A phased array method for detecting corrosion under pipe coatings

Abstract

The present application belongs to the technical field of pipeline corrosion detection, and particularly relates to a phased array detection method for a pipeline inner wall anticorrosion coating. Collecting information of the pipeline to be detected: the pipeline is divided into straight pipe sections, elbow pipe sections and variable diameter pipe sections; the test block is made of the same batch of materials as the pipeline to be detected, and the acoustic performance is consistent with the pipeline to be detected; a plurality of anticorrosion coating free areas are engraved on the test block for sensitivity setting; a multi-channel device is selected, and the device has a partition scanning function; the phased array and full focus detection are used to realize the detection of the pipeline inner anticorrosion coating in full volume and without defect type; the focus depth is set according to the pipeline to be detected, and the optimal focus aperture is calculated; the detection capability is verified; the on-site detection is implemented; a plurality of groups of data collected on site are integrated to establish a three-dimensional imaging result; the three-dimensional imaging is analyzed to evaluate and feedback the service state information of the anticorrosion coating of the pipeline to be detected. The present application solves the problems of missed detection, incomplete coverage and inability to detect in the prior art.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of pipeline corrosion detection, and particularly relates to a phased array detection method for a pipeline inner wall anticorrosive coating. BACKGROUND

[0002] The seawater cooling source pipeline belongs to a nuclear power plant cooling system, and is mainly used for cooling a reactor. The seawater is sucked by a pump and delivered to a heat exchanger, and then the seawater that absorbs heat is delivered to a drainage channel by a drainage pipeline. The system is also called a final heat sink, and involves key elements such as efficiency improvement, environmental protection, and cost control. The carrying medium in the cooling system is corrosive seawater, so the inner wall of the pipeline adopts a combined protection measure of cathodic protection and brushing of an anticorrosive coating. If the pipeline lining is aged, scratched, and locally defective to cause small-area damage to leak the carbon steel base material, a small anode and a large cathode are formed, which will cause a great corrosion current to be generated in the anode part to accelerate the corrosion of the region or even perforation, and affect the safe operation and economic benefits of the nuclear power unit. Therefore, it is of great significance to detect the pipeline, identify whether the pipeline lining material and the pipeline base material are delaminated and peeled off, identify before the corrosion area is expanded, and exclude hidden dangers in advance.

[0003] The electric spark detector can only detect the missing part of the anticorrosive coating, cannot simultaneously detect the upper and lower surfaces, and has poor discrimination effect on partial peeling (not complete peeling). The eddy current detection can only detect the anticorrosive coating of the near-surface pipeline. The traditional ultrasonic detection is difficult because the outer wall of the pipeline generally contains multiple anticorrosive paint layers (brushing time is different, and drying time is different), four oil and two cloth processes (asphalt primer + asphalt + glass cloth + asphalt + glass cloth + asphalt + glass cloth + asphalt + polyvinyl chloride industrial film), and various heterogeneous materials cause serious energy loss and signal acquisition loss of the ultrasonic wave during transmission. The electrochemical corrosion detection method realizes the corrosion detection of the pipeline by measuring the piezoresistive impedance value, but is highly dependent on the environment and can only reflect the surface information, cannot evaluate the damage of the deep or hidden part of the pipeline, and has weak anti-interference ability and is easily affected by external stray current and electromagnetic interference.

[0004] Nondestructive testing refers to the development and application of technical methods for inspecting materials or parts without damaging their intended utility and usability. The purpose is to detect, locate, measure, and evaluate; to evaluate integrity, properties, and composition; and to measure geometric characteristics. The purpose is to detect structural integrity and defect conditions of equipment (components) generated during manufacturing and use, to discover faults in time, and to ensure 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 produce mechanical vibrations through multiple ultrasonic transducers built-in, thereby emitting ultrasonic waves at different angles. The ultrasonic waves are transmitted into the object under test through a coupling agent, and the propagation speed depends on the properties (density and elastic modulus) of the object under test. In the process of ultrasonic wave propagation, when encountering heterogeneous interfaces with different acoustic impedance, the ultrasonic wave is reflected and transmitted, the transducer receives the reflected echo, converts the mechanical vibration into an electrical signal, processes the input signal through an amplifier and a signal processing unit, performs filtering and gain compensation, and displays it on the screen in A-scan, B-scan, C-scan, and D-scan. Through the propagation time of the ultrasonic wave in the interface and the propagation speed of the medium, the distance of the ultrasonic wave in the medium can be calculated, i.e. the thickness of the medium.

[0009] With the development of computer technology, a full focus imaging algorithm technology based on phased array ultrasonic imaging has emerged. The full focus technology is an imaging algorithm based on full matrix data acquisition. Through delay-and-sum processing of the sound beam paths of all wafer elements, high-precision dynamic focusing of small defects in complex structures such as curved surfaces, welds and composite materials is achieved. Compared with the traditional phased array technology, the traditional phased array technology is fixed single depth detection, and the full focus technology is dynamic focusing of the excited beam, which has high precision and high resolution. The imaging algorithm of full area data acquisition reduces the loss of information of the detected area caused by human factors. The main implementation steps of the full focus algorithm are to define the detection range, set the number of pixel points or the imaging resolution; calculate the signal delay of a single pixel point, obtain the corresponding amplitude value for any A-scan signal transmission / reception element; superimpose the A-scan amplitude value of the pixel point; traverse all pixel points to form a TFM detection image, as shown in Figure 3 The full focus technology realizes the real-time imaging characteristics of the detected area, which is convenient for the operating personnel to quickly identify and determine the service state of the on-site object under test or to realize quantitative analysis of the object under test.

[0010] The existing pipeline corrosion coating technology has limited detection range. For example, the electrochemical method can only detect the surface layer of the outer wall of the pipeline, the eddy current detection method is generally suitable for surface or near-surface defects, the depth range is 0.1 mm to 10 mm, and it is affected by the conductivity of the detected material, the type of probe and the frequency; the electric spark method is generally used for detecting the peeling of the pipeline surface corrosion coating, the operation of the personnel has a greater impact on the detection results, and the reproducibility of the detection results is not strong, and the on-site environment is complex. In order to ensure the safe operation of the system, the thickness of the pipeline wall is usually greater than 10 mm, and the thickness of the corrosion coating is usually hundreds of microns to several millimeters. The traditional ultrasonic detection has insufficient precision and is easily disturbed by the on-site environment, and cannot save the detection records to provide effective support for subsequent processing work. The above-mentioned technologies cannot detect the corrosion coating on the inner wall of the pipeline, which affects the safe and stable operation of the heat removal cold source pipeline of the industrial system. SUMMARY

[0011] The purpose of the present application is to provide a phased array detection method for the inner wall anticorrosion coating of a pipeline, to solve the problems of missed detection, incomplete coverage and inability to detect in the background art, to combine the advantages of phased array technology and the particularity of full focusing technology, to draw a 3D ultrasonic imaging result graph, to fill the technical gap in the field of anticorrosion coating detection, to provide technical guarantee measures for the application of seawater cooling source pipelines during manufacturing and service, and to lay a solid quality foundation for promoting the safe and stable operation of industrial site pipelines.

[0012] To achieve the above purpose, the technical solution adopted by the present application is:

[0013] A phased array detection method for the inner wall anticorrosion coating of a pipeline:

[0014] Step 1, collect the information of the pipeline to be detected: divide the pipeline into straight pipe sections, elbow pipe sections and reducing pipe sections;

[0015] Step 2, reference block design: the reference block is made of the same batch of materials as the pipeline to be detected, and its acoustic performance is consistent with that of the pipeline to be detected; a plurality of anticorrosion coating-free areas are engraved on the reference block for sensitivity setting;

[0016] Step 3, selection of detection equipment: select a multi-channel device with partition scanning function; use phased array and full focusing detection to realize full volume and non-defect type detection of the anticorrosion coating inside the pipeline;

[0017] Step 4, set the focusing depth according to the pipeline to be detected and calculate the optimal focusing aperture;

[0018] Step 5, verify the detection capability;

[0019] Step 6, implement on-site detection;

[0020] Step 7, integrate the multiple groups of data collected on site to establish a three-dimensional imaging result;

[0021] Step 8, analyze the three-dimensional imaging, evaluate and feedback the service state information of the anticorrosion coating of the pipeline to be detected.

[0022] The information of the pipeline to be detected in step 1 includes the material and specifications of the pipeline, i.e. wall thickness, outer diameter and pipe section length.

[0023] The thickness of the single-layer anticorrosion coating on the step 2, the test block is set to 400 μm; the three anticorrosion coating thicknesses of the rectangular area on the test block are different, which are used to verify the minimum detectable anticorrosion coating thickness; the size of the anticorrosion coating-free strip area on the test block is different, which simulates the anticorrosion coating falling off in the field conditions, and the minimum anticorrosion coating area can be detected; the size of the anticorrosion coating-free circular area on the test block is different, which simulates the anticorrosion coating falling off in the field conditions, and the minimum anticorrosion coating area can be detected; the size of the anticorrosion coating-free rectangular area on the test block is different, which simulates the anticorrosion coating falling off in the field conditions, and the minimum anticorrosion coating area can be detected.

[0024] The number of wafers excited by the detection equipment in step 3 is not less than 32 wafers per time.

[0025] The detection equipment in step 3 selects a TOPAZ64 portable ultrasonic phased array instrument, the working frequency is 0.25-25 MHZ, the minimum gain step is 0.1 dB; the probe selects a linear array probe with a frequency of 5 MHZ, the number of wafers is 64, the spacing between each wafer is 0.3 mm, the wedge block is model M12, the angle is 0 degrees, the material is made of low-attenuation polystyrene, and the sound speed is 2300 m / s.

[0026] The material of the detected pipeline in step 4 is carbon steel, the acoustic impedance is 4.5*10 6 g / cm 2 ·s, the longitudinal wave speed is 5920 m / s; the anticorrosion coating material is epoxy resin, the acoustic impedance is 0.27* 6 g / cm 2 ·s~0.36*10 6 g / cm 2 ·s, and the sound speed ranges from 3000 to 4000 m / s.

[0027] The frequency of the detection equipment in step 4 is set to 5 MHz, the sampling rate is set to 10 Mhz, the mode is set to true depth, the filter is set to bandpass 2.5 MHz-15 MHz; the detected pipeline modeling is set, the model is set to a φ960*12 mm pipeline, the length is 60 mm, the inclination angle is set to 90°, the focusing depth is 15 mm, the forward mode is set to absolute, the path is set to L-L mode, the maximum display depth is set to 40 mm, the maximum horizontal length is 60 mm, the width is set to 60 mm, the acquisition resolution is set to 256*256, the depth resolution is 0.13λ, the horizontal resolution is 0.20λ, the first array wafer is No. 1, the last array wafer is No. 32, and the focusing aperture is set to 32.

[0028] The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is used, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified benchmark simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the benchmark sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

[0029] The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is used, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified benchmark simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the benchmark sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

[0030] The step 5, before scanning, it is guaranteed that the detection surface is free of scratches, scales, paints or other dirt affecting the movement of the probe, the surface roughness Ra is less than or equal to 6.3 μm, the benchmark sensitivity is increased by 6 dB during scanning, the phased array probe is axially scanned on the outer surface, the scanning speed is less than 150 mm / s during the scanning process, and the probe has at least 15% coverage.

[0031] The step 6, according to the partition of the pipeline in step 1, the independent ultrasonic phased array instrument full focus detection parameter is set, the ultrasonic phased array instrument is equipped with an encoder when used, manual scanning is used according to the specific detection pipeline, and it is guaranteed that the probe is attached to the outer wall of the detected pipeline during the scanning process.

[0032] The step 7 is two-dimensional gridding of the detected analog test block, the area length and width are 1m*1m, the horizontal and vertical axis interval is 0.1m; the full focusing technology is adopted to detect each array of the excitation probe to make all arrays receive, the delay focusing calculation is performed on any pixel point in the detection area, the A scan, B scan, C scan and D scan data are recorded according to the full focusing phased array ultrasonic detection data, the scan direction, step direction and depth in the original detection data are respectively set as x, y and z axis data according to the cross section information in the detection data and the gridding two-dimensional plane, the amplitude height difference is set as color difference display, the processed two-dimensional data is rearranged as three-dimensional data volume, the three-dimensional data volume is voxelized and divided into the minimum volume elements of the system, the image reconstruction is performed by using the voxelized data volume, the initial voxel grid is valued, the data source is the x, y and z axis data corresponding to the scan direction, step direction and depth in the original detection data, and the threshold is set as 20%, the data volume with the echo amplitude value higher than 20% is extracted by the isosurface extraction, is highlighted in the three-dimensional image, the smoothing filter is used to reduce the image noise, and the contrast and brightness of the three-dimensional ultrasonic imaging model are adjusted to enhance the image visual effect.

[0033] The step 8 is that the anticorrosive coating signal with the amplitude height exceeding 20% of the reference sensitivity wave height is extracted in the three-dimensional image, when the difference between the thickness of the anticorrosive coating and the nominal thickness is greater than 15%, it is determined that the anticorrosive coating in the area is missing, and the shape, position and area of the anticorrosive coating falling area are extracted for related processing.

[0034] The step 8 is that when the phased array A scan detection is used, whether the anticorrosive coating delamination echo signal exists between the first echo signal and the second echo signal of the pipeline metal interface, the amplitude height exceeding 20% of the reference sensitivity is the anticorrosive coating interface echo signal, whether the anticorrosive coating on the inner wall of the pipeline in the area falls is judged, if the anticorrosive coating echo signal does not appear in the echo signal or the amplitude height does not reach 20% of the reference sensitivity, it is determined that the anticorrosive coating in the area falls, when the single sound beam axis cannot judge the anticorrosive coating, the full focusing imaging is used to observe the B scan, C scan and D scan scanning result graph, when the discontinuous and delaminated image appears in the scanning result graph, it is determined that the anticorrosive coating on the inner wall in the area falls.

[0035] The step 8 is that the voxel gridding data is initialized according to the preset outer diameter of the detected pipeline of 960mm, the pipeline thickness of 12mm and the length of 60mm, the corresponding x, y, z and amplitude height are valued, the three-dimensional imaging is formed, the position information is recorded, the thickness of the falling anticorrosive coating and the area of the falling anticorrosive coating are calculated, and the pipeline is processed according to the related regulations, the anticorrosive coating falling signal lower than 20% of the reference sensitivity wave height is recorded, when the defect amplitude is lower than the reference sensitivity, it is proved that the defect is very serious, at this time, the related processing should be performed.

[0036] The application has the following beneficial effects:

[0037] The application utilizes the characteristics and advantages of the full-focus phased array ultrasonic technology to realize the detection of the anticorrosive coating of the inner wall of the pipeline, solves the problem of missed detection and difficult detection of the anticorrosive coating of the inner wall of the pipeline, fills the technical blank of detecting the anticorrosive coating of the inner wall from the outer wall of the pipeline, and realizes the detection of the pipeline in different zones according to the type of the pipeline section, the direction of the water flow and the position thereof, determines the parameter setting, model establishment and probe encoder selection of the phased array ultrasonic instrument, and the like. The application has a wide range of application, is suitable for the detection of the anticorrosive coating of the seawater pipeline, and is also suitable for the pipelines under different working conditions such as the buried pipeline and the oil pipeline. The full-focus phased array ultrasonic detection is suitable for pulse A scanning, B scanning, C scanning and D scanning, and the probe selected by the ultrasonic instrument can be a linear array probe or a surface array probe. The three-dimensional voxel gridding imaging method is utilized to draw a three-dimensional scanning model from the two-dimensional scanning data, to improve the detection accuracy, and the imaging result can provide accurate positioning and size measurement of the anticorrosive coating of the inner wall of the pipeline, and the three-dimensional imaging result reduces the possibility of missed detection. The detection time is reduced, and the data detection efficiency is improved. The detection result supports archiving and realizes remote evaluation, improves the data analysis efficiency, realizes the detection of the complex structure pipeline with various anticorrosive coatings, and provides data support for the safe and stable operation of the pipeline system. The detection method is novel and unique, simple to operate, practical, accurate in detection result, high in detection efficiency, low in cost, free of radiation and pollution, and the detection record can be saved. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic view of the coordinate definition and structural parameters of the linear array probe.

[0039] Figure 2 is a schematic view of the phased array focusing and deflection.

[0040] Figure 3 is a schematic view of the full-focus acquisition.

[0041] Figure 4 is a full-focus actual scanning imaging diagram.

[0042] Figure 5 is a schematic view of the contact type detection sound radiation.

[0043] Figure 6 is a schematic view of the ultrasonic detection view.

[0044] Figure 7 is a schematic view of the detection block of the anticorrosive coating.

[0045] Figure 8 is a schematic view of the three-dimensional imaging of the ultrasonic voxel gridding.

[0046] Figure 9 is a logic diagram of the implementation of the application.

[0047] Figure 10 is the signal diagram of the detection result of the pipeline with the anticorrosion coating not falling off in the example of the application.

[0048] Figure 11 is the full-focus imaging result diagram of the pipeline with the anticorrosion coating not falling off in the example of the application.

[0049] Figure 12 is the signal diagram of the detection result of the anticorrosion coating of the pipeline with the anticorrosion coating falling off.

[0050] Figure 13 is the full-focus imaging result diagram of the pipeline with the anticorrosion coating falling off in the example of the application. DETAILED DESCRIPTION

[0051] The application will be described in detail below in combination with the drawings and specific embodiments.

[0052] A phased array detection method for the anticorrosion coating of the inner wall of a pipeline, comprising the following steps:

[0053] Step 1, collecting information of the object to be detected; the pipeline system is divided into straight pipe sections, elbow pipe sections and reducing pipe sections, and the material and specifications of the pipe to be detected include wall thickness, outer diameter, pipe section length and the like.

[0054] Step 2, reference block design; the reference block is made of the same batch of materials as the workpiece to be detected, and the acoustic performance is consistent with the detected part. A plurality of anticorrosion coating-free areas are engraved on the test block for setting the sensitivity. The plurality of anticorrosion coating-free areas are used for setting the reference sensitivity, and the single anticorrosion coating thickness is set to 400 μm. Three rectangular areas with different anticorrosion coating thicknesses are used to verify the minimum detectable anticorrosion coating thickness of the detection system. The anticorrosion coating-free strip-shaped areas with different sizes simulate the anticorrosion coating falling off under the field conditions, and the minimum anticorrosion coating area can be detected. The anticorrosion coating-free circular areas with different sizes simulate the anticorrosion coating falling off under the field conditions, and the minimum anticorrosion coating area can be detected. The anticorrosion coating-free rectangular areas with different sizes simulate the anticorrosion coating falling off under the field conditions, and the minimum anticorrosion coating area can be detected.

[0055] Step 3, selection of detection equipment; the detection equipment required needs to be selected as a multi-channel equipment, and the equipment has a partition scanning function, and the number of single excitation chips should be not less than 32 chips. By using the characteristics of phased array and full-focus detection, the full volume of the anticorrosion coating in the pipeline is detected without distinguishing the defect types.

[0056] The TOPAZ 64 portable ultrasonic phased array instrument is selected in the application, the working frequency of the TOPAZ 64 is 0.25-25 MHZ, the minimum gain step is 0.1 dB; the screen height linearity and the amplitude control linearity of the ultrasonic instrument meet the ASME specification requirements, have a step-by-step guide with strong intuitiveness, can simplify and accelerate the setting process; all have a wide frequency band and high sensitivity, perfect DAC and TCG functions, and are convenient for echo evaluation. The linear array probe with a frequency of 5 MHZ is selected as the probe, the number of wafers is 64, the spacing between the wafers is 0.3 mm, the wedge block is of the M12 model, the angle is 0 degrees, the material is made of low-attenuation polystyrene, and the sound speed is about 2300 m / s.

[0057] Step 4, calculating the best simulation parameter setting of the detected object; according to the focus depth of the detected object, the best focus aperture is calculated, the focus aperture is large, the amplitude at the focus of the probe is increased, and after being increased to a certain degree, the sound field divergence energy at the non-focus position is seriously attenuated, the extension out of the focus area is reduced, and when the focus depth is limited, the strong grating lobe energy is caused by the large active aperture, and a pseudo image is formed. The parameters should be simulated and reasonably set before the detection process, the detection resolution is improved, the best imaging effect is obtained, and the phased array detection efficiency is ensured.

[0058] (1) calculating the best radiation sound field of the rectangular wafer probe

[0059]

[0060]

[0061] N S - near field zone distance, L- wafer length, W- wafer width, Ks- correction coefficient, λ- wavelength.

[0062] (2) calculating the sound beam directivity

[0063]

[0064] D (theta) - sound beam directivity function, D (theta e) - contribution of a single array element to the directivity function, D (theta p) - contribution of a point source array to the directivity function, theta s- phased array beam deflection angle, lambda- wavelength, e- single wafer width

[0065] p- array element center spacing, n- number of array elements included in the active aperture;

[0066] The metal material of the pipe to be detected in the application is carbon steel, the acoustic impedance is 4.5*10 6 g / cm 2 ·s, the longitudinal wave speed is 5920 m / s; the anticorrosion coating material is epoxy resin, and the acoustic impedance is 0.27 6 g / cm2 ·s~0.36*10 6 g / cm 2 •s, the speed of sound ranges from 3000 to 4000 m / s.

[0067] Calculate sound pressure reflectivity and sound pressure transmittance

[0068]

[0069] r - sound pressure reflectivity, t - sound pressure transmittance, Z2 - acoustic impedance of epoxy resin interface, Z1 - acoustic impedance of carbon steel interface.

[0070] 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.

[0071] 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.

[0072] Step 5: Verify the system's detection capabilities;

[0073] Ultrasonic detection process: set the focusing rule on the phased array instrument, use the bottom of the standard test block CSK-IA to move the phased array probe to measure the delay of each wafer of the phased array probe. Then place the phased array probe on the reference test block, under the same reference simulation parameters, find the several different depth without anticorrosive coating parts of the pipeline anticorrosive coating test block in turn, adjust the interface echo amplitude of the lowest echo height to 80% of the full screen scale when the instrument gain value is the reference sensitivity, and record the instrument gain values of the three without anticorrosive coating regions in turn; use the reference sensitivity under different thicknesses to detect the detection capability of the anticorrosive coating test block at the same depth area, and record.

[0074] Set the focusing rule on the phased array instrument, use the R50mm arc on the standard test block CSK-IA to move the phased array probe to find the maximum echo at each angle, and the ultrasonic phased array detector will automatically compensate for the delay at each angle. Use the 15mm deep, φ1mm horizontal through hole on the standard test block CSK-IA to move the phased array probe to find the maximum echo at each angle, and the ultrasonic phased array detector will automatically compensate for the sensitivity at each angle. Then place the phased array probe on the reference test block, find the without anticorrosive coating region of the anticorrosive coating test block under the same reference, find the without anticorrosive coating part of the first anticorrosive coating region and the second anticorrosive coating region and the third anticorrosive coating region of the test block. Obviously, the thicknesses of these multiple anticorrosive coatings are different, and the phased array display echo signals are different. Adjust the minimum anticorrosive coating region with the smallest distinguishable anticorrosive coating signal to 80% of the full screen scale when the instrument gain value is the reference sensitivity, and record the instrument gain values of the signals with other anticorrosive coating thicknesses greater than that region in turn; then record the probe moving in the same anticorrosive coating region to find the minimum distinguishable anticorrosive coating area under a single thickness, and record it.

[0075] Before scanning, ensure that the detection surface is free of scratches and oxidation scale, paint or other dirt that affects the movement of the probe, and the surface roughness Ra is ≤6.3μm. During scanning, first increase the reference sensitivity by 6dB for scanning, and perform axial scanning on the outer surface with the phased array probe. During the scanning process, the scanning speed is less than 150mm / s, and the probe has at least 15% coverage.

[0076] Step 6, implement field detection; according to the partitioning of the pipeline system in step 1, set independent phased array ultrasonic equipment full focusing detection parameters, and use the phased array instrument to detect, or manually scan according to the specific detection object, and ensure that the probe is in close contact with the outer wall of the detected pipeline to prevent poor coupling from causing deviations in the detection results.

[0077] Step 7, integrate the multiple groups of data collected on site to establish a three-dimensional imaging result; the two-dimensional grid of the test analog block is established, with an area of 1m*1m (length* width), and a horizontal and vertical axis interval of 0.1m.

[0078] When a single detection mode is detected by using the full focusing technology, the angle range of the emitted sound beam will interfere with the determination of the anticorrosive coating on the inner wall of the pipeline due to the defect signals and geometric structure signals of part of the pipeline. The full focusing technology can excite each element of the probe to make all elements receive, delay focusing calculation for any pixel point in the detection area, and record A scan, B scan, C scan, and D scan data according to the full focusing phased array ultrasonic detection data. According to the cross-sectional information in the detection data, the original detection data in the scanning direction, the stepping direction, and the depth are set as x, y, and z axis data respectively, the amplitude height difference is set as color difference display, and the processed two-dimensional data is rearranged as a three-dimensional data body. The three-dimensional data body is voxelized and divided into the smallest volume elements of the system, and the image is reconstructed using the voxelized data body. The voxel grid is initialized and valued, the data source is the x, y, and z axis data corresponding to the scanning direction, the stepping direction, and the depth in the original detection data, and the threshold is set to 20%. The data body with an echo amplitude higher than 20% is extracted by isosurface extraction, and is displayed in high light in the three-dimensional image for easy observation. The image noise is reduced by using a smoothing filter, and the contrast, brightness, etc. of the three-dimensional ultrasonic imaging model are adjusted to enhance the image visual effect.

[0079] Step 8, analyze the three-dimensional imaging model in step 7, evaluate and feedback the service state information of the anticorrosive coating of the detected pipeline; in the three-dimensional image, the anticorrosive coating signal with a recording amplitude height exceeding 20% of the reference sensitivity wave height is extracted, and when the difference between the thickness of the anticorrosive coating and the nominal thickness is greater than 15%, it is determined that the anticorrosive coating in the region is missing. The shape, position, area, etc. of the anticorrosive coating shedding area are extracted and processed.

[0080] When phased array A scan detection is used, according to whether there is an anticorrosive coating delamination echo signal between the first echo signal and the second echo signal of the pipeline metal interface, the amplitude height of the reference sensitivity is more than 20% as the anticorrosive coating interface echo signal, and whether the anticorrosive coating on the inner wall of the pipeline in the region is shed is determined. If the anticorrosive coating echo signal does not appear in the echo signal or the amplitude height under the reference sensitivity does not reach 20%, it is determined that the anticorrosive coating in the region is shed. When the single sound beam axis cannot determine the anticorrosive coating, full focusing imaging is used to observe the B scan, C scan, and D scan scanning result graph, and when discontinuous and layered images appear in the scanning result graph, it is determined that the anticorrosive coating on the inner wall in the region is shed.

[0081] According to the preset outer diameter of the detected pipeline is 960mm, the pipeline thickness is 12mm, the length is 60mm initialization voxel gridding data, and the corresponding x, y, z and wave amplitude height are valued, forming a 3D image. Record the position information, and measure the thickness and area of the falling anticorrosive coating, and then according to the relevant provisions, the pipeline is processed.

[0082] The anticorrosive coating falling signal below 20% of the reference sensitivity wave height is recorded. When the defect amplitude is lower than the reference sensitivity, it proves that the defect has been very serious, and at this time the relevant treatment should be done on the parts.

Claims

1. A method for detecting anticorrosion coating on the inner wall of a pipeline by phased array, characterized in that: the anticorrosion coating on the inner wall of the pipeline is detected from the outer wall of the pipeline; step 1, collecting information of the pipeline to be detected: the pipeline is divided into straight pipe sections, elbow pipe sections and reducing pipe sections; step 2, referring to block design: the reference block is made of the same material as the pipeline to be detected and has the same acoustic performance as the pipeline to be detected; a plurality of anticorrosion coating-free areas are engraved on the reference block for setting sensitivity; step 3, selecting a detection device: a multi-channel device is selected, and the device has a partition scanning function; the phased array and full-focus detection are used to realize full-volume and non-defect-type detection of the anticorrosion coating on the pipeline; step 4, setting the focus depth and calculating the optimal focus aperture according to the pipeline to be detected; step 5, verifying the detection capability; step 6, implementing field detection; step 7, integrating multiple groups of data collected on site to establish a three-dimensional imaging result; step 8, analyzing the three-dimensional imaging to evaluate and feedback the service state information of the anticorrosion coating on the pipeline to be detected; in the step 2, the single-layer anticorrosion coating on the reference block has a thickness of 400 μm; three rectangular areas on the reference block have different anticorrosion coating thicknesses for verifying the minimum detectable anticorrosion coating thickness; the size of the anticorrosion coating-free strip-shaped area on the reference block is different, which simulates the strip-shaped anticorrosion coating falling off on site and can detect the minimum anticorrosion coating area; the size of the anticorrosion coating-free circular area on the reference block is different, which simulates the circular anticorrosion coating falling off on site and can detect the minimum anticorrosion coating area; the size of the anticorrosion coating-free rectangular area on the reference block is different, which simulates the rectangular anticorrosion coating falling off on site and can detect the minimum anticorrosion coating area; in the step 3, the number of single-shot chips of the detection device is 32; in the step 3, the detection device is a TOPAZ64 portable ultrasonic phased array instrument, the working frequency is 0.25-25 MHZ, the minimum gain step is 0.1 dB; the probe is a linear array probe with a frequency of 5 MHZ, the number of chips is 64, the spacing between each chip is 0.3 mm, the wedge block is model M12, the angle is 0 degrees, the material is low-attenuation polystyrene, and the sound speed is 2300 m / s; in the step 4, the frequency of the phased array ultrasonic wave of the detection device is set to 5 MHz, the sampling rate is set to 10 Mhz, the mode is set to true depth, the filter is set to bandpass 2.5 MHz-15 MHz; the model of the pipeline to be detected is set to a pipeline with a diameter of φ960 mm*12 mm, a length of 60 mm, an inclination angle of 90°, a focus depth of 15 mm, an absolute mode, an L-L mode, a maximum display depth of 40 mm, a maximum horizontal length of 60 mm, a width of 60 mm, a collection resolution of 256*256, a depth resolution of 0.13λ, a horizontal resolution of 0.20λ, a first array element chip of No.1, a last array element chip of No.32, and a focus aperture of 32; in the step 1, the information of the pipeline to be detected includes the material and specifications of the pipeline, and the specifications include the wall thickness, the outer diameter and the length of the pipe section. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 2. The method of claim 1, wherein: ​ 3. The method of claim 1, wherein: The step 4 is that the material of the detected pipeline is carbon steel, the acoustic impedance is 4.5*10 6 g / cm 2 ·s, the longitudinal wave speed is 5920 m / s; the material of the anticorrosive coating is epoxy resin, the acoustic impedance is 0.27*10 6 g / cm 2 ·s~0.36*10 6 g / cm 2 ·s, and the speed range is 3000~4000 m / s.

4. The method of claim 1, wherein: The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

5. The method of claim 1, wherein: The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn. The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

6. The method of claim 1, wherein: The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

7. The method of claim 1, wherein: The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn. The step 5, the ultrasonic phased array instrument is set to focus rule, the bottom end of the standard test block CSK-IA is utilized, the phased array probe is moved to measure the delay of each wafer of the phased array probe, then the phased array probe is placed on the reference test block, under the unified reference simulation parameter, the several depth different no anticorrosive coating parts of the pipeline anticorrosive coating test block are found in turn, the interface echo amplitude of the lowest echo height among them is adjusted to the instrument gain value of 80% of the full screen scale when the reference sensitivity, and the instrument gain values of the three no anticorrosive coating regions are recorded in turn.

8. The method of claim 1, wherein: The step 7 is two-dimensional gridding of the detected analog test block, the area length and width are 1m*1m, the horizontal and vertical axis interval is 0.1m; the full focusing technology is used to detect each array of the excitation probe to make all arrays receive, the delay focusing calculation is carried out on any pixel point in the detection area, the A scan, B scan, C scan and D scan data are recorded according to the full focusing phased array ultrasonic detection data, the scan direction, step direction and depth in the original detection data are respectively set as x, y and z axis data according to the cross section information in the detection data and the gridding two-dimensional plane, the amplitude height difference is set as color difference display, the processed two-dimensional data is rearranged as three-dimensional data volume, the three-dimensional data volume is voxelized and divided into the minimum volume elements of the system, the image reconstruction is carried out by using the voxelized data volume, the initial voxel grid is valued, the data source is the x, y and z axis data corresponding to the scan direction, step direction and depth in the original detection data, and the threshold is set as 20%, the data volume with the echo amplitude value higher than 20% is extracted by the isosurface extraction, is highlighted in the three-dimensional image, the smoothing filter is used to reduce the image noise, and the contrast and brightness of the three-dimensional ultrasonic imaging model are adjusted to enhance the image visual effect.

9. The method of claim 1, wherein: The step 8 is that the anticorrosive coating signal with the amplitude height exceeding 20% of the reference sensitivity wave height is extracted in the three-dimensional image, when the difference between the thickness of the anticorrosive coating and the nominal thickness is greater than 15%, it is judged that the anticorrosive coating in the area is missing, and the shape, position and area of the anticorrosive coating falling area are extracted for related processing.

10. The method of claim 1, wherein: The step 8 is that when the phased array A scan detection is used, whether the anticorrosive coating delamination echo signal exists between the first echo signal and the second echo signal of the pipeline metal interface, the amplitude height of the reference sensitivity is higher than 20% as the anticorrosive coating interface echo signal, whether the anticorrosive coating on the inner wall of the pipeline in the area falls is judged, if the anticorrosive coating echo signal does not appear in the echo signal or the amplitude height under the reference sensitivity does not reach 20%, it is judged that the anticorrosive coating in the area falls, when the single sound beam axis cannot judge the anticorrosive coating, the full focusing imaging is used to observe the B scan, C scan and D scan scanning result graph, when the discontinuous and delaminated image appears in the scanning result graph, it is judged that the anticorrosive coating on the inner wall in the area falls.

11. The method of claim 1, wherein: The step 8 is that according to the preset outer diameter of the detected pipeline of 960mm, the pipeline thickness of 12mm and the length of 60mm, the voxel gridding data is initialized, and the corresponding x, y, z and amplitude height are valued, the three-dimensional imaging is formed, the position information is recorded when the ultrasonic A scan anticorrosive coating signal is missing or the B, C and D scan images appear discontinuous and delaminated images, the thickness of the falling anticorrosive coating and the area of the falling anticorrosive coating are calculated, and the pipeline is processed according to the related regulations, the anticorrosive coating falling signal lower than 20% of the reference sensitivity wave height is recorded, and when the defect amplitude is lower than the reference sensitivity, it is proved that the defect is very serious, and at this time, the related processing should be carried out.

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