bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Application Method of Floor Response Spectrum Method Assisted by Time History Analysis for Multiply Supported Piping System
Authors: Yoshida Ayaka , Takayama Yoshihiro , Tsushima Toshiyuki , Hioki Hiroaki , Shudo Hiromichi
Published: November 2024

The independent support motion (ISM) response spectrum method is currently used in seismic analysis to calculate the response of piping systems subjected to independent excitations at several points of a supporting structure. This approach leads to considerable over estimation when the maximum responses by multiple excitations are combined by the absolute sum rule, while this may result in underestimation when the maximum responses by the multiple excitations are combined by the square root of sum of squares rule. Then authors have developed an advanced method of the ISM approach named SATH (spectrum method assisted by time history analysis), which was presented in PVP2020. In the SATH method, both floor response spectra and time histories of floor acceleration are used as independent inputs of support excitations. The maximum responses by multiple excitations are combined using correlation coefficients calculated by taking into account each time history of modal response due to independent inputs of support excitations. When the SATH method is applied to actual design using broadened FRS, the structural frequency uncertainty corresponding to broadened FRS should be considered in the calculation of correlation coefficients. The applicability of the SATH method to the structural frequency uncertainty was presented in ICONE2020. Furthermore, when piping systems are subjected independent excitations at several points of a supporting structure, the response of piping systems can be considered to have two different components. One is due solely to the inertia of the mass (the dynamic component) and the other is due to the time-varying differential motion of the support point (the pseudo-static component). Here, the dynamic component consists of two parts: the damped-periodic response (dynamic response) and the residual rigid response (high frequency response). Then authors have improved the SATH method to cope with above three responses (dynamic response, high frequency response and pseudo-static response), which was presented in ASME PVP 2023. Thus, since its presentation at ASME PVP 2020, the SATH method has been evaluated and improved several times and is now an appropriate method to use in design.

In this paper, the entire procedure of the SATH method, which combines the dynamic response using broadened FRS, with the high-frequency response and the pseudo-static response, is described as an actual design method. In addition, the advantages of the SATH method in design are clarified by comparing the response by the SATH method with that by the conventional method (the uniform response spectrum analysis method and the independent support motion response spectrum analysis method) for a three-dimensional piping system model subjected to independent excitations at several points of a supporting structure.
Fracture Toughness of Cold Formed Heavy Wall Plates in 2 ¼ Cr 1Mo ¼ V Low Alloy Steel
Authors: Palombo Marco , Doni Giorgia , Sandon Stefano , Fusari Fausto
Published: November 2024

The 2 ¼ Cr 1Mo ¼ V is widely applied for the design of high pressure and temperature equipment.

For large and heavy wall pressure equipment the cylindrical shell barrels can be carried either by forging or by plate forming to achieve the required dimensions.

Plate forming may have an impact on the material properties based upon temperature and deformation level for the involved plate thickness. Some specifications claim for a preheating temperature to be applied during plate forming of low alloyed steel. Such preheating in case of heavy wall plate thickness and inherent overall large dimensions has to be carried out in furnace with difficulties to keep the required temperature during the whole forming sequence and with inherent impact on the fabrication schedule. Eventually, a significant amount of gas consumption is envisaged.

A test campaign has been launched to investigate the real necessity of such preheating by forming of test plate coupons at different deformation levels with and without preheating. The base material selected was a low alloy 2 1/4 Cr 1 Mo Vanadium modified steel for which a preheating temperature of 177°C (minimum) is generally requested.

After forming, non-destructive examinations have been carried out followed by conventional mechanical test such as tensile strength and impact test aimed to investigate the resulting plate quality among the different forming conditions.

Material soundness can be impaired by existing flaws such as cracks, voids and metallurgical inclusions.

In order to better investigate the potential risk of crack propagation from existing defect under the applied stress, fracture mechanics tests according to ASTM E1820 have been carried out to characterize the possible different crack propagation behavior, by forming at room temperature and at preheating temperature of 177°C.

In this work the test campaign and the obtained results are presented, analyzed and discussed.
Probabilistic Fracture Mechanics Analysis Framework for the APAL Project
Authors: Bass B. Richard , Williams Paul T. , Dillström Peter , Tiete Ralf , Blasset Sebastien , Pistora Vladislav
Published: November 2024

The paper describes the development of a new probabilistic analysis framework designed to support the work scope of the Advanced Pressurized Thermal Shock Analysis for Long-Term Operations (APAL) Project. The APAL Project is funded in part by the European Atomic Energy Community (EURATOM) Work Program for Nuclear Safety. The primary objectives of APAL include the development of advanced probabilistic Pressurized Thermal Shock (PTS) assessment methods for reactor pressure vessels (RPVs) in the European Union (EU), including the quantification of safety margins for long term operation (LTO) and the development of best-practices guidance. The APAL Project goes beyond the state of the art by considering the uncertainties provided in the descriptions of RPV loading transients and by defining a margin based on a maximum allowable reference temperature (ART).

One of the required actions within the APAL Project is focused on defining an appropriate benchmark for probabilistic analysis of an RPV subjected to PTS loading. This benchmark will be applied when performing analyses using advanced probabilistic PTS assessment methods. Consensus APAL documents have identified specific modeling elements required to define and analyze this benchmark. Those elements include: (a) the Master-Curve distribution for fracture toughness, (b) capabilities for enhanced underclad crack analysis, and (c) specific correlations for fluence attenuation and reference temperature shifts due to radiation damage and embrittlement of the RPV wall. These capabilities were identified by the Probabilistic Structural Integrity of a Pressurized Water Reactor Pressure Vessel (PROSIR) Project, sponsored by OECD NEA/CSNI.

Several APAL participating organizations use the probabilistic fracture mechanics (PFM) computer code Fracture Analysis of Vessels – Oak Ridge (FAVOR), v16.1, exclusively for PTS analyses of RPVs; however, some modelling elements required by APAL are not included in FAVOR. Pursuant to the above new analysis requirements, one of the APAL participants, Oakridge Consulting International (OCI), Inc., implemented the above modelling capabilities into an advanced probabilistic analysis framework based on FAVOR, v16.1. The new PFM framework has been named Code for Advanced PTS Analysis for Long-Term Operation of RPVs (CAPAL), to distinguish it from the original FAVOR, v16.1, code.

This paper presents an overview of the CAPAL computational framework and the new capabilities implemented by OCI. Applications of the latter, described herein, demonstrate that CAPAL incorporates the specific modeling methodologies required to meet APAL’s objectives for performing advanced probabilistic analyses of the APAL-defined benchmarks focused on PTS integrity assessments of nuclear RPVs.
Influence of High Temperature Water on AISI 304 and ER 347 Regarding Their Threshold Value
Authors: Veile Georg , Grimm Michael , Weihe Stefan , Rudolph Jürgen
Published: November 2024

Welded joints are critical areas of components exposed to cooling water in NPP. For the improvement of the safety-critical fatigue design, an accurate analysis of the fatigue behavior in corrosive medium is essential. For this purpose, ER 347 weld material with its increased ferrite content and AISI 304 were investigated in medium conditions. Fatigue tests were carried out in air as well as in medium conditions of BWR at 240 °C, 70 bar pressure and 400 ppb dissolved oxygen and PWR at 300 °C, 100 bar pressure and 2.5 ppm dissolved hydrogen. Regarding fatigue tests in BWR conditions, possible contact corrosion induced by an extensometer in high temperature water is avoided by using a LVDT signal that replicated correlating data of strain-controlled fatigue test in air. To further improve implementation of the fatigue tests and reduce conservatism, the methods of past research projects were extended to model hardening and softening of fatigue specimen with an extended analytical equation for the LVDT signal. In the case of ER 347 the strain amplitude of 0.15 % proved to be within the so-called threshold value, where the influence of corrosive high temperature water is no longer detectable compared to fatigue tests in air stopped after 106 cycles. However, AISI 304 showed failure at this strain amplitude.
Research and Development of Three-Dimensional Isolation System For Sodium Cooled Fast Reactor Part 9: Evaluating Seismic Isolation Performance Through Seismic Response Analysis
Authors: Fukasawa Tsuyoshi , Somaki Takahiro , Yukawa Masaki , Hirayama Tomoyuki , Watakabe Tomoyoshi , Yamamoto Tomohiko , Okamura Shigeki , Miyazaki Masashi , Uchita Masato , Miyagawa Takayuki , Fujita Satoshi
Published: November 2024

This paper elucidates the isolation performance of a newly developed three-dimensional seismic isolation system through seismic response analysis. The seismic response analysis was conducted by incorporating the hysteresis characteristics obtained from static loading tests, for both each individual element and the assembled system.

To evaluate the design feasibility of the isolation system, static loading tests were judiciously conducted, considering a wide array of loading conditions, including beyond-design basis ground motions. Using the accumulated test data, a new analytical model was devised, capable of precisely capturing the hysteresis loops of each element. The hysteresis characteristics of the overall system were successfully elucidated through a static loading test on a half-scale model that assembled each element, with these results detailed in Parts 7 and 8.

The authors conducted a seismic response analysis, utilizing analytical models derived from the static loading test results of the half-scale model. This analysis incorporated the loading path obtained from 3D FEM analysis. The findings reveal that this three-dimensional isolation system, compared to horizontal isolation systems comprising rubber bearings and oil dampers, provides enhanced isolation performance against both design basis and beyond-design basis ground motions.
Concrete Cracking Modelling due to Reinforcement Bar Corrosion
Authors: Jarvis Wesley J. , Browning Kelvin M. , De Haan - De Wilde F. H. E.
Published: November 2024

Nuclear Power Plants (NPP) and research reactors built during the mid-20th century often have incomprehensive material characteristics for their concrete structures. This lack of quality records frequently leads to challenges when attempting to demonstrate safety during life extension projects or when specific modelling is necessary for plants SSCs when design regulations are updated with new or revised requirements.

In the framework of long-term operation (LTO), there is limited knowledge about ageing and the structural integrity of concrete structures. In order to increase the knowledge in the field of civil structures, this paper focuses on investigating the ageing mechanisms of civil structures at NRG, Petten, and using the previously calibrated chloride ingress model (PVP2023-105650) to determine expected internal pressure generation due to reinforcement bar (rebar) corrosion within a FEA model to predict concrete cracking.

In the most recent paper, PVP2023-105650, the modelling of ageing effects has been investigated by reducing material strength properties and developing a chloride ingress model calibrated to the HFR chimney. The model allows the predictions of rebar diameter reduction and internal pressure generation due to rust production. The FEA model developed under PVP2022-84008 was altered considering the reduced material properties and rebar diameter to gain a better insight into how it affected the determined concrete damage under a heavy drop impact.

The purpose of this research paper is to better understand the effect of internal pressure generation due to rust production and to allow the simulation of crack generation due to this degradation mechanism. The model has been calibrated to the results obtained from the HFR chimney. It is seen through the FEA simulation generated in Ansys that there is a close correlation to reality when modelling the calculated internal pressures using the previously developed chloride ingress model. The model is limited in its scope to the HFR chimney where the concrete information was obtained. Furthermore, the model must be recalibrated for each time period as the contact stiffness varies over time. The modelling method is also sensitive to a reduction of mesh size which is contrary to the majority of FEA models.

In the future, core samples of relevant HFR areas should be taken to determine the chloride concentration and rebar corrosion. This can allow for more data points for model calibration when simulating concrete cracking due to rebar corrosion.
Microstructure and Creep Performance of Wire Arc Additive Manufactured Grade 91 Steel
Authors: Wang Yiyu , Zhang Wei , Wang Yanli , Feng Zhili
Published: November 2024

In this work, creep performance of an as-built Grade 91 steel using wire-arc additive manufacturing (WAAM) was tested using a unique creep testing system integrated with in-situ high-temperature digital image correlation (DIC) strain mapping capability. The test results show creep lifetime of this as-built Grade 91 steel is much higher than that of Grade 91 steel weldments, even slightly above the mean lifetime of the conventional Grade 91 steels. In addition, highly nonuniform creep deformation in the as-built specimen was clearly captured by the DIC measurements, and correlated to the characterized inhomogeneous microstructures in multi-scales. Microstructure heterogeneities, including different martensite lath sizes, tempering degree of martensite matrix, and variations in precipitates, exist in two distinctive regions. A soft region, considered as the reheated “heat affected zone” (HAZ), has fine equiaxed grains, smaller martensite blocks, more precipitates, and a lower hardness. These microstructure features made these reheated HAZ regions more vulnerable to creep strength degradation, showing a larger creep deformation in the DIC measurements. A hard region with coarse columnar grains, less-tempered martensite matrix, and finer precipitates, exhibits a higher hardness and a better creep resistance. This study has clearly demonstrated that microstructure and creep strength variations at the meso-scale exist in the WAAM builds and should be carefully considered in WAAM process and material qualifications.
Simplified Fragility Assessment Method for Piping Systems in Seismic PRA
Authors: Ono Yohei , Nakajima Masato , Sakai Michiya , Shimazu Ryuya
Published: November 2024

Assessing the fragility of piping systems in nuclear power plants is time-consuming due to the many piping systems present. Applying elastic-plastic finite element analysis (FEA) becomes imperative when considering elastic-plastic deformation. This study introduces a simplified fragility assessment method predicated on the assumption of fatigue failure as the predominant mode of piping system failure.

The simplified fragility assessment method required pertinent design information. While it obviated the need for additional elastic-plastic FEM, it elastic-plastic deformation through a coefficient, denoted as Ke. The coefficient facilitated the consideration of plastic deformation. The simplified evaluation involved the computation of a time history strain amplitude derived from the response displacement of a single degree of freedom (SDOF) system subjected to the floor response acceleration of a piping system. Postulating that the maximum alternating stress intensity corresponded to the maximum displacement range enabled the determination of the time history stress amplitude. The time history strain amplitude was computed by dividing the time history alternating stress intensity by Young’s modulus. The usage factor was derived from the time-history strain amplitude and a best-fit curve for fatigue. The subsequent calculation of failure probability involved the usage factor, variabilities, and the capacity for fatigue failure. Systematic variation of the maximum floor response acceleration derived the assessment of failure probabilities for each acceleration level, a composite fragility curve and the median acceleration.

The developed method expedited the fragility evaluation of piping systems than the conventional elastic-plastic FEA. The median acceleration capacity, as determined by the simplified fragility assessment method, surpassed that obtained through the conventional method based on primary stress. It is more conservative than the result obtained through elastic-plastic FEA.
Experimental Study on Applicability of Triboelectric Film Sensors for Integrity Monitoring of Shear Bolted Joints
Authors: Wang Chu , Miura Nanako , Hiraga Motoaki , Masuda Arata
Published: November 2024

Many structures such as bridges, buildings, or automobiles use various joining methods such as screws, rivets, welding, gluing, and caulking to join members together. In particular, the shear bolted joints is widely used as a joining method that facilitates assembly and disassembly, while being accompanied by a troublesome problem of bolt loosening due to repeated shear force. In the previous study, we proposed a self-powered film-shaped triboelectric sensor made of inexpensive materials, being installed between the contact surfaces at the joint, to monitor the loosening of tensile bolted joints. The principle of the sensor is that it detects microscale relative motions between the contacting surfaces at the joint as the triboelectric induced voltage, when the integrity of the joint is deteriorated due to the decrease in the bolt’s fastening force. In this study, we apply our sensor to shear bolted joints. A sensor is designed, fabricated, and tested in a single-bolt shear joint subjected to lateral shear forces. As a fundamental experiment, we designed a drop test to apply a lateral impact to bolted structures, simulating the lateral loads experienced by bolted assemblies in real-world situations. Under various fastening forces of the bolt, we observed the sensor’s voltage output when subjected to the same impact force or lateral load. The analysis focuses on the relationship between the sensor’s voltage output signal, the impact, and the fastening force of the bolted structure.
Studies on Pipeline Polyethylenes in Hydrogen Gas Environments Using In-Situ and Ex-Situ Characterization Methods
Authors: Leveille Michael P. , Crain Christopher A. , Strange Nicholas A. , Banerjee Debasis , Nissen April , McDonald Anthony , Shin Yongsoon , Piontkowski Zachary T. , Menon Nalini C. , Simmons Kevin
Published: November 2024

Polymeric materials are commonplace in the natural gas infrastructure as distribution pipes, coatings, seals, and gaskets. Under the auspices of the U.S. Department of Energy HyBlend program, one of the means to reduce greenhouse gas emissions is with replacing natural gas, either partially or completely, with hydrogen. This approach makes it imperative that we conduct near-term and long-term materials compatibility research in these relevant environments. Insights into the effects of hydrogen and hydrogen gas blends on polymer integrity can be gained through both ex-situ and in-situ analytical methods. Our work represented here highlights a study of the behavior of pipeline polyethylene (PE) materials, including HDPE (Dow 2490 and GDB50) and MDPE (Ineos and legacy Dupont Aldyl A), when exposed to hydrogen by means of in-situ X-ray scattering and ex-situ Raman spectroscopy techniques. These methods complement each other in analyzing polymer microstructure. Data collected revealed that the aforementioned polymers did not show significant changes in crystallinity or morphology under the exposure conditions tested. These studies help establish techniques to study real-time effects of hydrogen gas on polymer structure and chemistry, which is directly related to pipeline mechanical strength and longevity of service.
Effect of Dynamic Recrystallisation on the Fatigue Life of the Out-of-Plane Gusset Welded Joint Treated by Ultrasonic Impact Treatment
Authors: Yamaguchi Atsushi , Togasaki Yu , Honda Takashi , Sasaki Tetsuya
Published: November 2024

An ultrasonic impact treatment (UIT) is a peening method, commonly used as a post-weld treatment to improve the fatigue strength of welded joints. In this study, fatigue tests were conducted on out-of-plane gusset welded joints treated with UIT, comparing their fatigue life to that of as-welded (AW) joints to assess the effects of UIT on fatigue life. The material used for the out-of-plane gusset welded joints was WEL-TEN 950PE. UIT was found to increase the fatigue life of WEL-TEN 950PE by more than tenfold. The improvement in fatigue life attributed to UIT, is believed to stem from the introduction of compressive residual stress, alleviation of stress concentration at weld toes, and grain refinement beneath the weld toes. Three-dimensional elastic stress analysis showed that the stress concentration factor Kt at the weld toe decreased from 3.3 to 2.5 as the UIT transfers the shape of the needle tip to the weld toe. Additionally, residual stresses measured by X-ray stress analysis showed a shift from a maximum tensile residual stress of 300 MPa to a compressive residual stress of 650 MPa. Microstructural observation using laser microscopy revealed that the grain structure of WEL-TEN 950PE was refined from the surface to 300 μm, by UIT.
Experimental and Numerical Analyses for the Evaluation of Hydrogen As an Energy Source for Thermal Testing of Transport Packages of Radioactive Material
Authors: Naster Maximilian , Gleim Tobias , Wille Frank
Published: November 2024

In this paper we present a new hydrogen-based test rig for an ongoing feasibility study of using hydrogen as an energy source for the thermal testing of transport packages containing radioactive materials. The test rig will be capable of combusting hydrogen for a wide range of different burner geometries, mass flows and if necessary hydrogen blends. As this type of fire test according to the IAEA [1] boundary conditions does not yet exist, a large number of preliminary investigations, safety assessments and calculations must be carried out in order to develop a viable concept for hydrogen fires. In the first step of the feasibility study, the temperature, structure, and radiation of various hydrogen flames are surveyed. In future works, the results will make it possible to design burner frames that are suitable for fire reference tests in order to make comparisons with pool and propane fires used in assessment procedures today, cf. [2]. In parallel comparative numerical simulations are conducted to model the thermal behaviour of hydrogen flames using the software package Ansys® [3]. On the one hand, the numerical simulations support the experiments by providing an overview of numerous parameters and the measuring range; on the other hand, they will help with the design of the burner frame in future work. This paper gives an overview in the design and capabilities of the test rig. Furthermore, the results of the parameter studies show that burner geometry and mass flow provide a significant design margin for the thermal shape of the hydrogen flames. In addition, the results of the initial numerical calculations will be used to determine the necessary sensors, the positions, and their operating range. Only the optimal interaction allows a controlled system that permits user-defined hydrogen fires.
A Review of Check Valves in Unsteady Flow: Behavior, Analysis, and Design
Authors: Lang Scott , Schreuder Jans , Witte Dylan , Dudley Mark
Published: November 2024

Check valves intend to prevent reverse flow with minimal impact to normal forward flow. They respond to transient conditions, and improper selection may result in unmitigated check valve slam — causing massive transient pressure surge that can easily cause damage throughout the connected piping network.

Dynamic characteristics show the dependence of closure velocity on fluid deceleration. This paper aims to clarify, summarize, and qualify the use of these curves in liquid flow. Computer simulation models and examples are described along with comparisons to field data. Basic design principles, guidelines for identifying at-risk systems, and strategies for check valve selection are presented.
Predicting Acoustically Vibration Induced Resonance From Modal Analysis
Authors: Arjunan Raj , Niu Yaying , Ghosh Arindam , Karzcub Denis
Published: November 2024

Preliminary results from experiments and finite-element models for a joint industry project (JIP) to investigate acoustically induced vibration (AIV) have been presented in past conferences. The dynamic stress concentration ratio (DSCR) was found to vary significantly between modes (namely in the 0–400Hz frequency range) although it was unclear how this should be applied to quantify overall dynamic stress levels and the risk of fatigue failure. More detailed assessment of the experimental data has confirmed the presence and significance of low-frequency higher-order structural modes (0–400Hz) with a significantly higher DSCR and the strong forced excitation of these structural modes below the cut-off frequency of higher-order acoustic modes (i.e. higher-order structural modes excited by planar acoustic modes below the acoustic cut-off frequency of higher-order modes). These observations lead to a need to extend the study of AIV of piping to cover planar acoustic modes in addition to the traditional consideration of only higher-order acoustic modes. Fundamental to this is the need to address risk factors associated with low-frequency pipe modes with very high DSCR under conditions (namely high gas flow velocity and high flow capacity orifice plates) in the presence of significant low-frequency planar acoustic modes. Finite element analysis is used to show the nature of the modes, locations, and levels of highest dynamic stress and how this relates to the boundary condition effects of a structural discontinuity such as a branch connection or pipe support. The strong excitation of planar acoustic modes is likely to be particular to piping with geometry leading to quarter and half wavelength acoustic resonances such as those experienced in the sub-header of the JIP test arrangement. Some preliminary results from acoustic modal and structural-acoustic harmonic analysis are also presented as a supporting activity to quantify the nominal overall increase in dynamic stress associated with low-frequency AIV.
Rapid Fault Diagnosis of LNG Receiving Terminal Transportation Operation Process Based on SOM-KPCA
Authors: Xiao Shangrui , Hu Jinqiu , Zhang Laibin
Published: November 2024

Accurate and rapid diagnosing, identifying and locating faults in LNG terminals are essential for ensuring the safe functioning and high-quality output of LNG terminals. The use of intelligent data-driven fault diagnosis methods has received extensive attention. Nevertheless, conventional data-driven fault diagnosis methods require a large amount of annotated data and historical events, resulting in huge labor and time costs. In this paper, an unsupervised and rapid fault diagnosis method is proposed for the external transportation operation of LNG terminals based on Self-Organizing Map and Kernel Principal Component Analysis (SOM-KPCA). The SOM-KPCA fault diagnosis model is used for dimensionality reduction and clustering with the real-time monitoring label-free data of the LNG terminals. The fault diagnosis boundary conditions are set based on the system high and low alarm threshold, data association, temporal trends, and eigenvalues, and fault diagnosis is performed on a cluster basis. By removing the necessity for data annotation and historical event observation, the SOM-KPCA fault diagnosis model significantly reduces the amount of time needed to diagnose faults. For example, in the low-pressure pump and high-pressure pump pressurization transportation process of an LNG terminal’s export operation, the accuracy of SOM-KPCA fault diagnosis reached 86.21%, with a precision rate of 90.38%. Rapid fault diagnosis in the LNG terminal’s export operating process is made possible by a significant reduction in both the computational complexity of fault diagnosis data and the SOM-KPCA clustering time, as compared with SOM clustering without dimensionality reduction.
Optimizing Coke Drum Keyhole Dimensions Using Statistical Modeling
Authors: Fernando John , Kwok Henry , Chan Luke , Penso Jorge
Published: November 2024

To extend the fatigue life of coke drum skirt-to-vessel attachment welds, keyholes have become an important consideration in skirt design. The amount of stress reduction they offer to the weld depends on the geometric specifications of the keyholes, namely the slot dimensions, relief-hole diameter, and the distance between the top relief hole and the top of the skirt. Although the directional impact that varying each keyhole parameter has on stress reduction can be intuited, the exact functional relationships are not well established. This results in significant computational efforts at the design stage to iteratively rank keyhole designs based on fatigue-life performance. To help mitigate the need for extensive simulations, the current study investigates a large parameter space of keyhole designs for two commonly used skirt designs to identify functional trends between keyhole parameters and stress. The functional relationship in certain cases is found to be not only non-linear, but also non-monotonic. However, the variation in stress reduction is well-predicted through simple linear regression models when the parameter space is constrained to include only keyhole dimensions typically used in coke drum designs for various practical reasons. The resulting regression models have the potential to significantly reduce computational efforts when optimizing coke drum skirt designs.
Research and Application of Crude Oil Storage Tank Integrity Management
Authors: Qi Sheng , Shuai Jian , Li Yuntao , Shi Lei , Mei Yuan , Ren Wei
Published: November 2024

Crude oil storage tanks are subject to corrosion and settlement due to their location in coastal areas, resulting in leaks, fires and explosions. In order to secure crude oil storage tanks, a crude oil storage tank integrity management system with safety target as the core and eight elements such as management process and inspection technology as components is proposed to guide the integrity management of crude oil storage tanks throughout their life cycle for the first time. The cyclic process of storage tank integrity management with data acquisition, risk assessment, integrity assessment, decision response and efficiency evaluation as the main steps is formed and applied as a method of integrity management implementation. The effectiveness of crude oil storage tank integrity management was verified within the oil depots in China. The results show that the integrity management system is effective and the risks of 38 storage tanks are accurately characterized. The integrity of the storage tank is accurately analyzed by relevant standards and finite element models. Finally, decision response measures and efficiency evaluation methods are obtained. Crude oil storage tank integrity management can provide significant support information for managers on how to optimize risk management strategies and achieve limited resource allocation.
Numerical and Experimental Study of Detection of Linear Damage of Pressure Equipment Using Electromagnetic Acoustic Resonant Method
Authors: Wang Zhe , Fan Zhichao , Tang Jian , Cheng Jingwei , Ji Tian , Wang Haibin , Bu Yangguang
Published: November 2024

Currently, the application of electromagnetic ultrasound methods in damage detection such as corrosion thinning of pressure equipment is constantly expanding. It has the advantages of non-contact, no couplant and non-polishing required. However, the detection accuracy is limited by low energy transfer efficiency and time-domain signal distortion at high temperatures environment. Combining electromagnetic ultraosnic testing and acoustic resonance methods, a multi-period signal excitation transducer is used to obtain the frequency-domain resonance information of the test piece, which can effectively improve the energy intensity of echo. This paper firstly establishes an electromagnetic acoustic resonance (EMAR) detection model based on the magneto-electric-force-acoustic transduction mechanism. Then, the sound field distribution and time/frequency domain response characteristics of EMAR was studied and a magnetically concentrated transducer is designed. Flat-bottom holes are used as the detection standard of corrosion thinning in this paper. Based on the developed EMAR detection system, the experiments for detection of flat-bottom holes and thickness measurement at high temperature environment were carried out. The correlation between local corrosion thinning and transducer size has been proven. The measurement error of wall thickness at 500°C and atmospheric pressure of 1 bar using EMAR method is within ±0.1mm. This study lays a foundation for quantitative detection and monitoring applications of damage to pressure equipment with high temperatures or corrosion layers.
Dependence of Blast Shielding on Stand-Off Distance
Authors: Geng Jihui , Thomas Kelly
Published: November 2024

A key component of hazard evaluations involving explosions is the determination of hazard zone boundaries, which includes evaluation of standoffs to given blast overpressure values and the associated building damage. Many such evaluations use a simplified methodology which assumes that the blast wave propagates from the explosion source to the target location without interacting with intervening buildings or structures (i.e., without blast wave shielding). This is obviously a perfectly acceptable approach for a screening study, but blast wave shielding effects can be significant in certain circumstances (e.g., within a building group). In addition, the blast shielding effect depends on blast wave parameters (overpressure and duration) and structural dimensions. It is well known that the blast overpressure decreases with stand-off distance while blast positive duration increases with increasing stand-off distance. This paper extends the prior work, focusing on the determination of the blast shielding as a function of standoff distance. Only the high explosive (HE) source was examined in this study as there is a definite single blast chart to characterize the blast parameters vs scaled distribution.
Numerical Study of a C-ring in a Bimetallic Joint of a Cryogenic Propellant Tank
Authors: Rose K. A. Jesna , H. M. Umer , Nair Remya , Thomas Suresh Mathew , Asraff A. K.
Published: November 2024

In the realm of cryogenic pressure vessels, bolted flanged joints employ a spring-energized C-ring mechanism to achieve a leak-tight seal. The application of clamping force during the torquing process compresses the C-ring, generating adequate sealing pressure. The different thermal expansion behaviours of mating surfaces and C-rings in a cryogenic environment can affect contact pressure at the C-ring. Moreover, these joints must endure external pressures and vibrational loads, exacerbating the relaxation of the C-ring and contributing to potential leaks. This study delves into a numerical simulation of a bimetallic joint operating in a cryogenic environment under varying pressure loads. A more comprehensive and accurate simulation of a standard C-ring is conducted, and the obtained outcomes are cross-referenced against experimental data in the existing literature. Furthermore, an extensive nonlinear finite element simulation is performed to fathom the linear load (C-ring load per unit circumference) fluctuations experienced by a C-ring in a bimetallic joint of a cryogenic pressure vessel, as well as the effects of external pressure loading. The findings highlight a reduction in sealing pressure at the contact area when subjected to cryogenic pressure loads. Nevertheless, the relaxation arising from both cryogenic conditions and external pressures remains within permissible thresholds. These results are subsequently validated through an LN2 pressure test applied to a simplified version of the joint configuration.
Theoretical Analysis of Natural Frequencies and Mode Shapes of Piping Systems With Tees
Authors: Tamura Shinji
Published: November 2024

The vibration of piping system subjected to earthquake is a severe problem. However, the actual piping system is seems to be too complicated to analyze theoretically. Therefore, the finite element method is used to obtain the natural frequencies and mode shapes. Recently, the author have proposed the theoretical analysis method for the piping system with elbows, which is extended from Leissa and Qatu’s approach. In this method, the connection conditions at the elbows derive the characteristic equation of the piping system. In this paper, the proposed approach is further extended for the piping system with tees.
The Use of a Carbon Fibre Reinforcement System for the Mitigation of Acoustically Induced Vibration
Authors: Middleton Chris , Swindell Rob , Borland Gordon , Holstad Ole , Van Der Kooij Kari
Published: November 2024

Mitigation of acoustically induced vibration (AIV) on ‘live’ flare systems poses a series of challenges; any modification should be non-intrusive and, also, wherever possible, avoid hot work (e.g. welding).

This paper describes a series of tests, sponsored by Equinor ASA, which were performed on a full-size steel alloy piping spool using specialist facilities at the University of Southampton, UK, to quantify the effectiveness of carbon fibre reinforced polymer wrap in mitigating the high frequency structural response of the pipe to broadband high frequency acoustic excitation. The objectives of the tests were (i) to establish the potential benefit in terms of the dynamic stress reduction with increasing wrap thickness, and (ii) obtain valuable damping and modal data for the purposes of validating finite element predictions.

Conclusions are drawn concerning the results obtained and the lessons learned, along with other key practical considerations. Recommendations are also drawn regarding further qualification testing.
Enabling the Use of Carbon Steel for CO2 Transport, Processing, and Intermediate Storage
Authors: Rensman Jan-Willem , Krom Alfons
Published: November 2024

Anthropogenic CO2 in the atmosphere must be lowered to keep global warming to a minimum. Avoiding CO2 production will be essential, but capturing CO2 from process streams may contribute to a faster decrease. CO2 impurities must be removed to allow cost efficient use of engineering materials such as carbon steels. After drying and sufficient purification, CO2 becomes an essentially non-corrosive fluid.

The operating conditions are not particularly challenging from a structural integrity point of view. However, there are transient conditions that need to be addressed.

The paper will focus on enabling the use of carbon steel for gaseous CO2 transport piping, liquefaction plants, compressor stations, intermediate liquefied CO2 storage, and long-distance transport piping. The paper will present a European perspective on low temperature design with carbon steels since the European codes facilitate low temperature design with fracture-mechanics-based methods. The paper will address threats from internal low temperature transient conditions due to depressurizing and repressurizing, cooling in and around holes and orifices, and design against running fracture in high pressure pipelines.
Fatigue Behavior in Air of 316L Stainless Steel Obtained by Additive Manufacturing in the Frame of the NUCOBAM European Project
Authors: Guilbert Séverine , Doremus Luc , Chitty Walter-John , Hermant Alexandre , Quibel Jonathan
Published: November 2024

Additive Manufacturing (AM) opens new opportunities for the nuclear industry by reducing manufacturing costs for complex geometries compared to traditional manufacturing methods. Nevertheless, it should be verified that components obtained by AM meet the performances needed regarding safety-related function and operational requirements as the usual materials used in the nuclear industry. The NUCOBAM (Nuclear Components Based on Additive Manufacturing) European project aims at developing a methodology to qualify components produced via AM. Laser Powder Bed Fusion and the austenitic stainless steel 316L are the AM method and the material under study for this project.

One of the major mechanical degradation mechanisms undergone by nuclear materials is fatigue. Therefore, one of the key points of NUCOBAM’s material characterization program is the low cycle fatigue behaviour in air of the AM processed 316L. A complete test matrix has been designed including several strain amplitudes between 0.2% and 1% and test temperatures (room temperature or 300°C). The other parameters under study are the machining direction (resulting in z-oriented or x-oriented specimens), the porosity ratio, the grain structure, the specimen post processing heat treatment, and the thermal ageing heat treatment. This paper aims at giving an overview of the fatigue test program results and discuss them in the light of microstructural characterizations. A comparison of the fatigue mean curve from NUREG/CR-6909 rev1 obtained for wrought stainless steel is discussed.

This study was performed on behalf of the NUCOBAM European project that received funding from the Euratom 2014-2018 under grant agreement No 945313.
Delayed Hydride Cracking Initiation Evaluation of a Fretting Flaw in a CANDU Reactor Zr-Nb Pressure Tube With Consideration of Finite Length of the Flaw and Flaw Shielding Effect
Authors: Scarth Douglas , Xu Steven , Doddihal Preeti , Kawa Dennis , Ip Monique
Published: November 2024

In-service evaluation of a flaw that is detected in a Zr-Nb alloy pressure tube in a CANada Deuterium Uranium (CANDU) nuclear reactor includes an analysis to demonstrate that delayed hydride cracking will not initiate from the flaw. The flaw can be assessed either as planar or volumetric with a blunt root radius. A flaw caused by fretting due to flow-induced vibration was detected by ultrasonic examination in a Zr-Nb alloy pressure tube in a CANDU nuclear reactor. The flaw was replicated to obtain details of flaw geometry. The flaw is volumetric in nature, and is comprised of two axially oriented features that were joined by a ligament. This flaw was evaluated for delayed hydride cracking initiation in accordance with the Canadian Standards Association Standard N285.8. Two-dimensional elastic finite element stress analysis of the flaw was performed. An adjustment factor on the applied stress that took into account the finite axial length of the flaw was used to produce a lower and more representative peak flaw-tip stress as compared with an assumed “infinite” length of the flaw in the two-dimensional finite element stress analysis. The proximity of the two features of the flaw generated a stress shielding effect which was also accounted for in the evaluation for delayed hydride cracking initiation. The flaw met the acceptance criteria for prevention of delayed hydride cracking initiation, and the pressure tube was returned to service. This paper provides a summary of the delayed hydride cracking initiation evaluation of this flaw, and highlights the methods adopted to reduce conservatism in the evaluation.
Leakage Rate Models for Cracked Pipes
Authors: Brigante Francesco , Pasti Fabio , de Haan – de Wilde F. H. E.
Published: November 2024

This paper presents a leakage prediction study for Leak Before Break (LBB) assessments. The LBB concept has emerged as an essential tool for ensuring the safety of nuclear installations and pressurized piping systems. The approach is backed by accurate estimation of leakage rates from postulated cracks. In this study the methodology is based on the UK procedure for assessing structures containing defects (R6). The research is part of the ongoing in-house development of a software for LBB analyses and it aims to better understand and improve leak rate prediction methodologies for LBB assessments. The software is comprised of structural integrity modules and thermal hydraulic modules. This study presents the implementations of different coolant leak rates flow models, the Henry-Fauske model for flashing subcooled fluids and as single-phase Bernoulli model for lower temperatures. The thermal-hydraulics Henry Fauske model is evaluated against available experimental data and the differences are discussed. The Bernoulli based model is compared with another software. The implemented procedure is compared with two different software results for the structural modules. The structural calculations show coherence between the implemented procedure and the benchmark software that is based on the same methodology. In contrast the results are considerably different respect to another available software. The data show the significance and limitations of each model in various cases.
Recent Dynamic Events in Modern Large CCGT Plants – Case Studies, Findings and Corrective Actions
Authors: Johny Anita , Mollitor Barrie , Jackson Peter
Published: November 2024

This paper presents the findings for investigative studies conducted for various transient incidents commonly known to occur in CCGT plants. The damage from transient events can range in severity. Effects such as insulation damage and minor pipe deflections from small-scale transient effects can be repaired effectively without extraneous efforts. However, reactions such as piping vibrations, damaged supports and/or weld failures can directly impact plant operability — resulting in forced plant outages.

High energy piping systems become more susceptible to damage when transient events such as steam/water hammer or slug flow occurs in combination with improper drainage. The locations most known to be at risk are the Hot Reheat or High Pressure bypass valve outlet where the source of condensate is an attemperator and the Feed Water system. Inoperable or frozen drain legs, and start-up vents that are closed rapidly during start-ups are some other common sources. The case studies detailed in this paper explore the correlation of condensate build-up in piping and the resultant dynamic loads. Case study findings analyzed underscore the importance of following proper drainage protocols during plant start-ups and shut-downs. Additionally, supports that provide the most optimal protection against dynamic transients such as rigid restraints and snubbers (shock suppressors) are discussed.