bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Instantaneous Flow-Rate Coefficients and FIV Characteristics of Tainter Gates at Large Openings
Authors: Anami Keiko , Ishii Noriaki , Oku Tatsuya , Knisely Charles , Tsuji Takuma
Published: November 2014

Tainter gates become dynamically stable at large gate openings, even though they usually exhibit intense dynamic instability at small gate openings. To assess which factors govern this stability at large openings, model investigations were conducted. The present study focuses on discharge characteristics and hydrodynamic pressures at large gate openings. The model tests were conducted using a 1/27-scaled 2-dimensional model of the Folsom Dam Tainter gate. The instantaneous flow-rate coefficient was obtained from LDV measurements of flow velocity accompanying periodic changes in the gate opening. Measurements of the hydrodynamic pressure associated with the flow-rate variation were also used to determine instantaneous flow-rate coefficients. Comparison of the directly measured instantaneous flow-rate coefficient form LDV measurements with that obtained from pressure measurements suggests that the flow field is less receptive to disturbances due to gate motion at larger gate openings. With increased gate openings, the fluctuating fluid force acting on the gate decreases, making the gate dynamically stable.
Acoustic Analysis of a Rotary Control Valve
Authors: Bossi Filippo Carlo , Malavasi Stefano
Published: November 2014

High performance control valves may be subjected to noise problems especially when gas is the operating fluid. Depending on some geometric characteristics, the noise production can be characterized by broad band noise or tonal noise. When the latter condition occurs, the generated noise could overcome the limit of acceptance and the device does not respect the standard of usability. In a previous work, a dependency between the tonal noise and the main geometrical characteristics of a control rotary valve has been settled by experimental tests. Starting from these fluid dynamic observations in this work we coupled the modal analysis of the structure with experimental data to deeply understand this phenomenon. The natural frequencies of different perforated plates placed in a circular duct (configuration which mimics the full open control valve condition) are therefore considered to verify which of them are responsible of the tonal noise, generated by the interaction between the flow field and the acoustic one, observed in the experimental tests. To do this, the frequency modes consistent with the tonal noise generation, are numerically investigated by changing the geometrical characteristic of the device. By considering the rotary valve fully open, we especially investigated the effects of the plate thickness, the hole diameter and distribution.
Creep Deformation Analysis of Grade 91 Steels and Prediction of Creep Strength Properties
Authors: Kimura Kazuhiro , Sawada Kota , Kushima Hideaki
Published: November 2014

Creep deformation behavior was analyzed on Grade T91 steels and an empirical equation was derived to express creep strain as a function of time. Creep rupture life prediction was investigated by means of the derived empirical equation. Influence of creep rupture strain on creep rupture life predicted by the derived equation was small over a range of creep rupture strain from 0.05 to 0.30, especially creep rupture strain of 0.10 and above. Prediction accuracy of creep rupture life of the equation was better than that of creep rupture data analysis with a Larson-Miller parameter. Heat-to-heat variation of long-term creep rupture strength was appropriately observed. Minimum creep rate, onset of tertiary creep, and time to specific strain are easily predicted by the equation.
Failure Analysis Cases of Stress Corrosion Cracking in Complex Media Environments
Authors: Ai Zhibin , Chen Xuedong , Fan Zhichao , Li Rongrong
Published: November 2014

The phenomenon of stress corrosion cracking extensively exists in equipments and pipelines of process plants due to aggravated tendency of raw materials to poor quality, especially in complex media environment, the factors causing stress corrosion cracking are very complex, sometimes a certain medium plays a dominating role, sometimes several kinds of media act together, and sometimes the actions of some media change to each other in different periods. In this paper, the laws of competition, promotion or suppression among multiple mechanisms upon stress corrosion cracking due to multiple causes are described through failure analysis of stress corrosion cracking accident cases such as cracking of inner wall cladding of cyclone separator for coal chemical plant, explosion of gasification furnace for coal chemical plant, etc., and analysis and judgment methods of their dominating mechanisms, influential laws of secondary mechanisms and preventive measures are proposed.
Simulation of the Dynamic Response of a Sloshing Liquid to Horizontal Movements of the Tank
Authors: Brandely Anaïs , Schotté Jean-Sébastien , Lefrançois Emmanuel , Hagege Benjamin , Ohayon Roger
Published: November 2014

The dynamic response of a sloshing liquid to horizontal movements of a rectangular tank with a small amplitude is studied here by a numerical approach issued from a commercial CFD code. This numerical model solves Navier-Stokes equations considering a two-phase flow. In order to check the localized turbulence effects on the global fluid behavior, the averaged Navier-Stokes equations are solved with laminar option and with a k–ω SST turbulence model. The Volume Of Fluid (VOF) method is adopted to track the distorted free surface. The previous CFD solution is compared with a linearized approach based on the potential flow theory taking into account viscous effects. This model considers a single phase flow and is much less expensive in CPU time, especially thanks to the use of modal projection techniques. Both models are validated and applied on several cases. Free surface sloshing elevation and global forces, obtained for various excitation amplitudes and frequencies, are compared. Perfect and viscous liquids are considered.
Structural Design of Metallic Components in ISO 13628-7
Authors: Kirkemo Finn
Published: November 2014

ISO 13628-7 (ISO-7) for completion and workover (C/WO) riser systems was published in 2005 and adopted back by API as API RP 17G 2nd edition 2006 (identical). ISO-7 gives requirements and recommendations for the design, analysis, materials, fabrication, testing and operation of C/WO riser systems. This paper provides a brief introduction and background to some of the design and material requirements in ISO-7. The main focus is on requirements for calculation of static and cyclic (fatigue) capacities of metallic components in the C/WO riser system subjected to pressure and external loads. Some differences between ISO-7, API 6A (6A), API 6X (6X), API 17D (17D), ASME VIII Div. 3 (Div.3) and ASME VIII Div.2 (Div.2) are also included.
Large Openings in Cylindrical Pressure Vessels: An Assessment Based on Absolute Size
Authors: Chandiramani Dipak K. , Gopalakrishnan Shyam , Mathkar Ameya
Published: November 2014

Clauses UG-36 through UG-43 of ASME Section VIII Division 1 [1], describe the method of calculating the adequacy of compensation of openings in shells, using an area-replacement method. The method is based on determining and suitably replacing the missing metal area along any section, with metal available or provided, within the limits of reinforcement on the shell and nozzle.

Clause UG-36 (b) of ASME Section VIII Division 1 provides limits on the size of the opening for applicability of Clauses UG-36 through UG-43. If these limits are exceeded, supplemental rules of Clause 1-7 of Appendix 1 need to be complied with or alternatively the rules of Clause 1-10 of Appendix 1 may be applied.

The rules for large openings as stated in the Code are not dependent upon the absolute size of the nozzle and shell. For example, same calculations would be required to be carried out whether a nozzle of NPS 1 is attached to a shell of NPS 1.5 or a nozzle of NPS 16 is attached to a shell of NPS 24.

The work presented in this paper is an attempt to determine whether the additional calculations in Clause 1-7 need to be carried out for finished openings exceeding the limits of UG-36(b) irrespective of the absolute size of the nozzle and shell. This has been done by carrying out calculations for a wide range of nozzle-shell combinations and comparing the results so obtained with the results of a Finite Element Analysis.
Stress Analysis and Sealing Performance Evaluation of Bolted Pipe Flange Connections With Smaller and Larger Nominal Diameter Under Repeated Temperature Changes
Authors: Omiya Yuya , Sawa Toshiyuki
Published: November 2014

Pipe flange connections with gaskets in chemical plants, electric power plants and other industrial plants are usually exposed to elevated internal pressure with cyclic thermal condition. It is important to investigate the sealing performance of pipe connections under long term severe thermal exposure swings to ensure operational safety. In this study, the effects of cyclic thermal conditions on the sealing performance and mechanical characteristics in larger and smaller nominal diameter of pipe flange connection are examined using FEM calculations. Helium gas leakage is predicted using the contact gasket stress obtained from the FEM results. On other hand, the leakage tests using the smaller nominal diameter of pipe flange connection were conducted to measure the amount of helium gas leakage and to compare with the predicted amount of gas leakage. As the results, the contact gasket stress distributions were changed dramatically under cyclic thermal condition and elevated internal pressure. In the pipe flange connections with smaller nominal diameter, the contact gasket stress was the smallest in the restart condition. On other hand, the minimum contact gasket stress in the pipe flange connection with larger nominal diameter was depending on the materials of connection. In the pipe flange connection with larger nominal diameter, the contact gasket stress distributed and changed in the radial direction due to the flange rotation. A fairly good agreement was found between the experimental leakage result and predicted leakage results.
Effect of In Plane and Out of Plane Bending on Weld Residual Stresses
Authors: Bonnaud Etienne , Gunnars Jens
Published: November 2014

When manufacturing cylindrical or conical structures from metal plates, residual stresses originate from both welding and bending. The sequence in which these fabrication steps are carried out is essential as it can radically change the final distribution of residual stresses. To study this effect, detailed welding and bending simulations have been performed on both axial and circumferential X-welds of a 316L stainless steel cylindrical vessel. Bending after welding is shown to reduce residual stresses markedly more than bending before welding and the benefit on critical crack size is illustrated by a Fracture Mechanics analysis.
Thermo-Mechanical Numerical Analysis in Steel Plates Butt Welded
Authors: Martinez Manuel , Gonzalez Marco , Barragan Antonio
Published: November 2014

In this work, 2D and 3D Finite Element models to simulate the temperature distribution and residual stress in butt-welded steel plates with the aid of computer simulation, using the commercial software Abaqus®, are developed. The work is carried out in two stages: 1) An analysis of heat transfer in transient state regardless of the structural part is performed, and 2) Thermal and structural responses are sequentially coupled in a thermo-mechanical process simulation in order to determine the final residual stresses induced during progressive heating and subsequent cooling. The results show that for 2D and 3D models the residual stress distribution for relatively thick plate welding can be characterized by a state of stresses plane, dominated by longitudinal stresses. The main difference between both models occurs for transverse stress σY where the values for 3D are significantly greater than for 2D.
A Study on Development of Optimum FE Analysis Model on Welding Stress Analysis for CEDM Penetration Nozzle
Authors: Ryu Tae-young , Choi J. B. , Lee Kyoung S.
Published: November 2014

For decades, the PWSCC on the penetration nozzles like BMI and CEDM nozzles are widely occurred all around the world. The PWSCC is dependent on the tensile stress condition, specific materials and chemical environment. Therefore, to evaluate the severity of the PWSCC, prediction of the welding residual stress on the J-groove welding part in the penetration nozzles is essential. Residual stress can be measured by using experimental methods like deep-hole drilling and X-ray diffraction, etc. However, the results of experimental methods are quite doubtable and these methods are hard to apply on the actual equipment. Therefore, computational approach like the FE analysis has been considered. The FE analysis results are very sensitive to the FE model density and analysis conditions. In this paper the optimized FE model for the residual stress analysis will be developed in the case of CEDM penetration nozzle. The optimized parameters contains bead number and mesh density. The bead numbers along the longitudinal and circumferential directions are considered and the mesh density in each the bead is also considered. The model will be verified by numerical error control.
Through-Wall Bending Stress Equations for the Design of Safety-Related Buried Piping
Authors: Marohl Michael P. H. , Moenssens Mark A.
Published: November 2014

In the design of buried piping, resistance of the pipe-soil system to the applied vertical load is a significant design consideration. Application of a resultant vertical load perpendicular to the longitudinal pipe axis results in ovalization of the pipe, with resulting vertical pressures in the soil bedding and horizontal pressures in the soil backfill adjacent to the pipe, as well as internal forces and moments in the pipe wall. For pipes that are relatively rigid compared to the soil backfill, the developed internal forces in the pipe hoop and resulting internal moments in the wall tend to be higher than a more flexible pipe with a stiffer soil backfill. For many buried pipes, design to consider through-wall bending stress is not included and consideration of a buckling allowable is considered adequate. However, for safety-related pipes, investigation to include the through-wall bending stress is considered important.

Although estimation of the internal hoop stresses in a buried pipe is relatively straight forward, several different methodologies are presented in various industry documents for calculating the through-wall bending stress due to the resulting internal moments. Recommended approaches for calculating the through-wall bending stress vary depending on the pipe material, wall thickness, wall type, deflection, burial condition and other factors. A sensitivity study comparing various theories estimating the through-wall bending stress in a buried pipe subject to external loads with a vertical resultant force is performed. The range of variables is assessed to determine the applicability of the results to typical safety-related piping. This study presents the results of the sensitivity study and provides recommendations for the calculation and incorporation of through-wall bending stress in the design of buried safety related piping.
Predictions of Residual Stresses and Deformations in Pipe Bends Produced Using Cold, Warm and Induction Bending Processes
Authors: Ding Y. , Yetisir M. , Khajehpour S.
Published: November 2014

Cold bending, warm bending (bending with local heating) and induction bending are three manufacturing processes widely used to produce pipe bends. The cold and warm bending processes have been used for the fabrication of carbon steel feeder bends for CANDU® reactors, and the induction bending process was considered for the fabrication of stainless steel feeder pipes for an advanced CANDU reactor. Bending processes result in plastic deformation, and inevitably, introduce residual stresses in the deformed pipes. Residual stresses in feeder bends are believed to be a very important contributing factor in feeder cracking. Different bending processes result in widely different residual stress patterns and magnitudes in pipe bends. Hence, it is important to understand the effect of bending processes and the process parameters used on the residual stress distribution in the bent pipes. Numerical models have been successfully developed to predict the residual stresses and the deformed shapes induced by cold, warm and induction bending processes. This paper provides a comprehensive review of the predicted residual stress distributions, ovality and wall-thickness variations of the cold, warm and induction bends. The predicted results were compared to earlier measurements of spare CANDU feeder bends and test bends. Advantages and disadvantages of the three bending processes are summarized. Numerical approaches for the modeling of residual stresses could be of benefit to engineering estimates of residual stresses in feeder pipes for safety evaluation of nuclear reactors.
A Parametric Study of Rm/T and Weld Repair Effects on Through-Wall Axial and Hoop WRS Distributions in BWR Nozzle Dissimilar Metal Welds
Authors: Novotny Tyler D. , Oberembt Clark J. , Qin Minghao
Published: November 2014

Weld residual stress (WRS) distributions are an important input into fracture mechanics evaluations necessary to determine the residual lives of dissimilar metal welds (DMWs). Since the DMW geometry and the presence or absence, size, and location of weld repairs is nozzle specific, finite element WRS analysis is often used to predict through-wall weld residual stress distributions. It is important to note that despite small differences in plant specific geometry or weld location specific weld repair geometry there are substantial similarities between the configurations that have been evaluated in the numerous weld specific finite element WRS analyses documented in the literature. Important insight can be gained from parametric studies of simplified geometries in order to understand the significance of different parameters on the resulting WRS distributions. The results of such studies can allow engineers to focus resources on refining accuracy of critical inputs and to support simplified model development suitable for incorporation into design and fitness for service codes. This paper documents the results of various studies performed to validate the ability to use a simplified pipe-to-pipe model for simulating relative effects on through-wall WRS distributions of pipe and weld repair geometry, investigate the effect of pipe mean radius to wall thickness ratio, weld repair depth (ID and OD), and weld repair sequence. Fifteen cases are analyzed. The dimensions selected for each case span a range of wall thickness, Rm/t and depth of repair values representative of typical Boiling Water Reactor (BWR) nozzle DMWs. The results are used as input into a simplified WRS model presented in a separate paper [17].
On the Flow-Excited Acoustic Resonance of Isolated Cylinder(s) in Cross-Flow
Authors: Arafa Nadim , Mohany Atef , Hassan Marwan
Published: November 2014

The flow-excited acoustic resonance of single and multiple cylinders in cross-flow is investigated experimentally. The effect of the cylinder(s) proximity to the acoustic particle velocity nodes of the first three acoustic cross-modes is presented. During the experiments, the acoustic cross-modes of the duct housing the cylinders are self-excited. For the case of a single cylinder, it is observed that although the cylinder’s location doesn’t significantly affect the vortex shedding process, it affects the mechanism of the flow-excited acoustic resonance and the levels of the generated acoustic pressure. When the cylinder is shifted away from the acoustic particle velocity anti-node of a specific acoustic cross-mode, a combination of cross-modes is excited with intensities that seem to be proportional to the ratio of the acoustic particle velocities of these modes at the cylinder’s location. For the case of two and three isolated cylinders positioned simultaneously side-by-side in the duct, it is observed that when the cylinders are positioned at different acoustic particle velocity anti-nodes of different cross-modes, the intensities of the excited acoustic resonance of these cross-modes are amplified compared to those with single cylinder. Nevertheless, when one cylinder is positioned at the acoustic particle velocity anti-node for a specific cross-mode and another cylinder is positioned at its acoustic particle velocity node, i.e. a cylinder that should excite the resonance and another one that should supress it, respectively; the excitation always takes over and the resonance occurs. Moreover, as the cylinder moves closer to the duct’s wall, the Strouhal number value decreases due to the interference between the wake of the cylinder and the wall. Therefore, the acoustic resonance for this case occurs at slightly higher flow velocities.
A Unified Constitutive Model for High Temperature Multiaxial Creep-Fatigue and Ratcheting Response Simulation of Alloy 617
Authors: Islam Nazrul , Quayyum Shahriar , Hassan Tasnim
Published: November 2014

The study is developing a unified constitutive model for Alloy 617 which is the prime candidate material considered for intermediate heat exchanger (IHX) of next generation nuclear power plant. Alloy 617 can experience long term exposure to elevated temperatures as high as 950°C, however, the ASME design code (Subsection NH) does not include design provisions for this temperature range. In addition, the Draft Alloy 617 Code Case specifies that the inelastic design analysis for temperatures above 649°C must be based on unified constitutive model. Therefore, this study focuses on developing a unified constitutive model to simulate high temperature uniaxial and multiaxial creep-fatigue and creep-ratcheting responses of Alloy 617. As multiaxial response simulation is a key factor for design-by-analysis of IHX, a set of biaxial tests with varying degrees of loading non-proportionality has been performed at different steady temperatures within 25°C–950°C, and with different strain rates and strain ranges. From the tests, it has been observed that temperature, strain rate, strain ranges and non-proportionality of loading path greatly influences the creep-fatigue and creep-ratcheting responses of Alloy 617. Thus, development of a unified constitutive model considering dependence of these parameters is required. The current Chaboche viscoplasticity model with static recovery term can simulate uniaxial responses very well but it overpredicts biaxial ratcheting responses. Hence, a modified Chaboche model has been developed to improve biaxial ratcheting simulations. Multiaxial modeling features of non-proportionality and ratcheting are investigated. These modeling features and improved response simulations are presented in the paper.
Flow-Induced Vibration Tests of Research Reactor Fuel in the Chalk River Single Channel Test Rig
Authors: Janzen V. P. , Smith B. A. W. , Fisher N. J. , Taylor C. E. , Whan T.
Published: November 2014

A series of out-reactor vibration and endurance tests have been carried out in support of design changes for nuclear fuel used in a 30 MWt research reactor. Vibration frequencies and amplitudes were measured in and out of flow, and the effect of proposed design changes on vibration levels was determined. Component wear was measured following endurance tests, and the fretting-wear performance was predicted for extended periods of time in operation. Based on the calculated maximum wear depth versus time, external wear of bundle wear pads due to flow-induced vibration is not expected to affect the function of the fuel-bundle endplates and spacers. Various aspects of this work are generally applicable to similar tests of power-reactor and other research-reactor fuel.
Low-Cycle Fatigue Failure Responses of Long and Short Radius Elbows
Authors: Fenton Matthew , Hassan Tasnim
Published: November 2014

Low-cycle fatigue experiments of short radius elbows were conducted and the recorded responses were compared with the long radius elbow responses from literature. Elbow components are widely used in piping systems in energy and chemical industries; however, the fatigue failure prediction of elbows remains a challenge. Additionally, the selection criteria between a long or short radius elbow merely considers the long radius elbow as standard, and to use short radius elbows only when spacing requirement prohibit a long radius elbow. The ASME design code provides some guidance for fatigue design of elbows but it is not known if the short radius elbow fatigue failures can be predicted. Hence, low-cycle fatigue experiments of short radius elbows were conducted and force, displacement, and strain data under cyclic loading were recorded. The recorded fatigue responses were critically analyzed for understanding the difference in fatigue lives between long and short radius elbows. These results are presented and discussed in the paper.
Update on European Standards and Guidelines for Managing the Integrity of Bolted Joints
Authors: Noble Robert
Published: November 2014

2013 saw a number of significant issues of Standards and Guidelines associated with Bolted Joints and 2014 will see the release of “The Energy Institute Guidelines for the Management of Integrity of Bolted Joints in pressurized systems.” The first guidelines were introduced in 2002 in response to a drive to reduce Hydrocarbon leakage in the UK Offshore Industry; the third edition sees the industry once again targeting Hydrocarbon Leak Reduction. This paper will give an overview of the Guidelines — and discuss the key changes on the previous versions and alignment with the recently published ASME PCC-1-2013. CEN have also been active in issuing new key documents: July 2013 saw the publication of the harmonized calculation standard. En1591-1. Late 2013 saw the training and competence standard EN1591-4 published. The paper will discuss developments in Europe with the aim of complementing and harmonizing with the work of ASME.
Comparison of Stainless Steels for High-Pressure Hydrogen Service
Authors: San Marchi Chris , Somerday Brian P.
Published: November 2014

Type 316/316L austenitic stainless steels are considered the benchmark for resistance to hydrogen embrittlement in gaseous hydrogen environments. Type 316/316L alloys are used extensively in handling systems for gaseous hydrogen, which has created engineering basis for its use. This material class, however, is relatively expensive compared to other structural metals including other austenitic stainless steels, thus the hydrogen fuel cell community seeks lower-cost alternatives. Nickel content is an important driver of cost and hydrogen-embrittlement resistance; the cost of austenitic stainless steels is largely determined by nickel content, while high nickel content generally improves resistance to hydrogen embrittlement. These circumstances create the perception that less-expensive grades of austenitic stainless steels are not appropriate for hydrogen service. While other grades of austenitic stainless steels are generally more susceptible to hydrogen embrittlement, in many cases the hydrogen-affected properties are superior to the properties of materials that are considered acceptable, such as aluminum alloys and A-286 austenitic stainless steel. In this paper, the properties of a variety of austenitic stainless steels are compared with the aim of promoting the consideration of a wider range of austenitic stainless steels to reduce cost and reduce weight of high-pressure components for hydrogen service.
Flow-Induced Vibration of an Elastically-Mounted Cylinder Undergoing Forced Rotation
Authors: Wong Ka Wai Lawrence , Lo Jacono David , Sheridan John
Published: November 2014

Flow-induced vibration (FIV) has received considerable attention in recent decades. However, investigations of elastically-mounted cylinders undergoing forced rotation are limited. The present study aims to experimentally investigate the vibration response of a circular cylinder undergoing free transverse oscillations and forced rotation at a low mass ratio. The experiments were conducted in a free surface water channel on a cylinder attached to a motor and supported on an air bearing to provide low damping transverse oscillations and cylinder rotation. The amplitude response at constant rotation rates (α) of α = 1, 2 exhibits free oscillation response behaviour. Held at a constant reduced velocity, increasing α did not monotonically decrease the amplitude response of the cylinder. At reduced velocities associated with the upper branch response the oscillation amplitude increased until α = 2. At α = 2, the peak amplitude increased by 57% over a non-rotating cylinder. The cylinder’s oscillation frequency response is similar to that of a non-rotating cylinder with marginal reduction.
A Non-Isotropic Approach to Predict Fatigue Crack Growth of Embedded Flaw in Engineering Criticality Assessment
Authors: Carlucci Antonio , Li Jun , Mcirdi Kamel , Auvret Pierre-Louis
Published: November 2014

An analytical method to predict the fatigue crack growth of embedded flaw in metallic structure has been established by using a non-isotropic approach. Within Engineering Criticality Assessment, the embedded flaw is considered as planar elliptical defect located inside of structure wall thickness. In the analytical standard assessment procedure [1], since only the minor ligament (the shortest distance between material surface and embedded crack tip) is applied to calculate the stress intensity factor, the fatigue crack propagation prediction in height direction is symmetrical for each side. Therefore, the crack growth is overestimated when, as it usually is the case, the embedded flaw is not centered and/or submitted to non-uniform stress range in the wall thickness of the structure.

The proposed method allows to predict the fatigue crack propagation rate in asymmetrical way, by taking into account respectively the minor and major ligament, in order to remove the above conservatism and consequently to improve the ECA results for embedded defects.
Fitness-for-Service Fracture Assessments of Dissimilar Pipe Girth Welds Incorporating New Crack Driving Force Solutions
Authors: de Souza Rodolfo F. , Ruggieri Claudio
Published: November 2014

The increasing demand for energy and natural resources has spurred a flurry of exploration and production activities of oil and natural gas in more hostile environments, including very deep water offshore production. Currently, structural integrity of submarine risers and flowlines conducting corrosive and aggressive hydrocarbons represents a key factor in operational safety of subsea pipelines. Advances in existing technologies favor the use of CMn steel pipelines (for example, API X65 grade steel) clad or mechanically lined with a corrosion resistant alloy (CRA), such as Alloy 625, for the transport of corrosive fluids. This work focuses on a fitness-for-service defect assessment procedure for strength mismatched welded components incorporating new crack driving force and limit load solutions. The study broadens the applicability of current evaluation procedures for J and CTOD which enter directly into structural integrity analyses and flaw tolerance criteria to provide a fairly comprehensive body of numerical solutions for crack driving forces in mismatched girth welds with circumferential surface cracks. This investigation also provides mismatch yield load solutions which are central to accurately predict failure load in strength mismatched structures subjected to large scale plasticity and ductile behavior. An approach is utilized to analyze the potential effects of the undermatching girth weld on critical flaw sizes for a typical lined pipe employed in subsea flowlines having a girth weld made of Alloy 625.
Statistical Approach of Stress Concentration Factor (SCF) Within Pipeline Girth Welds
Authors: Auvret Pierre-Louis , Carlucci Antonio , Li Jun , MCirdi Kamel
Published: November 2014

Engineering design must take care of local peaks within stress field, in order to provide relevant forecast of material behavior. Within pipeline girth welds, pipe misalignment is an ordinary cause of significant stress concentrations. The matching of pipe ends depends of the quality of alignment procedure but it is also much influenced by pipe fabrication tolerances. In general, misalignment is estimated considering the maximal and minimal values of each pipe size according to pipe fabrication tolerances. But, in practice, the probability to get a such case is very low. This paper describes how to improve the calculation of stress concentration factor (SCF) through a statistical analysis of pipe dimensions. The use of actual pipe measurements is not necessary even if it provides better SCF estimation. Indeed the distribution of pipe size can be estimated through the fabrication tolerances which require acceptable capacities of the manufacturing system.
Optimised Neural Network Prediction of Residual Stress Profiles for Structural Integrity Assessment of Pipe Girth Welds
Authors: Mathew Jino , Moat Richard J. , Bouchard P. John
Published: November 2014

Defect assessment procedures such as BS7910, R6, FITNET and API 579-1 provide simplified estimates or upper bound profiles that can be used to characterize residual stresses present in a weld. Some of the bounding through-thickness profiles used in these procedures are designed based on expert judgment and examination of residual stress measurements that exhibit wide scatter. As a consequence, structural integrity assessment of defects in welded components can be overly conservative by a large margin, and may lead to unnecessary and costly repair or inspection. This paper presents a novel approach based on artificial neural networks to predict residual stress profiles in austenitic stainless steel pipe girth welds. The network is trained using a set of baseline experimental residual stress data and then validated using previously unseen data. The committee of networks has been optimized using a Bayesian approach and the upper bound curve is determined from the histogram network of output distributions. The performance and suitability of the neural network approach is discussed by comparison with stress profiles recommended in the R6 procedure and followed by an assessment of whether the use of neural network bounding profiles can lead to non-conservative estimates of stress intensity factor in fracture assessments.
Design and Analysis of Flanged Skirt Splices for Tall Pressure Vessel Towers
Authors: Stefanovic Radoslav , Ranieri Peter , Dorado Jose I. , Miller George
Published: November 2014

Pressure vessel towers used in the petrochemical and chemical industry are designed to accommodate numbers of internals including trays and beds resulting in tall vertical structures. Transportation of tall towers from the fabrication shop to the construction site presents challenges that can result in high transportation costs or a logistically impossible task of moving the vessel. One of the solutions to this problem is to shorten the tower for transport by cutting part of the tower skirt and welding it in the field. Depending on the location, welding on site can be expensive, labour intensive and may cause problems in the quality of the weld and the tower being out of level. Using a flanged skirt connection will reduce the field labour spent on connecting the bottom part of the skirt to the rest of the vessel. The challenge that lies in front of designers is that the current codes and available literature do not give a specific design and calculation guidance for implementing such a solution. This paper looks at different analytical methods to be used for the design of a skirt splice. Methods provided by Jawad and Farr, the Canadian Institute of Steel Construction, the American Institute of Steel Construction, and the Peterson Method from the European Commission’s High-Strength Tower in Steel for Wind Turbines (HISTWIN) are analyzed. Based on this analysis, the most optimal and safe design and fabrication methodology for implementing a Flanged Skirt Connection is proposed.
Seismic Evaluation Method for Piping Systems With Local Wall Thinning Caused by LDI
Authors: Sakai Michiya , Morita Ryo , Matsuura Shinichi , Inada Fumio , Onishi Shigenobu , Kugimoto Mitsuo
Published: November 2014

The earthquake-proof safety of piping systems with local wall thinning due to liquid droplet impingement erosion (LDI) was evaluated using a hybrid experiment which has been incorporated a numerical analysis of the whole system with a static loading test of elbow pipe model. Seismic performance effects of wall thinned elbow were clarified by comparing three cases of different thickness elbow models such as no defect, 50% defect and 75% defect. No damage was observed for in-plane and out-of-plane bending of elbows in the 75% condition under a seismic load equal to five times the design basis earthquake required to reach allowable stress level. In addition, torsion buckling occurred and through wall crack penetrated by cyclic loading under eight times large amplitude the above mentioned seismic motion.
Characteristics of Aerodynamic Sound Radiated From Two Finned Cylinders
Authors: Hamakawa Hiromitsu , Matsuoka Hiroki , Hosokai Kazuki , Nishida Eiichi , Kurihara Eru
Published: November 2014

In the present paper the attention is focused on the characteristics of aerodynamic sound radiated from two finned cylinders with tandem and staggered arrangement exposed to cross-flow. We measured the spectrum of SPL and flow velocity for the cylinder spacing ratios ranged from 0 to 1.05 in the transverse direction and the ratios from 1.24 to 6.8 in the flow direction at Reynolds number of 1.0×105−1.9×105. As a result, we found that the peak SPL and Strouhal number of vortex shedding for two finned cylinders depend on the cylinder spacing ratios as well as those for bare cylinders. The peak SPL of the spectrum varied complexly with the tube spacing ratio. The peak levels of SPL for tandem finned cylinders were approximately 8 dB lower than that for the tandem bare cylinders. At the cylinder spacing ratio of 1.24 in the flow direction, the peak SPL for two finned cylinders at the cylinder spacing ratio of 0.72 in the transverse direction was about 8 dB larger than that for tandem finned cylinders. The peak SPL depended on the spanwise correlation length of the Karman vortex formed in the near wake of the downstream of two finned cylinders.
A Piezoelectric Regenerative Damper for Low-Frequency Application
Authors: Masuda Arata , Hiraki Yasuhiro , Yamane Koki , Sone Akira
Published: November 2014

In this study, a design of a regenerative damper for low-frequency applications, such as vibration suppression of long period infrastructures, tanks and pipings, and maritime and offshore structures, is presented. In this design, the low-frequency input motion to the damper is transformed to a high-frequency motion of piezoelectric cantilever oscillators by mechanical switching, so that the input work into the damper during the loading phase induces the free vibration of the oscillator. The mechanical energy of the free vibration is converted to the electric energy by a high efficiency interfacing circuit. In this paper, a conceptual model is mathematically formulated and tested to evaluate the potential performance of the proposed idea. It is shown that the combination of the mechanical switching with a circuit switching interface technique can expect the enhancement of the energy regeneration efficiency up to 30%.
Proposal of the Screening Method for Prevention of the Accumulation of the Ratcheting Strain Derived From the Movement of the Temperature Distribution
Authors: Okajima Satoshi , Wakai Takashi , Ando Masanori , Inoue Yasuhiro , Watanabe Sota
Published: November 2014

The prevention of excessive deformation by thermal ratcheting is important in the design of high-temperature components of fast breeder reactors (FBR). This includes evaluation methods for a new type of thermal ratcheting caused by a traveling temperature distribution. Igari et al. [1] proposed a mechanism-based evaluation method to evaluate thermal ratcheting caused by temperature distributions traveling long and short distances.

In this paper, we simplify the existing method and propose a screening method to prevent thermal ratcheting strain in the design of practical components. The proposed method consists of two steps to prevent the continuous accumulation of ratcheting strain.

The first step is to determine whether all points through the wall thickness are in the plastic state. This is based on an equivalent stress, which comprises the primary stress, the thermal membrane stress, and the thermal bending stress. When the equivalent stress is less than the yield strength of the cylinder material, overall plastic deformation through the wall thickness does not occur. When the equivalent stress exceeds the yield strength in some regions of the cylinder, the ranges of these regions are measured for the second step. To prevent the acceleration of the plastic deformation due to creep, we define the upper limit of the equivalent stress based on the relaxation strength, Sr.

The second step is to determine whether the accumulation of the plastic strain saturates (i.e. if shakedown occurs). For this purpose, we define the screening criteria for the range of the plastic region. When the range of the plastic region is sufficiently small, residual stress is generated in the direction opposite to the plastic deformation direction. As a result of residual stress, further accumulation of the plastic deformation is suppressed, and finally shakedown occurs. If the range of the plastic region exceeds the defined criteria, a more detailed evaluation method (e.g. inelastic finite element analysis) may be used for the component design.

To validate the proposed method, we performed a set of elasto-plastic finite element method (FEM) analyses, with the assumption of elastic perfectly plastic material.
Application of Infrared Thermal Imaging Technology in Liquid Ammonia Storages Inspection
Authors: Liu Yan-Lei , Tao Chen , Wang Bing , Li Wei-Zhong , Xu Gen-Fu , Yu Bing
Published: November 2014

Liquid ammonia storage leakage accident occurred frequently in recent years. In this paper, the Infrared thermal imaging Technology had been presented by introducing the applications of liquid ammonia storage inspection. It was indicated that the infrared thermal imaging technology had irreplaceable advantages in equipment insulation condition assessment, funneled detection, heat level judgment, electrical equipment failure hidden. The experiments showed that infrared thermal imaging technology could provide scientific references for early diagnosis and preventive maintenance of devices. And it had widely application prospect in the ammonia refrigeration system safety inspections.
Comparison Between Cyclic Testing and Analysis of Piping Bends With Local Thinning
Authors: Reinhardt Wolf , Duan Xinjian
Published: November 2014

A series of tests on small-bore Carbon steel piping specimens with bends has been performed within the Feeder Bend Testing Program. The objective of the tests was to explore the effect of global and local wall thinning on the structural behaviour of feeder pipes in CANDU® reactors. Tests involved both cyclic and monotonic bending loading together with static pressure in order to obtain information about both the ultimate load carrying capacity and the fatigue life.

The specimens were thinned locally to below the NB-3600 pressure based wall thickness within or near the bend. Results of cyclic tests are reported and discussed. For one of the tests, a fatigue crack initiation and a fatigue crack growth analysis were performed. The results have relevance as an evaluation of the conservatism of traditional piping design methods, as well as a benchmark for fitness-for-service approaches, such as flaw tolerance evaluation.
A Round Robin Program of Master Curve Evaluation Using Miniature C(T) Specimens: 3rd Report — Comparison of T0 Under Various Selections of Temperature Conditions
Authors: Yamamoto Masato , Kimura Akihiko , Onizawa Kunio , Yoshimoto Kentaro , Ogawa Takuya , Mabuchi Yasuhiro , Viehrig Hans-Werner , Miura Naoki , Soneda Naoki
Published: November 2014

The Master Curve approach for the fracture toughness evaluation is expected to be a powerful tool to ensure the reliability of long-term used RPV steels. In order to get sufficient number of data for the Master Curve approach coexistent with the present surveillance program for RPVs, the utilization of miniature specimens, which can be taken from broken halves of surveillance Charpy specimens, is important. CRIEPI developed the test technique for the miniature C(T) specimens (Mini-CT), whose dimensions are 4 × 10 × 10 mm, and verified the basic applicability of Master Curve approach by means of Mini-CT for the determination of fracture toughness of typical Japanese RPV steels. A round robin program is organized in order to assure the robustness of the testing procedure to the difference in testing machines or operators. The first and second round robin tests (PVP2012-78661 [1], PVP2013-97936 [2]) suggested that the reference temperature T0 evaluation technique by Mini-CT specimen potentially is fairly robust in regard to difference in testing machines and operators, and gives similar loading rate dependency to the larger C(T) specimens. As the final year of the round robin program, “blind tests” were carried out. Here, detailed material information such as the type of materials, estimated T0, existing fracture toughness data for the material, were not given with the specimen, and 6 organizations independently selected the test temperature based on Charpy full curve of the tested material. The selection of test temperature has the variation of −120 °C to −150 °C among the organizations. 8 to 20 specimens in a set were subjected to the Master Curve evaluation and all the 6 organizations successfully obtained valid T0. The scatter range in T0 was at most 16 °C, which was within the acceptable scatter range specified in ASTM E1921-10e1. The selection of test temperature seems to give limited effect as like as that in larger specimens.
Estimations of C* and COD for Non-Idealized Axial Through-Wall Cracks in Cylinders Under Creep Conditions
Authors: Won Min-Gu , Choi Jae-Boong , Huh Nam-Su
Published: November 2014

The present paper provides C*-integral and COD for non-idealized through-wall cracks in cylinders under creep conditions. These solutions are based on detailed 3-dimensional Finite Element (FE) analyses which can be used for structural integrity assessment of nuclear piping. To cover a practical interest range, two types of creep conditions and two types of estimation methods were considered. Furthermore, axial through-wall crack model with internal pressure was considered. As for creep conditions, secondary creep (Norton creep), primary-secondary creep (RCC-MR creep) were considered. To estimate C*-integral and COD for non-idealized axial through-wall crack, GE/EPRI and ERS method were used and the results were compared with numerical solutions. Finally, an appropriate estimating methods for each creep condition were suggested.