bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards an Improvement of Allowable Planar Flaws of ASME Code Section XI Acceptance Standards for Ferritic Steel Materials
Authors: Lacroix Valéry , Dulieu Pierre , Hasegawa Kunio
Published: November 2023

In case of flaw detection during In-Service inspection of nuclear components, ASME Code Section XI provides Acceptance Standards to determine whether the flaw can be considered as harmless or should be further evaluated.

For ferritic steel materials, the size of allowable planar flaws is given in Table IWB-3510-1. To facilitate the assessment, the allowable flaw size only depends on three parameters : the component thickness, the flaw aspect ratio and the proximity of the flaw to the surface. However, a graphical analysis of the impact of those parameters highlights some inconsistencies. The allowable flaw depth evolution is discontinuous between the ranges of thickness. Besides, the allowable flaw depth increases indefinitely with component thickness, which is not consistent with finite fracture toughness of materials. Finally, while the aspect ratio dependence of the allowable flaw depth has been clearly described in EPRI NP-1406-SR (1980), no clear technical basis has been found to explain the component thickness dependence. Consequently, the need to revise the allowable planar flaws of ASME Code Section XI Acceptance Standards using a robust technical basis is brought to light.

This paper details the inconsistencies related to the present allowable planar flaws table and proposes improvement points to revise the allowable planar flaw Table IWB-3510-1.
Revision of Allowable Planar Flaw Tables of ASME B&PV Code Section XI for Ferritic Steel Materials
Authors: Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio
Published: November 2023

When in-Service inspection detects flaw in nuclear components, Acceptance Standards of ASME Code Section XI provide allowable flaw sizes to assess the flaw severity and to identify the need for further evaluation. For ferritic vessel welds, the size of allowable planar flaws is given in Table IWB-3510-1.

Considering some inconsistencies highlighted in this table, a revision using a robust technical basis is conducted. For that purpose, a methodology is developed following ASME philosophy and including some basic criteria to ensure component safety by preventing plastic collapse and brittle failure. As far as the prevention from plastic collapse is concerned, a uniform limit load reduction is considered whatever the flaw aspect ratios. For the prevention of brittle failure, a reference surface flaw configuration (flaw size, aspect ratio and component thickness) is defined to derive a reference stress intensity factor that should not be exceeded. Then, all the flaw configurations corresponding to this reference stress intensity factor are identified to derive a set of allowable flaw size curves. At last, the most penalizing flaw sizes between both failure modes are retained to define the new allowable flaws.

This methodology is applied to surface flaws with various aspect ratios and component thicknesses. It is also coherently applied to subsurface flaws considering the proximity of the flaw to the surface as an additional parameter. Finally, a revision of the allowable planar flaw Table IWB-3510-1 of ASME Code Section XI Acceptance Standards is proposed.
Study on Vertical Load Acting on Whole Roof of Cylindrical Tanks in Nonlinear Sloshing Including Extremely Large Load
Authors: Ikesue Shunichi , Morita Hideyuki , Sago Hiromi , Yokoi Shinobu , Yamamoto Tomohiko
Published: November 2023

When a cylindrical tank is excited by seismic waves, liquid surface motion occurs in the tank. This motion is referred to as sloshing. When a large amplitude sloshing occurs, the liquid surface collides with the roof of the tank, and an impulsive vertical load acts on the roof.

In our previous study, we proposed a predictive evaluation method of the vertical load. The proposed method consists of an impact pressure model, a simplified nonlinear sloshing liquid surface model, and a local liquid surface wave model. The predictive evaluation method almost agreed with test results of the vertical loads acting on load measurement equipment which is attached to a part of the roof of the test model. However, it is necessary to verify the predictive evaluation method for the vertical load acting on the whole roof.

In this study, we proposed the modified predictive evaluation method to deal with large excitation amplitudes and verified this method for the vertical load on the whole roof by the CFD analysis. The modified predictive evaluation method tended to be larger than the CFD analysis under the high and low roof height conditions. On the other hand, the CFD analysis result was extremely larger than the modified predictive evaluation method under the middle roof height condition, despite the small excitation amplitude. In addition, the CFD analysis and the test under the same condition were extremely larger than the modified predictive evaluation method in the maximum load on load measuring equipment.

In this study, we have also discussed this extremely large load, by the CFD analysis. We have found that the previous weak roof collision made the liquid surface a flat shape, and the collision between the flat liquid surface and the roof caused the extremely large load. The result shows that the collision history between the liquid surface and the roof has a significant effect on the vertical load on the roof.
NORSOK U-001 5th Edition 2021 for Subsea Production Systems
Authors: Kirkemo Finn , Muff Anthony David , Stewart Barry , Wormsen Anders
Published: November 2023

NORSOK U-001 provides general requirements for the development, design and manufacture of subsea production systems intended for use on the Norwegian Continental Shelf. NORSOK U-001 5th edition was released in December 2021. Annex B defines requirements for the structural design, materials and fabrication of subsea wellhead, subsea trees, and completion/workover riser systems. An overview and background for the estimation of the static structural capacity as given in this Annex are presented in this paper.

Static structural design analysis methods for combined loading design and pressure design of riser load path components are presented. The link between material requirements and the assumptions made by the finite element based static design analysis methods are emphasized (e.g., ductile failure). Examples of their use for the design of common subsea components such as pipes, wellhead connectors and bolted flanges are given.

The static structural design analysis methods in Annex B have evolved from previous revisions of this standard to address gaps and the missing link between the analysis methods and material properties. The paper ends with a discussion on the limitations of the current edition and outlines future work that could be undertaken to improve and simplify future revisions of Annex B in NORSOK U-001.
Numerical Analysis and Research on Sealing Performance of Flange Connection System in Gas Station
Authors: Li Feng , Zhang Laibin , Dong Shaohua , Wu Wenping
Published: November 2023

Gas stations are vital components in gas gathering and transportation systems. Flanges establish a crucial connection between pipelines, as well as between pipelines and gas station equipment. They primarily rely on the pre-tightening force generated by the bolts to achieve metal sealing. The pre-tightening force is transmitted to the gasket to generate sufficient sealing pressure and avoid fluid medium leaks. The main cause of leakage is a contact gap between the flange and the gasket, which can result in the sealing failure of the flange connection system. The sealing performance of the flange system determines the airtightness of the pipeline system. This paper combined theoretical analysis and simulation to examine the sealing performance of flange system connections in gas stations. Different tightening forces and preloading force sequences were used to numerically analyze the sealing performance of the individual flange components. The compression-rebound characteristics of the flange gaskets and the bolt preload sequences were analyzed, yielding the following results: (1) At different pre-tightening forces, the overall flange stress was uniformly distributed, while the bolt stress was concentrated at the inner side of the stud and the contact position between the bolt and the flange. The stress distribution on the gasket was uniform, with a higher outer than inner stress. (2) The compression rebound curve indicated a certain nonlinearity in the flange gasket at different preloads. Furthermore, the preload caused a flexible graphite metal gasket wound. The degree of elastic or plastic deformation in the gasket increased at a higher preload. Although a higher preload increased the sealing capacity in an appropriate range, excessive preloading induced plastic gasket deformation, causing it to lose its original compression resilience and resulting in seal failure. (3) The flange interaction varied at different loading sequences, while different pre-tightening sequences produced elastic interaction. Therefore, the bolts that were tightened first more significantly affected pre-tightening than those tightened later. Changes were evident in the stress distribution of the gasket, which showed improved sealing performance under sequential and cross-loading.
Effect of High Pressure Hydrogen Gas on Fatigue and Fracture Properties of API X65 LinepIpe Steels
Authors: Nishihara Yoshihiro , Okano Hiroshi
Published: November 2023

Hydrogen is one of the promising energy carriers for achieving a carbon neutral society. The pipeline system is positioned as a major type of infrastructure which will be indispensable for mass transportation of gaseous hydrogen. It is acknowledged that existing natural gas pipelines can be used safely to transport hydrogen blends up to 10 or 20 %. However, it is also known that the mechanical properties of steels are significantly degraded by hydrogen embrittlement, even under small partial pressures of hydrogen. Material degradation is considered in the hydrogen pipeline code ASME B31.12. This code requires evaluation of the fracture and fatigue properties of linepipe materials used under hydrogen, and a critical assessment is conducted so that fracture of the pipeline can be avoided during its service life. In the present study, the hydrogen absorption properties, fracture toughness and fatigue crack growth properties under a 25 MPa hydrogen gas environment were investigated by using 3 kinds of linepipe steels manufactured by different methods. The materials were API X65 linepipe steel, which were manufactured as ERW, LSAW and seamless (SMLS) linepipes. Although all the materials showed a bainitic ferrite generally called, each microstructure had distinctive characteristics attributable to the manufacturing process. While all the linepipe steels showed better fracture toughness and fatigue crack growth rates than the ASME B. 31.12 design curve, their hydrogen absorption properties, fracture toughness in hydrogen gas and fatigue crack growth properties in hydrogen gas differed due to their crystal structures, even though the strength grade of the materials. In the steels used in this study, the fracture toughness and fatigue crack growth characteristics under a hydrogen atmosphere were insensitive to the influence of absorbed hydrogen, and were considered to be influenced by the material factors that determine the fracture toughness and fatigue crack growth characteristics in the atmosphere.
Technical Basis of ASME B31.12 Code Case 218: Use of Enhanced Materials Performance Factors (Hf and Mf) of 1.0
Authors: Xu Kang , Rana Mahendra
Published: November 2023

ASME B31.12 provides piping and pipeline design and construction standards specific for H2 service. Due to the material degradation mechanisms in presence of high-pressure hydrogen, B31.12 imposes a significant reduction in allowable stresses by applying materials performance factors (Hf and Mf) in thickness and design pressure calculations. The reduction factor is as much as 54% for high strength piping and pipeline materials at high hydrogen pressures. The application of the materials performance factors significantly penalizes the use of high strength piping and pipeline materials. In the light of recent developments in understanding hydrogen degradation mechanisms, it is recognized that alternative design and fabrication technologies can be employed to mitigate the risk of hydrogen embrittlement without such penalties. Using fracture mechanics approaches, it has been demonstrated that the materials performance factors can be relaxed by implementing additional requirements in non-destructive examination (NDE) and heat treatment. A B31.12 Code Case has been developed to provide alternative rules to relax the materials performance factors. This Code Case has been approved by ASME B31 Committee and Board on Pressure Technology Codes and Standards, and is ready to be used by code users. This paper reviews the background on Materials Performance Factors in current code, and documents the technical justifications of eliminating these factors.
Simulation Analysis and Experimental Study on Pipeline Circumferential Crack Detection Based on Residual Magnetism Effect
Authors: Wei Haotian , Dong Shaohua , Ma Yundong , Xu Lushuai , Zhao Jiahao , Zhang Hang
Published: November 2023

A method for crack detection on the surface of pipelines that uses residual magnetic detection technology based on the hysteresis effect after magnetizing the pipeline to magnetic saturation has been developed in this study. Support vector regression (SVR) was employed for quantitative assessment. This paper reviewed the magnetization process of the magnetizer, the generation of residual magnetism effect, and the detection of residual magnetic fields. An experimental and theoretical study examined how the crack size affects residual magnetic anomalies. The simulation results indicated that the characteristic values of the residual magnetic anomaly changed in a roughly linear fashion at a more significant crack depth. As the crack width increased, the variations in residual magnetic anomaly characteristic quantities were relatively mild. The input values were denoted by the extracted characteristic amounts. The width and depth parameters of the crack were used as output values. A trained SVR model was employed to estimate the crack size. The crack widths and depths were accurately determined at 62.5% and 85.42%, respectively by combining this detection method, SVR, and the experimental results. This study demonstrated the feasibility of using residual magnetic detection technology, combined with SVR, to detect circumferential cracks in pipelines, which is an essential supplement to internal magnetic flux leakage detection and assessing pipelines.
Near-Neutral pH Stress Corrosion Crack Test Results and Potential Application to Crack Growth Retardation and Hydrogen Sensitivity in Pipeline Steels
Authors: Tiku Sanjay , Lamborn Lyndon , Nelson Greg , Tehinse Olayinka
Published: November 2023

Over a five-year period, a series of fatigue crack growth experiments have been conducted in air and in a bubbling CO2 environment to induce diffusible hydrogen ingress. While the main objective of the hydrogen-charging research targeted characterization of near-neutral stress corrosion crack growth, many of the findings can inform emerging hydrogen transport crack threat management. Summarizing and highlighting these findings and trends could benefit the pipeline industry and accelerate research toward international net zero carbon objectives.

Crack growth retardation in X52 and X65 were found to be readily achieved with an overload cycle, both in air and with hydrogen charging. Subsequent underload cycles were shown to cause resumption of crack advancement: such underload cycles are typical of pipeline operations. Grade X65 pipe steel samples with hydrogen charging were found to be sensitive to underload cycles with significantly higher da/dN growth rates.

Crack retardation models currently available were evaluated using the AFGROW crack growth modeling software to determine and compare model performance to test results. Potential implications of these findings to mainline pipe integrity management are considered in light of crack threat management methods, specifically periodic hydrostatic test methodologies, including emerging hydrogen transport considerations.
Safe Life of Line Pipe in Hydrogen Blended Transport
Authors: Wang Duncan , Hogan James , Lamborn Lyndon
Published: November 2023

A multi-year collaborative project with the Natural Sciences and Engineering Research Council (NSERC) of Canada and the University of Alberta Edmonton (UoA) was launched in October of 2022. The project considers the potential effects of emerging commodity transport demands in support of Canadian Net Zero 2050. The project seeks a deeper understanding of the mechanisms that govern the long-term fatigue behavior of spiral welded pipelines towards informing maintenance scheduling and design. Multi-scale testing and modelling approaches involving materials, fluids, and their interactions are to be pursued. Methodologies developed and knowledge gained have cross-over applicability to seamless and long-seam welded pipe.

Recent full-scale pipeline fatigue testing for various geometric deformations was found to be sufficient to develop preliminary governing S-N curves for pipeline steels in air. A projection of a governing S-N curve family for pipeline steels which are subject to diffusible hydrogen is baselined through correlation with testing under diffusible hydrogen conditions. Full-scale fatigue tests of stress concentrators in carrier pipe steels indicate that a large percentage of the useful fatigue life consists of the crack initiation portion of the life cycle and may be leveraged in making integrity management decisions.

Finally, in this work, the governing S-N curve is resolved into a safe-life plot versus the spectrum severity indicator cycles. This allows operators to project a practical lower bound safe life horizon for line pipe with typical stress concentrators. The study concludes that a multi-year project remains a prudent approach in the event some pipeline operators begin hydrogen or CO2 transport service before the project concludes in 2026.
Influence of Insensitive Strain Region for Strain Rate on Fatigue Life of Stainless Steel in PWR Primary Water Environment
Authors: Kamaya Masayuki
Published: November 2023

It has been shown that the degree of fatigue life reduction due to the pressurized water reactor environment depends on strain rate. It was reported that there was an insensitive strain zone, at which the strain rate had little influence on the fatigue life. The insensitive strain zone existed from the minimum peak strain to a threshold strain, which was determined empirically. This study aimed at determining the insensitive strain zone that corresponds to the crack mouth closure. Fatigue test runs were conducted using cylindrical hollow specimens of Type 316 stainless steel. The cold worked material was also used for the fatigue test. The strain rate was changed at a pre-determined strain, at which the crack mouth was deduced to be opened. It was shown that the fatigue life was almost the same regardless of the strain rate at the insensitive strain zone. Also, the insensitive strain zone could be determined by assuming the crack mouth opened when the stress reached zero in the strain rising phase.
High-Pressure High-Temperature Design Verification and Validation of Well Completion Tools
Authors: Zhou Zhong , Weber Jamie , Yin Shengjun , Apichartthabrut Terapat , Murphy Rob , Abeidoh Abdel Hamid , Zhong Allan
Published: November 2023

While all oil and gas wells operate at pressures and temperatures greater than ambient conditions, wells that are considered high-pressure and high-temperature experience even more challenging operating conditions. These high-pressure, high-temperature (HPHT) wells have pressures greater than 15,000 psi and/or temperatures in excess of 350 °F. These harsh operating conditions result in unique design and safety challenges that are not experienced in more conventional wells. Despite these technical difficulties, the significant resource potential of HPHT wells has attracted development for many years and with advancing technology, the number of HPHT wells is increasing.

Permanent downhole barriers are one of the most critical design challenging tools used in HPHT wellbores. These barriers must reliably hold high differential pressures for decades without leaks, movement, or other failure modes. Experimental and validation testing is expensive and inherently limited in duration of the tests. As a result, HPHT-specific nonlinear numerical simulation is used to complement the physical tests for better reliability, safety, and reduced development time. The HPHT design verification analysis is used to demonstrate compliance with engineering standards, regulatory requirements, and independent third-party review.

This paper presents an analysis procedure for HPHT completion tools through the results from a case study on a permanent bridge plug, a type of downhole pressure isolation tool. The structural integrity is evaluated for multiple loading scenarios per the ASME BPVC Section VIII Division 3 (2017), and the fatigue analysis is conducted based on well-load histograms during the life of the well in accordance with the ASME BPVC Section VIII Division 2 (2017) and API 579-1/ASME FFS-1 (2016). This analysis includes nonlinear finite element analysis, temperature and sour environment effects on materials, and the surface finish effects on structural reliability. The simulations are validated through both component-level and assembly-level testing.

The successful implementation of the HPHT design verification analysis played a significant role in the successful and timely development of the downhole pressure isolation tool.
Research and Development of Viscous Fluid Dampers for Improvement of Seismic Resistance of Thermal Power Plants: Part 13 Fragility Analysis Based on Structural Health Monitoring
Authors: Minagawa Keisuke , Aida Kiyoshi , Fujita Satoshi
Published: November 2023

Thermal power plants are one of the critical infrastructure facilities that support modern society. A boiler is a main large structure in a thermal power plant, and it is suspended from its support structure not to restrict thermal expansion, thus it is easy to respond during earthquakes. Therefore, steel dampers are usually installed in boiler structures to absorb vibration energy by plastic deformation of steel. In the meantime, aftershocks of the Great East Japan Earthquake in 2011 have occurred frequently in the Tohoku region even now. For example, in February 2021 and March 2022, large earthquakes of magnitudes 7.3 and 7.4, respectively, occurred in the same epicenter area as the Great East Japan Earthquake. In addition, the long duration and long period ground motions have been focused on after the Great East Japan earthquake. Therefore steel damper has high risk of fatigue failure by earthquakes. Given these backgrounds, it is necessary to improve the seismic resistance of boiler structures, especially for steel dampers.

In this study, we have proposed application of viscoelastic dampers in boiler structures instead of conventional steel dampers. Viscoelastic dampers absorb vibration energy by fluid resistance of a viscoelastic fluid. Component tests of the viscoelastic damper and seismic response analysis using a multi-mass point system and frame model have been conducted in the previous papers. As a result, it was confirmed that the viscoelastic dampers have high vibration control performance and long life. Then, many acceleration sensors have been installed on an actual boiler structure to improve the accuracy of the analytical model used in seismic response analysis, and actual seismic responses have been observed since 2021. In PVP 2023, fragility analysis using seismic response measured in actual seismic events is introduced. Fragility analysis is a powerful tool to quantitatively assess the risk of structural damage. This paper demonstrates the usefulness of structural health monitoring.
Closed Form Formulae of Interaction Factors for Twin Coplanar and Parallel Elliptical Cracks
Authors: Gilles Philippe , Germain Célia , Albrecht David , Desrayaud Cyrille
Published: November 2023

Crack interaction has been a widely studied topic. However exact formulae for crack interaction factors exist only for the case of coplanar through-wall cracks embedded in an infinite elastic medium subjected to normal loading.

Fitness-For-Service (FFS) and regulatory codes provide rules allowing determining whether multiple flaws shall be combined into a single flaw or evaluated separately. However, these rules set thresholds beyond which flaws are replaced by an envelope sometimes over conservative.

This paper presents closed form formulae for interaction factors of two equal elliptical cracks embedded in an isotropic elastic medium subjected to normal loading. The formulae are based on theoretical developments and Finite Element computations achieved by ESI France in a frame of a large program driven by EDF dealing with interaction of volumetric defects. These defects are modelled as cracks in a conservative way.

Based on the interaction formulae between two cracks, an equivalent crack is defined. These cracks are selected considering the strongest interaction. The process is then repeated with the remaining cracks.
Production Low Toughness Case Histories When Manufacturing Low Alloy Steel Pressure Equipment in the Petrochemical Industry
Authors: Dalal Mitul , Hosack Allie , Penso Jorge
Published: November 2023

Low alloy steels containing chromium and molybdenum (CrMo steels) are widely used in pressure equipment in the petrochemical industry. However, if their manufacturing and production welding are not properly controlled, or if they are operating beyond their design conditions, these steels can exhibit brittle behavior at higher than expected temperatures. There are recommendations and requirements in the industry for controlling key parameters during welding. Before they are performed, production weld procedures must be reviewed against the test results from mock-ups to meet certain requirements such as impact toughness, X-bar, and J-factor. However, there is not much industry guidance for assuring the production welding occurs as per the reviewed parameters. This paper discusses three case histories of CrMo alloyed pressure equipment. One of the case histories is for a reactor, and the second case history is for a heat exchanger. The final case history discussed is for piping material. Details of manufacturing, production welding, and testing are discussed in the case histories. For some of the case histories, this includes finding lower impact toughness during production test welding than was expected based on the procedure qualification record. Finally, the paper discusses the importance of additional steps that could be added to the inspection test plan to improve the monitoring of production welding.
Fitness-for-Service Assessment of Refractory Lined Duct With Hot Spot
Authors: Yoo Eui Jong , Kim Chongmyung , Choi Capjoo
Published: November 2023

The duct line in FCC unit is generally designed using carbon steel with inside refractory lining for a high temperature of service fluid. The refractory could be degraded during operation due to various causes. When the refractory is damaged and a high temperature of service fluid is affected to the duct directly, the surface of the duct is exposed to the elevated temperature, and it is called a hot spot. The temperature increase of hot spot does not lead to immediate failure, but it causes structural rupture or bulging of the duct due to creep in the long term. When hot spot occurs, the steam cooling method is generally used to mitigate the creep damage by spraying the steam onto the hot spot area. In case of extensive hot spot, it is difficult to apply the steam cooling method properly. If hot spot is not controlled by mitigation method, it is necessary to check the fitness-for-service of the duct line and determine the remaining life to prepare the maintenance plan to replace or repair the steel part and refractory lining of the duct line.

In this paper, a case study of fitness-for-service assessment is performed for the refractory lined duct with extensive hot spot in FCC unit. Piping stress analysis is performed to calculate stresses by weight and pressure. And remaining life against creep damage is evaluated with ASME B31.3 Appendix V. And detailed finite element analysis is performed under same condition, and creep life is calculated according to API 579 Part 10 Level 2 Assessment.

Through this process, fitness-for-service assessments for the refractory lined duct with hot spot are compared and its effectiveness is discussed.
Residual Stresses Impact on Fast Fracture Risk - Experimental Evaluation on Vessel Low Alloy Steel Plates
Authors: Louerat Jules , Doremus Luc , Ancelet Olivier , Marie Stephane , Chapuliot Stephane , Dahl Anna
Published: November 2023

Framatome and EDF have launched an important R&D program which aims at evaluating the effective impact of residual stresses on the fracture initiation in the brittle-to-ductile transition regime, on vessel low alloy steel plates including a surface defect.

The test program is designed to allow a direct comparison of the tests results, with and without residual stresses, other factors being equal, to address the impact of the residual stresses in the brittle-to-ductile transition domain. High level of residual stresses of secondary nature have been generated on specimens, at the vicinity of defects, without modifying the local material toughness by avoiding the introduction of significant plastic deformation close to the defect.

Specimens are pre-cracked and tested by 4 points bending. Results show an impact of residual stresses on the fatigue crack growth rate but none on the fracture risk in the transition and upper shelf of the brittle-to-ductile transition. Significant impact is only observed at the lower shelf of the material.

It is shown that local approach using Beremin model clearly catches these results. It also demonstrates that residual stresses can be neglected for fracture assessment analysis in the upper part of the brittle-to-ductile transition for high toughness nuclear vessel low alloy steels.
Applicability of Non-Uniformly Varying the Fin Density of Tandem Finned Cylinders As a Viable Vortex and Noise Suppression Technique
Authors: Alziadeh Mohammed , Mohany Atef
Published: November 2023

This article explores the applicability of using non-uniform finned tubes in tandem arrangement at L/Deq(avg) = 2.5 to suppress flow-induced acoustic resonance. Particle Image Velocimetry (PIV) measurements are performed to visualize the vortex development in the wake before and during flow-induced acoustic resonance. Acoustic pressure measurements are performed to characterize the aeroacoustic response of the tandem finned tubes. It was found that non-uniform finned tubes weaken the vortex shedding process and reduce the sound pressure level (SPL) during flow-induced acoustic resonance associated with the vortex shedding process by 50%. However, non-uniform finned tubes do not hinder the instability of the shear layers within its gap. This makes non-uniform finned tubes susceptible to flow-induced acoustic resonance associated with the instability of the gap shear layers. During this type of acoustic resonance excitation, highly discrete and well-organized vortex cores are formed in the gap and wake of both uniform and nonuniform finned tubes with SPL similar to that generated by the uniform finned tubes. A summary of the results are presented in the paper.
CFD Investigation of Effects of Different Feed Injection Schemes on Reaction Coking in an Industrial RFCC Riser
Authors: Chen Sheng , Yan Zihan , Chen Ming , Liu Mengxi , Liu Juanbo , Xie Guoshan
Published: November 2023

Heavier and poorer crude oils often produce more reaction coke and lower yield of target product such as gasoline and LPG in a commercial FCC riser, and then affect the safety and running period of reactor. Our previous cold-model simulation indicated that a modification from the conventionally upward feed injection scheme to a downward one improves the oil-catalyst mixing. This work aims to improve oil cracking reaction and avoid coking process with a downward feed injection scheme, wherein the feed jets counter-currently impact the catalyst particle flow from riser bottom. A twelve-lump kinetics and vaporization of liquid oil were considered in a multiphase Eulerian model with the energy minimization multi-scale drag and mass model (EMMS). The extent of fixed coke near riser wall was predicted with our fixed coking model in simulation. Comparison with simulation date of upward feed injection scheme is conducted in terms of the profiles of oil gas component and fixed coke and the yields of gasoline and LPG at riser outlet. The results show that the simulation approach can accurately predict the complex processes of gas-liquid-solid three-phase flow, vaporization and reaction coking. Big discrepancies of multiphase flow and mixing occurs in the feed injection zone. The counter-current feed injection scheme can accelerate the vaporization of liquid oil droplets and speed up the heat and mass transfer compared with the traditional upward scheme; moreover, it can also improve the product yields and obviously reduce the deposition of coke near riser wall, especially in the feed injection zone. An optimal feed injection velocity with the counter-current scheme can greatly improve the conversion of raw oil, increase the yield of desired products such as gasoline and LPG, and reduce the amount of coke produced by reaction (19.49%).
A Mechanical Performance Comparison Between GMCL and Hybrid Gaskets
Authors: Abdelgalil Abdelgader
Published: November 2023

The paper provides a mechanical performance comparison between two types of gaskets; the GMCL and the Hybrid gaskets. A nonlinear FEA modeling was used to determine the pressure variations across the gasket face. The models determine pressure distribution on gasket face during installation, followed by gradual increase in pressure and temperature to represent normal operation condition. In all of these stages, the details of: gasket seating, gasket sealing and flange face rotation are all determined and compared.
Reliability and Life Assessment of Coke Drums Through Boat Sample-Based Testing
Authors: Saini Nitin , Lyu Zhe , Suzuk Yasin , Skinner Travis , Ju Feng , Iverson Millar , Bohra Sudeep , Li Leijun
Published: November 2023

Life assessment of coke drums is vital to prevent circumferential through-wall cracking and to ensure it’s safe and serviceable. Cracking in the shell/skirt-shell junction/welds, permanent distortion, and bulging (due to the ratcheting effect) are common damage mechanisms due to low cycle thermal fatigue. The difficulties in performing an insightful inspection and life assessment are limited by the wall thickness, location heterogeneity due to service conditions, and test methods. In this study, a boat sample-based testing procedure is developed for the life assessment of coke drums. The boat samples are extracted from four different locations named crack, bulge, notch, and benchmark from a 40-year serviced coke drum. The boat samples are machined for sub-size smooth tensile, notched tensile, low-cycle fatigue, and Charpy toughness specimens. Smooth tensile, notched tensile and low-cycle fatigue tests are performed at three test temperatures (room temperature, 250°C, and 480°C). The results of sub-size specimens are calibrated to full-size and compared with the knuckle plate (least temperature in the coke drum). The fracture toughness of boat samples is predicted by the Haggag method using the smooth tensile and metallographic results. The boat samples have gained strength but have a reduction in ductility and toughness compared with knuckle plate material. The boat samples have shown a change in the microstructure and hardness. Carbide precipitation is observed on the grain boundaries and within the ferrite grains. This precipitation might have reduced the ductility and toughness.
Evaluation of Cr-Mo Steels Welds Produced by Gas Tungsten Arc Welding With High Silicon Contained Solid Filler Rod to Omit Back Shielding
Authors: Takahashi Atsushi , Isono Shinya , Takauchi Hideaki
Published: November 2023

Where single-sided welding is applied to the fabrication and erection of piping, back shielding by inert gas and its maintenance for the first few layers is required for low alloy steels (LAS), stainless steels (SS) and nonferrous alloys to obtain good weldability and quality of welds.

However, installation and removal of back shielding isolations inside piping for the joint and the adjacent areas to be welded are sometimes impractical due to piping layout and construction sequence such as closure joints. And the unexpected remaining isolations sometimes become concerns for obstructing fluid flow or damaging piping components such as valves and rotating equipment during commissioning or after operation.

To solve the concerns, high silicon (Si) solid filler rod was experimented to SS welding by gas tungsten arc welding (GTAW) to omit back shielding, and positive results of the R&D were introduced in ASME PVP2022 [1]. The same concept using high Si solid filler rod for GTAW was expanded to welding for Cr-Mo steels and properties of the welds were studied by comparison of the welds produced by different concentration of Si in filler rods to the conventional GTAW with back shielding. This paper discusses and evaluates the potential of the GTAW with high Si solid filler rod which can omit the inert gas back shielding for Cr-Mo steels because positive results of the study were obtained as the same as the R&D for SS welds.
The Effect of Loss of Constraint on the Initiation of Ductile Fracture in a Mini-CT
Authors: Li Meng , Chaouadi Rachid , Uytdenhouwen Inge , Pardoen Thomas , Bonny Giovanni
Published: November 2023

As one of the most appealing miniaturized geometries for fracture toughness characterization, the miniature compact tension (mini-CT) geometry was demonstrated to provide reliable fracture toughness measurement in the ductile-to-brittle transition regime and Master Curve assessment. However, when using a mini-CT in the upper shelf (fully ductile) regime, the ductile crack initiation and the crack growth resistance tend to be underestimated for most of the investigated RPV steels.

Previous experimental investigations have attributed the underestimation of the crack resistance properties to two concurrent processes related to loss of constraint and cold working occurring in the ligament ahead of crack tip during cracking, and gave an engineering size correction that mainly accounts for the thickness of the specimens. In this study, finite element simulations and two micromechanics-based approaches: the Rice-Tracey void growth model and Thomason void coalescence model are combined, aimed at investigating the role that the loss of constraint plays in the initiation of ductile fracture in a mini-CT and providing numerical evidence to support the proposal of the size correction on the critical fracture toughness. The final objective of this paper is to estimate the ductile crack initiation behavior that would be obtained from a standard 1T-CT specimen by applying appropriate size correction on a mini-CT.

The results show that the method incorporating the finite element simulations and two micromechanics-based approaches can well describe the effects of loss of constraint for different materials, thus contributing to the size correction of critical fracture toughness of mini-CT in various conditions.
Ventilating Process and Pyrolysis Gas From High-Pressure - Reactor Conditions on Mini-Plant Scale
Authors: Imhoff Moritz , Busch Markus
Published: November 2023

Pressure relief systems for high-pressure applications such as the high-pressure polymerization process are calculated mostly via API 520[1]. Here and in other empirical methods like the DuPont method, the mass relief is calculated via the density of ethene for the given process conditions. The valve body characteristic is further considered. Different physical properties of an unburned and burned phase in the case of a ventilated deflagration are generally not considered. The objective of the presented work is to generate an in-depth understanding and increase the reliability of venting process gases exemplary from the high-pressure polymerization process regarding real scenarios like considering polymer content and pyrolysis products from ethene decomposition. A transient pressure relief model and method is employed with the help of an isentropic nozzle model and a real gas equation of state. Polymerization mixtures are relieved from pressure up to 2000 bar, throughout a defined nozzle diameter. Thermodynamic behavior of gas mixtures is calculated with a real gas equation of state. The ventilation of ethene with a polymer component up to 20 wt.% content does reduce the discharge coefficient in comparison to sole ethen. Still, the resulting depressurization rates are mostly faster due to the higher density of the mixture. When pyrolysis gas from ethene decomposition is ventilated, the increased temperatures from decomposition heat and the resulting products do affect the relief process in a systematic manner. Hereby the depressurization takes longer in comparison to the unburned phase. Calculated discharge coefficients are significantly reduced compared to polymerization mixtures.
Application of the J-Q Methodology to Consider the Geometrical Effect on Fracture for Large Steam-Generator Tubesheet
Authors: Ancelet Olivier , Marie Stephane , Chapuliot Stéphane , Parrot Aurore
Published: November 2023

In the frame of a Fracture Mechanics Assessement in the perforated part of the steam-generator tubesheet, a defect relying two holes is postulated, which represent a singular configuration compared to conventional FMA. Indeed the defect is relatively small in comparison to the plate thickness and the crack length is limited by the distance between two holes.

To take benefit of the geometry effect of this configuration, an application of the two parameters J-Q approach is performed on tubesheet component.

At first, the methodology was applied to define and validate the methodology on an experimental data base with different constraint levels. This data base contains numerous fracture tests performed by both EDF and Framatome on various specimen geometries extracted from a 18MND5 low alloy ferritic steel plate, in the brittle-to-ductile transition regime. C (T), SEN (T), SEN (B), and non-standard specimens [1].

Secondly this methodology is applied to predict the benefits of this approached for tubesheet configuration. Different configurations are tested: underclad defect, surface defect, mechanical loading, thermal shock, in the middle of the perforated zone or near the border of the perforated zone.

These applications show some significant constraint effect for underclad defect and some moderate effect for surface effect.

A methodology is proposed to correct the classical Engineering Fracture Mechanics Assessment to gain margins without considering any probability of failure or statical approach.
Suggested Procedure for Determining the PCC-1 Appendix O Gasket Properties
Authors: Girão Carlos D. , Veiga José C. , Meira Igor
Published: November 2023

The ASME Pressure Vessel and Boiler Code Section VIII – Appendix 2 – Rules for Bolted Flange Connections with Ring Type Joints [1] has been used successfully for many years. An experienced engineer will apply the rules and, in most cases, the vessel will be operated for many years without leakage. However, there have been many papers addressing its shortcomings [2–4]. The Gasket Properties of the Appendix 2 has never been updated with newer designs and materials. Its tabulated values are reminiscent of the “Asbestos time”. Properties such us maximum gasket stress and relaxation are not considered.

The ASME – PCC-1 – Pressure Boundary Bolted Flange Joint Assembly [5] has introduced the Appendix 0 – Assembly Bolt Stress Determination to address some of the problems associated with the Appendix 2. Several new gasket properties were introduced without a procedure to determine them. Two papers presented at PVP Conferences [6,7] proposed a protocol to determine some of the gasket properties.

In Europe the rules for calculating flanges and determining the gasket properties were updated with the EN 1591 - Flanges and their joints - Design rules for gasketed circular flange connections [8] and EN 13555 - Flanges and their joints – Gasket parameters and test procedures relevant to the design rules for gasketed circular flange connections [9]. Since their introduction there has been a major effort to test gaskets and determine their properties. Manufactures are publishing results and there are two public websites [10,11] where values are posted. With so many data available the purpose of this paper is to suggest a procedure to use the EN13555 data to determine the Appendix – O gasket properties.
Study on the Circumferential Pressure Distribution of the Tube Bundle in the Center of the Heat Exchanger
Authors: Qi Sijiu , Tan Wei , Zhu Guihong , Zhu Guorui
Published: November 2023

The fluidic vibration problem of heat exchanger tube bundle is an important factor causing its destruction. In this paper, a combination of experimental and numerical simulations is used to study the pressure distribution and inter-tube flow field on the central tube bundle of heat exchangers at low flow velocity, and to provide data support and theoretical support for the vibration analysis of the tube bundle.

Based on the computational fluid dynamics method, ANSYS Fluent software was used to perform numerical simulations for four types of arrangement: square triangle, square, corner triangle and corner square models with different incoming flow velocities and pitch ratios. The calculation results show that the stationary point of the central tube varies in position and number with the change of flow velocity at low flow velocity, and gradually stabilizes after the flow velocity increases. It is also observed that the standing point of the central tube gradually moves backward with the increase of the incoming flow velocity. The angular size of the boundary layer separation point: the angle of the corner triangle arrangement is the largest, the angle of the square triangle arrangement and the square arrangement is the second largest, and the angle of the corner square arrangement is the smallest; there is no significant change in the size of the pressure in the direction of incoming flow for different pitch ratios of the central tube, and the position of the standing point remains basically the same, but the pressure in the direction of the wake flow decreases slightly with the increase of the pitch ratio.

To verify the simulation results, a water-tunnel experimental setup was designed to measure the pressure distribution around the circumference of the tube bundle using an electronic pressure scanning valve. The experiments verified the vibration characteristics in the environment of a tube bundle arranged in a square triangle with a spacing ratio of 1.41, which is consistent with the trend of the simulation results and verifies the reliability of the simulation results.