JP2017191115A - Analyzing method of damage on piping - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a remaining life inspection method on a weld part of a heat resistant member capable of obtaining a remaining life parameter relevant to a remaining life of a weld part on a heat resistant member by efficiently evaluating creep damage generated on the weld part.SOLUTION: The damage analyzing method of piping constituted of a high chrome steel or a high-strength low-alloy steel, the method includes: a step to evaluate a state of damage in a first area inside the piping by using a phased-array ultrasonic flaw detector; a step to evaluate a state of damage in a second area at the surface side of the piping; and a step to analyze the crack propagation based on the evaluation results.SELECTED DRAWING: Figure 19

Description

  The present disclosure relates to a piping damage analysis method.

  Pipings used in steam equipment such as boilers and steam turbines are used in a high-temperature and high-pressure environment for a long period of time, so heat-resistant members formed from materials having excellent high-temperature strength are used. In this type of piping, creep damage such as creep voids and cracks progresses as the operation time elapses. Creep damage is known to proceed from the inside of the pipe when the pipe has a weld, and has a characteristic that it tends to occur particularly in the heat-affected zone.

  In the case of general piping, there is a considerable correlation between the damage state inside the pipe and the damage state on the pipe surface. Therefore, in the conventional inspection method, the damage state of the pipe surface is measured by a magnetic particle flaw detection (MT) method or the like, and the internal damage state is estimated and evaluated from the measurement result. However, it is formed from high-strength ferritic steel such as high-chromium steel containing about 9 to 12% by mass of chromium and high-strength low-alloy steel having a similar structure to high-chromium steel and containing about 2-3% by mass of chromium. In some cases, the above-described correlation may not be obtained in the pipes that have been used. For such pipes, by using ultrasonic measurement (UT, TOFD method, phased array method (hereinafter referred to as “PA method”), etc.) The damage condition inside the pipe is evaluated without relying on surface measurement.

  For example, Patent Document 1 discloses a method for evaluating creep damage in a metal material based on the results of ultrasonic noise analysis measurement and surface creep void number measurement.

JP 2002-31632 A

  Creep damage first occurs as minute damage inside the pipe, but once it occurs, it then spreads to the surroundings at a high rate of progress. Therefore, it is preferable to detect the creep damage at a stage where it is a minute damage. According to this viewpoint, the PA method capable of focusing the ultrasonic wave at an arbitrary position by arranging a plurality of probes and changing the transmission timing is suitable for detecting minute damage generated in the pipe. it is conceivable that.

  By the way, piping used for steam equipment such as boilers and steam turbines has a large number of welds over a long distance. Moreover, as for the welded steel pipe manufactured by welding the curved board | plate material, the welding part is extended along the longitudinal direction (for example, several 10-several 100 m). Since such a weld has a constant stress distribution in the stress analysis, it is unclear from which position the creep damage occurs. Therefore, it is necessary to conduct a full length inspection. However, since the PA method takes a relatively long measurement time, if the conventional PA method is directly applied to such a welded part, there is a problem that it takes a lot of time and cost for the inspection.

  An object of at least one embodiment of the present invention is to provide a piping damage analysis method made in view of the above problems.

  A method for inspecting the remaining life of a welded part of a heat-resistant member according to at least one embodiment of the present invention is a phased array ultrasonic flaw detection capable of creating a tomographic image based on an ultrasonic reflected wave received by a probe arranged at a measurement position. In the method for inspecting the remaining life of a welded part of a heat-resistant member using an apparatus, the heat contained in the welded part based on the tomographic image while scanning the probe along the extending direction of the welded part at a first speed. A high-speed PA measurement step for evaluating the damage state of the affected part, an inspection target region determination step for determining an inspection target region from the weld based on the evaluation result of the high-speed PA measurement, and the probe from the first speed A detailed PA measurement step for recording the tomographic image while scanning the inspection target area at a slow second speed, and a solution for determining the remaining life of the weld based on the recorded tomographic image. Characterized in that it comprises a step.

  According to the present embodiment, the damaged state is easily grasped over the entire welded portion by high-speed PA measurement, and an area having a relatively large damaged state is determined as an inspection target area according to the measurement result. And by performing detailed PA measurement only about the said inspection object area | region, a damage state can be evaluated efficiently and highly accurately, and a remaining life can be test | inspected. In particular, even if the welded part is a long distance, the range in which detailed PA measurement is performed is determined as an inspection target area by determining an area where damage is likely to exist by high-speed PA measurement. Accurate evaluation is possible while effectively reducing the time and cost required.

  In some embodiments, in the high-speed PA measurement step, the damage state is recorded in association with the measurement position of the probe, and is classified into a predefined class corresponding to the echo level of the reflected wave, In the inspection target region determination step, the measurement position included in the class corresponding to the echo level equal to or higher than a threshold is determined as the inspection target region.

  According to this embodiment, by classifying the welds into each class by high-speed PA measurement, it is possible to efficiently select an area where there is a high possibility of damage.

  In some embodiments, the method includes a magnetic particle flaw detection step for evaluating a damage state of the surface of the weld using a magnetic particle flaw detection method, and the damage state obtained in the magnetic particle flaw detection step and the analysis obtained in the analysis step Based on the result, a maintenance plan for the heat-resistant member is created.

  According to this embodiment, the damaged state of the weld surface, which is difficult to evaluate by the PA method, can be complemented by the magnetic particle flaw detection method. Thereby, damage evaluation with less leakage can be performed on the welded portion, and a higher quality inspection can be provided.

  In some embodiments, the reflected wave from the weld is totally reflected on the second surface of the heat-resistant member while the probe is disposed on the first surface of the heat-resistant member away from the weld. An oblique angle UT measurement step of measuring a damage state in the vicinity of the first surface of the weld based on the received ultrasonic signal is further provided.

  According to this embodiment, damage evaluation can be performed on the vicinity of the surface of the welded portion (in the range of several millimeters in depth), which is difficult to measure by the PA method or the magnetic particle flaw detection method, by the oblique angle UT measurement. Thereby, damage evaluation with less leakage can be performed on the welded portion, and a higher quality inspection can be provided.

  In some embodiments, the heat-resistant member is a cylindrical pipe, and the weld extends along the axial direction of the pipe.

  According to this embodiment, even when the welded portion exists over a long distance, it is possible to evaluate with high accuracy while effectively reducing the period and cost required for the above-described method.

  According to at least one embodiment of the present invention, it is possible to provide a method for inspecting the remaining life of a welded portion of a heat-resistant member capable of efficiently and accurately evaluating creep damage occurring in the welded portion.

It is a figure which shows schematic structure of the heat-resistant member which is the test object of the remaining life inspection method which concerns on at least 1 embodiment of this invention. It is the side view and sectional drawing of a part of piping shown in FIG. It is a schematic diagram which expands and shows the welding part of piping. It is a figure which shows typically the use condition of a flaw detector. It is a main flowchart which shows roughly the residual life inspection method of the welding part of the piping which concerns on at least 1 embodiment of this invention. It is a flowchart which shows the subroutine of the high-speed PA measurement process of FIG. It is a flowchart which shows the subroutine of the inspection object area | region determination process of FIG. It is a flowchart which shows the subroutine of the detailed PA measurement process of FIG. It is a flowchart which shows the subroutine of the analysis process of FIG. It is a table | surface which shows an example of the evaluation criteria used by S22. It is a figure which shows the thing corresponding to each class shown in FIG. 10 among the tomographic images obtained by high-speed PA measurement. It is a table | surface which shows an example of the criteria of a damage state based on the echo level in general PA measurement. It is a schematic diagram which shows the structural example for implement | achieving the automatic operation of a probe. FIG. 13 is a graph showing an example of a characteristic curve showing the correlation between the number density of creep voids and the remaining life parameter. It is a figure which shows the example of a measurement of MT method. It is a flowchart which shows the lifetime evaluation method which concerns on one Embodiment of this invention. FIG. 16 is a reference table for setting special conditions in S62 of FIG. 15; FIG. It is a figure which shows typically the mode of the measurement by the bevel UT method. It is a flowchart of the remaining life evaluation method which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Only.

  FIG. 1 is a diagram showing an overall structure of a heat-resistant member 1 which is an inspection target of a remaining life inspection method according to at least one embodiment of the present invention. FIG. 2 is a side view and a cross-sectional view of the pipe 10 which is a part of the heat-resistant member 1 shown in FIG. FIG. 3 is an enlarged schematic view showing the welded portion 12 of the pipe 10.

  The pipe 10 is a steam pipe used in a large plant facility. Since the length in the longitudinal direction ranges from several tens to several hundreds of meters, the pipe 10 is manufactured by welding both ends of two curved plate-like members 10a and 10b so as to have sufficient strength. . That is, welded portions 12a and 12b extending along the longitudinal direction are formed between the plate-like members 10a and 10b constituting the pipe 10.

  Since the pipe 10 is used under a high temperature condition for a long period of time, it is made of a heat-resistant steel material. Specifically, it is formed from a high chromium steel containing about 9 to 12% by mass of chromium or a high strength low alloy steel having a similar structure to the high chromium steel and containing about 2 to 3% by mass of chromium.

  As shown in FIG. 3, the welded portion 12 is located between the plate-like members 10 a and 10 b and includes a molten metal 14 and heat-affected portions 16 on both sides of the molten metal 14. Creep voids are generated in the heat-affected zone 16 when used at a high temperature for a long period of time. The number of creep voids increases with long-term use, and adjacent creep voids are connected to form a crack. Then, the crack grows gradually and eventually penetrates the welded portion 12 in the thickness direction, and internal fluid leaks. For this reason, in operation of a boiler etc., it is necessary to perform the remaining life inspection of the welding part 12 of the piping 10 appropriately.

  In at least one embodiment of the present invention, a flaw detector 20 using a phased array (PA) method is used to inspect such creep damage. Here, FIG. 4 is a diagram schematically showing a usage state of the flaw detection apparatus 20.

The flaw detection apparatus 20 includes a flaw detection apparatus main body 22 and a probe 24 electrically connected to the flaw detection apparatus main body 22.
The flaw detection apparatus main body 22 is configured by, for example, a computer, performs transmission / reception control of ultrasonic waves from the probe 24 and analysis processing of received signals, and displays the analysis result as a tomographic image on a display device (not shown) such as a display. It is configured to be possible.

  The probe 24 has an array element 29 including a plurality of vibration elements 27 arranged in a line. Each vibration element 27 is composed of a piezoelectric element, and is configured to vibrate when an electric signal is applied to emit an ultrasonic wave, and to output an electric signal corresponding to the amplitude of the ultrasonic wave when the ultrasonic wave is incident. Yes. The outgoing angle of the ultrasonic wave is configured to be controllable by adjusting the phase of an electric signal applied to the piezoelectric element.

  The probe 24 is disposed at a measurement position on the outer surface (first surface) 11 of the pipe 10, and the flaw detector main body 22 detects reflected ultrasonic waves using the probe 24. The flaw detector main body 22 creates a tomographic image associated with the measurement position coordinates based on the detection signal of the probe 24.

  FIG. 5 is a main flowchart schematically showing a remaining life inspection method for the welded portion 12 of the pipe 10 according to at least one embodiment of the present invention. The main flowchart includes a high-speed PA measurement step S10, an inspection target region determination step S12, a detailed PA measurement step S14, and an analysis step S16. Each of these steps has a subroutine shown in FIGS. Yes.

In the high-speed PA measurement step S10, the measurement sensitivity is set higher than usual, and the tomographic image of the welded portion 12 corresponding to the position of the probe 24 is displayed in real time while manually scanning the probe 24 along the welded portion 12. . The operator scans the probe 24 while confirming the damaged state of the welded portion 12 by referring to the tomographic image. The confirmed damage state is recorded for later use in association with the measurement position of the probe 24.
Thus, in the high-speed PA measurement step S10, the damaged state is simply measured with high measurement sensitivity over the entire welded portion 12 while scanning the probe 24. Thereby, even when the welded portion covers a wide range, it is possible to acquire reliable data on the damaged state in a relatively short time and at a low cost.

  In the inspection target area determination step S12, an inspection target area that requires further detailed inspection is determined based on the measurement result of S10. In this process, as a result of the high-speed PA measurement process S10, an area in which there is a possibility of damage is determined as an inspection target area. As described above, by determining the inspection target region based on the result of the high-speed PA measurement, the region to be inspected can be efficiently selected.

  In the detailed PA measurement step S14, detailed PA measurement is performed on the inspection target region. In the detailed PA measurement, the detailed damage state measurement by the PA method is performed on the inspection target region determined in the above process as compared with the high-speed PA measurement process S10. Specifically, as will be described later, the PA measurement is performed while sequentially moving the position of the probe 24 within the region to be inspected (that is, while the probe 24 is fixed at each measurement point and sequentially moved every time PA measurement is completed). carry out. As described above, in the detailed PA measurement process, evaluation is performed at a slower scanning speed and a shorter measurement pitch than in the high-speed PA measurement process, and therefore, evaluation by the PA method with higher accuracy and clearness is performed.

In the analysis step S16, the remaining life is evaluated by analyzing the welded portion 12 based on the various data acquired in S10-S14. The evaluation of the remaining life is performed, for example, by preliminarily defining a correspondence relationship between the damaged state and the remaining life parameter Pr related to the remaining life, and applying the measured data to the relationship to obtain the remaining life parameter Pr.
The remaining life is a time from the present time until the welded portion 16 breaks due to creep damage. However, the remaining life parameter Pr may be any value as long as it represents a value related to the remaining life of the welded portion 16. It may be a life consumption rate indicating the ratio of the time elapsed up to the present time with respect to the life.

With reference to FIG. 6, the subroutine of the high-speed PA measurement step S10 will be described in detail.
First, the flaw detector 20 is set to measurement conditions suitable for high-speed PA measurement (step S20). Here, the measurement conditions are set so that the measurement sensitivity is about 10-20 dB higher than the general PA measurement, and the probe 24 can be manually scanned. By setting to such measurement conditions, when the probe 24 is manually scanned, waveform information can be obtained to such an extent that the damage state can be easily grasped.

  Subsequently, the operator manually scans the probe 24 along the extending direction of the welded portion 12 (step S21), and evaluates the displayed tomographic image (step S22). As described above, the welded part 12 extends over a long distance along the longitudinal direction of the pipe 10. The operator scans the probe 24 along the welded portion 12 and evaluates the internal damage state based on the tomographic image displayed on the flaw detector main body 22 in real time. The damage is displayed in the form of dots or lines in the tomographic image, but may be easily distinguished by coloring.

  The presence or absence of damage in the heat affected zone 16 of the welded portion 12 has a great influence on the remaining life. Therefore, in S22, the operator may perform more accurate damage evaluation by paying attention to the presence or absence of damage in the heat affected zone 16 for evaluation.

In an embodiment, the damage evaluation in S22 may be performed by classifying in accordance with a preset evaluation criterion. Here, FIG. 10 is a table showing an example of the evaluation criteria used in S22.
This evaluation criterion is composed of four stages indicated by symbols “A”, “B”, “C”, and “D” according to the damage state. The symbol “A” corresponds to the case where the echo level is less than 25% and no significant instruction is seen in the waveform. The symbol “B” corresponds to the case where the echo level is 25% or more and less than 50% and the waveform includes an echo that can be distinguished from the surroundings. The symbol “C” corresponds to a case where the echo level is 50% or more and there is a high echo that can be distinguished from the surroundings in the waveform. The symbol “D” corresponds to a case where the echo level is 50% or more and high echoes are continuously distributed in the waveform.

  In the evaluation criteria, the case where the echo level is 50% or more is classified into symbols “C” and “D” based on the waveform. These differ in whether the damage state estimated from the waveform is point-like or continuous (for example, linear or planar). In the case where the waveform is continuous, these are distinguished in order to show that the damage has progressed compared to the case where the waveform is continuous.

  FIG. 11 is a diagram illustrating an example of measurement data corresponding to each class illustrated in FIG. 10 in the tomographic image obtained by the high-speed PA measurement. FIG. 11A shows an example of a tomographic image corresponding to class A, showing no damage throughout and showing a clean state. FIG. 11B is an example of a tomographic image corresponding to class B, and it is confirmed as a small trace of damage as indicated by an arrow. FIG. 11C is an example of a tomographic image corresponding to class C, and as shown by the arrows, damage to the ceiling that is larger than that in FIG. FIG. 11D is an example of a tomographic image corresponding to class D, and as shown by the arrows, linear damage exists in the heat affected zone 16, and the damage progresses compared to FIG. 11C. It means that

  Here, FIG. 12 is a table showing an example of a criterion for determining a damage state based on an echo level in general PA measurement. In general PA measurement, since the measurement sensitivity is relatively low, an echo level of 25% has been used as a determination threshold for damage. In the high-speed PA measurement of the present embodiment, the measurement sensitivity is set to be about 10-20 dB higher than that of the general PA measurement, so that it is difficult to identify the general PA measurement as indicated by the symbol “B” in FIG. Even in the region where the echo level is 25 to 50%, it can be used for the determination.

  When the determination based on the evaluation criterion is made in this way, the operator records the evaluation result in association with the measurement position of the probe 24 (step S23). Thereby, it is recorded in which class of the above-mentioned evaluation criteria each region of the welded portion extending over a long distance is classified. That is, an approximate idea can be made as to which area of the long weld can be damaged.

  Subsequently, the operator determines whether or not the high-speed PA measurement has been completed for the target range (the entire welded portion 12) (step S24). When the measurement is completed (step S24: YES), the subroutine is terminated and the process is returned to the main flowchart (FIG. 5) (return). On the other hand, when the measurement is not completed (step S24: NO), the process returns to S21 and the high-speed PA measurement is continued.

With reference to FIG. 7, the subroutine of the inspection target region determination step S12 will be described in detail.
The high-speed PA measurement result of S10 is acquired (step S30), and the areas whose evaluation levels are the symbols “C” and “D” are determined as inspection target areas from the result (step S31). This is because these areas have a high echo level of 50% or more, and therefore there is a high possibility that damage exists, and therefore there is a high need for detailed inspection.
Note that the symbol “B” may also be included in the inspection target area if the time required for the detailed PA measurement process described later can be further secured.
As described above, in the inspection target region determination step S12, it is possible to efficiently select the region for performing the detailed inspection based on the result of the high-speed PA measurement while suppressing the risk of inspection omission.

With reference to FIG. 8, the subroutine of detailed PA measurement process S16 is demonstrated in detail.
First, the flaw detection apparatus 20 is set to measurement conditions corresponding to the detailed PA measurement (step S40). Here, like the high-speed PA measurement process, the measurement conditions are set so that the probe 24 is automatically scanned while the measurement sensitivity is set to be about 10-20 dB higher than that of general PA measurement. The automatic scanning is set so that detailed PA measurement is performed on the region determined in the inspection target region determination step.

  Subsequently, automatic scanning of the probe 24 is started according to the measurement conditions set in step S40 (step S41), and PA measurement is performed at each position (step S42). Specifically, in the inspection target area, first, the probe 24 is fixed at the first position and PA measurement is performed, and then the probe 24 is fixed by moving to the second position included in the inspection target area. Measure. In this way, at each position in the inspection target region, PA measurement is performed with the probe 24 fixed, and automatic scanning is performed so as to sequentially move at a predetermined pitch interval (the pitch interval is the same as that during high-speed PA measurement). It is preferable to set it sufficiently smaller than the pitch interval (for example, the pitch interval is 0.5 mm).

  Here, FIG. 13 is a schematic diagram showing a configuration example for realizing the automatic operation of the probe 24. In the automatic scanning, a scanning body 26 with a probe 24 attached to the tip is attached to a guide 28 provided along the welded portion 12, and PA measurement is performed while being automatically moved along the guide 28. It is better to be realized by being controlled.

  Such automatic scanning and PA measurement are continued until the entire inspection target region is completed (step S43), and then the process returns to the main flow (FIG. 5).

  Detailed PA measurement at each point takes time compared to high-speed PA measurement. However, as described above, by performing the detailed PA measurement only on the inspection target region determined in advance based on the high-speed PA measurement result, the detailed PA measurement is significantly performed compared with the case where the detailed PA measurement is performed on the entire region of the welded portion 12. Time required and cost can be reduced.

With reference to FIG. 9, the analysis step S18 which is a subroutine will be described in detail.
In the analysis step 18, a characteristic curve showing the correlation between the creep void number density and the remaining life parameter Pr (for example, life consumption rate) is prepared in advance (step S50). FIG. 14 is a graph showing an example of a characteristic curve showing the correlation between the creep void number density and the remaining life parameter Pr.
The characteristic curve is stored in advance in a storage medium built in or externally attached to the flaw detector main body 22 that executes the analysis step S18.

Here, how to obtain the characteristic curve will be briefly described.
The characteristic curve is defined on the basis of a plurality of standard samples whose creep void number density and remaining life parameter Pr are known in advance. For these standard samples, a sample that requires the same or similar weld 12 as the pipe 10 to be inspected is subjected to a high-temperature creep test, and the high-temperature creep test is divided into several times and each time several standard samples are interrupted. It is prepared by extracting 32. Thereby, a plurality of standard samples 32 having different combinations of creep void number density and remaining life parameter Pr are created.

Then, by measuring the creep void number density and the remaining life parameter Pr for the plurality of standard samples prepared in this way, a characteristic curve as shown in FIG. 14 is obtained.
For example, the extraction is performed for a time corresponding to 20%, 40%, 60%, and 80% of the fracture time.

  Subsequently, a detailed tomographic image is created based on the data acquired in the detailed PA measurement process (step S51), and the creep void number density is evaluated by analyzing the tomographic image (step S52). Then, the corresponding remaining life parameter Pr is obtained by applying the actually measured value of the creep void number density thus evaluated to the characteristic curve prepared in S50 (step S53).

  As described above, in some embodiments according to the present invention, a high possibility of damage is selected as a region to be inspected by high-speed PA measurement, and detailed PA measurement is performed on the selected region. Residual life evaluation can be performed. Thereby, even if it is a case where a welding part covers a wide range, accurate evaluation can be implemented in a short period of time and low cost.

(Application example combining MT method)
In the remaining life evaluation method described above, damage evaluation inside the welded portion 12 was performed by combining two types of PA measurements (high-speed PA measurement and detailed PA measurement). Thus, the measurement using the PA method is very effective as a method for flaw detection inside the pipe 10 with high accuracy. However, since the range near the surface (for example, several mm from the surface) becomes a dead zone, flaw detection cannot be performed.

Therefore, in one embodiment of the present invention, it is possible to perform a more accurate life evaluation by further combining evaluation by the MT (magnetic particle flaw detection) method. The MT method can evaluate the presence or absence of a flaw on the surface of the pipe 10 by conducting a magnetic particle flaw detection.
Here, FIG. 15 is a diagram illustrating a measurement example of the MT method. In FIG. 15, it is shown that there is a continuous flaw of about 70 mm along the longitudinal direction of the pipe 10.

FIG. 16 is a flowchart showing a life evaluation method according to an embodiment of the present invention.
First, the surface state damage is evaluated by conducting magnetic particle flaw detection using the MT method (step S60). Further, the internal damage of the welded portion 12 is evaluated using the above-described PA method (see FIG. 5) (step S61). As described above, the pipe 10 to be inspected in the present embodiment is a high-chromium steel containing about 9 to 12% by mass of chromium, or has a structure similar to that of the high-chromium steel and about 2 to 3% by mass of chromium. Since it is formed from the high strength low alloy steel contained, there is little correlation between the surface and the internal damage state. Therefore, in steps S60 and S61, the damage state of the surface and the inner surface is independently evaluated by the MT method and the PA method.
Note that the order in which steps S60 and S61 are performed is not limited to this, and may be simultaneous or reverse.

  Subsequently, based on the evaluation results of steps S60 and S61, the maintenance of the user of the pipe 10 to be inspected is proposed for each case (step S62). FIG. 17 is a reference table for setting special conditions in S62 of FIG.

  First, when no surface damage is found by the MT method of S60 and the internal flaw height d measured by the PA method of S61 is less than or equal to the allowable internal flaw height da (ie, there is no abnormality on the surface and the inside of the pipe 10). Pattern A is selected and no treatment is required (step S63). In this case, the next inspection time, scheduled repair time, and scheduled replacement time are proposed as standard periodic inspections.

  On the other hand, when damage exceeding the allowable flaw internal height da is found by the PA method of S61 (that is, damage is confirmed inside even if there is no abnormality on the surface), the pattern C is selected. In this case, it is further determined whether or not the scratch height d is larger than the threshold da1, or whether or not the scratch length L is larger than the repairable scratch length La (step S64). When S64 is satisfied, a factory repair or a new pipe replacement is proposed for the pipe 10 (step S65). When S64 is not satisfied (step S64: NO), it is proposed to cope with the overlay repair of the welded portion 12 (step S66).

Subsequently, when surface damage is found by the MT method of S60 and the internal flaw height d measured by the PA method of S61 is less than or equal to the allowable internal flaw height da (that is, there is only an abnormality on the surface; If there is no abnormality), the pattern B is selected. In this case, the surface of the pipe 10 is ground to a predetermined thickness (several mm), and magnetic particle inspection is performed again by the MT method (step S67). Then, it is confirmed whether or not the surface scratch has disappeared (step S68). As a result, if the surface scratch disappears (step S68: YES), the surface is smoothed (step S69).
On the other hand, if the surface scratch still does not disappear (step S68: NO), the process proceeds to step S64 and the above process is performed.

  As described above, in the present embodiment, by combining the MT method, it is possible to evaluate a surface state that cannot be measured by the PA method. As a result, damage evaluation can be performed in the entire region of the pipe 10, and a higher quality inspection can be performed.

In one embodiment according to the present invention, a higher quality inspection can be performed by further combining the MT method and the PA method with another measurement method.
In this specification, examples of combining the replica method, the bevel UT method, and the shape measurement are shown as other measurement methods, but are not limited thereto.

  The replica method can inspect the surface state of the pipe 10 in the same manner as the MT method described above. Since replica collection time is required as compared with the MT method, measurement takes time, but detailed evaluation of the void generation situation can be performed. Therefore, for example, after the simple surface state evaluation by the MT method is performed over the entire welded portion 12, the replica method is focused on a portion having a high possibility of damage, thereby efficiently and accurately inspecting. It can be performed.

FIG. 18 is a diagram schematically showing a state of measurement by the oblique UT method. In the oblique angle UT method, the probe 24 disposed on the outer surface (first surface) 11 of the pipe 10 causes the reflected wave from the welded part 12 to be entirely reflected on the inner surface (second surface 13 which is the inner diameter side surface of the pipe 10). Reflect and receive. Thereby, flaw detection can be performed even in a range of a depth of several mm from the surface, which is difficult to measure by the PA method described above.
Note that the bevel angle UT does not require much time for measurement, and may be performed over the entire welded portion 12.

About the shape of the welding part 12 of the piping 10, an outer diameter, a wall thickness, and a molten metal shape are measured. In these shapes, information on the damage state of the inner surface and the surface of the welded portion 12 is reflected. Therefore, by performing shape measurement, it is possible to supplement the data of the above various evaluations and improve inspection accuracy.
In addition, since such a shape measurement is a work which requires a relatively long time, for example, it is preferable that the shape measurement is limited to a portion having a high possibility of damage by other evaluation.

  The remaining life evaluation method using these various measurements will be described. FIG. 19 is a flowchart of a remaining life evaluation method according to an embodiment of the present invention.

Based on the measurement results of the MT method (S70) and the replica method (S71), the surface damage state is evaluated (step S72).
On the other hand, regarding the internal damage state, in addition to the PA method (S73) shown in FIG. 5, the evaluation result of the oblique UT method shown in FIG. 18 is considered (step S74). Further, shape measurement (outer diameter, wall thickness, molten metal shape) is also considered (S75). Thereby, the crack propagation analysis (stress analysis) becomes possible by comprehensively evaluating the internal damage state by the PA method, the oblique UT method, and the shape measurement (step S76). Then, the remaining life evaluation is performed based on the analysis result (step S77).

  Incidentally, the remaining life evaluation in step S73 is performed by prescribing the correlation between the crack length and the remaining life parameter Pr in advance, for example, following the analysis step S16 in FIG. 5, and applying the actual measurement value obtained in S72. The corresponding remaining life parameter Pr may be obtained.

  Then, comprehensive evaluation is performed in consideration of the evaluation result regarding the surface obtained in S70 and the evaluation result regarding the inside obtained in S73, and a future maintenance procedure is determined (step S78).

  As described above, according to the present embodiment, an efficient and highly accurate remaining life evaluation can be performed over the entire welded portion 12 of the pipe 10.

  The present disclosure can be used for a pipe damage analysis method.

DESCRIPTION OF SYMBOLS 10 Piping 12 Welding part 14 Molten metal 16 Heat-affected part 20 Phased array flaw detector 22 Flaw detector main body 24 Probe

Claims (5)

A damage analysis method for piping made of high chromium steel or high strength low alloy steel,
A first evaluation step of evaluating the damage state of the first region inside the pipe using a phased array ultrasonic flaw detector;
A second evaluation step for evaluating a damage state in the second region on the surface side of the first region of the pipe;
Based on the evaluation results of the first evaluation step and the second evaluation step, an analysis step for performing crack propagation analysis;
A piping damage analysis method comprising: Before the analysis step, further comprising a shape measurement step of measuring the shape of the welded portion of the pipe,
The pipe damage analysis method according to claim 1, wherein the analysis step performs the crack propagation analysis using a measurement result of the shape measurement step.   The piping damage analysis method according to claim 1, wherein the second evaluation step is performed using an oblique angle UT method. A surface evaluation step for evaluating surface damage of the pipe;
A maintenance treatment determination step for determining a maintenance treatment in consideration of the evaluation results of the analysis step and the surface evaluation step, and
The pipe damage analysis method according to any one of claims 1 to 3, further comprising:   The pipe surface damage analysis method according to claim 4, wherein the surface evaluation step includes at least one of an MT method and a replica method.