A pipe wall thickness detection system and method with a thermal insulation layer

Abstract

The application discloses a pipeline wall thickness detection system and method with a thermal insulation layer. The pipeline wall thickness detection system with the thermal insulation layer comprises a detection module, a main control module, an upper computer and a power supply module. The application provides a pipeline wall thickness detection method based on the system, which can realize quantitative and nondestructive detection of the pipeline wall thickness under the thermal insulation layer, meet the requirement of rapid scanning of the pipeline with the thermal insulation layer in service, and realize integrity management of the whole life cycle of the pressure pipeline.

Description

Technical Field

[0001] This invention relates to the field of nondestructive testing technology, specifically to a pulsed eddy current nondestructive testing technology, and more particularly to a system and method for detecting the wall thickness of a pipe containing an insulation layer using pulsed eddy current nondestructive testing technology. Background Technology

[0002] Pipelines are widely used in the petrochemical industry for transporting goods. To reduce energy loss from high-temperature media and prevent direct contact between the pipeline and the outside environment, an insulation layer is often added to the outside of the pipeline. Simultaneously, a metal protective layer of a certain thickness is added over the insulation layer to protect it from damage by the external environment. Harsh working environments, improper installation of the protective layer, or natural conditions can easily damage the metal protective layer. Furthermore, the highly absorbent nature of the insulation material exacerbates the erosion of the pipeline's outer wall by rainwater and other natural media. When corrosion becomes severe enough, flammable and explosive substances transported inside the pipeline will leak, often leading to serious environmental pollution, personal injury, and property damage.

[0003] Therefore, effective monitoring and protection against corrosion beneath the insulation layer, along with life-cycle integrity management, are crucial measures to ensure extended service life of pipeline facilities. Non-destructive testing (NDT) of coated pipelines often requires removing the outer coating first, then performing conventional NDT methods, and finally re-wrapping the outer coating. This coating removal process significantly extends testing time and increases costs, especially for in-service pressure pipelines, which must be shut down before testing, resulting in even greater losses for the company. Therefore, researching NDT techniques for detecting internal pipeline corrosion without removing the outer coating is of significant practical importance.

[0004] Pulsed Eddy Current Testing (PECT) is a non-contact testing method based on the law of electromagnetic induction, applicable only to conductive materials. PECT detects defects by applying a primary magnetic field generated by an excitation coil to the test specimen. The eddy currents induced in the specimen generate a secondary magnetic field, which is then received by a Hall sensor, allowing analysis of the defect information. PECT uses a pulsed square wave excitation signal instead of the sinusoidal excitation used in traditional single-frequency eddy current technology, and the electromagnetic field signal picked up by the Hall sensor is also a pulsed signal. The advantages of PECT are mainly twofold: First, based on the Fourier transform method, the pulsed signal in PECT contains a rich frequency range, allowing it to penetrate thin metal protective layers and thick non-metallic insulation layers. This allows low-frequency signals to penetrate the test specimen, enabling the detection of pipe corrosion through the coating layer. Second, the special design of the PECT probe's excitation coil results in a strong magnetic field, allowing signal detection even at relatively high lift-off heights, and a large magnetic field coverage area, enabling the detection of large areas of metal corrosion. Therefore, pulsed eddy current testing technology has unique advantages and extremely broad application prospects in the defect detection of pressure pipelines with cladding layers.

[0005] Chen Xingle et al. from Beijing University of Aeronautics and Astronautics proposed a pulsed eddy current detection method for wall thickness corrosion of ferromagnetic pipes with coating. Based on the time-domain analytical solution of the pulsed eddy current detection model for ferromagnetic pipes, the method uses the induced voltage measurement curve to invert the parameters of the inspected ferromagnetic pipe, and then selects the wall thickness inversion result corresponding to the reference point as the reference value to calculate the change in wall thickness of the detection point relative to the reference point.

[0006] Han Yang et al. from Suzhou Thermal Power Research Institute Co., Ltd. proposed a pulsed eddy current detection method suitable for pipes with cladding. The method uses a host to generate a pulsed square wave signal and pass a pulsed current into the excitation coil, causing eddy currents to be generated in the pipe under test. The data acquisition card collects the time-domain induced voltage value generated by the detection coil due to the change of magnetic field. The host processes and analyzes the time-domain induced voltage value and displays it.

[0007] While the two methods mentioned above have solved the problem of quantitative detection of pipe wall thickness with coating, they require the probe to be fixed in position during the detection process to prevent movement and vibration. The probe can only be moved to the next position after the wall thickness detection at one location is completed. This detection method is not conducive to rapid scanning of wall thickness in long-distance pipelines and complex pipelines. Summary of the Invention

[0008] This invention proposes a pipe wall thickness detection system and method with insulation layer, which solves the technical problem of rapid wall thickness detection in long-distance pipelines and complex pipelines, which is limited by traditional technology. It can realize quantitative non-destructive detection of pipe wall thickness under insulation layer, meet the needs of rapid inspection of in-service pipelines with insulation layer, and realize integrity management of pressure pipelines throughout their entire life cycle.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A pipe wall thickness detection system with insulation layer, characterized in that it includes the following functional modules:

[0011] The detection module has a detection probe, which includes an excitation coil that generates an alternating magnetic field through a pulse excitation signal, and a Hall sensor that receives changes in the magnetic field and generates an induced voltage.

[0012] The main control module generates pulse excitation signals with adjustable frequency and duty cycle; acquires the induced voltage signals from the Hall sensor; and sends the acquired data to the host computer for backend processing.

[0013] The host computer receives data transmitted from the main control module; processes the induced voltage signal, extracts feature signals, and performs inverse calculation to solve for the pipe wall thickness; and completes data visualization and storage.

[0014] The power supply module provides power to the detection probe, main control module, and host computer.

[0015] The detection probe has a cylindrical outer shell frame; the cylindrical outer shell frame is filled with an iron core; the cross-sectional shape of the iron core along the central axis of the cylinder is a hollow "I" shape; the Hall sensor is set at the bottom of the hollow space of the iron core, and the remaining part of the hollow space of the iron core is filled with thermally conductive material; the excitation coil is wound around the gaps on both sides of the "I" shape of the iron core.

[0016] More preferably, the thermally conductive material is epoxy resin.

[0017] More preferably, the detection module has a plurality of detection probes, and the plurality of detection probes form an array.

[0018] More preferably, each of the detection probes is built into a probe holder, and adjacent probe holders are hinged together by connecting structures at their bottom sides to form the array.

[0019] More preferably, the hinged connection structure is a detachable connection structure.

[0020] More preferably, the system further includes a position measurement module for measuring and recording the position information of the pipe wall where the system is located.

[0021] This invention also provides a method for detecting the wall thickness of pipes containing insulation layers using the above-described system, characterized by comprising the following steps:

[0022] S1. Place the detection probe in the area to be inspected on the pipe wall containing the insulation layer;

[0023] S2. The main control module generates a continuous pulse excitation signal and inputs it into the excitation coil of the detection probe;

[0024] S3. A coupled electromagnetic field is formed in the space between the pipe wall under test and the detection probe. The Hall sensor is used to convert the detected magnetic induction intensity signal into a corresponding voltage signal.

[0025] S4. Input the voltage signal from S3 to the back-end filtering and amplification unit to filter out noise voltage signals in the voltage signal and amplify the signal by a certain factor.

[0026] S5. The pulse voltage signal obtained after filtering and amplification in S4 is acquired by AD, and the amplitude of the pulse voltage signal is extracted.

[0027] S6. The thinning of the pipe wall thickness is inverted by the change in the amplitude of the pulse voltage signal.

[0028] Further preferably, the method further includes S0, establishing the relationship between the pulse voltage signal amplitude and the pipe wall thickness, specifically including,

[0029] A pipe wall sample of the same material as the pipe wall to be tested is selected, and n experiments are set up. In the i-th experiment (i=1,2,…,n), the sample is the pipe wall thickness reduced by Δd_i, and the change in pulse voltage signal amplitude Δu_i is measured. The pipe wall thickness-amplitude equation Δu_i=a*Δd_i+b is obtained by linear fitting with Δd_i as the abscissa and Δu_i as the ordinate, where a and b are constant coefficients determined by linear fitting.

[0030] At this time, in step S6, the change in the amplitude of the measured pulse voltage signal is Δu_0. Substituting Δu_0 into the pipe wall thickness-amplitude equation, the corresponding pipe wall thickness d_0 is obtained.

[0031] More preferably, the pulse voltage signal is a differential peak signal with the basic pipe wall thickness as a reference signal.

[0032] Compared with existing technologies, this invention provides a pipe wall thickness detection system and method with insulation layer, which solves the technical problem of rapid wall thickness detection in long-distance pipelines and complex pipelines that is limited by traditional technologies. It can realize quantitative non-destructive detection of pipe wall thickness under insulation layer, meet the needs of rapid inspection of in-service pipelines with insulation layer, and realize integrity management of pressure pipelines throughout their entire life cycle. Attached Figure Description

[0033] Figure 1 These are simulated on-site inspection photos of the detection system of this invention;

[0034] Figure 2 This is a flowchart of the detection block of the detection system of the present invention;

[0035] Figure 3 This is a schematic diagram of the structure of the detection probe array of the detection system of the present invention;

[0036] Figure 4 This is a schematic diagram of the detection probe of the present invention;

[0037] Figure 5 This is a schematic diagram of the finite element model optimized for use in this invention;

[0038] Figure 6 This is a schematic diagram of the original detection signal results of the present invention;

[0039] Figure 7 This is a schematic diagram of the differential peak signal of the present invention;

[0040] Figure 8 This is a graph showing the linear fitting relationship between the differential peak value and the pipe wall thickness in this invention.

[0041] Figure 9 This is a graph showing the relationship between the number of coil turns and the differential peak value of the present invention.

[0042] Figure 10 This is a graph showing the relationship between the inner diameter of the coil and the differential peak value of the present invention.

[0043] Figure 11 This is a schematic diagram illustrating the optimization of the iron core thickness according to the present invention;

[0044] Figure 12 This is a schematic diagram illustrating the optimized core height of the present invention;

[0045] Figure 13 This is a schematic diagram of the linear fitting of the 50mm metal plate thickness and voltage peak value in this invention;

[0046] Figure 14 This is a schematic diagram illustrating the real-time display of detection results by the host computer software of this invention. Detailed Implementation

[0047] like Figure 1-2 As shown, the pipe wall thickness detection system with insulation layer of this invention includes the following functional modules: Detection module 1, which has a detection probe, including an excitation coil that generates an alternating magnetic field through a pulse excitation signal, and a Hall sensor that receives changes in the magnetic field and generates an induced voltage; Integrated circuit box 2, which integrates a main control module and a power supply module. The main control module generates a pulse excitation signal with adjustable frequency and duty cycle, collects the induced voltage signal from the Hall sensor, and sends the collected data to a host computer for backend processing. The power supply module provides power to other modules and devices; Host computer 3, which receives the data transmitted by the main control module, processes the induced voltage signal, extracts feature signals, realizes the inverse calculation of pipe wall thickness, and completes data visualization and storage. In addition, an acquisition module (which can be set in integrated circuit box 2) can be set between the main control module and the detection module. The acquisition module can include a filtering and amplification unit to filter out noise voltage signals in the voltage signal and amplify the signal by a certain factor. At the same time, in order to measure and record the detection position in real time during movement, this invention also configures a position measurement module 4 for the detection system. The position measurement module is preferably a rotary encoder.

[0048] To quickly and comprehensively inspect pipe wall thickness, multiple detection probes 5 are arranged in an array. The probe holder 6 needs to be suitable for both flat plate inspection and pipe inspection. Therefore, an array probe holder for pipe wall thickness inspection with insulation is proposed, such as... Figure 3 As shown, each detection probe 5 is built into a probe holder 6, and adjacent probe holders 6 are hinged together by connecting structures 7 on both sides at the bottom to form an array. Multiple probe holders 6 can be bent by hinges to perfectly fit various surfaces of pipes or plates, meeting the needs of array detection probe movement detection. Figure 3 The diagram shows an array formed by four sets of detection probes 5 and probe clamps 6. The hinged connection structure 7 is detachable, allowing the number of detection probes 5 and probe clamps 6 to be adjusted according to the curvature radius and specific dimensions of the pipe wall to achieve a better fit. The probe clamps 6 at both ends are also connected to handles 8 to facilitate movement of the array of detection probes.

[0049] To facilitate movement, the detection probe should be as small as possible while meeting measurement accuracy requirements, such as... Figure 4 As shown, the detection probe 5 specially designed in this invention has a cylindrical outer shell frame 5-1; the cylindrical outer shell frame 5-1 is filled with an iron core 5-2; the cross-sectional view of the iron core 5-2 along the central axis 5-3 of the cylinder (i.e. Figure 4The cross-sectional view of the iron core (5-2) is a hollow "I" shape; a Hall sensor 5-4 is installed at the bottom of the hollow space of the iron core, and the remaining part of the hollow space of the iron core is filled with thermally conductive material 5-5; the excitation coil 5-6 is wound around the gaps on both sides of the "I" shape of the iron core 5-2. The thermally conductive material 5-5 of this invention is preferably an epoxy resin material with good thermal conductivity to encapsulate the detection probe.

[0050] The dimensions of each structural component in the detection probe 5 of the "I"-shaped iron core provided by this invention are as follows: Figure 4 As shown, the "I"-shaped iron core 5-2 has an inner radius of [missing information]. r 1 The outer radius is R The height is H 1 Hall sensor 5-4 is located at the bottom center of detection probe 5; excitation coil 5-6 is uniformly wound with an inner radius of [missing information]. r The outer radius is R The height is H c .

[0051] In eddy current testing, when the ratio of the pipe radius to the coil radius is large, the pipe problem is often approximated as a flat plate to facilitate simulation and solution. This pipe model can be simplified to a three-layer flat plate structure (e.g., Figure 5 As shown in the figure, the three layers from top to bottom are the protective layer 9-1, the insulation layer 9-2, and the pipe wall 9-3. A 2D finite element model of the pipe wall thickness with insulation layer was established.

[0052] Research has shown that by selecting an appropriate excitation frequency and ensuring that the skin depth of the eddy current is greater than the wall thickness of the high-strength steel pipe, changing the pipe wall thickness can yield a distribution diagram of the detection signal versus the pipe wall thickness, as shown in the figure. Figure 6 As shown ( Figure 6 The wall thickness corresponding to each line in the middle and Figure 7 (The order from left to right is exactly the opposite).

[0053] Using an electromagnetic signal with a wall thickness of 9.0 mm as a reference signal (assuming no pipe wall corrosion), the electromagnetic signals for different pipe wall thicknesses are differentially analyzed with the reference signal to obtain a graph showing the relationship between the differential signal and the pipe wall thickness. Figure 7 As shown.

[0054] Depend on Figure 7 It can be seen that the differential signal gradually decreases with increasing pipe wall thickness. The peak value of the differential signal is extracted and fitted with the pipe wall thickness; the resulting fitting relationship is as follows: Figure 8 As shown.

[0055] from Figure 8It can be seen that the differential peak value and the pipe wall thickness exhibit a good linear relationship. Based on this, the linear relationship between the peak value of the differential voltage of the detection signal and the pipe wall thickness at different lift-up heights can be calibrated according to this linear law. A fitting formula for the differential peak value of the detection signal and the wall thickness at a certain lift-up height can be obtained. Then, based on this fitting formula, an inverse solution can be performed to achieve quantitative detection of the pipe wall thickness.

[0056] To improve the performance of the detection probe in detecting pipe wall thickness, and address the issue of small differential peak values, optimization of the probe can be considered. During optimization, the key performance indicator to consider is the amplitude B of the differential signal. z This improves the sensitivity of the differential signal to changes in pipe wall thickness. The excitation coil process needs to consider four factors, namely the coil inner diameter... r outer diameter of the coil R Coil height H c Number of winding turns N In the optimized scheme of this invention, the parameters considered are the inner diameter of the coil, the height of the coil, and the number of turns. After these three parameters are determined, the outer diameter of the coil can be obtained after the winding process is completed. Qualitative analysis of the interaction of the three parameters—the inner diameter of the coil, the height of the coil, and the number of turns—was conducted at two levels, as shown in Table 1.

[0057]

[0058] Based on the type and level of the factors to be investigated, and considering the interaction between the three factors, the sum of the degrees of freedom is: 3×(2-1) + 3×(2-1)×(2-1) = 6. The experiment is arranged according to the L8(27) orthogonal array, as shown in Table 2.

[0059] Analysis of the experimental results in Table 2 shows that the number of coil turns has the greatest impact on the differential peak value, followed by the coil inner diameter and coil height. Based on the degree of influence of each parameter on the probe's differential peak value, optimization experiments were designed accordingly.

[0060]

[0061] Based on the existing design optimization logic of large probes, namely the results of orthogonal experiments, the number of coil turns that has the greatest impact on the probe's detection performance is optimized first.

[0062] As shown in Table 2.1 and Figure 9 As shown, the rate of increase of differential peak value slows down after the number of coil turns exceeds 600; taking into account the need for differential peak value, probe weight reduction and heat reduction, the number of coil turns is set to 600.

[0063] The simulation models under different coil inner diameters are shown in Table 2.2;

[0064]

[0065]

[0066] From the relationship between coil inner diameter and differential peak value Figure 10 The results show that the differential peak value obtained after coil simulation with a coil inner diameter of 14mm reached its maximum, and this set of coil parameters is the optimal parameter obtained in this optimization.

[0067] Simultaneously, an iron core is introduced to strengthen the magnetic field, thereby increasing the differential peak value. The height of the iron core... H 1 and thickness (i.e.) r - r 1 Optimization was performed by keeping the core height constant and varying the core thickness between 2mm and 10mm, while considering both the differential peak value and the core weight. A final core thickness of 5mm was then determined. Alternatively, keeping the core thickness at 5mm, the core height was varied between 47mm and 63mm, and again, considering both the differential peak value and the core weight, a final core thickness of 55mm was determined. This yielded the optimized core parameters, as shown below. Figure 11-12 As shown.

[0068] The optimal parameters of the detection probe obtained through optimization are shown in Table 3.

[0069]

[0070] The optimal parameters for the detection probe have been given. Based on different application scenarios and working conditions of the device, a range of relatively good probe parameters is given, as shown in Table 4. The other parameters are not the optimal parameters in the optimization, but they still have relatively good performance and can meet the needs of various situations.

[0071]

[0072] If the lift-off height of the excitation signal and the probe remains constant, the differential peak value of the detection signal obtained by the pulse eddy current detection system exhibits a linear distribution relationship with the pipe wall thickness, as shown in equation (1).

[0073] Δu=aΔd+b(1)

[0074] Where Δu is the differential peak value of the pipeline detection voltage under pulse excitation, Δd is the wall thickness reduction of the pipeline under test, b is the intercept of the fitting relationship between the differential peak value of the detection signal and the wall thickness reduction at a certain lift height, and a is the slope of the fitting relationship between the differential peak value of the detection signal and the wall thickness reduction at a certain lift height.

[0075] The pulse eddy current detection system obtains the differential peak value of the detection signal, which is then substituted into formula (1) to solve for the wall thickness reduction of the tested pipe. The difference between this value and the calibrated pipe wall thickness is used to obtain the remaining pipe wall thickness.

[0076] Based on the above principles, the present invention employs the aforementioned system for detecting the wall thickness of pipes containing insulation layers, specifically including the following steps:

[0077] S1. Place the detection probe in the area to be inspected on the pipe wall containing the insulation layer;

[0078] S2. The main control module generates a continuous pulse excitation signal and inputs it into the excitation coil of the detection probe;

[0079] S3. A coupled electromagnetic field is formed in the space between the pipe wall under test and the detection probe. The Hall sensor is used to convert the detected magnetic induction intensity signal into a corresponding voltage signal.

[0080] S4. Input the voltage signal from S3 to the back-end filtering and amplification unit to filter out noise voltage signals in the voltage signal and amplify the signal by a certain factor.

[0081] S5. The pulse voltage signal obtained after filtering and amplification in S4 is acquired by AD, and the amplitude of the pulse voltage signal is extracted.

[0082] S6. The thinning of the pipe wall thickness is inverted by the change in the amplitude of the pulse voltage signal.

[0083] To establish the relationship between the pulse voltage signal amplitude and the pipe wall thickness, it also includes S0, specifically including...

[0084] A pipe wall sample of the same material as the pipe wall to be tested is selected, and n experiments are set up. In the i-th experiment (i=1,2,…,n), the sample is the pipe wall thickness reduced by Δd_i, and the change in pulse voltage signal amplitude Δu_i is measured. The pipe wall thickness-amplitude equation Δu_i=a*Δd_i+b is obtained by linear fitting with Δd_i as the abscissa and Δu_i as the ordinate, where a and b are constant coefficients determined by linear fitting.

[0085] At this time, in S6, the change in the amplitude of the measured pulse voltage signal is Δu_0. Substituting Δu_0 into the pipe wall thickness-amplitude equation, the corresponding pipe wall thickness d_0 can be obtained.

[0086] Example

[0087] The Hall sensor used is SS495A, with a power supply voltage of 4.5V-10.5V. The specific parameters of this detection probe are shown in Table 3. The winding is made of 1mm diameter enameled wire, and the core material is pure iron with a relative permeability of about 10000.

[0088] The test pieces were selected as flat plates of different thicknesses made of X60 steel, with thicknesses of 3.4mm, 3.8mm, 4.2mm, 4.6mm, 5.0mm, 5.4mm, 5.8mm, 6.2mm, 6.6mm, 7.0mm, 7.4mm, 7.8mm, 8.2mm, 8.6mm, and 9.0mm respectively; the lift-off height of the detection probe was set to 50mm.

[0089] The testing environment for high-strength steel pipe wall thickness testing system with insulation layer is as follows: Figure 1 As shown.

[0090] By sequentially testing regions of different pipe thicknesses and repeating the experiment five times, collecting experimental data, and taking the average value, a fitting curve of the relationship between metal plate thickness and voltage peak value can be obtained, such as... Figure 13 As shown.

[0091] As the thickness of the metal plate increases, the corresponding peak voltage will increase. The fitted curve is Δu = 2.073Δd - 0.01392, R0 2 The value is 0.9894, which proves that Δu has a linear response to Δd. For every 1 mm change in Δd, the corresponding peak value changes by 2.073 mV.

[0092] Similarly, by changing the lift-off height of the detection coil to 40mm, 30mm, 20mm, and 10mm and performing the same steps, all the fitting results were obtained as shown in Table 5.

[0093]

[0094] As the lift-off height decreases, the value of k in the fitted curve shows an increasing trend, and the overall linearity is relatively good, indicating that the system has a good linear response to the thickness variation of high-grade steel plates and the peak value of the differential voltage. However, in the detection process of pipelines with insulation layers, there is often a large lift-off height due to the presence of a certain thickness of insulation layer (the lift-off height basically corresponds to the thickness of the insulation layer). The magnetic field strength of the coil will decrease rapidly with the increase of distance. The method of this invention is basically unaffected by the increase of lift-off height and has excellent adaptability.

[0095] The lift-off height was set to 40mm. The thickness inversion experiment was carried out by selecting the fitting curve with a lift-off height of 40mm in the host computer software. The results are shown in Table 6.

[0096]

[0097] The thickness inversion error is within ±0.5mm, indicating that the proposed method and system for detecting the wall thickness of high-grade steel pipes with insulation layers has good detection accuracy. Simultaneously, the software interface on the host computer allows for a direct visualization of the probe's movement information and the variation of the metal wall thickness with mileage during the detection process. Figure 13 As shown, the testing process is convenient and efficient, and the test results are intuitive and clear.

[0098] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A pipe wall thickness detection system with insulation layer, characterized in that, Includes the following functional modules: The detection module has a detection probe, which includes an excitation coil that generates an alternating magnetic field through a pulse excitation signal, and a Hall sensor that receives changes in the magnetic field and generates an induced voltage. The main control module generates pulse excitation signals with adjustable frequency and duty cycle; acquires the induced voltage signals from the Hall sensor; and sends the acquired data to the host computer for backend processing. The host computer receives data transmitted from the main control module; processes the induced voltage signal, extracts feature signals, and performs inverse calculation to solve for the pipe wall thickness; and completes data visualization and storage. The power supply module provides power to the detection probe, main control module, and host computer. The detection probe has a cylindrical outer shell frame; the cylindrical outer shell frame is filled with an iron core; the cross-sectional shape of the iron core along the central axis of the cylinder is a hollow "I" shape; the Hall sensor is arranged at the bottom of the hollow space of the iron core, and the remaining part of the hollow space of the iron core is filled with thermally conductive material; the excitation coil is wound around the gaps on both sides of the "I" shape of the iron core. The structural components of the detection probe with the "I"-shaped iron core are as follows: the inner radius r1 of the "I"-shaped iron core is 8-10mm, the outer radius R is 30mm, and the height H1 is 53-58mm; the inner radius r of the excitation coil is 13-15mm, the outer radius R is 30mm, and the height H1 is... c The diameter is 41-46mm, and the number of turns N is 500-700; The detection module has multiple detection probes, which form an array; each detection probe is built into a probe holder, and adjacent probe holders are hinged to each other through a connection structure at their bottom sides to form the array.

2. The detection system according to claim 1, characterized in that, The thermally conductive material is epoxy resin.

3. The detection system according to claim 1, characterized in that, The hinged connection structure is a detachable connection.

4. The detection system according to any one of claims 1-3, characterized in that, The system also includes a position measurement module for measuring and recording the position information of the pipe wall where the system is located.

5. A method for detecting the wall thickness of a pipe containing an insulation layer using the detection system described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Place the detection probe in the area to be inspected on the pipe wall containing the insulation layer; S2. A continuous pulse excitation signal is generated by the control module and input into the excitation coil of the detection probe; S3. A coupled electromagnetic field is formed in the space between the pipe wall under test and the detection probe. The Hall sensor is used to convert the detected magnetic induction intensity signal into a corresponding voltage signal. S4. Input the voltage signal from S3 to the back-end filtering and amplification unit to filter out noise voltage signals in the voltage signal and amplify the signal by a certain factor. S5. The pulse voltage signal obtained after filtering and amplification in S4 is acquired by AD, and the amplitude of the pulse voltage signal is extracted. S6. The thinning of the pipe wall thickness is inverted by the change in the amplitude of the pulse voltage signal.

6. The detection method according to claim 5, characterized in that, The method further includes S0, establishing the relationship between the pulse voltage signal amplitude and the pipe wall thickness, specifically including, A pipe wall sample of the same material as the pipe wall to be tested is selected, and n experiments are set up. In the i-th experiment (i = 1, 2, ..., n), the sample is the pipe wall thickness reduced by Δd_i, and the change in pulse voltage signal amplitude Δu_i is measured. The pipe wall thickness-amplitude equation Δu_i = a * Δd_i + b is obtained by linear fitting with Δd_i as the abscissa and Δu_i as the ordinate, where a and b are constant coefficients determined by linear fitting. At this time, in step S6, the change in the amplitude of the measured pulse voltage signal is Δu_0. Substituting Δu_0 into the pipe wall thickness-amplitude equation, the corresponding pipe wall thickness d_0 is obtained.

7. The detection method according to claim 5 or 6, characterized in that, The pulse voltage signal is a differential peak signal with the basic pipe wall thickness as a reference signal.

Images