bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitigating Failures in Ferritic-Austenitic Dissimilar Metal Joints in Petrochemical Industry
Authors: Penso Jorge A. , Belanger Patrick 
Published: January 2014

There are several failure mechanisms that might affect ferritic-austenitic dissimilar metal welds (DMWs) in petrochemical plants and refineries. Examples are cracking due to creep, stress corrosion cracking (SCC), sulphide SSC, thermal fatigue, brittle fracture, pitting corrosion, and hydrogen embrittlement. Of these, creep, SCC, and hydrogen embrittlement are perhaps of greater interest.
Industry has many lessons learned; however, still experiences high consequence failures. This work describes the most common failure mechanisms in dissimilar ferritic-austenitic welds and summarizes a guidance to prepare welding procedures and reduce the likelihood of failures. This guidance is based on a literature review and industry experience.
The metallurgical characteristics of the damage observed in both service and laboratory test samples indicate that creep rupture is the dominant failure mode for Dissimilar Metal Welds (DMW) in some high temperature service conditions. However, it has also been observed that temperature cycling contributes significantly to damage and can cause failure even when primary stress levels are relatively low.
Therefore, a creep-fatigue assessment procedure is required as part of a remaining life calculation. API 579-1/ASME FFS-1 2007 Fitness-For-Service standard includes a compendium of consensus methods for reliable assessment of the structural integrity of equipment containing identified flaws or damage. Part 10 of API 579-1 includes a method for protection against failure from creep-fatigue. In the assessment of DMW, a creep-fatigue interaction equation is provided to evaluate damage caused by thermal mismatch, sustained primary stresses, and cyclic secondary loads [Ref.1].
Failures due to hydrogen embrittlement cracking (HEC) mechanisms are not uncommon and are also described in this paper [Ref. 2].
Finally, a case history of a DMW failure in a steam methane furnace, which is common in the petrochemical industry, is described and shown as an example of a failure mitigation approach.
Development of BWR Steam Dryer Loading Evaluation Methods Through Scale Model Tests Under Actual Steam Conditions
Authors: Takahashi Shiro , Okuyama Keita , Tamura Akinori , Mabuchi Yasuhiro , Kubota Teppei , Yoshikawa Kazuhiro 
Published: January 2014

It has been demonstrated that intense fluctuating pressures acted on the steam dryer in a boiling water reactor (BWR) at higher velocity flows than in normal operation through actual BWR plant tests [1] and scale model air tests [2]. The cause of the dryer loading was considered as flow-induced acoustic resonance at the stub pipes of safety relief valves (SRVs) in the main steam lines (MSLs). Acoustic resonance was considered to be generated by interaction between the sound field and an unstable shear layer across the closed side branches of the SRV stub pipes.
We have started a research program on BWR dryers to develop their loading evaluation methods. Some air scale tests were conducted and those are useful for evaluation of occurrence of acoustic resonance in SRV stub pipes and characteristics of fluctuating pressure in MSLs. However, it is a possibility that differences in pressure conditions and fluid proprieties caused the dryer loading to be underestimated. In the present study, we conducted scale tests under actual steam conditions to evaluate the scale model test methods for BWR dryer loading estimation.
The Hitachi Utility Steam Test Leading facility (HUSTLE) was used for the scale model steam tests of MSLs and a steam dryer. Steam which was at the same pressure and temperature conditions as an actual BWR was used in the tests. The test apparatus consisted of the steam dryer, steam dome and 4 MSLs with 20 SRV stub pipes.
We demonstrated that acoustic resonance occurred in the SRV stub pipes and fluctuating pressure which propagated from the SRVs to the dryer caused fluctuating stress on the steam dryer at the SRV resonance frequency. The increasing of fluctuating pressure due to the double vortex mode which occurred at a Strouhal number (St) from 0.8 to 0.9 could be clearly seen in the scale model steam tests unlike in the air tests. It was possible that self excited acoustic resonance was affected by the low pressure conditions and different fluid proprieties for the scale model air tests. However, no significant influence from steam pressure was seen at more than 3MPa. Normalized fluctuating pressure was almost the same regardless of pressure. We verified that normalization by dynamic pressure in the main pipe was a reasonable approach for evaluation of fluctuating pressure in the SRV stub pipes. Increasing of fluctuating pressure due to the double vortex mode was clearly distinguished for SRV stub pipes but became smaller for MS pipes and had insignificant impact on the dryer loading.
EC FP7 Structural Performance of MULTI-METAL Component: Project Overview
Authors: Karjalainen-Roikonen Paivi , Keim Elisabeth , Gilles Philippe , Blasset Sébastien 
Published: January 2014

The purpose of this paper is to introduce a new EUROATOM project focusing on the structural integrity assessment of dissimilar metal weld. The project started in February 2012 and will last 3 years. 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). Within MULTIMETAL, the main objectives are:
- Develop a codification for fracture resistance testing in multi-metal specimens.
- Develop harmonized procedures for dissimilar metal welds integrity assessment.
The underlying aim of the project is to provide recommendations for a good practice approach for the integrity assessment (especially testing) of dissimilar metal welds as part of overall integrity analyses including leak-before-break (LBB) procedures.
The project will promote the development of a common understanding for structural integrity assessment of dissimilar metal welds (DMWs) in existing and future nuclear power plants (NPPs) in EU member states. It will provide the technical basis for the development of harmonized European codification for multi-metal components, which is currently non-existing. A trainee program will be finally developed and text book as well as learning materials will be issued. The project will interact with the European Network of Excellence NULIFE and NUGENIA.
Alternate Requirements for Protection Against Pressurized Thermal Shock (PTS)
Authors: Parker Stephen M. , Palm Nathan A. , Pitoiset Xavier 
Published: January 2014

Plants in the United States (U.S.) and many plants outside of the U.S. are required to meet the regulations of the Pressurized Thermal Shock (PTS) Rule, 10 CFR 50.61. The Alternate Pressurized Thermal Shock (PTS) Rule (10 CFR 50.61a) was approved by the U.S. Nuclear Regulatory Commission (NRC) and included in the Federal Register, with an effective date of February 3, 2010. This Alternate Rule provides a new metric and screening criteria for PTS. This metric, RTMAX-X, and the corresponding screening criteria are far less restrictive than the RTPTS metrics and screening criteria in the original PTS Rule (10 CFR 50.61).
The Alternate PTS Rule was developed through probabilistic fracture mechanics (PFM) evaluations performed for selected U.S. pilot plants. A Generalization Study was also performed which determined that the plants used for these evaluations were representative of and applicable to the U.S. Pressurized Water Reactor (PWR) nuclear power plant fleet.
Plants outside of the U.S. may be interested in implementing the Alternate PTS Rule. However, direct implementation of the Alternate PTS Rule may not be possible due to differences in plant design, embrittlement prediction techniques, inservice inspection requirements, etc. The objective of this paper is to explore the use the Alternate PTS Rule by PWR plants outside of the U.S. by proposing methods to account for the potential differences mentioned above.
Evaluation of Growth of Subsurface Crack by Fatigue: Simulation of Penetration of Internal Flaw to Surface of the Structure
Authors: Kikuchi Masanori , Yamada Shinya , Serizawa Ryousuke , Li Yulong 
Published: January 2014

In nuclear power plant, there is a proximity rule to evaluate subsurface crack, which exists near free surface of the structure. If the distance between this subsurface crack to free surface exceeds some limit, this subsurface crack is transformed to surface crack, and residual fatigue life is evaluated. Subsurface crack has many parameters, such as, crack length, crack depth, distance between crack front to free surface, and aspect ratio of subsurface crack. As a result, proximity rule is proposed by many organizations, and each rule is different from each other largely. It is necessary to verify which is more preferable, but to determine it experimentally is very difficult due to existence of many parameters. Numerical simulation is needed for this purpose.
This problem is simulated using S-version FEM. Using S-FEM, subsurface is modeled independently from global structure, and crack growth is easily simulated. In maintenance code of nuclear power plant, initial defects are modeled as elliptical cracks in a normal plane to tension loading direction, and growth rate is estimated in this plane. But by using S-FEM, real defect shape is modeled realistically, and crack growth by fatigue is simulated. Usually, such small defects are subjected to multi-axial loading, and crack growth behaviors are very complicated. Finally, detect shape becomes elliptical or circular crack in a plane normal to tension loading direction in the structure. Fatigue cycles for these growing processes are calculated, and conservativeness of this maintenance code is discussed. Then subsurface crack growth is simulated. Inner subsurface crack grows toward free surface, penetrate to free surface and grows as a surface crack. These processes are simulated smoothly by S-FEM. Parametric studies are conducted for this problem, and proximity rules are verified with numerical results.
Flange Tightening Evaluation Method for Flat Face Flange With Full Face Gasket
Authors: Mori Masako , Nebu Akira , Kanno Takashi 
Published: January 2014

Appropriate flange tightening methods for flat face flanges with full face gaskets are discussed to improve the sealing performance of the bolted flange joints and the workability of flange tightening work.
In general, relatively larger tightening torque is required for a flat face flange with a full face gasket compared to the flange with a ring gasket when we calculate the required tightening torque based on the latest Non-mandatory Japanese Industrial Standard (JIS) evaluation method, “JIS B 2205-1991, Basis for calculation of pipe flanges”[1].
Especially, for the flat face flanges with large diameter and with fewer tightening bolts, this tendency becomes stronger.
This problem sometimes causes a conflict when the flange torque calculation of the minimum required torque value to resist hydrostatic end force at the maximum design pressure of the flange is larger than the maximum allowable torque derived from flange or bolt strength.
So, in this paper, surface stress of several diameter flange faces were measured to clarify whether or not the required stress is applied on the surface of the flat face flanges with full face gaskets.
In addition, pressure tests were carried out to clarify the sealing performance under the condition of circumferentially non-uniform tightening load in each diameter flat face flange with full face gasket.
Based on these test results, minimum flange-tightening bolt axial loads have been summarized to ensure the sealing performance of the flat face bolted flanges with full face gaskets.
Estimates of Plastic Limit Loads of Thick-Walled Cylinders With Non-Idealzied Through-Wall Cracks
Authors: Han Tae-Song , Huh Nam-Su , Shim Do-Jun 
Published: January 2014

In order to assess a structural integrity of cracked components made of highly ductile material based on fully plastic fracture mechanics concept, an accurate plastic limit load of components of interest is crucial element. Such a plastic limit load can also be applied to estimate elastic-plastic J-integral based on the reference stress concept. In this context, during last several decades, many efforts have been made to suggest plastic limit load solutions of cracked cylinder.
Recent works for evaluating rupture probabilities of nuclear piping indicate that the only use of idealized circumferential through-wall crack leads to very conservative results which in turn gives higher rupture probabilities of nuclear piping, thus the considerations of more realistic crack shape during crack growth due to primary water stress corrosion cracking (PWSCC) and fatigue and axial through-wall crack were recommended to come up with more realistic rupture probabilities of nuclear piping. Then, the needs of fracture mechanics parameters of non-idealized through-wall cracks both in axial and circumferential directions have been raised.
In the present work, the plastic limit loads of thick-walled cylinder with non-idealized axial and circumferential through-wall cracks are proposed based on detailed 3-dimensional finite element analyses. The present results can be applied either to assess structural integrity of thick-walled nuclear piping with non-idealized through-wall cracks or to calculate elastic-plastic J-integral using the reference stress concept.
Experimental and Numerical Investigation of Pipe T-Junctions Under Strong Cyclic Loading
Authors: Papatheocharis Theocharis , Diamanti Kalliopi , Varelis George E. , Perdikaris Philip C. , Karamanos Spyros A. 
Published: January 2014

Tee pipe junctions are piping components widely used in industrial and pipeline applications. Their performance under severe loading conditions may be critical for the structural integrity of an industrial facility. When these components are subjected to repeated loading associated with cyclic plasticity, failure is possible. The present work is a combined experimental and numerical effort which examines the behavior of piping branch T-junctions subjected to strong cyclic out-of-plane bending. The first part of this paper describes the experimental investigation of the junction performance. Tests are conducted in a constant and varying amplitude displacement-controlled mode resulting to failure in the low-cycle fatigue range. The overall behavior of each specimen in terms of fatigue life, as well as the evolution and concentration of local strains are monitored throughout the testing procedure.
The experimental investigation is supported by finite element modeling, developed to simulate the experiments. Advanced cyclic plasticity material models are employed and emphasis is given on the local strains developed at the critical part of the T-junctions where first cracking occurs.
A New Generalized Nonlinear Superposition Theory and its Applications in Modeling Corrosion-Fatigue
Authors: Wei Zhigang , Luo Limin , Rybarz Marek , Nikbin Kamran 
Published: January 2014

Corrosion-fatigue and stress corrosion cracking have long been recognized as the principal degradation and failure mechanisms of materials under combined corrosive environment and sustained/cyclic loading conditions. These phenomena are strongly material and environment dependent, and cycle-dependent fatigue and time-dependent matter diffusion/chemical reaction at the crack tip can be operational simultaneously. How to include these cycle-dependent and time-dependent phenomena in a single model and how to study the failure mechanisms interaction are big challenges posed to material scientists and engineers.
In this paper the current linear superposition theories for modeling cycle-dependent and time-dependent corrosion-fatigue and stress corrosion cracking phenomena are reviewed first. Subsequently, a generalized nonlinear superposition theory is proposed to incorporate possible nonlinear interaction or synergistic effect among the underlying mechanisms. The unified model derived from the new theory, depending on the specific materials and loading condition and environment, can be reduced to pure corrosion, pure fatigue, stress corrosion cracking and corrosion-fatigue. Finally, for the first time, a new breakthrough parameter is defined in this paper to quantitatively describe the interaction or synergistic effect between two different operating mechanisms, such as time- and cycle-dependent mechanisms.
Conceptual Design of a Spiral Wound Pipeline With Manufactured Residual Stresses
Authors: Scott Colin , Finneran Shane 
Published: January 2014

There are several common engineering composites that are designed to take advantage of manufactured residual stresses. Concrete may be designed with pre-stressed steel tendons. Engineering ceramic composites may be designed with mismatch in thermal properties of the components to produce residual stresses and enhance crack deflection properties. Metal matrix composites may also be designed with mismatch in elastic properties of the component to enhance crack deflection properties.
The objective of this work is to explore the possibility of designing a spiral wound pipe with enhanced mechanical properties. Consider a sheet of steel wound into a spiral in preparation for welding into pipe. Consider then that it is twisted prior to and during welding of the spiral. When the weld solidifies and the torque is released, the pipe would, in principle, maintain some of the stress of the twist. The spiral could be twisted either “inwards” or “outwards” prior to the weld, and the result would be residual tension or compression.
This work is based entirely on theory and analysis. Analyses are performed that predict the residual stresses incurred during the proposed manufacturing technique, and the resulting stresses due in-service conditions. In principle, pipe design and manufacture could be adjusted for either onshore pipelines subject to internal pressure, or offshore pipelines subject to hydrostatic pressures at depth. Both possibilities are considered.
Case Studies in Local Heat Treatment of Pressure Vessels Applying WRC-452 Principles
Authors: Miller George , Kirkpatrick Kenneth , Antalffy Les P. 
Published: January 2014

The Welding Research Council (WRC) Bulletin 452 titled “Recommended Practices for Local Heating of Welds In Pressure Vessels”(1) was first published in June 2000. This document considers various issues associated with the local heating of welds in pressure vessels and addresses the application of controlled heat in the weld metal, heat affected zone (HAZ) and a limited volume of base metal around the weld.
ASME Boiler and Pressure Vessel Code Section VIII Division 1, paragraphs UW-40, (a) 3 and 8 require that post weld heat treatment (PWHT) be carried out in a manner such that the thermal gradients are not harmful. WRC Bulletin 452 provides guidelines for local PWHT to satisfy this requirement.
This paper provides examples of local PWHT (if not heated as a whole vessel in a furnace) based upon utilizing a soak band and calculated heated band and gradient band widths based upon WRC 452 recommendations. The paper addresses both circumferential and spot PWHTs and demonstrates that the guidelines provided in WRC 452 can also be used as a starting point for determining the band widths for spot PWHT.
Evaluation of Mass Transfer Coefficient Under Swirl Flow Generated by the Combination of Pipe Elements: Part 2
Authors: Yamamoto Kei , Suzuki Shota , Nakamura Takao 
Published: January 2014

Flow accelerated corrosion (FAC) is a major pipe wall thinning phenomena in power plants. The management of pipe wall thinning has been carried out to pipe elements such as elbow, orifice, etc. of the piping system in power plants. The combination of analytical codes and measurement of pipe wall thinning is usually applied to thinning estimation methods. In piping system, several pipe elements which are connected in series may generate swirl flow. Therefore the arrangement of pipe elements is considered to affect thinning phenomena seriously. So the behavior of swirl flow is one of the major research targets to improve the accuracy of simulation codes. In Mihama Unit 3 pipe degradation accident in 2004, it was pointed out that the swirl flow caused by the piping layout might influence thinning rate behind orifice.
In the article Part1, we focus on the conditions and parameters (combination, distance, etc. of pipe elements) that affect the generation of swirl flow and analyze the effect of such parameters in mass transfer coefficient behind pipe elements. The generation of swirl flow is confirmed analytically in this study.
In the article part2, we develop new defined effective friction velocity considering the ratio between the change of average flow velocity and the change of turbulent velocity in the straight pipe. The effect of swirl flow on geometry factor is also evaluated by the new defined effective friction velocity. We also focus on the flow field of main-stream in the swirl flow. The result of analysis shows the generation of twin vortex under some combinations of pipe elements and suggests that twin vortex may affect the distribution of geometry factor. We compare the analytical results and estimate the cause of Mihama Unit 3 pipe degradation accident. The results of this study will be reflected to the evaluation of fluid-dynamic factor of FAC and improve the accuracy of simulation codes in near future.
Automatic Fatigue Monitoring Based on Real Loads - Calculation Example of a Flange
Authors: Jouan Benoît , Bergholz Steffen , Rudolph Jürgen , König Günter , Manke Andreas 
Published: January 2014

The ageing management of power plants is nowadays a main issue for all nuclear industry actors: states, regulatory agencies, operators, designers or suppliers. Consequently, lots of operators have to deal with demanding security requirements to ensure the operation of power plants. Regarding with fatigue assessment of nuclear components, stringent safety standards are synonymous of new parameters to take into account in the fatigue analysis process, for instance: new design of fatigue curves, consideration of environmental parameters or stratification effects. In this context AREVA developed within the integral approach AREVA Fatigue Concept (AFC) new tools and methods to live up to operators’ expectations. Based on measured thermal loads, the Fast Fatigue Evaluation (FFE) process allows for highly-automated and reliable data processing to evaluate time-dependant cumulative usage factors of mechanical components. Calculation and management of results are performed with the software FAMOSi, thus impact of operating cycles on components in terms of stress but also with regard of fatigue can be taken into account to plan an optimized decision related to the plant operation or maintenance activities.
The FFE process was exemplary applied in 2012 in the EnBW Power Plant of Neckarwestheim (GKN II) to perform an informative fatigue diagnose of a spray line flange for different operating cycles. This paper describes the calculation methodology but also some relevant results to point out the benefits of this method to the ageing management of mechanical parts.