A Ground-Based Pipeline Defect Detection Technology Based on Alternating Electromagnetic Excitation

Abstract

This invention discloses a ground-based pipeline defect detection technology based on alternating electromagnetic excitation. The steps are as follows: collecting basic information on the steel pipeline, including pipeline size, burial depth, and material; determining the excitation frequency; calibrating the electromagnetic signal strength of the foundation; detecting pipeline defects; classifying and grading pipeline defects by using the electromagnetic signal waveform, the cooperative variation characteristics between different components, and a quantitative calculation model of pipeline damage degree; and combining this with the regional risk assessment to determine the pipeline failure risk and provide corresponding maintenance and repair recommendations. This provides a more accurate and efficient solution for trenchless ground-based pipeline inspection.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipeline safety technology, and in particular to a pipeline defect ground detection technology based on alternating electromagnetic excitation. Technical Background

[0002] Pipelines, as the primary means of transporting oil and gas energy, possess advantages such as high transport capacity and low operating costs, serving as a lifeline for ensuring national modern energy security. Long-distance oil and gas pipelines are numerous, extensive, and distributed across complex environments. Under the combined effects of internal pressure, temperature differences, soil loads, and the medium, they are highly susceptible to defects such as stress concentration and volume loss. Furthermore, they are prone to fracture failure under both internal and external loads, seriously threatening safe pipeline operation, leading to leaks, fractures, and significant economic and property losses. Therefore, regular pipeline inspections are necessary to monitor their safety status and ensure safe operation.

[0003] Existing methods for sensing pipeline safety status mainly include open-cut inspection, represented by ultrasonic stress testing, and trenchless inspection using magnetic flux leakage (MFL) internal detection. Open-cut inspection carries the risk of disturbing the geological structure of the target pipeline and inducing geological disasters. Internal detection requires a launch and receiver cylinder for support, and fixed inspection paths between stations cannot meet the specific inspection needs of certain risk sections. Furthermore, the operation of internal detectors is subject to specific operating conditions; pressure reduction and throttling operations decrease pipeline transport efficiency, resulting in economic losses. Non-contact magnetic sensing, with its advantages of being trenchless and not limited by pipe diameter or operating conditions, has become one of the main methods for inspecting buried pipelines.

[0004] However, geomagnetic excitation-based pipeline magnetic tomography (MTM) has the following drawbacks:

[0005] 1. Low signal strength and insufficient usability. The non-contact ground signals collected in actual detection are geomagnetically excited. Under large lift conditions, the signal attenuates severely in space, resulting in low signal strength.

[0006] 2. The detection signal is easily affected by the detection environment, making it impossible to quantitatively evaluate pipeline damage. In actual detection, there are interferences such as stray currents and geomagnetic field fluctuations, and the repeatability between different rounds is poor, making it impossible to quantitatively evaluate pipeline defect damage.

[0007] 3. Inability to identify defect types on the ground. Existing detection methods lack signal processing capabilities, and can only locate defects on the ground through signal fluctuations, failing to uncover the correlation between signals and defects, thus failing to identify pipeline defect types. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a ground-based pipeline defect detection technology based on alternating electromagnetic excitation. Leveraging the differences in metallographic and microstructural effects caused by stress at the defect location and corrosion products, the technology utilizes secondary excitation generated by alternating current at the defect location to enhance the ground-based detection signal strength. This represents a breakthrough from "weak excitation, weak signal" to "strong excitation, strong signal," providing technical support for the quantitative analysis of stress in circumferential welds.

[0009] The technical solution provided by this invention to solve the above-mentioned technical problems is a pipeline defect ground detection technology based on alternating electromagnetic excitation, including a pipeline defect ground detection device and method based on alternating electromagnetic excitation. The pipeline defect ground detection method based on alternating electromagnetic excitation is characterized by the following steps:

[0010] S1. Collect the basic design parameters of the pipeline to be inspected, determine the pipeline section to be inspected according to the site requirements, and mark the pipeline route and burial depth using a pipe probe to complete the preliminary work for ground inspection of pipeline defects based on alternating electromagnetic excitation.

[0011] S2. Defects are detected under different frequency conditions, and the optimal excitation frequency is determined by comparing the detection results of different rounds.

[0012] S3. The basic strength of the electromagnetic signal of the pipeline to be tested is calibrated, and the basic strength of the electromagnetic signal is corrected and calibrated by the signal correction model according to the actual pipeline diameter and burial depth information.

[0013] S4. Connect the alternating excitation device to the cathodic protection potential test pile through the wire, apply alternating current to the pipeline at the optimal excitation frequency, and the tester wearing a wearable alternating electromagnetic excitation pipeline defect ground detection device moves at a constant speed along the pipeline axis to detect the degree of pipeline defect damage.

[0014] S5. By using the electromagnetic signal waveform, the coordinated change characteristics between different components, and the quantitative calculation model of pipeline damage degree, pipeline defects are classified and graded for identification. Combined with the regional level, the risk of pipeline failure is judged, and corresponding maintenance and repair suggestions are given.

[0015] Preferably, in step S2, the method for determining the optimal excitation frequency includes the following steps:

[0016] S21. Apply excitation current to the pipeline through the cathodic protection potential test pile, and apply arbitrary excitation frequency to the pipeline;

[0017] S22. Conduct pre-inspection of potentially risky pipe sections along the pipeline axis until an abnormal electromagnetic signal is detected, and the pipeline defect or damage is located.

[0018] S23. Adjust the frequency of the alternating excitation current, repeatedly detect the located defect location, compare the amplitude of electromagnetic signal changes under different frequency conditions, and select the excitation frequency with the largest amplitude change as the optimal excitation frequency.

[0019] Preferably, the electromagnetic signal in step 2 is obtained by differentially analyzing the induced intensity of the collected electromagnetic signal, aiming to eliminate background magnetic field strength interference through differential analysis. The electromagnetic signal is divided into G... ix G iy G iz Three components and modulus G i The formula for calculating the amplitude of the electromagnetic signal change is:

[0020] ΔG i =G imax -G iave (1)

[0021] In the formula, ΔG i G represents the amplitude of the electromagnetic signal change, in nT / m; imax The maximum value of the acquired defect electromagnetic signal is nT / m; G imax This represents the average value of the electromagnetic signal at the non-defect location.

[0022] Preferably, in step S3, the electromagnetic signal basic strength calibration method includes the following steps:

[0023] S31. Apply an excitation current to the pipeline through a cathodic protection potential test pile, with the current frequency being the optimal excitation current obtained from the test.

[0024] S32. Select a normal pipe or circumferential weld for testing, obtain the amplitude of electromagnetic signal component changes, and determine the basic electromagnetic signal strength of the normal pipe or circumferential weld.

[0025] S33. Record the burial depth and pipe diameter information of the pipeline, and use the electromagnetic signal height correction model to analyze the basic strength three components and the modulus ΔG. istax ΔG istay ΔG istaz With ΔG ista Perform correction calibration.

[0026] Preferably, the calculation formula for the electromagnetic signal height correction model is:

[0027]

[0028] In the formula, G ista Electromagnetic signal strength under standard altitude conditions, nT / m; G iThe intensity of the collected electromagnetic signal is represented by f1(D), f1(D), k1, and k2, which are undetermined parameters related to the pipe burial depth and wall thickness, obtained through burial depth testing. D is the pipe diameter in meters, and h is the pipe burial depth in meters.

[0029] Preferably, the pipeline defect classification and grading evaluation method described in step S5 includes the following steps:

[0030] S51. Based on the pipe burial depth recorded by the pipe probe during the inspection, the electromagnetic signal strength is converted into the electromagnetic signal strength under standard height conditions using the electromagnetic signal height correction model.

[0031] S52. Based on the waveform (single-peak fluctuation, sinusoidal fluctuation) and signal coordination change characteristics between components of the electromagnetic signals compared in the early stage (different types of defects cause single or multiple signal changes), ground identification of pipeline defect types is achieved.

[0032] S53. Extract the maximum change value of a specific component or modulus of the electromagnetic signal according to the defect type, and obtain the degree of pipeline damage by referring to the initial pressure of the pipeline and using the pipeline damage degree F-value calculation model that considers the pipeline stress state.

[0033] S54. Referring to the pipeline defect damage degree and maintenance management method, provide corresponding maintenance recommendations based on the pipeline damage degree F value.

[0034] Preferably, in step S5, the calculation model for the pipeline damage degree F value considering the pipeline stress state is as follows:

[0035]

[0036] In the formula, F represents the degree of pipeline damage; f(σ) is a correction factor considering the pipeline stress state; ΔG ista This parameter represents the electromagnetic signal variation under standard height conditions. Depending on the actual defect type, this parameter can be replaced with the three components of the electromagnetic signal variation, ΔG. istax ΔG istay ΔG istaz , nT / m; ΔG ista0 This parameter represents the reference change value of the electromagnetic signal under standard height conditions. Depending on the actual defect type, this parameter can be replaced with the three components ΔG of the reference change value of the electromagnetic signal, according to actual needs. istax ΔG istay ΔG istaz Three components, nT / m.

[0037] Preferably, in step S5, the degree of pipeline defect damage and the maintenance management method are as follows:

[0038] 0.4 < F < 1, the damage degree of pipeline defects in low- and medium-risk areas is level one, low risk. It is recommended that the pipeline be used normally. The damage degree of pipeline defects in high-risk areas is level two, medium risk. It is recommended that the pipeline be used under monitoring.

[0039] 0.2 < F < 0.4, the damage degree of pipeline defects in low- and medium-risk areas is level two, medium risk. It is recommended that the pipeline be used under monitoring. The damage degree of pipeline defects in high-risk areas is level three, high risk. It is recommended that the pipeline be repaired immediately.

[0040] 0 < F < 0.2, the damage degree of pipeline defects in low-, medium- and high-risk areas is all level three, high risk. It is recommended that the pipeline be repaired immediately.

[0041] The beneficial effects of the present invention are as follows:

[0042] 1. The detection method for strengthening the non-contact signal intensity by alternating electromagnetic excitation current proposed by the present invention strengthens the non-contact signal intensity on the ground through the secondary excitation caused by the current distortion at the defect position, and improves the positioning accuracy and detection rate of defects.

[0043] 2. The second-order exponential form electromagnetic signal height correction model proposed by the present invention solves the problems of missed detection and false detection caused by abnormal signal jitter due to pipeline burial depth fluctuations during the detection process. The collected electromagnetic signals are corrected to the signal intensity under the standard height through the model, providing a basis for the evaluation of the damage degree of defects.

[0044] 3. The present invention proposes a classification and recognition method for identifying pipeline defect types through the waveform and co-variation law of electromagnetic signal components, and establishes a damage degree evaluation method in combination with the signal fluctuation amplitude. The combination of the two realizes the classification and grading evaluation of buried steel pipeline defect damage.

[0045] 4. Referring to the classification and grading evaluation method for buried steel pipeline defect damage proposed by the present invention, the failure risk of the pipeline is evaluated according to the defect damage degree of the pipeline and the regional risk level, and corresponding maintenance, management measures and methods are established. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below only relate to some embodiments of the present invention and do not limit the present invention.

[0047] Figure 1 It is a schematic diagram of the ground detection method for pipeline defects based on alternating electromagnetic excitation of the present invention;

[0048] Figure 2 It is a schematic diagram of the device for alternating excitation and signal collection of the pipeline of the present invention;

[0049] Figure 3 This is a schematic diagram of the stress concentration defect signal collected by the present invention;

[0050] Figure 4 This is a schematic diagram of the defect signals of the circumferential weld seam collected by the present invention.

[0051] The figure shows

[0052] 1—Buried pipeline, 2—Magnetic gradient meter, 3—Cathode protection pile, 4—Alternating excitation device, 5—Connecting wire, 6—Pipeline cover, 7—Magnetic gradient meter, 8—RTK positioning device, 9—Engineering host computer, 10—Wearable frame, 11—Backpack shoulder strap, 12—Alternating excitation device. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Unless otherwise defined, the technical or scientific terms used in this disclosure should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar words used in this disclosure, mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly. The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0054] like Figures 1 to 4 As shown, a ground-based pipeline defect detection technology based on alternating electromagnetic excitation includes the following steps:

[0055] S1. Collect the basic design parameters of the pipeline to be inspected, determine the pipeline section to be inspected according to the site requirements, and mark the pipeline route and burial depth using a pipe probe to complete the preliminary work for ground inspection of pipeline defects based on alternating electromagnetic excitation.

[0056] S2, such as Figure 1 As shown, defects are detected under different frequency conditions, and the optimal excitation frequency is determined by comparing the detection results of different rounds.

[0057] The method for determining the optimal excitation frequency includes the following steps:

[0058] S21. Apply excitation current to the pipeline through the cathodic protection potential test pile, and apply arbitrary excitation frequency to the pipeline;

[0059] S22. Conduct pre-inspection of potentially risky pipe sections along the pipeline axis until an abnormal electromagnetic signal is detected, and the pipeline defect or damage is located.

[0060] S23. Adjust the frequency of the alternating excitation current and repeatedly detect the located defect location. Compare the amplitude of electromagnetic signal changes under different frequency conditions and select the excitation frequency with the largest amplitude change as the optimal excitation frequency. Through comparative experiments, it was found that the optimal excitation frequency for a 1016mm x 80 pipe is 62.1kHz.

[0061] Preferably, the electromagnetic signal in step 2 is obtained by differentially analyzing the induced intensity of the collected electromagnetic signal, aiming to eliminate background magnetic field strength interference through differential analysis. The electromagnetic signal is divided into G... ix G iy G iz Three components and modulus G i The formula for calculating the amplitude of the electromagnetic signal change is:

[0062] ΔG i =G imax -G iave (4)

[0063] In the formula, ΔG i G represents the amplitude of the electromagnetic signal change, in nT / m; imax The maximum value of the acquired defect electromagnetic signal is nT / m; G imax This represents the average value of the electromagnetic signal at the non-defect location.

[0064] S3. Calibrate the basic electromagnetic signal strength of the pipeline to be tested. The target pipe section diameter is 1016mm. Correct and calibrate the basic electromagnetic signal strength using a signal correction model.

[0065] The basic method for calibrating the strength of electromagnetic signals includes the following steps:

[0066] S31. Apply an excitation current to the pipeline through a cathodic protection potential test pile, with the current frequency being the optimal excitation current obtained from the test.

[0067] S32. Select a normal pipe or circumferential weld for testing, obtain the amplitude of electromagnetic signal component changes, and determine the basic electromagnetic signal strength of the normal pipe or circumferential weld.

[0068] S33. Record the burial depth and pipe diameter information of the pipeline, and use the electromagnetic signal height correction model to analyze the basic strength three components and the modulus ΔG. istax ΔG istay ΔG istaz With ΔG ista Perform correction calibration.

[0069] Preferably, the calculation formula for the electromagnetic signal height correction model is:

[0070] G ista =Gi / [1.489e -5.01h +0.122e -1.1429h (5)

[0071] where G ista is the electromagnetic signal intensity under standard height conditions, nT / m; G i is the electromagnetic signal intensity collected; f1(D), f1(D), k1, k2 are undetermined parameters related to the pipeline burial depth and wall thickness, obtained through burial depth test experiments; D is the pipeline diameter, m; h is the pipeline burial depth, m.

[0072] S4. Connect the alternating excitation device to the cathodic protection potential test pile through wires, apply an alternating current to the pipeline at the optimal excitation frequency, and as shown in the wearable detection equipment Figure 2 , the tester wears the ground detection device for pipeline defects with alternating electromagnetic excitation and advances uniformly along the pipeline axis to detect the damage degree of pipeline defects;

[0073] S5. Through the electromagnetic signal waveform, the co-variation characteristics between different components and the pipeline damage degree quantitative calculation model, classify and grade the pipeline defects, and combine the regional grade to judge the pipeline failure risk, and give corresponding maintenance suggestions.

[0074] S51. According to the pipeline burial depth recorded by the pipe detector during the detection, a total of two defects were detected. The electromagnetic signal intensity was converted into the electromagnetic signal intensity under standard height conditions through the electromagnetic signal height correction model described above. The corrected signals are as shown in Figure 3 , Figure 4 ;

[0075] S52. As shown in Figure 3 , a single-peak fluctuation appears in the z-component of the electromagnetic signal, sinusoidal fluctuations appear in the x and y components, and the z signal shows asymmetry. Therefore, this defect is a stress concentration defect. As shown in Figure 4 , sinusoidal fluctuations appear in the y and z components of the electromagnetic signal, and the x signal shows a "zigzag" characteristic. Therefore, the defect is metal loss;

[0076] S53. Extract the maximum change value of a specific component or modulus of the electromagnetic signal according to the defect type, refer to the initial pressure of the pipeline, and obtain the pipeline damage degree through the pipeline damage degree F value calculation model considering the pipeline stress state;

[0077] S54. Refer to the pipeline defect damage degree and maintenance management methods, and give corresponding maintenance suggestions based on the pipeline damage degree F value. For stress concentration pipelines, use the z-component of the electromagnetic signal to evaluate the pipeline damage degree, and for metal loss pipelines, use the x-component of the electromagnetic signal to evaluate the pipeline damage degree;

[0078] The stress concentration pipeline damage evaluation model is shown in Equation (6):

[0079]

[0080] In the formula, the electromagnetic signal change value ΔG istaz is the z-component of the electromagnetic signal, nT / m,

[0081] The metal loss pipeline damage evaluation model is shown in Formula (7):

[0082]

[0083] In the formula, the electromagnetic signal change value ΔG istax is the x-component of the electromagnetic signal, nT / m,

[0084] Figure 3 In ΔG istaz the change amount is 4787 nT, so the calculated F value is 0.27, Figure 4 In ΔG istax the change amount is 230 nT, and the calculated F value is 0.55;

[0085] The pipeline defect damage degree and the maintenance and management method are as follows:

[0086] 0.4 < F < 1, the pipeline defect damage degree in low, medium, and high-risk areas is level one, low risk, and it is recommended that the pipeline be used normally;

[0087] 0.2 < F < 0.4, the pipeline defect damage degree in low and medium areas is level two, medium risk, and it is recommended that the pipeline be used under monitoring. The pipeline defect damage degree in high-risk areas is level three, high risk, and it is recommended that the pipeline be repaired immediately;

[0088] 0 < F < 0.2, the pipeline defect damage degree in low, medium, and high-risk areas is all level three, high risk, and it is recommended that the pipeline be repaired immediately.

[0089] According to the above pipeline defect damage degree grading standard, the stress concentration pipe section is located in a high-risk area, the F value is between 0.2 and 0.4, the risk assessment result is high risk, and it is recommended to repair immediately. The metal loss pipeline is located in a medium-risk area, the F value is between 0.4 and 1, the risk assessment result is low risk, and it is recommended that the pipeline be used normally.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for ground detection of defects in a pipeline based on alternating electromagnetic excitation, characterized in that, It comprises the following steps: S1, collecting the basic design parameters of the pipeline to be detected, determining the pipeline section to be detected according to the field requirements, calibrating the pipeline direction and burial depth through the pipe detector, and completing the preliminary work of the pipeline defect ground detection based on alternating electromagnetic excitation; S2, detecting the defect under different frequency conditions, and determining the optimal excitation frequency by comparing the detection results of different rounds; S3, calibrating the basic strength of the electromagnetic signal of the pipeline to be detected, and correcting and calibrating the basic strength of the electromagnetic signal according to the actual pipeline diameter and burial depth information through the signal correction model; Step S3 comprises the following steps: S31, applying an excitation current to the pipeline through the cathodic protection potential test pile, and the current frequency is the optimal excitation current obtained by testing; S32, selecting a normal pipeline and ring weld for detection to obtain the amplitude of the electromagnetic signal component change and determine the basic electromagnetic signal strength of the normal pipeline and ring weld; S33, record the buried depth and pipe diameter information of the pipeline, correct and calibrate the basic strength three components and modulus Δ G istax , Δ G istay , Δ G istaz and Δ G ista ​ The calculation formula of the electromagnetic signal height correction model is: （1） In the formula, G ista G is the electromagnetic signal intensity under the standard height condition, nT / m; G i G is the electromagnetic signal intensity collected; f 1( D )、 f 2 ( D )、 k 1、 k 2 is a to-be-determined parameter related to the pipe burial depth and wall thickness, which is obtained through a burial depth test experiment; D D is the pipe diameter, m; h H is the pipe burial depth, m; S4, connecting the alternating excitation device to the cathodic protection potential test pile through the wire, applying alternating current to the pipeline at the optimal excitation frequency, and the tester wearing the wearable alternating electromagnetic excitation pipeline defect ground detection device advances along the pipeline axis at a uniform speed to detect the pipeline defect damage degree; S5, classifying and grading the pipeline defects through the electromagnetic signal waveform, the cooperative change characteristics between different components, and the pipeline damage degree quantitative calculation model, combining with the regional grade to judge the pipeline failure risk, and giving the corresponding maintenance and repair suggestions; Step S5 comprises the following steps: S51, converting the electromagnetic signal strength into the electromagnetic signal strength under the standard height condition through the electromagnetic signal height correction model according to the pipeline burial depth recorded by the pipe detector during detection; S52, realizing ground recognition of pipeline defect type according to the waveform and component signal cooperative change characteristics of the electromagnetic signal compared in advance; S53, according to the defect type, extract the maximum change value of a certain component or modulus of the electromagnetic signal, refer to the initial pressure of the pipeline, and obtain the pipeline damage degree by considering the stress state of the pipeline F value calculation model to obtain the pipeline damage degree; S54, reference pipeline defect damage degree and maintenance management method, based on pipeline damage degree F a corresponding maintenance suggestion is given; In step S5, the pipe damage degree F The value calculation model is as follows: （2） In the formula, F The value is the degree of pipeline damage; f(σ ) is a correction coefficient considering the stress state of the pipeline; Δ G ista is the electromagnetic signal change value under standard height conditions, according to the actual defect type, this parameter can be replaced by the electromagnetic signal change value three components Δ G istax , Δ G istay , Δ G istaz , nT / m; Δ G ista0 is the electromagnetic signal reference change value under standard height conditions, according to the actual defect type, this parameter can be replaced by the electromagnetic signal reference change value three components Δ G ista0x , Δ G ista0y , Δ G ista0z three components, nT / m.

2. The pipeline defect ground detection method based on alternating electromagnetic excitation according to claim 1, comprising the following features in step S2: S2 1, applying an excitation current to the pipeline through the cathodic protection potential test pile, and applying an arbitrary excitation frequency to the pipeline; S22, pre-detecting the potential risk pipeline section along the pipeline axis until the electromagnetic signal appears abnormally, and locating the pipeline defect damage; S23, adjusting the alternating excitation current frequency, repeatedly detecting the located defect position, comparing the electromagnetic signal change amplitude under different frequency conditions, and selecting the excitation frequency under the maximum change amplitude as the optimal excitation frequency; The electromagnetic signal in step 2 is obtained by differentiating the sensed intensity of the collected electromagnetic signal, aiming to eliminate the interference of the background magnetic field intensity by differentiation. The electromagnetic signal is divided into G ix 、 G iy 、 G iz Three components and modulus G i The amplitude of the electromagnetic signal change is calculated as follows: （3） where Δ G i is the electromagnetic signal change amplitude, nT / m; G imax is the maximum value of the electromagnetic signal collected for the defect; G iave is the average value of the electromagnetic signal for the non-defect position.

3. The pipeline defect ground detection method based on alternating electromagnetic excitation according to claim 1, in step S5, the pipeline defect damage degree and the repair and maintenance management method are as follows: 0.4 F <1, the pipeline defect damage degree in low and medium risk areas is level one, low risk, and it is recommended that the pipeline be used normally, and the pipeline defect damage degree in high risk areas is level two, medium risk, and it is recommended that the pipeline be used under monitoring; 0.2 F <0.4, the defect damage degree of the pipeline is secondary, the risk is medium, it is suggested that the pipeline is used under monitoring, and the defect damage degree of the pipeline in a high-risk area is tertiary, the risk is high, and it is suggested that the pipeline is immediately repaired. 0 F <0.2, the defect damage degree of pipeline in low, medium and high risk areas is three levels, high risk, it is recommended to repair the pipeline immediately.

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