Pulse type ultrasonic instrument detection method for coating shedding condition in pipeline

Abstract

The invention provides a pulse-type ultrasonic instrument detection method for the falling condition of a coating in a pipeline, and the method comprises the steps: detecting a to-be-detected pipeline by using a pulse-type ultrasonic instrument, and if matrix metal interface echo signals appear for multiple times and amplitude signals with the amplitude lower than that of the matrix metal interface echo signals appear after multiple metal interface echoes in a single period, determining that the to-be-detected pipeline falls off. If the difference value between the measured value of the coating thickness and the nominal thickness is within the allowable deviation range of the coating process, judging that the coating is not thinned and does not fall off, and the matrix metal is not corroded; if matrix metal interface echo signals appear for many times and coating interface signals do not appear later, determining that the matrix metal is not corroded and the coating falls off; and if the matrix metal interface echo signals do not appear for many times, determining that the matrix metal is corroded and the coating falls off. According to the method, the falling condition of the coating in the pipeline is detected through the pulse type ultrasonic instrument, so that the problems that damage to the coating in the pipeline cannot be detected through an original pipeline coating detection method, and personnel and equipment have risks and are easily limited by the environment during detection are solved.

Description

Technical Field

[0001] This application belongs to the technical field of pipeline corrosion detection, and specifically relates to a pulsed ultrasonic instrument detection method for the situation of internal pipeline coating peeling off. Background Technique

[0002] Seawater pipelines belong to the seawater transportation pipeline system and are widely used in industries such as thermal power / nuclear power plants, seawater desalination, offshore platforms, port facilities, and seawater aquaculture. With the development and utilization of marine resources, the use of seawater pipelines has become increasingly frequent, and they can be used for seawater intake for equipment cooling or as a water supply system, etc. The seawater inside the pipeline contains a large amount of salts and chlorides, which are highly corrosive to metals. In an environment with oxygen, high temperature, high flow rate, and pollution, how to detect pipeline damage in a timely manner is a key issue. To avoid major accidents, a large number of non-destructive testing technologies are applied in the manufacturing, use, and inspection links of pipelines.

[0003] The pipeline uses alloy steel as the base metal and undergoes anti-corrosion treatment on the inner and outer surfaces, adopting a combined protection measure of cathodic protection and anti-corrosion coating. Due to the long-term exposure of the pipeline to a humid environment, the aging, erosion, and local defects of the pipeline lining cause small-area damage and expose the carbon steel base material, thus forming a small anode and a large cathode, which will cause a large corrosion current to be generated in the anode part, accelerating the corrosion of this area and even causing perforation, affecting the safe operation of the pipeline system.

[0004] For the detection of internal pipeline coating peeling off, electric spark detection is usually used. The electric spark detection method mainly applies a high-voltage electric field on the surface. When there are defects, the high-voltage electric field will break down at the defects to generate an electric spark current, and the instrument receives the current signal to judge the defect position in the detection area. The specific implementation steps of the electric spark detection method are as follows: preparation work, check that the electric spark detector is in good working condition, and select an appropriate detection voltage according to the material and thickness of the material to be detected; probe connection, place the ground wire of the electric spark detector on the exposed metal part of the pipeline to be detected, and install the high-voltage probe electrode on the electric spark detector; start detection, set the detection voltage, move the high-voltage motor end to the surface of the pipeline coating, move it slowly and evenly. When there are pinholes or cracks in the coating, the electric spark detector will generate sparks and sound alarms. The electric spark detection method is generally applicable to the integrity detection of external pipeline coatings, but in the process of use, it involves high voltage and generates electric sparks when detecting coating peeling off, which is prone to risks in the implementation process. Moreover, this detection method can only detect the coating peeling off on the surface or near the surface and cannot detect deep internal pipeline coating defects. And there is a hidden safety hazard of short circuit when used in a humid environment, and the high-voltage electric spark may break through the coating and cause minor damage to the thin coating on the surface of the pipeline to be detected.

[0005] Another detection method for coating detachment inside a pipeline is eddy current testing. Eddy current testing is based on the principle of electromagnetic induction. An alternating current passes through a detection coil to generate an alternating electromagnetic field. When interacting with a conductive material, a vortex-like induced current is generated inside the material. When there are defects inside the material, the flow path of the eddy current is disturbed. By using the detection coil to receive the impedance change, the position and nature of near-surface defects can be identified. Eddy current testing is commonly used to detect surface and near-surface defects of conductive materials. By virtue of the eddy current density, distribution, and impedance change picked up by the detection coil in absolute and differential probes, the integrity of the area is judged. However, the detection depth of this detection method is limited. It is only applicable to detecting surface and near-surface defects, and the signal is easily affected by material properties, shape, temperature, etc. It cannot detect the coating detachment inside the pipeline. It has high requirements for the detection environment and has limitations in on-site implementation. Summary of the Invention

[0006] In view of this, the present application provides a pulsed ultrasonic instrument detection method for coating detachment inside a pipeline. By using a pulsed ultrasonic instrument to detect the coating detachment inside the pipeline and observing the echo signal of the matrix metal interface to determine whether the coating detachment phenomenon is detected, it is intended to solve the problems that the existing pipeline coating detection methods cannot detect the coating damage inside the pipeline, there are risks for personnel and equipment during detection, and it is easily restricted by the environment during detection.

[0007] The present application provides a pulsed ultrasonic instrument detection method for coating detachment inside a pipeline. This pulsed ultrasonic instrument detection method for coating detachment inside a pipeline includes steps 10 to 40.

[0008] Step 10: According to the information of the pipeline to be detected, determine a pulsed ultrasonic instrument for detecting coating detachment inside the pipeline to be detected. The pulsed ultrasonic instrument has the detection ability to identify the thinnest coating detachment coating area.

[0009] Step 20: Use the pulsed ultrasonic instrument to detect the pipeline to be detected. If multiple echo signals of the matrix metal interface appear, and a signal with an amplitude lower than that of the echo signal of the matrix metal interface appears after multiple metal interface echoes within a single period, calculate the measured coating thickness value according to the coating propagation speed and the signal propagation time and compare it with the nominal thickness. If the difference value between the measured coating thickness value and the nominal thickness is within the allowable deviation range of the coating process, it is determined that the coating inside the pipeline to be detected has not thinned or detached, and the matrix metal of the pipeline to be detected has not corroded.

[0010] Step 30: If multiple echo signals of the matrix metal interface appear and no coating interface signal appears after multiple echo signals of the matrix metal interface, it is determined that the matrix metal of the pipeline to be detected has not been corroded and the coating inside the pipeline to be detected has detached.

[0011] Step 40: If the multiple matrix metal interface echo signals do not appear, it is determined that the matrix metal is corroded and the inner coating of the pipeline to be detected has peeled off.

[0012] In a specific embodiment of the present application, the pulsed ultrasonic detector method for detecting the peeling off of the inner coating of the pipeline further includes Step 50.

[0013] Step 50: If the peeling off of the coating occurs, record the position where the coating interface echo signal does not appear as the reference point, move the probe of the pulsed ultrasonic detector until the coating interface signal appears, record it as the boundary of the peeling off position of the coating at the target position. After determining the boundary, measure and record the peeling off area of the coating.

[0014] In a specific embodiment of the present application, Steps 11 to 14 are a specific implementation manner of Step 10.

[0015] Step 11: According to the information of the pipeline to be detected, determine the performance indexes of the pulsed ultrasonic detector for detecting the peeling off of the inner coating of the pipeline to be detected.

[0016] Step 12: Considering the frequency and wafer size of the probe comprehensively, determine the probe used by the pulsed ultrasonic detector.

[0017] Step 13: Fabricate a comparison test block. The comparison test block has the same material, thickness, and forming process as the pipeline to be detected. A uniform coating made of the same material as the outer wall of the pipeline to be detected is provided on the outer wall of the comparison test block. Coating intact areas, completely peeled off coating areas, and multiple coating thinning areas with different coating thicknesses are provided on the inner wall of the comparison test block. The peeling off position of the coating of the comparison test block is determined according to the thinnest coating thickness required for the inner coating of the pipeline to be detected.

[0018] Step 14: Use the pulsed ultrasonic detector determined in Step 11 and the probe determined in Step 12 to detect the completely peeled off coating area and the coating thinning areas of the comparison test block fabricated in Step 13, so as to verify that the pulsed ultrasonic detector has the detection ability to identify the thinnest peeled off coating area of the coating.

[0019] In a specific embodiment of the present application, the formation method of the peeling off structure of the coating of the comparison test block is as follows: Coat the upper and lower surfaces of the matrix metal test block made of the same material with a coating. Before and after coating, use a measuring tool to calibrate the thickness of the test block matrix and the coating thickness; or, polish at different peeling off positions of the inner coating area of the comparison test block to thin the coating to different coating thicknesses, and polish at the corresponding positions of the completely peeled off coating area of the inner coating of the comparison test block until the metal matrix appears.

[0020] In a specific embodiment of the present application, if the thinnest coating thickness required for the inner coating of the pipeline to be detected is 400 μm, the thicknesses of the multiple coating thinning areas are respectively set to be 400 μm to 1000 μm.

[0021] In a specific embodiment of the present application, steps 141 to 143 are a specific implementation of the above step 14.

[0022] Step 141: Adjust the parameters of the pulsed ultrasonic instrument.

[0023] Step 142: Place the probe determined in step 12 on the area with intact coating of the reference block, and adjust the gain of the pulsed ultrasonic instrument so that the echo signal of the base metal interface of the reference block reaches 60% - 80% of the full screen.

[0024] Step 143: Place the probe on multiple coating thinning areas with different coating thicknesses of the reference block respectively, and slowly move the probe smoothly towards the area where the coating has completely peeled off. When the coating signal in the interface displayed by the pulsed ultrasonic instrument disappears, determine that there is an obvious change in the waveform signal, and determine that the position where the waveform signal shows a difference is the interface between the area with coating and the area where the coating has completely peeled off, that is, verify that the pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling area through the reference block.

[0025] In a specific embodiment of the present application, the performance indicators of the pulsed ultrasonic instrument include: vertical linear range 5% - 95%, error ≤ 6%, horizontal linear range 0 - 90%, error ≤ 2%, total gain ≥ 60 dB, accuracy ± 1 dB per 20 dB.

[0026] In a specific embodiment of the present application, if the coating is an epoxy resin coating, the probe used by the pulsed ultrasonic instrument is a single crystal straight probe with 5 MHz and a circular wafer diameter of 14 mm.

[0027] In a specific embodiment of the present application, the base metal material of the pipeline to be detected is carbon steel, with an acoustic impedance of 4.5×10 6 g / cm 2 ·s and a longitudinal wave velocity of 5920 m / s.

[0028] In a specific embodiment of the present application, the material of the coating is epoxy resin, with an acoustic impedance of 0.27× 6 g / cm 2 ·s - 0.36×10 6 g / cm 2 ·s and a sound velocity range of 3000 - 4000 m / s.

[0029] The beneficial effects of the technical solution of the present application are: the pulsed ultrasonic instrument detection method provided in the embodiment of the present application is used to detect the shedding of the inner coating of the pipeline, which is easier to implement for field detection and in-situ detection of the pipeline, and the detection method is simple to operate and is not limited by the detection site, and has the following beneficial effects: 1) It can intuitively reflect the location of the coating shedding area on the pipeline for subsequent maintenance; 2) It can realize qualitative detection of the coating shedding phenomenon, and judge whether the shedding is debonding or thinning; whether the metal matrix of the pipeline is corroded; 3) It can realize portable detection of the inner coating of the pipeline, is not limited by the detection site, and is suitable for field detection and in-situ detection; 4) The pulsed ultrasonic instrument detection method is not restricted by the environment and has no requirements for noise and humidity; 5) The pulsed ultrasonic instrument detection method is highly safe and does not pose a danger to the pipeline or personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure shows a flow chart of a pulsed ultrasonic instrument detection method for pipeline inner coating shedding provided in one embodiment of the present application.

[0031] Figure 2 The figure shows the thinnest coating shedding size in a pulsed ultrasonic instrument detection method for pipeline inner coating shedding provided by an embodiment of the present application.

[0032] Figure 3 Shown is a schematic diagram of a comparison test block produced by a pulsed ultrasonic instrument detection method for pipeline inner coating shedding provided in an embodiment of the present application.

[0033] Figure 4 Shown is a schematic diagram of the step coating thickness of a comparison test block provided in an embodiment of the present application.

[0034] Figure 5 Shown is a waveform diagram of a comparative test block provided in an embodiment of the present application, in which the coating is not damaged and the base metal is intact.

[0035] Figure 6 Shown is a waveform diagram of a comparative test block provided in an embodiment of the present application, in which the coating is corroded and damaged but the base metal is intact.

[0036] Figure 7 Shown is a waveform diagram showing the corrosion and shedding of the coating on the comparative test block and the corrosion of the base metal provided in one embodiment of the present application.

[0037] Figure 8 The figure shows a waveform diagram showing that the inner coating of the pipeline to be inspected is not damaged and the base metal is intact, provided by an embodiment of the present application.

[0038] Figure 9 The figure shows a waveform diagram of a pipeline to be inspected provided in an embodiment of the present application, in which the inner coating is damaged by corrosion but the base metal is intact.

[0039] Figure 10 The figure shows a waveform diagram of the corrosion and peeling of the inner coating of a pipeline to be detected and the corrosion of the base metal provided by an embodiment of the present application. Detailed implementation manners

[0040] When ultrasonic waves propagate from one medium to another medium, at the interface of the two media, a part of the energy is reflected back into the original medium, which is called the reflected wave; another part of the energy passes through the interface and propagates in the other medium, which is called the transmitted wave. When the sound wave penetrates the heterogeneous interface, the distribution of sound energy and the propagation direction are related to the acoustic impedance on both sides of the interface. When the acoustic impedance of the incident wave medium is much greater than that of the transmitted wave medium, the ultrasonic wave is almost completely reflected and there is no transmission; when the difference in acoustic impedance between the two media is very small, it is almost completely transmitted and there is no reflection; when there is a certain acoustic impedance between the two media, there are two phenomena of reflection and transmission of the sound wave at the heterogeneous interface. By analyzing the reflected echo received by the sensor, the position, shape and size of the ultrasonic wave in the defect and the propagation time of the medium can be analyzed, and the propagation distance of the medium in the sound beam propagation direction can be calculated, that is, when the sound wave is vertically incident, the thickness of the object to be detected can be measured.

[0041] The pulse ultrasonic detector generates a short-time high-voltage pulse through the built-in pulse generator, applies it to the transmitting transducer (usually a piezoelectric wafer) to generate mechanical vibration, and thus emits ultrasonic waves. The ultrasonic waves are transmitted into the object to be detected through the coupling agent, and the propagation speed depends on the properties of the object to be detected (density and elastic modulus). When the ultrasonic wave propagates, when it encounters a heterogeneous interface with different acoustic impedances, the reflection and transmission of the ultrasonic wave are emitted. The transmitting transducer receives the reflected echo, converts the mechanical vibration into an electrical signal, and after being processed by the amplifier and input into the signal processing unit, it is filtered and gain-compensated, and then displayed in the form of A-scan (amplitude-time) on the display screen. By the propagation time of the ultrasonic wave in the interface and the propagation speed of the medium, the propagation distance of the ultrasonic wave in the medium, that is, the thickness of the medium, can be calculated.

[0042] Based on the above analysis and research, aiming at the problems that the existing pipeline coating detection method cannot detect the damage of the inner coating of the pipeline, there are risks for personnel and equipment during detection, and it is easily restricted by the environment during detection, the present application provides a pulse ultrasonic detector detection method for the peeling condition of the inner coating of the pipeline, specifically a method for determining the peeling degree and peeling area of the inner coating of the pipeline, so as to solve the problems that the existing pipeline coating detection method cannot detect the damage of the inner coating of the pipeline, there are risks for personnel and equipment during detection, and it is easily restricted by the environment during detection.

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0044] Figure 1 It is a flowchart of a pulsed ultrasonic instrument detection method for the situation of in-pipe coating peeling in an embodiment of the present application. As Figure 1 shown, the pulsed ultrasonic instrument detection method for the situation of in-pipe coating peeling provided by the present application may include the following implementation steps.

[0045] Step 10: Determine a pulsed ultrasonic instrument for detecting the peeling of the in-pipe coating according to the information of the pipeline to be detected. The pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling coating area.

[0046] Step 20: Use the pulsed ultrasonic instrument to detect the pipeline to be detected. If multiple base metal interface echo signals appear, and a signal with an amplitude lower than that of the base metal interface echo signal appears after multiple metal interface echoes within a single period, calculate the measured coating thickness according to the coating propagation speed and the signal propagation time and compare it with the nominal thickness. If the difference value between the measured coating thickness and the nominal thickness is within the allowable deviation range of the coating process, it is determined that the in-pipe coating of the pipeline to be detected has not thinned or peeled, and the base metal of the pipeline to be detected has not corroded.

[0047] Step 30: If multiple base metal interface echo signals appear and no coating interface signal appears after the multiple base metal interface echo signals, it is determined that the base metal of the pipeline to be detected has not been corroded and the in-pipe coating of the pipeline to be detected has peeled off.

[0048] It should be noted that the coating can be an anti-corrosion coating. Correspondingly, the coating interface signal can be an anti-corrosion coating interface signal.

[0049] Step 40: If multiple base metal interface echo signals do not appear, it is determined that the base metal has been corroded and the in-pipe coating of the pipeline to be detected has peeled off.

[0050] Specifically, the probe can be coupled to the outer surface of the pipeline to be detected, and the probe is slowly moved to ensure that there is a certain overlap of the probe wafers in the moving area. During the process of detecting the inner surface of the pipeline to be detected, the echo signal of the matrix metal interface is observed to determine whether the coating peeling phenomenon is detected. By observing the multiple echo signals of the matrix metal interface existing in the pulse reflection echo signal, the presence of the echo signal of the matrix metal interface and the coating interface signal in the echo signal is analyzed, and the internal coating condition of the pipeline to be detected is divided into three cases: both the matrix metal and the coating are intact (that is, the inner coating of the pipeline to be detected is not thinned or peeled off, and the matrix metal of the pipeline to be detected is not corroded), the matrix metal is intact but the coating is missing (that is, the matrix metal of the pipeline to be detected is not corroded, and the inner coating of the pipeline to be detected is peeled off), and the coating is missing and the matrix metal is corroded (that is, the matrix metal is corroded, and the inner coating of the pipeline to be detected is peeled off).

[0051] The pulsed ultrasonic detector method provided by the embodiment of the present application is used for detecting the peeling of the inner coating of the pipeline, which is easier to implement for field detection and in-situ detection of the pipeline. Moreover, this detection method is simple to operate and is not restricted by the detection site, and has the following beneficial effects: 1) It can intuitively reflect the position of the coating peeling area on the pipeline for subsequent maintenance; 2) It can realize the qualitative detection of the coating peeling phenomenon, and judge whether the peeling is debonding or thinning; whether the pipeline metal matrix is corroded; 3) It can realize the portable detection of the inner coating of the pipeline, is not restricted by the detection site, and is applicable to field detection and in-situ detection; 4) This pulsed ultrasonic detector method is not restricted by the environment and has no requirements for noise and humidity; 5) This pulsed ultrasonic detector method has strong safety and does not pose risks to the pipeline and personnel.

[0052] In at least one embodiment of the present application, the pulsed ultrasonic detector method for the peeling situation of the inner coating of the pipeline further includes step 50.

[0053] Step 50: If the coating peeling situation occurs, record the non-occurrence of the coating interface echo signal as the reference point, move the probe of the pulsed ultrasonic detector until the coating interface signal appears, record it as the boundary of the coating peeling position at the target position, and after determining the boundary, measure and record the coating peeling area.

[0054] Specifically, it is stipulated that the abnormal area where the coating signal does not appear is the reference point, and the probe of the pulsed ultrasonic detector is moved around. When the coating interface signal appears in the reflection signal diagram, it is the boundary point. Try to obtain as many boundary points as possible in a single detection to determine the size of the anti-corrosion layer peeling area.

[0055] In the above embodiment, step 50 proposes a measurement and calculation method for the anti-corrosion coating peeling area, which quantitatively describes the current corrosion situation.

[0056] In at least one embodiment of the present application, steps 11 to 14 are a specific implementation manner of step 10.

[0057] Step 11: According to the information of the pipeline to be detected, determine the performance indicators of the pulsed ultrasonic instrument for detecting the inner coating peeling of the pipeline to be detected.

[0058] In the embodiment of the present application, a pulsed ultrasonic instrument (or called pulsed ultrasonic detector, pulsed emission ultrasonic detector) is used. An electrical signal is applied through the equipped probe. The piezoelectric material in the probe generates high-frequency vibration and then emits ultrasonic waves of a specified frequency. The probe receives the ultrasonic waves propagated and reflected in the object to be detected, and determines whether there is coating peeling by detecting the signal, and conducts qualitative and quantitative evaluation.

[0059] In some embodiments, the determined performance indicators of the pulsed ultrasonic instrument include: vertical linear range 5% - 95%, error ≤ 6%, horizontal linear range 0 - 90%, error ≤ 2%, total gain (attenuation) amount ≥ 60 dB, accuracy ±1 dB per 20 dB.

[0060] Step 12: Considering the frequency and wafer size of the probe comprehensively, determine the probe used by the pulsed ultrasonic instrument.

[0061] The probe used by the pulsed ultrasonic instrument is used to generate and receive ultrasonic waves. Through cable connection, the detection data is transmitted to the ultrasonic detector. The probe generally consists of piezoelectric material and a probe housing. The performance of the probe affects the characteristics of the emitted ultrasonic waves, and thus affects the detection ability of the detection. The main functions are to convert received electrical energy into sound energy and receive reflected sound energy and convert it into electrical energy. The performance indicators affecting the probe mainly but not limited to: frequency, bandwidth, pulse width, static capacitance, wafer size, sensitivity, directivity, coupling effect, probe material, durability, etc.

[0062] Among the above performances, frequency and wafer size are key factors. Frequency determines the detection ability of ultrasonic waves to the object to be inspected. Low-frequency probes have strong penetration ability and longer wavelengths, which are suitable for detecting large defects with better detection depth; high-frequency probes have faster attenuation and general penetration ability, and are more suitable for detecting near-surface, surface or thin workpiece materials. The wafer size mainly affects resonance characteristics, probe sensitivity, response speed, etc. In addition to the above effects, frequency and wafer size jointly affect the near field area and beam divergence angle of the probe, affecting the judgment and positioning of defects. The near field area refers to the area where the ultrasonic wave emitted by the probe has a relatively short emission path distance, with a length ranging from a single wavelength to several wavelengths. The propagation characteristics of ultrasonic waves in this near field area are different from those in the far field area, with complex interference, diffraction, and uneven energy distribution, affecting the accuracy and effectiveness of detection; the beam divergence angle is the angle at which the sound wave beam emitted from the probe spreads during propagation. Due to the interference of the wavefront phase, the sound beam does not propagate in a single straight line but spreads out, with stronger central beam energy and higher detection accuracy. Among them, the calculation formula for the near field area N is , is the wave source area, is the medium wavelength. The beam divergence angle expressing the beam directivity The calculation formula is , where is the medium wavelength, is the wafer size, is a constant factor related to the intercepted amplitude reduction value. When it drops by 6 dB, = 0.51; when it drops by 12 dB, = 0.7, and when it drops by 20 dB, = 1.08.

[0063] Based on the above analysis, when selecting a probe, two indicators of the probe need to be comprehensively considered, including the frequency and wafer size of the probe, which can not only achieve the penetration of the base metal but also realize the identification and detection of the peeling off of the thinnest coating; specifically, the greater the attenuation of the structural material, the smaller the frequency used. For detecting the base metal with a large thickness, it is beneficial to use a probe with a large wafer size, and for detecting near-surface defects, it is more appropriate to use a small-size probe. The thinnest detectable coating thickness is 400 μm. As Figure 2 shown, it is a schematic diagram of the thinnest coating that can be detected in the pulsed ultrasonic detector detection method for detecting the peeling off of the inner coating of the pipeline provided by the embodiment of the present application.

[0064] The probe used in the determined pulsed ultrasonic instrument is used to detect the minimum detectable defect size of the coating inside the pipeline. The probe can be a wide-band narrow-pulse probe. The wide band enables the probe to receive echo signals of multiple frequencies, expanding the effective signal reception range; the narrow-pulse probe concentrates the ultrasonic energy in a short time, providing higher time resolution and helping to improve the resolution ability for the anti-corrosion coating during detection; high signal-to-noise ratio, with a narrow pulse width, reducing the overlapping time between the noise signal and the effective signal, and improving the signal-to-noise ratio.

[0065] In some embodiments, if the coating is an epoxy resin coating (such as a zinc-containing epoxy resin coating), the probe used in the determined pulsed ultrasonic instrument is a single-crystal straight probe with a frequency of 5 MHz and a circular wafer diameter of 14 mm. In this way, while ensuring sufficient energy, the scanning area of the probe is reduced, improving the detection ability for small-area coating peeling regions. In addition, by selecting the performance indicators of the determined pulsed ultrasonic instrument and the performance of the probe used in the pulsed ultrasonic instrument, the minimum recognizable anti-corrosion coating thickness is shortened to 400 μm.

[0066] Step 13: Fabricate a comparison test block. The comparison test block has the same material, thickness, and forming process as the pipeline to be detected. A uniform coating of the same material as the outer wall of the pipeline to be detected is provided on the outer wall of the comparison test block, and areas with intact coatings, areas with completely peeled coatings, and multiple coating thinning areas with different coating thicknesses are provided on the inner wall of the comparison test block. The coating peeling position of the comparison test block is determined according to the thinnest coating thickness required for the detection of the coating inside the pipeline to be detected.

[0067] Specifically, the outer wall of the comparison test block is provided with an outer surface coating, the inner wall of the comparison test block is provided with an inner surface coating, and areas with intact coatings (also known as defect-free areas), areas with completely peeled coatings (also known as non-coated areas, corresponding to complete debonding), and multiple coating thinning areas with different coating thicknesses (corresponding to different coating thinning situations) are provided at designated positions on the inner wall of the comparison test block.

[0068] The comparison test block can effectively determine whether the thinnest coating peeling of the pipeline coating is recognized. When fabricating the comparison test block, materials, thicknesses, and forming processes that are the same or similar to those of the pipeline to be detected should be selected; among them, the comparison test block includes a pipeline simulation body, coating thinning areas with different thicknesses brushed on the inner wall of the pipeline, and a coating completely peeled area with a preset size is formed at a designated position on the comparison test block.

[0069] In at least one embodiment of the present application, the formation method of the coating peeling structure of the reference block is as follows: Coat the upper and lower surfaces of the substrate metal block of the same material with a coating. Before and after coating, use a measuring tool to calibrate the thickness of the substrate block and the coating thickness; or, polish at different coating peeling positions in the coating area of the reference block to thin the coating to different coating thicknesses, and polish at the corresponding positions in the area where the coating has completely peeled off in the reference block until the metal substrate appears.

[0070] The coating peeling positions of the reference block are determined according to the thinnest coating thickness required to be detected for the internal coating of the pipeline to be detected. As Figure 3 shown, it is a physical diagram of the reference block made by using the pulsed ultrasonic detector method for detecting the peeling of the internal coating of the pipeline provided by the embodiment of the present application. Figure 3 It is a schematic diagram of the inner wall of the reference block. The coating peeling positions of the reference block include the area where the coating on the inner surface of the reference block has completely peeled off and the coating thinning area, etc.

[0071] The thicknesses of multiple coating thinning areas can be set according to actual needs. In some embodiments, if the thinnest coating thickness required to be detected for the internal coating of the pipeline to be detected is 400 μm, the thicknesses of multiple coating thinning areas are respectively set to 400 μm to 1000 μm. For example, 400 μm, 600 μm, 800 μm, 1000 μm.

[0072] Step 14: Use the pulsed ultrasonic detector determined in step 11 and the probe determined in step 12 to detect the area where the coating has completely peeled off and the coating thinning area of the reference block made in step 13, so as to verify that the pulsed ultrasonic detector has the detection ability to identify the thinnest coating peeling coating area.

[0073] In the above embodiments, the reference block contains coating peeling defects simulating various shapes and is provided with coatings of different thicknesses, so as to improve and quantify the detection ability of the whole set of systems. After verifying the detection ability of the pulsed ultrasonic detector with the reference block, then detect the pipeline to be detected. On the basis that the pulsed ultrasonic detector can detect the thinnest coating peeling coating area, detect the internal surface coating of the pipeline to be detected to detect whether there is coating peeling on the internal surface of the pipeline to be detected, and the position of the detected defect in the depth direction inside the pipeline to be detected, realizing a quantitative description of the pipeline coating peeling situation.

[0074] The detection principle of the pulsed ultrasonic instrument detection method for the in-pipe coating peeling situation provided by the embodiments of the present application is as follows: The pulsed ultrasonic instrument emits an electrical signal, which is converted into an ultrasonic signal by the probe, and the signal is transmitted to the inside of the pipeline or the reference block to be detected. When the ultrasonic wave encounters defects (such as cracks, cavities, inclusions, delaminations, etc.), reflection and attenuation phenomena occur. When it is transmitted to the interface, the acoustic impedance changes on both sides, and part of the acoustic wave returns and is received by the probe. By measuring the time difference between the transmitted ultrasonic wave and the received reflected wave, the position of the defect can be determined. By collecting the above information and analyzing the echo signals of the matrix metal interface and the coating echo signal, the detection of the in-pipe coating is realized. Figure 4 The figure is a schematic diagram for detecting the coating peeling of the object to be detected by using the pulsed ultrasonic instrument detection method for the in-pipe coating peeling provided by the embodiments of the present application. Figure 8 , Figure 9 , Figure 10 Showing the ultrasonic signal diagrams of various pipeline corrosion situations in the embodiments, Figure 8 It is a schematic diagram of the waveform in the area where the coating is intact, Figure 9 It is a schematic diagram for detecting the disappearance of the coating interface signal, Figure 10 It is a schematic diagram for detecting coating peeling and corrosion of the matrix metal inside the pipeline, Figure 8 and Figure 9 Both are the waveforms of "multiple echo reflections" of the pipeline.

[0075] In at least one embodiment of the present application, steps 141 to 143 are a specific implementation manner of the above step 14.

[0076] Step 141: Adjust the parameters of the pulsed ultrasonic instrument.

[0077] Step 142: Place the probe determined in step 12 in the area where the coating of the reference block is intact, and adjust the gain of the pulsed ultrasonic instrument so that the echo signal of the matrix metal interface of the reference block reaches 60% - 80% of the full screen.

[0078] In at least one embodiment of the present application, the matrix metal material of the pipeline to be detected is carbon steel, and the acoustic impedance is 4.5×10 6 g / cm 2 ·s, and the longitudinal wave sound velocity is 5920 m / s; the material of the coating is epoxy resin, and the acoustic impedance is 0.27× 6 g / cm 2 ·s~0.36×10 6 g / cm 2 ·s, and the sound velocity range is 3000 - 4000 m / s.

[0079] If the matrix metal material of the pipeline to be detected is carbon steel and the material of the coating is epoxy resin, according to the sound pressure reflectivity calculation formula , Z is the interfacial acoustic impedance. The sound pressure reflectivity between the base metal and the epoxy resin coating is -0.85, the sound pressure refractive index is 0.15, and the sound intensity reflectivity is 0.72. That is, part of the ultrasonic waves are reflected at the junction of the base metal and the epoxy resin coating, and part are refracted into the epoxy resin for propagation. Moreover, the energy of the ultrasonic waves refracted into the epoxy resin coating for propagation is lower than the ultrasonic signal reflected at the interface. The acoustic impedance of air is 0.00004×10 6 g / cm 2 ·s, the sound pressure reflectivity is -0.99, and the sound waves refracted into the epoxy resin coating are totally reflected at the interface between the epoxy resin coating and the air. Observe the waveform displayed on the fluorescence screen. There are metal interface echo signals and coating interface echo signals within a single period. The sound velocity of carbon steel is greater than that of epoxy resin, and the energy of the carbon steel echo signal is higher than that of the epoxy resin echo signal. On the display interface of the A-type pulsed ultrasonic instrument, the epoxy resin coating interface signal appears on the right side of the metal echo signal on the x-axis, and the amplitude height is lower than that of the carbon steel metal echo signal.

[0080] Step 143: Place the probe on multiple coating thinning areas with different coating thicknesses of the reference test block, and slowly move the probe smoothly towards the area where the coating has completely peeled off. Determine that the waveform signal changes significantly. When the coating signal disappears on the display interface of the pulsed ultrasonic instrument, determine that the waveform signal changes significantly, and determine that the position where the waveform signal shows differences is the interface between the coated area and the area where the coating has completely peeled off. That is, verify that the pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling area through the reference test block.

[0081] For example, in the above embodiment, the determination process of the coating peeling situation is as follows: First, adjust the parameters of the pulsed ultrasonic instrument. The pulse repetition frequency is 200 Hz, the energy is 150 V, the damping is 100 Ω, the pulse width is 100 μs, and the signal mode is bidirectional (corresponding to Step 141); then place the probe on the area where the coating of the reference test block is intact, and adjust the gain of the pulsed ultrasonic instrument so that the base metal interface echo signal of the reference test block (to determine whether it is the metal interface echo signal of the pipeline, you can dip your hand in the coupling agent (such as industrial paste CG-08) and pat the corresponding position on the lower panel where the probe is placed. If the waveform changes with the patting frequency, it is the base metal interface echo signal) reaches 60% - 80% of the full screen (corresponding to Step 142). Place the probe on the areas where the coating of the reference test block has not peeled off. If both the base metal interface echo signal and the coating wave signal appear, it means that the coating interface signal can be clearly identified. The coating inside the pipeline in this area has not peeled off and the base metal has not been corroded. Place the probe on areas with different coating thicknesses of the reference test block, and compare the signal diagrams to determine the thinnest detectable coating, and then the detection can be carried out in this state (corresponding to Step 143).

[0082] After verifying the thinnest detectable coating on the structural member through a reference block, finally, the internal coating of the pipeline to be detected is inspected. The probe is coupled to the outer wall of the pipeline to be detected, and the probe is slowly moved to ensure the overlapping of the moving area of the probe. If multiple base metal interface echo signals appear and the coating interface echo signal does not appear, it is determined that the internal coating of the pipeline in this area has peeled off and the base metal has not been corroded; if neither multiple base metal interface echo signals nor coating interface echo signals appear, the coating in this area has peeled off and the base metal inside the pipeline has been corroded (corresponding to steps 10 to 40 above).

[0083] When the situation of the internal coating of the pipeline peeling off while the base metal inside the pipeline is not corroded or the coating of the pipeline peeling off while the base metal is corroded occurs as described above, the size of the corrosion damage area can be measured. At the position where the coating interface signal is missing, taking this position as the reference point, the probe is moved to the surrounding area. When the coating interface signal appears, it indicates that the coating at this position has not peeled off, which is the boundary point of the peeling area. As many boundary points as possible are measured according to the detection requirements to improve the area measurement accuracy of the corrosion damage position. After the boundary detection of the corrosion area is completed, the area size of the corrosion area is calculated and recorded.

[0084] The pulsed ultrasonic detector detection method for the peeling of the internal coating of the pipeline provided by the embodiment of the present application selects the type and performance indicators of the pulsed ultrasonic detector used for detecting the peeling of the internal coating of the pipeline, and selects the probe used by the pulsed ultrasonic detector, including the frequency and wafer size of the probe; and a reference block is made according to the material, thickness and forming process of the pipeline to be detected; thus, the selected pulsed ultrasonic detector and probe are used. First, the reference block is used to detect the coating peeling area and the intact coating area, and on the basis of determining the thinnest coating that can be detected on the pipeline, the pipeline to be detected is detected to detect whether the internal coating of the pipeline has peeled off and whether the base metal inside the pipeline has been corroded.

[0085] The following demonstrates the implementation manner of the pulsed ultrasonic detector detection method for the peeling of the internal coating of the pipeline provided by the embodiment of the present application through a specific implementation example.

[0086] During the daily open-pipe maintenance and repair of a certain type of seawater pipeline, it is found that some parts of the pipeline are rusty. However, the operation department needs to clearly indicate the specific location and the degree of corrosion damage on the inner wall of the specific pipe section of the pipeline system and the size of the corrosion damage area to evaluate whether the pipeline needs to be replaced.

[0087] The detection method of pulsed ultrasonic instrument for pipeline internal coating peeling provided by the embodiment of the present application is used to detect a certain pipe section. The instrument used is CTS-9009PLUS, and the probe is a straight probe with 5MHz / 14, a center frequency of 4.49Mhz, and a pulse width of 73.9%. First, place the probe on the good area of the test block and adjust the base metal interface echo signal to 80% of the full screen, as Figure 5 , Figure 6 and Figure 7 shown. It is a schematic diagram of the base metal interface echo signal for detecting the good area of the test block in the embodiment of the present application. Determine the thinnest coating thickness found on the reference test block. After verification, place the probe on the outer wall of the pipeline again. The waveforms are as Figure 8 , Figure 9 and Figure 10 shown. It is a schematic diagram of the waveforms for detecting the coating peeling area of the pipeline in the embodiment of the present application. The base metal interface echo signal and the coating interface signal appear in the multiple reflection waves. At this time, it can be judged that the base metal is not corroded and the internal coating of the pipeline is not peeled off, because if the base metal in the pipeline is not corroded and there is a coating, the multiple reflection waves should contain both the base metal interface echo signal and the coating interface signal at the same time; move to other areas. At this time, only the base metal interface echo signal appears in the multiple reflection signals, indicating that the internal coating of the pipeline in this area has been corroded to the thinnest detectable thickness, but the base metal on the inner wall of the pipeline is still not corroded; change the detection area again and find that there is no multiple reflection base metal interface echo signal, indicating that the coating in this area has peeled off and the base metal has been corroded. The sound beam is scattered and absorbed by the metal in the corroded area, and the multiple reflection base metal interface echo signal cannot be formed.

[0088] Figures 5 to 10 In the horizontal axis coordinate in ,

[0088] , Figures 5 to 10 is the sound path scanned by the probe (sound path = time * sound speed), and the unit is millimeter (mm). The vertical axis coordinate is the ultrasonic amplitude (or simply called wave amplitude). Figures 5 to 10 reflects the specific situation of the ultrasonic wave propagating in the base metal and the anti-corrosion coating.

[0089] It should be noted that the combination method of each technical feature in the embodiment of the present application is not limited to the combination method recorded in the embodiment of the present application or the combination method recorded in the specific embodiment. All the technical features recorded in the present application can be freely combined or combined in any way, unless contradictions occur between them.

[0090] As shown in the present application and the claims, unless the context clearly indicates an exceptional situation, words such as "a", "one kind" and / or "the" are not specifically singular, but may also include plural. Generally speaking, the term "comprising" only indicates the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0091] Although the embodiments disclosed in the present application are as described above, the content is only for facilitating understanding of the present application and is not intended to limit the present application. Any person skilled in the art within the scope of the present application may make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present application. However, the scope of patent protection of the present application shall still be subject to the scope defined by the appended claims.

Claims

1. A pulsed ultrasonic instrument detection method for the situation of internal coating peeling off in a pipeline, characterized in that, Including: Step 10: Determine a pulsed ultrasonic instrument for detecting the coating peeling inside the pipeline to be detected according to the information of the pipeline to be detected. The pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling area. Step 20: Use the pulsed ultrasonic instrument to detect the pipeline to be detected. If multiple base metal interface echo signals appear, and a signal with an amplitude lower than that of the base metal interface echo signal appears after multiple metal interface echoes within a single period, calculate the measured coating thickness value according to the coating propagation speed and the signal propagation time and compare it with the nominal thickness. If the difference value between the measured coating thickness value and the nominal thickness is within the allowable deviation range of the coating process, it is determined that the coating inside the pipeline to be detected has not thinned or peeled, and the base metal of the pipeline to be detected has not corroded. Step 30: If multiple base metal interface echo signals appear and no coating interface signal appears after multiple base metal interface echo signals, it is determined that the base metal of the pipeline to be detected has not been corroded and the coating inside the pipeline to be detected has peeled off. Step 40: If multiple base metal interface echo signals do not appear, it is determined that the base metal has been corroded and the coating inside the pipeline to be detected has peeled off.

2. The pulse ultrasonic instrument detection method for the pipeline inner coating peeling situation according to claim 1, characterized in that Also including: Step 50: If coating peeling occurs, record the position without the coating interface echo signal as a reference point, move the probe of the pulsed ultrasonic instrument until a coating interface signal appears, record it as the boundary of the coating peeling position at the target location, and after determining the boundary, measure and record the coating peeling area.

3. The pulsed ultrasonic instrument detection method for the situation of internal pipeline coating peeling according to claim 1, characterized in that, Step 10 includes: Step 11: Determine the performance indicators of the pulsed ultrasonic instrument for detecting the coating peeling inside the pipeline to be detected according to the information of the pipeline to be detected. Step 12: Considering the frequency and wafer size of the probe comprehensively, determine the probe used by the pulsed ultrasonic instrument. Step 13: Manufacture a comparison test block. The comparison test block has the same material, thickness and forming process as the pipeline to be detected. The outer wall of the comparison test block is provided with a uniform coating of the same material as the outer wall of the pipeline to be detected. Coating intact areas, completely peeled coating areas and multiple coating thinning areas with different coating thicknesses are provided on the inner wall of the comparison test block. The coating peeling position of the comparison test block is determined according to the thinnest coating thickness required to be detected for the coating inside the pipeline to be detected. Step 14: Use the pulsed ultrasonic instrument determined in Step 11 and the probe determined in Step 12 to detect the completely peeled coating area and the coating thinning area of the comparison test block manufactured in Step 13 to verify that the pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling area.

4. The pulse ultrasonic detector method for detecting the peeling condition of the inner coating of a pipeline according to claim 3, characterized in that, The formation method of the coating peeling structure of the comparison test block is as follows: Coat the upper and lower surfaces of the base metal test block of the same material, and use a measuring tool to calibrate the thickness of the test block base and the coating thickness before and after coating; or, polish at different coating peeling positions in the coating area of the comparison test block to thin the coating to different coating thicknesses, and polish at the corresponding positions in the completely peeled coating area of the comparison test block until the metal matrix appears.

5. The pulse ultrasonic instrument detection method for the situation of inner coating peeling off in a pipeline according to claim 3, characterized in that, If the thinnest coating thickness required to be detected for the coating inside the pipeline to be detected is 400 μm, the thicknesses of the multiple coating thinning areas are respectively set to 400 μm to 1000 μm.

6. The pulse ultrasonic instrument detection method for the situation of inner coating peeling off in a pipeline according to claim 3, characterized in that, Step 14 includes: Step 141: Adjust the parameters of the pulsed ultrasonic instrument. Step 142: Place the probe determined in Step 12 on the area with intact coating of the reference block, and adjust the gain of the pulsed ultrasonic instrument so that the echo signal of the base metal interface of the reference block reaches 60% - 80% of the full screen. Step 143: Place the probe on multiple coating thinning areas with different coating thicknesses of the reference block respectively, and slowly move the probe smoothly towards the area where the coating has completely peeled off. When the coating signal in the interface displayed by the pulsed ultrasonic instrument disappears, determine that there is an obvious change in the waveform signal, and determine the position where the waveform signal shows a difference as the interface between the coating and the area where the coating has completely peeled off, that is, verify that the pulsed ultrasonic instrument has the detection ability to identify the thinnest coating peeling area through the reference block.

7. A pulsed ultrasonic instrument detection method for the situation of internal coating peeling in a pipeline according to any one of claims 1 to 6, characterized in that, The performance indicators of the pulsed ultrasonic instrument include: vertical linear range 5% - 95%, error ≤ 6%, horizontal linear range 0 - 90%, error ≤ 2%, total gain ≥ 60 dB, accuracy ± 1 dB per 20 dB.

8. A pulsed ultrasonic instrument detection method for the condition of in-pipe coating peeling according to any one of claims 1 to 6, characterized in that, If the coating is an epoxy resin coating, the probe used by the pulsed ultrasonic instrument is a single crystal straight probe with a frequency of 5 MHz and a circular wafer diameter of 14 mm.

9. A pulsed ultrasonic instrument detection method for the situation of in-pipe coating peeling according to any one of claims 1 to 6, characterized in that, The base metal material of the pipeline to be detected is carbon steel, with an acoustic impedance of 4.5×10 6 g / cm 2 ·s and a longitudinal wave velocity of 5920 m / s.

10. A pulsed ultrasonic instrument detection method for the situation of internal coating peeling in a pipeline according to any one of claims 1 to 6, characterized in that, The material of the coating is epoxy resin, with an acoustic impedance of 0.27× 6 g / cm 2 ·s to 0.36×10 6 g / cm 2 ·s, and the sound velocity range is 3000 - 4000 m / s.

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