bluuebunny/crossref_metadata_2025_split huggingface dataset:
Leakage Rate Models for Cracked Pipes
Authors: Brigante Francesco , Pasti Fabio , de Haan – de Wilde F. H. E. 
Published: November 2024

Abstract
This paper presents a leakage prediction study for Leak Before Break (LBB) assessments. The LBB concept has emerged as an essential tool for ensuring the safety of nuclear installations and pressurized piping systems. The approach is backed by accurate estimation of leakage rates from postulated cracks. In this study the methodology is based on the UK procedure for assessing structures containing defects (R6). The research is part of the ongoing in-house development of a software for LBB analyses and it aims to better understand and improve leak rate prediction methodologies for LBB assessments. The software is comprised of structural integrity modules and thermal hydraulic modules. This study presents the implementations of different coolant leak rates flow models, the Henry-Fauske model for flashing subcooled fluids and as single-phase Bernoulli model for lower temperatures. The thermal-hydraulics Henry Fauske model is evaluated against available experimental data and the differences are discussed. The Bernoulli based model is compared with another software. The implemented procedure is compared with two different software results for the structural modules. The structural calculations show coherence between the implemented procedure and the benchmark software that is based on the same methodology. In contrast the results are considerably different respect to another available software. The data show the significance and limitations of each model in various cases.
Recent Dynamic Events in Modern Large CCGT Plants – Case Studies, Findings and Corrective Actions
Authors: Johny Anita , Mollitor Barrie , Jackson Peter 
Published: November 2024

Abstract
This paper presents the findings for investigative studies conducted for various transient incidents commonly known to occur in CCGT plants. The damage from transient events can range in severity. Effects such as insulation damage and minor pipe deflections from small-scale transient effects can be repaired effectively without extraneous efforts. However, reactions such as piping vibrations, damaged supports and/or weld failures can directly impact plant operability — resulting in forced plant outages.
High energy piping systems become more susceptible to damage when transient events such as steam/water hammer or slug flow occurs in combination with improper drainage. The locations most known to be at risk are the Hot Reheat or High Pressure bypass valve outlet where the source of condensate is an attemperator and the Feed Water system. Inoperable or frozen drain legs, and start-up vents that are closed rapidly during start-ups are some other common sources. The case studies detailed in this paper explore the correlation of condensate build-up in piping and the resultant dynamic loads. Case study findings analyzed underscore the importance of following proper drainage protocols during plant start-ups and shut-downs. Additionally, supports that provide the most optimal protection against dynamic transients such as rigid restraints and snubbers (shock suppressors) are discussed.
Development and Validation of an Effective Screening Process for Thermal-Hydraulic Phenomena With Relevance to Thermal Loads in Nuclear Power Plants Piping System
Authors: Rudolph Luciana , Trewin Richard , Buettner Robert , Fuchs Thomas 
Published: November 2024

Abstract
In nuclear power plants (NPP), there is a series of pipe junctions with a main pipe connected to closed-end branch pipe, in which degradation due to high cycle thermal fatigue potentially can occur. The identification of those locations in NPP piping systems is highly important to decide on mitigation activities. Thermal-fatigue cracking due to thermal stresses in a branch pipe occurs at the fluctuating boundary created by the turbulent penetration of hot liquid from the main pipe into the nominally cold liquid of the branch line. The branch flow is nominally stagnant due to, e.g., a closed valve in the branch, but flow can recirculate within the branch. This is a thermal-hydraulic phenomenon also known as the “Farley-Tihange” phenomenon. The proposed screening process consists of two steps: a fast-running thermal-hydraulic tool as a pre-screening step, and a detailed analysis of the three-dimensional flow by means of computational fluid dynamics (CFD) as final step. In the present study, the accuracy and effectiveness of the developed screening tool is evaluated. The results are compared with available experimental data from the open literature, such as vortex penetration depth in the branch pipe. The fast-running thermal-hydraulic tool sorts the junctions into those that are potential risk locations where thermal fatigue is a possibility, and those where thermal fatigue can be conservatively ruled out. The branches identified as potential risks are analyzed in a detailed CFD simulation to generate sufficient information to take further expert decisions, such as installation of a fatigue monitoring system or design changes.
Structural Capacity Estimation of Subsea Flanges Using Various Codes and Standards
Authors: Karpanan Kumarswamy , Kirkemo Finn , Subramanian Kannan 
Published: November 2024

Abstract
High-pressure flanges of varying sizes, starting from 1/2″ are used in subsea oil and gas production equipment such as trees, manifolds, risers, valves, etc. These flanges are designed up to 20 ksi operating pressure with a test pressure of 30 ksi. Additionally, flanges used in subsea applications are exposed to high bending, shear, and torsional loads. API 6A flanges with BX gaskets are commonly used in subsea and surface oil and gas production equipment. API TR 6AF1 and API TR 6AF2 technical reports provide the pressure, bending, and tension capacity of these flanges. The flange capacity is presented as capacity charts. It should be noted that the API flanges are designed to the criteria of API 6A. Along with standard API flanges, subsea equipment also uses non-standard flanges, also known as Other-End Connections (OEC).
In this paper, a subsea API 7 1/16″-15K standard flange design and analysis is presented. This flange is analyzed to design criteria from various codes and standards used in the oil and gas industry such as API 6A, API 6X, API 17D, API17G, API 16A, ASME VIII-2, ASME VIII-3, and NORSOK U-001. These codes and standards allow elastic, elastic perfectly plastic (limit load), and elastic-plastic finite element analysis to estimate the flange capacity. The flange design capacity estimated based on these codes and standards is presented and compared against the existing API 6AF flange capacity. The flange capacity includes functional capacity (leakage and hub separation) and structural capacity (bolt capacity and flange capacity). This paper also discusses the conservatism and limitations in each of these codes and standards for the flange design. The analysis procedures presented in this paper can be used for designing OECs.
A Review of Relief Valves in Unsteady Flow - Behavior, Analysis, and Design
Authors: Dudley Mark , Schreuder Jans , Witte Dylan , Rorabaugh Devin , Lang Scott 
Published: November 2024

Abstract
Pressure relief devices (PRDs) are used to protect system components from high pressures. Appropriately sized devices eliminate these high pressures while relieving a minimal amount of process fluid. As a result, they are frequently found in both incompressible and compressible systems to relieve overpressures. However, relief devices are historically known to be ineffective for handling surge overpressures. While PRD standards and sources simply encourage the avoidance of surge, it is an inevitability within most systems and the interaction between surge and PRDs, both conventional and surge-mitigating, are investigated here within.
This paper discusses the basics of PRD terminology, mathematical PRD models, and PRD computer simulation modeling with associated examples. Basic design principles, guidelines for identifying at-risk-for-surge systems, and relief valve selection criteria for surge mitigation are presented.
Non-Conservative Fracture Toughness Measurements Due to Unintentional Trace Oxygen Impurities in Hydrogen Gas
Authors: Nibur Kevin 
Published: November 2024

Abstract
It is recognized that oxygen gas impurities can inhibit the deleterious effects of hydrogen gas on mechanical properties of steels. Most commonly, the effect of oxygen on hydrogen assisted fatigue has been studied. An increase in the measured hydrogen-assisted fracture toughness has been reported to result from oxygen gas impurities, but few efforts have been made to understand how much oxygen can be present in hydrogen gas without altering measured fracture toughness values. Routine measurements of the post-test oxygen content has revealed various instances where the measured oxygen content was unintentionally higher than expected. This paper will present some of these chance observations in which unintentionally elevated oxygen levels resulted in elevated fracture toughness measurements. Oxygen concentrations as low as 0.1 part per million have been observed to effectively inhibit hydrogen assisted fracture under certain conditions. These observations indicate the extreme importance of understanding and controlling the levels of trace oxygen impurities in hydrogen gas during fracture toughness measurements to avoid anomalously high measurements. Finally, it should be noted that these observations apply only to fracture measurements performed at laboratory test time scales (typically measured in hours); it is not currently understood whether similar trace levels of oxygen will inhibit crack growth in structures operated over operational time scales measured in months to years.
Case Study on a Cracking Failure in UNS N06693 Weld for Steam Generator Applications
Authors: Pickle Tim , Kho Kok-Theng , Penso Jorge , Yu Zhenzhen 
Published: November 2024

Abstract
UNS N06693 is a Ni-base alloy that provides metal dusting corrosion resistance in steam generator pipes with operating temperatures above 500°C. A crack failure occurred in a 6.5mm thick similar weld pipe joint, located at both fusion zone and heat affected zone, after about 10 years in service and 2 months after weld repair in adjacent weld, which warranted an investigation into possible root causes of failure. This study investigates the potential failure mechanisms that may arise during service (such as stress relaxation cracking, stress corrosion cracking, ductility dip cracking, and creep failure) for UNS N06693 in order to understand the observed cracking behavior. In this year, preliminary fractography, metallurgical characterization, thermodynamic and kinetic CALHAD simulations, and investigation into potential contributing factors (e.g., weld procedure specifications (WPS) and post weld heat treatment (PWHT)) to failure have been completed. The fracture surfaces indicate brittle, intergranular failure, such that no shear lips were observed, and radial lines (crack propagation) were primarily observed in weld fusion zone. Metallurgical characterization near the fracture surface is conducted to reveal the contributing factors to failure, such as intermetallic phases (e.g., Cr-rich α-phase) and distribution of carbide particles (e.g., intergranular chromium carbides), that may contribute to reduced cracking and sensitization resistance. Blocky, intergranular Cr-rich precipitates, either Cr-rich α-phase or Cr-rich M23C6., are observed behind secondary cracks. Based on the initial findings, contributing factors for failure considered are increase in tensile residual stresses due to nearby repair field weld and grain boundary embrittlement due to coarse, blocky Cr-rich phase that likely developed during initial PWHT and within the 10-year service window. In the following year, a more in-depth metallurgical characterization, discussion on contributing causes and possible mitigation strategies for improving microstructural stability and performance-based weldability (e.g., weld procedure and PWHT design), and conclusions with root cause analysis will be provided.
Case Study: Lip Seal Retrofit Analysis Using Finite Element Method for Heat Exchanger
Authors: Pasnik Louis , Gu Ming (Forrest) , Seipp Trevor G. 
Published: November 2024

Abstract
A high-pressure heat exchanger channel with integral tubesheet was upgraded from low chrome to austenitic materials, while the shell-side material remained ferritic. Due to concerns with thermal differential radial expansion between the austenitic tubesheet and the ferritic shell-side flange, an Omega-type lip seal design was incorporated, replacing the traditional flat lip seal design.
The finite element method was used in a transient thermal-mechanical and fatigue analysis of the lip seal loop and internal fillet welds. Historic plant operating data from past startups, upsets, and shutdowns was used to define idealized transient fluid temperatures and film coefficients which were applied to the model.
The internal fillet welds connecting the lip seal halves to the flange and tubesheet pairs were found to be limiting. Due to the requirement to reuse the existing ferritic shells, improvements were made to the fatigue life by incorporating groove welds in combination with the fillet welds.
Alloy Effects in Steels for Explosive Containment Vessels
Authors: Mueller Joshua J. , Gibson Joshem , Thrun Melissa 
Published: November 2024

Abstract
Explosive containment vessels (ECVs), such as those utilized to contain the detonation products of explosives during bomb/munition disposal or containment of experiments on explosive devices, are required to be fabricated from high-integrity materials to ensure the safety of people and/or property in the vicinity of the vessel. Candidate materials for ECV construction are desired to exhibit high strength and high toughness to prevent ductile exhaustion and/or brittle failure induced by impulsive loading; a non-trivial requirement given that, generally, materials exhibit poorer toughness with increasing strength. Additionally, vessel manufacturability (e.g. weldability and component thickness) also needs also to be considered when selecting materials for ECVs.
Los Alamos National Laboratory has had success using both A723 and HSLA-100 steel alloys for ECV applications. The present article provides a background on these two alloys and compares them from the perspectives mentioned above. A723 is better suited for thick-section and non-welded applications, whereas HSLA-100 is better suited for thinner (&lt; ∼10 cm) vessel components but also supports welding without post-weld heat treatment. Discussion is included regarding how the effects from the alloy compositions of these two steels enables them to perform in complementary applications. This discussion is extended to current alloy development for ECVs which seeks to improve performance and manufacturability.
Investigating In-Situ Fracture Behaviors of Polymer Pipeline Materials in Hydrogen and Hydrogen-Methane Blended Gas Environments
Authors: Ko Seunghyun , Qiao Yao , Nickerson Ethan , Shin Yongsoon , Han Kee Sung , Kuang Wenbin , Simmons Kevin 
Published: November 2024

Abstract
To reduce carbon emissions, the US natural gas infrastructure is seen as a primary solution for efficiently transporting hydrogen gas. Blending hydrogen gas with natural gas and transporting it across a national infrastructure could save significant infrastructure costs. To properly operate the infrastructure under the new gas system, it is critical to understand material compatibility with hydrogen under various conditions. The Blended Gas CRADA, a Hyblend project, is established to determine the material compatibility of existing natural gas pipes with hydrogen gas.
In this study, we investigate the in-plane fracture behaviors of MDPEMarlex and HDPEGDB exposed to hydrogen and hydrogen-methane blended gas. Single-edge notch bending geometry is used. All tests are executed in-situ with the gas environment. The experimental results show a significant effect of the gas environment on HDPEGDB specimens, reducing 5% (H2) to 42% (Blended gas) of specific fracture energy compared to non-aged specimens. For the MDPEMarlex, the effects of the gas environment have increased the specific fracture energy by 10% (H2) to 15% (Blended gas). Fracture surfaces of the tested samples are observed using an electronic microscope. The in-plane fracture surface of HDPEGDB shows a pronounced dimple fracture pattern after exposure to hydrogen and blended gas. The expanded fracture pattern contributes to lower the specific fracture energy. These observations provide critical information for validating polymer pipeline materials when interact with hydrogen and hydrogen-blend gas.
Research and Development of Three-Dimensional Isolation System for Sodium-Cooled Fast Reactor: Part 8 — Assembly Static Test Results of Three-Dimensional Isolated Device by Bi-Axial Loadings
Authors: Somaki Takahiro , Yukawa Masaki , Fukasawa Tsuyoshi , Hirayama Tomoyuki , Uchita Masato , Miyagawa Takayuki , Okamura Shigeki , Yamamoto Tomohiko , Watakabe Tomoyoshi , Miyazaki Masashi , Fujita Satoshi 
Published: November 2024

Abstract
The authors have been developing the three-dimensional isolation system for the Sodium-cooled Fast Reactor (SFR). The three-dimensional isolation device consists of the laminated rubber bearing performing the horizontal isolation function, four-disc spring units, the sliding elements, strength members such as the horizontal support function, and dampers in the horizontal and vertical directions.
We carried out the half-scaled assembly static tests under several bi-axial severe conditions from seismic design base loads to significantly exceeding seismic design base loads, as shown in Part 7. The test specimen was assembled elements of which the three-dimensional seismic isolation system is composed, but the horizontal and vertical damping devices were not modeled because of the static loading tests.
This paper describes tests results, focusing on the following items.
• Behavior of smooth operation and ensuring the independency of horizontal isolation and vertical isolation performances
• Hypothesis and verification of load transfer mechanism under horizontal and vertical loads superposition
• Effect of reinforcing plates on the loading force reduction of horizontal support function
• Conditions of the specimen after tests and discussion
Residual Stresses in Layered Pressure Vessel Nozzles
Authors: Brust Frederick W. 
Published: November 2024

Abstract
The National Aeronautics and Space Administration (NASA) has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure scattered across their various space centers across the US. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels because vessel replacements costs are high. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. Most tanks have between 4 and up to 32 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. A prior effort published in the 2022 ASME PVP conference provided results which consider weld residual stress and fracture assessment of some layered pressure vessels.
This paper adds to that effort by presenting results for the nozzle welds that attach to the layered pressure vessels. Weld residual stresses are the most important driver in the fracture response of the tanks because the toughness of the materials is rather low. In this paper, the WRS fields for three different nozzles are presented. The first nozzle considered, labeled V267-270, is a 1,530.35 mm (60.25 inch) inner diameter nozzle welded to a 15-layer tank and summarizes the WRS fields produced. The second nozzle considered here is a nozzle welded to a 1524 mm (60-inch) inner diameter 8-layer tank. The third nozzle weld considered is a 50.8-mm (2-inch) small nozzle weld. Both the residual stress fields are presented along with discussion of the potential fracture response of the nozzle and tank interface. Finally, the effect of repair welds in the nozzles are presented also.
Parametric Evaluation of Fillet Welded Patches With Reinforcing Plug Welds for Pressure Vessels Using Finite Element Analysis
Authors: Alian Ahmed , Moussa Ahmed , Nguyen Luat , Malik Sadath 
Published: November 2024

Abstract
The inspection of the Moderator Purification System Heat Exchanger identified microbiological corrosion at several locations on the shell side. The minimum measured thicknesses at different locations are projected to be lower than the pressure based minimum wall thickness when projected to the targeted end of life of the vessel. To ensure a continuous and safe operation of the heat exchanger until replacement, this work presents a repair strategy of the corroded areas on the shell using fillet welded patches with reinforcing plug welds following the procedure in Article 207 of ASME PCC-2-2022 edition. Plug welds can be engineered to bear a share of up to 30% of the patch plate’s load and must be appropriately positioned to carry their allotted portion of the load. The plug welds serve to decrease the bending moments experienced by the fillet welds, enabling the repair of large defects. ASME PCC-2 provides a wide range for the plug welds geometrical parameters (such as distance from the edge and diameter). In this work, a parametric 3D finite element study is performed to determine the optimized configuration of plug welds that reduces the stresses in the fillet welds. The results show significant reductions in the fillet weld stresses, up to 50%, when the diameter and distance from the patch edge to the plugs are varied within the limits provided by the ASME PCC-2 guidelines.
Aerobic Energy Turnover and Exercise Economy Profile During Race Simulation in a World-Record-Breaking Male Full-Distance Triathlete
Authors: Christensen Peter M. 
Published: November 2024

Purpose: To investigate metabolism and exercise economy during prolonged race simulation (>4 h) in a world-class, full-distance triathlete to help guide/adjust strategies for training, nutrition, hydration, and thermoregulation. Methods: Two experimental race-simulation days, designed to mimic the demands of a full-distance triathlon, were executed by a world-class male triathlete (MD; 25 y, body weight 82 kg, 6.2 L·min−1, blood lactate threshold ∼410 W, and 18 km · h−1 in cycling and running) who at the time ranked second in the world. Race simulation was performed 23 and 10 days prior to competing in Challenge Roth 2023, where MD won in a new world record/best time (7:24:40 h:min:s). Both test days lasted ∼4 to 5 hours with physiologic testing every ∼45 to 60 minutes in a “stationary” setting during cycling on a direct-mount trainer (∼320 W) and treadmill running (16 km · h−1), enabling gas exchange measurements ( and respiratory exchange ratio) and other physiologic measurements of interest (ie, core temperature and heart rate). This was combined with “real activity” as repeated loops in an open-air field setting at expected race pace in swimming, biking, and running. Results: was maintained at ∼4.2 L·min−1, with carbohydrates being the dominant fuel for oxidation as respiratory exchange ratio values dropped from ∼1 at the start of cycling to ∼0.85 during running. Cycling economy was stable, whereas a slight impairment in running economy occurred over time. Conclusion: High aerobic energy turnover and stable exercise economy can be maintained in a world-class record-breaking triathlete for prolonged period of time (+4 h), showcasing the importance of both for success in competition.