bluuebunny/crossref_metadata_2025 huggingface dataset:
The PODS Data Model
Authors: Brush Ron
Published: March 2009

PODS the Pipeline Open Data Standard (ISAT 2.0) is a new data model that has been developed by a group of application developers, with the support of GTI (formerly Gas Research Institute). The presentation will consist of two parts. The first will present the business case for PODS and the PODS Association. The second part will describe technical aspects of the data model. The purpose of PODS is to promote a database standard in the pipeline industry so companies can avoid custom data designs and applications, costly data migration, and reduce development risk. Vendors benefit by developing applications and processes that can be shared by different customers. This paper will give an overview of the business case for industry and vendor participants to use PODS. To manage the PODS data model, a new PODS Association has been formed which will oversee the continued development of the model and extensions through focused working groups comprised of industry and vendor members. This presentation will describe the purpose and operation of the PODS Association. Finally, this presentation will focus on the PODS data model itself and the important concepts. The focus will be on some of the core data model tables, how ESRI users can easily use the model, and future directions.
Fracture in Wrinkled Linepipe Under Monotonic Loading
Authors: Das Sreekanta , Cheng J. J. Roger , Murray David W.
Published: March 2009

Buried pipelines may undergo large deformations due to geotechnical movements, temperature effects, and fluid pressure which result in axial loads, shear loads, moments and various complex combinations of these loads and load histories. Consequently, localized buckles and wrinkles may form in the pipe wall and, subsequently, fractures may develop at wrinkle locations. Previous research showed that large deformation due to monotonically applied symmetric loading can produce accordion type wrinkle geometry but fracture is not normally produced unless strain reversals at the wrinkle location occur due to the application of variable loads. Recently, a field fracture that developed in an NPS10 pipe was brought to University of Alberta Structures Laboratory for investigation. From the description of the load history at the failure location, and the inspection of the deformed geometry and fracture surface, it was recognized that no significant strain reversals had occurred in this particular wrinkled pipe segment. Examination implied that the final failure was a “tearing” failure resulting from monotonic application of a longitudinal load not aligned with the axis of the pipe. However, the true load history that caused the pipe to fracture at the wrinkle location was unknown. To verify the nature of the failure mechanism, and determine the characteristics contributing to its formation, it was felt necessary to attempt to reproduce similar failures in a wrinkle by subjecting it simultaneously to monotonically applied axial load and shear. Two full-scale tests applying axial load, and a shear load with different boundary conditions were carried out on NPS12 pipe. The second test produced a deformed geometry and a fracture configuration very similar to the one that developed in the field. This paper describes the test procedure for these two tests and the mechanics of the fracture. It is concluded that, with the appropriate load history and boundary conditions, fractures can be triggered at wrinkle locations by monotonic loading histories.
Qualification of Procedures for Welding Onto In-Service Pipelines
Authors: Bruce William A.
Published: March 2009

When welding onto an in-service pipeline, to facilitate a repair or to install a branch connection using the “hot tapping” technique, two risks need to be considered. The first is the risk of burnthrough, where the welding arc causes the pipe wall to be penetrated allowing the contents to escape. The second is the risk of hydrogen cracking that arises from the fast cooling rates that tend to be produced by the ability of the flowing contents to remove heat from the pipe wall. To prevent hydrogen cracking, at least one of the three conditions necessary for its occurrence must be eliminated. Beyond the use of low-hydrogen electrodes to minimize hydrogen levels, it is prudent to develop and use procedures that minimize the formation of crack susceptible microstructures. This paper reviews existing methods for selecting parameters and qualifying procedures for welding onto in-service pipelines. HAZ hardness is an indicator of the susceptibility of a microstructure to cracking. A widely-used value below which it is generally agreed that hydrogen cracking is not expected is 350 HV. Unfortunately, there is no one hardness level above which the risk of hydrogen cracking becomes unacceptable. This paper also describes the development of a hardness evaluation criterion that can be used to quantify the trade-offs that can be made between HAZ hardness, hydrogen level, and chemical composition. Finally, the results of a recently-completed group-sponsored project, where procedures for welding onto in-service pipelines were developed over a wide range of conditions, are also reviewed. The results can be used to select an appropriate procedure that is resistant to hydrogen cracking for a particular application. The use of these results allows in-service welding to be carried out in a safe, cost-effective manner, allowing both economic and environmental benefits to be realized by avoiding pipeline shutdown and interruption of service.
State-of-the-Art Quality Control During Production of SAW Linepipes
Authors: Liessem Andreas , Grimpe Fabian , Oesterlein Ludwig
Published: March 2009

An essential prerequisite for a longitudinally welded large-diameter pipe to meet the most stringent quality requirements are efficient production units and the latest technologies for online quality control. To capture all data obtained during the various steps of production and testing and to control these data within close tolerances, an integrated IT-system covering all production stages — from the steel mill to the pipe coating — is indispensable to ensure a precise traceability of data and products. By an extensive automation of data acquisition and control, the factor of human errors can be excluded. In the following we would like to give you an overview of measures and investments which have already been realized by Europipe over the last years or which are going to be introduced with the aim to meet customer’s ever increasing demands on quality.
Characterizing Pressure Fluctuations on Buried Pipelines in Terms Relevant to Stress Corrosion Cracking
Authors: Van Boven G. , Sutherby R. , King F.
Published: March 2009

Pressure records for high pressure hydrocarbon pipelines that have previously shown to have occurrences of trans-granular stress corrosion cracking (tSCC) were supplied by ten Canadian Energy Pipeline Association (CEPA) member companies. These pressure records were analyzed by performing six methods of pressure cycle counting described in the ASTM standard E1049-85. A comparison was made of the magnitude and frequency of these counted pressure cycles at compressor/pump discharge and suction locations as well as intermediate locations along the pipeline. An attempt to relate the derived pressure cycles to tSCC growth was made by applying previously published “superposition” type cumulative damage models in calculating tSCC growth rates. Information about the relative importance of fatigue growth in the total tSCC lifecycle as well as the ability to distinguish tSCC susceptible areas on a pipeline based on differences in pressure cycles was gained. Characteristic pressure cycle spectra were developed from the supplied pressure data which describes the different modes of pipeline operation including liquid or gas hydrocarbon transportation as well as mainline or lateral operation which may be of use in further research efforts in this area.
To Comply: Why Should I?
Authors: Robert Chantal , Be´langer Nadia
Published: March 2009

The National Energy Board (NEB) is a Canadian federal regulatory agency whose mandate under the NEB Act is to regulate the construction and operation of interprovincial and international oil, gas and commodity pipelines; the construction and operation of international and designated interprovincial power lines; the setting of tolls and tariffs for oil and gas pipelines under its jurisdiction; the export of oil, natural gas and electricity, and the import of natural gas. International and interprovincial pipelines are subject to the statutory requirements of the NEB Act and Regulations made by the NEB. The regulations typically incorporate consensus standards such as the Canadian Standards Association (CSA Z662 - Oil and Gas Pipeline Systems). The NEB tracks and monitors compliance to ensure that companies fulfill the requirements of the Act and Regulations as well as any conditions imposed at the time of approval of the facilities. In carrying out its mandate, the NEB promotes the safety of people, the protection of property and the environment, and economic efficiency in the Canadian public interest. Recently, the NEB has implemented a formal system to track and monitor compliance. In approving new projects, the NEB imposes conditions outlined in approval Orders and Certificates. It then tracks these conditions for compliance, completeness and effectiveness. The compliance information is gathered mainly from activities such as inspections, audits and company filings. This paper explores in greater detail the NEB’s role in terms of tracking and monitoring compliance, NEB expectations of regulated companies and the effectiveness of a self-reporting condition. It also discusses the advantages for companies to be in compliance and its importance.
A Maxwell-Stefan Approach for Predicting Mixing Effects in Contiguous Batches of Multi-Product Pipelines
Authors: Arau´jo Ofe´lia Q. F. , de Medeiros Jose´ L. , Carvalho Hellen P. M.
Published: March 2009

Transient phenomena in the liquid batch interfacial zone are addressed based on: (i) a reliable compositional description; and (ii) mass transfer modeling. In phase (i), compositional models are proposed for transported fluids, with parameters estimated by maximum likelihood procedures to match known characterizing data, like distillation curve, density, viscosity and heteroatom weight fractions. In phase (ii), the transient mixing problem is posed on the continua of axial position in the duct, and described by Maxwell-Stefan formalism for multicomponent mass transfer between two contiguous semi-infinite fluids. Turbulent effects are considered on calculation of mass transfer coefficients, and rigorous thermodynamic driving forces are accounted for through component fugacities predicted by equations of state. The model was solved by the finite element method and the resulting set of ordinary differential equations in time was numerically integrated enabling determination of the mixing zone, calculation of property profiles and monitoring loss of product specifications.
New Technology Spiral SAW Pipes for Onshore and Offshore Oil and Gas Pipelines
Authors: Avagianos Josef , Papamantellos Kostas
Published: March 2009

The world production capacity on large-diameter welded pipe amounts to more than 12 million tons per year 20–25% are produced as spiral sub-arc welded (SAW) pipes, with the balance of 75–80% being longitudinal SAW pipes (from plates). For most spiral-weld producers, a sizeable portion of line pipe is for water transportation, rather than hydrocarbon. In the past, the relative structural weakness of spiral-welded pipe, due to larger welded area, limited the growth of its use in the oil industry. With the development of more advanced production technology, the acceptance of spiral-welded pipes in the oil and gas industry has increased significantly. In this paper, the principals of the spiral manufacturing technology from coil by the two-step-method are introduced and the innovations of Corinth Pipework’s production facility are outlined in detail, including the sophisticated NDT techniques and the Quality Management System.
Finite Element Models for the Prediction of the Failure Pressure of Pipelines With Long Corrosion Defects
Authors: Noronha Dauro Braga , Benjamin Adilson Carvalho , de Andrade Edmundo Queiroz
Published: March 2009

PETROBRAS is conducting a research project with the purpose of investigating the behavior of pipelines with long corrosion defects. In the first phase of this project a database containing the results of nine burst tests of tubular specimens with flat bottom defects was generated. The second phase of the project aims at appraising the performance of two different finite element models: a shell model and a solid model. This paper describes the application of these models in the analysis of four tubular specimens of the PETROBRAS database. The failure pressures predicted by the two types of finite element models are compared with the burst pressures measured in the laboratory tests. Also a comparison between the results obtained by these models is presented. It is concluded that the solid model is more accurate than the shell model, but both models proved to be capable of simulating the corroded pipe burst tests adequately.
Effects of Vaneless Diffuser Geometries on Rotating Stall
Authors: Abidogun K. B.
Published: March 2009

Detailed experimental investigation was carried out to document the effects of vaneless diffuser diameter and width ratios on the fundamental characteristics of flow perturbation in the vaneless diffuser of a centrifugal blower. In addition, a benchmark set of experimental data will be provided to aid numerical investigation of instabilities in the vaneless diffuser flowfield in particular and the entire compression system in general. The current data showed that a decrease of the diffuser width, at constant impeller angular speed, resulted in a decrease of the critical flow coefficient. The data further revealed that a decrease in the diffuser diameter ratio, resulted in an increase in the frequency of rotating stall. Variation of the diffuser width does not have any appreciable effect on the frequency of rotating stall. The effects of flow coefficient on stall characteristics are also reported.
Repair Strategy to Reduce Operation and Service Interruption in a 48” Natural Gas Pipeline
Authors: Mun˜oz Raul Algarra , Martinez Gonzalez Jose L. , Serratt Daniel Morales
Published: March 2009

This paper describes the damage caused by a tropical storm to a 48” gas pipeline considered to be the main natural gas supplier within Mexico’s distribution network. Included is a detailed description of the temporary and permanent repairs and rehabilitation carried out. The pipeline section damaged during this natural event is located in a wide water crossing of the river “Tecolutla” in Veracruz, southern Mexico. The construction process to make a new crossing included horizontal drilling using state of the art technology, extensively applied and improved within the industry during the past 10 years. To accomplish the operation, a novel technique was applied, since the pipeline dimensions (48” diameter and 853 m length), required special tools and equipment. Only twice before in the world have projects similar to this one been attempted. This was the first ever application in Mexico. Therein lies the uniqueness and importance of its successful completion, despite the logistical problems and unforeseen difficulties that the contractor was presented with, such that at times it appeared that the work would not be successfully completed. The need to keep the pipeline operating during the project caused delays in most of the scheduled activities. A key factor to ensuring a successful end to this project was the contractor selection. Supervision and quality control were also important issues during the project’s development. The horizontal drilling approach allowed different arrangements for the pipeline crossing to be assessed. The arrangement chosen avoids the use of a gate valve and a bypass on the right side of the crossing, with the advantage of keeping this pipeline section 7 metres below the riverbed.
Geotechnical Characterization of the Weber River Crossing, Utah, for HDD Feasibility for the 2003 Kern River Pipeline Expansion
Authors: Keaton Jeffrey R. , Steelman Roy L.
Published: March 2009

The 2003 Kern River Pipeline Expansion will loop 635 miles of 36-inch high-pressure natural gas pipeline between southwest Wyoming and southern California and 82 miles of 42-inch pipeline in southern California. The Weber River near Coalville in Summit County, Utah, will be crossed using horizontal directional drilling (HDD) techniques. The original Kern River Pipeline was constructed across the Weber River using conventional open-cut methods in 1991, but environmental factors and the close proximity to other pipelines made HDD a reasonable option to consider. The Weber River floodplain is approximately 3500 feet wide at the pipeline crossing, and contains Interstate Highway 80, US Highway 189, and a paved frontage road. Geometry of the slopes above the floodplain results in an overall HDD horizontal length of 4750 feet with an elevation difference of 88 feet. The geologic setting of the Weber River crossing consists of Cretaceous marine and non-marine sedimentary rocks and Quaternary alluvial and colluvial deposits. The rocks are chiefly sandstone, siltstone, and claystone, with local limestone and coal. Sedimentary beds dip to the west at 10 to 30 degrees, and fractures dip at 60 to 80 degrees. The siltstone and claystone are soft to moderately soft, whereas the sandstone and limestone are moderately hard to hard. The alluvial deposits consist of silty sand to sandy gravel, and the colluvial deposits consist of silty clay to silty sand. A north-trending, west-dipping normal fault shown on published maps nearly coincides with Interstate 80. Geotechnical conditions at the proposed HDD crossing were evaluated by drilling six borings to depths ranging from 100 to 150 feet, and collecting ground penetrating radar (GPR) data at 11 profile lines covering 2170 feet of floodplain. The GPR profile lines were interrupted by channels of the Weber River, canals, and Interstate 80. A 25 MHz antenna was used to obtain radar penetration to effective depths of 50 feet or more. The contact between alluvial deposits and bedrock was detected at depths ranging from 20 to 50 feet. Local relief of the alluvial/bedrock contact was found to be on the order of 10 feet. DrillPath 2 and DrillMud programs were used for a preliminary evaluation of the HDD feasibility. A maximum HDD installation depth of approximately 105 feet was used, and fracture pressures were evaluated for a pilot hole and four stages of back-reaming. Locations of frac-out concern were identified. Final HDD design was performed by others.
Dynamic Simulation as a Tool for Optimizing Pressure Control Valve Performance
Authors: Broyles Jack W. , Shirt Roger W.
Published: March 2009

Control valves installed for pump station pressure control are typically tuned and commissioned at the low end of the flow range and well below the safe operating limits in order to avoid pressure excursions and line shutdowns during commissioning. Tuning parameters selected for best performance at low flowrates often produce poor performance at high flowrates requiring dampened tuning parameters and slower valve actuator speeds. This results in sluggish responses to pressure changes. Enbridge has undertaken a case study to examine three control valves which exhibited poor control characteristics. The goal of this study was to produce an optimal tuning strategy that could be implemented with a high degree of confidence over the entire range of operating conditions. To accomplish this, the IDEAS (AMEC Technologies, Inc.) dynamic simulation software package was utilized. The pipeline was modeled from the pump station upstream of the station of interest to the downstream pump station. The model consists of pipeline sections, pumps, control valves and other process elements that are hydraulically linked. Station discharge and suction pressures are controlled via PI controllers with adjustable set points, ramp rates and tuning constants. Valve full stroke actuator speed can also be varied. Information required to develop the simulation model included station elevations, pipeline lengths, pump curves and control valve Cv curves. The three simulation models developed for this study have been calibrated against process data by adjusting piping resistances. The inherent nonlinearities present in the control valve system were quantified through use of the simulation model. Various strategies to alleviate the adverse effects of these nonlinearities have been studied. Use of a simulation tool also resulted in increasing the awareness of trade-offs present in design and tuning of control valve systems.
Rotating Machinery Acoustics: A Complete Coupling Contributes to the Impeller Fatigue Failure
Authors: Motriuk Roman W.
Published: March 2009

Complex dynamic fields such as pulsation, vibration and noise are generated in turbo-machinery systems. These fields are created by the acoustic waves propagating in gaseous media and interacting with the turbo-machine casing and its components. The acoustic loads result from the flows nonuniformity, flow path obstacles or the machine kinematics. The acoustic waves frequently interact with the structural modes inside the turbo-machine. Such interactions may contribute significantly to structural failures and therefore are of primary interest to a machine designer. High ‘efficiency’ couplings usually lead to structural failures while low ‘efficiency’ couplings are not important. Thus, assessment of the coupling ‘efficiency’ is crucial in the calculation of failure probabilities. This knowledge could also be used during the root cause failure analysis or in the machine re-design process. The most ‘efficient’ coupling takes place when the so-called joint acceptance function, representing spatial coupling ‘efficiency’ and the transfer function, representing time coupling ‘efficiency’, describe full coincidence of the acoustic and structural modes. Partial couplings are usually unimportant due to their low ‘efficiency’. This paper attempts to explain partial and complete coupling concepts based on example of a failed compressor impeller. Some practical design remedies to avoid impeller failures are given while predicting the complete coupling.
Enbridge Comparison of Crack Detection In-Line Inspection Tools
Authors: Wilkie Garrett H. , Elm Tanis J. , Engen Don L.
Published: March 2009

Enbridge Pipelines Inc. operates the world’s longest and most complex liquids pipeline network. As part of Enbridge’s Integrity Management Program In-Line Inspections have been and will continue to be conducted on more than 15,000 km of pipeline. This extensive program is comprised of a mature metal loss and geometry inspection component as well as a crack inspection program utilizing the most sophisticated In-Line Inspection (ILI) tools available. Enbridge conducted its first ultrasonic crack inspection with the British Gas Elastic Wave Vehicle (Now GE Power Systems – Oil & Gas – PII Pipeline Solutions) in September 1993 on a Canadian portion of it’s 864–mm (34”) diameter line. The Elastic Wave Vehicle was also used for crack detection on additional segments of this same 864–mm (34”) diameter line during the following years, 1994, 1995 and 1996. Enbridge then conducted its first crack inspection with the Pipetronix UltraScan CD tool (Now also GE Power Systems – Oil & Gas – PII Pipeline Solutions) in November 1997 on a segment of this 864–mm (34”) diameter line that was previously inspected with the Elastic Wave Vehicle. The UltraScan CD tool was then utilized again in 1999, 2000 and 2001 completing crack inspection of the Canadian portion of this 864–mm (34”) diameter line. Enbridge conducted its first magnetic crack inspection with the PII TranScan (TFI) Circumferential Magnetic inspection tool in December 1998 on a United States portion of another 864–mm (34”) diameter line. This same section of line was subsequently inspected with the PII UltraScan CD tool in July 2001. This paper discusses the comparison of results from overlapping crack inspection data analysis from these three PII crack detection tools. Specifically, the overlap of the UltraScan CD and Elastic Wave Vehicle along with the overlap of the UltraScan CD and TranScan (TFI) tool. The relative performance of each crack detection tool will be explored and conclusions drawn.
Impact of Thin Film Coatings on Cathodic Protection
Authors: Warnke Daryle , Holtsbaum W. Brian
Published: March 2009

Thin film coatings, such as fusion bonded epoxy (FBE) coatings have become more popular as an underground pipeline coating especially on large diameter pipelines. This together with improved construction techniques has resulted in very effective coatings. They do however present additional considerations in a cathodic protection design. This paper deals with some issues that one must bear in mind related to cathodic protection when dealing with these superior coatings including a modification to empirical data in cathodic protection pre-designs, an upper polarized potential to prevent cathodic disbondment, inspection in horizontal directionally drilled crossings, an increased effect of telluric currents and an increased possibility of hazardous induced AC potentials. Examples are presented and discussed.
Guidelines for the Seismic Design and Assessment of Natural Gas and Liquid Hydrocarbon Pipelines
Authors: Honegger Douglas G. , Gailing Richard W. , Nyman Douglas J.
Published: March 2009

Guidelines for the seismic design of oil and gas pipelines have not been updated in a single reference document since 1984, when the American Society of Civil Engineers released their publication, Guidelines for the Seismic Design of Oil and Gas Pipeline Systems. Since 1984, substantial progress has been made in identifying and quantifying seismic hazards, understanding pipeline response under large, displacement-controlled strain conditions, and analytical methods for assessing pipeline response to permanent ground displacement. In 1998, the Pipeline Research Council International, Inc. (PRCI) initiated a project to update seismic design guidelines for pipelines with the goal of incorporating advances in current engineering practice since the early 1980s and to create a document that can be regularly updated to take advantage of new research findings. The PRCI project to develop the guidelines was undertaken by two investigators heavily involved in the 1984 American Society of Civil Engineers guidelines. Two teams of independent expert reviewers were used during the project to assure the recommended practices were technically consistent with the current state of knowledge of seismic hazard assessment, pipeline behavior, and analysis methods.
Cactus: Guadalajara LPG Pipeline System Rehabilitation
Authors: Graciano Luis Sanchez , Paz Hernan , Urednicek Mirek
Published: March 2009

This paper describes the work that was undertaken to re-qualify the Cactus-Guadalajara LPG pipeline for a higher MAOP without taking the pipeline out of service for a hydrostatic test. It demonstrates how geo-positioning technology, high-resolution in-line inspection, and data management systems can be successfully utilized for such project, even when the record-keeping associated with previous pipeline repairs has been deficient. By establishing a geo-referenced pipeline asset management system that integrates physical asset description, operational data, internal inspection and pipeline repair data, a sound foundation has been created for the future integrity management of this pipeline.
Influence of Gradually Moving Slopes on Pipelines
Authors: Barlow J. Peter
Published: March 2009

The river valleys in the plains of Western Canada and the Northwestern United States are relatively young in a geological time scale and often have extensive landslide activity on the valley slopes. Depending on the geology, these landslides can have very low movement rates and show little or no visible signs of slope movement, but still be relevant for the integrity of pipelines. Pipelines installed in gradually moving landslide terrain are subject to some risk of damage, depending on the details of the installation and the level of activity of the slide. Directionally drilled pipeline installations can be particularly vulnerable to this type of slope movement relative to long term integrity. A number of case histories are reviewed that involved pipeline installations on slopes that were moving at slow but persistent rates. Measures were successfully implemented at several of the slopes to lower the risk to the pipelines. Many of these cases involved relatively low cost drainage measures that significantly reduced the risk of pipeline damage.
SUPDUT: An Environment to Implement Logic Control Applications for Pipelines
Authors: de J. Bernardo Luiz F. , Cid Eliane A. , de T. A. Correia Paulo , Milidiu´ Ruy L. , dos S. Liporace Frederico
Published: March 2009

The reliable operation of product transfers in pipelines is essential to the economic results of a pipeline company. This operation heavily depends on calculations performed over real time raw and historical data to assure the expected level of confidence in the operational results. This paper describes the development of a software environment, SUPDUT (abbreviation for the portuguese term Supervisor de Oleodutos, or Pipeline Supervisor), to be used in the development, organization, execution and maintenance of operational applications and to support their communication with other corporate and basic real time systems (SCADA). Application in this context means all kinds of operational or corporate calculations that require information from SCADA. The main advantage of the SUPDUT architecture is that it simplifies the application development and maintenance process, by providing a server that deals with all the complexity related to SCADA communication and application scheduling. The application developer therefore does not need to be concerned with those issues. It also makes the application development independent from the SCADA that collects real time data. The environment is designed to facilitate a simple and rapid implementation of new applications with a minimal impact on the system. Other important SUPDUT environment features are: complete object-oriented design, planned support for distributed applications and reliable application scheduling, support for a wide range of application scheduling options, support for multiple SCADA, support for multiple languages for application development (FORTRAN, C, C++ and Java) and robustness to the addition of new applications. The SUPDUT environment requirements definition and design are completed, and it is in its coding phase as this paper is being written. The first production version of the software is expected to be delivered by the end of 2002.
The Corrosion Behavior of Welded Line Pipes in Wet H2S Environment
Authors: Feng Yaorong , Huo Chunyong , Yan Feng
Published: March 2009

The corrosion behavior of over-bending and under-bending formed Spiral Submerged Arc Welded (SSAW) steel pipes in NACE solution has been investigated by use of the self-designed full-scale corrosion test unit. It indicates that the H2S damage of welded pipes characteristics Blister and Stress Corrosion Cracking (SCC). The blister number, diameter, and crack number is increasing as the increasing of applied stress. The residual stress of welded pipes has a large effect on the H2S corrosion resistance, the tensile residual stress has a detrimental effect, and while the compression residual stress is beneficial to H2S corrosion resistance. The damage mechanism of the welded pipes in H2S containing solution under the presence of applied stress and residual stress has not only Hydrogen Induced Cracking (HIC), but also Stress Corrosion Cracking, and the applied stress and residual stress promote not only Stress Corrosion Cracking, but also Hydrogen Induced Cracking. The test results reveal that improving pipe’s weld surface quality, lowering tensile residual stress, and also control the operating stress are the key measures for controlling the wet H2S corrosion of welded steel pipes. Suggestions for selection of line pipes in different service conditions have been made.
Margins of Safety in FPSO Hull Strength
Authors: Hamdan Fadi H. , Burgan Bassam A. , White Robert
Published: March 2009

FPSOs are being increasingly used for deeper water and for a variety of functions related to offshore drilling, production and storage. Some FPSOs are being converted from tankers which have been designed using a traditional Class Rule type approach, while other FPSOs are being designed according to a more advanced hydrodynamic/Finite Element (FE) type approach. The traditional design procedures of FPSOs are based on simplifying component-based approaches that may underestimate the loading (in comparison to advanced hydrodynamic models) but provide a large factor of safety on the capacity. Results from studies for certain UK Central North Sea FPSOs seem to indicate that the safety factor for the two approaches is similar, since the advanced hydrodynamic/FE approach tends to result in higher loadings but also higher capacities. However it is not clear to what extent these results can be applied to other FPSOs or to other areas. Another issue that is addressed is the apparent variation in reserve strength against hogging and sagging bending moments. This is particularly true for double hull FPSOs which tend to have a higher capacity at the bottom of the hull in comparison to the deck. The purpose of this paper is to collate available data on the range of variation of safety factors of currently used FPSOs, and to consider how more consistent margins of reserve strength for various FPSO configurations under various loading conditions might be achieved.
The Accident of the P-36 Platform: The Rupture of the Emergency Drainage Tank
Authors: Videiro Paulo Mauricio , Cyranka Carlos , Nunes Giovani C. , Melo Aglairton P.
Published: March 2009

On March 15, 2001, the P-36 Platform had an accident, which led to the sinking of the unit. The platform was in operation in Roncador Field, at Campos Basin, in 1360 m water depth. This paper describes the analyses performed to validate the hypothesis that the first main event in the accident was the structural rupture of the starboard Emergency Drainage Tank. This tank was located inside the aft-starboard column of the platform. With the internal shell tank rupture due to overpressure, equipment and piping inside the column were damaged, causing the flooding of pontoon and column with water, raw oil and gas, that ignited resulting in the second event, an actual explosion.
Wake-Induced Large-Amplitude Low-Frequency Motions of a Vertical Riser in the Wake of an Upstream Riser
Authors: Wu Wusheng , Huang Shan , Barltrop Nigel
Published: March 2009

It is concluded from our previous work that a vertical riser situated in the wake of an upstream riser can lose its stability when the current velocity exceeds a critical value. The ensuing irregular motion of the downstream riser is characterised by its large amplitude and low frequency. A numerical method is further developed in this paper to simulate the wake-induced large-amplitude low-frequency motions of the downstream riser as it wanders about in the wake. While an accurate structural model for riser clashing is still yet to be developed, the preliminary results presented here do indicate that in considering the riser impact velocity it is inadequate to use the VIV velocity alone as the wake-induced motion can have a significant contribution to the riser impact velocity.
Towards the Integration of Analysis and Design of Mooring Systems and Risers: Part I — Studies on a Semisubmersible Platform
Authors: Senra Stael Ferreira , Correa Fabricio Nogueira , Jacob Breno Pinheiro , Mourelle Ma´rcio Martins , Masetti Isai´as Quaresma
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] The present paper begins describing a “basic” classic, uncoupled methodology, and proceeds with 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. These issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The companion paper [1] proceeds describing a fully coupled methodology, and some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.
The Directional Characteristics of Breaking Waves Generated by the Directional Focusing in a Wave Basin
Authors: Hong Keyyong , Liu Shuxue
Published: March 2009

A directional wave focusing is formulated and applied to generate three-dimensional breaking waves in multidirectional wave basin. Based on the theoretical development, an experimental scheme for the generation of directional breaking waves in model basin is established. The characteristics of breaking waves are analyzed in a view of focusing efficiency and the effects of associated parameters, such as the directional range, frequency width and center frequency, on the wave focusing are studied in detail. An experimental investigation of the maximum amplitude distribution, the evolution of time series and spectrums during the wave packet propagation, and the variation of the water surface parameters is extensively carried out. It reveals that the focusing wave characteristics are significantly influenced by the wave directionality and the breaking criteria for directional waves are distinctly different from those for unidirectional waves.
Probabilistic Inspection Optimization of Free-Span Surveys for Subsea Gas Pipelines
Authors: Tronskar Jens P. , Sigurdsson Gudfinnur , Fyrileiv Olav , Forli Olav , Kiefer Joseph H. , Lewis Colin
Published: March 2009

Probabilistic methods have been used to develop the basis for free-span inspection of a gas pipeline system in the South China Sea. The objective of the probabilistic analysis was to study the probability of fatigue failure associated with postulated planar flaws in the HAZ of repair welds performed on some of the girth welds. The impact of flaws on the fatigue life under different free-span conditions were studied. Conventional free-span analysis involves computation of allowable free-span lengths based on onset of in-line vibrations and does not normally consider fatigue crack growth. To consider the effect of the weld flaws on the failure probability a combined probabilistic fatigue and fracture model is required. For the particular pipelines analysed automatic ultrasonic testing (AUT) was used replacing the conventional radiography of the girth welds. Conservatism in the free-span assessment can then be significantly reduced by taking into account detailed flaw sizing information from the AUT. The inspection records provide distribution of flaw height, length and position. Combined with information on current distribution, material strength and fracture toughness distribution, a detailed probabilistic fatigue crack growth and unstable fracture assessment can be conducted as per the Det Norske Veritas (DNV) 2000 Rules for Submarine Pipeline Systems [1] using the response models of the DNV Guideline 14 for free-span analyses [2]. The objective of this analysis is to estimate the critical free-span lengths and the time for fatigue cracks to penetrate the pipe wall.
Prediction and Testing (ASTM E-837-89) of Residual Stresses in Structures (Operated in SOHIC Environment) Caused by Welding
Authors: Armand Sasan , Jones Stan
Published: March 2009

The study and testing of the structural behavior of a failed pipe with a spiral weld seam was conducted. Our study and testing was part of a larger failure investigation to determine the influence of residual stress for initiation of hydrogen stress cracking. Finite element and structural testing methods were used to guide the study for determination of residual stresses. All properties used in our study were measured per ASTM A-370. The validation of the finite element model of the pipe was conducted against the test results per ASTM E-837-89. The difference in predicted and measured residual stresses was 3% at the ID of the structure. Due to the small differences in the results from analysis and testing, no correlation was required, and the test-validated finite element model was used to predict the total stresses due to the manufacturing processes and operational loads. Based on the validation results, one can conclude that the finite element technique is accurate for predicting residual welding stresses. The finite element technique, however, is far less time -consuming and thus less expensive method than mechanical testing for determining the residual stresses.
Effects of Lateral Stability on the Design of HT/HP Flowlines
Authors: Ma Wei , Andrieux Olivier , Sauvage Pierrick , Parsloe Nicolas , Burban Pierre-Yves
Published: March 2009

This paper discusses key effects of the lateral stability on pipeline design and especially on axial creeping under thermal and pressure cyclic loading when connected through catenary risers to large offset floating platforms. A recent industrial study by Tornes [1] has shown that, under repeated heat-up and cool-down of the transported fluid and assumed lateral stability, some high temperature and/or high pressure deepwater flowlines experience some gradual net axial displacement towards the colder outlet ends. The present paper will further demonstrate that the flowlines may have much larger net axial displacement under repeated production shut-downs if they are laterally unstable. Detailed discussions on the phenomenon are given to 1) Flowline layout as functions of curve radius and routing, global slope and detailed seabed profile, 2) Axial and lateral friction forces applied, 3) Submerged weight of the considered flowline, 4) Operating parameters including cyclic pressure and temperature variations, and 5) catenary riser tensions. The paper provides sufficient details and results for the deepwater pipeline ratcheting phenomenon through extensive finite element analyses. The models will mainly cover production flowlines in both elevation profile and plan layout. The results are also compared with theoretical calculations. Some important considerations on deepwater pipeline design are widely described. It is hoped that the discussions presented in this paper will allow operators to address this issue at the earliest stages of the field development and benefit pipeline designers.
A New Approach for the Reconstruction of Significant Wave Height Time-Series
Authors: Arena Felice , Puca Silvia , Tirozzi Brunello
Published: March 2009

A Neural Network (NN) model is proposed for the reconstruction of significant wave height time series, without any increase of the error of the NN output with the number of reconstructed data. The input of the NN model are correlated data, obtained from nearby stations: no data of the same series we are modelling are used. A weighted error function during the learning phase is also considered to improve the modelling of the higher significant wave height. Furthermore the equivalent triangular storm model is applied to test the ability of the NN model to reconstruct the sea storms. The comparison between actual data of a NOAA buoy moored off San Francisco (California) and the data reconstructed by NN model shows a good agreement, both during calm time periods and during storms.
Reflection and Transmission of Ship Waves by Floating Barriers
Authors: Miao Quan-Ming , Chwang Allen T.
Published: March 2009

The reflection and transmission of ship waves by vertical floating barriers located on both sides of a fairway are investigated by the modified Dawson’s method in this paper. The free surface is specially treated to take into account the floating barriers. The wave pattern and the wave energy density between and outside the barriers are obtained. It is found that the reflection and transmission performance of a barrier is associated with its width and height. For a wider or higher barrier, more ship waves are reflected by it. A vertical floating barrier with a reasonable width and height can reduce ship waves in the outer region very efficiently.
Dynamic Stability of FPSO-Shuttle Systems: An Analytical Procedure and Practical Results
Authors: Matter Ge´rson B. , Sales Joel S. , Sphaier Sergio H.
Published: March 2009

The paper deals with the dynamics of floating systems (FPSO units) moored in deep water in the presence of currents. The offloading operation is carried out in a tandem arrangement from the FPSO to a Shuttle ship of lesser capacity. According to the classical theory of dynamic systems, a study of the behavior of floating units is performed by determining the equilibrium position and then analyzing the stability around this position. The time domain analysis is also used to compare the results. This procedure is extended to the case of systems in a spread mooring configuration and with turret.
Low Damping of Cylinders Vibrating in Still Water
Authors: Hover F. S. , Smogeli O̸. , Harper J. A. , Triantafyllou M. S.
Published: March 2009

We performed laboratory tests of a smooth rigid cylinder oscillating in still water, with L/D in the range 3.3–26.2, Keulegan-Carpenter numbers KC = 2 − 7, and β = 1000 − 6000. Within these ranges, drag coefficients are seen to increase with increasing KC, decrease with increasing β, and decrease with increasing L/D. The values, especially with high L/D, are somewhat lower than those reported by Sarpkaya.
Field Tests on Suction Pile Installation in Sand
Authors: Cho Y. , Lee T. H. , Park J. B. , Kwag D. J. , Chung E. S. , Bang S.
Published: March 2009

A series of field suction pile installation tests have been conducted inside the Onsan harbor located in southeastern Korea during the summer of 2001. The suction piles were made of steel, having inside diameters ranging from 0.5 meters to 2.5 meters and the length of five meters. The seafloor soil condition at the site is predominantly silty sand. Instrumentation includes the detailed measurement of the applied pressure vs. pile penetration and retrieval length relationships; the pile alignment during installation through a tiltmeter; and the pore water pressures both inside and outside the pile.