bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Theoretical Investigations on the Characteristics of Ice Floes Broken by Ships Sailing Ahead in Level Ice
Authors: Myland Daniela
Published: November 2019

Although the hull shapes of modern ice breaking vessels seem to be quite similar at a first glance, there are significant differences in their ice breaking performance. A significant amount of research effort was spent on investigations of the icebreaking process and the resulting forces. However, little information is available on the correlations between ice floe characteristics, hull shape parameters, ice properties and the ice resistance. Thus, systematic model tests in level ice and pre-sawn ice with four icebreaking ship models of one ship type have been conducted to gain new insight on these correlations. During the tests in level ice under water video records have been taken from below the ship model. Video frames have been analyzed by application of a dedicated image analysis procedure which is mainly based on a number of semiautomatic scripts applied in Matlab®. Results of the analysis are presented and discussed within this paper.
Optimization Design of FPSO Central Cooling Water System Based on Pipe Network Fluid Analysis
Authors: Zhang Huan , Yuan Hongtao , Wang Chao , Kong Weiwen , Xu Jiangguo , Wang Zhaoqiang
Published: November 2019

Marine power generator plays important role to guarantee the normal operation of all subsystems of FPSO, in which cooling device are emphasized on its reliability and stability. As the main cooling system of FPSO power generator, the design of central cooling water system is very important. Traditional pipeline network system design is mainly based on the design manual and empirical formula, which single pipeline is designed for circulation of different media. Lacking the concept of system integrity, which results in the weak integrated design without rational consideration. In this paper, a FPSO central cooling water system is taken as the research object. Based on the initial design scheme, it is different from the empirical and singularity of traditional design, and the impact of the pipe network of cooling water system to that of other systems in the whole vessel is put into consideration on the comprehensive way. From the economic point of view, the study on the pipe network of flow balance is carried out, and the optimization scheme of the central cooling water pipe network system is proposed.
A 6-DOFs Hardware-in-the-Loop System for Wind Tunnel Tests of Floating Offshore Wind Turbines
Authors: Fontanella Alessandro , Bayati Ilmas , Taruffi Federico , La Mura Francesco , Facchinetti Alan , Belloli Marco
Published: November 2019

This article presents a hardware-in-the-loop (HIL) methodology developed at Politecnico di Milano (PoliMi) to perform wind tunnel tests on floating offshore wind turbines (FOWTs). The 6-DOFs HIL setup is presented, focusing on the main differences with respect to a previous 2-DOFs system. Aerodynamic, rotor and control related loads, physically reproduced by the wind turbine scale model, must be measured in real-time and integrated with the platform numerical model. These forces contribute to couple wind turbine and floating platform dynamics and their correct reproduction is of fundamental importance for the correct simulation of the floating system behavior. The procedure developed to extract rotor loads from the available measurements is presented, discussing its limitations and the possible uncertainties introduced in the results. Results from verification tests in no-wind conditions are presented and analyzed to identify the main uncertainty sources and quantify their effect on the reproduction of the floating wind turbine response to combined wind and waves.
Analysis of Mechanical Properties of Carbon Fiber Reinforced Spiral Rod in Umbilical
Authors: Zhang Yu , Cheng Ning-yi , Zhao Yi , Zhang Peng
Published: November 2019

Nowadays, the weight of steel pipelines restricts the development process of deep-water oil and gas. Using spiral carbon fiber reinforced rod instead of the steel armored layer in the umbilical can effectively solve the contradiction between carrying capacity and self-weight of the umbilical cable in the deep-water oil and gas development process. In this paper, using anisotropic carbon fiber materials, the stiffness matrix of the spiral carbon fiber reinforced rod under the tension-torsion coupled load is deduced through mathematical analysis and finite element calculation. It is found that the results of various stiffness coefficients obtained by mathematical analysis are closed to the finite element calculation. In addition, the integral form of carbon fiber reinforced umbilical is determined preliminarily, and the overall mechanical properties of umbilical are carried out. It is found that carbon fiber reinforced spiral rod in umbilical could have good mechanical properties with less weight.
Analysis of the Pitting Corrosion’s Effect on the Residual Strength of Submerged Pressure Shell
Authors: Xu Weijun , Chen Tianyi , Li Chenfeng , Zhou Xueqian , Liu Feng
Published: November 2019

Submerged pressure shell’s corrosion situation is more serious due to bad work environment, complex structure and difficulty of maintenance. Based on the analysis of calculation method of submerged pressure shell structures with non-corrosion, the calculation formula of pressure shell with pitting corrosion is given. The Finite Element Model is constructed and its residual strength is investigated. The relationships between shell stress and some parameters, such as radius of corrosion pit, depth of corrosion pit and location of corrosion pit are studied. Based on the finite element analysis results, the effect of radius of corrosion pit on the stress of pressure shell with pitting corrosion is analyzed. Furthermore, the influence coefficients of residual strength of pressure shell due to depth and location of pitting corrosion are determined, which provide a reference for the strength evaluation of submerged pressure shell with pitting corrosion.
Response Characteristics of a Floating Structure With Moon Pools Installed With Vertical Axis Wind Turbines
Authors: Nakamura Mitsuru , Ikoma Tomoki , Eto Hiroaki , Aida Yasuhiro , Masuda Koichi
Published: November 2019

This paper describes characteristics of motion responses and tether tensions of a floating structure with four moon pools, on which one or two vertical axis wind turbines are installed.

In this study, the authors proposed a twin-VAWT installed floating system, which was a pontoon based structure. However four moon pools were set on. The study conducted model experiments in a wave tank using regular waves with 0.6 to 2.0 seconds in wave periods and 0.02 and 0.04 m in wave height. The model had four moon pools and was installed with one or two vertical axis turbine models. From it, gyroscopic moment effects were investigated. Besides, the study performed numerical calculations with the linear potential theory based method which were a Green function method.

As a results, responses of the twin-turbine model are not affected by gyroscopic moment. The study discusses motion responses and tether tensions with nonlinear behaviours from mainly the experimental results.
Response Based Time Domain Structural Analysis on Floating Offshore Platform
Authors: Kyoung Johyun , Samaria Sagar , Kim Jang Whan , Duffy Brian
Published: November 2019

Performing the structural analysis and its integrity evaluation is the ultimate goal of design. However, design value estimation based on load-based analysis is still used as a conventional procedure in the offshore industry. The conventional method can be overly conservative and unrealistic with inconsistent load conditions since external loads such as mooring/riser and higher order hull response is inconsistently considered based on simplified linear assumptions. To assess the reliable integrity of a floating offshore platform, the response-based analysis has been successfully applied.

This paper presents a response-based time domain structural analysis of a floating offshore platform. Direct time domain structural analysis is applied by mapping of external environment loads on the floating platform at every instantaneous time interval. Accordingly, correct phase relationship between the various external loads and hull motion including nonlinear effects can be considered. For computational efficiency, present study uses a set of load components based on an efficiently selected basis function for hull motion and environment loadings. The stress time history is obtained directly by synthesizing the load components, and hence an actual time-domain structural response can be captured effectively. Thus, same structural analysis results can be used to evaluate both strength and fatigue criterion for a floating offshore structure.

Present analysis method is successfully applied to the evaluation of extreme global strength for a conventional semisubmersible platform. Present time domain analysis result on the structure response is compared with conventional load-based analysis result.
Trajectory Prediction of Moored Vessels With Reduced Station Keeping Capability due to Exceeded Anchor Load Limits
Authors: Josten Michał
Published: November 2019

This paper presents the development and application of an in-house manoeuvring method for the prediction of the track of a moored vessel in the case of a temporary or total loss of station keeping capability as a result of exceeded permissible anchor loads. The described method is implemented in the in-house ship design environment E4, which already contains a method for manoeuvring simulations. The equations of motion are solved for three degrees of freedom: surge, sway and yaw. Any effects due to dynamic heel are considered quasi-statically. The method is based on a force model with components for environmental and body forces as well as propeller, rudder and steering forces for dynamic positioning applications. For the purpose of mooring system analysis an additional force component for the mooring line loads is introduced by using load-deflection curves. These curves can be calculated within E4 or imported from other sources. The resulting method allows detailed response calculations in the time-domain and can be used in various applications due to its great computational efficiency. In the presented paper the method is used for the analysis of a marine casualty due to harsh weather conditions.
Numerical Simulation and Result Interpretation of Large Scale Fatigue Testing of Tubular X-Joint Close to Resonance Frequency
Authors: Thibaux Philippe , Van Wittenberghe Jeroen , Van Poucke Maarten
Published: November 2019

Fatigue testing of tubular joints is normally performed at a low frequency, making the tests typically very long. Recently, a new testing method has been developed where a specimen is excited close to its resonance frequency, making it possible to achieve testing frequencies higher than 20Hz. In the present investigations, different nodes representing an X-joint (diameter of the brace 711mm, wall thickness 20mm) were tested until failure in the resonance test set-up. The new testing method allows to load the full circumference of the weld with a nominal stress following an elliptic profile, such that the fatigue cracks can be initiated at many locations around the weld with similar probability of failure. The paper will present the strategy for the design of the specimen, aiming to achieve similar resonance frequencies for in-plane and out-of-plane bending and similar probability of failure along the welds. After reception of the specimen and testing, new finite element simulations were run and compared to the experimental response of the specimen. The influence of different aspect of the modelling will be discussed, with their influence on the identified resonance frequency and strain gauge readings. The investigation proves that it is possible to obtain a reasonably homogeneous hot spot values along the weld, resulting in the initiation of cracks not anymore dictated by the hot spot values, but by the local geometry of the weld.
Efficiency Assessment of the Composite Materials Repair Systems Intended for Corrosion Damaged Pipelines
Authors: Dumitrescu Andrei , Diniţă Alin
Published: November 2019

This paper presents the results of the research work carried out by the authors in order to evaluate the efficiency of the composite material wraps/sleeves (made of a polymeric matrix and reinforcing fabric) used to repair steel pipelines carrying hydrocarbons upon which local metal loss defects (generated by corrosion and/or erosion processes) have been detected. The pipeline repair technologies consisting of the application of composite material wraps are perceived as being advantageous alternative solutions for substituting the conventional technologies, which require welding operations to be performed in the pipe areas with defects.

The efficiency of the composite repair systems has been investigated by assessing the reinforcement effects (the restoration level of the damaged pipe mechanical strength) generated by the applied composite wraps as a function of their geometry and mechanical properties. To that purpose, numerical models based on finite elements have been developed and certified by comparing them with the results of several experimental programs previously performed by the authors. Finite elements simulations have also been conducted in the plastic region, taking into account material non-linearity.

The calculation methods proposed in literature (among which a method previously developed by the authors) to define the composite wrap dimensions (thickness and length) for a given pipe have also been investigated and compared to our numerical results in order to select the most adequate solution for the design of the composite repair system. The optimal values for the mechanical properties of the composite material used by the repair system have also been defined.
Well Integrity: Preliminary Risk Analysis for Different Well Life Cycle Phases
Authors: Abreu Danilo T. M. P. , Morais Carlos H. B. , Santos Joaquim , Colombo Danilo , Martins Marcelo R.
Published: November 2019

The life cycle of an oil well contains several phases, such as design, construction (drilling, completion and evaluation), production, intervention and abandonment. Moreover, each phase includes its particular operational modes (e.g., in the intervention phase there are wireline and coiled tubing operations). One of the main concerns during each phase refers to the risk of uncontrolled hydrocarbon flow to the environment, which is mitigated by measures that ensure well integrity through the use of well barriers. In this sense, the concept of two independent well barriers, reinforced by standards such as NORSOK D-010, leads the efforts in the industry, but does not clearly addresses the risks.

A failure in the well barrier elements leads to undesired events involving oil flow to the environment, damages to equipment and personnel loses. However a full comprehension of how these events contribute to the risk should take into account factors regarding the operational conditions. For instance, when the wellbore is exposed, an influx of hydrocarbons tends to release a biggest amount of oil to the environment than when the completion is installed. Additionally, older wells tend to sustain a smaller pressure when compared to other wells in the beginning of their life cycles — what also impacts on the consequences of undesired hydrocarbon flows. Nonetheless, these accidents should be pondered by their probability of occurrence for a full addressment of the risk.

In order to contribute to a risk-oriented view of issues related to well integrity, this work presents a customized Preliminary Risk Analysis framework. The simultaneous combination of well barrier elements failures constitutes the base of the analysis, which is complemented by control and monitoring measures. Hazards are also described according to their operational conditions, allowing treating this aspect separately.
An Experimental Development to Characterise the Flow Phenomena at the Near-Wellbore Region
Authors: Ahammad M. Jalal , Rahman Mohammad Azizur , Butt Stephen D. , Alam Jahrul M.
Published: November 2019

The understanding of rock characteristic and fluid flow behavior at the near-wellbore region is an important topic. Triaxial experiment setup can help to investigate these properties. In this research, a new triaxial experimental setup has been developed where the higher scale of the parameters such as higher reservoir pressure, and comparatively larger core sample can be used. High permeable synthetic porous samples are prepared to validate the device. The new triaxial experimental setup is validated with water as a base fluid. In the validation test, real samples and synthetic samples are used. First, flow in convergent direction is studied which represents as production at the in-situ condition. Then, the flow in divergent direction is examined that may represent the injection of fluid to enhance the hydrocarbon production. The near-wellbore flow phenomena are studied with real and synthetic samples. The results indicate that using this triaxial setup pressure drop and pressure buildup test can be explained. The new scientific setup is able to reduce the scale-up gap between laboratory data and field data to get actual reservoir flow phenomena.
Numerical Investigation for Vortex-Induced Vibrations of Steel-Lazy-Wave-Risers: Part II — CFD Study on Long Flexible Riser
Authors: Jang Hyunchul , Kim Jang Whan
Published: November 2019

Vortex-Induced Vibration (VIV) is one of the main sources of fatigue damage for long slender risers. Typical VIV assessment of risers is conducted using semi-empirical software tools in which the sectional hydrodynamic coefficients are derived from forced oscillation model tests on short rigid risers. The Steel Lazy Wave Riser (SLWR) with buoyancy sections is an attractive concept for improving fatigue performance in deep water developments, but there is limited model test data available for the hydrodynamic coefficients on SLWR’s. In Part I of the present study (Jang & Kim, 2019), CFD simulations are successfully validated against forced-oscillation model tests. In this paper, the feasibility of using CFD simulations for VIV response of a long flexible SLWR has been studied based on the CFD modeling practice developed in Part I. The CFD simulation is coupled with a simple structural model of the riser, and the structural equations of motions are solved via modal analysis. The simulation results capture all excitation frequencies measured from the model tests.
Analysis on the Influence of an Energy Storage System and its Impact to the Grid for a Wave Energy Converter
Authors: Stefek Jeremy , Bain Dominique , Yu Yi-Hsiang , Jenne Dale , Stark Greg
Published: November 2019

Reducing power fluctuations is essential for controlling the integration impacts of wave energy converter (WEC) plants in both distribution and transmission grids, and in stand-alone isolated power systems. This paper presents an analysis on the cost of and how a battery storage system can be used to further reduce the variation of power generated from the WEC due to the fluctuating nature of waves and its impact to the grid. The electrical power output from WEC-Sim simulations for the six sea states used in the Wave Energy Prize was analyzed to compute the peak power and power time history. The results were used to evaluate the battery storage capacity that is needed for a WEC system to provide reasonable power flow to the grid and estimate its cost based on the latest cost information for battery technologies published by the U.S. Energy Information Administration. Finally, a preliminary grid integration analysis was performed to demonstrate how WEC-generated power would contribute to a small island electricity system. As shown in the study, the instantaneous peak power is the primary cost driver for the battery storage and the power take-off system, and reducing the power fluctuations is essential for reducing the overall levelized cost of energy (LCOE). The power flow variation from WECs can be significantly reduced using battery storage without adding significant overall system costs, and the implementation of battery storage is essential for grid integration applications. There may also be additional opportunities to further investigate energy storage technologies that are specific to WEC applications to reduce these costs even further.
Numerical Investigation of Wave-Frequency Pontoon Responses of a Floating Bridge Based on Model Test Results
Authors: Shao Yanlin , Xiang Xu , Liu Jianyu
Published: November 2019

The wave-induced responses in the bridge girder of long floating bridges supported by pontoons are often dominated by the vertical modes, coupled horizontal modes and rotational modes about the longitudinal axis of the bridge girder. Pontoons with and without bottom flanges have been seen in recent floating bridge designs. Viscous flow separation around the sharp edges of the pontoon or the bottom flange may have strong influences on the hydrodynamic performance of the pontoon in terms of wave excitation, added mass and damping effects. Morison-type wave and current loads are normally included empirically in the early design phases to account for the viscous effects that cannot be covered by a potential-flow solution alone. Empirical drag coefficients and perhaps a correction to the potential-flow added mass are the inputs to such numerical models, which represents a part of the modelling uncertainties. Previous sensitivity studies using different drag coefficients in the ongoing Bjørnafjord floating bridge project in Norway indicate an influence up to 15% on the maximum vertical bending moment around the weak axis of the bridge girder.

This paper contributes to the understanding of viscous effects on the hydrodynamic characteristics, e.g. the added mass, damping and wave excitation loads, of a floating bridge pontoon with and without keel plate. This is achieved by exploring existing model tests for floating bridge pontoons, performing 2D Computational Fluid Dynamic (CFD) analysis for pontoon cross sections and numerical calibration in a simplified frequency-domain model with linearized drag loads. Scale effects are also investigated through CFD analyses in model and full scales.
Impacts of Condensate Storage on the Hull Structure Design of Semi Submersible Platform
Authors: Feng Jiaguo , Yu Yi , Li Da , Xie Bin , Xie Wenhui , Zhu Haishan , Wu Min
Published: November 2019

In order to develop the gas field in South China Sea, a deep-draft semi-submersible platform with 20000 m3 condensate storage tanks was selected. There is little industrial experience for semi-submersible platform with the condensate producing and storage tanks. This paper presents the impacts caused by the condensate producing and storage on the hull structure design in FEED phase. The design life is 30 years without returning to drydock for repair or maintenance.

The main unique features are illustrated as follows. Firstly, the double-wall voids (cofferdams) of 1.8 meters width were designen to prevent condensate leakage in the column around the condensate tanks. The double-wall bulkheads were connected by flats with manholes for maintenance access. this is different from conventional semi-submersible platform. Secondly, the non-watertight bulkheads in the middle of the condensate tank were needed to meet the efficient strength requirements for structural design. The upper and lower 2m height gaps on the bulkhead are convenient for the flowing of bottom condensate and top gas in condensate tank respectively. It is proven that the optimized design of continuous non-watertight bulkhead for the condensate tank is feasible, safe and reliable based on the global strength and fatigue analysis. Thirdly, The additional corrosion margin of 2mm was added to the boundary of frequently ballast and de-ballast tanks in the nodes and columns, and to the bottom plate and the side shell of 2m height from the bottom of condensate tanks considering the SEMI design life of 30 years. Fourth, the pressure head for condensate tank scantling design was increased by 10 m per condensate tank vent head location on topside. Fifth, there are some indirect effects due to the condensate storage, such as the increase of displacement and the load on the SEMI. Therefore, the hull structure needs to be reinforced, especially on the key connections, such as the column and pontoon connection, the deck and hull connection. It is recommended to pay attention to these critical locations with detailed local analyses.
Residual Stress in Girth Welds: Seeing Measurement Data Differently
Authors: Mirzaee-Sisan Ali , Wu Guiyi
Published: November 2019

This paper studies some of the recent residual stress measurement data on pipeline girth welds, which are available in the open literature, using a statistical approach. The measurement data points from residual stresses profiles are separated into three different zones, ie, outer zone, inner zone and middle zone, to study their distributions statistically. This statistical analysis indicates that for the region close to the outer surface, where welding is most likely to produce critical flaws, most of the reported measurement data points lie below the yield strength of the base metal. The paper concludes by presenting a case study using deterministic and probabilistic fracture analyses and providing some recommendations for further improvement of the relevant codes and standards.
Impact of the Uncertainties of the RAOs of a Semisubmersible Platform on the Performance of a Motion-Based Wave Inference Method
Authors: Mas-Soler J. , de Mello Pedro C. , Tannuri Eduardo A. , Simos Alexandre N. , Souto-Iglesias A.
Published: November 2019

Motion based wave inference allows the estimation of the directional sea spectrum from the measured motions of a vessel. Solving the resulting inverse problem is challenging as it is often ill-posed; as a matter of fact, statistical errors of the estimated platform response functions (RAOs) may lead to misleading estimations of the sea states as many noise values are severely amplified in the mathematical process. Hence, in order to obtain reliable estimations of the sea conditions some hypothesis must be included by means of regularization parameters. This work discusses how these errors affect the regularization parameters and the accuracy of the sea state estimations. For this purpose, a statistical quantification of the errors associated to the estimated transfer functions has been included in an expanded Bayesian inference approach. Then, the resulting statistical inference model has been verified by means of a comparison between the outputs of this approach and those obtained without considering the statistical errors in the Bayesian inference. The assessment of the impact on the accuracy of the estimations is based on the results of a dedicated model-scale experimental campaign, which includes more than 150 different test conditions.
Research on Characteristics of Removing Particles in Ship Exhaust Gas by Charged Droplet
Authors: Jiao Lei , Qian Zhaohui , Huang Dekai , Zhou Peilin , Chen Pengfei , Meng Lida
Published: November 2019

A traditional water scrubber is able to remove particles with a size over 200 μm in ship engine exhaust effectively. However, as the size of the particles decreases, the removal efficiency of the particles is gradually reduced, especially when the particle size is less than 50 μm, the method almost has little effect. This paper presents a study of charging particles in exhaust gas and water droplets to improve water scrubber’s efficiency in removing fine particles. The charging of the particles is mainly achieved through corona discharge, while the water droplets are charged by passing the high-voltage electricity to the nozzle. However, the feasibility and economics of these two methods have not been verified in other researches, so they are numerically simulated by Comsol Multiphysics software in this paper. The simulation results show that both particles and droplets can be charged steadily by the two methods. The numerical simulation results also indicate that the removal efficiency of particles in ship exhaust gas can be greatly improved by adding charges to droplets and particles at the same time. And a line chart of particle capture efficiency map under different particle sizes and change of droplets is obtained.
Interaction of Fixed Cylinder With Waves Through Weakly Coupled FNPT and Lagrangian Navier-Stokes
Authors: Agarwal Shagun , Sriram Venkatachalam , Murali K.
Published: November 2019

This paper presents a 2D/3D hybrid numerical model for studying the interaction of non-breaking waves with cylindrical structure. The work combines the strengths of mesh-based and particle-based methods, where the wave propagation is solved using 2D mesh-based potential theory model and the interaction with the structure is solved using 3D particle-based Navier-Stokes model. The paper presents the formulation of the two models and the weak-coupling methodology, along with recent improvements in the 3D MLPG_R (Mesh-less Petrov-Galerkin based on Rankine source solution) particle based method. The numerical results from interaction of fixed cylinder with solitary and focussed waves are compared with experimental data. The work demonstrates a significant reduction in simulation time for wave-structure interaction problems achieved using this hybrid approach without compromising on accuracy.
Effect of Flexible Joint Modelling Method on Deep Water Catenary Riser Hang-Off Fatigue Response
Authors: Hu Guanyu , Huang Chaojun , Yin Fengjie , Cerkovnik Mark , Yang Guangqiang
Published: November 2019

The Flexible joint is one of the most widely used hang-off systems for deep water catenary riser for its large rotation and load bearing capacity. The fatigue performance of riser hang-off region and fatigue load on the flexible joint highly depend on the rotational stiffness of the flexible joint. Thus, modelling the flexible joint stiffness to accurately simulate the behavior under cyclic bending cycles is critical in global riser fatigue analysis.

The load-displacement relationship of a flexible joint typically follows a nonlinear curve, and it shows hysteresis behavior when subject to cyclic bending cycles. However, in current industry practice, the flexible joint stiffness is modelled either as a nonlinear curve or simplified as a fixed value. These simplified methods sometimes can lead to unconservative or over conservative results in riser design. Modelling the flexible joint stiffness in an accurate approach becomes more important especially when the riser fatigue is critical at the hang-off region. In addition, the design of flexible joint will also be impacted by the fatigue load extracted from global fatigue analysis, which is also largely affected by the flexible joint stiffness modelling method. Thus, modelling a flexible joint by accounting for the nonlinear hysteretic stiffness is recommended. This paper compares the different modelling methodologies of the flexible joint for catenary riser hang-off and presents the impact on fatigue performance considering hysteretic behavior. This study considers the effects of wave amplitude and hosting vessel offset.

A case study is also presented on the application of all the modelling methods on fatigue performance of an SCR in the Gulf of Mexico. The fatigue behavior is compared for the different modelling methods considering long term wave motion and platform offsets. The impact on the results from different types of hosting platform is also discussed.
Safety and Risk Management Analysis of Accidents Related to Pressure Vessels and Piping in Alberta Petrochemical Industry From 2008 to 2017
Authors: Esouilem Mohamed , Bouzid Abdel-Hakim , Nadeau Sylvie
Published: November 2019

In recent decades, many accidents involving pressure vessels and piping components (PVP) have occurred in North-America. Several studies have been conducted to understand their causes and find suitable solutions to reduce their frequency. Most of the researches have focused on the technical causes of these accidents and the subsequent implementation of safety management strategies. These researches highlight that the main technical causes are leak and rupture. From this standpoint, it is important to deepen the study of leaks and ruptures accidents. In Alberta alone, the Alberta Energy Regulator (AER) demonstrated that more than 15 root causes initiated leak and rupture failures in PVP since 1990.

This paper presents an analysis of the frequency of accidents, their severity, their causes and the risk associated in the Alberta petrochemical industry from 2008 to 2017. This study proposes an exponential decay to estimate the frequency of accidents involving PVP and identifies the most important causes based on a severity analysis. The results based on the developed model show that there is a good agreement between the predicted and observed accidents frequency from 2008 to 2017. The severity analysis results show that the main factors contributing to accidents are corrosion, construction deficiency and overpressure. Finally, the proposed model of frequency and severity of observed and predicted PVP failures needs improvements to better predict the risks and be useful for prevention.
On the Microstructural Evolution and Porosity Consolidation in 316L Stainless Steel During Hot Isostatic Pressing
Authors: Cooper Adam J. , Tuck Olivia C. G. , Armson Samuel A. J. , Preuss Michael
Published: November 2019

If advanced manufacturing technologies are to be adopted over conventional manufacturing processes in the nuclear industry — the most regulatory challenging industry — rigorous fundamental studies that develop underpinning knowledge, materials performance data, and predictive capabilities are essential. Herein we have employed the use of electron backscatter diffraction (EBSD) and 3D X-ray computed tomography (XCT) to characterize microstructure evolution and porosity consolidation during the early stages of powder metallurgy hot isostatic pressing (PM-HIP). The data herein highlight the mechanisms through which the powder particle size distribution encourages localized plastic deformation and subsequent microstructural recrystallization of Type 316L stainless steel; the effect of powder particle size distribution on the rate of porosity consolidation is also discussed. Specifically, we have determined the temperature and pressure conditions that are required to initiate dynamic recrystallization during HIP, and explain how this is influenced by the powder particle size distribution.
Japanese Welding Guideline for Duplex Stainless Steels
Authors: Iwamoto Hiroyuki , Minami Fumiyoshi
Published: November 2019

A Japanese welding guideline for duplex stainless steels (DSSs)1) has been developed in a Sub-Committee of Chemical Plant Welding Research Committee in the Japan Welding Engineering Society. The guideline recommends 13 key points as a basis to prevent the unforeseen corrosion of weldments, which are based on practical experience in Japanese Oil & Gas and Chemical industries and similar published guidelines. The principal concept is how to obtain an acceptable ratio of ferrite/austenite phase balance along with no detrimental intermetallic compounds in the weld metal and heat affected zone. For the weld metal, consumable selection, the shielding and purging gas composition and weld heat input control are most critical. For HAZ, the nitrogen content of the base metal is most critical. This guideline is developed for DSS welders and welding engineers so as to understand the difference of DSS from standard austenitic stainless steel. This guideline is composed of three parts, the first is 13 basic recommendations, the second is to explain some technical aspects for these 13 key points and the third contains comprehensive data relating DSS base metal and weld metal including some important key points for each step of fabrication to understand the welding characteristics of DSS clearly.

This paper introduces the basic 13 recommendations for guidance purpose in addition to the mandatory requirements of the construction code in Japan.
New French Nuclear Pressure Equipment Regulation in 2019 and Use of Codes
Authors: Malouines Philippe , Wasylyk Andrew , Duranton Pascal
Published: November 2019

Nuclear regulations aim to minimize industrial risk, and assure the safety of workers and the public. In order to effective, regulations will often impact industrial processes and sometimes, industry organisation. It is therefore logical that any change in the regulation and its philosophy will have a significant impact on the industry.

This paper will present the evolution of the French regulations over the past 15 years, starting with the Nuclear Regulations which orientates the nuclear technology, toward maximizing safety of workers and public. Utilities and vendors have to comply with these regulations, which may modify the design and manufacturing process, and sometimes, industry organization. Through the case of the updating of French Nuclear order for pressure Equipment on September 3rd, 2018 [1], it will be reminded how the first Order in 2005 has affected current projects, and how nuclear codes has taken in account these new requirements from 2005 to 2015 [3]. It will be explained convergence of AFCEN codes requirements with regulation, and latest updating of ESPN Order in 2015 [3] and 2018 [1]. New approaches with Essential Safety Requirements, specific of European Regulation Pressure Equipment Directive in Europe (2014/68/UE) [7], give objectives to achieve, like risk analysis, Particular Material Appraisal (PMA), technical qualification of Material, among other, and they will be described, when they are applied to nuclear Equipment. Guides and AFCEN Technical Publication (PTAN) will illustrate in detail how the RCC M issued in 2018 [5] has been improved. The communication will conclude with the analysis of the effect of the new French regulation on nuclear reactor’s projects outside France.
Comparison of Ellipsoidal and Equivalent Torispherical Heads Under Internal Pressure: Buckling, Plastic Collapse and Design Rules
Authors: Zheng Jinyang , Li Keming , Yu Yehong , Zhang Zekun , Peng Wenzhu , Gu Chaohua , Xu Ping
Published: November 2019

Ellipsoidal and torispherical heads, whose geometric shapes are close, are usually used as end closures of internally pressurized vessels. In pressure vessel codes, for example, ASME BPVC Section VIII, ellipsoidal heads are designed as torispherical heads using geometric equivalency approaches. However, the difference between ellipsoidal and equivalent torispherical heads has not been studied in detail. In this paper, we first investigate the shape deviation between the two types of heads. Then we compare the elastic-plastic behaviors between ellipsoidal and equivalent torispherical heads as well as their failure modes, i.e., buckling and plastic collapse. It is found that ellipsoidal heads have more buckling resistance than equivalent torispherical heads, indicating that the current design rules for buckling failure based on the geometric equivalency approaches result in uneconomical design. Nevertheless, the shape deviation has little effect on plastic collapse pressures of ellipsoidal and equivalent torispherical heads, showing that the geometric equivalency approaches are applicable for such heads that fail by plastic collapse (bursting). In addition, the experimental and numerical results show that such heads experience geometric strengthening. The FE method considering the effect of geometric strengthening provides a good prediction about plastic collapse (bursting) pressure. However, the current design equation for bursting does not consider the effect of geometric strengthening, also leading to uneconomical design.

Therefore, in order to avoid uneconomical design, we recommend that (1) with respect to the buckling of ellipsoidal heads, a new design equation be proposed rather than implementing the geometric equivalency approaches, and (2) the current design equation for bursting be deleted, and a new design equation, considering the effect of geometric strengthening, be proposed for the bursting of ellipsoidal and torispherical heads subjected to internal pressure.
Elastic-Plastic Buckling Analysis of Spherical Latticed Shell of Large Scale Molten Salt Storage Tank
Authors: Tang Hui , Shi Qianyu , Wang Zhijian , Li Qi
Published: November 2019

In recent years, with the rapid development of solar thermal power technology in China, the key equipment molten salt storage tank is widely used. Instability is the primary failure mode for these large thin-walled structures. Thus, stability design for the molten salt storage tanks is significant. In this paper, the elastic and elastic-plastic buckling analyses of a spherical latticed shell are carried out with whole process load-deformation method considering geometric and material non-linearity. The critical buckling loads of these two analysis types are obtained from the load-deformation curve. Comparison between spherical latticed shells with channel beam and I-section beam is presented. The modeling method of finite element model for buckling analysis of latticed shell is discussed. This may provide a reference to the stability design of large scale storage tank.
European Project ATLAS+: Small and Large Scale Ductile Tearing Experiments on Ferritic Steel WB36 to Study Transferability of Material Ductile Properties
Authors: Dahl Anna , Moinereau Dominique , Le Delliou Patrick , Vincent Willy
Published: November 2019

The 4-years European project ATLAS+ (Advanced Structural Integrity Assessment Tools for Safe long Term Operation) has been launched in June 2017. One of its objectives is to study the transferability of material ductile properties from small scale specimens to large scale components and validate some advanced tools for structural integrity assessment.

The study of properties transferability is based on a wide experimental programme which includes a full set of fracture experiments conducted on conventional fracture specimens and large scale components (mainly pipes).

Three materials are considered in the programme : a ferritic steel WB36 typical from secondary feed water line in German PWR reactors, an aged stainless steel austenitic weld representative of EPR design and a typical VVER austenitic dissimilar weld (DMW).

This paper describes the experimental work conducted on the ferritic steel WB 36 (15NiCuMoNb5) and summarizes the experimental results available after 2 years of work.

Numerous mechanical tests have been conducted on a wide panel of fracture mechanics specimens for a full characterization of the ferritic steel: Tensile properties, Hardness, Charpy Energy, pre-cracked Charpy PCC, Master curve on CT and SENT specimens, ductile tearing properties on CT and SENT specimens.

In parallel, it is planned to test three 4PB large scale tests on pipings (FP1, FP2 and FP3) at room temperature on the EDF test facility with 3 configurations (shape, size and location) of cracks: through wall crack (TWC), internal and external ½ elliptical cracks. Progress of these large scale experiments is described including first results.
Stress Corrosion Cracking in Low Temperature Carbon Steel
Authors: Al-Harthi Sultan G. , Mohammad Sameer Mohammad Obaid
Published: November 2019

Repeated weld joints leaks were observed in newly commissioned non insulated low temperature carbon steel anhydrous ammonia pipes after few months of operations. A detailed investigation was carried out to identify the root cause which found to be usage of high strength filler wire which leads to stress corrosion cracking (SCC) and weld joints failure. Also, An Online advance inspection via Phased Array Ultrasonic Test (PAUT) was conducted to assess the condition of weld joints in anhydrous ammonia pipe loops. Moreover, three different samples of leaked weld joints were submitted for metallurgical failure analysis laboratory. The paper explains the root cause of the damage, Online PAUT inspection and the challenges faced during development of the rectification procedure and implementation.
Proposal of Ductile Damage Model Based on Unit Cell Analysis for Prediction of Ductile Crack Growth Resistance of Cracked Component
Authors: Yamada Takehisa , Ohata Mitsuru
Published: November 2019

The aim of this study is to propose the damage model on the basis of the mechanism for ductile fracture related to void growth and applicable to ductile fracture assessment for steels. In order to determine damage evolution law, void growth behavior in the material was investigated by elasto-plastic finite element analyses using unit cell model with an initial void. From the results of the unit cell analyses, it was evident that a void in unit cell grew nonlinearly with increasing applied macroscopic strain. Moreover, the relationships between normalized void volume fraction and normalized strain by each critical value corresponding to crack initiation were independent of stress-strain relationship of material and stress triaxiality state. Based on this characteristic associated with void growth, damage evolution law representing nonlinear damage accumulation was derived. Then, using the damage evolution law, ductile damage model reflecting void growth behavior and ductility of material was proposed.

For validation and application of the proposed damage model, ductile crack growth tests using bend specimens with a machined notch or a fatigue pre-crack were conducted for low carbon steel. The proposed damage model was implemented in finite element analyses and ductile crack growth simulations were performed for each bending test. Then, it was shown that the proposed model could accurately predict ductile crack growth resistance from machined notch root and fatigue pre-crack tip (R-curves) and the validity and applicability of proposed damage model to cracked components could be confirmed.
Review of Pressure Vessel Code Rules on Cold Forming Limits and Heat Treatment Requirements
Authors: Xu Kang , Rana Mahendra D. , White James
Published: November 2019

In pressure vessel fabrication, cold formed carbon and alloy steels are required to have a subsequent heat treatment because of the loss of ductility and toughness from cold forming. The requirements for heat treatment are dependent on the materials, thickness, amount of cold forming and service condition. There are significant differences among the pressure vessel codes on the requirements for cold forming heat treatment. In this paper, the code requirements for cold forming heat treatment are reviewed for ASME Section VIII Divisions 1 and 2, EN 13445-4 and GB-150. The technical basis of forming strain calculations is discussed. Based on experimental data on the impact toughness as a function of forming strain, and fracture mechanics studies on cold formed components, improved guidelines are proposed on cold forming limits for heat treatment.