N. Kasahara, T. Wakai, Izumi Nakamura, Takuya Sato, M. Ichimiya
As a lesson learned from the Fukushima nuclear power plant accident, the industry recognized the imporatance of mitigating accident consequences after Beyond Design Basis Events (BDBE). We propose the concept of applying fracture control to mitigate failure consequences of nuclear components under BDBE. Requirements are different between Design Basis Events (DBE) and BDBE. In the case of DBE, it requires preventing occurrence of failures, and thus, its structural approach is strengthening. On the other hand, BDBE requires mitigating failure consequences. The simple strengthening approach with DBE is inappropriate for this BDBE requirement. As the structural strengthening approach for mitigating failure consequences, we propose applying the concept of fracture control. The fundamental idea is to control the sequence of failure locations and modes. Preceding failures release loadings and prevent further catastrophic consequent failures. At the end, locations and modes of failure are limited. Absolute strength evaluation for each failure mode is not easy especially for BDBE. Fracture control, however, requires only relative strength evaluation among different locations and failure modes. Our paper discusses two sample applications of our proposed method. One is a fast reactor vessel under severe accident conditions. Our method controls the upper part of a vessel above the liquid coolant surface weaker than the lower part. This strength control maintains enough coolant even after a high pressure and high temperature condition causes failure of the reactor vessel because structural failure in the upper part releases internal pressure to protect the lower part. The other example is the piping under a large earthquake. Our proposal controls strength of supports weaker than the piping itself. When the supports fail first, natural frequencies of piping systems drop. When the natural frequencies of dominant modes are lower than the peak frequency of seismic loads, seismic loads hardly transfer to the piping and catastrophic failures such as collapse or break are avoided.
{"title":"Application of Fracture Control to Mitigate Failure Consequence Under BDBE","authors":"N. Kasahara, T. Wakai, Izumi Nakamura, Takuya Sato, M. Ichimiya","doi":"10.1115/pvp2020-21072","DOIUrl":"https://doi.org/10.1115/pvp2020-21072","url":null,"abstract":"\u0000 As a lesson learned from the Fukushima nuclear power plant accident, the industry recognized the imporatance of mitigating accident consequences after Beyond Design Basis Events (BDBE). We propose the concept of applying fracture control to mitigate failure consequences of nuclear components under BDBE.\u0000 Requirements are different between Design Basis Events (DBE) and BDBE. In the case of DBE, it requires preventing occurrence of failures, and thus, its structural approach is strengthening. On the other hand, BDBE requires mitigating failure consequences. The simple strengthening approach with DBE is inappropriate for this BDBE requirement.\u0000 As the structural strengthening approach for mitigating failure consequences, we propose applying the concept of fracture control. The fundamental idea is to control the sequence of failure locations and modes. Preceding failures release loadings and prevent further catastrophic consequent failures. At the end, locations and modes of failure are limited.\u0000 Absolute strength evaluation for each failure mode is not easy especially for BDBE. Fracture control, however, requires only relative strength evaluation among different locations and failure modes.\u0000 Our paper discusses two sample applications of our proposed method. One is a fast reactor vessel under severe accident conditions. Our method controls the upper part of a vessel above the liquid coolant surface weaker than the lower part. This strength control maintains enough coolant even after a high pressure and high temperature condition causes failure of the reactor vessel because structural failure in the upper part releases internal pressure to protect the lower part.\u0000 The other example is the piping under a large earthquake. Our proposal controls strength of supports weaker than the piping itself. When the supports fail first, natural frequencies of piping systems drop. When the natural frequencies of dominant modes are lower than the peak frequency of seismic loads, seismic loads hardly transfer to the piping and catastrophic failures such as collapse or break are avoided.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128073950","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}
Engineering critical structures, such as pressure vessels and pipelines, are designed to withstand a variety of in-service loading specific to their intended application. Random vibration excitation is observed in most of the structural component applications in the offshore, aerospace, and nuclear industry. Likewise, fatigue life estimation for such components is fundamental to verify the design robustness assuring structural integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still largely used for damage assessment on fatigue estimations, even though, its limitations are well-known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects, and trans-granular crack propagation are hardly predicted, indicates that a probabilistic characterization of the material behavior is needed. In this work, the methodology was applied to a Titanium alloy structural component. Low alloyed titanium alloys have no tendency to corrosion cracking in high-temperature high-pressure water containing impurities of chloride and oxygen found in a steam generator of nuclear power plants. The inherent uncertainties of the fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL) statistic method. Furthermore, a frequency domain technique is used to determine the response power spectrum density (PSD) function of a structural component subjected to a random vibration profile excitation. The fatigue life of the component is then estimated through a probabilistic linear damage cumulative model.
{"title":"Fatigue Life Estimation Using Frequency Domain Technique and Probabilistic Linear Cumulative Damage Model","authors":"Vagner Pascualinotto Junior, D. Burgos","doi":"10.1115/pvp2020-21536","DOIUrl":"https://doi.org/10.1115/pvp2020-21536","url":null,"abstract":"Engineering critical structures, such as pressure vessels and pipelines, are designed to withstand a variety of in-service loading specific to their intended application. Random vibration excitation is observed in most of the structural component applications in the offshore, aerospace, and nuclear industry. Likewise, fatigue life estimation for such components is fundamental to verify the design robustness assuring structural integrity throughout service. The linear damage accumulation model (Palmgren-Miner rule) is still largely used for damage assessment on fatigue estimations, even though, its limitations are well-known. The fact that fatigue behavior of materials exposed to cyclic loading is a random phenomenon at any scale of description, at a specimen scale, for example, fatigue initiation sites, inclusions, defects, and trans-granular crack propagation are hardly predicted, indicates that a probabilistic characterization of the material behavior is needed. In this work, the methodology was applied to a Titanium alloy structural component. Low alloyed titanium alloys have no tendency to corrosion cracking in high-temperature high-pressure water containing impurities of chloride and oxygen found in a steam generator of nuclear power plants. The inherent uncertainties of the fatigue life and fatigue strength of the material are characterized using the random fatigue limit (RFL) statistic method. Furthermore, a frequency domain technique is used to determine the response power spectrum density (PSD) function of a structural component subjected to a random vibration profile excitation. The fatigue life of the component is then estimated through a probabilistic linear damage cumulative model.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128195176","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}
Ryunosuke Sasaki, M. Ichimiya, Jinqi Lyu, N. Kasahara
Since the accident at the Fukushima Daiichi power plant, in addition to “design to prevent accidents”, “mitigating the severe accident” has come to be emphasized. Thus, it is necessary to evaluate the actual failure mode under beyond design basis events (BDBEs). In this study, authors focus on the failure mode of piping in nuclear power plants under excessive earthquakes. The piping design of nuclear power plants has been conservative assuming that seismic load acts as load-controlled and the collapse happens by maximum acceleration. However, the test conducted by Electric Power Research Institute (EPRI) confirmed that when excessive vibration load was applied to the piping with the elbow, ratchet deformation occurred with time and eventually collapsed. Unfortunately, this failure mechanism is not clear, so it is highly important to consider the actual failure mode, namely ratchet deformation leading to collapse. Authors tried to clarify the mechanism of ratchet deformation by experiments and analyses of inputting acceleration to a beam simulating piping. According to these results, it is identified that ratchet deformation is likely to occur when the vibration load whose frequency is lower than resonance frequency is applied, and is difficult to occur on the higher frequency area. Hereafter, the ratio of the frequency of vibration load to the natural frequency of beams is referred as “frequency ratio”. In this study, half-cycle vibration load was applied to the beam, and the frequency dependence of the collapse phenomenon was investigated.
{"title":"Frequency Dependency of Beam Collapse due to Vibration Loads","authors":"Ryunosuke Sasaki, M. Ichimiya, Jinqi Lyu, N. Kasahara","doi":"10.1115/pvp2020-21375","DOIUrl":"https://doi.org/10.1115/pvp2020-21375","url":null,"abstract":"\u0000 Since the accident at the Fukushima Daiichi power plant, in addition to “design to prevent accidents”, “mitigating the severe accident” has come to be emphasized. Thus, it is necessary to evaluate the actual failure mode under beyond design basis events (BDBEs). In this study, authors focus on the failure mode of piping in nuclear power plants under excessive earthquakes. The piping design of nuclear power plants has been conservative assuming that seismic load acts as load-controlled and the collapse happens by maximum acceleration. However, the test conducted by Electric Power Research Institute (EPRI) confirmed that when excessive vibration load was applied to the piping with the elbow, ratchet deformation occurred with time and eventually collapsed. Unfortunately, this failure mechanism is not clear, so it is highly important to consider the actual failure mode, namely ratchet deformation leading to collapse. Authors tried to clarify the mechanism of ratchet deformation by experiments and analyses of inputting acceleration to a beam simulating piping. According to these results, it is identified that ratchet deformation is likely to occur when the vibration load whose frequency is lower than resonance frequency is applied, and is difficult to occur on the higher frequency area. Hereafter, the ratio of the frequency of vibration load to the natural frequency of beams is referred as “frequency ratio”. In this study, half-cycle vibration load was applied to the beam, and the frequency dependence of the collapse phenomenon was investigated.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132148984","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}
American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF, Subparagraph NF-3121.11 does not require that thermal stresses in supports be evaluated. Historically, pipe support engineers have not been concerned with thermal stresses of pipe and component supports, but determining material temperature limits and allowable stresses have been a major role in designing and analyzing supports. Thus, heat transfer is often investigated in finding the temperature of pipe supports and parts of pipe supports that are not in direct contact with pipe or pipe components. There are also other Codes and standards that permit a reduction of temperature away from the outer surface of pipe or pipe components. In some but not all cases, Codes and standards explicitly address reduction of temperature for applications of utilizing thermal insulation. Additionally, the temperature distribution is established by specific geometrical parameters and their respective equations for employment by the pipe support engineer. These reductions are explored by utilizing fundamentals of heat transfer. Additionally, steady-state and transient thermal Finite Element Analyses (FEA) are used to establish computational models of simple geometric bodies in a range of atmospheric conditions. The effects of insulation on the thermal distribution are also represented through closed form solutions and FEA. The results of these analyses allow for assessment of, and recommendations for, the treatment of temperature reduction in Codes and standards.
{"title":"A Review of Temperature Reduction Methods in Codes and Standards for Pipe Supports","authors":"A. Mayes, P. Wiseman, Kshitij P. Gawande","doi":"10.1115/pvp2020-21297","DOIUrl":"https://doi.org/10.1115/pvp2020-21297","url":null,"abstract":"\u0000 American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 1, Subsection NF, Subparagraph NF-3121.11 does not require that thermal stresses in supports be evaluated. Historically, pipe support engineers have not been concerned with thermal stresses of pipe and component supports, but determining material temperature limits and allowable stresses have been a major role in designing and analyzing supports. Thus, heat transfer is often investigated in finding the temperature of pipe supports and parts of pipe supports that are not in direct contact with pipe or pipe components. There are also other Codes and standards that permit a reduction of temperature away from the outer surface of pipe or pipe components. In some but not all cases, Codes and standards explicitly address reduction of temperature for applications of utilizing thermal insulation. Additionally, the temperature distribution is established by specific geometrical parameters and their respective equations for employment by the pipe support engineer. These reductions are explored by utilizing fundamentals of heat transfer. Additionally, steady-state and transient thermal Finite Element Analyses (FEA) are used to establish computational models of simple geometric bodies in a range of atmospheric conditions. The effects of insulation on the thermal distribution are also represented through closed form solutions and FEA. The results of these analyses allow for assessment of, and recommendations for, the treatment of temperature reduction in Codes and standards.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116746898","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}
Pressure drop in a radial flow reactor occurs when process flow crosses the packed catalyst bed installed between the two concentric perforated screens during operation. This pressure drop generates the lateral bed stress against the reactor’s perforated screens to shift. The pressure drop will further grow as catalyst attrition increases in production. For an outward radial flow, the pressure drop may exert higher stresses to the outer screen as the packed bed is pushed toward it. An extreme case is when the entire catalyst bed could be pinned to the outer screen of the reactor by enough pressure drop. This could cause the internal components to be overly stressed on the excessive bed load, for which the components might not have been designed adequately. Predicting how radial pressure drop impacts the bed stress and shifts the load distribution is important in preventing mechanical failure during operation. In this study, an analytical model is derived based on Janssen’s theory, a classical semi-empirical granular solid material model, to examine a generic packed catalyst bed in an outward radical flow reactor. A modification to Janssen’s theory is introduced to include pressure drop in order to explore its effects on bed stress and load. The critical condition is derived.
{"title":"On the Study of Packed Catalyst Bed Stresses for Outward Radial Flow Reactors","authors":"D. Zhao, Mingxin Zhao","doi":"10.1115/pvp2020-21611","DOIUrl":"https://doi.org/10.1115/pvp2020-21611","url":null,"abstract":"\u0000 Pressure drop in a radial flow reactor occurs when process flow crosses the packed catalyst bed installed between the two concentric perforated screens during operation. This pressure drop generates the lateral bed stress against the reactor’s perforated screens to shift. The pressure drop will further grow as catalyst attrition increases in production. For an outward radial flow, the pressure drop may exert higher stresses to the outer screen as the packed bed is pushed toward it. An extreme case is when the entire catalyst bed could be pinned to the outer screen of the reactor by enough pressure drop. This could cause the internal components to be overly stressed on the excessive bed load, for which the components might not have been designed adequately. Predicting how radial pressure drop impacts the bed stress and shifts the load distribution is important in preventing mechanical failure during operation. In this study, an analytical model is derived based on Janssen’s theory, a classical semi-empirical granular solid material model, to examine a generic packed catalyst bed in an outward radical flow reactor. A modification to Janssen’s theory is introduced to include pressure drop in order to explore its effects on bed stress and load. The critical condition is derived.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114201998","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}
For new ASME pressure vessel designs that have a design pressure less than 10,000 psi (70 MPa), it is commonly questioned whether Section VIII, Division 1 or Division 2 should be used as the code of construction. Each code offers specific advantages and disadvantages depending on the specific vessel considered. Further complicating the various considerations is the new Mandatory Appendix 46 of Division 1 which allows the design rules of Division 2 to be used for Division 1 designs. With the various options available, determining the best approach can be challenging and is often more complex than only determining which code provides the thinnest wall thickness. This paper attempts to address many of the typical considerations that determine the use of Division 1 or Division 2 as the code of construction. Items to be considered may include administrative burden, certification process, design margins, design rules, and examination and testing requirements. From the considerations presented, specific comparisons are made between the two divisions with notable differences highlighted. Finally, sample evaluations are presented to illustrate the differences between each code of construction for identical design conditions. Also, material and labor estimates are compiled for each case study to provide a realistic comparison of the expected differential cost between the construction codes.
{"title":"General Criteria and Evaluations for the Selection of ASME Section VIII, Division 1 or 2 for New Construction Pressure Vessels","authors":"Nathan Barkley, M. Riley","doi":"10.1115/pvp2020-21602","DOIUrl":"https://doi.org/10.1115/pvp2020-21602","url":null,"abstract":"\u0000 For new ASME pressure vessel designs that have a design pressure less than 10,000 psi (70 MPa), it is commonly questioned whether Section VIII, Division 1 or Division 2 should be used as the code of construction. Each code offers specific advantages and disadvantages depending on the specific vessel considered. Further complicating the various considerations is the new Mandatory Appendix 46 of Division 1 which allows the design rules of Division 2 to be used for Division 1 designs. With the various options available, determining the best approach can be challenging and is often more complex than only determining which code provides the thinnest wall thickness.\u0000 This paper attempts to address many of the typical considerations that determine the use of Division 1 or Division 2 as the code of construction. Items to be considered may include administrative burden, certification process, design margins, design rules, and examination and testing requirements. From the considerations presented, specific comparisons are made between the two divisions with notable differences highlighted. Finally, sample evaluations are presented to illustrate the differences between each code of construction for identical design conditions. Also, material and labor estimates are compiled for each case study to provide a realistic comparison of the expected differential cost between the construction codes.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131640631","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}
Severe vibration is observed at FRP (Glass-Fiber-Reinforced Thermosetting-Resin) bypass line connected to discharge of sea water intake pump which is installed on offshore platform. To find out characteristic of the flow, CFD (Computational fluid dynamics) analysis is conducted, and result shows that it is produced by complex pulsating two phase flow formed by the high speed water jet at the resistance orifice which passes through several elbows. After CFD analysis, the force-time history result from CFD analysis is used in transient structural analysis. Based on the numerical analysis result, mechanical response of the pipe and structure for the initial piping system and reinforced piping system are verified and compared with criteria of Energy Institute guideline and NORSOK S-002. Also in order to demonstrate a validity of the numerical analysis and check soundness of the whole reinforced piping and structure system with vibration, site measurement is performed. Moreover, in order to check the stress level of piping, dynamic strain measurement is undertaken. This paper discusses the details on history of bypass line design to avoid air entrapment not to damage on seawater pump, and how the vibration issue is approached, and finally compared with industry standard for safety. Further, the paper presents the numerical analysis result that makes design modifications implement for bypass piping and structure during a commissioning, and various evaluation method that verify the soundness of piping and structure based on field vibration measurement.
{"title":"Vibration of FRP Bypass Piping of Sea Water Intake System in Offshore Platform","authors":"C. Choi, Y. Chu","doi":"10.1115/pvp2020-21458","DOIUrl":"https://doi.org/10.1115/pvp2020-21458","url":null,"abstract":"\u0000 Severe vibration is observed at FRP (Glass-Fiber-Reinforced Thermosetting-Resin) bypass line connected to discharge of sea water intake pump which is installed on offshore platform. To find out characteristic of the flow, CFD (Computational fluid dynamics) analysis is conducted, and result shows that it is produced by complex pulsating two phase flow formed by the high speed water jet at the resistance orifice which passes through several elbows. After CFD analysis, the force-time history result from CFD analysis is used in transient structural analysis. Based on the numerical analysis result, mechanical response of the pipe and structure for the initial piping system and reinforced piping system are verified and compared with criteria of Energy Institute guideline and NORSOK S-002. Also in order to demonstrate a validity of the numerical analysis and check soundness of the whole reinforced piping and structure system with vibration, site measurement is performed. Moreover, in order to check the stress level of piping, dynamic strain measurement is undertaken.\u0000 This paper discusses the details on history of bypass line design to avoid air entrapment not to damage on seawater pump, and how the vibration issue is approached, and finally compared with industry standard for safety. Further, the paper presents the numerical analysis result that makes design modifications implement for bypass piping and structure during a commissioning, and various evaluation method that verify the soundness of piping and structure based on field vibration measurement.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132528279","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}
In the late 1960s and early 1970s, the researchers of the NG-18 committee at the Battelle Institute in Columbus, Ohio completed a seminal study on the failure pressures of flaws in oil and gas pipelines. One of the key developments was the “log-secant” equation for the assessment of axial crack-like flaws. The model was later modified to improve its accuracy and precision. The Gamma Exponent Model (GEM) was recently developed for assessment of axial crack-like flaws in pipelines. The developer recognized that the NG-18 log-secant model was theoretically derived on length, and then empirically corrected for depth. The new GEM was theoretically derived on depth, and then empirically corrected for length. The new model is similar in mathematical form to the original NG-18 log-secant model, but there are some key differences. This work is a validation study of the GEM using axial crack failure pressure data from the industry literature. Laboratory tests with machined flaws, and hydrotest and in-service failures with natural metallurgical flaws, are also considered. The results of the GEM are compared to the equivalent failure predictions using other models. The strengths and limitations of the new model are discussed in the context of improved accuracy and precision for crack assessments.
{"title":"Validation of the New Gamma Exponent Model for Axial Crack Assessment in Oil and Gas Pipelines","authors":"C. Scott","doi":"10.1115/pvp2020-21003","DOIUrl":"https://doi.org/10.1115/pvp2020-21003","url":null,"abstract":"\u0000 In the late 1960s and early 1970s, the researchers of the NG-18 committee at the Battelle Institute in Columbus, Ohio completed a seminal study on the failure pressures of flaws in oil and gas pipelines. One of the key developments was the “log-secant” equation for the assessment of axial crack-like flaws. The model was later modified to improve its accuracy and precision.\u0000 The Gamma Exponent Model (GEM) was recently developed for assessment of axial crack-like flaws in pipelines. The developer recognized that the NG-18 log-secant model was theoretically derived on length, and then empirically corrected for depth. The new GEM was theoretically derived on depth, and then empirically corrected for length. The new model is similar in mathematical form to the original NG-18 log-secant model, but there are some key differences.\u0000 This work is a validation study of the GEM using axial crack failure pressure data from the industry literature. Laboratory tests with machined flaws, and hydrotest and in-service failures with natural metallurgical flaws, are also considered. The results of the GEM are compared to the equivalent failure predictions using other models. The strengths and limitations of the new model are discussed in the context of improved accuracy and precision for crack assessments.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123715049","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}
G. B. Trinca, Nicola Ronchi, F. Fusari, Emanuele Fiordaligi
Components that are subject to pressure, typical of the pressure vessel industry, can be designed using such calculation methods as “Design by Rule-DBF” or “Design by Analysis-DBA”. DBA, based on the FEM, is used increasingly often because, in addition to providing a reduction in thickness due to the lower uncertainty on the calculation, it helps to verify and study physical phenomena and complex geometry that are otherwise difficult to research while offering a more intuitive usability of the results. In this paper we wish to offer, in an educative and qualitative manner, a general overview of DBA from the creation of the model to obtaining the results, describing the types of analysis that can be carried out according to the constitutive model of the material used and the degree of accuracy that can be achieved. At the end, we cover some case studies in which DBA has been successfully used to verify design or particular conditions (such as heat treatments) for pressure vessels fabrication. The DBA calculation, described in this paper, is used with the same computational methods for high, medium or low pressure components, but it is clear that the most significant reduction in thickness is for high pressure components such as reactors, which is why the DBA calculation is particularly appreciated for this type of equipment. In the context of this paper “high pressure equipment” means when the ratio of the inner diameter to thickness of the walls is < 30.
{"title":"Alternative Design Approach by Finite Element Analysis for High Pressure Equipment","authors":"G. B. Trinca, Nicola Ronchi, F. Fusari, Emanuele Fiordaligi","doi":"10.1115/pvp2020-21540","DOIUrl":"https://doi.org/10.1115/pvp2020-21540","url":null,"abstract":"\u0000 Components that are subject to pressure, typical of the pressure vessel industry, can be designed using such calculation methods as “Design by Rule-DBF” or “Design by Analysis-DBA”. DBA, based on the FEM, is used increasingly often because, in addition to providing a reduction in thickness due to the lower uncertainty on the calculation, it helps to verify and study physical phenomena and complex geometry that are otherwise difficult to research while offering a more intuitive usability of the results. In this paper we wish to offer, in an educative and qualitative manner, a general overview of DBA from the creation of the model to obtaining the results, describing the types of analysis that can be carried out according to the constitutive model of the material used and the degree of accuracy that can be achieved. At the end, we cover some case studies in which DBA has been successfully used to verify design or particular conditions (such as heat treatments) for pressure vessels fabrication. The DBA calculation, described in this paper, is used with the same computational methods for high, medium or low pressure components, but it is clear that the most significant reduction in thickness is for high pressure components such as reactors, which is why the DBA calculation is particularly appreciated for this type of equipment. In the context of this paper “high pressure equipment” means when the ratio of the inner diameter to thickness of the walls is < 30.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115191592","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}
Mixing flow causes fluid temperature fluctuations near the pipe walls and may result in fatigue crack initiation. The authors have previously reported the loading sequence effect on thermal fatigue in a mixing tee. The fatigue damage around the hot spot, which was heated by the hot jet flow from the branch pipe, obtained by Miner’s rule was less than 1.0. Since the strain around the hot spot had waveforms with periodic overload, the loading sequence with periodic overload caused reduction of the fatigue life around the hot spot. In this study, the effect of a single overload on the fatigue crack growth rate was investigated in order to clarify the reduction of the fatigue life at the mixing tee due to strain with periodic overload. In addition, the prediction method of the fatigue life for the variable thermal strain at the mixing tee was discussed. It was shown the crack growth rate increased after an overload for both cases of tensile and compressive overloads. The effective strain amplitude increased after the application of a single overload. The fatigue life curve was modified by considering the increment of the effective strain range. The fatigue damage recalculated using the modified fatigue life curve was larger than 1.0 except in a few cases. The fatigue life could be assessed conservatively for variable strain at the mixing tee using the developed fatigue curve and Miner’s rule.
{"title":"Fatigue Life Prediction for Variable Strain at a Mixing Tee by Use of Effective Strain Amplitude","authors":"K. Miyoshi, M. Kamaya","doi":"10.1115/pvp2020-21127","DOIUrl":"https://doi.org/10.1115/pvp2020-21127","url":null,"abstract":"\u0000 Mixing flow causes fluid temperature fluctuations near the pipe walls and may result in fatigue crack initiation. The authors have previously reported the loading sequence effect on thermal fatigue in a mixing tee. The fatigue damage around the hot spot, which was heated by the hot jet flow from the branch pipe, obtained by Miner’s rule was less than 1.0. Since the strain around the hot spot had waveforms with periodic overload, the loading sequence with periodic overload caused reduction of the fatigue life around the hot spot. In this study, the effect of a single overload on the fatigue crack growth rate was investigated in order to clarify the reduction of the fatigue life at the mixing tee due to strain with periodic overload. In addition, the prediction method of the fatigue life for the variable thermal strain at the mixing tee was discussed. It was shown the crack growth rate increased after an overload for both cases of tensile and compressive overloads. The effective strain amplitude increased after the application of a single overload. The fatigue life curve was modified by considering the increment of the effective strain range. The fatigue damage recalculated using the modified fatigue life curve was larger than 1.0 except in a few cases. The fatigue life could be assessed conservatively for variable strain at the mixing tee using the developed fatigue curve and Miner’s rule.","PeriodicalId":150804,"journal":{"name":"Volume 3: Design and Analysis","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126211621","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}
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