Corrosion monitoring and early warning method

Abstract

The invention discloses a corrosion monitoring and early warning method, which comprises a corrosion probe device and a signal acquisition processor, integrates two technologies of electrochemical noise monitoring and acoustic emission monitoring at the same time, and integrates probe monitoring and body monitoring at the same time. Mutual verification of electrochemical noise and acoustic emission characteristic signals is adopted, probe monitoring and equipment monitoring are carried out at the same time, the probe and equipment monitoring are combined to jointly judge the corrosion behavior generated by the monitoring equipment / pipeline, and the accuracy of monitoring and early warning is improved. In addition, stress, a gradual change gap, a welding joint and dissimilar metal are flexibly introduced into the monitoring probe aiming at various possible corrosion, various corrosion types such as stress corrosion, pitting corrosion, crevice corrosion and galvanic corrosion can be considered at the same time, and preliminary judgment of the corrosion types is given while early warning of the corrosion state is carried out.

Description

Technical Field

[0001] The present application relates to the field of pipeline corrosion risk monitoring, and specifically to a corrosion monitoring and early warning method. Background Art

[0002] Pitting and stress corrosion cracking are common forms of local damage to metal materials. In addition, corrosion is concealed in the early stages and difficult to detect through conventional detection methods. They are often the main factors for equipment / pipeline failure and are prone to leakage, fire, explosion and other accidents. How to effectively monitor and detect the corrosion process is of great significance. Acoustic emission technology and electrochemical technology are common non-destructive monitoring methods with the advantages of high sensitivity, non-destructiveness and real-time online monitoring. However, they also have the disadvantages of complex on-site interference signals and high monitoring false alarm rate, which seriously reduce the on-site application effect and restrict the development of technology. Some people have also tried a combination of the two methods. Patent CN115901881A provides a stress corrosion cracking monitoring method, device, equipment and storage medium. The pitting events and microcrack initiation events of the first stage of stress corrosion cracking of the oil pipe steel sample are monitored by electrochemical noise signals; the crack propagation events and crack tearing events of the second stage of stress corrosion cracking of the oil pipe steel sample are monitored by acoustic emission signals. The main purpose is to improve the monitoring accuracy by taking advantage of the different sensitive stages of stress corrosion of the two methods. It is not a fusion of the two methods, and the algorithm for combining the two methods is not mentioned. It is only used for laboratory samples and is not suitable for field equipment. Summary of the invention

[0003] Based on the above problems, this application proposes a corrosion monitoring and early warning method to solve the problems of multiple interferences and high false alarm rates in single electrochemical noise monitoring and single acoustic emission monitoring, as well as the shortcomings of simple electrochemical noise and acoustic emission combined probes that do not directly reflect the conditions of the equipment / pipeline to be tested. The technical solution is as follows:

[0004] A corrosion monitoring and early warning method includes a corrosion probe device and a signal acquisition processor. The corrosion probe device includes two test pieces of the same material, two layers of insulating pads are arranged between the two test pieces, a reference electrode is arranged between the two insulating pads, a bending portion is arranged on the test piece, a loading bolt is arranged on the test piece, a circular hole is reserved on the test piece, the loading bolt passes through the circular hole, the loading bolt is sleeved in an insulating sleeve, the loading bolt passes through the reserved holes on the two test pieces, and the preloading of the test piece is achieved by rotating the nut. The ends of the two test pieces are sleeved in a sleeve, and an acoustic sensor is arranged on one of the test pieces; the wires of the two test pieces, the reference electrode and the acoustic sensor are led out of the sleeve and connected to the signal acquisition processor, and at least one acoustic sensor is installed on the outer wall of the device to be tested and connected to the signal acquisition processor; the signal acquisition processor analyzes and determines the corrosion state of the device to be tested by acquiring information from the corrosion probe device and the sensor installed on the device to be tested, and issues an early warning based on the calculation results.

[0005] Preferably, the corrosion state of the equipment to be tested is represented by a state value H, which is jointly determined by the corrosion factor Z and the equipment acoustic wave characteristic factor S, and the corrosion factor Z is set to X×Y; the signal acquisition processor obtains the electrochemical signal of the sample, which is marked as the probe electrochemical factor X; the acoustic wave signal of the acoustic sensor in the corrosion probe device is marked as the monitoring probe acoustic wave characteristic factor Y.

[0006] Preferably, the probe electrochemical factor X is the product of the trend factor Q and the difference factor W, that is, X=Q×W, wherein the trend factor Q is related to the linear fitting slope of the linear segment of the noise signal in the frequency domain, and when the slope is <10, X is 1, when the slope is [10-20], X takes a value of 0.6-0.9, and when the slope is >20, X takes a value of 0-0.2; the difference factor W is related to the current between the specimens in the corresponding time period, and the similarities and differences in the voltage change trends between the specimen and the reference electrode, and when the same direction W=0-0.2, when the opposite direction W takes a value of 0.8-1.6.

[0007] Preferably, the probe acoustic wave characteristic factor Y includes an attenuation factor A and a span factor B, that is, Y=A×B; the attenuation factor A is the ratio of the slope of the linear fitting curve of the peak point in the rising or falling phase of the characteristic waveform to the slope of the corresponding fitting curve of the characteristic library waveform, or the average of four corresponding ratios; the span factor B is the product of the ratio of the normalized spacing of the trough in the rising or falling phase.

[0008] Preferably, the device acoustic wave characteristic factor S includes a shape factor C, a position repetition factor D and a frequency factor E, that is, S=C×D×E;

[0009] Image factor C: the shape similarity between the acquired acoustic waveform of the acoustic sensor installed on the equipment under test and the characteristic waveform of the probe acoustic wave of the corrosion probe device, with a value between 0 and 1. The higher the similarity, the closer the value is to 1.

[0010] Position repetition factor D: Obtain the acoustic signal time through acoustic sensors distributed on the outer wall of the device to be measured, locate the sound source position, and determine the value of D according to the concentration degree of the occurrence positions. The more concentrated the area, the larger the value of D, and the value range is 0 - 1.5; when the positioning cannot be obtained, take D = 1;

[0011] Frequency factor E: It is the correlation between the interval of the same type of sound waves obtained by the acoustic sensors on the outer wall of the device to be measured and the interval of the sound waves obtained by the sensors in the corrosion probe device. The higher the correlation, the larger the value, and the value range is 0.5 - 1.

[0012] Preferably, the corrosion state value H of the device is jointly determined by the value of the corrosion factor Z and the acoustic wave characteristic factor S of the monitoring device. The corrosion state value H includes four categories, namely "high", "relatively high", "medium", and "low", as follows:

[0013] a < Z and a < S, H = high,

[0014] b < Z ≤ a, and a < S, H = relatively high,

[0015] a < Z and b < S ≤ a, H = relatively high,

[0016] b < Z ≤ a and b < S ≤ a, H = medium

[0017] Z ≤ b or S ≤ b, H = low

[0018] Where a and b are set classification constants, the value range of a is 0.7 - 0.9, and the value range of b is 0.3 - 0.5;

[0019] Send a warning according to the H value result and the set alarm value.

[0020] Preferably, the specimen is one of U-shaped, C-shaped or polygonal, and the material is made of the same metal or dissimilar metal welding material, and the welded joint is arranged in the middle of the bending part or at the junction of the bending and non-bending parts.

[0021] Preferably, a reference electrode is placed between two insulating pads; the width of the insulating pad should not be less than the width of the specimen, and the connection part of the reference electrode and the wire is placed at the part where the specimen starts to bend at the upper part, and the exposed part of the wire connection is sealed with insulating glue.

[0022] Preferably, the thickness of each of the insulating pads is 0.1 - 3 mm.

[0023] Beneficial effects

[0024] Compared with the existing technology, electrochemical signals and acoustic emission signals are different signals generated by the same behavior on the same test piece, with good corresponding characteristics and time correlation. Through the fusion analysis of electrochemical noise signals and acoustic signals, it is easy to distinguish corrosion information from noise information, and enhance the anti-interference ability. At the same time, through the fusion analysis of information collected by the sensor on the probe and the acoustic sensor on the device to be tested / pipeline body, the anti-interference ability and the pertinence of the evaluation are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the corrosion probe device structure.

[0026] Figure 2 This is a side view of the corrosion probe device structure.

[0027] Figure 3 This is a schematic diagram for use in this application.

[0028] In the figure, 1-1 test piece, 1-11 bending part, 1-2 loading bolt, 1-3 reference electrode, 1-4 insulating pad, 1-5 insulating gasket, 1-6 insulating sleeve, 1-7 casing, 1-8 built-in acoustic sensor, 1-9 flange, 2-external acoustic sensor, 3-signal acquisition processor, 4-equipment to be tested, 7-cable. DETAILED DESCRIPTION

[0029] The following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those of ordinary skill in the art to which the present application belongs. It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application.

[0030] A corrosion monitoring and early warning method, comprising a corrosion probe device and a signal acquisition processor, wherein the corrosion probe device comprises two test pieces 1-1 of the same material, two layers of insulating pads 1-4 are arranged between the two test pieces, a reference electrode 1-3 is arranged between the two insulating pads 1-4, a bending portion 1-11 is arranged on the test piece, a loading bolt 1-2 is arranged on the test piece, the part of the loading bolt 1-2 in contact with the test piece 1-1 is sleeved in an insulating sleeve 1-6, the loading bolt 1-2 passes through the two test pieces 1-1 and is tightened by rotating a nut to realize the test piece. Preload, the ends of the two specimens are sleeved in the sleeve 1-7, and an acoustic sensor 1-8 is provided on one of the specimens 1-1; the wires of the two specimens 1-1, the reference electrode 1-3 and the acoustic sensor (marked as the built-in acoustic sensor 1-8) are led out of the sleeve 1-7 and connected to the signal acquisition processor, and at least one acoustic sensor (external acoustic sensor 2) is installed on the outer wall of the device to be tested and connected to the signal acquisition processor; the other end of the sleeve 1-7 is welded with a flange 1-9, which is connected and sealed with the prefabricated pipe on the device to be tested 4 through the flange. The signal acquisition processor 3 collects the acoustic signal of the device to be tested. The signal acquisition processor is composed of an electrochemical signal acquisition unit, an acoustic signal acquisition unit, a control unit and a display unit, etc. The external acoustic sensor 2 and the built-in acoustic sensor 1-8 are both connected to the acoustic signal acquisition unit in the signal acquisition and analysis system, and the connecting wires of the two specimens are respectively connected to the electrochemical signal acquisition unit in the signal acquisition and analysis system, and the two specimens are respectively connected to the working electrode terminal and the counter electrode terminal, and the reference electrode 1-3 is connected to the reference electrode terminal. The signal acquisition processor comprehensively determines the corrosion state of the device under test by acquiring information from the corrosion probe device and the external acoustic sensor 2 installed on the device under test, and issues an early warning based on the calculation results.

[0031] During the working process, the signal acquisition and analysis system simultaneously collects the electrochemical noise signal and acoustic signal generated by the corrosion probe. Since the electrochemical signal and the acoustic emission signal are different signals caused by the same behavior on the same test piece, they have good corresponding characteristics and time correlation. Through the fusion analysis of the electrochemical noise signal and the acoustic signal, it is easy to distinguish the corrosion information with correlation and the noise information without correlation between the two, which enhances the anti-interference ability. At the same time, since the corrosion probe device introduces stress and gap conditions, and the welding conditions can be introduced through the welding test piece, it can achieve a closer to the actual environmental conditions of the on-site equipment / pipeline body. In addition, an acoustic sensor is also set on the equipment body. The signal characteristics of various corrosion and noise extracted by the corrosion probe device can be used for noise filtering and feature recognition of the acoustic sensor capture signal on the equipment body to be tested, which further improves the anti-interference ability and greatly reduces the false alarm rate. Realize online monitoring of various corrosion forms such as uniform corrosion, pitting corrosion, crevice corrosion, stress corrosion cracking, etc. of the equipment to be tested on site.

[0032] Installation method:

[0033] The specimen 1-1 is composed of two identical specimens. The specimens can be selected in various shapes that are easy to load, such as U-shaped, C-shaped or polygonal. The material used to make the specimens can be a uniform material or can be made of the same metal or different metal welding materials. The welding joint is preferably set in the middle of the curved part or at the junction of the curved and non-curved parts. The long side of the specimen is placed back to back, with two layers of insulating pads 1-4 placed in the middle, and the reference electrode 1-3 and its wire placed in the middle of the two layers of insulating pads. The width of the two layers of insulating pads should not be less than the width of the specimen. The position of the reference electrode and the specimen is adjusted. The connection part of the reference electrode and the wire is preferably placed at the part where the bending begins on the upper part of the specimen, and the exposed part of the wire connection is sealed with insulating glue. The distance between the two specimens and the size of the gap formed between the specimen and the insulating pad / reference electrode surface are adjusted by adjusting the thickness of the insulating isolation pad. The gap size is controlled to be 0.1 to 3 mm. Insert the insulating gasket 1-5 on the loading bolt 1-2 and the insulating sleeve 1-6 on the opening of the sample. Tighten the bolts passing through the sample with nuts. According to the required stress, the deformation of the sample is controlled by tightening the nuts. Usually, the sample needs to be loaded until plastic deformation occurs locally, thereby introducing a stress of 0 to σ on the sample. s (yield strength) gradual stress condition. The loaded specimen is connected to the wire, and the connection parts are also sealed with insulating glue. The long end of the specimen together with the wire connected to the specimen and the electrode are extended into the sleeve 1-7, and a built-in acoustic sensor 1-8 is installed on the long side of one of the specimens. A thin layer of coupling agent needs to be applied between the acoustic sensor and the specimen to maintain good contact. After passing the local lead break test, it is sealed and fixed with sealant. In order to facilitate disassembly, the outer casing of the sensor can also be installed to seal and fix it. An elastic clamping device, such as a spring, a spring sheet, etc., is set between the casing and the sensor. The connection and sealing of the sleeve 1-7 and the loaded specimen 1-1 are achieved by extruding the sealing ring or injecting sealant. The specific connection and sealing method needs to be selected according to the operating pressure and temperature.

[0034] The signal cables, electrode wires and connecting wires on the test piece of the built-in acoustic sensors 1-8 are uniformly led out of the sleeve 1-7, and connected and sealed with the prefabricated pipe on the device to be tested 4 through the flange. The led-out cable is connected to the signal acquisition and processing system 3. The built-in acoustic sensor is connected to the acoustic signal acquisition unit in the signal acquisition and analysis system, the sample with the built-in acoustic sensor is connected to the working electrode of the electrochemical signal acquisition unit in the signal acquisition and analysis system 3 through a wire, and the other sample is connected to the counter electrode of the electrochemical signal acquisition unit in the signal acquisition and analysis system through a wire, and the reference electrode is connected to the reference electrode of the electrochemical signal acquisition unit in the signal acquisition and analysis system through a wire. Then, according to the characteristics and structural dimensions of the internal medium of the device / pipeline to be tested, the external acoustic sensor is arranged. The specific arrangement position, quantity and sensor selection need to be selected and optimized according to the actual situation on site according to the corrosion site, the size of the area to be monitored, the sound attenuation, etc., which belongs to routine operation and will not be repeated. The acoustic sensor 2 arranged on the surface of the device to be tested or the pipeline is also connected to the acoustic signal acquisition unit in the signal acquisition and analysis system 3 through a cable. After completing the arrangement and signal inspection, you can start monitoring and recording data.

[0035] The collection and analysis system will perform fusion analysis and noise reduction on the collected information, and alarm and display abnormal information. The specific methods are as follows:

[0036] The corrosion state of the equipment to be tested is represented by the state value H, which is determined by the corrosion factor Z and the equipment acoustic wave characteristic factor S. The corrosion factor Z is set to X×Y; the signal acquisition processor obtains the electrochemical signal of the sample, which is marked as the probe electrochemical factor X; the acoustic wave signal of the acoustic sensor in the corrosion probe device is marked as the monitoring probe acoustic wave characteristic factor Y.

[0037] The probe electrochemical factor X is the product of the trend factor Q and the difference factor W, that is, X=Q×W, where the trend factor Q is related to the linear fitting slope of the linear segment of the noise signal in the frequency domain. When the slope is <10, X is 1, when the slope is [10-20], X is 0.6-0.9, and when the slope is >20, X is 0-0.2. The difference factor W is related to the current between the specimens in the corresponding time period, and the similarities and differences in the voltage change trends between the specimen and the reference electrode. In the same direction, W=0-0.2, and in the opposite direction, W is 0.8-1.6.

[0038] The probe acoustic wave characteristic factor Y includes the attenuation factor A and the span factor B, that is, Y=A×B; the attenuation factor A is the ratio of the slope of the linear fitting curve of the crest point of the characteristic waveform in the rising or falling stage to the slope of the corresponding fitting curve of the characteristic library waveform, or the average of four corresponding ratios; the span factor B is the product of the ratio of the normalized spacing of the trough in the rising or falling stage.

[0039] The acoustic wave characteristic factor S of the device includes the pictorial factor C, the position repetition factor D, and the frequency factor E, i.e., S = C × D × E;

[0040] Pictorial factor C: The shape similarity between the acoustic wave form obtained by the acoustic sensor installed on the device to be measured and the probe acoustic wave characteristic waveform of the corrosion probe device, which takes values between 0 and 1. The higher the similarity, the closer the value is to 1;

[0041] Position repetition factor D: The time of the acoustic signal is obtained through the acoustic sensors distributed on the outer wall of the device to be measured, and the sound - emitting position is located. The value of D is determined according to the concentration degree of the occurrence positions. The more concentrated the area is, the larger the value of D is, and the value range is 0 - 1.5; when the positioning cannot be obtained, take D = 1;

[0042] Frequency factor E: It is the correlation between the interval of the same type of acoustic waves obtained by the acoustic sensors on the outer wall of the device to be measured and the interval of the acoustic waves obtained by the sensors in the corrosion probe device. The higher the correlation, the larger the value, and the value range is 0.5 - 1.

[0043] The corrosion state value H of the device is jointly determined by the value of the corrosion factor Z and the acoustic wave characteristic factor S of the monitoring device. The corrosion state value H includes four categories, namely "high", "relatively high", "medium", and "low", as follows:

[0044] a < Z and a < S, H = high,

[0045] b < Z ≤ a, and a < S, H = relatively high,

[0046] a < Z and b < S ≤ a, H = relatively high,

[0047] b < Z ≤ a and b < S ≤ a, H = medium

[0048] Z ≤ b or S ≤ b, H = low

[0049] Where a and b are set classification constants. The value range of a is 0.7 - 0.9, and the value range of b is 0.3 - 0.5; early warnings are sent according to the H - value result and the set alarm value.

[0050] The present invention is applicable to corrosion scenarios such as uniform corrosion, pitting corrosion, stress corrosion, crevice corrosion, galvanic corrosion, etc., and can be widely applied to many industries such as petrochemical, electric power, new energy, etc., and has a very broad application prospect.

Claims

1. A corrosion monitoring and early warning method, characterized in that: It comprises a corrosion probe device and a signal acquisition processor, wherein the corrosion probe device comprises two test pieces of the same material, two layers of insulating pads are arranged between the two test pieces, a reference electrode is arranged between the two insulating pads, a bending portion is arranged on the test piece, a loading bolt is arranged on the test piece, the part of the loading bolt in contact with the test piece is sleeved in an insulating sleeve, the loading bolt passes through the two test pieces and is preloaded by rotating and tightening the nut, the ends of the two test pieces are sleeved in a sleeve, and an acoustic sensor is arranged on one of the test pieces; the wires of the test piece, the reference electrode and the acoustic sensor are led out from the sleeve and connected to the signal acquisition processor, and at least one acoustic sensor is installed on the outer wall of the device to be tested and connected to the signal acquisition processor; The signal acquisition processor analyzes and determines the corrosion status of the equipment under test by acquiring information from the corrosion probe device and the sensors installed on the equipment under test, and issues an early warning based on the calculation results.

2. A corrosion monitoring and early warning method according to claim 1, characterized in that: The corrosion state of the equipment to be tested is represented by the state value H, which is determined by the corrosion factor Z and the equipment acoustic wave characteristic factor S. The corrosion factor Z is set to X×Y; the signal acquisition processor obtains the electrochemical signal of the sample, which is marked as the probe electrochemical factor X; the acoustic wave signal of the acoustic sensor in the corrosion probe device is marked as the monitoring probe acoustic wave characteristic factor Y.

3. A corrosion monitoring and early warning method according to claim 2, characterized in that: The probe electrochemical factor X is the product of the trend factor Q and the difference factor W, that is, X=Q×W, where the trend factor Q is related to the linear fitting slope of the linear segment of the noise signal in the frequency domain. When the slope is <10, X is 1, when the slope is [10-20], X is 0.6-0.9, and when the slope is >20, X is 0-0.

2. The difference factor W is related to the current between the specimens in the corresponding time period, and the voltage change trends between the specimen and the reference electrode. In the same direction, W=0-0.2, and in the opposite direction, W is 0.8-1.

6.

4. A corrosion monitoring and early warning method according to claim 2, characterized in that: The probe acoustic wave characteristic factor Y includes the attenuation factor A and the span factor B, that is, Y=A×B; the attenuation factor A is the ratio of the slope of the linear fitting curve of the crest point of the characteristic waveform in the rising or falling stage to the slope of the corresponding fitting curve of the characteristic library waveform, or the average of four corresponding ratios; the span factor B is the product of the ratio of the normalized spacing of the trough in the rising or falling stage.

5. A corrosion monitoring and early warning method according to claim 2, characterized in that: The equipment acoustic wave characteristic factor S includes the image factor C, the position repetition factor D and the frequency factor E, that is, S = C × D × E; Image factor C: the shape similarity between the acquired acoustic waveform of the acoustic sensor installed on the equipment under test and the characteristic waveform of the probe acoustic wave of the corrosion probe device, with a value between 0 and 1. The higher the similarity, the closer the value is to 1. Position repeatability factor D: The acoustic signal time is obtained by the acoustic sensors distributed on the outer wall of the device to be tested, and the sound position is located. The D value is determined according to the concentration of the occurrence position. The more concentrated the area, the larger the D value is. The value range is 0-1.

5. When the position cannot be obtained, D=1; Frequency factor E: It is the correlation between the interval of similar sound waves obtained by the acoustic sensor on the outer wall of the equipment to be tested and the interval of sound waves obtained by the acoustic sensor in the corrosion probe device. The higher the correlation, the larger the value. The value range is 0.5 to 1.

6. A corrosion monitoring and early warning method according to claim 2, characterized in that: The corrosion state value H of the device is jointly determined by the value of the corrosion factor Z and the acoustic wave characteristic factor S of the device. The corrosion state value H includes four categories, namely "high", "relatively high", "medium" and "low", which are specifically as follows: a < Z and a < S, H = high, b < Z ≤ a, and a < S, H = relatively high, a < Z and b < S ≤ a, H = relatively high, b < Z ≤ a and b < S ≤ a, H = medium Z ≤ b or S ≤ b, H = low Where a and b are set classification constants. The value range of a is 0.7 - 0.9, and the value range of b is 0.3 - 0.5; An early warning is sent according to the H value result and the set alarm value.

7. A corrosion monitoring and early warning method according to claim 1, characterized in that: The specimen is one of U-shaped, C-shaped or polygonal. The specimen is a homogeneous material or a heterogeneous material with a welded joint. The heterogeneous material is welded by the same metal or dissimilar metals. The welded joint is arranged in the middle of the bending part or at the junction of the bending and non-bending parts.

8. A corrosion monitoring and early warning method according to claim 1, characterized in that: The width of the insulating pad should not be less than the width of the specimen. The connection part of the reference electrode and the wire is placed at the part where the specimen starts to bend at the upper part. The exposed part of the wire connection is sealed with insulating glue.

9. A corrosion monitoring and early warning method according to claim 1, characterized in that: There is a gradually increasing opening gap area between adjacent parts of the two specimens. The gap width formed between the two specimens is adjusted by the thickness of the insulating pad. The thickness of the insulating pad is 0.1 - 3 mm.

10. A corrosion monitoring and early warning method according to claim 1, characterized in that: The preloading of the specimen is controlled by rotating the nut, and gradually changing different stress conditions are introduced at different parts of the specimen.

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