Variable-diameter pipeline detection device and method suitable for elbow and concentric and stable

Abstract

This invention provides a detection device and method for bends, concentric and stable variable-diameter pipes. The detection device includes a magnetic flux leakage detection unit with a central adjustment mechanism, multiple elastic support mechanisms, and multiple detection probes. The method includes: establishing a finite element model; loading and solving a weld defect model and / or a pipe defect model; plotting curves of magnetic field strength and magnetic induction intensity based on the solution results; and accurately locating and / or determining the depth of defects in the pipe weld and / or pipe based on the curves. This invention can establish a two-dimensional axisymmetric model of the detection entity inside the pipe, and obtain the magnitude of axial and radial magnetic flux leakage signals under different defect depths, providing a basis for the subsequent detection of defects on the pipe weld.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline inspection technology, and more specifically, to an inspection device and method for bends, concentric and stable variable diameter pipelines. Background Technology

[0002] Currently, oil and natural gas are recognized worldwide as the most important energy sources, and they occupy an increasingly important position in my country's national economy. Ferromagnetic pipeline structures are widely used in critical sectors such as oil and natural gas transportation, chemical industry, and municipal construction. These pipelines are typically buried deep underground or submerged in the seabed. Due to long-term use, they inevitably suffer from varying degrees of corrosion from soil and seawater. If these pipelines are not inspected and maintained in a timely manner, accidents can have severe consequences from both a social and environmental perspective and from a national economic perspective. Statistics show that in oil and gas pipeline leaks and explosions, weld defects are one of the main factors affecting pipeline safety. Therefore, regularly inspecting pipelines using non-destructive testing techniques to ensure their proper functioning in engineering projects is of significant safety importance.

[0003] Currently, foreign researchers focus on pipe wall defects, neglecting other causes such as defects in welds, elbows, tees, and other special cases. These defects often affect inspection results and lead to misjudgments in practice. Due to the structural characteristics of these components, leakage magnetic fields are generated after the pipeline is magnetized. If the study of these leakage magnetic fields is ignored, they can easily be confused with defect leakage magnetic fields, causing considerable inconvenience to pipeline inspection and maintenance. Furthermore, existing oil pipeline inspection devices have poor adaptability and are not universally applicable. The same inspection device cannot be universally used for various types of pipelines. Currently in service, oil pipelines typically come in various diameters. When operating in the field (deep mountains or at sea), multiple sets of equipment are usually required to inspect oil pipelines of different diameters, creating considerable difficulties for equipment transportation and installation.

[0004] Chinese invention patent application CN108426943A, published on August 21, 2018, discloses a variable-diameter pipe magnetic flux leakage (MFL) detection device, comprising a variable-diameter support device, a MFL detection probe, and a caster wheel travel device. The variable-diameter support device supports the MFL detection probe against the inner wall of the pipe, maintaining a suitable distance between the probe and the pipe wall for MFL detection and ensuring detection effectiveness. Simultaneously, the extension and retraction of the MFL detection probe can be actively controlled, adjusting the diameter of the support device to adapt to different pipe diameters. The MFL detection probe consists of a detection sensor and a magnetizing device, used to detect pipe defects. The caster wheel travel device enables the passive movement of the detection device within the pipe. The MFL detection probe and the caster wheel travel device are evenly distributed on the variable-diameter support device. This invention realizes MFL detection in industrial variable-diameter pipes, with advantages such as strong pipe adaptability and ease of operation. Furthermore, this invention can be connected to a pipe-mounted mobile robot to form an automated pipe MFL detection system. However, the variable diameter support device and the multiple caster wheel travel device in this invention application adopt a split design, which is not conducive to maintaining good concentricity and stability continuously. Therefore, it reduces the accuracy and stability of the inspection to a certain extent. In addition, this invention application does not inspect the weld.

[0005] Chinese invention patent application CN111830123A, published on October 27, 2020, discloses a pipeline inspection device based on a rotating electromagnetic field. The device includes a main body with a servo motor fixed inside. Lead screws are driven on both sides of the servo motor, and a second nut is threaded onto the surface of each lead screw. A pivotally connected connecting rod is axially connected to both sides of the second nut, and a fixed plate is pivotally connected to one end of each pivotally connected rod. Several support rods are fixed to the surface of the fixed plate, and a drive motor is fixed to one end of each support rod. A roller is driven on one side of the drive motor. By adjusting the magnitude of the direct current, the leakage magnetic field signal at various defects in the pipe wall of the tested pipeline can reach the optimal magnetization intensity, ensuring the accuracy of the pipeline leakage magnetic field detection device in detecting various defects in the tested pipeline, thereby improving detection efficiency. The device has a scientifically sound structure, is safe and convenient to use, and provides significant assistance. However, this invention has poor adaptability and low detection accuracy when navigating bends in the pipeline. Summary of the Invention

[0006] The purpose of this invention is to address at least one of the aforementioned shortcomings of the prior art. For example, one objective of this invention is to provide a variable diameter pipe inspection device that differs from the structure of the prior art, possesses better concentricity and stability, and is suitable for bends.

[0007] To achieve the above objectives, the present invention provides a variable diameter pipe testing device suitable for bends, concentricity, and stability. The variable diameter pipe testing device includes a magnetic flux leakage detection unit with a central adjustment mechanism, multiple elastic support mechanisms, and multiple detection probes.

[0008] The central adjustment mechanism includes an adjustment head, an adjustment screw with a threaded section and a smooth section, a sleeve assembly, and a nut. The adjustment head is fixedly connected to the end of the adjustment screw near the threaded section. The nut is threadedly engaged with the threaded section. The sleeve assembly is fitted onto the smooth section of the adjustment screw so that the adjustment head can drive the adjustment screw to pivot in place within the sleeve assembly along the centerline of the pipe, thereby adjusting the relative distance between the nut and the sleeve assembly.

[0009] The elastic support mechanism includes an X-shaped support frame, an inner support plate, an elastic compression member, an outer support plate, a front guide wheel, and a rear guide wheel. The elastic compression member is disposed between the inner support plate and the outer support plate and enables the inner and outer support plates to be arranged around the center line of the pipeline. The inner support plate has a guide groove disposed at its front center along the center line of the pipeline. The X-shaped support frame has a front inner support point hinged to the sleeve assembly, a rear inner support point hinged to the nut, a rear outer support point hinged to the rear of the inner support plate, and a front outer support point that can slide with the guide groove of the inner support plate. The front guide wheel and the rear guide wheel are respectively disposed at the front and rear of the outer support plate.

[0010] The detection probe is mounted on the outer wall of the outer support plate and includes a hard brush, a magnetic sensor, a yoke, and a magnet.

[0011] Another object of the present invention is to provide a method for directly measuring the location and / or depth of defects or weld defects in variable diameter oil and gas pipelines by walking.

[0012] To address the aforementioned technical problems, another aspect of the present invention provides a method for detecting variable diameter pipes that are suitable for bends, concentricity, and stability. This method employs the variable diameter pipe detection device described above.

[0013] In one exemplary embodiment, the variable diameter pipe inspection method may include the following steps:

[0014] Step (1), establish a finite element model; first, establish a weld defect model and / or a pipe defect model. The weld defect model is established on both sides of the weld and includes an air layer, a pipe, a hard brush, a magnet, a yoke, and the weld. The pipe defect model is established on both sides of the pipe and includes an air layer, a pipe, a hard brush, a magnet, and a yoke. Then, assign different material properties to different areas of the weld defect model and / or the pipe defect model to distinguish and identify different materials.

[0015] Step (2) involves loading and solving the weld defect model and / or pipe defect model. First, mesh generation is performed. After the weld defect model and / or pipe defect model are built, the degree of mesh generation, mesh density, mesh shape, boundary conditions, and thickness are selected based on the boundary type and calculation accuracy. The magnetic circuit equation calculation formula for the static model is as follows: In the formula, F represents the magnetomotive force between the two magnets. Rm represents the total magnetic resistance of the hard brush, magnet, and yoke, Rg represents the magnetic resistance of the air gap between the hard brush and the pipe wall, and R1, R2, Rp, and Rc represent the magnetic resistance of the two pipe wall sections, the defect, and the pipe wall next to the defect, respectively.

[0016] Step (3): For the solution results of the weld defect model and / or pipeline defect model, plot the curves of magnetic field strength and magnetic induction intensity, and accurately locate and / or determine the depth of defects in the pipeline weld and / or pipeline based on the curves.

[0017] For example, the variable diameter pipe inspection method can, according to step (3), plot the corresponding axial magnetic flux leakage curve and / or radial magnetic flux leakage curve with the observation path as the abscissa and the axial magnetic flux leakage signal and / or radial magnetic flux leakage signal as the ordinate, and determine or compare the defect depth based on the signal magnitude of the axial magnetic flux leakage curve and / or radial magnetic flux leakage curve. The signal magnitude and defect depth are related in the following way:

[0018] When the pipeline is free of defects, the detected axial and / or radial magnetic flux leakage signals are a smooth curve. When the pipeline weld is defective, both the detected axial and radial magnetic flux leakage signals change.

[0019] For pipes and welds of the same thickness, when internal defects of the same depth are engraved, the axial and / or radial magnetic flux leakage signals detected at the weld defects tend to be greater than those detected at the pipe defects. Furthermore, the axial and / or radial magnetic flux leakage signals detected at the weld defects are equal to the superposition of the axial and / or radial magnetic flux leakage signals detected at the pipe defects and the corresponding axial and / or radial magnetic flux leakage signals detected when the weld is defect-free.

[0020] For pipes and welds of the same thickness, when there are external defects of the same depth, the axial and / or radial magnetic flux leakage signals detected at the weld defects tend to be greater than those detected at the pipe defects. Furthermore, the axial and / or radial magnetic flux leakage signals detected at the weld defects are equal to the superposition of the axial and / or radial magnetic flux leakage signals detected at the pipe defects and the corresponding axial and / or radial magnetic flux leakage signals detected when the weld is defect-free.

[0021] By comparing axial and / or radial magnetic flux leakage signals at different defect depths within the weld, it can be concluded that the detected axial and / or radial magnetic flux leakage signals increase with increasing defect depth.

[0022] By comparing axial and / or radial magnetic flux leakage signals at different defect depths outside the weld, it can be concluded that the detected axial and / or radial magnetic flux leakage signals decrease as the defect depth increases.

[0023] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0024] (1) The present invention uses a nut-based screw pair detector to achieve good concentricity and stability. Multiple detection units realize complete measurement of the pipe circumference. The introduction of elastic compression components increases the bending performance of the device. The universal joint structure connects the detector to the back of the drive unit to achieve the overall structure weight reduction and alleviate the power consumption of the drive body to a certain extent. Through reasonable design, it is ensured that the detector can realize bending detection and has good bending passability.

[0025] (2) Magnetic flux leakage (MFL) detection technology was employed to study the variations in axial and radial MFL signals in welded pipes with defects of different depths. A two-dimensional axisymmetric model with the pipe center as the axis of symmetry was established using finite element simulation software. Simulation analyses were conducted on multiple sets of defects at different depths, including comparisons between defect-free pipes and defect-free pipe welds; comparisons between internal pipe defects and internal pipe weld defects; comparisons between external pipe defects and external pipe weld defects; radial comparisons between internal pipe weld defects of different depths; and radial comparisons between external pipe weld defects of different depths. The axial and radial MFL signals obtained in post-processing were used to compare and analyze the results, providing a basis for subsequent defect detection in pipe welds. Attached Figure Description

[0026] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which:

[0027] Figure 1 A schematic diagram of an exemplary embodiment of the variable diameter pipe inspection device of the present invention is shown;

[0028] Figure 2a and Figure 2b A two-dimensional solid structure diagram of the internal detection of magnetic flux leakage in pipelines is shown;

[0029] Figure 3 A schematic diagram of the grid division is shown;

[0030] Figure 4 A diagram showing the distribution of magnetic field lines is provided.

[0031] Figure 5a A defect-free axial magnetic flux leakage signal diagram is shown;

[0032] Figure 5b A defect-free radial magnetic flux leakage signal diagram is shown;

[0033] Figure 6a The diagram shows the axial magnetic flux leakage signal of defects in the pipe weld.

[0034] Figure 6b The radial magnetic flux leakage signal of defects in the pipe weld is shown;

[0035] Figure 7a The diagram shows the axial magnetic flux leakage signal of external defects in the pipe weld.

[0036] Figure 7b The radial magnetic flux leakage signal of external defects in the pipe weld is shown.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Pipeline; 1.1 Weld; 2. Hard brush; 3. Magnetic sensor; 4. Yoke; 5. Magnet; 6. Outer support plate; 7. Elastic compression component; 8. Inner support plate; 9. Guide groove; 10. Support frame; 11. Nut; 12. Adjusting head; 13. Adjusting screw; 14. Sleeve; 15. Connecting flange; 16. Guide wheel; 17. End cap; 18. Single bearing; 19. Spacer; 20. Snap ring. Detailed Implementation

[0039] The present invention will be described in detail below with reference to exemplary embodiments, providing a detailed description of the variable diameter pipe inspection device and method applicable to bends.

[0040] It should be noted that "front", "back", "inner" and "outer" are used only to facilitate the description and formation of relative orientation or positional relationships, and do not indicate or imply that the part referred to must have that specific orientation or position.

[0041] In an exemplary embodiment of the present invention, a variable diameter pipe inspection device suitable for bends, concentricity and stability may consist of a magnetic flux leakage detection unit having a central adjustment mechanism, multiple elastic support mechanisms and multiple detection probes, a drive unit and a universal connector capable of connecting the drive unit to the front end of a sleeve assembly of the magnetic flux leakage detection unit.

[0042] Specifically, the central adjustment mechanism may include an adjustment head, an adjustment screw comprising a threaded section and a smooth section, a sleeve assembly, and a nut. The adjustment head is fixedly connected to the end of the adjustment screw near the threaded section; for example, the adjustment head may be integrally formed with the adjustment screw, taking the shape of a long screw. The nut is threadedly engaged with the threaded section; for example, the nut may be a nut itself. The sleeve assembly is fitted onto the smooth section of the adjustment screw, allowing the adjustment head to drive the adjustment screw to rotate in place within the sleeve assembly along the pipe centerline, thereby adjusting the relative distance between the nut and the sleeve assembly. For example, the sleeve assembly consists of a sleeve, an end cap, and a bearing. The sleeve has a blind end and an open end, essentially forming a tube with one open end. The end cap may be fixedly mounted on the open end of the sleeve and has a shaft hole through which the smooth section of the adjustment screw can pass. The bearing is positioned between the sleeve and the smooth section of the adjustment screw, enabling the smooth section of the adjustment screw to rotate within the sleeve. For example, the bearing can be two single bearings connected by a spacer, thereby providing better support and facilitating more stable rotation of the guide rod. Furthermore, the center adjustment mechanism may include a retaining ring that engages with an annular groove at the end of the guide rod to limit the axial position of the bearing.

[0043] The elastic support mechanism may include an X-shaped support frame, an inner support plate, an elastic compression member, an outer support plate, a front guide wheel, and a rear guide wheel. For example, the magnetic flux leakage detection unit includes multiple elastic support mechanisms evenly distributed in the circumferential direction of the central adjustment mechanism; for example, the number of elastic support mechanisms may be more than five.

[0044] The elastic compression member can be disposed between the inner support plate and the outer support plate, and can be arranged around the centerline (or central axis) of the pipe. That is, the elastic compression member can be disposed along the radial direction of the pipe, and is fixedly disposed as a connector in a compressed state between the inner support plate and the outer support plate, which are parallel to each other and are arranged around the central axis of the pipe. For example, the elastic compression member can be a compression spring. The inner support plate has a guide groove disposed at the front center of the inner support plate itself along the centerline of the pipe. The X-shaped support frame has a front inner fulcrum hinged to the sleeve assembly, a rear inner fulcrum hinged to the nut, a rear outer fulcrum hinged to the rear of the inner support plate, and a front outer fulcrum that can slide with the guide groove of the inner support plate. In other words, by using an X-shaped support frame positioned between the inner support plate and the nut and sleeve assembly of the central adjustment mechanism, the change in the relative distance between the nut and sleeve assembly on the central adjustment mechanism can be transmitted to the inner support plate. This is then transmitted via an elastic compression member to the front and rear guide wheels and the detection probe positioned on the outer support plate. This allows for the detection of movement in areas such as bends and recesses, improving detection accuracy. Furthermore, to better achieve a sliding fit with the guide groove of the inner support plate, the elastic support mechanism may further include a slider. This slider can be positioned within the guide groove of the inner support plate and can be fixedly connected to the front outer support point of the X-shaped support frame.

[0045] The front and rear guide wheels are respectively installed at the front and rear of the outer support plate, enabling them to roll forward or backward within the pipe wall under the drive of the drive unit and the guidance of the universal connector. For example, four guide wheels can be installed on each outer support plate, with two front guide wheels and two rear guide wheels, and their positions can be located at the four corners of the outer support plate.

[0046] The magnetic flux leakage detection unit includes a number of detection probes equal to the number of the elastic support mechanisms. Each detection probe is mounted on the outer wall of an outer support plate and includes a rigid brush, a magnetic sensor, a yoke, and a magnet. For example, each detection probe may include two magnets, and the coercive forces of these two magnets are radially opposite to each other in the pipe. For example, the rigid brush may be a steel brush.

[0047] Figure 1 This is a schematic diagram of the structure of a pipeline inspection device. (For example...) Figure 1As shown, in an exemplary embodiment of the present invention, the variable diameter pipe inspection device suitable for bends comprises a drive unit, a universal connector, and a magnetic flux leakage detection unit. The magnetic flux leakage detection unit comprises a central adjustment mechanism, multiple elastic support mechanisms, and multiple detection probes. The universal connector connects the drive unit to the front end (e.g., connecting flange 15) of the sleeve assembly of the magnetic flux leakage detection unit. Related components and reference numerals include: pipe 1, rigid brush 2, magnetic sensor 3, yoke 4, magnet 5, outer support plate 6, elastic compression member 7, inner support plate 8, guide groove 9, support frame 10, nut 11, adjusting head 12, adjusting screw 13, sleeve 14, connecting flange 15, guide wheel 16, end cap 17, single bearing 18, spacer 19, and retaining ring 20.

[0048] The central adjustment mechanism includes an adjustment head 12, an adjustment screw 13 comprising a threaded section and a smooth section, a sleeve assembly, a nut 11, and a retaining ring 20. The adjustment head is fixedly connected to the end of the adjustment screw near the threaded section; for example, the adjustment head can be integrally formed with the adjustment screw, taking the shape of a long screw. The nut 11 forms a threaded engagement with the threaded section; for example, the nut 11 can be a nut directly. The sleeve assembly is fitted onto the smooth section of the adjustment screw, allowing the adjustment head to drive the adjustment screw to rotate in place within the sleeve assembly along the centerline of the pipe 1, thereby adjusting the relative distance between the nut 11 and the sleeve assembly. For example, the sleeve assembly consists of a sleeve 14 (also called a central sleeve), an end cap 17, and a bearing. The sleeve has a blind end and an open end, essentially making the sleeve a tube with one open end. The end cap can be fixedly mounted on the open end of the sleeve and has a shaft hole through which the smooth section of the adjustment screw can pass. The bearing is positioned between the sleeve and the guide rod of the adjusting screw, enabling the guide rod to rotate within the sleeve. The bearing may consist of a spacer 19 and two single bearings 18 connected by the spacer, thus providing better support and ensuring more stable rotation of the guide rod. The retaining ring 20 engages with an annular groove at the end of the guide rod to limit the axial position of the bearing.

[0049] The elastic support mechanism may have an X-shaped support frame 10, an inner support plate 8, an elastic compression member 7, an outer support plate 6, and front and rear guide wheels 16. The magnetic flux leakage detection unit includes multiple elastic support mechanisms evenly distributed in the circumferential direction of the central adjustment mechanism.

[0050] The elastic compression member can be disposed between the inner support plate and the outer support plate, and can be arranged around the centerline (or central axis) of the pipe. That is, the elastic compression member can be disposed along the radial direction of the pipe, and is fixedly disposed as a connector in a compressed state between the inner support plate and the outer support plate, which are parallel to each other and are arranged around the central axis of the pipe. For example, the elastic compression member can be a compression spring. The inner support plate has a guide groove 9 disposed at the front center of the inner support plate itself along the centerline of the pipe. The X-shaped support frame has a front inner fulcrum hinged to the sleeve assembly, a rear inner fulcrum hinged to the nut, a rear outer fulcrum hinged to the rear of the inner support plate, and a front outer fulcrum that can slide with the guide groove of the inner support plate. In other words, by using an X-shaped support frame positioned between the inner support plate and the nut and sleeve assembly of the central adjustment mechanism, the change in the relative distance between the nut and sleeve assembly on the central adjustment mechanism can be transmitted to the inner support plate. This is then transmitted via an elastic compression member to the front and rear guide wheels and the detection probe positioned on the outer support plate. This allows for the detection of movement in areas such as bends and recesses, improving detection accuracy. Furthermore, to better achieve a sliding fit with the guide groove of the inner support plate, the elastic support mechanism may further include a slider. This slider can be positioned within the guide groove of the inner support plate and can be fixedly connected to the front outer support point of the X-shaped support frame.

[0051] The front and rear guide wheels are respectively installed at the front and rear of the outer support plate, enabling them to roll forward or backward within the pipe wall under the drive of the drive unit and the guidance of the universal connector. For example, four guide wheels can be installed on each outer support plate, with two front guide wheels and two rear guide wheels, and their positions can be located at the four corners of the outer support plate.

[0052] The magnetic flux leakage detection unit includes a number of detection probes equal to the number of the elastic support mechanisms. Each detection probe is mounted on the outer wall of an outer support plate and includes a rigid brush 2, a magnetic sensor 3, a yoke 4, and a magnet 5. For example, each detection probe may include two magnets, and the coercive forces of these two magnets are radially opposite to each other in the pipe.

[0053] In another exemplary embodiment of the present invention, the variable diameter pipe detection method applicable to bends, concentricity and stability is implemented using the above-described variable diameter pipe detection device.

[0054] Taking into account the characteristics of oil and gas pipelines and their defects, as well as welds and their defects, the inventors chose a two-dimensional axisymmetric measurement mode. By extracting one side of the axisymmetric model to represent the radial leakage magnetic signal, the modeling process and size can be greatly simplified and the computational complexity reduced while maintaining accuracy.

[0055] Specifically, the variable diameter pipe inspection method can be implemented through the following steps:

[0056] Step (1): Establish a finite element model.

[0057] First, establish weld defect models and / or pipe defect models. Weld defect models are established based on, for example... Figure 2b The weld 1.1 shown is symmetrically positioned on both sides. The weld defect model includes an air layer, a pipe, a hard brush (e.g., a steel brush), a magnet, a yoke, and the weld. The pipe defect model is established on both sides symmetrically positioned on the pipe, and includes an air layer, a pipe, a hard brush, a magnet, and a yoke. Here, the weld defect model and the pipe defect model can be established separately or together; when established together, the order is not strictly important. Figure 2a and Figure 2b Two-dimensional solid structure diagrams of pipeline magnetic flux leakage detection corresponding to pipes and welds are shown respectively.

[0058] Then, different material properties are assigned to different regions of the weld defect model to distinguish and identify different materials; and / or, different material properties are assigned to different regions of the pipe defect model to distinguish and identify different materials. These properties include: electrical conductivity, relative permittivity, and relative magnetic permeability. With these three parameters determined, a material can be identified. Two magnets are needed, their coercive forces acting parallel to the pipe axis and in opposite directions; for example, one along the positive pipe axis and the other along the negative pipe axis. This ensures that the distribution of magnetic field lines in the post-processing results of the model can form a loop, such as... Figure 4 As shown.

[0059] Step (2) involves loading and solving the weld defect model and / or pipe defect model.

[0060] First, mesh generation is performed, and the result is as follows: Figure 3 As shown, after the weld defect model and / or pipe defect model are built, the degree of mesh generation, mesh density, mesh shape, boundary conditions, and thickness should be selected according to the different boundary types and calculation accuracy. The magnetic circuit equation calculation formula for the weld defect model and / or pipe defect model is as follows: In the formula, F represents the magnetomotive force between the two magnets. Rm represents the magnetic flux through the pipe, Rg represents the magnetic resistance of the hard brush, magnet, and yoke, and R1, R2, Rp, and Rc represent the magnetic resistance of the air gap between the hard brush and the pipe wall, respectively. Figure 4 The magnetic resistance of the pipe wall, the defect, and the pipe wall next to the defect in the two pipe sections shown;

[0061] Step (3): Locate the defect based on the curve diagram.

[0062] For the solution results of the weld defect model, plot the curves of magnetic field strength and magnetic induction intensity, and accurately locate the defects (e.g., welds) in the pipeline welds based on the curves; and / or, for the solution results of the pipeline defect model, plot the curves of magnetic field strength and magnetic induction intensity, and accurately locate the defects (e.g., welds) in the pipeline based on the curves.

[0063] The exemplary embodiments of the variable diameter pipe inspection method are described in detail below with specific examples.

[0064] (1) The excitation device is set to include a yoke, a magnet and a steel brush. The pipe is made of X52 steel. The size of the yoke is 320x50x25 mm, the size of the magnet is 80x50x30 mm, and the size of the steel brush is 80x50x70 mm.

[0065] (2) As shown in Figure 2, 1 is the pipe, 1.1 is the weld, 2 is the steel brush in the hard brush, 4 is the yoke, and 5 is the magnet. Among them, the model length of the air layer is 250mm and the model width of the air layer is 600mm; the model length of the pipe is 8mm and the model width of the pipe is 360mm; the model length of the steel brush is 56.45mm and the model width of the air layer is 100mm; the model length of the magnet is 30mm and the model width of the air layer is 100mm; the model length of the yoke is 67.55mm and the model width of the air layer is 495mm.

[0066] (3) The magnetic permeability of the air near the pipe with defects is much different from that of the pipe. Therefore, the mesh division in this part is more refined, that is, the element size includes 9 levels from extremely fine to extremely coarse.

[0067] (4) Post-processing: The pipeline follows a two-dimensional axisymmetric form. The method used is to take the center of the pipeline as the axis of symmetry. Taking a 2mm defect in the pipeline as an example, one side is cut off to observe the distribution of magnetic lines of force. When there is a defect in the pipe wall, although most of the magnetic lines of force pass through the inside of the pipe wall, there is obvious magnetic leakage in both the inner and outer walls of the pipeline, which causes a leakage magnetic field to be generated around the defect.

[0068] (5) Calculation Results: When the pipeline is defect-free, the magnetic induction intensity B of the leakage magnetic field near the defect can be decomposed into an axial component Bx and a radial component By. The two component curves show small fluctuations, but both are approximately a fixed value. It can be concluded that the magnetic induction intensity changes little when the pipeline is defect-free, and is close to a constant value. However, when a defect is engraved on the inner wall of the pipeline, the distribution of the leakage magnetic field near the defect is distorted. In order to study the change of the magnetic induction intensity of the leakage magnetic field when the geometric dimensions of the pipeline defect change, the controlled variable method is used for research. Calculations were performed for four scenarios: no pipeline defects, defects on the inner and outer walls of the pipeline, no weld defects, and defects on the inner and outer walls of the weld. For each scenario, four groups of different defect depths (1mm, 1.5mm, 2mm, and 2.5mm) were compared. Two characteristic quantities are described using coordinate graphs: the axial and radial magnetic flux leakage signals of the pipeline. The vertical axis represents the peak-to-peak value of the magnetic flux leakage signal, and the horizontal axis represents the distance of the internal detector's observation path inside the pipeline to the defect. These two characteristic values ​​play a crucial role in the description of defects. This invention uses these two quantities to conduct comparative analysis of weld defects.

[0069] Defect depths were set to 1mm, 1.5mm, 2mm, and 2.5mm, from... Figure 5b , 6b As can be seen in Figure 7b, the radial magnetic flux leakage signal gradually decreases with increasing depth. The figure also shows that external defects in the pipe weld ( Figure 7b When the diameter is 1mm, the maximum radial signal value is approximately -50mT, indicating external defects in the pipe weld. Figure 7b At 1.5mm, the maximum radial signal value is approximately -60mT, and the curve is relatively smooth, as shown in the comparison diagram with a defect-free pipe weld. Figure 5b Similar shape, external defects in pipe welds ( Figure 7b When the diameter is 2mm, the curve shows a trend of first decreasing, then increasing, and then decreasing again, with a maximum value of about -80mT and a minimum value of about -100mT. This indicates external defects in the pipe weld. Figure 7b At 2.5mm, the maximum value is approximately -85mT, and the minimum value is approximately -110mT. This shows that as the depth of the pipe weld defect increases, the radial magnetic flux leakage signal gradually decreases with increasing depth. This is consistent with the conclusion regarding defects on the inner wall of the pipe weld (i.e., the magnetic flux leakage signal gradually decreases with increasing depth). Because the defect is on the pipe weld, compared to the defect on the outer wall of the weld, i.e., on the outer wall of the pipe, the distance between the internal detector and the defect in the pipe has a wall thickness. This wall thickness is relative to the weld thickness plus the pipe thickness. In this invention, the pipe thickness is set to 8mm, and the weld thickness is set to 2mm on each side. Due to the inverse superposition of the wall thickness, the outer wall defect of the pipe weld (… Figure 7bThe radial magnetic flux leakage signal of the defect gradually decreases as the defect depth increases. When the defect is inside the pipe, and an internal pipe detector is used, the detected signal will decrease as the wall thickness is reversed and the size of the defect is superimposed.

[0070] Defect depths were set to 1mm, 1.5mm, 2mm, and 2.5mm, from... Figure 5a , 6a As can be seen in Figure 7a, the axial magnetic flux leakage signal gradually decreases with increasing depth. The figure also shows that external defects in the pipe weld ( Figure 7a When the diameter is 1mm, the maximum axial signal value is about 20mT, indicating external defects in the pipe weld. Figure 7a When the diameter is 1.5mm, the maximum axial signal value is about 15mT, indicating external defects in the pipe weld. Figure 7a When the diameter is 2mm, the curve shows a trend of first rising, then falling, and then rising again, with a maximum value of about 15mT and a minimum value of about -10mT. This indicates external defects in the pipe weld. Figure 7a When the depth is 2.5mm, the maximum value is about 5 and the minimum value is about -5mT. This shows that when the depth of the pipe weld defect increases, the axial leakage magnetic signal gradually decreases with the increase of depth.

[0071] In summary, based on the principle of magnetic flux leakage detection and finite element theory, this invention uses a two-dimensional axisymmetric finite element analysis method to study the magnetic flux leakage field distribution and axial and radial magnetic flux leakage signal diagrams of pipeline welds under different defects, and summarizes the influence of different defect depths on magnetic flux leakage detection under defect magnetic flux leakage:

[0072] (1) When there are no defects in the pipeline, the detector inside the pipeline passes through the pipeline and the detected axial and radial magnetic leakage signals are both smooth curves. When the pipeline weld has defects of 1mm and 2mm, the detected axial and radial magnetic leakage signals change, and the deeper the defect, the more obvious the signal.

[0073] (2) For pipes and welds of the same depth (e.g., both 8 mm thick), when internal defects of the same depth are engraved, the axial and radial magnetic flux leakage signals detected at the weld defects tend to be greater than those detected at the pipe defects. Furthermore, the axial and radial magnetic flux leakage signals detected at the weld defects are equal to the superposition of the axial and radial magnetic flux leakage signals detected at the pipe defects and the axial and radial magnetic flux leakage signals detected when the weld is defect-free. This can be verified using defect values ​​of different depths.

[0074] (3) For pipes and welds of the same depth (e.g., both are 8 mm thick), when there are external defects of the same depth, the axial and radial magnetic flux leakage signals detected at the weld defect tend to be greater than those detected at the pipe defect. Furthermore, the axial and radial magnetic flux leakage signals detected at the weld defect are equal to the superposition of the axial and radial magnetic flux leakage signals detected at the pipe defect and the axial and radial magnetic flux leakage signals detected when the weld is defect-free. This can also be verified using defect values ​​of different depths.

[0075] (4) By comparing the axial and radial magnetic flux leakage signals of different defect depths (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm) in the weld seam, it can be concluded that as the defect depth increases, the detected axial and radial magnetic flux leakage signals become larger because the detector is close to the defect inside the pipe.

[0076] (5) By comparing the axial and radial magnetic leakage signals of different defect depths (e.g., 1 mm, 1.5 mm, 2 mm, 2.5 mm) of external defects in the weld, it can be concluded that as the defect depth increases, although the detector is close to the inside of the pipe, the defect is on the outside of the pipe. Since the pipe wall has a certain thickness, the closer to the defect, the smaller the detected axial and radial magnetic leakage signals become.

[0077] The influence of different defect depths on magnetic flux leakage detection under the aforementioned defect leakage magnetic field can also be summarized as follows:

[0078] The axial and radial magnetic flux leakage signals obtained from the calculation of pipeline weld defects are exactly opposite in peak-to-peak value to those obtained from the calculation of pipeline defects. The axial magnetic flux leakage signal of pipeline weld defects rises first and then falls, while the axial magnetic flux leakage signal of pipeline defects falls first and then rises. This is because the defects on the pipeline weld are formed by the opposite superposition of the weld thickness and the pipeline defects.

[0079] The axial and radial magnetic flux leakage signals of defects on the inner and outer walls of the pipe weld are equal to the superposition of the axial and radial magnetic flux leakage signals of defects on the inner and outer walls of the pipe and the axial and radial magnetic flux leakage signals of the weld without defects.

[0080] The axial and radial magnetic flux leakage signals of defects in pipe welds increase as the defects grow. Since the defects are inside the pipe, the detector used in this invention is an internal pipe detector. Therefore, the detected signals become more and more obvious as the defect approaches.

[0081] The axial and radial magnetic flux leakage signals of external defects in pipeline welds decrease as the defects increase in size because the defects are outside the pipeline and the detector is an internal detector. Therefore, when approaching the defects, due to the problem of the wall thickness being out of phase, the detected signals will weaken as the defects increase in size.

[0082] In summary, the beneficial effects of the present invention include one or more of the following:

[0083] First, the present invention uses a detector based on the principle of variable diameter of nut and screw pair to achieve good concentricity and stability. Multiple detection units realize complete measurement of the pipe circumference. The introduction of elastic compression component increases the bending performance of the device. The universal joint structure connects the detector to the back of the drive unit to achieve the overall structure weight reduction and alleviate the power consumption of the drive body to a certain extent. Through reasonable design, it is ensured that the detector can realize bending detection and has good bending passability.

[0084] Secondly, this invention establishes a two-dimensional axisymmetric model of the entity to be detected inside the pipeline. Under different defect depths, the magnitudes of axial and radial magnetic flux leakage signals are obtained, which are consistent with the data detected in actual experiments, providing a basis for the detection of defects on the weld seams of the pipeline in the later stages.

[0085] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A detection device for flexible, concentric, and stable variable-diameter pipes, characterized in that, The variable diameter pipe inspection device includes a magnetic flux leakage detection unit with a central adjustment mechanism, multiple elastic support mechanisms, and multiple detection probes, wherein... The central adjustment mechanism includes an adjustment head, an adjustment screw with a threaded section and a smooth section, a sleeve assembly, and a nut. The adjustment head is fixedly connected to the end of the adjustment screw near the threaded section. The nut is threadedly engaged with the threaded section. The sleeve assembly is fitted onto the smooth section of the adjustment screw so that the adjustment head can drive the adjustment screw to pivot in place within the sleeve assembly along the centerline of the pipe, thereby adjusting the relative distance between the nut and the sleeve assembly. The elastic support mechanism includes an X-shaped support frame, an inner support plate, an elastic compression member, an outer support plate, a front guide wheel, and a rear guide wheel. The elastic compression member is disposed between the inner support plate and the outer support plate and enables the inner and outer support plates to be arranged around the center line of the pipeline. The inner support plate has a guide groove disposed at its front center along the center line of the pipeline. The X-shaped support frame has a front inner support point hinged to the sleeve assembly, a rear inner support point hinged to the nut, a rear outer support point hinged to the rear of the inner support plate, and a front outer support point that can slide with the guide groove of the inner support plate. The front guide wheel and the rear guide wheel are respectively disposed at the front and rear of the outer support plate. The detection probe is mounted on the outer wall of the outer support plate and includes a hard brush, a magnetic sensor, a yoke, and a magnet.

2. The variable diameter pipe testing device suitable for bends, concentricity, and stability according to claim 1, characterized in that, The sleeve assembly includes a sleeve, an end cap, and a bearing. The sleeve has a blind end and an open end. The end cap is disposed at the open end of the sleeve and has a shaft hole through which the smooth rod section of the adjusting screw passes. The bearing is disposed inside the sleeve and connects the smooth rod of the adjusting screw to the inner wall of the sleeve.

3. The variable diameter pipe testing device suitable for bends, concentricity, and stability according to claim 1, characterized in that, The elastic support mechanism further includes a slider, which is disposed in the guide groove of the inner support plate and can be connected to the front outer support point of the X-shaped support frame.

4. The variable diameter pipe testing device suitable for bends, concentricity, and stability according to claim 1, characterized in that, The variable diameter pipe detection device also includes a drive unit and a universal connector that can connect the drive unit to the front end of the sleeve assembly of the magnetic flux leakage detection unit.

5. The variable diameter pipe testing device suitable for bends, concentricity, and stability according to claim 1, characterized in that, The magnetic flux leakage detection unit includes five or more evenly arranged elastic support mechanisms.

6. The variable diameter pipe testing device suitable for bends, concentricity, and stability according to claim 5, characterized in that, The magnetic flux leakage detection unit includes a number of detection probes equal to the number of the elastic support mechanism.

7. A method for inspecting bends, concentric and stable variable diameter pipes, characterized in that, The variable diameter pipe detection method is implemented using the variable diameter pipe detection device as described in any one of claims 1 to 6; the variable diameter pipe detection method includes the following steps: Step (1), establish a finite element model; first, establish a weld defect model and / or a pipe defect model, the weld defect model is established on both sides of the weld; the weld defect model includes an air layer, pipe, hard brush, magnet, yoke and weld, the pipe defect model is established on both sides of the pipe, the pipe defect model includes an air layer, pipe, hard brush, magnet and yoke; then, assign different material corresponding properties to different areas of the weld defect model and / or pipe defect model to distinguish and identify different materials; Step (2): Load and solve the weld defect model and / or pipe defect model. First, mesh generation: After the weld defect model and / or pipe defect model are built, the degree of mesh generation, mesh density, shape of the mesh, boundary conditions and thickness of the mesh should be selected according to the different boundary types and the accuracy of the calculation. The magnetic circuit equation calculation formula of the static model is: F=φ(Rm+2Rg+R1+R2+Rp||Rc), where F represents the magnetomotive force between the two magnets, φ represents the magnetic flux through the pipe, Rm represents the total magnetic resistance of the hard brush, magnets and yoke, Rg represents the magnetic resistance of the air gap between the hard brush and the pipe wall, and R1, R2, Rp and Rc represent the magnetic resistance of the two pipe walls, the defect and the pipe wall next to the defect, respectively. Step (3): For the solution results of the weld defect model and / or pipeline defect model, plot the curves of magnetic field strength and magnetic induction intensity, and accurately locate and / or determine the depth of defects in the pipeline weld and / or pipeline based on the curves.

8. The method for testing bends, concentric and stable variable diameter pipes according to claim 7, characterized in that, The variable diameter pipe detection method can draw the corresponding axial magnetic flux leakage curve and / or radial magnetic flux leakage curve with the observation path as the horizontal axis and the axial magnetic flux leakage signal and / or radial magnetic flux leakage signal as the vertical axis according to the step (3), and judge or compare the defect depth according to the signal magnitude of the axial magnetic flux leakage curve and / or radial magnetic flux leakage curve.

9. The method for testing bends, concentric and stable variable diameter pipes according to claim 8, characterized in that, The magnitude of the signal is related to the defect depth in the following way: When the pipeline is free of defects, the detected axial and / or radial magnetic flux leakage signals are a smooth curve. When the pipeline weld is defective, both the detected axial and radial magnetic flux leakage signals change. For pipes and welds of the same thickness, when internal defects of the same depth are engraved, the axial and / or radial magnetic flux leakage signals detected at the weld defects tend to be greater than those detected at the pipe defects. Furthermore, the axial and / or radial magnetic flux leakage signals detected at the weld defects are equal to the superposition of the axial and / or radial magnetic flux leakage signals detected at the pipe defects and the corresponding axial and / or radial magnetic flux leakage signals detected when the weld is defect-free. For pipes and welds of the same thickness, when there are external defects of the same depth, the axial and / or radial magnetic flux leakage signals detected at the weld defects tend to be greater than those detected at the pipe defects. Furthermore, the axial and / or radial magnetic flux leakage signals detected at the weld defects are equal to the superposition of the axial and / or radial magnetic flux leakage signals detected at the pipe defects and the corresponding axial and / or radial magnetic flux leakage signals detected when the weld is defect-free. By comparing axial and / or radial magnetic flux leakage signals at different defect depths within the weld, it can be concluded that the detected axial and / or radial magnetic flux leakage signals increase with increasing defect depth. By comparing axial and / or radial magnetic flux leakage signals at different defect depths outside the weld, it can be concluded that the detected axial and / or radial magnetic flux leakage signals decrease as the defect depth increases.

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