Thermal power plant high-temperature steam pipeline suitability evaluation method and system

Abstract

The present disclosure provides a thermal power plant high-temperature steam pipeline suitability evaluation method and system, which relates to the technical field of safety evaluation. The method comprises: identifying the damage mode of the pipeline to be evaluated based on the operation history data and material information of the pipeline to be evaluated, and determining a multi-level evaluation strategy according to the identified damage mode; performing multi-level safety evaluation on the pipeline to be evaluated according to the multi-level evaluation strategy based on the design parameters and material information, and obtaining the macroscopic safety state of the pipeline to be evaluated; extracting the actual operation condition data from the operation history data, and combining the damage evolution model to calculate the cumulative damage degree of the pipeline to be evaluated, so as to quantitatively characterize the macroscopic safety state; predicting the remaining life of the pipeline to be evaluated according to the cumulative damage degree; and outputting the suitability evaluation result including the remaining life and operation suggestion. The present disclosure can accurately predict the remaining life of the pipeline and provide reasonable operation suggestions, thereby providing a reliable basis for the safe operation and maintenance management of the pipeline.

Description

Technical Field

[0001] This disclosure relates to the field of safety assessment technology, and in particular to a method and system for evaluating the suitability of high-temperature steam pipelines in thermal power plants. Background Technology

[0002] High-temperature steam pipelines in thermal power plants are prone to creep, fatigue, and other damage under long-term high-temperature and high-pressure operation. Existing assessment methods mostly rely on single indicators or destructive sampling, lacking a multi-level evaluation system suitable for complex damage modes, and are difficult to quantitatively characterize the interaction between creep and fatigue damage, resulting in insufficient accuracy in remaining life prediction and failing to provide a reliable basis for the safe operation and scientific maintenance of pipelines. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this disclosure provides a method and system for evaluating the suitability of high-temperature steam pipelines in thermal power plants.

[0004] According to a first aspect of the present disclosure, a method for evaluating the suitability of a high-temperature steam pipeline in a thermal power plant is provided, comprising: Obtain the design parameters, material information, and operational history data of the pipeline to be evaluated; Based on the historical operating data and material information, the damage mode of the pipeline to be evaluated is identified, and a multi-level evaluation strategy is determined according to the identified damage mode. Based on the design parameters and material information, a multi-level safety assessment is performed on the pipeline to be assessed according to the multi-level assessment strategy to obtain the macroscopic safety status of the pipeline to be assessed. The actual operating condition data is extracted from the historical operating data, and the cumulative damage degree of the pipeline to be evaluated is calculated by combining the damage evolution model, so as to quantitatively characterize the macroscopic safety status. The remaining life of the pipeline to be evaluated is predicted based on the cumulative damage level; The output includes a usability evaluation result of the remaining lifespan and operational recommendations, which include continued operation, monitored operation, depressurized operation, or pipeline replacement.

[0005] In some embodiments, performing a multi-level security assessment on the pipeline to be assessed according to the multi-level assessment strategy includes: The first-level assessment is performed, and the ultimate load criterion is used to determine whether the pipeline under assessment meets the minimum safety factor requirement. If the minimum safety factor requirement is met, the pipeline to be evaluated is determined to have passed the first-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of the cumulative damage degree is entered. If the minimum safety factor requirement is not met, the pipeline to be evaluated is determined to have failed the first-level evaluation, triggering the execution of the second-level evaluation. The failure evaluation factor is calculated using the elastoplastic fracture mechanics method based on the failure evaluation diagram, and it is determined whether the failure evaluation factor is within the preset safety area. If the failure assessment factor is within the preset safety area, the pipeline to be evaluated is determined to have passed the second-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of the cumulative damage degree is entered. If the failure assessment factor is outside the preset safety zone, the pipeline to be evaluated is determined to have failed the second-level evaluation, triggering the execution of the third-level evaluation. The finite element method is used to perform detailed stress analysis and life prediction, and after the third-level evaluation is completed, the calculation step of the cumulative damage degree is entered.

[0006] In some embodiments, performing a first-level assessment, using the ultimate load criterion to determine whether the pipeline under assessment meets the minimum safety factor requirement, includes: The following formula is used to determine whether the pipeline to be evaluated meets the minimum safety factor requirement: ; in, The working membrane stress is calculated based on the operating pressure, pipe diameter, and wall thickness in the design parameters. The ultimate load is determined based on the material information. This is for the safety factor.

[0007] In some embodiments, performing the second-level evaluation, which involves calculating a failure assessment factor using an elastoplastic fracture mechanics method based on a failure assessment map, and determining whether the failure assessment factor is within a preset safe range, includes: The fracture ratio in the failure assessment factors is calculated based on the following formula. and load ratio : ; ; in, The applied stress intensity factor. For the fracture toughness of the material, The reference stress is determined based on the working thin film stress and defect size. The yield strength of the material; The fracture ratio The load ratio is used as the vertical axis. As the horizontal axis, the evaluation point is determined in the failure evaluation diagram; Whether the failure assessment factor is located within the preset safety area is determined based on whether the assessment point is located within the preset safety area defined by the preset safety curve of the failure assessment diagram.

[0008] In some embodiments, the step of extracting actual operating condition data from the historical operating data and calculating the cumulative damage degree of the pipeline to be evaluated in conjunction with a damage evolution model includes: Based on the aforementioned historical operating data, actual operating temperature and time history data are extracted; wherein, the time history data includes segmented operating times at different temperatures; For each temperature time interval, the breakage time at that temperature is calculated based on the following formula. : ; in, For the first The absolute temperature over a specific temperature period. The Larson-Miller parameters are determined based on the material information. These are material constants determined based on the material information; The creep cumulative damage degree of the pipeline to be evaluated is calculated based on the following formula, combined with the segmented operating time: ; in, This represents the cumulative creep damage degree. For the first The segmented running time for each temperature period For the first The breakage time corresponding to each temperature time period.

[0009] In some embodiments, the method further includes: The number of start-stop cycles, temperature cycle range, and load holding time of the pipeline to be evaluated are obtained. The number of start-stop cycles, temperature cycle amplitude, and holding time are input into the nonlinear damage interaction model. By calculating the nonlinear coupling effect between creep damage and fatigue damage, and combining it with the creep cumulative damage degree, the comprehensive damage degree is calculated, and the comprehensive damage degree is used as the final characterization value of the cumulative damage degree.

[0010] In some embodiments, the method further includes: Obtain the critical damage degree and current damage rate of the pipeline to be evaluated; The next inspection cycle is determined based on the following formula: ; in, For the next inspection cycle, The critical damage level, The overall damage level, Given the current damage rate, For design life, This represents the running time. The output includes the remaining lifespan and the usability evaluation results of the operational recommendations, including: the output includes the remaining lifespan, the next inspection cycle, and the usability evaluation results of the operational recommendations.

[0011] In some embodiments, the method further includes: Nonlinear ultrasonic technology was used to detect micro- and nanoscale damage in the pipeline material to be evaluated, and the ultrasonic nonlinear coefficient was obtained. The change of the ultrasonic nonlinear coefficient with service time is measured to establish a quantitative relationship between the ultrasonic nonlinear coefficient and the creep cumulative damage degree. The creep cumulative damage degree is corrected using the quantitative relationship, and the corrected creep cumulative damage degree is used to replace the original creep cumulative damage degree to recalculate the comprehensive damage degree and the remaining life.

[0012] In some embodiments, the method further includes: If the pipeline to be evaluated includes elbow components, the stress amplification factor is calculated using the elliptical section equivalent method. If the pipeline to be evaluated includes a tee component, the stress intensification factor method is used to calculate the stress intensification factor. The comprehensive local stress of the special component is calculated by combining the secondary stress caused by internal pressure, temperature, and the action of supports and hangers, as well as the stress amplification factor or the stress strengthening factor; the special component includes elbow components and tee components; When performing the first-level evaluation, the working film stress is replaced with the comprehensive local stress to update the results of the first-level evaluation; when performing the second-level evaluation, the reference stress is replaced with the comprehensive local stress to update the results of the second-level evaluation.

[0013] According to a second aspect of this disclosure, a system for evaluating the suitability of high-temperature steam pipelines in thermal power plants is provided, comprising: The information acquisition module is used to obtain the design parameters, material information, and historical operating data of the pipeline to be evaluated. The damage identification module is used to identify the damage mode of the pipeline to be evaluated based on the operation history data and material information, and to determine a multi-level evaluation strategy based on the identified damage mode. The multi-level evaluation module is used to perform a multi-level safety evaluation on the pipeline to be evaluated based on the design parameters and material information, and according to the multi-level evaluation strategy, to obtain the macroscopic safety status of the pipeline to be evaluated. The damage calculation module is used to extract actual operating condition data from the historical operating data and calculate the cumulative damage degree of the pipeline to be evaluated in combination with the damage evolution model, so as to quantitatively characterize the macroscopic safety status. A life prediction module is used to predict the remaining life of the pipeline to be evaluated based on the cumulative damage level. The conclusion output module is used to output a usability evaluation result including the remaining life and operating recommendations, which include continued operation, monitored operation, depressurized operation, or pipeline replacement.

[0014] The solution provided in this disclosure can obtain the design parameters, material information, and operational history data of the pipeline to be evaluated; identify the damage modes of the pipeline based on the operational history data and material information, and determine a multi-level evaluation strategy according to the identified damage modes; perform a multi-level safety assessment of the pipeline based on the design parameters and material information and according to the multi-level evaluation strategy to obtain the macroscopic safety status of the pipeline; extract actual operating condition data from the operational history data, and calculate the cumulative damage degree of the pipeline to be evaluated in combination with the damage evolution model to quantitatively characterize the macroscopic safety status; predict the remaining life of the pipeline to be evaluated based on the cumulative damage degree; and output a usability evaluation result including the remaining life and operational recommendations. This disclosure can accurately predict the remaining life of the pipeline and provide reasonable operational recommendations, providing a reliable basis for the safe operation and maintenance management of pipelines. Attached Figure Description

[0015] Figure 1 This illustration shows a flowchart of an evaluation method for the suitability of a high-temperature steam pipeline in a thermal power plant, as described in an embodiment of this disclosure.

[0016] Figure 2 A detailed flowchart illustrating the multi-level security assessment process in an embodiment of this disclosure is shown.

[0017] Figure 3 This diagram illustrates the structure of a high-temperature steam pipeline in a thermal power plant that is suitable for use in an evaluation system, according to an embodiment of this disclosure. Detailed Implementation

[0018] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0019] Before detailing the specific embodiments of this disclosure, the core concept of fitness-for-service (FFS) evaluation for high-temperature steam pipelines in thermal power plants will first be explained. FFS is an engineering evaluation method based on fracture mechanics and damage mechanics, aiming to scientifically determine whether in-service equipment with defects or that has undergone long-term service degradation can continue to operate safely. For the main steam pipelines and reheat steam pipelines of ultra-supercritical units, they are subjected to high temperatures above 600°C and high pressures above 25 MPa for extended periods. Materials (such as T92 / P92 martensitic heat-resistant steel) inevitably undergo microstructural evolution and mechanical property degradation. Traditional evaluation methods often rely on estimations of single design parameters or destructive pipe cutting and sampling. The former is too conservative or overly aggressive, while the latter can cause irreversible structural damage to large-diameter main pipelines. Therefore, a comprehensive evaluation method that can integrate multi-dimensional operational data, accurately identify complex damage modes, and achieve non-destructive quantitative characterization is urgently needed.

[0020] Next, with reference to specific embodiments, the evaluation method for the suitability of high-temperature steam pipelines in thermal power plants provided in this disclosure will be described in detail.

[0021] Figure 1 This illustration shows a flowchart of an evaluation method for the use of high-temperature steam pipelines in a thermal power plant, as described in an embodiment of this disclosure. This method can be executed by any industrial-grade server or evaluation workstation with powerful computing and data processing capabilities. Figure 1 As shown, the method includes the following steps S101 to S106.

[0022] S101, obtain the design parameters, material information, and operating history data of the pipeline to be evaluated.

[0023] In some embodiments, the pipelines to be evaluated mainly refer to the main steam pipelines, high-temperature reheat steam pipelines, and their associated bypass systems in thermal power plants that withstand extreme thermal parameters. Design parameters are the baseline data for the initial construction of the pipelines, covering design temperature, design pressure, pipeline outer diameter, nominal wall thickness, material grade, and the spatial orientation and support arrangement of the piping system. These parameters are typically extracted from the power plant's as-built drawings, the design institute's design specifications, and the pipeline stress analysis report. Material information delves into the microscopic and macroscopic mechanical properties of the material, including chemical composition ratios, heat-treated supply conditions, yield strength and tensile strength at room temperature and high temperature, fracture toughness, creep rupture strength curves, as well as the specific location of welds, welding procedure qualification reports, and post-weld heat treatment parameters. Operational history data is the pipeline's actual service record since commissioning, including temperature and pressure time-series curves, unit start-up and shutdown records, load variation rates, and non-destructive testing records, hardness test data, and metallographic reconstruction results from various metal supervision inspections, all collected at high frequencies through the plant-level monitoring information system (SIS). After acquiring this data, the system needs to perform rigorous data cleaning and timestamp alignment to remove abnormal spikes caused by sensor malfunctions and ensure high consistency of multidimensional data on the timeline, laying a solid data foundation for subsequent accurate assessment.

[0024] S102, based on historical operating data and material information, identify the damage modes of the pipeline to be evaluated, and determine a multi-level evaluation strategy based on the identified damage modes.

[0025] In the harsh operating environment of high temperature and high pressure, damage to pipeline materials is not dominated by a single mechanism, but rather the result of a complex interplay of multiple physicochemical processes. Common damage modes include creep damage caused by long-term high-temperature stress, thermal fatigue damage caused by frequent peak-shaving start-ups and shutdowns of the unit, creep-fatigue interactive damage resulting from the superposition of both, wall thinning caused by fluid erosion or oxidation, and crack-like defects generated during manufacturing or service. By analyzing the frequency of temperature fluctuations, the duration of peak temperatures, and the heat resistance and microstructure stability of materials in historical operating data, the system can accurately identify the dominant damage mode for the current pipeline segment. For example, for pipeline segments operating under base load, the primary damage mode is creep damage; while for pipeline segments participating in deep peak shaving, thermal fatigue and creep-fatigue interactive damage are dominant. After identifying the damage mode, the system matches a corresponding multi-level assessment strategy. This strategy of allocating assessment resources on demand avoids the waste of computing power caused by overly complex analysis of simple operating conditions, while ensuring the depth and reliability of the assessment model under complex damage modes, achieving a perfect balance between assessment efficiency and accuracy.

[0026] S103, based on design parameters and material information, performs multi-level safety assessments on the pipeline to be assessed according to a multi-level assessment strategy to obtain the macroscopic safety status of the pipeline to be assessed.

[0027] Multi-level safety assessment is a step-by-step structural integrity evaluation mechanism that progresses from simple to complex. This mechanism divides the assessment process into multiple logical levels, each employing mechanical models and safety criteria of varying complexity. In practice, the system first uses a low-cost, highly conservative primary analytical model for rapid screening to exclude pipeline sections that are absolutely safe at the macroscopic stress level. If the primary model cannot determine pipeline safety, or if the pipeline has known defects exceeding standards, the system automatically triggers a higher-level, more refined elastoplastic fracture mechanics model or a three-dimensional finite element numerical simulation model. This multi-level, progressive assessment method efficiently filters out low-risk areas and concentrates core computational resources on critical pipeline sections or structural discontinuities with potential failure risks. The final macroscopic safety status depends not only on theoretically calculated stress and strain levels but also comprehensively considers the overall structural continuity and defect stability of the pipeline, thus accurately defining at the macroscopic level whether the pipeline possesses the basic conditions for continued safe service and establishing clear boundaries for subsequent quantitative calculations of microscopic damage.

[0028] S104 extracts actual operating condition data from historical operating data and calculates the cumulative damage degree of the pipeline to be evaluated in combination with the damage evolution model, so as to quantitatively characterize the macroscopic safety status.

[0029] Actual operating condition data refers to the dynamic thermodynamic parameters of pipelines under real service environments, especially the temperature-time history and stress fluctuation amplitude during temperature and pressure changes. The damage evolution model, based on the theory of continuum damage mechanics, is a mathematical constitutive equation used to describe the nucleation, growth, and aggregation of defects such as micropores and microcracks within the material under the influence of time, temperature, and stress. By inputting the cleaned actual operating condition data into the matched damage evolution model, the system can accurately calculate the cumulative damage degree of the pipeline at the current moment. This cumulative damage degree is a dimensionless state variable between 0 and 1, where 0 represents a perfectly undamaged state and 1 represents macroscopic fracture failure. This value can intuitively and quantitatively characterize the degree of deterioration of the pipeline's macroscopic safety status. Compared to traditional qualitative rating methods (such as metallographic spheroidization rating based on expert experience), the quantitative characterization method not only reveals the pipeline's current true health level and eliminates the subjectivity of human judgment, but also provides an indispensable core state variable for the accurate extrapolation of its remaining life.

[0030] S105, predict the remaining life of the pipeline to be evaluated based on the cumulative damage level.

[0031] Remaining life refers to the theoretical time remaining for a pipeline to continue operating safely under its current damage state and anticipated future operating conditions until the cumulative damage reaches the critical failure threshold. After obtaining the current high-precision cumulative damage level, the system combines this with the power plant's future unit operation plans (such as expected annual start-up and shutdown frequency, load factor, and steam parameters) to perform forward time extrapolation using a damage evolution model. Specifically, the system first calculates the instantaneous damage rate under the current operating conditions. Then, assuming that future operating conditions change according to a predetermined plan or remain at a statistical average state, it uses nonlinear numerical integration or Monte Carlo probabilistic simulation methods to solve for the time required for the cumulative damage to evolve to the critical value. This life prediction method based on the actual cumulative damage state fully respects the irreversibility and nonlinear characteristics of the pipeline's historical service experience, making the prediction results more closely match the actual aging trajectory of the material. Simultaneously, by introducing the dispersion parameter of material properties, the system can also provide a confidence interval for the remaining life, offering a more comprehensive probabilistic perspective for the power plant's risk decision-making.

[0032] S106 outputs a usability evaluation result including remaining life and operational recommendations, which include continued operation, monitored operation, depressurized operation, or pipeline replacement.

[0033] The evaluation results serve as the final output to guide power plants in equipment lifecycle management and maintenance decisions. Based on the predicted remaining lifespan, the current level of cumulative damage, and the safety margin in multi-level assessments, the system automatically generates targeted, tiered operational recommendations. When the remaining lifespan is significantly longer than the next major overhaul cycle and the cumulative damage is at an extremely low level, the system recommends continued operation and maintaining the routine inspection plan. When the damage is close to the warning value but still has a certain safety margin, or when minor defects exist locally, the system recommends monitored operation and automatically shortens the non-destructive testing cycle and increases the density of measurement points. When excessive local stress in the pipeline leads to an abnormally rapid damage rate, or when material aging reduces pressure resistance, the system recommends reduced pressure operation or lowering the main steam temperature to slow down the damage evolution process through thermodynamic means. When the cumulative damage is approaching the critical threshold, the remaining lifespan cannot meet the minimum operating requirements, or a fatal defect endangering the overall structural integrity is discovered, the system forcibly recommends immediate shutdown and pipeline replacement. This intelligent tiered recommendation mechanism achieves seamless integration from underlying technical analysis to top-level management decisions.

[0034] This disclosure embodiment constructs a complete closed loop from multi-dimensional data acquisition, intelligent damage mode identification, multi-level step assessment to quantitative damage calculation and life prediction, thereby achieving a comprehensive and accurate evaluation of the serviceability of high-temperature steam pipelines and effectively improving the safety management level and economic operation efficiency of power plant pressure equipment.

[0035] Next, we will describe in detail the multi-level security assessment and special component handling methods in the embodiments of this disclosure, with reference to specific examples.

[0036] Figure 2 This diagram illustrates a multi-level security assessment process in an embodiment of this disclosure. Figure 2 As shown, a multi-level safety assessment is performed on the pipeline to be assessed in accordance with the multi-level assessment strategy, including the following steps S201 to S205.

[0037] S201, perform the first-level assessment, and use the ultimate load criterion to determine whether the pipeline under assessment meets the minimum safety factor requirements.

[0038] The first level of assessment is a rapid screening stage. Its core idea is to quickly eliminate pipe sections that are absolutely safe in terms of macroscopic static strength by using simplified ultimate load analytical criteria. The minimum safety factor is a safety margin preset based on relevant industry standards (such as ASME BPVC or GB / T 16507) and the performance dispersion of materials at high temperatures.

[0039] For example, the specific calculation for the first-level assessment is as follows: The assessment determines whether the pipeline meets the minimum safety factor requirement based on the following formula: ; in, The working membrane stress is calculated based on the operating pressure, pipe diameter, and wall thickness in the design parameters. The ultimate load is determined based on material information, and can also be understood as the high-temperature ultimate stress (such as the material's yield strength or endurance strength at the design temperature). This is for the safety factor.

[0040] Working thin film stress This reflects the average circumferential stress level of the pipeline under internal pressure and can be accurately calculated using the mean diameter formula. Ultimate load. This represents the maximum load that the pipe material can withstand before it yields completely. Its value is closely related to the material's yield strength and tensile strength at the design temperature. Safety factor. The value is typically between 1.5 and 2.5 to cover material property variations, wall thickness measurement errors, and unforeseen additional loads. This formula allows for rapid verification of the macroscopic static strength safety of pipelines at extremely low computational cost.

[0041] S202 If the minimum safety factor requirement is met, the pipeline to be evaluated is determined to have passed the first-level evaluation, the multi-level safety evaluation is terminated, and the calculation of cumulative damage degree is initiated.

[0042] If the pipeline meets the minimum safety factor requirements mentioned above, it indicates that its macroscopic structural integrity is good and there is no risk of overall plastic collapse. At this point, the system determines that it has passed the first-level assessment, and there is no need to perform subsequent complex fracture mechanics analysis or finite element simulation. It directly terminates the multi-level safety assessment and proceeds to the subsequent cumulative damage calculation step. This strategy of allocating assessment resources on demand avoids the waste of computing power caused by overly complex analysis of simple working conditions, and significantly improves the overall computational efficiency of the plant-wide pipeline assessment.

[0043] S203 If the minimum safety factor requirement is not met, the pipeline to be evaluated is determined to have failed the first-level evaluation, triggering the execution of the second-level evaluation. The failure evaluation factor is calculated using the elastoplastic fracture mechanics method based on the failure evaluation diagram, and it is determined whether the failure evaluation factor is within the preset safety area.

[0044] When a pipeline fails to meet the minimum safety factor requirements, it indicates a potential risk to its stress state or the presence of known defects exceeding the limits. The system automatically triggers a higher-level second-level assessment. The second-level assessment incorporates elastoplastic fracture mechanics theory, specifically targeting pipelines that may have crack-like defects or stress concentration areas. The Failure Assessment Diagram (FAD) is a classic tool for assessing the safety of structures with defects. It visually displays the risk of crack initiation and plastic instability by constructing a two-dimensional coordinate system of fracture ratio and load ratio.

[0045] For example, the specific calculation for the second-level assessment is as follows: the fracture ratio in the failure assessment factor is calculated based on the following formula. and load ratio : ; ;in, The external stress intensity factor. For the fracture toughness of the material, The reference stress is determined based on the working thin film stress and defect size. This represents the yield strength of the material.

[0046] Fracture ratio It characterizes the ratio of the stress field intensity at the crack tip to the material's resistance to crack propagation; load ratio This reflects the risk of overall structural plastic collapse. Preset safety curves are usually constructed based on the material's actual stress-strain curves, such as Option 2 or Option 3 curves in the R6 method.

[0047] S204 If the failure assessment factor is within the preset safety range, the pipeline to be assessed is determined to have passed the second-level assessment, the multi-level safety assessment is terminated, and the calculation of cumulative damage is initiated.

[0048] After calculating the fracture ratio and load ratio Then, the fracture ratio As the vertical axis, load ratio Using the x-axis as the horizontal axis, an assessment point is determined on the failure assessment diagram. Based on whether the assessment point lies within the preset safety region defined by the preset safety curve on the failure assessment diagram, it is determined whether the failure assessment factor also lies within the preset safety region. If the assessment point lies below the curve and within the safety region enclosed by the coordinate axes, it indicates that the defect is in a stable state under the current operating conditions and will not experience instability propagation, meaning the pipeline can safely serve. At this point, the system determines that the pipeline under evaluation has passed the second-level assessment, terminates the multi-level safety assessment, and proceeds to the cumulative damage calculation step, thereby saving computational resources while ensuring assessment accuracy.

[0049] S205 If the failure assessment factor is outside the preset safe zone, the pipeline to be assessed is determined to have failed the second-level assessment, triggering the execution of the third-level assessment. The finite element method is used to perform detailed stress analysis and life prediction, and after the third-level assessment is completed, the cumulative damage calculation step is entered.

[0050] If the assessment point is outside the preset safety zone, it indicates that the pipeline failed the first two levels of assessment, and its stress state is extremely complex or has severe structural discontinuities. At this point, the system triggers the highest level, the third-level assessment. The third-level assessment uses the finite element method to establish a three-dimensional solid model of the pipeline, accurately simulating the stress and strain distribution under internal pressure, temperature gradients, and external constraints. In the finite element analysis, special attention must be paid to the fineness of the mesh, especially at crack tips or abrupt structural changes; singular elements or high-density meshes should be used to capture stress singularities. Simultaneously, an accurate high-temperature creep constitutive model of the material (such as the Norton-Bailey model) must be introduced to reflect the nonlinear mechanical behavior and stress relaxation effects of the material under long-term high temperatures. Although the third-level assessment is computationally expensive, it provides the most detailed local stress and strain information, providing high-precision input parameters for subsequent damage calculations. After completing the third-level assessment, the system automatically proceeds to the cumulative damage calculation step.

[0051] In some embodiments, for special structures commonly found in pipelines, this disclosure also designs the following calculation method: if the pipeline to be evaluated includes elbow components, the stress amplification factor is calculated using the elliptical section equivalent method; if the pipeline to be evaluated includes tee components, the stress intensification factor method is used to calculate the stress intensification factor; combining the secondary stress caused by internal pressure, temperature, and support / hanger action, as well as the stress amplification factor or stress intensification factor, the comprehensive local stress of the special components is calculated; the special components include elbow components and tee components; when performing the first-level evaluation, the comprehensive local stress is used to replace the working membrane stress to update the results of the first-level evaluation; when performing the second-level evaluation, the comprehensive local stress is used to replace the reference stress to update the results of the second-level evaluation.

[0052] Specifically, the stress amplification factor is calculated using the elliptical section equivalent method, based on the following formula:

[0053] in, This is the stress amplification factor for the elbow component. The characteristic parameters of the bend are calculated using the following formula: , For pipe wall thickness, The bending radius of the elbow. The average radius of the pipe cross-section.

[0054] The stress hardening factor is calculated using the stress hardening factor method, based on the following formula:

[0055] in, The stress hardening coefficient of the tee component. These are the characteristic parameters of the tee, determined based on the ratio of the wall thickness and outer diameter of the branch pipe to the main pipe.

[0056] The comprehensive local stress of special components is calculated by combining the secondary stress caused by internal pressure, temperature, and the action of supports and hangers, as well as the stress amplification factor or stress intensification factor, based on the following formula:

[0057] in, To mitigate local stress, Stress amplification factor or stress hardening coefficient , The working membrane stress is calculated based on internal pressure. This represents the amplitude of secondary stress caused by thermal expansion and support constraints.

[0058] Elbows and tees are the most significant stress concentration points in high-temperature steam pipeline systems. The bending process of elbows leads to elliptical cross-sections and thinning of the outer wall thickness; the elliptical cross-section equivalent method can accurately calculate their stress amplification factor. Tees, on the other hand, experience complex stress concentration due to the discontinuity of the intersection line between the branch pipe and the main pipe, requiring the introduction of a stress intensification factor for correction. Furthermore, the obstruction of thermal expansion in the pipeline system and the constraints of supports and hangers generate significant secondary stresses. By comprehensively considering these factors and calculating the comprehensive local stress, replacing the basic stress parameters in the first and second level assessments with this comprehensive local stress, the assessment blind spots caused by underestimation of local stresses can be effectively eliminated, significantly improving the reliability of safety evaluations for special components.

[0059] Next, the cumulative damage calculation and correction method in the embodiments of this disclosure will be described in detail with reference to specific examples.

[0060] In some embodiments, actual operating condition data is extracted from historical operating data, and the cumulative damage degree of the pipeline to be evaluated is calculated in conjunction with a damage evolution model, including: Actual operating temperature and time history data are extracted based on historical operating data; the time history data includes segmented operating times at different temperatures; for each temperature segment, the breakage time at that temperature is calculated using the following formula: ; in, For the first The absolute temperature over a specific temperature period. The Larson-Miller parameters are determined based on material information. The material constants are determined based on the material information; the creep cumulative damage of the pipeline to be evaluated is calculated based on the following formula, combined with the segmented operating time: ; in, This represents the cumulative creep damage degree. For the first The segmented running time for each temperature period For the first The breakage time corresponding to each temperature time period.

[0061] Creep damage in high-temperature steam pipelines exhibits a strong temperature and stress dependence. To accurately assess creep damage under variable temperature and load conditions, this embodiment introduces the Larson-Miller parameter (LMP) method. Specifically, the aforementioned fracture time... The calculation formula is rigorously derived from the fundamental definition formula of the Larson-Miller parameter. The fundamental definition formula of the Larson-Miller parameter is expressed as: ,in Absolute temperature For the fracture time, Let be a material constant. By performing an algebraic transformation on this fundamental formula, dividing both sides of the equation by the absolute temperature... get Then, by rearranging the terms, we obtain Finally, by taking the exponent of 10 on both sides of the equation, the explicit expression for the fracture time can be derived. The absolute temperature over a specific temperature period. Substituting into this expression, we obtain the above-mentioned formula for calculating the first... Theoretical fracture time under a temperature time interval The final formula.

[0062] In actual calculations, the parameters can be determined first. Then, the fracture time is calculated. Specifically, firstly, the Larson-Miller parameters of the current pipe segment under the current stress state are determined based on the material information. .because Essentially, it is a comprehensive characterization parameter of the creep fracture properties of a material under a specific stress level. High-temperature creep strength data (i.e., the relationship curve between stress and Larson-Miller parameters or the Larson-Miller fitting equation) can be extracted from the material information. Combined with the working membrane stress or comprehensive local stress obtained from the preceding multi-level safety assessment, the specific stress state under the current stress condition can be calculated through table lookup interpolation or substitution into the fitting equation. Value. Simultaneously, material constants are determined based on material information. For martensitic heat-resistant steels such as T92 / P92 commonly used in thermal power plants, The value is typically between 20 and 25. Once the core parameters are defined... and material constants The system then discretizes the historical operating data into temperature intervals and extracts the absolute temperature for each temperature interval. Substitute it into the derived formula In the process, the theoretical fracture time at each temperature range was calculated. Finally, using the linear cumulative damage rule (Robinson's rule), the actual segmented running time for each temperature time interval is calculated. With the corresponding theoretical fracture time By dividing and summing over the entire process, the accurate creep cumulative damage can be obtained. This method, through rigorous mathematical derivation and parameter calibration, fully considers the complex temperature variations experienced by pipelines in actual operation, effectively avoiding the huge errors caused by using a single design temperature for evaluation, and significantly improving the scientific nature and accuracy of quantitative damage characterization.

[0063] In some embodiments, to further consider the influence of alternating loads, the method provided in this disclosure further includes: obtaining the number of start-stop cycles, temperature cycle amplitude, and holding time of the pipeline to be evaluated; inputting the number of start-stop cycles, temperature cycle amplitude, and holding time into a nonlinear damage interaction model; calculating the nonlinear coupling effect between creep damage and fatigue damage; combining the creep cumulative damage degree; and using the comprehensive damage degree as the final characterization value of the cumulative damage degree.

[0064] Specifically, the number of start-stop cycles, temperature cycle amplitude, and holding time are input into the nonlinear damage interaction model to calculate the comprehensive damage degree, including: First, fatigue damage is calculated based on the Coffin-Manson formula and the linear Miner's rule. :

[0065] in, The number of temperature cycle segments, For the first Segment temperature cycle amplitude The actual number of start-stop cycles. This represents the material fatigue failure life under the corresponding strain amplitude.

[0066] Then, the creep cumulative damage degree With fatigue damage degree Input the following nonlinear damage interaction model and calculate the current comprehensive damage degree. :

[0067] in, The creep-fatigue nonlinear interaction coefficient is determined based on material information and holding time. When the holding time is greater than a preset threshold, To characterize the mutually reinforcing effect of creep and fatigue.

[0068] When thermal power generating units participate in grid peak shaving, they experience frequent start-ups, shutdowns, and load fluctuations, which can induce thermal fatigue damage inside pipelines. More seriously, during the high-temperature load maintenance phase, creep damage and fatigue damage are not simply linearly superimposed, but exhibit a strong nonlinear interaction. A nonlinear damage interaction model, by introducing interaction coefficients or constructing a continuous damage evolution surface, can accurately quantify this coupling effect. Using the comprehensive damage degree as the final characterization value, it truly reflects the degree of pipeline deterioration under complex alternating operating conditions, filling the gap in traditional single creep assessment.

[0069] In some embodiments, in order to improve the microphysical basis of damage assessment, the method provided in this disclosure further includes: using nonlinear ultrasonic technology to detect micro- and nanoscale damage to the pipeline material to be assessed and obtaining the ultrasonic nonlinear coefficient; measuring the change of the ultrasonic nonlinear coefficient with service time and establishing a quantitative relationship between the ultrasonic nonlinear coefficient and the creep cumulative damage degree; using the quantitative relationship to correct the creep cumulative damage degree, and replacing the original creep cumulative damage degree with the corrected creep cumulative damage degree to recalculate the comprehensive damage degree and remaining life.

[0070] For example, establishing a quantitative relationship between the ultrasonic nonlinear coefficient and the cumulative creep damage specifically includes: obtaining the ultrasonic nonlinear coefficient of samples at different aging stages through offline accelerated creep tests. A quantitative relationship model is established using linear or quadratic polynomial fitting, based on the corresponding theoretical creep damage degree. For example: ,in, The ultrasonic nonlinear coefficient is the value of the material in its initial undamaged state. and is the fitting constant.

[0071] Before macroscopic creep fracture occurs, the internal microstructure of a material (such as dislocation multiplication, coarsening of precipitates, and nucleation of micropores) has already undergone significant evolution. Nonlinear ultrasonic technology, by exciting high-frequency longitudinal waves and receiving their second harmonic signals, can extremely sensitively capture these early micro- and nanoscale damages. During on-site inspection, the pipe insulation layer needs to be removed and the surface polished. A high-power radio frequency amplifier is used to excite the signal, and the fundamental and second harmonic amplitudes are extracted using a narrowband filter to calculate the ultrasonic nonlinear coefficient. The ultrasonic nonlinear coefficient is highly positively correlated with the material's micro-defect density. By establishing a quantitative mapping relationship between the ultrasonic nonlinear coefficient and the theoretical creep cumulative damage, the theoretical calculation value can be corrected in real time using ultrasonic data obtained from on-site nondestructive testing. This dual verification mechanism combining theoretical calculation and nondestructive testing effectively overcomes the problem of theoretical model parameter drift and significantly improves the confidence level of remaining life prediction.

[0072] In some embodiments, after obtaining the overall damage level, in order to guide the power plant's inspection plan, the method provided in this disclosure further includes: obtaining the critical damage level and current damage rate of the pipeline to be evaluated; and determining the next inspection cycle based on the following formula: ; in, For the next inspection cycle, The critical damage level, To assess the overall damage level, Given the current damage rate, For design life, The output includes the remaining service life and operational recommendations, representing the serviceability evaluation results.

[0073] Critical damage degree This is the threshold at which pipeline failure occurs, typically determined by material testing or industry standards. Current damage rate. This reflects the rate of pipeline deterioration. The first part of the formula calculates the theoretical time required to extrapolate from the current damage state to the critical state; the second part is based on the remaining time of the design life. The minimum of these two values ​​is taken as the next inspection cycle, ensuring timely intervention when damage accelerates while also ensuring that the inspection plan does not exceed the pipeline's design service life. Including the next inspection cycle in the evaluation results output gives the serviceability evaluation not only diagnostic capabilities but also forward-looking management guidance value.

[0074] Among them, the current damage rate The acquisition methods include: based on the comprehensive damage increment within the most recent assessment period. With the corresponding time increment Calculate the average damage rate, i.e. Alternatively, the actual operating condition data at the current moment can be substituted into the nonlinear damage interaction model to calculate the instantaneous damage evolution derivative under the current operating condition as the current damage rate. .

[0075] To more intuitively demonstrate the implementation process and technical effects of this disclosed technical solution, a detailed explanation will be provided below using a specific application case from a power plant.

[0076] In the serviceability evaluation project of the main steam pipeline of a 600MW ultra-supercritical unit in a power plant, the pipeline is made of P92 steel, with a design temperature of 605℃ and a design pressure of 26.15MPa. After 100,000 hours of continuous operation, a comprehensive evaluation was conducted using the methods provided in this disclosure.

[0077] First, during the basic pipeline information acquisition phase, the pipe diameter was determined to be φ457×78mm, and the actual wall thickness obtained from ultrasonic thickness measurement was 75mm. By reading historical data from the DCS system, it was confirmed that the actual operating temperature range was 598~605℃, the operating pressure range was 24.5~25.8MPa, the cumulative number of start-ups and shutdowns was approximately 1,200, and the average high-temperature load protection time per start-up and shutdown was 4 hours.

[0078] Subsequently, a first-level rapid screening assessment was performed. Based on the design parameters, the working membrane stress of the pipeline was calculated to be 65.5 MPa. A simplified criterion based on the ultimate load was adopted, and a safety factor was set. The value is 2.0. Calculations show that the ultimate load is much greater than the product of the working membrane stress and the safety factor. The first-level assessment result is a successful pass, indicating that the pipeline's macroscopic static strength is safe.

[0079] Next, we proceed to the second level of detailed analysis and damage assessment. In the creep damage assessment, the Larson-Miller parameter method, combined with the variable-temperature operating history, is used to calculate the cumulative creep damage. The value was 0.35. In the creep-fatigue interactive damage assessment, 1200 start-stop cycles and 4-hour load holding data were input into the nonlinear interactive model to calculate the comprehensive damage degree. The value is 0.28. Simultaneously, fracture mechanics assessment was performed based on the Failure Assessment Diagram (FAD), and the fracture ratio was calculated. The load ratio is 0.62. The value is 0.48, and the evaluation point is clearly located within the safe zone of the FAD curve, proving that the pipeline has no risk of crack instability.

[0080] To further verify the damage status, a nonlinear ultrasonic damage characterization technique was introduced. A longitudinal wave probe with a center frequency of 10 MHz was used to scan the pipeline, and the ultrasonic nonlinear coefficient was measured. The value is 0.085. Based on the quantitative relationship model calibrated in the previous accelerated aging test, this nonlinear coefficient was converted into an equivalent creep damage degree, which was 0.42. Since ultrasonic testing reflects the actual microstructural deterioration, the corrected value of 0.42 was adopted as the current final cumulative damage degree.

[0081] Finally, remaining service life prediction and serviceability determination are performed. The critical damage degree of P92 steel under this operating condition is known. The calculated damage rate is 0.8. for Substituting the values ​​into the inspection cycle formula, the predicted remaining pipeline life is approximately 152,000 hours. Considering the power plant's overhaul plan, it is recommended that the next inspection cycle be set at 5 years. The final operational suitability assessment conclusion is: the pipeline is in good condition; continued operation is recommended, along with regular monitoring.

[0082] Based on the same inventive concept, this disclosure also provides a suitability evaluation system for high-temperature steam pipelines in thermal power plants, as shown in the following embodiment. Since the principle of this suitability evaluation system for high-temperature steam pipelines in thermal power plants solves the problem is the same as that described above... Figure 1 The method embodiments shown are similar, therefore, the implementation of the evaluation system embodiment for the high-temperature steam pipeline of the thermal power plant can be found above. Figure 1 The implementation of the method embodiments shown will not be repeated here.

[0083] Figure 3 This diagram illustrates the structure of a high-temperature steam pipeline in a thermal power plant, as described in an embodiment of the present disclosure, for use in an evaluation system. Figure 3 As shown, the evaluation system 300 for the high-temperature steam pipeline of the thermal power plant includes: an information acquisition module 301, a damage identification module 302, a multi-level assessment module 303, a damage calculation module 304, a life prediction module 305, and a conclusion output module 306.

[0084] The information acquisition module 301 is used to acquire the design parameters, material information, and historical operating data of the pipeline to be evaluated. The damage identification module 302 is used to identify the damage mode of the pipeline to be evaluated based on the historical data of operation and material information, and to determine a multi-level evaluation strategy based on the identified damage mode. The multi-level assessment module 303 is used to perform multi-level safety assessments on the pipeline to be assessed based on design parameters and material information, and according to the multi-level assessment strategy, to obtain the macroscopic safety status of the pipeline to be assessed. The damage calculation module 304 is used to extract actual operating condition data from historical operating data and combine it with the damage evolution model to calculate the cumulative damage degree of the pipeline to be evaluated, so as to quantitatively characterize the macroscopic safety status. The life prediction module 305 is used to predict the remaining life of the pipeline to be evaluated based on the cumulative damage level. The conclusion output module 306 is used to output the usability evaluation results, including remaining service life and operating recommendations, including continued operation, monitored operation, depressurized operation, or pipeline replacement.

[0085] In some embodiments, the multi-level evaluation module 303 is used to perform a first-level evaluation, using the ultimate load criterion to determine whether the pipeline under evaluation meets the minimum safety factor requirement; if the minimum safety factor requirement is met, the pipeline under evaluation is determined to have passed the first-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of cumulative damage degree is entered; if the minimum safety factor requirement is not met, the pipeline under evaluation is determined to have failed the first-level evaluation, triggering the execution of the second-level evaluation, using the elastoplastic fracture mechanics method based on the failure assessment diagram to calculate the failure assessment factor, and determining whether the failure assessment factor is within a preset safety area; if the failure assessment factor is within the preset safety area, the pipeline under evaluation is determined to have passed the second-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of cumulative damage degree is entered; if the failure assessment factor is outside the preset safety area, the pipeline under evaluation is determined to have failed the second-level evaluation, triggering the execution of the third-level evaluation, using the finite element method to perform detailed stress analysis and life prediction, and after completing the third-level evaluation, the calculation step of cumulative damage degree is entered.

[0086] In some embodiments, the multi-level evaluation module 303 is used to determine whether the pipeline to be evaluated meets the minimum safety factor requirement based on the following formula: ;in, The working membrane stress is calculated based on the operating pressure, pipe diameter, and wall thickness in the design parameters. The ultimate load is determined based on material information. This is for the safety factor.

[0087] In some embodiments, the multi-level evaluation module 303 is used to calculate the fracture ratio in the failure assessment factor based on the following formula. and load ratio : ; ;in, The external stress intensity factor. For the fracture toughness of the material, The reference stress is determined based on the working thin film stress and defect size. The yield strength of the material; the fracture ratio As the vertical axis, load ratio As the horizontal axis, the assessment point is determined in the failure assessment diagram; based on whether the assessment point is located within the preset safety area defined by the preset safety curve of the failure assessment diagram, it is determined whether the failure assessment factor is located within the preset safety area.

[0088] In some embodiments, the damage calculation module 304 is used to extract actual operating temperature and time history data based on operating history data; wherein, the time history data includes segmented operating times at different temperatures; and for each temperature time segment, the fracture time at that temperature is calculated based on the following formula. : ;in, For the first The absolute temperature over a specific temperature period. The Larson-Miller parameters are determined based on material information. The material constants are determined based on the material information; the creep cumulative damage of the pipeline to be evaluated is calculated based on the following formula, combined with the segmented operating time: ;in, This represents the cumulative creep damage degree. For the first The segmented running time for each temperature period For the first The breakage time corresponding to each temperature time period.

[0089] In some embodiments, the damage calculation module 304 is used to obtain the number of start-stop cycles, temperature cycle amplitude, and holding time of the pipeline to be evaluated; input the number of start-stop cycles, temperature cycle amplitude, and holding time into the nonlinear damage interaction model; calculate the nonlinear coupling effect between creep damage and fatigue damage; combine the creep cumulative damage degree to calculate the comprehensive damage degree; and use the comprehensive damage degree as the final characterization value of the cumulative damage degree.

[0090] In some embodiments, the conclusion output module 306 is further configured to obtain the critical damage degree and current damage rate of the pipeline to be evaluated; and determine the next inspection cycle based on the following formula: ;in, For the next inspection cycle, The critical damage level, To assess the overall damage level, Given the current damage rate, For design life, This represents the total operating time. The output includes remaining service life and operational recommendations for a suitability evaluation, including: remaining service life, next inspection cycle, and operational recommendations for a suitability evaluation.

[0091] In some embodiments, the damage calculation module 304 is further configured to use nonlinear ultrasonic technology to detect micro- and nanoscale damage to the pipeline material to be evaluated, obtain the ultrasonic nonlinear coefficient; measure the change of the ultrasonic nonlinear coefficient with service time, establish a quantitative relationship between the ultrasonic nonlinear coefficient and the creep cumulative damage degree; use the quantitative relationship to correct the creep cumulative damage degree, and replace the original creep cumulative damage degree with the corrected creep cumulative damage degree to recalculate the comprehensive damage degree and remaining life.

[0092] In some embodiments, the multi-level evaluation module 303 is further configured to calculate the stress amplification factor using the elliptical section equivalent method if the pipeline to be evaluated includes an elbow component; calculate the stress intensification factor using the stress intensification factor method if the pipeline to be evaluated includes a tee component; calculate the comprehensive local stress of special components by combining the secondary stress caused by internal pressure, temperature and support / hanger action, as well as the stress amplification factor or stress intensification factor; the special components include elbow components and tee components; when performing the first-level evaluation, the comprehensive local stress is used to replace the working membrane stress to update the results of the first-level evaluation; when performing the second-level evaluation, the comprehensive local stress is used to replace the reference stress to update the results of the second-level evaluation.

[0093] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. A method for evaluating the suitability of high-temperature steam pipelines in thermal power plants, characterized in that, include: Obtain the design parameters, material information, and operational history data of the pipeline to be evaluated; Based on the historical operating data and material information, the damage mode of the pipeline to be evaluated is identified, and a multi-level evaluation strategy is determined according to the identified damage mode. Based on the design parameters and material information, a multi-level safety assessment is performed on the pipeline to be assessed according to the multi-level assessment strategy to obtain the macroscopic safety status of the pipeline to be assessed. The actual operating condition data is extracted from the historical operating data, and the cumulative damage degree of the pipeline to be evaluated is calculated by combining the damage evolution model, so as to quantitatively characterize the macroscopic safety status. The remaining life of the pipeline to be evaluated is predicted based on the cumulative damage level; The output includes a usability evaluation result of the remaining lifespan and operational recommendations, which include continued operation, monitored operation, depressurized operation, or pipeline replacement.

2. The method according to claim 1, characterized in that, The step of performing a multi-level safety assessment on the pipeline to be assessed according to the multi-level assessment strategy includes: The first-level assessment is performed, and the ultimate load criterion is used to determine whether the pipeline under assessment meets the minimum safety factor requirement. If the minimum safety factor requirement is met, the pipeline to be evaluated is determined to have passed the first-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of the cumulative damage degree is entered. If the minimum safety factor requirement is not met, the pipeline to be evaluated is determined to have failed the first-level evaluation, triggering the execution of the second-level evaluation. The failure evaluation factor is calculated using the elastoplastic fracture mechanics method based on the failure evaluation diagram, and it is determined whether the failure evaluation factor is within the preset safety area. If the failure assessment factor is within the preset safety area, the pipeline to be evaluated is determined to have passed the second-level evaluation, the multi-level safety evaluation is terminated, and the calculation step of the cumulative damage degree is entered. If the failure assessment factor is outside the preset safety zone, the pipeline to be evaluated is determined to have failed the second-level evaluation, triggering the execution of the third-level evaluation. The finite element method is used to perform detailed stress analysis and life prediction, and after the third-level evaluation is completed, the calculation step of the cumulative damage degree is entered.

3. The method according to claim 2, characterized in that, The first-level assessment, which uses the ultimate load criterion to determine whether the pipeline under assessment meets the minimum safety factor requirement, includes: The following formula is used to determine whether the pipeline to be evaluated meets the minimum safety factor requirement: ； in, The working membrane stress is calculated based on the operating pressure, pipe diameter, and wall thickness in the design parameters. The ultimate load is determined based on the material information. This is for the safety factor.

4. The method according to claim 2, characterized in that, The second-level assessment involves calculating the failure assessment factor using an elastoplastic fracture mechanics method based on a failure assessment map, and determining whether the failure assessment factor is within a preset safe range, including: The fracture ratio in the failure assessment factors is calculated based on the following formula. and load ratio : ； ； in, The applied stress intensity factor. For the fracture toughness of the material, The reference stress is determined based on the working thin film stress and defect size. The yield strength of the material; The fracture ratio The load ratio is used as the vertical axis. As the horizontal axis, the evaluation point is determined in the failure evaluation diagram; Whether the failure assessment factor is located within the preset safety area is determined based on whether the assessment point is located within the preset safety area defined by the preset safety curve of the failure assessment diagram.

5. The method according to claim 1, characterized in that, The step of extracting actual operating condition data from the historical operating data and calculating the cumulative damage degree of the pipeline to be evaluated using a damage evolution model includes: Based on the aforementioned historical operating data, actual operating temperature and time history data are extracted; wherein, the time history data includes segmented operating times at different temperatures; For each temperature time interval, the breakage time at that temperature is calculated based on the following formula. : ； in, For the first The absolute temperature over a specific temperature period. The Larson-Miller parameters are determined based on the material information. These are material constants determined based on the material information; The creep cumulative damage degree of the pipeline to be evaluated is calculated based on the following formula, combined with the segmented operating time: ； in, This represents the cumulative creep damage degree. For the first The segmented running time for each temperature period For the first The breakage time corresponding to each temperature time period.

6. The method according to claim 5, characterized in that, The method further includes: The number of start-stop cycles, temperature cycle range, and load holding time of the pipeline to be evaluated are obtained. The number of start-stop cycles, temperature cycle amplitude, and holding time are input into the nonlinear damage interaction model. By calculating the nonlinear coupling effect between creep damage and fatigue damage, and combining it with the creep cumulative damage degree, the comprehensive damage degree is calculated, and the comprehensive damage degree is used as the final characterization value of the cumulative damage degree.

7. The method according to claim 6, characterized in that, The method further includes: Obtain the critical damage degree and current damage rate of the pipeline to be evaluated; The next inspection cycle is determined based on the following formula: ； in, For the next inspection cycle, The critical damage level, The overall damage level, Given the current damage rate, For design life, This represents the running time. The output includes the remaining lifespan and the usability evaluation results of the operational recommendations, including: the output includes the remaining lifespan, the next inspection cycle, and the usability evaluation results of the operational recommendations.

8. The method according to claim 6, characterized in that, The method further includes: Nonlinear ultrasonic technology was used to detect micro- and nanoscale damage in the pipeline material to be evaluated, and the ultrasonic nonlinear coefficient was obtained. The change of the ultrasonic nonlinear coefficient with service time is measured to establish a quantitative relationship between the ultrasonic nonlinear coefficient and the creep cumulative damage degree. The creep cumulative damage degree is corrected using the quantitative relationship, and the corrected creep cumulative damage degree is used to replace the original creep cumulative damage degree to recalculate the comprehensive damage degree and the remaining life.

9. The method according to claim 3 or 4, characterized in that, The method further includes: If the pipeline to be evaluated includes elbow components, the stress amplification factor is calculated using the elliptical section equivalent method. If the pipeline to be evaluated includes a tee component, the stress intensification factor method is used to calculate the stress intensification factor. The comprehensive local stress of the special components is calculated by combining the secondary stress caused by internal pressure, temperature and the action of supports and hangers, as well as the stress amplification factor or the stress strengthening factor; the special components include elbow components and tee components. When performing the first-level evaluation, the working film stress is replaced with the comprehensive local stress to update the results of the first-level evaluation; when performing the second-level evaluation, the reference stress is replaced with the comprehensive local stress to update the results of the second-level evaluation.

10. A service evaluation system for high-temperature steam pipelines in thermal power plants, characterized in that, include: The information acquisition module is used to obtain the design parameters, material information, and historical operating data of the pipeline to be evaluated. The damage identification module is used to identify the damage mode of the pipeline to be evaluated based on the operation history data and material information, and to determine a multi-level evaluation strategy based on the identified damage mode. The multi-level evaluation module is used to perform a multi-level safety evaluation on the pipeline to be evaluated based on the design parameters and material information, and according to the multi-level evaluation strategy, to obtain the macroscopic safety status of the pipeline to be evaluated. The damage calculation module is used to extract actual operating condition data from the historical operating data and calculate the cumulative damage degree of the pipeline to be evaluated in combination with the damage evolution model, so as to quantitatively characterize the macroscopic safety status. A life prediction module is used to predict the remaining life of the pipeline to be evaluated based on the cumulative damage level. The conclusion output module is used to output a usability evaluation result including the remaining life and operating recommendations, which include continuing operation, monitoring operation, depressurization operation, or pipeline replacement.

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