Phased array detection method for anticorrosive coating on inner wall of pipeline

Abstract

The invention belongs to the technical field of pipeline corrosion detection, and particularly relates to a phased array detection method for an anti-corrosion coating on the inner wall of a pipeline. Collecting the information of the detected pipeline: dividing the pipeline into a straight pipe section, a bent pipe section and a variable-diameter pipe section; the reference test block is made of a material in the same furnace and the same batch as the detected pipeline, the acoustic performance of the reference test block is consistent with that of the detected pipeline, and a plurality of non-anticorrosive coating areas are engraved on the reference test block and used for setting sensitivity; selecting a multi-channel device, wherein the device has a partition scanning function; a phased array and full-focus detection are utilized to realize the detection of the whole volume of the anticorrosive coating in the pipeline without dividing defect types; setting a focusing depth according to the detected pipeline, and calculating an optimal focusing aperture; verifying the detection capability; carrying out field detection; integrating multiple groups of data acquired on site, and establishing a three-dimensional imaging result; and analyzing the three-dimensional imaging, and evaluating and feeding back the service state information of the anticorrosive coating of the detected pipeline. According to the invention, the problems of missing detection, incomplete coverage and incapability of detection in the prior art are solved.

Description

Technical Field

[0001] This invention belongs to the field of pipeline corrosion detection technology, specifically relating to a phased array detection method for anti-corrosion coatings on the inner wall of pipelines. Background Technology

[0002] Seawater cooling source pipelines belong to the nuclear power plant's cooling system and are primarily used to cool the reactor. Seawater is drawn in by pumps and transported to the heat exchanger, then drained through drainage pipes to the drainage ditch. This system, also known as the final heat sink, involves key elements such as efficiency improvement, environmental protection, and cost control. Since the medium within the cooling system is corrosive seawater, the inner walls of the pipelines employ a combined protection measure of cathodic protection and anti-corrosion coating. If aging, damage, or localized defects in the pipeline lining lead to small-area breakage exposing the carbon steel substrate, forming a small anode and a large cathode, the anode portion will generate a large corrosive current, accelerating corrosion and even perforation in that area, affecting the safe operation and economic benefits of the nuclear power unit. Therefore, pipeline inspection is crucial to identify delamination between the pipeline lining material and the substrate in advance, allowing for proactive treatment and elimination of potential hazards before the corrosion area expands.

[0003] Electric spark detectors can only detect missing parts of the anti-corrosion coating and cannot simultaneously inspect the upper and lower surfaces. They are also ineffective at identifying partial debonding (incomplete debonding). Eddy current testing can only detect the anti-corrosion coating near the surface of the pipe. Traditional ultrasonic testing is difficult because the outer wall of the pipe generally contains multiple layers of anti-corrosion paint (with different brushing and drying times) and a four-oil, two-cloth process (asphalt primer + asphalt + glass cloth + asphalt + glass cloth + asphalt + glass cloth + asphalt + PVC industrial film). The various heterogeneous materials cause significant energy loss during ultrasonic wave transmission, resulting in severe signal acquisition loss. Electrochemical corrosion detection methods detect corrosion in pipes by measuring piezoresistive impedance values, but they are highly dependent on the environment and can only reflect surface information. They cannot assess damage in deep or hidden parts of the pipe, and the system has weak anti-interference capabilities and is susceptible to external stray currents and electromagnetic interference.

[0004] Non-destructive testing (NDT) refers to the development and application of technical methods for inspecting materials or components in a manner that does not impair their intended practicality and usability. Its objectives include: detection, location, measurement, and evaluation; assessment of integrity, properties, and composition; and measurement of geometric characteristics. The purpose is to detect structural incompleteness and defects in equipment (components) that occur during manufacturing and use, to promptly identify faults, and to ensure the safe, efficient, and reliable operation of equipment.

[0005] Eddy current testing, based on the principle of electromagnetic induction, is a non-destructive testing method that utilizes the eddy currents generated in metallic materials under the influence of an alternating magnetic field to detect defects in conductive magnetic and non-magnetic materials by analyzing the magnitude and distribution of these eddy currents. When a detection coil carrying an alternating current approaches a conductive workpiece, eddy currents are induced in the workpiece due to the coil's magnetic field. The magnitude, phase, and flow pattern of these eddy currents are influenced by factors such as the workpiece's conductivity. The reaction magnetic field of the eddy currents causes a change in the impedance of the detection coil. Therefore, by measuring the change in the coil's impedance, the performance and presence of defects in the tested workpiece can be determined. Eddy current testing is generally limited to the surface or near the surface of metallic materials, resulting in low sensitivity for detecting internal defects. Therefore, it cannot detect the peeling of internal anti-corrosion coatings from the outside of metal pipes.

[0006] Ultrasonic testing belongs to the field of non-destructive testing methods. Based on the piezoelectric effect, when a high-frequency voltage is applied to both sides of a piezoelectric crystal, the crystal generates a mechanical vibration in the thickness direction due to the inverse piezoelectric effect, resulting in expansion and contraction. If the crystal has good coupling with the workpiece surface, the mechanical vibration propagates in the form of ultrasonic waves, which is called emission. Conversely, when ultrasonic waves reach the crystal due to reflection from heterogeneous interfaces, the crystal undergoes expansion and contraction under the action of the ultrasonic waves. At this time, due to the piezoelectric effect, charges of different polarities are generated on the two surfaces of the crystal, forming a high-frequency voltage at the ultrasonic frequency, which is called reception. Ultrasonic testing uses the ultrasonic echoes received by the probe to determine the extent of corrosion coating peeling off the inner wall of a pipeline. Traditional pulse A-scan displays results that are not intuitive, and the test data cannot be retained. The corrosion protection process on the outer wall of the pipeline contains multiple heterogeneous structures, which affects the transmission of sound waves and causes severe energy attenuation.

[0007] Industrial ultrasonic phased array technology originated from radar array technology. Based on Huygens' principle and Fermat's principle, it uses computer-controlled phased array ultrasonic probes to transmit and receive ultrasonic waves. Ultrasonic probes, also known as array probes, consist of multiple small arrayed chips that can independently transmit and receive ultrasonic waves, such as... Figure 1 As shown, the computer can control the time difference (phase difference) of the array elements to achieve precise focusing and scanning of the sound beam. Compared with traditional ultrasonic testing methods, it has the advantages of flexible pointing and enhanced energy through beam superposition. Scanning modes are generally linear scanning, sector scanning, and focused scanning. Phased array ultrasonic testing technology has imaging capabilities; by using the ultrasonic wave reflection signals received by the probe, the computer reconstructs the image of the detection area, forming B-scan, C-scan, S-scan, etc., to achieve defect localization and quantitative assessment. Phased array equipment can store detection data and can achieve functions such as dynamic playback, recording scan positions, and recording defect information according to the scanning method. This represents a significant improvement in the repeatability and verifiability of traditional pulse-echo ultrasound.

[0008] Phased array ultrasonic testing instruments generate mechanical vibrations through multiple built-in ultrasonic transducers, thereby emitting ultrasonic waves at different angles. The ultrasonic waves are transmitted to the object under test via a coupling agent, and their propagation speed depends on the properties of the object (density and elastic modulus). During propagation, when the ultrasonic waves encounter heterogeneous interfaces with different acoustic impedances, reflection and transmission occur. The transducers receive the reflected echoes, converting the mechanical vibrations into electrical signals. These signals are then amplified and input to a signal processing unit for filtering and gain compensation, before being displayed on the screen as A-scan, B-scan, C-scan, and D-scan. By comparing the propagation time of the ultrasonic waves within the interface with the propagation speed of the medium, the distance the ultrasonic waves travel in the medium, i.e., the thickness of the medium, can be calculated.

[0009] With the development of computer technology, a full-focusing imaging algorithm based on phased array ultrasonic imaging has emerged. Full-focusing technology is an imaging algorithm based on full-matrix data acquisition. It processes the acoustic beam paths of all crystal array elements using a delay summation method, achieving high-precision dynamic focusing on small defects in complex structures such as curved surfaces, welds, and composite materials. Compared to traditional phased array technology, which detects at a fixed single depth, full-focusing technology dynamically focuses all excitation beams, resulting in high precision and high resolution. The full-area data acquisition reduces the loss of information about the inspected area due to human factors. The main steps of the full-focusing algorithm are: defining the detection range and setting the number of pixels or imaging resolution; calculating the signal delay of a single pixel; acquiring the corresponding amplitude value for any A-scan signal transmitting / receiving array element; superimposing the A-scan amplitude values ​​of the pixel; and traversing all pixels to form a TFM detection image, such as... Figure 3 As shown, the all-focusing technology enables real-time imaging of the inspected area, facilitating operators to quickly identify and determine the service status of the inspected object or to perform quantitative analysis.

[0010] Existing pipeline corrosion protection coating technologies have limited detection ranges. For example, electrochemical methods can only detect corrosion on the outer surface of the pipeline wall; eddy current testing is generally suitable for surface or near-surface defects, with a depth range of 0.1 mm to 10 mm, and is affected by the conductivity of the tested material, probe type, and frequency; spark testing is generally used to detect the peeling of the pipeline surface corrosion protection coating, but human operation has a significant impact on the test results, and the results are not easily reproducible, while the on-site environment is complex. To ensure the safe operation of the system, the pipe wall thickness on-site is usually greater than 10 mm, and the corrosion protection coating thickness is generally from several hundred micrometers to several millimeters. Traditional ultrasonic testing lacks accuracy, is easily affected by on-site environmental interference, and cannot save test records to provide effective support for subsequent processing. All of the above technologies have the problem of not being able to detect corrosion protection coatings on the inner wall of pipelines, affecting the safe and stable operation of heat and cold source pipelines in industrial systems. Summary of the Invention

[0011] The purpose of this invention is to provide a phased array detection method for anti-corrosion coatings on the inner wall of pipelines, solving the problems of missed detection, incomplete coverage, and inability to detect in the aforementioned background technology. By combining the advantages of phased array technology and the special characteristics of full-focusing technology, the two detection methods are combined to generate a 3D ultrasonic imaging result map, filling the technical gap in the field of anti-corrosion coating detection, providing technical assurance measures for the application of seawater cold source pipelines in the manufacturing and service process, and laying a solid quality foundation for promoting the safe and stable operation of pipelines in industrial sites.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A phased array detection method for anti-corrosion coatings on the inner wall of pipelines: Step 1: Collect information on the pipeline to be inspected: Divide the pipeline into straight sections, bends, and diameter-changing sections; Step 2, Reference test block design: The reference test block is manufactured using materials from the same furnace and batch as the pipeline under test, and its acoustic performance is consistent with that of the pipeline under test. The reference test block has multiple areas without anti-corrosion coating engraved on it for sensitivity setting. Step 3, Selection of testing equipment: Select multi-channel equipment with zone scanning function; use phased array and full-focus detection to achieve full-volume detection of anti-corrosion coating inside the pipeline, regardless of defect type; Step 4: Set the focusing depth and calculate the optimal focusing aperture according to the pipeline being inspected; Step 5: Verify detection capabilities; Step 6: Conduct on-site testing; Step 7: Integrate multiple sets of data collected on-site to establish a three-dimensional imaging result; Step 8: Analyze the 3D imaging, assess and provide feedback on the service status of the anti-corrosion coating on the inspected pipeline.

[0013] Step 1, the information of the inspected pipeline includes the material and specifications of the pipeline—wall thickness, outer diameter, and pipe section length.

[0014] In step 2, the thickness of the single-layer anti-corrosion coating on the reference test block is set to 400 μm; three rectangular areas with different anti-corrosion coating thicknesses on the reference test block are used to verify the minimum detectable anti-corrosion coating thickness; strip areas without anti-corrosion coating of different sizes on the reference test block simulate the anti-corrosion coating peeling off under field conditions, and can detect the minimum detectable anti-corrosion coating area; circular areas without anti-corrosion coating of different sizes on the reference test block simulate the circular anti-corrosion coating peeling off under field conditions, and can detect the minimum anti-corrosion coating area; rectangular areas without anti-corrosion coating of different sizes on the reference test block simulate the rectangular anti-corrosion coating peeling off under field conditions, and can detect the minimum anti-corrosion coating area.

[0015] In step 3, the number of wafers excited by the detection equipment in a single operation shall not be less than 32.

[0016] In step 3, the detection equipment selected is a TOPAZ64 portable ultrasonic phased array instrument with a working frequency of 0.25-25MHz and a minimum gain step of 0.1dB; the probe is a 5MHz linear array probe with 64 crystals, a crystal spacing of 0.3mm, a wedge model of M12, an angle of 0 degrees, and made of low-attenuation polystyrene with a sound velocity of 2300m / s.

[0017] Step 4: The inspected pipe is made of carbon steel and has an acoustic impedance of 4.5*10. 6 g / cm 2 The longitudinal wave velocity is 5920 m / s; the anti-corrosion coating material is epoxy resin, and the acoustic impedance is 0.27* 6 g / cm 2 ·s~0.36*10 6 g / cm 2 •s, the speed of sound ranges from 3000 to 4000 m / s.

[0018] In step 4, the phased array ultrasonic frequency of the detection equipment is set to 5MHz, the sampling rate to 10MHz, the mode to true depth, and the filter to bandpass 2.5MHz-15MHz. The model of the inspected pipe is set as follows: a φ960*12mm pipe with a length of 60mm, a tilt angle of 90°, a focusing depth of 15mm, an absolute forward movement mode, an LL path establishment mode, a maximum display depth of 40mm, a maximum horizontal length of 60mm, a width of 60mm, a sampling resolution of 256*256, a depth resolution of 0.13λ, a horizontal resolution of 0.20λ, a first array element chip of number 1, a last array element chip of number 32, and a focusing aperture of number 32.

[0019] Step 5, ultrasonic testing process: A focusing rule is set on the ultrasonic phased array instrument. Using the bottom of the standard test block CSK-IA, the phased array probe is moved to measure the delay of each crystal of the phased array probe. Then, the phased array probe is placed on the reference test block. Under unified benchmark simulation parameters, several sections of the pipeline anti-corrosion coating test block with different depths and no anti-corrosion coating are found sequentially. The instrument gain value at the interface with the lowest echo height is adjusted to 80% of the full-screen scale as the benchmark sensitivity. The instrument gain values ​​of three areas without anti-corrosion coating are recorded sequentially. Using the benchmark sensitivity at different thicknesses, the detection capability of the anti-corrosion coating test block at the same depth area is tested and recorded.

[0020] Step 5 involves setting the focusing rule on the ultrasonic phased array instrument. Using the 50mm radius arc on the standard test block CSK-IA, the phased array probe is moved to find the maximum echo at each angle. The ultrasonic phased array instrument will automatically perform delay compensation at each angle. Using the 15mm deep, 1mm φ horizontal through-hole on the standard test block CSK-IA, the phased array probe is moved to find the maximum echo at each angle. The ultrasonic phased array instrument will automatically perform sensitivity compensation at each angle. Then, the phased array probe is placed on the reference test block, and the area without anti-corrosion coating on the anti-corrosion coated test block is found under the same reference. Locate the uncoated portions of the first, second, and third anti-corrosion coating areas of the reference test block. Since the anti-corrosion coating thicknesses differ, the echo signals displayed by the phased array also differ. Adjust the instrument gain value of the area with the smallest recognizable anti-corrosion coating signal to 80% of the full-screen scale as the reference sensitivity, and then record the instrument gain values ​​of signals with other anti-corrosion coating thicknesses greater than that area. After recording, move the probe within the same anti-corrosion coating area to find and record the smallest recognizable anti-corrosion coating area with a single recognizable thickness.

[0021] Step 5: Before scanning, ensure that the surface to be tested is free of scratches and oxide scale, paint or other contaminants that may affect the movement of the probe, and that the surface roughness Ra ≤ 6.3 μm. During scanning, increase the reference sensitivity by 6 dB. The phased array probe performs axial scanning on the outer surface. The scanning speed during the scanning process is less than 150 mm / s, and the probe has at least 15% coverage.

[0022] Step 6: Based on the pipe partitioning in Step 1, set independent ultrasonic phased array full-focus detection parameters. When using the ultrasonic phased array for detection, equip it with an encoder and perform manual scanning according to the specific pipe to be detected. During the scanning process, ensure that the probe is in contact with the outer wall of the pipe being inspected.

[0023] Step 7 involves creating a two-dimensional mesh of the simulated test block, with a length x width of 1m x 1m and a horizontal and vertical axis spacing of 0.1m. Using full-focusing technology, each array element of the detection excitation probe is activated to ensure all elements receive the signal. Delayed focusing calculations are performed on any pixel within the detection area. Based on the full-focusing phased array ultrasonic detection data, A-scan, B-scan, C-scan, and D-scan data are recorded. According to the correspondence between the cross-sectional information in the detection data and the meshed two-dimensional plane, the scanning direction, stepping direction, and depth in the original detection data are set as x, y, and z-axis data, respectively. The amplitude height difference is then set as a color difference display. The process involves rearranging the processed 2D data into a 3D data volume, voxelizing the 3D data volume into the smallest volume elements of the system, and using the voxelized data volume for image reconstruction. Values ​​are assigned to the initial voxel grid. The data source is the x, y, and z axis data corresponding to the scanning direction, step direction, and depth in the original detection data, and a threshold of 20% is set. Data volumes with echo amplitudes higher than 20% are extracted through isosurfaces and displayed in the 3D image with highlights. A smoothing filter is used to reduce image noise, and the contrast and brightness of the 3D ultrasound imaging model are adjusted to enhance the visual effect of the image.

[0024] Step 8 involves extracting the anti-corrosion coating signal from the three-dimensional image, where the recorded amplitude height exceeds 20% of the reference sensitivity wave height. If the difference between the anti-corrosion coating thickness and the nominal thickness is greater than 15%, it is determined that the anti-corrosion coating in that area is missing. The shape, location, and area of ​​the area where the anti-corrosion coating has fallen off are then extracted and processed accordingly.

[0025] Step 8, when using phased array A-scan for detection, is determined based on whether there is a layered echo signal of the anti-corrosion coating between the primary and secondary echo signals of the pipeline metal interface. If the amplitude height reaches 20% or more under the reference sensitivity, it is considered an echo signal of the anti-corrosion coating interface. This helps determine whether the anti-corrosion coating on the inner wall of the pipeline in that area has detached. If no anti-corrosion coating echo signal appears in the echo signal or the amplitude height does not reach 20% under the reference sensitivity, it is determined that the anti-corrosion coating in that area has detached. When a single sound beam axis cannot determine the anti-corrosion coating, the scanning results of B-scan, C-scan, and D-scan are observed using full-focus imaging. When discontinuous or layered images appear in the scanning results, it is determined that the anti-corrosion coating on the inner wall of that area has detached.

[0026] Step 8 involves initializing voxel mesh data based on the preset outer diameter of the inspected pipe (960mm), pipe thickness (12mm), and length (60mm), assigning values ​​to the corresponding x, y, z, and amplitude height to form a three-dimensional image, recording the location information, and calculating the thickness and area of ​​the detached anti-corrosion coating. Then, the pipe is treated according to relevant regulations. Anti-corrosion coating detachment signals with amplitude heights below 20% of the reference sensitivity are recorded. When the defect amplitude is lower than the reference sensitivity, it indicates that the defect is very serious, and appropriate treatment should be performed.

[0027] The beneficial effects achieved by this invention are as follows: This invention utilizes the characteristics and advantages of fully focused phased array ultrasonic technology to detect the anti-corrosion coating on the inner wall of pipelines, solving the problems of missed detection and difficulty in detecting anti-corrosion coatings on the inner wall of pipelines, and filling the technological gap of detecting anti-corrosion coatings on the outer wall of pipelines. It allows for zoned inspection of the pipeline, determining the parameter settings, model establishment, and probe encoder selection of the phased array ultrasonic instrument based on the pipe section type, water flow direction, and location. It has a wide range of applications, suitable not only for detecting anti-corrosion coatings in seawater pipelines but also for pipelines under different operating conditions such as buried pipelines and oil pipelines. Fully focused phased array ultrasonic testing is applicable not only to pulse A-scan, B-scan, C-scan, and D-scan, but also to the selection of both linear array and area array probes. Utilizing a three-dimensional voxel mesh imaging method, the two-dimensional scan data is transformed into a three-dimensional scan model, improving detection accuracy. The imaging results provide precise location and size measurement of anti-corrosion coating detachment inside the pipeline, and the three-dimensional imaging results reduce the possibility of missed detection; it also reduces detection time and improves data detection efficiency. The test results can be archived and remotely evaluated, improving data analysis efficiency. It enables the inspection of complex pipeline structures coated with multiple anti-corrosion coatings, providing data support for the safe and stable operation of pipeline systems. This testing method is novel, unique, simple to operate, practical, accurate, efficient, low-cost, radiation-free, pollution-free, and the test records can be saved. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the coordinate definition and structural parameters of a linear array probe.

[0029] Figure 2 This is a schematic diagram of phased array focusing and deflection.

[0030] Figure 3 This is a schematic diagram of full-focus acquisition.

[0031] Figure 4 It is a full-focus actual scanning image.

[0032] Figure 5 This is a schematic diagram of contact detection of sound radiation.

[0033] Figure 6 This is a schematic diagram of an ultrasonic testing view.

[0034] Figure 7 This is a schematic diagram of a reference test block for testing anti-corrosion coatings.

[0035] Figure 8 This is a schematic diagram of ultrasound voxel mesh 3D imaging.

[0036] Figure 9 This is a schematic diagram illustrating the implementation logic of the present invention.

[0037] Figure 10 This is a signal diagram of the detection results of pipelines with unremoved anti-corrosion coating in an example of the present invention.

[0038] Figure 11 This is a full-focus imaging result of a pipeline with an intact anti-corrosion coating in an example of the present invention.

[0039] Figure 12 This is a signal diagram of the detection results for the anti-corrosion coating on a pipeline that has detached from its anti-corrosion coating.

[0040] Figure 13 This is a full-focus imaging result of a pipeline with detached anti-corrosion coating in an example of the present invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0042] A phased array detection method for anti-corrosion coatings on the inner wall of a pipeline includes the following steps: Step 1: Collect information about the object to be inspected; divide the pipeline system into straight pipe sections, bends, and reducing pipe sections. The material and specifications of the pipeline to be inspected include wall thickness, outer diameter, and pipe section length.

[0043] Step 2: Reference Specimen Design; The reference specimen is manufactured using materials from the same furnace and batch as the workpiece under test, ensuring consistent acoustic performance. Multiple areas without anti-corrosion coating are engraved on the specimen for sensitivity settings. These areas are used to set the baseline sensitivity, with a single-layer anti-corrosion coating thickness of 400μm. Three rectangular areas with different anti-corrosion coating thicknesses are used to verify the minimum detectable anti-corrosion coating thickness of the detection system. Strip areas of different sizes without anti-corrosion coating simulate anti-corrosion coating peeling under field conditions, indicating the minimum detectable anti-corrosion coating area. Circular areas of different sizes without anti-corrosion coating simulate circular anti-corrosion coating peeling under field conditions, indicating the minimum detectable anti-corrosion coating area. Rectangular areas of different sizes without anti-corrosion coating simulate rectangular anti-corrosion coating peeling under field conditions, indicating the minimum detectable anti-corrosion coating area.

[0044] Step 3: Selection of Detection Equipment; The equipment required for detection should be multi-channel and have a zone scanning function, with at least 32 crystals excited in a single scan. Utilizing the characteristics of phased array and full-focus detection, it is possible to detect the entire volume of the anti-corrosion coating inside the pipeline, regardless of defect type.

[0045] In this invention, the TOPAZ64 portable ultrasonic phased array instrument is selected. The TOPAZ64 operates at a frequency of 0.25-25MHz with a minimum gain step of 0.1dB. The instrument's screen height linearity and amplitude control linearity meet ASME specifications, and it features a highly intuitive step-by-step wizard to simplify and accelerate the setup process. It also boasts wide bandwidth, high sensitivity, and comprehensive DAC and TCG functions for convenient echo evaluation. The probe used in this invention is a 5MHz linear array probe with 64 crystals, a crystal spacing of 0.3mm, M12 wedges, a 0-degree angle, and is made of low-attenuation polystyrene. The sound velocity is approximately 2300m / s.

[0046] Step 4: Calculate the optimal simulation parameter settings for the object under inspection. Based on the object under inspection, set the focusing depth and calculate the optimal focusing aperture. A larger focusing aperture increases the amplitude at the probe's focal point. After a certain point, the sound field energy diverges significantly at the non-focused areas, attenuating severely and reducing the area extending beyond the focal point. When the focusing depth is limited, a large activation aperture leads to strong grating lobe energy, forming artifacts. Parameters should be simulated and reasonably set before the inspection process to improve detection resolution, obtain the best imaging effect, and ensure the efficiency of phased array detection.

[0047] (1) Calculate the optimal radiated sound field of the rectangular crystal probe N S - Near-field distance, L - wafer length, W - wafer width, Ks - correction factor, λ - wavelength.

[0048] (2) Calculate the directivity of the sound beam D(θ) - beam directivity function, D(θe) - contribution of a single array element to the directivity function, D(θp) - contribution of the point source array to the directivity function, θs - phased array beam deflection angle, λ - wavelength, e - width of a single crystal wafer. p - center-to-center spacing of array elements, n - number of array elements contained in the active aperture; The metal material of the pipeline to be inspected in this invention is carbon steel, and its acoustic impedance is 4.5*10. 6 g / cm 2 The longitudinal wave velocity is 5920 m / s; the anti-corrosion coating material is epoxy resin, and the acoustic impedance is 0.27* 6 g / cm 2 ·s~0.36*10 6 g / cm 2 •s, the speed of sound ranges from 3000 to 4000 m / s.

[0049] Calculate sound pressure reflectivity and sound pressure transmittance r - sound pressure reflectivity, t - sound pressure transmittance, Z2 - acoustic impedance at the epoxy resin interface, Z1 - acoustic impedance at the carbon steel interface.

[0050] The acoustic pressure reflectivity of the pipe substrate metal and the epoxy resin anti-corrosion coating is -0.85, and the acoustic pressure refractive index is 0.15. This means that some ultrasonic waves are reflected at the interface between the pipe substrate metal and the epoxy resin anti-corrosion coating and then refracted into the epoxy resin for propagation. Furthermore, the energy of the ultrasonic waves refracted into the epoxy resin anti-corrosion coating is lower than the ultrasonic signal reflected at the interface. The acoustic impedance of air is 0.00004*10⁻⁴. 6 With a g / cm²·s and a sound pressure reflectivity of -0.99, the refracted sound waves undergo total internal reflection at the interface between the epoxy resin anti-corrosion coating and the air. Observing the waveform displayed on the fluorescent screen, within a single cycle, there are reflected echoes from the metal interface and the anti-corrosion coating interface. The sound velocity of carbon steel is greater than that of epoxy resin, and the energy of the carbon steel reflected echo is higher than that of the epoxy resin echo signal. In the A-scan display interface, this is manifested as the epoxy resin anti-corrosion coating signal appearing to the right of the metal echo signal on the x-axis, and its amplitude is lower than that of the carbon steel metal echo signal. In the B, C, and D scan interfaces, different colors are used to represent the differences in echo energy. Through ultrasonic echoes from multiple angles and with different energies, the internal condition of the anti-corrosion coating and the internal metal of the pipeline can be displayed.

[0051] The phased array ultrasonic frequency was set to 5MHz. Based on the Nyquist law fs≥2fmax, the sampling rate was set to 10MHz, the mode to true depth, and the filter to a bandpass filter of 2.5MHz-15MHz. The model of the object under inspection was set as a φ960*12mm pipe with a length of 60mm, a tilt angle of 90°, a focusing depth of 15mm, an absolute forward movement mode, an LL path establishment mode, a maximum display depth of 40mm, a maximum horizontal length of 60mm, a width of 60mm, a sampling resolution of 256*256, a depth resolution of 0.13λ, a horizontal resolution of 0.20λ, with the first element chip being number 1 and the last element chip being number 32. The focusing aperture was set to 32.

[0052] Step 5: Verify the system's detection capabilities; Ultrasonic testing process: A focusing rule is set on the phased array instrument. Using the bottom of the standard CSK-IA test block, the phased array probe is moved to measure the delay of each crystal on the probe. Then, the phased array probe is placed on a reference test block. Under unified baseline simulation parameters, several sections of the pipeline anti-corrosion coating test block at different depths without the anti-corrosion coating are sequentially identified. The instrument gain value at the interface with the lowest echo height is adjusted to 80% of the full-screen scale as the baseline sensitivity. The instrument gain values ​​for three areas without the anti-corrosion coating are recorded sequentially. Using the baseline sensitivity at different thicknesses, the detection capability for the area of ​​anti-corrosion coating peeling off at the same depth of the anti-corrosion coating test block is tested and recorded.

[0053] On the phased array instrument, a focusing rule is set. Using the 50mm radius arc on the standard test block CSK-IA, the phased array probe is moved to find the maximum echo at each angle. The ultrasonic phased array detector will automatically perform delay compensation at each angle. Using the 15mm deep, 1mm φ horizontal through-hole on the standard test block CSK-IA, the phased array probe is moved to find the maximum echo at each angle. The ultrasonic phased array detector will automatically perform sensitivity compensation at each angle. Then, the phased array probe is placed on the reference test block. Under the same reference, the area without anti-corrosion coating on the anti-corrosion coating test block is located. The areas without anti-corrosion coating in the first, second, and third anti-corrosion coating areas of the test block are also located. Obviously, the thickness of these anti-corrosion coatings is different, and the echo signals displayed by the phased array are also different. The instrument gain value of the area with the smallest recognizable anti-corrosion coating signal is adjusted to 80% of the full screen scale as the reference sensitivity, and the instrument gain values ​​of other anti-corrosion coatings with a thickness greater than that area are recorded in turn. After recording, the probe is moved in the same anti-corrosion coating area to find the smallest recognizable anti-corrosion coating area with a single recognizable thickness, and then recorded.

[0054] Before scanning, ensure the surface to be tested is free of scratches and impermeable materials such as oxide scale, paint, or other contaminants that could affect probe movement, with a surface roughness Ra ≤ 6.3 μm. During scanning, first increase the reference sensitivity by 6 dB and then perform an axial scan on the outer surface using the phased array probe. During the scan, the scanning speed should be less than 150 mm / s, and the probe should have at least 15% coverage.

[0055] Step 6: Conduct on-site testing; Based on the zoning of the pipeline system in Step 1, set independent phased array ultrasonic equipment full-focus testing parameters. When using phased array instruments for testing, an encoder should be provided, or manual scanning can be used depending on the specific object being tested. During the scanning process, ensure that the probe is in close contact with the outer wall of the pipeline being tested to prevent poor coupling from causing deviations in the test results.

[0056] Step 7: Integrate multiple sets of data collected on site to establish a three-dimensional imaging result; the simulated test block to be inspected is meshed in two dimensions, with a region of 1m*1m (length*width) and a horizontal and vertical axis spacing of 0.1m.

[0057] Using full-focusing technology for detection, the limitations of single-mode detection, due to the angular range of the emitted sound beam, can interfere with the determination of the anti-corrosion coating on the inner wall of the pipe due to defects and geometric structural signals in some pipes. Full-focusing technology excites each element of the probe, enabling all elements to receive the signal. Delayed focusing calculations are performed on any pixel within the detection area. Based on the full-focusing phased array ultrasonic detection data, A-scan, B-scan, C-scan, and D-scan data are recorded. Based on the cross-sectional information in the detection data and its correspondence to a gridded two-dimensional plane, the scanning direction, step direction, and depth in the original detection data are set as x, y, and z-axis data, respectively. Amplitude height differences are used for color differentiation display. The processed two-dimensional data is rearranged into a three-dimensional data volume. The three-dimensional data volume is voxelized and divided into the system's smallest volume elements. Image reconstruction is then performed using the voxelized data volume. To initialize the voxel mesh, the data source was the x, y, and z axis data corresponding to the scanning direction, stepping direction, and depth from the original detection data. A threshold of 20% was set, and data volumes with echo amplitudes higher than 20% were extracted using isosurfaces and highlighted in the 3D image for easy observation. A smoothing filter was used to reduce image noise, and the contrast and brightness of the 3D ultrasound imaging model were adjusted to enhance the visual effect of the image.

[0058] Step 8: Analyze the 3D imaging model from Step 7, evaluate and provide feedback on the service status information of the anti-corrosion coating of the inspected pipeline; extract the anti-corrosion coating signal with a recorded amplitude height exceeding 20% ​​of the reference sensitivity wave height from the 3D image; if the difference between the anti-corrosion coating thickness and the nominal thickness is greater than 15%, it is determined that the anti-corrosion coating is missing in that area. Extract and measure the shape, location, area, and other data of the area where the anti-corrosion coating has detached, and perform relevant processing.

[0059] When using a phased array A-scan for inspection, the presence of a layered echo signal of the anti-corrosion coating between the primary and secondary echo signals of the pipe's metal interface is used. An echo signal with an amplitude height exceeding 20% ​​at the reference sensitivity indicates an anti-corrosion coating interface echo signal. This helps determine whether the anti-corrosion coating on the inner wall of the pipe in that area has detached. If no anti-corrosion coating echo signal is found in the echo signal, or if the amplitude height is less than 20% at the reference sensitivity, the anti-corrosion coating in that area is considered detached. When a single sound beam axis cannot determine the anti-corrosion coating, full-focus imaging is used to observe the scan results of B-scan, C-scan, and D-scan. If discontinuous or layered images appear in the scan results, it indicates that the anti-corrosion coating on the inner wall of that area has detached.

[0060] Initialize voxel mesh data based on the preset outer diameter of the inspected pipe (960mm), pipe thickness (12mm), and length (60mm), and assign corresponding x, y, z, and amplitude height values ​​to form a 3D image. Record the location information, calculate the thickness and area of ​​the detached anti-corrosion coating, and then perform relevant treatments on the pipe according to relevant regulations.

[0061] Record the anti-corrosion coating peeling signal with a waveform height lower than 20% of the reference sensitivity. When the defect amplitude is lower than the reference sensitivity, it proves that the defect is already very serious. At this time, the component should be treated accordingly.

Claims

1. A phased array detection method for anti-corrosion coatings on the inner wall of pipelines, characterized in that: Step 1: Collect information on the pipeline to be inspected: Divide the pipeline into straight sections, bends, and diameter-changing sections; Step 2, Reference test block design: The reference test block is manufactured using materials from the same furnace and batch as the pipeline under test, and its acoustic performance is consistent with that of the pipeline under test. The reference test block has multiple areas without anti-corrosion coating engraved on it for sensitivity setting. Step 3, Selection of testing equipment: Select multi-channel equipment with zone scanning function; use phased array and full-focus detection to achieve full-volume detection of anti-corrosion coating inside the pipeline, regardless of defect type; Step 4: Set the focusing depth and calculate the optimal focusing aperture according to the pipeline being inspected; Step 5: Verify detection capabilities; Step 6: Conduct on-site testing; Step 7: Integrate multiple sets of data collected on-site to establish a three-dimensional imaging result; Step 8: Analyze the 3D imaging, assess and provide feedback on the service status of the anti-corrosion coating on the inspected pipeline.

2. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 1, the information of the inspected pipeline includes the material and specifications of the pipeline—wall thickness, outer diameter, and pipe section length.

3. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: In step 2, the thickness of the single-layer anti-corrosion coating on the reference test block is set to 400 μm; three rectangular areas with different anti-corrosion coating thicknesses on the reference test block are used to verify the minimum detectable anti-corrosion coating thickness; strip areas without anti-corrosion coating of different sizes on the reference test block simulate the anti-corrosion coating peeling off under field conditions, and can detect the minimum detectable anti-corrosion coating area; circular areas without anti-corrosion coating of different sizes on the reference test block simulate the circular anti-corrosion coating peeling off under field conditions, and can detect the minimum anti-corrosion coating area; rectangular areas without anti-corrosion coating of different sizes on the reference test block simulate the rectangular anti-corrosion coating peeling off under field conditions, and can detect the minimum anti-corrosion coating area.

4. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: In step 3, the number of wafers excited by the detection equipment in a single operation shall not be less than 32.

5. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: In step 3, the detection equipment selected is a TOPAZ64 portable ultrasonic phased array instrument with a working frequency of 0.25-25MHz and a minimum gain step of 0.1dB; the probe is a 5MHz linear array probe with 64 crystals, a crystal spacing of 0.3mm, a wedge model of M12, an angle of 0 degrees, and made of low-attenuation polystyrene with a sound velocity of 2300m / s.

6. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 4: The inspected pipe is made of carbon steel and has an acoustic impedance of 4.5*10. 6 g / cm 2 The longitudinal wave velocity is 5920 m / s; the anti-corrosion coating material is epoxy resin, and the acoustic impedance is 0.27* 6 g / cm 2 ·s~0.36*10 6 g / cm 2 •s, the speed of sound ranges from 3000 to 4000 m / s.

7. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: In step 4, the phased array ultrasonic frequency of the detection equipment is set to 5MHz, the sampling rate to 10MHz, the mode to true depth, and the filter to bandpass 2.5MHz-15MHz. The model of the inspected pipe is set as follows: a φ960*12mm pipe with a length of 60mm, a tilt angle of 90°, a focusing depth of 15mm, an absolute forward movement mode, an LL path establishment mode, a maximum display depth of 40mm, a maximum horizontal length of 60mm, a width of 60mm, a sampling resolution of 256*256, a depth resolution of 0.13λ, a horizontal resolution of 0.20λ, a first array element chip of number 1, a last array element chip of number 32, and a focusing aperture of number 32.

8. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 5, ultrasonic testing process: A focusing rule is set on the ultrasonic phased array instrument. Using the bottom of the standard test block CSK-IA, the phased array probe is moved to measure the delay of each crystal of the phased array probe. Then, the phased array probe is placed on the reference test block. Under unified benchmark simulation parameters, several sections of the pipeline anti-corrosion coating test block with different depths and no anti-corrosion coating are found sequentially. The instrument gain value at the interface with the lowest echo height is adjusted to 80% of the full-screen scale as the benchmark sensitivity. The instrument gain values ​​of three areas without anti-corrosion coating are recorded sequentially. Using the benchmark sensitivity at different thicknesses, the detection capability of the anti-corrosion coating test block at the same depth area is tested and recorded.

9. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 5: Set the focusing rule on the ultrasonic phased array instrument. Using the R50mm arc on the standard test block CSK-IA, move the phased array probe to find the maximum echo at each angle. The ultrasonic phased array instrument will automatically perform delay compensation at each angle. Using the 15mm deep, φ1mm horizontal through hole on the standard test block CSK-IA, move the phased array probe to find the maximum echo at each angle. The ultrasonic phased array instrument will automatically perform sensitivity compensation at each angle. Then, place the phased array probe on the reference test block. Under the same reference, find the area without anti-corrosion coating on the anti-corrosion coating test block. Find the areas without anti-corrosion coating in the first, second, and third anti-corrosion coating areas of the reference test block. The anti-corrosion coating thickness is different, and the echo signal displayed by the phased array is different. Adjust the instrument gain value of the area with the smallest recognizable anti-corrosion coating signal to 80% of the full screen scale as the reference sensitivity, and record the instrument gain values ​​of other anti-corrosion coating thicknesses greater than that area in turn. After recording, move the probe across the same anti-corrosion coating area to find and record the smallest identifiable anti-corrosion coating area with a single identifiable thickness.

10. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 5: Before scanning, ensure that the surface to be tested is free of scratches and oxide scale, paint or other contaminants that may affect the movement of the probe, and that the surface roughness Ra ≤ 6.3 μm. During scanning, increase the reference sensitivity by 6 dB. The phased array probe performs axial scanning on the outer surface. The scanning speed during the scanning process is less than 150 mm / s, and the probe has at least 15% coverage.

11. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 5, characterized in that: Step 6: Based on the pipe partitioning in Step 1, set independent ultrasonic phased array full-focus detection parameters. When using the ultrasonic phased array for detection, equip it with an encoder and perform manual scanning according to the specific pipe to be detected. During the scanning process, ensure that the probe is in contact with the outer wall of the pipe being inspected.

12. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 7 involves creating a two-dimensional mesh of the simulated test block, with a length x width of 1m x 1m and a horizontal and vertical axis spacing of 0.1m. Using full-focusing technology, each array element of the detection excitation probe is activated to ensure all elements receive the signal. Delayed focusing calculations are performed on any pixel within the detection area. Based on the full-focusing phased array ultrasonic detection data, A-scan, B-scan, C-scan, and D-scan data are recorded. According to the correspondence between the cross-sectional information in the detection data and the meshed two-dimensional plane, the scanning direction, stepping direction, and depth in the original detection data are set as x, y, and z-axis data, respectively. The amplitude height difference is then set as a color difference display. The process involves rearranging the processed 2D data into a 3D data volume, voxelizing the 3D data volume into the smallest volume elements of the system, and using the voxelized data volume for image reconstruction. Values ​​are assigned to the initial voxel grid. The data source is the x, y, and z axis data corresponding to the scanning direction, step direction, and depth in the original detection data, and a threshold of 20% is set. Data volumes with echo amplitudes higher than 20% are extracted through isosurfaces and displayed in the 3D image with highlights. A smoothing filter is used to reduce image noise, and the contrast and brightness of the 3D ultrasound imaging model are adjusted to enhance the visual effect of the image.

13. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 8 involves extracting the anti-corrosion coating signal from the three-dimensional image, where the recorded amplitude height exceeds 20% of the reference sensitivity wave height. If the difference between the anti-corrosion coating thickness and the nominal thickness is greater than 15%, it is determined that the anti-corrosion coating in that area is missing. The shape, location, and area of ​​the area where the anti-corrosion coating has fallen off are then extracted and processed accordingly.

14. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 8, when using phased array A-scan for detection, is determined based on whether there is a layered echo signal of the anti-corrosion coating between the primary and secondary echo signals of the pipeline metal interface. If the amplitude height reaches 20% or more under the reference sensitivity, it is considered an echo signal of the anti-corrosion coating interface. This helps determine whether the anti-corrosion coating on the inner wall of the pipeline in that area has detached. If no anti-corrosion coating echo signal appears in the echo signal or the amplitude height does not reach 20% under the reference sensitivity, it is determined that the anti-corrosion coating in that area has detached. When a single sound beam axis cannot determine the anti-corrosion coating, the scanning results of B-scan, C-scan, and D-scan are observed using full-focus imaging. When discontinuous or layered images appear in the scanning results, it is determined that the anti-corrosion coating on the inner wall of that area has detached.

15. The phased array detection method for the anti-corrosion coating on the inner wall of a pipeline according to claim 1, characterized in that: Step 8 involves initializing voxel grid data based on the preset outer diameter of the inspected pipe (960mm), pipe thickness (12mm), and length (60mm), assigning values ​​to the corresponding x, y, z, and amplitude height to form a three-dimensional image. The location information of missing anti-corrosion coating signals in ultrasonic A-scan or discontinuous / layered images in B, C, and D scans is recorded. The thickness and area of ​​the detached anti-corrosion coating are calculated. The pipe is then treated according to relevant regulations. Anti-corrosion coating detachment signals with amplitudes below 20% of the reference sensitivity are recorded. When the defect amplitude is below the reference sensitivity, it indicates a very serious defect, and appropriate treatment should be performed.

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