A safety evaluation method, system and device for irregular corrosion defect pipeline

Abstract

This invention discloses a method, system, and apparatus for safety assessment of pipelines with irregular corrosion defects, relating to the field of oil and gas pipelines. The method includes determining the coordinate data of the corrosion zone of the pipeline; constructing a finite element model of the pipeline based on the coordinate data and the pipeline's mechanical performance parameters, including at least one of yield strength, tensile strength, elastic modulus, and hardening index; applying pressure to the finite element model and determining the stress in the model under load; and determining the pressure corresponding to the stress exceeding the ultimate tensile strength as the pipeline's ultimate pressure value when the stress exceeds the ultimate tensile strength. The finite element model constructed using the coordinates of the corrosion zone and the mechanical performance parameters can simulate the actual structure of the pipeline, more closely reflecting its operating conditions. The simulation results obtained after applying pressure are more accurate, and the obtained ultimate pressure value is more reliable.

Description

Technical Field

[0001] This invention relates to the field of oil and gas pipelines, and in particular to a method, system, and apparatus for safety assessment of pipelines with irregular corrosion defects. Background Technology

[0002] During long-term use, oil and gas pipelines develop corrosion defects of various shapes due to corrosion, which are typically irregular in form. Traditional engineering assessment methods often assume that corrosion defects are regular geometric shapes, such as rectangles or ellipses, leading to an inaccurate reflection of the actual impact of corrosion defects and consequently affecting the assessment of pipeline load-bearing capacity and failure pressure. However, the failure pressure of pipelines with corrosion defects is significantly related to the changes in the defect profile, and assessments that simplify irregular defects often deviate considerably from the pipeline's actual burst capacity. Summary of the Invention

[0003] The purpose of this invention is to provide a method, system, and device for safety assessment of pipelines with irregular corrosion defects. By using the coordinates of the corrosion area and combining them with mechanical performance parameters to construct a finite element model, the actual structure of the pipeline can be simulated, which is closer to the pipeline's operating conditions. The simulation results obtained after applying pressure are more accurate, and the ultimate pressure value obtained is more reliable.

[0004] To address the aforementioned technical problems, this invention provides a method for safety assessment of pipelines with irregular corrosion defects, comprising:

[0005] Determine the coordinates of the corrosion zone in the pipeline;

[0006] Based on the coordinate data and the mechanical performance parameters of the pipeline, a finite element model of the pipeline is constructed. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index.

[0007] Pressure is applied to the finite element model, and the stress in the finite element model under load is determined;

[0008] When the stress exceeds the ultimate tensile strength, the pressure corresponding to the stress exceeding the ultimate tensile strength is determined as the ultimate pressure value of the pipeline.

[0009] On the other hand, determining the coordinate data of the corrosion zone in the pipeline includes:

[0010] Obtain point cloud data of the corrosion area of ​​the pipeline;

[0011] Remove outliers from the point cloud data;

[0012] Delete point cloud data whose values ​​exceed the corresponding physical value range;

[0013] Missing point cloud data is supplemented using linear interpolation.

[0014] The coordinate data of the eroded region are determined from the point cloud data after the deletion and addition operations.

[0015] On the other hand, removing outliers from point cloud data includes:

[0016] For any given point, determine the average distance to a preset number of adjacent points;

[0017] If the average distance is greater than the noise upper limit average distance, the point cloud data of the point is determined to be an outlier and deleted.

[0018] Alternatively, for any given point, determine the number of neighboring points within its radius.

[0019] If the number is less than the preset number, the point cloud data of the point is determined to be an outlier and deleted.

[0020] On the other hand, determining the coordinate data of the eroded region from the point cloud data after the deletion and supplementation operations includes:

[0021] Feature extraction is performed on the coordinate data from the point cloud data after deletion and addition operations. The coordinate data includes the coordinates of the maximum depth position, the axial length, the circumferential width, the coordinates of the axial front end position, the coordinates of the axial end position, the coordinates of the circumferential front end position, the coordinates of the circumferential end position, and the remaining wall thickness ratio.

[0022] On the other hand, based on the coordinate data and the mechanical performance parameters of the pipeline, a finite element model of the pipeline is constructed, including:

[0023] A finite element model of the pipeline is constructed based on the parameters of the maximum length, maximum width, and maximum depth of the corrosion zone.

[0024] By inputting the material and corresponding mechanical property parameters of the pipeline with different hydrogen doping ratios into the finite element model, the stress-strain relationship of the pipeline under different hydrogen doping ratios is obtained from the output of the finite element model.

[0025] On the other hand, the expression for the relationship between stress and strain is:

[0026] ;

[0027] in, For the true total strain of the material, For yield strain, For the actual stress of the material, For yield strength, , For elastic modulus, The hardening coefficient is... This is the hardening index.

[0028] On the other hand, after constructing the finite element model of the pipeline based on the coordinate data and the mechanical performance parameters of the pipeline, the process further includes:

[0029] Add fixed constraints to the ends of the pipe to limit the translation and rotation of the end nodes;

[0030] Apply a uniformly distributed internal pressure load to the inside of the pipe;

[0031] The pipeline is divided into grids, and the grid density of the corroded areas on the pipeline is greater than the grid density of the uncorroded areas.

[0032] On the other hand, determining the stress in the finite element model under load includes:

[0033] Determine the stress at any point in the pipeline in the three principal directions;

[0034] The equivalent stress at the point is determined based on the stress in the three principal directions, and the relationship of the equivalent stress is as follows:

[0035] ;

[0036] in, For equivalent stress, Let be the stress in the x-axis direction. The stress is in the y-axis direction. The stress is in the z-axis direction.

[0037] To address the aforementioned technical problems, this invention also provides a safety assessment system for pipelines with irregular corrosion defects, comprising:

[0038] Coordinate determination unit, used to determine the coordinate data of the corrosion area of ​​the pipeline;

[0039] The model building unit is used to build a finite element model of the pipeline based on the coordinate data and the mechanical performance parameters of the pipeline. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index.

[0040] A pressure application unit is used to apply pressure to the finite element model and determine the stress in the finite element model under load.

[0041] The ultimate pressure value determination unit is used to determine the pressure corresponding to the stress greater than the ultimate tensile strength as the ultimate pressure value of the pipeline when the stress is greater than the ultimate tensile strength.

[0042] To address the aforementioned technical problems, the present invention also provides a safety assessment device for pipelines with irregular corrosion defects, comprising:

[0043] Memory, used to store computer programs;

[0044] A processor is used to implement the steps of the above-described safety assessment method for pipelines with irregular corrosion defects when executing the computer program.

[0045] This application provides a method, system, and apparatus for safety assessment of pipelines with irregular corrosion defects, relating to the field of oil and gas pipelines. The method includes determining the coordinate data of the corrosion zone of the pipeline; constructing a finite element model of the pipeline based on the coordinate data and the pipeline's mechanical performance parameters, including at least one of yield strength, tensile strength, elastic modulus, and hardening index; applying pressure to the finite element model and determining the stress in the model under load; and determining the pressure corresponding to the stress exceeding the ultimate tensile strength as the pipeline's ultimate pressure value when the stress exceeds the ultimate tensile strength. The finite element model constructed using the coordinates of the corrosion zone combined with the mechanical performance parameters can simulate the actual structure of the pipeline, more closely reflecting its operating conditions. The simulation results obtained after applying pressure are more accurate, and the obtained ultimate pressure value is more reliable. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the prior art and embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A flowchart of a safety assessment method for pipelines with irregular corrosion defects provided by the present invention;

[0048] Figure 2 A schematic diagram of the structure of point cloud data provided by the present invention;

[0049] Figure 3 This is a schematic diagram of another point cloud data structure provided by the present invention;

[0050] Figure 4 The first finite element model diagram of irregular corrosion defects provided by the present invention;

[0051] Figure 5 The second type of finite element model diagram of irregular corrosion defects provided by the present invention;

[0052] Figure 6 The third type of finite element model diagram of irregular corrosion defects provided by the present invention;

[0053] Figure 7 The fourth type of irregular corrosion defect finite element model diagram provided by the present invention;

[0054] Figure 8 The present invention provides the actual stress-strain curves of X52 steel under different hydrogen doping ratios;

[0055] Figure 9 This invention provides a schematic diagram of the grid division of pipelines with irregular corrosion defects.

[0056] Figure 10 This invention provides a first type of stress comparison cloud map for regular and irregular corrosion defects;

[0057] Figure 11 This invention provides a second type of stress comparison cloud map for regular and irregular corrosion defects;

[0058] Figure 12 The third type of stress comparison cloud diagram for regular and irregular corrosion defects provided by the present invention;

[0059] Figure 13 The fourth type of stress comparison cloud diagram for regular and irregular corrosion defects provided by the present invention;

[0060] Figure 14 A schematic diagram of the structure of a safety assessment system for pipelines with irregular corrosion defects provided by the present invention;

[0061] Figure 15 This is a schematic diagram of the structure of a safety assessment device for pipelines with irregular corrosion defects provided by the present invention. Detailed Implementation

[0062] The core of this invention is to provide a method, system, and device for safety assessment of pipelines with irregular corrosion defects. By using the coordinates of the corrosion area and combining them with mechanical performance parameters to construct a finite element model, the actual structure of the pipeline can be simulated, which is closer to the pipeline's operating conditions. The simulation results obtained after applying pressure are more accurate, and the ultimate pressure value obtained is more reliable.

[0063] 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. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] Figure 1The flowchart of a safety assessment method for irregularly corroded pipelines provided by the present invention includes:

[0065] S11: Determine the coordinate data of the corrosion zone in the pipeline;

[0066] During long-term use, oil and gas pipelines develop corrosion defects of various shapes due to corrosion, which are typically irregular in form. Traditional engineering assessment methods often assume that corrosion defects are regular geometric shapes, such as rectangles or ellipses, leading to an inaccurate reflection of the actual impact of corrosion defects and consequently affecting the assessment of pipeline load-bearing capacity and failure pressure. Therefore, existing corrosion defect assessment methods often equate irregular corrosion defects to regular shapes to predict the failure pressure of pipelines with defects. However, the failure pressure of pipelines with corrosion defects is significantly related to the changes in the defect profile, and the assessment results of simplifying irregular defects often deviate considerably from the actual burst capacity of the pipeline.

[0067] Therefore, this application adopts a model simulation method. Before using the model to simulate the pipeline, it is necessary to determine the actual shape of the pipeline.

[0068] Figure 2 This is a schematic diagram of the structure of point cloud data provided by the present invention. Figure 3 This is a schematic diagram of another point cloud data structure provided by the present invention;

[0069] Coordinate data can be acquired by using a handheld 3D laser scanner to scan the contours of corrosion defect areas in in-service pipelines, obtaining 3D point cloud data of the corrosion area. (3D scan data point cloud processing is the process of processing and analyzing point cloud data acquired by a 3D laser scanner or other 3D acquisition equipment. Point cloud data is a collection of a large number of spatially discrete points, each of which contains spatial coordinates and other attributes such as color and normal vector.) This point cloud data is used to characterize the true spatial morphology of the corrosion defect area, providing basic data for subsequent reconstruction of the geometric model of irregular corrosion defects.

[0070] S12: Based on coordinate data and the mechanical performance parameters of the pipeline, construct a finite element model of the pipeline. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index.

[0071] Figure 4 This is a finite element model diagram of the first type of irregular corrosion defect provided by the present invention. Figure 5 This is a finite element model diagram of the second type of irregular corrosion defect provided by the present invention. Figure 6 This is a finite element model diagram of the third type of irregular corrosion defect provided by the present invention. Figure 7The fourth type of irregular corrosion defect finite element model diagram provided by the present invention;

[0072] Based on the processed 3D scan point cloud data, a finite element model of a pipeline with corrosion defects was constructed using finite element analysis software. Yield strength, tensile strength, elastic modulus, and hardening index under different hydrogen doping ratios were imported. The constructed finite element model more closely resembles the actual pipeline, and the simulation results are more accurate.

[0073] S13: Apply pressure to the finite element model and determine the stress in the finite element model under load;

[0074] S14: When the stress is greater than the ultimate tensile strength, the pressure corresponding to the stress greater than the ultimate tensile strength is determined as the ultimate pressure value of the pipeline.

[0075] After constructing the model, considering only the internal pressure of the pipeline, a uniformly distributed internal pressure load is applied to the inner surface of the pipeline. The evolution of stress in the corrosion defect area with increasing load is analyzed by gradually increasing the internal pressure. Specifically, in the finite element analysis, multiple analysis steps are set, and an increasing internal pressure value is applied in each analysis step. After each analysis step, the stress value of the node with the maximum equivalent stress in the corrosion defect area is extracted. These stress values ​​and the corresponding internal pressure values ​​are plotted as a stress-internal pressure curve. When the curve intersects with the ultimate tensile strength of the material (horizontal line), the internal pressure corresponding to the intersection point is the ultimate failure pressure.

[0076] This application provides a safety assessment method for pipelines with irregular corrosion defects, relating to the field of oil and gas pipelines. The method includes determining the coordinate data of the corrosion zone of the pipeline; constructing a finite element model of the pipeline based on the coordinate data and the pipeline's mechanical performance parameters, including at least one of yield strength, tensile strength, elastic modulus, and hardening index; applying pressure to the finite element model and determining the stress in the model under load; and determining the pressure corresponding to the stress exceeding the ultimate tensile strength as the pipeline's ultimate pressure value when the stress exceeds the ultimate tensile strength. The finite element model constructed using the coordinates of the corrosion zone combined with the mechanical performance parameters can simulate the actual structure of the pipeline, more closely reflecting its operating conditions. The simulation results obtained after applying pressure are more accurate, and the obtained ultimate pressure value is more reliable.

[0077] Based on the above embodiments:

[0078] In some embodiments, determining the coordinate data of the corrosion zone of the pipeline includes:

[0079] Obtain point cloud data of the corroded area of ​​the pipeline;

[0080] Remove outliers from the point cloud data;

[0081] Delete point cloud data whose values ​​exceed the corresponding physical value range;

[0082] Missing point cloud data is supplemented using linear interpolation.

[0083] Determine the coordinates of the eroded region from the point cloud data after deletion and addition operations.

[0084] The raw point cloud data obtained from the scan is preprocessed, including noise point removal, invalid point deletion, and missing value handling. For blank values ​​in the data, a column-wide deletion method is used for initial cleaning; for locally missing areas, linear interpolation is used to complete them, thereby ensuring the continuity and integrity of the erosion contour data.

[0085] Specifically, noise point removal usually involves statistical outlier filtering or radius filtering, which means looking at the distance distribution within the neighborhood of each point and judging points with significantly larger distances as outliers.

[0086] Invalid point removal: Points that are inherently unreliable during the scan, such as blanks, anomalies, and outliers, are removed. This includes removing large numbers of blank values ​​and points with minimal impact on defect depth. (Remove null columns, duplicate points, points outside the scan range, points significantly deviating from the pipe surface, and shallow points that contribute very little to defect depth.)

[0087] Missing values: A large number of blank values ​​in the source data are deleted in whole columns. When converting the point cloud data into text data that can be recognized in subsequent simulations, the identified blank values ​​are then linearly interpolated to ensure the data continuity of subsequent modeling.

[0088] In some embodiments, deleting outliers from point cloud data includes:

[0089] For any given point, determine the average distance to a preset number of adjacent points;

[0090] If the average distance is greater than the noise upper limit average distance, the point cloud data of the point is determined to be an outlier and deleted.

[0091] Alternatively, for any given point, determine the number of neighboring points within its radius.

[0092] If the number is less than the preset number, the point cloud data of the determined point is an outlier and is deleted.

[0093] For each point, calculate its average distance to its k nearest neighbors. Assume that the average distance of all points follows a Gaussian distribution, and calculate the global mean μ and standard deviation σ. If the average distance of a point exceeds μ ± α·σ, where α is a threshold multiple of the standard deviation, it is considered an outlier and removed. k is the number of neighboring points.

[0094] For each point, count the number of neighboring points within its radius R. If the number is less than min_neighbors, it is considered an isolated outlier and removed.

[0095] R is the search radius, which is related to the point cloud density, and min_neighbors is the minimum number of neighbors.

[0096] The acquired 3D point cloud data is processed for missing values. The whole column deletion method is used to remove a large number of blank values ​​in the source data and to remove point cloud data with little impact from the defect depth. Furthermore, when converting the point cloud data into text data that can be recognized during simulation, linear interpolation is performed on the identified blank values ​​to ensure the accuracy and consistency of the data.

[0097] Using processed 3D scan data, a 3D geometric model of the pipeline corrosion defect area is reconstructed through reverse modeling technology. This model can accurately reflect the complex geometric morphology of corrosion defects in actual pipelines, such as pits, depressions, and cracks. During this process, irregular corrosion defect areas are meticulously modeled to ensure their shape is highly consistent with the actual corrosion pattern.

[0098] In some embodiments, determining the coordinate data of the eroded region from the point cloud data after the deletion and supplementation operations includes:

[0099] Feature extraction is performed on the coordinate data from the point cloud data after deletion and addition operations. The coordinate data includes the coordinates of the maximum depth position, the axial length, the circumferential width, the coordinates of the axial front end position, the coordinates of the axial end position, the coordinates of the circumferential front end position, the coordinates of the circumferential end position, and the proportion of the remaining wall thickness.

[0100] In some embodiments, a finite element model of the pipeline is constructed based on coordinate data and the pipeline's mechanical performance parameters, including:

[0101] A finite element model of the pipeline is constructed based on the parameters of the maximum length, maximum width, and maximum depth of the corrosion zone.

[0102] By inputting the material and corresponding mechanical property parameters of the pipeline with different hydrogen doping ratios into the finite element model, the stress-strain relationship of the pipeline under different hydrogen doping ratios is obtained from the output of the finite element model.

[0103] Based on the maximum length, maximum width, and maximum depth parameters of the corrosion defects obtained from the scan, a corresponding regular corrosion defect pipeline model is established. When modeling the equivalent regular shape of the defect, in order to reduce stress concentration caused by excessively sharp defect geometric edges, the apex corners of the rectangular defect are rounded, and the rounding radius is the defect depth.

[0104] The impact of hydrogen doping ratio on failure pressure includes calculating the failure pressure under different hydrogen doping ratios, analyzing the effect of hydrogen doping on pipeline failure pressure, and using 25% and 50% hydrogen doping ratios as the dividing points to determine the impact of hydrogen doping transportation on pipeline failure pressure.

[0105] Figure 8 The present invention provides the actual stress-strain curves of X52 steel under different hydrogen doping ratios;

[0106] For example, when making a specific selection, X52 steel can be used, taking into account the influence of different hydrogen doping conditions on the mechanical properties of the material. The hydrogen doping ratios are 0, 2.5%, 12.5%, 25%, and 50%. The corresponding yield strengths are 393 MPa, 381 MPa, 388 MPa, 390 MPa, and 368 MPa; the tensile strengths are 508 MPa, 515 MPa, 519 MPa, 509 MPa, and 492 MPa; the elastic moduli are 196500 MPa, 190500 MPa, 194000 MPa, 195000 MPa, and 184000 MPa; and the Poisson's ratio is taken as 0.3 for all cases.

[0107] In some embodiments, the expression for the relationship between stress and strain is:

[0108] ;

[0109] in, For the true total strain of the material, For yield strain, For the actual stress of the material, For yield strength, , For elastic modulus, The hardening coefficient is... This is the hardening index.

[0110] The establishment of the finite element model includes discretizing the three-dimensional model using finite element analysis software, meshing it with C3D8R elements to ensure a small mesh size (e.g., 3mm) in corrosion defect areas and a coarser mesh in other areas to improve computational efficiency; setting appropriate boundary conditions, applying fully fixed constraints at the far end of the pipeline to prevent rigid body displacement during calculation; and applying uniformly distributed internal pressure loads to the inner surface of the pipeline to simulate the stress distribution under internal pressure. The material constitutive model setting steps include selecting X52 steel as the pipeline material, and adjusting parameters such as yield strength, tensile strength, and elastic modulus according to different hydrogen doping ratios.

[0111] Figure 9 This invention provides a schematic diagram of the grid division of pipelines with irregular corrosion defects.

[0112] In some embodiments, after constructing a finite element model of the pipeline based on coordinate data and the pipeline's mechanical performance parameters, the method further includes:

[0113] Add fixed constraints to the ends of the pipeline to limit the translation and rotation of the end nodes;

[0114] Apply a uniformly distributed internal pressure load to the inside of the pipe;

[0115] The pipeline is divided into grids, with the grid density of corroded areas being greater than that of uncorroded areas.

[0116] Based on the reconstructed 3D model of corrosion defects, a finite element model of the pipeline was established by discretization using finite element software (such as ANSYS or ABAQUS). C3D8R elements were used to mesh the pipeline, with a smaller mesh size used for the corrosion defect region to ensure accurate stress distribution calculation within that area. A coarser mesh was used for other pipeline regions to improve computational efficiency. In the finite element model, to avoid the influence of rigid body displacement, fixed constraints were applied to the far end of the pipeline, restricting the translation and rotation of the pipeline end nodes. Only internal pressure was considered as a load; a uniformly distributed internal pressure load was applied to the inner surface of the pipeline, pointing towards the outer diameter, to simulate the stress situation of the pipeline under operating conditions.

[0117] In some embodiments, determining the stress in a finite element model under load includes:

[0118] Determine the stress at any point in the pipeline in the three principal directions;

[0119] The equivalent stress at a point is determined based on the stress in the three principal directions. The formula for equivalent stress is:

[0120] ;

[0121] in, For equivalent stress, Let be the stress in the x-axis direction. The stress is in the y-axis direction. The stress is in the z-axis direction. Considering the thin-walled structure of the pipe, its radial stress is ignored.

[0122] The failure pressure calculation and failure criterion determination are performed using the von Mises stress criterion. When the von Mises stress in the corrosion defect area reaches the material's ultimate tensile strength, the pipeline fails. The ultimate failure pressure can be calculated from the intersection of the Mises stress-internal pressure curve and the material's tensile strength. When the von Mises stress determined by the following formula reaches a certain evaluation standard, the pipeline with corrosion defects is considered to have experienced strength failure. This can be understood from two aspects. First, in terms of stress distribution, the stress distribution within the corrosion area is uneven. Failure in the corrosion area does not occur synchronously as a whole, but usually starts from the location with the most severe local stress concentration and the smallest remaining wall thickness (that is, it starts from the most dangerous location and then expands). Therefore, it is possible that some parts of the corrosion area reach the failure condition first, while others have not yet failed.

[0123] However, when determining whether a pipeline has failed, we do not look at whether a few points in the corrosion zone have exceeded the limit, but rather whether the thickness of a certain local dangerous section / dangerous ligament has reached the failure condition as a whole. Once the dangerous local ligament reaches the failure criterion, the pipeline as a whole is considered to have entered a failure state.

[0124] The impact of hydrogen doping on pipeline failure pressure was further considered. The ultimate failure pressure of the pipeline was calculated for different hydrogen doping ratios (0%, 2.5%, 12.5%, 25%, and 50%). The results show that when the hydrogen doping ratio is below 50%, the failure pressure of the corrosion-defective pipeline fluctuates slightly, with a relatively small impact. However, when the hydrogen doping ratio reaches 50%, the pipeline failure pressure decreases significantly.

[0125] The true geometry of defects is reconstructed based on feature maps of laser 3D scanning point cloud data, solving the problem of stress distribution distortion caused by regularization. Parameter analysis includes:

[0126] The corrosion defect model reconstructed from 3D scanning data can further reflect the significant impact of corrosion defect morphology on the remaining strength of the pipeline.

[0127] Compared to regular shapes, by restoring the true corrosion defect contours of the pipeline, the predicted ultimate failure pressure was improved by 33.6%-47.0%;

[0128] Based on the established finite element model, the ultimate failure pressure of a pipeline with complex defects under internal pressure was analyzed under different hydrogen doping ratios. The results showed that the failure pressure fluctuation was <2.5% when the hydrogen doping ratio was ≤25%, and decreased by 3.3%-3.5% when the hydrogen doping ratio was ≥50%.

[0129] Comparing the stress cloud diagram of the pipeline failure with that of the hydrogen-free state, it can be found that the failure pressure of irregular defects with large depth differences changes more significantly at a 50% hydrogen doping ratio compared to the hydrogen-free state.

[0130] In practical applications, two sections of in-service X52 steel pipelines with corrosion defects were selected as research objects: the Yanshan-Mengzi section and the Guangnan-Yanshan section. The aim was to establish a finite element model of the pipeline with irregular corrosion defects based on three-dimensional contour scanning data of the corrosion defects obtained in the field, quantitatively solve its ultimate failure pressure, and further analyze the influence of the shape of the corrosion defects and different hydrogen doping ratios on the ultimate failure pressure of the pipeline. This provides a basis for evaluating the residual strength of pipelines with irregular corrosion defects and analyzing their suitability for hydrogen-doped transportation. Both pipeline sections are made of X52 steel, with an outer diameter of 457 mm and a wall thickness of 9.5 mm.

[0131] Step 1: Acquisition and feature extraction of 3D scanning data of on-site corrosion defects;

[0132] 1.1 A handheld 3D laser scanner was used to scan the contours of the corrosion defect area of ​​the in-service pipeline, acquiring 3D point cloud data of the corrosion area. (3D scan data point cloud processing is the process of processing and analyzing point cloud data acquired by a 3D laser scanner or other 3D acquisition equipment. Point cloud data is a collection of a large number of spatially discrete points. In addition to spatial coordinates, each point also has other attributes, such as color and normal vector.) The point cloud data is used to characterize the true spatial morphology of the corrosion defect area, providing basic data for subsequent reconstruction of the geometric model of irregular corrosion defects.

[0133] 1.2 The raw point cloud data obtained from the scan is preprocessed, including noise point removal, invalid point deletion, and missing value handling. For blank values ​​in the data, a column-wide deletion method is used for initial cleaning; for locally missing areas, a linear interpolation method is used to complete them, thereby ensuring the continuity and integrity of the erosion contour data.

[0134] 1.3 Feature extraction was performed on the corrosion defects (denoted as defect 1) of the Yanshan-Mengzi section pipeline. The maximum depth of defect 1 is 5.833 mm, and the maximum depth location is at -87.473 mm axially and 333.662° circumferentially; the axial length is 28.691 cm, and the circumferential width is 200.721°, which is approximately equivalent to 80.049 cm; the axial front end is -232.928 mm, the axial end is 53.983 mm, the circumferential front end is 258.391°, the circumferential end is 99.112°, and the remaining wall thickness ratio is 38.60% RWT.

[0135] 1.4 Feature extraction was performed on the corrosion defects (denoted as defect 2) in the Guangnan-Yanshan section of the pipeline. The maximum depth of defect 2 is 5.483 mm, located at 79.466 mm axially and 5.298° circumferentially; the axial length is 43.881 cm, and the circumferential width is 95.359°, which is approximately 38.03 cm; the axial front end is -154.934 mm, the axial end is 283.879 mm, the circumferential front end is 328.706°, the circumferential end is 64.066°, and the remaining wall thickness ratio is 42.28% RWT.

[0136] Step 2: Establishment of finite element geometric model and material parameters;

[0137] 2.1 The Yanshan-Mengzi section pipeline and the Guangnan-Yanshan section pipeline are denoted as YM pipeline and GY pipeline, respectively, and their corresponding corrosion defects are denoted as defect 1 and defect 2, respectively. A finite element model of the pipeline with irregular corrosion defects is established. The irregular model is constructed based on preprocessed 3D scan point cloud data to realistically reflect the spatial morphological characteristics of the corrosion area.

[0138] 2.2 In the process of constructing the irregular corrosion defect model, ANSYS was used to write a command flow script to map the point cloud data of the corrosion area into a three-dimensional solid mesh and generate the corresponding INP file. Then, it was imported into ABAQUS for nonlinear numerical calculation to improve the modeling efficiency and solution accuracy under complex corrosion profile conditions.

[0139] 2.3 Based on the maximum length, maximum width, and maximum depth parameters of the corrosion defects obtained from the scan, a corresponding regular corrosion defect pipeline model is established. When modeling the equivalent regular shape of the defect, in order to reduce stress concentration caused by the excessively sharp geometric edges of the defect, the apex corners of the rectangular defect are rounded, and the rounding radius is the defect depth.

[0140] 2.4 X52 steel was selected as the material, and the influence of different hydrogen doping conditions on the mechanical properties of the material was considered. The hydrogen doping ratios were 0%, 2.5%, 12.5%, 25%, and 50%. The corresponding yield strengths were 393 MPa, 381 MPa, 388 MPa, 390 MPa, and 368 MPa; the tensile strengths were 508 MPa, 515 MPa, 519 MPa, 509 MPa, and 492 MPa; the elastic moduli were 196500 MPa, 190500 MPa, 194000 MPa, 195000 MPa, and 184000 MPa; and the Poisson's ratio was taken as 0.3 for all cases.

[0141] 2.5 The Ramberg-Osgood constitutive model was used to characterize the elastoplastic mechanical behavior of X52 steel under different hydrogen doping conditions. The actual stress-strain relationship of the material was established based on the yield strength, tensile strength and elastic modulus parameters corresponding to different hydrogen doping ratios, which was used for subsequent ultimate failure pressure analysis.

[0142] Step 3: Boundary condition setting and mesh generation;

[0143] 3.1 To avoid rigid body displacement, boundary constraints are applied to the established finite element model of the pipeline. The far end of the pipe segment is completely fixed to restrict the translation and rotation of the end nodes, thereby ensuring the stability of the model calculation during internal pressure loading. The method is as follows: In ABAQUS, for all nodes on the far end face of the pipeline, set displacement constraints U1=U2=U3=0 and rotation constraints UR1=UR2=UR3=0.

[0144] 3.2 Regarding load settings, only the internal pressure of the pipeline is considered. A uniformly distributed internal pressure load is applied to the inner surface of the pipeline, and the evolution law of stress in the corrosion defect area with load increase is analyzed by gradually increasing the internal pressure. Specifically, in the finite element analysis, multiple analysis steps are set, and an increasing internal pressure value is applied in each analysis step. After each analysis step, the stress value of the node with the maximum von Mises equivalent stress in the corrosion defect area is extracted. These stress values ​​and the corresponding internal pressure values ​​are plotted as a "Mises stress-internal pressure curve". When the curve intersects with the ultimate tensile strength (horizontal line) of the material, the internal pressure corresponding to the intersection point is the ultimate failure pressure.

[0145] 3.3 The pipeline model was discretized using C3D8R elements. To balance computational accuracy and solution efficiency, a locally refined mesh was used in the corrosion defect region, while a relatively coarse mesh was used in the region far from the corrosion defect.

[0146] 3.4 For corrosion defect areas, the mesh length is set to 3mm, and 4 meshes are divided along the wall thickness direction to accurately capture the stress gradient changes in the wall thinning area and improve the accuracy of predicting the ultimate failure pressure of corrosion defects.

[0147] Step 4: Determine the failure criteria and solve for the ultimate failure pressure;

[0148] 4.1 The stress failure criterion is adopted as the basis for determining the ultimate failure of the pipeline. Specifically, when the von Mises equivalent stress over the entire ligament thickness of the corroded area reaches the material's ultimate tensile strength, the corresponding internal pressure is defined as the ultimate failure pressure of the pipeline with the corrosion defect. For X52 steel in the hydrogen-free state, the ultimate tensile strength is taken as 508 MPa.

[0149] 4.2 Finite element analysis was performed on defect 1 corresponding to the YM pipeline. The node with the largest von Mises equivalent stress in the defect region was extracted, and the relationship curve of the Mises stress at this node versus the internal pressure was plotted. When this curve reaches the ultimate tensile strength of 508 MPa, the corresponding internal pressure is the pipeline's ultimate failure pressure. The ultimate failure pressure of the YM pipeline under hydrogen-free conditions is 13.853 MPa.

[0150] 4.3 Analysis of the ultimate failure location of defect 1 shows that the maximum equivalent stress location is at 333.124° circumferentially and -85mm axially, corresponding to a remaining wall thickness of approximately 40.78%t. Compared with the location of the deepest corrosion point obtained from the 3D scan, the axial error is 2.473mm and the circumferential error is 0.538°, indicating that the established finite element model of irregular corrosion defects can accurately predict the critical location.

[0151] 4.4 The same method was used to perform finite element analysis on defect 2 corresponding to the GY pipeline. The ultimate failure pressure of the GY pipeline under hydrogen-free conditions is 15.317 MPa. The location of its maximum von Mises equivalent stress is located at 5.208° circumferentially and 77.246 mm axially. Compared with the location of the deepest corrosion point obtained by three-dimensional scanning, the axial error is 2.22 mm and the circumferential error is 0.09°, showing high consistency.

[0152] 4.5 To verify the reliability of the finite element method, a finite element verification model of a pipeline with regular corrosion defects was established based on the blast test data in the literature, and the finite element prediction results were compared with the blast test results.

[0153] Step 5: Analysis of the influence of corrosion defect shape on ultimate failure pressure;

[0154] 5.1 Establish regular corrosion defect models and irregular corrosion defect models respectively, and compare and analyze the stress distribution and ultimate failure pressure of the two models.

[0155] In regular corrosion defect models, the stress distribution is relatively uniform, and the maximum stress is generally located in the relatively central region inside the defect; while in irregular corrosion defect models, because the corrosion surface has real depth undulations, stress concentration is more likely to form in local areas.

[0156] Figure 10 This invention provides a first type of stress comparison cloud map for regular and irregular corrosion defects. Figure 11 This invention provides a second type of stress comparison cloud map for regular and irregular corrosion defects. Figure 12 The third type of stress comparison cloud map for regular and irregular corrosion defects provided by this invention Figure 13 The fourth type of stress comparison cloud diagram for regular and irregular corrosion defects provided by the present invention;

[0157] 5.2 For defect 1, the ultimate failure pressure predicted by the regular corrosion defect model is 10.367 MPa, while the ultimate failure pressure predicted by the irregular corrosion defect model is 13.853 MPa, the latter being 33.63% higher than the former.

[0158] 5.3 For defect 2, the ultimate failure pressure predicted by the regular corrosion defect model is 10.421 MPa, while the ultimate failure pressure predicted by the irregular corrosion defect model is 15.317 MPa, the latter being 46.95% higher than the former.

[0159] 5.4 The method of this embodiment is compared with existing residual strength evaluation methods such as ASME B31G-2009, DNVRP-F101, and RSTRENG. For defect 1, the predicted results of each method are 10.141 MPa, 10.870 MPa, 10.837 MPa, and 13.853 MPa, respectively; for defect 2, the predicted results of each method are 10.220 MPa, 10.733 MPa, 10.921 MPa, and 15.317 MPa, respectively. Traditional methods are based on the assumption of regular defects and are generally conservative, while the irregular corrosion defect model established based on the real contour of three-dimensional scanning can more accurately reflect the actual bearing capacity.

[0160] Step 6: Analysis of the influence of different hydrogen doping ratios on the ultimate failure pressure;

[0161] 6.1 Based on the finite element model of irregular corrosion defects, the variation law of ultimate failure pressure of YM pipeline and GY pipeline under different hydrogen doping ratios is further analyzed. The hydrogen doping ratios are 2.5%, 12.5%, 25% and 50%, respectively, and compared with the state without hydrogen.

[0162] 6.2 For the YM pipeline, the ultimate failure pressures at hydrogen doping ratios of 2.5%, 12.5%, 25%, and 50% were 14.040 MPa, 14.164 MPa, 13.887 MPa, and 13.408 MPa, respectively. Compared to 13.853 MPa in the hydrogen-free state, the changes were +1.35%, +2.25%, +0.25%, and -3.21%, respectively. The results indicate that under low hydrogen doping conditions, the ultimate failure pressure of the YM pipeline changes little, while when the hydrogen doping ratio reaches 50%, the failure pressure decreases significantly.

[0163] 6.3 For the GY pipeline, the ultimate failure pressures at hydrogen doping ratios of 2.5%, 12.5%, 25%, and 50% are 15.487 MPa, 15.605 MPa, 15.342 MPa, and 14.804 MPa, respectively. Compared to the 15.317 MPa in the hydrogen-free state, the changes are +1.10%, +1.88%, +0.16%, and -3.34%, respectively. This variation pattern is basically consistent with that of the YM pipeline.

[0164] The ultimate failure pressure of 6.4X52 steel corrosion-defect pipelines does not exhibit a monotonically decreasing trend with increasing hydrogen doping ratio. Instead, it is closely related to the changes in the tensile strength of the material under different hydrogen doping conditions. Within the hydrogen doping ratio range of 2.5% to 25%, the failure pressure shows only slight fluctuations; when the hydrogen doping ratio increases to 50%, the material performance weakening effect intensifies, and the ultimate failure pressure decreases accordingly.

[0165] 6.5 Further comparison of the two defects shows that, under 50% hydrogen doping conditions, the pressure drop of the pipeline failure corresponding to defect 2 is slightly greater than that of defect 1. This indicates that in a high hydrogen doping environment, the more obvious the geometric undulations of the corrosion defect surface, the more prominent its adverse effect on the pipeline's remaining load-bearing capacity.

[0166] Figure 14 This is a schematic diagram of a safety assessment system for pipelines with irregular corrosion defects provided by the present invention. The pipeline pressure determination system includes:

[0167] Coordinate determination unit 21 is used to determine the coordinate data of the corrosion area of ​​the pipeline;

[0168] Model building unit 22 is used to build a finite element model of the pipeline based on coordinate data and the mechanical performance parameters of the pipeline. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index.

[0169] Pressure application element 23 is used to apply pressure to the finite element model and determine the stress in the finite element model under load;

[0170] The ultimate pressure value determination unit 24 is used to determine the pressure corresponding to the stress greater than the ultimate tensile strength as the ultimate pressure value of the pipeline when the stress is greater than the ultimate tensile strength.

[0171] Based on the above embodiments:

[0172] Also includes:

[0173] Point cloud data acquisition unit, used to acquire point cloud data of the corrosion area of ​​the pipeline;

[0174] The outlier removal unit is used to remove outliers from point cloud data;

[0175] The value range deletion unit is used to delete point cloud data whose values ​​exceed the corresponding physical value range;

[0176] The supplementary unit is used to supplement missing point cloud data using linear interpolation.

[0177] The coordinate determination unit 21 is specifically used to determine the coordinate data of the eroded area from the point cloud data after the deletion and supplementation operations.

[0178] The outlier removal unit is specifically used to determine the average distance to a preset number of adjacent points for any given point.

[0179] If the average distance is greater than the noise upper limit average distance, the point cloud data of the point is determined to be an outlier and deleted.

[0180] Alternatively, for any given point, determine the number of neighboring points within its radius.

[0181] If the number is less than the preset number, the point cloud data of the determined point is an outlier and is deleted.

[0182] The coordinate determination unit 21 is specifically used to extract features from the point cloud data after the deletion and supplementation operations. The coordinate data includes the coordinates of the maximum depth position, the axial length, the circumferential width, the coordinates of the axial front end position, the coordinates of the axial end position, the coordinates of the circumferential front end position, the coordinates of the circumferential end position, and the ratio of the remaining wall thickness.

[0183] Model building unit 22 is specifically used to build a finite element model of the pipeline based on the parameters of the maximum length, maximum width and maximum depth of the corrosion zone;

[0184] By inputting the material and corresponding mechanical property parameters of the pipeline with different hydrogen doping ratios into the finite element model, the stress-strain relationship of the pipeline under different hydrogen doping ratios is obtained from the output of the finite element model.

[0185] The expression for the relationship between stress and strain is:

[0186] ;

[0187] in, For the true total strain of the material, For yield strain, For the actual stress of the material, For yield strength, , For elastic modulus, The hardening coefficient is... This is the hardening index.

[0188] Constraint addition unit is used to add fixed constraints to the ends of the pipe to limit the translation and rotation of the end nodes;

[0189] The load application unit is used to apply a uniformly distributed internal pressure load to the inside of the pipe.

[0190] Mesh generation cells are used to divide the pipeline into meshes, with the mesh density of corroded areas on the pipeline being greater than that of uncorroded areas.

[0191] The stress determination unit is used to determine the stress at any point in the pipeline in the three principal directions;

[0192] The equivalent stress determination element is used to determine the equivalent stress at a point based on the stress in the three principal directions. The formula for equivalent stress is:

[0193] ;

[0194] in, For equivalent stress, Let be the stress in the x-axis direction. The stress is in the y-axis direction. The stress is in the z-axis direction.

[0195] The description of the pipeline pressure determination system provided in this application is based on the above embodiments and will not be repeated here.

[0196] Figure 15 This invention provides a structural schematic diagram of a safety assessment device for pipelines with irregular corrosion defects. The device for determining pipeline pressure includes:

[0197] Memory 31 is used to store computer programs;

[0198] The processor 32 is used to implement the steps of the above-described safety assessment method for pipelines with irregular corrosion defects when executing a computer program.

[0199] The description of the pipeline pressure determination device provided in this application is based on the above embodiments and will not be repeated here.

[0200] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0201] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0202] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for safety assessment of pipelines with irregular corrosion defects, characterized in that, include: Determine the coordinates of the corrosion zone in the pipeline; Based on the coordinate data and the mechanical performance parameters of the pipeline, a finite element model of the pipeline is constructed. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index. Pressure is applied to the finite element model, and the stress in the finite element model under load is determined; When the stress exceeds the ultimate tensile strength, the pressure corresponding to the stress exceeding the ultimate tensile strength is determined as the ultimate pressure value of the pipeline.

2. The safety assessment method for pipelines with irregular corrosion defects as described in claim 1, characterized in that, Determine the coordinate data of the corrosion zone in the pipeline, including: Obtain point cloud data of the corrosion area of ​​the pipeline; Remove outliers from the point cloud data; Delete point cloud data whose values ​​exceed the corresponding physical value range; Missing point cloud data is supplemented using linear interpolation. The coordinate data of the eroded region are determined from the point cloud data after the deletion and addition operations.

3. The safety assessment method for pipelines with irregular corrosion defects as described in claim 2, characterized in that, Remove outliers from point cloud data, including: For any given point, determine the average distance to a preset number of adjacent points; If the average distance is greater than the noise upper limit average distance, the point cloud data of the point is determined to be an outlier and deleted. Alternatively, for any given point, determine the number of neighboring points within its radius. If the number is less than the preset number, the point cloud data of the point is determined to be an outlier and deleted.

4. The safety assessment method for pipelines with irregular corrosion defects as described in claim 2, characterized in that, Determining the coordinate data of the eroded region from the point cloud data after deletion and supplementation operations includes: Feature extraction is performed on the coordinate data from the point cloud data after deletion and addition operations. The coordinate data includes the coordinates of the maximum depth position, the axial length, the circumferential width, the coordinates of the axial front end position, the coordinates of the axial end position, the coordinates of the circumferential front end position, the coordinates of the circumferential end position, and the remaining wall thickness ratio.

5. The safety assessment method for pipelines with irregular corrosion defects as described in claim 1, characterized in that, Based on the coordinate data and the mechanical performance parameters of the pipeline, a finite element model of the pipeline is constructed, including: A finite element model of the pipeline is constructed based on the parameters of the maximum length, maximum width, and maximum depth of the corrosion zone. By inputting the material and corresponding mechanical property parameters of the pipeline with different hydrogen doping ratios into the finite element model, the stress-strain relationship of the pipeline under different hydrogen doping ratios is obtained from the output of the finite element model.

6. The safety assessment method for pipelines with irregular corrosion defects as described in claim 5, characterized in that, The expression for the relationship between stress and strain is: ； in, For the true total strain of the material, For yield strain, For the actual stress of the material, For yield strength, , For elastic modulus, The hardening coefficient is... This is the hardening index.

7. The safety assessment method for pipelines with irregular corrosion defects as described in claim 1, characterized in that, After constructing the finite element model of the pipeline based on the coordinate data and the mechanical performance parameters of the pipeline, the process further includes: Add fixed constraints to the ends of the pipe to limit the translation and rotation of the end nodes; Apply a uniformly distributed internal pressure load to the inside of the pipe; The pipeline is divided into grids, and the grid density of the corroded areas on the pipeline is greater than the grid density of the uncorroded areas.

8. The safety assessment method for pipelines with irregular corrosion defects as described in any one of claims 1 to 7, characterized in that, Determining the stress in the finite element model under load includes: Determine the stress at any point in the pipeline in the three principal directions; The equivalent stress at a given point is determined based on the stress in the three principal directions, and the relationship between the equivalent stresses is as follows: ； in, For equivalent stress, Let be the stress in the x-axis direction. The stress is in the y-axis direction. The stress is in the z-axis direction.

9. A safety assessment system for pipelines with irregular corrosion defects, characterized in that, include: Coordinate determination unit, used to determine the coordinate data of the corrosion area of ​​the pipeline; The model building unit is used to build a finite element model of the pipeline based on the coordinate data and the mechanical performance parameters of the pipeline. The mechanical performance parameters include at least one of yield strength, tensile strength, elastic modulus, and hardening index. A pressure application unit is used to apply pressure to the finite element model and determine the stress in the finite element model under load. The ultimate pressure value determination unit is used to determine the pressure corresponding to the stress greater than the ultimate tensile strength as the ultimate pressure value of the pipeline when the stress is greater than the ultimate tensile strength.

10. A safety assessment device for pipelines with irregular corrosion defects, characterized in that, include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the steps of the safety assessment method for irregularly corroded pipelines as described in any one of claims 1 to 8.

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