bluuebunny/crossref_metadata_2025 huggingface dataset:
Technical Basis of a Code Case to Provide a Strain-Based Acceptance Limits for Service Level D Evaluation of Piping Systems Under Section III of ASME Boiler and Pressure Vessel Code
Authors: Wen Jie , Adams Timothy M.
Published: November 2019

Section III, non-mandatory Appendix F and mandatory Appendix XXVII provide the evaluation rules for Service Level D loads. Appendix F, article F-1341.2 permits plastic analysis, but provides only a stress-based acceptance criteria. Strain-based acceptance criteria for use in Appendix XXVII is under development. Strain-based acceptance criteria for Level D service limits for piping would be beneficial, especially, for regions where extremely high seismic events exist. A Code Case for strain-based acceptance criteria for level D service limits of piping is being developed in Section III of the ASME Boiler and Pressure Vessel Code. This paper presents the technical basis of the strain-based acceptance criteria Code Case. The authors reviewed extensive literatures which were published over last 50 years to build the foundation of the Code Case. A historical background of the seismic rules is given to explain why the load cycles are limited to 20 as in Section III, Division I, Subsection NB/NC/ND-3622.2 This paper also explains the consideration of reversing dynamic load and non-reversing dynamic load and how they are combined in the analysis. Comparison to current Appendix F (Appendix XXVII) acceptance criteria and some existing test results are provided to show the acceptability and conservatism of this Code Case.
Thermal Aging Assessment and Microstructural Investigations of Alloy 52 Dissimilar Metal Welds for Nuclear Components
Authors: Yescas Miguel , Joly Pierre , Roch François
Published: November 2019

Dissimilar Metal Welds (DMW) are commonly found between the ferritic low alloy steel heavy section components and the austenitic stainless steel piping sections in nuclear power plants. In the EPR™ design which is the latest FRAMATOME Pressurized water reactor (PWR) these DMW involve a narrow gap technology with no buttering, and only one bead per layer of a nickel base alloy weld filler metal (Alloy 52).

In order to assess the thermal aging performance of this relatively new narrow gap DMW design, a significant internal R&D program was launched some years ago. Several representative mock-ups were thoroughly characterized in the initial condition as well as in the thermal aged condition, up to 50,000 hours aging at 350°C. The characterisations were focused on the fusion line between the ferritic low alloy steel (LAS) and the nickel base alloy since a particular microstructure is present in this area, especially in the carbon depleted area of the Heat Affected Zone (HAZ) which is often regarded as the weak zone of the weld joint. Metallography, hardness, nanohardness, chemical analyses, and Atom Probe Tomography, as well as fracture toughness tests were carried out on different specimens in different thermal aging conditions. The results show that the fracture toughness behaviour in the ductile-brittle domain of the low alloy steel carbon depleted HAZ at the interface with the alloy 52 weld metal of the DMWs is excellent, even for a thermal ageing equivalent to 60 years at service temperature. This was found in spite of the carbon depleted zone of the HAZ, the variations of hardness, chemical composition, particularly the carbon gradients, and the thermal aging effect induced by phosphorous segregation at grain boundaries.
Design Equation for Minimum Required Thickness of a Cylindrical Shell Subject to Internal Pressure Based on Von Mises Criterion
Authors: Lu James , Millet Barry , Kirkpatrick Kenneth , Mosher Bryan
Published: November 2019

Design equation (4.3.1) for the minimum required thickness of a cylindrical shell subjected to internal pressure in Part 4 “design by rule (DBR)” of the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 [1] is based on the Tresca Yield Criterion, while design by analysis (DBA) in Part 5 of the Division 2 Code is based on the von Mises Yield Criterion. According to ASME PTB-1 “ASME Section VIII – Division 2 Criteria and Commentary”, the difference in results is about 15% due to use of the two different criteria. Although the von Mises Yield Criterion will result in a shell wall thickness less than that from Tresca Yield Criterion, Part 4 (DBR) of ASME Division 2 adopts the latter for a more convenient design equation. To use the von Mises Criterion in lieu of Tresca to reduce shell wall thickness, one has to follow DBA rules in Part 5 of Division 2, which typically requires detailed numeric analysis performed by experienced stress analysts.

This paper proposes a simple design equation for the minimum required thickness of a cylindrical shell subjected to internal pressure based on the von Mises Yield Criterion. The equation is suitable for both thin and thick cylindrical shells. Calculation results from the equation are validated by results from limit load analyses in accordance with Part 5 of ASME Division 2 Code.
The Effect of Pedicle Screw Thread Shape on the Stress Concentration Under Lateral Bending
Authors: Yang Yucheng , Ma Qin
Published: November 2019

Pedicle screws (PS) are frequently used in medical spinal column fixation. Despite 7 out of 100 pedicle screws fracture inside of the patients’ body and under the claim that lateral bending is the main failure mode, little research has addressed the stress characteristics and the fracture location of the PS under lateral bending. This study focuses on the effect of thread design on the magnitude and location of maximum stress concentration. Four types of thread shapes are considered including V-shape, square-shape, buttress, and reverse buttress. Three-dimensional (3D) finite element (FE) methods are used in this investigation. A load of 150 Newton is applied at the screw head to simulate lateral bending. The models are created in SolidWorks. The 3D FE analysis is performed using the standard coding of ANSYS Workbench 19.1. Based on this study, it is found that the high stress concentration is located at the cortical bone region rather than at the cancellous bone region. Although the general stress patterns are similar, the PS thread shape design and the thread fillet radius may significantly affect on the magnitude and location of maximum stress concentration.
Selection of the Test Specimens for Seismic Tests of Air-Operated Valve Actuators for Nuclear Power Plants
Authors: Kojima Nobuo , Tsutsumi Yoshitaka , Matsubara Yoshinao , Nishino Koji , Ito Yasuyuki , Kubota Ryo , Suzuki Shigeki
Published: November 2019

The soundness for the function of air-operated valves in nuclear power plants during earthquake has been investigated via seismic test results and so forth. Since the seismic response acceleration has increased more and more with a recent reassessment of design earthquake ground motions conducted according to the revised Japanese nuclear safety regulation, it is necessary to evaluate the soundness for the function of various valves subject to large acceleration beyond design basis. The air-operated valves currently installed in the nuclear power plants in Japan play the important roles in the sever accident events. In this study, we classified them based on the valve type, manufactures and the previous test results. Furthermore, we proposed the strategy for evaluating the seismic-proof and the seismic test condition for examining the soundness of the dynamic function. Here, the dynamic function is defined as the function required under and after earthquakes.
A Multi-Factor Comprehensive Evaluation Method for Pipeline Integrity
Authors: Yang Jing , Wang Xiaolin
Published: November 2019

Pipeline integrity management is widely used as an effective means for pipeline safety management, in which integrity evaluation is an important part. To some extent, pipeline integrity can be interpreted as the safety condition of the pipeline, while safety is an eternal topic for pipeline operators. In numerous recent studies, the evaluation of pipeline integrity generally focuses on the evaluation of remaining strength and/or residual life, which is based on the defect size such as corrosion, dents, etc., obtained during inspection. However, pipeline integrity is not only related to the pipe body, all factors that may threaten the operation safety of the pipe should be considered, including the pipe body, ancillary facilities, the pipe security system, and the surrounding environment, etc.. Although some comprehensive models have been established recently to assess pipeline condition, there still exist limitations for practical application, such as quantification of integrity and complexity of analysis. Therefore this paper presents the development of a comprehensive integrity evaluation method based on multi-factor analysis. The method is developed by an integrated application of fuzzy mathematics, grey correlation analysis theory, and the artificial neural network technique. After establishing integrity evaluating indexes, fuzzy analysis is used to quantify and classify pipeline integrity, and grey correlation analysis to screen key influence indicators. Then a comprehensive predictive evaluation model can be generated using large amount of relevant sample data based on the artificial neural network technique. In the end of the paper, a simple case is applied to validate feasibility of this comprehensive integrity evaluation method. The comprehensive evaluation method is expected to be applied to determine the condition of pipeline integrity, and to grade and rank the integrity condition of pipes, so as to assist and optimize pipeline maintenance decision for pipeline operators.
INCEFA-PLUS: Increasing Safety in NPPs by Covering Gaps in Environmental Fatigue Assessment
Authors: Mottershead Kevin , Bruchhausen Matthias , Cicero Sergio , Cuvilliez Sam
Published: November 2019

INCEFA-PLUS is a five year project supported by the European Commission HORIZON2020 programme. The project commenced in mid-2015. Sixteen organisations from across Europe have combined forces to deliver new experimental data which will support the development of improved guidelines for assessment of environmental fatigue damage to ensure safe operation of nuclear power plants. Within INCEFA-PLUS, the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue endurance of austenitic stainless steels in light water reactor environments are being studied experimentally, these being issues of common interest to all participants. The data obtained is being collected and standardised in an online environmental fatigue database, implemented with the assistance of an INCEFA-PLUS led CEN workshop on this aspect. Towards the end of the project it is planned that INCEFA-PLUS will develop and disseminate methods for including the new data into assessment approaches for environmental fatigue degradation.

This paper provides an overall update on project developments since it was last presented at PVP2018 [1]. As well as being a standalone paper, this document will also serve as an introduction to a companion paper being submitted to cover data generated by the project in more detail [2]. In particular, this paper summarises:

• The results for Phases 1 & 2 testing.

• The plans for Phase 3 testing.

• A summary of emerging sensitivities to, and interdependencies between:

o Mean strain and stress, surface finish, strain amplitude and hold time.

o Environment.

o Material.

o Laboratory.

• The latest thinking on the direction of the project in its final year.

• The latest thoughts on how the project results will be used to advance development of improved assessment guidelines.

• A summary of dissemination achieved and planned.

• Ideas for work after the end of INCEFA-PLUS.
Evaluation of Laser Peening for Mitigation of Primary Water Stress Corrosion Cracking in Pressurized Water Reactors
Authors: Marlette Stephen , Bovid Stan
Published: November 2019

For several decades pressurized water reactors have experienced Primary Water Stress Corrosion Cracking (PWSCC) within Alloy 600 components and welds. The nuclear industry has developed several methods for mitigation of PWSCC to prevent costly repairs to pressurized water reactor (PWR) components including surface stress improvement by peening. Laser shock peening (LSP) is one method to effectively place the surface of a PWSCC susceptible component into compression and significantly reduce the potential for crack initiation during future operation. The Material Reliability Program (MRP) has issued MRP-335, which provides guidelines for effective mitigation of reactor vessel heads and nozzles constructed of Alloy 600 material. In addition, ASME Code Case N-729-6 provides performance requirements for peening processes applied to reactor vessel head penetrations in order to prevent degradation and take advantage of inspection relief, which will reduce operating costs for nuclear plants.

LSP Technologies, Inc. (LSPT) has developed and utilized a proprietary LSP system called the Procudo® 200 Laser Peening System. System specifications are laser energy of 10 J, pulse width of 20 ns, and repetition rate of 20 Hz. Scalable processing intensity is provided through automated focusing optics control. For the presented work, power densities of 4 to 9.5 GW/cm2 and spot sizes of nominally 2 mm were selected. This system has been used effectively in many non-nuclear industries including aerospace, power generation, automotive, and oil and gas. The Procudo® 200 Laser Peening System will be used to process reactor vessel heads in the United States for mitigation of PWSCC. The Procudo® 200 Laser Peening System is a versatile and portable system that can be deployed in many variations.

This paper presents test results used to evaluate the effectiveness of the Procudo® 200 Laser Peening System on Alloy 600 material and welds. As a part of the qualification process, testing was performed to demonstrate compliance with industry requirements. The test results include surface stress measurements on laser peened Alloy 600, and Alloy 182 coupons using x-ray diffraction (XRD) and crack compliance (slitting) stress measurement techniques. The test results are compared to stress criteria developed based on the performance requirements documented in MRP-335 and Code Case N-729-6. Other test results include surface roughness measurements and percent of cold work induced by the peening process. The test results demonstrate the ability of the LSP process to induce the level and depth of compression required for mitigation of PWSCC and that the process does not result in adverse conditions within the material.
Analysis on Engineering Calculations for Connected Double Tubesheets
Authors: Zhu Guodong , Qian Caifu , Shou Binan , Xie Guoshan , Han Zhiyuan
Published: November 2019

Calculation procedures for the connected double tubesheets is based on single tubesheet in current standards. Current situation, calculation methods and calculation procedures were introduced in this paper. Some options in calculation procedure for connected double tubesheets were not specified yet in standards and make engineers confused. It was point out that deformation features and stress levels in tubesheet can be qualitatively analyzed by means of two key constrain parameters m and K. The two Parameters are helpful to analyze the differences and relations between single tubesheet and double tubesheets in engineering design. Examples were calculated with different procedure options to compare with FEA after qualitatively analysis. The reasonability of different calculation procedures was discussed based on inner and outer tubesheet respectively. The preferences of procedure options were put forward to improve and perfect specification in current standards finally.
Research on Post-Fire Metallographic Structure and Hardness of Quenched and Tempered High Strength Steel 07MnMoVR
Authors: Shao Shanshan , Jia Guodong , Cao Luowei , Deng Guide
Published: November 2019

Quenched and tempered high strength steel 07MnMoVR provides an excellent combination of strength and toughness potentially providing significant cost savings in petrochemical industry. Exposure to fire will subject steel to thermal conditions that may alter the material’s microstructure and properties. The extent of the fire damage and the potential reusability of the components can be evaluated by fitness-for-service (FFS) assessment after a fire event. According to API 579-1/ASME FFS-1, metallurgical investigation and mechanical testing are the chief means for the assessment of fire damage. This paper presents the details of an experimental investigation on the post-fire metallographic structure and hardness of 07MnMoVR steel. Metallographic analyses and hardness testing were performed on coupons exposed to elevated temperatures varying from 550°C to 850°C for half an hour to 8 hours and then naturally cooled in air or cooled by water.

The results show that the microstructure of as-received 07MnMoVR steel consisted of tempered sorbite and bainite. With increasing heat exposure temperature, bainite disappeared gradually. The recovery and recrystallization of ferrite began to occur after heat exposure at 650°C for 5hrs. When the heat exposure temperature exceeded 750°C, the effects of duration time and cooling rate on microstructure were both significant. A linear correlation is indicated by fitting the ultimate tensile strength and hardness. Due to the drastically degradation of impact toughness of 07MnMoVR steel after heat exposure exceeded 650°C, it is suggested that the removal and testing of material samples shall be utilized to evaluate the fire damage of components, besides replication or in-situ field metallography and hardness testing. This study can provide basis data and guidelines for the fitness-for-service assessment of 07MnMoVR steel suffered from a fire event.
HRSG-Pipeline Weld Residual-Stress Measurement to Assess Influence Over Creep-Analysis Results From Italian Code, American Standard
Authors: Grisolia Ottaviano , Scano Lorenzo , Piccini Francesco , Lo Conte Antonietta , De Agostinis Massimiliano , Fini Stefano
Published: November 2019

Previous study carried out residual stress characterization for the welds of the high-temperature-section (superheater / reheater) lower headers of the bottom-supported heat-recovery steam generator (HRSG). Modeling the gas-tungsten arc, manual welding process considered only weld-lay for the ASTM A 335-Grade P22 finned-tube angle joint to the cylinder. Present study aims at indirectly assessing findings of previous analysis measuring maximum residual stress on the joint’s exservice material. To achieve that a tee similar to the previous was not available: for both experimental and numerical analyses present study considers a P22 circumferential “V”-groove butt joint on HRSG pipeline section, creep-operated for the same period and temperature as the previous case. In the experimental activity X-ray diffraction method (or alternatively, hole-drilling strain gage one) applies as close as possible to the weld, being residual stress maximum at the fusion boundary. Thermal analysis for the previous case also showed it keeps nearly constant during weld cooling, relaxing most during creep: after 200,000 hours of operation, welding-process simulation predicted a maximum residual stress of 70 MPa; tee-joint creep-analysis found out a maximum equivalent stress of 91 MPa. As for the sample withdrawal, dimensions should be sufficient to avoid any interference with measurement area. The experimental procedures should comply with the European standard EN 15305 on the matter (the American standard ASTM E 837 for the alternate method). Comparison of analysis results for the two cases, confirms tendencies previously found out in creep-behavior, though different equivalent stress contributions. Comparison of predicted and observed residual stress values should allow for validation of numerical models used in both welding process and stress analysis.
Improvement of Low-Temperature Toughness in Weld Metal Made of 9Cr-1Mo-V Steel by GTAW Method
Authors: Nakano Masakatsu , Tanaka Tomohiro , Abe Masamitsu , Nakatani Mitsuyoshi , Terasaki Hidenori
Published: November 2019

Energy demand will increase due to global population growth in the future. As one of solutions for the demand, it will be necessary to operate petroleum service plants more efficiently. To improve refining efficiency, operation at higher temperatures is required of reactors used in high-pressure hydrogen service at the plants. 9Cr-1Mo-V steel has excellent creep strength compared to 2 1/4Cr-1Mo steel and 2 1/4Cr-1Mo-V steel, which have been conventionally applied to reactors, and has been already put into commercial use for boilers of thermal power plants, etc. Further application of 9Cr-1Mo-V steel is expected for reactors at petroleum refining plants. As materials applied to reactors, low-temperature toughness should be considered for weld joints in addition to creep strength. However, 9Cr-1Mo-V steel has poor low-temperature toughness compared to 2 1/4Cr-1Mo steel and 2 1/4Cr-1Mo-V steel. As for the welding methods applied to reactors, Submerged Arc Welding (SAW), Shielded Metal Arc Welding (SMAW), and Gas Tungsten Arc Welding (GTAW) can be used. The 9Cr-1Mo-V steel weld metals formed by SAW and SMAW have a high oxygen content, and their low-temperature toughness is inferior to that of the weld metal formed by GTAW. On the other hand, the GTAW weld metal has a low oxygen content and excellent low-temperature toughness. Therefore, GTAW is an effective way to improve the toughness of the weld metal. However, GTAW has low productivity compared with others, so it is necessary to apply to a narrow groove and a hot wire method to improve the productivity.

In this paper, the application of narrow gap GTAW using the hot wire method was considered for welding of 9Cr-1Mo-V steel. When using the hot wire method, productivity of GTAW increases in comparison to the conventional method, leading to increased weld pass thickness. With the increase in pass thickness, the area of coarse grains increases because of decreasing thermal effect by the subsequent pass, then the low-temperature toughness decreases. Therefore, in order to improve the low-temperature toughness by refining the grains of the GTAW weld metal, the melt-run method, arc re-melting without adding fillers, was conducted after the former weld pass metal solidified. The weld metal from the melt-run method had finer grains compared with those of the weld metal without the melt-run method, and the low-temperature toughness increased. On the other hand, the melt-run method requires two processes: welding and melt-run. Therefore, a tandem electrode GTAW machine was produced in which an electrode for welding and the other one for melt-run were placed continuously to make it possible to execute welding and a melt-run without a time lag. As a result, it is possible to manufacture reactors made of 9Cr-1Mo-V steel for petroleum refining plants with sufficient low-temperature toughness by applying a welding method with narrow gap GTAW and a melt-run method combined.
Plastic Collapse Stresses for Thick Wall Pipes With External Cracks
Authors: Hasegawa Kunio , Li Yinsheng , Lacroix Valery , Mares Vratislav
Published: November 2019

Bending stress at plastic collapse for a circumferentially cracked pipe is predicted by limit load equation provided by the Appendix C of the ASME Code Section XI. The equation of the Appendix C is applicable for pipes with both external and internal surface cracks. On the other hand, the authors have developed an equation taking into account the pipe mean radii at non-cracked area and at cracked ligament area. From the comparison of Appendix C equation and the new equation, the plastic collapse stress estimated by the Appendix C equation gives 20 to 30% less conservative bending capacity prediction for external cracked pipes with small Rm/t, where Rm is the pipe mean radius and t is the pipe wall thickness. This paper discusses the limitation of the use of Rm/t for the Appendix C equation.
Study on Key Process Parameters of the Local Post Weld Heat Treatment by Electric Heating for the Large Thick-Walled Pressure Vessel Cylinder Butt Weld
Authors: Ji Fang , Deng Guide , Sun Liang , Liu Cenfan , Zhao Xiaonan
Published: November 2019

The local post weld heat treatment for pressure vessel cylinder butt circumferential weld performed by resistance heating a shielded band around the entire circumference. The width of heated band must be large enough to ensure that the temperature of the weld, heat-effect zone and a portion of base metal adjacent to the weld should meet the requirement given in the standards. When the diameter of pressure vessel cylinder is enough large to allow the installation of heater and thermal insulation on the inner surface of wall, the circumferential butt weld heated simultaneously on interior and exterior surface of cylinder wall is more energy economical. However, GB/T 30583-2014 don’t provide the recommended width of heated band for the local post weld heat treatment performed by heating simultaneously on the inner and outer surface of cylindrical wall when the wall thickness is large than 50mm. So numerical simulation was carried out to study the effect of the width of heated band on the soak band temperature distribution when the local post weld heat treatment for cylinder pressure vessel with the thickness rang of 60mm∼100mm performed by heating simultaneously on interior and exterior surface in this paper. The results show that the widths of heated band should be not less than six times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 60mm∼70mm with a diameter of 2000 mm performed by heating simultaneously on interior and exterior surface and the widths of heated band should be not less than five times thickness when post weld heat treatment for cylinder pressure vessel butt welds whose thickness is 70mm∼100mm.
Study on Buckling Strength Reduction Factor for Vertical Vessel Skirts With Access Opening by Elastic-Plastic Analysis
Authors: Takahashi Takuma , Kataoka Shunji , Uno Yoshiaki , Miyashita Toshikazu
Published: November 2019

Access opening is a key geometric feature of vertical vessel skirts. To ensure the structural stability of skirts, buckling strength reduction caused by openings shall be numerically evaluated.

In the previous study, Buckling Strength Reduction Factor (BSRF) was introduced as a design factor representing the effects of openings. However BSRF is based on the elastic bifurcation buckling under axial compressive load. The relations between BSRF and practical design conditions, such as bending moment, material plasticity, and local deformation, are not yet evaluated.

The purpose of this paper is to develop the buckling design method for vertical vessel skirts with access opening by investigating the relation between BSRF in consideration of practical design conditions and conventional design concepts for straight cylinder. The finite element analyses of buckling strength were conducted for cylindrical shells with and without openings under bending moments. In addition, nonlinear buckling behaviors of skirts with opening were studied by elastic-plastic analyses and limit-load analyses. These studies revealed the relation between BSRF and conventional buckling design concepts. Based on these results, a new buckling design approach which includes the application BSRF was proposed. This proposed approach provides a practical guide for buckling design of vertical vessel skirts with access opening.
Probabilistic Methods: Risk Based Design and Assessment
Authors: Cathcart H. , Horne G. , Parkinson J. , Moffat A. , Joyce M.
Published: November 2019

Structural integrity assessments typically aim to calculate the integrity of a component under nominal or best estimate conditions. To account for potential variability and uncertainty present in the system, safety factors are often applied to assessment inputs and outputs. This approach does not allow the level of conservatism present to be quantified, often leading to over-conservatism or inadvertent non-conservatism. Probabilistic assessments explicitly calculate the probability of failure based on distributions of the input parameters and hence quantify the margin present in the assessment, leading to a greater understanding of the system.

In this study a creep-fatigue damage assessment of a transiently loaded piping component is used as a vehicle to investigate some of the challenges and benefits of probabilistic assessments. A probabilistic assessment of the component life is compared to a lower-bound deterministic calculation to identify the mismatch in margin between the two results. The potential inaccuracies introduced when reducing the computational burden of Monte Carlo simulations with response surface methodologies are explored and tested. Finally, two challenges when attempting to underwrite a very low probability of failure are tackled: the inference of the shape of a distribution’s tails from limited experimental data and the uncertainty of extreme percentiles of finite Monte Carlo samples.
Generic Proximity Rules for Multiple Radially Oriented Planar Flaws: Technical Basis of Code Case N-877 Revision 1
Authors: Dulieu Pierre , Lacroix Valéry , Hasegawa Kunio
Published: November 2019

In the case of planar flaws detected in pressure components, flaw characterization plays a major role in the flaw acceptability assessment. When the detected flaws are in close proximity, proximity rules given in the Fitness-for-Service (FFS) Codes require to combine the interacting flaws into a single flaw. However, the specific combination criteria of planar flaws vary across the FFS Codes. These criteria are often based on flaw depth and distance between flaws only. However, the level of interaction depends on more parameters such as the relative position of flaws, the flaw sizes and their aspect ratio. In this context, revised and improved proximity criteria have been developed to more precisely reflect the actual interaction between planar flaws. Thanks to numerous three-dimensional XFEM analyses, a wide range of configurations has been covered, including interaction between two surface flaws, interaction between two subsurface flaws and interaction between a surface flaw and a subsurface flaw. This paper explains in detail the steps followed to derive such generic proximity rules for radially oriented planar flaws.
Research on Risk Assessment Method and System Development of Small Ammonia Refrigeration Units
Authors: Li Xiang , Wang Weihua , Jing Weike , Shi Jin , Zhuang Fakun
Published: November 2019

In recent years, ammonia leakage accidents occur frequently, which causes a great concern in China. Based on traditional risk analysis methods and the equipment characteristics, a risk evaluation method for small ammonia refrigeration units is proposed. The method includes a risk assessment model based on area division, a failure probability assessment method based on expert scoring system, a failure consequence assessment method based on regional population density and consequence mitigation measures, and a HAZOP risk correction method. Based on the proposed method, a risk assessment system of small ammonia refrigeration units is developed. This risk assessment method and system will provide a scientific basis to carry out the cold storage management in China.
Addressing Shell Mode Vibration in Ducts in Refinery With Computational Models and Field Data
Authors: Chakraborty Ishita , Paul Anup , Szasz Gyorgy
Published: November 2019

This paper describes the work performed to study the shell mode vibration of a large cross-section flue gas duct. The work involved the collection of field vibration data, as well as predictive computational models associated with finite element analysis (FEA) and computational fluid dynamics (CFD). The goal of this work was to use predictive models to ascertain whether a proposed design change would reduce the vibration levels of the duct under similar operating conditions. The vibration observed in the duct was identified as a flow induced vibration (FIV) which excited the shell modes of the duct walls.

This case study serves as an example of using predictive computational models (FEA and CFD), calibrated with vibration response data from field measurements, to represent the real world situation as closely as possible within specified budget and schedule constraints. Such calibrated models can be useful for forecasting the effectiveness of various proposed design changes.
Isochronous Stress-Strain Curves for Alloy 617
Authors: Messner M. C. , Sham T.-L.
Published: November 2019

Alloy 617 is a high temperature nickel based material that could have significant design advantages when compared to austenitic steels in very high temperature reactor applications. Several high temperature design methods, including Section III, Division 5 of the ASME Boiler & Pressure Vessel Code, require a model for the creep and high temperature plastic deformation of a material, quantified as a set of isochronous stress-strain curves. This paper describes the development of a model for the high temperature deformation of Alloy 617. This model is then used to generate design hot tensile and isochronous stress strain curves suitable for use in Section III, Division 5 and other high temperature design methods.
Development of Simplified Model Test Methods for Creep-Fatigue Evaluation
Authors: Wang Y. , Jetter B. , Messner M. C. , Sham T.-L.
Published: November 2019

The Simplified Model Test (SMT) approach is an alternative creep-fatigue evaluation method that no longer requires the use of the damage interaction diagram, or D-diagram. The reason is that the combined effects of creep and fatigue are accounted for in the test data by means of a SMT specimen that is designed to replicate or bound the stress and strain redistribution that occurs in actual components when loaded in the creep regime. However, creep-fatigue experiments on SMT key feature articles are specialized and difficult to perform by the general research community. In this paper, two innovative SMT based creep-fatigue experimental methods are developed and implemented. These newly-developed SMT test methods have resolved all the critical challenges in the SMT key feature article testing and enable the potential of further development of the SMT based creep-fatigue evaluation method into a standard testing method. Scoping test results on Alloy 617 and SS 316H using the newly developed SMT methods are summarized and discussed. The concepts of the SMT methodology for creep-fatigue evaluation are explained.
Finite Element Verification of Engineering Equations for Prediction of Structural Strength of Annulus Spacers in CANDU Nuclear Reactors
Authors: Doddihal Preeti , Kawa Dennis , Scarth Douglas , Chen Yu
Published: November 2019

The core of a CANDU (CANada Deuterium Uranium) pressurized heavy water reactor includes several hundred horizontal fuel channels that pass through a calandria vessel containing the heavy water moderator. In each fuel channel, annulus spacers are used to maintain the gap between the cold calandria tube and the hot pressure tube, a pressurized vessel containing the nuclear fuel in contact with heavy water coolant. In order to carry the loads between the pressure tube and calandria tube, the annulus spacers are required to possess adequate structural strength throughout the operating life of the reactor. The Inconel X-750 spacers used in some reactor units are susceptible to irradiation induced degradation. As irradiation fluence increases with operating time, material embrittlement has been observed due to helium bubble formation in the X-750 spacer material. An engineering approach for assessing the structural strength of CANDU annulus spacers has been recently developed. When the ductility of the material is relatively low, the region susceptible to fracture under applied tensile stress may be adequately idealized as a strip-yield process zone surrounded by elastic material and associated with restraining stress. The engineering approach is based on applying the strip-yield process zone methodology to fracture at a nominally smooth surface. Finite element modeling was undertaken to simulate the strip-yield based fracture process zone. The finite element analyses and results are presented in this paper. The finite element results verify the engineering equations developed to assess the structural strength of annulus spacers.
A Method to Estimate Deformation Strains in the Context of Coke Drum Life Assessments: Part 1
Authors: Huang John , Subramanian Kannan , Boster Patrick , Bedoya Julian J.
Published: November 2019

In this paper, an analytical method to estimate the deformation strains that can quantify the severity of bulges, as it applies to coke drums, is presented. The proposed method is based on classical shell theory and API 579-1/ASME FFS-1 (2016) procedures involving triaxiality limits. In this first part of the work, only the theoretical development is presented along with the comparison of the results from this theoretical approach with two case studies that emulate the bulging due to different loading scenarios. The developed approach is then applied to a deformed coke drum. In the next part of this paper, the application of this approach on selected in-service coke drums that are equipped with strain gages will be presented. The authors would like to emphasize the well-known fact that the coke drum is a complex pressure vessel for which any single simplified assessment technique may not be sufficient to quantify the life or fitness-for-service (FFS) of a coke drum due to the complexities associated with the various parameters that affect the mechanical integrity of the coke drum. This paper is an attempt to advance the assessment techniques that are currently utilized in the industry.
The Design and Analysis of a Containment Vacuum and Pressure Vessel System
Authors: Bernardin John , Hathcoat David , Sattler David , Spernjak Dusan , Swensen Erik , Llobet Megias Anna
Published: November 2019

A nested confinement (inner) and containment (outer) vessel system is under development to conduct small shock-physics experiments in a high-speed proton imaging facility at Los Alamos National Laboratory. The dual vessel system is necessary to serve as a qualified confinement system and containment buffer boundary between a high explosives experiment and the environment.

The paper describes the preliminary engineering design and analyses that have been performed on the outer containment pressure vessel, following ASME BPVC Sect. VIII Div. 1, for both pressure and vacuum conditions. Other engineering attributes which will be presented include an internal support structure for a nested inner vessel, an external integrated support and alignment structure for the complete vessel system, and the vacuum and gas handling equipment.
Method B Fatigue Screening in ASME BPV Code, Section VIII, Division 2, Part 5
Authors: Kirkpatrick Kenneth , Johnson Christopher R. , Mann J. Adin
Published: November 2019

ASME Boiler and Pressure Vessel Code (BPVC), Section VIII, Division 2, Part 5 Method B fatigue screening is intended to be a quick and simple method that is sufficiently conservative to screen components in cyclic service thus not requiring detailed fatigue analysis. The method assesses pressure, thermal, and mechanical loads separately. The basis for each portion of the method is discussed along with an alternative bases for the assessments. Each assessment is reformulated as a fatigue damage factor and all variables are provided so that the intent of each equation is clearly identifiable. A penalty factor will be included in each equation rather than assuming one penalty for all designs, the reformulation creates penalty for non-fatigue resistant designs and reduces the penalty for fatigue resistant designs. Examples are given showing the potentially non-conservative results if a summed damage is not used.
Experimental Determination of the Ratcheting of the Porosity for the Study of Ductile Rupture Under Cyclic Loading Conditions
Authors: Remmal Al Mahdi , Marie Stéphane , Leblond Jean-Baptiste
Published: November 2019

It is known that for ductile porous materials, cyclic loadings lead to lower fracture strains than monotone ones. This reduction of ductility probably arises from an effect called “ratcheting of the porosity” that consists of a continued increase of the mean porosity during each cycle with the number of cycles. Finite element based micromechanical simulations confirmed this interpretation. Recently the authors proposed a Gurson-type “layer model” better fit that Gurson’s original one which does not predict the ratcheting of the porosity, for the description of the ductile behavior under cyclic loading conditions. A very good agreement was obtained between the results of the micromechanical simulations and the model predictions for a rigid-hardenable material. Yet, the ratcheting of the porosity is a consequence of both hardening and elasticity; and the theory of sequential limit analysis used in order to get the “layer model” is strictly applicable in the absence of elasticity. Based on an expression of the porosity rate accounting for elasticity, a proposal was made to improve the new model with regard to elasticity. Simultaneously to this theoretical work, an experimental program was conducted on a model material in order to assess experimentally this new model. The material is a HIPed 316L stainless steel, with Al2O3 almost spherical inclusions acting like porosities, complying with the hypothesis made to derive the theoretical model. Notched tensile specimens, with a center section of 4mm, were cyclically loaded. Several tomographies were performed at ESRF, using a 120 keV beamline and 3x3 microns detector, in order to prove experimentally the ratcheting effect of the porosity. The void growth through the cycles is precisely described and the experimental results could then be processed and compared to the numerical porosities predictions of the model. This paper presents the experimental activity of this PhD program.
Recent Developments in the R5 Procedures for Assessing the High Temperature Response of Structures
Authors: Hughes Daniel G. J. , Chevalier Marc , Dean David W.
Published: November 2019

The R5 procedures have been developed within the UK power generation industry to assess the integrity of nuclear and conventional plant operating at high temperatures. Within R5, there are specific procedures for assessing creep-fatigue crack initiation in initially defect-free components (Volume 2/3), components containing defects (Volume 4/5), dissimilar metal weldments (Volume 6) and similar metal ferritic weldments under steady loading (Volume 7).

A key driver for continued developments in the R5 Procedure is the operational feedback from thirty years of operation of the UK Advanced Gas-Cooled Reactor (AGR) fleet. This experience from operation of the UK AGR fleet can be used to inform the design and operation of future high temperature reactors. Some of the lessons learnt from long-term operation of austenitic stainless steels at high temperatures are detailed briefly within this paper.

Further, this paper briefly outlines the current R5 procedures and then focuses on two significant recent developments in these procedures: treatment of carburisation and its impact on creep-fatigue crack initiation and improved methods for predicting creep-fatigue crack growth under combined primary and secondary loads.
Impact of the Harsh Environment on E-Glass Epoxy Composite
Authors: Idrisi Amir Hussain , Ismail Mourad Abdel-Hamid , Abdel-Magid Beckry , Mozumder Mohammad , Afifi Yaser
Published: November 2019

Composite materials are being used in many industrial applications such as automobile, aerospace, marine, oil and gas industries due to their high strength to weight ratio. The long-term effect of sustained loads and environmental factors that include exposure to UV light, temperature, and moisture have been under investigation by many researchers. The major objective of this study is to evaluate the effects of harsh environment (e.g. seawater and high temperature) on the structural properties of E-glass epoxy composite materials. These effects were studied in terms of seawater absorption, permeation of salt and contaminants, chemical and physical bonds at the interface and degradation in mechanical properties. Samples were immersed in seawater at room temperature (23°C), 65°C and 90°C for the duration of 6 months. Results show that seawater absorption increased with immersion time at 23°C and 65°C, whereas the weight of the specimens decreased at 90°C. The moisture causes swelling at 23°C and 65°C and breakdown of chemical bonds between fiber and matrix at 90°C. It is observed that high temperature accelerates the degradation of the E-glass epoxy composite. At 90°C, the tensile strength of E-glass epoxy sharply decreased by 72.92% but no significant change was observed in modulus of elasticity of the composite.
Modeling of Cracked Pipe System: Effect of Boundary Conditions on Displacement-Controlled and Load-Controlled Leak-Before-Break
Authors: Uddin M. , Wilkowski G. , Kurth E. , Hill L. , Bagnoli K.
Published: November 2019

In recent years, there has been a growing interest of using Leak-Before-Break (LBB) concept in the refining industry. LBB methodology has been applied in the nuclear industry for decades, but generally for elimination of hardware for dynamic rupture control at the design stage. However, in the refining industry the purpose of the LBB application could be quite different than for the nuclear industry. In the refining industry the purpose of LBB is to show in-service leakage can be detected well ahead the potential for rupture allowing for ample time for safe replacement of piping.

This paper explores conditions in which LBB can be applied to refinery piping. Initially, the analysis was conducted using a finite element model of a typical pipe system with its design boundary conditions under operating loadings, i.e., gravity, pressure, thermal and hanger loadings. The results with various circumferential crack sizes show a displacement-controlled manner (LBB is easy to satisfy) for the pipe system mainly due to higher secondary stresses, i.e., thermal loadings. However, the pipe system behaved in a load-controlled manner (LBB is harder to satisfy) when some of the boundary conditions were changed simulating a possible support failure and/or hanger failure. This paper investigates how boundary conditions can change a displacement-controlled LBB behavior to load-controlled LBB for a representative pipe system and the implications regarding leak rate detection capability. The effect of material’s toughness reduction due to high-temperature hydrogen-attack (HTHA) damage was also included in these analyses. The procedure outlined here can be applied to a piping system to identify piping supports that are critical for inspection to demonstrate LBB, and the anticipated leak rate before reaching critical flaw size.