bluuebunny/crossref_metadata_2025 huggingface dataset:
An Introduction to ASD and LRFD and Its Application to Pressure Vessels and Piping
Authors: Kirkpatrick Kenneth , Millet Barry , Mosher Bryan , Wey Eric , Mejia Felipe
Published: November 2023

This paper is an introduction to Allowable Stress Design (ASD-Stress), Allowable Strength Design (ASD) and Load and Resistance Factor Design (LRFD) and their application to pressure equipment. Many new and experienced mechanical engineers have little or no previous exposure to LRFD which results in misunderstandings between mechanical and structural engineers regarding the meaning and interpretation of loads (particularly wind and seismic). Some history regarding the Specification for Structural Steel Buildings (ANSI/AISC 360) will be provided noting how changes in the specification over the years have influenced the design codes for pressure vessels and piping. Additionally, some background will be presented regarding the load combinations and loads provided by different versions of ASCE 7 otherwise known as the Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The design methodologies, loads, load combinations and associated factors will be discussed and demonstrated how they should be applied to the design of pressure vessels and piping. Lastly, design and serviceability examples will be provided.
Understanding Hydrogen Leakage With Standard ASME B16.20 and ASME B16.21 Gaskets
Authors: General Justinn , Norman Dale
Published: November 2023

The hydrogen industry has been identified as a key decarbonization technology with its demand projected to grow five-fold, which can be seen by the influx of capital investment from the United States and globally. Several new projects are breaking ground with the goal of producing 50 million metric tons/year by 2050 in the United States and 500 million metric tons/year globally.

Currently, for several of the standards that are being used, such as ASME B31.12-2019 [1] (Hydrogen Piping and Pipelines), a majority of the sealing components call for standard gaskets from ASME B16.20 [2] and ASME B16.21 [3]. However, much is still relatively unknown regarding the potential leak rates of these standard gaskets or if the use poses any potential risks. In order to support the industry, we have performed EN 13555 [4] leak testing using 100% hydrogen across several different gaskets: ASME B16.20 [2] spiral wound, grooved metal gaskets, and alternate geometries and constructions, ASME B16.21 [3] rings with different materials including expanded polytetrafluoroethylene (ePTFE), nitrile butadiene rubber (NBR), and fluoroelastomer (FKM).

From what was observed, the permeability of hydrogen from the gaskets evaluated varies based on several different factors such as: sealing design, material, and facing material, some of which has a greater effect on creating a seal. This paper will discuss in depth the results of these gaskets tested with hydrogen and additionally make correlations to its sealability using helium.
Effect of Differential Oxidation of Graphite Crystallites on the Elastic Moduli of Nuclear Graphites
Authors: Spicer James B. , Contescu Cristian I. , Arregui-Mena José David , Lin Lianshan , Berry Ellen , Gallego Nidia C.
Published: November 2023

The physical properties of nuclear graphites are heavily influenced by a range of defects that arise as a result of the manufacturing processes used to produce these materials. Among these defects, porosity plays an important role in determining properties of bulk graphite including the elastic responses, strength and toughness. It is well known that oxidation processes affect porosity and impact these properties as a result of the modification of the graphite pore structure. During oxidation, porosity increases as a result of chemical reactions between graphite and gas phase species. These reactions occur at rates governed by the availability of reaction sites including those on graphite crystallite basal planes and edge planes. Beyond reaction site availability, differences in reactivity among various portions of the graphite microstructure influence morphological and physical changes to the graphite as porosity evolves. In particular, differences in reactivity between edge and basal plane sites reduce the connectivity of graphite crystallites sharing edge connections more rapidly than the junctions between other portions of the microstructure. This work examines the effect of site reactivities using first-order rate equations to describe differential changes to the graphite microstructure. These changes are related to the elastic connectivity of graphite crystallites and are used to assess the changes in the moduli as porosity increases.
Effects of Cold Temperature on Steel Supports
Authors: Wiseman Phillip , Darade Animesh Anil
Published: November 2023

Power-generating plants in the cold regions of the world can have temperatures below −10°C. Steel being the primary material of the piping systems in the energy-producing plant changes its properties when installed in such a freezing environment. So for temperatures below −10°C majority of the steels tends to become more brittle and their toughness is also affected. Some of the carbon steels can retain the same properties until they reach a temperature of −20°c. The suitability of piping systems for temperatures below the ambient temperatures is a function of several variables such as loading, manufacturing procedures, and material properties, also parameters that generally control the susceptibility for brittle fractures are material toughness, crack size, and tensile stress level. There is a need for a screening criterion to decide the suitability of steel which is generally fulfilled by following the codes. If a certain material falls beyond the limit then it is required to undergo impact testing.

Various types of restraints such as struts, shock absorbers, and dynamic clamps are seen in the piping industry which generally serves the purpose of providing support between piping and building structures. This paper mainly focuses on dynamic clamps, specifically dynamic yoke clamps. This type of dynamic clamp has a close fit around the pipe and acts as a restraint for some occasional events such as water hammers, seismic events, etc. This paper also discusses the design and analysis of dynamic yoke clamps subjected to different loads. The results obtained from the analyses are assessed as per different codes to determine whether the impact test is necessary or not. To fall within the limit as per the codes, changes can be made in the geometry, material, and loading.
Effect of Grain-Size on the Creep Residual Life Evaluation in the Framework of the API 579-1 Standard
Authors: Scano Lorenzo , Piccini Francesco , Palomba Salvatore , Bruno Matteo , Esposito Luca
Published: November 2023

Creep is a classic inelastic-strain accumulation mechanism of pressure components exposed to high temperature. Due to the long-term exposure, the residual life is usually checked accounting for the steady-state creep, namely the dominant regime in terms of contribution to the accumulated creep strain. The creep-strain accumulation directly depends on the stress field via a constitutive equation that reflects the underlying microstructural phenomenon, namely diffusion and dislocation glide+climb. Moreover, creep diffusion, dominant at low stress, is known to be grain-size dependent. Commonly, the grain-size effect is neglected for two reasons: I) the diffusive regime is completely ignored; II) the structure is considered to have a uniform texture and the same average grain-size. Unfortunately, every time a welding joint is made, the HAZ undergoes a microstructural change, often resulting in a local refinement of the grain-size.

In two previous papers by two of the authors [1][2], the impact of a diffusive plus dislocational creep formulation on the API 579-1 [3] creep residual life was studied for a low-alloy ASME SA-335 P22 butt-weld. In this work the analysis was extended in order to include the impact of the microstructure in terms of grain-size, considering that it directly affects the diffusive creep rate. A FE inelastic model was built up for a butt-weld and the weld zones were characterized with respect to their grain-size. The creep constitutive equations were set up for diffusive and dislocational secondary creep, including the grain-size contribution to the former. The custom user-subroutine employed in the FEA was able to determine the creep-strain accumulation and the API 579-1 creep damage based on the Larson-Miller theory within the different weld zones and the results indicated a damage concentration in the fine-grained intercritical HAZ, which is consistent with the Type-IV cracking of welds in the creep regime.
A Universal Inelastic Constitutive Model for High Temperature Deformation
Authors: Chen Tianju , Messner Mark C.
Published: November 2023

Recent work by the ASME Code Committees established a new Nonmandatory Appendix Z to Section III, Division 5 of the ASME Boiler and Pressure Code that provides constitutive models for use with the Section III, Division 5 Class A design by inelastic analysis rules. These models promote the use of the more accurate design by inelastic analysis methods by alleviating the designer or owner from the burden of developing and validating a model themselves. Models for four materials — Grade 91 steel, 316H stainless steel, the nickel-based Alloy 617, and the nickel-iron-chromium Alloy 800H — have either been approved or are under consideration at the cognizant ASME Code Committees. All four models have significantly different mathematical forms. While differences in material behavior may justify or require treating each material with a bespoke model, the mathematical exposition and detailed explanation required to describe and document the models in the Code is a significant logistical challenge. That challenge carries over to implementing the models for use in design calculations, as the computer implementations of the models are likewise significantly different. This paper explores the feasibility of a universal high temperature inelastic constitutive model, general enough to accurately capture the key material behavior of these four materials. If such a model exists, it would greatly simplify the new Appendix Z and further reduce the investment required by designers needed to apply the design by inelastic analysis rules. This work therefore attempts to define a generalized constitutive model, fits the model form for the four materials using an extensive experimental test database, collected as part of the effort to develop the original constitutive models, and evaluates the accuracy of the universal models by comparing model predictions against both the experimental data and the current models endorsed or under consideration by the ASME Code Committees.
Evaluation of the Defect Width Effect on the Burst Pressure of a Corroded Pipeline Repaired Using Composite Materials
Authors: Silva Silva-Santisteban Rodrigo , Zhou Wenxing
Published: November 2023

In this study, the corrosion defect width effects on the burst pressure of composite repaired corroded (CRC) pipelines are investigated using extensive parametric elasto-plastic finite element analyses. The finite element model includes constitutive material modelling of both steel and composite and is validated using full-scale burst tests reported in the literature. The parametric analysis considers different values of the defect depths, lengths and widths, and properties of the materials to assess the effect of the defect width as a function of other parameters that affect the burst pressure. The dependency of the critical failure mechanism and burst pressure on the defect shape and size is observed based on the analysis results.
Fracture Mechanics Analysis of Multi-Purpose Canister Under Impact Loading
Authors: Jeong Jae-Yoon , Kim Cheol-Ho , Kim Yun-Jae , Oh Chang-Young , Kim Hune-Tae
Published: November 2023

Multi-purpose canisters (MPCs) made of austenitic stainless steel are used to store spent nuclear fuels (SNF) for long periods. During long-term storage, chloride-induced stress corrosion cracking (CISCC) can occur on the external surface of MPC. In this respect, a structural integrity assessment of MPC with possible CISCC defects under accident scenarios such as drop accidents during transportation needs to be performed.

In this paper, fracture mechanics analysis is performed to calculate critical crack sizes under the 9m drop accident suggested at IAEA (International Atomic Energy Agency) SSR-6 (rev. 1). For the MPC model, the KORAD (Korea Radioactive Waste Agency)-21 model was used. Elastic-plastic impact simulation was firstly performed using the strain-rate dependent material properties to identify critical locations showing the highest stresses during impact. The postulated crack is assumed to be the external semi-elliptical longitudinal and circumferential crack. Then fracture mechanics analysis is performed using the failure assessment diagram (FAD) approach. The reference stress was calculated using the method suggested in API 579/ASME FFS-1. The stress intensity factor is calculated using the weight function method in ASME Section XI, Appendix A. Using the FAD approach, the critical crack size is calculated. The sensitivity analysis is performed to investigate the effect of the strain rate on calculated critical crack sizes.
Artificial Neural Network Aided Source Locating for Hazardous Gas Leakage Based on Simulation
Authors: Liu Min , Chen Sheng , Li Fei , Shi Jiarui , He Meng , Wang Jiangyun , Xie Guoshan , Jiang Haiyi
Published: November 2023

Rapid source locating of high-risk gas leakage is the key to identification and early pre-control of risks in chemical industrial parks. In this work, a multi-scale dispersion model is established by coupling the traditional atmospheric diffusion model with the diffusion parameters accounting for the turbulent vortex structure, to improve the accuracy of gas diffusion prediction. The locating of the leakage source is performed based on fixed-points monitoring of the gas concentration produced by simulations with multi-scale dispersion model. The relationship between the monitored dataset and the source location is then established through artificial neural network. Finally, a rapid locating method for gas leakage is built. The results show that the simulation accuracy of the diffusion area predicted by the current multi-scale dispersion model with considering the influence of turbulent vortex structure can be significantly improved in comparison with the traditional method. And the leakage source location can be accurately located within 3 s by using the rapid locating method. This source locating method can provide support for the identification, early pre-control of risks, emergency response and rescue of accidents in chemical industrial parks, thereby enhancing security resilience.
Prediction of Crude Oil Viscosity for Pipeline Operation Safety Using Optimized GRNN Model
Authors: Zhang Jianming , Wang Xiaolin , Shi Lei , Cui Kaiyan , Chang Liang , Sun Qianyao , Zhao Yatong
Published: November 2023

In the whole process of crude oil storage and transportation, the obtaining of the viscosity of crude oil timely and accurately is very important for the safe operation of crude oil pipelines. This paper proposes a new method to predict crude oil viscosity based on Generalized Recurrent Neural Network (GRNN), Particle Swarm Optimization (PSO) and K-Means Clustering Algorithm, which are different from the normal measurement in the laboratory. Feature selection, focusing on obtaining most closely related components to the viscosity of crude oil at 50 °C from the content of Kantian residual carbon, sulfur, nitrogen, water, salt, acid value, ash, colloid, asphaltene, wax, Fe, Ni, Cu and V, is introduced by using the Maximal Information Coefficient (MIC) and Sequential Floating Forward Selection (SFFS) Algorithm. The density and pour point, which are easily available, are determined as the final input of the GRNN by physical property correlation analysis to replace the most related components obtained. For most practical engineering problems that only have a small data set with partial poor samples, the K-Means Clustering Algorithm is introduced in the model to analyze the distribution characteristics of the samples and avoid the impact on the prediction results caused by poor data set. It effectively makes model evaluation more convincing. A Generalized Recurrent Neural Network (GRNN) with the parameter optimization by Particle Swarm Optimization (PSO) is constructed as prediction model. The final results show that the optimized GRNN prediction model in this paper has a good performance on prediction accuracy and stability at the viscosity of crude oil.
Modeling the Fatigue Life of Ni-Based Alloys
Authors: Falaakh Dayu Fajrul , Park Jae Phil , Bahn Chi Bum
Published: November 2023

In this study, we attempted to model the fatigue life of Ni alloys by employing probabilistic approaches, i.e., survival regressions. The selected models included the Weibull AFT and RSF models. The input variables for the models were the strain amplitude, strain rate, temperature, concentration of dissolved oxygen, and material category (i.e., base or weld). The dataset was divided into two subsets, i.e., training and test sets. The training set was used to train the models, while the test set was used to evaluate the models’ predictions. Several performance metrics were used to measure the model predictabilities, including the c-index, R2, and PCC. Based on performance metrics computed using test sets, all the selected models showed satisfactory performances. The RSF appeared to have better predictability than the AFT model. It was shown that the survival regression models could quantify prediction uncertainty, which is important given the limited fatigue data on Ni alloys.
Effect of Postweld Heat Treatment and Temper Bead Welding on the Hydrogen Induced Cracking Susceptibility in the Heat Affected Zone of SA-508 Pressure Vessel Steel
Authors: Mohammadi Abbas , McCracken Steven L. , Alexandrov Boian T.
Published: November 2023

ASME Case N-888, Similar and Dissimilar Metal Welding Using Ambient Temperature SMAW and Machine GTAW Temper Bead Technique, requires a 48-hour hold time before nondestructive examination (NDE) can be performed to ensure hydrogen induced cracking (HIC) did not occur. The objective of this work is to evaluate the effect of postweld heat treatment (PWHT) and temper bead welding (TBW) on the HIC susceptibility in the coarse-grained heat affected zone (CGHAZ) in welds of SA-508 pressure vessel steel. A previously published study used the Gleeble™ thermo-mechanical simulator to recreate six CGHAZ microstructural conditions: as-welded (AW), PWHT-ed, and single TBW reheats to 675°C, 700°C, 725°C, and 735°C. Detailed microstructural characterization of all microstructural conditions and preliminary HIC results were reported. The HIC susceptibility was evaluated using the Delayed Hydrogen Cracking Test (DHCT) at a diffusible hydrogen level significantly exceeding those introduced by the GTAW and SMAW processes. This study completed the HIC susceptibility evaluation of the six CGHAZ conditions and generated a “worst-case scenario” ranking of the TBW@700°C, TBW@725°C, and TBW@735°C as highly resistant, PHWT as resistant, TBW@675 °C as slightly susceptible, and as-welded CGHAZ as susceptible to HIC. Ongoing research is evaluating the HIC susceptibility of the six CGHAZ microstructural conditions at diffusible hydrogen levels corresponding to GTAW and SMAW processes and aiming to determine the critical hydrogen content that would cause HIC. The results from this study will be used to consider potential elimination of the NDE hold time requirement in Case N-888.
Residual Stresses Generation Process on Vessel Low Alloy Steel Cracked Plates Without Modification of the Material Properties
Authors: Louerat Jules , Doremus Luc , Ancelet Olivier , Marie Stephane , Chapuliot Stephane , Dahl Anna , Perez Gregory
Published: November 2023

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

The paper presented here deals with the process used for introduction the residual stresses in the selected mock up. The goal of the process is to generate residual stresses over 300 MPa in the thickness at the vicinity of the crack. The principle retained is to locally produce small inelastic compression strains, around the crack, using a thermal spot imposed in the centre of a plate on both sides. The vicinity of the defect is then quickly heated by induction so as its prevented thermal expansion induces compression stresses, which, in the case sufficiently high temperatures are reached, cause both inelastic creep and plastic strains, inducing tensile residual stressing at the end of the cooling phase.

The process has been designed by finite elements modelling based on a fine material behaviour modelling in the plastic-viscous domain. The thermal cycle has been defined to reach a residual stresses level between 300 MPa and 400 MPa up to the mid-thickness of the plate.

The experimental developments confirm the relevance of the thermal cycle defined through the numerical investigation, showing a good reproducibility, and expected residual stresses levels.
Consideration of Geometrical Effect in Fracture Mechanics Assessment for a Vessel Low Alloy Steel
Authors: Louerat Jules , Ancelet Olivier , Marie Stephane , Chapuliot Stephane , Dahl Anna
Published: November 2023

Numerous fracture tests have been performed by EDF and Framatome on various specimen geometries extracted from a 18MND5 ferritic steel plate, in the brittle-to-ductile transition regime. C(T), SEN(T), SEN(B), and non-standard specimens have been tested.

Based on those data, the work presented here proposes a robust identification methodology which allows the prediction of constraint effect with minor consequences of the choices of the Beremin model formulation (classical model or more complex model with a stress threshold, or a plastic strain correction) and on m parameter on the final interpretation.

Results demonstrate geometrical effects, resulting in a temperature shift of KIC distribution of most specimens to higher values than those obtained on C(T) specimens and the capability of the proposed strategy to correctly predict the experimental results.

The final goal of this work is to propose a methodology applicable in Engineering Fracture Mechanics Assessment to gain margins without considering any probability of failure or statistical approach.
Study on the Effect of Material Constraint on the Stress-Strain Behavior of Pipeline Girth Weld
Authors: Zhang Yinhui , Wang Fuxiang , Shuai Jian , Xuan Wenbo , Lei Zhengqiang , Yang Hui , Zhang Tieyao
Published: November 2023

For the study of the pipeline girth weld, the key to ensure the accuracy of the finite element analysis result is to obtain the accurate constitutive relationships. However, due to the complex material composition of the girth weld, it is difficult to obtain the accurate stress-strain curves. At present, the digital image correlation (DIC) testing is an important method to obtain the stress-strain curves of the girth weld. However, when this method is used for testing, there will be the material constraint effect caused by weld mismatch. The material constraint will have an important effect on the accuracy of the test result. Especially for the undermatched weld and the softened heat affected zone, the effect is more significant. This effect will make the measured stress significantly deviate from the true value and ultimately affect the accuracy of the finite element analysis result. However, there is still no sufficient study on this issue. Therefore, it is necessary to further study the effect of the material constraint on the stress-strain behavior of the weld.

In this study, the finite element analysis method is used to simulate the data processing process during the DIC test, including strain extraction and stress calculation. The girth weld is simplified to include the weld metal (WM) and the base metal (BM), that is, the properties of the heat affected zone (HAZ) and BM are the same. The effects of the geometric dimension and the mismatch degree of the weld are analyzed. The stress-strain curves inputted into the finite element model are compared with the stress-strain curves calculated based on the test method, and then the effect of the material constraint is determined. The results show that for the undermatched weld, the calculated stress based on the test method is greater than the true stress of the weld, and this difference is related to the weld size and the mismatch degree. When the weld width is large, the calculated stress is close to the true stress. With the decrease of the weld width, the calculated stress deviates from the true stress gradually. With the increase of the weld mismatch degree, the deviation of the calculated stress from the true value gradually increases. For the overmatched weld, the calculated stress is less than the true stress of the weld, but the difference is relatively small. This is due to the fact that the overmatched weld specimen will fracture in BM, and the fracture position is relatively far away from the weld, which makes the effect of the material constraint relatively small. In summary, the material constraint effect makes BM have an important effect on the deformation of the weld and changes the stress state of the weld. The results obtained in this study are important for further analyzing the weld material constraint effect and proposing a correction method for DIC test result.
Phase Shift Migration Approach Using Full Matrix Capture Optimization for Multi-Layer Ultrasonic Imaging
Authors: Cheng Jingwei , Fan Zhichao , Chen Xuedong , Xu Xiangting , Bu Yangguang , Wang Haibin , Wang Zhe
Published: November 2023

Ultrasonic phased array testing is a widely used nondestructive testing method seen in regular inspection of pressure vessels and pressure pipelines. However, some complex structures of multiple layers give rise to impracticality of existing imaging techniques on accurately evaluating the size and shape of defects within inner layer. In this study, a method to measure sound velocity of multi-layer structure is first established based on the full matrix capture (FMC) data, thereby automatically estimating the sound velocity of the coupling layer and ultimately optimizing the phased array focal law for the unknown multi-layered structure. The FMC-based phase shift migration (PSM) imaging method for multi-layer structures is then explored. This method processes the FMC data in the frequency-wavenumber domain and utilizes the wave motion equation layer by layer in the depth direction to realize the imaging of the target layer. In order to resolve online inspection of multi-layered structure (e.g. oil-immersion detection of tank floor), the experiments are conducted on a test specimen covered with sludge. Our finding is that the FMC-based PSM imaging method can realize the high-resolution imaging of the side drilled hole with 1mm diameter under the unknown multi-layer coupling condition. The results suggest that this method could deliver great potential to accurately locate and quantitatively evaluate small buried defects within the inner layer of complexly coupled structure and self-calibrate the fundamental imaging parameter in undiscovered coupling state.
Failure Behavior and Influencing Factors of the Sealing Structure for Type IV Hydrogen Cylinder
Authors: Tao Jiahui , Fan Zhichao , Xu Peng , Wang Lu , Ma Shuhao
Published: November 2023

Due to their exceptional benefits in terms of low cost, light weight, corrosion resistance, and fatigue resistance, composite overwrapped pressure cylinders with plastic liners (type IV) for high pressure hydrogen storage have attracted interest on a global scale. The sealing structure in the bottle mouth of the hydrogen cylinder is a type of material-dissimilar seal between metal and plastic, and it significantly affects the safety performance and fatigue life of Type IV cylinders. In this study, the failure behavior and mechanism of the sealing structure were investigated. The sealing performance of the bottle mouth structure was experimentally assessed by testing a type IV hydrogen cylinder with a working pressure of 70 MPa. In addition, ABAQUS was utilized to create a finite element (FE) model of the bottle mouth sealing structure, taking into account the cylinder’s deformation compatibility. On the basis of the FE model, the influence of rubber O-ring hardness, rubber O-ring thermal deformation, and the thermal sensitivity of the plastic liner’s mechanical characteristics on the structure of the bottle mouth seal was examined. These findings can contribute to the design and optimization of the sealing structure for a composite overwrapped pressure cylinder with a plastic liner for hydrogen storage.
High Temperature Performance Comparison of Spiral-Wound and Kammprofile Gaskets
Authors: Wang Lu , Fan Zhichao , Tao Jiahui , Ma Shuhao
Published: November 2023

Both spiral-wound and kammprofile gaskets are used extensively at high temperature applications such as refineries, petrochemical plants, power plants, etc. In recent years, the use of kammprofile gaskets have seemed to gain momentum over the conventional spiral-wound gaskets. Since the application conditions of the two types of gaskets are similar, in addition to the lack of comprehensive comparisons of two gaskets performance especially high temperature performance, it is difficult for engineers to decide which gasket to use. In this paper, mechanical properties tests at high temperature are carried out, the compression resilience curves, modulus of resilience and stress relaxation of two types of gaskets are compared. Furthermore, the high temperature sealing performance of two types of gaskets are studied by using a NPS 3, Class 300 bolted flanged joint. The mass leakage rate at different test temperatures and internal pressures are obtained.
Study on the Effect of Material Characteristic on the Limit Pressure of the Pipeline Girth Weld Containing Welding Defect
Authors: Ren Wei , Shuai Jian
Published: November 2023

For long-distance oil and gas pipelines, pipeline construction is actually a vast project which involves longdistance welding process. Because of technology and artificial factors, there are various types of welding defects in pipeline girth welds, such as cracks, porosity, slag inclusions, inadequate penetration, incomplete fusion and so on. Pipeline is often subject to a series of adverse conditions, including cyclic loading, pressure fluctuation, corrosion, high temperature, shock and so on, which seriously impair the performance of pipeline. Girth weld defect is one of the underlying causes, which leads to early damage to welded structure and arouses catastrophic accident. Therefore, the quality control of pipeline welds is very important to ensure the safety of pipelines. It is necessary to carry out stress analysis on the girth weld of pipeline containing welding defects to provide technical basis for the size control of pipeline weld defects. In order to study the influence of material characteristic on the limit pressure of pipeline girth weld containing porosity, based on the real structure of the girth weld, a finite element model of pipeline girth weld containing porosity was established. Stress analysis with different size of porosity was performed. And the effect of the yield strength, hardening exponent and mismatch on the limit pressure of the girth weld were analyzed. The appropriate failure criterion is selected to determine the failure of pipeline girth weld with porosity. It turned out that the local maximum Mises stress of porosity defect increases with the increase of yield strength and the strength matching factor. The local plastic area of porosity defect increases with the increase of hardening exponent. The pipeline limit pressure increases with the increase of yield strength and the strength matching factor, and the pipeline limit pressure decreases with the increase of porosity defect size under the internal pressure. The finite element results provide a reference for the tolerance size of girth weld defects, which is of great significance for making full use of the performance of pipe material and improving the quality and efficiency for pipeline safety management.
Data-Driven Stress Intensity Factor Solutions for Axial Outside Surface Cracks in Thin-Walled Cylinders
Authors: Zhu Xian-Kui , Zhu Jesse B. , Duncan Andrew J.
Published: November 2023

In the flaw evaluation, fracture mechanics methods require calculation of stress intensity factor, K, in fitness-for-service (FFS) codes, such as API 579 and ASME BPVC Section XI. For a surface crack in a cylinder, the K calculation becomes to compute the influence coefficients G0 and G1 in the FFS codes. API 579 provides finite element analysis-based tabular data of G0 and G1 for selected cylinder size (t/Ri), crack aspect ratio (a/c), crack depth ratio (a/t), and crack tip locations. Recently, curve-fit solutions of G0 and G1 were obtained for surface cracks at the deepest and surface points. For an arbitrary cylinder size, however, three-parameter interpolations are still needed for estimating the G0 and G1.

To simplify the K factor calculation, the present authors (PVP2022-86164) developed a data-driven K factor solution for axial outside surface cracks in thick-walled cylinders (D/t ≤ 20) based on the API 579 tabular data of G0 and G1 for axial outside semi-elliptical surface cracks at the deepest and surface points using the machine learning technology. This paper further develops a data-driven K factor solution for axial outside surface crack in thin-walled cylinders (D/t ≥ 20) using the artificial neural network (ANN). The sigmoid activation function is adopted in the optimal learning algorithm for the ANN model to learn from the API 579 tabular data of G0 and G1 and to predict the K solutions at the deepest and surface points for an arbitrary cylinder or crack size. The proposed ANN model contains three input variables, one hidden layer with five neurons, and one output variable. The data-driven solutions of G0 and G1 at the deepest and surface points of the axial outside semi-elliptical surface cracks are validated by the existing closed-form solutions for thin-walled cylinders.
A Comparative Study on AI/ML-Based Transient Temperature Predictions and Real-Time Operational Transient Temperature Data of Coke Drum
Authors: Srinivasan Balaji , V. Srinivasan
Published: November 2023

Uncertainties in real-time operational practice result in the deviation of actual as-operated time-varying parameters from planned operational time-varying parameters. Coke drums experience severe transient thermal-induced cyclic stresses resulting in unanticipated, low cycle, fatigue damage. The health of coke drums is of great importance as it is associated with the increased need for inspection frequencies and unwelcome shutdowns. As a result, the need for online monitoring and prediction of the integrity of components of coke drums is growing among plant operators.

In setting up an asset health integrity and monitoring system, operators must decide among timeliness, precision, and reliability. The time-varying transient temperature is the dominant parameter that has a stimulating effect on the fatigue life of coke drums. Establishing a methodology to predict the future transient temperature of typical operational sequences is of great significance to predict the health status of coke drums.

In this work, Artificial Intelligence and Machine learning (AI/ML) are used to develop a predictive model. Using the data of transient thermal temperature of a coke drum recorded during its operation, the AI/ML-based prediction model is trained. The case study of an effort to generate transient temperature predictions using AI/ML algorithms is presented in this paper. The results obtained from this model are compared to the realtime as-operated transient temperature data set. Further, this AI/ML-based predictive model is planned to be used in a Digital Twin for preventive maintenance of coke drums.
Evaluation of Crack Initiation Probability by FERMAT Code in Conformity With the Procedure by a Japanese Industrial PFM Guideline
Authors: Miyashiro Satoshi , Sakai Takayuki , Nagai Masaki , Yamamoto Masato
Published: November 2023

The implementation of probabilistic fracture mechanics (PFM) on integrity assessment standards of reactor pressure vessels (RPVs) is not yet actualized in Japan. The most recent information on how PFM will be used in the near future is provided by the guideline JEAG 4640-2018, which describes a standard approach for evaluating the failure frequency of RPVs based on PFM. Central Research Institute of Electric Power Industry is creating a new PFM analysis code FERMAT (Fracture mechanics Evaluation of RPV MATerials) for future application of PFM in Japan. Our code is based on JEAG 4640-2018 and has a minimum design for practical usage in RPV structural integrity assessments. With a graphical user interface, all processes can be handled in a single piece of code. In the present study, calculation results by FERMAT were compared with another Japanese PFM code PASCAL4 with a model case targeting Japanese RPV. The distribution of temperature and stress evaluated by FERMAT and PASCAL4 were very similar. The stress intensity factor calculated by FERMAT and PASCAL4 was well corresponding with each other. Additionally, sampled values for reference temperature for nil-ductile transition were confirmed. The probability and the frequency of crack initiation were compared between FERMAT and PASCAL4. The outcomes assessed using those codes were closely related to one another.
Level-3 Fitness-for-Service Assessment of Carbon Steel Piping Component Having Local Metal Loss
Authors: Rafique Muhammad Raheel
Published: November 2023

Carbon Steel (CS) lines operating under susceptible temperature range can have highly localized thickness loss due to Corrosion under Insulation (CUI), through penetration or entrapment of water or moisture and contamination due to external source (i.e. rain, marine environment etc.) underneath the external jacketed insulation. Thickness loss in the piping component beyond its corrosion allowance limit or minimum required thickness value (as per code requirements), requires Fitness-For-Service (FFS) assessment to ensure the mechanical integrity of the piping component, in order to continue the operation safely. In this work, the FFS assessment was performed for a Carbon Steel Line in Hydrocarbon service, having local metal loss beyond its minimum required thickness value at the vicinity of the structural discontinuity i.e. branched connection and its bracing to header weld joint. Level-3 assessment was performed considering Limit Load Analysis Method through Finite Element Analysis (FEA) as per acceptance criteria specified in API-579 Part-2 & 5. Where, all applicable loads were factored at multiple load steps, and the convergence of the solution was ensured up to the acceptable load limit step. The results of the analysis then used to predict the remaining life of the piping component, ensuring the protection against gross plastic collapse due to low thickness.
Pitting Corrosion Resistance in the Heat-Affected Zone of No-Backing Gas (NBG) Austenitic Stainless Steel Welds
Authors: Cary Claire , Penso Jorge , Sridhar Narasi , Fink Carolin
Published: November 2023

Stainless steel welds for service applications in corrosive environments are typically performed using gas tungsten arc welding (GTAW) with an inert backing gas in order to minimize or prevent root pass contamination and oxidation. Back purging adds significant cost and complexity to stainless steel pipe welding due to access restrictions, personnel safety, and/or economic factors. In this study, two no-backing gas welds (NBG) were made on Type 304L austenitic stainless steel pipe with Type 316 filler metal. Two different shielding gas mixtures were used (98% Ar-2% CO2 and 90% He-7.5% Ar-2.5% CO2) for the NBG welds. Open gap root pass welds were performed using modified short circuit gas metal arc welding (SC-GMAW) process. A hot pass was welded with pulsed GMAW process. Fill and cap passes were made with flux-cored arc welding (FCAW) process. Cyclic potentiodynamic polarization (CPP) measurements based on ASTM G61 were performed locally on the backside surface heat-affected zone as a function of distance from the fusion line. Electrochemical corrosion testing was done using a simple syringe cell setup. Pitting corrosion resistance of the NBG welds was compared to a reference weld made with 100% argon backing gas and conventional GTAW for the root and hot pass.
Advances and Challenges in Powder Metal Hip Processing for the Production of Large Components
Authors: Peters Daniel T. , Gandy David W. , Puerta Doug , McLaughlin Robert
Published: November 2023

There has been a significant movement in advancing the use of large hot-isostatically pressed (HIP) powdered metal parts in various industries recently. This is driven by a desire to reduce lead times, generate near-net shaped components, eliminate welds, improve inspection characteristics, and to address other constraints for applications where large forgings and castings are currently used in several industries.

Much of this interest in large HIP technology is currently being driven by the near-term commercialization of small modular reactors (SMRs) and advanced reactor (ARs) throughout the world, but particularly within the USA[1]. A consortium within the USA has been investigating the design of a large, 160 inches (4.05m) diameter × 160 inches (4.05 m) length HIP for several years now and hope to move toward manufacture of a large HIP unit within the next 18 months. Similarly, in the UK a slightly larger HIP unit (∼4.5m) referred to as Titan is also being considered. Interest is also growing in other countries including Korea, Sweden, and Japan towards design and production of a large HIP unit to support nuclear and other applications.

This paper is an attempt to summarize recent advancements in developing an ultra-large HIP system and discuss challenges in developing HIP equipment of this scale.
Pipe Plugs: A Survey of Historical Development and Current Technology
Authors: Cornelius Austin E. , Garza Armando , de Leon John Rey , Sallee Richard , Sue Casey
Published: November 2023

Piping isolation and gripping test plugs have been utilized for many years to evaluate and maintain the integrity of pipe and piping systems, yet accidents still occur resulting in damage to equipment, lost time, personnel injury, and death. Fluid processing often requires high temperatures and pressures. Some of the fluids present chemical hazards to personnel, the environment, and equipment. In order to ensure that this hazardous, but important work can take place as safely as possible, pipe plugs have been developed to help isolate, test, and validate the related systems and equipment for use. Over the last half century the petrochemical industry has increased the emphasis on safety. Recently, for example, the Post Construction Committee of the American Society of Mechanical Engineers has addressed many issues for safe pressure testing in the recommended practices of ASME PCC-2. While many of these improvements are on the procedural side, recently there has been a significant push in industry to improve the safety and limit the damage to the piping systems under test by improving the underlying technology.

What follows is an account of the developmental history of the technology, including how each successive innovation has made improvements as well as noting their limitations. The newest innovations represent a step change in reliability and safety for both personnel and equipment, some by making significant changes from previous gripping plug designs. It is of critical importance that those responsible for deciding which technology to use for their particular service and/or testing needs are aware of the inherent safety and reliability concerns with older gripping devices, which, in some cases, are still sold and used. These new developments have the potential to save money by reducing test preparation time, and reducing or eliminating the need for post-test repairs or removal of portions of the pipe damaged by the grippers. Responsible parties should be aware that new innovations now exist which could potentially save lives and reduce cost by decreasing the risk of serious accidents.
Deterministic Leak-Before-Break Treatment of Uncertainties: Part 1 – Theoretical Basis
Authors: Kozluk Michael J. , Al-Dojayli Maher , Pavia Renita , Mileta Ernie
Published: November 2023

The Canadian CANDU® Industry has developed and is implementing a composite analytical approach (CAA) to demonstrate, with high confidence, appropriate safety margins for deterministic nuclear safety analysis of large-break loss-of-coolant accident events in existing CANDU reactors. A key element of the CAA is the deterministic leak-before-break (CAA/DLBB) assessment for postulated through-wall cracks in all butt welds in the large-diameter primary heat transport system piping and reactor headers.

This paper describes a systematic approach for quantifying the uncertainty in the CAA/DLBB assessment. The proposed approach integrates the uncertainties of the key leak-rate parameters into a single metric (a quantitative indicator of the uncertainty in the CAA/DLBB assessment, a.k.a., performance indicator). This approach ensures that the uncertainty in individual key parameters is not taken out of the context of the uncertainty of the other key parameters. A brief description of the CAA/DLBB evaluation process is presented and the leak-rate factor is adopted as the figure of merit. Next, the key leak-rate effect factors are identified and the uncertainty in each is established. This is followed by a description of two statistical approaches that can be used to propagate the uncertainties for the bounding postulated break location and to determine the level of uncertainty associated with the CAA/DLBB assessment. In Part 2 of the paper, the application of the approach is illustrated.
Structural Integrity Assessments of Nuclear Graphite: Managing Uncertainty and Variability
Authors: Horne Graeme , Young Amanda , Kent Daniel , Gray Richard , Joyce Mark
Published: November 2023

The UK has decades of experience designing, operating and extending the lives of graphite moderated reactors, including the currently operating fleet of EDF’s Advanced Gas-cooled Reactors (AGR). This paper summarises some of the analysis used to substantiate the graphite safety cases for their continued operation. In particular, the use of graphite brick modelling, using a physically-based material model, to describe the behaviour of irradiated graphite. The material model is calibrated to measurements made during regular inspections of the cores, capturing variability and uncertainty in addition to a central estimate. A probabilistic wrapper is applied to the brick modelling, to make predictions of the onset and rate of keyway root cracking, which is a damage mechanism of particular concern. It is hoped that this experience can help inform the development of design codes required for the proposed future graphite-moderated reactor technologies.