Intermediate-frequency high-precision detection method

Abstract

The invention provides a medium-frequency high-precision detection method, which comprises the following steps: integrally evaluating a workpiece to be detected, and determining a high-risk part and an easily-corroded position of the workpiece to be detected; performing pulsed eddy current large-area rapid scanning on the high-risk part and the easily corroded position to obtain a primary scanning map; analyzing the primary scanning map, and determining a corrosion area and a suspected small defect area; replacing a high-precision probe to carry out pulsed eddy current high-precision scanning detection on the suspected small defect area to obtain a high-precision scanning atlas, analyzing the initial scanning atlas and the high-precision scanning atlas, determining the position of the small defect, and marking the position; ultrasonic thickness measurement is carried out on the marked position, and wall thickness value reinspection is carried out; according to the invention, a plurality of composite detection modes are adopted, and a plurality of corrosion defects of the detected pipe fitting are comprehensively detected; according to the detection method, the detection rate and the detection efficiency of small defects are greatly improved, and the omission ratio is reduced to the greatest extent.

Description

Technical Field

[0001] The invention relates to the technical field of eddy current detection, and in particular to a medium frequency high-precision detection method. Background Art

[0002] Eddy current testing is based on the principle of electromagnetic induction. Its basic principle is as follows: when an AC signal is used to excite a coil, the coil will generate an excitation magnetic field. At this time, if a conductor approaches, an eddy current signal will be generated in the conductor, and the eddy current will generate an eddy current magnetic field acting on the coil. The thickness of the conductor will cause the eddy current signal to change, thereby affecting the eddy current magnetic field. This change is finally reflected in the coil. Therefore, by obtaining this change on the coil through corresponding methods, the thickness of the conductor can be distinguished and calculated.

[0003] The emergence of pulsed electromagnetic is a major advancement in eddy current testing technology. It is different from single-frequency eddy current and multi-frequency eddy current in terms of excitation method. Pulsed electromagnetic uses high-power square wave as the excitation signal. The wide spectrum characteristics of the square wave determine that the pulse contains rich spectral content, so only one scan is needed to obtain defect information at different depths in the multi-layer structure. Different from the steady-state analysis method used in single-frequency eddy current, pulsed electromagnetic uses transient analysis method. The detection signal contains rich characteristic information, and pulsed electromagnetic detection is relatively easy to collect and process, with fast detection speed and high detection efficiency, which facilitates the realization of detection automation and visualization processing.

[0004] Metal pressure pipelines are a type of special pressure-bearing equipment with a very complex working environment. They are often subjected to the combined effects of high temperature, high pressure, low temperature, flammable and explosive, toxic or corrosive media, and have potential leakage and explosion hazards. During the use of metal materials, stress, medium and temperature operating conditions will cause material corrosion, erosion thinning and cracking. Therefore, it is of great significance to quickly detect and effectively diagnose on-site metal pipelines without surface grinding and cleaning. In the study of the main damage modes of metal pipelines, material corrosion thinning is one of the most important damage modes that affect the long-term safe operation of pressure equipment. Therefore, corrosion detection is a major detection method in pressure pipeline detection, and it is also a major technical indicator for safety status rating and life assessment of pressure pipelines.

[0005] In the current pipeline corrosion defect detection, magnetic particle detection, X-ray detection, ultrasonic detection and other detection methods have been widely used, but from the comprehensive consideration of detection sensitivity, equipment cost, detection efficiency, detection accuracy and other aspects, the low-frequency electromagnetic detection method has the advantages of high detection efficiency, less on-site auxiliary engineering, and low detection cost; however, for the detection of pipeline corrosion defects, traditional electromagnetic detection sensors can only scan a single point, and it is very time-consuming and labor-intensive to conduct full coverage detection of a large area. The detection rate and detection efficiency of small defects are low, and missed detection is prone to occur.

[0006] After a detailed search of the prior art, the applicant obtained the following closest comparative documents:

[0007] Comparative Document 1: In a pulse eddy current detection device and method for corrosion defects on the outer wall of a pipeline with application number 2021106306970, a pulse eddy current detection method for corrosion defects on the outer wall of a pipeline is mentioned, which includes the following steps: a. Select the size of the array probe detector with the corresponding circumferential distribution according to the diameter of the pipeline to be detected, and set the signal generator parameters according to the wall thickness of the detected pipeline; b. Open the quick-release wrench, open the outer arc plate by rotating the shaft, and then open the array probe detector, and then install the array probe detector on the outside of the pipeline to be tested, and close the quick-release wrench to fix it; c. Turn on the motor to drive the array probe detector to move along the pipeline to be tested, and at the same time, perform 360° pulse eddy current detection on the pipeline to be tested under service conditions through the array probe in the array probe detector; d. Use a power amplifier to amplify the pulse excitation signal emitted by the signal generator. The method of the present invention can realize the display and storage of the signal data of 360° pulse eddy current detection of the pipeline under test, and the data collected by the pipeline under test is analyzed and compared by the computer to obtain the defect situation of the pipeline under test; the beneficial effect of the method of the present invention is that the spring slide bar is used to compress and rebound the sliding roller on the dirt or coating on the outer wall surface of the pipeline under test, which plays a role in the obstacle crossing of the pulse eddy current detection device, and at the same time ensures that the distance between the array probe and the pipeline surface remains unchanged as much as possible, and the quick-disassembly structure of the present invention can realize the rapid disassembly and installation of the device through the quick-disassembly structure without affecting the normal operation and integrity of the pipeline, which is convenient and fast, has a clear purpose and is highly practical.

[0008] Although the above application adopts eddy current testing, it still cannot solve the technical problems that it is time-consuming and labor-intensive to conduct full coverage testing of a large area, the detection rate and efficiency of small defects are low, and missed detection is prone to occur.

[0009] Therefore, it is necessary to provide a new technical solution to solve the above technical problems. Summary of the invention

[0010] The present application provides a medium frequency high-precision detection method, comprising the following steps:

[0011] Conduct an overall assessment of the workpiece to be tested and determine the high-risk areas and corrosion-prone locations of the workpiece to be tested;

[0012] Perform pulse eddy current rapid large-area scanning of high-risk areas and corrosion-prone locations of the workpiece to be tested to obtain the initial scanning map;

[0013] Analyze the initial scan map to identify the corrosion area and suspected small defect areas;

[0014] Replace the high-precision probe to perform pulse eddy current high-precision scanning and detection on the suspected small defect area to obtain a high-precision scanning map. Analyze the initial scanning map and the high-precision scanning map to determine the location of the small defect and mark the location;

[0015] Ultrasonic thickness measurement is performed on the marked locations to recheck the wall thickness value and the problem areas are marked on site.

[0016] As a preferred solution, ultrasonic thickness measurement is performed on the determined corrosion area.

[0017] As a preferred solution, pulsed eddy current large-area rapid scanning performs axial and circumferential scanning of high-risk areas and corrosion-prone locations of the workpiece to be tested.

[0018] As a preferred solution, determining the corrosion area includes determining the overall size of the corrosion area.

[0019] As a preferred solution, the location of small defects is expanded for detection.

[0020] As a preferred solution, ultrasonic thickness measurement is performed to re-inspect the marked small defects.

[0021] As a preferred solution, a large-area rapid pulse eddy current scan is performed on the high-risk parts and corrosion-prone locations of the workpiece to be tested to obtain an initial scan map. At the same time, the remaining conventional locations are randomly inspected and a large-area rapid pulse eddy current scan is performed to obtain an initial scan map.

[0022] This application first conducts an overall assessment of the workpiece to be tested, selects high-risk and corrosion-prone locations on the workpiece to be tested, and then uses pulse eddy current to quickly scan a large area, reducing the area of ​​the pulse eddy current large-area rapid scanning and improving work efficiency. Then, a variety of detection coordination methods, namely a variety of composite detection modes, are used to conduct a comprehensive detection of various corrosion defects of the workpiece to be tested. This detection method greatly improves the detection rate and detection efficiency of small defects and minimizes the missed detection rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the detection flow chart of this application;

[0024] Figure 2 This is a schematic diagram of the initial scan of the atlas; DETAILED DESCRIPTION

[0025] The following is combined with Figure 1 The specific implementation of the present invention is described in detail. It should be noted that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0026] This embodiment provides a high-precision intermediate frequency detection method, including the following steps:

[0027] An overall assessment is conducted on the workpiece to be tested, and high-risk and corrosion-prone locations of the workpiece to be tested are selected; the high-risk and corrosion-prone locations of the workpiece to be tested are confirmed based on the high-risk locations determined by previous records, or the approximate risk locations are first determined by existing technologies such as guided wave. The high-risk and corrosion-prone locations of the workpiece to be tested selected by existing technologies such as guided wave are judged based on different characteristic signals presented on the spectrum;

[0028] The pulse eddy current large-area rapid scanning is performed on the high-risk and corrosion-prone locations of the workpiece to be tested to obtain the initial scanning map; wherein, the pulse eddy current large-area rapid scanning is performed on the high-risk and corrosion-prone locations of the workpiece (pipe fitting) to be tested in the axial and circumferential directions respectively;

[0029] The initial scan map is analyzed to determine the corrosion area and the suspected small defect area. More preferably, determining the corrosion area includes determining the overall size of the corrosion area; Figure 2 As shown, the circled position is the crack defect position, that is, the corrosion area; the intact part map is shown at the zero point of the ordinate, and the suspected small defect area is in the negative area indicated by the ordinate;

[0030] Replace the high-precision probe to perform pulse eddy current high-precision scanning and detection on the suspected small defect area to obtain a high-precision scanning map, analyze the initial scanning map and the high-precision scanning map, determine the location of the small defect, and mark the location; preferably, expand the detection of the location of the small defect to ensure that it will not be missed and the detection accuracy will be guaranteed; the expansion detection is mainly divided into two steps: first, expand the detection area until the overall state of the detected area is intact; second, adjust the detection parameters of the high-precision probe and expand the detection of the problem area;

[0031] Ultrasonic thickness measurement is performed on the marked position to re-check the wall thickness value, and the problem area is marked on-site; the specific error of the re-checked wall thickness value is considered valid within 5%. If it is found that the re-checked wall thickness error is not met, the suspected small defect area will be re-tested.

[0032] As a preferred solution, ultrasonic thickness measurement is repeated on the determined corrosion area to further improve the detection accuracy and avoid false detection.

[0033] Preferably, in order to further improve the accuracy of detection and avoid missed detection, a large-area rapid pulse eddy current scan is performed on high-risk areas and corrosion-prone locations of the workpiece to be tested to obtain an initial scan map. In the step of obtaining an initial scan map, the remaining conventional locations are spot-checked and a large-area rapid pulse eddy current scan is performed to obtain an initial scan map.

[0034] To summarize, the present application firstly conducts an overall assessment of the workpiece to be tested, selects high-risk and corrosion-prone locations of the workpiece to be tested, and then uses pulse eddy current to quickly scan a large area, thereby reducing the area of ​​the pulse eddy current large-area rapid scanning and improving work efficiency. Then, a variety of detection coordination methods, namely a variety of composite detection modes, are used to conduct a comprehensive inspection of various corrosion defects of the workpiece to be tested. This detection method greatly improves the detection rate and detection efficiency of small defects, and minimizes the missed detection rate.

[0035] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the various possible combinations of this application will not be described separately.

[0036] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A medium frequency high-precision detection method, characterized in that: The steps include: Conduct an overall assessment of the workpiece to be tested and determine the high-risk areas and corrosion-prone locations of the workpiece to be tested; Perform pulse eddy current rapid large-area scanning of high-risk areas and corrosion-prone locations of the workpiece to be tested to obtain the initial scanning map; Analyze the initial scan map to identify the corrosion area and suspected small defect areas; Replace the high-precision probe to perform pulse eddy current high-precision scanning and detection on the suspected small defect area to obtain a high-precision scanning map. Analyze the initial scanning map and the high-precision scanning map to determine the location of the small defect and mark the location; Ultrasonic thickness measurement is performed on the marked locations to recheck the wall thickness value and the problem areas are marked on site.

2. A medium frequency high-precision detection method according to claim 1, characterized in that: Conduct ultrasonic thickness measurement re-inspection on the identified corrosion areas.

3. The medium frequency high-precision detection method according to claim 1, characterized in that: Determining the area of ​​corrosion includes determining an overall size of the area of ​​corrosion.

4. The intermediate frequency high-precision detection method according to claim 1, characterized in that: Pulse eddy current rapid large-area scanning scans the high-risk areas and corrosion-prone locations of the workpiece in the axial and circumferential directions.

5. The medium frequency high-precision detection method according to claim 1, characterized in that: Expanded detection of small defect locations.

6. The medium frequency high-precision detection method according to claim 1, characterized in that: Re-inspect the marked small defects by ultrasonic thickness measurement.

7. The medium frequency high-precision detection method according to claim 1, characterized in that: In the step of performing large-area rapid pulse eddy current scanning on high-risk locations and locations prone to corrosion of the workpiece to be tested to obtain an initial scanning map, random inspections are performed on other conventional locations to obtain an initial scanning map through large-area rapid pulse eddy current scanning.

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