bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simplified Method for Analyzing Pressure Vessel Response to Explosion Generated Drag Loading
Authors: Hundl Jacob , Millet Barry , Kirkpatrick Kenneth , Mosher Bryan
Published: November 2023

A simplified method for analyzing pressure vessel response to blast overpressure incidents was developed, refined, and verified in papers PVP2021-61854 and PVP2022-84746. The simplified method presented in the two papers showed how it was possible to analyze the loading and effects of a blast wave generated by an explosion (positive phase overpressure incident) on vertical pressure vessels without utilizing traditional analysis software. However, the simplified method presented in the two papers did not consider or provide provisions for examining equipment loading solely from explosive generated drag loading (negative phase over-pressure event). During the execution and detailed design of an offshore liquified natural gas (LNG) facility, drag loads were added as part of the design criteria for certain pressure vessels by the offshore classification society and the third-party health safety and environmental (HSE) group contracted to study the possibility and probability of an explosion. This paper will show the development, implementation, and results from a simplified method for analyzing pressure vessel response to drag loading which utilizes the dynamic load factor (DLF) and assumes a single degree of freedom (SDOF) system to remove the use of any specialized finite element analysis (FEA) software from the analysis. The paper will examine the actual pressure vessels andapplicable design loads which were required to be evaluated by the project and compare the results of simplified analysis to a traditional analysis which uses an industry standard structural analysis FEA software. The loadings which were generated by the analysis were compared to the allowable stresses in industry codes and standards for acceptance.
API 582 – 4th Edition – Additions and Clarifications to the 3rd Edition
Authors: Colwell Richard L. , Layo William E.
Published: November 2023

In 2023 the 4th Edition of API Recommended Practice 582, “Welding Guidelines for the Chemical, Oil, and Gas Industries” will be issued. The document has undergone a significant revision, including major restructuring, and inclusion of new consensus industry recommendations for welding creep-strength enhanced ferritic alloys (e.g. P91), welding Heat Resistant Alloys, and Controlled Deposition Welding. This paper will outline the new structure, and provide a detailed explanations of recent changes in the recommended practice.
The Effect of Lubrication on Percent of Red Rust and Break-Out Torque of PTFE Coated Fasteners
Authors: General Justinn , Norman Dale , Bao Tommie
Published: November 2023

Polytetrafluoroethylene (PTFE) coated fasteners have been commonly used in various industry applications for both its corrosion resistance and lubricity during bolt up. There is a wide array of different brands and various process methods to apply PTFE on fasteners, that offer similar performance. However, there is a resounding question regarding if lubrication is needed during bolt up of PTFE fasteners and if there are any benefits to corrosion resistance and break-out.

For this study, we used two applicators of Xylan 1424 and one applicator of Flurokote #1, all PTFE based coatings. The samples were subjected to salt spray environment in accordance with ASTM B117 at 1,500 hours, 2,000 hours, 2,500 hours, and 4,000 hours. The studs were torqued to load the ASTM A193 B7 fasteners to 50% of the minimum yield, where half of the studs were torqued without lubrication and the other half were lubricated with Jet-Lube 550 Extreme. At each of the time intervals, the percentage of red rust on the stud and two nuts were measured and the break-out torque was recorded.

Numerous observations were made as to the relationship between application of lubrication and without regarding both corrosion and break out torques. This paper will talk in depth as to the benefits of using lubrication on PTFE coated fasteners.
Notch Effect on Creep-Fatigue Behavior of Alloy 617 at Elevated Temperature
Authors: Hou Peijun , Wang Yanli , Sham Ting-Leung
Published: November 2023

High-temperature reactor structural components are often under the complex multiaxial creep-fatigue (CF) loading conditions throughout the lifetime because of geometric and/or metallurgical discontinuities and complex loading paths. To assess the multiaxial CF deformation behavior and to evaluate the CF design rules in the ASME BPVC Section III, Division 5, Subsection HB, Subpart B, experimental and numerical studies are performed on Alloy 617 at 950°C using notch specimen geometries under CF loading in this study.

Two types of notch specimen geometries, shallow-notch and sharp V-notch were designed for Alloy 617 per ASTM Standard E292-09. Experimental procedures were developed, and tests at 950°C were performed under CF loading with tension hold time using the two notch specimen geometries. The information collected from the experiments included the average axial stress relaxation histories, the changes in the relaxation behavior as a function of applied cycles, and failure information. Additionally, an inelastic constitutive model of Alloy 617 was used in the finite element analyses of the notch specimens to determine the stress triaxiality distributions, local and average stress relaxation behavior, and local elastic follow-up. The results from the experimental and numerical studies on the CF of notch specimens are compared with those on standard uniaxial smooth bar specimens. The notch effect on the CF deformation and failure of Alloy 617 is summarized and the assessment of the design rules regarding the treatment of multiaxial stress relaxation is discussed.
Considerations for Graphite in the Design, Qualification and Operation of Advanced Reactor Cores
Authors: Booler Owen A. , Davies Mike W.
Published: November 2023

Graphite has been used historically in nuclear reactor cores for its excellent neutron moderation properties. However, the complex material behaviour inherent in irradiated graphite has resulted in several structural integrity challenges that has constrained the lifetime of the reactor core. Working towards understanding how graphite behaves in irradiated core conditions and its safety performance has allowed for the successful life extension of the UK Advanced Gas-cooled Reactors (AGR) fleet to operate beyond their original design limits. Some of the key challenges with graphite is that due to its polycrystalline nature, the material behaviour is complex which is compounded when considering the irradiated environment; where degradation changes the material behaviour, leading to differential shrinkage and significant tensile stresses. This in turn affects the structural performance and thermal hydraulics, all of which have a consequence to the safe operation of the reactor core. Therefore, serious consideration of graphite in the design of next generation reactors will not only primarily secure safety in the design but could also reduce cost and increase the return on investment. Here, we identify seven main considerations for graphite in the design, qualification and operation of advanced reactor cores that will not only aid in meeting design code requirements (specifically ASME III Division 5) and regulator conformance, but will also improve the commercial viability of future nuclear power.
The Fundamental Sealing Characteristics Evaluation for Metal Hollow O-Ring Gaskets
Authors: Yamamoto Kohei , Sawa Toshiyuki , Itano Kohei
Published: November 2023

Metal hollow O-ring gaskets have been used in bolted flanged connections for high-pressure piping. Some studies have been conducted on their deformation characteristics. However, the sealing performance of the connections, which is important for practical use, has not been fully elucidated. The purpose of this study is to investigate the effects of metal hollow O-ring under compression on the sealing performance. So, the effects of the thickness ratio of O-ring to the diameter of it on the sealing performance are examined using both FEM stress analysis and the leakage measurements in platen tests. A helium leak detector was used to measure the amount of leakage from the O-ring alone in the platen test, and the compression behavior was investigated using FEM analysis to show the relationship between the contact stress and the amount of leak rate. As a result, it is demonstrated that the leak rate can be predicted using the maximum contact stress. Additionally, the relationship between the contact force η per unit length (load per unit length) and the displacement for bolted flange connections with O-ring gaskets is examined both experiments and the FEM analysis.
Graphite-Molten Salt Considerations for Components in Nuclear Applications
Authors: Gallego Nidia C. , Geringer Josina W. , Windes William
Published: November 2023

The new high-temperature reactor (HTR) designs being considered for future Generation IV nuclear reactor deployment include designs using molten salt as the primary coolant. These molten salt-cooled graphite core designs pose new material compatibility challenges that are not considered within the gas-cooled HTR designs that have been previously built and operated. Although early indications from the Molten Salt Reactor Experiment (MSRE) in the 1960s were that molten salts could be considered chemically inert to graphite, recent studies revealed additional physical and thermal interactions that the molten salt imposes that may be just as significant as the chemical reactivity. Specifically, molten salt intrusion into the open pore structure of nuclear graphite grades can cause additional internal stresses within the microstructure, exacerbating the stress accumulation from irradiation-induced dimensional change. Additionally, designs using a molten salt-containing liquid fuel could produce hot spots within graphite structural components, causing local thermal stresses. Abrasion and erosion concerns are magnified with molten salt because of their extremely high density (some salts have higher densities than the structural graphite components). Finally, the graphite-graphite and fuel pebble-graphite tribological behavior are distinctly different within the molten salt from the inert gas environments and must be investigated. These topics and others are currently under investigation within the US Department of Energy Advanced Reactor Technologies graphite program and will be discussed in depth.
Determining Burst Strength of Thin and Thick-Walled Pressure Vessels Through Parametric Finite Element Analysis
Authors: Johnson William R. , Zhu Xian-Kui , Wiersma Bruce , Sindelar Robert
Published: November 2023

Previous work on pressure vessel (PV) burst strength established a numerical technique for determining the more accurate Zhu-Leis burst strength from the pressure-Mises stress curve provided by finite element analyses (FEA). That work was not applied to capture the burst strength for thick-walled pipes. Recent analytical developments have resulted in a thick-walled Zhu-Leis burst strength solution. This work examines this solution using FEA calculations. To do so, the FEA stress was measured at multiple points through the wall thickness of the PV and compared to the analytical thick-walled solution to determine the best measurement location through the thickness. To further examine the burst pressure for different vessel sizes and materials, we developed a parametric code, using the Abaqus Python application programming interface, to rapidly iterate over 60 different combinations of geometries and material properties. This code also extracted stress data from the FEA results and analyzed the numerical pressure-Mises stress curves to find the critical point corresponding to the Zhu-Leis burst pressure. A linear regression model was developed which can very accurately predict the PV burst pressure. This regression model applies over a range of pipeline steels from grade B to X80, and diameter-to-thickness (D/t) ratios from 6 to 120.
Measuring Damping in Linear and Nonlinear Systems
Authors: Goyder Hugh
Published: November 2023

It is shown how measurements of the decaying response of a vibrating system, following an initial disturbance, can be analysed to extract natural frequency and damping properties. Typically, such data contains a superposition of many vibration modes. By using filtering, it is demonstrated how individual modes can be extracted. The filtering must be done in a special way that involves reversing the data in time and passing it through a narrow band filter and truncating the data. Reversing the data prevents the filter characteristics contaminating the filter output. If the data is from a linear system then the natural frequency and damping are preserved by this process. If the data is nonlinear then the instantaneous frequency and damping are also preserved but are modified in a way that can be reversed. It is shown how all the effects of the filtering can be eliminated so that the decaying response of each mode is obtained. This approach provides a useful extension to experimental modal analysis that is applicable to nonlinear systems.
CFD Study on High-Pressure Hydrogen Leakage and Explosion of Hydrogen Energy Tram in Tunnel
Authors: Tian Tiantian , Lu Chen , Ha Wenlong , Zhao Yiming , Hua Zhengli , Peng Wenzhu , Gu Chaohua
Published: November 2023

As hydrogen energy is gradually being applied to vehicles, confirming the safety level is becoming important. Meanwhile, tunnels are common in cities. Compared with hydrogen fuel cell cars (HFCVs), hydrogen fuel cell trams have a larger size and the corresponding space of the tram tunnel is also narrower. However, most hydrogen fires in confined spaces are HFCVs. The consequences of hydrogen leakage and explosion in a tunnel of the hydrogen energy tram are different. Therefore, computational fluid dynamics (CFD) method was used to study the hydrogen diffusion and explosion caused by the accidental opening of the thermal pressure relief device (TPRD) of the high-pressure hydrogen storage cylinders on the hydrogen energy tram in the tunnel. The effect of the number of TPRDs opening and the speed of wind on the formation of flammable hydrogen clouds is discussed. The simulation results show that the burning area generated by igniting the hydrogen cloud can cover more than one hundred meters, and overpressure can cause serious injuries to the human body. High temperature and overpressure can be relieved by the wind. In case of accidental hydrogen leakage, the tram should be blocked until the tram continues to move to a safe area and there should be forced ventilation in the tunnel. This research highlights the importance of ensuring the safety of hydrogen fuel cell trams in confined spaces such as tunnels.
Case Study on the Acceptance of a Unique Refractory Material in ASME Section VIII
Authors: Peters Daniel T. , Kapadia Rahul , Hoeijmakers Maarten , Koestenbauer Harald , Niggl Florian
Published: November 2023

The use of hot isostatically pressed isotropic pure molybdenum was recently processed through ASME Section VIII. This is a unique material for the manufacture of pressure vessels as pure molybdenum is typically used for applications such as refractory, resistance wire for heating elements and structural thermal barrier components for internal furnaces for hot isostatic presses. There are several specifications for coverage of molybdenum such as ASTM B387, Standard Specification for Molybdenum and Molybdenum Alloy Bar, Rod, and Wire [1], and ASTM B386/B386M, Standard Specification for Molybdenum and Molybdenum Alloy Plate, Sheet, Strip, Foil, and Ribbon [2].

This paper demonstrates the test data needed for ASME approval of this unique material. The paper highlights the gaps in ASME Section II, Part D Appendix 5 and attempts to illustrate the “other information required by the Construction Committee” which may be needed for new materials today. This includes not only the data required by ASME Section II Part D, Appendix 5 [3,4], but also includes additional data which is required for more modern design by analysis techniques, such as elastic-plastic local strain limits and generation of true stress – true strain curves. This paper will also discuss alternative design philosophy approaches which were adopted in lieu of traditional approaches in areas such as fatigue analysis, determination of minimum design metal temperature (MDMT), and alternative approaches to examination and inspection of the material.
Study on the Mechanical Response of Gas Cylinders Under Shock Load
Authors: Fang Zhou , Wu Gang , Song Ce , Yuan Jun , Wang Zhe
Published: November 2023

In order to ensure the safe operation of pressure vessel cylinders in the service stage, the mechanical response law of gas cylinders under dynamic load under different working conditions is clarified. In this study, numerical simulation was used to study the different shock loads of gas cylinders at different positions. The finite element analysis results of the impact load of the cylinder when the sphere and cone are used as the percussive objects are compared and analyzed, and it is concluded that the steel cylinder will cause obvious deformation of the cylinder as a whole when subjected to the impact load, and the maximum deformation position is located at the top head or the connection between the top head and the cylinder. Because of the presence of the saddle, the shock load acts on the bottom head, and the equivalent force distribution is mainly distributed in the lower half of the cylinder. When acting on the cylinder or the connection between the cylinder and the top head, the equivalent force is distributed throughout the cylinder, but regardless of where the shock load is applied, the maximum equivalent force occurs at the connection between the cylinder and the saddle, where the stress concentration is generated. The cylinder bears the impact load applied by different percussive objects, the incidence speed increases, the maximum deformation and equivalent force generated by the cylinder increase, and there are also certain differences in the value when the cylinder bears the impact load applied by the sphere and the cone, indicating that when the cylinder bears the impact load, the type of percussion has a certain impact on the equivalent force of the cylinder.
Study on Anti-Instability Inflation Pressure of Vehicle-Mounted Type Ⅳ Hydrogen Storage Cylinder
Authors: Liu Zezhong , Chen Zhiwei , Jia Xiaoliang , Ji Fang
Published: November 2023

In this paper, the 70 Mpa vehicle-mounted type IV hydrogen storage cylinder fully wound by carbon fiber with plastic liner is studied. Based on the analytical method, the analytical analysis model of fiber-wound hydrogen storage cylinder is built to obtain the functional relationship between fiber winding parameters and the external pressure of the liner. In addition, the critical buckling load of the hydrogen storage cylinder liner is obtained through the finite element method. The mapping relationship between fiber winding parameters and anti-instability inflation pressure is constructed; a calculation method of anti-inflation pressure in the process of fiber winding of type IV hydrogen storage cylinder is proposed, and the effect of inflation pressure with the increase of fiber winding layer is studied. The calculation method of inflation pressure can provide theoretical guidance for the selection of inflation pressure in the manufacturing process.
On the Quantification of Accidental Gas Release From Pressurized Vessels
Authors: Rosti Annalisa , Brunesi Emanuele , Dacarro Filippo , Dubini Paolo , Marino Alessandra , Nosenzo Giorgio , O’Reilly Gerard J.
Published: November 2023

NaTech accidents may pose significant risk to human safety, not only for potential structural and non-structural damage but also considering the possible release of hazardous substances into the environment. In the context of risk-based management of industrial facilities, the detection and quantification of accidental release of toxic substances from pressurized pipelines and tanks are thus of primary concern. Based on these considerations, this paper presents a simplified analytical model for assessing the accidental release of gas from pressurized vessels. Taking advantage of pressure and temperature measurements acquired by fiber-optic (FO) sensors, the proposed model allows for quantifying the mass outflow rate, averaged in a given time window, and for estimating the leakage area. To this end, the model is capable of identifying the time at which the discharge process starts and following its evolution over time. The capability of the proposed analytical model is demonstrated by comparing predictions with results from several experimental tests, specifically carried out for simulating the release of gas from a vessel, pressurized at different initial pressure thresholds and equipped by FO sensors. Estimates from the developed analytical model can be also exploited for assessing concentrations of chemicals in the industrial plant and simulating their spatial diffusion over time, thus supporting the generation of environmental health risk maps.
Master Curve Evaluation Using Miniature C(T) Specimens as Part of a Round Robin Program Within the FRACTESUS Project
Authors: Naziris Frideriki , Hernandez Pascual Rebeca , Metzler Timo , Gaganidze Ermile , Uytdenhouwen Inge , Kolluri Murthy
Published: November 2023

Surveillance testing is the basis for all reactor pressure vessel (RPV) integrity and lifetime assessments to evaluate the validity of the RPV embrittlement trend curve used for a specific reactor. Most of the standard surveillance programmes, do not contain sufficient number of surveillance specimens for beyond the original design life of 40 years. Thus, testing methods based on small / sub-sized specimens are considered. Experimental programmes on un-irradiated RPV steels have proven that miniature compact tension (∼4*10 *10 mm3) specimens, mini-CT, can successfully be used for fracture toughness characterization in the transition regime to determine reference temperature (T0) based on the master curve method. However, application of miniature testing techniques on irradiated materials in hot cells comes along with several technical challenges such as remote controlled machining, application of the extensometers, manipulator sensitivity, accurate sample geometry measurement etc. In addition, the optimal test temperature range for obtaining valid KIc values for the mini-CT specimen is narrow and consequently sufficient number of specimens should be tested to guarantee a reliable valid T0-value.

Within the FRACTESUS project, European and International efforts are joined to establish the foundation of small specimen fracture toughness validation and demonstration to achieve change in code and standards allowing to address the various national regulatory authority concerns. As part of the third work package (WP3), high-fluence fracture toughness data, on well characterized RPV materials, will be produced to serve as input for the guidelines of future testing.

To assure the robustness of the testing procedures to the difference in testing machines or operators, a round robin (RR) exercise on un-irradiated materials is organised among the partners of WP3. This work presents the preliminary results of the mini-CT fracture toughness data on un-irradiated RPV SA508 Cl. 3 material which was independently tested by four institutes: CIEMAT, KIT, SCK CEN and NRG. All four institutes determined T0 according to the ASTM E1921 standard and the results are compared and discussed.
A Comprehensive Sample Problem for Section III Division 5 Design by Elastic Analysis
Authors: Barua Bipul , Messner M. C.
Published: November 2023

High temperature advanced nuclear reactor technologies could play an important role in moving the U.S. towards a zero-carbon future. Efforts to transform the U.S. nuclear industry have entered the full bloom, energized by billions of dollars in funding through the Department of Energy’s Advanced Reactor Demonstration Program (ARDP). New reactors in the U.S. will most likely be designed to the ASME Boiler & Pressure Vessel Code, Section III, Division 5 rules for safety related components in elevated temperature service. The goal of this paper is to provide the reactor designers with a comprehensive sample problem, detailing the step-by-step design calculations in Section III, Division 5, design by elastic analysis rules. The sample design problem is a 316H pressure vessel with a nozzle, similar to the pressure vessel and primary inlet nozzle in the intermediate heat exchanges of the Clinch River Breeder reactor plant. The sample problem considers several Service Level-A (normal condition) and Service Level-B (upset condition) loads. The sample problem uses Multiphysics Object Oriented Simulation Environment (MOOSE), an open source finite element Code developed by Idaho National Laboratory, for thermal and structural analysis. For design calculations, the sample problem utilizes U.S. Nuclear Regulatory Commission’s software package “ASME Section III, Division 5 Design Tool”, originally developed at Argonne National Laboratory.
Post Irradiation Examination of Pressurized Water Reactor Stainless Steel Internal Components
Authors: Lach Timothy G. , Chen Xiang (Frank)
Published: November 2023

Internal structural components of pressurized water reactors (PWR), such as baffle former bolts, are subjected to significant neutron irradiation and mechanical stresses at elevated temperatures during plant operation. Over the long operation of the power plant, these conditions lead to potential degradation and reduced load-carrying capacity of these bolts. To understand property degradation more fully, to confirm the results of experimental irradiation programs, and to predict operational lifetime performance of structural materials in internal components, post irradiation examination of harvested materials from operating nuclear reactors is required. In this work, two high fluence 316 stainless steel baffle former bolts were retrieved from a commercial Westinghouse two-loop downflow type PWR and then sectioned for analysis via mechanical testing and microstructural characterization. The irradiation damage fluctuated along the bolt length with damage levels from 15 to 41 displacements per atom with the bolt head receiving approximately twice the neutron damage levels as that of the bolt thread section. Mechanical testing evaluations showed extensive irradiation hardening and a sharp decrease in fracture toughness in all parts of the bolt, though with limited variation along the bolt length. Microstructural characterization using analytical scanning transmission electron microscopy and atom probe tomography showed significant radiation induced precipitation, segregation, and dislocation loop and cavity formation. However, unlike the mechanical behavior, there was considerable variation along the bolt length but opposite of what may be expected, with more precipitation and cavity formation in the bolt thread where the neutron radiation dose is less than in the bolt head where the neutron radiation dose is higher. The cause of this variation is likely due to gradients in temperature, neutron energy spectra, and gamma irradiation.
Probabilistic Fracture Mechanics Evaluation of PWR Cast Austenitic Stainless Steel Piping Components – Axial Cracking Methods and Results
Authors: Fuhr Kevin , Wolfson Matt , White Glenn , Burkardt Markus , Shim Do Jun
Published: November 2023

The material microstructure of cast austenitic stainless steel (CASS) materials challenges the reliability of ultrasonic examination techniques, particularly detection of axial cracks and depth sizing of circumferential cracks. As such, the qualification requirements for ultrasonic examination of CASS piping in accordance with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC), Section XI, Mandatory Appendix VIII, have not been developed.

In addition to the limitations of ultrasonic testing (UT) examination, CASS material is subject to thermal aging, which causes degradation of its fracture toughness over time. The extent of toughness degradation depends on the ferrite phase (δ-Fe) content of the particular component.

A probabilistic fracture mechanics (PFM) approach was applied to support development of examination requirements in light of the current nondestructive examination (NDE) limitations for CASS components. The PFM evaluations were performed using a software code developed specifically for this purpose called PIPER-CASS. This paper describes the approach and results obtained for postulated axial cracking (e.g., from a preexisting fabrication flaw) in CASS piping. This work is intended to support development of ASME BPVC, Section XI, Mandatory Appendix VIII, Supplement 9, for CASS and an alternative to the current Section XI, Subarticle IWB-2500 (Examination Categories B-F and B-J) examination requirements specific to CASS piping.
Combined Hydrogen Embrittlement and Strain Rate Sensitivity of Annealed and Forged 304L Steel
Authors: Wheeler Robert W. , Ronevich Joseph , San Marchi Chris , Foulk James W. , Diab Mazen , Alleman Coleman
Published: November 2023

In this work, the combined effects of strain rate and internal hydrogen (from gaseous precharging) on the tensile properties of 304L austenitic stainless steel in both annealed and forged conditions are characterized. Due to its high corrosion resistance, strength, and formability, 304L has a wide variety of applications, including pressure vessels, valves, and other manifold components. While both the strain rate sensitivity and hydrogen effects on 304L have been reported in the past, the combined influence of internal hydrogen and strain rate on the tensile flow curves has not been studied. To better understand these effects, uniaxial tensile tests were performed at strain rates varying between approximately 10−2 and 10−5 per second both with and without internal hydrogen. The combined influence of strain rate and internal hydrogen on the tensile flow curves and strain-induced martensite are reported and discussed. It was found that the 0.2% offset yield stress increased with increasing strain rate for both conditions (with and without internal hydrogen), at nearly a constant rate per decade. Additionally, for the annealed material, the relative change in stress was shown to be approximately equivalent (an increase of 45 MPa) when comparing the fastest strain rate (10−2 /s) with the slowest rate (10−5 /s) for both with and without internal hydrogen. The influence of internal hydrogen on rate dependent parameters are also discussed for the forged 304L.
Numerical Analysis of Permanent Deformation in Pressure Vessels due to Weld Overlay
Authors: Dandekar Akshay , Gordon Andrew , Kulkarni Mandar
Published: November 2023

Pressure vessels are regularly exposed to corrosive chemicals and oxidizers, which could cause loss of material from the vessel internal diameter and reduced wall thickness. Weld overlay (WOL) is performed to deposit a material layer on either the internal or external surface to compensate for lost material so that the pressure vessel satisfies API 579 Fitness for Service guidelines to remain safely in service. In addition to being a remediation for general and local metal loss, WOL may also be performed to restore wall thickness after grinding out crack like flaws developed in pressure vessels. The WOL process deposits a layer of molten material on the remaining shell base material. During this process, the base material shows rapid heat buildup, which is then subsequently dissipated through conduction and convection. The change in the temperature causes localized expansion and contraction of shell, which induces thermal stress and permanent deformation. It is important to analyze the permanent deformation as it can impact the performance of the pressure vessel. In addition, the material buildup also results in a change in the shell geometry and hence API 579 – 4.6.2.4 also recommends performing a follow up analysis to ensure continued acceptability of the design [1].

Several factors such as material composition, material melting point, weld speed, weld zone thickness, voltage, thickness of existing and deposited material can affect the resulting thermal stress and permanent deformation. Tests to analyze the impact of these parameters are expensive in terms of time and money and, thus, computer simulations could be advantageous. In addition, a computational parametric approach could also help identify optimal overlay patterns, which would minimize shell distortions while minimizing overall process costs.

This study presents four different approaches to analyze the effect of weld overlay on the thermal stress and permanent deformation in the pressure vessel. Both sequentially coupled and fully coupled thermal-mechanical approaches are analyzed and compared. The effect of these approaches on the permanent deformation and its impact on the RSF (remaining strength factor) of the structure are studied. The method introduced could further be expanded to perform parametric studies to understand the effect of each input parameter on the permanent deformation in the pressure vessel at the end of weld overlay along with its impact on the overall acceptability of the structure post the remediation process.
Experimental Investigation on the Pull-Out Strength of Flexibly Expanded Tube-to-Tubesheet Joints
Authors: Ma Xin , Dong Wenli , Wang Xiaoliang , Ge Zhiqiang
Published: November 2023

Mechanics and technical points of flexible expansion process of tube-to-tubesheet joints in shell-and-tube heat exchangers were briefly introduced. A series of experiments were performed on flexibly expanded tube-to-tubesheet joints to verify the pull-out strength. Carbon steel 20 and stainless steel S30408, two kinds of materials frequently used as tube in heat exchanger construction in China, are employed in the experiment. Specially developed rubber expansion equipment was employed to simulate the flexible expansion process in the experiment as well. Grooves with different widths and depths were used to investigate their influence on the pull-out strength. The results show that the pull-out strength of tube-to-joints with no annular ring grooves in tube holes grows with the increase of expanding pressure during the initial stage of expanding process, and the growth approaches naught when the expanding pressure reached a certain value. Compared with the ungrooved tube-to-tubesheet joints, the pull-out strength of the grooved ones is much higher and can well satisfy the requirements specified in China code & standard at the experimental conditions. The width of groove has remarkable effects on the pull-out strength of joint, and an optimum width of groove exists for a given pipe specifications. Especially, the expansion degree recommended in Chinese standard for heat exchanger is not suit for flexibly expanded tube-to-tubesheet joints.
Identification of Typical Damage Mechanism of Coke Drum in Delayed Coking Unit
Authors: Ma Xin , Xie Yi , Ge Zhiqiang
Published: November 2023

Coke drums are large pressure equipment critical to the delayed coking unit (DCU) of refineries, which are used for the carbonization reaction involving dehydrogenation, rearrangement and polymerization. Due to the complexity of the internal process medium, the variability of structure and severe operation loads, many potential damage mechanisms may occur in the in-service coke drums. Failures such as corrosion, bulging and local thinning of the drum body; cracking at the connection between outlet nozzle and drum body and the fillet weld in skirt-to-conical head joints have been frequently found. Therefore, it is very important for a pressure vessel inspector to identify the exact potential damage mechanisms at a specific place of the coke drum. In this article, typical damage mechanisms of coke drum in delayed coking unit are identified according to the component content of internal process medium, the construction materials of the coke drums, and the structure features of the vessel. The main characterizations, the crucial influencing factors, and the control measures are put forward as well. Based on some inspection examples of coke drums, the causes of typical failures and the corresponding inspection and detection methods are given to provide reference for pressure vessel inspectors and periodic inspection of coke drums.
Meridional Direction Limits for Local Primary Membrane Stress Between Sm and 1.1Sm
Authors: Sulwinski Rafal , Li Qi , Johnston Rusty , Kilambi Sreelatha
Published: November 2023

BPVC Section VIII Division 2 defines primary membrane stress in a region of stress as local if the distance over which equivalent linearized stress exceeding 1.1 Sm does not exceed √(Rt) in the meridional direction. Current edition of BPVC Section VIII Division 2 code does not define meridional distance for primary membrane stress between Sm and 1.1 Sm. As a result, users are forced to treat the region between Sm and 1.1 Sm as general primary membrane stress which leads to a potential for failure in stress analysis or the need to use more costly elastic-plastic analysis.

Existing research and data by Ferry et al. on ASME Section III in 1983 indicate that there is a need to address meridional distance where stress is below 1.1 Sm [1]. Currently there are no limits on meridional distance when localized primary membrane stress is between Sm and 1.1 Sm. This paper presents possible scenarios with lower primary membrane stress. Considering the same stress gradient (the change in stress to the change in meridional distance) permissible in current edition of the code, this paper suggests meridional distance limits 1.25√(Rt) when maximum local primary membrane stress is between Sm and 1.1 Sm.
Stress Relaxation Cracking, A Misunderstood Problem in the Process Industry
Authors: Rensman Jan-Willem , Spindler Mike W. , Shargay Cathleen
Published: November 2023

Many high temperature material failures in pressure equipment in the chemical and refining process industry have been attributed to Stress Relaxation Cracking (SRC) or Reheat Cracking (RC) as it is called in the UK. SRC/RC failures are being reported frequently in the literature [1][2][3][4][5], in spite of construction in accordance with high temperature design codes for pressure equipment. Very few preventive measures have been incorporated in process equipment design codes.

Several SRC/RC theories have been proposed [4][7][6]. The mechanism is often described in terms of a degraded microstructural state before damage starts to accumulate. This has not led to predictions on if or when failure occurs, although somewhat successful mitigation strategies [8][9] have been defined, which involve heat treatments of materials and fabricated structures.

In this paper, the current understanding of in-service SRC/RC will be summarized with a primary on austenitic stainless steels and Nickel alloys. It will be explained why some mitigation strategies work and what are the practical implications for the process industry. The usefulness of various testing programs for alloy characterization and susceptibility ranking will be briefly discussed, and the paper will highlight the capabilities of the UK nuclear power industry’s R5 “Assessment Procedure for the High Temperature Response of Structures” [10] for the prediction of SRC/RC.
The Potential and Challenges of Quantum Computing for Engineering Applications
Authors: Reich Alton , Carroll David , Carlson Timothy , Reich Miranda , Disalvo Roberto
Published: November 2023

Quantum computing has generated splashy headlines with pronouncements of “quantum supremacy”, but the reality is much more complicated than simple headlines can capture. Quantum computers are designed to use the interactions between quantum objects, such as electron spins, to perform useful computations. This paper will provide an overview of some of the engineering challenges involved in developing quantum computers and highlight some potential applications of interest to the mechanical engineering community.

These challenges include the need to isolate the quantum bits — the logic elements used in quantum computers — from the environment to protect them from external sources of noise. In some quantum computer designs, this requires cooling the quantum bits to temperatures below 1 degree Kelvin, which requires specialized refrigeration systems.

Potential future applications of quantum computers, particularly for mechanical engineers, rely on the promise of increased computational power for solving complex problems that have many degrees of freedom. This includes solving large systems of equations for finite element analysis and computational fluid dynamics, and in computational chemistry for materials optimization.

Quantum computing is clearly a future technology — more development is needed before it will be used for engineering applications. That said, there are clear potential applications in mechanical engineering, and it will be a future technology that will be used for engineering analysis-based design optimization, digital twin development, and other relevant applications.
Fluid Transients Ignited the San Bruno Gas Pipeline Explosions
Authors: Leishear Robert A.
Published: November 2023

Gas pipeline explosions and deaths occur year after year, and a primary cause for those explosions is now known. For decades, these explosions were attributed to corrosion and other incidental causes, but the extent of pipeline damages cannot be explained by corrosion.

Pipelines are obliterated by large explosions, and pipelines explode from the inside to the outside. Pipes cannot explode in this manner unless air is present inside the pipes. To date, all previous investigations assumed that the gas industry prevents all air from entering pipelines, and this question about air was not raised in previous government investigations. Accordingly, explosion causes were not understood. Acknowledging that air is inside pipelines at the time of explosions, the ignition cause can be explained.

When fluid transients occur in pipelines, flammable gases compress and heat to explode at the autoignition temperatures of the gases. In natural gas piping, explosions occur at system low points where air collects, since methane (natural gas) is lighter than air; and in propane, ethane, or butane systems, explosions occur at system high points, since these gases are heavier than air. In the absence of this Leishear Explosion Theory, the fact that pipes explode outward cannot be explained.

An incorrect claim could be made that the stored energy of methane is so great that the pipes explode, but calculations show that this energy is inadequate to create the large craters created during pipeline explosions. In other words, air is required for internal gas pipeline explosions, fluid transients cause pressures to blow up pipelines, these transients may be caused by sudden valve slams, where slam valves are used to control gas flow in pipelines.

To understand the fundamental physics of pipeline explosions, a San Bruno natural gas pipeline explosion will be evaluated as an example of this explosion theory.
Sound production biomechanics in three-spined toadfish and potential functional consequences of swim bladder morphology in the Batrachoididae
Authors: Han Sang Min , Land Bruce R. , Bass Andrew H. , Rice Aaron N.
Published: November 2023

The relationship between sound complexity and the underlying morphology and physiology of the vocal organ anatomy is a fundamental component in the evolution of acoustic communication, particularly for fishes. Among vertebrates, the mammalian larynx and avian syrinx are the best-studied vocal organs, and their ability to produce complex vocalizations has been modeled. The range and complexity of the sounds in mammalian lineages have been attributed, in part, to the bilateral nature of the vocal anatomy. Similarly, we hypothesize that the bipartite swim bladder of some species of toadfish (family Batrachoididae) is responsible for complex nonlinear characters of the multiple call types that they can produce, supported by nerve transection experiments. Here, we develop a low-dimensional coupled-oscillator model of the mechanics underlying sound production by the two halves of the swim bladder of the three-spined toadfish, Batrachomoeus trispinosus. Our model was able to replicate the nonlinear structure of both courtship and agonistic sounds. The results provide essential support for the hypothesis that fishes and tetrapods have converged in an evolutionary innovation for complex acoustic signaling, namely, a relatively simple bipartite mechanism dependent on sonic muscles contracting around a gas filled structure.
m
6
A RNA demethylase AtALKBH9B promotes mobilization of a heat-activated long terminal repeat retrotransposon in
Arabidopsis
Authors: Fan Wenwen , Wang Ling , Lei Zhen , Li Hui , Chu Jie , Yan Mengxiao , Wang Yuqin , Wang Hongxia , Yang Jun , Cho Jungnam
Published: November 2023

Transposons are mobile and ubiquitous DNA molecules that can cause vast genomic alterations. In plants, it is well documented that transposon mobilization is strongly repressed by DNA methylation; however, its regulation at the posttranscriptional level remains relatively uninvestigated. Here, we suggest that transposon RNA is marked by m
6
A RNA methylation and can be localized in stress granules (SGs). Intriguingly, SG-localized AtALKBH9B selectively demethylates a heat-activated retroelement,
Onsen
, and thereby releases it from spatial confinement, allowing for its mobilization. In addition, we show evidence that m
6
A RNA methylation contributes to transpositional suppression by inhibiting virus-like particle assembly and extrachromosomal DNA production. In summary, this study unveils a previously unknown role for m
6
A in the suppression of transposon mobility and provides insight into how transposons counteract the m
6
A-mediated repression mechanism by hitchhiking the RNA demethylase of the host.
Engineered IL-7 synergizes with IL-12 immunotherapy to prevent T cell exhaustion and promote memory without exacerbating toxicity
Authors: Kang Seounghun , Mansurov Aslan , Kurtanich Trevin , Chun Hye Rin , Slezak Anna J. , Volpatti Lisa R. , Chang Kevin , Wang Thomas , Alpar Aaron T. , Refvik Kirsten C. , Hansen O. Isabella , Borjas Gustavo J. , Shim Ha-Na , Hultgren Kevin T. , Gomes Suzana , Solanki Ani , Ishihara Jun , Swartz Melody A. , Hubbell Jeffrey A.
Published: November 2023

Cancer immunotherapy is moving toward combination regimens with agents of complementary mechanisms of action to achieve more frequent and robust efficacy. However, compared with single-agent therapies, combination immunotherapies are associated with increased overall toxicity because the very same mechanisms also work in concert to enhance systemic inflammation and promote off-tumor toxicity. Therefore, rational design of combination regimens that achieve improved antitumor control without exacerbated toxicity is a main objective in combination immunotherapy. Here, we show that the combination of engineered, tumor matrix-binding interleukin-7 (IL-7) and IL-12 achieves remarkable anticancer effects by activating complementary pathways without inducing any additive immunotoxicity. Mechanistically, engineered IL-12 provided effector properties to T cells, while IL-7 prevented their exhaustion and boosted memory formation as assessed by tumor rechallenge experiments. The dual combination also rendered checkpoint inhibitor (CPI)–resistant genetically engineered melanoma model responsive to CPI. Thus, our approach provides a framework of evaluation of rationally designed combinations in immuno-oncology and yields a promising therapy.