bluuebunny/crossref_metadata_2025 huggingface dataset:
K-Factor Testing of PTFE-Coated Studs
Authors: Hamilton Scott , Meigs Dan , Blake Tom , Oldiges Don
Published: November 2022

Vendors offer PTFE-coated studs to provide corrosion resistance in harshly corrosive environments. Vendors advertise PTFE-coated studs as having reduced K-Factor compared to uncoated studs, and differences of opinion exist on whether or not lubrication is required when assembling joints with PTFE-coated studs. In fact, some end users have adopted the practice of assembling joints with PTFE-coated studs without lubrication when the stud is used for the first time and then applying lubrication when studs are reused.

This study tested the K-Factor of a set of studs in different sizes from seven vendors to determine what K-Factor should be expected when using PTFE-coated studs, how much variation in K-Factor one should expect between vendors and sizes, and the effect lubrication has on variability in K-Factor. K-Factors were derived using an automated test fixture that plotted K-Factor vs bolt load across a range of loads from 30 ksi to 80 ksi.

This study found there is significant variation in K-Factor from vendor to vendor, from stud size to stud size, and even within individual lots of a single size from a single vendor. The study found that without lubrication, the average K-Factor increased significantly with bolt load, making prediction of gasket stress difficult. The study concluded that properly lubricating PTFE-coated studs during assembly significantly reduces the variability seen in unlubricated studs.
Seismic Test and Seismic Response Analysis of U-Shaped Tube Bundle With Triangular Arrays in Steam Generator
Authors: Hirota Kazuo , Monde Masatsugu , Ono Naoki , Nakamori Tomohito , Matsubara Masahito , Mineno Tomonori , Taguchi Koshi
Published: November 2022

Ensuring a complete integrity of steam generators’ tubes during earthquakes is critical. So far, excitation tests have been conducted for various square array tube bundles in order to grasp vibration behavior during seismic excitation. A seismic analysis method using a simple model has been developed and subsequently verified by comparing the results against those of the above mentioned tests.

In this study, seismic excitation tests were carried out for a U-shaped tube bundle with a triangular close-packed array using a full-scale test specimen as the triangular tube array with thinner anti-vibration bars (AVBs) has different vibration characteristics compared with a squared array one.

Natural frequencies, modes and stress distribution in the tube bundle, obtained during the experiment, were applied in order to verify the seismic analysis method through the use of a linear analysis model with all tubes and AVBs connected to each other by linear springs as well as with a nonlinear analysis model with gap elements to simulate contact and sliding between all tubes and AVBs.

The vibration displacement of the top of the tube bundle calculated by the linear model were in good agreement with the test result. Stress distribution in the tube array calculated using the nonlinear model were in good agreement with the test result. It has been concluded that the linear and nonlinear analysis models are applicable to seismic analysis including for the case of a U-shaped triangular tube array in a steam generator.
Modeling Refractory Stiffness for Piping Flexibility Analysis
Authors: Nadarajah Chithranjan
Published: November 2022

Refractory is commonly used in pipes for cold wall design. Generally, to analyze refractory lined piping, a piping stress analysis is done using commercially available piping flexibility analysis software. In the stress analysis, the refractory weight and stiffnesses are included in the piping model. From the piping analysis, the calculated sustained and expansion stresses are compared with ASME B31.3 [1] allowable stresses and the forces and moments from the analysis are used in the design of attached equipment (vessel nozzle, valves, expansion joints etc.) piping restraints and supports.

In this paper it will be shown that for a piping stress analysis, using the combined stiffness of the refractory and pipe material on the straight section of the pipe is satisfactory but when it is used on the bends, it will result in un-conservative resultant forces and moments from thermal expansion. To obtain satisfactory resultant forces and moments, the calculated refractory stiffnesses on the bends should be increased in the piping model. The piping stress analysis results were verified with finite element results and past experimental work.
A Critique of Steam Hammer Load Analysis Methods
Authors: Walters Trey W.
Published: November 2022

One of the key assumptions in modern steam hammer load analysis is based on an incomplete understanding of steam wave behavior. Compression waves generated after a valve closure steepen much more quickly than previously thought. The resulting forces generated on pipe runs separated by elbows can be significantly higher than those predicted using current methods. To be more specific, current methods may give unconservative pipe force estimates — potentially resulting in unsafe designs. Using a more complete understanding of gas wave speed, quantitative examples are given which show the larger forces which occur as a result of wave steepening. Suggestions on how to improve load estimation are discussed.
Effect Of The Mean Temperature of Storage Site on Chloride-Induced Stress Corrosion Cracking Rate in ASME Code Case N-860: Case Study
Authors: Jeong Jae-Yoon , Kim Yun-Jae , Lam Poh-Sang , Kim Seunghyun , Kim Gi-Dong
Published: November 2022

Spent nuclear fuels (SNFs) are stored in stainless steel canisters at Independent Spent Fuel Storage Installations (ISFSIs) typically near the seashore. During long-term storage of these canisters in the dry cask storage system (DCSS), chloride-induced stress corrosion cracking (CISCC) could occur due to the deliquescence of concentrated salt deposits on the canister surface. To evaluate such flaws on the accessible exterior metallic portions of containment systems while in service, the ASME Section XI Code Case N-860 provides inservice inspection requirements for aging management of canisters manufactured with welded austenitic stainless steels. It is noteworthy that CISCC crack growth rate (CGR) model in Code Case N-860 consists of the constitutive equations with temperatures (canister surface temperatures, storage site yearly mean temperature, and ambient temperature measured at overpack inlet) and is independent of stress intensity factor or other environmental factors.

In this work, the mean temperature effect of the local storage site on the CGR is analyzed based on the CISCC CGR model in Code Case N-860. The specified mean temperature in the Code Case is calculated yearly however, the crack growth by CISCC can be evaluated differently if the mean temperature of storage site with a large annual range of temperature such as South Korea is applied. In that case, the monthly mean temperature is adjusted as the yearly mean temperature so the effect of averaging range for calculating the mean temperature is analyzed. Firstly, climate data of some candidate sites for the storage in South Korea are measured from Korea Meteorological Administration (KMA). The climate data of the Diablo Canyon Power Plant located in California (United States) is obtained from National Weather Service (NWS) for comparison. Yearly data from 2012 to 2020 are applied and the crack growth is estimated for sites of different annual ranges.
Fatigue Design Sensitivities of Stationary Type 2 High-Pressure Hydrogen Vessels
Authors: Emery John M. , Grimmer Peter , Wheeler Robert , San Marchi Chris , Ronevich Joseph
Published: November 2022

Type 2 high-pressure hydrogen vessels for storage at hydrogen refueling stations are designed assuming a predefined operational pressure cycle and targeted autofrettage conditions. However, the resulting finite life depends significantly on variables associated with the autofrettage process and the pressure cycles actually realized during service, which many times are not to the full range of the design. Clear guidance for cycle counting is lacking, therefore industry often defaults to counting every re-pressurization as a full range pressure cycle, which is an overly conservative approach. In-service pressure cycles used to predict the growth of cracks in operational pressure vessels results in significantly longer life, since most in-service pressure cycles are only a fraction of the full design pressure range. Fatigue crack growth rates can vary widely for a given pressure range depending on the details of the residual strains imparted during the autofrettage process because of their influence on crack driving forces. Small changes in variables associated with the autofrettage process, e.g., the target autofrettage overburden pressure, can result in large changes in the residual stress profile leading to possibly degraded fatigue life.

In this paper, computational simulation was used for sensitivity studies to evaluate the effect of both operating conditions and autofrettage conditions on fatigue life for Type 2 high-pressure hydrogen vessels. The analysis in this paper explores these sensitivities, and the results are used to provide guidance on cycle counting. In particular, we identify the pressure cycle ranges that can be ignored over the life of the vessel as having negligible effect on fatigue life. This study also examines the sensitivity of design life to the autofrettage process and the impact on life if the targeted residual strain is not achieved during manufacturing.
An Initial Assessment of the Creep-Rupture Strengths for Weldments With Alloy 800H Base Metal and Alloy 617 Filler Metal
Authors: Rupp Ryann E. , Sham Ting-Leung
Published: November 2022

In Section III, Division 5 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Alloy 800H is qualified for elevated-temperature nuclear construction for temperatures up to 760°C (1400°F) and a maximum service life of 300,000 hours. There are two permissible filler metals for Alloy 800H weldments specified in Division 5: ENiCrFe-2 (Alloy A) and ERNiCr-3 (Alloy 82). Low creep-rupture strengths of these weldments at the upper limits of the qualified temperatures and service lives may restrict the design envelope for elevated-temperature nuclear construction with Alloy 800H. As a result, an alternative filler metal is desired to improve the creep-rupture strengths of Alloy 800H weldments for the qualified temperatures and service lives.

This work investigates an overmatched filler metal. Specifically, a weldment with Alloy 800H base metal and Alloy 617 filler metal fabricated by semiautomated gas tungsten arc welding is investigated. A scoping creep-rupture test program was conducted of cross-weld specimens at temperatures ranging from 750 to 1000°C (1292 to 1832°F). Preliminary results on the creep-rupture strengths of the Alloy 800H weldment with an Alloy 617 filler metal do not show significant improvement compared to the filler metals currently qualified in Division 5 for Alloy 800H weldments. Consequently, work is in progress to investigate a matching filler metal.
On the Effect of Hot-Box Size on Coke Drum Skirt Fatigue Life
Authors: Fernando John , Kwok Henry , Wong Leanne , Chan Luke
Published: November 2022

Due to the severe cyclic thermal and structural loading that coke drums experience during operation, thermo-mechanical low-cycle fatigue failure has become a prominent consideration in the design of coke drums. Fatigue failure is commonly observed at the skirt-to-shell attachment weld, due to thermal gradients that develop during heating and cooling cycles. To reduce temperature differences between the coke drum shell and skirt near the attachment weld, “hot-boxes” are often implemented in skirt designs. Hot-boxes are enclosed regions of space near the attachment weld that maintain the skirt at temperatures similar to the nearby shell through natural convection and radiation. The present study investigates the effect of hot-box emissivity and height on the fatigue life of the attachment weld for skirt designs with and without keyholes. The results presented herein indicate that, for the skirt height investigated, fatigue life has negligible sensitivity to the height of the hot-box when no keyholes are present on the skirt. In contrast, varying fatigue performance is observed as a function of hot-box height when keyholes are included as part of the skirt design. Although the functional relationship between hot-box height and fatigue life for the skirt design with keyholes is non-monotonic, the results provide directional insight into the optimization of hot-box size.
Computational Fluid Dynamics Modeling of Dry Cask Simulator With Crosswind
Authors: Jensen Ben J. , Suffield Sarah R. , Higley Megan E.
Published: November 2022

The purpose of this study is to create a STAR-CCM+ model of the Belowground Vertical Dry Cask Simulator (BVDCS) at Sandia National Laboratories (SNL) and validate the model with SNL’s experimental results. The BVDCS consists of a single boiling water reactor assembly fitted with electric heaters encompassed by a containment vessel and shell to represent a belowground spent nuclear fuel (SNF) dry storage system. Blowers are located near the inlet and outlet of the BVDCS to simulate crosswind conditions. In addition to the experimental results, the STAR-CCM+ model developed for this study is compared with a previous computational fluid dynamics (CFD) model in a different software program, which is used as a software-to-software benchmark. The experimental results provide a dataset to compare the STAR-CCM+ model results for a variety of different conditions. The main objective is to validate and improve STAR-CCM+ CFD models for spent nuclear fuel storage systems with explicitly modeled external environments and “wind driven” crossflows. These CFD models aid in the study of external particle deposition in spent nuclear fuel storage systems, which is important to predicting the significance of chloride induced stress corrosion cracking (CISCC). In addition to experimental comparison, a sensitivity analysis is performed using the STAR-CCM+ model. The sensitivity analysis provides a quantitative assessment of the sensitivity of various parameters. This helps provide information on various parameters that are of particular importance to constructing a model representative of real life systems. The STAR-CCM+ model compared well to the experimental results showing similar responses to changes in crosswind flow, and however several parameters are identified for model improvement.
Baseline Design of High-Pressure Confinement Vessel for Proton Radiography of Shock Physics Experiments
Authors: Spernjak Dusan , Fister Matthew , Fehlmann Kevin , Scarafiotti Jesse , Lakey Matthew , Bustos Gerald , Cardon Devin
Published: November 2022

A unique vessel system is being developed to facilitate proton imaging of small-scale shock physics experiments at Los Alamos National Laboratory (LANL). The main components of the system are the Inner Pressure Confinement Vessel (IPCV, which hosts the physics experiment), the Outer Pressure Containment Vessel (OPCV) and Beam Pipes and Auxiliary Hardware (BPAH). The IPCV is an explosively loaded high-pressure vessel which is mounted inside the statically loaded OPCV. The OPCV is attached to a proton beamline. The OPCV and beam pipes form a containment pressure barrier. The detonation of high explosive (HE) inside the IPCV drives material to extreme loading conditions, which are imaged using a proton beam and an imaging system. The IPCV needs to satisfy the ASME Boiler and Pressure Vessel Code, Section VIII, Division 3, Code Case 2564, while allowing for maximum resolution of proton radiography across a sufficiently large field of view.

The main components of the IPCV are the vessel body, top and bottom covers, side covers, and radiographic window assemblies. The covers have different feedthroughs mounted on them, such as feedthrough devices for sending or receiving electrical and optical signals across the pressure boundary. The covers also have gas lines with valves for venting the vessel volume. The sealing strategy incorporates a tortuous path and a minimum of 3 O-rings at each vessel cover. The O-ring grooves are designed and tested to seal the vessel before and after the explosive experiment, and to minimize the burp (limited release) during the explosion. While the IPCV is designed for a relatively small HE amount of 30 g TNT equivalent, the radiographic window is located only a few cm away from the HE, which is unique to this specialized high-pressure vessel. To achieve the optimal imaging resolution across the required field of view of 2cm by 2cm, the radiographic windows need to be very thin, located extremely close to the HE, and made of low-attenuating material such as Beryllium. This paper provides an overview of the baseline design, analysis, and testing of the IPCV and its subassemblies.
Numerical Simulation on the Influence of Elbow Structure on Hydrogen Flame Propagation Process in Pipes
Authors: Mei Yuan , Shuai Jian , Qi Sheng , Huang Zhonghong
Published: November 2022

Combustible gas accounts for an increasing proportion of energy in countries. As the main transportation tool of combustible gas, the safety of pipeline has always been the focus of researchers. When the gas explodes, the accident consequences are greatly affected by the pipeline structure. The study on the hydrogen explosion characteristics of a typical pipe structure (elbow structure) is carried out in the paper. The results show that in pipes with large elbow angles, the flame front can form local cavity regions as flame passes through the elbows. The influence of elbow structure on flame propagation is mainly concentrated in the middle and late stages. In the middle stage, the elbow structure creates a relatively closed space in advance, so that the speed peak-2 occurs earlier than the straight pipe. In the later stage, the acceleration effect produced by the outer wall (concave wall) plays a leading role, and the flame accelerates for the third time after passing through the elbow. There is an interactive relationship between the development of the explosion overpressure and the flame propagation in the elbow.
Gaseous Hydrogen Charging and Fatigue Testing on IN718
Authors: Ebling Fabien , Wackermann Ken
Published: November 2022

IN718 is a precipitation hardened nickel-based superalloy, which is well known for its high strength, good corrosion and creep resistance from low to high temperatures. It is therefore a popular material for numerous applications. Nevertheless, it is known that hydrogen can strongly affect the mechanical properties of IN718. Some questions still need to be clarified to ensure the safe use of components in a hydrogen environment.

In this work, the hydrogen uptake in a gaseous hydrogen environment and tensile and fatigue properties of pre-charged IN718 were investigated. Specimen were charged at 350°C and 100 bar hydrogen pressure. It turned out, that saturation was reached after 10 days with a hydrogen content of about 27 wppm. Tensile tests showed a loss of elongation to failure and reduction of area for the pre-charged specimen. Hydrogen effects were also evident in the low cycle fatigue test. The cycles to failure were significantly reduced. Investigations of the fracture surfaces showed clear differences in crack growth of non-charged and pre-charged tensile and fatigue specimen.
Seismic Test Results of the Main Steam Isolation Valve for Japanese Boiling Water Reactor Nuclear Power Plants (Part 2)
Authors: Itabashi Hideaki , Tsutsumi Yoshitaka , Nishino Koji , Kumagai Shin , Kubota Ryo , Tanemura Shota
Published: November 2022

The functional requirements of Main Steam Isolation Valves (MSIVs) provided in the Boiling Water Reactor (BWR) nuclear power plants in Japan have been previously evaluated via seismic tests and so forth. However, since the response acceleration has increased in line with a recent reassessment of standard earthquake ground motions, it is necessary to evaluate seismic operability with respect to high acceleration. In addition, from the viewpoint of equipment fragility in seismic PRA, it is necessary to determine practical seismic operability limits.

We already confirmed that MSIV has capable of maintaining correct function for response accelerations up to 15 × 9.8 m/s2 in all directions (see Ref.[1]) using a resonant shaking table in the Central Research Institute of the Electric Power Industry (CRIEPI) (see Ref.[2]), which is capable of seismic tests at acceleration levels previously unachievable.

Additional seismic tests for a MSIV were conducted and we obtained results confirming that validated seismic operability was possible even at response accelerations as high as 20 × 9.8 m/s2.

The seismic operability results obtained for this MSIV will be applied to a fragility analysis of seismic PRA.
An Investigation About the Ageing Behaviour of Pre-Applied Threadlockers
Authors: De Agostinis Massimiliano , Croccolo Dario , Fini Stefano , Olmi Giorgio , Robusto Francesco , Scapecchi Chiara
Published: November 2022

Pre-applied threadlockers are widely adopted in industrial applications, due to their favorable features in terms of handling of the fastener and savings in terms of assembly-line dosing systems. In the practice, fasteners with the pre-applied adhesive may undergo storage and/or shipping in harsh environmental conditions, both in terms of temperature and humidity. Questions may arise as to whether such thermal-hygroscopic aging (prior to assembly): (i) affects the tribological properties of the fastener at tightening and/or (ii) the breakaway torque of the fastener after curing. By means of an experimental approach, this work primarily aims at answering the first question, indeed scarcely covered by the literature. As for the second question, measurement of the breakaway torque is carried out for the sake of comparison with the data provided by the adhesives datasheets, where available. Based on a common bolt and plate configuration, the study involves different pre-applied threadlockers in terms of strength grade, among several hygrothermal conditions, representative of frequent storage/shipping conditions. The experimental data have been analyzed by means of the ANOVA tools to assess the effectiveness of the input parameters (adhesive type and aging conditions) on the response in terms of both thread friction coefficient at tightening and breakaway torque of the fastener after tightening completion and complete polymerization. Guidelines useful to the design engineer are reported in the conclusions.
Statistical Analyses of Austenitic Stainless Steel High Cycle Fatigue Data to Support a Revised Design Factor for Design Fatigue Curve Development
Authors: Morley Andrew , McLennan Alec
Published: November 2022

In the 2009 addendum to the ASME BPV Code [1], new design fatigue curves were adopted for austenitic stainless steel and nickel-based alloys. These changes followed publication of NUREG/CR-6909 [3] which, in addition to describing a methodology to account for environmental effects on fatigue, challenged both the mean air curve underlying the design fatigue curve and factors used to define the design position from this mean behaviour.

The methodology to build the design curve starts with the mean air curve obtained by laboratory testing, a correction is made for mean stress effects and then the resulting curve is translated by coefficients, referred to within this paper as design factors, applied on stress or on cycles, with the lower of the two translated curves defining the design curve. The translation by these design factors is to account for factors present in service applications but not present in the laboratory testing and also to provide a conservative position accounting for scatter in fatigue behaviour.

Following a detailed review of the appropriate factor on cycles in NUREG/CR-6909 [3], the revised ASME design curve replaced the historic design factor of 20 on cycles with a factor of 12, although a later revision of NUREG/CR-6909 [4] further refined this to below 10, the factor of 12 remains. The historic design factor of 2 on stress was not reviewed in any detail NUREG/CR-6909 and was not changed at this time. However, a number of reviews previously and since [5],[6] and [7] have suggested that a design factor of 2 is excessive compared to the aim of describing a 95% bounding curve position.

This paper presents a series of statistical analyses of the same austenitic stainless steel data used to generate the mean curve fit underlying the current design curve, supplemented with additional, high-quality, modern data to demonstrate that a substantially-reduced factor on stress would be appropriate to the aims of describing a 95% bounding curve.

In conjunction with other recent literature, these analyses present a strong basis for revision of this historic excess-conservatism while maintaining a suitably-conservative position. However, as such blanket conservatisms are reduced, the limitations, simplifications and assumptions of the current curve form and design curve construction must be discussed and evaluated, this wider context is described to support further discussion.
Complex Lattice Structure-Based Heat Exchangers Through Additive Manufacturing: Opportunities and Challenges
Authors: Wong Jerome , Qureshi Ahmed , Mertiny Pierre
Published: November 2022

Cellular structures are a class of materials that offer greater stiffness, strength-to-weight ratio, good energy absorption capacity, and high heat transfer capability compared to solid parts. Metallic lattice structures have been applied in different industry sectors, such as in biomedical implants, lightweight components, energy absorbers, and catalytic reactors. With the development of advanced manufacturing techniques, especially additive manufacturing (AM), lattice structures with complicated designs can be produced. Lattice structure-based heat exchangers produced by AM techniques have recently gained significant attention due to their promising performance. Interconnected cavities in lattice structures provide flow of fluid and effective thermal conductivity, which is desirable in heat exchangers. AM methods provide the possibility to promote tortuosity and intricate flow patterns leading to improved performance of heat exchangers. Between different AM techniques, laser powder bed fusion (LPBF) proved to be a suitable method for the manufacture of heat exchangers. Using LPBF methods, the distribution and geometry of cavities in the structure can be controlled with an accuracy that is typically better than for other AM methods. Although LPBF-produced heat exchanger showed enhanced thermal conductance, there are limitations associated with LPBF fabrication, such as surface roughness and need for post processing. In order to bridge this gap, the effects of different process parameters and levels of structural complexity in LPBF processes need to be evaluated. In this context, the present contribution constitutes a position paper that contrasts the opportunities that LPBF may provide for the fabrication of heat exchangers with the challenges that need to be overcome to realize design solutions that meet industry demands.
Seismic Vulnerability Assessment and Fragility Functions Derivation for Steel Storage Legged Tanks
Authors: Gabbianelli Giammaria , Perrone Daniele , Nascimbene Roberto , Paolacci Fabrizio
Published: November 2022

The major earthquakes that occurred worldwide in the last decades highlighted the seismic vulnerability of industrial structures and their components. Beyond the need to avoid human losses, the damages experienced by industrial facilities, both in terms of structural, non-structural and plant elements, significantly affected the economy of such areas. On the one hand, often the damages of non-structural components and their contents immediately lead to significant monetary loss. On the other hand, the leakage of toxic contents or the disruption of mechanical equipment can conduct to down-time of industrial plants. Following the 2012 Emilia earthquake in Italy, one of the most damaged components in industrial facilities, among others, was the steel storage legged tank.

This research aims to investigate the seismic vulnerability of such elements by defining suitable fragility functions, also useful for future loss estimation studies. Several engineering demand parameters (EDPs) were selected in order to line up the damages observed in the aftermath of earthquakes. To draw general conclusions, several legged tanks were selected and analyzed. A suitable record selection has been performed, for which the average spectral acceleration (AvgSa) was selected as intensity measure (IM). Once adequate performance objectives were defined, the legged tank archetypes were analyzed by means of multiple-stripe analyses (MSA) to calculate the fragility functions and to highlight the most critical elements and tank configurations.
Use of HDPE Piping in Buried Nuclear Class 3 Systems Categorized as Low Safety Significant
Authors: O’Sullivan J. E. (Jim)
Published: November 2022

Code Case N-755 and ASME Section III Appendix XXVI were developed by ASME for providing deterministic rules for new construction of Class 3 buried piping using High Density Polyethylene (HDPE) piping. These rules contain many special treatment requirements consistent with deterministic rule making, that have essentially put HDPE out of economic contention with other choices for replacement of degraded buried Class 3 piping such as using thicker-walled carbon steel piping, low alloy piping material, or even AL6XN. Re-evaluation of buried portions of Class 3 safety-related service water and cooling water piping using the risk-informed provisions of 10 CFR 50.69 or Code Case N-752 should result in recategorization of most buried Class 3 service water piping as Low Safety Significant, enabling relaxation of many of those special treatment requirements.

This paper describes an approach that will apply ASME Section III Appendix XXVI for replacement of Class 3 buried piping categorized as Low Safety Significant while exempting the design and construction from several special treatment requirements of Section III Appendix XXVI. This approach provides alternative treatment provisions for material procurement, design, fabrication, installation, and testing of technically superior HDPE piping as a cost-competitive permanent replacement for degraded buried safety related Class 3 carbon steel piping.
Study on the Bonding Strength and Corrosion Resistance of Low-Pressure Cold Sprayed Al/Al2O3 Composite Coatings on Pressure Vessel Steel Substrate
Authors: Wang Yonggang , Liu Xin , Sun Liang
Published: November 2022

Due to the complex working environment, the defects were easily produced on the surface of pressure vessel plate, such as scratch, wear and corrosion pit, which reduced the service life of equipment. As a new surface coating preparation technology, cold spraying technology can be used to effectively repair and protect the substrate. With the development of cold spraying technology, more and more metal powders are used to prepare functional coatings, but aluminum powders are used most frequently due to significant plasticity and corrosion resistance. However, pure aluminum coating have a obvious shortcoming with lower bonding strength, and most of bonding strength values of coatings and steels are about 14.6 MPa. With the aim to improve the mechanical properties more of pure Al, the most representative one is the inclusion of ceramic particles as reinforcement to produce dense coatings. Thus, the Al-Al2O3 composite coatings of the different Al2O3 weight fractions were deposited on the surface of pressure vessel plate by cold spraying technology. The strength and corrosion resistance of the coatings were evaluated by tensile test, corrosion weight loss measurement and electrochemical test. The results show that the bonding strength of pure Al coating is the lowest among the four cold spray coatings, and the bonding strength sharply increases while the coating increased Al2O3 particles, and the largest values with bonding strength of Al-Al2O3 is as high as 45.4 MPa. The tensile test was carried out under the allowable stress of pressure vessel. Observations under optical microscope (OM) were also done, and the coating has excellent quality and no new cracks and holes. The corrosion weight-loss of the substrate and composite coatings were measured, and the corrosion weight loss rate of Al-Al2O3 was 5 times lower than that of pressure vessel plate. In addition, for all the coatings, the values of weight loss had little changes. It is observed that the values of the composite coating was exhibited a peak with an increasing of the Al2O3 content. The Al-20wt.%Al2O3 was shown the best corrosion resistance and the value of weight loss was 0.11(g/cm2*h), which probably was attributed to the effect of the lower porosity. Potentiodynamic polarization curves were shown the corrosion current density of composite coatings were one order of magnitude lower than that of the substrate. Therefore, we concluded that the corrosion resistance is obviously better than that of the substrate, which can effectively protect the substrate and delay the service life of the pressure vessel plate.
Study on Skirt Base Ring Reinforcement for Tailing of Vertical Vessels
Authors: Mihara Yuki , Kataoka Shunji , Okami Atsushi , Takahashi Kyohei
Published: November 2022

EPC contractors / manufacturers design and use the lugs attached on the skirt for tailing of vertical vessels. To avoid the overstressing and deformation of the skirt base ring due to tailing load, the reinforcing beams attached inside the base ring may be considered. Since the design rules for tailing devices are not described in ASME BPVC Section VIII, the soundness of the tailing design could be left to the judgement of individual parties. In past projects, the deformation of the skirt base ring during lifting work at construction site occurred and gave huge impact on construction schedule and cost.

As per the theoretical calculation for the design of the skirt base ring reinforcements, the beams are generally considered as “rigid” structure. Based on the results in this paper, it can be said that the base ring may be overstressed and largely deformed if the axial stiffness of the reinforcing beams is not properly taken into the consideration of tailing design, especially for large diameter vessels.

This paper provides the basic concept and practical design consideration of the skirt base ring subject to tailing load by investigating the tendency of bending moment and residual plastic deformation of the skirt base ring with several types of reinforcing beam arrangement.
Stress Evaluation of a Three-Point Supported Heat Exchanger
Authors: Raman Senthil Kumar
Published: November 2022

This paper focuses on developing formula-based method to predict shell stresses in a high-pressure heat exchanger with three-point supports. It compares the results with Finite Element Analysis (FEA) based design procedure. High pressure heat exchanger is supported with two saddles on shell (fixed and sliding saddles) and one lug support on channel due to heavy thk. tubesheet and channel flanges. Heat exchanger vessel part is considered as a hollow circular beam and closed form solutions are derived using continuous beam theory. Three-dimensional (3D) Finite Element model is developed using Ansys® and three types of meshing options are considered i.e., tetrahedron mesh, hex dominant mesh, and shell element mesh. Linear static structural analysis is performed, and shell membrane plus bending stresses are extracted by linearizing the axial stresses along the Stress Classification Lines at four shell locations using PVRC 3D stress criteria (Bulletin WRC 429). Longitudinal membrane plus bending stresses are calculated for the severe most design load case: Internal pressure, superimposed tubesheet weight and ship motion acceleration loads. Stress values which are obtained by formula-based approach and FEA are compared at four shell locations and conclusions are drawn.
Multiphase Flow Induced Forces for Horizontal and Vertical Systems
Authors: Pereboom Hajo , Belfroid Stefan
Published: November 2022

Multiphase flow is a known source of vibrations in piping systems. Multiple experimental campaigns have focused on the force spectrum on horizontal bend systems. To evaluate the evolution of multiphase forces through a vertical loop, experiments have been done on an air-water, two inch pipe system consisting of four bends at near-atmospheric conditions. Forces are measured at each bend by clamping the pipe and measuring the strain. The experiments consist of two phases with the same loop in both a vertical and horizontal orientation. The change in orientation reveals the difference between a vertical and horizontal force development for the same u-shape geometry. The results show a difference in force development through the bends in a vertical system compared to the horizontal orientation. The force on the lower bend in an upwards orientated pipe plateaus on a minimum value for low gas velocities. The other bends in the system do not show this behavior. The effect of a vertical section on the coherence between the bends is investigated and compared with the horizontal orientation. Due to the larger difference in flow pattern in the vertical parts of the loop the coherence between the bends is lower when compared with the horizontal layout.
Numerical Method to Determine Fracture Toughness Under Hydrogen Environment From Small Punch Test Data and Experimental Validation
Authors: Seo Ki-Wan , Hwang Jin-Ha , Kim Yun-Jae
Published: November 2022

This paper proposes a simple method to predict the fracture toughness of hydrogen-embrittled material using a hydrogen-embrittlement constant. The effect of hydrogen-embrittlement on fracture strain can be quantified via hydrogen-embrittlement constant, and it can be obtained by simulating small punch test in hydrogen. The fracture toughness of hydrogen-embrittled material can be simply estimated by multiplying the constant on fracture toughness of the un-embrittled material. The result of estimation shows good agreement with the published experimental data.
Creep Fatigue Damage Assessment of the Welded Structures of High-Temperature Pressure Equipment Based on DIC Technology
Authors: Fan Zhichao , Zhou Yu , Chen Xuedong
Published: November 2022

In recent years, pressure equipment tends to operate under higher temperature and higher pressure with the rapid development of world economy, resulting in greater significance of creep fatigue damage that is strongly temperature and time dependent. This brings new challenges to the design, manufacturing, operation and maintenance management of the high-temperature pressure equipment. The welded structure of high-temperature pressure equipment exhibits heterogenous microstructures with mismatched mechanical properties, as well as the unavoidable weld defects. Damage characterization, life design and failure assessment of welded structures have always been challenging difficulties. Hence, the welded structure is the weakest link for creep fatigue failure. The present paper introduces the research progress on creep fatigue damage assessment method for the welded structures of high-temperature pressure equipment in China, based on the digital image correlation (DIC) technology and the ductility exhaustion theory. It involves in-situ characterization of heterogenous creep deformation of welded joints by using the digital image correlation technology, creep damage assessment of welded structures by finite element modeling, evaluation of strain enhancement effect and life-based creep fatigue strength design of high-temperature welded structures, etc. This method can provide useful guidance for establishing the prevention and control schemes for creep fatigue damage of high-temperature welded structures.
Load Loss as a Factor Impacting Gasket Leakage
Authors: Rice Dale A. , Waterland Jerry
Published: November 2022

After flange assembly and following a period of operation, some of the compressive stress on a gasket is lost due to factors such as temperature, pressure, flange movement, and material composition. Increased leakage (fugitive emissions) is often a result of gasket stress loss; however, the increased, operating leak rate is not necessarily directly proportional to the degree of gasket stress loss. A study was conducted using a previously published leak rate model based on an equation set derived from the Pressure Vessel Research Council to provide a demonstration of the impact of load loss (under operating conditions) on the predicted gasket leak rate. The model incorporates system pressure and gasket stress as input variables along with gasket specific factors determined from room temperature tightness test data. Model-derived leak rate data have been plotted as a function of gasket assembly stress for several material types including polytetrafluoroethylene, compressed fiber, and flexible graphite. Plot trends were found to vary noticeably by material type as well as by manufacturer. The derived model outputs are a confirmation that predicted leak rates are not linearly proportional to the degree of gasket stress loss. The results of this study may be instructive to the end user for comparing predicted leak rates of gasket materials over a gasket stress loss range associated with a given application.
Fracture and Tensile Characterization of Additively Manufactured Type 300 Series Stainless Steel in the Baseline and Hydrogen Charged Conditions
Authors: Krentz Tim , Korinko Paul , McWilliams Anthony
Published: November 2022

Savannah River National Laboratory (SRNL) has characterized powder bed fusion processed Type 304L stainless steel for use as hydrogen storage and process vessels. As part of this characterization, a simple cylinder (C-cylinder) and a “D-cylinder” were fabricated using two different Laser Powder Bed Fusion (L-PBF) machines at two different sites. These four sample cylinders were electrical discharge machined (EDM) into cylindrical blanks and rectangular blanks and subsequently finished machined into tensile samples and single edge notched three-point bend fracture toughness samples, respectively. The microstructures of the cylinders were optically characterized parallel to the build direction and perpendicular to the build direction at three elevations. Samples were hydrogen charged using conditions to generate approximately 70 wppm (3700 appm) hydrogen. The sub-sized cylindrical tensile samples and fracture toughness samples were non-destructively characterized using computed tomography with a voxel size of nominally 80 microns. Metallographic analysis and CT indicated the samples are virtually pore free and exhibit the expected microstructure of L-PBF processing. The mechanical test samples were tested in the baseline and hydrogen charged conditions to determine the tensile and fracture toughness behavior; based on previous results, the baseline tensile and fracture properties are comparable to wrought material and the hydrogen properties exhibit similar characteristics to wrought materials.
A Critical Understanding of “Low-Stress” Spiral Wound Gaskets
Authors: Jamison Alton
Published: November 2022

Low-stress spiral wound gaskets are marketed as an alternative to standard spiral wound gaskets, requiring less torque to seat the gasket. Spiral wound gaskets are common commodities used in piping reliability staff are constantly looking for different alternatives. Multiple manufacturers offer a low-stress version of spiral wound gaskets. Do these spiral wound gaskets offer a low-stress solution, and do they perform better than a standard spiral wound gasket? This paper will go beyond the marketing of “low-stress” spiral wound gaskets and examine the construction and engineering behind these gasket designs. Manufacturers of spiral wound gaskets have made subtle changes and the “low-stress” technology has become a common theme throughout the spiral wound gasket market. Multiple chemical and petrochemical plants use these designs in their piping systems and sometimes as replacements for ASME recommended spiral wound gaskets with inner rings. Low-stress spiral wound gaskets have multiple designs from additional graphite in the filler to an anti-buckling design which are marketed as requiring less initial preload to seat. This paper will examine the validity of these gaskets and determine if they are low-stress and if they provide a credible seal in a bolted flanged joint. [1]
Large-Scale Parametric Modeling of Spent Nuclear Fuel Dynamics in the 30 cm Package Drop Scenario
Authors: Kadooka Kevin , Fitzpatrick James , Klymyshyn Nicholas
Published: November 2022

Packages used to transport spent nuclear fuel (SNF) are required by the U.S. Code of Federal Regulations 10 CFR 71.71 to demonstrate satisfactory performance during a drop scenario. While the CFR is meant to ensure safe package function, it does not evaluate survival of the SNF within. The U.S. Department of Energy Spent Fuel and Waste Science and Technology program is working on closing the knowledge gap related to the response of SNF to external mechanical loads, including the 30 cm package drop scenario in the CFR. In support of this effort, LS-DYNA finite element simulations were developed by Pacific Northwest National Laboratory (PNNL) to model generic drop scenarios at both the package and fuel assembly level. The models were validated against one-third scale package and full scale fuel assembly drop test data and were exercised to predict fuel cladding strains in a narrow range of model configurations.

This work describes a large-scale parametric study conducted by PNNL using the previously developed and validated PWR finite element model, with the addition of a new generic BWR assembly model. The motivation for the parametric study was to characterize the broad range of SNF responses in the 30 cm package drop scenario. This was accomplished by varying the drop orientation, fuel assembly type (17 × 17 PWR and 10 × 10 BWR), burnup, cladding temperature, spacer grid buckling load, package mass, impact limiter stiffness, and mechanical gap conditions within the basket. A MATLAB framework was developed to automate LS-DYNA model generation and execution on PNNL institutional computing resources. In total, over 2000 simulations were performed. For each simulation, the SNF response was quantified in terms of permanent grid deformation, fuel rod contact pressure, and strains within the fuel rods, guide tubes, and water rods. The results provide valuable insight into the range of responses that could be reasonably expected from SNF in the 30 cm drop scenario, as well as the sensitivity to each input parameter. The results of this parametric study are a key component of the testing and modeling strategy the Spent Fuel and Waste Science and Technology program is using to close the external loads knowledge gap.