bluuebunny/crossref_metadata_2025 huggingface dataset:
Computerized Realtime X-Ray Inspection of Consumer Waste Product for Hazardous Materials
Authors: Korkala Gary , Robbins Ken , Chon David
Published: January 2009

This presentation describes the design and manufacture of a computer controlled x-ray scanning system for the fully automated inspection of waste for hazardous materials. Of particular importance was the necessity to accurately detect various sizes of propane tanks and large heavy metal objects. In addition, rejects had to be accurately identified and each image saved for archival requirements. The equipment utilized, material handling, software development and implementation is detailed herein. The problems of establishing a stable image in a harsh environment required ruggedizing all of the components as well as positive pressure air delivery and air conditioning of the computer and related electronic enclosures. The use of commercially available equipment and latest detector technology were utilized as much as possible to reduce costs and to provide a reliable low maintenance system that also included the ability to conduct diagnostics and software upgrades remotely via computer.
Benchmarking Documentation and Record Keeping: A Key to Successfully Evaluating Resource Recovery Facility Performance Over Time
Authors: Lehman Andrew T.
Published: January 2009

Based on multi-year reviews done at a number of modern Resource Recovery Facilities (RRFs), this paper will recommend benchmarks for several operations parameters and associated documentation in order to facilitate a comprehensive evaluation of waste-to-energy facility operational and environmental performance over time.
Dancing the Emissions Limitation Limbo: How Low Dare You Go?
Authors: Rigo H. Gregor
Published: January 2009

After promulgation of the New Source Performance Standards (NSPS) and Emissions Guidelines (EG) for Large and Small Municipal Waste Combustors (MWCs), the Environmental Protection Agency (EPA) entered a new regulatory arena – regulating the remaining risks to public health and the environment after Maximum Available Control Technology (MACT) is applied. The residual risk from MWCs is expected to be negligible; however, the public, and some state and local regulators are now looking for ways to assure continuation of the exemplary emissions performance being measured at many of these retrofit sources. Hence, the question now becomes: how low can an achievable emissions limitation be? Confidence should not be placed in a source’s ability to continually meet the low emissions limitations embodied in the MWC EGs and NSPSs. Contrary to assertions in the Response to Comments for the Small MWC regulations [1], the Environmental Protection Agency could not have properly considered and incorporated measurement uncertainty into its dioxin guidelines; no one knew the uncertainty of total dioxin measurements above 28 ng/dsm3 corrected to 7 percent O2 until 2001 when the work supporting this paper was performed. When the 13 ng/dsm3 corrected to 7 percent O2 NSPS for MWCs was developed, the data needed to determine measurement uncertainty of most Section 129 pollutants had not even been collected. Further, asserting that the data used to derive the NSPS emissions limitations include measurement error, and therefore, any data-derived emissions limitations inherently consider that error, is only true if the measurement error is much smaller (say less than 10 percent) than the short and long term variations in emissions performance. Beginning with a set of three total dioxin measurements that averaged 4 ng/dsm3 corrected to 7 percent O2, the emissions limitation meeting the 95 percent statistical confidence level criterion underlying many NSPS, is almost 15 ng/dsm3 corrected to 7 percent O2. If the statistical criterion is changed to inclusion of “almost all” the expected results when these facilities continue to emit as they did during the original data acquisition, the emissions limitation becomes almost 18 ng/dsm3 corrected to 7 percent O2. Consequently, sources must not agree to standards that do not properly consider measurement method precision if they want to avoid exceedances when everything is working properly.
What’s Happening With Green Power Marketing and the Latest on Renewable Energy Credits: How Much Are They Worth and Who Owns Them?
Authors: Davidov Robin , Plitch Larry , Pollatos Chris
Published: January 2009

The subject of the presentation is Green Power Marketing for Waste To Energy Facilities. Many WTE projects signed long term energy contracts under the rules of PURPA. Several projects signed short term agreements. In other cases, power contacts were sold or assigned by the original purchaser or the project voluntarily agreed to a buy out. In any case, power markets have changed and are continuing to change. One of the most significant changes is the deregulation of the electricity market. WTE projects are no longer required to sell power to a captive utility. While electricity continues to flow through the same transmission lines, those lines may be owned by a different entity than the power purchaser, and will certainly end up as a transaction cleared by the regional power grid. In addition to “energy” and “capacity”, power can be sold as “green” or “renewable” for additional revenues. WTE power can be sold to wholesale purchasers for resale. Some WTE owners are becoming licensed to sell retail power, or arranging to wheel power to the local government which owns the WTE facility. WTE owners and operators depend on energy revenues to offset capital and operating costs. It is critical to understand how power marketing works. Most importantly, it is incumbent on each WTE owner/operator to make sure that Renewable Portfolio Standards established on the State and Federal level include WTE as a defined and eligible source of power. In the absence of Federal legislation, each State may set its own rules and requirements. Furthermore, States can set a renewable energy requirement for its purchases of energy. The panelists will present clear examples of the above from three points of view: Mr. Larry Plitch is an attorney who spent many years with Wheelabrator, and now markets power for Wheelabrator and other WTE owners. Ms. Robin Davidov is the Executive Director of the Northeast Maryland Waste Disposal Authority in Baltimore, Maryland. The Authority developed and financed three WTE facilities in Maryland, and owns two of the facilities. Ms. Davidov has been managing power sales for ten years, and most recently negotiated an electricity sales agreement with Mirant Americas Energy Marketing, L.P. Mr. Chris Pollatos is a Director with Mirant, and will speak about his experience in purchasing power from WTE and other renewable sources as well as wholesale power sales, including the sale of Renewable Energy Credits.
City of Tampa, McKay Bay Retrofit: Before and After
Authors: Patton Sherman R.
Published: January 2009

The City of Tampa’s solution to solving their waste disposal problems started almost 30 years ago. A conventional refractory lined incinerator equipped with a wet quench scrubber was constructed and operated by the City, starting in 1965. The old incinerator would often belch black soot and smoke and in 1979 was shutdown for environmental concerns. The City selected Waste Management Energy Systems, then a subsidiary of Waste Management Inc., to design, build, and operate for 20 years, a tried and proven waste combustor linked with a heat recovery boiler, electrostatic precipitator, and a turbine generator. This system was placed into operation in 1985 and the last two units were operated until July 2000 when compliance with the Clean Air Act required their retrofit. In 1996, the City assembled a Project Team consisting of consultants that specialized in various aspects of solid waste disposal including: permitting, design, operations, and construction oversight. After several years of design, procurement, and negotiations, Wheelabrator was selected as the successful vendor to design, construct, and operate the retrofitted facility. Construction began in April 1999 and went into commercial operation in January 2002.
Substance and Perceptions of Environmental Impacts of Dioxin Emissions: An Interim Report
Authors: Themelis N. J. , Deriziotis P.
Published: January 2009

The emission of dioxins is perceived widely as a major environmental impact of combustion processes. This paper will report the results of an extensive study of published data on a) the rate of formation of dioxins from all U.S. sources; b) the pre-MACT and post-MACT performance of individual Waste-to-Energy (WTE) plants in the U.S. and how post-MACT emissions compare with the 1998 EU standard (0.1 ng/dscm); c) how the contribution of WTEs has changed with time; and d) the measured impacts of WTE dioxin emissions on soil/plant concentrations and on public health. The study has shown that since 1987 the U.S. dioxin emissions have decreased by a factor of four and by now WTEs are a miniscule source. Also, that even at the earlier high emission levels, the dioxin levels in soil samples close to WTE facilities did not exhibit an increase over regional background concentrations. Finally, the paper contrasts public perceptions of the dioxin threat with scientific studies of observed effects on the environment and on public health.
Influence of Current Direction on VIV of a Steel Catenary Riser
Authors: Le Cunff C. , Averbuch D. , Biolley F.
Published: January 2009

The evaluation of fatigue damage due to vortex induced vibrations is an important part of riser design. For asymmetric configurations like steel catenary riser, or export line, the modal basis is divided into in-plane and out-of-plane modes, corresponding respectively to an eigenshape in the plane or perpendicular to the plane of the structure. Most industrial codes computing VIV response are based on a frequency analysis to obtain the amplitude of vibrations perpendicular to the current direction. Therefore, for current which are not in-plane or out-of-plane, the mode selection is not possible. Either the current direction is modified or the current is projected into the main direction of the configuration. In the present article, we investigate the influence of current direction on SCR response. Calculations are performed with a coupled fluid structure solver based on strip theory. Navier-Stokes equations are solved in two dimensions in slices perpendicular to the riser axis, and provides the hydrodynamic loading to the structural code. The displacement of the riser is then computed and used as boundary conditions for the new fluid step. Three directions and two upper depth current profiles are investigated. The first profile excites the low modes of the riser and the response is direction dependant. For the second profile with higher velocity, the crossflow responses are similar for all three current directions while the in-line responses differ mainly due to a low frequency first mode motion. Comparisons with a modal approach are then discussed.
Application of RAM Methods in the Structural Reliability Assessment of Corroded Offshore Pipelines
Authors: Inkabi Kofi S. , Bea Robert G.
Published: January 2009

A comprehensive reliability based formulation is proposed for the assessment of the integrity of corroded pipelines. In this formulation, the inspection technique, the pipeline geometric, material, and operational characteristics, and Limit State model for burst are combined in a general approach. This approach is illustrated with application to evaluation of an in-service gas pipeline.
Burst Database Verification Study for Corroded Line-Pipe
Authors: Inkabi Kofi S. , Bea Robert G.
Published: January 2009

A significant amount of effort over the past 20 years has been directed towards the experimental testing of corroded linepipe subjected to static internal pressure. This effort has led to the development of a number of empirical limit state models (e.g., ANSI/ASME B31G). Various studies have recently been completed to determine which limit state model is best suited for use in closed-form reliability evaluations using published burst databases compiled by the Pipeline Research Council International (PRCI) and Det Norske Veritas (DNV). Unfortunately, the results of these studies are inconsistent with little to no explanation why. This paper in-part accounts for the skewed results of previous studies by cleansing the PRCI and DNV burst databases of corroded line-pipe tests of flawed information and thus assembling the verifiable 2003 University of California, Berkeley (UCB) Burst Database. The errors found in these databases are statistically significant enough that extreme caution should be used when applying them in a reliability design, assessment, or management framework. Lastly, the relative performance of seven limit state models were analyzed with the 2003 UCB Burst Database and conclude that although a unbiased variation of ASME B31G is competitive, RAM PIPE I is the best overall limit state model of the seven evaluated.
Guidelines for Engineering Critical Assessments for Pipeline Installation Methods Introducing Cyclic Plastic Strain
Authors: Wa¨stberg Stig , Pisarski Henryk , Nyhus Ba˚rd
Published: January 2009

Conventional flaw assessment procedures are not explicitly developed for situations with large cyclic plastic strains, e.g. for pipelines installed by the Reeling method, and if used indiscriminately may give un-reliable results. In order to resolve this dilemma DNV, TWI and Sintef conducted a Joint Industry Project (Fracture Control for Installation Methods Introducing Cyclic Plastic Strain – Development of Guidelines for Reeling of Pipelines) to provide guidelines on testing and assessment procedures that can be employed by the industry. The project included Materials Testing, FEM Analyses and Validation Testing of Pipe Segments as well as Full Scale Pipes. This paper summarizes the Guideline document that was developed in the project.
The Fatigue Life Estimation Method From the Stress Concentration Region With Zero Defect: An Application to the Fatigue Crack Growth Simulation Code “FLARP” for the In-Plane Gusset Welded Joint
Authors: Toyosada Masahiro , Gotoh Koji , Konuma Keitaro , Sueda Akira
Published: January 2009

In-plane gusset welded joints are very popular and used in many steel constructed structures. Fatigue life estimations for this type of joint have been performed by applying the fatigue crack growth simulation code “FLARP” developed by the authors. The fatigue crack shows the typical opening/closing behavior during fatigue crack growth. The plastic deformed layer in the crack wake, which represents the loading history indirectly, contributes to the behavior. The consideration of crack closure is essential in the estimation of the fatigue life. FLARP enables the quantitative simulation of the fatigue crack opening/closing. By considering the cyclic plastic behavior ahead of a fatigue crack tip, the improved effective stress intensity factor range (ΔKRPG) to denote the fatigue crack propagation law, which is formulated by replacing the crack opening load with the Retensile Plastic zone Generating load (RPG load), was defined. ΔKRPG is adopted as the parameter for the fatigue life estimation by FLARP. The validity of the fatigue life estimation by FLARP is confirmed by comparing the estimated S-N curves with the experimental results for the in-plane gusset welded joints.
Design Features of Risers for the Extendable Draft Platform (EDP)
Authors: Xu Lixin , Xu Qi , Hough Colin , Murray John
Published: January 2009

The Extendable Draft Platform (EDP) is a deep draft semisubmersible with an extendable heave suppression pontoon, designed as a drilling and production floating platform for deepwater field development. The EDP supports both top tensioned risers (TTRs) for dry-trees and steel catenary risers (SCRs) for export risers and subsea wells. The TTRs can be supported at their tops by tensioners mounted on the main deck, and the SCRs can be connected to the EDP either by porches external to hull or by pull-tubes internal to the hull columns. This paper discusses design features of the EDP risers, including TTR tensioning system and coupled effects on hull motion performances, riser keel guide design and wear allowances, and SCR hang-off options. Also investigated are the effects of the EDP’s low motions on the riser systems, for instance, the wave induced fatigue of SCRs is significantly improved for the EDP, in comparison with a conventional semisubmersible of similar payload. Furthermore, designs of the EDP as well as riser systems can be optimized for different prevailing environmental conditions, such as those of West Africa, Brazil, West of Shetland, and the Gulf of Mexico. The EDP provides an effective and reliable way to support dry-trees and SCRs for a wide range of deepwater applications.
A RANS Based Method for the Estimation of Ship Roll Damping With Forward Speed
Authors: Salui Kumar B. , Shigunov Vladimir , Vassalos Dracos
Published: January 2009

For the prediction of ship roll motion, viscous effects must be taken into account. Several methods, experimental and theoretical, have previously been used to calculate hydrodynamic forces in roll motion. Theoretical methods applied so far to this problem have been based mainly on potential flow models, which cannot account for viscous effects adequately or need pre-defined flow separation like vortex methods. Recent development of computer hardware enables application of methods based on flow field discretisation such as finite-difference methods to solution of problems of practical ship design such as ship motions and control. In the present study, a Reynolds-Averaged Navier-Stokes solver is used to calculate hydrodynamic loads during forced roll motion at different Froude numbers. The solution method adopted is based on unstructured finite-volume discretisation with collocated arrangement of flow variables. A pressure-correction algorithm (SIMPLE) is used for the pressure-velocity coupling. A standard k–ε model is used for the turbulence modeling. An advanced differencing scheme called high-resolution interface capturing (HRIC) is used for accurate resolution of the free surface in the scope of a multiphase-type description. A high-speed hard chine vessel with and without skeg is studied. Close agreement is found between the present calculations and experimental results.
Dynamic Simulation of Offloading Operation Considering Wave Interaction Between Vessels
Authors: Tannuri Eduardo A. , Bravin Tiago T. , Simos Alexandre N. , Alves Karime H. , Nishimoto Kazuo , Ferreira Marcos D.
Published: January 2009

Almost all simulators of offshore systems evaluate wave forces using frequency-domain potential analysis. A wave analysis software is previously executed, considering several incidence angles and generating a data base which is used by the simulator. This database contains drift coefficients, RAOs and exciting forces for all incidences. During the simulation, the simulator only performs queries depending on the actual heading of the vessel related to waves. The simulation of multi-body systems cannot be performed in the same way, since the relative positions of the bodies change during simulation time, altering the influence of each ship on the overall wave field and its effect on the others. So, for each time step a new frequency-domain analysis should be performed, considering the vessel positions at that instant and updating the database used by the simulator. However, the computational effort necessary to perform such simulation turns this approach prohibitive for conventional computers and workstations. The wave forces are evaluated only in a predefined configuration of the vessels, or considering the vessels independently. Such approaches neglect all interactions and the complex dynamics behavior that results from it. The University of Sa˜o Paulo has been developing since 2001, the Numerical Offshore Tank (NOT), a 120 processor cluster with the ability to perform detailed simulations considering bodies and lines dynamics very efficiently. In order to simulate offloading operations accurately, the commercial wave analysis software WAMIT was integrated to the NOT simulation code, allowing the “update” of wave coefficients data base every time the vessels configuration changes significantly. WAMIT code was adapted to perform parallel processing, greatly reducing the execution time and allowing the simulations to be performed in approximately 7 hours for the analysis of a 3-hour operation. Without WAMIT parallelization, this time would increase by a factor approximately equal to the number of wave frequencies considered in the simulation. This paper discusses the results obtained by the simulations of offloading operations in the presence of waves, detailing the effects that arise when the bodies interaction is taken into account. Effects are sensed in the equilibrium position, in the first order vertical motions and low-frequency oscillation.
Structural Reliability Applications in Developing Risk-Based Inspection Plans for a Floating Production Installation
Authors: Ku A. , Serratella C. , Spong R. , Basu R. , Wang G. , Angevine D.
Published: January 2009

This paper outlines the essential steps taken in performing structural reliability calculations during the process of laying out a risk-based inspection program. The structural reliability analysis described in this paper essentially takes the deterministic finite element method (FEM) stress/fatigue analysis results, coupled with uncertain degradation mechanisms (e.g. corrosion rate, crack propagating parameters, etc.), and tracks the time-varying structural reliability index of the structural components under consideration. This can then be used to determine the timing for inspection of structural components. For the assessment of structural strength, an efficient and straightforward method is proposed to calculate the time-variant reliability index. This method is verified by an example problem and compared to the random process first-passage reliability solutions. Load combination issue is briefly discussed, in which an approach stems from the ABS Dynamic Loading Approach (DLA) coupled with concepts from Turkstra’s rule. This proposed simplistic load combination approach is verified through an example problem in which the result is compared to the solution calculated from a more sophisticated approach. Establishment of target reliability levels is also briefly discussed. For the assessment of fatigue behavior for welded connections, both S-N curve based and fracture mechanics based reliability methods are discussed. Their usefulness will be discussed in terms of both inspection interval as well as selecting the proper sampling percentage of connections to inspect. Statistical correlation among a group of similar connections is discussed to assist the selection of appropriate locations in the population of the aforementioned sampling. The usefulness of fatigue reliability analysis is also demonstrated by an example problem.
Multi-Strip Numerical Analysis for Flexible Riser Response
Authors: Schulz Karl W. , Meling Trond S.
Published: January 2009

A multi-strip numerical method, combining solution of the incompressible Reynolds Averaged Navier-Stokes (RANS) equations with a finite-element structural dynamics response, has been developed to analyze the flow-structure interaction of long, flexible risers. This solution methodology combines a number of individual hydrodynamic simulations corresponding to individual axial strips along the riser section with a full 3D structural analysis to predict overall VIV loads and displacements. The hydrodynamic loading for each riser strip is derived from a 2D finite-volume discretization of the governing RANS equations which is applicable to both single and multiple riser configurations. The entire flow-structure solution procedure is carried out in the time domain via a loose coupling strategy, such that the hydrodynamic loads from each riser strip are summed to obtain the overall loading along the span of each riser. This loading is then used to integrate forward a single time-step in the riser equations of motion to obtain an updated riser displacement profile. Closure of the coupled flow-structure method is achieved by updating the riser displacements for each of the corresponding hydrodynamic strips in the next time-step integration. The developed multi-strip method is applied to a single bare riser subjected to both uniform and shear current profiles. The flow conditions and riser configuration were chosen to match the Marintek rotating rig experiments, and comparisons between experimental and numerical results are presented for several flow configurations and axial tensions. In addition, a parametric study is presented using 16, 32, and 64 hydrodynamic strips for a given flow configuration to ascertain the sensitivity of the results to the number of strips chosen.
The Stress Analysis and Residual Stress Evaluation of Pressure Armour Layers in Flexible Pipes Using 3D Finite Element Models
Authors: Fernando Upul S. , Tan Zhimin , Sheldrake Terry , Clements Richard
Published: January 2009

A pressure armour layer is an essential feature of un-bonded flexible pipes. The layer is made of an inter-locked helically wound metal wire of profiled section, whose primary use is to provide the circumferential strength of the pipe to resist internal pressure. The general design philosophy of the layer is defined in API 17J in terms of the stress “utilisation” factor that specifies the maximum allowable average hoop stress in the layer, which is conventionally produced by the elastic stress analysis. During pressure armour layer manufacturing (a cold forming process), the armour wire is however subjected to a sequence of cyclic bending and twisting deformations which take it beyond its material elastic limit. This paper presents FE structure models for investigating the detailed local and residual stress variation during the forming process, and the subsequent stress relaxation as a result of the factory acceptance test (FAT). A study case is presented for illustrating the typical stress and strain behaviour after FAT pressurization. The paper also introduces X-ray diffraction technology as a method for residual stress measurement on full scale samples.
Design and Installation of Buried Heated Pipelines at the Capixaba North Terminal Offshore Brazil
Authors: Solano Rafael Familiar , de Azevedo Fa´bio Braga , Vaz Murilo Augusto , de Oliveira Cardoso Carlos
Published: January 2009

The export pipelines of the Capixaba North Terminal (TNC) offshore Brazil will be operating with a great thermal stability potential due to the high temperatures that are necessary to assure an adequate flow. This paper focuses on the challenges for the design and installation group, due to the very strict maximum allowable imperfection (prop), in order to find a feasible solution for the installation process by a conventional lay barge. Also, the paper employs a finite element model and carries out a parametric study based on the soil coverage requirements and the maximum allowable imperfection originated from laying operations and pipeline burial process. The upheaval buckling will be studied in full detail in order to evaluate predefined curvatures, with the objective of finding the minimum cover height to limit the pipeline displacement and thus assuring its integrity. This work also aims to establish a numeric tool that will serve as basis for the upheaval buckling analysis in new pipeline design.
Evaluation of a Dynamic Positioning Thruster Wake Using Laser Doppler Velocimetry
Authors: El-Lababidy Said , Bose Neil , Liu Pengfei
Published: January 2009

To provide information on the wake characteristics of Dynamic Positioning (DP) thrusters when operating with and without a nozzle under varied operating conditions, experiments were done on a ducted propeller model in a cavitation tunnel. The propeller flow field was measured with a two-component Laser Doppler Velocimetry (LDV) system, up to 1.5 diameters downstream. These experiments were carried out with and without the nozzle, and the results are presented here for a pitch/diameter ratio of 1.2 and an advance coefficient of 0.4. This paper shows and compares the results of the DP thruster near wake hydrodynamic characteristics obtained by the LDV system when operating with and without a nozzle.
Sea Ice Crushing Under Uniaxial Compression and Tension Models
Authors: Vershinin Stanislav A. , Truskov Pavel A. , Kouzmitchev Konstantin V.
Published: January 2009

The paper describes phenomenological models of ice crushing in compression and tension at a constant strain rate. They present the fundamentals of loaded ice behavior depending on objective factors, such as ice grain structure, salinity and temperature, and on subjective factors such as specimen size and testing methodology. The theoretical analysis is compared with experimental data.
Numerical Prediction of Spar Motions Considering Top Tension Riser Stiffness
Authors: Chen Cheng-Yo , Nurtjahyo Prahoro
Published: January 2009

Spar motions are often predicted without explicitly considering the stiffness effect of the buoyancy can of top tension risers (TTRs). This may result from the inability of most motion prediction programs to take this effect into consideration. The forces exerted by the TTR buoyancy can on the spar provide a net beneficial righting moment. Hence, neglecting the effect of TTR stiffness could produce excessive predicted spar motions, particularly maximum pitch angle. The derived spar configurations based on such predicted motions are likely to be conservative and not optimal. This paper proposes a simple “Linearized P-Delta” model to account for the effect of TTR stiffness on spar motions. The predicted motions using the proposed model are compared with the model test results for a production truss spar in the Gulf of Mexico. The comparison results indicate that the proposed model is quite rigorous and correlates reasonably well with the model test results.
Deterministic and Probabilistic Fracture Mechanics Analysis of Pipeline Weld Flaws Accounting for Crack Tip Constraint Effects
Authors: Tronskar Jens P. , Li Zhang
Published: January 2009

The acceptability of weld defects during line pipe manufacture and pipeline construction is governed by international codes and standards such as the DNV OS-F101 or API1104. These are universal standards applicable for a wide range of pipeline usage conditions, which include typical workmanship criteria for flaw acceptance. It is, however, possible to establish more precise and often less conservative acceptance criteria using a Fitness-For-Service (FFS) approach through the application of procedures such as those of BS 7910. These are based on applying deterministic or probabilistic fracture mechanics principles on specific loading, materials and toughness properties and service conditions of a pipeline. This paper describes the conventional assessment methodology and more advanced approaches to account for crack tip constraint, dynamic loading due to VIV associated with free-spans. The paper highlights two cases as examples where the approaches have been applied for assessing the criticality of weld defects detected during pipeline construction and their impact on the reliability during service.
Integrity Management System for Fixed Offshore Structures Inspection Strategy
Authors: El-Reedy Mohamed A.
Published: January 2009

The GUPCO offshore structure management system was developed as a part of an integrated infrastructure management system. This paper presents a case study of providing an integrity management system for inspection, evaluation and repair of the fixed offshore platforms in Gulf of Suez. The management system procedure is presented focusing on the first step for defining the highly risky weight to the lower risky weight structure based on API criteria for assessment of the existing structures. The risk analysis methodology for developing design and assessment criteria for fixed offshore structure based on consequence of failure is illustrated. In our case study the assessment method is applied for a number of fixed offshore structures. The above methodology is performed after theoretical assessment and then verifying by using ROV subsea inspection for the fixed offshore structure. Comparison between the actual structure performance and the predicting risk assessment for the structure from the model will be studied. The overall management system will be illustrated in scope of predictive maintenance philosophy and reliability for all offshore structures.
Crack Growth During Full Scale Reeling Simulation of Pipes With Girth Welds
Authors: O¨rjasaeter Oddvin , Hauge Olav Jan , Ba¨rs Guy , Kvaale Per Egil
Published: January 2009

Installation of pipelines by reeling has proved to be an effective method. However, the pipe bending results in very high stress and strain and cannot be handled by conventional design rules, as stated in design codes, e.g. [2]: High strain crack growth must be assessed according to specific case-by-case selected criterions. In the present work the performance of 10” and 12 3/4” pipes with typical weld defects is studied — from initiation of cracks at notches to final fracture. Information was obtained from several sources: full scale cyclic bending of pipes, FE simulations, and small-scale tests. The plasticity during reeling operations results in substantial non-linear behavior due to varying cross section properties, cyclic creep, and different material response at tensile and compression side of the pipe. Hence, a full scale reeling simulation must be carefully planned and include sufficient tolerances. Critical cracks in pipe girth welds initiate mainly from the surface (undercuts, lack of penetration, or lack of fusion), but potentially also internally (lack of fusion or large pores). Various configurations of these parameters were investigated in full scale pipe tests. It was possible to verify both crack propagation during the reeling cycles, and the point of final fracture (for ECA verifications). In pipe design on must assure safe conditions for both reeling operations and for later in-service loading. Proper design tools must be available. Several methods for high strain crack growth analysis were considered and also compared to small-scale specimen data. Conventional strain-life methodology failed to predict the crack propagation accurately. A new approach including a tensile strain range parameter offered promising results.
Verification of 2D Wave Spectra Produced by Wave Models
Authors: Caˆndido Jose´ , Pires Henrique Oliveira , Pontes M. Teresa
Published: January 2009

In this paper a methodology for assessing the accuracy of full directional wave spectra produced by wind-wave models is presented and tested. This methodology includes graphical and parametric comparisons of model directional spectra against data obtained from directional buoys. Results of the verification of 3rd generation wind-wave models using directional buoy data show that in general the accuracy of model directional results is good. In addition it was found that this methodology is well suited to identify the occurrence of different wave systems in the same sea state, namely swells within the same frequency band but with different origins.
A Numerical Method to Solve the Static Problem of a Catenary Riser
Authors: da Silveira Lauro Massao Yamada , Martins Clo´vis de Arruda
Published: January 2009

The static configuration of a catenary riser can be obtained, with a good approximation, by a perfectly flexible cable model. However, such a model cannot deal with all the boundary conditions, as for an ideal cable there is no continuity of curvature at the touchdown point, at the top and at the points where there is change in the submerged weight. At the touchdown region, for instance, the cable model overestimates the maximum curvature. For real risers, the bending stiffness effect is relevant only at small boundary layers around the points where the cable model cannot represent well the curvature continuity. This represents a big problem in the numerical integration of the differential equation of the riser, as the leading order term is very small. One approach that can be adopted is to use firstly a perfect cable model and correct later the results with analytical expressions obtained from a boundary layer method. For a two-dimensional formulation it was already shown that this approach is very good. For a three-dimensional formulation, however, such expressions are very difficult to derive and the problem must be solved numerically. This work presents a numerical method to solve the differential equation of a catenary riser, including the bending stiffness. The results obtained are compared to analytical boundary layer solutions, for a two-dimensional case, and to a full nonlinear well-known commercial computer code.
Fatigue Life Assessment of Fillet Welded Joint Considering the Relaxation and Redistribution of Residual Stresses
Authors: Jang Chang Doo , Song Ha Cheol , Jo Young Chun
Published: January 2009

This paper presents the fatigue life assessment procedure for the welded joint of ship structure. Test model is a boxing fillet specimen, the idealized welded joint model of longitudinal and transverse members in ship structure. Fatigue test was executed according to the 14-points S-N method of JSME, and experimental data were presented in the S-N curve based on HSS (Hot Spot Stress) approach. To define the fatigue life of crack initiation and crack propagation, S-N data for each length of crack were appraised. In this study, the new FE analysis algorithms for the estimation of residual stress relaxation due to external load and residual stress redistribution due to crack propagation were proposed to assess the effect of residual stresses on crack growth precisely. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis. In the analysis of crack propagation, the SIF (Stress Intensity Factor) range was evaluated by 1/4-point displacement extrapolation method, and the effect of welding residual stresses on fatigue behaviors was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data from the analysis.
Pipeline-Seabed Interaction in Soft Clay
Authors: Hesar M.
Published: January 2009

Offshore pipelines laid on the seabed in a snake configuration and transporting hydrocarbon products under high pressure/high temperature are becoming a cost effective alternative to trenching and burial. However, there appears to be a major disparity between the level of sophistication and accuracies inherent in the structural FE models used for expansion and lateral buckling analysis of pipelines, and the degree of crudity in adopting and using Coulomb friction values. This Paper reports the findings of a programme of geotechnical finite element analyses performed for a project where some 91km of 26” gas pipeline was designed to be laid in a snake configuration. The seabed soils were predominantly very soft clay. The ABAQUS/Explicit finite element program was used with an adaptive meshing technique to analyse the embedment and large lateral ploughing movements of the pipelines by a distance of several diameters. It was found that the FE model predicts the initial pipeline embedment into soil accurately and rectifies the inaccuracies inherent in published plasticity-based closed form solutions. A new non-dimensional relationship is proposed for estimating pipeline embedment in soft clays. The effect of important parameters such as the soil-pipeline interface friction, operating submerged weight and initial embedment, were all captured. Predicted cyclic lateral ploughing showed similarities to the observed response in reported model tests. The results were used in the structural FE model of the pipelines to analyse the expansion and lateral buckling problems and hence design the number and critical lay curvature of snakes as well as other important features.
Application of Direct Boundary Element Method to Three Dimensional Hydrodynamic Analysis of Interaction Between Waves and Floating Offshore Structures
Authors: Kazemi Saeid , Incecik Atilla
Published: January 2009

A three-dimensional hydrodynamic analysis of interaction between a floating offshore structure and sea waves has been carried out using a novel approach which is based on the weighted residual technique and the direct boundary element method. The main advantage of the direct boundary element method is the fact that one can determine the total velocity potential directly. Direct BEM is more versatile and computationally more efficient than indirect BEM. Besides, the BEM can easily be coupled with other numerical methods, e.g. finite element method (FEM) in order to carry out structural analysis of deck of the platform due to impact. Firstly, the boundary value problem of three-dimensional interaction between regular sea waves and a semi-submersible will be described. Secondly, the direct boundary element method has been applied to predict hydrodynamic behaviour of Khazar Semi-Submersible Drilling Unit (KSSDU), which is the largest semi-submersible drilling platform under construction for a location in the Caspian Sea, North of Iran. The rigid body motion responses in six degrees of freedom of KHAZAR semi-submersible in response to encountering waves have been calculated by using the direct boundary element method. The results obtained from the direct BEM will be compared with those obtained by the results based on the conventional boundary element method (indirect BEM) which were obtained by the designers of KHAZAR semi-submersible.
Statistics of TLP Tendon Tension Behaviour During Hurricane Lili
Authors: Morandi Alberto , Martinez Diego , Smith Charles
Published: January 2009

Hurricane Lili permitted an assessment of the global performance of several deepwater structures under a major environmental event. The US Minerals Management Service (MMS) commissioned American Global Maritime Inc. (AGMI) to collect and assess information on the performance of the deepwater production facilities that were impacted by Lili. The Shell Brutus Tension Leg Platform (TLP) provided comprehensive measurements of winds, motions and tendon tensions during Lili. The tendon tension data recorded was analyzed in both the time and frequency domain and tendon tension statistics were comparable to the relevant design values. Other relevant comparisons included natural period and damping estimates. Overall the design ‘recipe’ adopted for Brutus was sufficient to prevent exceedance of design capacities and damage to the hull structure and tendons during Hurricane Lili. The lessons learned from the analyses and recommendations for further work are also summarized in this paper.
Heave and Pitch Response of an Offshore Platform With Air Cushion Support in Shallow Water
Authors: Thiagarajan K. P. , Morris-Thomas M. T. , Spargo A.
Published: January 2009

Model tests were conducted on two 1:100 scaled models of a typical concrete gravity substructure at the University of Western Australia. The two models had dimensions 0.5m length × 0.5m width with the first model being a sealed closed bottom box of height 0.1m and the second model being an open bottom box with skirt length of 0.1m. The open bottom model had the capacity to hold an air cushion with dimensions 0.49m width × 0.49m length × 0.08m height. Each model was floated at a constant draft of 0.1m and tested in water depths ranging between 0.03m (shallow) and 0.8m (deep). The environment comprised of regular waves with periods ranging between 0.6s and 3.5s and amplitude of 0.08m–0.02m. To quantify the dynamic response the heave and pitch motion of each model were measured. The model test results were compared with a theoretical solution based on long wavelength, linear wave assumptions applied to a box shaped floating vessel without an internal free surface. Results show that experimental trends compare reasonably well with analytical solution. Added mass values were predicted from heave and pitch decay tests. The results show that introducing air cushion support into a CGS increases the pitch response, while having little effect of the heave motion. The theory is also used to delineate regions of safe and unsafe tow-out operations of the air cushion structure.
Shallow Water PEMEX Production Platform With Large Production Capacity in Cantarell
Authors: Matus Hugo , Ghosh Susobhan , Hazarika Debendra
Published: January 2009

Many pile mounted jacket type fixed platforms in shallow water have been installed during the last fifty years for producing oil. However, a production platform in 165 feet of water that produces 414,000 barrels of oil and 436 million standard cubit foot of gas per day (mmscfd) is not so common. In November 2003, such a platform has been installed by PEMEX (Petroleos Mexicanos) in the AKAL-L complex of Cantarell field located in the bay of Campeche. The Cantarell field development is a very high-profile development undertaken by PEMEX at a cost of more than US $10 billion. Although it is a shallow water platform, many design considerations are quite challenging because of the methods of construction, loadout, transportation, installation, etc. For example, the production deck of this installation weighs approximately 11,500 tonnes, including rigging. In the early stage of design, it required consideration of one-piece construction vs. multi-piece construction for cost effectiveness. The decision process included considerations of not only the capabilities of fabrication facilities, but also the availability and capacity of an installation/crane barge, such as the Saipem S-7000. The deck was finally constructed in five modules, one large 7000 tonnes module, and four smaller modules for generator and compressors each weighing approximately 900 tonnes. Proper planning of loadout, lifting operations and related engineering issues proved crucial to the successful installation of the platform. The deck of the platform was built in Dragados Offshore yard in Ca´diz, Spain, and was then dry towed on a large deck cargo barge, S-44, owned by Saipem. The water level at the loadout dock site and range of tides in the area made it necessary to ground the S-44 during deck loadout. Grounding of the barge raised several engineering issues, such as, the adequacy of the barge structure during the loadout operation, preparation of the mudline at the dock, developing of a detailed ballasting sequence, inspection of barge structure before sail-away, etc. The transportation of the deck not only required proper design of seafastening structures, but also required verifying the structural integrity of the deck and other structures of the module. This paper presents an overview of the design features of the platform as well as the methods of loadout, transportation and installation.