In order to gain a better understanding of the detrimental effects of grain boundaries on the creep and fatigue life of a nickel based directionally solidified super alloys, the effect of the grain mis-orientation and temperature changes on the internal stresses were investigated. The changes of cooling rate, nuclei count and stress level and components in different parts of the casting were considered during solidification process in a Bridgeman furnace. During solidification, constriction of grain growth in one direction, which is due to the heat transfer direction, eliminates grains with large mis-orientations. The remaining grains are close to [001] direction. Temperature profile of the modeled carrot samples demonstrated a significant variation in the cooling rate along the axis of the sample. The mis-orientation of the grains was also characterized. Stress components and effective stress were calculated and it was shown that the effective stress is lower than the yield stress of the alloy.
{"title":"Evolution of Temperature, Microstructure and Inter-Granular Stresses During Directionally Solidification Process of a Ni-Based Superalloy","authors":"M. Torfeh, J. Aghazadeh, S. Nakhodchi","doi":"10.1115/PVP2018-85046","DOIUrl":"https://doi.org/10.1115/PVP2018-85046","url":null,"abstract":"In order to gain a better understanding of the detrimental effects of grain boundaries on the creep and fatigue life of a nickel based directionally solidified super alloys, the effect of the grain mis-orientation and temperature changes on the internal stresses were investigated. The changes of cooling rate, nuclei count and stress level and components in different parts of the casting were considered during solidification process in a Bridgeman furnace. During solidification, constriction of grain growth in one direction, which is due to the heat transfer direction, eliminates grains with large mis-orientations. The remaining grains are close to [001] direction. Temperature profile of the modeled carrot samples demonstrated a significant variation in the cooling rate along the axis of the sample. The mis-orientation of the grains was also characterized. Stress components and effective stress were calculated and it was shown that the effective stress is lower than the yield stress of the alloy.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125026208","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}
S. Asada, A. Hirano, Toshiyuki Saito, Yasukazu Takada, Hideo Kobayashi
In order to develop new design fatigue curves for carbon steels & low-alloy steels and austenitic stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). The study on design fatigue curves was actively performed in the subcommittees. In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database (≈6000 data) was constructed and the accurate best-fit curves of carbon steels & low-alloy steels and austenitic stainless steels were developed. Design factors were investigated. Also, a Japanese utility collaborative project performed large scale fatigue tests using austenitic stainless steel piping and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect, surface finish effect and size effect. Those test results were provided to the subcommittee and utilized the above studies. Based on the above studies, a new fatigue evaluation method has been developed.
{"title":"Development of New Design Fatigue Curves in Japan: Proposal of a New Fatigue Evaluation Method","authors":"S. Asada, A. Hirano, Toshiyuki Saito, Yasukazu Takada, Hideo Kobayashi","doi":"10.1115/PVP2018-84432","DOIUrl":"https://doi.org/10.1115/PVP2018-84432","url":null,"abstract":"In order to develop new design fatigue curves for carbon steels & low-alloy steels and austenitic stainless steels and a new design fatigue evaluation method that are rational and have clear design basis, Design Fatigue Curve (DFC) Phase 1 subcommittee and Phase 2 subcommittee were established in the Atomic Energy Research Committee in the Japan Welding Engineering Society (JWES). The study on design fatigue curves was actively performed in the subcommittees.\u0000 In the subcommittees, domestic and foreign fatigue data of small test specimens in air were collected and a comprehensive fatigue database (≈6000 data) was constructed and the accurate best-fit curves of carbon steels & low-alloy steels and austenitic stainless steels were developed. Design factors were investigated. Also, a Japanese utility collaborative project performed large scale fatigue tests using austenitic stainless steel piping and low-alloy steel flat plates as well as fatigue tests using small specimens to obtain not only basic data but also fatigue data of mean stress effect, surface finish effect and size effect. Those test results were provided to the subcommittee and utilized the above studies.\u0000 Based on the above studies, a new fatigue evaluation method has been developed.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"273 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116079329","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}
The current paper examines the effects of corrosion induced wall thinning on buckling of domed closures onto cylindrical vessels. It is assumed that corrosion is axisymmetric and that the wall is corroded on inside, only. The ratio of corroded wall thickness, tc, to the non-corroded thickness, t, is varied between 0.10 ≤ tc/t ≤ 1.0. Both depth of corrosion and its meridional extend are varied during numerical calculations. Three modelling scenarios for placement of corrosion are considered: (i) corrosion confined to the knuckle, (ii) corrosion spanning evenly the knuckle and spherical parts, and (iii) patchtype area positioned at the apex. Numerical results indicate that the following factors influence buckling performance of the dome: (i) meridional position of corroded area, (ii) depth of corrosion itself, and (iii) meridional span of corroded wall. For example, wall thinning of 10 % over 10 % of meridional length causes almost 20 % drop in buckling strength. The largest drop of load carrying capacity is found when the corroded wall is at the knuckle/crown junction. Here it is shown that assessment of strength based on the collapse mechanism is not only wrong but dangerous. For the case of the corroded dome, the collapse pressure overestimates the load carrying capacity associated with asymmetric bifurcation buckling by 40 %.
{"title":"Buckling of Corroded Torispherical Shells Under External Pressure","authors":"J. Błachut","doi":"10.1115/PVP2018-84309","DOIUrl":"https://doi.org/10.1115/PVP2018-84309","url":null,"abstract":"The current paper examines the effects of corrosion induced wall thinning on buckling of domed closures onto cylindrical vessels. It is assumed that corrosion is axisymmetric and that the wall is corroded on inside, only. The ratio of corroded wall thickness, tc, to the non-corroded thickness, t, is varied between 0.10 ≤ tc/t ≤ 1.0. Both depth of corrosion and its meridional extend are varied during numerical calculations. Three modelling scenarios for placement of corrosion are considered: (i) corrosion confined to the knuckle, (ii) corrosion spanning evenly the knuckle and spherical parts, and (iii) patchtype area positioned at the apex. Numerical results indicate that the following factors influence buckling performance of the dome: (i) meridional position of corroded area, (ii) depth of corrosion itself, and (iii) meridional span of corroded wall. For example, wall thinning of 10 % over 10 % of meridional length causes almost 20 % drop in buckling strength. The largest drop of load carrying capacity is found when the corroded wall is at the knuckle/crown junction. Here it is shown that assessment of strength based on the collapse mechanism is not only wrong but dangerous. For the case of the corroded dome, the collapse pressure overestimates the load carrying capacity associated with asymmetric bifurcation buckling by 40 %.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129741477","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}
Boiler tubes experience reductions in wall thickness due to erosion and corrosion mechanisms while in use. Due to this localized thinning, the tube becomes susceptible to gross plastic deformation, which eventually causes the tube to rupture. This study presents a non-linear finite element analysis of different geometric configurations of localized boiler tube defects. A defected boiler tube with three variants of the localized thinned area, having different geometrical shapes (flat, n-shape and u-shape) was modeled and subjected to a simulated internal pressure. The effect of the defect geometrical shapes and their dimensions (shape aspect ratios, defect length, width and depth) on the failure of the tube while in use were investigated. From the numerical results, the stress concentration factors (SCF) associated with each defect were obtained, and it was observed that these play a more significant role than the amount of material removal in influencing the failure of the tubes. This relationship between the SCF and the defect geometry characteristics helps to predict which tube with a localized thinning geometry is safe for continued operation or will fail, and hence to categorize the severity of defects to prioritize maintenance spending. The result of this work will serve as a guide to categorize the severity of external boiler tube defects. This is relevant whenever a constrained economic environment does not allow for all boiler tubes with defects to be replaced.
{"title":"Effect of Defect Geometry of Localized External Erosion on Failure of Boiler Tubes","authors":"I. E. Kalu, H. Inglis, Stanley Kok","doi":"10.1115/PVP2018-84787","DOIUrl":"https://doi.org/10.1115/PVP2018-84787","url":null,"abstract":"Boiler tubes experience reductions in wall thickness due to erosion and corrosion mechanisms while in use. Due to this localized thinning, the tube becomes susceptible to gross plastic deformation, which eventually causes the tube to rupture. This study presents a non-linear finite element analysis of different geometric configurations of localized boiler tube defects. A defected boiler tube with three variants of the localized thinned area, having different geometrical shapes (flat, n-shape and u-shape) was modeled and subjected to a simulated internal pressure. The effect of the defect geometrical shapes and their dimensions (shape aspect ratios, defect length, width and depth) on the failure of the tube while in use were investigated. From the numerical results, the stress concentration factors (SCF) associated with each defect were obtained, and it was observed that these play a more significant role than the amount of material removal in influencing the failure of the tubes. This relationship between the SCF and the defect geometry characteristics helps to predict which tube with a localized thinning geometry is safe for continued operation or will fail, and hence to categorize the severity of defects to prioritize maintenance spending. The result of this work will serve as a guide to categorize the severity of external boiler tube defects. This is relevant whenever a constrained economic environment does not allow for all boiler tubes with defects to be replaced.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126491455","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}
The fracture toughness KJc of the material in the ductile to brittle transition temperature (DBTT) range exhibits both test specimen thickness (TST) dependence and temperature dependence. Attention has been paid to the master curve (MC) method, which provides an engineering approach to address these two issues. Although MC is intended to be applied to arbitrary ferritic material whose yield stress is within the range of 275 to 825 MPa, the KJc value must be obtained to determine the material dependent reference temperature T0. The applicable range of MC method is restricted to T0 ± 50 °C. Previous studies indicate that additional pre-tests to obtain T0 are necessary; thus, there might be some unwritten requirement to the test temperature for the KJc temperature dependence prediction in MC method to work effectively. If testing must be conducted for the material of interest at some restricted temperature, a more flexible KJc temperature dependence prediction can possibly be obtained for a wide temperature range in the DBTT range, if the simplified and direct scaling (SDS) method, which predicts fracture “load” from yield stress temperature dependence proposed previously is applied. In this study, the SDS method was applied to two different steels: Cr-Mo steel JIS SCM440 and 0.55% carbon steel JIS S55C. Both tensile and fracture toughness tests were performed over a wide range of temperatures, specifically, −166 to 100 °C for SCM440 and −166 to 20 °C for S55C. The SDS method (i.e., fracture load is proportional to 1/(yield stress)) was initially validated for the specimens in the DBTT range. Finally, a simplified method was proposed and initially validated to predict the KJc temperature dependence, by applying the SDS using the EPRI plastic J functional form.
{"title":"Prediction of Fracture Toughness Temperature Dependence Over a Wide Temperature Range Using Simplified and Direct Scaling Method","authors":"Takashi Inoue, T. Meshii","doi":"10.1115/PVP2018-84172","DOIUrl":"https://doi.org/10.1115/PVP2018-84172","url":null,"abstract":"The fracture toughness KJc of the material in the ductile to brittle transition temperature (DBTT) range exhibits both test specimen thickness (TST) dependence and temperature dependence. Attention has been paid to the master curve (MC) method, which provides an engineering approach to address these two issues. Although MC is intended to be applied to arbitrary ferritic material whose yield stress is within the range of 275 to 825 MPa, the KJc value must be obtained to determine the material dependent reference temperature T0. The applicable range of MC method is restricted to T0 ± 50 °C. Previous studies indicate that additional pre-tests to obtain T0 are necessary; thus, there might be some unwritten requirement to the test temperature for the KJc temperature dependence prediction in MC method to work effectively. If testing must be conducted for the material of interest at some restricted temperature, a more flexible KJc temperature dependence prediction can possibly be obtained for a wide temperature range in the DBTT range, if the simplified and direct scaling (SDS) method, which predicts fracture “load” from yield stress temperature dependence proposed previously is applied. In this study, the SDS method was applied to two different steels: Cr-Mo steel JIS SCM440 and 0.55% carbon steel JIS S55C. Both tensile and fracture toughness tests were performed over a wide range of temperatures, specifically, −166 to 100 °C for SCM440 and −166 to 20 °C for S55C. The SDS method (i.e., fracture load is proportional to 1/(yield stress)) was initially validated for the specimens in the DBTT range. Finally, a simplified method was proposed and initially validated to predict the KJc temperature dependence, by applying the SDS using the EPRI plastic J functional form.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131732487","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}
Delayed coker drums are unique in hydrocarbon processing facilities in that estimating their true design and service life has been problematic. Generally, pressure containing equipment in these facilities is designed using the notion of design life based on required pressure thickness and corrosion allowance considerations. Hence, pressure containing equipment is routinely monitored by facility inspectors for wall thickness. Although many analysts have ascribed coke drum failure to “thermal stress cycling”, the difficulty posed by the operation of coke drums results in an inability to measure or calculate the magnitude of the thermo-mechanical “stresses” and the actual number of significant exposures, that is, cycles causing fatigue damage. As well, the use of Code construction practices has been generally misapplied, for this specific equipment, as the practices are intended to define a safe design life rather than a service life. Indirect measures of service life based on shell bulge severity have fallen from favor by being ineffective. A trend to use a strain index method is somewhat more appealing but is based on static load and monotonic material property considerations rather than those properties indicative of thermal cyclic operation. Recent work has shown that thermo-mechanical strain cycling can be characterized quantitatively and used to determine a cyclic service life for both undamaged and damaged coke drums. This paper discusses some of the engineering specifics to generate a high probability estimate of coke drum fatigue service life for a new drum, a damaged-stable drum, drums with weld overlay and for drums exhibiting incremental damage.
{"title":"Further Considerations for the Determination of Service Life for Delayed Coker Drums","authors":"John J. Aumuller, Toshiya Yamamoto, Zengtao Chen","doi":"10.1115/PVP2018-84005","DOIUrl":"https://doi.org/10.1115/PVP2018-84005","url":null,"abstract":"Delayed coker drums are unique in hydrocarbon processing facilities in that estimating their true design and service life has been problematic. Generally, pressure containing equipment in these facilities is designed using the notion of design life based on required pressure thickness and corrosion allowance considerations. Hence, pressure containing equipment is routinely monitored by facility inspectors for wall thickness.\u0000 Although many analysts have ascribed coke drum failure to “thermal stress cycling”, the difficulty posed by the operation of coke drums results in an inability to measure or calculate the magnitude of the thermo-mechanical “stresses” and the actual number of significant exposures, that is, cycles causing fatigue damage. As well, the use of Code construction practices has been generally misapplied, for this specific equipment, as the practices are intended to define a safe design life rather than a service life.\u0000 Indirect measures of service life based on shell bulge severity have fallen from favor by being ineffective. A trend to use a strain index method is somewhat more appealing but is based on static load and monotonic material property considerations rather than those properties indicative of thermal cyclic operation.\u0000 Recent work has shown that thermo-mechanical strain cycling can be characterized quantitatively and used to determine a cyclic service life for both undamaged and damaged coke drums. This paper discusses some of the engineering specifics to generate a high probability estimate of coke drum fatigue service life for a new drum, a damaged-stable drum, drums with weld overlay and for drums exhibiting incremental damage.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"154 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122053892","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}
Egler D. Araque, Daryl K. Rutt, Darren Love, Stephen Park, Rick D. Clark, Jason Dawson
The frequency and extent of vessel bulging and cracking being registered in delayed coke drums throughout the global coking industry has accelerated significantly as refinery operators reduce their cycle times. Several theoretical approaches have been developed to identify how a bulged area may lead to drum damage; however, limited information has been presented to match the theoretical predictions with actual surface damage reported by coke drum operators. The results of hundreds of laser scans spanning the last 25 years have been analyzed to correlate vessel bulging with observed surface damage. Specific categorizations of bulge profiles, and the proximity of these to circumferential weld seams (circs), have been calibrated against hundreds of real-world examples of drum damage and failure, including through wall cracking and stress cracking of the cladding, and further associated with the triggers for repair strategies implemented by industry leading refiners. Strong correlations between specific aspects of bulge profiles and the presence of surface damage were found resulting in an assessment tool that can rank and prioritize coke drum distortions on the likelihood of damage, and can serve as a useful guide for planning future coke drum maintenance.
{"title":"Correlating Coke Drum Profiles With Observed Surface Damage","authors":"Egler D. Araque, Daryl K. Rutt, Darren Love, Stephen Park, Rick D. Clark, Jason Dawson","doi":"10.1115/PVP2018-84766","DOIUrl":"https://doi.org/10.1115/PVP2018-84766","url":null,"abstract":"The frequency and extent of vessel bulging and cracking being registered in delayed coke drums throughout the global coking industry has accelerated significantly as refinery operators reduce their cycle times. Several theoretical approaches have been developed to identify how a bulged area may lead to drum damage; however, limited information has been presented to match the theoretical predictions with actual surface damage reported by coke drum operators.\u0000 The results of hundreds of laser scans spanning the last 25 years have been analyzed to correlate vessel bulging with observed surface damage. Specific categorizations of bulge profiles, and the proximity of these to circumferential weld seams (circs), have been calibrated against hundreds of real-world examples of drum damage and failure, including through wall cracking and stress cracking of the cladding, and further associated with the triggers for repair strategies implemented by industry leading refiners.\u0000 Strong correlations between specific aspects of bulge profiles and the presence of surface damage were found resulting in an assessment tool that can rank and prioritize coke drum distortions on the likelihood of damage, and can serve as a useful guide for planning future coke drum maintenance.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129715817","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}
The overall framework for a Level 2 assessment of local thermal hot spot in pressure vessels was first developed by Seshadri [1]. The assessment procedure invokes the concept of integral mean of yield and the concept on a reference volume to determine the reduction of load capacity caused by hot spot damage. This paper investigates the accuracy of this assessment by comparing the results of the Level 2 assessment with a Level 3 assessment (inelastic finite element analysis). Three examples with varying pressure component and hot spot sizes are considered. The comparison yielded a low variance between the Level 2 and Level 3 assessments with the Level 2 assessment being more conservative.
{"title":"Integral Mean of Yield Concept Applied to Thermal Hot Spots: Validation of a Level 2 Damage Assessment Method","authors":"Henry Kwok, Simon Yuen, J. Penso","doi":"10.1115/PVP2018-85068","DOIUrl":"https://doi.org/10.1115/PVP2018-85068","url":null,"abstract":"The overall framework for a Level 2 assessment of local thermal hot spot in pressure vessels was first developed by Seshadri [1]. The assessment procedure invokes the concept of integral mean of yield and the concept on a reference volume to determine the reduction of load capacity caused by hot spot damage. This paper investigates the accuracy of this assessment by comparing the results of the Level 2 assessment with a Level 3 assessment (inelastic finite element analysis). Three examples with varying pressure component and hot spot sizes are considered. The comparison yielded a low variance between the Level 2 and Level 3 assessments with the Level 2 assessment being more conservative.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128494845","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 a failure assessment diagram (FAD) and crack size based comparison of the ASME BVPC Section XI Nonmandatory Appendix C and Nonmandatory Appendix H and the British Standard BS 7910:2013 Option 1 assessment methods. The Section XI appendix C evaluates the acceptability of a flaw by determining the expected failure mechanism and by comparing the flaw size with allowable flaw size limits or by comparing the applied stress to the allowable stress. The Section XI appendix H and BS7910 employ a FAD based approach that simultaneously considers brittle fracture, ductile crack extension prior to reaching the limit load and exceedance of the limit load due to the gross plasticity in the cross section. The assessment is performed by calculating the assessment point coordinates and evaluating whether the point is located on the safe side of the FAD line. The three methods are compared for simplified austenitic and ferritic pipes under internal pressure and bending loads with postulated axial and circumferential internal surface flaws. The methods are applied to generate limiting flaw size diagrams for each component under the specified loads. Additionally, the limiting flaw size results are presented in the FAD plots. To maintain comparability between the results, identical input data are used with each analysis approach but using the method-specific formulae. The performed comparison shows that most often the limiting state is governed by the 75 % flaw depth rule in Section XI article IWB-3640. The largest differences between the methods are observed for cracks with a high length to depth ratio. The difference to the tabulated allowable planar flaws in Article IWB-3514 is typically high. When increasing the applied load to values approaching the limit load, differences in the limiting flaw sizes between the methods are observed, mostly due to the different limit load models and different assumptions on the utilization of the post-yield capacity. Besides the presented flaw size comparison, the paper presents a quick tool suitable for ranking different piping segments based on failure potential and for quick scoping evaluations of indications found in inspections. The case specific scoping tool is a map of yearly flaw size lines providing the information on which flaw sizes would grow to the final limiting size in a specified timeframe.
{"title":"Comparison of ASME XI and BS7910 Allowable Surface Flaw Size Evaluation Procedures in Piping Components","authors":"Juha Kuutti, A. Oinonen","doi":"10.1115/PVP2018-84276","DOIUrl":"https://doi.org/10.1115/PVP2018-84276","url":null,"abstract":"This paper presents a failure assessment diagram (FAD) and crack size based comparison of the ASME BVPC Section XI Nonmandatory Appendix C and Nonmandatory Appendix H and the British Standard BS 7910:2013 Option 1 assessment methods. The Section XI appendix C evaluates the acceptability of a flaw by determining the expected failure mechanism and by comparing the flaw size with allowable flaw size limits or by comparing the applied stress to the allowable stress. The Section XI appendix H and BS7910 employ a FAD based approach that simultaneously considers brittle fracture, ductile crack extension prior to reaching the limit load and exceedance of the limit load due to the gross plasticity in the cross section. The assessment is performed by calculating the assessment point coordinates and evaluating whether the point is located on the safe side of the FAD line. The three methods are compared for simplified austenitic and ferritic pipes under internal pressure and bending loads with postulated axial and circumferential internal surface flaws. The methods are applied to generate limiting flaw size diagrams for each component under the specified loads. Additionally, the limiting flaw size results are presented in the FAD plots. To maintain comparability between the results, identical input data are used with each analysis approach but using the method-specific formulae.\u0000 The performed comparison shows that most often the limiting state is governed by the 75 % flaw depth rule in Section XI article IWB-3640. The largest differences between the methods are observed for cracks with a high length to depth ratio. The difference to the tabulated allowable planar flaws in Article IWB-3514 is typically high. When increasing the applied load to values approaching the limit load, differences in the limiting flaw sizes between the methods are observed, mostly due to the different limit load models and different assumptions on the utilization of the post-yield capacity.\u0000 Besides the presented flaw size comparison, the paper presents a quick tool suitable for ranking different piping segments based on failure potential and for quick scoping evaluations of indications found in inspections. The case specific scoping tool is a map of yearly flaw size lines providing the information on which flaw sizes would grow to the final limiting size in a specified timeframe.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130265467","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}
H. Nabeshima, Yasuhiko Shishido, Nobuhisa Kouno, Takushi Murakami
Coke drums undergo cyclic operations typically in temperatures ranging from the ambient temperature to about 500°C. Generally, coke drums are fabricated from clad plates consisting of chromium-molybdenum low alloy steel as the base metal and ferritic stainless steel typically Type 410S stainless steel (TP.410S) as cladding material. TP.410S cladding material is used for protection against sulfide corrosion. Coke drums frequently display major cracking on the inside surface of their circumferential weld along the fusion line between restoration weld and the TP.410S cladding. Moreover, an array of cracks commonly referred to as “elephant skin” are typically observed proximity to the major cracks. These cracks have been reported by multiple papers, particularly in the API Technical Report 934-G, up to the present and primarily attributed to the thermal fatigue which occurs from the repeated thermal loads experienced during each operating cycle. When the existence of severe cracks is recognized, users are forced to schedule extensive repairs. The authors conducted fatigue tests employing coupons made from two kinds of cladding material, TP.410S and Alloy 625, which simulate the circumferential weld seam of coke drums. The paper summarizes the essential properties for the cladding material in order to delay cracking on the inside surface and proposes new common cladding materials which could be employed for coke drums based on test results.
{"title":"A Proposal of Cladding Materials for Coke Drum Based on Fatigue Tests","authors":"H. Nabeshima, Yasuhiko Shishido, Nobuhisa Kouno, Takushi Murakami","doi":"10.1115/PVP2018-84357","DOIUrl":"https://doi.org/10.1115/PVP2018-84357","url":null,"abstract":"Coke drums undergo cyclic operations typically in temperatures ranging from the ambient temperature to about 500°C. Generally, coke drums are fabricated from clad plates consisting of chromium-molybdenum low alloy steel as the base metal and ferritic stainless steel typically Type 410S stainless steel (TP.410S) as cladding material. TP.410S cladding material is used for protection against sulfide corrosion.\u0000 Coke drums frequently display major cracking on the inside surface of their circumferential weld along the fusion line between restoration weld and the TP.410S cladding. Moreover, an array of cracks commonly referred to as “elephant skin” are typically observed proximity to the major cracks. These cracks have been reported by multiple papers, particularly in the API Technical Report 934-G, up to the present and primarily attributed to the thermal fatigue which occurs from the repeated thermal loads experienced during each operating cycle. When the existence of severe cracks is recognized, users are forced to schedule extensive repairs.\u0000 The authors conducted fatigue tests employing coupons made from two kinds of cladding material, TP.410S and Alloy 625, which simulate the circumferential weld seam of coke drums. The paper summarizes the essential properties for the cladding material in order to delay cracking on the inside surface and proposes new common cladding materials which could be employed for coke drums based on test results.","PeriodicalId":384066,"journal":{"name":"Volume 3B: Design and Analysis","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116144956","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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