bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Frequency Piping Vibration and Noise
Authors: Price Stephen , Smith Donald R.
Published: March 2009

Many gas transmission facilities utilizing centrifugal compressors and large diameter piping experience high amplitude high-frequency noise and vibration. In addition to being a nuisance noise problem, failures of thermowells, instrumentation, and attached small-bore piping can result. Such problems can also occur in the piping itself when high flow velocities and internal obstructions are present. Many times, high frequency noise problems are treated with acoustical insulation (lagging) on the pipe. However, with an understanding of the underlying physics of two- and three-dimensional acoustics it is often possible to modify the piping design to reduce or eliminate the high frequency energy. Two high-frequency energy generation mechanisms predominate in most industrial processes; flow induced (Vortex shedding) and pulsation at multiples of running speed (blade-pass frequency). Once this energy is generated, amplification may occur from acoustical and/or structural resonances, resulting in high amplitude vibration and noise. Many tools exist for analysis of structural resonances and one-dimensional acoustical resonances. Analysis of high-order acoustics can be accomplished using sophisticated numerical methods (FEA, or BEA); however, a simplificaiton of the three dimensional wave equation which has been reduced to a function of zeroes of the 1st order Bessel function, the speed of sound, and internal pipe dimension can also be used successfully. Several references provide lists of the zeroes of the Bessel function; however, most of these references only provide solutions up to m,n = 6. Field tests have identified cross-wall modes up to m = 30. Therefore, a table is provided for zeros for m = 0–32 and n = 0–8.
Evaluation of Green Inhibitors
Authors: Papavinasam Sankara , Doiron Alex , Revie R. Winston
Published: March 2009

Producing pipelines are protected from internal corrosion by the application of corrosion inhibitors. Environmental effects of corrosion inhibitors have received increased attention in recent years, especially for offshore pipelines. In response to the drive for more environmentally friendly inhibitors, several “green” corrosion inhibitors have been developed. In the design of new classes of corrosion inhibitors, there is a need to take into account the various environmental regulations that exist. In this paper, the criteria for selecting green inhibitors as used in various part of the world are reviewed. The current test methods, their reproducibility and effectiveness, and their accuracy in relation to the selection of green inhibitors are discussed.
TransCanada PipeLines: An Expert Advisory System for Pipeline Operations
Authors: Kerkhof Jack , Williams Lawrence , Mah Ken , Kmet John
Published: March 2009

This paper describes a new approach to provide advanced advisory information intended to complement the systems used by Gas Controllers operating the TransCanada gas pipeline. The “Advisory System” is based upon Gas Controller knowledge and experience captured into an expert system and integrated with signal processing of SCADA in real-time. The Advisory System continuously applies its knowledge seeking and identifying deviations from normal and efficient operation, determining whether these deviations are significant, and presenting warnings and possible causes through a web-enabled user interface. The technology monitors both steady-state variations from normal operation and the transient effects of unintentional or abnormal conditions. Discussed are system requirements, and the unique approach taken to monitor, tune, evaluate and communicate conclusions. The results achieved, Gas Controller feedback, and future directions are presented, including the successful rapid detection of a linebreak incident.
Right-of-Way and Pipeline Monitoring in Permafrost: The Norman Wells Pipeline Experience
Authors: Doblanko Rick M. , Oswell James M. , Hanna Alan J.
Published: March 2009

Enbridge Pipelines (NW) Inc. (Enbridge) owns and operates a 323.9 mm outside diameter crude oil pipeline from Norman Wells, Northwest Territories, Canada to Zama, Alberta, Canada (Norman Wells Pipeline). The first of its kind in North America, this pipeline, completely buried in discontinuous permafrost, is approximately 869 kilometres in length. The pipeline, designed to operate at ambient temperatures, was constructed during the winter seasons of 1983–1984 and 1984–1985 and began operations in April 1985. Enbridge (formerly Interprovincial Pipe Line (NW) Ltd.), under various regulatory terms and conditions, is required to monitor and report the effects of pipeline construction and operations associated with the environment and right-of-way. The company has been an active participant in joint research and monitoring working groups consisting of various departments of the Government of Canada, Government of Northwest Territories, and other agencies. Over the past seventeen years, Enbridge has developed a monitoring and surveillance program that ensures the safe operation of the pipeline and protection of the environment. Any significant issues arising from the monitoring program result in mitigative actions based on engineering assessments. Furthermore, Enbridge is mandated to inform the appropriate agencies of issues resulting from the monitoring program. This paper will focus on the terrain and geotechnical monitoring programs initiated by Enbridge over its years of operation of this pipeline and will discuss topics including operations and maintenance activities key to pipelines installed in discontinuous permafrost, condition of the pipeline, and the on-going terrain and slope monitoring program.
The Measurement and Control of Residual Stress in Spiral Sub-Merged Arc Welded Pipe
Authors: Xiong Qingren , Feng Yaorong , Huo Chunyong
Published: March 2009

The problems related to the measurement and control of residual stress in the production of SSAW pipe are analyzed based on tests: (1) The relationship between circumferential opening in cut-ring test and residual stress from mechanical cutting stress releasing test; (2) The effects of severing position on the measured opening; (3) The effects of hydrostatic test on residual stress of SSAW pipe; (4) The supplementary specification of SSAW pipe. It is put forward that the circumferential opening varies with the severing position, and the normal hydrostatic test mainly bring about the redistribution of the residual stress as well as the decrease of that. The appropriate higher pressure can reduce residual stress considerably. Some suggestions about the supplementary specification related to residual stress of SSAW pipe were brought forward.
Study of High Vapour Pressure Pipeline Safety
Authors: Grzyb David W. , Hallihan Michael F.
Published: March 2009

The Alberta Energy and Utilities Board (EUB) recently initiated a study to examine and evaluate whether existing regulations and standards adequately ensure the safe operation of High Vapour Pressure (HVP) pipelines in Alberta. An engineering consultant was contracted to review the performance history of HVP pipelines, determine the predominant failure modes and causes, compare Alberta performance against other jurisdictions, and provide a report containing recommendations for improvements. The consultant concluded that the predominant cause of HVP pipeline failures has been interference from outside parties, followed equally by material deficiencies and corrosion. The report also concluded that HVP pipelines in Alberta have been operating at a failure frequency approximately 30 per cent less than the failure frequency of hazardous liquids pipelines in the United States. The paper first provides a brief description of the role of the EUB in Alberta, followed by a summary of HVP pipeline performance. A description of the methodology used to conduct the study follows, along with the conclusions and recommendations made by the consultant. A process for the verification of the proposed changes by the affected stakeholders is then described, followed finally by a description of how any proposed regulatory changes may be completed.
Effective Use of an Alliance to Deliver Pipeline Maintenance Services
Authors: McFarlane Wayne G. , Marsollier Allen
Published: March 2009

Pipeline companies face a difficult task in cost-effectively managing pipeline maintenance activities. Complexity is introduced due to geographical expanse, remote locations, access to qualified contractors and the desire to hire locally, and contract management of available suppliers. Pipeline companies have traditionally provided maintenance activities through in-house resourcing, or management of a multitude of available contractors. With increasing efforts to focus in-house resources on core pipeline operations, there has been a corresponding shift in moving noncore maintenance activities to outside providers. This has introduced an increase in administration costs associated with supplier qualification activities, document management and payment processing. TransCanada PipeLines Limited has developed a model where core skills have been retained to perform critical activities in-house and less essential services have been contracted out, along with the management of the subcontracts. This model relies on a central dispatch service along with a large base of subcontractors strategically located along our pipeline system to provide these services. The process involves two basic steps — managing subcontractors and performing work. Managing subcontractors is the key to the process. This part of the process proactively provides TransCanada with qualified subcontractors at the right place, the right time and for the best price. This paper will discuss the alliance model we’ve implemented in conjunction with Ledcor Industrial Maintenance Ltd. for contracted services and how this arrangement is crucial to our success in managing maintenance activities cost effectively. We will describe the model, how it was developed and implemented, how it works and some of the benefits that make it a successful contribution to regional operations. We will also discuss some of the key lessons learned. Further details on the process will be presented, along with the bottom-line benefits associated with this type of relationship.
Feedback and Mapping Control of Natural Gas Engines
Authors: Sorge Greg
Published: March 2009

Automatic controls have been used on all types of machinery since the first complicated machines became popular in the 19th century. Controls are used to maintain pressures, temperatures, operating speeds, flows and many other operating parameters. Natural gas engines have used a variety of controls for various purposes since the first natural gas engines were produced. This paper will discuss the history of mechanical controls used on natural gas engines and the introduction and application of electronic controls. The paper will discuss open loop (mapping) and closed loop (feedback) type controls and common applications of each. Mechanical control systems such as governors, fuel regulators, fuel mixing valves, thermostats, and turbocharger wastegates will be discussed and classified as open or closed loop controls. Electronic control systems such as governors, air/fuel ratio controls, detonation controls, and turbocharger controls will also be discussed and classified. This paper will also discuss state of the art controls which perform numerous functions to get desired performance, and can be communicated with remotely.
Gas Compressor Station Rebuild
Authors: Durrani Jawad , Forbes William
Published: March 2009

Gas Compressor Station design, procurement, construction and commissioning normally takes well over 12 months. Earth Tech recently redesigned, procured, rebuilt and commissioned in 5 months, a new 14 MW/19,000 HP turbine driven gas compressor station near Red Bluff – California. This was a fast paced EPCM project. The previous Turbine driven Gas Compressor Station was damaged beyond repair in an oil fire on November 6th, 2001. A new Station, with bigger capacity using state of the art technology, was to be employed. The Construction Team was able to complete the onsite demolition through to commissioning in just over 3 months. This urgency was necessary to meet the client’s anticipated summer loads. The project was staffed around the clock for much of this 3-month period. Even with the intense manpower loading and the simultaneous presence of 4 subcontractors, this project was able to keep its stellar safety record — resulting in no injuries. It was very much a team effort with relentless dedication and planning utilizing the vast knowledge and experience of all parties involved. Key challenges for all parties were to maintain schedule while not sacrificing safety, quality or scope. These challenges were amicably and professionally managed. The client’s standards and specifications were met or exceeded in all cases.
Studies on VIV Fatigue Behavior in SCRS of Hybrid Riser Systems
Authors: Vieira Luciano Tardelli , Jacob Breno Pinheiro , Fernandes Antonio Carlos , Franciss Ricardo
Published: March 2009

The main objective of this work is to demonstrate the application of an analysis methodology for hybrid riser configurations. Such configurations are based on submerged buoys that are connected by jumpers to a floating production unit (a FPSO vessel for instance), and by risers to the seabottom. The focus is on VIV-induced fatigue behavior of the steel catenary risers that connect the buoy to the seabottom. The methodology employs numerical tools for the nonlinear static analysis, modal analysis, VIV and fatigue behaviour. The application of the methodology is illustrated with the analysis of a practical case study located in Campos Basin.
Application of a Modified Truss Element to the Analysis of Flexible Risers
Authors: de Morais Ma´rcio Cardoso , Jacob Breno Pinheiro
Published: March 2009

This work presents studies on the implementation and application of a specialized non-linear finite element for modeling of very flexible risers. Results of parametric analyses involving flexible risers are presented, and compared with those obtained by using classical truss or beam elements. The parametric study also includes the sensitivity to variation in mesh refinement. As a conclusion, the applicability of the modified truss element in structural analysis of flexible risers can be assessed.
Seasonal Modelling of Multivariate Distributions of Metocean Parameters
Authors: Fouques Se´bastien , Myrhaug Dag , Nielsen Finn Gunnar
Published: March 2009

Statistical information about the joint occurrence of metocean parameters is of importance for many offshore activities. For instance, in marine operations, environmental limitations may be brought about by both wind and wave conditions. Thus, knowledge of their joint occurrence is important as the persistence duration and the seasonal dependence of wind and waves appear to be of large interest. However, such a modelling becomes difficult as the number of considered variables increases, especially when utilizing a common parameterization of some conditional distributions. This paper proposes a general methodology that aims at modelling seasonal joint distributions of n such parameters from their correlation structure and the n marginal distributions fitted by generalized gamma ones. Two methods are proposed in order to derive an approximate joint distribution from the modelled margins. The first one matches the correlation matrix only, whereas the second one, which is based on a multivariate Hermite polynomials expansion of the multinormal distribution, is able to match joint moments of order higher than two. However, more restrictive conditions are shown by the latter. An application to the simple example of the joint occurrence of significant wave height and the mean wind velocity at the 10m elevation is used to illustrate the methods. Eventually, examples of applications like simultaneous persistence of wind and wave conditions as well as seastate forecasting from statistics are given.
An Assessment of EOF Current Scatter Diagrams With Respect to Riser VIV Fatigue Damage
Authors: Meling Trond Stokka , Eik Kenneth Johannessen , Nygaard Einar
Published: March 2009

The accuracy of current modelling is critical when considering deepwater riser fatigue damage caused by vortex-induced vibrations (VIV). In the present study the use of empirical orthogonal functions (EOF) to extract the governing characteristics from huge amounts of current measurements has been assessed. The amplitudes of the time varying principal components (PC) have been organized into bins in scatter diagrams. The accuracy of this scatter diagram approach with different numbers of EOF modes involved has been evaluated in terms of riser VIV fatigue damage.
Hydrodynamic and Environmental Impact of Constructing a Closure Dam Near Seawater Intakes of a Power and Desalination Plant
Authors: Mohamed Khaled A.
Published: March 2009

Power and desalination plants are very important in the Arabian Gulf region to provide water and electricity. Abu Dhabi, United Arab Emirates has a number of power and desalination plants. One of these plants is Umm Al Nar plant. It is located inside a lagoon north of Abu Dhabi Island, which is the North Lagoon. Hydrodynamic study was carried out to investigate the impact of constructing a temporary closure dam in the tidal water near the plant intake on the flow pattern and the recirculation of effluent discharges from the outfall to the intake of the plant. The effect of the proposed dam on the mangroves in the vicinity of the plant was investigated. Two dimension hydrodynamic numerical flow model simulates the study area was used in the study. The hydrodynamic and environmental impact of the proposed dam was evaluated by comparing the results of the model computations with and without the dam simulation.
Spectral Analysis of Irregular Wave Impact on the Structure in Splash Zone
Authors: Ren Bing , Wang Yongxue
Published: March 2009

The spectral analysis from experimental data of irregular wave impact on the structures with large dimension in the splash zone is presented. The experiments were conducted in the large wave-current tank in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. In the experiment, the target spectrum is JONSWAP spectrum, the significant wave height H1/3 is in the range from 0.1m to 0.3m, and the peak period of spectrum Tp in the range from 1.0s to 2.0s. The ratio of s/H1/3, which refers to the clearance of the subface of the structure above still water level (s) to the incident wave height, is between −0.1 and 0.4. The spectral analysis results of the irregular wave impact pressure on the subface of the structure under various case studies are presented. The distribution of spectral moment of the impact pressure on the structure along the subface is given. And the influence of different incident wave parameters and relative clearance s/H1/3 on the average spectral moment of impact pressure are discussed.
Corrosion Testing of Reinforcement in Simulated Annulus Environments of Flexible Pipelines
Authors: Underwood N. J.
Published: March 2009

The multi-layered unbonded structure of a flexible pipe creates an inherent internal volume known as an annulus. This annulus envelops the hoop pressure and tensile reinforcements of the pipe. This presents very specific corrosion conditions if seawater intrudes or water condenses in the annulus and no protection system operates to prevent corrosion. This paper describes an investigation into the effect on general corrosion as a result of this environment utilising small-scale test cells. This was undertaken as an attempt to simulate the corrosion conditions that may occur in differing zones of a flexible pipeline. The cell environment was varied by use of both de-ionised water and seawater. The system was saturated with CO2 and CH4 to simulate permeation of this gas through the polymer pressure sheath. Electrochemical and weight loss measurements were undertaken in order to quantify the corrosion rate in these simulated environments. This approach attempts to give useful information regarding the nature of carbon steel tensile reinforcements used in flexible pipeline under operational conditions.
Mechanics of Offshore Pipelines in Several Operating States and Analyzing Software
Authors: Zeng Xiaohui , Liu Chuntu , Xing Jingzhong
Published: March 2009

Offshore pipelines are indispensable structures during the marine petroleum exploitation. There are manifold operation states having to do with pipelines such as in situ operation, span, trenching, pipelaying, lifting of pipe/riser, etc. The behavior of pipelines in one state differs greatly from the others. In addition, the structure configuration, the sea severity, and the seabed soil conditions are complex. Therefore, strength analysis of offshore pipelines becomes a rather difficult and onerous task. Presently, there is a lot of technological difficulty in the course of analysis, among which are not only theoretical problems such as geometric non-linearity and moveable boundary, but also practical problems. To tackle the problems, analytical methods, numerical methods such as FEM and shooting method are adopted respectively and jointly. Based on the theoretical research, integrated software named ‘Offshore Pipelines Strength Analysis’ is developed. This software can carry through strength analysis of pipelines in different operating state, being up to the requirement of engineers. The theoretical background and interface of the software are presented.
Simulation of a Turbulent Polymer Solution Flow Over a Flat Plate
Authors: Chyczewski Thomas S. , Grube Nathan E. , Joslin Ronald D.
Published: March 2009

A non-Newtonian fluid Direct Numerical Simulation (DNS) tool is developed to predict the reduction of turbulent skin friction drag observed when the fluid is a dilute polymer solution. Results obtained with this tool are to be used to develop a Reynolds Averaged Navier Stokes (RANS) design tool that will allow the design of ship hulls and other external bodies that benefit in a predictable way from polymer-induced drag reduction. The FENE-P dumbbell model for viscoelastic fluids is used to provide the non-Newtonian stresses. The approach is tested with a turbulent flat-plate boundary layer case (Reδ* = 1000). The inflow data is generated by a recycling method extended to include the polymer stresses. Results are presented for a coarse grid case in which the turbulence is not completely resolved and consist primarily of comparisons between Newtonian and polymer ocean turbulence characteristics, such as turbulence intensity and velocity profiles. Although the predicted drag is lower for the polymer solution case, it is not as significant as experimental observation. This discrepancy is attributed to the coarseness of the simulation.
Fracture Toughness of the API 5L X65 Steel Submitted to Intercritical Heat Treatments
Authors: Sant’anna Pedro C. , Rizzo Ernandes M. , Gomes Samuel Irati N. , Ferreira Itamar
Published: March 2009

The intercritical heat treatment effect on the mechanical properties of the API 5L X65 steel, microalloyed with Ti and Nb, widely used in welded structures, was investigated. The embrittlement, observed by several authors in the intercritical region of the heat affected zone of welds performed in HSLA steels, is closely related to the volume fraction of M-A constituent, formed in the cooling. Just upon the homogenization and normalizing heat treatments, the specimens were submitted to different intercritical heat treatments, performed at 780 °C for 30 minutes and cooled with various Δt8/5 rates, with the purpose of varying the microstructure. High fracture toughness was obtained with the lower cooling rate. Also, it was verified that the low M-A constituent volume fraction was not enough to promote reduction on the fracture toughness.
Inspection of Offshore Flexible Risers With Electromagnetic and Radiographic Techniques
Authors: du Chaffaut B. A. , Jarrousse J.-L. , Chambellan D. , Rattoni B. , Sollier T. , Lechien J. L. , Bucherie C.
Published: March 2009

Bureau Veritas, CEA and IFP studied the feasibility of on-site inspection of metal layers in the upper part of flexible risers (link between seabed and surface) used by the offshore petroleum industry. The upper part of the flexible pipe is currently the one that is the most subjected to constraints, particularly inside the stiffener. Unexpected events added to operational strain may cause cracking and breaking of these layers. Until now, no device was available to check the integrity of the various layers of the flexible risers. The authors developed electromagnetic and radioscopic techniques to inspect the upper parts of the risers. They determined the possibilities and the limits of these techniques in the detection of breaks. Inside the stiffener, at the end of the riser, the method is intrusive. Outside the stiffener, for the current length of the riser, the method is either intrusive, either non-intrusive. An internal instrumentation carrier was built for laboratory tests and an external carrier was designed for instruments positioning. This last carrier is able to move along the pipe step by step and to rotate the source and the detector around the flexible pipe on more than 360°.
Morphology and Pipeline Design Through a Dynamic Landfall Area: The Black Sea Pipeline Case
Authors: Chen Z. , Venturi Marco , Bijker R.
Published: March 2009

The Blue Stream pipeline project is a gas transportation system for the delivery of processed gas from a gas station in the southern Russia across the Black Sea to Ankara, Turkey. The Turkish landfall of the offshore pipeline in the Black Sea is located near Samsun, see Figure 1 for the pipeline route. One of the main aspects of the design of pipeline through a morphologically dynamic area such as landfall is the required burial depth (Chen et al, 1998, 2001 and Bijker et al 1995). The burial depth is the result of an optimisation between: • safety of the pipeline (which often requires a large burial depth), and • environmental impact and trenching costs (a small burial depth means less dredging and less environmental impact). This paper presents a method of predicting the future extremely low seabed level in a morphologically dynamic landfall area, which is required to determine the burial depth of the pipeline. Both short term and long term coast evolution were assessed to quantify the expected lowest seabed level along the pipeline route in the landfall area during the pipeline lifetime of 50 years. The results were used to determine the required pipeline burial depth. The long term morphological changes originate from long term variations in the morphological system (e.g. river input), gradient in the longshore sediment transport and long term variations in the hydrodynamic conditions. The short-term morphological changes originate from beach profile variations due to cross-shore sediment transport as a result of seasonal and yearly variations in the wave and current conditions. Numerical modelling was applied to compute the longshore and cross-shore sediment transport rates and the resulting coastline evolution and cross-shore profile evolution. The longshore transport model was validated using the available data on the coastline changes in the past 20 years, which was derived from the satellite images. The 50-year lowest seabed level has been determined as the sum of the coastline retreat and the cross-shore evolution in the next 50 years.
Wave Induced Pressures on Pipelines Near a Sloping Boundary Due to Regular Waves
Authors: Roopsekhar K. A. , Sundar V.
Published: March 2009

The hydrodynamic pressures due to regular waves around the circumference of a pipeline near a sloping rigid bed and placed parallel to the wave direction have been measured. The pressures were integrated to obtain the force time history, from which the peak horizontal and vertical forces were evaluated. The effects of relative clearance of pipe from the bed and its relative position from the toe of the sloping bed on the pressures and forces on the pipeline as a function scattering parameter and wave steepness are reported. The reflection characteristics of the sloping bed in the presence of the pipeline are reported as a function of surf similarity parameter and compared with the results from existing literature. The details of the model setup, experimental procedure, results and discussion are presented in this paper.
Effect of Seaward Side Wave Screens on the Dynamic Pressures on a Vertical Wall
Authors: Ramakrishnan Balaji , Vallam Sundar
Published: March 2009

The performance of two vertical wave screens formed by pipes on the reducing the pressures due to waves on a vertical wall placed on its leeward side has been investigated through an experimental program. The variations in the reflection characteristics of the wall are also studied. Of the two screens the porosity of the seaward side screen was maintained constant, while, the porosity of the one in between this screen and the wall was varied. Thus, four different screen porosity combinations in a random wave field were studied. The effects of the screen porosity on the reflection from the wall and the dynamic pressures on the vertical wall have been reported as a function of relative dissipating chamber width. The details of models, instrumentation, analysis of the data and the results are presented and discussed in this paper. Provision of double chamber screen system with appropriate porosity combination is very effective in reducing the reflection from a vertical wall.
Towards the Integration of Analysis and Design of Mooring Systems and Risers: Part II — Studies on a DICAS System
Authors: Correa Fabri´cio Nogueira , Senra Stael Ferreira , Jacob Breno Pinheiro , Masetti Isai´as Quaresma , Mourelle Ma´rcio Martins
Published: March 2009

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1]. That paper describes a “basic” classic, uncoupled methodology, and comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented in the companion paper [1], and these issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The present paper proceeds describing some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.
Numerical Simulations of the Flow Around Flexible Cylinders
Authors: Yamamoto Cassio T. , Fregonesi Rodrigo A. , Meneghini Julio R. , Saltara Fabio
Published: March 2009

In the offshore industry fluids are conveyed from the seabed to the platform through slender structures named risers. These risers are subject to shear and oscillatory flows due to currents and waves respectively, flows with a very high degree of complexity, with changes of intensity and direction the deeper the water depth. The main purpose of this work is to investigate the hydroelastic interactions which take place between flexible cylinders and fluid forces. The cylinders are subject to uniform flow, and the hydrodynamic forces are estimated by CFD, in a quasi three-dimensional fashion. This article presents the results of an investigation being carried out at the University of Sa˜o Paulo and sponsored by the Brazilian Oil Company Petrobras. In this research a discrete vortex method is used to simulate the flow around a flexible cylinder. A description of this method can be found at Yamamoto et al. (OMAE 2001). A finite element structural model based on the Euler-Bernoulli beam theory was developed. In order to evaluate the dynamic response, a general equation of motion is solved through a numerical integration scheme in the time domain. The hydrodynamic forces are evaluated in two-dimensional strips. The technique used is the Discrete Vortex Method, which is a Lagrangian numerical scheme to simulate an incompressible and viscous fluid flow. The calculations are compared with experiments of a cantilever flexible cylinder immersed in a current, see Fujarra [6]. The reduced velocity vs. non-dimensional amplitude curve obtained in our calculations is compared with the experimental results. Visualizations of the wake indicate a hybrid mode of vortex shedding along the span. A 2S mode is found in regions of low amplitudes, changing to a 2P mode in the regions o larger amplitudes. The position of the transition of the modes varies with the reduced velocity. A practical case of marine risers is also presented. In this case the results for various uniform currents acting on a single, flexible cylinder, representing a riser of 120m with 100m under water, are shown. Envelopes of maximum and minimum in-line and transverse displacements are presented.
Mooring Dynamics Phenomena Due to Slowly-Varying Wave Drift
Authors: Bernitsas Michael M. , Matsuura Joa˜o Paulo J. , Andersen Torgrim
Published: March 2009

The effects of slowly-varying wave drift forces on the nonlinear dynamics of mooring systems have been studied extensively in the past 30 years. It has been concluded that slowly-varying wave drift may resonate with mooring system natural frequencies. In recent work, we have shown that this resonance phenomenon is only one of several possible nonlinear dynamic responses of mooring systems to slowly-varying wave drift excitation. We were able to reveal new phenomena based on the design methodology developed at the University of Michigan for autonomous mooring systems and treating slowly-varying drift as an external time-varying force. In this paper, the U of M methodology is used systematically to reveal seven phenomena induced by mean and slowly-varying drift forces; one of those is resonance. Conceptually, numerous qualitatively different behaviors may be induced. The next step towards comprehensive identification of such phenomena is taken by introducing the method of harmonic balance to study nonautonomous mooring systems.
An In-Depth Look at the Effectiveness of Smart Materials for Monitoring and Control of Composite Structural Panels
Authors: Riley Mark , Taheri Farid
Published: March 2009

In recent years the field of smart structures, including sensing and control, has been growing at an extraordinary rate. As of today, however, there has been relatively little work performed in applying this technology for monitoring and control of offshore and marine structures. In offshore environment, structures are subjected to critical loading cycles (e.g., wave action, temperature changes, and heavily corrosive environment to name a few), unparalleled to those in any other environment. With the costs that are associated with the manufacturing of marine vessels and structures, and their day-to-day operations and maintenance cost, the selection of an effective method of monitoring their performance and integrity, as well as their control is of paramount importance. In this paper, we will present a brief, yet detailed description of the different smart materials that are available for structural monitoring and control, such as electrorheological fluids, shape memory alloys, fiber optics, piezoelectrics, and magnetostrictives. We will also discuss the applications of these materials, including their advantages and shortfalls. The outlined discussion will help the reader to select the most optimum smart material for a given application. The paper will further discuss an ongoing investigation of a piezoelectric system that is currently being developed for implementation into fiber-reinforced composite panels used in marine vessel applications.
An Investigation of the Non-Linear Transverse Vibrations of Parametrically Excited Vertical Marine Risers and Cables Under Tension
Authors: Chatjigeorgiou I. K. , Mavrakos S. A.
Published: March 2009

The present paper examines specific aspects of the non-linear dynamics of vertical marine cables and risers. The formulation of the dynamic system accounts for both elastic and bending effects and can satisfactorily describe the dynamic behavior of a riser or a tensioned vertical marine cable. The analysis is restricted in the study of transverse vibrations of the dynamic system under consideration. We first examine the free vibration of the system and consequently the forced transverse vibration due to motions imposed longitudinally. That is, we examine the coupled longitudinal and transverse inducted motions in the 2D reference plane, including damping effects. We first examine the un-damped system and consequently we assess the effects of damping by incorporating the damping terms into the theoretical model. The study is conducted both theoretically and numerically and the resultant theoretical conclusions are evaluated with the corresponding numerical predictions in regards to the dynamic behavior of the system.
Analysis of the Dynamical Behaviour of an Offshore Supply Vessel With Water on Deck
Authors: Laranjinha Manuel , Falzarano Jeffrey M. , Soares Carlos Guedes
Published: March 2009

This paper describes a study of the influence of the water on deck on the dynamical behavior of an offshore supply vessel with a large open aft deck. The deck under certain load and sea conditions can become partially or totally immersed. This study focuses on the roll motion that can be of large amplitude and therefore has implications and risks for the ship’s safety. The Glimm’s method is used to model the three-dimensional flow of shallow water on the deck. A parametric study is made in order to show the effect of the relevant parameters. It is shown that the water on deck has a significant influence on the ship’s dynamical response.
Development of X80 Grade Induction Bend Pipe
Authors: Ishikawa Nobuyuki , Endo Shigeru , Kondo Joe , Takagishi Masaaki
Published: March 2009

API X80 grade induction bend pipe was developed using longitudinally submerged arc welded pipe as a mother pipe and applying subsequent quenching after induction heating and tempering in the full length portion. As a preliminary study for optimizing manufacturing process, the effect of heating process in induction bending had been investigated, and full length quenching and tempering process was recommended in order to obtain satisfying strength as X80 grade and superior toughness for the bend portion and tangent, as well. Based on the above examination, API X80 grade induction bend pipe with the pipe size of 761.0mmOD × 20.7mmWT, bending radius of three times the pipe diameter and bending angle of 90 degree, was manufactured by applying the full length quenching and tempering process, using a UOE pipe which has relatively lower chemistry with Ceq of 0.44%. It was proved that the trial X80 bend pipe has sufficient tensile properties for all portion in the transverse and longitudinal direction, measured by round bar tensile specimens. However, by using API standard full-thickness specimen, yield strength of all portion in the transverse direction and yield strength of the intrados in the longitudinal direction showed lower value than those obtained by round bar specimens because of the Bauschinger effect caused by flattening of the specimen. Owing to low chemistry of the mother pipe and optimized induction bending condition, the bend portion as well as the tangent showed quite low Charpy transition temperature and large absorbed energy even under −60 °C, and superior toughness was also achieved in the seam weldment.
Crack Initiation Strength of Structural Steel Members Having Experienced Large Compressive Strain
Authors: Yajima Hiroshi , Kho Yunbo , Satoh Susumu , Nishikawa Kazuto , Yamamoto Motomichi
Published: March 2009

In the present report, an attempt was made to quantify the crack initiation strength for structural steel members having experienced large compressive prestrain due to buckling collapse. First, a tension test of the prestrained material was performed on JIS SS400 steel. The influence of prestraining on the mechanical properties of the material was investigated. Next, a crack initiation test and an elastoplastic large deformation FE-analysis for strip specimens were performed. The specimens were bent into various curvatures after undergoing buckling and the relationship between crack initiation and applied straining was examined. Finally, in order to investigate the crack initiation behavior for structural members subjected to cyclic bending load after undergoing buckling collapse, a crack initiation test and an elastoplastic large deformation FE-analysis for strip specimens under cyclic bending load were performed.
Texas Tower 4: Lessons for Design of Offshore Structures
Authors: Bea Robert G. , Jin Zhaohui
Published: March 2009

The Texas Towers were a series of platforms installed off the U.S. East coast in the 1950’s to support early warning radar facilities. Texas Tower 4 (TT4) was installed in a record setting water depth of 185 feet in 1957. At this time, TT4 was heralded as an ‘engineering marvel’; a major innovative ocean engineering accomplishment. In December 1960, the decision was made to decommission TT4, but before this could be done the platform failed during a storm in January 1961 with the loss of the lives of all personnel that were onboard. A satisfactory explanation was never developed that detailed exactly how the structure failed. In 1999, a study was commissioned by the American Bureau of Shipping to study the failure of TT4. The objective of this study was to see if with modern ocean engineering technology (storm forces, structure capacities), the details of failure of the structure could be re-created. This paper summarizes the results from this study.
Influencing Competence in Structural Integrity Management
Authors: Billington C. J. , Caruana S. A.
Published: March 2009

The offshore industry has experienced significant changes in the regulation and control of oil and gas exploration and production. The move away from the prescriptive approach towards a goal-setting regime gives Duty Holders greater control and accountability over the safety management of operations. Whilst this approach encourages greater ownership of safety by Duty Holders and provides greater flexibility, it also places greater demands and responsibility for ongoing integrity management, particularly when operational life is extended beyond the original specification with the need to account for the ageing mechanisms. Therefore it is increasingly important to ensure that those responsible for integrity management have all the necessary competences for this task and that the Duty Holder provides the necessary system competence to support this activity. This paper examines the factors which influence competence throughout the life-cycle of Structural Integrity Management (SIM) activities, and provides a model that relates this to a systematic safety management context.
Experimental Evaluation of Leak-Before-Break (LBB) Behavior for High-Grade Line Pipes With an Axial Through-Wall Flaw
Authors: Kawaguchi Shinobu , Nakayama Masato , Hagiwara Naoto , Masuda Tomoki , Toyoda Masao
Published: March 2009

Leak-before-break (LBB) behavior was evaluated for two series of conventional line pipes (X65) and three series of high-grade line pipes (X80) with various fracture toughness value. Full-scale hydrostatic burst tests were conducted for the line pipes with an axial through-wall flaw to determine hoop stress for LBB. The experimental results were then compared to the estimation using a Charpy V-notched impact energy (CVN)–based equation by Battelle. The present study clarified that the CVN-based equation was applicable to the pipes with CVN energy less than 130 J. On the contrary, the equation was not applicable to the pipes with CVN energy grater than 130 J. The results of instrumented Charpy tests showed that the load versus load-point displacement response for the high CVN energy pipes was different from that for the low CVN energy pipes. Therefore, the applicability of the CVN-based equation was dependent on the load versus load-point displacement response. This result suggested that the CVN-based equation should be modified to evaluate the LBB criterion for the pipes with relatively high toughness.
Aspects of Nonlinear Random Wave Kinematics
Authors: Myrhaug Dag , Stansberg Carl Trygve , Wist Hanne Therese
Published: March 2009

Statistics of the nonlinear free surface elevation as well as the nonlinear random wave kinematics in terms of the horizontal velocity component in arbitrary water depth are addressed. Two different methods are considered: a simplified analytical approach based on second-order Stokes wave theory including the sum-frequency effect only, and a second-order random wave model including both sum-frequency and difference-frequency effects. The paper compares results for the statistics of the nonlinear free surface, and the consequences of neglecting the difference-frequency effect in the first method are discussed.
Calculation of Riser Damages by the Collision of a Supply Boat to the FPSO
Authors: Li Yousun
Published: March 2009

Accidentally a supply boat may collide with the FPSO. Riser systems may be hung on the hull of the FPSO. The components of the riser systems, such as the riser pipes, riser supports, and the fenders for riser protection, will be squeezed during a boat-FPSO collision. This presentation discusses a calculation method, based on energy and momentum conservations, for possible damages to riser components by boat-FPSO collisions. The collision direct on the riser pipe and a collision to the riser protection fender system are used as examples to discuss the method of damage predictions.
Experiences With Bolts and Fasteners Offshore: A Need for R & D
Authors: Fischer Karl P.
Published: March 2009

The biggest users of bolts are the auto and aerospace industries. In the oil and gas industry bolted connections are often used for high integrity systems and are thus vital for the long term performance of (the given structure) e.g. structural components, pressurised vessels and piping. It is therefore of paramount importance that bolted connections can be designed and installed to provide the required service life for the various exposure and service conditions. Bolting can fail for a number of reasons (e.g. overload, fatigue or corrosion). The materials selection and manufacturing, bolt fabrication, applied protective coating and the final bolt installation are all factors which need to executed adequately to ensure that a long service performance. The actual service conditions and the external environment impact and maintenance will subsequently determine the service life of the bolting. To improve the reliability of bolted connections, a joint industry project” “Corrosion protection and maintenance of bolting and fasteners” was initiated by DNV in 2001. The initial part of the project will be to provide a summary of the best practice for corrosion protection of bolted connections for offshore application. Here bolted connection embrace materials selection of bolts, corrosion protection of bolts and performance of bolts on flanges and other mechanical connections (e.g. cranes). The main part of the project is a 10 year testing program of pretensioned stud bolts. The exposure program will be performed in the marine atmospheric zone, splash zone and submerged zone. This will be performed at the DNV seawater laboratories in Bergen and at the LaQue Center, North Carolina, US.