bluuebunny/crossref_metadata_2025 huggingface dataset:
Reducing Compressor Station Ambient Noise Level by Controlling Compressor Internal Noise Source
Authors: Liu Zheji , Jahnke Bill , Marczak Mike , Kiteck Paul
Published: March 2009

Dresser-Rand single stage pipeline booster compressors have been popular for gas transmission applications due to their high efficiency. As more compressors are installed in natural gas compressor stations close to populated areas, the noise level emitted from the compressor stations becomes a concern. To address the potential community noise concerns, Dresser-Rand recently developed a very effective noise control device — the Duct Resonator array or DR array, to attenuate the internal noise of the compressor, which is typically a major noise source of a compressor station. This technology has been validated by extensive in-house experimental study to be acoustically effective and yet have no measurable adverse effect on aerodynamic performance. This paper discusses the application of DR arrays in two compressors that are in-service at a Williams Gas Pipeline compressor station. Note: the DR arrays are now included in the third unit addition. A successful collaboration among the compressor manufacturer, the compressor user, and a third party acoustics expert was coordinated to take acoustic measurements independently to evaluate the noise reduction provided by the DR arrays. The comprehensive acoustic data acquisition included sound pressure level and sound intensity level measurements around each of the two compressors and several noise level surveys both inside and outside of the compressor building. Noise testing was first performed on each of the two compressors prior to the installation of the DR arrays and was repeated after the compressor hardware modification with DR arrays. A comparison of the noise data recorded before and after the installation of the DR arrays confirmed that the compressor noise level inside the compressor building and the noise level outside of the building were reduced significantly. The DR array has proved to be an efficient and effective device for reducing noise and vibration levels of both existing and new centrifugal compressors and associated piping.
Smart PIG “Fingerprint” Inspections Can Lead to Fitness for Purpose Assessments and Contractual Disputes
Authors: Palmer-Jones Roland , Hopkins Phil , Nafis Popi , Wintle Gordon
Published: March 2009

A recent ‘fingerprint’ smart pigging inspection recorded over 40,000 metal loss (corrosion) features in a 57km 42” diameter, dry gas pipeline supplying a major LNG facility in Indonesia. The pipeline had been in operation for less than 6 months. Assessment of these results by the inspection company identified 10 sections of pipe that required repair according to ASME B31.G, indicating that the pipeline was not ‘fit for purpose’. The pipeline operator immediately cut out these 10 sections to ensure the continued safe operation of the new pipeline. A detailed pipeline corrosion study subsequently identified the features as corrosion that had occurred during transport and storage of the line pipe. In addition, the corrosion was found to be less severe than initially thought and the same work assessed the remaining defects and, calculations using DNV Guideline RP F101, showed that the features were all acceptable. It was concluded that the high sensitivity of the smart pigging tool, combined with the failure to identify the cause of the features and the simple initial feature assessment overestimated the significance of the corrosion defects. This demonstrates the need for good care and inspection of line pipe during transport storage and construction. It also highlights the need to conduct engineering assessments to determine the inspection philosophy and to quantify the ‘workmanship’ level of metal loss features acceptable on a fingerprint run, before the run takes place. Otherwise new pipelines containing ‘custom and practice’ defects could be the subject of lengthy and costly disputes between operator and constructor. This paper proposes a method for assessing baseline survey data that provides an acceptance level for pre-existing defects. This methodology will assist operators in assessing smart pigging data from new pipelines.
Corridor Pipeline: Hartley Creek Crossing
Authors: O’Rourke Dan J.
Published: March 2009

Construction of the 493 km Corridor Pipeline System commenced in summer 2000, and is scheduled for completion in 2002. The system connects the two major components of the Athabasca Oil Sands Project — the Muskeg River Mine, north of Ft. McMurray and the Upgrader adjacent to Shell Canada Limited’s Scotford Refinery, near Fort Saskatchewan. The pipeline will also link the Upgrader with terminals in the Edmonton Area. The system includes dual pipelines (610 mm and 323.9 mm O.D.) as well as associated pump stations and valve sites. Corridor Pipeline Limited is a wholly-owned subsidiary of BC Gas Inc. Corridor pipeline crosses Hartley Creek near the south boundary of Shell’s lease C-13, north of Ft. McMurray, in the Ft. McKay First Nations traditional lands. An evaluation of the proposed crossing completed for the project application identified the location as highly sensitive to pipeline construction activities because of the high fish habitat quality and historical presence of sport and coarse fish. Although a fish survey completed for the above evaluation identified only coarse fish species, the provincial approval for the project required a trenchless crossing method unless authorized in writing by the Director. After completing detailed geotechnical and fisheries assessments of the crossing site, authorization from the director was subsequently obtained to complete the crossing using an isolation method. Planning and consultation with Ft. McKay First Nations to construct through their traditional lands incorporated aspects of traditional ecological knowledge. As part of the program, Corridor Pipeline committed to completion of a traditional plant survey. The results of the survey identified Hartley Creek as having cultural significance to the band. The riparian zone in this area supports a large concentration of food and medicinal plant species. Specialized mitigative measures were incorporated in order to maintain the density and diversity of the Hartley Creek riparian zone. This paper presents information with regard to the environmental studies and the regulatory process used to obtain approval to complete construction of the Hartley Creek crossing using an isolation method instead of the trenchless method originally required by the provincial government. It also explains the consultation program with the Ft. McKay First Nations and environmental planning used to maintain the density and diversity of riparian vegetation at this culturally significant crossing location.
Life Extension of a High Pressure Transmission Pipeline Using Structural Reliability Analysis
Authors: Francis Andrew , Gardiner Mike , McCallum Marcus
Published: March 2009

Pipeline designers and operators recognize that the commercial viability of operating high-pressure gas pipelines decreases with time. This is because the structural integrity levels of the pipeline decrease, due to the action of deterioration processes such as corrosion and fatigue, until the level of mitigation required to ensure adequate safety levels becomes uneconomical. For this reason pipelines are assigned a nominal design life of typically 40 years. This paper describes the application of structural reliability analysis to a high-pressure natural gas pipeline having both onshore and offshore sections, in order to determine the extent to which the asset life could be increased beyond the design life without any significant reduction in reliability and hence safety levels. The approach adopted was to identify the credible failure modes that could affect each of the onshore and offshore sections and determine the probability of failure due to each failure mode taking account of the uncertainties in the parameters that affect each mode. Based on a detailed consideration of the results of the study it was concluded that the life of the asset considered here could be extended to 60 years without any significant reduction in safety levels. Moreover, it was concluded that if certain mitigating measures were to be implemented in the future then it would be possible to increase the asset life to significantly more than 60 years.
Random Field Modeling of Rainfall-Induced Soil Movement
Authors: Konuk I. , Akpan U. O. , Brennan D. P.
Published: March 2009

Natural oil and gas transmission pipeline networks often traverse regions where potential slow ground movements may affect pipeline structural integrity. One of the primary causes of slow ground movement in any region involves the duration, amount, and intensity of rainfall. The phenomenon of rainfall-induced slow ground movement is characterized by both spatial and temporal variability, and involves uncertainties that are best modeled using a probabilistic methodology. A random field modeling strategy is formulated in this study, in which spatial and temporal correlations between rainfall and ground movement are accounted for. The random field formulation advanced in the current study has a number of significant features and capabilities, including modeling the spatial and temporal relationship between rainfall and slope movement for specified pipeline routes, predicting the likelihood of exceeding slope movement thresholds for various precipitation levels and intensities, and providing maps of risk for slope movement, which can be used as a guide in pipeline route planning, selection, and adaptation strategies for the design and maintenance of oil and gas infrastructure. These capabilities have been implemented and encapsulated into the software tool VSLOPE, which has been tested using monthly rainfall and field data for various locations.
Sectional Modeling of a Centrifugal Compressor
Authors: Hill D. Lee
Published: March 2009

The prediction of compressor performance using steady-state methods has had limited success for multistage configurations. Accepted limitations of the computational methods such as streamline curvature effects have been ignored because of a more dominant issue of the interface between the rotating and stationary components and the change in pitch between the vaned-stationary components. The most common model reported in the literature for centrifugal compressor stage analysis is known as the frozen-rotor or implicit model. Its selection, however, is normally driven for numerical stability reasons not for accuracy. The literature has shown that this method does not provide physically correct solutions for off-design predictions. The current work attempts to improve the steady-state modeling approach by employing an interface modeling that assumes that the tip speed is much greater than the through flow velocity. This model is referred to as circumferential averaging and is less stable than the frozen rotor model. The next proposed improvement is to model all of the vaned-stationary passages in order to preserve geometric periodicity. The last novel improvement is in the area of the diffuser inlet region where a portion of the secondary flow path is included to resolve the entrance loss into the diffuser. This approach was used to model two sections of a high pressure centrifugal compressor. The results are presented for design and off-design flows. The calculations are compared with test data taken from full scale testing.
Advanced Radiographic Scanning, Enhancement and Electronic Data Storage
Authors: Savoie Charles , Rivest Darryl
Published: March 2009

It is a well-known fact that radiographs deteriorate with time. Substantial cost is attributed to cataloguing and storage. To eliminate deterioration issues and save time retrieving radiographs, laser scanning techniques were developed in conjunction with viewing and enhancement software. This will allow radiographs to be successfully scanned and stored electronically for future reference. Today’s radiographic laser scanners are capable of capturing images with an optical density of up to 4.1 at 256 grey levels and resolutions up to 4096 pixels per line. An industrial software interface was developed for the non-destructive testing industry so that certain parameters such as scan resolution, number of scans, file format and location to be saved could be adjusted as needed. Once the radiographs have been scanned, the tiff images are stored, or retrieved into Radiance software (developed by Rivest Technologies Inc.), which will help to properly interpret the radiographs. Radiance was developed to allow the user to quickly view the radiograph’s correctness or enhance its defects for comparison and future evaluation. Radiance also allows the user to zoom, measure and annotate areas of interest. Physical cost associated with cataloguing, storing and retrieving radiographs can be eliminated. You can now successfully retrieve and view your radiographs from CD media or dedicated hard drive at will. For continuous searches and/or field access, dedicated hard drives controlled by a server would be the media of choice. All scanned radiographs will be archived to CD media (CD-R). Laser scanning with a proper acquisition interface and easy to use viewing software will permit a qualified user to identify areas of interest and share this information with his/her colleagues via e-mail or web data access.
Deformation and Ductile Cracking Behavior of X80 Grade Induction Bends
Authors: Muraoka Ryuji , Ishikawa Nobuyuki , Endo Shigeru , Yoshikawa Masaki , Suzuki Nobuhisa , Kondo Joe , Takagishi Masaaki
Published: March 2009

Permanent ground movement is expected in seismic areas and in permafrost regions, and pipelines buried in those areas need to be designed to have sufficient deformability. Especially, bends need to have superior deformability, because it was pointed out in the recent earthquake event that deformation tends to concentrate in the connection region of pipelines. Severe deformation can lead to a fracture of the pipe wall and this may cause explosion of the pipeline or leakage of the gas, which need to be prevented in the areas with high population density. In spite of the importance of deformability for pipe bends, there are only a few reports on this issue. Furthermore, those investigations are limited for up to X65 grade induction pipe bends. In this study, two types of API X80 grade induction pipe bends, 610mmOD × 11.0mmWT and 610mmOD × 16.6mmWT, bending radius of three times the pipe diameter and bending angle of 90 degree for both, were manufactured using longitudinally submerged arc welded pipes as mother pipes. And large scale bending test using X80 grade pipe bend was conducted by applying closing displacement on the tangents under the internal pressure of 12MPa by water. Bending load was continuously applied up to the maximum load point, and then prescribed displacement was applied until twice the maximum load point. Local deformation was shown in the middle of the bend portion, however, no cracking was observed. Furthermore, EF analysis of bending test was performed for precise estimation of stress/strain response of pipe bend, and analytical results were compared with experimental data. These bending tests proved that large deformability could be expected on the X80 grade pipe bends even under the high internal pressure. In order to investigate ductile cracking behavior of the X80 grade induction pipe bend, notched round bar tensile tests were also conducted, and the criterion for ductile cracking was compared with X65 grade bend material. Relation between equivalent plastic strain and stress triaxiality at a ductile crack initiation point was determined by FE analysis, and this analysis proved that X80 grade bend material has enough resistance to ductile cracking compared to X65 grade bend. This result also corresponds to the results of the bend test, which is showing enough deformability of the X80 grade induction bends.
G.I.R.I.N.O.: A Pipeline Robot — Get Inside Robot to Impel Normal Operation
Authors: Salvi dos Reis Ney Robinson
Published: March 2009

The present intervention systems, for solving pipeline blockage or leak problems, are reaching their limits. New realities demand new technology for unusual interventions. In looking for better solutions, it was necessary to bypass the traditional methods used by the oil industry in order to investigate the inner surface of the pipeline. This work describes the development of a remote controlled apparatus, which is flow rate independent. This device could move freely inside the pipelines. A robot and its remote control operation system are the important factors, which would response to these new demands. The robot could be designed with special features such as the introduction of a specific solvent to dissolve or break the blockage; it could also be used as a tool-carrier. The system is able to drive accurately to the problem point, and use the adequate device to inspect and even to repair the inner surface structure of the pipeline.
Geometric Inspection Tool for 3-Inch Diameter Pipeline
Authors: da Silva Jose´ Augusto Pereira , Pinho Adriano F. , de Andrade Freitas Miguel
Published: March 2009

Geometric inspections are frequently performed during the construction and operation of pipelines of 6 to 40-inch diameter to detect dents and ovalizations that affect the pipe structural integrity, favor pipe corrosion, and hinder the use of magnetic inspection tools. However, no inspection pigs for pipelines of less than 4-inch diameter were available in the worldwide market. The great demand for such a specific inspection tools lead the Brazilian company PIPEWAY to developed a geometric pig capable of running 3-inch diameter pipes. PIPEWAY 3-inch Geometric Pig built in microprocessor and software allow graphic visualization and analysis, describing the inspecting operations and results. The 3-inch Geometric Pig is composed of several modules loaded with the sensors, the controller, the mass memory (that stores pig run data), the battery pack, and the odometer. What makes such pig a special tool is the deep integration of advanced technology with mechanics.
Pipeline Inspection Operations With Geometric Pigs: Campos Basin Main Results
Authors: Baldez Marcelo , da Silva Jose´ Augusto Pereira , Miranda Ivan Vicente Janvrot , Camerini Claudio Soligo
Published: March 2009

The increasing use of geometric pigs in the last five years has significantly contributed to the quality of pipelines in construction, as well as to geometric defect detection, assessment and identification, improving pipeline maintenance and overall quality. Geometric pigs with advanced built-in electronics allow precise defect sizing, helping pipeline integrity analysis. This paper presents actual anomalies detected by geometric pigs through comprehensive assessment and anomaly identification.
The BOS Compressor: An Economical Compressor Developed to Serve the Higher Speed, Higher Rod Load, and Higher Horsepower Requirements of the Gas Pipeline, Storage, Gathering, Process, and Similar Industries
Authors: Blazejewski Theodore E. , Moudgil Rajneesh
Published: March 2009

Traditionally, large slow speed integral gas engines were used in Pipeline applications. Today, the need exists for smaller high-speed units with a lower total installed cost and quicker return on investments. Utilizing well over 100 years of gas compressor experience, Dresser-Rand has developed a new Big Oilfield Separable (BOS) frame and Dresser-Rand Advanced Reciprocating Technology (DART) cylinder line-up to serve the high-speed engine and motor driven Pipeline/Injection markets. By incorporating a longer stroke capability, this compressor also serves the electric motor driven Process Gas markets. First, this paper will identify the complete design, development, and test verification of the frame and running gear. Second, this paper will then identify the complete design, development, and performance verification of the DART cylinder. Together, the BOS frame and DART cylinders provide an economical replacement to the older slow speed integral gas engines that are utilized in Pipeline applications.
Rapid Analysis Tool for High-Level Risk Assessment of Pipelines
Authors: Colquhoun Iain R. , Choong Evelyn , Kania Richard , Gao Ming , Wickenhauser Pat
Published: March 2009

When the benefits of using risk-based decision making in pipeline integrity management programs have been identified, operators are immediately faced with the challenge of large amounts of risk analysis work. This work frequently has to be done with minimum resources and/or in logistic situations that require a graduated approach extending over several years. In answering this challenge, a starting point must be identified that focuses resources where the risks are greatest. Since these locations are generally unknown in the first instance, the need exists to have a tool available to perform a first or high-level assessment to identify areas requiring further or more detailed study to support the integrity management program. The need also exists to have a robust tool that can be used to direct the assessments of smaller lines that might not require the detailed attention generally given to larger diameter transmission lines. This paper describes the extension of a simple indexing methodology comprising both theoretical and historical components to produce such a tool. It describes the use of so-called “smart” defaults to account for missing data, and a rudimentary decision model that can be used to grade the risk results. Examples are given of applications of the methodology to a gathering system and to the high-level evaluation of a transmission system. The paper also compares the results obtained to other, more detailed methodologies.
A Solution for Noise Associated With a Series Staged DLE Combustion System
Authors: James D.
Published: March 2009

Over recent years, Rolls-Royce has been at the forefront of the development of low emissions combustion technology in the industrial aero-derivative gas turbine marketplace. The solution developed embodies dry low emissions (DLE) combustion. However, this lean burn technology carries with it the inherent issue of acoustic resonance i.e. combustion noise. This paper will discuss the Rolls-Royce solution adopted for the Industrial RB211 to control the noise issues associated with DLE combustors whilst consistently achieving less than 25vppm NOx emissions. The author discusses the problems associated with DLE emissions and details the history of the RB211 DLE solution from the initial ‘biased primary’ fuelling to the current active noise control system that embodies a ‘short combustor’ with a ‘variable split secondary’ fueling system. Finally, by discussing development results and in-field experience since the new product development, the full capability and flexibility of this solution will be demonstrated.
Pipeline Maintenance Management: A Crucial Tool to Improve Safety and Efficiency
Authors: Krebs Alastair E.
Published: March 2009

For any pipeline company to be successful and be seen as a respected global citizen, the impact of its operation on health, safety and the environment must be minimal and its productivity must be optimized at the lowest possible costs. In order to accomplish this an integrated maintenance management process must align to the business needs without impact on safety and the environment. This process must create an environment where by maintenance events are measured to determine their impact on the safety, environmental, and business goals. As a result the maintenance strategy is adapted to maximize the safety, environmental and business performance. An integrated maintenance management process will enhance the revenue earning capability of the business and not be a burden on it. To make the difference, a step change in thinking is required. For example: • Reducing maintenance activity whilst improving performance. • Establishing a benchmark performance model for the pipeline asset. • Maintenance must be seen as a dynamic process continually striving to improve performance. • Maintenance as a tool to identify and reduce health, safety, environmental and business risks to a level as low as reasonably practicable (ALARP). • Maintenance as a contributing factor to an increase in revenue earning capability through an increase in efficiency, as opposed to maintenance seen purely as a cost burden. • Maintenance management as a structured tool to reduce inventory and lifecycle costs, instead of subjective judgement. • Maintenance management as a tool to capture and protect corporate maintenance and operational knowledge, versus the costly process of reinventing the wheel over and over again by repetitive unwanted events. This way of thinking requires vision and commitment of the upper (corporate) management level as the maintenance and operational departments can never reach this goal individually. Subsequently, it requires total commitment of all departments and a proactive approach towards integrated asset management. Maintaining multi-million dollar pipeline assets is not an easy task and the costs involved are enormous. This paper describes an adaptive approach for an Integrated Maintenance Management System where the maintenance strategies are directed to where they will most benefit the safety, environmental and business goals of the asset.
The Use of Flow Improvers to Decrease Pressure Drop in Multiphase Pipelines
Authors: Kang C. , Jepson W. P.
Published: March 2009

Experiments were performed in a 10-cm diameter, 44 m long Plexiglas pipes, multiphase flow loop to examine the effect of flow improver in slug flow at inclinations of ±5degrees. Superficial liquid velocities between 0.5 and 1.5 m/s and superficial gas velocities between 2 and 6 m/s were studied. A 2.5 cP oil at 25 °C was used and water cut was 10%. The experiments were undertaken at a pressure of 0.13 MPa and a temperature of 25 °C with carbon dioxide as the gas. The effectiveness of flow improver on pressure drop and slug frequency was examined for concentrations ranging from 0 ppm to 50 ppm. The results showed that the flow improver was effective in reducing the pressure drop significantly at all superficial liquid and gas velocities. The flow improver concentration of 50 ppm was more effective than 25 ppm for all cases. At superficial gas velocities of less than 4 m/s and all liquid velocities with 50 ppm flow improver, the effectiveness of flow improver in upward flow was around 30%. At superficial liquid and gas velocities of 1.0 and 2 m/s with 50 ppm flow improver concentration, the effectiveness of up to 64% was achieved in downward flow. The slug frequency in both upward and downward flows decreased significantly in all cases with addition of flow improver. For example, at superficial liquid and gas velocities of 1.5 and 2 m/s, the slug frequency in downward flow decreased from 43 to 14 slugs/min. when 50 ppm of chemical was added. The flow pattern in downward flow was changed from slug flow to stratified flow at several velocities, which led to a large decrease in the pressure drop.
Regulations of Pipelines in Canada
Authors: Jeglic Franci
Published: March 2009

This paper provides an overview of the regulatory framework for pipelines in Canada. Canada is an oil and gas producing, consuming and exporting country. To accomplish these functions, the production, transmission and distribution companies operate about 700,000 km (440,000 miles) of pipelines. These companies and their pipelines are regulated by federal, provincial or territorial regulatory agencies. Provincial or territorial agencies regulate those pipelines that are fully contained within the province or territory. The federal regulatory agency (the National Energy Board) regulates all those pipelines that cross provincial or international borders. Most of the powers of regulatory agencies emanate from pipeline acts. Under these acts, the regulatory agencies may make regulations which may be approved by their governments. Regulations provide for public safety and environmental protection for the design, construction, operation, repair, maintenance and abandonment of pipelines.
Operational Experience of Transneft on Construction of Baltic Pipeline System First Phase Objects
Authors: Bezverkhov Anatoliy A.
Published: March 2009

Oil Transporting Company Transneft is a world leader in the field of oil transportation, basic tasks of which are timely and qualitative oil delivery to consumers both in Russia and outside Russia under conditions of equal access to the system of oil-trunk pipelines.
Advanced Indentation Techniques: NDE for Flow Properties and Residual Stresses of Pipelines
Authors: Choi Yeol , Son Dongil , Jang Jae-Il , Park Joon , Kim Woo-Sik , Kwon Dongil
Published: March 2009

Structural integrity assessment is indispensable for preventing catastrophic failure of industrial structures/components/facilities that are faced with time-dependent and environmentally-accelerated degradation. This diagnosis of operating components should be done periodically for safe maintenance and economical repair. However, conventional standard methods for mechanical properties have the problems of bulky specimen, destructive and complex procedure of specimen sampling. So, an advanced indentation technique has been developed as a potential method for non-destructive testing of in-field structures. This technique measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation such as yield strength, tensile strength and work-hardening index. Also the advanced indentation technique can evaluate residual stresses based on the concept that indentation load-depth curves were shifted with the direction and the magnitude of residual stress applied to materials. In this study, we characterized the tensile properties and welding residual stress of various Industrial pipeline steels through the new techniques, and the results are introduced and discussed.
Offshore Inspection Cost Reduction by Inspection Planning Based on Survey Records, Fatigue and Reliability Analysis
Authors: Rodriguez J. Efrain , Garcia Mario , Perez Arturo
Published: March 2009

An approach to identify fatigue sensitive joints to be considered in an inspection programme is presented. Joint selection is based on inspection records, fatigue and reliability analysis. Fatigue analysis is used to identify fatigue sensitive tubular joints, thus reliability analysis and inspection records are used to assess the joint selection. The objective is to reduce the number of inspected joints whilst maintaining the platform risk level within acceptable limits. A relation between the reliability index β, a weighted average stress range value and tubular joint geometrical expressions is presented for the selection of joints for inspection. Experience obtained from inspection records is considered for an assessment of the joints selected for inspection. Cost reduction is determined from a comparison of this approach with inspection programmes applied in the past.
Thermal Conductivity of Consolidating Offshore Clayey Backfill
Authors: Newson T. A. , Brunning P. , Stewart G.
Published: March 2009

Pipelines that transmit untreated products are prone to waxing and hydrate formation unless the fluid is kept above certain temperatures. Since bare pipe can have relatively high thermal conductivity, pipes can be buried to utilise the thermal properties of the surrounding soil. However, the thermal conductivity of clayey offshore trench backfill as it consolidates is poorly understood. This paper describes a series of laboratory tests on offshore clayey sediments to investigate the coupled compressibility and thermal conductivity behaviour. The compressibility behaviour of the soil samples was characterised using a specially designed oedometer apparatus. Measurements of thermal conductivity were taken periodically during the loading sequence. This data was used to model the behaviour of the backfill in a hypothetical jetted offshore trench using finite element analysis. The laboratory testing indicated that the stress-strain behaviour of the undisturbed and reconstituted material seems to be typical of similar onshore clayey soils. The data showed lower thermal conductivities for both the undisturbed and reconstituted soils than have previously been reported by industry for these types of soil. The results have provided extremely useful data on the fundamental behaviour of offshore clayey sediments and have given confidence in predictions of the coupled consolidation and thermal conductivity behaviour of jetted offshore soils using finite element analysis.
A LRFD Code Format for Accounting Long-Term Variation of Multiple Load Effects
Authors: Videiro Paulo Mauricio , Sudati Sagrilo Luis Volnei , Prates de Lima Edison Castro
Published: March 2009

This paper proposes a Load and Resistance Factors Design (LRFD) code format for structural components of offshore structures under multiple load effects. This code format accounts for the long-term variation of seastate and the actual correlation between dynamic load effects due to environmental actions. Ultimate limit states are formulated in terms of an Interaction Ratio (IR) random variable, such that the long-term extreme value of IR greater than unity means component failure. The long-term distribution of IR is obtained by combining the distribution of each short-term seastate. The short-term response of the generally nonlinear IR is determined by time domain simulation, taking into account partial load and resistance factors. The IR short-term distribution may be fitted, for instance, by using Rayleigh or Weibull distribution. The main advantages of the proposed code format are: • This code format accounts implicitly and correctly for the actual correlation among all dynamic environmental load processes. • Structural designers have used interaction ratios for a long time. Hence, it is straightforward to evolve from a deterministic stage of looking for IR < 1, as in old Working Stress Design codes, to a code format where the aim is to design structural components with long term IR extreme value < 1. The feasibility of the proposed code format is demonstrated by calibrating partial factors for beam-column cylindrical members based on components of a Floating Production System Semi-submersible hull.
An Assessment of Current U.S. Pipeline Flushing Practice and Decommissioning Requirements: How Clean Is Clean?
Authors: Smith Robert W.
Published: March 2009

This paper will discuss an assessment of current industry practice with respect to decommissioning requirements for offshore pipeline flushing and purging operations — specifically addressing corrosion and cleanliness in out-of-service and decommissioned offshore pipelines. The results, observations, and conclusions will also be discussed, from the ongoing research project entitled “Assessment of Current Pipeline Flushing and Decommissioning Requirements - Research and Field Testing Phase A” that was funded through the Technology Assessment & Research (TAR) Program of the U.S. Minerals Management Service. Data collected during this study has specific application to regulation and effectiveness of industry practice for future pipeline and flowline flushing, purging, and decommissioning. The main applications from this research are: 1) Understanding how a pipeline corrodes while out of service; 2) Determining whether the line is fit for service for possible reuse; and 3) Determining the cleanliness of decommissioned offshore oil and gas pipelines. The study results will lead to a more in-depth understanding of the condition of out-of-service and decommissioned pipelines as well as an improved public perception of the use and reuse of submerged pipelines for oil and gas activities on the Outer Continental Shelf of the United States.
Corrosion Fatigue of Steel Armours in Flexible Risers
Authors: Andersen Tore Roberg
Published: March 2009

Fatigue life calculation of flexible risers is normally based on the assumption that the annulus is dry. Experience has, however, shown that the annulus may become water flooded. Carbon dioxide and hydrogen sulphide permeate from the bore and into the annulus, making the annulus environment corrosive. In such conditions the influence of corrosion fatigue on fatigue life has to be taken into account. A test program was performed to investigate the corrosion fatigue performance of steel armour in water containing carbon dioxide. The results showed that the corrosive environment reduced the fatigue life to about 1/10 to 1/50 of that derived in air. The lifetime was significantly shorter in the environment with 0.1 bar compared to 0.01 bar, indicating that corrosion fatigue becomes more pronounced as the corrosivity increases. The work shown that corrosion fatigue has to be considered for flexible risers with annulus that is or may be water flooded.
The Fuzzy Reliability Optimum Design of Offshore Jacket Platforms
Authors: Zhai Gangjun , Kang Haigui , Xu Facong
Published: March 2009

In consideration of the fuzzy constraint boundary and through analysis of structural reliability, a model of structural fuzzy optimum design is established based on reliability for offshore jacket platforms. According to the characteristics of offshore jacket platforms, the tolerance coefficient of the constraint boundary is determined with the fuzzy optimization method. The optimum level cut set λ*, which is the intersection of the fuzzy constraint set and fuzzy objective set, is determined with the bound search method, and then the fuzzy optimum solution of fuzzy optimization problem is obtained. The center offshore platform SZ36-1 is designed with the fuzzy optimum model based on reliability above; the results are compared with those from deterministic optimum design and fuzzy optimum design. The tendency of design variables and its reasons in the above three methods are analyzed. The results of an example show that the fuzzy optimum design based on reliability is stable and reliable.
VIV Response of Long Free Spanning Pipelines
Authors: Nielsen Finn Gunnar , So̸reide Tore H. , Kvarme Stig Olav
Published: March 2009

Vortex induced vibration (VIV) of free spanning pipelines in current is considered. In standard VIV estimation, one mode of oscillation is considered only. Increasing the length of the span, several modal shapes may be excited. Further, due to the sag effect of a long free span, the dynamic properties in vertical and horizontal direction of the span are different. This causes a much more complex VIV response pattern for long free spans than for short spans. The observed VIV response of long free spans during model testing is discussed. Hypotheses that may explain the observed behaviour are presented. Also a format of new design principles for long free spans is outlined.
Velocity Effects on Conical Structure Ice Loads
Authors: Matskevitch Dmitri G.
Published: March 2009

Existing design codes and most methods for ice load calculation for conical structures do not take velocity effects into account. They were developed as an upper bound estimate for the load from slow moving ice which fails in bending against the cone. Velocity effects can be ignored when the structure is designed for an area with slow ice movement, for example, the nearshore Beaufort Sea. Sakhalin structures will be exposed to ice moving at velocities up to about 1.5 m/sec. Model tests show that quasi-static methods may underestimate the ice load on a steep cone when the interaction velocity is that high. The present paper summarizes results of published model tests with conical structures that show a velocity effect. An empirical correction factor to the Ralston method is developed to account for the increase in cone load with ice velocity. The paper also discusses velocity effects on ice failure length and possible transition from bending failure to an alternative failure mode when the ice velocity is high.
Suppression of Vortex Induced Vibrations of Circular Cylinders Using Radial Water Jets
Authors: Skaugset Kjetil B. , Larsen Carl M.
Published: March 2009

For oilfield developments in deep water, it is of utmost importance to accurately predict vortex induced vibrations (VIV) of risers and free span pipelines subjected to ocean current. In order to prolong operational life of such structures, VIV suppression devices such as helical strakes or shrouds are often employed. Such devices will, however, imply certain disadvantages such as drag amplification and increased operational costs. Therefore the quest for effective suppression devices with a minimum of such drawbacks is still ongoing. The present paper presents a novel approach for VIV suppression based on radial water jets from a prescribed pattern of circular openings in the cylinder wall. Jet flow will introduce a disturbance that will change VIV amplitudes. The alternation of the flow pattern must be understood to have both 2-dimensional (2-D) and 3-D effects. 2-D effects will influence the local pressure on the cylinder surface by altering the separation point as well as creating a general disturbance to the flow, while the 3-D effects involve changes in correlation of the vortex shedding process along the span of the cylinder. The disturbance to the flow pattern is expected to yield reduced VIV amplitudes. Results will be presented from experiments in a towing tank testing three 2m long spring supported cylinders with diameter 0.1m and two different patterns of radial water jets. The volume flow rate and reduced velocity have been varied in the tests. Oscillation amplitudes, frequencies, added mass and lift and drag force coefficients are presented and compared to a smooth cylinder.
Free and Forced Sloshing Motions in a 2-D Numerical Wave Tank
Authors: Frandsen Janette B. , Borthwick Alistair G. L.
Published: March 2009

This article describes a 2D numerical wave tank that utilises stretched mappings in order to resolve accurately the moving free surface of a liquid. It is assumed that the flow is incompressible and inviscid. Numerical solutions of the governing nonlinear potential flow equations are obtained using a finite-difference time-stepping scheme on σ-transformed grids. Free and forced sloshing motions are simulated in a rectangular tank, and the results compare well with analytical and other numerical methods. It is concluded that the present potential flow model provides a simple way of simulating steep non-breaking waves, that may be readily extended to the prediction of 3D wave motions.
Laboratory Study of ADCP Wave Measurements
Authors: Shih H. H. , Strong B.
Published: March 2009

The National Ocean Service (NOS) collects real-time environmental data to support mission activities including navigation safety, coastal hazard mitigation, and coastal resource management. Near shore wave information is important for these activities and is of growing interest to marine user groups. Acoustic Doppler current profiler (ADCP) are a primary tool for NOS current measurement programs. Recent technology development has added wave measurement capability to these instruments and provided a convenient way for wave monitoring. However, only limited field comparative studies have been conducted. The need to further understand the performance of these instruments and their operation requirements exists. Tests under controlled laboratory conditions offer certain advantages over field intercomparisons including reduced measurement uncertainties, isolation of variables, and is generally cost effective. This paper describes the study of wave measurement performance of a RDI 1200 KHz ADCP in a wave basin with prescribed waves consist of regular, irregular, and multi-directional waves. The steepness and peak energy frequency for each type of waves, and the orientation of ADCP acoustic beams relative to incident waves were varied. A Linear Array of five ultrasonic sensors and a SonTek 5 MHZ ADVOcean instrument were used to provide reference for intercomparison. The ADCP shows good measurement resolutions and agrees well with the reference measurements.
Prediction of Extreme Roll Motion on an FPSO Using Long Term Statistics
Authors: Vestbo̸stad Tone M. , Haver Sverre , Andersen Odd Jan , Albert Arne
Published: March 2009

This paper presents a method for predicting extreme roll motion on an FPSO using long-term statistics. The method consists of a long-term simulation where a database of consecutive short-term sea states with combined weather conditions, including direction and magnitude of wind, wind waves and swell waves, is used. The vessel heading in given weather conditions is simulated. For each combined sea state, the short-term roll motion maxima are calculated to form a long-term probability distribution, and the extreme roll motion, e.g. the 100-year value, can be estimated from the distribution. For an example FPSO, the results from the long-term analysis have been compared with full-scale measurements, giving a validation of the method. This paper is a shortened version of [1].
A Study of Slowly Varying Drift Forces on Multi-Body Floating System
Authors: Inoue Yoshiyuki , Ali Mir Tareque
Published: March 2009

The mean and slowly varying drift forces play a vital role in the study of the behavior of moored offshore structures, because their mean periods are close to the natural period of oscillation of the system that causes large motion amplification. The present study is based on far-field method where the velocity potential is calculated by 3D sink-source technique. The numerical calculations have been carried out for a parallel arrangement of FPSO and an LNG carrier. The numerical accuracy in the determination of the wave exciting forces and the hydrodynamic reacting forces influences the motion response that eventually affects the drift forces and moments of each body. The computations of motion responses and drift forces are carried out for a number of different wave heading angles and for different separation distances between the FPSO and LNG carrier. The numerical results are compared with the experimental ones to justify the validity of the improved numerical accuracy of the present computations. It has been observed that due to the lack of accuracy in the numerical scheme adopted for the computer code, the computed results of drift forces and moments sometimes shows completely opposite trend than that of the experimental ones.
Operators Experience With Flexible Risers
Authors: Per Olsen Gudmund , Rongved Ketil
Published: March 2009

Norsk Hydro has more than 150 flexible dynamic risers and service lines in operation. Norsk Hydro’s experience with flexible risers started in 1987 when Petrojarl 1 commenced test production at the Oseberg Field. The paper tells the story about Norsk Hydro’s experience through the 15 years of trials with a new and complicated product. This paper will focus on “what went wrong”. This may seem unfair to the product! However, without flexibles we would probably not have seen such successful field developments as the Troll B and C, Njord, Visund and Snorre B. Challenging production and installation schemes have been put forward and fulfilled. However, hopefully this paper can give an insight in failure modes, and so forth give input to enhanced solutions in order to avoid similar situations in the future. This paper gives an overview over the different approaches which have been taken to give a better qualification of the lifetime prediction of the risers. Some of the specific projects will be presented in detail in other papers on this conference.