Qualitative and quantitative detection method for leakage defect of high-temperature pressure pipeline in non-stop state

Abstract

The invention discloses a qualitative and quantitative detection method for leakage defects of a high-temperature pressure pipeline in a non-stop state. The method comprises the following steps: establishing a finite element model for laser ultrasonic detection of the high-temperature pipeline; laser parameters are changed in the model, and optimal detection parameters are found; integrating the articulated arm and the laser ultrasonic probe; a simulation sample is manufactured, laser ultrasonic excitation double waves are adopted for detection, and a detection process is obtained; and scanning the leakage pipeline defect to determine the position, the property and the size of the leakage defect. According to the invention, accurate detection of leakage defects can be carried out in a non-stop state of a unit. By means of the mode that the movable articulated arm carries the pulse laser and the laser interferometer, qualitative and quantitative detection of leakage defects is achieved, crack defects with the length smaller than 5 mm and the depth smaller than 0.2 mm and corrosion with the minimum depth of 0.2 mm can be detected, and the positioning error is smaller than or equal to 0.1%. The device has a series of advantages of non-stop detection, remote control, no need of polishing the pipeline surface, non-contact probe, high detection precision and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing of high-temperature pressure pipelines. Specifically, it particularly relates to a method for qualitatively and quantitatively detecting leakage defects in high-temperature pressure pipelines under the condition of non-stop operation, which is applicable to leakage inspection of high-temperature pressure pipelines with cladding layers in thermal power plants, nuclear power plants, energy storage power plants, heat supply, etc. When a high-temperature pressure pipeline leaks, when the general area is determined, the leakage defects can be accurately qualitatively and quantitatively analyzed by this method, providing a scientific basis for the decision-making of power plants. Background Art

[0002] Important pipelines such as the four major pipelines in thermal power plants, the conventional island pipelines in nuclear power plants, the heat transfer pipelines in energy storage power plants, and the thermal heating pipe networks operate under harsh working conditions. Under long-term high-temperature and high-pressure operation, the pipelines inevitably have different defects and are prone to expand into harmful defects, resulting in serious accidents such as pipeline leakage, threatening the safe operation of the units.

[0003] These pipelines are usually heat-insulated pipelines with cladding layers, and the medium is steam or high-temperature water. Once a leak occurs, there is a lack of evaluation data on the severity of the leak source defects, resulting in a lack of scientific basis for maintenance decisions and seriously affecting the safe and economic operation of thermal power plants.

[0004] Existing detection methods such as ultrasonic, magnetic particle, penetrant, and radiographic testing cannot be used to detect pipelines in a leaking state. The existing technology lacks a method for qualitatively and quantitatively analyzing defects when a pipeline leaks under the condition of non-stop operation. Summary of the Invention

[0005] In order to solve the defects existing in the above-mentioned prior art, the purpose of the present invention is to provide a method for qualitatively and quantitatively detecting leakage defects in high-temperature pressure pipelines under the condition of non-stop operation. Qualitative and quantitative detection of defects is achieved by means of a movable articulated arm carrying a pulsed laser and a laser interferometer.

[0006] The technical means adopted by the present invention are as follows:

[0007] A method for qualitatively and quantitatively detecting leakage defects in high-temperature pressure pipelines under the condition of non-stop operation, comprising the following steps:

[0008] S1: Establish a finite element model for laser ultrasonic detection of high-temperature pipelines.

[0009] S2: Change the laser parameters in the model to find the optimal detection parameters.

[0010] S3: Integrate the articulated arm and the laser ultrasonic probe.

[0011] S4: Fabricate a simulation specimen, and use laser ultrasonic excitation of dual waves for detection to obtain the detection process.

[0012] S5: Scan the leakage pipeline defects to determine the location, nature and size of the leakage defects.

[0013] Further, in the step S1, a finite element physical model for laser ultrasonic detection of high-temperature pipelines is established by using COMSOL simulation software, and simulated thinning defects, axial and circumferential crack defects are set in the welds and base metals at typical positions such as elbows, tees, and straight pipe sections.

[0014] The thinning defect has a wall thickness of 0.2 mm, and the defect thinning reaches 30%, which is evenly arranged at equal intervals along the thickness direction. The minimum crack defect is set to 5×0.2 mm (length×depth), and is located on the outer surface, 1 / 2 wall thickness, and inner surface of the pipeline respectively.

[0015] Further, in the step S2, the laser parameters are changed in the model to find the best detection parameters. The changed laser parameters include power density, laser wavelength, pulse width, repetition frequency, etc.

[0016] The pulsed laser wavelength is 1064 nm, the pulse width is 6 - 10 ns, the maximum repetition frequency is 15 - 25 Hz, and the single-pulse laser energy range is 0 - 50 MJ. The laser parameters are repeatedly adjusted within the above ranges, and the double-wave mixing mode is used to simulate the detection of ultrasonic signals. When the clearly obtained clear echo signal can accurately display the defect location (the positioning error is within 0.1%), this detection parameter is the best parameter.

[0017] Further, the incident direction of the laser scanning probe adopts two methods: normal incidence and oblique incidence. Normal incidence makes the laser beam vertically incident on the pipeline surface for detecting thinning-type defects. Oblique incidence makes the laser incident at a certain angle with the normal of the pipeline surface, and the angle is in the range of 30 - 60°.

[0018] Further, the articulated arm is composed of a base, a support arm and a robotic arm. A probe clamping device is arranged at the front end of the robotic arm; the support arm is connected to the base, the rear end of the robotic arm is connected to the support arm, and the robotic arm can rotate around the support arm and translate the probe through a telescopic device.

[0019] A clamping part for clamping a pulsed laser and a laser interferometer is arranged at the front end of the probe clamping device, and an angle adjusting device is arranged on the clamping part to adjust the included angle between the pulsed laser and the laser interferometer and the surface of the pipeline to be detected by telescoping the angle adjusting device.

[0020] Further, an unpowered mobile trolley is used to carry the articulated arm, and a mobile power supply is arranged on the mobile trolley, which is used to supply power to the pulsed laser and the laser interferometer. After adjusting the detection parameters, the trolley is pushed to realize the scanning along the axis of the overhead pipeline.

[0021] Further, in S4, the simulated specimens include three types: crack defect specimens, corrosion specimens, and thickness change specimens;

[0022] The crack defect specimens simulate the crack defects on the pipeline wall. The depth, length, and direction of the cracks can be varied to test the sensitivity and capabilities of the system;

[0023] The corrosion specimens simulate the corrosion or corrosion pits on the pipeline wall. The defect is set to a wall thickness of 0.2 mm, and the defect thinning reaches 30%. Corrosion of different degrees and shapes can be used to test the detection capabilities of the system;

[0024] The thickness change specimens are the thickness reduction areas on the pipeline wall. The thickness values change in an arithmetic progression. There are 5 sets of ψ5 mm simulated defects with a thickness difference of 1 mm and 5 sets of ψ5 mm simulated defects with a thickness difference of 2 mm, which are used to test the measurement accuracy of the system.

[0025] Further, laser ultrasonic excitation of dual waves is used for detection to obtain the detection process. The thickness change specimens are detected by normal incidence excitation of body waves. When the system displays the depth positions of all 10 defects in two groups and the deviation does not exceed 5%, the system test accuracy meets the detection requirements;

[0026] Laser ultrasonic guided waves are used, and the thickness crack defect specimens are detected by oblique incidence. The oblique incidence angle is adjusted within the range of 30 - 60°. When the crack defect positions, depths, and sizes displayed by the system are equivalent to the set parameters, and the horizontal position deviation does not exceed 1% and the depth deviation does not exceed 5%, the crack defect detection process meets the requirements;

[0027] Laser ultrasonic body waves are used, and the corrosion specimens are detected by normal incidence excitation of body waves, and the detection accuracy obtained from the thickness change specimens is used for detection. When all the set defects are displayed and the depth information is equivalent to the simulated set parameters, the corrosion defects meet the detection technical requirements.

[0028] Further, the specific steps of S5 are as follows: The articulated arm and ultrasonic probe integrated in S3 are used to scan the leakage area. The distance between the pulsed laser and the laser interferometer and the surface of the pipeline to be detected is 0.5 - 1 meter;

[0029] The detection process obtained in S4 is used to perform circumferential and axial scans of the leakage area;

[0030] While the pulsed laser emits a pulsed laser beam, a synchronous acquisition signal is sent to the data acquisition card; The ultrasonic waves excited by the pulsed laser cause vibrations on the sample surface. The dual-wave mixing interferometer converts the vibration displacement information into an analog signal, which is collected by the data acquisition card and then transmitted to the computer for data processing, analysis, and imaging to obtain the depth, position, and size information of the defects, and complete the qualitative and quantitative detection of the leakage defects.

[0031] Compared with the prior art, the present invention has the following advantages: The present invention can accurately detect leakage defects under the condition that the unit is not shut down. By means of a movable articulated arm carrying a pulsed laser and a laser interferometer, qualitative and quantitative detection of leakage defects can be realized. Cracks with a length less than 5 mm and a depth less than 0.2 mm, as well as corrosion with a minimum depth of 0.2 mm, can be detected, and the positioning error is less than or equal to 0.1%. It has a series of advantages such as non-stop detection, remote control, no need to polish the pipeline surface, non-contact of the probe, and high detection accuracy, providing a sufficient scientific basis for the maintenance decision-making of power plants. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 It is the flowchart of the method according to the embodiment of the present invention;

[0034] Figure 2 It is the schematic diagram of the articulated arm structure.

[0035] In the figure: 1, base; 2, support arm; 3, robotic arm; 4, laser interferometer; 5, pulsed laser; 6, probe clamping device; 7, pipeline to be detected. Detailed Embodiments

[0036] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail the present invention.

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the sake of convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be interpreted as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0040] In addition, it should be noted that the use of words such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Without further statement, the above words have no special meaning and thus cannot be construed as limiting the protection scope of the present invention.

[0041] Reference Figure 1 , a method for qualitatively and quantitatively detecting leakage defects in a high-temperature pressure pipeline under non-stop operation, comprising the following steps:

[0042] S1: Establish a finite element model for laser ultrasonic detection of high-temperature pipelines.

[0043] S2: Change the laser parameters in the model to find the optimal detection parameters.

[0044] S3: Integrate the articulated arm and the laser ultrasonic probe.

[0045] S4: Fabricate a simulation specimen, and use laser ultrasonic excitation of dual waves for detection to obtain the detection process.

[0046] S5: Scan the leakage pipeline defects to determine the location, nature, and size of the leakage defects.

[0047] For the above-mentioned S1, a finite element physical model for ultrasonic detection of high-temperature pipelines using laser ultrasound is established by COMSOL simulation software, and thinning defects, axial and circumferential crack defects are simulated in the welds and base metals at typical positions such as elbows, tees, and straight pipe sections.

[0048] Furthermore, the thinning defects are set to range from 0.2 mm to 30% of the wall thickness and are evenly arranged in an arithmetic progression along the thickness direction. The minimum crack defect is set to 5×0.2 mm (length × depth) and is located at the outer surface, 1 / 2 wall thickness, and inner surface of the pipeline respectively.

[0049] For the above-mentioned S2, change the laser parameters in the model to find the optimal detection parameters.

[0050] Changing the laser parameters includes power density, laser wavelength, pulse width, repetition frequency, etc.

[0051] Furthermore, the pulsed laser wavelength is 1064 nm, the pulse width is set to 8 ns, the maximum repetition frequency is 20 Hz, and the single-pulse laser energy range is 45 mJ. The double-wave mixing mode is used to simulate the detection of ultrasonic signals. When the clearly obtained clear echo signal can accurately display the defect position (within a positioning error of 0.1%), this detection parameter is the optimal parameter.

[0052] For the above-mentioned S3, integrate the articulated arm and the laser ultrasonic probe. An example of the integration of the articulated arm is as

[0053] Furthermore, the articulated arm is composed of a base 1, a support arm 2, and a robotic arm 3. A probe clamping device 6 is provided at the front end of the robotic arm.

[0054] For the above-mentioned S3, integrate the articulated arm and the laser ultrasonic probe. An example of the integration of the articulated arm is as Figure 2 shown

[0055] Furthermore, the support arm 2 is connected to the base 1, the rear end of the robotic arm 3 is connected to the support arm 2, and the robotic arm 3 can rotate around the support arm 2 and translate the probe through a telescopic device.

[0056] Furthermore, a probe clamping device 6 is provided at the front end of the robotic arm. A clamping part for clamping the pulsed laser 5 and the laser interferometer 4 is provided at the front end of the probe clamping device 6, and an angle adjustment device is provided on the clamping part to adjust the angle between the pulsed laser 5 and the laser interferometer 4 and the surface of the pipeline 7 to be detected by telescoping the angle adjustment device.

[0057] Furthermore, a probe clamping device 6 is provided at the front end of the robotic arm. A clamping part for clamping the pulsed laser 5 and the laser interferometer 4 is provided at the front end of the probe clamping device 6, and an angle adjustment device is provided on the clamping part to adjust the angle between the pulsed laser 5 and the laser interferometer 4 and the surface of the pipeline 7 to be detected by telescoping the angle adjustment device.

[0058] Furthermore, a non-powered mobile trolley is used to carry the articulated arm. A mobile power source is provided on the mobile trolley, which is used to supply power to the pulsed laser and the laser interferometer. After adjusting the detection parameters, the trolley is pushed to achieve the scanning along the axial direction of the overhead pipeline.

[0059] In step S4, a simulated specimen is made and detected by using dual-wave laser ultrasonic excitation to obtain the detection process.

[0060] Furthermore, the simulated specimens include three types: crack defect specimens, corrosion specimens, and thickness change specimens.

[0061] Furthermore, the crack defect specimens simulate the crack defects on the pipeline wall, and the depth, length, and direction of the cracks can be changed to test the sensitivity and capabilities of the system.

[0062] Furthermore, the corrosion specimens simulate the corrosion or corrosion pits on the pipeline wall, and the defects are set to be 0.2 mm to 30% of the wall thickness. Corrosion with different degrees and shapes can be used to test the detection capabilities of the system.

[0063] Furthermore, the thickness change specimens are the areas with reduced thickness on the pipeline wall. The thickness values change in an arithmetic progression. There are 5 sets of ψ5 mm simulated defects with a thickness difference of 1 mm and 5 sets of ψ5 mm simulated defects with a thickness difference of 2 mm, which are used to test the measurement accuracy of the system.

[0064] Furthermore, detection is carried out by using dual-wave laser ultrasonic excitation to obtain the detection process. The thickness change specimens are detected by using normal incidence to excite body waves. When the system displays the depth positions of all 10 defects in two groups and the deviation does not exceed 5%, the test accuracy of the system meets the detection requirements.

[0065] Furthermore, laser ultrasonic guided waves are excited, and the thickness crack defect specimens are detected by using an oblique incidence method. The oblique incidence angle is adjusted within the range of 30° to 60°. When the crack defect positions, depths, and sizes displayed by the system are equivalent to the set parameters, and the horizontal position deviation does not exceed 1% and the depth deviation does not exceed 5%, the crack defect detection process meets the requirements.

[0066] Furthermore, laser ultrasonic body waves are excited, and the corrosion specimens are detected by using normal incidence to excite body waves, and the detection accuracy obtained from the thickness change specimens is used for detection. When all the set defects are displayed and the depth information is equivalent to the simulated set parameters, the corrosion defects meet the detection technical requirements.

[0067] In step S5, the leakage pipeline defects are scanned to determine the positions, natures, and sizes of the leakage defects.

[0068] Furthermore, an articulated arm integrated with S3 and an ultrasonic probe are used to scan the leakage area, and the pulsed laser and the laser interferometer are 0.5 to 1 meter away from the surface of the pipeline to be detected.

[0069] Furthermore, the detection process obtained by S4 is used to perform circumferential and axial scans on the leakage area.

[0070] Furthermore, while the pulsed laser emits a pulsed laser beam, a synchronous acquisition signal is sent to the data acquisition card; the ultrasonic wave excited by the pulsed laser causes the surface vibration of the sample, and the double-wave mixing interferometer converts the vibration displacement information into an analog signal, which is collected by the data acquisition card and then transmitted to the computer for data processing, analysis and imaging to obtain the depth, position and size information of the defect, and complete the qualitative and quantitative detection of the leakage defect.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A qualitative and quantitative detection method for leakage defects in high-temperature pressure pipelines without stopping the machine, characterized in that: The following steps are involved: S1: Establish a finite element model for laser ultrasonic testing of high-temperature pipelines; S2: Change the laser parameters in the model to find the optimal detection parameters; S3: integrated articulated arm and laser ultrasound probe; S4: making a simulated sample, using laser ultrasonic excitation double waves for testing, and obtaining the testing process; S5: Scan the leaking pipeline defects to determine the location, nature and size of the leaking defects.

2. The method according to claim 1, characterized in that In S1, a finite element physical model of laser ultrasonic testing of high-temperature pipelines is established by COMSOL simulation software, and thinning defects, axial and circumferential crack defects are simulated in the welds and parent materials of elbows, tees, and straight pipe sections; The thinning defect is 0.2mm wall thickness, the defect thinning reaches 30%, and it is evenly arranged along the thickness direction; the minimum crack defect is set to 5×0.2mm, which is located on the outer surface, 1 / 2 wall thickness, and inner surface of the pipe respectively.

3. The method according to claim 1, characterized in that In S2, laser parameters are changed in the model to find the optimal detection parameters, and the changed laser parameters include power density, laser wavelength, pulse width, and repetition frequency; The pulse laser wavelength is 1064nm, the pulse width is 6-10ns, the maximum repetition frequency is 15-25Hz, and the single pulse laser energy range is 0-50MJ. The laser parameters are repeatedly adjusted within the above range. The dual-wave mixed mode is used to simulate the detection of ultrasonic signals. When the clear echo signal obtained can accurately display the defect position, this detection parameter is the optimal parameter.

4. The method according to claim 1, characterized in that The incident direction of the laser scanning probe adopts two modes: normal incidence and oblique incidence. Normal incidence makes the laser beam vertically incident on the pipe surface, which is used to detect thinning defects; oblique incidence makes the laser beam incident at a certain angle with the normal line of the pipe surface, and the angle is in the range of 30 to 60°.

5. The method according to claim 1, characterized in that The articulated arm is composed of a base, a support arm and a mechanical arm, and a probe clamping device is arranged at the front end of the mechanical arm; the support arm is connected to the base, and the rear end of the mechanical arm is connected to the support arm, and the mechanical arm can rotate around the support arm, and translate the probe through the telescopic device; The front end of the probe clamping device is provided with a clamping part for clamping the pulse laser and the laser interferometer, and the clamping part is provided with an angle adjustment device, and the angle between the pulse laser and the laser interferometer and the surface of the pipeline to be detected is adjusted by telescopic angle adjustment device.

6. The method according to claim 5, characterized in that An unpowered mobile trolley is used to carry the articulated arm. The mobile trolley is equipped with a mobile power supply, which is used to power the pulse laser and laser interferometer. After adjusting the detection parameters, the trolley is pushed to achieve axial scanning of the overhead pipeline.

7. The method according to claim 1, characterized in that In S4, the simulated specimens include crack defect specimens, corrosion specimens, and thickness variation specimens; The crack defect specimen simulates the crack defect on the pipe wall; The corrosion specimen simulates the corrosion or corrosion pit on the pipe wall. The defect is set to 0.2mm wall thickness, and the defect thinning reaches 30%. Corrosion of different degrees and shapes can be used to test the detection capability of the system. The thickness variation specimen is the area with reduced thickness on the pipe wall. The thickness value changes equidistantly and progressively. A group of 5 ψ5mm simulated defects with a thickness difference of 1mm and a group of 5 ψ5mm simulated defects with a thickness difference of 2mm are used to test the measurement accuracy of the system.

8. The method according to claim 1, characterized in that Laser ultrasonic excitation dual waves are used for detection to obtain the detection process; normal incidence excitation body waves are used to detect thickness variation samples. When the system displays all 10 defect depth positions in two groups and the deviation does not exceed 5%, the system test accuracy meets the detection requirements; Adopt laser ultrasonic excitation guided wave, adopt oblique incidence to detect thickness crack defect specimens, and the oblique incidence angle is adjusted within the range of 30-60°; when the crack defect position, depth, and size displayed by the system are equivalent to the set parameter deviation, and the horizontal position deviation does not exceed 1%, and the depth deviation does not exceed 5%, the crack defect detection process meets the requirements; Laser ultrasonic excitation body waves are used, normal incidence excitation body waves are used to detect corrosion samples, and the detection accuracy obtained by thickness variation samples is used for detection; when all the set defects are displayed and the depth information is equivalent to the parameters set in the simulation, the corrosion defects meet the detection technical requirements.

9. The method according to claim 1, characterized in that: The specific steps of step S5 are as follows: using the articulated arm and ultrasonic probe integrated in S3 to scan the leakage area, with the pulse laser and laser interferometer being 0.5 to 1 meter away from the surface of the pipeline to be inspected; Using the detection process obtained by S4, the leakage area is scanned circumferentially and axially; When the pulse laser emits a beam of pulsed laser, it sends a synchronous acquisition signal to the data acquisition card; the ultrasonic wave excited by the pulse laser causes the surface of the sample to vibrate, and the dual-wave hybrid interferometer converts the vibration displacement information into an analog signal, which is collected by the data acquisition card and transmitted to the computer for data processing, analysis and imaging to obtain the depth, position and size information of the defect, and complete the qualitative and quantitative detection of leakage defects.

Images