A numerical simulation evaluation method for deep penetration sections of in-service steel pipelines

Abstract

The present invention relates to a pipeline numerical simulation evaluation method, and specifically to a numerical simulation evaluation method for deep penetration sections of in-use steel pipelines. The method comprises the following steps: simulating the damage to the anti-corrosion layer of the deep penetration pipeline, finding out the change law and corresponding relationship of the cathodic protection potential and other parameters of the corresponding entry and exit points, and establishing a data analysis model; correcting or improving the data analysis model; collecting parameter information of the deep penetration section pipeline, inputting the information into the data analysis model, simulating the potential and current density distribution diagram; analyzing the potential and current density distribution diagram, and obtaining the cathodic protection detection result of the deep penetration pipeline. The method of the present invention measures the protection potential and other parameters of the entry and exit points of the deep penetration section pipeline, and infers the relevant parameters such as the cathodic protection current density of the deep penetration section pipeline, and then evaluates the integrity of the anti-corrosion layer of the deep penetration section pipeline, thereby overcoming the problem that the state of the anti-corrosion layer of the deep penetration section pipeline is difficult to detect.

Description

Technical Field

[0001] The present invention relates to a method for numerical simulation evaluation of pipelines, in particular to a method for numerical simulation evaluation of deep penetration sections of in-service steel pipelines. Background Art

[0002] Research on domestic and foreign materials has found that some explorations have been carried out on the evaluation of the anti-corrosion coating of pipelines in the directional drilling crossing sections. These explorations can be generally summarized into three methods: the current-potential method, the energized potential switching method (energized potential method, polarization offset criterion), and the surface resistivity method of the anti-corrosion coating.

[0003] Potential-current feeding method: The calculation results of this method are affected by some uncertain factors and need to be tested when the pipeline is not jointed. For on-line pipelines that have been jointed, only the feeding method can be used to detect the anti-corrosion coating and estimate the resistance. It is only applicable to pipelines that have not been connected to other pipe sections after the horizontal directional drilling crossing is completed, and is not applicable to in-service steel pipelines. Methods such as energized potential offset are affected by many factors and the results have large deviations. The method proposed by R.A. Gummow is difficult to obtain data and is not practical in the field.

[0004] Huang Xuesong et al. in "Numerical Analysis and Safety Evaluation Method for Third-Party Damage of Gas Transmission Pipelines" established a numerical model of the third-party excavator bucket teeth acting on the pipeline by using the classical Hertz contact theory and the ANSYS finite element simulation software, and studied the damage degree of the pipeline under different bucket tooth impact angles and impact depths. The results show that: as the penetration depth of the excavator bucket teeth increases, the deformation of the inner and outer walls of the pipeline becomes larger, and the pit deformation of the pipeline is more obvious after unloading the internal pressure. Based on the research and analysis of the residual stress of the gas transmission pipeline, this paper considers the comprehensive evaluation of the pit depth and stress, and conducts a systematic analysis of the damaged pipeline. The conclusion gives the evaluation criteria for replacing the damaged pipeline with the critical value of six percent of the pipeline strain and the maximum value of the pit depth on the outer surface of the pipeline as a reference. Finally, a risk assessment and analysis of the impact of excavator bucket teeth during the construction of a certain pipe section is carried out, providing a scientific basis for the risk prevention and control plan for the third-party damage of the actual on-site gas transmission pipeline.

[0005] Chinese Patent Application CN111027240A discloses a buried pipeline safety assessment method and related equipment. After establishing a three-dimensional nonlinear finite element model of the buried pipeline, a training set is established according to the corresponding relationship between the pipeline stress influence parameters under different working conditions and the pipeline stress. Among them, the pipeline stress corresponding to the pipeline stress influence parameters under different working conditions is obtained by means of finite element numerical simulation, which is more accurate and convenient than the theoretical calculation method; and because the neural network has a strong nonlinear processing ability, the training set can be used for neural network training to obtain a pipeline stress prediction model. When calculating the structural reliability of the buried pipeline according to the pipeline structure reliability calculation algorithm, the pipeline stress prediction model can be used to quickly obtain the pipeline stress, reducing the calculation time required for the pipeline stress while ensuring the accuracy of the calculation results, improving the calculation efficiency of the structural reliability of the buried pipeline, and improving the level of safety operation management and technology of the buried pipeline.

[0006] Chinese Patent Application CN110020399A discloses a method for determining the position of internal corrosion evaluation of pipelines, belonging to the field of pipeline corrosion. The method includes: dividing the target pipeline into multiple sub-pipelines; obtaining the water accumulation probability, corrosion probability, and liquid holdup rate of the sub-pipelines; multiplying the water accumulation probability by the corrosion probability to obtain the total corrosion probability of the sub-pipelines; when the total corrosion probability of the sub-pipelines is greater than a first preset value and the liquid holdup rate is greater than a second preset value, determining the sub-pipeline as the position in the target pipeline that needs to be evaluated for internal corrosion. The method provided by the invention simultaneously considers the influence of water accumulation probability, corrosion probability, and liquid holdup rate on pipeline internal corrosion, can accurately determine the position in the target pipeline that needs to be evaluated for internal corrosion, and can provide a reliable judgment basis for the overall internal corrosion evaluation of the pipeline.

[0007] Chinese Patent Application CN106777760A discloses a method for predicting stray current in metal pipelines based on numerical analysis. At present, the grounding electrode of a direct current transmission system can cause stray current in nearby metal pipelines, resulting in electrochemical corrosion of the metal pipelines. The present invention first simplifies the situation of the target metal pipeline and the grounding electrode of the direct current transmission system; then constructs a mathematical model of the stray current in the metal pipeline caused by the grounding electrode of the direct current transmission system; then, based on the mathematical model, restricts the area of the metal pipeline and the grounding electrode of the direct current transmission system and determines the corresponding boundary conditions; constructs a geometric model of the target metal pipeline; finally, uses the mathematical model and the geometric model, and uses numerical simulation software to perform simulation, and calculates the magnitude of the stray current in the metal pipeline. The invention provides a basis for the anti-corrosion measures of metal pipelines by estimating the magnitude of the stray current of the grounding electrode of the direct current transmission system on nearby metal pipelines.

[0008] At present, there is a need to provide a method for more accurately and easily operating the evaluation of the anti-corrosion layer of the deep penetration section of the pipeline. Summary of the Invention

[0009] To solve the above problems, the present invention provides a numerical simulation evaluation method for the deep penetration section of a steel pipeline in use. By measuring the protection potentials of the pipeline entry point and exit point of the deep penetration section and other parameters, the present invention method calculates relevant parameters such as the cathodic protection current density of the deep penetration section of the pipeline, and then evaluates the integrity of the anti-corrosion coating of the deep penetration section of the pipeline, overcoming the problem that it is difficult to detect the state of the anti-corrosion coating of the deep penetration section of the pipeline.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] The present invention provides a numerical simulation evaluation method for the deep penetration section of a steel pipeline in use, which includes the following steps:

[0012] Simulate the damage condition of the anti-corrosion coating of the deep penetration pipeline, find out the variation rules and corresponding relationships of the cathodic protection potentials of the corresponding entry point and exit point and other parameters, and establish a data analysis model;

[0013] Modify or improve the data analysis model;

[0014] Collect the parameter information of the deep penetration section of the pipeline, input the information into the data analysis model, and simulate the potential and current density distribution maps;

[0015] Analyze the potential and current density distribution maps to obtain the cathodic protection detection results of the deep penetration pipeline.

[0016] Preferably, the boundary element method is used to establish a data analysis model for the stray current interference and the numerical and state evaluation of cathodic protection.

[0017] Further preferably, the following mathematical analysis model is established:

[0018]

[0019] In the formula, the voltage drops of the cable, the cathode body, and the anode body have extremely little influence on the model and can be ignored, that is: Δφ a = 0, Δφ c = 0, Δφ cable1 = 0, and Δφ cable2 = 0. Therefore, the model is simplified to:

[0020]

[0021] In the formula, V is the electrolyte region to be calculated and solved; φ is the potential at each point within the solution region; x, y, and z are spatial coordinates; Γ A is the medium boundary surrounding the auxiliary anode body; φ a / s is the soil potential around the auxiliary anode body; φ a is the potential of the auxiliary anode body; Δφ a / sis the potential of the auxiliary anode with respect to the electrolyte, i.e., the polarization potential of the auxiliary anode commonly referred to; j a is the polarization current density on the surface of the auxiliary anode; σ is the conductivity of the electrolyte; Γ C is the electrolyte boundary surrounding the cathode body, φ c is the potential of the cathode body; Γ 1 is the electrolyte insulation boundary.

[0022] Preferably, the method for collecting the cathodic protection potential at the entry point and the exit point: Install the intelligent test pile for pipeline cathodic protection at the entry point and the exit point of the pipeline crossing section, and regularly send the collected potential data to the computer database remotely through the network to achieve automatic collection and archiving of the cathodic protection potential.

[0023] Preferably, the method for correcting or improving the data analysis model is: Apply the data model to the actual pipeline, adopt the method of excavation verification to collect the actual potential and other parameters at the entry point and the exit point of the pipeline, compare the calculated data of the experimental data module, and correct and improve the established experimental data model;

[0024] Then select other deep crossing sections for excavation, collect the required data, check the corrected mathematical model, and make corrections and improvements again until the requirements are met.

[0025] Further preferably, select 3 - 5 deep crossing pipelines for excavation, and collect pipeline data, protection potential, energized potential, off - energized potential, soil resistivity, protection potential distribution, protection current density.

[0026] Preferably, the pipeline parameter information collected for the deep crossing section includes the burial depth of the sacrificial anode of the deep crossing section pipeline, pipeline diameter, distribution trend, soil resistivity, cathodic protection potential and off - energized potential at the entry and exit points.

[0027] Preferably, draw the potential and current density distribution maps of the on - site measured values and the model calculated values for comparison, and judge the cathodic protection effect of the deep crossing pipeline according to the size of the deviation from the normal range of the calculated values.

[0028] Preferably, if the potential at any point of the entry and exit points is greater than - 0.85V, it is considered that the pipeline protection requirement is not met, and if the current density exceeds the given range, it is considered that there is a damaged point in the anti - corrosion coating.

[0029] Further preferably, normalize the conductivity with 1000Ω·cm and evaluate the anti - corrosion coating according to the indicators in the standard. If the conductivity is less than 2μS / m 2 the evaluation conclusion is excellent.

[0030] The present invention also provides an evaluation system for the deep penetration section of a steel pipeline in use, including a data acquisition system, a data processing system, and a result display system; the data acquisition system is used to collect the burial depth of sacrificial anodes of the pipeline in the deep penetration section, the pipeline diameter, the distribution trend, the soil resistivity, the cathodic protection potential and the off-potential at the entry and exit points of the soil.

[0031] The data processing system includes the modified or improved mathematical model in the above-mentioned evaluation method.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The method of the present invention calculates relevant parameters such as the cathodic protection current density of the pipeline in the deep penetration section by measuring the protection potentials at the entry and exit points of the pipeline in the deep penetration section and other parameters, and then evaluates the integrity of the anti-corrosion coating of the pipeline in the deep penetration section. The present invention solves the problem that the state of the anti-corrosion coating of the deep penetration section of the pipeline cannot be detected.

[0034] The method of the present invention can install the intelligent test pile for cathodic protection of the pipeline at the entry and exit points of the pipeline crossing section, and remotely send the collected potential data to the computer database through the network at regular intervals, realizing the automatic collection and archiving of the cathodic protection potential. The anti-corrosion coating of the pipeline crossing section can be evaluated or monitored at any time through the computer, without the need for on-site manual measurement, reducing the workload. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0036] Figure 1 It is a flow chart of the method for establishing a numerical analysis model in the numerical simulation evaluation method for the deep penetration section of a steel pipeline in use according to a specific embodiment of the present invention;

[0037] Figure 2 It is a schematic diagram of the simulation process of the cathodic boundary condition back-calculation algorithm according to a specific embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the protection potential measurement according to a specific embodiment of the present invention;

[0039] Figure 4 It is a schematic diagram of the potential attenuation model of the long-distance pipeline according to a specific embodiment of the present invention;

[0040] Figure 5 It is a diagram of the simulation result of the pipeline potential distribution according to a specific embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which the present invention belongs.

[0042] It should be noted that the terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0043] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0044] Embodiment 1

[0045] As Figure 1 shown, the numerical simulation evaluation method for the deep penetration section of the in-use steel pipeline includes the following steps:

[0046] Simulate the damage of the anti-corrosion layer of the deep penetration pipeline, find out the change rules and corresponding relationships of the cathodic protection potential and other parameters of the corresponding entry point and exit point, and establish a data analysis model; The mathematical analysis model is established as follows:

[0047]

[0048] In the formula, the voltage drops of the cable, the cathode body and the anode body have extremely little influence on the model and can be ignored, that is: Δφ a = 0, Δφ c = 0, Δφ cable1 = 0 and Δφ cable2 = 0, so the model is simplified to:

[0049]

[0050] In the formula, V is the electrolyte region to be calculated and solved; φ is the potential at each point in the solution region; x, y, z are spatial coordinates; Γ A is the medium boundary around the auxiliary anode body; φ a / s is the soil potential around the auxiliary anode body; φ a is the potential of the auxiliary anode body; Δφ a / s is the potential of the auxiliary anode to the electrolyte, that is, the so-called auxiliary anode polarization potential; j a is the polarization current density on the surface of the auxiliary anode; σ is the conductivity of the electrolyte; Γ C is the electrolyte boundary surrounding the cathode body, φc is the cathode body potential; Γ 1 is the electrolyte insulation boundary.

[0051] Select 3 - 5 sections of deep - penetrating pipeline excavation, and collect parameters such as pipeline data, protection potential, on - (off - ) current potential, soil resistivity, protection potential distribution, protection current density, etc.

[0052] Compare the actual measured parameters with the calculation results of the data analysis model, correct the parameters in the data analysis model, and modify or improve the data analysis model;

[0053] Repeat the verification and modification of the data analysis model until the simulation accuracy rate meets the requirement of being greater than 85%.

[0054] Collect the pipeline parameter information of the deep - penetrating section, input the information into the data analysis model, and simulate the potential and current density distribution maps;

[0055] Analyze the potential and current density distribution maps to obtain the cathodic protection detection results of the deep - penetrating pipeline. If the potential at any point of the entry and exit points is greater than - 0.85V, it is considered that the pipeline protection requirement is not met. If the current density exceeds the given range, it is considered that there is a damaged point in the anticorrosive coating.

[0056] Embodiment 2

[0057] The numerical simulation evaluation method for the deep - penetrating section of the in - service steel pipeline includes the following steps:

[0058] Simulate the damage condition of the anticorrosive coating of the deep - penetrating pipeline, find out the variation laws and corresponding relationships of the cathodic protection potential and other parameters at the corresponding entry and exit points, and establish a data analysis model; The established mathematical analysis model is as follows:

[0059]

[0060] In the formula, the voltage drops of the cable, cathode body, and anode body have extremely little influence on the model and can be ignored, that is: Δφ a = 0, Δφ c = 0, Δφ cable1 = 0, and Δφ cable2 = 0, so the model is simplified to:

[0061]

[0062] In the formula, V is the electrolyte region to be calculated and solved; φ is the potential at each point in the solution region; x, y, z are spatial coordinates; Γ A is the medium boundary around the auxiliary anode body; φ a / s is the soil potential around the auxiliary anode body; φ a is the auxiliary anode body potential; Δφ a / sis the potential of the auxiliary anode with respect to the electrolyte, i.e., the so-called polarization potential of the auxiliary anode; j a is the polarization current density on the surface of the auxiliary anode; σ is the electrical conductivity of the electrolyte; Γ C is the electrolyte boundary surrounding the cathode body, φ c is the potential of the cathode body; Γ 1 is the electrolyte insulation boundary.

[0063] Anode boundary: The cathodic protection current flowing into the crossing section is measured by methods such as current test piles, voltage drop / line resistance, current loop method, and PCM current attenuation evaluation.

[0064] Cathode boundary: It includes the combined effects of coating and polarization characteristics and cannot be directly measured in the case of directional drilling. The cathode boundary conditions are deduced inversely from directly measurable parameters.

[0065] The simulation process of the inverse algorithm for cathode boundary conditions is as Figure 2 shown.

[0066] Use a protection potential measuring device as Figure 3 shown to measure the protection potential at the entry and exit points of the deep - buried pipeline.

[0067] Select 3 - 5 sections of the deep - buried pipeline for excavation, and collect parameters such as pipeline data, protection potential, on - off potential, soil resistivity, protection potential distribution, and protection current density.

[0068] Compare the actually measured parameters with the calculation results of the data analysis model, correct the parameters in the data analysis model, and modify or improve the data analysis model;

[0069] Repeat the verification and modification of the data analysis model to meet the requirement that the simulation accuracy rate is greater than 85%.

[0070] Collect the pipeline parameter information of the deep - buried section, input the information into the data analysis model, and simulate the potential and current density distribution maps;

[0071] Analyze the potential and current density distribution maps to obtain the cathodic protection detection results of the deep - buried pipeline.

[0072] Establish a long - distance pipeline potential attenuation model as Figure 4 described, and use the measured potentials at the entry and exit points of the crossing to calculate the potential attenuation. Starting from the entry and exit points of the crossing, divide the pipeline of the upstream and downstream continua into several pipe segments along the axial direction. Each pipe segment is connected to each other at a limited number of nodes to form an aggregate of pipe segments that replaces the continuum.

[0073] The resistivity of the external anti-corrosion layer is measured in accordance with the standard GBT 21246-2007 "Measurement Method for Cathodic Protection Parameters of Buried Steel Pipelines". The longitudinal resistances of each pipe section are connected end to end and are connected to the ground through transition resistances. The potential difference at the entry end of the crossing is represented by U_1, and the potential difference at the exit end is represented by U_2. When the pipeline is divided into n pipe sections, R_(2i-1) represents the longitudinal resistance of the i-th pipe section, and R_2i represents the transition resistance of the i-th pipe section.

[0074] Let the length of the crossing be L; the outer diameter of the i-th pipe section be D_i, the inner diameter be d_i, the length be l_i, and the resistivity of the pipe material be ρ_i. Then the line resistance of this pipe section is

[0075] R_(2i-1) = 4ρ_il_i / [π(D_i^2 - d_i^2)]

[0076] Calculation formula of the analytical method

[0077] The general calculation formula for the distribution of the applied potential E and current I along the pipeline is

[0078] E = (Ae αx + Be -αx )R 2i

[0079]

[0080] Where: A, B - constants determined by the boundary conditions respectively;

[0081] r T — The resistance of the pipeline per unit length, Ω / m;

[0082] R T — The transition resistance of the pipeline per unit length, Ω·m;

[0083]

[0084] Through on-site testing, the voltage drop across the crossing section of the pipeline and the decay of the current in the pipe are obtained. Among them, the average voltage drop:

[0085]

[0086] Assume that there are n break points in the crossing section, and the leakage current at each break point is ΔI0. Then there is:

[0087] n * ΔI0 = ΔI

[0088] For a single break point with a diameter of D, the voltage drop ΔV0:

[0089]

[0090] It is derived that:

[0091]

[0092] Further obtain:

[0093]

[0094]

[0095] Suppose there are n defects, calculate the current, size, and current density of each defect, and evaluate the protection effect at the defect. The larger n is, the larger the current density is, and the better the protection effect is. When n takes 1, it is the most dangerous case. For the crossing section with the largest conductivity of the anti-corrosion layer under the test condition, when the power supply output is 9.9V / 1.4A, the flowing current is 0.012A. The current density and potential under different numbers of defects are shown in Table 1 below.

[0096] Table 1

[0097]

[0098]

[0099] When and only when there is only one defect, the protection potential does not meet the standard, which is -0.85 Vcse. In other cases, the potential at the defect point is more negative and meets the protection criterion.

[0100] The simulation results of the pipeline potential distribution are as Figure 5 shown.

[0101] Calculate the surface resistivity of the anti-corrosion layer according to the method provided in NACE TM0102-2002 "Measurement of Protective Coating Electrical Conductance on Underground Pipelines". Measure the current in the middle of the pipe section at each site on-site. Subtract the upstream and downstream currents to obtain the current leaking through the pipe section. At the same time, use the average voltage drop at both ends of the upstream and downstream as the voltage drop of the pipe section, and then the surface resistivity / conductivity of this pipe section can be obtained. Normalize the conductivity with 1000 Ω·cm and evaluate the anti-corrosion layer according to the indicators in the standard. When the conductivity is less than 2 μS / m 2 the evaluation conclusion is excellent.

[0102] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A numerical simulation evaluation method for deep penetration section of in-service steel pipeline, characterized in that: The method adopts the deep penetration section evaluation system of in-service steel pipelines and is implemented through the following steps: Simulate the damage of the anti-corrosion layer of deep-penetrating pipelines, find out the change rules and corresponding relationships of the cathodic protection potential and other parameters at the corresponding entry and exit points, and establish a data analysis model; Modify or improve the data analysis model; Collect the deep penetration pipeline parameter information, input the information into the data analysis model, and simulate the potential and current density distribution map; Analyze the potential and current density distribution diagrams to obtain the cathodic protection test results of deep-penetrating pipelines; The boundary element method is used to establish the data analysis model for stray current interference and cathodic protection numerical and status assessment; The mathematical analysis model is established as follows: In the formula, the voltage drop of the cable, cathode body and anode body has little effect on the model and can be ignored, that is: Δφ a =0, Δφ c =0, Δφ cable1 = 0 and Δφ cable2 =0, so the model is simplified to: Where V is the electrolyte area to be solved; Φ is the potential at each point in the solution area; x, y, z are spatial coordinates; Γ A is the dielectric boundary surrounding the auxiliary anode body; φ a / s is the soil potential around the auxiliary anode; φ a is the auxiliary anode body potential; Δφ a / s is the auxiliary anode to electrolyte potential, commonly known as the auxiliary anode polarization potential; a is the auxiliary anode surface polarization current density; σ is the conductivity of the electrolyte; Γ C is the electrolyte boundary surrounding the cathode body, φ c is the cathode body potential; Γ1 is the electrolyte insulation boundary; Cathodic protection potential collection method at the entry and exit points: Install pipeline cathodic protection intelligent test piles at the entry and exit points of the pipeline crossing section, and regularly send the collected potential data to the computer database through the network remotely to realize automatic collection and archiving of cathodic protection potential; The method for revising or improving the data analysis model is: applying the data analysis model to the actual pipeline, collecting the actual potential and other parameters of the pipeline entry and exit points by excavation verification, comparing the calculated data of the experimental data module, and revising and improving the established experimental data analysis model; Then select other deep penetration sections for excavation, collect the required data, check the revised data analysis model, and make corrections and improvements again until it meets the requirements; Select 3-5 sections of deep pipeline excavation and collect pipeline data, protection potential, power-on potential, power-off potential, soil resistivity, protection potential distribution, and protection current density; Collect deep-penetration pipeline parameter information including the buried depth of sacrificial anodes, pipeline diameter, distribution direction, soil resistivity, cathodic protection potential and power-off potential of the entry and exit points of the deep-penetration pipeline; The potential and current density distribution diagrams are plotted to compare the field measurement values ​​with the model calculation values, and the cathodic protection effect of deep-penetrating pipelines is judged based on the deviation from the normal range of the calculated values. If the potential at any point of the soil entry and exit is greater than -0.85V, it is considered that the pipeline protection requirements are not met; if the current density exceeds the given range, it is considered that the anti-corrosion layer has a damaged point; The conductivity is normalized with 1000Ω·cm, and the anti-corrosion layer is evaluated according to the indicators in the standard. The conductivity is less than 2μS / m 2 The evaluation conclusion is excellent; The deep penetration section evaluation system for in-use steel pipelines includes a data acquisition system, a data processing system and a result display system; the data acquisition system is used to collect the buried depth of sacrificial anodes of deep penetration section pipelines, pipeline diameter, distribution direction, soil resistivity, cathodic protection potential and power-off potential of soil entry and exit points; the data processing system includes the modified or improved data analysis model in the above-mentioned evaluation method.

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