bluuebunny/crossref_metadata_2025 huggingface dataset:
Technical Basis for Revisions to ASME Section XI Code Case N-597-2 on Requirements for Analytical Evaluation of Pipe Wall Thinning
Authors: Scarth Douglas A. , Davis Michael , Rush Phil , Xu Steven X.
Published: November 2015

Code Case N-597-2 provides procedures and acceptance criteria for the evaluation of piping items subjected to wall thinning mechanisms such as flow-accelerated corrosion (FAC). The acceptance criteria ensure that margins equivalent to those of the ASME B&PV Code are maintained. Subsequent to the publication of Code Case N-597-2, the U.S. Nuclear Regulatory Commission (NRC) found the Code Case conditionally acceptable. A number of task items have been undertaken by the ASME Section XI Working Group on Pipe Flaw Evaluation (WGPFE) to address the NRC conditions. A 2006 ASME Pressure Vessels and Piping (PVP) Division conference paper was published to provide an expanded explanation of the technical basis for Code Case N-597-2. A 2009 PVP paper was published to provide results of validation of evaluation procedures and acceptance criteria in Code Case N-597-2 against experimental and historic wall thinning events. More recently, revisions to Code Case N-597-2 have been made and were proposed as N-597-3. Significant changes have been made in the proposed revised Code Case to clarify the technical requirements and address the NRC concerns over N-597-2. The technical basis for revising Code Case N-597-2 is provided in this paper.
Effect of Adhesive Nano-Additives on Static Load Transfer Capacity and Failure Mode of Bonded Steel-Magnesium Single Lap Joints
Authors: Nassar Sayed A. , Moustafa Kassem , Wu Zhijun , Tzelepis Demetrios
Published: November 2015

An experimental procedure and test setup is used for investigating effect of using nanoparticle additives to the adhesive on the load transfer capacity (LTC) of bonded magnesium (Mg)-steel (St) single lap joints (SLJ). Investigated variables include the nano-powder material (Alumina vs. Silica), particulate size (20 nm vs. 80 nm), and concentration in the adhesive (2.5% wt. vs 5.0 % wt.). Two different levels of surface roughness on the bonded area are used; namely, sanding the bond area with G60 or G180 sand paper. Test data and SEM failure mode analysis are provided.
Stability of an Axially Moving Flexible Cantilevered Plate in an Axial Flow
Authors: Fujita Katsuhisa , Matsumoto Keiji
Published: November 2015

When a flexible plate of machines and structures is in axial flow, increasing the flow velocity induces the dynamic instability. Also, the similar instability occurs for a thin film wound to a coil form and a band saw driven with high transport speed even if we consider there is no effect of fluid. However, if a flexible plate is very light, and the rigidity is weak, the dynamic instability of a plate is thought to be affected both by the transport speed of plate and by the surrounding fluid. In this paper, the stability analysis is performed using the velocity potential based on the boundary conditions between the surrounding fluid and the plate. The numerical studies are performed as for a cantilevered plate. The case of an axially moving plate in a still fluid, the case of a stationary plate subjected to an axial flow, and the case of an axially moving plate in neglecting the effect of surrounding fluid are examined. And, the effect of the transport speed of cantilevered plate on the dynamic stability is discussed. Furthermore, another stability analysis is also performed by using the non-circulatory aerodynamic theory, and the numerical analysis results are examined and discussed.
Results of EC FP7 Structural Performance of MULTI-METAL Component Project: Dissimilar Metal Welds Fracture Resistance Investigation
Authors: Keinänen Heikki , Keim Elisabeth , Karjalainen-Roikonen Paivi , Blasset Sébastien , Gilles Philippe , Nicak Tomas
Published: November 2015

The purpose of this paper is to disseminate the results of an EURATOM project MULTI-METAL focusing on the structural integrity assessment of dissimilar metal welds. The project started in February 2012 and ended in February 2015. The project is coordinated by VTT with 10 partner organizations from Europe : Technical Research Centre of Finland, Finland (VTT) – Coordinator, AREVA NP, France and Germany (ANP), Commissariat à l’Énergie Atomique et aux energies alternatives, France (CEA), Joint Research Centre of the European Commission, Belgium (JRC), EdF-Energy, United Kingdom (BE), Bay Zoltán Foundation for Applied Research, Hungary (BZF), Electricité de France, France (EDF), TECNATOM, Spain (TEC), Jožef Stefan Institute, Slovenia (JSI), Studsvik Nuclear AB, Sweden (STU).

The underlying aim of the project is to provide recommendations for a good practice approach for the integrity assessment (especially testing) of tough dissimilar metal welds as part of overall ductile integrity analyses; this has been presented in the project overview [1].

Experience on typical DMWs concerning manufacturing, residual stresses, flaw assessment and testing have been reviewed. The specimens were taken from mock-ups of welded plates. Three DMWs design variants have been covered: narrow gap DMW with Ni-52, DMW with austenitic steel buttering and a DMW with Nienriched austenitic steel buttering. Mechanical characterization and fracture mechanics testing (CT, SEN(B) and SEN(T) specimens) have been performed. Interpretation of the test has required numerical analysis since the standard ASTM E1820 [2] (CT, SEN(B)) and guidelines dealing with SEN(T) [3][4] are not directly intended to cover DMW.

The motivation of the project and its results are generally presented and discussed.
A Determination Method of Bolt Preload for Bolted Pipe Flange Connections With Metal Gaskets Under Internal Pressure
Authors: Kondo Koji , Sawa Toshiyuki
Published: November 2015

FEM calculations and leakage experiments are carried out for bolted flanged connections with metal flat gaskets. It is found that the sealing performance of bolted flanged connections with raised face metal gaskets under internal pressure is improved significantly when the contact gasket stress reaches the gasket yield stress. In our FEM calculations it is demonstrated that the contact gasket stress at the outside diameter is bigger than that at the inside diameter due to the flange rotation. It is also found from the leakage test results and the FEM calculations that the sealing performance of the bolted flange connections with metal flat gasket is better than that of the metal gasket in platen device tests,. In addition, the contact stress in the joints with RTJ (ring type joint) gasket is examined and 4 stress peaks on the oval type and 8 peaks on the octagonal type are found. From the obtained results, a method for determining the bolt preloads in the bolted joints using flat metal gaskets and RTJ gaskets under internal pressure is proposed taking account the given allowable leak rate. Finally, the leak rates for bolted flanged connections tightened under internal pressure are compared with the experimental results. The new method can be proposed for determining the bolt preload for bolted flange connections with metal gaskets under internal pressure at room temperature.
Optimization of Hyper Compressors Configuration and Related Plant Arrangement
Authors: Maggi Carmelo , Tognarelli Leonardo , Giorgetti Stefano
Published: November 2015

A good design of hyper compressors is heavily dependent by the good understanding of all critical aspects of the LDPE plant and on the implementation of appropriate technical solutions, during the design phase, to identify and resolve problems that may arise during the operation of the plant.

The various aspects have to be investigated keeping in mind to reach an optimum performance in agreement with the customer’s requirements.

The real effort is starting at the first design stages where all different departments are involved for dynamic loads acting on the foundation, the torsional analysis involving the motor supplier and the pulsation/vibration considerations interfacing the engineering company, the suppliers of high pressure equipment and the end users.

All the stress levels, the pulsation and vibrations have to be minimized. Such results are influenced by the layout of the plant and the arrangement of the cranks of the compressor’s crank-shaft.

This latter decision can improve the pulsation level, but affect the loads on the foundations.

Here is the optimization of some technical aspects to be faced with the approval of all actors involved.
Qualification, Condition Monitoring, and Management of Ageing of Low Voltage Cables in Nuclear Power Plant
Authors: Kang Ki Sig
Published: November 2015

The International Atomic Energy Agency (IAEA) organized an international Coordinated Research Project (CRP) on qualification, condition monitoring, and management of low voltage cables for life management in nuclear power plant. A total of 16 organizations from Technical Service Organizations (TSOs), and Research & Development Organization participated in the CRP and tested and presented their experimental results. The CRP members are actively engaged in providing cable samples, thermal and radiation ageing of cables, and electrical, mechanical, and chemical testing of cables samples.

Preliminary analysis of the test data received show that, for some of the Condition Monitoring (CM) methods, good correlation is observed with ageing time and there is consistency in measurements between the different test labs carrying out the tests. The level of correlation with ageing time and the degree of variability between labs is dependent on the material being tested and the CM method being used.
Fracture Characteristics of 9%Ni Steel at Low Temperature
Authors: Xiong Qingren , Huo Chunyong , Gong Shaotao , Luo Jinheng , Zhang Jiming , Li He
Published: November 2015

The fracture characteristics of several types of tensile specimens of 9%Ni steel at low temperature was studied, and the Notch (Crack) Sensitivity and Notch (Crack) Relative Strength decreased (increased) Ratio of notch (crack) specimen were studied, while the crack preparation method of the crack specimen was discussed. The results indicate that the Notch (Crack) Sensitivity and Notch (Crack) Relative decreased (increased) Ratio can be used to evaluate the low temperature low stress brittle fracture resistance of the material. 9%Ni steel has good brittle fracture resistance at low temperature. The crack preparation principle of the crack tensile specimen was put forward.
Hydrogen Transport and Hydrogen-Assisted Cracking in SUS304 Stainless Steel During Deformation at Low Temperatures
Authors: Zhang Lin , An Bai , Iijima Takashi , San Marchi Chris , Somerday Brian
Published: November 2015

The behaviors of hydrogen transport and hydrogen-assisted cracking in hydrogen-precharged SUS304 austenitic stainless steel sheets in a temperature range from 177 to 298 K are investigated by a combined tensile and hydrogen release experiment as well as magnetic force microscopy (MFM) based on atomic force microscopy (AFM). It is observed that the hydrogen embrittlement increases with decreasing temperature, reaches a maximum at around 218 K, and then decreases with further temperature decrease. The hydrogen release rate increases with increasing strain until fracture at room temperature but remains near zero level at and below 218 K except for some small distinct release peaks. The MFM observations reveal that fracture occurs at phase boundaries along slip planes at room temperature and twin boundaries at 218 K. The role of strain-induced martensite in the hydrogen transport and hydrogen embrittlement is discussed.
Creep Crack Growth Testing Under Secondary and Combined Loading
Authors: Kapadia P. , Davies C. M. , Dean D. W. , Nikbin K. M.
Published: November 2015

Two novel fracture mechanics specimens were developed to enable creep crack growth (CCG) studies, under secondary and combined loading, to be carried out in laboratory controlled environments. Test samples were produced by the insertion of wedges into the mouths of C(T) specimens such that the geometrical misfit of the wedge induced on effective residual stresses. It is shown that the extent of crack tip plasticity generated during wedge insertion was limited which made these specimens ideal for CCG testing under secondary loading. Samples were also made by strategically placing electron beam welds in C(T) specimens, such that the weld induced residual stresses provided the crack driving force in subsequent CCG tests.

These specimens were used to perform crack growth studies under secondary and combined loading conditions in Type 316H stainless steel at 550°C for up to 1,300 h, where crack extensions of up to ≈5 mm occurred. The experimental results are presented and compared to relevant CCG tests published in literature. It is shown that CCG testing under secondary and combined loading conditions requires the creep ductility of the material to be sufficiently low to ensure crack initiation occurs. A low creep ductility was achieved in this study by uniformly pre-compressing the material to 8% plastic strain.
Mechanical and SCC Behavior of an API5L Steel Casing Within the Context of Deep Geological Repositories for Radioactive Waste
Authors: Bumbieler F. , Necib S. , Morel J. , Crusset D. , Armand G.
Published: November 2015

Andra, the French national radioactive waste management agency, is in charge of studying the possibility of disposal of High Level activity Wastes (HLW) in deep geological repositories. The concept of HLW cells consists of horizontal micro-tunnels of about 0.7 m in diameter, equipped with a steel casing. In order to ensure the reliability of the casing, particularly with respect to Stress Corrosion Cracking (SCC), several in-situ experiments dedicated to the analysis of its short term mechanical and corrosion behavior have been performed at Andra’s Underground Research Laboratory (URL) as well as in surface laboratory.

Reduced and full scale in-situ experiments consisting of equipping boreholes parallel to the major horizontal stress (σH) with instrumented steel tubing, have been performed to analyze the mechanisms involved in the casing/rock interface. The main characteristics of the short term mechanical load applied by the rock have been determined from local strain and convergence measurements. Although in-situ stress is isotropic in the section of boreholes parallel to σH, measurements exhibit a strongly anisotropic load.

SCC experiments conducted on different steel grades, in contact with the clay host rock containing CO2/H2 revealed that general corrosion is the main type of corrosion expected for steel casings.

However, the selected steel casing must have a sufficiently high yield strength (above 400 MPa) to reduce the risk of early stage plasticity due to host rock anisotropic convergence and thus to overcome SCC. API5LX65 steel seems to meet both mechanical and corrosion requirements, therefore being likely the appropriate material for the manufacture of the casing.
Innovative Repair of a Holed Through Pressure Vessel
Authors: Taagepera Jaan , Sparkman Barry , Ostrikoff Ryan
Published: November 2015

A trayed column at an operating facility suffered a loss of containment incident and was shut down. The damage to the steel is thought to have been caused by loose tray components which rattled around and eventually wore through the shell. An initial repair plan involving welded repairs was proposed. This plan would entail a field post weld heat treat (PWHT) due to the process environment of the vessel. Upon further developing the PWHT plan it was determined that this approach was costly and would have excessive lost profit opportunity (LPO) due to the time it would take to execute and the criticality of this vessel to plant operations. Instead, a second approach involving no field welding was devised, vetted, fabricated, and implemented. The facility was able to restart the process, saving several days of production. A permanent repair or replacement will be planned and implemented at the next planned shutdown.
Equi-Biaxial Loading Effect on Austenitic Stainless Steel Fatigue Life
Authors: Bradaï S. , Gourdin C. , Courtin S. , Le Roux J. C. , Gardin C.
Published: November 2015

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures.

In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension.

Two calibration tests (with strain gauges and image correlation) were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship.

Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to −1.

The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent.

These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components.
Buckling of a Flat Plate in a Confined Axial Flow
Authors: Adjiman Julie , Doaré Olivier , Moussou Pierre
Published: November 2015

Static instability of flexible structures forced by a parallel flow, a.k.a. divergence, has been the subject of a relatively small amount of studies, unlike flutter. In order to prepare future studies of the collective behaviour of several slender structures coupled by the fluid in axial flow, the canonical case of a flat flexible plate clamped at both ends is investigated numerically and experimentally. The onset of divergence is determined throughout a series of calculation of the fluid forces generated by a prescribed deformation of the plate. Using the Galerkin method, these fluid forces are expanded in the basis of the natural modes; they exactly balance the mechanical forces when the fluid velocity reaches the instability threshold. The instability velocity can be determined by an eigenvalue calculation involving the fluid force expansion and the modal stiffnesses of the plate. Comparisons are provided with 2D analytical calculations and with an experiment performed with a 0.3m×0.03m mylar plate at Reynolds numbers varying between 104 and 105. A fair agreement is observed between the 3D potential calculation and the experiments, whereas the 2D analytical solution underestimates the instability velocity by a factor higher than 2.
Disposition Curves for Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels in Light Water Reactor Environments
Authors: Eason Ernest D. , Pathania Raj
Published: November 2015

This paper presents irradiation-assisted stress corrosion cracking (IASCC) disposition curves developed in a multi-year international data collection, data review and modeling project. More than 800 IASCC crack growth rate (CGR) data points were collected from six laboratories worldwide, and an international panel of experts reviewed and ranked the data. The better-ranked data were used to calibrate empirical models for IASCC CGR in boiling water reactor (BWR) normal water chemistry (NWC) and hydrogen water chemistry (HWC) environments and in pressurized water reactor (PWR) primary water environments. The mean models were shifted upward to the 75th percentile of the calibration data for use as crack disposition curves. The disposition curves are presented in this paper and compared with data used for fitting and data not used for fitting, including field data from BWR core shrouds and additional laboratory data. The paper is intended as a basis document for possibly incorporating the new disposition curves in the ASME code.
Structural Design, Manufacturing and Maintenance Technology of Flange Seal for Pressure Equipment Based on Leak Rate Control
Authors: Xuedong Chen , Jun Cui , Yunrong Lu , Zhichao Fan
Published: November 2015

In recent years, Chinese petrochemical plants have been continuously developing towards the direction of extreme conditions such as high temperature, high pressure, aggressive medium, large scale, etc. Once the seal structure of the pressure equipments for petrochemical plants leaks, it will not only cause material loss and nonscheduled shutdown, but also may cause disastrous accidents such as fire, poisoning, environment pollution, personal casualties, etc. This paper focuses on the flange seal structure of pressure equipment for petrochemical plants, makes comparison analysis of the standards/codes of different countries, points out the deficiency of Chinese current standards/codes and gives the advice that controlling leak rate of volatile organic compounds (VOCs) to 2×10−5mg/s • mm as the target to conduct relevant research on design, manufacture, installation and maintenance of flange seal that satisfies leakage rate control requirement and improvement of design standard.
Effect of the Shapes of Diversion Umbrellas on Temperature Field in a Large Spherical Tank During Heat Treatment Processes
Authors: Ji Fang , Wang Xiaomei , Deng Guide , Feng Jingliang , Liang Haifeng
Published: November 2015

Internal combustion method is widely used to reduce residual stress of large spherical tanks in China, when post weld heat treatment of the spherical tanks is required. During the heat treatment processes diversion umbrellas set in the spherical tanks can be utilized to drop the maximal difference of wall temperatures of the spherical tanks. Numerical simulation based on Fluent software was carried out to study the effect of an A-shaped diversion umbrella and three V-shaped diversion umbrellas with different angles on internal flow and wall temperatures of a 10000 m3 spherical tank. The results show that the V-shaped diversion umbrellas have better performance than the A-shaped one, but the angles of the V-shaped diversion umbrellas from 100° to 140° have little effect on maximum wall temperature differences of the spherical tank during the heat preservation stage of the heat treatment processes.
An Experimental Investigation of Added Mass and Damping in Submerged Pipework
Authors: Goyder Hugh
Published: November 2015

Oil and gas pipework located on the sea floor may sometimes suffer from vibration and possible failure due to fatigue. The vulnerable pipework is usually the small diameter (typically 2 in) pipes in manifold systems. In order to assess this pipework for vibration it is necessary to know the natural frequencies and damping which are significantly influenced by the surrounding fluid. Measurements have been made on an L-shaped pipe to determine how it is affected by the fluid. Interestingly the effect on damping is small. Consequently experiments have also been performed to see the effect of adding vanes to the pipe. This provides a non-linear form of damping. Special signal processing methods have been developed to investigate this damping effect. The paper presents values for damping for pipes with and without vanes. The effect of the vanes is to significantly increase the damping.
Thermal-Structure Analysis and Engineering Calculation for Double Tubesheets of Heat Exchanger
Authors: Zhu Guodong , Shou Binan
Published: November 2015

Structure’s features and current engineering design situation of double tubesheet are introduced in this paper. TEMA code plays an important role in double tubesheet design, but no more information concerning how to get metal temperature is presented in TEMA code. Engineering calculation shows that the temperature distribution in double tubesheet does not meet the hypothesis in TEMA code completely. In this paper, the thermal-field feature is shown by finite element analysis, important factors of boundary conditions such as contact resistance, slot air etc. are put forward, which will affect thermal-analysis of double tubesheet. It is pointed out that thermal-field analysis is the significant step in design of double tubesheet. It was found that the total heat transfer effect in expansion joint has greater influence on stress distribution. An example of equivalent coefficient of heat conductivity method based on thermal-structure coupling is presented to demonstrate a simplified boundary treatment method in expansion joint between tubes and sheet. This paper gives suggestions for double tubesheet design finally.
A Comparison of Forces in Two- and Three-Dimensional Flow Past an Oscillating Cylinder
Authors: Peppa Sofia , Kaiktsis Lambros , Frouzakis Christos , Triantafyllou George
Published: November 2015

DNS results are presented for three-dimensional flow past a circular cylinder forced to oscillate both in the transverse and in-line direction with respect to a uniform stream, at Reynolds number equal to 400, and are compared against simulation results for two-dimensional flow. The cylinder follows a figure-eight motion, traversed either counter-clockwise or clockwise in the upper half-plane for a flow stream from left to right. The transverse oscillation frequency is equal to the natural frequency of the Kármán vortex street. The Navier-Stokes equations are solved using a spectral element code, and the forces acting on the cylinder are computed for both three- and two-dimensional flow. The results demonstrate that the effect of cylinder oscillation on the flow structure and forces differs substantially between the counter-clockwise and the clockwise oscillation mode. For the counter-clockwise mode, forcing at low amplitude decreases the flow three-dimensionality, with the wake becoming increasingly three-dimensional for transverse oscillation amplitudes higher than 0.25–0.30 cylinder diameters, with corresponding discrepancies in forces with respect to two-dimensional flow. For the case of clockwise mode, a strong stabilizing effect is found: the wake becomes two-dimensional for a transverse oscillation amplitude of 0.20 cylinder diameters, and remains so at higher amplitudes, resulting in nearly equal values of the force coefficients for three- and two-dimensional flow.
Burst Pressure Prediction of Cracked Steam Generator Tube Using FE Damage Analysis
Authors: Jeon Jun-Young , Kim Yun-Jae , Kim Jin-Weon
Published: November 2015

This paper predicts burst pressures of the steam generator tubes with multiple cracks using finite element (FE) damage analysis. Alloy 690(TT) tube (the outer diameter of 19.05 mm and the thickness of 1.07 mm) widely used in the nuclear power plant is considered in this study. Ductile failure at each element is predicted with the damage model known as ‘multi-axial fracture strain model’ as well as crack propagation is simulated by stress reduction technique in the FE analysis. Simplified ductile damage model for Alloy 690(TT) are determined using tube tensile test data and elastic-plastic FE analysis. FE damage analysis results are sensitive to the element size used in the crack propagation region. Using notched tube fracture test data, proper element size for Alloy 690(TT) is found. Single, collinear, parallel, non-aligned axial-cracks are considered in the simulations and the predicted burst pressures are compared with burst test data.
Study on the Safety Integrity of the Pressure Relief Capacity of Pressure Bearing Systems With Relief Characteristics Consideration
Authors: Zhu Jianxin , Fang Xiangrong , Kang Haizhou , YunRong Lu , Xuedong Chen
Published: November 2015

The relief characteristic of safety valve plays an important role on system relief capacity. Based on the analysis of the influence of setting pressure, back pressure, discharger area on relief capacity, a relief curve development method was proposed that takes into account the backpressure based on API 520 standard. The relief curve method is then applied in the analysis of the relief capacity of pressure bearing systems. By taking into consideration the multiple pressure relief characteristics in pipe network, the safety integrity of multiple pressure reliefs was studied and an associated assessment procedure was proposed. The method and corresponding procedure are important contributions for the assessment of safety integrity of relief capacity in pressure bearing system.
Finite Element Analysis on the Application of Mini-C(T) Test Specimens for Fracture Toughness Evaluation
Authors: Takamizawa Hisashi , Tobita Tohru , Ohtsu Takuyo , Katsuyama Jinya , Nishiyama Yutaka , Onizawa Kunio
Published: November 2015

Fracture toughness evaluation by the Master Curve method using 4-mm-thick miniature compact tension (mini-C(T)) specimens taken from the broken halves of surveillance Charpy specimens has been proposed. In the present study, we performed finite element analysis (FEA) to examine the difference in the constraint effect of the crack tip for differently sized C(T) and precracked Charpy v-notch specimens. The constraint effect of the mini-C(T) specimens in terms of the T-stress and Q-parameter was similar to that of the larger C(T) specimens. In addition, to optimize the fatigue precracking conditions for the mini-C(T) specimen, plastic zone distribution analysis was performed by FEA. Using plastic zone distribution analysis, we demonstrated that a wider machined notch and shorter fatigue precrack length than that in conventional configurations can be applied for narrow and straight notches. We also obtained the fracture toughness data for two kinds of SA533B-1 steels and one weld metal with different sizes in addition to the data obtained in our previous study. It was shown that the reference temperature To obtained from the mini-C(T) specimens was in good agreement with those from other specimens. We compared the fracture toughness data, including the plane strain fracture toughness value obtained by 4T-C(T) specimens, with T41J-based fracture toughness curves proposed in a recent study. Most of the data, including the 4T-C(T) and irradiated specimens, were enveloped by the proposed lower-bound curve.
Dynamic Stability Identification of a Full-Scale Tainter-Gate and Extension of Gate-Opening Range for Operation
Authors: Anami Keiko , Ishii Noriaki , Knisely Charles W.
Published: November 2015

To assure the complete stability and long-term safe operation of the large number of Tainter gates used worldwide, an effective method of distinguishing those gates susceptible to instability from unsusceptible gates is essential. This paper presents a case study of the dynamic stability identification of an operational Tainter gate in Japan, based on field vibration testing using steel-rod breaking excitation. First, an overview of the field vibration test and the in-water natural vibration characteristics of the gate is presented. The dynamic stability of the gate was identified from the test results in conjunction with our previously developed theoretical analysis. From the specific test data for a limited number of operating conditions, our theoretical analysis permits assessment of the dynamic stability of the gate for all operating conditions. In particular, the dynamic stability of the gate for small gate openings was confirmed, and subsequently validated by long-duration ambient excitation tests with very small gate openings. This study was the first attempt at operating the gate at openings smaller than the conventional minimum recommended opening. As a result, not only did the field test validate the gate’s reliability for long-term operation, but it also permitted an extension of the gate-opening range for operation.
Fatigue Life of Austenitic Stainless Steel in Hydrogen Environments
Authors: San Marchi Chris , Zimmerman Jonathan A. , Tang X. , Kernion Samuel J. , Thürmer Konrad , Nibur Kevin A.
Published: November 2015

Gas-handling components for high-pressure gaseous hydrogen (such as in the fuel system of fuel cell electric vehicles) are manufactured almost exclusively from austenitic stainless steels. Relatively few studies, however, have evaluated the fatigue life of this class of steels in hydrogen environments, especially at low temperature. Low temperature is important for two reasons: (1) austenitic stainless steels show an apparent minimum in tensile ductility at temperature near 220K when exposed to hydrogen environments; and (2) the service temperature range for the automotive industry is generally consider to be 233K to 358K (−40°C to +85°C). While the temperature of maximum hydrogen embrittlement from tensile tests is very near the minimum of the service temperature range, it remains unclear if the same trend applies to fatigue life properties. In this paper, we evaluate the effect of hydrogen on fatigue life of strain-hardened Type 316L. The tested alloy features a relatively high nickel content of 12 wt% and high yield strength of 590 MPa. Additionally, reduction of cost and weight of hydrogen-handling components is necessary to enhance the competitiveness of fuel cell vehicle technologies. Cost reductions can be achieved by considering alloys with lower nickel content, while higher strength materials enable lower weight. Simple estimates of cost and weight reductions that can be realized are discussed.
Effect of Aging Temperature on Fracture Toughness of Cast Austenitic Stainless Steel
Authors: Miura Yasufumi , Yamamoto Masato
Published: November 2015

In this study, fracture toughness of cast austenitic stainless steel aged at 300–450°C for up to 15000 h were investigated using fracture toughness test, Charpy impact test and indentation hardness test. Test material was statically casted grade CF-3M stainless steel. As a result of the tests, it was found that the fracture toughness and the Charpy absorbed energy tended to decrease with the increase of aging time. However, the behavior of thermal embrittlement varied at each aging temperature. In particular, the fracture toughness of the specimens aged at 300°C was almost the same as that of the unaged specimens. At elevated temperature, the differences of the fracture toughness between unaged specimens and aged specimens were smaller than that of tested at room temperature.
Web Based Software for Quick Screening of Pipework Vibration Threats in LNG Plants
Authors: Lee Gary Y. H.
Published: November 2015

Since the publication of the Energy Institute (EI) Guidelines for avoidance of vibration induced fatigue failure of pipework [1], Shell has incorporated the acceptance criteria into the design philosophy and adopted them in vibration induced fatigue best practice as an RBI (risk based inspection) module. In tandem, with a practical application of these guidelines in assessing in service pipework’s susceptibility to vibration induced fatigue using a screening methodology, a web based software called Pipework LOF was developed incorporating these assessment procedures. The software is a screening tool based on the Guidelines and Shell’s Best Practice Guidelines [2] intended for use by engineers with awareness level understanding of vibration. The results are in the form of traffic light signals providing a screening criteria to highlight hot spots (red signal pipework) in need of further inspection or evaluation to check on parameters that govern its susceptibility to vibration induced fatigue. A useful and popular function of the software is the sensitivity tab which allows for the opportunity during the assessment stage to alter certain process or mechanical parameters of the pipework to lower the Likelihood of Failure value and alter its traffic light severity. At present, this software has been rolled out to Shell’s LNG plants with good feedback and customer satisfaction. Where it has been rolled out, operating sites now have the capability to address vibration problems and do a first pass screening. Any further assessment will be more focused to tackle the source of the vibration by removing its mechanism.
Structure Design and Analysis of a Locking Band Type Quick Opening End Closure Using a New Saddle-Shaped Sealing Ring for Natural Gas Filters
Authors: Chen Ping , Zhou Shumin , Shi Ying
Published: November 2015

A quick opening closure using a new rubber sealing ring was proposed in this paper, which can be used in natural gas transmission filters. An innovative saddle-shaped sealing ring with the feature of floatability was designed for substituting of traditional rubber C-ring. A lager gap could be allowed between the door and the top flange which made the assembling and disassembling easier than before. The theory of strength calculation and check for the whole steel structure were also presented. For an actual engineering case, a device with internal diameter of DN1550 (62inches) and design pressure of 12.6MPa (1827.5psi) was designed by rule according to Chinese national standard GB150 and analyzed by FEA (ANASYS). In addition, the sealing performance was simulated by FEM analysis (ABAQUS). Finally, the prototype was produced and the experiments for its sealing and load-bearing performance using hydrostatic test and stress test were carried out successfully.
Coalescence Pressure Evaluation of Multiple Through-Wall Cracks in Steam Generator Tube Using Elastic-Plastic Finite Element Analyses
Authors: Hong Jin-Won , Choi Jae-Boong , Huh Nam-Su
Published: November 2015

During an in-service inspection, if multiple cracks have been found in a nuclear component, the crack interaction effect due to adjacent cracks should be taken into account to characterize the detected multiple cracks into equivalent single combined crack or independent single crack. However, there must be many factors to be considered to quantify crack interaction effect, many experimental and numerical works should be made to propose robust guidelines on crack interaction effect depending on material characteristics of interest.

Although many works have been made during the past few years to evaluate crack interaction effect of steam generator tubes with multiple cracks, the robust guidelines are still lacking.

In this study, systematic 3-dimensional (3D) elastic-plastic finite element (FE) analyses are performed for steam generator tubes with multiple through-wall cracks. As for geometries of multiple through-wall cracks, four different cases are considered; axial collinear cracks, axial parallel cracks, circumferential collinear cracks, and circumferential parallel cracks. The geometric variables affecting the Pc (coalescence pressure), i.e. crack length and distance between multiple cracks, are systematically varied in the present study.

Based on the coalescence pressure evaluation model proposed by authors in the previous study and the present FE results, the Pc of steam generator tubes with multiple cracks are investigated.
Experimental Investigation for Acoustic Resonance in Tandem Branches Under Each Dry and Wet Steam Flow
Authors: Uchiyama Yuta , Morita Ryo
Published: November 2015

Flow-induced acoustic resonances of piping system containing closed side-branches are sometimes encountered in power plants. In the United States, the steam dryer in boiling water reactor had been damaged by high cycle fatigue due to acoustic-induced vibration under a power uprating condition. The steam piping systems of current power plants often have nearly saturated wet steam condition. The side-branches of current power plants vary in their configuration (single, tandem, and coaxial), number, and so on. Therefore, many types of flow-induced acoustic resonance at branch piping have been investigated by many researchers. However, most of previous studies were under air flow condition and there were few previous experiments under wet steam flow. In this study, some types of the acoustic resonance at branch piping are investigated by conducting experiments under each dry and wet steam conditions. As a result, it is clarified that influence of branch configurations (single or tandem) on resonance amplitude and frequency under steam flow. In addition, their differences between dry and wet steam are discussed.
Estimation of Stress Intensity Factor for Circumferential Through-Wall Cracked Elbows Subjected to In-Plane Bending
Authors: Surh Han-Bum , Kim Jong Wook , Kim Min Kyu , Won Min-Gu , Kim Moon Ki , Choi Jae-Boong , Huh Nam-Su
Published: November 2015

The stress intensity factor (SIF) is the major fracture mechanics parameter in LEFM concept. Since the SIF can be used for not only calculation of J-integral based on the GE/EPRI and reference stress method but also evaluation of fatigue crack growth, an accurate estimation of the SIF is an important issue for the piping in nuclear power plant. Recently, there is a need to develop the SIF solution which can cover wide geometric variables since there are on-going efforts that are developing next generation reactors in Korea, which is designed to thin-walled structures. For the through-wall cracked straight pipes, many researchers have proposed the SIF solutions which can cover wide range of wall thickness. However, since only limited solutions have been proposed yet for the through-wall cracked elbows, a research related to the SIF estimation for the elbows with wide geometric variables should be performed. In this study, the extended SIF solution for circumferential through-wall cracked elbows subjected to in-plane bending is proposed as the tabulated form through the finite element (FE) analyses. Wide elbow geometries are selected to range between 5 and 50 of Rm/t and range between 2∼20 of Rb/Rm. The existing solutions are then reviewed by comparing with the FE results. Furthermore, effects of geometric variables on the SIF are addressed through systematic investigation of FE based SIF results. These investigated results are expected to contribute to the development of closed form solution for the circumferential through-wall cracked elbows subjected to in-plane bending.
Design Development of a Vacuum Vessel With Detachable Top Lid Configuration
Authors: Joshi Jaydeep , Yadav Ashish , Gangadharan Roopesh , Girish Mudalakeri , Ulahannan Shino , Reddy Vinay Kumar Abbavaram Ramakrishna , Rotti Chandramouli , Bandyopadhyay Mainak , Chakraborty Arun
Published: November 2015

In the Indian Test Facility (INTF), a Vacuum Vessel is designed to house neutral beam components to provide transmission for length of ∼20 meters which enables characterization of neutral beam parameters.

INTF Vacuum vessel is designed in cylindrical shape and has a detachable top-lid for mounting as well as removal of internal components during installation and maintenance phases of test facility. Principal challenges involved in this are designing the detachable top lid and positioning the appropriate stiffeners within the space available on the vessel for meeting functional and operational requirements of in-vacuum deflection to less than 5mm (0.196 in.) and it is limited to 1mm (0.039 in.) in certain areas on the vessel. Moreover, ASME code [3] does not have design formulation for this detachable top lid configuration directly, hence, there is a need to adopt the available recommendations ASME code [3], assess their applicability, adopt appropriate one, improvise and affect it and validate it by Finite Element Analysis (FEA).

This paper presents the comprehensive design methodology adopted for INTF Vacuum Vessel design and optimization of various parameters to meet the operational and functional requirements within the constraints of other mandatory interfaces. This paper also presents its manufacturing plan, fabrication challenges and current status of vessel fabrication.
Finite Element Analysis of Flange Joint With Single and Twin Gaskets Under External Bending Load
Authors: Nelson N. Rino , Prasad N. Siva , Sekhar A. S.
Published: November 2015

Gasketed flange joint is a vital component in pressure vessels and piping systems. Flange joint is usually subjected to bending load due to expansion, wind load, self-weight, etc. Most of the flange design methods use equivalent pressure to include the effect of external bending loads. It becomes complex when the joint is subjected to bending load at elevated temperatures, due to the nonlinear behavior of gasket material. In the present work, performance of the flange joint has been studied under external bending load at elevated temperatures. A 3D finite element model is developed, considering the nonlinearities in the joint due to gasket material and contact between its members along with their temperature dependent material properties. The performance of the joint under different bolt preloads, internal fluid pressures and temperatures is studied. Flange joint with two gaskets (twin gasketed joint) placed beside each other radially, is also analyzed under external bending moment. The maximum allowable bending moments at different internal temperatures, for single and twin gasketed joints with spiral wound gasket are arrived.
Relation Between Front-Face and Load-Line Displacements on a C(T) Specimen by Elastic-Plastic Analysis
Authors: Miura Naoki , Momoi Yasunori , Yamamoto Masato
Published: November 2015

The use of miniature C(T) specimens makes it possible for the direct determination of the reference temperature of reactor pressure vessel steels, because they can be taken from the broken halves of the Charpy specimens used for surveillance program to monitor neutron irradiation embrittlement. Fracture toughness tests using C(T) specimens usually need the measurement of load-line displacement, however, it is difficult to mount a clip gauge inside the miniature specimen due to the limitation of the specimen size. A pair of knife edges is machined at the front face of the miniature C(T) specimen to mount a clip gauge with razor blade tips, and the front-face displacement is translated to the load-line displacement. When front-face displacement measurements are made, the load-line displacement can be inferred by multiplying the measured values by the constant 0.73. This conversion factor has been simply derived from the assumption of the linear deformation around a supposed point of rotation. In this study, the conversion factor was directly evaluated by using a three-dimensional elastic-plastic finite element analysis for the miniature C(T) specimens, and the adequacy of the conversion factor was investigated.