bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Validation of Flaw Evaluation Procedure for Axial PWSCC in Alloy 600 Reactor Vessel Head Penetration Nozzles
Authors: Fuhr Kevin , Schmidt Gideon , White Glenn , Harrington Craig
Published: November 2023

The analytical flaw evaluation procedure of Subsubarticle IWB-3660 and Nonmandatory Appendix O of the ASME Boiler and Pressure Vessel Code, Section XI is available to PWR licensees to disposition the detection of primary water stress corrosion cracking (PWSCC) in Alloy 600 reactor vessel head penetration nozzles. This procedure can be applied to accept a detected axial flaw for continued service if the flaw dimensions projected to the end of the evaluation period do not exceed the acceptance criteria of Table IWB-3663-1. The crack growth prediction for future operation must consider the PWSCC crack growth due to applicable loadings, including the tensile weld residual stresses that can dominate the stress state.

Following the detection of leakage in an Alloy 600 reactor vessel closure head control rod/element drive mechanism (CRDM) penetration in a U.S. PWR, a retrospective review of examination data provided several operating cycles of size information for the axial PWSCC flaw in the nozzle that was determined to be the cause of the leakage. This experience is a unique opportunity to compare the detailed data for flaw size evolution with the PWSCC growth predicted for the earliest observed flaw dimensions per the Section XI flaw evaluation procedure as a validation exercise.
Development of Code-Specific RSFa for Use in API 579-1/ASME FFS-1 Assessments
Authors: Nunez Joseph , Hay Clifford , Bedoya Julian
Published: November 2023

For metal loss assessments in the 2021 edition of API 579-1/ASME FFS-1 (hereinafter “API 579”), the Remaining Strength Factor (RSF) is “utilized to define the acceptability of a component for continued service.” The RSF is defined as the ratio of the plastic collapse load of the damaged component divided by that of the undamaged component. For metal loss assessments, the RSF is a function of the corroded geometry, as evidenced in the equations in Part 5 of API 579 and as documented in WRC 505. If the calculated RSF is less than an allowable RSF (RSFa), then the MAWP of the component must be reduced by the ratio of RSF/RSFa; otherwise, the component is acceptable at the undamaged MAWP. The recommended value for RSFa in API 579 is 0.90.

The 2007 edition of API 579 included Table 2.3 which provided recommended RSFa values based on the construction code, although the value of RSFa was listed as 0.90 for all codes in the table; the inclusion of this table (which was subsequently removed in the 2016 edition) was ostensibly for the purpose of eventually providing different values for different construction codes. To provide different values of RSFa, a permissible stress value distinct from the construction codes is needed, such that the RSFa for each construction code could be adjusted to provide a constant margin against burst pressure. This approach does not eliminate the possibility of including penalizing factors for certain construction details and/or codes which have less-rigorous inspection requirements or for similar reasons.

In a prior ASME PVP paper (PVP2022-84710), a generic equation was introduced to allow for quantification of the likelihood of ductile failure as a function of applied stress based on the semi-log assumption in API 581 (i.e., in the section related to pressure relief devices). Leveraging this approach, this study introduces an equation for a code-specific RSFa which allows for a constant margin against burst pressure for different construction codes.

Comparison of the proposed RSFa definition across different construction codes is illustrated with an example.
Shear Layer Instability in the Gap of Tandem Cylinders and Its Coupling With Higher Order Acoustic Modes
Authors: Noufal Rasha , Mohany Atef
Published: November 2023

This paper presents an experimental investigation of the aeroacoustic response from tandem cylinders in cross flow at different positions with respect to the acoustic particle velocity nodes and anti-nodes of different cross-modes. The objective is to better understand the role of the shear layer instability in the gap between the cylinders on the excitation of acoustic resonance and its coupling with higher-order acoustic modes. The results show that the tandem cylinders’ position with respect to the acoustic particle velocity anti-nodes of the cross-modes is a significant factor in determining the excitation of the dominant acoustic mode. Moreover, placing multiple rows of tandem cylinders at various positions with respect to the acoustic standing waves of the cross-modes in the duct promotes the coupling between the shear layer instability and the acoustic modes, even for the cases that didn’t trigger such excitation when the tandem cylinders were placed in a single row.
Development of a Web-Based Design Evaluation Platform for Elevated Temperature Design as per ASME Section III Division 5, ASME CC-2843 and RCC-MRx
Authors: Lee Hyeong-Yeon , Nam Ki-Ean , Huh Nam-Su , Kim Min-Kyu
Published: November 2023

An integrated web-based design evaluation platform of HITEP (HIgh Temperature design Evaluation Program) covering the three elevated temperature design rules of ASME BPVC Section III Division 5 Subsection HB (hereafter ‘ASME-HB’), ASME Code Case 2843-2 (hereafter ‘CC-2843’) and RCC-MRx, in addition to light water reactor design rules of ASME BPVC Section III Division 1 Subsection NB (hereafter ‘ASME-NB’) has been developed. CC-2843 is recently published code case of ASME Section VIII Division 2 based on the ASME-HB procedures with explicit consideration of creep. The evaluation module of ASME-NB has been added because the low-temperature design evaluations should be also conducted for a high-temperature component depending on temperature fluctuations. The HITEP platform can be used with high reliability and efficiency for the design of high temperature pressure boundary components or piping systems subjected to high-temperature operation at creep regime in a Generation IV nuclear reactor systems, renewable plants and advanced thermal power plants. In addition to those high-temperature applications, the platform can be applied to design of Generation III+ light water reactor systems. It was shown that the platform can be reliably and efficiently used for the elevated temperature design (hereafter ‘ETD’) of pressure boundary components and piping systems. The HITEP platform has been successfully used for the ETD of pressure boundary components and piping systems of the two large scale sodium test facilities of the STELLA-2 that is currently under operation and the thermal energy storage test facility of the TESET that is under construction at KAERI.
Creep-Fatigue Life Evaluation of Modified Grade 91 Tube Sheet Structures Under Flexible Loading Conditions
Authors: Islam Nazrul , Hossain Md Sumon
Published: November 2023

This study evaluates the creep-fatigue strength of a tube-sheet structure using elastic and inelastic constitutive models based methods. Such a tube-sheet structure of the Sodium Fast Reactors (SFR) developed by the Japan Atomic Energy Agency is one of the critical components to design because of its complex structural geometry. The creep-fatigue loading condition of SFR is also a challenge to properly address the combined effect of the loading condition, especially at the critical locations of the components like the numerous holes. Hence, this study develops a 3D FE model of the SFR’s tube-sheet structure to evaluate the combined creep-fatigue damage. The test model was subjected to ten years of severe thermal flexible loading conditions using a large-scale sodium loop, in which elevated-temperature sodium at 600°C and 250°C was flowed repeatedly and kept at the final temperature for 10 years and 1h. Similar start-up and shutdown conditions are maintained for 12 months and 1h, 6 months and 1h, 3 months and 1h, 1 month and 1h, respectively. Using the sodium temperature data obtained during the test, heat transfer analysis and stress analysis were carried out. Various constitutive models are used for the evaluation of creep-fatigue. The creep-fatigue life of the component is initially determined using elastic analysis-based stress redistribution locus and simple elastic follow-up methods. These elastic analysis-based methods are compared with the inelastic constitutive models e.g., bilinear and Chaboche model coupled with time hardening creep. Finally, the effect of flexible operation conditions is evaluated in the Campbell diagram with the elastic and inelastic analysis-based methods to show the applicability of these methods for life prediction.
A Survey of Failure Rate of In-Service Pressure Vessels in China’s Non-Nuclear Industry
Authors: Song Libin , Li Jun , Han Zhiyuan , Xie Guoshan , Deng Guide , Li Zhifeng
Published: November 2023

Failure rate is very important for the reliability and risk assessment of in-service pressure vessels. As early as in the 1970s and 1980s, the failure rate data of in-service pressure vessels has been collected in various countries, such as Europe and the United States, and in great detail. These data were incorporated into the relevant reliability database such as OREDA and CEMHD5. However, the failure rate data of pressure vessels in China is rarely reported so far, which limits the development of reliability and risk assessment technology for the pressure vessels in non-nuclear and nuclear industries. In this paper, about fifty thousand in-service pressure vessels data in China’s non-nuclear industry were collected. The potential and catastrophic failure rate were counted based on exponential distribution model. The statistical results were compared and analyzed with those of other countries such as the United States, the United Kingdom and Germany. The analysis results showed that the thickness thinning and cracking caused by corrosive medium were two main causes for pressure vessel failures in China. The failure rate of in-service pressure vessels in China is higher than that in the Europe and the United States countries, which may be caused by the high sulfur and high acid crude oil.
A Failure-Probability- and Damage-State-Based Fatigue and Creep Model for Estimating Reliability of Stainless Steel 316L(N) Components in Thermal Fatigue
Authors: Fong Jeffrey T. , Marcal Pedro V. , Cohn Marvin J. , Heckert N. Alan
Published: November 2023

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Committee has recently developed a new Section XI (Nuclear Components Inspection) Division 2 Code named “Reliability and Integrity Management (RIM).” RIM incorporates a new concept known as “System-Based Code (SBC)” originally due to Asada and his colleagues (2001–2004), where an integrated approach from design to service inspection is introduced using three new types of statistical quantities: (1) “system reliability index,” or “system co-reliability target” for any system consisting of structures and components, (2) “structural co-reliability,” for any structure, and (3) “component co-reliability” for any component, where co-reliability is defined as “1 – reliability” and is equal to failure probability. In a recent paper published in the International Journal of Pressure Vessels and Piping (Vol. 173 (2019), pp. 79–93). Fong, Heckert, Filliben, and Freiman developed a new theory of fatigue and creep rupture life modeling for metal alloys at room and elevated temperatures such that the co-reliability of a smooth component can be estimated from fatigue and creep rupture test data with simple loading histories. In this paper, we extend the theory to include a methodology to estimate the failure probability (or, co-reliability) of a stainless steel 316L(N) component undergoing a complex loading history such as a thermal fatigue cycle. To illustrate an application of this new modeling approach, we present a numerical example using (a) the experimental test data of 7 specimens of S.S. 316L(N) in creep at 565 C as published by Kilian Wasmer in his Ph.D. thesis (Imperial College London, 2003), (b) the experimental test data of 10 specimens of S.S. 316L(N) in creep at 650 C also by Wasmer (Ph.D. thesis, 2003), and (c) a thermal fatigue loading history of 1 hour of creep at 650 C at an operating creep stress of 73 MPa, and 300 hours of creep at 565 C at the same creep stress to simulate a hypothetical powerplant thermal fatigue operation. The significance and limitations of this new damage-state-based approach to modeling creep and to estimate the component failure probability (or, co-reliability) of steel components in creep at elevated temperatures with complex histories are discussed.
Experimental Analysis of Dynamic Operations of the Main Steam Relief Isolation Valve Used in Nuclear Power Plants
Authors: Zhou Weihao , Zong Chaoyong , Li Qingye , Jiang Songzhi , Liu Yanliang , Song Xueguan
Published: November 2023

Main steam relief isolation valve (MSRIV) is one type of advanced control valve used in pressurized water reactors (PWR), such as Hualong One (HPR 1000 in China) and European Pressurized Reactor (EPR). It can provide overpressure protection for the steam generator (SG) and used for waste heat discharging. However, MSRIV may show undesirable operations such as reclose slow under high pressure & temperature conditions (e.g., 8.9 MPa & 316 °C) and/or cannot be opened timely under low pressure & temperature conditions (e.g., 0.14 MPa & 316 °C). To explore the root causes of these undesirables, an experimental based analysis was specially carried out in this paper. For valve performance measurement, an experimental test rig was developed, thereby not only dynamic responses of the MSRIV under different operating conditions, but also the influence of valve key parameters can be analyzed. The results show that both the system pressure and the throttle area have great influence on the dynamics of the MSRIV. Upon the same disk throttle area, the valve opening time decrease with the inlet pressure, while the valve reclosing time increase with it. For the same inlet pressures, larger throttle area usually led to longer valve opening time and the shorter valve closing time. The results obtained in this study not only provide a reference for the valve early design stage, but also can be used as a criterion for the subsequent numerical modeling works which is of great importance for the flow details acquisition and valve mechanism exploration.
Explosive Hydrocode Modeling and Proof Testing of the HsERA-26 Containment Vessel
Authors: Tribble Megan , Ludwigsen John , Stofleth Jerome , Fleming Darryn
Published: November 2023

An inherited containment vessel design that has been used in the past to contain items in an environmental testing unit was brought to the Explosives Applications Lab to be analyzed and modified. The goal was to modify the vessel to contain an explosive event of 4g TNT equivalence at least once without failure or significant girth expansion while maintaining a seal. A total of ten energetic tests were performed on multiple vessels. In these tests, the 7075-T6 aluminum vessels were instrumented with thin-film resistive strain gages and both static and dynamic pressure gauges to study its ability to withstand an oversize explosive charge of 8g. Additionally, high precision girth (pi tape) measurements were taken before and after each test to measure the plastic growth of the vessel due to the event. Concurrent with this explosive testing, hydrocode modeling of the containment vessel and charge was performed. The modeling results were shown to agree with the results measured in the explosive field testing. Based on the data obtained during this testing, this vessel design can be safely used at least once to contain explosive detonations of 8g at the center of the chamber for a charge that will not result in damaging fragments.
The Effects of Fluid Working Conditions on Flange Face Corrosion
Authors: Hakimian Soroosh , Bouzid Abdel-Hakim , Hof Lucas A.
Published: November 2023

The second most common cause of hydrocarbon leakage is corrosion in offshore platforms. In seawater and hydrocarbon services, bolted flange joints can be susceptible to corrosion at their flange face. The current work considers corrosion of bolted flanged gasketed joints using the COQT fixture (COrrosion Quantification Test) to evaluate corrosion in flange faces. According to the literature, both crevice corrosion and galvanic corrosion widely occur in bolted flanged gasketed connections, creating leakage paths of the pressurized fluid. Leakage failure in bolted flanged gasketed joints can cause hazards to the environment and human safety. Corrosion in bolted gasketed joints was investigated in the literature. However, these studies do not consider the influence of the operating parameters such as fluid flow, pressure, pH, conductivity, temperature, and gasket contact pressure.

With the developed COQT fixture, which was introduced in the previous paper, different electrochemical techniques can be applied to measure flange corrosion under controlled test conditions. The polarization technique will be used to measure and compare the corrosion rate of flange at different fluid flow rates, and gasket contact stresses. The flange sample material is ASTM A105, and the gasket material is Teflon. Electrochemical tests are conducted with a solution of 3.5% NaCl. Confocal microscopy is used to visualize the morphology of the damaged zones on the surface, and localize and quantify the pits size caused by corrosion, respectively. Comparing the results of the electrochemical tests and the microscopic studies will identify the most influent factor on the corrosion rate of flanges.
Blister Damage Evolution in Plastic Liner of Type IV Hydrogen Storage Vessel Studied by Fracture Mechanics
Authors: Shi Hao , Peng Wenzhu , Wei Liqing , Kang Qiubing , Chen Qi , Hua Zhengli
Published: November 2023

Type IV vessels are widely used for high-pressure hydrogen storage onboard vehicles due to their advantages in lightweight, durability, economy, etc. However, the plastic liner of type IV vessel is likely to blister, which can further cause the liner to fracture and hydrogen leakage. Many types of research have revealed that blistering in the plastic liner occurs when the vessel is depressurizing. High-pressure hydrogen diffuses through the liner and occupies the preexisting cavities inside it, causing cracking-like blisters under internal pressure in the cavities when external pressure decreases. A model based on fracture mechanics was deployed to predict the blister damage evolution in the plastic liner. The blister damage propagation was evaluated by the stress intensity factor, which is related to the high-pressure hydrogen acting on the cavity. The blister damage evolution inside the plastic liner with different materials was studied. Besides, the effects of the depressurization rate, the cavity location, and the number of cavities on blister damage were also studied. The kinds of materials play an essential role in blister damage evolution. It was found that the material with increased tensile properties prevented crack growth better. The external pressure acting on the liner affects the size of crack growth in the blistering process. And the damage varies with the location and number of cavities. The interaction between cavities could change the stress field in the liner, which affects crack growth.
Evaluation of the Fracture Toughness of Short Carbon Fiber Reinforced Thermoplastic Composites
Authors: Shi Jianfeng , Zong Xinwei , Jiang Weili , Yao Riwu , Zheng Jinyang
Published: November 2023

Short carbon fiber reinforced thermoplastic composites (SCFRTCs) are widely applied in aerospace, transportation, shipping, and other fields because of their excellent mechanical properties and high recyclability. The fracture toughness, which is an essential characteristic of the resistance of materials to crack propagation, is considered a critical aspect of the long-term performance of SCFRTCs structures. In this work, the fracture toughness of SCFRTCs is characterized through three-point bending tests. The stress intensity factor KIC of SCFRTCs is calculated, and the influence of short carbon fiber (SCF) fraction on the fracture toughness is investigated. The strain field during the crack propagation process in the three-point bending test is measured and analyzed by digital image correlation (DIC) method. Scanning electron microscope observation is carried out to investigate the mechanism of SCFs in the micro-cracks initiation and propagation. The results demonstrate that a higher SCF fraction increases the fracture toughness of SCFRTCs, which is expressed as the maximum increase of 73.7% when the SCF fraction is 9.8 wt%. Furthermore, it is found that adding SCFs reduced the strain level at the crack tip, and the SEM observations suggest that SCFs played a bridging role on both sides of the crack. Overall, the results of this study confirm that SCFs can inhibit crack propagation and thus improve the fracture toughness of SCFRTCs.
A Review on Hydrogen Production From Ocean Renewable Energy and the Application Status
Authors: Shi Jianfeng , Xia Ruoxi , Zheng Xingyu , Yao Riwu , Zheng Jinyang
Published: November 2023

Ocean renewable energy development is strategically significant to the world’s low-carbon energy transformation. Many ocean renewable energy development projects have been carried out or are under planning. Combining green hydrogen and ocean renewable energy is ideal for developing ocean renewable energy. This paper first surveyed the main ocean renewable energy hydrogen production projects worldwide. Detailed information about these projects’ technical routes and the scale of renewable energy development were then summarized. With ocean renewable energy development gradually moving towards greater offshore distance and water depth, large-scale and low-cost ocean renewable energy development has become a critical concern in industry and academia. Therefore, a comparison about the energy transmission mode is then carried out. Furthermore, based on the current ocean renewable energy development projects, the development trend of hydrogen production from ocean renewable energy was analyzed, including increased offshore distance and water depth, development of floating wind platforms, and large-scale wind turbines. Meanwhile, the main technical challenges are discussed in detail to achieve large-scale and low-cost ocean renewable energy development.
Fatigue Crack Growth Analysis in Pipe Fittings Using Finite Element Analysis
Authors: Radhakrishnan Harish , Manuel Jacob
Published: November 2023

The finite element method is used to study the fatigue crack growth in a T-joint pipe fitting. We show the convenience of the method to model fatigue crack growth when an initial crack is in a section of pipe where, simplification to standard geometry sections is not possible or is difficult. The conventional Paris-law is used to govern the crack growth. After evaluating fracture parameters on the initial crack, the number of cycles needed to advance the crack by an incremental size is computed. The direction of crack growth is calculated by assuming the incremental growth happens in the maximum circumferential stress direction. The fracture topology is modified accounting for crack growth and the process of computing fracture parameters and incrementally growing the crack is repeated. The method is robust and can account for fracture growth under residual stress fields commonly seen in areas welded areas. We demonstrate the versatility of the method and its use in computing fatigue fracture growth for pressurized equipment under a variety of structural and thermal loads.
Elastic-Plastic Analysis for Crossover Piping by Using ASME Code Case N-900 and JSME Code Case NC-CC-008
Authors: Shibukuwa Kenichi
Published: November 2023

In 2019, two remarkable code cases (ASME CC-N900[1]/JSME NC-CC-008[2]) regarding seismic design method by elastic-plastic analysis were published by ASME/JSME almost simultaneously. However, there are few practical applications by both code cases in actual seismic design work. In the case of seismic design of crossover piping across the building isolation boundary, which are supported at many points, the seismic design of crossover has the difficult issue to be addressed and it is necessary to resolve overstressed piping due to both large seismic anchor movements and large seismic inertia forces. It is difficult to resolve this issue and perform the rational seismic design by current ASME code cases. This paper recommends the specific seismic design rules for crossover piping, based on fatigue evaluation example of EPRI PFDRP TEST-30 by both code cases (ASME CC-N900/JSME NC-CC-008) and provides the results of study regarding the technical issues of elastic-plastic analysis to develop the rational seismic design rules in the future.
Reliability of a Composite Lined Pipe for Trenchless Rehabilitation of Thermal Pipelines Based on a Two-Heating-Season Long Field Test in China
Authors: Wang Yingdi , Yan Shuo , Zeng Xiangjing , Zhang Liang , Shi Jianfeng
Published: November 2023

The advantages of trenchless rehabilitation of underground pipelines in construction and maintenance costs have been widely acknowledged. In this work, a two-heating-season (∼5800 h) long field test was carried out to verify the reliability of thermal pipeline rehabilitation using a composite structure of lined pipe in a thermal station in China. The average working temperature and pressure ranges in the primary heat network are 90 °C and 0.5 MPa, respectively. The critical mechanical and thermal properties of the materials are analyzed and compared before and after the field test. The results show that the melting temperature and crystallization temperature have increased by 0.6 °C and 3.1 °C, respectively. Further, there is no obvious degradation in weight in the working temperature range of the thermal pipeline network. The tensile strength has been increased by 71.38% after the field test, and only a 2.44% decrease in fracture strength was observed. The results indicate that the composite lined pipe is still available for application in the thermal pipe in the working condition of the present work.
Study on the Applicability of GTN Model on Fracture Evaluation for Plate Specimen With a Surface Crack Using a BWR Reactor Pressure Vessel Material
Authors: Ogawa Takuya , Hayashi Takahiro , Yoshida Shuichi , Itatani Masao , Saito Toshiyuki
Published: November 2023

Cases of stress corrosion cracking (SCC) in Ni-base alloy weld metals welded to the low alloy steel (LAS) in reactor pressure vessel (RPV) components have led to discussions on the possibility of SCC propagating into the RPV. The JSME Fitness-for-Service code provides fracture evaluation methodology based on linear elastic fracture mechanics for SCC into the RPV, assuming neutron irradiation in the RPV beltline region. It is considered, however, more rational methodology of fracture evaluation can be applied to the RPV components such as a bottom head component of boiling water reactor (BWR) since the effect of neutron irradiation is considered to be negligible. In the previous studies, the fracture mode of RPV material has been investigated by using a large-scale, heavy forged steel part named “bottom head ring”, manufactured for a recent BWR. The authors reported that the results of fracture tests showed ductile failure and the fracture loads evaluated using the elastic-plastic fracture mechanics (EPFM) methodology have showed fairly good agreement with the maximum loads in the fracture tests on plate specimens with a semi-elliptical surface crack.

In the present study, the applicability of damage mechanics analysis by using Gurson-Tvergaard-Needleman (GTN) model, which can analyze ductile fracture behavior due to nucleation, growth and coalescence of voids in metallic materials, to fracture evaluation for a RPV bottom head component of BWR was investigated. GTN model parameters of the tested material were investigated by comparison of the relationship between load and load-line displacement (LLD) obtained by the JIc fracture toughness tests with that obtained by finite element analysis (FEA) using GTN model. And a set of GTN model parameters that can reproduce the load-LLD relationship by the tests were determined. Fracture analysis for the plate specimens with a semi-elliptical surface crack were performed by using the GTN model parameters determined. It was found that relationship between load and crack mouth opening displacement (CMOD) obtained by the FEA showed a good agreement with that obtained by the fracture tests of the plate specimens. Furthermore, the fracture behavior observed in the FEA using GTN model also showed good agreement with that in the fracture test, such as necking behavior on the plate specimens, ductile crack extension traces on the fracture surfaces and crack penetration. The results obtained in the present study totally supported the applicability of the GTN model to RPV bottom head component.
Development of a New Thermo-Mechanical Load and Fatigue Monitoring Approach Based on Electromagnetic Acoustic Transducers - EMUS-4-STRESS
Authors: Weikert-Müller Miriam , Weber Fabian , Thieltges Sascha , Smaga Marek , Silber Fabian , Rudolph Jürgen , Bergholz Steffen , Bechtgold Eduard
Published: November 2023

Fatigue monitoring systems based on direct global and local temperature measurements are successfully being applied in facilities worldwide. Local temperature measurement is carried out by way of thermocouples on the outer wall of piping sections close to fatigue relevant components. The detectability and re-solvability of the corresponding inner wall temperatures — required for the fatigue assessment — is limited in the case of fast and high frequency load cycles occurring e.g. due to non-stationary mixing or vortex penetration processes of cold and hot flows. These kind of limitations are motivation for the development of a complementary nondestructive system using electromagnetic acoustic transducers (EMATs) in order to measure the ultrasonic time-of-flight (TOF).

Recent results of a respective cooperative R&D project (Fraunhofer IZFP Saarbrücken, RPTU Kaiserslautern-Landau, MPA Stuttgart, Framatome GmbH) on the applicability of the electromagnetic acoustic transducer technology for the purpose of fatigue monitoring will be discussed in this paper. The validation of the method was realized under various laboratory and operational conditions on different test rigs (uniaxial standard fatigue tests, component bending tests, pressurized pipe tests, heated plate tests, heated pipe tests, fluid structure interaction FSI test facility at MPA Stuttgart). A new test rig at the Framatome premises allowed for the simulation of different temperature transients and the application of thermocouple based and EMAT based measurements. Furthermore, both measurement types were applied at the MPA fluid structure interaction (FSI) test rig for a realistic cold-hot mixing scenarios.

It is the final aim of the project to determine the time history of fatigue relevant loading at fatigue relevant locations as the basis for complex fatigue monitoring according to the formula fatigue monitoring = continuous load monitoring + periodic (or continuous) engineering fatigue assessment.
Experimental Investigation of Combined Axial Flow and Jet Cross-Flow on PWR Mock-Up Array
Authors: Gad-el-Hak Ibrahim , Mureithi Njuki , Karazis Kostas
Published: November 2023

Some pressurized water reactors (PWRs) are designed to relieve the pressure increase in the barrel-baffle region associated with a loss of coolant accident (LOCA). Flow holes, called LOCA holes, are introduced in the baffle plates to equalize the pressure difference between the core side and the barrel-baffle region. However, it has been found that jet flow emanating from LOCA holes induces fretting wear of the fuel rods at the spacer grid position during normal operation. The effect of jet in transverse flow (JITF) on a PWR mock-up array should be investigated in order to determine the rod array response and, as a result, to set safe operating conditions for these reactors.

This research looks at the effect of axial flow velocity on the stability of a single-span 6 × 5 square rod bundle having a prototypical fuel assembly dimensions in some designs of pressurized water reactor cores. The axisymmetrically flexible rods in the highly compact array are instrumented with four strain gauges to measure the two-dimensional rod displacements. Then, the response of the rod bundle under combined flows (i.e. JITF) is measured for three test axial flow velocities, VAxial = 1.0 m/s, 1.5 m/s, and 2.0 m/s. The experimental results show that the critical jet cross-flow velocity increases with the axial flow velocity. This is attributed to the bending effect of axial flow on the jet flow (i.e. jet trajectory). The critical flow velocities are collected to provide a stability map of the arrays subjected to the jet in transverse flow.
Geometrical Effect of Tube Array on Prediction of Fluidelastic Instability – Single Phase Air Flow
Authors: Elhelaly Amro , Weaver David , Riznic Jovica R. , Hassan Marwan
Published: November 2023

Flow-induced vibrations (FIV) are a major consideration in the design of shell and tube heat exchangers. Among the FIV excitation mechanisms, fluidelastic instability (FEI) is by far the most important mechanism that can significantly compromise the structural integrity of tube arrays. Traditionally, FEI was thought to only occur in the transverse direction. The recent tube failures of replacement steam generators showed that FEI could occur in the streamwise direction and be equally devastating. This has sparked intensive efforts to uncover the nature of this new phenomenon.

The current work presents an experimental investigation program which was initiated to systematically uncover fundamental aspects of this phenomenon. Experiments were carried out in an airflow wind tunnel at the University of Guelph in the Fluid-Structure Interaction Laboratory. The aim of this study was to investigate the geometrical effect of tube array types on the FEI in both the transverse and streamwise directions. The stability of a single flexible tube and multiple flexible tubes in tube arrays were tested. Parallel triangle and normal triangle arrays were tested at pitch ratios in the range of 1.25 to 1.7. A compression between the available experimental data and the current result was presented and conclusions were drawn. The results show that the stability threshold is sensitive to the pitch-to-diameter ratio of the array and the number of flexible tubes especially in the streamwise direction.
Modelling of Residual Stresses in Multi-Pass Pipe Circumferential Butt Welds Made of Austenitic Stainless Steel to Provide Indicators for SCC Risk Classification
Authors: Robin V. , Hendili S. , Delmas J. , Hilal S. , Iampietro D. , Abbas M. , Jutteau S.
Published: November 2023

Prediction of residual stresses in welds is essential in order to evaluate the integrity of a component subject to degradation mechanisms such as Stress Corrosion Cracking. During welding operations, complex thermo-mechanical and metallurgical processes take place and lead to microstructural changes such as dynamic recovery and dynamic recrystallization. These microstructural changes induce a modification of hardening behavior that should be taken into account to accurately evaluate residual stresses through numerical simulations. In the as-welded conditions, multi-pass pipe circumferential butt welds made of austenitic stainless steel show a typical residual stress profile through the wall of the welded joint. Such a shell bending profile places the inner half of the weld joint wall and its vicinity in compression in the axial direction. However, tensile zones can appear in the inner wall near the axis of the weld.

A large simulation campaign was carried out in order to cover different welding configurations and confirm these trends. This digital chart is built on the basis of a design of experiments of 100 Numerical Simulations of Welding per diameter and schedule. The parameters are:

- Diameter, thickness,

- Welding processes (GTAW, SMAW...),

- Groove shape.

This set of simulations show the systematic presence of a compression zone on the inner side, with some variability depending on the welding conditions and geometry. The classification of SCC risk is then defined by a set of two indicators that can be related to crack initiation (stress, strain hardening near the surface) and propagation (stress, strain hardening in the bulk). Considering in service loads in addition to realistic Weld Residual Stresses (WRS) makes Stress Intensity Factor (SIF) analysis feasible considering idealized crack position and orientation.
Elimination of the 48-Hour Hold for Ambient Temperature Temper Bead Welding With Austenitic Weld Metal
Authors: McCracken Steven L. , Patel Asif
Published: November 2023

Temper bead welding rules in the ASME Section XI code and code cases have historically required a 48-hour hold (wait period) after the temper bead weldment has cooled to ambient temperature prior to performing the final nondestructive examination (NDE). The purpose of the 48-hour wait period is to ensure that if delayed hydrogen induced cracking (HIC) occurs it is detected by the final acceptance examination. Delayed HIC is known to occur up to 48 hours after the weldment cools to ambient temperature when appropriate welding techniques and low hydrogen practices are not applied. A recent revision to Case N-888, the ambient temperature temper bead case for SMAW and Machine GTAW, eliminates the 48-hour hold for temper bead welds on P-No. 1 and P-No. 3 base material when austenitic weld metal is used. This paper summarizes the technical basis for this change and references operating experience that demonstrates the 48-hour hold is inconsequential and there is no potential for HIC when temper bead welding is deployed with low hydrogen practices and austenitic weld metal.
Effect of Temperature and Seawater Exposure on Glass/Polyurethane Composite: Experimental and Failure Analysis
Authors: Idrisi Amir Hussain , Ismail Mourad Abdel-Hamid
Published: November 2023

The lack of durability is the major issue faced by polymers and their composites for saline water exposure. The experimental investigation of seawater exposure of Fiber reinforced polymer (FRP) composite is limited to a short period of time. Also, this small range of data was used in the development of the prediction model. The present paper reports a long-term experimental investigation and prediction of the durability of FRP composites exposed to seawater at different temperatures. E-glass/polyurethane samples were exposed to 23 °C, 45 °C and 65 °C seawater for up to 2700 days (90 months). Tensile tests evaluated the mechanical performance of the composite as a function of exposure time, and a strength-based technique was used to assess the durability. The experimental results revealed that the tensile strength of the composite reduced by 37.6% and 63.6% after immersion of 90 months in seawater at 23 and 65 °C, respectively. The prolonged immersion in seawater results in plasticization and swelling in the composite material, which accelerates the fiber/matrix debonding. Failure analysis was performed to investigate the failure mode of the samples. SEM micrographs indicate fiber/matrix debonding, potholing, fiber pull-out, river line marks, and matrix cracking which indicates deterioration in the tensile properties of the composites.
Fatigue Analysis of a Pressure Swing Adsorption Vessel
Authors: Kumar Raman Senthil
Published: November 2023

Pressure Swing Adsorption technology is used to separate any gas from a mixture of gases under pressure according to the gas molecular characteristics and its affinity for an adsorbent material. The process operates at near-ambient temperatures and specific adsorptive materials (e.g., activated carbon, molecular sieves, etc.) are used to preferentially adsorb the target gas at high pressure. The process then swings to low pressure to desorb the adsorbed material.

Adsorption and desorption normally take place alternately at equal time intervals which sets the pressure cycle in a pressure vessel. The cycles are usually produced by internal pressure or vacuum caused by the swing operation. This paper focuses on an investigation to determine the design fatigue life of an adsorption vessel subjected to over 10 million cycles of design internal pressure and vacuum. The paper also highlights the effect of reaching full vacuum conditions on the fatigue life of the vessel during the pressure cycle.

The fatigue evaluation is performed considering the normal operation of the equipment during the entire life cycle of the plant. The adsorber vessel under investigation replaces an existing vessel due to the improved process performance requirements of the plant and hence provided with four leg supports welded directly to the vessel head to avoid modifications to existing base supports in the plant. A 3D model of the full vessel is considered, meshed and the fatigue evaluation is done as per ASME Sec VIII Div. 2, Part 5, Annexure 3-F.1. FEA software ANSYS® is used to perform the stress analysis. Vessel fatigue life is estimated according to the alternating stresses at the highest stress point i.e., at the leg to head junction.
Computational Analysis of a Piping Structure Subject to Thermal Striping
Authors: Harper Chris , Crowther Paul , Chauvet Christian
Published: November 2023

Fatigue failure of piping structures due to thermal striping occurs when hot and cold flow streams are mixed at a piping junction. Interaction of the two streams can lead to formation of a shear layer and periodic vortex shedding at the mixing boundary of the hot and cold fluid. The impact of these vortices on the inside pipe wall result in variable thermal loads on the inner pipe wall and localized high cycle thermal stresses. It is a relatively infrequent but potentially catastrophic degradation mechanism in many industries, which see mixing of fluid flows with large temperature differences.

This paper describes the effect of thermal striping induced fatigue failure of piping structures and an approach for analysis using a combination of Computational Fluid Dynamics (CFD) and structural Finite Element Analysis (FEA). The fluid dynamics analysis is first completed in this study where a cold flow stream is mixed with a hot flow stream at a piping T-junction. It predicts the flow and temperature fluctuations in the system and provides the frequency and amplitude of oscillations. The structural mechanics analyses are employed to extract time-dependent strain and stress values of the pipe under thermal loadings. Afterwards, the fatigue life of the pipe is obtained using fatigue failure analysis which is then used to verify the study approach by comparing the results with those of a real incident in an oil and gas plant.

The effect of installing an internal nozzle is investigated and confirmed by the computational approach. Finally, a criterion for when thermal striping may be of concern in a piping layout and should be analyzed further is proposed.
A Study on Reliability of Piping System Supported by Elasto-Plastic Support Subjected to Nonstationary Seismic Waves
Authors: Shintani Atsuhiko , Nakagawa Chihiro , Ito Tomohiro
Published: November 2023

The responses of piping systems subjected to nonstationary seismic waves are investigated. A piping system subjected to non-stationary artificial seismic waves is modeled using L-shaped piping supported by elasto-plastic supports. The nonstationary seismic waves are produced through a stationary stochastic Gaussian noise process weighted by a deterministic function. This deterministic function has similar seismic frequency characteristics as an actual earthquake. The power of an artificial seismic wave is adjusted by equalizing the power of the white Gaussian noise. Next, the reliability of the piping based on its stress, energy absorption ratio from the support, and energy absorption balance are employed as indices. Based on these indices, the response of piping subjected to nonstationary seismic waves is investigated and compared to the response subjected to stationary Gaussian noise. The reliability of the piping system, the energy absorption ratio of the supports, and the energy absorption balance based on the application of white noise and nonstationary waves as inputs are investigated.
Hydrocracker Gasket Lipseal Design and Fabrication Learning
Authors: Perilloux Charles , Huff Mary Catherine , Adams Amy , Rhodes John , Penso Jorge , Stierwald Robert
Published: November 2023

In this paper, reliability underperformance of welded lipseal is analyzed. A fillet weld located between the channel cover and lipseal on a hydrocracker second stage feed/effluent exchanger developed leaks. The reactor effluent fluid comprises hydrogen, naphtha and diesel above 1,900psig. Before the leaks occurred, there were multiple start-up and shutdown cycles. These cycles created sufficient stress to drive cracking though the fillet weld of the seal. During the failure investigation, some deviations in weld location and size were identified. The stress from subsequent thermal cycles was high enough to exceed the weld strength.

The lip height created a difficult angle for the welder to work. This resulted in less metal being applied in some areas and variation in weld placement. The flange and gasket area were too restricted to use a fillet gauge. Liquid penetrant inspection and hydrotest were not robust enough barriers to prevent the leaks.

Finite element-based fatigue analyses following industry standard API 579-1/ASME FFS-1 was performed. It found that a minimum weld size above what was found in the failure inspection was required to sustain observed fatigue cycles. The finite element model was calibrated using results of an infrared inspection.

Recommendations following investigation include design and fabrication modifications to minimize occurrences of similar events. The importance of considering potential severe cyclic service scenarios in the design is highlighted. Similar seal weld leaks have been reported in the industry.
Life Management of Pressure Swing Absorbers
Authors: Karstensen Annette , Seipp Trevor , Nadarajah Chithranjan
Published: November 2023

Pressure cycles in a hydrogen environment can seriously affect the fatigue life of pressure swing absorbers (PSAs). PSAs are typically designed for a 20 to 30-year life and by the time the intended design life is approaching, many operators are challenged with making decisions as to whether they need to purchase new vessels or explore whether or not life extension is a viable option.

In many cases, towards the end of design life or during midlife (50–60% of design life), operators elect to conduct a life extension study that includes a Level 3 Fitness for Service assessment and Finite Element Analysis (FEA) to evaluate the areas of high stress where fatigue cracks might initiate. The outcome from the FEA is used to develop an inspection strategy. In most cases, it will show that the areas of high stress are around the inlet and outlet nozzles. However, most PSA vessels are well fabricated with nozzles or manways having integral reinforcement and blended nozzle welds, making these areas less susceptible to crack initiation.

In the authors’ experience, the real integrity concern is weld peaking in the long seams and/or weld misalignment, and this will not be highlighted by an FEA made from design drawings. Therefore, this paper examines the effect on weld peaking at the longitudinal seams on the fatigue life. However, other potential crack locations are at internal attachment welds, for example, where the inlet screen is welded to the bottom head and these should in general also be considered when inspection strategies and integrity management plans are developed for PSA vessels.

The work described in this paper highlights how it is possible to operate PSAs beyond design life by developing inspection plan based on a fracture mechanics approach and basing the underlying FEA stress analysis on laser scan data to capture the level of weld peaking in the long seam welds.