Johannes Becker, C. Richards, Guenter Sundag, Ronald Wittig
A large majority of urban gas distribution pipelines are designed to accommodate future integrity management surveys with in-line inspection (ILI) tools. However, even with typical inspection design parameters considered, many pipelines end up on a “difficult-to-inspect” list and/or fall into a “gray” zone. Often this is due to operational parameters, which may have adverse effects on how in-line inspection technologies perform during a survey. One of these effects may be stop-start behaviors of the tool itself. Although most segments meet minimum technical specifications to conduct ILI surveys, vintage pipeline design practices, such as numerous 1.5D bends, multiple heavy wall transitions, and narrow ID fittings, consistently present ongoing issues when running ILI tools in gas distribution lines. The first assessment characteristically indicates that standard inspection tools are viable solutions for these types of pipelines, but results from previous inspections typically indicate, after the first inspection of the pipeline, that standard technologies should not be applied, or rather, do not deliver satisfactory results. New methodologies and technologies are required to reduce, if not eliminate, the incidents of stationary tools and the resultant areas of degraded data while improving overall data quality. In the end, operators consider these lines a critically important component of their entire system and are keen to gain a clear picture of the assets’ integrity. Suitable in-line inspection solutions are therefore in demand to instill confidence in the assets safe and efficient operation. This paper outlines several elements, including technologies, procedures, or mechanical adaptations, that are often overlooked when selecting and applying inspection and/or cleaning technologies to these gray-zone pipelines. Applying these elements may allow for inspection tools to traverse various obstacles and debris fields encountered while still providing high-resolution data sets. A detailed case study of a NPS 08” pipeline will be used to support the content. This pipeline did not provide the required operational parameters to gather acceptable data when utilizing standard ILI technologies. This NPS 08” line contained various challenges, such as: • Unknown or unreliable pipeline information, specifically for bend radii and wall thicknesses • No previous cleaning and inspection records • Low operational pressures of 1000 to 2100 kPa • Pipeline length over 100 km • MOP restrictions did not allow for higher pressures • Flow rate was only available within limited windows • Cleanliness was unknown and assumed to be a concern • Pipe grade documentation required verification Many technical challenges were encountered in the initial stages of the project. The lessons learned will be discussed and outlined to better support the approach chosen. In the end, tailored geometry and low-friction MFL technologies, capable of safely traversing the pip
{"title":"Improving Data Collection With In-Line Inspection in Low-Pressure Gas Distribution Networks","authors":"Johannes Becker, C. Richards, Guenter Sundag, Ronald Wittig","doi":"10.1115/IPC2020-9481","DOIUrl":"https://doi.org/10.1115/IPC2020-9481","url":null,"abstract":"\u0000 A large majority of urban gas distribution pipelines are designed to accommodate future integrity management surveys with in-line inspection (ILI) tools. However, even with typical inspection design parameters considered, many pipelines end up on a “difficult-to-inspect” list and/or fall into a “gray” zone. Often this is due to operational parameters, which may have adverse effects on how in-line inspection technologies perform during a survey. One of these effects may be stop-start behaviors of the tool itself. Although most segments meet minimum technical specifications to conduct ILI surveys, vintage pipeline design practices, such as numerous 1.5D bends, multiple heavy wall transitions, and narrow ID fittings, consistently present ongoing issues when running ILI tools in gas distribution lines. The first assessment characteristically indicates that standard inspection tools are viable solutions for these types of pipelines, but results from previous inspections typically indicate, after the first inspection of the pipeline, that standard technologies should not be applied, or rather, do not deliver satisfactory results. New methodologies and technologies are required to reduce, if not eliminate, the incidents of stationary tools and the resultant areas of degraded data while improving overall data quality.\u0000 In the end, operators consider these lines a critically important component of their entire system and are keen to gain a clear picture of the assets’ integrity. Suitable in-line inspection solutions are therefore in demand to instill confidence in the assets safe and efficient operation.\u0000 This paper outlines several elements, including technologies, procedures, or mechanical adaptations, that are often overlooked when selecting and applying inspection and/or cleaning technologies to these gray-zone pipelines. Applying these elements may allow for inspection tools to traverse various obstacles and debris fields encountered while still providing high-resolution data sets.\u0000 A detailed case study of a NPS 08” pipeline will be used to support the content. This pipeline did not provide the required operational parameters to gather acceptable data when utilizing standard ILI technologies.\u0000 This NPS 08” line contained various challenges, such as:\u0000 • Unknown or unreliable pipeline information, specifically for bend radii and wall thicknesses\u0000 • No previous cleaning and inspection records\u0000 • Low operational pressures of 1000 to 2100 kPa\u0000 • Pipeline length over 100 km\u0000 • MOP restrictions did not allow for higher pressures\u0000 • Flow rate was only available within limited windows\u0000 • Cleanliness was unknown and assumed to be a concern\u0000 • Pipe grade documentation required verification\u0000 Many technical challenges were encountered in the initial stages of the project. The lessons learned will be discussed and outlined to better support the approach chosen. In the end, tailored geometry and low-friction MFL technologies, capable of safely traversing the pip","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"205 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134130485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ye. A. Petrov, J. Dubuc, Michael H. Murray, T. Edward
Inline inspection data from several runs spanning many years is available for individual pipeline segments, but compilation of this data into a comprehensive picture of pipeline integrity necessarily relies on computational tools. A critical advantage of modern data storage, analysis, and visualization techniques is the relative ease of performing statistical assessments of integrity operations. Data from a single user of OneBridge Solution’s software may comprise over 1,000 in-line inspections (ILI) runs, hundreds of pipe segments, several million aligned anomalies, and thousands of repair records. Automated alignment of ILI data allows a single physical anomaly to be reliably tracked through many years of growth and repeated measurement and then correlated to repair records. We present a study of cases where ILI anomaly measurements warranted a dig operation in which repair actions were either performed or found to be unnecessary. The fraction of dig operations leading to a productive repair varies with the condition triggering the dig and discretionary choices about dig condition parameters. The analysis is done through the exploration of different methods of corrosion growth forecasting in use by operators and how they compare. The measures that have been taken into consideration for the purpose of this study include half-life vs. pit-to-pit where the effectiveness of identifying and mitigating fast-growing anomalies is compared across models. Further exploration of how forecasting and building a dig program based on pit-to-pit alignments and a comprehensive growth model through the advances in data science and machine learning can bring efficiency improvements and an overall reduction in risk. We analyze the relationship between these parameters, ILI measurements, repair-to-dig ratios and the impact on operational spend. We examine whether a reduction in overall inspection frequency and expenses is possible through advanced growth modeling. Ultimately this would provide a more accurate view of long-term operating costs and allow for operators to consider scenarios relating to repair and replacement of assets.
{"title":"Statistical Analysis of Dig Operations Leading to Productive Repairs","authors":"Ye. A. Petrov, J. Dubuc, Michael H. Murray, T. Edward","doi":"10.1115/IPC2020-9493","DOIUrl":"https://doi.org/10.1115/IPC2020-9493","url":null,"abstract":"\u0000 Inline inspection data from several runs spanning many years is available for individual pipeline segments, but compilation of this data into a comprehensive picture of pipeline integrity necessarily relies on computational tools. A critical advantage of modern data storage, analysis, and visualization techniques is the relative ease of performing statistical assessments of integrity operations. Data from a single user of OneBridge Solution’s software may comprise over 1,000 in-line inspections (ILI) runs, hundreds of pipe segments, several million aligned anomalies, and thousands of repair records. Automated alignment of ILI data allows a single physical anomaly to be reliably tracked through many years of growth and repeated measurement and then correlated to repair records.\u0000 We present a study of cases where ILI anomaly measurements warranted a dig operation in which repair actions were either performed or found to be unnecessary. The fraction of dig operations leading to a productive repair varies with the condition triggering the dig and discretionary choices about dig condition parameters. The analysis is done through the exploration of different methods of corrosion growth forecasting in use by operators and how they compare. The measures that have been taken into consideration for the purpose of this study include half-life vs. pit-to-pit where the effectiveness of identifying and mitigating fast-growing anomalies is compared across models. Further exploration of how forecasting and building a dig program based on pit-to-pit alignments and a comprehensive growth model through the advances in data science and machine learning can bring efficiency improvements and an overall reduction in risk.\u0000 We analyze the relationship between these parameters, ILI measurements, repair-to-dig ratios and the impact on operational spend. We examine whether a reduction in overall inspection frequency and expenses is possible through advanced growth modeling. Ultimately this would provide a more accurate view of long-term operating costs and allow for operators to consider scenarios relating to repair and replacement of assets.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124948461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Alexander, J. Rickert, R. Dotson, F. Freitas, S. Slater, Christopher De Leon
Crack management has become a major focus for many gas and liquid transmission pipeline operators. Failures associated with crack-like features have been a concern for both pipe operators and regulatory agencies. As a result, pipeline operators are excavating large numbers of features for not only in-line inspection (ILI) validation purposes, but also to make repairs. Additionally, ILI technologies have advanced significantly in recent years and are identifying an increasing number of features with greater levels of accuracy. With increased data generation, operators are faced with an unprecedented amount of information that requires response prioritization. Because of high levels of conservatism associated with today’s assessment methods, pipeline operators are spending a significant amount of capital excavating crack-like features. There is a need for improved assessment methods that integrates testing simulated / synthetic crack-like features. This paper will provide details on a study funded to systematically generate crack-like features in pipeline materials with the application of cyclic internal pressure loading. Synthetic crack-like features were generated in 12.75-inch × 0.250-inch, Grade X42 pipe material using electronic discharge machining (EDM) to form notches. Notch depths were 10% of the nominal wall thickness and ranged from 1-inch to 3-inches in length. The pipe samples were then pressure cycled to achieve microcracking at the base of each notch. Initial stages of the program involved sectioning features to quantify crack growth levels. Once a systematic process for growing cracks from EDM starter notches had been validated, testing involved cyclic pressure fatigue to failure and burst testing. The advantage with the crack generation methodology used in this study was the ability to generate sharp, crack-like features without altering the microstructure of the pipe material in the vicinity of the feature. Programs such as the one presented in this paper are useful for both generating features in pipeline materials and quantifying behavior of pipeline materials subjected to cyclic pressure and burst loading.
{"title":"Generation and Monitoring of Synthetic Crack-Like Features in Pipeline Materials Using Cyclic Pressure Loading","authors":"C. Alexander, J. Rickert, R. Dotson, F. Freitas, S. Slater, Christopher De Leon","doi":"10.1115/IPC2020-9781","DOIUrl":"https://doi.org/10.1115/IPC2020-9781","url":null,"abstract":"\u0000 Crack management has become a major focus for many gas and liquid transmission pipeline operators. Failures associated with crack-like features have been a concern for both pipe operators and regulatory agencies. As a result, pipeline operators are excavating large numbers of features for not only in-line inspection (ILI) validation purposes, but also to make repairs. Additionally, ILI technologies have advanced significantly in recent years and are identifying an increasing number of features with greater levels of accuracy. With increased data generation, operators are faced with an unprecedented amount of information that requires response prioritization.\u0000 Because of high levels of conservatism associated with today’s assessment methods, pipeline operators are spending a significant amount of capital excavating crack-like features. There is a need for improved assessment methods that integrates testing simulated / synthetic crack-like features. This paper will provide details on a study funded to systematically generate crack-like features in pipeline materials with the application of cyclic internal pressure loading. Synthetic crack-like features were generated in 12.75-inch × 0.250-inch, Grade X42 pipe material using electronic discharge machining (EDM) to form notches. Notch depths were 10% of the nominal wall thickness and ranged from 1-inch to 3-inches in length. The pipe samples were then pressure cycled to achieve microcracking at the base of each notch.\u0000 Initial stages of the program involved sectioning features to quantify crack growth levels. Once a systematic process for growing cracks from EDM starter notches had been validated, testing involved cyclic pressure fatigue to failure and burst testing. The advantage with the crack generation methodology used in this study was the ability to generate sharp, crack-like features without altering the microstructure of the pipe material in the vicinity of the feature. Programs such as the one presented in this paper are useful for both generating features in pipeline materials and quantifying behavior of pipeline materials subjected to cyclic pressure and burst loading.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121165168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is demonstrated potential for failures to occur on station piping assets in facilities, therefore it is critical to take measures to manage preventable releases. In 2018, Enbridge developed a reliability model that uses available asset information to quantify the likelihood of failure of station piping assets. Enbridge based this model on the CFER PIRIMID software, with some modifications to minimize the use of default values and to meet the company’s integrity management program requirements. With successful implementation of station piping model, Enbridge realized opportunity to develop a much-needed flange model leveraging the station piping model. Historical leak data indicates that flanged connections often experience a higher leak frequency than other assets in a facility. While there are industry guidelines that provide guidance for the assembly of process flange connections in a facility, there are few that discuss integrity management of flange connections once they are operational. Most published condition assessment flange models require inputs which are not readily available, e.g. condition of flange faces and gaskets. These inputs often require the flange to be disassembled just to obtain the data. For pipeline operators, data gathering is even more challenging as there are stations (with numerous flanges) that are spread out along the entire pipeline. Given the high number of flange connections and their wide variation in parameters within transmission pipeline facilities, there is benefit in developing a reliability-based model to guide the integrity management of flange connections. A reliability model that works in two stages was developed for this purpose. The pre-inspection assessment stage was designed to utilize available inputs to prioritize groups of flanges for inspection, and the post-inspection assessment (second) stage is then applied to select the specific flanges that require maintenance action. Enbridge utilized industry guidelines, relevant standards, historical failure data, and subject matter experts’ inputs to develop the station piping and flange models. This paper will discuss the design concepts, model architectures, the contributing factors, and their sensitivities to the likelihood of failure results. These concepts may be utilized by any operator managing such assets, and the model designs may be tailored to suit a wide range of facility environments.
{"title":"Integrity Management of Flange Connections Using Reliability Model","authors":"S. Haider, M. Sen, Doug Lawrence, Angela Rodayan","doi":"10.1115/IPC2020-9512","DOIUrl":"https://doi.org/10.1115/IPC2020-9512","url":null,"abstract":"\u0000 There is demonstrated potential for failures to occur on station piping assets in facilities, therefore it is critical to take measures to manage preventable releases. In 2018, Enbridge developed a reliability model that uses available asset information to quantify the likelihood of failure of station piping assets. Enbridge based this model on the CFER PIRIMID software, with some modifications to minimize the use of default values and to meet the company’s integrity management program requirements. With successful implementation of station piping model, Enbridge realized opportunity to develop a much-needed flange model leveraging the station piping model.\u0000 Historical leak data indicates that flanged connections often experience a higher leak frequency than other assets in a facility. While there are industry guidelines that provide guidance for the assembly of process flange connections in a facility, there are few that discuss integrity management of flange connections once they are operational. Most published condition assessment flange models require inputs which are not readily available, e.g. condition of flange faces and gaskets. These inputs often require the flange to be disassembled just to obtain the data. For pipeline operators, data gathering is even more challenging as there are stations (with numerous flanges) that are spread out along the entire pipeline.\u0000 Given the high number of flange connections and their wide variation in parameters within transmission pipeline facilities, there is benefit in developing a reliability-based model to guide the integrity management of flange connections. A reliability model that works in two stages was developed for this purpose. The pre-inspection assessment stage was designed to utilize available inputs to prioritize groups of flanges for inspection, and the post-inspection assessment (second) stage is then applied to select the specific flanges that require maintenance action.\u0000 Enbridge utilized industry guidelines, relevant standards, historical failure data, and subject matter experts’ inputs to develop the station piping and flange models. This paper will discuss the design concepts, model architectures, the contributing factors, and their sensitivities to the likelihood of failure results. These concepts may be utilized by any operator managing such assets, and the model designs may be tailored to suit a wide range of facility environments.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121263331","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Inline Inspection Internal Measurement Unit (ILI IMU) data analysis is a well understood but often under-utilized technology for detecting, defining, assessing and monitoring soil to pipeline interactions. The technology has been successfully used to detect landslide interactions since 1996 [1]. Operators can be provided with a vendor analysis (initial bending strain or run to run movements) and/or processed raw data for either internal or third-party raw data Analysis [2]. Vendor Analysis typically identifies major soil/pipeline interactions but primarily reports dig related settlements [3] and static construction related features. Raw data analysis is typically used to define interactions and provide detailed pipe shapes and deformations within targeted pipeline segments. An approach for determining ILI IMU analysis/data requirements for individual ILI run segments for any size of pipeline system is presented. Guidelines for analysis are provided for Operators to optimize efforts based on the hazards encountered in individual pipelines or pipeline systems. The process includes feature screening, integrity/geotechnical specialist review and risk control/mitigation measures, if required. To facilitate the feature screening process, a classification system for ILI IMU features is presented based on their type, activity and source modified from the system presented in [3].
{"title":"Incorporating Inline Inspection Internal Measurement Unit Data Analysis Into Integrity Management Programs","authors":"Douglas Dewar","doi":"10.1115/IPC2020-9495","DOIUrl":"https://doi.org/10.1115/IPC2020-9495","url":null,"abstract":"\u0000 Inline Inspection Internal Measurement Unit (ILI IMU) data analysis is a well understood but often under-utilized technology for detecting, defining, assessing and monitoring soil to pipeline interactions. The technology has been successfully used to detect landslide interactions since 1996 [1]. Operators can be provided with a vendor analysis (initial bending strain or run to run movements) and/or processed raw data for either internal or third-party raw data Analysis [2]. Vendor Analysis typically identifies major soil/pipeline interactions but primarily reports dig related settlements [3] and static construction related features. Raw data analysis is typically used to define interactions and provide detailed pipe shapes and deformations within targeted pipeline segments.\u0000 An approach for determining ILI IMU analysis/data requirements for individual ILI run segments for any size of pipeline system is presented. Guidelines for analysis are provided for Operators to optimize efforts based on the hazards encountered in individual pipelines or pipeline systems. The process includes feature screening, integrity/geotechnical specialist review and risk control/mitigation measures, if required.\u0000 To facilitate the feature screening process, a classification system for ILI IMU features is presented based on their type, activity and source modified from the system presented in [3].","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116649369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chike Okoloekwe, M. Fowler, A. Virk, N. Yoosef-Ghodsi, Muntaseer Kainat
Dents in a pipe result in alteration of its structural response when subjected to internal pressure. Excavation activities further lead to change in load and boundary conditions of the pipe segment which may exacerbate the stress state within the dented region. Depending on the severity of a dent, excavation under full operating pressure may lead to failure, injuries or fatalities. Although uncommon, an incident has been reported on a gas pipeline where a mechanical damage failed during investigation leading to one death and one injury [10]. While current pipeline regulations require that operators must depressurize a line to ensure safe working conditions during repair activities, there are no detailed provisions available in the codes or standards on how an operator should determine such a safe excavation pressure (SEP). As a result, the safe excavation process of dents has received attention in the industry in recent years. A detailed review of the recent research on dent SEP showed that the current recommendations are primarily dependent on one of two aspects: careful assessment of inline inspection (ILI) data, or a fitness for service (FFS) assessment of the dent feature leveraging numerical models. Enbridge Liquid Pipelines had previously demonstrated a feature specific assessment approach which incorporated both ILI data and finite element analysis (FEA) to determine the SEP. This assessment also accounted for uncertainties associated with material properties and ILI tool measurement. In the previous publication, the authors demonstrated a methodology for assessing the SEP of dents at a conceptual level from both deterministic and reliability-based standpoints. In this paper, a validation study has been performed to compare the results of fracture mechanics based FEA models against ten full scale burst tests available in literature. The study showed good agreement of the burst pressure of dent-crack defects predicted by FEA models with those observed in the full-scale tests. The assessment method is further streamlined by incorporating the API 579 [14] Failure Assessment Diagram (FAD) method on an uncracked FEA model as opposed to explicitly incorporating the crack geometry in the FEA model. The results of FEA in conjunction with FAD are compared with the full-scale tests to ensure accuracy and conservatism of burst pressure prediction. A reliability-based approach is then designed which accounts for the uncertainties associated with the analysis. A case study is presented where the reliability-based SEP assessment method has been implemented and feature specific SEP has been recommended to ensure target reliability during excavation.
{"title":"Reliability-Based Assessment of Safe Excavation Pressure for Dented Pipelines","authors":"Chike Okoloekwe, M. Fowler, A. Virk, N. Yoosef-Ghodsi, Muntaseer Kainat","doi":"10.1115/IPC2020-9399","DOIUrl":"https://doi.org/10.1115/IPC2020-9399","url":null,"abstract":"\u0000 Dents in a pipe result in alteration of its structural response when subjected to internal pressure. Excavation activities further lead to change in load and boundary conditions of the pipe segment which may exacerbate the stress state within the dented region. Depending on the severity of a dent, excavation under full operating pressure may lead to failure, injuries or fatalities. Although uncommon, an incident has been reported on a gas pipeline where a mechanical damage failed during investigation leading to one death and one injury [10]. While current pipeline regulations require that operators must depressurize a line to ensure safe working conditions during repair activities, there are no detailed provisions available in the codes or standards on how an operator should determine such a safe excavation pressure (SEP). As a result, the safe excavation process of dents has received attention in the industry in recent years.\u0000 A detailed review of the recent research on dent SEP showed that the current recommendations are primarily dependent on one of two aspects: careful assessment of inline inspection (ILI) data, or a fitness for service (FFS) assessment of the dent feature leveraging numerical models. Enbridge Liquid Pipelines had previously demonstrated a feature specific assessment approach which incorporated both ILI data and finite element analysis (FEA) to determine the SEP. This assessment also accounted for uncertainties associated with material properties and ILI tool measurement. In the previous publication, the authors demonstrated a methodology for assessing the SEP of dents at a conceptual level from both deterministic and reliability-based standpoints. In this paper, a validation study has been performed to compare the results of fracture mechanics based FEA models against ten full scale burst tests available in literature. The study showed good agreement of the burst pressure of dent-crack defects predicted by FEA models with those observed in the full-scale tests. The assessment method is further streamlined by incorporating the API 579 [14] Failure Assessment Diagram (FAD) method on an uncracked FEA model as opposed to explicitly incorporating the crack geometry in the FEA model. The results of FEA in conjunction with FAD are compared with the full-scale tests to ensure accuracy and conservatism of burst pressure prediction. A reliability-based approach is then designed which accounts for the uncertainties associated with the analysis. A case study is presented where the reliability-based SEP assessment method has been implemented and feature specific SEP has been recommended to ensure target reliability during excavation.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132973892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Steel pipelines undergo the following sequential stages prior to high pH stress corrosion cracking (HpHSCC) failure, viz., formation of environmental condition, initiation of the intergranular cracks followed by cracks coalescence to form critical crack size (Stage I), mechanically dictated crack growth with higher rate (Stage II) compared to Stage I, rapid crack propagation to failure (Stage III). From fracture mechanics perspective, the crack size reaches the critical value at the onset of stage II; consequently, stress intensity factor (K) ahead of the crack tip exceed the critical value (KISCC). Although many researches have been devoted to understanding HpHSCC behavior, the mechanical conditions that accelerate the onset of stage II remains unknown. This study investigates the mechanical loading conditions that yield to early onset of stage II with respect to the most severe loading condition in operating pipeline, underload-minor-cycle type of pressure fluctuation. In this study, several loading scenarios were applied to pre-cracked CT specimens exposed to 1 N NaHCO3-1N Na2CO3 at 40° C and −590 mVSCE. The first series of tests were conducted through applying variable amplitude loading waveforms to determine the K value below the KISCC. It was observed the crack growth rate decreases from 1.5 × 10−7 mm/s to 2.5 × 10−8 mm/s when Kmax decreases from 36 to 15 MPa·m0.5. Then, both constant amplitude and variable amplitude loading scenarios with the Kmax = 15 MPa·m0.5 were applied to pre-cracked CT specimens. It was observed that low R-ratio constant amplitude cycles yield to highest crack growth rate (3.6 × 10−7 mm/s), which was one order of magnitude higher than other waveforms. However, comparing the intergranular crack advancement per block resulted in similar crack growth rates for those waveforms containing low R-ratio cycles. These results imply that stage I of crack growth is assisted by fatigue due to low R-ratio cycles. It was observed that loading/unloading frequency of low R-ratio cycles has a direct relation with crack growth rate at stage I, i.e., high frequency cycles accelerate onset of stage II. The implication of these results for pipeline operator is that pressure fluctuation, particularly large and rapid pressure fluctuation at the sites susceptible to HpHSCC, threatens the pipeline integrity. Avoiding such pressure fluctuations, if possible, increase pipeline lifespan and prevents catastrophic damages by intergranular stress corrosion crack growth through delaying the onset of stage II of HpHSCC crack growth.
{"title":"The Impact of Pressure Fluctuations on the Early Onset of Stage II Growth of High pH Stress Corrosion Crack","authors":"H. Niazi, Hao Zhang, Lyndon Lamborn, Weixing Chen","doi":"10.1115/IPC2020-9511","DOIUrl":"https://doi.org/10.1115/IPC2020-9511","url":null,"abstract":"\u0000 Steel pipelines undergo the following sequential stages prior to high pH stress corrosion cracking (HpHSCC) failure, viz., formation of environmental condition, initiation of the intergranular cracks followed by cracks coalescence to form critical crack size (Stage I), mechanically dictated crack growth with higher rate (Stage II) compared to Stage I, rapid crack propagation to failure (Stage III). From fracture mechanics perspective, the crack size reaches the critical value at the onset of stage II; consequently, stress intensity factor (K) ahead of the crack tip exceed the critical value (KISCC). Although many researches have been devoted to understanding HpHSCC behavior, the mechanical conditions that accelerate the onset of stage II remains unknown. This study investigates the mechanical loading conditions that yield to early onset of stage II with respect to the most severe loading condition in operating pipeline, underload-minor-cycle type of pressure fluctuation. In this study, several loading scenarios were applied to pre-cracked CT specimens exposed to 1 N NaHCO3-1N Na2CO3 at 40° C and −590 mVSCE. The first series of tests were conducted through applying variable amplitude loading waveforms to determine the K value below the KISCC. It was observed the crack growth rate decreases from 1.5 × 10−7 mm/s to 2.5 × 10−8 mm/s when Kmax decreases from 36 to 15 MPa·m0.5. Then, both constant amplitude and variable amplitude loading scenarios with the Kmax = 15 MPa·m0.5 were applied to pre-cracked CT specimens. It was observed that low R-ratio constant amplitude cycles yield to highest crack growth rate (3.6 × 10−7 mm/s), which was one order of magnitude higher than other waveforms. However, comparing the intergranular crack advancement per block resulted in similar crack growth rates for those waveforms containing low R-ratio cycles. These results imply that stage I of crack growth is assisted by fatigue due to low R-ratio cycles. It was observed that loading/unloading frequency of low R-ratio cycles has a direct relation with crack growth rate at stage I, i.e., high frequency cycles accelerate onset of stage II. The implication of these results for pipeline operator is that pressure fluctuation, particularly large and rapid pressure fluctuation at the sites susceptible to HpHSCC, threatens the pipeline integrity. Avoiding such pressure fluctuations, if possible, increase pipeline lifespan and prevents catastrophic damages by intergranular stress corrosion crack growth through delaying the onset of stage II of HpHSCC crack growth.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114594418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents data analytics that demonstrates the safe implementation of defect assessment models which use uncertain measurements of defect and material properties as inputs. Even though this validation is done for a corrosion assessment model implementation, it can be generalized for any defect assessment validation where the inputs have uncertainty (as they do in implementation). The questions arising from the validation of the Plausible Profiles (Psqr) model and related review led to a large amount of data analytics to demonstrate various aspects of safety in implementation. The data analytics demonstrates how the safety of model implementation can be verified using a well-designed set of data. The validation of Psqr model was conducted on a unique set of data consisting of metal-loss corrosion clusters with Inline Inspection (ILI) reported size, laser scan-measured dimension, and well monitored burst testing pressure. Therefore, this validation provided an unprecedented set of validation data that could represent many perspectives, such as model performance (with all uncertainties associated with other parameters removed), in-the-ditch decision scenario, and ILI-based decision scenario. Moreover, the morphologies of the 30 corrosion clusters tested is a good representation of large corrosion clusters that have failed historically in the pipeline industry. One of learnings from post-ILI failures due to corrosion in the industry is that corrosion morphology played a significant role. Previous model validations were mostly performed on simple single anomalies or simple clusters with few individual corrosion anomalies. It is important that a corrosion model is validated using real corrosion morphologies that are representative of in-service conditions. The analysis of this unprecedented and comprehensive set of data led to great learning and revealed how safety can be achieved optimally with good understanding of how uncertainties associated with ILI sizing error, material property, model error, and safety factors interact and play into integrity. It also revealed the role of common misunderstandings that are barriers to effective pipeline integrity assessment. Overcoming these misunderstandings have helped in developing a more effective ILI based corrosion management program that will avoid more failures and reduce unnecessary integrity actions.
{"title":"A Data Driven Validation of a Defect Assessment Model and its Safe Implementation","authors":"S. Kariyawasam, Shenwei Zhang, Jason Yan","doi":"10.1115/IPC2020-9690","DOIUrl":"https://doi.org/10.1115/IPC2020-9690","url":null,"abstract":"\u0000 This paper presents data analytics that demonstrates the safe implementation of defect assessment models which use uncertain measurements of defect and material properties as inputs. Even though this validation is done for a corrosion assessment model implementation, it can be generalized for any defect assessment validation where the inputs have uncertainty (as they do in implementation).\u0000 The questions arising from the validation of the Plausible Profiles (Psqr) model and related review led to a large amount of data analytics to demonstrate various aspects of safety in implementation. The data analytics demonstrates how the safety of model implementation can be verified using a well-designed set of data.\u0000 The validation of Psqr model was conducted on a unique set of data consisting of metal-loss corrosion clusters with Inline Inspection (ILI) reported size, laser scan-measured dimension, and well monitored burst testing pressure. Therefore, this validation provided an unprecedented set of validation data that could represent many perspectives, such as model performance (with all uncertainties associated with other parameters removed), in-the-ditch decision scenario, and ILI-based decision scenario. Moreover, the morphologies of the 30 corrosion clusters tested is a good representation of large corrosion clusters that have failed historically in the pipeline industry. One of learnings from post-ILI failures due to corrosion in the industry is that corrosion morphology played a significant role. Previous model validations were mostly performed on simple single anomalies or simple clusters with few individual corrosion anomalies. It is important that a corrosion model is validated using real corrosion morphologies that are representative of in-service conditions.\u0000 The analysis of this unprecedented and comprehensive set of data led to great learning and revealed how safety can be achieved optimally with good understanding of how uncertainties associated with ILI sizing error, material property, model error, and safety factors interact and play into integrity. It also revealed the role of common misunderstandings that are barriers to effective pipeline integrity assessment. Overcoming these misunderstandings have helped in developing a more effective ILI based corrosion management program that will avoid more failures and reduce unnecessary integrity actions.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114807420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Z. Shirband, Adrian Gosselin, S. Guest, Lee Falcon
For continued safe operation of pipelines, thousands of integrity digs are conducted every year to repair ILI detected defects. Integrity-driven pipeline excavations can be quite costly, present significant scheduling challenges with landowner consultation and seasonal access limitations, and an unmitigated defect may have required a pressure reduction or service outage, resulting in a loss of revenue from the asset. Dents are known to be one of the drivers for many integrity excavations, especially for liquid pipelines. A pipeline with a minimal mechanical deformation is not expected to fail immediately, however, severe pressure cycles combined with the geometric distortion can cause fatigue crack initiation and growth that can lead to failure. To account for the possibility of fatigue failure, recent changes to pipeline codes, such as CSA Z662, are requiring pipeline operators to repair any dent susceptible to fatigue failure unless an engineering assessment proves it is fit for service. A commonly used dent fatigue assessment methodology is outlined in API RP 579, also known as the EPRG-2000 model. The assessment methodology uses an S-N curve from DIN 2413 part 1 with a safety factor of 10, which has been derived from undamaged pressurized pipe sections experiencing pressure cycles with stress ratios of zero, and separate stress enhancement factors for dents and gouges which take into account the shape of dents and gouges. To account for the effect of mean stress, Gerber mean stress correction, which has been developed for pressure cycles with stress ratios of −1 (i.e., for fatigue bar specimens), is also applied on pressure cycles. According to the literature, API 579 Level 2 fatigue assessment methodology results in very conservative estimates of fatigue lives compared to experimental data. This paper will discuss the potential factors resulting in conservative assessments and propose refinements in the methodology. This will include the safety factor used for pipes with known operating pressure fluctuations and the mean stress correction model suitable for a pipeline with pressure cycles that have R ratios greater than zero. The acceptable number of cycles obtained using the proposed refinements were compared to experimental data and EPRG-1995 model’s predictions — the comparison revealed that the proposed methodology results in a more realistic safety margin for dented pipelines. The proposed methodology can be used as a part of engineering assessments in mechanical damage integrity management programs to improve the pipeline operator’s understanding of a dent’s remaining life and enable a more appropriate repair timeline.
为了管道的持续安全运行，每年进行数千次完整性挖掘，以修复ILI发现的缺陷。以完整性为导向的管道挖掘成本相当高，在土地所有者咨询和季节性访问限制方面存在重大的调度挑战，并且未缓解的缺陷可能需要降低压力或中断服务，从而导致资产收入损失。众所周知，凹痕是许多完整性挖掘的驱动因素之一，特别是对于液体管道。机械变形最小的管道不会立即失效，然而，剧烈的压力循环加上几何变形会导致疲劳裂纹的萌生和扩展，从而导致失效。为了考虑疲劳失效的可能性，最近对管道规范(如CSA Z662)进行了修改，要求管道运营商修复任何容易产生疲劳失效的凹痕，除非工程评估证明该凹痕适合使用。API RP 579概述了常用的凹痕疲劳评估方法，也称为EPRG-2000模型。评估方法使用DIN 2413第1部分的S-N曲线，其安全系数为10，该曲线是从经历应力比为零的压力循环的未损坏的加压管段中得出的，并且考虑到凹痕和沟槽的形状，对凹痕和沟槽进行单独的应力增强因子。为了考虑平均应力的影响，已经为应力比为- 1的压力循环(即疲劳杆试样)开发的Gerber平均应力校正也应用于压力循环。根据文献，与实验数据相比，API 579 2级疲劳评估方法对疲劳寿命的估计非常保守。本文将讨论导致保守评估的潜在因素，并提出改进方法。这将包括用于已知工作压力波动的管道的安全系数，以及适用于压力循环R比大于零的管道的平均应力修正模型。使用所提出的改进方法获得的可接受循环次数与实验数据和EPRG-1995模型的预测进行了比较，对比表明，所提出的方法对凹陷管道的安全裕度更为现实。所提出的方法可以作为机械损伤完整性管理项目工程评估的一部分，以提高管道运营商对凹痕剩余寿命的理解，并制定更合适的修复时间表。
{"title":"Pipeline Plain Dent Fatigue Assessment: Shedding Light on the API 579 Level 2 Fatigue Assessment Methodology","authors":"Z. Shirband, Adrian Gosselin, S. Guest, Lee Falcon","doi":"10.1115/IPC2020-9655","DOIUrl":"https://doi.org/10.1115/IPC2020-9655","url":null,"abstract":"\u0000 For continued safe operation of pipelines, thousands of integrity digs are conducted every year to repair ILI detected defects. Integrity-driven pipeline excavations can be quite costly, present significant scheduling challenges with landowner consultation and seasonal access limitations, and an unmitigated defect may have required a pressure reduction or service outage, resulting in a loss of revenue from the asset. Dents are known to be one of the drivers for many integrity excavations, especially for liquid pipelines. A pipeline with a minimal mechanical deformation is not expected to fail immediately, however, severe pressure cycles combined with the geometric distortion can cause fatigue crack initiation and growth that can lead to failure. To account for the possibility of fatigue failure, recent changes to pipeline codes, such as CSA Z662, are requiring pipeline operators to repair any dent susceptible to fatigue failure unless an engineering assessment proves it is fit for service.\u0000 A commonly used dent fatigue assessment methodology is outlined in API RP 579, also known as the EPRG-2000 model. The assessment methodology uses an S-N curve from DIN 2413 part 1 with a safety factor of 10, which has been derived from undamaged pressurized pipe sections experiencing pressure cycles with stress ratios of zero, and separate stress enhancement factors for dents and gouges which take into account the shape of dents and gouges. To account for the effect of mean stress, Gerber mean stress correction, which has been developed for pressure cycles with stress ratios of −1 (i.e., for fatigue bar specimens), is also applied on pressure cycles. According to the literature, API 579 Level 2 fatigue assessment methodology results in very conservative estimates of fatigue lives compared to experimental data. This paper will discuss the potential factors resulting in conservative assessments and propose refinements in the methodology. This will include the safety factor used for pipes with known operating pressure fluctuations and the mean stress correction model suitable for a pipeline with pressure cycles that have R ratios greater than zero. The acceptable number of cycles obtained using the proposed refinements were compared to experimental data and EPRG-1995 model’s predictions — the comparison revealed that the proposed methodology results in a more realistic safety margin for dented pipelines. The proposed methodology can be used as a part of engineering assessments in mechanical damage integrity management programs to improve the pipeline operator’s understanding of a dent’s remaining life and enable a more appropriate repair timeline.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133988905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A full encirclement thin layer steel laminated sleeve system has been designed, developed, and optimized for pipeline integrity management applications. Development goals included the elimination of thixotropic concerns as well as the exclusion of the degradation of material properties of composite repairs. Elimination of cyclical fatigue of welded repairs and safety concerns associated with hot work were also considerations. The use of thin layer steel with a modulus matched to base pipe and steel’s homogenous isotropic properties enable axial calculations and evaluation of strain-based concerns. The thin layer steel laminated design results in extremely high fracture toughness and promotes intrinsic mitigation of potential future third party damage. The resulting system has demonstrated the reliable engineering data and analysis required for pipeline repairs and demonstrates applicability for the augmentation of existing pipes without defects. An Engineering Critical Assessment (ECA) has been completed. This ECA follows the industry’s precedents of ASME B31G and ASME PCC-2 Article 4 type assessments and provides operators with greater functionality. This ECA has been named the Leewis Augmentation Analysis (LAA) and is presented, reviewed, and discussed. Third party full scale ASME PCC-2 style burst testing has been completed. The results are presented. Highly instrumented tests were also conducted to determine an effective modulus of elasticity of the installed system as well as a determination of any delay in system acceptance of load. As installed, an effective modulus of 14 million psig (96526.60 MP)a with loading in layer 3 of the laminate at only 50 micro strain is reviewed. Long term creep and cyclical fatigue testing of the steel/adhesive laminate is presented and reviewed. 10 million cycles at 50% of ultimate lap shear has been achieved, which exceeds current industry practice by several orders of magnitude. The classic metal loss defect mitigation principle is reviewed and updated in light of these available technical advances. Finally, the implications for mitigation of both stress and strain dependent integrity concerns is discussed.
针对管道完整性管理应用，设计、开发并优化了一种全包围薄层钢夹套系统。发展目标包括消除触变问题，以及排除复合材料修复材料性能的退化。消除焊接修复的周期性疲劳以及与热工相关的安全问题也被考虑在内。使用模量与基管相匹配的薄层钢，以及钢的均匀各向同性，可以进行轴向计算和基于应变的评估。薄层钢层压设计具有极高的断裂韧性，并促进了潜在的未来第三方损伤的内在缓解。由此产生的系统证明了管道维修所需的可靠工程数据和分析，并证明了对现有管道进行无缺陷扩建的适用性。工程关键评估(ECA)已经完成。该ECA遵循ASME B31G和ASME pc -2第4条类型评估的行业先例，并为操作员提供更大的功能。该ECA被命名为lelewis增强分析(LAA)，并被提出、审查和讨论。第三方全尺寸ASME PCC-2型爆炸测试已完成。并给出了实验结果。还进行了高度仪器化的测试，以确定安装系统的有效弹性模量，以及确定系统接受负载的任何延迟。安装后，在仅50微应变的层压板第3层中加载时，有效模量为1400万psig (96526.60 MP)a。介绍并评述了钢/胶粘剂层合板的长期蠕变和循环疲劳试验。在50%的极限剪切速率下实现了1000万次循环，超过了目前的工业实践几个数量级。根据这些现有的技术进步，对经典的金属损耗缺陷缓解原理进行了回顾和更新。最后，对应力和应变相关的完整性问题的影响进行了讨论。
{"title":"Full Encirclement Engineered Laminated Steel Sleeve System for Repairs and Augmentation of Pipelines: The Engineering Development, Validation Test Results, and Implications for Mitigation of Both Stress and Strain Dependent Integrity Threats","authors":"S. Laughlin, K. Leewis, C. Alexander","doi":"10.1115/IPC2020-9303","DOIUrl":"https://doi.org/10.1115/IPC2020-9303","url":null,"abstract":"\u0000 A full encirclement thin layer steel laminated sleeve system has been designed, developed, and optimized for pipeline integrity management applications. Development goals included the elimination of thixotropic concerns as well as the exclusion of the degradation of material properties of composite repairs. Elimination of cyclical fatigue of welded repairs and safety concerns associated with hot work were also considerations. The use of thin layer steel with a modulus matched to base pipe and steel’s homogenous isotropic properties enable axial calculations and evaluation of strain-based concerns. The thin layer steel laminated design results in extremely high fracture toughness and promotes intrinsic mitigation of potential future third party damage. The resulting system has demonstrated the reliable engineering data and analysis required for pipeline repairs and demonstrates applicability for the augmentation of existing pipes without defects.\u0000 An Engineering Critical Assessment (ECA) has been completed. This ECA follows the industry’s precedents of ASME B31G and ASME PCC-2 Article 4 type assessments and provides operators with greater functionality. This ECA has been named the Leewis Augmentation Analysis (LAA) and is presented, reviewed, and discussed.\u0000 Third party full scale ASME PCC-2 style burst testing has been completed. The results are presented. Highly instrumented tests were also conducted to determine an effective modulus of elasticity of the installed system as well as a determination of any delay in system acceptance of load. As installed, an effective modulus of 14 million psig (96526.60 MP)a with loading in layer 3 of the laminate at only 50 micro strain is reviewed. Long term creep and cyclical fatigue testing of the steel/adhesive laminate is presented and reviewed. 10 million cycles at 50% of ultimate lap shear has been achieved, which exceeds current industry practice by several orders of magnitude. The classic metal loss defect mitigation principle is reviewed and updated in light of these available technical advances. Finally, the implications for mitigation of both stress and strain dependent integrity concerns is discussed.","PeriodicalId":273758,"journal":{"name":"Volume 1: Pipeline and Facilities Integrity","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130986173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：