Multi-layer penetration imaging detection system and method for corrosion defects under thermal insulation layer

Abstract

The invention relates to a multi-layer penetration imaging detection system and method for corrosion defects under a thermal insulation layer. The invention discloses a multi-layer penetration imaging detection system for corrosion defects under a thermal insulation layer. The multi-layer penetration imaging detection system comprises pulsed eddy current detection equipment, a controller, a Mecanum fixed walking device and a variable-diameter detection probe shell, the pulsed eddy current detection equipment comprises a transmitting unit and a receiving unit; the pulsed eddy current detection equipment is provided with N sensors; the transmitting unit is connected with a signal identification module; a multi-layer penetration imaging detection method for corrosion defects under a thermal insulation layer comprises the following steps: step 1, hardware installation; step 2, data acquisition; 3, data preprocessing; and 4, processing and displaying data. The detection system and method have the following advantages that the thermal insulation layer does not need to be dismantled, the safety coefficient is high, the procedure is simple, the detection period is short, and the detection precision is high; the detection efficiency is improved, the three-dimensional position of the defect can be judged, and data is visualized through data processing.

Description

Technical Field

[0001] The invention relates to the technical field of pulse eddy current real-time online monitoring, and in particular to a multi-layer penetration imaging detection system and method for corrosion defects under a thermal insulation layer. Background Art

[0002] Corrosion Under Insulation (CUI) is a common corrosion phenomenon, which mainly occurs on the outer surface of the pipe covered with the insulation layer. The occurrence of this phenomenon may be caused by the destruction of the insulation layer structure, water absorption or infiltration of the insulation material, valve leakage, cleaning water and rainwater inflow.

[0003] Inspection for corrosion under insulation is the most direct and effective means to timely discover hidden dangers of external corrosion of equipment or pipelines. Due to the presence of outer iron or aluminum sheets and insulation materials, CUI is highly concealed and often difficult to detect at the first time, which brings great difficulties to daily CUI inspection. Removing and restoring insulation for macroscopic inspection is often expensive.

[0004] The traditional method of testing under the insulation layer by removing the insulation layer for testing has the following defects: it requires a large number of personnel, a large workload, cumbersome procedures, a long testing cycle, a high risk factor, poor testing accuracy, and the inability to guarantee the quality after the insulation layer is repaired. Specifically, the traditional pipeline corrosion testing covered with the insulation layer requires the insulation layer to be removed and polished before testing; the insulation layer is repaired after the test; and most of the pipelines are in an overhead state. During the test, a large number of scaffoldings need to be set up, and the workers need to hold the detection probes to work, which consumes a lot of personnel.

[0005] The existing means of inspecting pipe fittings without removing the insulation layer have problems such as poor point measurement and detection accuracy, and cannot effectively find the location of hidden dangers. Their application in industrial inspection is very limited.

[0006] Pulsed eddy current technology can detect the corrosion state under the insulation layer without removing the insulation layer, but the insulation layer used in general industry is 5-10cm thick. Therefore, it is necessary to lift 5-10cm for detection. Lifting will produce a lift-off effect, which refers to the phenomenon that the changing electromagnetic field acts near the conductor, causing eddy currents to be generated in the conductor. When the relative position between the detection coil and the test piece changes, the eddy current density generated by the detection coil on the test piece will change. This phenomenon is called the "lift-off effect."

[0007] The detection accuracy of the sensor is closely related to its diameter. The larger the sensor, the worse the detection accuracy. If the detection diameter doubles, the detection accuracy becomes 1 / 8 of the original accuracy. Moreover, the larger the sensor diameter, the easier it is to be interfered with.

[0008] The present invention is based on multi-layer penetration imaging detection technology, which increases data density. At the same time, by improving the sensor structure and changing the scanning method, the sensor diameter is reduced by more than half while the lift-off height remains unchanged, and the detection accuracy is improved by more than eight times, thereby better solving the problem of corrosion detection under the insulation layer. Summary of the invention

[0009] In order to overcome the above shortcomings, the present invention provides a multi-layer penetration imaging detection system for corrosion defects under the insulation layer, including a pulsed eddy current detection device, a controller, a Mecanum fixed walking device and a variable diameter detection probe shell; Pulse eddy current testing equipment connected to the controller; The pulsed eddy current testing device includes a transmitting unit and a receiving unit; The pulsed eddy current testing equipment is provided with N sensors, where N is greater than or equal to 3; The transmitting unit is connected to a signal recognition module, and the signal recognition module is used to identify the frequency of the pulsed eddy current; The signal recognition module is connected to a circuit switching module; the circuit switching module is used for switching the circuits between N sensors; The circuit switching module is connected to the sensor probe; The sensor is a cylindrical high-penetration sensor; The cross-sectional diameter of the high-penetration sensor is 2cm-4cm, which is half of the cross-sectional diameter of the conventional sensor used for detection without removing the insulation layer. The wire diameter of the high penetration sensor is 0.3-0.8mm; A magnetic core is added inside the high-penetration sensor to increase the primary magnetic field emitted by adding the magnetic core; compared with a sensor with the same parameters but without a magnetic core, the penetration strength is increased by one to three times; The magnetic core is made of manganese-zinc ferrite or nickel-zinc ferrite, with a diameter of 8-10 mm and a length of 30-60 mm; The magnetic core is added by inserting it into the coil; The scanning direction of the high-penetration sensor is perpendicular to the direction of the magnetic flux lines of the high-penetration sensor; The probe of each sensor includes an excitation coil and a detection coil; Each of the excitation coils is wirelessly connected to the transmitting unit, and each of the detection coils is connected to the receiving unit; The pulsed eddy current testing device is wirelessly connected to a data processing terminal; The pulsed eddy current testing device is bidirectionally wirelessly connected to the controller; N sensors are arranged on a variable diameter detection probe shell; the variable diameter detection probe shell is adapted to different diameters of the pipeline to be tested; the variable diameter detection probe shell is connected to a Mecanum fixed walking device, and the Mecanum fixed walking device shell drives the N sensors to move along the x-axis or y-axis direction on the pipeline to be tested; The controller is connected to the Mecanum fixed walking device.

[0010] Preferably, the pulsed eddy current testing equipment, the controller, and the Mecanum fixed walking device are all externally connected to a power source.

[0011] Preferably, the data processing end is connected to a data display end.

[0012] Preferably, the pulsed eddy current detection equipment shell is connected to cloud storage to save data.

[0013] Preferably, the controller is connected to a sensor signal indicator light.

[0014] Preferably, the Mecanum fixed walking device comprises a fixed connecting frame 2 and a Mecanum wheel 16; the fixed connecting frame 2 is arc-shaped, and a left connecting groove 3 and a right connecting groove 4 are respectively provided at both ends of the fixed connecting frame 2.

[0015] Preferably, the variable diameter detection probe shell includes a locust bionic stretching structure, a first outer mounting shell 5, two less than N intermediate outer mounting shells 6, and an Nth outer mounting shell 7; The outer mounting shell is sheathed with an inner mounting shell; the sensor is placed in the inner mounting shell; a wedge 18 is inserted into the bottom of the outer mounting shell, and the wedge 18 is used to complete the fitting of different pipe diameters through different arcs; The left and right ends of the top surfaces of the first outer mounting shell 5, the middle outer mounting shell 6 and the third outer mounting shell 7 are respectively provided with through holes; The locust bionic stretching structure comprises a plurality of pins 14, a first stretching group and a second stretching group; the first stretching group comprises a first front stretching member 8 and a first rear stretching member 9, and the second stretching group comprises a second front stretching member 10 and a second rear stretching member 11; the front stretching member and the rear stretching member are hinged via a drive shaft, a driving shaft outer sleeve is provided with a unidirectionally rotatable ratchet 13, the ratchet 13 is covered with a fixedly connected twist cover, the twist cover on the left is a left twist cover 12, and the twist cover on the right is a right twist cover 17, and the insertion of the pin 14 into the ratchet teeth of the ratchet can limit the rotation of the ratchet 13; The left through hole of the first outer mounting shell 5 is connected to the left connecting slot 3 via a sliding shaft, and the right through hole of the first outer mounting shell 5 is hinged to the second rear stretching member 11; the left through hole of the middle outer mounting shell 6 is hinged to the second front stretching member 10, and the right through hole of the middle outer mounting shell 6 is hinged to the first rear stretching member 9; the left through hole of the third outer mounting shell is hinged to the first front stretching member 8, and the right through hole of the third outer mounting shell is connected to the right connecting slot 4 via a sliding shaft; Pull out the pin 14, twist the left twist cover 12, drive the left ratchet 13 to rotate, so that the angle between the first front stretching member 8 and the first rear stretching member 9 is reduced or increased; twist the right twist cover 17, drive the right ratchet 13 to rotate, so that the angle between the second front stretching member 10 and the second rear stretching member 11 is reduced or increased; the size of the detection range is adjusted by changing the angle. When the angle is reduced to 15°, the minimum detection range is 6cm, which is suitable for pipe fittings with a diameter of 50mm (DN50 pipe fittings); when the angle is increased to 60°, the increased detection range is up to 18cm, which is suitable for pipe fittings with a diameter greater than 600mm (DN600 pipe fittings).

[0016] The relative angles of the three probes at the same curvature can be adapted to the diameter of the pipe to be tested.

[0017] A multi-layer penetration imaging detection method for corrosion defects under an insulation layer comprises the following steps: Step 1: Hardware Installation Calculate the diameter of the sensor based on the thickness of the insulation layer; The relationship between the sensor diameter and the insulation layer thickness is: ; Where: t ranges from 2 to 5, q refers to the thickness of the insulation layer, and p refers to the diameter of the sensor; Select the appropriate diameter sensor according to the thickness of the insulation layer; N sensors are respectively mounted on N inner mounting shells in a manner that the magnetic field emitted at one time is parallel to the surface of the pipe to be tested, and then the N inner mounting shells are respectively mounted on N outer mounting shells, and the fitting of different pipe diameters is completed by replacing the wedges to change the curvature, and then the outer mounting shell with the installed sensors is connected to the locust bionic stretching structure, and the equipped variable diameter detection probe shell is connected to the Mecanum fixed walking device and is covered on the outer coating of the pipe to be tested; The magnetic field in the traditional detection method is a magnetic field in the vertical direction of the pipe being tested. The vertical magnetic field is changed to a magnetic field in the parallel direction of the pipe being tested. When the parallel magnetic field passes through the defect position, the degree of distortion is greater, and the defect reaction in the detection result is more obvious. The detection capability is improved by changing the direction of the magnetic field. Step 2: Data Collection The N sensors are driven by the Mecanum fixed walking device to scan the pipeline to be tested by circumferential and axial movement along the pipeline to be tested; the controller sends a signal to the pulsed eddy current testing device, the transmitter unit of the pulsed eddy current testing device using the fixed pulsed eddy current signal sends an excitation square wave, the excitation coil of the sensor probe receives the excitation square wave, the excitation coil inputting the excitation square wave signal forms an electromagnetic field in the corrosion area of ​​the pipe to be monitored, the detection coil of the probe of the pulsed eddy current sensor receives the magnetic induction signal, and transmits the magnetic induction signal back to the receiving unit of the pulsed eddy current testing device; Step 3: Data Preprocessing The data collected by the same sensor on the pipe coating is divided into N sets of data. N sensors get a total of N sets of data. The N sets of data are named: A1, A2, ..., A N ; Assume a sensor contains co measurement points, each with sc time windows; If N sensors are linked, the number of time windows and measurement points of each sensor are the same; Therefore, each data set contains sc*co data points; Step 4: Data processing and display; S1. Data Characterization For each sensor data, perform the following operations: Take A1 as an example 1) Select the point with the largest value in A1 as the reference point; 2) Compare other measuring points in A1 with the reference measuring point to obtain , and then enlarge the compared number to get B1; ; Where a and b are adjustment parameters, both a and b are greater than 0; OthersA2、A3、…、A N Do the same operation to get B2, B3, ..., B N ; 3) Select the time window data that is not affected by the transmitting magnetic field and has little noise from B1, and the selected data is C1; For B2, B3, ..., B N Do the above operations to obtain the characteristic data C2, C3, ..., C N ; The characteristic data C1, C2, ..., C N Arrange the N sensors in the order to obtain a three-dimensional matrix data of size N*co*sc; S2. Determine the corrosion situation The characteristic data C1, C2, ..., C N According to the arrangement of N sensors, a three-dimensional matrix of size N*co*sc is obtained, in which the smaller the characteristic data, the more serious the corrosion; There is an exponential variation between the average of the minimum values ​​of the characteristic data in different time windows and the degree of corrosion; Assume that the average of the minimum values ​​of the characteristic data in different time windows is x, and the corrosion degree is y. Substitute this value into the following formula to obtain the corrosion degree y: ; c and d are parameters obtained through experiments, e is a natural constant, c>0, d<0; S3. Data Visualization Draw a three-dimensional graph based on the obtained three-dimensional matrix data of size N*co*sc. After obtaining the feature data, put the data under the same time window in the same layer. The size of the data is represented by color. Use a specified color depth to linearly map the size of the feature data and draw a multi-layer penetration image. The darker the specified color, the more serious the corrosion. The multi-layer penetration image can display the corrosion situation of different wall thickness intervals. The expanded image is like a schematic diagram of the pipeline to be tested after slicing it layer by layer. The beneficial effects of the present invention are: The multi-layer penetration imaging detection system and method for corrosion defects under the insulation layer described in the present invention have the following advantages: 1. There is no need to remove the insulation layer of the equipment and pipeline inspection points, no need to repair the insulation layer, no need to set up scaffolding, only need to install the variable diameter detection probe and Mecanum fixed walking device on the pipeline to be tested, with high safety factor, simple procedure and short detection cycle.

[0018] 2. Improved detection accuracy from the following aspects: 1) Setting up variable diameter detection probe and Mecanum fixed walking device to assist detection improves stability and detection efficiency; 2) Changing the sensor structure to increase penetration depth, optimizing the sensor to a high penetration sensor, increasing the sensor wire diameter to 0.3-0.8mm to increase the strength of the primary magnetic field and increasing the magnetic core to enhance its penetration strength; the corrosion area can be detected to 25cm 2 Around, large area thinning defects with corrosion degree greater than 30% of the wall thickness; 3) Change the vertical magnetic field to a magnetic field parallel to the pipe being tested. By changing the direction of the magnetic field, the magnetic flux lines cut more easily on the pipe defects and increase the deformation of the magnetic flux lines. 4) The detection efficiency is improved through N sensors, and the three-dimensional position of the defect can be determined. The data can be visualized through data processing, and the wall thickness of the pipe can be penetrated in a layered manner like a CT scan, so that the state and degree of corrosion can be seen more intuitively; Through multi-layer penetration imaging technology, the data is visualized to more clearly show the defects. By utilizing the richness of the data and the algorithm of corrosion under insulation layer, the defect detection capability and detection accuracy are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a block diagram of a multi-layer penetration imaging detection system for corrosion defects under insulation layer; Figure 2 It is a flow chart of a multi-layer penetration imaging detection method for corrosion defects under the insulation layer; Figure 3 A three-dimensional diagram of the state where the Mecanum fixed walking device and the variable diameter detection probe shell are installed on the pipeline to be tested; Figure 4 A plan view of the state where the Mecanum fixed walking device and the variable diameter detection probe shell are installed on the pipeline to be tested; Figure 5 This is a stereoscopic view of the Mecanum fixed walking device and the variable diameter detection probe shell after assembly; Figure 6 A stereogram of the fixed walking gear for Mecanum; Figure 7 It is a three-dimensional diagram of a housing of a variable diameter detection sensor; Figure 8 A three-dimensional diagram of the locust bionic tensile structure; Fig. 9 A three-dimensional diagram of the locust bionic tensile structure; Fig.10 This is a cross-sectional view of the locust bionic tensile structure; Fig.11 It is a partial enlarged view of the ratchet structure; Fig.12 A perspective view of the mounting shell and wedge; Fig.13 A perspective view of the installation shell; Fig.14 is a stereogram of a wedge; Fig.15 It is a graph obtained by mapping the data of each time window to colors; Fig.16 The graph is obtained by displaying each layer of the data in each time window separately; Fig.17 This is the original curve diagram of the defect detection of the same tube as the case in the embodiment: Fig.18This is a multi-layer penetration imaging image of the corrosion defect of the same pipe as the case in the embodiment; Fig.19 This is the original curve diagram of the defect detection of the sample tube of Case 2 in the embodiment: Fig. 20 This is a multi-layer penetration imaging image of the corrosion defect of the sample tube of Case 2 in the embodiment; Fig.21 This is a multi-layer penetration imaging image of defect detection of a pipeline under the insulation layer at a petrochemical site in case 3 of the embodiment; Among them: 1-pipeline to be tested; 2-fixed connecting frame; 3-left connecting slot; 4-right connecting slot; 5-first outer mounting shell; 6-middle outer mounting shell; 7-Nth outer mounting shell; 8-first front stretching member; 9-first rear stretching member; 10-second front stretching member; 11-second rear stretching member; 12-left twist cover; 13-ratchet; 14-pin; 15-spring; 16-Mecanum wheel; 17-right twist cover; 18-wedge block. DETAILED DESCRIPTION

[0020] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings.

[0021] A multi-layer penetration imaging detection system for corrosion defects under an insulation layer, comprising a pulsed eddy current detection device, a controller, a Mecanum fixed walking device and a variable diameter detection probe shell; Pulsed eddy current testing equipment connected to the controller; The pulsed eddy current testing device includes a transmitting unit and a receiving unit; The pulsed eddy current testing equipment is provided with N sensors, where N is greater than or equal to 3; The transmitting unit is connected to a signal recognition module, and the signal recognition module is used to identify the frequency of the pulsed eddy current; The signal recognition module is connected to a circuit switching module; the circuit switching module is used for switching the circuits between N sensors; The circuit switching module is connected to the sensor probe; The sensor is a cylindrical high-penetration sensor; The cross-sectional diameter of the high-penetration sensor is 2cm-4cm, which is half of the cross-sectional diameter of the conventional sensor used for detection without removing the insulation layer. The wire diameter of the high penetration sensor is 0.3-0.8mm; A magnetic core is added inside the high-penetration sensor to increase the primary magnetic field emitted. Compared with sensors with the same parameters but without a magnetic core, the penetration strength is increased by one to three times. The magnetic core is made of manganese-zinc ferrite or nickel-zinc ferrite, with a diameter of 8-10 mm and a length of 30-60 mm; The magnetic core is added by inserting it into the coil; The scanning direction of the high-penetration sensor is perpendicular to the direction of the magnetic flux lines of the high-penetration sensor; The probe of each sensor includes an excitation coil and a detection coil; Each of the excitation coils is wirelessly connected to the transmitting unit, and each of the detection coils is connected to the receiving unit; The pulsed eddy current testing device is wirelessly connected to the data processing end; The pulsed eddy current testing device is bidirectionally wirelessly connected to the controller; N sensors are arranged on a variable diameter detection probe shell; the variable diameter detection probe shell is adapted to different diameters of the pipeline to be tested; the variable diameter detection probe shell is connected to a Mecanum fixed walking device, and the Mecanum fixed walking device shell drives the N sensors to move along the x-axis or y-axis direction on the pipeline to be tested; The controller is connected to the Mecanum fixed walking device.

[0022] Preferably, the pulsed eddy current testing equipment, the controller, and the Mecanum fixed walking device are all externally connected to a power source.

[0023] Preferably, the data processing end is connected to a data display end.

[0024] Preferably, the pulsed eddy current detection equipment shell is connected to cloud storage to save data.

[0025] Preferably, the controller is connected to a sensor signal indicator light.

[0026] Preferably, Figure 6 As shown, the Mecanum fixed walking device includes a fixed connecting frame 2 and a Mecanum wheel 16; the fixed connecting frame 2 is arc-shaped, and the two ends of the fixed connecting frame 2 are respectively provided with a left connecting groove 3 and a right connecting groove 4.

[0027] like Figure 7 As shown, preferably, the variable diameter detection probe shell includes a locust bionic stretching structure, a first outer mounting shell 5, N-2 intermediate outer mounting shells 6, and an Nth outer mounting shell 7; Take N as 3 for example; first outer mounting shell 5, middle outer mounting shell 6, third outer mounting shell 7, The outer mounting shell is sheathed with an inner mounting shell; the sensor is placed in the inner mounting shell; a wedge 18 is inserted into the bottom of the outer mounting shell, and the wedge 18 is used to complete the fitting of different pipe diameters through different arcs; The left and right ends of the top surfaces of the first outer mounting shell 5, the middle outer mounting shell 6 and the third outer mounting shell 7 are respectively provided with through holes; The locust bionic stretching structure comprises a plurality of pins 14, a first stretching group and a second stretching group; the first stretching group comprises a first front stretching member 8 and a first rear stretching member 9, and the second stretching group comprises a second front stretching member 10 and a second rear stretching member 11; the front stretching member and the rear stretching member are hinged via a drive shaft, a driving shaft outer sleeve is provided with a unidirectionally rotatable ratchet 13, the ratchet 13 is covered with a fixedly connected twist cover, the twist cover on the left is a left twist cover 12, and the twist cover on the right is a right twist cover 17, and the insertion of the pin 14 into the ratchet teeth of the ratchet can limit the rotation of the ratchet 13; The left through hole of the first outer mounting shell 5 is connected to the left connecting slot 3 via a sliding shaft, and the right through hole of the first outer mounting shell 5 is hinged to the second rear stretching member 11; the left through hole of the middle outer mounting shell 6 is hinged to the second front stretching member 10, and the right through hole of the middle outer mounting shell 6 is hinged to the first rear stretching member 9; the left through hole of the third outer mounting shell is hinged to the first front stretching member 8, and the right through hole of the third outer mounting shell is connected to the right connecting slot 4 via a sliding shaft; Pull out the pin 14, twist the left twist cover 12, and drive the left ratchet 13 to rotate, so that the angle between the first front stretching member 8 and the first rear stretching member 9 is reduced or increased; twist the right twist cover 17 to drive the right ratchet 13 to rotate, so that the angle between the second front stretching member 10 and the second rear stretching member 11 is reduced or increased; a reduced angle is suitable for thinner pipes, and an increased angle is suitable for thicker pipes.

[0028] Preferably, the controller is a single chip microcomputer.

[0029] A multi-layer penetration imaging detection method for corrosion defects under an insulation layer comprises the following steps: Step 1: Hardware Installation Calculate the diameter of the sensor based on the thickness of the insulation layer; The relationship between the sensor diameter and the insulation layer thickness is: ; Where: t ranges from 2 to 5, q refers to the thickness of the insulation layer, and p refers to the diameter of the sensor; Select the appropriate diameter sensor according to the thickness of the insulation layer; N sensors are respectively mounted on N inner mounting shells in a manner that the primary magnetic field (transmitting magnetic field) is parallel to the surface of the pipe to be tested, and then the N inner mounting shells are respectively mounted on N outer mounting shells, and the fitting of different pipe diameters is completed by replacing the wedges to change the curvature, and then the outer mounting shell with the installed sensors is connected to the locust bionic tensile structure, and the equipped variable diameter detection probe shell is connected to the Mecanum fixed walking device and is covered on the outer sheath of the pipe to be tested; The magnetic field in the traditional detection method is a vertical magnetic field. The vertical magnetic field is changed to a magnetic field parallel to the pipe being tested. When the parallel magnetic field passes through the defect position, the degree of distortion is greater, and the defect reaction in the detection result is more obvious. The detection capability is improved by changing the direction of the magnetic field.

[0030] Step 2: Data Collection The N sensors can be driven by the Mecanum fixed walking device to scan the pipeline to be tested by circumferential and axial movement along the pipeline to be tested; the controller sends a signal to the pulsed eddy current testing device, uses a fixed pulsed eddy current signal to transmit to the transmitting probe of the sensor, and the transmitting unit of the pulsed eddy current testing device sends an excitation square wave; the excitation coil of the probe of the pulsed eddy current sensor receives the excitation square wave, and the excitation coil inputting the excitation square wave signal forms an electromagnetic field in the corrosion area of ​​the pipe to be monitored; the detection coil of the probe of the pulsed eddy current sensor receives the magnetic induction signal, and transmits the magnetic induction signal back to the receiving unit of the pulsed eddy current testing device; Improve the detection capability by changing the direction of the magnetic field, from vertical to parallel magnetic field, and from scanning in the Z direction to scanning in the Y direction; Step 3: Data Preprocessing The data collected by the same sensor on the pipe coating is divided into N sets of data. N sensors get a total of N sets of data. The N sets of data are named: A1, A2, ..., A N ; Assume a sensor contains co measurement points, each with sc time windows; If N sensors are linked, the number of time windows and measurement points of each sensor are the same; Therefore, each data set contains sc*co data points; Step 4: Data processing and display; S1. Data Characterization For each sensor data, perform the following operations: Take A1 as an example 1) Select the measuring point with the largest value in A1 as the reference point; 2) Compare other measuring points in A1 with the reference measuring point to obtain , and then enlarge the compared number to get B1; ; Where a and b are adjustment parameters, both a and b are greater than 0; OthersA2、A3、…、A N Do the same operation to get B2, B3, ..., B N ; 3) Select the time window data that is not affected by the transmitting magnetic field and has little noise from B1, and the selected data is C1; For B2, B3, ..., B N Do the above operations to obtain the characteristic data C2, C3, ..., C N ; The characteristic data C1, C2, ..., C N Arrange the N sensors in the order to obtain a three-dimensional matrix data of size N*co*sc; S2. Determine the corrosion situation The characteristic data C1, C2, ..., C N According to the arrangement of N sensors, a three-dimensional matrix of size N*co*sc is obtained, in which the smaller the characteristic data, the more serious the corrosion; There is an exponential variation between the average of the minimum values ​​of the characteristic data in different time windows and the degree of corrosion; Assume that the average of the minimum values ​​of the characteristic data in different time windows is x, and the degree of corrosion is y. This value can be substituted into the following formula to obtain the degree of corrosion y: ; c and d are parameters obtained through experiments, e is a natural constant, c>0, d<0; S3. Data Visualization Draw a three-dimensional graph based on the obtained three-dimensional matrix data of size N*co*sc. After obtaining the feature data, put the data under the same time window in the same layer. The size of the data is represented by color. Use a specified color depth to linearly map the size of the feature data and draw a multi-layer penetration image. The darker the specified color, the more serious the corrosion. The multi-layer penetration image can display the corrosion situation of different wall thickness intervals. The expanded and placed image will be a schematic diagram of the pipeline to be tested after slicing it layer by layer; Fig.16 shown.

[0031] principle: The principle of the system is mainly a multi-layer penetration imaging detection method for corrosion under the insulation layer. It uses a fixed pulse eddy current signal to be transmitted to the transmitting probe of the high-penetration sensor. The three sensors can work alternately to perform detection at different positions. When the three high-penetration sensors move on the insulation layer, the equipment transmits pulse signals through the high-penetration sensors and receives the induction signals generated on the metal. It tests three groups of sensor signals at the same time and finally splices the three groups of signals into a corrosion condition map of the metal surface.

[0032] The pulse signal is captured by the single chip microcomputer, and the speed of N (for example, three) sensors is switched according to the required pulse signal frequency. According to the working frequency of the three sensors, there is a working indicator light. After each work is completed and the signal is stopped, the switching and operation of the three sensors are stopped.

[0033] The main function of the outer mounting shell is to load coils of different sizes and connect the stretching structure at the same time; a 54mm diameter and 40mm deep cavity is machined inside the outer mounting shell for loading, and the two cavities opened at the left and right ends of the upper part are used to install the sliding shaft through interference fit and keyway to complete the forward and backward movement; The inner mounting shell consists of two parts, left and right, and its main function is to protect the coil, improve assembly accuracy, and ensure lift-off. It can hold coils with an outer diameter of less than 47mm; The wedge can be fitted to different pipe diameters by changing the arc. It is cheap to process and easy to replace, which can improve the efficiency of the inspection process and reduce equipment costs. The locust bionic stretching structure is designed based on the high flexibility and controllability of the locust's hind legs. It mainly consists of a front stretching member, a rear stretching member, a ratchet, a drive shaft, and a twist cover. The front stretching member and the rear stretching member are optimized based on the physiological structure of the locust and the physical structure of the generated processing, so that it can be rotated and adjusted by 150°. The angle control is mainly completed by the ratchet and the spring shaft. The ratchet is a partial intermittent mechanism with an operating range of 30° to 150°, and the step-by-step adjustment is completed by the positioning of the spring shaft.

[0034] In order to achieve the fixation and movement of the equipment on the pipe, and considering the poor movement conditions on the surface of the pipe, this equipment uses a Mecanum wheel as a motion carrier. The Mecanum wheel can move in the x-axis and y-axis to achieve the required range of motion in the pipeline inspection process. The Mecanum wheel can cushion shock under certain conditions due to the special structure and material of the wheel, and it can move in multiple directions to facilitate circumferential movement. Its fixation is mainly completed by the multi-directional support and extrusion of the wheel.

[0035] Multi-layer penetration imaging technology is used to analyze whether there is external corrosion in the pipeline under the insulation layer. If there is external corrosion, multi-layer penetration imaging can intuitively show whether there is a stable defect signal in the four layers of data after the second turning point of the original curve.

[0036] Application Cases Case 1:

[0037] Table 1 Defects of sample pipes model Material Wall thickness defect Defect width Defect depth Surface corrosion Carbon Steel 19mm Thinning 10mm 10mm When the insulation layer is 5cm thick, the high penetration sensor used is 1.5CM in diameter and 0.5mm in wire diameter. Fig.18 The corrosion morphology of different wall thickness ranges can be seen in the figure, and the corrosion depth and corrosion ratio can be calculated. The corroded areas will turn yellow-red, and the green parts are uncorroded areas. There is a completely green uncorroded layer, which means that corrosion has not yet occurred at this wall thickness.

[0038] from Fig.17From the original curve of Case 1, we can see that the data before the first turning point (1-15 layers) represent the magnetic saturation platform, the middle part (16-20 layers) represent the data significantly affected by the insulation layer, and the data after the second turning point (after the 21st layer) represent the effective data of the pipeline detection under the insulation layer. Fig.18 The figure shows that the color changes from layer 19, and the defect signal stabilizes from layer 21, indicating that the signal contacts the thinning area. Surface corrosion affects all available time windows, so all layers after layer 21 show yellow-red in the corroded part.

[0039] Case 2: Table 2 Defects of surface corrosion samples model Material Wall thickness defect Defect width Defect depth Surface corrosion Carbon Steel 12mm Thinning 12mm 2-3mm The test was carried out when the thickness of the insulation layer was 3cm. The high penetration sensor used had a diameter of 1CM and a wire diameter of 0.1mm. Fig. 20 The corrosion morphology of different wall thickness ranges can be seen in the figure, and the corrosion depth and corrosion ratio can be calculated. The corroded areas will turn yellow-red, and the green parts are uncorroded areas. There are completely green corrosion areas, which means that corrosion has not yet occurred at this wall thickness.

[0040] from Fig.19 From the original curve of Case 2, we can see that the data before the first turning point in the original curve (1-4 layers) represent the magnetic saturation platform, the middle part (5-13 layers) represent the data that are obviously affected by the insulation layer, and the data after the second turning point (after 14 layers) represent the effective data of the pipeline detection under the insulation layer.

[0041] Fig. 20 The defect signal is stable starting from layer 13, which means the signal has reached the thinning area. Surface corrosion affects all available time windows, so all layers after layer 13 show yellow-red in the corroded part.

[0042] Case 3: On-site testing at a petrochemical company The test was carried out when the thickness of the insulation layer was 4cm. The high penetration sensor used had a diameter of 1CM and a wire diameter of 0.1mm. Fig.21 The corrosion morphology of different wall thickness ranges can be seen in the figure, and the corrosion depth and corrosion ratio can be calculated. The corroded areas will turn yellow-red, and the green parts are uncorroded areas. There are completely green corrosion areas, which means that corrosion has not yet occurred at this wall thickness.

[0043] Fig.21 The defect signal is stable starting from layer 17, which means the signal has reached the thinning area. Surface corrosion affects all available time windows, so all layers after layer 17 show yellow-red in the corroded part.

[0044] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multi-layer penetration imaging detection system for corrosion defects under insulation layer, characterized in that: It includes pulsed eddy current testing equipment, a controller, a Mecanum fixed walking device and a variable diameter testing probe shell; Pulse eddy current testing equipment connected to the controller; The pulsed eddy current testing device includes a transmitting unit and a receiving unit; The pulsed eddy current testing equipment is provided with N sensors, where N is greater than or equal to 3; The transmitting unit is connected to a signal recognition module, and the signal recognition module is used to identify the frequency of the pulsed eddy current; The signal recognition module is connected to a circuit switching module; the circuit switching module is used for switching the circuits between N sensors; The circuit switching module is connected to the sensor probe; The sensor is a cylindrical high-penetration sensor; The cross-sectional diameter of the high penetration sensor is 2cm-4cm; The wire diameter of the high penetration sensor is 0.3-0.8mm; A magnetic core is added inside the high penetration sensor; The magnetic core is made of manganese-zinc ferrite or nickel-zinc ferrite, with a diameter of 8-10 mm and a length of 30-60 mm; The magnetic core is added by inserting it into the coil; The scanning direction of the high-penetration sensor detection direction is perpendicular to the direction of the magnetic flux lines of the high-penetration sensor; The probe of each sensor includes an excitation coil and a detection coil; Each of the excitation coils is wirelessly connected to the transmitting unit, and each of the detection coils is connected to the receiving unit; The pulsed eddy current testing device is wirelessly connected to a data processing terminal; The pulsed eddy current testing device is bidirectionally wirelessly connected to the controller; N sensors are arranged on a variable diameter detection probe shell; the variable diameter detection probe shell is adapted to different diameters of the pipeline to be tested; the variable diameter detection probe shell is connected to a Mecanum fixed walking device, and the Mecanum fixed walking device shell drives the N sensors to move along the x-axis or y-axis direction on the pipeline to be tested; The controller is connected to the Mecanum fixed walking device.

2. A multi-layer penetration imaging detection system for corrosion defects under insulation layer according to claim 1, characterized in that: The pulsed eddy current testing equipment, the controller, and the Mecanum fixed walking device are all externally connected to a power source.

3. The multi-layer penetration imaging detection system for corrosion defects under the insulation layer according to claim 2 is characterized in that: The data processing end is connected to the data display end.

4. A multi-layer penetration imaging detection system for corrosion defects under insulation layer according to claim 3, characterized in that: The pulsed eddy current detection equipment shell is connected to cloud storage to save data.

5. A multi-layer penetration imaging detection system for corrosion defects under insulation layer according to claim 4, characterized in that: The controller is connected with a sensor signal indicator light.

6. A multi-layer penetration imaging detection system for corrosion defects under insulation layer according to claim 5, characterized in that: The Mecanum fixed walking device comprises a fixed connecting frame (2) and a Mecanum wheel (16); the fixed connecting frame (2) is arc-shaped, and a left connecting groove (3) and a right connecting groove (4) are respectively provided at two ends of the fixed connecting frame (2).

7. A multi-layer penetration imaging detection system for corrosion defects under insulation layer according to claim 6, characterized in that: The variable-diameter detection probe shell comprises a locust bionic stretching structure, a first outer mounting shell (5), two intermediate outer mounting shells (6) less than N, and an Nth outer mounting shell (7); The outer mounting shell is sheathed with an inner mounting shell; a sensor is placed in the inner mounting shell; a wedge (18) is plugged into the bottom of the outer mounting shell, and the wedge (18) is used to fit different pipe diameters through different arcs; The left and right ends of the top surfaces of the first outer mounting shell (5), the middle outer mounting shell (6) and the third outer mounting shell are respectively provided with through holes; The locust bionic stretching structure comprises a plurality of pins (14), a first stretching group and a second stretching group; the first stretching group comprises a first front stretching member (8) and a first rear stretching member (9), and the second stretching group comprises a second front stretching member (10) and a second rear stretching member (11); the front stretching member and the rear stretching member are hingedly connected via a drive shaft, a unidirectionally rotatable ratchet (13) is disposed on the outer sleeve of the drive shaft, the ratchet (13) is covered with a fixedly connected twist cover, the twist cover on the left side is a left twist cover (12), and the twist cover on the right side is a right twist cover (17), and the rotation of the ratchet (13) can be restricted by inserting the pin (14) into the ratchet teeth of the ratchet; The left through hole of the first outer mounting shell (5) is connected to the left connecting groove (3) via a sliding shaft, and the right through hole of the first outer mounting shell (5) is hingedly connected to the second rear stretching member (11); the left through hole of the middle outer mounting shell (6) is hingedly connected to the second front stretching member (10), and the right through hole of the middle outer mounting shell (6) is hingedly connected to the first rear stretching member (9); the left through hole of the third outer mounting shell is hingedly connected to the first front stretching member (8), and the right through hole of the third outer mounting shell is connected to the right connecting groove (4) via a sliding shaft; The pin (14) is pulled out and the left twist cover (12) is twisted to drive the left ratchet (13) to rotate, thereby reducing or increasing the angle between the first front stretching member (8) and the first rear stretching member (9); the right twist cover (17) is twisted to drive the right ratchet (13) to rotate, thereby reducing or increasing the angle between the second front stretching member (10) and the second rear stretching member (11); when the angle is reduced to 15°, the minimum detection range is 6 cm, which is suitable for pipes with a diameter of 50 mm; when the angle is increased to 60°, the maximum increased detection range is 18 cm, which is suitable for pipes with a diameter greater than 600 mm.

8. A multi-layer penetration imaging detection method for corrosion defects under insulation layer, characterized in that: The following steps are involved: Step 1: Hardware Installation Calculate the diameter of the sensor based on the thickness of the insulation layer; The relationship between the sensor diameter and the insulation layer thickness is: ; Where: t ranges from 2 to 5, q refers to the thickness of the insulation layer, and p refers to the diameter of the sensor; Select the appropriate diameter sensor according to the thickness of the insulation layer; N sensors are respectively mounted on N inner mounting shells in a manner that the magnetic field emitted at one time is parallel to the surface of the pipe to be tested, and then the N inner mounting shells are respectively mounted on N outer mounting shells, and the fitting of different pipe diameters is completed by replacing the wedges to change the curvature, and then the outer mounting shell with the installed sensors is connected to the locust bionic stretching structure, and the equipped variable diameter detection probe shell is connected to the Mecanum fixed walking device and is covered on the outer coating of the pipe to be tested; Step 2: Data Collection The N sensors are driven by the Mecanum fixed walking device to scan the pipeline to be tested by circumferential and axial movement of the pipeline to be tested; the controller sends a signal to the pulsed eddy current testing device, and the transmitting unit of the pulsed eddy current testing device using the fixed pulsed eddy current signal sends an excitation square wave, the excitation coil of the probe of the sensor receives the excitation square wave, the excitation coil inputting the excitation square wave signal forms an electromagnetic field in the corrosion area of ​​the pipe to be monitored, and the detection coil of the probe of the pulsed eddy current sensor receives the magnetic induction signal and transmits the magnetic induction signal back to the receiving unit of the pulsed eddy current testing device; Step 3: Data Preprocessing The data collected by the same sensor on the pipe coating is divided into N sets of data. N sensors get a total of N sets of data. The N sets of data are named: A1, A2, ..., A N ; Assume a sensor contains co measurement points, each with sc time windows; If N sensors are linked, the number of time windows and measurement points of each sensor are the same; Therefore, each data set contains sc*co data points; Step 4: Data processing and display S1. Data Characterization For each sensor data, perform the following operations: Take A1 as an example 1) Select the point with the largest value in A1 as the reference point; 2) Compare other measuring points in A1 with the reference measuring point to obtain , and then enlarge the compared number to get B1; ; Where a and b are adjustment parameters, both a and b are greater than 0; OthersA2、A3、…、A N Do the same operation to get B2, B3, ..., B N ; 3) Select the time window data that is not affected by the transmitting magnetic field and has little noise from B1, and the selected data is C1; For B2, B3, ..., B N Do the above operations to obtain the characteristic data C2, C3, ..., C N ; The characteristic data C1, C2, ..., C N Arrange N sensors in a certain order to obtain a three-dimensional matrix data of size N*co*sc; S2. Determine the corrosion situation The characteristic data C1, C2, ..., C N According to the arrangement of N sensors, a three-dimensional matrix of size N*co*sc is obtained, in which the smaller the characteristic data, the more serious the corrosion; There is an exponential variation between the average of the minimum values ​​of the characteristic data in different time windows and the degree of corrosion; Assume that the average of the minimum values ​​of the characteristic data in different time windows is x, and the corrosion degree is y. Substitute this value into the following formula to obtain the corrosion degree y: ; c and d are parameters obtained through experiments, e is a natural constant, c>0, d<0; S3. Data Visualization Draw a three-dimensional graph based on the obtained three-dimensional matrix data of size N*co*sc. After obtaining the feature data, put the data under the same time window in the same layer. The size of the data is represented by color. Use a specified color depth to linearly map the size of the feature data and draw a multi-layer penetration image. The darker the specified color, the more serious the corrosion. The multi-layer penetration image can display the corrosion conditions in different wall thickness ranges. The expanded and placed image is like a schematic diagram of the pipeline to be tested after slicing it layer by layer.

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