Corrosion and crack detection method for tubular structures

Abstract

To more accurately detect the corrosion or crack in a shielded part of a pipe-like steel structure in comparison with a case where the present configuration is not adopted.SOLUTION: On a surface of an exposed part F1 of a steel pipe P, a plurality of AE sensors 11 for detecting AE (acoustic emission) waves is installed in tandem in a pipe axis direction, and the corrosion or crack which occurs in a shielded part F2 is detected based on waveform data obtained from the AE waves detected by the plurality of AE sensors 11.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a method for detecting corrosion and cracks in tubular structures. [Background technology]

[0002] As a technique for diagnosing the soundness of tubular steel structures using non-destructive testing, a technique is known in which corrosion and cracks are detected from measurements taken by AE (Acoustic Emission) sensors installed in the structure (e.g., Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-106342 Summary of the Invention [Problem to be solved by the invention]

[0004] Some tubular steel structures are partially shielded by concrete or other shielding material. However, the installation method (e.g., installation location, number, etc.) of AE sensors that can accurately detect corrosion and cracks in the shielded areas has not been established. For this reason, depending on the installation method of the AE sensors, it may not be possible to detect corrosion and cracks in the shielded areas.

[0005] An object of the present invention is to provide a method for more accurately detecting corrosion and cracks in shielding parts of tubular steel structures than when this configuration is not adopted. [Means for solving the problem]

[0006] The invention described in claim 1 is a method for detecting corrosion and cracks in a tubular structure, characterized in that a plurality of AE sensors for detecting AE (acoustic emission) waves are installed in a vertical row in the axial direction of the tube on the surface of the exposed portion of the tubular steel structure having a shielded portion and an exposed portion, and corrosion and cracks occurring in the shielded portion are detected based on waveform data obtained from the AE waves detected by each of the plurality of AE sensors. The invention described in claim 2 is a corrosion and crack detection method for a tubular structure described in claim 1, characterized in that the shielded portion is a portion shielded by a shielding object that penetrates the structure, and the multiple AE sensors are installed close to the shielding object but not in contact with it. The invention described in claim 3 is a corrosion and crack detection method for tubular structures described in claim 1, characterized in that the multiple AE sensors are installed in a vertical row in the axial direction of the pipe at predetermined intervals. The invention described in claim 4 is a corrosion and crack detection method for tubular structures described in claim 3, characterized in that the predetermined interval is 5 cm (centimeters) to 20 cm. The invention described in claim 5 is a corrosion and crack detection method for tubular structures described in claim 1, characterized in that each set of the multiple AE sensors is installed at multiple positions on the surface of the exposed portion. The invention described in claim 6 is a corrosion and crack detection method for tubular structures described in claim 5, characterized in that one or more of the sets are arranged at intervals so as to be parallel in the axial direction of the pipe. The invention described in claim 7 is a corrosion and crack detection method for tubular structures described in claim 6, characterized in that the position at which each of the one or more sets is installed is determined based on the size of the central angle formed by the center point of a circle or approximate circle representing the cross section of the tubular steel structure and a straight line connecting each of the one or more sets. The invention described in claim 8 is the corrosion and crack detection method for a tubular structure described in claim 7, characterized in that the size of the central angle is a right angle or approximately a right angle. The invention described in claim 9 is a corrosion and crack detection method for tubular structures described in claim 8, characterized in that one of the one or more sets is installed in the ceiling part of the cross section. The invention described in claim 10 is a corrosion and crack detection method for tubular structures described in claim 1, characterized in that it determines whether the source of the AE wave is in the shielded portion or the exposed portion based on the difference between the waveform data of an AE sensor of the multiple AE sensors that is installed closer to the shielded portion and the waveform data of an AE sensor that is installed farther away than the AE sensor. The invention described in claim 11 is a corrosion and crack detection method for tubular structures described in claim 10, characterized in that the difference is due to the timing relationship of the detection of the AE wave, which is identified from the waveform data. The invention described in claim 12 is a corrosion and crack detection method for tubular structures described in claim 1, characterized in that the trigger for recording the waveform data is ±1 mV (millivolt) or more, the number of bits is 4 bits or more, the sampling interval is 50 ns (nanoseconds) or more, the number of sampling points that can record the entire waveform is set based on the sampling interval, and a high-pass filter below the resonant frequency of the multiple AE sensors is used. The invention described in claim 13 is a corrosion and crack detection method for tubular structures described in claim 1, characterized in that corrosion and cracks that have occurred in the shielded portion within an evaluation range of up to 100 cm (centimeters) from the boundary between the shielded portion and the exposed portion. [Effects of the Invention]

[0007] According to the present invention of claim 1, it is possible to more accurately detect corrosion and cracks in the shielding portion of a tubular steel structure than when this configuration is not adopted. According to the present invention of claim 2, by installing the AE sensor so that it does not come into contact with the shielding object, it is possible to suppress the intrusion of noise through the shielding object. Also, by installing the AE sensor close to the shielding object, it is possible to suppress missed detection due to the attenuation of AE waves. Furthermore, it is possible to suppress missed detection of longitudinal waves due to the speed difference between longitudinal waves and shear waves. According to the present invention, by installing multiple AE sensors at predetermined intervals, it becomes possible to compare waveform data. Also, by arranging multiple AE sensors in a vertical row, it becomes possible to determine whether the AE wave has propagated from a shielded area. According to the present invention, by installing a plurality of AE sensors at intervals of 5 to 20 cm, comparison of waveform data becomes easy. According to the present invention of claim 5, it is possible to prevent AE waves from going undetected when the tubular steel structure is a large-diameter steel pipe. According to the present invention of claim 6, it is possible to prevent AE waves from going undetected when the tubular steel structure is a large-diameter steel pipe. According to the present invention of claim 7, when the tubular steel structure is a large-diameter steel pipe, etc., it may be impossible to detect AE waves generated at a distant location with only one set. Even in such cases, the efficiency of inspection can be improved by predetermining a central angle that defines an installation position where two or more sets can cooperate to detect AE waves. According to the present invention of claim 8, there are cases where AE waves generated at a distant location cannot be detected by a single group, such as when the tubular steel structure is a large-diameter steel pipe. Even in such cases, by predetermining a central angle that defines an installation position where two or more groups can cooperate to detect AE waves, it is possible to prevent AE waves from being missed when they are detected. According to the present invention of claim 9, by installing one set on the ceiling, it is possible to suppress poor contact between the AE sensor and the structure due to the influence of gravity, while also suppressing missed detection of AE waves. According to the present invention of claim 10, it is possible to easily determine whether corrosion or cracks have occurred in a "shielded portion" or an "exposed portion" based on the difference in the waveforms of the AE waves detected by each of the multiple AE sensors. According to the present invention of claim 11, it is possible to easily determine whether corrosion or cracks have occurred in a "shielded portion" or an "exposed portion" from the timing relationship of the propagation of the waveforms of the AE waves detected by each of the multiple AE sensors. According to the present invention of claim 12, corrosion and cracks in the shielding parts of tubular steel structures can be detected more accurately than when this measurement condition is not adopted. According to the present invention of claim 13, corrosion and cracks occurring in areas near boundaries that are prone to corrosion and cracks due to wind and rain can be detected more accurately. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a signal processing system to which the present embodiment is applied. [Figure 2] 2 is a diagram illustrating an example of a functional configuration of an AE wave detection device that constitutes the signal processing system of FIG. 1. FIG. [Figure 3] 2 is a diagram illustrating an example of the functional configuration of a signal processing device that constitutes the signal processing system of FIG. 1. FIG. [Figure 4] 2 is a diagram illustrating an example of a hardware configuration of a determination terminal that constitutes the signal processing system of FIG. 1. FIG. [Figure 5] FIG. 2 is a diagram illustrating an example of a functional configuration of a control unit of a determination terminal. [Figure 6] 10 is a flowchart showing an example of a processing flow of the AE wave detection device. [Figure 7] 10 is a flowchart showing an example of a processing flow of the signal processing device. [Figure 8] 10 is a flowchart showing an example of a flow of processing by a determination terminal. [Figure 9]3A and 3B are diagrams showing a specific example of the configuration of a jig for firmly fixing the AE sensor of FIG. 2 to a steel pipe. (A) is a front cross-sectional view of the jig. (B) is a bottom view of the jig. (C) and (D) are side views of the jig. [Figure 10] 2 is firmly fixed using the jig shown in Fig. 9. (A) is a diagram showing the state immediately before the AE sensor is fixed, and (B) is a diagram showing the state after the AE sensor 11 has been fixed. [Figure 11] 1A and 1B are diagrams showing an example of the installation of multiple AE sensors. (A) is a perspective view of a steel pipe on which multiple AE sensors are installed. (B) is a cross-sectional view of the steel pipe on which multiple AE sensors are installed, cut perpendicular to the pipe axis. [Figure 12] 12A and 12B are diagrams showing specific examples of waveform data from each of the multiple AE sensors in Fig. 11. (A) is a diagram showing waveform data from each of the multiple AE sensors that detected an AE wave propagating from the shielded portion side in Fig. 11A. (B) is a diagram showing waveform data from each of the multiple AE sensors that detected an AE wave propagating from the exposed portion side in Fig. 11A. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. (Configuration of signal processing system) FIG. 1 is a diagram showing an example of the overall configuration of a signal processing system 1 to which this embodiment is applied. The signal processing system 1 is configured by connecting an AE wave detection device 10, a signal processing device 30, and a judgment terminal 50 via a network 90. ​​The network 90 is, for example, a LAN (Local Area Network), the Internet, etc. The signal processing system 1 is a system for performing non-destructive testing using the AE testing method. The AE testing method in this embodiment is a non-destructive testing method in which an AE sensor detects AE waves (surface acoustic waves) generated by minute deformations or fractures that occur on the surface or inside of a tubular steel structure (hereinafter referred to as a "steel pipe"), thereby enabling non-destructive monitoring of damage.

[0010] The signal processing system 1 of this embodiment functions as a corrosion and crack detection system that nondestructively detects corrosion and cracks caused by rust and the like in steel pipes. The steel pipes that are the subject of nondestructive testing by the signal processing system 1 have a thickness of 10 mm or less, preferably approximately 3 mm to 8 mm. The steel pipes that are the subject of nondestructive testing have both a shielded portion and an exposed portion. The term "shielded portion" refers to a portion of the steel pipe that is concealed by a shielding material such as concrete and therefore cannot be visually inspected. For example, if a steel pipe penetrates a concrete bridge pier and a portion of the steel pipe is therefore hidden by the pier, the portion that cannot be visually inspected is the shielded portion. The term "exposed portion" refers to a visible portion of the steel pipe other than the shielded portion. The signal processing system 1 detects corrosion and cracks that occur in the shielded portion of the steel pipe, but is particularly effective in detecting corrosion and cracks that occur within an evaluation range of 100 cm (centimeters) from the boundary between the shielded and exposed portions.

[0011] The AE wave detection device 10 that constitutes the signal processing system 1 detects AE waves generated by corrosion and cracks that occur in both the shielded and exposed parts of the steel pipe, for example, natural breakdown of accumulated iron rust (iron oxide, corrosion products), and converts the AE waves into an electrical signal (hereinafter referred to as "AE signal") and outputs it. The detailed configuration and processing flow of the AE wave detection device 10 will be described later.

[0012] The signal processing device 30 constituting the signal processing system 1 acquires the AE signal output from the AE wave detection device 10 and performs various processes. Examples of the processes performed by the signal processing device 30 include analyzing the AE signal, generating various information based on the analysis results, storing the generated information, and transmitting the information to the determination terminal 50. Examples of the information generated by the processing of the signal processing device 30 include waveform data. The detailed configuration of the signal processing device 30 and the processing flow will be described later.

[0013] The judgment terminal 50 constituting the signal processing system 1 acquires waveform data transmitted from the signal processing device 30, and judges, based on the waveform data, whether the source of the AE waves is a shielded part or an exposed part of the steel pipe. The judgment terminal 50 also stores various types of information. Examples of the information stored by the judgment terminal 50 include waveform data and judgment results of the source of the AE waves. The judgment terminal 50 also outputs various types of information. Examples of the information output by the judgment terminal 50 include waveform data and judgment results of the source of the AE waves. The detailed configuration and processing flow of the judgment terminal 50 will be described later.

[0014] The configuration of the signal processing system 1 described above is one example, and it is sufficient that the signal processing system 1 as a whole has the function of realizing the above-mentioned processing. Therefore, some or all of the functions of realizing the above-mentioned processing may be shared or cooperated within the signal processing system 1. This facilitates processing by the signal processing system 1 as a whole, and also makes it possible for the processes to complement each other. For example, the signal processing device 30 may function as a stand-alone device as an example of the corrosion and crack detection system of the present invention.

[0015] (Configuration of AE wave detection device) FIG. 2 is a diagram showing an example of the functional configuration of the AE wave detection device 10 that constitutes the signal processing system 1 of FIG. The AE wave detection device 10 functions by using AE sensors 11-1 to 11-n (n is an integer value of 2 or more), a control unit 12, preamplifiers 13-1 to 13-n, an output unit 14, and a condition setting unit 15. When there is no need to distinguish between the AE sensors 11-1 to 11-n, they will be collectively referred to as the "AE sensor 11." When referring to the "AE sensor 11," the preamplifiers 13-1 to 13-n will be collectively referred to as the "preamplifier 13."

[0016] The AE sensor 11 is a sensor made up of a piezoelectric element, and functions as a sensor that detects AE waves (surface acoustic waves) generated on the surface or inside of the steel pipe. Specifically, the AE sensor 11 converts the AE waves into an AE signal, which is an electrical signal, by utilizing the piezoelectric effect of the piezoelectric element. The piezoelectric element that makes up the AE sensor 11 is made of piezoelectric ceramics or the like with high conversion capabilities in order to detect minute strains caused by the propagation of AE waves. Examples of piezoelectric ceramics include PZT (lead zirconate titanate).

[0017] In this embodiment, the multiple AE sensors 11 constituting one set are installed vertically in the pipe axial direction at a predetermined interval. For example, when a set consisting of two AE sensors 11 is installed, it is preferable to place the two AE sensors 11 at a distance of 5 cm (centimeters) to 20 cm apart. By placing such a distance, it is possible to determine the difference in arrival time from the waveform data of the AE waves detected by each of the two AE sensors 11 based on the timing of the AE wave detection. As a result, it is possible to determine whether the detected AE waves were generated in a shielded portion of the steel pipe or in an exposed portion.

[0018] The AE sensor 11 is installed so that it is close to the shielding object through which the steel pipe passes, but does not come into contact with it. By installing the AE sensor 11 at a position close to the shielding object, missed detection due to attenuation of the AE wave and missed detection of longitudinal waves due to the difference in speed between longitudinal waves and shear waves are suppressed. Furthermore, by preventing the AE sensor 11 from coming into contact with the shielding object, noise that may be introduced when the AE sensor 11 comes into contact with the shielding object is suppressed.

[0019] Furthermore, it is preferable that the AE sensor 11 be firmly fixed to the surface of the steel pipe. By firmly fixing the AE sensor 11 to the surface of the steel pipe, detection omissions due to poor contact with the surface of the steel pipe are suppressed. In this case, for example, a jig may be used to firmly fix the AE sensor 11 to the surface of the steel pipe. Specific examples of such a jig will be described later with reference to FIGS. 9 and 10.

[0020] In this embodiment, each group consisting of multiple AE sensors 11 is installed at one or more positions on the surface of the exposed portion of the steel pipe. When multiple groups consisting of multiple AE sensors 11 are installed at each of two or more positions, the two or more groups are installed at intervals so that they are parallel to each other in the pipe axial direction. By installing two or more groups at intervals in this manner, the two or more groups can detect AE waves in cooperation with each other, thereby reducing missed detections. For example, when the steel pipe is a large-diameter steel pipe, it is possible to reduce missed detections in cases where AE waves generated at a distant location cannot be detected by a single group alone.

[0021] When two sets are installed parallel to each other in the axial direction of the pipe, the installation positions of each set are determined based on the size of the central angle (hereinafter referred to as the "installation angle") formed by the center of the circle or approximate center of the circle representing the cross section of the steel pipe and the lines connecting each of the two sets. Once this installation angle and the installation position of one set are determined, the installation position of the other set is automatically determined. For example, if a suitable installation angle that allows the two sets to work together to detect AE waves without omission is known from past inspection results, the two sets are installed according to that installation angle. In this regard, past inspection results have shown that the suitable installation angle is a right angle or a nearly right angle.

[0022] If the installation angle is a right angle or nearly a right angle, when one of the two sets is installed on the ceiling of the steel pipe, the remaining set will be installed at the 3 o'clock or 9 o'clock direction, with the ceiling being at 12 o'clock on a clock. In this case, because one set is installed on the ceiling, it is possible to prevent contact failure due to the effect of the AE sensor's own weight while also reducing the risk of AE wave detection failure.

[0023] The control unit 12 controls the overall functions of the AE wave detection device 10. The preamplifier 13 functions as an amplifier that amplifies the weak AE signals output from each of the AE sensors 11-1 to 11-n. The output unit 14 outputs the AE signals amplified by the preamplifier 13 to the signal processing device 30. The condition setting unit 15 acquires setting information transmitted from the determination terminal 50, and sets measurement conditions for the AE wave detection device 10 based on the setting information.

[0024] The measurement conditions of the AE wave detection device 10 set by the condition setting unit 15 are described below. Based on past measurement results, it is preferable that the measurement conditions of the AE wave detection device 10 be set to the following values. When the measurement conditions are set to the following values, corrosion and cracks in the shielding portion of the steel pipe can be detected more accurately than when the measurement conditions are not set to the following values. Specifically, among the measurement conditions, the trigger for recording waveform data is set to ±1 mV (millivolt) or more. The number of bits is set to 4 bits or more. The sampling interval is set to 50 ns (nanoseconds) or more. The number of sampling points is set to a number that allows the entire waveform to be recorded based on the preferred sampling interval. A high-pass filter that is set to a frequency equal to or lower than the resonant frequency of the multiple AE sensors is used.

[0025] (Configuration of signal processing device) FIG. 3 is a diagram showing an example of the functional configuration of the signal processing device 30 that constitutes the signal processing system 1 of FIG. In the signal processing device 30, a control unit 31, an acquisition unit 32, a processing unit 33, a storage unit 34, and an output unit 35 function.

[0026] The control unit 31 controls the overall functions of the signal processing device 30 . The acquisition unit 32 acquires the AE signal output from the AE wave detection device 10. A filter 321 and a main amplifier 322 function in the acquisition unit 32. The filter 321 extracts an AE signal in a frequency band required for analysis from the AE signal amplified by the preamplifier 13. The main amplifier 322 amplifies the AE signal extracted by the filter 321 again.

[0027] The processing unit 33 performs various processes on the AE signal acquired by the acquisition unit 32. Examples of the processes performed by the processing unit 33 include analyzing the AE signal and generating waveform data based on the analysis results. The processing unit 33 includes a signal analysis unit 331 and a waveform data generation unit 332. The signal analysis unit 331 analyzes the AE signal acquired by the acquisition unit 32. The waveform data generation unit 332 generates waveform data based on the analysis results of the signal analysis unit 331. The waveform data generated by the waveform data generation unit 332 is stored in the storage unit 34. A specific example of the waveform data generated by the waveform data generation unit 332 will be described later with reference to FIG. 12 .

[0028] The memory unit 34 is a storage area that stores various types of information. The memory unit 34 is configured, for example, with a hard disk drive (HDD), a solid state drive (SSD), a semiconductor memory, or the like. The memory unit 34 includes, for example, a signal memory unit 341 and a waveform memory unit 342. The signal memory unit 341 stores the AE signal acquired by the acquisition unit 32. The waveform memory unit 342 stores waveform data generated by the processing unit 33. Specifically, for example, the waveform memory unit 342 stores binary data (.dat) of voltage and time (Vt), which serves as raw data of the waveform data. The output unit 35 outputs various types of information. For example, the output unit 35 outputs waveform data generated by the waveform data generation unit 332 of the processing unit 33 to the determination terminal 50.

[0029] (Configuration of the judgment terminal) FIG. 4 is a diagram showing an example of the hardware configuration of the determination terminal 50 that constitutes the signal processing system of FIG. The determination terminal 50 has a control unit 51, a memory 52, a storage unit 53, a communication unit 54, an operation unit 55, and a display unit 56. These units are connected to each other via a data bus, an address bus, a PCI (Peripheral Component Interconnect) bus, etc.

[0030] The control unit 51 is a processor that controls the functions of the determination terminal 50 through the execution of various software such as an OS (operating system) and application software. The control unit 51 is configured, for example, by a CPU (Central Processing Unit). The memory 52 is a storage area that stores various software and data used for executing the software, and is used as a working area for calculations. The memory 52 is configured, for example, by a RAM (Random Access Memory).

[0031] The storage unit 53 is a storage area that stores input data for various software programs, output data from various software programs, etc. The storage unit 53 is configured with, for example, an HDD, SSD, semiconductor memory, etc. that are used to store programs, various setting data, etc. The storage unit 53 stores databases for storing various information, such as a waveform DB 531 that stores waveform data, and a determination result DB 532 that stores determination results for the source of AE waves, etc.

[0032] The communication unit 54 transmits and receives data to and from the signal processing device 30 and the outside via the network 90. ​​The operation unit 55 is composed of, for example, a keyboard, a mouse, mechanical buttons, and switches, and accepts input operations. The operation unit 55 also includes a touch sensor that forms a touch panel integrally with the display unit 56. The display unit 56 is composed of, for example, a liquid crystal display or an organic EL (Electro Luminescence) display used to display information, and displays image and text data, etc. Examples of information displayed on the display unit 56 include waveform data, determination results of the source of AE waves, etc.

[0033] FIG. 5 is a diagram illustrating an example of the functional configuration of the control unit 51 of the determination terminal 50. As shown in FIG. In the control unit 51 of the determination terminal 50, a transmission control unit 501, a waveform data acquisition unit 502, an occurrence source determination unit 503, and a display control unit 504 function.

[0034] The transmission control unit 501 controls the transmission of various types of information to the AE wave detection device 10. For example, the transmission control unit 501 controls the transmission of setting information for setting measurement conditions for the AE wave detection device 10, the setting information having been input by the operation unit 55, to the AE wave detection device 10.

[0035] The waveform data acquisition unit 502 acquires the waveform data transmitted from the signal processing device 30. The waveform data acquired by the waveform data acquisition unit 502 is stored in the waveform DB 531 of the storage unit 53 and managed.

[0036] The generation source determination unit 503 determines whether the source of the AE waves is in a shielded portion or an exposed portion, based on the waveform data acquired by the waveform data acquisition unit 502. Specifically, the generation source determination unit 503 determines whether the source of the AE waves is in a shielded portion or an exposed portion, based on the intervals between the positions where the multiple AE sensors 11 are installed and the timing relationship between when the AE waves are detected by each of the multiple AE sensors 11.

[0037] For example, suppose two AE sensors 11-1 and 11-2 are installed vertically in the tube axis direction. In this case, it is determined whether the source of the AE wave is in a shielded portion or an exposed portion based on the distance between the locations where the AE sensors 11-1 and 11-2 are installed and the difference in time between when the AE wave is generated and when it reaches each of the AE sensors 11-1 and 11-2. The result of the determination of the source by the source determination unit 503 is displayed on, for example, the display unit 56.

[0038] The display control unit 504 controls the display of various information on the display unit 56. For example, the display control unit 504 controls the display of waveform data acquired by the waveform data acquisition unit 502 on the display unit 56. The display control unit 504 also controls the display of the result of the source determination made by the source determination unit 503 on the display unit 56.

[0039] (Processing flow of the signal processing system) Figures 6 to 8 show flowcharts illustrating an example of the processing flow of the signal processing system 1. In the examples of Figures 6 to 8, it is assumed that a set of two AE sensors 11 is installed in an exposed portion of a steel pipe. FIG. 6 is a flowchart showing an example of the flow of processing by the AE wave detecting device 10. In the AE wave detecting device 10, when setting information is transmitted from the determination terminal 50 (YES in step 601), the condition setting unit 15 acquires the setting information (step 602) and sets the measurement conditions of the AE wave detecting device 10 based on the acquired setting information (step 603). On the other hand, if setting information has not been transmitted (NO in step 601), the condition setting unit 15 repeats step 601 until setting information is transmitted.

[0040] Each of the two AE sensors 11 constituting a pair starts measurement (step 604), and when it detects an AE wave propagating from a shielded or exposed portion of the steel pipe (YES in step 605), it converts the detected AE wave into an AE signal and outputs it (step 606). The preamplifier 13 then amplifies the output AE signal (step 607), and the output unit 14 outputs the amplified AE signal to the signal processing device 30 (step 608). On the other hand, if neither of the two AE sensors 11 detects an AE signal (NO in step 605), step 605 is repeated until each of the two AE sensors 11 detects an AE signal.

[0041] FIG. 7 is a flowchart showing an example of the flow of processing by the signal processing device 30. In the signal processing device 30, when an AE signal is output from the AE wave detection device 10 (YES in step 701), the acquisition unit 32 acquires the AE signal (step 702). Then, the signal analysis unit 331 of the processing unit 33 analyzes the AE signal (step 703). On the other hand, if the acquisition unit 32 has not acquired an AE signal (NO in step 701), step 701 is repeated until the acquisition unit 32 acquires an AE signal.

[0042] Next, the waveform data generating unit 332 generates waveform data based on the analysis result in step 703 (step 704), and the storage unit 34 stores the waveform data generated in step 704 (step 705). Then, the output unit 35 outputs the waveform data generated in step 704 to the determination terminal 50 (step 706).

[0043] FIG. 8 is a flowchart showing an example of the flow of processing by the determination terminal 50. In the determination terminal 50, when setting information for setting the measurement conditions of the AE wave detection device 10 is input (YES in step 801), the operation unit 55 accepts the input (step 802). Then, under the control of the transmission control unit 501, the communication unit 54 transmits the setting information to the AE wave detection device 10 (step 803). On the other hand, if setting information for setting the measurement conditions has not been input (NO in step 801), the determination terminal 50 repeats step 801 until setting information for setting the measurement conditions is input.

[0044] Next, when waveform data is transmitted from the signal processing device 30 (YES in step 804), the waveform data acquisition unit 502 acquires the transmitted waveform data (step 805). On the other hand, when waveform data is not transmitted (NO in step 804), the determination terminal 50 repeats step 804 until waveform data is transmitted.

[0045] Next, the generation source determination unit 503 determines whether the source of the AE waves is in the shielded portion or the exposed portion based on the waveform data acquired in step 805 (step 806). Specifically, whether the source of the AE waves is in the shielded portion or the exposed portion is determined based on the distance between the positions where the two AE sensors 11 are installed and the timing relationship between the detection of the AE waves by each of the two AE sensors 11. Next, under the control of the display control unit 504, the display unit 56 displays the determination result from step 806 (step 807).

[0046] (Example) 9 is a diagram showing a specific example of the configuration of a jig 100 for firmly fixing the AE sensor 11 of FIG. 2 to a steel pipe. (A) is a front cross-sectional view of the jig 100. (B) is a bottom view of the jig 100. (C) and (D) are side views of the jig 100. As shown in FIGS. 9(A) to 9(D), the jig 100 has a main body portion 101, a sliding portion 102, an elastic body 103, a fixing portion 104, and a connecting portion 105.

[0047] The main body 101 forms the main body of the jig 100. There are no particular restrictions on the material of the main body 101, and for example, carbon fiber reinforced resin, which has excellent strength and water resistance, can be used. The sliding portion 102 is a space formed in part of the main body 101, in which the AE sensor 11 of FIG. 2 slides. The elastic body 103 is a member that slides the AE sensor 11 toward the surface of the steel pipe by using elastic energy generated by being pressed against the AE sensor 11 and contracting. The elastic body 103 presses the AE sensor 11 against the surface of the steel pipe P with a constant pressure, thereby preventing poor contact between the AE sensor 11 and the surface of the steel pipe P. For example, a spring or the like can be used as the elastic body 103.

[0048] The fixing part 104 is a member for fixing the main body 101 to the surface of the steel pipe P with the AE sensor 11 pressed against the surface of the steel pipe P. For example, a neodymium magnet or the like can be used as the fixing part 104, as it is expected to have a high adhesive force to the steel pipe P without affecting the detection of AE waves. A nut is embedded in the connecting part 105 for attaching the jig 100 to the tip of a rod. If the inspector is unable to approach the steel pipe P and install the jig 100 with his or her own hands, the inspector attaches the jig 100 to the tip of a rod and installs the jig 100 on the steel pipe P.

[0049] Figure 10 is a diagram showing how the AE sensor 11 of Figure 2 is firmly fixed using the jig 100 of Figure 9. (A) is a diagram showing the state immediately before the AE sensor 11 is fixed, and (B) is a diagram showing the state after the AE sensor 11 has been fixed. As shown in Figure 10(A), fixing portions 104 made of neodymium magnets or the like are arranged at two locations on the bottom surface of the jig 100, so that the bottom surface of the jig 100 is firmly fixed to the surface of the steel pipe P. At this time, as shown in Figure 10(B), an elastic body 103 presses the AE sensor 11 against the surface of the steel pipe P, so that poor contact between the AE sensor 11 and the surface of the steel pipe P can be suppressed.

[0050] 11 is a diagram showing an example of installation of multiple AE sensors 11. (A) is a perspective view of a steel pipe P on which multiple AE sensors 11 are installed. (B) is a cross-sectional view of the steel pipe P on which multiple AE sensors 11 are installed, cut perpendicularly to the pipe axis direction. It is assumed that the multiple AE sensors 11 shown in FIG. 11 are fixed to the surface of the steel pipe P using the jig 100 shown in FIGS. 9 and 10.

[0051] In the installation examples shown in Figures 11(A) and 11(B), AE sensors 11-1 and 11-2 form a first set, and AE sensors 11-3 and 11-4 form a second set. Note that in Figure 11(A), gaps are seen between AE sensors 11-1 and 11-2 and between AE sensors 11-3 and 11-4, but these are depicted for convenience so that it can be understood from the drawing that the two AE sensors 11 are installed in a vertical row in the tube axial direction. In reality, AE sensors 11-1 and 11-2, and AE sensors 11-3 and 11-4 are both connected via connectors 105 shown in Figure 9. That is, a distance of 5 cm to 20 cm is provided between AE sensors 11-1 and 11-2, and between AE sensors 11-3 and 11-4, via connectors 105, and the AE sensors are installed in a vertical row in the tube axial direction in this state.

[0052] Furthermore, AE sensor 11-1 of the first set and AE sensor 11-3 of the second set are each installed at a position close to, but not in contact with, the boundary B between the exposed portion F1 and the shielded portion F2, which is shielded by the shielding object D that penetrates the steel pipe P. This allows corrosion and cracks that have occurred in the shielded portion F2 within an evaluation range H of 100 cm (centimeters) from the boundary B to be suitably detected.

[0053] Furthermore, the first and second sets are installed at a distance from each other so that they are parallel to each other in the pipe axial direction. Specifically, as shown in FIG. 11(B), the first and second sets are installed so that the installation angle A is a right angle. That is, the first set is installed on the ceiling of the steel pipe, and the second set is installed at the 9 o'clock position, with the ceiling of the steel pipe being the 12 o'clock position on a clock. This allows detection by the second set installed at the 9 o'clock position even in cases where the first set installed at the 12 o'clock position alone cannot detect AE waves generated at a distant location (for example, the 6 o'clock position), such as when the steel pipe P is a large-diameter steel pipe. As a result, AE waves generated at a distant location (for example, the 6 o'clock position) can be detected by the second set installed at the 9 o'clock position. As a result, AE waves can be prevented from being missed.

[0054] Figure 12 shows specific examples of waveform data from each of the multiple AE sensors 11 in Figure 11. (A) shows waveform data from each of the AE sensors 11-1 to 11-4 that detected an AE wave propagating from the shielded portion F2 side in Figure 11(A). (B) shows waveform data from each of the AE sensors 11-1 to 11-4 that detected an AE wave propagating from the exposed portion F1 side in Figure 11(A).

[0055] 12(A), a comparison of the waveform data of AE sensor 11-1 with that of AE sensor 11-2 shows that the AE wave reaches AE sensor 11-1 before AE sensor 11-2. Furthermore, a comparison of the waveform data of AE sensor 11-3 with that of AE sensor 11-4 shows that the AE wave reaches AE sensor 11-3 before AE sensor 11-4. Therefore, it can be inferred that the AE wave has propagated from the side of shielding portion F2 in FIG. 11(A), and it is determined that corrosion or cracks have occurred in shielding portion F2.

[0056] 12(B), a comparison of the waveform data from AE sensor 11-1 with that from AE sensor 11-2 reveals that the AE wave reaches AE sensor 11-2 before AE sensor 11-1. Furthermore, a comparison of the waveform data from AE sensor 11-3 with that from AE sensor 11-4 reveals that the AE wave reaches AE sensor 11-4 before AE sensor 11-3. Therefore, it can be inferred that the AE wave propagated from the exposed portion F1 side in FIG. 11(A), and it is determined that corrosion or cracks have occurred in the exposed portion F1.

[0057] (Other embodiments) Although the present embodiment has been described above, the present invention is not limited to the above-described embodiment. Furthermore, the effects of the present invention are not limited to those described in the above-described embodiment. For example, the configuration of the signal processing system 1 shown in FIG. 1, the functional configuration of the AE wave detection device 10 shown in FIG. 2, the functional configuration of the signal processing device 30 shown in FIG. 3, the hardware configuration of the determination terminal 50 shown in FIG. 4, and the functional configuration of the determination terminal 50 shown in FIG. 5 are merely examples for achieving the object of the present invention and are not particularly limited. It is sufficient that the signal processing system 1 shown in FIG. 1 is provided with a function that can execute the above-described processing as a whole, and the hardware and functional configurations used to realize this function are not limited to the above-described examples.

[0058] Furthermore, the order of the processing steps of the AE wave detection device 10 shown in Fig. 6, the processing steps of the signal processing device 30 shown in Fig. 7, and the processing steps of the determination terminal 50 shown in Fig. 8 is merely an example and is not particularly limited. The processing is not limited to being performed in chronological order according to the order of the steps shown in the figures, and may be performed in parallel or individually without necessarily being performed in chronological order.

[0059] 9 to 12 are merely examples and are not particularly limited. For example, the jig 100 shown in the examples of Fig. 9 and Fig. 10 may have the following configuration, and various embodiments may be possible. That is, an AE sensor fixing member (for example, the jig 100 in FIGS. 9 and 10) for fixing an AE sensor (for example, the AE sensor 11 in FIG. 2) that detects AE waves emitted from a steel structure to the structure is a main body (for example, the main body 101 in FIG. 9) in which a sliding portion (for example, the sliding portion 102 in FIG. 9) is formed, which serves as a space in which an AE sensor for detecting AE waves slides; an elastic body (e.g., elastic body 103 in FIG. 9) that presses the AE sensor against the surface of the structure (e.g., steel pipe P in FIG. 10) by using elastic energy generated by the AE sensor being pressed against the surface of the structure and contracting; a fixing portion (for example, fixing portion 104 in FIG. 9) that fixes the main body portion to the surface of the structure in a state in which the AE sensor is pressed against the surface of the structure; Equipped with. This stabilizes the position of the AE sensor because the elastic body presses the AE sensor against the steel structure that is the sensing target. In addition, the fixing part fixes the main body to the steel structure, so the position of the AE sensor is also stabilized.

[0060] The main body may be made of carbon fiber reinforced resin containing carbon fiber and resin, the elastic body may be a spring, and the fixed portion may be a neodymium magnet. This allows the spring to press the AE sensor against the steel structure, stabilizing the position of the AE sensor. Furthermore, the magnetic force of the neodymium magnet strongly attracts the main body to the steel structure, firmly fixing the main body to the surface of the structure. As a result, the position of the AE sensor is further stabilized. Furthermore, the main body is made of carbon fiber reinforced resin, which increases its strength. [Explanation of symbols]

[0061] 1...signal processing system, 10...AE wave detection device, 11...AE sensor, 12...control unit, 13...preamplifier, 14...output unit, 15...condition setting unit, 30...signal processing device, 31...control unit, 32...acquisition unit, 33...processing unit, 34...storage unit, 35...output unit, 50...determination terminal, 51...control unit, 52...memory, 53...storage unit, 54...communication unit, 55...operation unit, 56...display unit, 501...setting information transmission control unit, 502...waveform data acquisition unit, 503...source determination unit, 504...display control unit, 90...network

Claims

1. A plurality of AE sensors for detecting AE (acoustic emission) waves are installed at predetermined intervals in a vertical row in the axial direction of a tubular steel structure having a shielded portion and an exposed portion adjacent to each other in the axial direction of the tube on the surface of the exposed portion, detecting corrosion and cracks occurring in the shielded portion based on waveform data obtained from the AE waves detected by each of the plurality of AE sensors; The predetermined interval is between 5 cm (centimeters) and 20 cm. Corrosion and crack detection methods for tubular structures.

2. A tubular steel structure having a shielded portion and an exposed portion adjacent to each other in the axial direction of the pipe, wherein a plurality of AE sensors for detecting AE (acoustic emission) waves are installed in a vertical row in the axial direction of the pipe on the surface of the exposed portion; detecting corrosion and cracks occurring in the shielded portion based on waveform data obtained from the AE waves detected by each of the plurality of AE sensors; The plurality of sets of AE sensors are installed at a plurality of positions on the surface of the exposed portion, for each set. Corrosion and crack detection methods for tubular structures.

3. One or more of the sets are arranged at intervals so as to be parallel in the tube axial direction. The corrosion and crack detection method for a tubular structure according to claim 2.

4. The position where each of the one or more sets is installed is determined based on the size of the central angle formed by a straight line connecting the center point of a circle or an approximate circle showing the cross section of the tubular steel structure and each of the one or more sets. The corrosion and crack detection method for a tubular structure according to claim 3.

5. The central angle is a right angle or a nearly right angle. The corrosion and crack detection method for a tubular structure according to claim 4.

6. One of the one or more sets is installed on the ceiling of the cross section. The corrosion and crack detection method for a tubular structure according to claim 5.

7. A tubular steel structure having a shielded portion and an exposed portion adjacent to each other in the axial direction of the pipe, wherein a plurality of AE sensors for detecting AE (acoustic emission) waves are installed in a vertical row in the axial direction of the pipe on the surface of the exposed portion; detecting corrosion and cracks occurring in the shielded portion based on waveform data obtained from the AE waves detected by each of the plurality of AE sensors; It is characterized in that it is determined whether the source of the AE wave is in the shielded part or the exposed part based on the difference between the waveform data of an AE sensor, among the plurality of AE sensors, that is installed at a position closer to the shielded part in the tube axis direction and the waveform data of an AE sensor that is installed at a position farther from the shielded part in the tube axis direction. Corrosion and crack detection methods for tubular structures.

8. The difference is a difference due to a timing relationship of when the AE wave is detected, which is identified from the waveform data. The corrosion and crack detection method for a tubular structure according to claim 7.

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