Method for detecting weld seams of pipelines or containers by using a flexible array eddy current probe

Abstract

The present application relates to a method for detecting welds of pipelines or containers using a flexible array eddy current probe, which is applicable to the detection of surface and near-surface discontinuity defects of welds of pipelines or containers with a diameter greater than DN50. The flexible array eddy current probe includes a flexible wedge base, an array coil, and a highly elastic gasket. The three are closely fitted. The gasket is embedded with magnetic wheels for the eddy current probe to slide. The side wall of the flexible wedge base is provided with a probe marking part for positioning the eddy current probe. Through the array arrangement of the present application combined with two preset electronic scanning methods, C-scan detection of the covered parts of pipeline welds and heat-affected zones is achieved. The eddy current probe of the present application can be applied to workpieces with coatings. The magnetic wheels are embedded at the four corners of its gasket, which can closely adhere to the surface of the arc-shaped workpiece, perform more stable sliding scanning to reduce the influence of lift-off signals, obtain more stable data, and have two scanning methods in the horizontal and vertical directions, with high detection rates for horizontal and vertical defects, clear imaging, and convenient for later re-inspection.

Description

Technical Field

[0001] The present application relates to the field of nondestructive testing technology, and specifically to a method for detecting pipe or container welds using a flexible array eddy current probe. The flexible array eddy current probe is suitable for detecting surface and near-surface discontinuity defects in pipe or container welds with a diameter greater than DN50. Background Art

[0002] During pipeline and container inspections, regulations require a certain percentage of welds to undergo nondestructive surface testing (NDT). Surface defects are often more destructive than internal defects. Magnetic particle testing and penetrant testing are widely used. Magnetic particle testing requires the weld surface to be free of coating and the material to be ferromagnetic. Magnetic particle testing, however, cannot be performed on nonferromagnetic materials like stainless steel and titanium. Penetrant testing is often used for surface flaw detection, but it also requires the surface to be free of oil stains and coatings. While power and chemical companies can typically perform hot-drying after shutting down operations, grinding is not an option for natural gas pipelines and containers that operate year-round. The only alternative is to use solvent-based water to remove the anti-rust paint, a process that is not only ineffective but also increases the workload.

[0003] Eddy current testing, with its rapid, non-contact, highly sensitive detection capabilities, and compatibility with all conductive materials, can perfectly address these challenges. However, conventional single-probe eddy current testing often requires a small coil size to maintain sensitivity, resulting in low efficiency for scanning a single curved surface. Furthermore, welds with excess height and coating, as well as the uneven surface texture of the weld, combined with the lift-off effect caused by the relative motion of the probe and the curved surface during scanning, can make it difficult to determine if a weld is defective.

[0004] The inventor has previously conducted in-depth research on the use of eddy current probes to detect curved workpieces. For specific technical solutions, please refer to application number: 202010057697.1. Name: A contoured flexible array eddy current probe and detection method. The function of detecting the entire surface of a curved workpiece with a stationary probe is achieved through contoured array coils, a special coil arrangement, and an electronic scanning method. However, this application covers the entire array probe for a static scan of the workpiece, and replaces manual scanning with electronic scanning to form a top-down plan view of the workpiece. It has an efficient detection effect on small workpieces, but cannot detect workpieces with long welds such as pressure vessels and pipelines. This application has a good detection effect on relatively flat curved workpieces such as turbine blades, but the effect is average when the workpiece surface is not smooth and flat. Summary of the Invention

[0005] The purpose of this application is to solve the problem of surface inspection of butt welds where it is inconvenient to remove the coating or apply penetrant and magnetic suspension fluid, as well as the problems of large interference in detection signals, large detection blind spots, and low detection efficiency in ordinary eddy current detection due to the lift-off effect. A flexible array eddy current probe for the butt weld of pipes and containers is provided. By using a wedge base made of a specific flexible material and a gasket with a magnetic wheel, a special arrangement method of the detection coil and an electronic scanning method are adopted to detect the weld with coating, and it can move and scan stably and smoothly to achieve the function of C imaging.

[0006] This application proposes a method for detecting the weld of a pipe or container with a flexible array eddy current probe. The flexible array eddy current probe includes a flexible wedge base 1, a flexible array coil 2 attached to the flexible wedge base 1, a flexible wear-resistant gasket 3 attached to the other side of the array coil 2, a magnetic wheel 4 for the eddy current probe to slide is embedded in the gasket 3, and a probe marking part 5 for positioning the eddy current probe is provided on the side wall of the flexible wedge base 1; the array coil 2 includes a square flat coil 2-1 and a flexible circuit board 2-2. The coil 2-1 is a self-inductive coil, which is both an excitation coil and a detection coil; multiple coils 2-1 with the same size and parameters are arranged longitudinally in three columns, and two adjacent coils 2-1 in different columns are arranged in a staggered manner to form an irregular coil arrangement array. The distance between two coils 2-1 is t, the outer diameter of the coil 2-1 is d, the distance t between any two coils 2-1 is the same, and t < d; place the flexible array eddy current probe on the surface of the workpiece to be detected, align the probe marking part 5 with the area to be detected of the workpiece to be detected, and apply a certain pressure to make the gasket 3 of the flexible array eddy current probe fully contact with the area to be detected; in two ways of transverse scanning and longitudinal scanning, connect the excitation signal respectively under the control of the time-division multiplexer according to the spatial order and time order. Every two coils 2-1 form a differential bridge, and the output signal of this bridge is used as the detection signal; if there is no defect, the feedback signal of the weld to the coil is the same, and the output value of the bridge is zero. When there is a defect under the coil, the impedance of the defect feedback to the detection coil changes, the bridge loses balance, and the output signal is proportional to the change amount of the impedance, thereby reflecting the information of the defect. Different scanning orders have different sensitivities to the direction of the defect. When the defect direction is perpendicular to the eddy current direction, the defect detection sensitivity is the highest. The two scanning methods are imaged respectively, and two C imaging diagrams on the same time or the same spatial axis are formed, respectively reflecting the transverse and longitudinal defect imaging diagrams.

[0007] Further, the flexible circuit board 2-2 is based on polyimide.

[0008] Further, the two coil terminals 2-11 of the coil 2-1 are welded to the flexible circuit board 2-2, and a magnetic core 2-12 is embedded in the center of the coil 2-1.

[0009] Further, the array coil 2 and the gasket 3 are bonded together with a thixotropic insulating glue having good electrical insulation properties.

[0010] Further, the probe marking portion 5 is provided at the center scale line on the side wall of the flexible wedge base 1.

[0011] Further, the magnetic wheels 4 are embedded in the four corners of the gasket 3. The magnetic wheels 4 include magnetic balls 4-1 and springs 4-2. When the magnetic balls 4-1 roll, the springs 4-2 cause the magnetic balls 4-1 to be compressed and stretched synchronously with the gasket 3.

[0012] Further, the materials of the flexible wedge base 1 and the gasket 3 are selected from IIR butyl rubber and PEBA.

[0013] The above technical solution has the following advantages or beneficial effects: By means of the special arrangement of the coils and the electronic scanning method, high-efficiency detection of defects in multiple directions is realized, effectively solving the problem of difficult detection of coated welds. It avoids the influence of the lift-off effect in single-probe eddy current detection in the prior art, such as large detection signal interference, large detection blind area, and low detection efficiency. It greatly improves the detection accuracy and working efficiency. And the base with magnetic wheels can reduce the trouble of manual support during actual detection, can be adsorbed on the workpiece, and can slide smoothly and stably for scanning, having great popularization and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those skilled in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0015] Figure 1 is a schematic structural diagram of a flexible array eddy current probe for pipeline or container weld detection according to an embodiment of the present application.

[0016] Figure 2 is a schematic structural diagram of the array coil of the flexible array eddy current probe according to an embodiment of the present application.

[0017] Figure 3 is a schematic structural diagram of a single coil of the array coil of the flexible array eddy current probe according to an embodiment of the present application.

[0018] Figure 4 is a schematic structural diagram of the magnetic wheel of the flexible array eddy current probe according to an embodiment of the present application.

[0019] Figure 5 is a circuit diagram for measuring the coils of the flexible array eddy current probe according to an embodiment of the present application.

[0020] Figure 6 Schematic diagram of the detection principle of a flexible array eddy current probe according to an embodiment of the present application.

[0021] Figure 7 Schematic diagram of the lateral scanning of the array coil of the flexible array eddy current probe according to an embodiment of the present application.

[0022] Figure 8 Schematic diagram of the longitudinal scanning of the array coil of the flexible array eddy current probe according to an embodiment of the present application.

[0023] Figure 9 Scanning imaging diagram of the flexible array eddy current probe for a workpiece according to an embodiment of the present application.

[0024] Figure 10 Scanning imaging diagram of the flexible array eddy current probe for another workpiece according to an embodiment of the present application.

[0025] Figure 11 Principle block diagram of the detection system of the flexible array eddy current probe according to an embodiment of the present application.

[0026] Among them, 1. Flexible wedge base; 2. Array coil; 2-1. Coil; 2-2. Flexible circuit board; 2-11. Coil terminal; 2-12. Magnetic core; 3. Gasket; 4. Magnetic wheel; 4-1. Magnetic ball; 4-2. Spring; 5. Probe marking part. Specific embodiments

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and are intended to explain the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0028] Refer to Figure 1 , a specific embodiment of the present application proposes a flexible eddy current probe for detecting the butt weld of a pipeline and a container, including a flexible wedge base 1, an array coil 2 attached to the flexible wedge base 1, and a gasket 3 made of a high-strength flexible pressure-relieving and resilient and wear-resistant material such as IIR butyl rubber or PEBA attached to the other side of the flexible array coil 2. The gasket 3 is embedded with a magnetic wheel 4 for the eddy current probe to slide, and a probe marking part 5 for positioning the eddy current probe is provided on the side wall of the flexible wedge base 1.

[0029] The flexible wedge base 1 has a certain flexibility and has a certain bending space in the vertical direction, and is made of a high-elasticity insulating material such as IIR butyl rubber or PEBA. The gasket 3 is attached to the array coil 2 with a thixotropic insulating glue having good electrical insulation performance.

[0030] In order to make the scanning trajectory of the eddy current probe as linear as possible during scanning, preferably, the probe marking portion 5 is provided at the center scale line on the side wall of the flexible wedge base 1, which is convenient for positioning the eddy current probe.

[0031] Reference Figure 2 and 3 Referring to [relevant reference] and [relevant reference], a specific embodiment of the present application provides a flexible eddy current probe for detecting the butt weld of a pipeline and a container. The array coil 2 includes a square flat coil 2-1 and a flexible circuit board 2-2 with polyimide as the base material. A plurality of coils 2-1 with the same size and parameters are arranged longitudinally in three columns, and two adjacent coils 2-1 in different columns are arranged in a staggered manner to form an irregular array. The coil 2-1 is a self-inductive coil, which is both an excitation coil and a detection coil. When a certain coil in the flexible eddy current probe is excited, it can be used as a detection coil to collect signals by itself.

[0032] The coil 2-1 is arranged on the flexible circuit board 2-2 in a printed circuit manner to form a printed circuit with high reliability and good flexibility. The distance between two coils 2-1 is t, the outer diameter of the coil 2-1 is d, the distance t between any two coils 2-1 is the same, and t < d. Since the action range of the eddy current is twice the outer diameter d of the coil 2-1, such a design can ensure that the eddy current generated by the coil can completely cover the area between the two coils to avoid missed detection.

[0033] In order to improve the detection sensitivity of the coil 2-1 and reduce the mutual influence between the coils 2-1, a magnetic core 2-12 is embedded in the center of the coil 2-1. The magnetic core is made of an iron-based amorphous alloy with high magnetic permeability. Two coil terminals 2-11 of the coil 2-1 are welded to the flexible circuit board 2-2, so that the array coil 2 has the characteristics of light weight, thin thickness and free bending, and is convenient for closely fitting with the flexible wedge 1.

[0034] Since the base material uses a flexible polyimide material, it can ensure that the fitting surface is consistent with the surface of the workpiece. In order to prevent loss caused by friction between the array coil 2 and the workpiece to be measured during sliding and to fit the weld more closely, a gasket 3 is connected to the other side of the array coil 2. This gasket has high elasticity and is prone to elastic deformation under pressure. In addition, in order to move the probe smoothly and stably, the magnetic wheels 4 are embedded at the four corners of the gasket 3.

[0035] Reference Figure 4 Referring to [relevant reference], a specific embodiment of the present application provides a flexible eddy current probe for detecting the butt weld of a pipeline and a container. The magnetic wheel 4 includes a magnetic ball 4-1 and a spring 4-2. While the magnetic ball 4-1 rolls, the spring 4-2 makes it synchronously compress and stretch with the gasket 3 under pressure, avoiding the magnetic ball 4-1 from affecting the fitting of the gasket 3 and the workpiece to be measured.

[0036] Reference Figure 5 , a specific embodiment of the present application proposes a flexible eddy current probe for detecting the butt weld of a pipeline and a container. The connection form of the measurement circuit of the array coil 2 is as Figure 5 shown. Every two coils and a resistor form a differential bridge circuit, and the output Uo of the bridge.

[0037] Z1·R = Z2·R

[0038]

[0039] Since ΔZ1 << Z1, ΔZ2 << Z2, and Z1 = Z2 = Z

[0040]

[0041] z is the impedance of the coil under no-load conditions.

[0042]

[0043]

[0044]

[0045]

[0046]

[0047] When a = 1,

[0048]

[0049] The output voltage is proportional to the change in impedance.

[0050] When a sine wave signal of a certain frequency is applied to the bridge, the coil generates an alternating magnetic field around it. This magnetic field generates an eddy current of the same frequency in the conductor (workpiece to be measured). This eddy current also generates an alternating magnetic field. At this time, the total magnetic field linked in the coil is the superposition of the original magnetic field and the eddy current magnetic field. From L = Ψ / I, the inductance of the coil will change. Due to the presence of resistance in the conductor, the eddy current will also generate eddy current loss, and this energy loss is converted into resistance and incorporated into the coil. Therefore, the eddy current causes a change in the impedance Z = R + jL of the coil. When there is a defect in the workpiece, the defect causes a change in the eddy current in that area, thereby causing a change in the impedance of the coil.

[0051] Reference Figure 6, a specific embodiment of the present application proposes a flexible eddy current probe for detecting the butt weld of a pipeline and a container. When there are no defects on the surface of the workpiece to be measured, the eddy currents generated under the two coils are the same, and the impedance changes of the coils are the same. At this time, the output voltage of the bridge is 0. Now there is a defect on the workpiece. If the defect is within the action range of coil 1, this defect causes the impedance change of coil 1 to be ΔZ1. At this time, the output voltage of the measurement circuit If the defect is within the action range of coil 2, this defect causes the impedance change of coil 2 to be ΔZ2, and the output voltage Since the two coils are exactly the same, the impedance changes ΔZ1 = ΔZ2 caused by the same defect. From the above analysis, it can be seen that when the defect is within the action range of different coils, the phases of the output voltages differ by 180 degrees. Thus, the position of the defect can be judged.

[0052] Compared with the workpiece to be measured, the conductivity of media such as air or oil in the defects of the workpiece to be measured is very low, almost approaching zero. Eddy currents cannot pass through the defects and need to be diffracted as shown on the Figure 6 right side. Therefore, when the direction of the defect in the workpiece to be measured is parallel to the connection line of the two coil groups, the detection rate of the defect is the highest. The present application designs two scanning methods according to the shape of the defect, namely, a transverse scanning method for defects perpendicular to the detection direction or with a large angle with the detection direction, and a longitudinal scanning method for defects parallel to the detection direction or with a small angle with the detection direction. Each group of coils is connected to the reserved output port to output a differential signal, and after processes such as amplification, filtering, and detection, a scanning image is finally formed.

[0053] Reference Figure 7 , a specific embodiment of the present application proposes a transverse scanning method for a flexible eddy current probe for detecting the butt weld of a pipeline and a container. The scanning direction of its coils is transverse, aiming at transverse defects. Starting from the starting section of the arrow, each coil is connected to at least 2 multiplex switches, and the on and off of the switches are controlled by software. The two coils energized at each moment can be arbitrarily combined. When the multiplexer selects coils 1 and 2 to be energized, eddy currents are formed within the workpiece within the range of twice the coil diameter, and the lift-off noise signals and defect signals in the workpiece are picked up. Then, the signals picked up by the two coils are differentially output, which can eliminate the influence of noise signals to the greatest extent. Then, coil 1 is disconnected and coil 3 is connected. At this time, it is the combination of coil 2 - coil 3, and so on. Alternate combinations are formed in the direction of the arrow to form a detection coil group for scanning.

[0054] Reference Figure 8, a specific embodiment of the present application proposes a longitudinal scanning method for a flexible eddy current probe used for detecting butt welds between pipes and containers. The coil scanning direction is longitudinal, aiming at detecting longitudinal defects where the detection direction of the probe scanning the workpiece is parallel or has a small included angle. Starting from the starting section of the arrow, each coil is connected to at least 2 multiplexing switches, and the on-off of the switches is controlled by software. The 2 energized coils at each moment can be arbitrarily combined. When the multiplexer selects coils 1 and 2 to be energized, eddy currents are formed within the workpiece within a range of 2 times the coil diameter, and the lift-off noise signals and defect signals within the workpiece are picked up. Then, the signals picked up by the two coils are differentially output to eliminate the influence of noise signals to the greatest extent. Then, coil 1 is disconnected and coil 3 is connected. At this time, it is the combination of coil 2 - coil 3, and so on. Alternately combine in the direction of the arrow to form a detection coil group for scanning.

[0055] Reference Figure 9 and Figure 10 , a specific embodiment of the present application proposes a longitudinal scanning method for a flexible eddy current probe used for detecting butt welds between pipes and containers, and scans two artificially simulated test block workpieces. Figure 9 On the left are artificially simulated round holes, transverse, longitudinal, and oblique defects on the test block workpiece. Scanning the test block workpiece in the figure from left to right, the upper right corner is the imaging of the longitudinal scanning method, and the lower right corner is the imaging of the transverse scanning method. It can be seen that both scanning methods have good detection effects on round holes. When scanning defects with obvious orientations, the transverse scanning and longitudinal scanning cooperate with each other. For example, when performing longitudinal scanning, longitudinal defects parallel to the connection line of the two coil groups have good detection effects. Figure 10 Above are artificially simulated transverse, longitudinal, and round hole defects on the test block workpiece. Scanning the test block workpiece in the figure from left to right along the weld, the middle is the imaging of the longitudinal scanning method, and the lower part is the imaging of the transverse scanning method. It can be seen that both scanning methods have good detection effects on round holes. When scanning defects with obvious orientations, the transverse scanning and longitudinal scanning cooperate with each other, and the imaging visual effect is more refreshing, which is also convenient for reinspecting defects through other detection methods later.

[0056] The transverse scanning method and the longitudinal scanning method, these two scanning methods are specifically aimed at detecting defects in different directions, and have a higher defect detection rate than the traditional composite scanning sequence. In addition, imaging the two scanning methods separately at the same time can make the visual effect more refreshing, which is also convenient for judging the trend of connecting defects and reinspecting with other detection methods.

[0057] Reference Figure 11, a block diagram of a detection system for a flexible eddy current probe for detecting the butt weld of a pipeline and a container is proposed in a specific embodiment of the present application. The oscillator outputs a sinusoidal signal with an adjustable frequency, which is amplified by a power amplifier circuit to provide sufficient current to the probe. The detection signal of the probe is amplified by an amplifier and sent to a phase-sensitive detection circuit to detect the amplitude and phase of the signal. The size and position of the defect are judged by the amplitude and phase. The detected signal is amplified and filtered by a conditioning circuit, and then sent to a microprocessor for processing after A / D conversion. Digital filtering, storage, and processing imaging of the signal are completed in the processor, and then sent to a display for display. Through the setting of the scanning sequence in the human-machine interaction interface, the microprocessor controls the scanning sequence of the array probe through a multiplexer switch to ensure that the coils connected simultaneously each time are always in a completely symmetrical position to avoid the influence of edge effects; at the same time, it also ensures that the scanning traverses all coils to avoid missed detection. The scanning sequence cooperates with the imaging software algorithm to output a visual detection result.

[0058] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Without departing from the spirit and scope of the present application, the present application will have various changes and improvements, and these changes and improvements all fall within the scope of the present application claimed.

Claims

1. A method for detecting the weld of a pipeline or a container by using a flexible array eddy current probe, characterized in that: The flexible array eddy current probe includes a flexible wedge base (1), a flexible array coil (2) attached to the flexible wedge base (1), a flexible wear-resistant gasket (3) attached to the other side of the array coil (2), a magnetic wheel (4) for the eddy current probe to slide is embedded in the gasket (3), and a probe marking part (5) for positioning the eddy current probe is provided on the side wall of the flexible wedge base (1); The array coil (2) includes a square flat coil (2-1) and a flexible circuit board (2-2). The coil (2-1) is a self-inductance coil, which is both an excitation coil and a detection coil; Multiple coils (2-1) with the same size and parameters are arranged longitudinally in three columns, and two adjacent coils (2-1) in different columns are arranged in a staggered manner to form an irregular coil arrangement array. The distance between two coils (2-1) is t, the outer diameter of the coil (2-1) is d, the distance t between any two coils (2-1) is the same, and t < d; The detection method is to place the flexible array eddy current probe on the surface of the workpiece to be detected, align the probe marking part (5) with the area to be detected of the workpiece to be detected, and apply a certain pressure to make the gasket (3) of the flexible array eddy current probe fully contact with the area to be detected; In two ways of transverse scanning and longitudinal scanning, the excitation signals are respectively connected under the control of the time-division multiplexer in the spatial order and the time order. Every two coils (2-1) form a differential bridge, and the output signal of this bridge is used as the detection signal; If there is no defect, the feedback signals of the weld to the coils are the same, and the output value of the bridge is zero. When there is a defect under the coil, the impedance of the defect feedback to the detection coil changes, the bridge loses balance, and the output signal is proportional to the change amount of the impedance, thereby reflecting the information of the defect; Different scanning orders have different sensitivities to the direction of the defect. When the defect direction is perpendicular to the eddy current direction, the defect detection sensitivity is the highest. The two scanning methods are respectively imaged, and are divided into two C imaging diagrams with the same time or the same space axis, respectively reflecting the transverse and longitudinal defect imaging diagrams; The two coil terminals (2-11) of the coil (2-1) are welded to the flexible circuit board (2-2), and a magnetic core (2-12) is embedded in the center of the coil (2-1); The probe marking part (5) is provided at the center scale line on the side wall of the flexible wedge base (1); The magnetic wheels (4) are embedded at the four corners of the gasket (3). The magnetic wheels (4) include magnetic balls (4-1) and springs (4-2). When the magnetic balls (4-1) roll, the springs (4-2) make the magnetic balls (4-1) synchronously compressed and stretched along with the gasket (3); 2. The method for detecting the weld of a pipeline or a container by using the flexible array eddy current probe according to claim 1, wherein: The flexible circuit board (2-2) uses polyimide as the base material; 3. The method for detecting the weld of a pipeline or a container by using the flexible array eddy current probe according to claim 1, characterized in that: The array coil (2) and the gasket (3) are attached with a thixotropic insulating glue with good electrical insulation performance; 4. The method for detecting the weld of a pipeline or a container by using the flexible array eddy current probe according to claim 1, wherein: The materials of the flexible wedge base (1) and the gasket (3) are selected from IIR butyl rubber and PEBA.

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