Petroleum chemical equipment creep service safety evaluation method and system

Abstract

The present application provides a kind of petrochemical equipment creep service safety evaluation method and system, it is related to the creep service safety evaluation technical field of petrochemical equipment, first according to the load fluctuation amplitude of component, material performance index and service defect type, set the limit condition of each level evaluation, by judging whether component meets corresponding condition, into corresponding evaluation process, define evaluation calculation pressure, service time and evaluation temperature in the evaluation process, and calculate three-way principal stress based on evaluation calculation pressure, and screen the screening curve and damage curve of corresponding material, calculate total creep damage, 1st level evaluation is determined by comparing total creep damage with threshold value, 2nd level and 3rd level evaluation need to be judged whether there is plastic collapse risk by primary reference stress and plastic collapse determination criterion first, then determine the result by combining total creep damage with allowable value comparison, 3rd level evaluation uses finite element calculation and directly determines that crack type defect does not pass.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of creep service safety evaluation of petrochemical equipment, in particular to a creep service safety evaluation method and system for petrochemical equipment. BACKGROUND

[0002] When pressure-bearing equipment such as pressure vessels, pressure pipelines, storage tanks, etc. are operated for a long time in a high-temperature and high-pressure environment, the material will exhibit a creep phenomenon. Creep is a slow plastic deformation of the material under the action of sustained stress, which may eventually lead to material degradation, crack propagation, and even failure. Since pressure-bearing equipment is widely used in the petrochemical, power, metallurgical and other industries, accurate evaluation of creep damage is crucial to ensure the safe operation of the equipment. Traditional creep damage evaluation methods mainly rely on manual detection, experience judgment and offline laboratory analysis, which have problems such as low efficiency, strong subjectivity and insufficient precision.

[0003] Traditional methods rely on the experience of personnel and relevant standards for qualitative judgment, such as assessing the degree of creep damage through visual inspection, hardness testing or metallographic analysis. However, this method is highly subjective and difficult to quantify the damage level, and requires a high level of expertise from the detection personnel, which can easily lead to misjudgment due to human factors; some enterprises use sampling analysis, such as electron microscope observation, creep test, etc. to evaluate the creep damage of materials. Although laboratory data is more accurate, this method requires sampling, has a long detection period, is high in cost, and cannot achieve real-time monitoring, making it difficult to meet the needs of modern industry for efficient operation and maintenance; in recent years, finite element analysis has been used to simulate the creep damage process, but this method is complex, requires high-precision material models and a large number of input parameters, and is time-consuming to calculate, making it difficult to be quickly applied in engineering sites. In addition, finite element simulation usually requires professional personnel to operate, limiting its popularity in daily detection in enterprises; although the existing standard GB / T 35013-2018 provides an evaluation method for creep damage, the evaluation method is complex, the evaluation process is time-consuming, and the manual calculation workload is large, making it difficult to quickly draw conclusions during equipment operation. Therefore, although the existing standard provides a theoretical basis, it has obvious shortfalls in practicality in terms of quickly, accurately, consistently and efficiently evaluating creep damage and making intelligent decisions in engineering sites. This is one of the core pain points that the intelligent evaluation system aims to solve, by appropriately optimizing the standard, algorithmizing the standard logic, automating the process, intelligently making decisions and conveniently operating, significantly improving the practical value of the evaluation process.

[0004] The above information disclosed in the BACKGROUND section only serves to enhance the understanding of the background of the present disclosure, and therefore it can include information that does not constitute the prior art known to those of ordinary skill in the art. SUMMARY

[0005] The purpose of this invention is to provide a method and system for evaluating the creep service safety of petrochemical equipment, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for evaluating the creep service safety of petrochemical equipment, comprising the following steps:

[0008] Based on the load fluctuation amplitude, material performance indicators, and service defect types of components, the constraints for Level 1, 2, and 3 evaluations are set; the components are evaluated by determining whether they meet the constraints of the corresponding level of evaluation.

[0009] According to the evaluation selection process of level 1, 2 or 3, the process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time.

[0010] In Level 1 evaluation, a total creep damage threshold is set. Under a single operating condition, the maximum operating time of the component is obtained by extracting the evaluation temperature and evaluation calculation pressure in step 2. If it is higher than the service time, the evaluation is passed; otherwise, the process of calculating total creep damage is entered. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, the process of entering Level 2 or Level 3 evaluation is determined according to the limitations of each evaluation.

[0011] In the Level 2 evaluation, a primary reference stress is calculated using classical formulas of elasticity. A plastic collapse criterion is constructed based on the material type. If the primary reference stress is greater than the plastic collapse criterion, the evaluation is deemed to fail. The evaluation is then judged to proceed to Level 3 based on the constraints of each evaluation. If the stress is lower than the plastic collapse criterion, the evaluation is deemed to pass and proceed to the calculation of total creep damage. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, the evaluation proceeds to Level 3.

[0012] In the Level 3 evaluation, stress calculation is performed using the finite element method. The evaluation procedure is the same as that for Level 2 evaluation, and components with crack-like defects are directly judged as failing the evaluation.

[0013] Furthermore, based on the load fluctuation amplitude, material performance indicators, and service defect types of the components, the method for setting the limiting conditions for Level 1, 2, and 3 evaluations is as follows:

[0014] The load fluctuation amplitude includes pressure fluctuation amplitude and temperature fluctuation amplitude. Material performance indicators include minimum Brinell hardness and carbon content. Component defects and damage include localized thinning, trenching, pitting corrosion; hydrogen bulging, hydrogen-induced cracking, stress-directed hydrogen-induced cracking, stress corrosion cracking; out-of-roundness, bulging, depressions, or recessed grooves exceeding the standard; crack-like defects; microstructural abnormalities such as high-temperature hydrogen corrosion or severe graphitization; and no obvious deformation of the component due to fire or overheating. Professional assessors will determine whether the component has the aforementioned defects and damage.

[0015] Record the load fluctuation amplitude during operation, extract the maximum pressure, minimum pressure, maximum temperature, and minimum temperature experienced by the component during operation, and calculate the pressure fluctuation amplitude:

[0016]

[0017] In the formula, ΔP represents the pressure fluctuation amplitude, P max P represents the maximum pressure. min P represents the minimum pressure. design Indicates design pressure;

[0018] Calculation of temperature fluctuation amplitude:

[0019] ΔT=T max -T min

[0020] In the formula, ΔT represents the amplitude of temperature fluctuation, and T max T represents the maximum temperature. min Indicates the minimum temperature;

[0021] When ΔP≥10% or ΔT≥30°, and two or more periodic changes occur during operation, the component is deemed to be subjected to cyclic load; for material performance index testing, the minimum Brinell hardness is set to a1 and the carbon content is set to a2, the service defect type of the component is checked, and it is determined whether the aforementioned defects and damage exist;

[0022] When a component's original design meets the relevant specifications or standards, does not bear cyclic loads, its material performance indicators exceed the specified values, and the service defect type does not contain the aforementioned defects and damages, it is judged to meet the Level 1 evaluation constraint conditions; when a component's original design meets the relevant specifications or standards, does not bear cyclic loads, and the service defect type does not contain the aforementioned defects and damages, the component's operating condition history is recorded, and its future operating conditions are known, it is judged to meet the Level 2 evaluation constraint conditions; when it bears cyclic loads, and the crack-type defects do not include stress corrosion cracking, it is judged to meet the Level 3 evaluation constraint conditions.

[0023] Furthermore, the method for determining the corrections for the evaluation calculation pressure, service time, and evaluation temperature is as follows:

[0024] In Level 1 evaluation, the actual operating temperature of the component under a single operating condition, or the actual operating temperature of each operating condition under multiple operating conditions, is used as the evaluation temperature. If there is a load-bearing weld in the component, and the weld direction is perpendicular to the direction of the maximum principal stress controlling the calculated wall thickness, 14°C needs to be added to the actual operating temperature as the evaluation temperature. The actual operating pressure of the component under a single operating condition, or the actual operating pressure of each operating condition under multiple operating conditions, is used as the evaluation calculation pressure. The total past operating time and the planned future operating time under the current operating condition are used as the service time of that operating condition. For historical operating conditions that are not currently in use, the service time is only the cumulative operating time of that condition in the historical period.

[0025] In the Level 2 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure, and the past operating time and the future planned operating time are taken as the service time.

[0026] In the Level 3 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure, and the past operating time and the future planned operating time are taken as the service time.

[0027] Furthermore, the method for calculating the triaxial principal stress by evaluating the pressure and selecting the evaluation principal stress, and then screening the corresponding material's screening curve and damage curve, is as follows:

[0028] In Level 1 evaluation, the location with the most severe wall thinning is selected as the evaluation principal stress based on the triaxial principal stress. Based on the actual structure of the component, the triaxial principal stress is calculated using the corresponding mechanical formulas based on the evaluation calculation pressure and wall thickness. The maximum principal stress is then selected as the evaluation principal stress.

[0029] σ max =max{σ1, σ2, σ3}

[0030] In the formula, σ max σ1, σ2, and σ3 represent the maximum principal stress, and σ3 represent the triaxial principal stresses.

[0031] In the Level 2 evaluation, the location with the most severe wall thinning is selected as the evaluation principal stress based on the triaxial principal stress. Based on the actual structure of the component, the triaxial principal stress is calculated using the corresponding mechanical formula, and the equivalent stress is selected as the evaluation principal stress. The formula used to calculate the equivalent stress is as follows:

[0032]

[0033] In the formula, σ e Indicates equivalent stress;

[0034] In the Level 3 evaluation, a finite element model is established, and the equivalent stress is calculated at the weakest point of each defect according to the same rules as in the Level 2 evaluation. The maximum value is then used as the principal stress for evaluation.

[0035] According to the creep test method specified in GB / T 35013-2018, the creep performance of the above materials was tested under different temperatures and stress conditions, and the creep fracture time and creep damage rate data corresponding to each temperature-stress combination were obtained.

[0036] Using temperature as the x-axis and stress as the y-axis, the maximum operating time of the same material under different temperature-stress combinations is fitted to form a continuous curve as a screening curve.

[0037] With temperature as the x-axis and stress as the y-axis, the creep damage rate of the same material under different temperature-stress combinations is fitted to form a continuous curve as the damage curve.

[0038] Based on the material type of the component, the corresponding material type screening curve and damage curve are matched in the material database. The maximum running time is the safe threshold for creep fracture time, and the creep damage rate is the damage increment per unit time.

[0039] Furthermore, the method for determining the maximum running time based on the screening curve, the creep damage rate based on the damage curve, and calculating the total creep damage by combining the service time is as follows:

[0040] In Level 1 evaluation, the principal stress, evaluation temperature, and material type are extracted. The maximum operating time corresponding to the combination is obtained from the screening curve of the corresponding material, and the creep damage rate of the combination is obtained from the damage curve of the corresponding material. Combined with the service time, the total creep damage formula is constructed:

[0041]

[0042] In the formula, R represents total creep damage. j t represents the creep damage rate for the j-th operating condition. j This represents the service time of the j-th operating condition, where j is a positive integer greater than 0. It represents the index of the operating condition. When the component has a single operating condition, j = 1. When the component has multiple operating conditions, j = 1, ..., n0, where n0 represents the total number of operating conditions.

[0043] In the Level 2 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining time with the total creep damage formula.

[0044] In the Level 3 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining time with the total creep damage formula.

[0045] Furthermore, in the Level 1 evaluation, a total creep damage threshold is set. The method for obtaining the maximum operating time of the component under a single operating condition based on the evaluation temperature and evaluation calculation pressure extracted in step 2 is as follows:

[0046] Set total creep damage threshold Under a single operating condition, the maximum operating time is obtained through the corresponding screening curve based on the component's evaluation temperature, evaluation principal stress, and material type.

[0047] Furthermore, the method for constructing plastic collapse judgment criteria based on material type is as follows:

[0048]

[0049] In the formula, σ pys This represents the criteria for determining plastic collapse, σ. ys This indicates the yield strength corresponding to the type of material.

[0050] Furthermore, in the Level 3 evaluation, the method for stress calculation using the finite element method is as follows:

[0051] A finite element model incorporating service defects is established for the component, ensuring the model matches the actual state of the component. The maximum operating temperature under each operating condition is selected as the evaluation temperature, and the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure. The evaluation temperature and evaluation calculation pressure are applied to the finite element model as thermal and force boundary conditions, respectively. The triaxial principal stress is obtained at the weakest point of each defect. The primary reference stress is calculated using classical formulas of elasticity, and the equivalent stress is calculated using the equivalent stress formula. If the primary reference stress exceeds the plastic collapse criterion, the evaluation is deemed unsuccessful; otherwise, the equivalent stress is used as the evaluation principal stress. Combining the evaluation temperature and material type, the creep damage rate corresponding to this combination is obtained from the damage curve of the corresponding material. The total creep damage is calculated using the total creep damage formula, combined with time. If the total creep damage is lower than a preset allowable value, the evaluation is deemed successful; otherwise, the evaluation is deemed unsuccessful.

[0052] The present invention also provides a creep service safety evaluation system for petrochemical equipment. This system is used to perform the aforementioned creep service safety evaluation method for petrochemical equipment, and includes:

[0053] The evaluation selection module is used to set the constraints for Level 1, 2, and 3 evaluations based on the component's load fluctuation amplitude, material performance indicators, and service defect type. The component is evaluated by determining whether it meets the constraints of the corresponding level of evaluation.

[0054] The process construction module is used to select a process based on the evaluation level 1, 2 or 3. The process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time.

[0055] The Level 1 evaluation module is used in Level 1 evaluation. It sets the total creep damage threshold and obtains the maximum operating time of the component based on the evaluation temperature and evaluation calculation pressure extracted in step 2 under a single operating condition. If it is higher than the service time, the evaluation is passed; otherwise, it enters the total creep damage calculation process. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, it is determined whether to enter Level 2 or Level 3 evaluation based on the limitations of each evaluation.

[0056] The Level 2 evaluation module is used in Level 2 evaluation. It calculates the primary reference stress using classical formulas of elasticity and constructs a plastic collapse judgment criterion based on the material type. If the primary reference stress is greater than the plastic collapse judgment criterion, the evaluation is deemed to fail. It then determines whether to proceed to Level 3 evaluation based on the constraints of each evaluation. If the stress is lower than the plastic collapse judgment criterion, the evaluation is deemed to pass and proceed to the calculation of total creep damage. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, it proceeds to Level 3 evaluation.

[0057] The Level 3 evaluation module is used in Level 3 evaluation. It uses finite element method for stress calculation and the evaluation procedure is the same as that of Level 2 evaluation. Components with crack-like defects are directly judged as failing the evaluation.

[0058] Compared with the prior art, the beneficial effects of the present invention are:

[0059] This invention sets 1 to 3 levels of evaluation constraints based on the load fluctuation amplitude, material performance indicators, and service defect types of components. It also establishes a 3-level progressive evaluation process based on theoretical foundations, ranging from simple defect-free components to those with complex defects such as cracks. This process quantifies the damage degree through standardized data calculations by clearly defining the input parameters required for each stage, enabling rapid screening, dual determination of plastic collapse and creep damage, and precise finite element evaluation of complex defects. It avoids relying on human experience for qualitative judgment, achieving rapid output of evaluation results for simple defect-free conditions and accurate analysis of complex defect components. This allows for rapid application in engineering fields without the need for offline testing based on laboratory analysis. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the overall method flow of the present invention;

[0061] Figure 2 This is a damage curve diagram of 20G carbon steel according to the present invention;

[0062] Figure 3 This is a logic diagram for the creep damage grading evaluation of the present invention;

[0063] Figure 4 This is a schematic diagram of the overall system structure of the present invention. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0065] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0066] Example:

[0067] Please see Figures 1 to 3 The present invention provides a technical solution:

[0068] A method for evaluating the creep service safety of petrochemical equipment, comprising the following steps:

[0069] Step 1: Based on the load fluctuation amplitude, material performance indicators, and service defect type of the component, set the evaluation constraints for levels 1, 2, and 3; sequentially evaluate the component by determining whether it meets the constraints of the corresponding level of evaluation;

[0070] Construct Level 1 evaluation constraints;

[0071] The limitations for Level 1 evaluation are:

[0072] (a) The original design meets the relevant specifications or standards.

[0073] (b) Not subject to cyclic loads

[0074] (c) The minimum Brinell hardness or carbon content of the material reaches or exceeds the specified value.

[0075] (d) The component is free from the following defects or damage: local thinning, trenching, pitting; hydrogen bulging, hydrogen-induced cracking, stress-directed hydrogen-induced cracking, stress corrosion cracking; out-of-roundness, bulging, depression or recessed grooves exceeding the standard; crack-like defects; abnormal microstructure such as high-temperature hydrogen corrosion or severe graphitization; the component is free from obvious deformation caused by fire or overheating, such as sagging, bulging or severe oxidation;

[0076] The restrictions for Level 2 evaluation are:

[0077] (a) The original design meets the relevant specifications or standards.

[0078] (b) Not subject to cyclic loads

[0079] (c) The component is free from the following defects: localized thinning, trenching, pitting; hydrogen bulging, hydrogen-induced cracking, stress-directed hydrogen-induced cracking, stress corrosion cracking; out-of-roundness, bulging, depressions, or recessed grooves exceeding the standard; crack-like defects; abnormal microstructure such as high-temperature hydrogen corrosion or severe graphitization; and the component is free from obvious deformation caused by fire or overheating, such as sagging, bulging, or severe oxidation.

[0080] (d) The operating conditions of the component are recorded in history, and the future operating conditions are known;

[0081] The restrictions for Level 3 evaluation are:

[0082] (a) Not subjected to cyclic loads

[0083] (b) Crack-type defects do not include stress corrosion cracking;

[0084] For material performance testing, a minimum Brinell hardness value of a1 and a carbon content value of a2 are set. Meeting relevant specifications or standards in the original design ensures the initial state of the equipment conforms to specifications, eliminating inherent risks caused by design flaws. Cyclic loading accelerates the coupled damage of creep and fatigue, increasing the difficulty of evaluation. Level 1, as a rapid evaluation, temporarily disregards such complex conditions, focusing only on simple creep under stable loads. Brinell hardness and carbon content are key indicators of a material's creep resistance; insufficient hardness may indicate material deterioration, while excessive carbon content may affect high-temperature stability. Meeting these requirements ensures the material itself is in a qualified creep resistance state. Defects such as localized thinning, cracks, and hydrogen-induced cracking significantly amplify stress concentration, accelerating creep damage. Level 1 evaluation eliminates these defects, ensuring the evaluated object is in an ideal state of "defect-free interference," allowing for rapid determination through subsequent simplified algorithms.

[0085] Level 2 evaluation is a more precise evaluation after failing Level 1, with less stringent restrictions. Its core objective is to conduct a more detailed multi-condition damage accumulation analysis on equipment that fails Level 1 evaluation but whose condition remains controllable. It maintains the basic restrictions of Level 1 evaluation, namely excluding design flaws, cyclic loads, and severe defects, ensuring that the evaluated object remains in a conventional state "calculated using theoretical formulas." Compared to Level 1 and the newly added historical and future known operating conditions, it guarantees accurate calculation of total creep damage.

[0086] Level 3 evaluation, as a technology that fails the first two levels but still has evaluation value, requires in-depth analysis to avoid excessive costs caused by directly determining "repair / replacement". Therefore, cyclic loading is still required, but complex states of equipment under non-cyclic loading are allowed. However, stress corrosion cracking progresses extremely quickly and has extremely high risks, which are difficult to accurately assess even with finite element analysis. Therefore, it is directly excluded. Ordinary cracks, such as creep cracks, can be calculated by finite element analysis of the damage after stress concentration. The risks are not too high and they still have evaluation value. The overall logic is to be progressively graded to achieve a balance between safety, efficiency and cost.

[0087] The specific process for determining whether a system is subject to cyclic loading is as follows:

[0088] Record the load fluctuation amplitude during operation, extract the maximum pressure, minimum pressure, maximum temperature, and minimum temperature experienced by the component during operation, and calculate the pressure fluctuation amplitude:

[0089]

[0090] In the formula, ΔP represents the pressure fluctuation amplitude, P max P represents the maximum pressure. min P represents the minimum pressure. design Indicates design pressure;

[0091] Calculation of temperature fluctuation amplitude:

[0092] ΔT=T max -T min

[0093] In the formula, ΔT represents the amplitude of temperature fluctuation, and T max T represents the maximum temperature. min Indicates the minimum temperature;

[0094] When ΔP≥10% or ΔT≥30°, and two or more periodic changes occur during the operating time, the component is deemed to be subjected to cyclic load.

[0095] The professional assessor first determines whether the component meets the Level 1 evaluation criteria. If it does, it proceeds directly to Level 1 evaluation. If it does not meet the criteria, the assessor further determines whether the component meets the Level 2 evaluation criteria. If it does, it proceeds to Level 2 evaluation.

[0096] If the component does not meet the Level 2 evaluation criteria, it is necessary to further determine whether it meets the Level 3 evaluation criteria; if it does, it proceeds to Level 3 evaluation.

[0097] Step 2: Select the evaluation process according to level 1, 2 or 3. The process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time.

[0098] In Level 1 evaluation, the actual operating temperature is used as the evaluation temperature under a single operating condition, while under multiple operating conditions, the actual operating temperature of each condition is used as the evaluation temperature. This is because under a single operating condition, the equipment is in a stable temperature environment for a long time, and the actual operating temperature can directly reflect the creep conditions that the equipment materials are subjected to, ensuring consistency with the actual creep environment of the materials. Under multiple operating conditions, the equipment will experience different temperature conditions, and the creep damage rate of the materials corresponding to different temperatures varies significantly. For example, the creep damage rate at 300℃ and 400℃ may differ by more than 10 times. If a uniform temperature, such as the average temperature or the maximum temperature, is used, it will mask the actual damage contribution under different operating conditions, resulting in a distortion of the total creep damage calculation.

[0099] If the component has load-bearing welds, the weld direction is determined by consulting the original design drawings or on-site inspection. The direction of the maximum principal stress is obtained to control the calculated wall thickness. The calculated wall thickness value is used to ensure that the material does not undergo plastic deformation or fracture under the most dangerous stress. The most dangerous stress is the maximum principal stress, and the direction refers to the spatial orientation of this maximum principal stress within the equipment structure. If the weld direction is 90°±5° to the direction of the maximum principal stress, then 14°C is added to the actual operating temperature as the evaluation temperature; otherwise, the actual operating temperature is used. The weld direction is 90°±5° to the direction of the maximum principal stress. At 0°±5°, the two are approximately perpendicular. The load-bearing weld is the structural connection part of the equipment. When the weld direction is perpendicular to the direction of the maximum principal stress, the stress direction of the weld metal is consistent with the weld length direction. Stress concentration is likely to occur at defects such as the weld root and fusion line. The stress value may reach 1.5-2 times that of the base material. At the same time, due to the heat effect of welding, the grains in the weld area may be coarse or there may be residual stress. Its creep resistance is usually slightly lower than that of the base material. Therefore, its actual creep risk is higher than that under normal conditions. By artificially increasing the evaluation temperature by 14°C, the evaluation results can be made conservative. In the appendix of GB / T 35013-2018 standard, for butt welds of carbon steel and low alloy steel, the operating temperature can be increased by 10°C-15°C in the creep evaluation to reflect the creep weakness of the weld area. Increasing the evaluation temperature by 14°C is based on the industry practice of evaluating high-temperature pressure equipment.

[0100] For example, the direction of the weld can be directly obtained from the layout drawing of the circumferential weld of the cylinder of a pressure vessel and the longitudinal / circumferential weld of a pipeline. The drawing usually indicates the relationship between the geometric direction of the weld and the axis of the component. If the direction of the weld cannot be known from the original design drawing, the actual extension direction of the weld can be measured by visual inspection or portable testing equipment, and its relative angle with the main structure of the component, i.e., the specific angle with the axis, can be recorded. The circumferential weld is usually perpendicular to the axis of the cylinder / pipeline, and the longitudinal weld is usually parallel to the axis of the cylinder / pipeline. The principal stress refers to the normal stress acting in a specific direction at a certain point inside the material. For pressure-bearing equipment, under high temperature and high pressure conditions, due to the load of internal pressure, structural self-weight and other loads, a complex stress state will be generated inside the material. Through mechanical analysis, it can be decomposed into three principal stresses in mutually perpendicular directions, i.e., the three-dimensional principal stress, denoted as σ1, σ2 and σ3 respectively. In the evaluation of level 1, level 2 and level 3, the three-dimensional principal stress is the basis for calculating the evaluation principal stress.

[0101] The total past operating time and the planned future operating time under the current operating condition are taken as the service time of the operating condition. For historical operating conditions that are not currently in operation, the service time is only the cumulative operating time of the operating condition in the historical period.

[0102] In Level 2 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, and the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure. The damage rate is strongly positively correlated with temperature and stress. Therefore, the selection of evaluation parameters must be able to reflect the damage risk under the worst operating conditions. Otherwise, the creep hazard of the equipment under extreme conditions may be underestimated. Its essence is to use the parameters of the worst operating conditions to represent the overall risk of multiple operating conditions, to ensure that this risk is not underestimated, and to take the past operating time and the future planned operating time as the service time.

[0103] Similarly, in the Level 3 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, and the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure. The worst operating condition parameters are still used as the evaluation benchmark to ensure that even under extreme conditions, creep damage at the defect can be fully assessed, and past operating time and future planned operating time are used as the service time.

[0104] In Level 1 evaluation, the location with the most severe wall thinning is selected based on the triaxial principal stress. The triaxial principal stress is calculated using the corresponding mechanical formulas based on the actual structure of the component, the evaluation calculation pressure, and the wall thickness. For example, for cylindrical containers or pressure pipelines, the formula for calculating the triaxial principal stress is:

[0105]

[0106] In the formula, P represents the evaluation calculation pressure, D represents the inner diameter, and δ represents the actual wall thickness at the location where the wall thickness reduction is most severe.

[0107] For a spherical container, the formula for calculating the triaxial principal stresses is:

[0108]

[0109] For flat cover or flange connection structures, the formula for calculating the triaxial principal stress is:

[0110]

[0111] In the formula, R represents the effective radius of the flat cover, and δ1 represents the thickness of the flat cover;

[0112] The maximum principal stress is selected as the evaluation principal stress:

[0113] σ max =max{σ1, σ2, σ3}

[0114] In the formula, σ max Indicates the maximum principal stress;

[0115] In the Level 2 evaluation, the location with the most severe wall thinning is selected as the evaluation principal stress based on the triaxial principal stress. Based on the actual structure of the component, the triaxial principal stress is calculated using the corresponding mechanical formula, and the equivalent stress is selected as the evaluation principal stress. The formula used to calculate the equivalent stress is as follows:

[0116]

[0117] In the formula, σ e Equivalent stress reflects the degree of difference in principal stresses in different directions. If the difference in the three principal stresses is significant, the formula result will increase as the difference increases. It reflects the risk of shear deformation caused by uneven stress in all directions inside the material and is an important driving factor for creep damage. At high temperatures, creep mechanisms such as grain boundary slip and dislocation movement inside the material are more easily activated under shear stress, leading to accelerated damage. It is more accurate than Level 1 evaluation.

[0118] In the Level 3 evaluation, a finite element model is established, and the stress values ​​at the locations with complex defects are accurately output. The equivalent stress at the weakest point of each defect is calculated according to the same rules as in the Level 2 evaluation. Among all the calculated equivalent stresses, the maximum value is taken as the principal stress for evaluation, so that the evaluation of the location with the highest risk is fully assessed instead of the whole.

[0119] According to the creep test method specified in GB / T 35013-2018, the standard has clear specifications for test equipment, sample preparation, loading method, data recording, etc. The creep performance of the above materials is tested under different temperature and stress conditions. The temperature and stress can be determined according to the actual application conditions of the material to obtain the creep fracture time and creep damage rate data corresponding to each temperature-stress combination.

[0120] Using temperature as the x-axis and stress as the y-axis, the maximum operating time of the same material under different temperature-stress combinations is fitted to form a continuous curve as a screening curve.

[0121] With temperature as the x-axis and stress as the y-axis, the creep damage rate of the same material under different temperature-stress combinations is fitted to form a continuous curve as the damage curve.

[0122] Based on the material type of the component, the corresponding material type screening curve and damage curve are matched in the material database. The maximum running time is the safe threshold for creep fracture time, and the creep damage rate is the damage increment per unit time.

[0123] In Level 1 evaluation, the evaluation principal stress, evaluation temperature, and material type are extracted. The maximum running time corresponding to this combination is obtained from the screening curve of the corresponding material. The evaluation principal stress and evaluation temperature correspond to the stress and temperature of the two curves. The creep damage rate of this combination is obtained from the damage curve of the corresponding material. Combined with time, the total creep damage formula is constructed:

[0124]

[0125] In the formula, R represents total creep damage. j t represents the creep damage rate for the j-th operating condition. j This represents the service time of the j-th operating condition, where j is a positive integer greater than 0. It represents the index of the operating condition. When the component has a single operating condition, j = 1. When the component has multiple operating conditions, j = 1, ..., n0, where n0 represents the total number of operating conditions.

[0126] In the Level 2 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining the service time with the total creep damage formula.

[0127] In the Level 3 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining the service time with the total creep damage formula.

[0128] The overall evaluation process is as follows:

[0129] In the evaluation of components, a graded and progressive evaluation process is adopted. First, based on the load fluctuation, material properties and service defect type of the equipment, the constraints of Level 1, Level 2 and Level 3 evaluation are set. The equipment is then judged in turn to determine whether it meets the conditions of a certain level, and thus enters the corresponding level evaluation.

[0130] In the Level 1 evaluation process, after acquiring the evaluation temperature, evaluation calculation pressure, and service time data of the component, the total creep damage is calculated by combining the screening curve and damage curve of the corresponding material and compared with a set threshold. If the total creep damage is lower than the threshold, the Level 1 evaluation is passed; otherwise, it is necessary to check whether the equipment meets the restrictions of Level 2 and Level 3 evaluations in sequence, and then proceed to the corresponding level of evaluation.

[0131] In the Level 2 evaluation process, after determining the evaluation temperature, evaluation calculation pressure, and service time data for the component, a reference stress is first calculated using elasticity formulas and compared with a yield strength threshold set based on the material type. If the reference stress is greater than the threshold, the Level 2 evaluation is directly deemed unsuccessful. If the reference stress is lower than the threshold, the total creep damage needs to be further calculated and compared with a preset allowable value. If the total creep damage is lower than the allowable value, the Level 2 evaluation is deemed successful; otherwise, it is deemed unsuccessful. If the Level 2 evaluation is unsuccessful, it is necessary to verify whether the Level 3 evaluation restrictions are met to determine whether to proceed to the Level 3 evaluation.

[0132] In the Level 3 evaluation process, if a component has crack-like defects, it is directly deemed to have failed the Level 3 evaluation. For components without crack-like defects, after determining the evaluation temperature, evaluation calculation pressure, and service time data, a reference stress is calculated based on the finite element model and compared with a set material yield strength threshold. If the reference stress is higher than the threshold, the Level 3 evaluation is deemed to have failed; if the reference stress is lower than the threshold, the total creep damage is calculated and compared with a preset allowable value. If the total creep damage is lower than the allowable value, the Level 3 evaluation is deemed to have passed; otherwise, the Level 3 evaluation is deemed to have failed.

[0133] When a component does not meet the Level 3 evaluation criteria or fails the Level 3 evaluation, the system outputs the result of repairing, replacing, or retiring the component.

[0134] Step 3: In the Level 1 evaluation, a total creep damage threshold is set. Under a single operating condition, the maximum operating time of the component is obtained based on the evaluation temperature and evaluation calculation pressure extracted in Step 2. If it is higher than the service time, the evaluation is passed; otherwise, the process of calculating total creep damage is entered. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, the process of entering Level 2 or Level 3 evaluation is determined based on the limitations of each evaluation.

[0135] Set total creep damage threshold Creep damage is the cumulative deterioration of materials under high temperature and continuous stress. Based on a large amount of test data for heat-resistant steels commonly used in petrochemicals, such as 15CrMo and 20G, when the creep damage reaches 0.25, the material still retains about 70%-80% of its original load-bearing capacity, and the subsequent deterioration rate does not accelerate significantly. If the test is passed at this time, it can ensure the safe operation of the equipment in the short term and reserve a sufficient intervention window for future periodic inspections.

[0136] The total past operating time and the planned future operating time under the current operating condition are taken as the service time of the operating condition. For historical operating conditions that are not currently in operation, the service time is only the cumulative operating time of the operating condition in the historical period.

[0137] In the Level 1 evaluation under a single operating condition, the actual operating temperature is used as the evaluation temperature. If the weld direction is 90°±5° to the direction of the maximum principal stress, then 14°C is added to the actual operating temperature as the evaluation temperature. The actual operating pressure of the component under a single operating condition is used as the evaluation calculation pressure. Based on the component's evaluation temperature, evaluation principal stress, and material type, the maximum operating time is obtained through the corresponding screening curve and compared with its service life. If the maximum operating time is greater than the service life, the Level 1 evaluation is passed, and the result of continued service is output. The constraints of the Level 1 evaluation have eliminated all factors that may amplify the deviation between theoretical life and actual risk. At this time, complex damage accumulation is not considered. From the perspective of the material's basic creep life, the existing and planned service life of the equipment is still within the safe range. For example, the material can operate safely for 10 years, but only needs to operate for 8 years in reality. Therefore, it can be directly judged as passing. When the maximum operating time is lower than the service life, the creep damage rate is obtained by comparing the damage curve based on the component's evaluation temperature, evaluation principal stress, and material type. Combined with the service time, the total creep damage is calculated through the total creep damage formula. When the Level 1 evaluation is passed, the result of continued service is output. Table 1 shows the output table of the Level 1 evaluation single operating condition. In the Level 1 evaluation single operating condition, the maximum running time and service time under 40 groups of various component materials are compared, and the total creep damage is compared with the total creep damage threshold. The result of whether the Level 1 evaluation is passed is output. In the table, more than 60% of the conditions are directly judged to pass because the maximum running time is greater than the actual service time, without the need to calculate complex damage. The rest are judged to enter the Level 2 and Level 3 evaluation. The screening is efficient and accurate.

[0138] Table 1 Output Table of Single Operating Condition Results for Level 1 Evaluation

[0139]

[0140]

[0141] like Figure 2 As shown, this is a damage curve plot for 20G carbon steel. Red and yellow represent higher damage rates, while blue and purple represent lower damage rates. The horizontal axis, as temperature increases, becomes more reddish-yellow, indicating that high temperature accelerates creep damage. Similarly, the vertical axis, with higher pressure, becomes brighter, indicating that high pressure intensifies damage. This plot provides a visual representation of the creep damage rate at a specific temperature and pressure.

[0142] In Level 1 evaluation, for multiple operating conditions, this means the equipment will experience different combinations of temperature and pressure. If the weld direction is at 90°±5° to the direction of the maximum principal stress, then 14°C is added to the actual operating temperature as the evaluation temperature. Each operating condition may correspond to a different creep rate. The actual operating pressure of each operating condition under multiple operating conditions is taken as the evaluation calculation pressure, and the actual operating temperature of each condition is taken as the evaluation temperature to accurately match the state of each condition and ensure accurate calculation of the damage for each condition. Then, combined with the service time, the total creep damage can be calculated using the total creep damage formula. If the cumulative creep damage is considered to be within acceptable limits, a Level 1 evaluation is passed, and the decision to continue service is made. If the degradation caused by multiple operating conditions exceeds the safety range of Level 1 evaluation, the Level 1 evaluation fails. The system then checks whether the component meets the limitations of Level 2 and Level 3 evaluations and determines whether to conduct an evaluation. If the limitations of Level 2 and Level 3 evaluations are not met, the system outputs the result of repairing or replacing the component or retiring it.

[0143] Step 4: In the Level 2 evaluation, the primary reference stress is calculated using the classical formula of elasticity. A plastic collapse judgment criterion is constructed based on the material type. If the primary reference stress is greater than the plastic collapse judgment criterion, the evaluation is deemed to fail. The determination of whether to proceed to Level 3 evaluation is based on the constraints of each evaluation. If the stress is lower than the plastic collapse judgment criterion, the evaluation is deemed to pass and the process of calculating total creep damage is initiated. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, the Level 3 evaluation is initiated.

[0144] In Level 2 evaluation, the primary reference stress is calculated using elasticity formulas based on the actual structure of the component. Among the failure modes of pressure-bearing equipment, plastic collapse is a more urgent risk than creep. Plastic collapse can occur in a short period of time, directly leading to equipment failure or even an accident. The primary reference stress is the maximum structural stress calculated based on elasticity, reflecting the instantaneous load-bearing capacity of the equipment under the current load. For example, for cylindrical containers / pipes, the formula used to calculate the primary reference stress is:

[0145]

[0146] In the formula, σ ref Indicates a primary reference stress;

[0147] For a spherical container, the formula used to calculate the primary reference stress is:

[0148]

[0149] Constructing criteria for determining plastic collapse:

[0150]

[0151] In the formula, σ pys This represents the criteria for determining plastic collapse, σ. ys This indicates the yield strength corresponding to the material type. It is constructed based on the differences in the high-temperature mechanical properties of materials and the targeted prevention and control of the risk of plastic collapse. The essence of plastic collapse is that the material undergoes uncontrollable large-area plastic deformation under stress. Austenitic stainless steel and nickel-based alloys are typical high-temperature creep-resistant materials. Even when the stress is close to the yield strength, they are not prone to sudden plastic flow. Other materials, such as carbon steel and low alloy steel, are prone to plastic abrupt changes due to grain boundary weakening and carbide precipitation when the stress is close to the yield strength. For example, if a large area of ​​swelling occurs suddenly, the yield strength will decrease significantly at high temperature. By introducing a coefficient of 0.75, the judgment threshold is actively reduced, and additional safety redundancy is reserved to make the judgment more in line with the actual performance of the material. The yield strength can be found in the material standard specifications. For example, the yield strength values ​​of Q345 steel and other steels at different thicknesses are clearly specified in the low alloy high-strength structural steel.

[0152] When σ ref >σ pys If the external load currently borne by the equipment exceeds the safe bearing capacity of the material, instantaneous plastic collapse may occur, such as container bulging or pipe rupture. Therefore, the Level 2 evaluation is deemed unsuccessful. The Level 3 evaluation criteria are used to determine whether to proceed to the Level 3 evaluation for a more accurate assessment of whether the component can continue to serve. If the Level 3 evaluation criteria are not met, the results of repairing or replacing the component or retiring it are output.

[0153] When σ ref ≤σ pys At that time, it was considered that the possibility of instantaneous plastic collapse was small, so the process of calculating total creep damage was initiated. The evaluation principal stress, evaluation temperature, and material type were extracted, and the creep damage rate corresponding to this combination was obtained from the damage curve of the corresponding material. Combined with time, the total creep damage was calculated using the total creep damage formula, and then the allowable value of total creep damage was set. and The allowable value for creep damage is usually a conservative threshold determined based on material safety margins and equipment risk levels. It needs to be set by professional assessors according to the actual situation. For example, based on engineering practice and industry conventions, the allowable value for total creep damage is usually limited to 0.2 to 0.6, and can be set to 0.5. At this point, based on the evaluation temperature, evaluation principal stress, and material type, the creep damage rate is obtained through the damage curve, and the difference between the current total creep damage and the allowable total creep damage value is calculated:

[0154]

[0155] In the formula, ΔD represents the difference between the current total creep damage and the allowable total creep damage value. This represents the total creep damage tolerance value, and this difference directly quantifies the damage margin that the equipment can still withstand.

[0156] The remaining service life is calculated based on the difference between total creep damage and the allowable total creep damage value, and the creep damage rate.

[0157]

[0158] In the formula, t rem This indicates the remaining service life. This evaluation, once passed, outputs the results of continued service and remaining service life.

[0159] when At that time, it was considered that the "remaining damage space" of the equipment had been exhausted, and damage jumps may occur due to sudden fluctuations in operating conditions, such as short-term high temperature and high pressure, which could directly lead to failure, crack propagation, leakage, etc. Therefore, this evaluation was deemed unsuccessful, and the result was output as repair, replacement or decommissioning of the component. Table 2 shows the output table of the Level 2 evaluation results. Among the operating conditions that passed the plastic collapse judgment, that is, the operating conditions where the single reference stress is lower than the plastic collapse judgment criterion, 10 were judged to fail the Level 2 evaluation because the total creep damage was greater than 0.5. This reflects that even if plastic collapse does not occur in the short term, the long-term creep damage accumulation will exceed the safe value. For example, the total damage of serial number 3, 0.52 > 0.5, was judged to fail, avoiding the risk of failure due to gradual deterioration, and subsequently determining whether to enter the Level 3 evaluation.

[0160] Table 2. Level 2 Evaluation Result Output Table

[0161]

[0162]

[0163] Step 5: In the Level 3 evaluation, stress calculation is performed using the finite element method. The evaluation procedure is the same as that for Level 2 evaluation, and components with crack-like defects are directly judged as failing the evaluation.

[0164] In Level 3 evaluation, if a component has crack-like defects, the evaluation is directly deemed unsuccessful. This is because crack-like defects have irreversible risk amplification characteristics under high-temperature creep conditions. For example, the stress concentration factor at the crack tip can be 5-10 times higher. The crack propagation rate is affected by multiple factors such as temperature, stress, crack length, and material microstructure, making it difficult to predict accurately even through finite element analysis. The risk of continued service far exceeds the controllable range of the evaluation system. Therefore, the result is directly output as repair, replacement, or decommissioning of the component to avoid catastrophic accidents due to evaluation errors. If the component has no crack-like defects, the maximum operating temperature under each operating condition is selected. Temperature is used as the evaluation temperature, and the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure to ensure that the evaluation results are conservative. Finite element analysis simulates the geometric shape of defects through mesh subdivision. Therefore, stress calculation is performed on the model using finite element analysis software such as ANSYS to obtain the triaxial principal stress at the weakest point of each defect. The equivalent stress is selected as the evaluation principal stress. For equipment containing defects, the triaxial stress difference at the defect is usually much greater than that of the base material. For example, the circumferential stress at the depression is much higher than the axial stress. Using the equivalent stress, which reflects the triaxial stress difference, can more realistically reflect the creep risk at the defect. The formula used to calculate the equivalent stress is:

[0165]

[0166] The maximum value is selected from the equivalent stress at the weakest point of all defects as the evaluation principal stress for Level 3 evaluation, so that the risk of the weakest point is also fully assessed. The damage curve of the corresponding material is selected according to the evaluation temperature, evaluation principal stress and material type of the component to obtain the creep damage rate. Combined with the service time of each operating condition, the total creep damage is calculated by the total creep damage formula.

[0167] Calculating the primary reference stress, Level 3 evaluation targets equipment with complex defects such as bulges and dents, but no cracks. These devices experience localized stress concentration due to these defects. More accurate stress calculations avoid misjudgments caused by simplified models or approximate calculations. In this case, the primary reference stress is compared with the plastic collapse judgment criterion. If σ... ref >σ pys This indicates that the stress at the defect has exceeded the material's safe bearing capacity threshold, which may lead to sudden collapse. The evaluation is deemed a Level 3 failure, and the result is that the component should be repaired, replaced, or decommissioned.

[0168] If σ ref ≤σ pys It was considered that the possibility of instantaneous plastic collapse was small. Subsequently, the total creep damage calculated in the Level 3 assessment was compared with the preset allowable value for total creep damage. If the total creep damage has not yet reached the conservative threshold, the component can continue to be used.

[0169] Based on the evaluation temperature, evaluation principal stress, and material type, the creep damage rate is obtained through the damage curve, and the difference between the current total creep damage and the allowable total creep damage value is calculated:

[0170]

[0171] In the formula, ΔD represents the difference between the current total creep damage and the allowable total creep damage value. This indicates the allowable total creep damage value;

[0172] The remaining service life is calculated based on the difference between total creep damage and the allowable total creep damage value, and the creep damage rate.

[0173]

[0174] This evaluation is passed and outputs the results of continued service and remaining service life;

[0175] when When the total creep damage exceeds the conservative threshold, it indicates that microscopic void connections, severe grain boundary weakening, or other issues may have occurred. Continued service may lead to damage jumps due to minor fluctuations in operating conditions. In this case, the evaluation is deemed unsuccessful, and the result is output as either repair / replacement or decommissioning of the component. Table 3 shows the output of the Level 3 evaluation results. For components with complex defects, such as bulges or dents but no fatal cracks, finite element analysis is used to determine whether the component should continue to serve. After excluding crack-type defects, items 6 and 40 fail because the primary reference stress exceeds the plastic collapse criterion. In operating conditions where the primary reference stress is lower than the plastic collapse criterion, some fail the Level 3 evaluation because the total creep damage is greater than 0.3. This compensates for the limitations of the first two levels of evaluation in assessing complex defects. Overall, the evaluation is progressively graded into Levels 1, 2, and 3, ultimately achieving a balance between rapid identification of low-risk equipment and refined analysis. The evaluation of creep service safety of petrochemical equipment is more efficient and accurate.

[0176] Table 3 Output Table of Level 3 Evaluation Results

[0177]

[0178]

[0179] like Figure 3 The diagram shows the creep grading evaluation flowchart for petrochemical equipment. It realizes a system of graded screening, progressive evaluation, and precise analysis, and finally outputs the result of whether to continue service or repair and replace. Users only need to input temperature, pressure, service time, and material properties to quickly review whether most components have passed the Level 1 evaluation. No complicated analysis and calculation are required. Only components with higher risks will enter the subsequent evaluations, which is adapted to the evaluation process from simple to complex.

[0180] Please see Figure 4 The present invention also provides a creep service safety evaluation system for petrochemical equipment, used to perform the above-mentioned creep service safety evaluation method for petrochemical equipment, comprising:

[0181] The evaluation selection module is used to set the constraints for Level 1, 2, and 3 evaluations based on the component's load fluctuation amplitude, material performance indicators, and service defect type. The component is evaluated by determining whether it meets the constraints of the corresponding level of evaluation.

[0182] The process construction module is used to select a process based on the evaluation level 1, 2 or 3. The process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time.

[0183] The Level 1 evaluation module is used in Level 1 evaluation. It sets the total creep damage threshold and obtains the maximum operating time of the component based on the evaluation temperature and evaluation calculation pressure extracted in step 2 under a single operating condition. If it is higher than the service time, the evaluation is passed; otherwise, it enters the total creep damage calculation process. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, it is determined whether to enter Level 2 or Level 3 evaluation based on the limitations of each evaluation.

[0184] The Level 2 evaluation module is used in Level 2 evaluation. It calculates the primary reference stress using classical formulas of elasticity and constructs a plastic collapse judgment criterion based on the material type. If the primary reference stress is greater than the plastic collapse judgment criterion, the evaluation is deemed to fail. It then determines whether to proceed to Level 3 evaluation based on the constraints of each evaluation. If the stress is lower than the plastic collapse judgment criterion, the evaluation is deemed to pass and proceed to the calculation of total creep damage. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, it proceeds to Level 3 evaluation.

[0185] The Level 3 evaluation module is used in Level 3 evaluation. It uses finite element method for stress calculation and the evaluation procedure is the same as that of Level 2 evaluation. Components with crack-like defects are directly judged as failing the evaluation.

[0186] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0187] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0188] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0189] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating the creep service safety of petrochemical equipment, characterized in that, The specific steps include: Based on the load fluctuation amplitude, material performance indicators, and service defect types of components, the constraints for Level 1, 2, and 3 evaluations are set; the components are evaluated by determining whether they meet the constraints of the corresponding level of evaluation. According to the evaluation selection process of level 1, 2 or 3, the process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time. In Level 1 evaluation, a total creep damage threshold is set. Under a single operating condition, the maximum operating time of the component is obtained by extracting the evaluation temperature and evaluation calculation pressure in step 2. If it is higher than the service time, the evaluation is passed; otherwise, the process of calculating total creep damage is entered. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, the process of entering Level 2 or Level 3 evaluation is determined according to the limitations of each evaluation. In the Level 2 evaluation, a primary reference stress is calculated using classical formulas of elasticity. A plastic collapse criterion is constructed based on the material type. If the primary reference stress is greater than the plastic collapse criterion, the evaluation is deemed to fail. The evaluation is then judged to proceed to Level 3 based on the constraints of each evaluation. If the stress is lower than the plastic collapse criterion, the evaluation is deemed to pass and proceed to the calculation of total creep damage. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, the evaluation proceeds to Level 3. In the Level 3 evaluation, stress calculation is performed using the finite element method. The evaluation procedure is the same as that of the Level 2 evaluation, and components with crack-like defects are directly judged to fail the evaluation. The load fluctuation amplitude includes pressure fluctuation amplitude and temperature fluctuation amplitude. Material performance indicators include minimum Brinell hardness and carbon content. Component defects and damage include localized thinning, trenching, pitting corrosion; hydrogen bulging, hydrogen-induced cracking, stress-directed hydrogen-induced cracking, stress corrosion cracking; out-of-roundness, bulging, depressions, or recessed grooves exceeding the standard; crack-like defects; microstructural abnormalities such as high-temperature hydrogen corrosion or severe graphitization; and no obvious deformation of the component due to fire or overheating. Professional assessors will determine whether the component has the aforementioned defects and damage. Record the load fluctuation amplitude during operation, extract the maximum pressure, minimum pressure, maximum temperature, and minimum temperature experienced by the component during operation, and calculate the pressure fluctuation amplitude: In the formula, Indicates the amplitude of pressure fluctuation. Indicates maximum pressure. Indicates minimum pressure. Indicates design pressure; Calculation of temperature fluctuation amplitude: In the formula, Indicates the amplitude of temperature fluctuation. Indicates the maximum temperature. Indicates the minimum temperature; when or Furthermore, if two or more periodic changes occur during the operating time, the component is deemed to be subject to cyclic load; for material performance testing, a minimum Brinell hardness value is set. The specified carbon content is Inspect the service defect types of the components to determine whether the aforementioned defects and damages exist; When a component's original design meets the relevant specifications or standards, does not bear cyclic loads, its material performance indicators exceed the specified values, and the service defect type does not contain the aforementioned defects and damages, it is judged to meet the Level 1 evaluation constraint conditions; when a component's original design meets the relevant specifications or standards, does not bear cyclic loads, and the service defect type does not contain the aforementioned defects and damages, the component's operating condition history is recorded, and its future operating conditions are known, it is judged to meet the Level 2 evaluation constraint conditions; when it bears cyclic loads, and the crack-type defects do not include stress corrosion cracking, it is judged to meet the Level 3 evaluation constraint conditions.

2. The method for evaluating the creep service safety of petrochemical equipment according to claim 1, characterized in that: The method for determining the corrections for evaluation calculation pressure, service time, and evaluation temperature is as follows: In Level 1 evaluation, the actual operating temperature of the component under a single operating condition or the actual operating temperature of each operating condition under multiple operating conditions is used as the evaluation temperature. If there is a load-bearing weld in the component and the weld direction is perpendicular to the direction of the maximum principal stress controlling the calculated wall thickness, 14℃ should be added to the actual operating temperature as the evaluation temperature. The actual operating pressure of a component under a single operating condition, or the actual operating pressure of each operating condition under multiple operating conditions, is used as the evaluation calculation pressure. The total past operating time and the planned future operating time under the current operating condition are used as the service time of the operating condition. For historical operating conditions that are not currently in use, the service time is only the cumulative operating time of the operating condition in the historical period. In the Level 2 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure, and the past operating time and the future planned operating time are taken as the service time. In the Level 3 evaluation, the maximum operating temperature under each operating condition is selected as the evaluation temperature, the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure, and the past operating time and the future planned operating time are taken as the service time.

3. The method for evaluating the creep service safety of petrochemical equipment according to claim 2, characterized in that: The method for calculating the triaxial principal stress by evaluating the pressure and selecting the evaluation principal stress, and then screening the corresponding material's screening curve and damage curve, is as follows: In Level 1 evaluation, the location with the most severe wall thinning is selected as the evaluation principal stress based on the triaxial principal stress. Based on the actual structure of the component, the triaxial principal stress is calculated using the corresponding mechanical formulas based on the evaluation calculation pressure and wall thickness. The maximum principal stress is then selected as the evaluation principal stress. In the formula, Indicates the maximum principal stress. Indicates the triaxial principal stress; In the Level 2 evaluation, the location with the most severe wall thinning is selected as the evaluation principal stress based on the triaxial principal stress. Based on the actual structure of the component, the triaxial principal stress is calculated using the corresponding mechanical formula, and the equivalent stress is selected as the evaluation principal stress. The formula used to calculate the equivalent stress is as follows: In the formula, Indicates equivalent stress; In the Level 3 evaluation, a finite element model is established, and the equivalent stress is calculated at the weakest point of each defect according to the same rules as in the Level 2 evaluation. The maximum value is then used as the principal stress for evaluation. According to the creep test method specified in GB / T 35013-2018, the creep performance of the above materials was tested under different temperatures and stress conditions, and the creep fracture time and creep damage rate data corresponding to each temperature-stress combination were obtained. Using temperature as the x-axis and stress as the y-axis, the maximum operating time of the same material under different temperature-stress combinations is fitted to form a continuous curve as a screening curve. With temperature as the x-axis and stress as the y-axis, the creep damage rate of the same material under different temperature-stress combinations is fitted to form a continuous curve as the damage curve. Based on the material type of the component, the corresponding material type screening curve and damage curve are matched in the material database. The maximum running time is the safe threshold for creep fracture time, and the creep damage rate is the damage increment per unit time.

4. The method for evaluating the creep service safety of petrochemical equipment according to claim 3, characterized in that: The method for determining the maximum operating time based on the screening curve, the creep damage rate based on the damage curve, and calculating the total creep damage by combining the service time is as follows: In Level 1 evaluation, the principal stress, evaluation temperature, and material type are extracted. The maximum operating time corresponding to the combination is obtained from the screening curve of the corresponding material, and the creep damage rate of the combination is obtained from the damage curve of the corresponding material. Combined with the service time, the total creep damage formula is constructed: In the formula, Indicates total creep damage. Indicates the first Creep damage rate under each operating condition Indicates the first Service life under various operating conditions A positive integer greater than 0, representing the index of the operating condition. When the component has a single operating condition, When the component operates under multiple conditions, , Indicates the total number of operating conditions; In the Level 2 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining time with the total creep damage formula. In the Level 3 evaluation, the evaluation principal stress, evaluation temperature and material type are extracted, the creep damage rate corresponding to the combination is obtained from the damage curve of the corresponding material, and the total creep damage is calculated by combining time with the total creep damage formula.

5. The method for evaluating the creep service safety of petrochemical equipment according to claim 3, characterized in that: In Level 1 evaluation, a total creep damage threshold is set. The method for obtaining the maximum operating time of the component under a single operating condition, based on the evaluation temperature and evaluation calculation pressure extracted in step 2, is as follows: Set total creep damage threshold In a single operating condition, the maximum operating time is obtained through the corresponding screening curve based on the component's evaluation temperature, evaluation principal stress, and material type.

6. The method for evaluating the creep service safety of petrochemical equipment according to claim 1, characterized in that: The method for constructing plastic collapse judgment criteria based on material type is as follows: In the formula, This indicates the criteria for determining plastic collapse. This indicates the yield strength corresponding to the type of material.

7. The method for evaluating the creep service safety of petrochemical equipment according to claim 4, characterized in that: In Level 3 evaluation, the finite element method is used for stress calculation as follows: A finite element model incorporating service defects is established for the component, ensuring the model matches the actual state of the component. The maximum operating temperature under each operating condition is selected as the evaluation temperature, and the maximum operating pressure under each operating condition is selected as the evaluation calculation pressure. The evaluation temperature and evaluation calculation pressure are applied to the finite element model as thermal and force boundary conditions, respectively. The triaxial principal stress is obtained at the weakest point of each defect. The primary reference stress is calculated using classical formulas of elasticity, and the equivalent stress is calculated using the equivalent stress formula. If the primary reference stress exceeds the plastic collapse criterion, the evaluation is deemed unsuccessful; otherwise, the equivalent stress is used as the evaluation principal stress. Combining the evaluation temperature and material type, the creep damage rate corresponding to this combination is obtained from the damage curve of the corresponding material. The total creep damage is calculated using the total creep damage formula, combined with time. If the total creep damage is lower than a preset allowable value, the evaluation is deemed successful; otherwise, the evaluation is deemed unsuccessful.

8. A creep service safety evaluation system for petrochemical equipment, characterized in that: The system is used to perform a creep service safety evaluation method for petrochemical equipment as described in any one of claims 1-7: The evaluation selection module is used to set the constraints for Level 1, 2, and 3 evaluations based on the component's load fluctuation amplitude, material performance indicators, and service defect type. The component is evaluated by determining whether it meets the constraints of the corresponding level of evaluation. The process construction module is used to select a process based on the evaluation level 1, 2 or 3. The process includes determining the evaluation calculation pressure, service time and evaluation temperature correction, calculating the triaxial principal stress through the evaluation calculation pressure and selecting the evaluation principal stress, screening the screening curve and damage curve of the corresponding material, determining the maximum running time based on the screening curve, determining the creep damage rate based on the damage curve, and calculating the total creep damage in combination with the service time. The Level 1 evaluation module is used in Level 1 evaluation. It sets the total creep damage threshold and obtains the maximum operating time of the component based on the evaluation temperature and evaluation calculation pressure extracted in step 2 under a single operating condition. If it is higher than the service time, the evaluation is passed; otherwise, it enters the total creep damage calculation process. When the total creep damage is lower than the total creep damage threshold, the evaluation is passed. Otherwise, it is determined whether to enter Level 2 or Level 3 evaluation based on the limitations of each evaluation. The Level 2 evaluation module is used in Level 2 evaluation. It calculates the primary reference stress using classical formulas of elasticity and constructs a plastic collapse judgment criterion based on the material type. If the primary reference stress is greater than the plastic collapse judgment criterion, the evaluation is deemed to fail. It then determines whether to proceed to Level 3 evaluation based on the constraints of each evaluation. If the stress is lower than the plastic collapse judgment criterion, the evaluation is deemed to pass and proceed to the calculation of total creep damage. If the total creep damage is lower than the preset allowable value, the Level 2 evaluation is deemed to pass; otherwise, it proceeds to Level 3 evaluation. The Level 3 evaluation module is used in Level 3 evaluation. It uses finite element method for stress calculation and the evaluation procedure is the same as that of Level 2 evaluation. Components with crack-like defects are directly judged as failing the evaluation.

Images