bluuebunny/crossref_metadata_2025 huggingface dataset:
Electromagnetic Lithium Ring Compression for Magnetized Target Fusion Application: Shell Buckling
Authors: Edalatfar Fatemeh , Santos Lemuel , Jayhooni Hashem , Dick Jean-Sebastien
Published: November 2024

Magnetized target fusion (MTF) relies on rapidly compressing magnetized plasma within a flux conserver to attain fusion conditions. Maintaining the smoothness and symmetry of the plasma-facing surface during compression is crucial, as any asymmetric deformation or buckling of the solid metal shell can disrupt magnetic confinement, reducing plasma temperature, and lifetime.

To establish the criteria for preventing buckling in solid ring implosions, we assess the effectiveness of the dynamic plastic flow buckling model. This assessment involves analyzing buckling phenomena in magnetically driven, imploding lithium rings. This investigation includes a total of 5 experiments with variations in collapse velocities, radius-to-thickness ratios, and initial ring temperatures. We capture and analyze the collapse trajectories and deformations of the rings during implosion using computer vision techniques. To establish material properties required for the theory, we utilize the Johnson-Cook model for the lithium ring with strain and strain rate extracted from the experiments. Using the extracted material properties and ring dimensions and employing the analytical model, we predict critical buckling velocities and dominant modes for each experimental scenario.

We observe qualitative agreement between the experiment and analytical model within measurement uncertainty, indicating the potential to define design, manufacturing, and quality requirements for larger-scale Magnetized Target Fusion experiments using solid shells to achieve fusion conditions.
Assessing a Hydroprocessing Reactor After a High Temperature Excursion
Authors: Batts Kevin , Penso Jorge , Hau Jorge , Dalal Mitul
Published: November 2024

A thick cold wall conventional 2.25Cr 1Mo steel with 347SS weld overlay and internal insulating refractory was affected during an external high temperature excursion in a resid hydrocracker unit. The reactor is part of a two-train unit with each train including two reactors. Reactor normal operating condition is 424–441 °C (795–825 °F) and 186 bar (2700 psig). A comprehensive metallurgical, non-destructive and fitness for service per API 579-1/ASME FFS-1 [1] assessment was completed before deciding to place the reactor in service. MTI publication No. 30: “Damage Assessment: Investigating Fires, Explosions, and Storm Damage in Chemical Plants” [2] was used as guidance as well.

The fitness for service assessments included shell out-of-roundness, leaning and distortion and local thin areas as consequence of scoop samples removal. An integrated computational materials engineering (ICME) approach was taken as part of the assessment for the future-service capabilities of a thick-walled steel pressure vessel that was damaged by overheating. Removal of scoop samples allowed for metallurgical characterization and mechanical property assessment. No repair was needed at the scoop sample locations. Indications of weld overlay disbonding were not reported. The different assessments supported the decision to place back the reactor in service with complementary monitoring plans. The reactor was returned to service and operated over two years, until the refinery was closed.
Development of the Buckling Evaluation Method for Large Scale Vessels in Fast Reactors Made of Grade 91 Steel and Austenitic Stainless Steel With Large Initial Imperfections
Authors: Okafuji Takashi , Miura Kazuhiro , Sago Hiromi , Murakami Hisatomo , Watakabe Tomoyoshi , Ando Masanori , Miyazaki Masashi
Published: November 2024

The current buckling design code of Class 1 vessels for fast reactors (FRs) power plant in Japan, “Design and Construction for Nuclear Power Plants, Division 2 Fast Reactors” by the Japan Society of Mechanical Engineers, focuses primarily on plastic buckling of austenitic steel vessel. For next-generation FRs, the higher-yield material, especially ASME Grade 91 steel, plans to be applied to the vessels such as steam generators in addition to austenitic steel. Seismic isolation system is also being devised in the next plant to meet the design seismic load in Japan.

To accommodate these conditions, the standard buckling strength equations were proposed in the previous study, which were modified by considering elastic-plastic buckling of vessel. The modified equations consisted of elastic-plastic axial compression, bending, shear buckling, and their interactions, as well as ASME/BPVC Code Case N-284, considering the reduction of buckling strength by cyclic larger vertical load with long-period lower horizontal load under the horizontal seismic isolation plant design. The applicability of the modified buckling equations was confirmed by a series of buckling tests and analyses under monotonic or cyclic axial compressive load accompanied with constant horizontal load in the previous studies. Thorough the experiment and simulation results, the conservatism of the modified equations has been confirmed to Grade 91 steel and austenitic stainless steel vessels with circumferential wrinkle shape corresponding to the elephant foot buckling mode as a significant initial imperfection, under the dominant cyclic axial compressive load accompanied with horizontal load.

In the most of tests and analyses in previous studies, the amplitude of the initial imperfections of vessels was less than or equal to half the wall thickness. However, depending on the fabrication method, the initial imperfection of the large scale vessels might be larger than that. Therefore, a correction factor was proposed to reduce the buckling strength calculated by the modified equations for large initial imperfections.

In this study, a series of elastic-plastic buckling analyses considering large displacement and large strain theories was conducted on Grade 91 steel and austenitic stainless steel vessels which have a wide range of dimensions, initial imperfection amplitude, and vertical/horizontal load ratio. The analysis results showed that the correction factor generally expressed a reduction tendency of buckling strength corresponding to initial imperfection amplitude, and the modified equations are applicable to the vessels in FRs power plant even for large initial imperfection amplitude which exceeds half the wall thickness.
Hydrogen Vessel Weld Porosity Stress Analysis Using CT Scan Data
Authors: Jiang Hao , Winder Drew , Armitage Douglas , Summerlot Nick
Published: November 2024

The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory produces the most intense, pulsed neutron beams in the world for various scientific research experiments and industrial development activities. The neutrons spalled from a mercury target are moderated and directed into instrument channels by the Inner Reflector Plug (IRP), which is designed for the purpose of moderating, reflecting, and shielding these neutrons. The SNS lower IRP is the bottom-most segment of the inner reflector plug components. The lower IRP is a complex structure consisting of an aluminum vessel, beryllium and stainless-steel reflectors, water and cryogenic hydrogen moderators, neutron poisons, and various channels for neutron transport. The lower IRP must be replaced regularly due to consumption of the neutron poisons and embrittlement of the structural materials from radiation.

The hydrogen moderators are constructed from 6061-T6 aluminum. Each hydrogen moderator has a vessel with concentric tubing for supply and return of 18K hydrogen. The hydrogen moderator vessel is welded to a connecting tube using gas tungsten arc welding (GTAW). Radiographic Testing (RT) of a moderator vessel during fabrication indicated porosity within the weld but did not define the location or shape of the porosity. For a better definition of the weld defects, the computed tomography (CT) scan technique was used to produce an accurate 3D image of the weld and weld defects. This paper will describe the procedure to incorporate the CT scan porosity data into the finite element model of a hydrogen moderator with a GTAW weld to determine fitness-for-service. The stress analysis was performed to evaluate the weld defects and to qualify the GTAW weld via the ASME BPVC design criteria.
Plastic Constraint Correction Factor X for Brittle Fracture in Ductile-Brittle Transition Temperature Region
Authors: Hojo Kiminobu , Hirota Takatoshi , Nagoshi Yasuto , Fukahori Takuya , Shimizu Kazuma , Shimodaira Masaki , Ogawa Takuya , Yashirodai Kenji , Ohata Mitsuru , Minami Fumiyoshi
Published: November 2024

In order to predict fracture behavior of a reactor vessel in the ductile-brittle transition temperature region under pressurized thermal shock, a plastic constraint correction factor χ is intended to be introduced into a Japan Welding Society standard. The WES standard will have two levels’ fracture assessments, Level I, a simplified assessment, and Level II, a detailed assessment. The plastic constraint correction factor χ for Level I will be provided by formulas with the parameters, yield strength σy, strength ratio Ry defined by the ratio of yield strength σy to ultimate strength σB, and the Weibull shape factor m with some application limitations. Further, the plastic correction factor χ should depend on geometry factors, such as flaw depth a, flaw aspect ratio a/c, and structure’s thickness. In this paper, sensitivity analyses were performed for thickness, flaw depth, flaw aspect ratio, strength ratio, and the Weibull shape parameter m to apply the plastic constraint correction factor χ for Level I assessment to various reactor vessels. Also, temperature dependency of the Weibull parameters, m and σu was investigated. Based on these results, the formulas of χ were revised and the application limitations for the parameters were expanded. This paper will be one of technical basis for the WES standard.
Non-Linear Buckling Analysis of Thin-Walled Cylindrical Shell Having Large Openings
Authors: Rafique Muhammad Raheel
Published: November 2024

It was required to introduce multiple large openings (windows) in an internal liner shell of a vessel to facilitate the inspection and repair of refractory behind the liner on the main shell. As a part of repair procedure, the castable refractory behind the liner required dry-out at around 520°C. Analysis was performed based on API 579-1/ASME FFS-1; Annex 2D/ASME Sec VIII Div.2; Protection Against Collapse From Buckling, in order to evaluate if the liner shell with large openings could withstand its own weight and high dry-out temperature without any additional support(s). For finite element analysis (FEA), the 3D Model was generated by considering the actual size and orientation of the windows as required at site. At first, Linear Static Structural Analysis was performed by applying gravity load, and then the solution of the linear static analysis was used to perform Eigenvalue buckling analysis to obtain different mode shapes. Selecting appropriate mode shape(s) with suitable load multiplier and scale factor, non-linear Elastic-Plastic Analysis was performed by considering plastic behavior of the material and gravity (self-weight) as well as thermal (dry-out temperature around 520°C) loads. The solution converged, and the protection against collapse from buckling was ensured. Subsequently, the repair activities and thermal dry-out of refractory were performed successfully, without any impact on the liner shell.
Pressure Vessel Design With Strain Rate Sensitive Materials: Lessons From a Refractory Material
Authors: Hajy Akbary Farideh , Hoeijmakers Maarten , Kapadia Rahul S. , Peters Daniel T. , Richardson Ian , Koestenbauer Harald
Published: November 2024

In pressure vessel design, understanding material toughness is critical. This challenge becomes more pronounced when designing vessels using strain rate sensitive materials, due to their low toughness determined from high strain rate tests, such as impact tests. This paper is focused on the design of a pressure vessel made from nominally pure molybdenum, with toughness properties sensitive to the strain rate, due (in part) to its body-centred cubic (BCC) structure. The material is manufactured from a powder subjected to hot isostatic pressing. The applied approach presented here not only describes some of the factors involved in characterizing materials for a pressure vessel design, but also presents a general approach that should be applicable to other strain rate sensitive materials. In this paper we consider the measurement of fracture toughness and other material properties at different temperatures, including the criteria for specimen design, and determining test parameters based on the intended application. We also consider the information necessary for pressure vessel lifetime assessment, based on a fracture mechanics approach.
Proposed Compression Testing Validation for Large ASME B16.20 Spiral Wound Gaskets
Authors: Bao Tommie , Hugo C. Von
Published: November 2024

ASME spiral wound gaskets are widely used in many different industries. It is one of the most common gasket types and readily available in the market. During construction of spiral wound gaskets, the manufacturer is responsible for determining the filler thickness and density of windings. To validate those selections, the gaskets must pass a leakage and compression criteria set by ASME.

For this paper, we will focus on the compression test as required in B16.20 and using criterion values supplied in section SW-2.2 Construction. Testing of smaller gaskets is a relatively straightforward process, however, this is not feasible for larger NPS and pressure class gaskets. The primary obstacle is the available force from a compression test machine. Common compression machines have limited upper load. Another constraint is the diameter of the compression machine’s plates. These limitations make testing for large gaskets impractical, especially when dealing with gaskets for ASME B16.47 Series A and B flanges.

In this paper we are proposing a method to understand the compression performance of larger gaskets by testing them in segments, where the gasket is positioned partially under the compression machine and applied forces are based on the applicable gasket contact area.
Experimental and Analytical Verification of ASME Section III, Division 5 Creep-Fatigue Design Rules
Authors: Wang Yanli , Jetter Robert , Sham Ting-Leung
Published: November 2024

The continuous advancement of structural materials and the growing demands for more reliable and economical structural components in high-temperature reactor applications have necessitated the development of comprehensive design methodologies and design rules. Mechanical degradation of structural components at elevated temperatures subjected to cyclic deformation is controlled by the creep-fatigue damage. Over the past few decades, diligent research efforts have been dedicated to refining the development of elevated temperature design rules in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC), Section III, Division 5 and to develop conservative design rules that can effectively guard against the risk of creep-fatigue failure.

In ASME Section III, Division 5, for a design to pass the creep-fatigue acceptance criteria, creep damage and fatigue damage are evaluated separately, and these damages must not violate the bi-linear creep-fatigue interaction diagram, i.e., the so-called D-diagram. The creep-fatigue damage evaluation procedure assumes that the effects of the actual cyclic loading sequence can be bounded by assuming that the individual loading cycles are uniformly distributed throughout the component design life. In this study, creep-fatigue experiments with variable amplitudes and loading sequencies were designed and performed on Alloy 617 at high temperatures. The results were analyzed to evaluate the loading history effect on creep-fatigue damage accumulation and to verify the assumptions for the creep-fatigue evaluation design rules.
A Simplified Approach Used to Evaluate Equipment Nozzles for Offshore Cyclic Wave Conditions
Authors: Kirkpatrick Kenneth , Millet Barry , Mosher Bryan , Lu James , Miller George
Published: November 2024

The dynamic nature of wave loading in the offshore marine environment creates many fatigue design challenges. Process equipment (pressure vessels, pumps, heat exchangers, etc.) has been mounted on marine facilities and ships since the dawn of powered ships. In the last century more and more sophisticated process units have been ship or platform mounted. This began with the offshore exploration, production of oil and gas in the 1930’s and the advent of nuclear propulsion for ships and submarines in the 1950’s. The nuclear propulsion industry has addressed the fatigue issues since the beginning. In the oil and gas industry, offshore marine facilities and ships, in particular, which includes barges, fixed leg platform, semi-submersibles, tension leg platforms, SPARS, jack-up rigs and FPSO, fatigue on process equipment may have been mostly ignored. Today the software used to evaluate marine facilities and ships for dynamic sea states produces fatigue design data (in terms of accelerations and frequencies) that can be used in the evaluation of process equipment. When evaluating pressure vessels, each vessel contains many nozzles, each nozzle is subjected to multiple loading conditions, and it may be a very large task to evaluate each nozzle for the applied cyclic conditions. This paper will present a simplified stress-based method used to evaluate the process nozzles for accumulative fatigue damage. A simple example will be provided showing how to develop the allowable stress and how it is applied. It is possible that this method may also be expanded to cover components other than nozzles.
Optimizing Preload in a HPHT API 6BX Flange When Subject to Thermal Loading
Authors: Owen Ruth , Ward Peter , Farnell Richard , Christie Andrew
Published: November 2024

This paper uses finite element models of an API flange to consider the suitability of the maximum bolt preload permitted by API 17D, 67% of the bolt’s material yield stress [1]. The flange was reviewed under ambient temperature, and under a large thermal gradient. Pressure and external tension were also considered. The performance of the flange under these conditions was then used to inform the selection of an optimal preload, to maximize the load capacity.
Investigation of Shape Behaviour of Opening on Cylindrical Shell As Per ASME SEC.VIII DIV.1: A Comparative Study of Various Codes of Construction
Authors: Pathre Sujay S. , Gopalakrishnan Shyam , Qadeer Mohammad Abdul , Mathkar Ameya
Published: November 2024

Owing to various practical requirements, pressure vessels are frequently designed with openings of diverse shapes, sizes, and placements. According to the requirements outlined in ASME Sec. VIII Div. 1 Code [1], specifically in section UG-36 (a), it is advisable that openings in the cylindrical or conical sections of vessels, as well as in formed heads, should ideally assume circular, elliptical, or obround shapes. When an elliptical or obround opening has a long dimension which exceeds twice the short dimension, it becomes necessary to add extra reinforcement to mitigate the risk of excessive distortion due to twisting moments. However, it is important to note that the ASME Sec. VIII Div. 1 Code does not provide rules for conducting such assessments and instead directs designers to use section U-2(g).

The primary objective of this paper is to investigate the behavior of these openings situated on the cylindrical surface of vessels, focusing on scenarios where the ratio of the long dimension to the short dimension falls in the proximity of 2.0. This study involved a comprehensive examination of various International Codes, including ASME SEC.VIII DIV.2 [2], PD5500 [3], EN 13445 [4] and AD 2000-Merkblatt [6], to gain insights into their respective requirements. Furthermore, finite element analysis (FEA) was conducted to evaluate the resultant stresses, thereby corroborating the findings of the various International Codes.
Non-Destructive Examination Limits for Fracture Mechanics Design of High Pressure High Temperature Subsea Equipment
Authors: Daflon Thiago , Stewart Barry , Lee Sam , Parayitham Sashidhar
Published: November 2024

The design and operation of High Pressure / High Temperature (HP/HT) equipment in the oil and gas industry using API 17TR8 drives requirements for fracture mechanics fatigue verifications. The inputs used as part of the fracture mechanics assessment require to be defined in order to ensure the integrity of the assumptions and results. Such assessments assume the HP/HT product may include an initial flaw that is equal to the size of the minimum indication detectable by the defined Non-destructive Examination (NDE) technique used as part of the part quality requirements. This size of this initial flaw can have a large impact on the overall fatigue life of the product and can influence the operating conditions of the subsea operator. Therefore, the smaller the initial crack size that is detectable the longer the subsea operating window and the harder the conditions that can be tolerated.

Historically, in the subsea oil and gas industry, API 6A limits on detectable flaws have been assumed but these limits do not define the Probability of Detection (POD) or confidence level of the NDE techniques used. This paper outlines a test methodology for deriving the POD and confidence level of NDE techniques based on the use EDM notches in sample plates. Results of the testing show the ability of the NDE techniques used in the test to detect initial EDM notches that align with the API 6A limits of 1/16″ long flaws with a POD of 90% and with a confidence level of 80%. The impact of using this size of initial flaw on the fracture mechanics assessment of a HP/HT product is outlined with significant improvements in fatigue life achieved.
Coke Drum Skirt Life-Cycle Management
Authors: Seijas Antonio , Berry Alex
Published: November 2024

Delayed coking is a form of thermal cracking used for processing “bottom barrel” residuum in a refinery delayed coking unit (DCU). Coke drums, which are key components of the process, are subject to thermal cyclic and aggressive operating conditions and have a finite life. A safe and reliable operation before replacement requires special considerations to manage the key aspects defining the coke drum life-cycle. The skirt to vessel connection has been identified as one of the critical locations limiting the coke drum life; the skirt-to-vessel weld is vulnerable to fatigue cracking, while the skirt itself is vulnerable to bulging and key holes cracking. In this paper, key aspects of coke drum life-cycle management will be discussed, covering the useful life of coke drum skirts from “cradle” to “grave.” Important aspects such as supplemental requirements for skirt design and fabrication, specialized in-service inspection, on-line monitoring, engineering assessment, repairs and replacements will be covered in detail. This paper includes a short literature review of common skirt designs and damage mechanisms of greatest concern with consideration given to fabrication of skirts for both new coke drums and skirt retrofitting projects. Five case studies are reviewed in detail including: the analysis of the skirt configuration for a new pair of coke drums; two coke drum set skirt retrofitting projects; two skirt repair events in two separate coke drum sets. The paper will include closing remarks and recommendations to help improve the management of skirts for these complex and critical pressure vessels.
Evolution of Thermoelastic Stresses in a Finite-Width Slab or Thick Cylinder With a Growing or Receding Boundary
Authors: Kumar Pavan , Segall Albert , Drapaca Corina
Published: November 2024

Semi-analytical thermoelastic stress solutions for a single phase, homogeneous, and finite-width slab or thick cylinder with a constant-velocity growing or receding boundary under Unit-Loading were derived. Initially, a semi-analytical solution for the heat equation for a slab with a growing or receding boundary was derived in the Laplace domain and a series representation then used to approximate the inverse Laplace transformin the time domain. Conformal mapping was then used to transform the slab solution to an annulus. The resulting semi-analytical solutions were then used with established integral elasticity-equations to determine the resulting transient stress-states. All solutions allow for convection on the fixed boundary that is the opposite side for a plate and outer radius for the cylinder. Once derived, the semi-analytical stress predictions were compared to finite-element simulations with excellent agreement. Given the changing thickness, both the thermal and stress-states cannot reach true steady-state equilibrium, especially for faster growth or recession rates. Indeed, the temperature states and resulting stresses become somewhat linear with respect to time, reflecting the constant velocity of growth or recession. In practice, the resulting solutions can be used to determine transient stresses during machining, wear, erosion, corrosion, and/or additive manufacturing, especially for lower temperature solid-state methods such as cold-spray.
EAF, Transferability to Operation and Improving Prospects
Authors: Solin Jussi , Seppänen Tommi
Published: November 2024

Environment assisted fatigue (EAF) research in simulated reactor coolant waters has shown variable reductions in fatigue lives of laboratory specimens. Unless otherwise shown, the results are assumed transferable to the pressure boundaries of primary coolant circuits. By experiments and regression analysis determined environmental penalty factors have been adopted as means to adjust the allowable numbers of fatigue transients in reactor components. These Fen factors play a central role in transfer of EAF lab data to fatigue management and risk informed inspection at the plant.

This paper reports lessons learned in experimental and analytical research of EAF aiming to understand and reliably measure Fen factors for improved transferability to the codified fatigue assessment of stainless reactor components.

We have earlier reported inability to repeat the Fen factors proposed for the conservative high temperature & low-rate edge, when applying direct strain control in PWR water. This issue and ongoing research aiming to develop improved Fen models will be addressed. In addition, a thermodynamic point of view is introduced and discussed. The thermodynamic model fits poorly to the lowest Fen factors for low temperatures and/or high strain rates, which is probably also an area not well supported by experimental data but may still be relevant in PWR operation.

Challenges in determining Fen factors, their transferability to plant operation and possibilities for improvements will be discussed.
Simplified Elevated Temperature Service Elastic Methods for Section III, Division 5 Class A Metallic Pressure Boundary Components
Authors: Pease Derrick
Published: November 2024

The goal of this paper is to provide simplified elevated temperature service elastic stress evaluation methods and criteria that are numerically identical to the current ASME BPVC Section III, Division 5 rules but in a form that is easier to understand and apply. For the most part the elastic rules and methods have remained the same since their original development in the mid to late 1900s. The current rules cover several elastic evaluation criteria based on gross inelastic deformation, progressive inelastic deformation, and creep-fatigue damage as well as some limited buckling rules. Gross Inelastic deformation rules include time-based use-fractions which can be simplified by defining specific load stress intensity nomenclature and values used to lookup allowed durations from the time-dependent material curves. Significant creep ratcheting Test No. A-1 and A-2 can be combined and simplified by comparing a total stress intensity to a significant creep stress intensity limit. Negligible creep ratcheting Test No, A-3 can be simplified by defining a negligible creep stress intensity range limit based on the sum of the portions of the stress limit associated with the temperatures at cold and hot extremes of the stress cycle. Fatigue and creep rules include multiple methods for determining damage. Clarification of the different methods is included to provide a graded approach in determining fatigue and creep damage. For fatigue damage, several of the parameters used to determine the modified maximum equivalent strain range can be simplified.
A Multi-Scale Minimum Time-To-Failure Reliability Model for Creep, Creep Crack Initiation, and Creep Crack Growth of a 2-1/4-Cr-1-Mo Steel at 565 °C and a BK-7 Glass at 20 °C
Authors: Fong Jeffrey T. , Freiman Stephen W. , Cohn Marvin J. , Heckert N. Alan
Published: November 2024

The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) Committee has recently developed a new Section XI (Nuclear Components Inspection) Division 2 Code named “Reliability and Integrity Management (RIM).” RIM incorporates a new concept known as “System-Based Code (SBC)” originally due to Asada and his colleagues (2001–2004), where an integrated approach from design to service inspection is introduced using three new types of statistical quantities: (1) “system reliability index,” or “system co-reliability target” for any system consisting of structures and components, (2) “structural co-reliability,” for any structure, and (3) “component co-reliability” for any component, where co-reliability is defined as “1 – reliability” and is equal to failure probability. In a recent paper published in the International Journal of Pressure Vessels and Piping (Vol. 173 (2019), pp. 79-93), Fong, Heckert, Filliben, and Freiman developed a new theory of fatigue and creep rupture life modeling for metal alloys and brittle materials at room and elevated temperatures such that the co-reliability of a smooth component can be estimated from fatigue and creep rupture test data with simple loading histories. In this paper, we extend the theory to include a methodology to estimate the failure probability (or, co-reliability) of a 2-1/4-Cr-1-Mo ferritic steel component undergoing a loading history of creep, creep crack initiation, and creep crack growth at 565 °C, and a brittle material such as BK-7 glass undergoing dynamic fatigue at 20 °C. To illustrate an application of this new modeling approach, we present a numerical example using (a) the experimental test data of 2-1/4-Cr-1-Mo ferritic steel in creep at 565 °C as published by Kilian Wasmer in his Ph.D. thesis (Imperial College London, 2003), (b) the experimental test data of 2-1/4-Cr-1-Mo ferritic steel in creep crack initiation and growth at 565 °C also by Wasmer (Ph.D. thesis, 2003), and (c) the experimental test data of 35 specimens of BK-7 glass loaded to failure at a range of constant stressing rates at 20 °C (in an unpublished laboratory report by Freiman, Fuller, Quinn, Quinn, and Carter (1993)). The significance and limitations of this new damage-state-based approach to modeling creep and to estimate the component failure probability (or, co-reliability) of steel and brittle components in creep and fatigue are discussed with the addition of a new example case of the simple fatigue loading of an AISI4340 steel at a stress amplitude of 282 MPa in Room Temperature.
General Elastic Analysis on Atmospheric Liquid Storage Tank
Authors: Zhao Mingxin
Published: November 2024

A study is presented to analyze atmospheric liquid storage tank using the general elasticity theory. The tank is modeled as axisymmetric structure with a cylindrical wall and a flat floor at bottom subject to hydrostatic pressure. Deformation is derived from the complete solution form of the governing differential equation. Different boundary conditions at the bottom of tank wall, including free, fixed, and elastic, are examined. The corner joint between the tank wall and floor is investigated using elastic plate theory. Equivalent torsional and radial springs at the corner joint are generated as the elastic constraints for the tank wall. Further, the solution equation is expanded for the general condition of tank wall, which consists of multiple shell courses with different thicknesses. The expanded solution equations are obtained using the compatibility conditions by assuming continuity and smoothness between adjacent shell courses in equilibrium state. In addition, the equations are transformed into modular matrix equation form for each pair of adjacent shell courses, and the top or bottom constraints of the tank wall. All modular matrix equations are assembled to form the complete matrix equation for the entire tank wall for computational implementation.
Construction Rules, Preservice Inspection Rules, and Nuclear Safety
Authors: Benson Michael , Honcharik John , Rudland David
Published: November 2024

Construction of nuclear sites is an important topic, as governments and utilities are seeking to decarbonize. The rules governing construction and preservice examination play a vital role in providing stakeholder confidence that safety-related nuclear components will perform their intended function under normal operating and accident conditions. Construction rules provide sound fabrication procedures, while preservice examination provides an important verification step prior to placing the finished component into service. This paper reviews the construction and preservice examination rules for U.S. nuclear plants and discusses how they interact.
Effect of Temperature on the Fatigue Crack Growth Rates of Austenitic Stainless Steels in an Air Environment for ASME Code Section XI
Authors: Morley Andrew , Negyesi Martin , Hasegawa Kunio
Published: November 2024

Fatigue crack growth rates da/dN for stainless steels in air environment are provided by the ASME Boiler and Pressure Vessel Code in Section XI. The fatigue crack growth rates are given by da/dN = CF(ΔK)n, where CF is the fatigue crack growth rate coefficient, n is the fatigue crack growth rate exponent and ΔK is the stress intensity factor range. The coefficient CF consists of a temperature parameter, ST, and a scaling parameter, SR, which is a function of the stress ratio, R.

A function for the ST parameter is given in Appendix Y of ASME Code Section XI: ST=10[−8.714+1.34×10−3T−3.34×10−6T2+5.95×10−9T3] where T is the temperature in °C.

However, the functional form is cumbersome and the original basis for the temperature function is questionable, consisting mostly of testing outside of the bounds of the temperatures of interest to its application in ASME Code Section XI Appendix Y.

Following a review of the literature for test data at temperatures more directly relevant to the Code, the function of the temperature parameter is reviewed. An alternative equation for ST for stainless steels in an air environment is proposed for ASME Code Section XI Appendix Y, based on the literature experimental data surveyed in this study.
An Investigation of Stress Intensification Factors of Laterals Compared to Tees
Authors: Rathinasabapathy Mohan , Rivas Cristobal
Published: November 2024

In 2018 and prior versions of ASME B31.3 code, Appendix D provided Stress Intensification Factors (SIFs) and Flexibility Factors (also known as k-factors) for elbows and 90-degree branch connections (i.e., tees), but not for laterals. In the 2020 version of ASME B31.3 code, Appendix D was replaced by ASME B31J 2017 for SIFs and k-factors of various piping components. ASME B31J 2017 Note 7 states that laterals, which are reinforced fabricated, unreinforced fabricated, contoured, or branch welded-on fitting (weldolet) connections may use the same SIFs as their corresponding 90-degree branch connections provided the following conditions are met: Branch pipe axis normal to within 45 degrees of the header surface, D/T < 50, d/D ≤ 0.6, itb taken equal to iob.

“Normal to within 45 degrees” may be interpreted as less than 45 degrees, while the intent of the code may be to include the 45-degree laterals, which are the most common in the industry. This paper investigates whether the SIFs of above mentioned 90-degree branch connections can be used for corresponding 45-degree branch connections based on Finite Element Analysis (FEA). In addition, this paper explores the validity of D/T and d/D limits, and if they can be extended.
Assessment of ASME VIII-1 UG-20(f) Using Fracture Mechanics Per API-579-1/ASME FFS-1 (2021)
Authors: Finn Thomas P. , Hay Clifford A. , Bedoya Julian J. , Pioszak Greger
Published: November 2024

Paragraph UG-20(f) of the ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 1 provides guidance on applicable impact test exemptions for design temperatures no colder than −20 °F (−29 °C) under certain conditions (e.g. material/thickness combinations; hydrostatically tested; no shock loadings). Functionally, this paragraph allows for design at temperatures colder than UCS-66 permits for equivalent material/thickness combinations without the requirement for impact testing.

A similar provision to UG-20(f) was included in Part 3 of API RP 579 (2000) and in API-579-1/ASME FFS-1 (2007); however, it was removed in the 2016 edition of API-579-1/ASME FFS-1 and has not been reintroduced in subsequent editions.

This study reviews the requirements of UG-20(f) using the fracture mechanics perspective from the latest (2021) release of API-579-1/ASME FFS-1. The provisions in API-579-1/ASME FFS-1 (2021) for considering constraint effects (Annex 9H) and crack front integration (Annex 9I) are included in this analysis so that the magnitude of their effects can be understood. Since UG-20(f) requires a hydrotest for most situations, a review of the warm pre-stress effects per Annex 9F is also included. The results of this study indicate that an update to the current thickness limitation for Curve B materials is recommended.

No recommendations for the overall disposition of paragraph UG-20(f) are provided in this study; however, it is anticipated that the analysis contained herein could assist various Standards Development Committees in decisions related to potential future updates.
Evaluation of Service Removed HP40-Modified Reformer Tubes and Development of Multi-Axial Pressurization Testing in Full-Size Components
Authors: Bridges Alex , Griscom Eeva , Gagliano Michael , Siefert John , Penso Jorge , Barrass Jordan
Published: November 2024

Steam methane reforming (SMR) is the most widely used process for bulk hydrogen production and accounts for most of the hydrogen produced worldwide. As this is an highly endothermic reaction, large amount of heat must be supplied to the system, thus requiring heat resistant materials capable of withstanding continued operation at temperatures exceeding 1,500°F (815°C). In this study, microstructural characterization and mechanical testing was conducted on in-service exposed HP40-modified material. Creep damage and changes in precipitate structure were characterized using a variety of microscopy tools. The effect of microstructural evolution on high temperature creep performance due to long-term aging was investigated using standard creep testing methods using round bar specimens. Additional challenges, such as variation in material pedigree, impact of grain structure on performance and importance of test sample orientation are also discussed. The results show that long-term exposure to high temperatures will reduce the overall life of components; however, the resulting ductility increased in samples exposed to the highest temperature. To address challenges with traditional life management procedures, a method for full-scale, high temperature pressurized creep testing of SMR furnace tube samples is being developed and initial results are presented and compared against those from traditional creep specimen geometries.
Acoustic Induced Fatigue of Girth Welds
Authors: Mann J. Adin , Swindell Rob , Hart Noel
Published: November 2024

Assessing the risk of acoustic induced vibration (AIV) fatigue cracks at fittings between pipes, especially at small bore connections, is critical for designing a robust piping system. Girth welds are axisymmetric discontinuities. Examples will be shown of girth weld fatigue that are caused by acoustic induced vibration. These examples are expected to be more common as the asymmetric fittings such as branch connections are designed to be less susceptible to acoustic induced fatigue and then other parts of the piping system become a location for fatigue risk. For example, in some systems with robust asymmetric fittings, the acoustic excitation is allowed to increase assuming that the asymmetric fitting is sufficiently robust. In such a situation, the next location for a fatigue risk can be a girth weld. There are also applications at elevated temperatures where the interaction with creep can reduce the fatigue life. Examples of a girth weld crack in a steam cleanout line, a liner in a Fluid Catalytic Cracker (FCC) overhead line, and in a silencer diffuser will be shown. AIV assessments using the Energy Institute Guidelines for the Avoidance of Vibration Induced Fatigue and other commonly used AIV assessment methods will be shown. An assessment methodology will be proposed for potential use as an industry standard.
Mitigation of Vane Pass Pulsation Induced Vibration in a Crude Oil Pumping Station
Authors: Mann J. Adin , Hart Noel , Tillotson Elizabeth , Sexton Charles
Published: November 2024

The pumps to maintain the flow in long distance crude oil pipelines are typically large, such as 10 kHP pumps. In the example that is shown, the initial piping design and operation resulted in vibration induced fatigue cracks in small bore connections. The frequency of peak vibration was at the vane pass frequency of the pump and was propagated through the piping system as an internal acoustic field. While not the typical acoustic induced vibration of a blowdown system, the impact and mechanisms are the same. Mitigations addressed the problem with seven approaches: (1) modify the design of the pump, (2) modify operating conditions of the pump, (3) apply constrained layer damping to the pipe walls, (4) apply stiffening rings to the pipe, (5) change fitting type on small-bore connections, (6) brace and modify the remaining small-bore connections, and (7) remove all but essential small-bore connections. The impact of the mitigations to the piping system will be presented based on test data for multiple operating conditions. The results show the effectiveness of 4 piping mitigations: stiffening rings, removal of non-necessary small bore piping connections, constrained layer damping, and bracing the remaining small-bore piping with engineered bracing. Recommendations for design approaches are given so that the risk of vibration induced fatigue is minimized through an effective initial piping structure design.
Case Study: Installation and Operation of Non-ASME Stamped Pressure Vessels in the United States
Authors: Barkley Nathan , Chatham Everett , Baquero Kevin
Published: November 2024

The overwhelming majority of pressure vessels installed in the United States are constructed and stamped to the ASME Boiler and Pressure Vessel Code, particularly Section VIII Division 1, as required by most states’ pressure equipment laws. In states where there are laws mandating pressure vessel construction to ASME Section VIII, vessels constructed and stamped to a different construction code or certification body are not allowed unless the state’s laws provide an exception, and the state’s governing body, such as a board, accepts the non-ASME stamped equipment. A vessel that is accepted in this manner typically referred to as a “state special.” Alternatively, a similar exception and approval is needed for previously installed equipment that was not designed to any pressure vessel code, but new operating conditions exceed the state’s applicability limits for pressure, typically 15 psig, or other criteria.

This paper presents two case studies. The first case study examines a case where pressure vessels that were CE stamped in accordance with the European Union’s Pressure Equipment Directive (PED) were requested to be installed in a US state. The next case study examines a case where a vessel was originally built to be non-pressure containing in the 1950s, but recent operational changes raised the possible pressure the vessel could experience higher than the exemptions provided by the state. In both cases, the fundamental considerations and approach for gaining state/jurisdictional acceptance are discussed. Additionally, a review of the US states where pressure vessel laws exist and the states’ specific requirements for pressure vessel installation and operation is provided.
Consideration of Constraint Effect in Fracture Mechanics Assessment for a Vessel Low Alloy Steel
Authors: Louerat Jules , Ancelet Olivier , Marie Stephane , Chapuliot Stephane , Dahl Anna
Published: November 2024

Numerous fracture tests have been performed by EDF and Framatome on various specimen’s geometry extracted from a 18MND5 ferritic steel plate, in the brittle-to-ductile transition regime. C(T), SE(T), SE(B), and non-standard specimens have been tested. This database has been recently updated with SE(T) tests performed in the lower shelf of the transition domain.

This work highlights a robust methodology which allows to predict constraint effect with minor consequences of the choices of the Weibull stress model formulation (classic model, consideration of stress threshold...) and on m parameter on the final interpretation.

A local approach based deterministic industrial method is proposed to consider this effect in Engineering Fracture Mechanics Assessment without considering any probability of failure or statistical approach. It allows to evaluate constraint effect at discrete locations along the crack tip. Its application on industrial cases shows that parameters set have limited impact on constraint effect prediction.