Method for evaluating residual strength of submarine corroded pipeline based on stress concentration theory

Abstract

The invention provides a method for evaluating the residual strength of a submarine corroded pipeline based on a stress concentration theory. The method comprises the following steps: acquiring basic parameters and corrosion defect parameters of a pipeline with corrosion defects; the ultimate bearing capacity of the complete pipeline is obtained based on the basic parameters of the pipeline with the corrosion defect; acquiring a pipeline defect coefficient according to the corrosion defect parameter, and identifying a pipeline corrosion defect type; based on the pipeline corrosion defect type and the pipeline defect coefficient, obtaining a pipeline corrosion defect stress concentration coefficient; and according to the pipeline defect coefficient and the pipeline corrosion defect stress concentration coefficient, obtaining the residual strength of the corroded pipeline so as to evaluate the safety state of the pipeline. Compared with a standard recommendation evaluation method, the method is more accurate, and more accurate decision support can be provided for pipeline integrity management.

Description

Technical Field

[0001] This application belongs to the technical field of subsea pipeline engineering, and relates to a method for evaluating the remaining strength of pipelines, in particular to a method for evaluating the remaining strength of corroded subsea pipelines based on the stress concentration theory. Background Art

[0002] Subsea pipelines are the lifeline of offshore oil and gas development. As offshore oil and gas exploration and development work gradually moves towards deep and far seas, the service environment of subsea pipelines becomes increasingly harsh. The significant increase in the pressure of oil and gas wells and the concentration of corrosive substances (such as CO2, H2S, chlorides) makes the pipeline corrosion problem more prominent. The corrosion damage of subsea pipelines will cause major safety accidents and then trigger environmental disasters. Therefore, it is necessary to accurately evaluate the remaining strength of corroded pipelines and correspondingly adjust the operating pressure of the pipelines to ensure the safe operation of the pipelines.

[0003] Currently, there are two commonly used methods for evaluating the remaining strength of corroded subsea pipelines:

[0004] One is to evaluate based on empirical or semi-empirical formulas. Comparing the calculation results of this method with the pipeline burst test data, there is a problem of large calculation result errors, and it is easy to cause the evaluation results to be too conservative when guiding engineering practice, affecting the economy of the project.

[0005] The other is to evaluate based on finite element simulation. This method has higher calculation accuracy, but a finite element model needs to be established, so the calculation efficiency is low.

[0006] In summary, the currently adopted methods for evaluating the remaining strength of corroded subsea pipelines all have problems such as large calculation errors and inability to effectively guide engineering practice. There is an urgent need to determine an accurate method for evaluating the remaining strength of corroded subsea pipelines based on burst tests. Summary of the Invention

[0007] The purpose of this application is to provide a method for evaluating the remaining strength of corroded subsea pipelines based on the stress concentration theory, which is used to solve the problem that in the prior art, due to the evaluation of the remaining strength of corroded subsea pipelines often relying on empirical or semi-empirical formulas, the evaluation results have too large errors, resulting in the inability to effectively guide engineering practice.

[0008] In a first aspect, the present application provides a method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory, including the following steps: obtaining the basic parameters of the corroded pipeline with defects and the corrosion defect parameters; obtaining the ultimate bearing capacity of the intact pipeline based on the basic parameters of the corroded pipeline with defects; obtaining the pipeline defect coefficient according to the corrosion defect parameters and identifying the type of pipeline corrosion defect; obtaining the stress concentration coefficient of the pipeline corrosion defect based on the type of pipeline corrosion defect and the pipeline defect coefficient; obtaining the remaining strength of the corroded pipeline according to the pipeline defect coefficient and the stress concentration coefficient of the pipeline corrosion defect to evaluate the safety state of the pipeline.

[0009] In one implementation of the first aspect, the basic parameters of the corroded pipeline with defects include: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure; the corrosion defect parameters include: corrosion defect length, corrosion defect depth.

[0010] In one implementation of the first aspect, obtaining the ultimate bearing capacity of the intact pipeline based on the basic parameters of the corroded pipeline with defects includes: calculating the ultimate bearing capacity of the intact pipeline according to the recommended practice of the specification; the calculation formula for the ultimate bearing capacity of the intact pipeline is:

[0011]

[0012] where P b (t) represents the ultimate bearing capacity of the intact pipeline; t represents the pipeline wall thickness; D represents the pipeline diameter; f u represents the tensile strength of the pipeline.

[0013] In one implementation of the first aspect, obtaining the pipeline defect coefficient according to the corrosion defect parameters and identifying the type of pipeline corrosion defect includes: obtaining the pipeline defect coefficient based on the basic parameters and corrosion defect parameters of the corroded pipeline with defects; the pipeline defect coefficient includes: pipeline corrosion depth coefficient and pipeline corrosion length coefficient; identifying the type of pipeline corrosion defect based on the pipeline corrosion length coefficient.

[0014] In one implementation of the first aspect, the formula for the pipeline corrosion depth coefficient is:

[0015]

[0016] The formula for the pipeline corrosion length coefficient is:

[0017]

[0018] where k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient; t represents the pipeline wall thickness; D represents the pipeline diameter; l represents the corrosion length of the pipeline defect; d represents the corrosion depth of the pipeline.

[0019] In an implementation manner of the first aspect, identifying the type of pipeline corrosion defect based on the pipeline corrosion length coefficient includes: selecting a segmentation point according to requirements and dividing the pipeline into several segments; fitting each of the segments with a piecewise function; setting a determination threshold according to the fitting result and actual requirements; comparing the pipeline defect coefficient with the determination threshold to identify the type of pipeline corrosion defect; including: when the pipeline corrosion length coefficient is greater than or equal to the determination threshold, it is determined as long corrosion; when the pipeline corrosion length coefficient is less than the determination threshold, it is determined as short corrosion.

[0020] In an implementation manner of the first aspect, obtaining the stress concentration coefficient of the pipeline corrosion defect based on the type of pipeline corrosion defect and the pipeline defect coefficient includes: constructing a pipeline defect coefficient matrix based on the pipeline defect coefficient; performing fitting based on the pipeline defect coefficient matrix to construct a mapping relationship between the depth and length of the pipeline corrosion defect; calculating the stress concentration coefficient of the pipeline corrosion defect according to the mapping relationship; the formula for the stress concentration coefficient of the pipeline corrosion defect is:

[0021]

[0022] where SCF 有效 represents the stress concentration coefficient of the pipeline corrosion defect; [D] represents the calculation matrix of the corrosion defect depth; [N] represents the calculation coefficient matrix; [L] represents the calculation matrix of the corrosion length; f(d, l) represents the binary relationship function of the corrosion defect depth and the corrosion defect length; k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient.

[0023] In an implementation manner of the first aspect, the calculation formula for the remaining strength of the corroded pipeline is:

[0024]

[0025] where P f (l, d) represents the remaining strength of the corroded pipeline; P b (t) represents the ultimate bearing capacity of the intact pipeline; SCF 有效 represents the stress concentration coefficient of the pipeline corrosion defect.

[0026] In a second aspect, the present application provides an evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, including: an acquisition module for acquiring the basic parameters of a pipeline with corrosion defects and the corrosion defect parameters; a first calculation module for obtaining the ultimate bearing capacity of a complete pipeline based on the basic parameters of the pipeline with corrosion defects; a defect calculation and identification module for obtaining a pipeline defect coefficient according to the corrosion defect parameters and identifying the type of pipeline corrosion defect; a stress concentration calculation module for obtaining the stress concentration coefficient of the pipeline corrosion defect based on the type of pipeline corrosion defect and the pipeline defect coefficient; and a pipeline strength evaluation module for obtaining the remaining strength of the corroded pipeline according to the pipeline defect coefficient and the stress concentration coefficient of the pipeline corrosion defect to evaluate the safety state of the pipeline.

[0027] In a last aspect, the present application provides an evaluation electronic terminal for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, including: a processor and a memory. The memory is used for storing a computer program; the processor is connected to the memory and is used for executing the computer program stored in the memory so that the evaluation device for the remaining strength of the submarine corroded pipeline based on the stress concentration theory executes the evaluation method for the remaining strength of the submarine corroded pipeline based on the stress concentration theory.

[0028] As described above, the evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory of the present application has the following

[0029] Beneficial effects:

[0030] (1) The present application provides an evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, which can calculate the stress concentration coefficient at the corrosion defect according to the ultimate bearing capacity of the complete pipeline; furthermore, obtain the remaining strength of the corroded pipeline; this evaluation result is more consistent with the pipeline burst test result compared with the traditional code recommended practice, and can better fit and evaluate the variation law of the remaining strength of the corroded pipeline with the pipeline diameter, wall thickness, tensile strength, corrosion defect length, and corrosion defect depth, solving the problem that the evaluation result of the existing code recommended practice is too conservative.

[0031] (2) The evaluation method for the remaining strength of a corroded pipeline based on the stress concentration theory of the present application can provide more accurate decision support for pipeline integrity management. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It shows a schematic diagram of a hardware application scenario in an embodiment of the evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in the present application.

[0033] Figure 2It shows a schematic flow chart of the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory in an embodiment of the present application.

[0034] Figure 3 It shows a schematic flow chart of the corrosion type determination process of the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory in an embodiment of the present application.

[0035] Figure 4 It shows a schematic flow chart of S4 in the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory of the present application.

[0036] Figure 5 It shows a schematic principle structure diagram of the evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory in an embodiment of the present application.

[0037] Figure 6 It shows a schematic principle structure diagram of the evaluation electronic terminal for the remaining strength of a submarine corroded pipeline based on the stress concentration theory in an embodiment of the present application.

[0038] Description of component labels

[0039] 11 Data acquisition module

[0040] 12 Calculation module

[0041] 13 Evaluation module

[0042] 51 Acquisition module

[0043] 52 First calculation module

[0044] 53 Defect calculation and identification module

[0045] 54 Stress concentration calculation module

[0046] 55 Pipeline strength evaluation module

[0047] 61 Processor

[0048] 62 Memory Detailed implementation manners

[0049] The following uses specific specific examples to illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0050] It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present application in a schematic manner. Therefore, only the components related to the present application are shown in the drawings, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and proportion of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0051] The following embodiments of the present application provide an evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, which solves the problem in the prior art that the evaluation of the remaining strength of a submarine corroded pipeline often relies on empirical or semi-empirical formulas, resulting in too large an error in the evaluation results, and further leading to the problem that engineering practice cannot be effectively guided.

[0052] As Figure 1 shown, the schematic diagram of the hardware application scenario in an embodiment of the evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in the present application specifically includes: a data acquisition module 11, a calculation module 12, and an evaluation module 13. Among them, the acquisition module 11 is used to acquire the diameter, wall thickness, tensile strength, operating pressure, corrosion defect length, and corrosion defect depth of the corroded pipeline; the calculation module 12 is connected to the acquisition module 11 and is used to calculate the ultimate bearing capacity of the complete pipeline according to the diameter, wall thickness, and tensile strength of the pipeline; obtain the pipeline defect sensitivity coefficient according to the corrosion defect length, calculate the corrosion defect length coefficient and corrosion depth coefficient according to the corrosion defect length and corrosion defect depth, determine whether the evaluated corrosion defect is a long corrosion defect or a short corrosion defect, and obtain the pipeline corrosion defect stress concentration coefficient according to the pipe diameter, wall thickness, tensile strength, corrosion defect length, corrosion defect depth, and corrosion defect type; obtain the remaining strength of the pipeline according to the pipeline defect sensitivity coefficient and the pipeline corrosion defect stress concentration coefficient. The evaluation module 13 is connected to the calculation module 12 and is used to evaluate the safety state of the pipeline according to the remaining strength of the corroded pipeline and in combination with the operating pressure required by the pipeline.

[0053] Next, the evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory provided in the embodiments of the present application will be described in detail with reference to the accompanying drawings in the embodiments of the present application.

[0054] In the prior art, evaluation based on finite element simulation is commonly used.

[0055] (1) The AGA NG-18 formula is an empirical formula established based on fracture mechanics theory, and the evaluation result is too conservative. Most subsequent empirical formulas are corrected based on this theory.

[0056]

[0057] In the formula, Pb is the remaining strength of the pipeline, σ s is the yield strength of the pipe material, d is the depth of the corrosion defect, t is the wall thickness of the pipeline, M is the expansion coefficient, and L is the length of the corrosion defect.

[0058] (2) The ASME - B31G formula corrects the conservatism of the NG - 18 formula, but there are certain risks in the evaluation results.

[0059] Determine the expansion coefficient by judging the type of corrosion defect;

[0060] When L 2 / (Dt) ≤ 50,

[0061] When L 2 / (Dt) ≥ 50,

[0062] (3) API RP 579 corrects the conservatism of the NG - 18 formula, but the calculation error is still relatively high.

[0063]

[0064] Among them, σ u is the tensile strength of the pipe material.

[0065] (4) DNV RP F101 corrects the conservatism of the NG - 18 formula, but the calculation error is still relatively high.

[0066]

[0067] The calculation accuracy of the above - mentioned method is relatively high, but a finite - element model needs to be established. Therefore, overall, the calculation efficiency of this method is low, and it is easy to produce a situation where the evaluation result error is too large. Therefore, the present application adopts the following method for processing.

[0068] Please refer to Figure 2 , which shows the flow schematic diagram of the evaluation method for the remaining strength of a submarine corroded pipeline based on the stress - concentration theory in an embodiment of the present application. As Figure 2 shown, this embodiment provides an evaluation method for the remaining strength of a submarine corroded pipeline based on the stress - concentration theory.

[0069] The evaluation method for the remaining strength of a submarine corroded pipeline based on the stress - concentration theory specifically includes the following steps:

[0070] S1, Obtain the basic parameters of the pipeline with corrosion defects and the corrosion - defect parameters.

[0071] In this embodiment, the basic parameters of the pipeline with corrosion defects include but are not limited to: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure, etc. The corrosion defect parameters include but are not limited to: corrosion defect length, corrosion defect depth, etc.

[0072] Specifically, relevant parameters of the pipeline to be detected can be obtained through various channels (such as pipeline design units or construction units, etc.), such as: relevant parameters of the pipeline can be obtained by referring to pipeline design materials (such as: pipeline material, pipeline outer diameter, pipeline wall thickness, pipeline tensile strength, design pressure, elastic modulus, Poisson's ratio, yield stress, etc.). Some basic parameters can also be obtained through on-site measurement.

[0073] In addition, for obtaining corrosion defect parameters, professional corrosion detection instruments such as ultrasonic detectors, magnetic particle detectors, eddy current detectors, etc. can be used to detect the corrosion of the pipeline. These instruments can accurately measure parameters such as the depth, length, and width of the corrosion defects.

[0074] Then, during the corrosion detection, the position information of each corrosion defect should be recorded in detail, including the specific position of the defect on the pipeline (such as: the distance from the starting point of the pipeline), the direction of the defect (such as: axial or circumferential), etc. According to the results of the corrosion detection, the morphological characteristics of the corrosion defects are evaluated, such as the shape of the defect (such as: circular, elliptical, rectangular, etc.), the edge condition of the defect (such as: whether it is smooth, whether there are cracks, etc.).

[0075] Finally, the obtained corrosion defect parameters are combined with the basic parameters of the pipeline for comprehensive analysis. This helps to understand the degree of influence of the corrosion defects on the overall strength of the pipeline and whether repair measures need to be taken.

[0076] S2. Obtain the ultimate bearing capacity of the complete pipeline based on the basic parameters of the pipeline with corrosion defects.

[0077] In this embodiment, according to the recommended practice of the specification, the ultimate bearing capacity of the complete pipeline is calculated.

[0078] Specifically, according to the basic parameters of the pipeline with corrosion defects obtained above (such as: the ultimate bearing capacity of the complete pipeline, pipeline wall thickness, pipeline diameter, pipeline tensile strength, etc.), combined with the ultimate bending moments corresponding to different pipelines (such as: non-pressure pipelines, pressure pipelines), the calculation is carried out through the formula of the ultimate bearing capacity of the pipeline.

[0079] The calculation formula for the ultimate bearing capacity of the complete pipeline is:

[0080]

[0081] Wherein, P b(t) represents the ultimate bearing capacity of the complete pipeline; t represents the pipeline wall thickness; D represents the pipeline diameter; f u represents the tensile strength of the pipeline.

[0082] It should be noted that when calculating, multiple factors such as the material, size, and working environment of the pipeline need to be fully considered, and appropriate calculation methods and models should be adopted to ensure the accuracy and safety of the calculation results. At the same time, various details and precautions in the calculation process also need to be noted to ensure the reliability and effectiveness of the calculation results.

[0083] S3. Obtain the pipeline defect coefficient based on the corrosion defect parameters and identify the pipeline corrosion defect type. The specific steps are as follows:

[0084] S31. Based on the basic parameters and corrosion defect parameters of the pipeline with corrosion defects, obtain the pipeline defect coefficient; the pipeline defect coefficient includes: the pipeline corrosion depth coefficient and the pipeline corrosion length coefficient.

[0085] In this embodiment, the basic parameters of the pipeline with corrosion defects obtained (such as: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure, etc.) are preprocessed. First, outliers or invalid data are removed to ensure the accuracy and consistency of the data. Then, the pipeline corrosion depth coefficient k1 and the pipeline corrosion length coefficient k2 are obtained respectively through the calculation of the pipeline defect coefficient.

[0086] The formula for the pipeline corrosion depth coefficient is:

[0087]

[0088] The formula for the pipeline corrosion length coefficient is:

[0089]

[0090] Among them, k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient; t represents the pipeline wall thickness; D represents the pipeline diameter; l represents the pipeline defect corrosion length; d represents the pipeline corrosion depth.

[0091] S32. Identify the pipeline corrosion defect type based on the pipeline corrosion length coefficient. Please refer to Figure 3 .

[0092] In this embodiment, segment points are selected according to requirements, and the pipeline is divided into several segments; a piecewise function is used to fit each of the segments; according to the fitting result and actual requirements, a judgment threshold is set; the pipeline corrosion defect coefficient is compared with the judgment threshold to identify the type of pipeline corrosion defect. Among them, the judgment criteria include: when the pipeline corrosion length coefficient is greater than or equal to the judgment threshold, it is judged as long corrosion; when the pipeline corrosion length coefficient is less than the judgment threshold, it is judged as short corrosion.

[0093] Specifically, a piecewise function is used for fitting. That is: first, select segment points. According to the distribution of data and actual requirements, appropriate segment points are selected. For example, according to the distribution of the k2 value, one or more segment points can be selected to distinguish short corrosion and long corrosion. Then, fit the piecewise function: for each segment, an appropriate function form (such as a linear function, a quadratic function, etc.) is used for fitting. Methods such as the least squares method and nonlinear regression can be used to solve the parameters of the fitting function. Finally, the goodness of fit (such as the R 2 value, mean square error, etc.) is calculated to evaluate the quality of the fitting result. If the fitting result is not ideal, the segment points or function form can be adjusted and refitting can be performed.

[0094] Furthermore, according to the fitting result and actual requirements, a judgment threshold is set to distinguish short corrosion and long corrosion.

[0095] For example, the judgment threshold is preferably set to 3. It can be known that 1. A threshold (such as k2 = 3) is set to distinguish short corrosion and long corrosion.

[0096] Judge the corrosion defect: for each corrosion defect, according to the comparison result of its k2 value and the threshold, it is judged as short corrosion (k2 < 3) or long corrosion (k2 ≥ 3).

[0097] It should be noted that the selection of segment points should be flexibly adjusted according to the actual situation to obtain a better fitting effect. When judging the type of corrosion defect, multiple factors such as corrosion depth, corrosion length, and the operating state of the pipeline should be comprehensively considered to ensure the accuracy of the judgment.

[0098] S4. Based on the pipeline corrosion defect type and the pipeline defect coefficient, obtain the stress concentration coefficient of the pipeline corrosion defect. Please refer to Figure 4 which shows the schematic flowchart of S4 in the video text position location method described in this application. As Figure 4 shown, S4 includes the following steps:

[0099] S41. Based on the pipeline defect coefficient, construct a pipeline defect coefficient matrix;

[0100] S42. Fit based on the pipeline defect coefficient matrix to construct the mapping relationship between the depth and length of pipeline corrosion defects;

[0101] S43. Calculate the stress concentration factor of the pipeline corrosion defect according to the mapping relationship.

[0102] The formula for the stress concentration factor of the pipeline corrosion defect is:

[0103]

[0104] Where SCF 有效 represents the stress concentration factor of the pipeline corrosion defect; [D] represents the calculation matrix of the corrosion defect depth; [N] represents the calculation coefficient matrix; [L] represents the calculation matrix of the corrosion length; f(d, l) represents the binary relationship function between the corrosion defect depth and the corrosion defect length; k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient.

[0105] Specifically, first define the matrices [D], [N], [L]; where [D] contains the matrix of all corrosion defect depths; [N] contains the coefficient matrix required to calculate the stress concentration factor, and these coefficients may be obtained based on experimental data or theoretical derivations; [L] contains the matrix of all corrosion defect lengths.

[0106] It should be noted that here [N] is based on finite element simulations for different pipeline sizes, pipeline tensile strengths, and defect parameters to obtain the remaining strength of the pipeline under each calculation condition, and based on this, parameter fitting is carried out.

[0107] Then, according to the coupling influence relationship between the corrosion defect depth and length, select a suitable form of binary function (such as: polynomial function, exponential function, logarithmic function, etc.). This function should be able to reflect the combined influence of the corrosion depth and length on the stress concentration factor. Use experimental data or existing corrosion pipeline data to fit the parameters of the binary relationship function through regression analysis or other optimization methods.

[0108] Next, introduce the binary relationship function f(d, l) into the basic formula to correct the basic formula. Then use the corrected formula to calculate the stress concentration factor SCF 有效 of each corrosion defect to ensure the accuracy and consistency of the data during the calculation process.

[0109] For example: According to calculate the stress concentration factor of the corrosion pipeline; where SCF 有效 is the stress concentration factor of the corrosion pipeline, [D] is the calculation matrix of the corrosion defect depth, [N] is the calculation coefficient matrix.

[0110] For short corrosion defects:

[0111]

[0112] For long corrosion defects:

[0113]

[0114] [L] is the calculation matrix of the corrosion length,

[0115] To consider the coupling influence relationship of corrosion depth and corrosion length on the remaining strength of the pipeline and improve the calculation accuracy and rationality, a binary relationship function f(d, l) of corrosion defect depth and corrosion defect length is used to correct the fitting formula.

[0116] That is: For short corrosion defects:

[0117]

[0118] For long corrosion defects:

[0119] f(d, l) = -1.587 + 1.974·k1 + 0.5467·k2 - 0.6249·k1 2 - 0.4924·k1·k2.

[0120] It should be noted that when calculating the stress concentration coefficient of the corroded pipeline, the coupling influence relationship of corrosion depth and corrosion length on the remaining strength of the pipeline needs to be considered. Here, the fitting formula is corrected by using a binary relationship function, so as to improve the calculation accuracy and rationality.

[0121] S5. According to the pipeline defect coefficient and the pipeline corrosion defect stress concentration coefficient, obtain the remaining strength of the corroded pipeline to evaluate the safety state of the pipeline.

[0122] In this embodiment, finite element analysis software can be used to model and analyze the corroded pipeline to obtain the actual stress distribution of the pipeline under specific loads. Then, according to the mechanical properties and working environment of the pipeline material, determine the allowable stress of the pipeline. Considering the strength reduction caused by corrosion defects, apply a strength reduction factor to correct the allowable stress. This factor can be determined according to the theoretical stress concentration coefficient and the actual stress situation. Finally, use the corrected allowable stress and the geometric parameters of the pipeline to calculate the remaining strength of the corroded pipeline. This usually involves performing a limit state analysis on the pipeline to determine whether the pipeline will fail under specific loads.

[0123] Furthermore, compare the calculated remaining strength with relevant engineering standards or specifications to evaluate the safety of the pipeline. If the remaining strength is lower than the safety standard, appropriate maintenance plans or repair schemes need to be developed to ensure the safe operation of the pipeline.

[0124] The calculation formula for the remaining strength of the corroded pipeline is as follows:

[0125]

[0126] Wherein, P f (l,d) represents the remaining strength of the corroded pipeline; P b (t) represents the ultimate bearing capacity of the intact pipeline; SCF 有效 represents the stress concentration factor of the pipeline corrosion defect.

[0127] Specifically, local corrosion of the pipeline will cause a drastic change in the pipeline cross-section, leading to stress concentration in the pipeline. In engineering, the stress concentration factor is used to represent the degree of sharp increase in stress. The theoretical stress concentration factor The actual stress condition of the structure is expressed as σ 实 = SCF·σ n . Therefore, the remaining strength of the corroded pipeline can be calculated through calculation.

[0128] The following is an illustration of the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory of the present application in the form of specific embodiments.

[0129] First, 23 groups of burst test data in the public literature are selected, and the basic parameters of the corroded pipeline, corrosion defect parameters, and burst test results are obtained as shown in Table 1.

[0130] Table 1 Basic parameters of the pipeline with corrosion defects and corrosion defect parameters

[0131]

[0132]

[0133] Combined with the data in Table 1, the ultimate bearing capacity of the intact pipeline is calculated through the formula ; according to the defect sensitivity coefficient of the corroded pipeline is calculated. Then, according to the calculation formulas of k1 and k2, the corrosion depth coefficient and corrosion length coefficient of the pipeline are calculated respectively, and the type of corrosion defect is determined. According to the stress concentration factor of the corroded pipeline is calculated; wherein, SCF is the stress concentration factor of the corroded pipeline, [D] is the calculation matrix of the corrosion defect depth, [N] is the calculation coefficient matrix;

[0134] For short corrosion defects:

[0135]

[0136] For long corrosion defects:

[0137]

[0138] [L] is the calculation matrix of the corrosion length:

[0139] f(d, l) is a binary relation function regarding the corrosion defect depth and the corrosion defect length.

[0140] Therefore, for short corrosion defects:

[0141]

[0142] For long corrosion defects:

[0143]

[0144] Combining the various parameters obtained above, according to the remaining strength of the corroded pipeline is calculated. The calculation results are shown in Table 2, and the comparison with the burst test results and various specifications is shown in Table 3.

[0145] Table 2 Basic parameters of the pipeline with corrosion defects and corrosion defect parameters

[0146] Serial number Ultimate bearing capacity of the complete pipeline Defect sensitivity coefficient Length coefficient Depth coefficient Stress concentration coefficient Remaining strength 1 25.87377655 0.984496124 1.20 0.25 1.057646448 24.48 2 25.89434721 0.983860555 1.154 0.31 1.082115832 23.96 3 25.55573398 0.980694981 0.97 0.26 1.043354298 24.51 4 27.00044358 0.995024876 1.73 0.25 1.201457286 22.49 5 27.00044358 0.99009901 0.87 0.50 1.166143767 23.19 6 27.00044358 0.995024876 1.73 0.50 1.421957696 19.02 7 27.00044358 0.995024876 1.73 0.75 1.794018345 15.08 8 24.5163838 0.99510284 1.54 0.85 1.937270422 12.69 9 28.32214361 0.99009901 0.87 0.50 1.166143767 24.32 10 26.0394823 0.975609756 0.66 0.47 1.115041173 23.41 11 24.78523487 0.975369458 0.65 0.67 1.258744415 19.79 12 36.96576634 0.991735537 2.11 0.3 1.41879662 26.12 13 60.29740587 0.991735537 1.67 0.15 1.117053328 54.03 14 60.29740587 0.991735537 1.67 0.3 1.209890199 49.91 15 26.0394823 0.975609756 0.66 0.47 1.115041173 23.41 16 15.36710985 0.998303359 4.54 0.78 3.14067445 4.90 17 15.36710985 0.998269896 4.45 0.17 0.974228322 15.77 18 15.36710985 0.99830652 4.55 0.40 1.273269514 12.07 19 15.36710985 0.998297872 4.52 0.11 0.956474393 16.07 20 34.90002068 0.998003992 5.87 0.47 2.345726674 14.90 21 34.90002068 0.998003992 5.87 0.57 2.851235406 12.26 22 33.95931719 0.996102884 4.54 0.72 2.512877006 13.55 23 10.3373113 0.989182172 1.02 0.49 1.183379744 8.75

[0147] Table 3 Comparison of the calculation results with the burst test and the empirical formulas of various specifications

[0148]

[0149]

[0150] Therefore, as can be seen from the above table, the calculation result of the method of the present invention is better than the practice of the current specification recommended empirical formula, closer to the burst test data of the pipeline with corrosion defects, and can provide more accurate decision-making support for the integrity management of submarine pipelines in engineering.

[0151] The method provided by this application is to establish a finite element static analysis model of a pipeline with corrosion defects based on limited burst test data of corroded pipelines; verify the accuracy of the established finite element model by comparing with the burst test of corroded pipelines; compare the burst pressure of the burst test and the internal pressure load of the finite element model reaching the tensile strength of the pipeline. Conduct a sensitivity analysis of the remaining strength of the pipeline with corrosion defects considering the corrosion depth, corrosion length, pipe diameter, wall thickness, and tensile strength; conduct multi-parameter fitting based on the stress concentration theory. The fitting result here is significantly more accurate than the practice recommended by the specification, and the calculation efficiency is significantly improved compared with the finite element simulation method.

[0152] The method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory provided in this application is based on the ultimate bearing capacity of a complete pipeline, calculates the stress concentration coefficient at the corroded defect, and then obtains the remaining strength of the corroded pipeline. Such an evaluation result is more consistent with the pipeline burst test result compared with the traditional code-recommended practice, can better fit and evaluate the variation law of the remaining strength of the corroded pipeline with the pipeline diameter, wall thickness, tensile strength, corroded defect length, and corroded defect depth, and solves the problem that the evaluation result of the existing code-recommended practice is too conservative. At the same time, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0153] The protection scope of the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in the embodiments of this application is not limited to the execution order of the steps listed in this embodiment. Any solution achieved by adding or subtracting steps of the prior art and replacing steps according to the principle of this application is included in the protection scope of this application.

[0154] This embodiment further provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory as Figure 1 described.

[0155] At any possible combination level of technical details, this application can be a system, a method, and / or a computer program product. The computer program product can include a computer-readable storage medium, on which computer-readable program instructions for enabling a processor to implement various aspects of this application are loaded.

[0156] The computer-readable storage medium can be a tangible device that can hold and store instructions used by an instruction execution device. The computer-readable storage medium can be, for example, (but not limited to) an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above.

[0157] The embodiments of this application further provide a system for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory. The system for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory can implement the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in this application. However, the implementation device of the method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in this application includes, but is not limited to, the structure of the system for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory listed in this embodiment. Any structural deformation and replacement of the prior art according to the principle of this application are included in the protection scope of this application.

[0158] The following will describe in detail the evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory in conjunction with the drawings.

[0159] This embodiment provides an evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, including:

[0160] Please refer to Figure 5 , which shows the schematic diagram of the principle structure of the evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory described in this application in an embodiment. As Figure 5 shown, the evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory includes: an acquisition module 51, a first calculation module 52, a defect calculation and identification module 53, a stress concentration calculation module 54, and a pipeline strength evaluation module 55.

[0161] The acquisition module 51 is used to acquire the basic parameters of the pipeline with corrosion defects and the corrosion defect parameters.

[0162] In this embodiment, the basic parameters of the pipeline with corrosion defects include, but are not limited to: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure, etc. The corrosion defect parameters include, but are not limited to: corrosion defect length, corrosion defect depth, etc.

[0163] The first calculation module 52 is used to obtain the ultimate bearing capacity of the intact pipeline based on the basic parameters of the pipeline with corrosion defects

[0164] In this embodiment, according to the recommended practice of the specification, the ultimate bearing capacity of the intact pipeline is calculated.

[0165] Specifically, according to the previously obtained basic parameters of the pipeline with corrosion defects (such as: the ultimate bearing capacity of the intact pipeline, pipeline wall thickness, pipeline diameter, pipeline tensile strength, etc.), combined with the corresponding ultimate moments of different pipelines (such as: non-pressure pipeline, pressure pipeline), it is calculated through the formula of the ultimate bearing capacity of the pipeline.

[0166] The calculation formula for the ultimate bearing capacity of the intact pipeline is:

[0167]

[0168] Among them, P b (t) represents the ultimate bearing capacity of the intact pipeline; t represents the pipeline wall thickness; D represents the pipeline diameter; f u represents the pipeline tensile strength.

[0169] The defect calculation and identification module 53 is used to obtain the pipeline defect coefficient according to the corrosion defect parameters and identify the types of pipeline corrosion defects.

[0170] In this embodiment, based on the basic parameters and corrosion defect parameters of the pipeline with corrosion defects, a pipeline defect coefficient is obtained; the pipeline defect coefficient includes: a pipeline corrosion depth coefficient and a pipeline corrosion length coefficient.

[0171] Perform data preprocessing on the obtained basic parameters of the pipeline with corrosion defects (such as: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure, etc.), first remove outliers or invalid data to ensure the accuracy and consistency of the data. Then, the pipeline corrosion depth coefficient k1 and the pipeline corrosion length coefficient k2 are obtained respectively through the calculation of the pipeline defect coefficient.

[0172] The formula for the pipeline corrosion depth coefficient is:

[0173]

[0174] The formula for the pipeline corrosion length coefficient is:

[0175]

[0176] Among them, k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient; t represents the pipeline wall thickness; D represents the pipeline diameter; l represents the pipeline defect corrosion length; d represents the pipeline corrosion depth.

[0177] Identify the type of pipeline corrosion defect based on the pipeline corrosion length coefficient.

[0178] In this embodiment, select a segmentation point according to requirements and divide the pipeline into several segments; use a piecewise function to fit each segment; set a judgment threshold according to the fitting result and actual requirements; compare the pipeline defect coefficient with the judgment threshold to identify the type of pipeline corrosion defect. Among them, the judgment criteria include: when the pipeline corrosion length coefficient is greater than or equal to the judgment threshold, it is judged as long corrosion; when the pipeline corrosion length coefficient is less than the judgment threshold, it is judged as short corrosion.

[0179] The stress concentration calculation module 54 is used to obtain the pipeline corrosion defect stress concentration coefficient based on the pipeline corrosion defect type and the pipeline defect coefficient.

[0180] In this embodiment, construct a pipeline defect coefficient matrix based on the pipeline defect coefficient; perform fitting based on the pipeline defect coefficient matrix to construct a mapping relationship between the pipeline corrosion defect depth and length; calculate the pipeline corrosion defect stress concentration coefficient according to the mapping relationship.

[0181] The pipeline strength evaluation module 55 is used to obtain the remaining strength of the corroded pipeline according to the pipeline defect coefficient and the pipeline corrosion defect stress concentration coefficient to evaluate the safety state of the pipeline.

[0182] In this embodiment, finite element analysis software can be used to model and analyze the corroded pipeline to obtain the actual stress distribution of the pipeline under specific loads. Then, according to the mechanical properties of the pipeline material and the working environment, the allowable stress of the pipeline is determined. Considering the strength reduction caused by corrosion defects, a strength reduction factor is applied to correct the allowable stress. This factor can be determined based on the theoretical stress concentration factor and the actual stress situation. Finally, the remaining strength of the corroded pipeline is calculated using the corrected allowable stress and the geometric parameters of the pipeline.

[0183] Build an evaluation model for the remaining strength of submarine corroded pipelines based on the stress concentration theory. The evaluation system for the remaining strength of submarine corroded pipelines based on the stress concentration theory can better fit and evaluate the variation law of the remaining strength of corroded pipelines with the pipeline diameter, wall thickness, tensile strength, corrosion defect length, and corrosion defect depth, and solves the problem that the evaluation results of the existing code recommended practices are too conservative.

[0184] It should be noted that it should be understood that the division of each module of the above system is only a logical function division. In actual implementation, it can be fully or partially integrated into a physical entity, or physically separated. And these modules can all be implemented in the form of software called by a processing element; they can also all be implemented in the form of hardware; or some modules can be implemented in the form of software called by a processing element, and some modules can be implemented in the form of hardware. The processing element mentioned here can be an integrated circuit with signal processing capabilities. In the implementation process, the above steps or each module can be completed through the hardware integrated logic circuit or software-form instructions in the processor element.

[0185] The above modules can be one or more integrated circuits configured to implement the above methods. For example: one or more application specific integrated circuits (ASICs), or, one or more microprocessors (digital signal processors, DSPs), or, one or more field programmable gate arrays (Field Programmable Gate Arrays, FPGAs), etc. Again, when a certain module above is implemented in the form of a processing element scheduling program code, the processing element can be a general-purpose processor, such as a central processing unit (Central Processing Unit, CPU) or other processors that can call program code. Again, these modules can be integrated together and implemented in the form of a system-on-a-chip (SOC).

[0186] Please refer to Figure 6, which shows the schematic diagram of the principle structure of the evaluation electronic terminal for the remaining strength of submarine corroded pipelines based on the stress concentration theory in an embodiment of the present application. As Figure 6 shown, this embodiment provides an evaluation electronic terminal for the remaining strength of submarine corroded pipelines based on the stress concentration theory. The evaluation electronic terminal for the remaining strength of submarine corroded pipelines based on the stress concentration theory includes: a processor 61 and a memory 62; the memory 62 is used to store computer programs; the processor 61 is connected to the memory 62 and is used to execute the computer programs stored in the memory 62, so that the evaluation electronic terminal for the remaining strength of submarine corroded pipelines based on the stress concentration theory executes each step of the evaluation method for the remaining strength of submarine corroded pipelines based on the stress concentration theory as described above.

[0187] Preferably, the memory may include a random access memory (Random Access Memory, abbreviated as RAM), and may also include a non-volatile memory, such as at least one disk memory.

[0188] The above-mentioned processor may be a general-purpose processor, including a central processing unit (Central Processing Unit, abbreviated as CPU), a network processor (Network Processor, abbreviated as NP), etc.; it may also be a digital signal processor (Digital Signal Processing, abbreviated as DSP), an application specific integrated circuit (Application SpecificIntegrated Circuit, abbreviated as ASIC), a field programmable gate array (Field Programmable Gate Array, abbreviated as FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components.

[0189] In summary, the evaluation method for the remaining strength of submarine corroded pipelines provided by the present application has the following beneficial effects:

[0190] The evaluation method for the remaining strength of submarine corroded pipelines provided by the present application calculates the stress concentration coefficient at the corrosion defect based on the ultimate bearing capacity of the intact pipeline, and then obtains the remaining strength of the corroded pipeline. Such an evaluation result is more consistent with the pipeline burst test result than the traditional code-recommended method, and can better fit and evaluate the variation law of the remaining strength of the corroded pipeline with the pipeline diameter, wall thickness, tensile strength, corrosion defect length, and corrosion defect depth, solving the problem that the evaluation result of the existing code-recommended method is too conservative. At the same time, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0191] The above embodiments are only illustrative of the principles and effects of the present application and are not intended to limit the present application. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present application should still be covered by the claims of the present application.

Claims

1. An evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, characterized in that, It includes the following steps: Obtain the basic parameters of the pipeline with corrosion defects and the corrosion defect parameters; Obtain the ultimate bearing capacity of the intact pipeline based on the basic parameters of the pipeline with corrosion defects; Obtain the pipeline defect coefficient according to the corrosion defect parameters and identify the type of pipeline corrosion defect; Obtain the stress concentration coefficient of the pipeline corrosion defect based on the type of pipeline corrosion defect and the pipeline defect coefficient; Obtain the remaining strength of the corroded pipeline according to the pipeline defect coefficient and the stress concentration coefficient of the pipeline corrosion defect to evaluate the safety status of the pipeline.

2. The method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 1, wherein The basic parameters of the pipeline with corrosion defects include: pipeline diameter, pipeline wall thickness, pipeline tensile strength, design pressure; The corrosion defect parameters include: corrosion defect length, corrosion defect depth.

3. The evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 1, characterized in that, Obtaining the ultimate bearing capacity of the intact pipeline based on the basic parameters of the pipeline with corrosion defects includes: Calculate the ultimate bearing capacity of the intact pipeline according to the recommended practice of the specification; The calculation formula for the ultimate bearing capacity of the intact pipeline is: Among them, P b (t) represents the ultimate bearing capacity of the complete pipeline; t represents the pipe wall thickness; D represents the pipe diameter; f u represents the tensile strength of the pipeline.

4. The evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 1, characterized in that, Obtaining the pipeline defect coefficient according to the corrosion defect parameters and identifying the type of pipeline corrosion defect includes: Obtain the pipeline defect coefficient based on the basic parameters and corrosion defect parameters of the pipeline with corrosion defects; the pipeline defect coefficient includes: pipeline corrosion depth coefficient and pipeline corrosion length coefficient; Identify the type of pipeline corrosion defect based on the pipeline corrosion length coefficient.

5. The method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 4, wherein The formula for the pipeline corrosion depth coefficient is: The formula for the pipeline corrosion length coefficient is: Wherein, k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient; t represents the pipeline wall thickness; D represents the pipeline diameter; l represents the corrosion length of the pipeline defect; d represents the corrosion depth of the pipeline.

6. The method for evaluating the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 4, wherein Identifying the type of pipeline corrosion defect based on the pipeline corrosion length coefficient includes: Select the segmentation points according to the requirements and divide the pipeline into several segments; Use piecewise functions to fit each of the segments; Set a determination threshold according to the fitting result and actual requirements; Compare the pipeline defect coefficient with the determination threshold to identify the type of pipeline corrosion defect; including: when the pipeline corrosion length coefficient is greater than or equal to the determination threshold, it is determined as long corrosion; when the pipeline corrosion length coefficient is less than the determination threshold, it is determined as short corrosion.

7. The evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 1, characterized in that Obtaining the stress concentration coefficient of the pipeline corrosion defect based on the type of pipeline corrosion defect and the pipeline defect coefficient includes: Construct a pipeline defect coefficient matrix based on the pipeline defect coefficient; Perform fitting based on the pipeline defect coefficient matrix to construct the mapping relationship between the corrosion depth and length of the pipeline corrosion defect; Calculate the stress concentration coefficient of the pipeline corrosion defect according to the mapping relationship; The formula for the stress concentration coefficient of the pipeline corrosion defect is: Among them, SCF 有效 represents the stress concentration factor of pipeline corrosion defects; [D] represents the calculation matrix of corrosion defect depth; [N] represents the calculation coefficient matrix; [L] represents the calculation matrix of the corrosion length; f(d, l) represents the binary relation function of the corrosion defect depth and the corrosion defect length; k1 represents the pipeline corrosion depth coefficient; k2 represents the pipeline corrosion length coefficient.

8. The evaluation method for the remaining strength of a submarine corroded pipeline based on the stress concentration theory according to claim 1, wherein The calculation formula for the remaining strength of the corroded pipeline is as follows: Among them, P f (l, d) represents the remaining strength of the corroded pipeline; P b (t) represents the ultimate bearing capacity of the intact pipeline; SCF 有效 represents the stress concentration factor of the pipeline corrosion defect.

9. An evaluation system for the remaining strength of a submarine corroded pipeline based on the stress concentration theory, characterized in that It includes: An acquisition module, configured to acquire the basic parameters of the pipeline with corrosion defects and the corrosion defect parameters; A first calculation module, configured to obtain the ultimate bearing capacity of the intact pipeline based on the basic parameters of the pipeline with corrosion defects; A defect calculation and identification module, configured to obtain the pipeline defect coefficient according to the corrosion defect parameters and identify the pipeline corrosion defect type; A stress concentration calculation module, configured to obtain the stress concentration coefficient of the pipeline corrosion defect based on the pipeline defect coefficient and the pipeline corrosion defect type; A pipeline strength evaluation module, configured to obtain the remaining strength of the corroded pipeline according to the pipeline defect coefficient and the stress concentration coefficient of the pipeline corrosion defect, so as to evaluate the safety state of the pipeline.

10. An electronic terminal, characterized in that, It includes: A processor and a memory; The memory is used to store computer programs; The processor is connected to the memory and is configured to execute the computer programs stored in the memory, so that the evaluation device for the remaining strength of the submarine corroded pipeline based on the stress concentration theory executes the evaluation method for the remaining strength of the submarine corroded pipeline based on the stress concentration theory according to any one of claims 1 to 8.

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