the storage device 1 described above, each inspection method described above as an inspection method suitable for the flaw detection inspection of the outer surface is stored as a database. Further, in the storage device 1 described above, the additional measurement items described above are stored as a database in association with the inspection method suitable for the flaw detection inspection of the outer surface. In the storage device 1 described above, the nondestructive inspection method described above is stored as a database as a nondestructive inspection method for finding the local life consumption rate on the outer surface. In the storage device 1 described above, each inspection method described above as an inspection method suitable for flaw detection inspection of the inside of the evaluation target portion near the outer surface is stored as a database. Further, in the above-described storage device 1, there is information on the flow of processing to be performed in step S3 for inspecting the evaluation target region, including the processing for determining whether or not to measure the additional measurement items. Stored as a database. The flow of the processing will be explained later.

(Inspection method suitable for flaw detection inspection of parts around inner slits)
In the flaw detection inspection of the peripheral portion of the inner surface slit, the inner surface slit exists within the flaw detection range from the beginning, but the existence range of the inner surface slit changes depending on the welding state. Therefore, it is difficult to distinguish between the inner slit and the flaw in the flaw detection inspection of the portion around the inner slit. Therefore, in the flaw detection inspection of the part around the inner surface slit, cracks that can be visually observed such as macroscopic cracks are detected, and all detected cracks are visually observed like macroscopic cracks without distinguishing them from inner surface slits. are treated as observable cracks.

For example, as an inspection method suitable for flaw detection inspection of the part around the inner slit, ultrasonic inspection by conventional UT method, ultrasonic inspection by TOFD method, ultrasonic inspection by phased array method, ultrasonic inspection by synthetic aperture method, ultrasonic inspection by high frequency UT method An ultrasonic inspection, an ultrasonic inspection by an ultrasonic noise method, etc. can be mentioned.
In addition, the parameters necessary for improving the accuracy of the remaining life evaluation of the part to be evaluated based on the inspection results by the inspection method suitable for the flaw detection inspection of the part around the inner surface slit are, for example, the dimensions, shape, and dimensions of the part to be evaluated. temperature and material properties.

Measurement items for additional measurement to acquire the dimensions and shape of the part to be evaluated include, for example, the shape of the heat affected zone (HAZ) due to welding, the surface shape of the weld metal, the outside of the pipe (mother pipe) in the nozzle Examples include the diameter and the thickness of the mother pipe.
The measurement items of the additional measurement for acquiring the temperature of the evaluation target portion and the measurement items of the additional measurement for acquiring the material properties of the evaluation target portion are as described above.

The above-described storage device 1 stores, as a database, each inspection method described above as an inspection method suitable for the flaw detection inspection of the peripheral portion of the inner surface slit. Further, in the storage device 1 described above, the additional measurement items described above are stored as a database in association with the inspection method suitable for the flaw detection inspection of the portion around the inner surface slit. Further, in the above-described storage device 1, there is information on the flow of processing to be performed in step S3 for inspecting the evaluation target region, including the processing for determining whether or not to measure the additional measurement items. Stored as a database. The flow of the processing will be explained later.

In step S2 for selecting the inspection method and additional measurement items, 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 performs flaw detection of the evaluation target portion. An inspection method suitable for the inspection and additional measurement items for improving the accuracy of the remaining life evaluation of the portion to be evaluated based on the inspection result by the inspection method are read from the database of the storage device 1 . Then, the terminal device 2 displays the read inspection method and the additional measurement item on the display unit 2a of the terminal device 2, for example.
In addition, the terminal device 2 reads from the database of the storage device 1 information on the flow of processing to be performed in step S3 for inspecting the evaluation target region. Then, the terminal device 2 displays, for example, the display unit 2a of the terminal device 2, the read information of the flow of processing to be performed in step S3 of inspecting the evaluation target region.
In addition, when the read inspection method is suitable for flaw detection inspection of the outer surface, for example, the display unit 2a of the terminal device 2 displays a non-destructive inspection method for obtaining a local life consumption rate, An inspection method suitable for flaw detection inspection of the inside of the portion to be evaluated near the outer surface is also displayed.

That is, in the step S2 of selecting an inspection method and additional measurement items, inspection is performed using a database that defines inspection methods and additional measurement items for each combination of the type of evaluation target portion and the thickness of the evaluation target portion. This is the step of selecting a method and measurement items.
Thus, according to the plant inspection method according to some embodiments, since the step S2 of selecting the inspection method and the additional measurement items is provided, the inspection method and Measurement items can be quickly selected.

(Details of step S3 for inspecting the evaluation target site)
In step S3 for inspecting the evaluation target portion, the evaluation target portion is subjected to the flaw detection inspection as follows.

(1) When the part to be evaluated is the part where the largest damage is likely to occur inside the plate thickness For example, if the part to be evaluated is the part where the largest damage is likely to occur In step S2 of selecting measurement items, the flowchart shown in FIG. 4 is presented.
FIG. 4 is a flowchart showing the flow of processing to be performed in step S3 for inspecting the evaluation target portion when the evaluation target portion is the portion where the greatest damage is likely to occur inside the plate thickness. In step S3 for inspecting the portion to be evaluated, the inspector performs a flaw detection inspection of the portion to be evaluated according to the flowchart shown in FIG. additional measurement.

In step S301, the inspector performs a flaw detection inspection inside the plate thickness of the portion to be evaluated, and detects the position and size of flaws inside the plate thickness.
In step S301, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the synthetic aperture method, ultrasonic inspection by the high frequency UT method, ultrasonic inspection by the ultrasonic noise method, A flaw detection inspection inside the plate thickness is performed by any inspection method such as an ultrasonic inspection. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items, as described above.

Next, in step S302, the inspector determines whether there is an internal flaw, that is, a flaw inside the plate thickness of the portion to be evaluated, from the results of the flaw detection inspection performed in step S301. If it is determined in step S302 that no flaw exists, the process ends.
If it is determined in step S302 that a flaw exists, the process proceeds to step S303, and the inspector determines whether or not the detected flaw exists in the vicinity of the dead zone in the inspection method performed in step S301.
If the detected flaw does not exist in the vicinity of the dead zone, the process proceeds to step S306, which will be described later. If the detected flaw exists in the vicinity of the dead zone, the inspector proceeds to step S304 and implements the measures for reducing the dead zone described above. The measure for reducing the dead zone is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.
As described above, when implementing measures to reduce the dead zone, for example, the inspection of the outer surface and the removal of excess build-up from the welded portion are performed. In addition, when implementing measures to reduce the dead zone, an outer surface inspection or a flaw detection inspection inside the plate thickness of the portion to be evaluated may be performed after the removal of the surplus of the welded portion.

In this way, in the plant inspection method according to some embodiments, step S304 inspects the interior of the evaluation target portion, and inspects the inside of the evaluation target portion within a predetermined distance from the dead zone of the inspection method on the outer surface side of the evaluation target portion. If flaws are detected, further inspection should be conducted using an inspection method that inspects the outer surface of the evaluation target area, or after removing the weld surplus in the evaluation target area, the inside of the evaluation target area is a step of inspecting Therefore, it is possible to suppress the influence of the dead zone related to the inspection method.

After implementing the measures to reduce the dead zone in step S304, in step S305, the inspector determines whether or not the flaws existing in the vicinity of the dead zone within the plate thickness are continuous with the flaws on the outer surface.

If it is determined in step S305 that the flaw existing in the vicinity of the dead zone inside the plate thickness is not continuous with the flaw on the outer surface, in step S306, the inspector checks the plate thickness without considering the flaw on the outer surface. The size of the internal flaw is acquired from the result of the flaw detection inspection in step S301.
If it is determined in step S305 that the flaw existing in the vicinity of the dead zone inside the plate thickness is continuous with the flaw on the outer surface, in step S309, the inspector checks the inside of the plate thickness including the flaw on the outer surface. The size of the flaw is acquired from the result of the flaw detection inspection in step S301.

In step S307, the inspector uses the size of the flaw acquired in step S306 or step S309 to improve the accuracy of the remaining life evaluation when performing the remaining life evaluation of the evaluation target portion in step S4. Decide if it is necessary. Specifically, the size of the flaw obtained in step S306 and the simple determination graph shown in FIG. 5 are referred to determine whether or not it is necessary to improve the accuracy of remaining life evaluation.
FIG. 5 is a graph in which the horizontal axis represents the stress acting on the portion to be evaluated, and the vertical axis represents the ratio between the size of the flaw and the thickness of the portion to be maintained. Straight lines L1 to L7 in the graph of FIG. 5 indicate the case where the remaining life until the detected flaw penetrates the evaluation target site is 20,000 hours. The difference between the straight lines L1 to L7 is the temperature difference in the maintenance target portion, and the temperature in the maintenance target portion increases toward the left side in FIG. That is, the straight line L1 represents the highest temperature, and the straight line L7 represents the lowest temperature. The above 20,000 hours is the time obtained by adding about 3,000 hours to the about 17,000 hours, which is the time until the next regular inspection in two years, for example.

The inspector obtains the ratio between the size of the flaw and the plate thickness of the maintenance target portion obtained in step S306, and evaluates the ratio during the operation of the plant from, for example, the operating status of the plant. Obtain the stress and temperature acting on the target site. Then, it is confirmed which position in the graph shown in FIG. 5 is the point corresponding to the obtained ratio and stress, and the positional relationship with any of the straight lines L1 to L7 corresponding to the obtained temperature.

If the point corresponding to the determined ratio and stress is within the area on the left side of any of the straight lines L1 to L7 corresponding to the determined temperature, and is separated from the straight line to some extent, the detected flaw penetrates the evaluation target site. It can be determined that the remaining life until the end exceeds 20,000 hours. In this case, in step S307, the inspector determines that there is no need to improve the accuracy of the remaining life evaluation when performing the remaining life evaluation in step S4 for evaluating the remaining life of the evaluation target portion. The process in step S3 for inspecting is terminated.

In addition, the point corresponding to the determined ratio and stress is within the area on the left side of any of the straight lines L1 to L7 corresponding to the determined temperature, but is close to the straight line, or is on the straight line or to the right of the straight line. If it is within the area of , it can be determined that the remaining life until the detected flaw penetrates the evaluation target site may be less than 20,000 hours. In this case, in step S307, the inspector judges that it is necessary to improve the accuracy of the remaining life evaluation when performing the remaining life evaluation in step S4, and proceeds to step S308. .

In step S308, the inspector performs additional measurement of additional measurement items. As described above, additional measurement items are presented to the inspector in step S2 for selecting the inspection method and additional measurement items. After performing the additional measurement, the inspector ends the processing in step S3 for inspecting the evaluation target region.

Thus, in the plant inspection method according to some embodiments, step S307 is a step of determining whether or not additional measurement is necessary based on the flaw length obtained from the inspection result of the portion to be evaluated. The plant inspection method according to some embodiments includes a step of determining whether or not additional measurement is necessary based on the flaw length obtained from the inspection result of the portion to be evaluated. can be easily determined based on Moreover, if it is determined that additional measurement is not necessary, additional measurement is not required, which is efficient.

Further, in the plant inspection method according to some embodiments, the need for additional measurement is determined based on the size of the flaw acquired in step S306 and the simple determination graph shown in FIG. That is, the threshold value of the flaw length used to determine the necessity of additional measurement is determined according to at least one of the temperature condition and the stress condition of the evaluation target portion during operation of the plant. Therefore, since at least one of the temperature condition and the stress condition of the portion to be evaluated during the operation of the plant is reflected in the flaw length threshold value used for determining the necessity of additional measurement, the accuracy of determining the necessity of additional measurement can be improved.

(2) When the evaluation site is the site where the greatest damage to the outer surface is likely to occur. In step S2 of selecting , the flowchart shown in FIG. 6 is presented.
FIG. 6 is a flow chart showing the flow of processing to be performed in step S3 for inspecting the evaluation target region when the evaluation target region is the region where the greatest damage to the outer surface is likely to occur. In step S3 for inspecting the portion to be evaluated, the inspector performs a flaw detection inspection of the portion to be evaluated according to the flowchart shown in FIG. additional measurement.

In step S321, the inspector inspects the outer surface of the portion to be evaluated to detect flaws on the outer surface.
In step S321, the outer surface is inspected by any one of magnetic particle inspection, liquid penetrant inspection, MT transfer method inspection, eddy current inspection, and the like. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items, as described above.

Next, in step S322, the inspector determines the presence or absence of flaws on the outer surface from the results of the inspection performed in step S321. If it is determined in step S322 that no flaw exists, the process proceeds to step S326, which will be described later.
In step S322, when it is determined that a flaw exists, the process proceeds to step S323, and the inspector evaluates the vicinity of the outer surface in order to inspect how far the flaw on the outer surface extends into the inside of the evaluation target site. The inside of the target part is inspected for flaw detection. In step S323, the inspector conducts ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the synthetic aperture method, ultrasonic inspection by the high frequency UT method, ultrasonic noise A flaw detection inspection is performed on the inside of the evaluation target portion in the vicinity of the outer surface by any inspection method among ultrasonic inspections according to the method. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.

In step S324, the inspector acquires the depth (size) of the flaw appearing on the outer surface based on the inspection result of the flaw detection inspection performed in step S323, and proceeds to step S307. Note that the processing in steps S307 and S308 in FIG. 6 is the same as the processing in steps S307 and S308 shown in FIG. 4, and thus description thereof is omitted.

In step S326, if the replica of the evaluation target region does not exist, the inspector ends the processing in step S3 for inspecting the evaluation target region, and if the replica of the evaluation target region exists, proceeds to step S327.
In step S327, the inspector performs a non-destructive inspection (NED) based on the replica of the portion to be evaluated to calculate the local life consumption rate on the outer surface. In step S327, the inspector uses the void number density method, the void area ratio method, the structure comparison method, the precipitate intergranular distance method, the A parameter method, the grain deformation method, the void grain boundary length method, and the carbide composition measurement. The local life consumption rate on the outer surface is calculated based on any inspection method among the methods. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items.

In step S328, the inspector determines whether the local life consumption rate on the outer surface calculated in step S327 exceeds a predetermined value. Assuming that the time point at which visually observable cracks occur is 100%, the predetermined value is, for example, 90%, but the predetermined value is not limited to 90%.
If the local life consumption rate on the outer surface calculated in step S327 exceeds 90%, the process proceeds to step S323, and the inspector performs the processing of step S323 described above.
If the local life consumption rate on the outer surface calculated in step S327 is 90% or less, the inspector ends the processing in step S3 for inspecting the evaluation target portion.

In this way, in the plant inspection method according to some embodiments, the outer surface of the evaluation target part is inspected, and the local life consumption rate and the time when visually observable cracks occur is set to 100% A step S327 of calculating a local life consumption rate is included. Further, in the plant inspection method according to some embodiments, when the calculated life consumption rate exceeds a predetermined value, step S323 of performing an inspection by an inspection method for inspecting the inside of the evaluation target portion. Prepare. Therefore, it is possible to inspect how far the flaw has progressed from the outer surface to the inside of the site to be evaluated.

(3) When the part to be evaluated is the part where the largest damage is likely to occur around the inner slit For example, if the part to be evaluated is the part around the inner slit where the largest damage is likely to occur And in step S2 of selecting additional measurement items, the flowchart shown in FIG. 7 is presented.
FIG. 7 is a flow chart showing the flow of processing to be performed in step S3 for inspecting the evaluation target region when the evaluation target region is the region where the inner surface slit peripheral region is most likely to be damaged. In step S3 for inspecting the portion to be evaluated, the inspector performs a flaw detection inspection of the portion to be evaluated according to the flowchart shown in FIG. additional measurement.

In step S341, the inspector inspects the inner surface slit peripheral portion of the evaluation target portion to detect the position and size of the flaw on the inner surface slit peripheral portion.
In step S341, ultrasonic inspection by the conventional UT method, ultrasonic inspection by the TOFD method, ultrasonic inspection by the phased array method, ultrasonic inspection by the synthetic aperture method, ultrasonic inspection by the high frequency UT method, ultrasonic inspection by the ultrasonic noise method, A flaw detection inspection of the portion around the inner surface slit is performed by any inspection method such as ultrasonic inspection. Each of these inspection methods is presented to the inspector in step S2 for selecting the inspection method and additional measurement items, as described above.

Next, in step S342, the inspector determines the presence or absence of flaws around the slit on the inner surface based on the results of the flaw detection performed in step S341. If it is determined in step S342 that no flaw exists, the process ends.
If it is determined in step S342 that a flaw exists, the process proceeds to step S343, and the inspector acquires the size of the flaw around the inner slit from the results of the flaw detection inspection in step S341, and proceeds to step S307. Note that the processes in steps S307 and S308 in FIG. 7 are the same as the processes in steps S307 and S308 shown in FIG. 4, so description thereof will be omitted.

As described above, in the plant inspection method according to some embodiments, if the part to be maintained is, for example, a thick longitudinal welded part in a straight pipe or an elbow of piping, the largest Damage is likely to occur. Therefore, as described in (1) above, the inspector follows the flowchart shown in FIG. A decision is made as to whether or not to measure, and additional measurements are taken as necessary.
That is, the inspection method set for the longitudinal welded portion having a thickness exceeding the specified value is an inspection method for inspecting the inside of the longitudinal welded portion as the portion to be evaluated. Therefore, the inspection method is suitable for longitudinal welds having a wall thickness exceeding the specified value.
In addition, in the plant inspection method according to some embodiments, if the maintenance target portion is a longitudinal weld portion having a thickness exceeding a specified value, an inspection method suitable for flaw detection inspection inside the plate thickness is selected. Therefore, an item including the pipe cross-sectional shape of the pipe, that is, the shape of the cross section when the pipe is viewed from the pipe axis direction, is selected as the measurement item for the additional measurement. Therefore, measurement items are selected that are suitable for longitudinal welds having a wall thickness exceeding the specified value.

In addition, in the plant inspection methods according to some embodiments, if the portion to be maintained is, for example, a thick cylindrical welded portion, the outer surface of the cylindrical welded portion is most likely to be damaged. Therefore, as described in (2) above, the inspector performs a flaw detection inspection of the evaluation target portion by an inspection method suitable for the flaw detection inspection of the outer surface according to the flowchart shown in FIG. 6, and measures additional measurement items. If necessary, additional measurements are taken.
That is, the inspection method established for the circumferential welded portion having a thickness exceeding the specified value is an inspection method for inspecting the outer surface of the circumferential welded portion as the portion to be evaluated. Therefore, the inspection method is suitable for circumferential welds having a wall thickness exceeding the specified value.

In addition, in the plant inspection methods according to some embodiments, if the portion to be maintained is, for example, a thin cylindrical welded portion, the greatest damage is likely to occur inside the plate thickness of the cylindrical welded portion. Therefore, as described in (1) above, the inspector follows the flowchart shown in FIG. A decision is made as to whether or not to measure, and additional measurements are taken as necessary.
That is, the inspection method set for the circumferential welded portion having a thickness equal to or less than the specified value is an inspection method for inspecting the inside of the circumferential welded portion as the portion to be evaluated. Therefore, the inspection method is suitable for circumferential welds having a wall thickness equal to or less than the specified value.

In addition, in the plant inspection method according to some embodiments, if the part to be maintained is, for example, a nozzle welded part, the outer surface of the nozzle welded part and the part surrounding the slit on the inner surface are most likely to be damaged. Therefore, as described in (2) above, the inspector conducts flaw detection of the portion to be evaluated using an inspection method suitable for flaw detection of the outer surface according to the flowchart shown in FIG. Conduct inspections, determine whether or not to measure additional measurement items, and perform additional measurements as necessary. In addition, the inspector, as described in (3) above, follows the flowchart shown in FIG. Conduct a flaw detection inspection of the part, determine whether or not to measure additional measurement items, and perform additional measurement as necessary.
That is, the inspection method set for the nozzle welded portion is an inspection method for inspecting the outer surface of the nozzle welded portion and the portion around the internal slit as the portion to be evaluated. Therefore, the inspection method is suitable for nozzle welds.

The present invention is not limited to the above-described embodiments, and includes modifications of the above-described embodiments and modes in which these modes are combined as appropriate.
For example, in the above-described several embodiments, the part to be evaluated was the welded part in the steam pipes of multiple systems that connect between the boiler and the steam turbine in the thermal power plant, but the welded part to be evaluated is the boiler However, the plant inspection method according to the present invention can be applied to various welded parts exposed to high temperature and high pressure, and parts other than welded parts.

1 storage device 2 terminal device

Claims (13)

A plant inspection method comprising:
By the inspection method set for each combination of the type of evaluation target part including at least one of the circumferential welded part or longitudinal welded part of the pipe, or the nozzle welded part, and the thickness of the evaluation target part, a step of inspecting the site to be evaluated;
a step of selecting measurement items for additional measurement for obtaining parameters necessary for improving the accuracy of the remaining life evaluation of the evaluation target portion performed based on the inspection result of the evaluation target portion by the inspection method;
A plant inspection method comprising selecting the inspection method and the measurement item using a database defining the inspection method and the additional measurement item for each of the combinations of the type of the evaluation target portion and the thickness of the evaluation target portion; The plant inspection method according to claim 1, comprising: 3. The plant inspection method according to claim 1, further comprising a step of determining necessity of said additional measurement based on a flaw length obtained from said inspection result of said evaluation target portion by said inspection method. 4. The plant according to claim 3, wherein the threshold value of the flaw length used for determining the necessity of the additional measurement is determined according to at least one of temperature conditions and stress conditions of the evaluation target portion during operation of the plant. Inspection methods. 5. The inspection method set for the longitudinal welded portion having a thickness exceeding a specified value is an inspection method for inspecting the inside of the longitudinal welded portion as the evaluation target portion. The plant inspection method described in . 6. The inspection method set for the circumferential welded portion having a thickness exceeding a specified value is an inspection method for inspecting the outer surface of the circumferential welded portion as the portion to be evaluated. 1. A plant inspection method according to 1. 7. The inspection method set for the circumferential welded portion having a wall thickness equal to or less than a specified value is an inspection method for inspecting the inside of the circumferentially welded portion as the portion to be evaluated. A method for inspecting the plant according to item 1. 8. The inspection method set for the nozzle welded portion is an inspection method for inspecting an outer surface of the nozzle welded portion as the portion to be evaluated and a portion around an internal slit. The plant inspection method described in . The inspection method set for the nozzle weld is at least one of ultrasonic inspection by conventional UT method, ultrasonic inspection by TOFD method, magnetic particle inspection, penetrant inspection, inspection by MT transfer method, and eddy current inspection. The plant inspection method according to claim 8, comprising: 10. The pipe cross-sectional shape of the pipe is selected as the measurement item if the portion to be evaluated inspected by the inspection method is the longitudinal weld portion having a wall thickness exceeding a specified value. A method for inspecting the plant according to item 1. The measurement items include the pipe outer diameter, plate thickness, pipe cross-sectional shape, weld metal shape, shape of the heat-affected zone due to welding heat, temperature of the evaluation target portion during operation of the plant, and 11. The plant inspection method according to any one of claims 1 to 10, including at least one of hardness of the evaluation target portion. Inspection for inspecting the inside of the part to be evaluated, and inspecting the outer surface of the part to be evaluated when a flaw is detected inside a predetermined distance from the dead zone of the inspection method on the outer surface side of the part to be evaluated. 12. The method according to any one of claims 1 to 11, further comprising a step of inspecting the inside of the evaluation target portion again after performing the inspection by the method or removing the surplus of the welded portion in the evaluation target portion. A method for inspecting the plant according to item 1. a step of inspecting the outer surface of the evaluation target part and calculating a local life consumption rate, which is a local life consumption rate and takes the point of time when visually observable cracks occur as 100%;
13. The method according to any one of claims 1 to 12, further comprising a step of performing an inspection by an inspection method for inspecting the inside of the evaluation target portion when the calculated life consumption rate exceeds a predetermined value. Plant inspection method.

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