Method for quickly positioning leakage defect of high-temperature pressure pipeline with coating layer

Abstract

The invention discloses a method for quickly positioning leakage defects of a high-temperature pressure pipeline with a coating layer. The method comprises the following steps: S1, measuring and calculating the surface emissivity of the high-temperature pressure pipeline with the coating layer; s2, acquiring infrared thermal imaging data of the high-temperature pressure pipeline with the coating layer; s3, leakage information extraction, noise reduction and optimization are carried out on the feature image obtained in the S2, and an approximate leakage area of the high-temperature pressure pipeline with the coating layer is obtained; s4, acoustic emission detection is carried out according to the approximate leakage areas determined in S1 to S3; and S5, multi-point multi-time acoustic emission detection is carried out, and the specific leakage position of the high-temperature pressure pipeline with the coating layer is determined. The precision of the pipeline leakage position can be determined within the length range of 1% through infrared thermal imaging and acoustic emission combined detection, and accurate position information is provided for further qualitative and quantitative detection of defects.

Description

Technical Field

[0001] The present invention relates to the technical field of rapid inspection of leakage defects in high-temperature pressure pipelines, and in particular to a method for rapid positioning of leakage defects in high-temperature pressure pipelines with a coating layer. The method is suitable for leakage inspection of high-temperature pressure pipelines with a coating layer in thermal power, nuclear power, energy storage power plants, heating, etc. When a leakage occurs in a high-temperature pressure pipeline, the method can be used to rapidly locate the leakage position and preliminarily determine the size of the leakage source. Background Art

[0002] Important pipelines such as the four major pipelines in thermal power plants, conventional island pipelines in nuclear power plants, heat transfer pipelines in energy storage power plants, and thermal heating pipeline networks operate in harsh conditions. Under long-term high-temperature and high-pressure operation, the pipelines inevitably have various defects that can easily expand into hazardous defects, leading to serious accidents such as pipeline leakage, threatening the safe operation of the units.

[0003] These pipes are usually insulated pipes with coatings, insulation layers or paint, and the medium is steam or high-temperature water. Once a leak occurs, it is difficult to determine the leak location or assess the severity of the leak source defect in a short period of time, resulting in unit shutdown and maintenance, seriously affecting the safe and economical operation of the thermal power plant.

[0004] At present, the main detection methods for non-stopping of coated pipes are infrared and X-ray inspections. The approximate location of the leak is determined by infrared thermal imaging technology, and the size of the defect is determined by X-rays. However, the above methods have the problem that the infrared thermal imaging position determination is not accurate, and the X-ray detection method requires the exact location of the defect to be known in advance. There is a contradiction between the two. Infrared thermal imaging technology cannot provide accurate location information for X-ray detection. 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 quickly locating leakage defects of high-temperature pressure pipelines with coating layers. The approximate location of the defect is determined by infrared thermal imaging detection method, and the defect positioning accuracy is further determined within 1% of the length using acoustic emission detection method, providing technical data support for accurate inspection of defects.

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

[0007] A method for quickly locating leakage defects of a high-temperature pressure pipeline with a coating layer, comprising the following steps:

[0008] S1: Calculation of surface emissivity of high-temperature pressure pipeline with coating.

[0009] S2: Infrared thermal imaging data acquisition of high-temperature pressure pipelines with coatings.

[0010] S3: Extract leakage information, reduce noise and optimize the feature image obtained in S2 to obtain the approximate leakage area of ​​the high-temperature pressure pipeline with a coating layer.

[0011] S4: Carry out acoustic emission detection according to the leakage area determined by S1 to S3.

[0012] S5: Multi-point and multiple acoustic emission detection to determine the specific leakage location of the high-temperature pressure pipeline with coating.

[0013] Furthermore, the S1 specifically includes the following steps: firstly, measuring and estimating the surface emissivity of the high-temperature pressure pipeline with the coating layer, and improving the accuracy of the temperature measurement result of the high-temperature pressure pipeline with the coating layer by accurately measuring the surface emissivity of the high-temperature pressure pipeline with the coating layer;

[0014] Specifically, a tape with known emissivity is attached to the surface of the high-temperature pressure pipeline with a coating layer, and it is ensured that the tape is in good contact with the surface of the high-temperature pressure pipeline with a coating layer. Before testing, it is ensured that the tape with known emissivity and the surface of the high-temperature pressure pipeline with a coating layer are in thermal equilibrium;

[0015] Place tapes with known emissivity at representative locations such as pipes, elbows, and tees;

[0016] After the thermal balance between the tape and the pipe system is established, the temperature difference between the tape and the adjacent coating layer of the pipe system shall not exceed 5°C;

[0017] The surface emissivity of the high-temperature pressure pipe with the coating is found by changing the emissivity value in the infrared camera software until the object temperature equals the known surface temperature of the tape.

[0018] Furthermore, the S2 adopts a patrol method to implement traversal detection of infrared thermal imaging of high-temperature pressure pipelines with coating layers.

[0019] When using the patrol method for traversal testing, ensure that the angle between the observation line of sight and the surface normal of the tested object is between 0° and 40°;

[0020] Through the abnormal temperature of the outer surface of the high-temperature pressure pipeline with a coating layer, according to the temperature difference and the heat radiation area, it is analyzed whether the temperature difference is caused by the insulation layer damage or the pipeline itself leakage. When the abnormal heat radiation area is less than 4㎡ and there is no heat diffusion phenomenon, it is the insulation layer damage. When the abnormal heat radiation area is greater than 4㎡ and there is heat diffusion phenomenon, it is suspected that the pipeline itself is leaking.

[0021] Furthermore, in S3, leakage information extraction, noise reduction and optimization are performed on the feature image obtained in S2 to obtain an approximate leakage area of ​​the high-temperature pressure pipeline with a coating layer;

[0022] According to the characteristics of pipeline steam leakage spreading under the insulation layer, when the abnormal heat radiation area is greater than 4㎡, the approximate location of the pipeline leakage is determined by filtering noise reduction and image enhancement, and the accuracy of the pipeline leakage location is increased to 80% through the infrared image segmentation algorithm.

[0023] Furthermore, the filtering and noise reduction uses Gaussian filtering to remove noise points, and the following formula is used for noise reduction processing:

[0024]

[0025] Where G(x ij ) is the denoised infrared data of the surface state of the high-temperature pressure pipeline with a coating; k is a constant, which mainly determines the filtering strength of the Gaussian function; m is the mean value of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating; σ is the standard deviation parameter of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating.

[0026] Furthermore, the image enhancement method is to obtain regional pixel values ​​through the above formula, convert the pixel values ​​into temperature values, and determine the approximate location of the leakage through the boundary formed by the temperature abnormality area.

[0027] Furthermore, in S4, acoustic emission detection is performed according to the leakage area determined in S1 to S3.

[0028] First, based on the 80% accuracy rate of pipeline leakage location, acoustic emission technology is used to further improve the accuracy of defect location.

[0029] Carry out acoustic emission signal preprocessing and signal-to-noise ratio optimization. Detect environmental noise, use environmental noise as a benchmark, analyze and process detection signals, suppress environmental noise interference, and improve signal-to-noise ratio.

[0030] Furthermore, according to the leakage area determined by infrared thermal imaging detection technology, the leakage area is analyzed separately. If the leakage area is in the straight pipe section, the acoustic emission detection position is determined to be within 0 to 20 meters on one side of the leakage area; if the leakage area is in the elbow or tee, the acoustic emission detection position is within 0 to 20 meters on both sides of the elbow or tee.

[0031] Furthermore, the signal collection and display of the acoustic emission equipment adopts two modes: screen display and leakage sound output for human ear judgment.

[0032] Furthermore, the acoustic emission detection frequency band is set in the 30-60 kHz frequency band.

[0033] Furthermore, after the insulation layer is cut open by a mechanical device, the probe is placed at the detection position of the working steel pipe for detection.

[0034] Furthermore, the frequency is continuously adjusted in the 30-60kHz frequency band. When both the screen display and the human ear judgment of the leakage sound reach the maximum value, and the difference in the screen sound volume values ​​inside and outside the pipeline reaches the maximum value, the detection is carried out using this frequency band as the optimal detection frequency band.

[0035] Furthermore, in S5, multi-point and multiple-time acoustic emission detection is performed to determine the specific leakage location of the pipeline.

[0036] The optimal detection frequency band is used to perform multi-point detection within the detection range of 0 to 20 meters. When the position of the leak point detected multiple times has the highest overlap, it is the pipeline leak point. Through the combined detection of infrared thermal imaging and acoustic emission, the defect location accuracy can be determined within 1% of the length.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] The present invention discloses a method for quickly locating leakage defects in a high-temperature pressure pipeline with a coating layer. Compared with the prior art, the above scheme has the following technical effects: the pipeline leakage position can be accurately determined within 1% of the length through combined detection of infrared thermal imaging and acoustic emission, providing more accurate position information for further qualitative and quantitative detection of defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 is a flow chart of a method according to an embodiment of the present invention; DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0045] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0046] refer to Figure 1 The embodiment of the present invention discloses a method for quickly locating leakage defects in a high-temperature pressure pipeline with a coating layer, comprising the following steps:

[0047] S1: Calculation of pipe surface emissivity.

[0048] S2: Pipeline infrared thermal imaging data acquisition.

[0049] S3: Extract leakage information, reduce noise and optimize the feature image obtained in S2 to obtain the approximate area of ​​pipeline leakage.

[0050] S4: Carry out acoustic emission detection according to the leakage area determined by S1 to S3.

[0051] S5: Perform multiple acoustic emission tests at multiple points to determine the specific leakage location of the pipeline.

[0052] In S1, the surface emissivity of the pipe with the coating layer is first measured and estimated, and the accuracy of the pipe temperature measurement result is improved by accurately measuring the surface emissivity of the pipe;

[0053] Use 3M electrical tape (known emissivity 0.95) to stick on the surface of the pipe with the coating layer, and ensure that the tape is in good contact with the pipe surface. Before testing, ensure that the tape with known emissivity is in thermal equilibrium with the pipe surface;

[0054] After the thermal balance between the tape and the pipe system is established, the temperature difference between the tape and the adjacent coating layer of the pipe system shall not exceed 5°C;

[0055] The emissivity of the coated pipe surface was found by changing the emissivity value in the camera software to 0.95 until the detected coated pipe surface temperature equaled the known tape surface temperature.

[0056] S2, adopts patrol method to realize traversal detection of high temperature pipeline infrared thermal imaging;

[0057] When the inspection method is used for traversal testing, ensure that the angle between the observation line of sight and the surface normal of the tested object is between 0° and 40°. In this embodiment, 25° is used for traversal testing.

[0058] Through the abnormal temperature of the outer surface of the pipeline, according to the size of the temperature difference and the heat radiation area, it is analyzed whether the temperature difference is caused by insulation damage or pipeline leakage. When the abnormal heat radiation area is less than 4㎡ and there is no heat diffusion phenomenon, it is a suspected pipeline leakage area. When the abnormal heat radiation area is greater than 4㎡ and there is heat diffusion, it is a suspected pipeline leakage area.

[0059] Furthermore, in S3, leakage information is extracted, denoised and optimized on the feature image obtained in S2 to obtain the approximate area of ​​the pipeline leakage.

[0060] According to the characteristics of pipeline steam leakage spreading under the insulation layer, when the abnormal heat radiation area is greater than 4㎡, the approximate location of the pipeline leakage is determined by filtering noise reduction and image enhancement, and the accuracy of the pipeline leakage location is increased to 80% through the infrared image segmentation algorithm.

[0061] Furthermore, the filtering and noise reduction uses Gaussian filtering to remove noise points, and the following formula is used for noise reduction processing:

[0062]

[0063] Where G(x ij ) is the denoised infrared data of the surface state of the high-temperature pressure pipeline with a coating; k is a constant, which mainly determines the filtering strength of the Gaussian function; m is the mean value of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating; σ is the standard deviation parameter of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating.

[0064] Furthermore, the image enhancement method is to obtain regional pixel values ​​through the above formula, convert the pixel values ​​into temperature values, and determine the approximate location of the leakage through the boundary formed by the temperature abnormality area.

[0065] Furthermore, in S4, acoustic emission detection is performed according to the leakage area determined in S1 to S3.

[0066] First, based on the 80% accuracy rate of pipeline leakage location, acoustic emission technology is used to further improve the accuracy of defect location.

[0067] Carry out acoustic emission signal preprocessing and signal-to-noise ratio optimization. Detect environmental noise, use environmental noise as a benchmark, analyze and process detection signals, suppress environmental noise interference, and improve signal-to-noise ratio. For example, when the average environmental noise is 75db, use 75db as a benchmark and input it into the acoustic emission instrument as the benchmark noise for noise reduction processing.

[0068] Furthermore, according to the leakage area determined by infrared thermal imaging detection technology, the leakage area is analyzed separately. If the leakage area is in the straight pipe section, the acoustic emission detection position is determined to be 15 meters on one side of the leakage area; if the leakage area is in the elbow or tee, the acoustic emission detection position is 15 meters on both sides of the elbow or tee.

[0069] Furthermore, the signal collection and display of the acoustic emission equipment adopts two modes: screen display and leakage sound output for human ear judgment.

[0070] Furthermore, after the insulation layer is cut open by a mechanical device, the probe is placed at the detection position of the working steel pipe for detection to ensure that the acoustic emission probe is in direct contact with the steel pipe wall.

[0071] Furthermore, the acoustic emission detection frequency band is set in the 30-60kHz frequency band. The frequency is continuously adjusted in the 30-60kHz frequency band. When the screen display and the leakage sound judgment by the human ear reach the maximum value, and the difference between the screen sound volume values ​​inside and outside the pipeline reaches the maximum value, the detection is carried out using this frequency band as the optimal detection frequency band. In this embodiment, the 45kHz frequency band is used for detection after experimental testing.

[0072] S5, multiple-point and multiple-time acoustic emission detection, to determine the specific leakage location of the pipeline.

[0073] Furthermore, a 45kHz frequency band is used to carry out detection at 15 meters on one side of the straight pipe section and at 15 meters on both sides of the elbow or tee. Multiple points are tested multiple times. When the location of the defect is in doubt, another point is selected within the range of 0 to 20 meters for testing. For example, when the positioning deviation is inconsistent during multi-point detection in the circumferential direction at the 15-meter position, the 10-meter position can be selected for multi-point detection in the circumference. When the overlap of the displayed positions of the defects in multiple detections is the highest, this displayed position is the pipeline leakage point.

[0074] Through the combined detection of infrared thermal imaging and acoustic emission, the defect positioning accuracy can be determined within 1% of the length.

[0075] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, 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 method for quickly locating leakage defects in a high-temperature pressure pipeline with a coating layer, characterized in that: The following steps are involved: S1: Calculation of surface emissivity of high-temperature pressure pipeline with coating; S2: Infrared thermal imaging data acquisition of high temperature pressure pipeline with coating; S3: extracting leakage information, reducing noise and optimizing the feature image obtained in S2 to obtain the approximate leakage area of ​​the high-temperature pressure pipeline with a coating layer; S4: Carry out acoustic emission detection according to the approximate leakage area determined by S1 to S3; S5: Multi-point and multiple acoustic emission detection to determine the specific leakage location of the high-temperature pressure pipeline with coating.

2. The method according to claim 1, characterized in that The S1 specifically includes the following steps: Attach a tape with known emissivity to the surface of the high-temperature pressure pipe with a coating layer, and ensure that the tape is in good contact with the surface of the high-temperature pressure pipe with a coating layer; tape with known emissivity is arranged according to representative positions of the pipe system, elbows, and tees; Before the test, ensure that the tape with known emissivity is in thermal equilibrium with the surface of the high-temperature pressure pipe with the coating. After the thermal equilibrium between the tape and the pipe system is established, the temperature difference between the tape and the adjacent coating surface of the pipe system shall not exceed 5°C. The surface emissivity of the high-temperature pressure pipe with the coating is found by changing the emissivity value in the infrared camera software until the object temperature equals the known surface temperature of the tape.

3. The method according to claim 1, characterized in that S2 specifically includes the following steps: using the patrol method to implement infrared thermal imaging traversal detection of high-temperature pressure pipelines with coating layers, When using the patrol method for traversal testing, ensure that the angle between the observation line of sight and the surface normal of the tested object is between 0° and 40°; Through the abnormal temperature of the outer surface of the high-temperature pressure pipeline with a coating layer, according to the size of the temperature difference and the heat radiation area, it is analyzed whether the temperature difference is caused by damage to the insulation layer or leakage of the pipeline itself.

4. The method according to claim 3, characterized in that When the abnormal heat radiation area is less than 4㎡ and there is no heat diffusion phenomenon, it means the insulation layer is damaged. When the abnormal heat radiation area is greater than 4㎡ and there is heat diffusion phenomenon, it is a suspected leakage area of ​​the pipeline itself.

5. The method according to claim 1, characterized in that In step S3, filtering and noise reduction uses Gaussian filtering to remove noise points, and the following formula is used for noise reduction processing: Where G(x ij ) is the denoised infrared data of the surface state of the high-temperature pressure pipeline with a coating; k is a constant, which mainly determines the filtering strength of the Gaussian function; m is the mean value of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating; σ is the standard deviation parameter of the original infrared data of the surface state of the high-temperature pressure pipeline with a coating; The regional pixel value is obtained by the above formula, the pixel value is converted into a temperature value, and the approximate location of the leak is determined by the boundary formed by the temperature abnormality area.

6. The method according to claim 1, characterized in that In step S4, the leakage area determined by infrared thermal imaging detection technology is analyzed separately. If the leakage area is in the straight pipe section, the acoustic emission detection position is determined to be within 0 to 20 meters on one side of the leakage area; if the leakage area is at the elbow or tee, the acoustic emission detection position is within 0 to 20 meters on both sides of the elbow or tee.

7. The method according to claim 1, characterized in that In step S4, after the insulation layer is cut open by a mechanical device, the probe is placed at the detection position of the working steel pipe for detection, and the frequency is continuously adjusted in the 30-60kHz frequency band. When the screen display and the human ear judgment of the leakage sound both reach the maximum value, and the difference in the screen sound volume values ​​inside and outside the pipeline reaches the maximum value, this frequency band is used as the optimal detection frequency band for detection.

8. The method according to claim 1, characterized in that In step S5, the optimal detection frequency band is used to perform multi-point detection within a detection range of 0 to 20 meters. The position with the highest overlap of leakage points detected multiple times is the pipeline leakage point.

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