Differential eddy current internal detection probe, array probe, and defect detection device and method

Abstract

The invention discloses a differential eddy current internal detection probe, an array probe and a defect detection device and method, and relates to the technical field of pipeline nondestructive detection. The differential eddy current internal detection probe comprises an excitation coil, a first receiving coil and a second receiving coil, the first receiving coil and the second receiving coil are symmetrically attached to two sides of the excitation coil, the bottom surface of the first receiving coil, the bottom surface of the excitation coil and the bottom surface of the second receiving coil are located in the same plane, when the pipeline to be tested is magnetized by direct current, the differential eddy current internal detection probe detects the inner surface defects, buried defects and outer surface defects of the pipeline to be tested, when the pipeline to be tested is not magnetized by direct current, the differential eddy current internal detection probe detects the inner surface defects of the pipeline to be tested, so that the inner surface defects, buried defects and outer surface defects of the pipeline to be tested can be detected by combining eddy current detection and direct current magnetization, and a unique structure of single excitation and dual reception is adopted, so that the signal-to-noise ratio can be improved, and the detection and quantification of tiny defects can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline nondestructive testing, and in particular to a differential eddy current internal testing probe, an array probe, and a defect detection device and method. Background Art

[0002] Eddy current nondestructive testing is a widely used nondestructive testing method with the advantages of high sensitivity and non-contact. Eddy current nondestructive testing detects defects in materials by inducing changes in eddy currents. When performing high-speed pipeline testing, in order to increase the detection accuracy, it is necessary to increase the eddy current excitation frequency. However, due to the influence of the skin effect, the eddy current penetration depth decreases with the increase of the eddy current excitation frequency, making it difficult to detect buried defects and external surface defects of the pipeline. In addition, its high sensitivity also leads to large output signal noise, which is difficult to quantify.

[0003] Based on this, there is an urgent need for a technology that can detect buried defects and external surface defects of pipelines with a high signal-to-noise ratio. Summary of the invention

[0004] The purpose of the present invention is to provide a differential eddy current internal detection probe, an array probe and a defect detection device and method, which can detect inner surface defects, buried defects and outer surface defects of a tested pipeline, and have a high signal-to-noise ratio, and can realize the detection and quantification of tiny defects.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A differential eddy current internal detection probe, the differential eddy current internal detection probe comprising: an excitation coil, a first receiving coil and a second receiving coil;

[0007] The excitation coil is located between the first receiving coil and the second receiving coil; the first receiving coil and the second receiving coil are symmetrically attached to both sides of the excitation coil, and the bottom surface of the first receiving coil, the bottom surface of the excitation coil and the bottom surface of the second receiving coil are located in the same plane, forming the bottom surface of the differential eddy current internal detection probe;

[0008] The excitation coil is used to be supplied with an alternating current to generate an induced eddy current field in the measured pipeline;

[0009] The winding directions of the first receiving coil and the second receiving coil are opposite; the first receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the first position of the measured pipeline, and output a first voltage signal; the second receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the second position of the measured pipeline, and output a second voltage signal; the first position is a position in the measured pipeline corresponding to the position of the first receiving coil; the second position is a position in the measured pipeline corresponding to the position of the second receiving coil;

[0010] The differential eddy current internal detection probe is located in the measured pipeline, and the bottom surface of the differential eddy current internal detection probe is parallel to the axis of the measured pipeline; when the measured pipeline is DC magnetized, the differential eddy current internal detection probe is used to detect inner surface defects, buried defects and outer surface defects of the measured pipeline based on the difference between the first voltage signal and the second voltage signal; when the measured pipeline is not DC magnetized, the differential eddy current internal detection probe is used to detect inner surface defects of the measured pipeline based on the difference between the first voltage signal and the second voltage signal; the types of inner surface defects, buried defects and outer surface defects include cracks and corrosion.

[0011] In some embodiments, the excitation coil, the first receiving coil and the second receiving coil are all semicircular coils wound by wires, and the outer surface of the semicircular coil includes two semicircular surfaces, a curved surface and a flat surface, and the semicircular surface includes a straight line segment and an arc segment;

[0012] The plane of the first receiving coil is aligned with a straight line segment of a semicircular surface of the excitation coil, and the plane of the second receiving coil is aligned with a straight line segment of another semicircular surface of the excitation coil;

[0013] The bottom surface of the first receiving coil is a semicircular surface of the first receiving coil; the bottom surface of the excitation coil is a plane of the excitation coil; and the bottom surface of the second receiving coil is a semicircular surface of the second receiving coil.

[0014] In some embodiments, the difference between the inner and outer diameters of the semicircular surface of the excitation coil, the height of the first receiving coil, and the height of the second receiving coil are equal.

[0015] An array probe, comprising a plurality of the above-mentioned differential eddy current internal detection probes;

[0016] The plurality of differential eddy current internal detection probes are distributed in a circumferential array; the frequencies of the alternating currents passed through the exciting coils of adjacent differential eddy current internal detection probes are different.

[0017] In some embodiments, the array probe further includes a first discrimination signal transmission electronic system and a second discrimination signal transmission electronic system;

[0018] Select any one of the differential eddy current internal detection probes as the first differential eddy current internal detection probe, and sort all the differential eddy current internal detection probes in a clockwise direction or a counterclockwise direction; the first discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes with odd numbers in the sorting; the second discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes with even numbers in the sorting;

[0019] The first discrimination signal transmission electronic system has the same structure as the second discrimination signal transmission electronic system; the first discrimination signal transmission electronic system comprises an excitation source, a power amplifier, a discriminator and a filter amplifier circuit connected in sequence;

[0020] The excitation source is used to generate an alternating current of a predetermined frequency; the predetermined frequencies of the alternating currents generated by the first discrimination signal transmission electronic system and the second discrimination signal transmission electronic system are different;

[0021] The power amplifier is connected to the differential eddy current internal detection probe; the power amplifier is used to amplify the alternating current of a predetermined frequency and pass the amplified alternating current into the differential eddy current internal detection probe;

[0022] The frequency discriminator is connected to the differential eddy current internal detection probe; the frequency discriminator is used to extract a signal of a predetermined frequency from a mixed frequency signal output by the differential eddy current internal detection probe; the mixed frequency signal includes a first voltage signal and a second voltage signal;

[0023] The filtering and amplifying circuit is used to amplify and filter the signal of a predetermined frequency to reduce noise, thereby obtaining a signal after filtering and reducing noise.

[0024] A defect detection device, comprising a DC magnetization component and a detection component; the detection component is the above-mentioned differential eddy current internal detection probe or the above-mentioned array probe;

[0025] The DC magnetization component is located in the pipeline to be measured and contacts the inner surface of the pipeline to be measured; the DC magnetization component is used to perform DC magnetization on the pipeline to be measured;

[0026] The detection component is located in the pipeline to be tested; the detection component is used to detect inner surface defects, buried defects and outer surface defects of the pipeline to be tested when the pipeline to be tested is DC magnetized, and to detect inner surface defects of the pipeline to be tested when the pipeline to be tested is not DC magnetized; the types of inner surface defects, buried defects and outer surface defects include cracks and corrosion.

[0027] In some embodiments, the DC magnetization component includes a U-shaped magnetic yoke, and the first magnetic pole and the second magnetic pole of the U-shaped magnetic yoke are in contact with the inner surface of the measured pipe; the detection component is located between the first magnetic pole and the second magnetic pole, and the distance from the detection component to the first magnetic pole is equal to the distance from the detection component to the second magnetic pole;

[0028] A coil is installed on the U-shaped magnetic yoke, and when a DC current is passed through the coil, the measured pipeline is DC magnetized; or permanent magnets are installed on both the first magnetic pole and the second magnetic pole to DC magnetize the measured pipeline.

[0029] A defect detection method is based on the above-mentioned defect detection device and operates, and the defect detection method comprises:

[0030] When it is necessary to detect external surface defects or buried defects, the DC magnetization component is used to DC magnetize the pipeline under test, and the detection component is used to perform defect detection on the pipeline under test;

[0031] When it is necessary to detect inner surface defects, the detected pipeline is detected by using a detection component; or, the detected pipeline is DC magnetized by using a DC magnetization component, and the detected pipeline is detected by using a detection component.

[0032] In some embodiments, when the detection component is a differential eddy current internal detection probe, the defect detection method further includes:

[0033] When it is necessary to detect defects with a defect angle within the range of 0 degrees to 45 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be perpendicular to the axial direction of the measured pipe; when it is necessary to detect defects with a defect angle within the range of 45 degrees to 90 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be parallel to the axial direction of the measured pipe; the defect angle is the angle between the length direction of the defect and the axial direction of the measured pipe.

[0034] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0035] The present invention is used to provide a differential eddy current internal detection probe, an array probe and a defect detection device and method. The differential eddy current internal detection probe comprises an excitation coil, a first receiving coil and a second receiving coil. The excitation coil is located between the first receiving coil and the second receiving coil. The first receiving coil and the second receiving coil are symmetrically attached to the two sides of the excitation coil. The bottom surface of the first receiving coil, the bottom surface of the excitation coil and the bottom surface of the second receiving coil are located in the same plane. When the measured pipeline is magnetized by direct current, the differential eddy current internal detection probe detects the inner surface defects, buried defects and outer surface defects of the measured pipeline. When the measured pipeline is not magnetized by direct current, the differential eddy current internal detection probe detects the inner surface defects of the measured pipeline, so that the inner surface defects, buried defects and outer surface defects of the measured pipeline can be detected by combining eddy current detection and direct current magnetization. The unique structure of single excitation and dual reception is adopted, which can improve the signal-to-noise ratio and realize the detection and quantification of tiny defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 A schematic diagram of the structure of the excitation coil provided in Example 1 of the present invention; wherein, Figure 1 (a) is the front view of the excitation coil; Figure 1 (b) is the left side view of the excitation coil; Figure 1 (c) is a top view of the excitation coil; Figure 1 (d) is a three-dimensional diagram of the excitation coil.

[0038] Figure 2 A schematic diagram of the structure of a receiving coil provided in Embodiment 1 of the present invention; wherein: Figure 2 (a) is a top view of the receiving coil; Figure 2 (b) is the left side view of the receiving coil; Figure 2 (c) is the front view of the receiving coil; Figure 2 (d) is a three-dimensional diagram of the receiving coil.

[0039] Figure 3 A schematic diagram of the structure of a differential eddy current internal detection probe provided in Example 1 of the present invention; wherein: Figure 3 (a) is a top view of the differential eddy current internal detection probe; Figure 3 (b) is the left view of the differential eddy current internal detection probe; Figure 3 (c) is the front view of the differential eddy current internal detection probe; Figure 3 (d) is a stereoscopic image of the differential eddy current internal detection probe.

[0040] Figure 4 Schematic diagram of two detection methods provided in Example 1 of the present invention; wherein, Figure 4 (a) is the detection method in which the pipeline under test is not subjected to DC magnetization; Figure 4 (b) is the detection method of DC magnetization of the tested pipeline.

[0041] Figure 5 A schematic diagram of the characteristic curve of the ferromagnetic material provided in Example 1 of the present invention.

[0042] Figure 6 A schematic diagram of the defect detection principle provided in Example 1 of the present invention; wherein: Figure 6 (a) is a schematic diagram of the detection principle without defects; Figure 6 (b) is a schematic diagram of the detection principle of inner surface defects; Figure 6 (c) Schematic diagram of the detection principle of external surface defects.

[0043] Figure 7 Schematic diagram of two placement methods provided in Example 1 of the present invention; Figure 7 (a) Placement method for detecting defects of 0°-45°; Figure 7 (b) is the placement method for detecting defects of 45°-90°.

[0044] Figure 8 Schematic diagram of voltage-position curves of two placement methods provided in Example 1 of the present invention.

[0045] Fig. 9 This is a schematic diagram of the structure of the array probe provided in Example 2 of the present invention.

[0046] Fig.10 This is a connection principle diagram of the frequency discrimination signal transmission electronic system provided in Example 2 of the present invention.

[0047] Fig.11 This is a schematic structural diagram of the DC magnetization component provided in Example 3 of the present invention.

[0048] Fig.12 A schematic diagram of the principle of the defect detection method provided in Example 4 of the present invention.

[0049] Explanation of symbols:

[0050] 1-semicircular surface; 2-curved surface; 3-plane surface; 4-excitation coil; 5-first receiving coil; 6-second receiving coil; 7-differential eddy current internal detection probe; 8-U-shaped magnetic yoke; 9-first magnetic pole; 10-second magnetic pole; 11-coil. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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. 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.

[0052] The purpose of the present invention is to provide a differential eddy current internal detection probe, an array probe and a defect detection device and method, which can detect inner surface defects, buried defects and outer surface defects of a tested pipeline, and have a high signal-to-noise ratio, and can realize the detection and quantification of tiny defects.

[0053] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Example 1

[0055] This embodiment is used to provide a differential eddy current internal detection probe (also called a differential sensing probe), which adopts a unique single-excitation dual-reception differential structure. The differential eddy current internal detection probe includes: an excitation coil, a first receiving coil, and a second receiving coil.

[0056] The excitation coil is located between the first receiving coil and the second receiving coil, and the first receiving coil and the second receiving coil are symmetrically attached to the two sides of the excitation coil, that is, the first receiving coil and the second receiving coil are symmetrically placed on the two sides of the excitation coil and attached to the side surfaces of the excitation coil. The bottom surface of the first receiving coil, the bottom surface of the excitation coil, and the bottom surface of the second receiving coil are located in the same plane, forming the bottom surface of the differential eddy current internal detection probe. Since the bottom surface of the first receiving coil, the bottom surface of the excitation coil, and the bottom surface of the second receiving coil are located in the same plane (that is, in the same plane), the distances from the first receiving coil, the excitation coil, and the second receiving coil to the inner surface of the measured pipeline can be made consistent, avoiding affecting the subsequent defect detection process by differential.

[0057] The excitation coil is used to be passed an alternating current, which can generate a changing magnetic field in space and generate an induced eddy current field in the measured pipeline.

[0058] The winding directions of the first receiving coil and the second receiving coil are opposite. Preferably, except for the opposite winding directions, the other parameters of the first receiving coil and the second receiving coil are exactly the same. The first receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the first position of the measured pipeline, and convert it into a voltage signal for output, outputting a first voltage signal. The second receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the second position of the measured pipeline, and convert it into a voltage signal for output, outputting a second voltage signal. Among them, the first position is the position in the measured pipeline corresponding to the position of the first receiving coil, that is, the position in the measured pipeline below the first receiving coil, and the second position is the position in the measured pipeline corresponding to the position of the second receiving coil, that is, the position in the measured pipeline below the second receiving coil.

[0059] The differential eddy current internal detection probe of the present embodiment adopts a single excitation + dual reception differential coil structure, which reduces the volume of the traditional differential coil. Compared with the dual excitation differential coil structure, it reduces the energy consumption, and the signal-to-noise ratio of the differential output is relatively high, which can realize the detection and quantification of tiny defects. Therefore, the differential eddy current internal detection probe of the present embodiment has the advantages of small size, low energy consumption, high signal-to-noise ratio, and the ability to detect tiny defects.

[0060] In this embodiment, the structure of the excitation coil is as follows: Figure 1 As shown, the semicircular structure is formed by winding the wire, and the first receiving coil and the second receiving coil have the same structure. Figure 2As shown, it adopts a semicircular structure wound by a wire. That is, the excitation coil, the first receiving coil and the second receiving coil are all semicircular coils wound by a wire, and the outer surface of the semicircular coil includes two semicircular surfaces 1, a curved surface 2 and a plane 3, and the semicircular surface 1 includes a straight line segment and an arc segment. Among them, the wire can be a copper wire.

[0061] On the basis that the excitation coil, the first receiving coil and the second receiving coil are all semicircular coils, the structure of the differential eddy current internal detection probe is as follows: Figure 3 As shown, the excitation coil 4 is placed vertically in the middle, and a pair of receiving coils (i.e., the first receiving coil 5 and the second receiving coil 6) are placed horizontally and symmetrically on both sides of the excitation coil 4, and the bottom surfaces of the excitation coil 4 and the pair of receiving coils are in the same plane, so that the distances between the excitation coil 4 and the pair of receiving coils and the inner surface of the measured pipe are consistent. Specifically, the plane 3 of the first receiving coil 5 fits with a straight line segment of a semicircular surface 1 of the excitation coil 4, and the plane 3 of the second receiving coil 6 fits with a straight line segment of another semicircular surface 1 of the excitation coil 4. The bottom surface of the first receiving coil 5 is a semicircular surface 1 of the first receiving coil 5, the bottom surface of the excitation coil 4 is the plane 3 of the excitation coil 4, and the bottom surface of the second receiving coil 6 is a semicircular surface 1 of the second receiving coil 6.

[0062] In this embodiment, the difference D between the inner and outer diameters of the semicircular surface 1 of the excitation coil 4, the height H of the first receiving coil 5, and the height H of the second receiving coil 6 are equal, that is, H=D, which is conducive to better fitting of the excitation coil 4 and the first receiving coil 5 and the second receiving coil 6.

[0063] In order to realize the detection of inner surface defects, buried defects and outer surface defects by high-frequency excitation eddy current technology, this embodiment combines eddy current detection with DC magnetization, so that the buried defects and outer surface defects of the pipeline present an uneven distribution of magnetic permeability on the inner surface, so that the defect characteristics are "mapped" on the inner surface. When it is necessary to detect the defects of the tested pipeline, the differential eddy current internal detection probe is placed in the tested pipeline, and the bottom surface of the differential eddy current internal detection probe is placed horizontally with the inner surface of the tested pipeline, that is, the differential eddy current internal detection probe is located in the tested pipeline, and the bottom surface of the differential eddy current internal detection probe is parallel to the axis of the tested pipeline. When the pipeline under test is magnetized by DC, the differential eddy current internal detection probe is used to detect inner surface defects, buried defects and outer surface defects of the pipeline under test based on the difference between the first voltage signal and the second voltage signal; when the pipeline under test is not magnetized by DC, the differential eddy current internal detection probe is used to detect inner surface defects of the pipeline under test based on the difference between the first voltage signal and the second voltage signal; the types of inner surface defects, buried defects and outer surface defects include cracks and corrosion.

[0064] Specifically, Figure 4 As shown, Figure 4The scanning direction in represents the moving direction of the differential eddy current internal detection probe along the pipeline under test, that is, the axial direction of the pipeline under test. The defect detection methods of the differential eddy current internal detection probe of this embodiment are divided into two types:

[0065] (1) Figure 4 As shown in (a), the pipeline under test is not DC magnetized. At this time, the differential eddy current internal detection probe can only detect the inner surface defects of the pipeline under test.

[0066] (2) Figure 4 As shown in (b), the pipeline under test is subjected to DC magnetization. At this time, the differential eddy current internal detection probe can detect the inner surface defects, buried defects and outer surface defects of the pipeline under test.

[0067] The material of the tested pipeline in this embodiment is ferromagnetic material. After the tested pipeline is determined, the B (magnetic induction intensity)-H (magnetic field intensity) curve and μ corresponding to the material of the tested pipeline can be obtained. Δ (Incremental permeability)-H (magnetic field strength) curve, such as Figure 5 As shown, based on the BH curve and μ Δ -H curve can adjust the DC magnetization degree of the measured pipeline. Preferably, in this embodiment, the measured pipeline is magnetized to Figure 5 The incremental permeability sensitive area is shown as μ Δ -H curve, the curve segment where the incremental permeability changes rapidly with the change of magnetic field strength. Figure 5 The incremental magnetic permeability sensitive area can be determined, and then the magnetic field strength of the measured pipeline can be adjusted to be within the range of the magnetic field strength corresponding to the incremental magnetic permeability sensitive area.

[0068] After the tested pipeline is subjected to DC magnetization, buried defects and external surface defects will cause the relative magnetic permeability of the corresponding position on the inner surface of the pipeline to decrease. The decrease in relative magnetic permeability will increase the penetration depth of the eddy current at that position and increase the intensity of the eddy current field at the same penetration depth. Compared with the defect-free position, the eddy current field generated is different, and ultimately the output current of the receiving coil is different, thereby achieving the purpose of detecting inner surface defects, buried defects and external surface defects of the pipeline.

[0069] like Figure 6 (a) is a schematic diagram of the detection principle when the pipeline under test has no defects. Figure 6In (a), L1 is the distance from the first receiving coil 5 to the inner surface of the measured pipe, and L2 is the distance from the second receiving coil 6 to the inner surface of the measured pipe. After the AC excitation (i.e., alternating current) is passed into the excitation coil 4, a changing magnetic field will be generated in the measured pipe below the first receiving coil 5 and the second receiving coil 6. According to Lenz's law, an induced eddy current field will be generated inside the measured pipe, including the induced eddy current field J1 below the first receiving coil 5 and the induced eddy current field J2 below the second receiving coil 6, further generating an induced magnetic field. The first receiving coil 5 and the second receiving coil 6 can both receive the induced magnetic field generated by the pipe below them, and output the first voltage signal and the second voltage signal respectively. Since the intensities of the induced eddy current fields below the first receiving coil 5 and the second receiving coil 6 are the same, the magnetic field signals they receive are also completely symmetrical, so the first voltage signal and the second voltage signal are equal, and the value of the output differential signal is 0 at this time. It should be noted that regardless of whether the measured pipe is DC magnetized, the results are the same, that is, the value of the differential signal is 0.

[0070] like Figure 6 (b) is a schematic diagram of the detection principle of the inner surface defects of the measured pipeline. The size of the induced eddy current fields J1 and J2 is related to the relative magnetic permeability μ and the electrical conductivity σ of the measured pipeline surface. When the second receiving coil 6 is above the defect, since the material at the inner surface defect is air (the electrical conductivity σ is 0), the lift-off value (i.e., the distance value) L2 between the second receiving coil 6 and the inner surface of the measured pipeline is greater than the lift-off value L1 between the first receiving coil 5 and the inner surface of the measured pipeline. Under the same excitation, the larger the lift-off value, the greater the attenuation of the excitation magnetic field intensity, resulting in a smaller eddy current field generated on the inner surface of the measured pipeline. Therefore, the induced eddy current field J2 is smaller than the induced eddy current field J1, and the second voltage signal generated by the second receiving coil 6 is smaller than the first voltage signal generated by the first receiving coil 5. At this time, the output differential signal is less than 0. It should be noted that regardless of whether the measured pipeline is DC magnetized, the results are the same, that is, the value of the differential signal is greater than 0.

[0071] like Figure 6 (c) is a schematic diagram of the detection principle of the outer surface defects of the tested pipeline, which illustrates the principle of detecting the outer surface defects of the tested pipeline under DC magnetization. Figure 6In (c), δ1 is the penetration depth of the induced eddy current field J1, and δ2 is the penetration depth of the induced eddy current field J2. The outer surface defect will cause the magnetic field strength H at the corresponding position of the inner surface to increase, resulting in a decrease in the magnetic permeability μ. The smaller the magnetic permeability μ, the slower the attenuation of the induced eddy current field J along the penetration depth direction, and the greater the eddy current density at the same depth d. When the second receiving coil 6 is above the outer surface defect, the overall intensity of the induced eddy current field J2 is greater than the induced eddy current field J1, and the second voltage signal generated by the second receiving coil 6 is greater than the first voltage signal generated by the first receiving coil 5. At this time, the output differential signal is greater than 0, and the phases of the differential signals generated by the inner and outer surface defects are opposite.

[0072] This embodiment adopts a combination of differential eddy current and DC magnetization to make the buried defects and external surface defects of the pipeline present an uneven distribution of magnetic permeability on the inner surface, so that the defect characteristics are "mapped" on the inner surface. The differential eddy current internal detection probe of this embodiment has the advantage of detecting inner surface defects, buried defects and external surface defects under high-frequency excitation.

[0073] In this embodiment, when it is necessary to detect defects with a defect angle within the range of 0-45 degrees, the normal vector of the fitting surface of the first receiving coil 5 and the excitation coil 4 of the differential eddy current internal detection probe is set to be perpendicular to the axial direction of the measured pipe; when it is necessary to detect defects with a defect angle within the range of 45-90 degrees, the normal vector of the fitting surface of the first receiving coil 5 and the excitation coil 4 of the differential eddy current internal detection probe is set to be parallel to the axial direction of the measured pipe. The defect angle is the angle between the length direction of the defect and the axial direction of the measured pipe.

[0074] Specifically, the bottom of the differential eddy current internal detection probe is placed horizontally with the inner surface of the tested pipe. There are two ways to place the probe:

[0075] (1) Figure 7 As shown in (a), the excitation coil 4 is placed horizontally in the scanning direction, and the excitation coil 4 is placed in the direction perpendicular to the normal vector of the fitting surface of the first receiving coil 5 of the differential eddy current internal detection probe and the excitation coil 4. The scanning direction is the movement direction of the differential eddy current internal detection probe along the measured pipeline, that is, the axial direction of the measured pipeline, which is equivalent to the normal vector of the fitting surface of the first receiving coil 5 of the differential eddy current internal detection probe and the excitation coil 4 being perpendicular to the axial direction of the measured pipeline. At this time, two receiving coils placed left and right relative to the axis of the measured pipeline (that is, the first receiving coil 5 and the second receiving coil 6) successively pass through the defect. This method is suitable for detecting defects with an angle of 0°-45° between the defect direction and the scanning direction. The defect direction refers to the length direction of the defect.

[0076] (2) Figure 7As shown in (b), the excitation coil 4 is placed perpendicular to the scanning direction, which is equivalent to the normal vector of the fitting surface of the first receiving coil 5 and the excitation coil 4 of the differential eddy current internal detection probe being parallel to the axial direction of the measured pipeline. At this time, the two receiving coils placed in front and behind (i.e., the first receiving coil 5 and the second receiving coil 6) pass through the defect successively. This method is suitable for detecting defects with an angle of 45°-90° between the defect direction and the scanning direction.

[0077] like Figure 8 As shown in the figure, the two placement methods are used to scan cracks from 0 to 90 degrees. Obviously, normal vector vertical scanning (i.e., the normal vector is perpendicular to the axis of the tested pipe) is suitable for detecting defects of 0°-45°, and normal vector parallel scanning (i.e., the normal vector is parallel to the axis of the tested pipe) is suitable for detecting defects of 45°-90°.

[0078] The differential eddy current internal detection probe of the present embodiment has two placement methods, one is suitable for detecting defects where the angle between the defect direction and the scanning direction is 0°-45°, and the other is suitable for detecting defects where the angle between the defect direction and the scanning direction is 45°-90°. This makes the differential eddy current internal detection probe of the present embodiment have the advantage of being able to detect defects at any angle.

[0079] In this embodiment, the distance can be quantitatively detected by the output signal of a single receiving coil. The farther the differential eddy current internal detection probe is from the surface of the pipeline to be measured, the smaller the output signal value of the single receiving coil is. Therefore, in this embodiment, the output signal and the distance can be calibrated in advance. After obtaining the output signal (i.e., the first voltage signal or the second voltage signal) of a single receiving coil (i.e., the first receiving coil 5 or the second receiving coil 6), the calibration result can be used to determine the distance between the single receiving coil and the surface of the pipeline to be measured. Specifically, the calibration method can be implemented using a BP neural network model, that is, the BP neural network model is trained in advance according to multiple historical output signals and the distance corresponding to each historical output signal to obtain a trained BP neural network model. After obtaining the output signal of a single receiving coil, the output signal is directly used as input, and the distance between the single receiving coil and the surface of the pipeline to be measured can be determined using the trained BP neural network model.

[0080] This embodiment can also determine whether there is a defect and the defect type under a certain receiving coil by performing differential processing on the output signals of the two receiving coils, thereby achieving the purpose of defect detection and identification. When the differential signal is not 0, it means that there is a defect under the receiving coil. When no defect is detected when the measured pipeline is not DC magnetized, and a defect is detected when the measured pipeline is DC magnetized, it means that the defect under the receiving coil is a buried defect or an outer surface defect. When a defect is detected when the measured pipeline is not DC magnetized, and a defect is also detected when the measured pipeline is DC magnetized, it means that the defect under the receiving coil is an inner surface defect.

[0081] The data of a single receiving coil of the present embodiment can be used for quantitative distance measurement, and the data of two receiving coils can be differentially processed to identify quantitative defects, so that the differential eddy current internal detection probe of the present embodiment has the advantages of being able to achieve distance measurement and defect detection.

[0082] Example 2

[0083] This embodiment is used to provide an array probe, which includes a plurality of differential eddy current internal detection probes described in Embodiment 1.

[0084] like Fig. 9 As shown, a plurality of differential eddy current internal detection probes 7 are distributed in a circumferential array, and the frequencies of the alternating currents applied to the excitation coils of adjacent differential eddy current internal detection probes 7 are different.

[0085] In this embodiment, the array probe further includes a first discrimination signal transmission electronic system (i.e. Figure 8 System 1 in the system) and the second discrimination signal transmission electronic system (i.e. Figure 8 System 2 in the figure) is used to achieve the purpose of different frequencies of alternating currents passed through the excitation coils of adjacent differential eddy current internal detection probes 7.

[0086] Any differential eddy current internal detection probe 7 is selected as the first differential eddy current internal detection probe, and all differential eddy current internal detection probes 7 are sorted in a clockwise or counterclockwise direction. The first discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes 7 with odd numbers in the sorting, and the second discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes 7 with even numbers in the sorting, that is, the first discrimination signal transmission electronic system is connected to the 1st, 3rd, 5th, 7th, 9th... differential eddy current internal detection probes, and the second discrimination signal transmission electronic system is connected to the 2nd, 4th, 6th, 8th, 10th... differential eddy current internal detection probes, so that two adjacent differential eddy current internal detection probes 7 are connected to different discrimination signal transmission electronic systems, that is, they are connected to the first discrimination signal transmission electronic system and the second discrimination signal transmission electronic system respectively.

[0087] like Fig.10 As shown, the first discrimination signal transmission electronic system has the same structure as the second discrimination signal transmission electronic system. The first discrimination signal transmission electronic system includes an excitation source, a power amplifier, a discriminator and a filter amplifier circuit connected in sequence.

[0088] The excitation source is used to generate an alternating current (also called AC excitation) of a predetermined frequency according to actual working conditions, and transmit it to the power amplifier. The predetermined frequencies of the alternating currents generated by the excitation source in the first discrimination signal transmission electronic system and the second discrimination signal transmission electronic system are different. The predetermined frequency of the alternating current generated by the first discrimination signal transmission electronic system is a specific excitation frequency 1, and the predetermined frequency of the alternating current generated by the second discrimination signal transmission electronic system is a specific excitation frequency 2, thereby making the frequencies of the alternating currents passed into the two adjacent differential eddy current internal detection probes 7 different.

[0089] The power amplifier is connected to the differential eddy current internal detection probe 7. The power amplifier is used to amplify the alternating current of the predetermined frequency generated by the excitation source according to the actual working condition requirements, and pass the amplified alternating current into the differential eddy current internal detection probe 7 to which it is connected. The frequency of the amplified alternating current is still the predetermined frequency.

[0090] The frequency discriminator is connected to the differential eddy current internal detection probe 7. The frequency discriminator is used to extract a signal of a predetermined frequency from the mixed frequency signal output by the differential eddy current internal detection probe 7, and transmit it to the filter amplifier circuit. The mixed frequency signal includes a first voltage signal and a second voltage signal, and the signal of the predetermined frequency includes a first voltage signal and a second voltage signal with a frequency of the predetermined frequency.

[0091] The filter amplifier circuit is used to amplify and filter the signal of a predetermined frequency to reduce noise, thereby obtaining a signal after filtering and reducing noise.

[0092] The array probe of this embodiment may further include an acquisition and storage system, which is respectively connected to the filter amplifier circuit in the first frequency discrimination signal transmission electronic system and the filter amplifier circuit in the second frequency discrimination signal transmission electronic system. The filter amplifier circuit is used to transmit the filtered and denoised signal to the acquisition and storage system. The acquisition and storage system can acquire and store the filtered and denoised signal in real time.

[0093] The first discrimination signal transmission electronic system and the second discrimination signal transmission electronic system of this embodiment can respectively generate AC excitation of a specific frequency, which is transmitted to the connected differential eddy current internal detection probe 7 after passing through the power amplifier. Because the discrimination signal transmission electronic systems connected to two adjacent differential eddy current internal detection probes 7 are different, the excitation frequencies in the adjacent differential eddy current internal detection probes 7 are different. At the same time, the discriminator can extract the received signal of a specific frequency, further reducing the interference of the signals between the adjacent differential eddy current internal detection probes 7. The signal output by the discriminator is transmitted to the filter amplifier circuit for amplification and filtering noise reduction, and finally stored by the acquisition storage system.

[0094] The frequency discrimination signal transmission electronic system designed to match the present embodiment can add excitations of different frequencies to adjacent differential eddy current internal detection probes 7, and at the same time can extract signals with the same frequency as the excitation coil in the corresponding receiving coil, thereby reducing interference between adjacent differential eddy current internal detection probes 7 and reducing noise. This makes the array probe of the present embodiment have the advantage of using AC excitations of different frequencies for adjacent differential eddy current internal detection probes 7, thereby reducing interference between the differential eddy current internal detection probes 7.

[0095] This embodiment provides an array of orthogonal excitation differential sensing probes and a demodulation signal transmission electronic system, which can perform non-destructive testing on oil and gas pipelines. When the tested pipeline is not magnetized, the inner surface defects (such as cracks, corrosion and other defects) of the tested pipeline can be detected; when the tested pipeline is magnetized to the incremental magnetic permeability sensitive area, the inner surface defects, buried defects and outer surface defects of the tested pipeline can be detected under high-frequency excitation. The combination of a single excitation coil + a dual receiving coil used by the differential eddy current internal detection probe 7 can improve the signal-to-noise ratio of the collected signal. At the same time, the unique coil structure also reduces the volume of a single differential eddy current internal detection probe 7, which can effectively increase the number of arrays and increase the detection accuracy when performing a circumferential array. The matching demodulation signal transmission electronic system can add excitations of different frequencies to adjacent differential eddy current internal detection probes 7, and can extract signals with the same frequency as the excitation coil in the corresponding receiving coil, thereby reducing interference between adjacent differential eddy current internal detection probes 7 and reducing noise.

[0096] Example 3

[0097] This embodiment is used to provide a defect detection device, which includes a DC magnetization component and a detection component. The detection component is the differential eddy current internal detection probe described in Example 1 or the array probe described in Example 2.

[0098] The DC magnetization component is located in the measured pipeline and contacts the inner surface of the measured pipeline. The DC magnetization component is used to perform DC magnetization on the measured pipeline.

[0099] The detection component is located in the pipeline under test. The detection component is used to detect inner surface defects, buried defects and outer surface defects of the pipeline under test when the pipeline under test is DC magnetized. When the pipeline under test is not DC magnetized, the inner surface defects of the pipeline under test are detected. The types of inner surface defects, buried defects and outer surface defects include cracks and corrosion.

[0100] like Fig.11 As shown, the DC magnetization component includes a U-shaped magnetic yoke 8, and the first magnetic pole 9 and the second magnetic pole 10 of the U-shaped magnetic yoke 8 are both in contact with the inner surface of the measured pipe. The detection component is located between the first magnetic pole 9 and the second magnetic pole 10, and the distance from the detection component to the first magnetic pole 9 is equal to the distance from the detection component to the second magnetic pole 10.

[0101] A coil 11 is installed on the U-shaped magnetic yoke 8. When a DC current is passed through the coil 11, the U-shaped magnetic yoke 8 and the measured pipeline form a complete magnetic circuit, and the measured pipeline is DC magnetized; alternatively, permanent magnets are installed on both the first magnetic pole 9 and the second magnetic pole 10 to DC magnetize the measured pipeline.

[0102] When a coil 11 is installed on a U-shaped magnetic yoke 8 and a DC current is passed through the coil 11 to perform DC magnetization on the measured pipeline, the DC magnetization degree of the measured pipeline can be adjusted by adjusting the magnitude of the DC current; when a permanent magnet is installed on both the first magnetic pole 9 and the second magnetic pole 10 to perform DC magnetization on the measured pipeline, the DC magnetization degree of the measured pipeline can be adjusted by adjusting the material and volume of the permanent magnet.

[0103] Example 4

[0104] like Fig.12 As shown, this embodiment is used to provide a defect detection method, which works based on the defect detection device described in Example 3. The defect detection method includes:

[0105] When it is necessary to detect external surface defects or buried defects, the pipeline under test is DC magnetized by a DC magnetizing component, and the pipeline under test is detected by a detection component; when it is necessary to detect internal surface defects, the pipeline under test is detected by a detection component; or, the pipeline under test is DC magnetized by a DC magnetizing component, and the pipeline under test is detected by a detection component.

[0106] When the detection component is a differential eddy current internal detection probe, the defect detection method further includes: when it is necessary to detect a defect with a defect angle within a range of 0 degrees to 45 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be perpendicular to the axial direction of the measured pipeline; when it is necessary to detect a defect with a defect angle within a range of 45 degrees to 90 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be parallel to the axial direction of the measured pipeline; the defect angle is the angle between the length direction of the defect and the axial direction of the measured pipeline.

[0107] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A differential eddy current internal detection probe, characterized in that: The differential eddy current internal detection probe comprises: an excitation coil, a first receiving coil and a second receiving coil; The excitation coil is located between the first receiving coil and the second receiving coil; the first receiving coil and the second receiving coil are symmetrically attached to both sides of the excitation coil, and the bottom surface of the first receiving coil, the bottom surface of the excitation coil and the bottom surface of the second receiving coil are located in the same plane, forming the bottom surface of the differential eddy current internal detection probe; The excitation coil is used to be supplied with an alternating current to generate an induced eddy current field in the pipeline under test; The winding directions of the first receiving coil and the second receiving coil are opposite; the first receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the first position of the measured pipeline, and output a first voltage signal; the second receiving coil is used to receive the induced magnetic field generated by the induced eddy current field at the second position of the measured pipeline, and output a second voltage signal; the first position is a position in the measured pipeline corresponding to the position of the first receiving coil; the second position is a position in the measured pipeline corresponding to the position of the second receiving coil; The differential eddy current internal detection probe is located in the pipeline to be tested, and the bottom surface of the differential eddy current internal detection probe is parallel to the axis of the pipeline to be tested; when the pipeline to be tested is DC magnetized, the differential eddy current internal detection probe is used to detect inner surface defects, buried defects and outer surface defects of the pipeline to be tested based on the difference between the first voltage signal and the second voltage signal; when the pipeline to be tested is not DC magnetized, the differential eddy current internal detection probe is used to detect inner surface defects of the pipeline to be tested based on the difference between the first voltage signal and the second voltage signal; the types of inner surface defects, buried defects and outer surface defects include cracks and corrosion; The excitation coil, the first receiving coil and the second receiving coil are all semicircular coils wound by wires, the outer surface of the semicircular coils includes two semicircular surfaces, a curved surface and a flat surface, and the semicircular surface includes a straight line segment and an arc segment; The plane of the first receiving coil is aligned with a straight line segment of a semicircular surface of the excitation coil, and the plane of the second receiving coil is aligned with a straight line segment of another semicircular surface of the excitation coil; The bottom surface of the first receiving coil is a semicircular surface of the first receiving coil; the bottom surface of the excitation coil is a plane of the excitation coil; the bottom surface of the second receiving coil is a semicircular surface of the second receiving coil; The difference between the inner and outer diameters of the semicircular surface of the excitation coil, the height of the first receiving coil, and the height of the second receiving coil are equal.

2. An array probe, characterized in that: The array probe comprises a plurality of differential eddy current internal detection probes as claimed in claim 1; The plurality of differential eddy current internal detection probes are distributed in a circumferential array; the frequencies of the alternating currents passed through the exciting coils of adjacent differential eddy current internal detection probes are different.

3. An array probe according to claim 2, characterized in that: The array probe further includes a first discrimination signal transmission electronic system and a second discrimination signal transmission electronic system; Select any one of the differential eddy current internal detection probes as the first differential eddy current internal detection probe, and sort all the differential eddy current internal detection probes in a clockwise direction or a counterclockwise direction; the first discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes with odd numbers in the sorting; the second discrimination signal transmission electronic system is connected to the differential eddy current internal detection probes with even numbers in the sorting; The first discrimination signal transmission electronic system has the same structure as the second discrimination signal transmission electronic system; the first discrimination signal transmission electronic system comprises an excitation source, a power amplifier, a discriminator and a filter amplifier circuit connected in sequence; The excitation source is used to generate an alternating current of a predetermined frequency; the predetermined frequencies of the alternating currents generated by the first discrimination signal transmission electronic system and the second discrimination signal transmission electronic system are different; The power amplifier is connected to the differential eddy current internal detection probe; the power amplifier is used to amplify the alternating current of a predetermined frequency and pass the amplified alternating current into the differential eddy current internal detection probe; The frequency discriminator is connected to the differential eddy current internal detection probe; the frequency discriminator is used to extract a signal of a predetermined frequency from a mixed frequency signal output by the differential eddy current internal detection probe; the mixed frequency signal includes a first voltage signal and a second voltage signal; The filtering and amplifying circuit is used to amplify and filter the signal of a predetermined frequency to reduce noise, thereby obtaining a signal after filtering and reducing noise.

4. A defect detection device, characterized in that: The defect detection device comprises a DC magnetization component and a detection component; the detection component is the differential eddy current internal detection probe according to claim 1 or the array probe according to claim 2; The DC magnetization component is located in the pipeline to be measured and contacts the inner surface of the pipeline to be measured; the DC magnetization component is used to perform DC magnetization on the pipeline to be measured; The detection component is located in the pipeline to be tested; the detection component is used to detect inner surface defects, buried defects and outer surface defects of the pipeline to be tested when the pipeline to be tested is DC magnetized, and to detect inner surface defects of the pipeline to be tested when the pipeline to be tested is not DC magnetized; the types of inner surface defects, buried defects and outer surface defects include cracks and corrosion.

5. A defect detection device according to claim 4, characterized in that: The DC magnetization component includes a U-shaped magnetic yoke, and the first magnetic pole and the second magnetic pole of the U-shaped magnetic yoke are both in contact with the inner surface of the measured pipe; the detection component is located between the first magnetic pole and the second magnetic pole, and the distance from the detection component to the first magnetic pole is equal to the distance from the detection component to the second magnetic pole; A coil is installed on the U-shaped magnetic yoke, and when a DC current is passed through the coil, the measured pipeline is DC magnetized; or permanent magnets are installed on both the first magnetic pole and the second magnetic pole to DC magnetize the measured pipeline.

6. A defect detection method, based on the defect detection device according to claim 4, characterized in that: The defect detection method comprises: When it is necessary to detect external surface defects or buried defects, the DC magnetization component is used to DC magnetize the pipeline under test, and the detection component is used to perform defect detection on the pipeline under test; When it is necessary to detect inner surface defects, the detected pipeline is detected by using a detection component; or, the detected pipeline is DC magnetized by using a DC magnetization component, and the detected pipeline is detected by using a detection component.

7. A defect detection method according to claim 6, characterized in that: When the detection component is a differential eddy current internal detection probe, the defect detection method further includes: When it is necessary to detect defects with a defect angle within the range of 0 degrees to 45 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be perpendicular to the axial direction of the measured pipe; when it is necessary to detect defects with a defect angle within the range of 45 degrees to 90 degrees, the normal vector of the fitting surface of the first receiving coil and the excitation coil of the differential eddy current internal detection probe is set to be parallel to the axial direction of the measured pipe; the defect angle is the angle between the length direction of the defect and the axial direction of the measured pipe.

Images