bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Numerical Investigations Into the Station Keeping and the Offloading Performances of Hyundai LNG-FPSO
Authors: Lee In-Hye , Park Moon-Kyu , Moon Joong-Soo , Sim Woo-Seung , Shin Hyun-Soo 
Published: November 2013

Hyundai Heavy Industries Co., Ltd. has developed a LNG-FPSO with production capacity of 2.5 MTPA to meet the demand of the offshore LNG well development in near future. This paper presents the experimental and the numerical study on the mooring and the offloading performances of the developed LNG-FPSO.
In the FEED design stage, the turret mooring system and the offloading mooring system with side-by-side arrangement were designed using the quasi-dynamic method and verified through the model tests using the truncation method in the basin. It is known that the quasi-dynamic method is very efficient to calculate many environmental combinations for the evaluation of the turret mooring system and the offloading availability. And the numerical parameters for the truncated system are calibrated with the model test results with the same truncated set-up and it is expanded into the full depth model.
In this study, it was verified that the safety of the station keeping system under the extreme environmental condition and the offloading performance satisfied the design requirement. Especially, the hydrodynamic and mechanical couplings between LNG-FPSO and LNG carrier were considered as the important parameters in the offloading availability with ship-to-ship arrangement. Finally, the design parameters such as the relative motion, line tension and fender load of offloading system were evaluated with considering the dynamic positioning system.
Ultra Heavy Wall Linepipe X65: Severe In-Service Straining of Lined Pipes
Authors: Di Vito Luigi , Ferino Jan , Amato Stefano , Mannucci Gianluca , Crippa Stefano , Tintori Federico , Darcis Philippe 
Published: November 2013

Tenaris and Centro Sviluppo Materiali (CSM) carried out a Joint Industrial Project aimed at developing heavy wall line pipes. The suitability for very severe applications, involving high service pressures and temperatures, the latter causing large strain fluctuations, in presence of an aggressive sour environment, is analyzed both theoretically and experimentally, including small and full pipe models and tests. Five papers have been already presented on this project, in previous OMAE conferences.
The present paper focusses on Lined Heavy Wall Pipes for the adoption in presence of extremely aggressive conveyed fluids. As in-service large strains are involved in the JIP envisaged scenarios, the risk of liner buckling is necessarily concerned. To evaluate the suitability of lined heavy pipes in presence of in-service severe straining, a finite element study has been performed aimed at quantifying the limits for pipe deformability without occurrence of liner buckling.
Two full scale tests on lined pipe strings have been also performed, imposing the very severe straining sequence previously determined as extreme for pipeline resistance. The sequence has been applied both in pure axial (tensile / compressive) loading and in bending conditions. The latter has been performed in very low internal pressure conditions to conservatively verify the resistance to liner buckling. In both cases, the lined heavy wall pipe resisted the severe straining sequence without any liner buckling, pipe excessive ratcheting or any other damage compromising the serviceability of the pipe.
A Comparison Study of Pressure Vessel Design Using Different Standards
Authors: Askestrand Frode Tjelta , Gudmestad Ove Tobias 
Published: November 2013

Several codes are currently available for design and analysis of pressure vessels. Two of the main contributors are the American Society of Mechanical Engineers providing the ASME VIII code, Ref /4/ and the Technical Committee for standardization in Brussels providing the European Standard, Ref /2/.
Methods written in bold letters will be considered in the discussion presented in this paper.
The ASME VIII code, Ref /4/, contains three divisions covering different pressure ranges:
Division 1: up to 200 bar (3000 psi)
Division 2: in general
Division 3: for pressure above 690 bar (10000 psi)
In this paper the ASME division 2, Part 5, “design by analysis” will be considered. This part is also referred to in the DNV-OS-F101, Ref /3/, for offshore pressure containing components.
Here different analysis methods are described, such as:
Elastic Stress Analysis
Limit Load Analysis
Elastic Plastic Analysis
The Elastic Stress Analysis method with stress categorization has been introduced to the industry for many years and has been widely used in design of pressure vessels. However, in the latest issue (2007/2010) of ASME VIII div. 2, this method is not recommended for heavy wall constructions as it might generate non-conservative analysis results.
Heavy wall constructions are defined by: (R/t ≤ 4) with dimensions as illustrated in Figure 1.
In the case of heavy wall constructions the Limit Load Analysis or the Elastic-plastic method shall be used. In this paper focus will be on the Elastic-plastic method while the Limit Load Analysis will not be considered.
Experience from recent projects at IKM Ocean Design indicates that the industry has not been fully aware of the new analysis philosophy mentioned in the 2007 issue of ASME VIII div.2. The Elastic Stress Analysis method is still (2012) being used for heavy wall constructions.
The NS-EN 13445-3; 2009, Ref /2/, provides two different methodologies for design by analysis:
Direct Route
Method based on stress categories.
The method based on stress categories is similar to the Elastic Stress Analysis method from ASME VIII div. 2 and it will therefore not be considered in this paper.
Structural Integrity Assessment of Aging Fixed Steel Offshore Jacket Platforms: A Persian Gulf Case Study
Authors: Golpour Hamid , Zeinoddini Mostafa , Khalili Hadi , Golbaz Ali , Yaghubi Yashar , Adl Mahmood Reza , Ranjbar Pooya , Saberi Reza , Matin Nikoo Hamid 
Published: November 2013

The existing knowledge on the structural integrity assessment of offshore platforms may benefit from case studies on the life extension evaluations of aging structures. This paper presents a case study for the structural integrity assessment of an existing 8 legged aging drilling platform located in the Persian Gulf. The platform is now 42 years old and the objective of the study is to check its fit for purpose for a life extension of 25 years beyond 2012. The structural model is based on the best estimates of the existing conditions of the platform.
A number of analysis approach such as i) assessment based on the previous exposures, ii) linear (elastic), iii) equivalent linear (or the linear global analysis with local overload considerations), and iv) non-linear analysis methods have been used to estimate the structural integrity of the platform.
The paper provides further background, clarifications and proposed updates to API-RP 2A-Section 17. The paper is divided into three parts. Section 1 is a discussion on the background of the previous assessment study and perspective view on why the case study platform needs to be assessed. Section 2 and Section 3 include the finding of the code-noncompliance points of the platform based on the recommendations of API RP 2A-2007. Section 4 presents the remedy actions recommended for the fit for purpose of the platform.
Vortex-Induced Motion Evaluation on Semi-Submersible Platforms Using a Time Domain Methodology
Authors: de Lacerda Thiago Ângelo Gonçalves , Ellwanger Gilberto Bruno , Senra Stael Ferreira 
Published: November 2013

As exploitation activities moves into fields located in deep water, the industry has been addressing studies aiming at concepts of platforms that reduce the influence of environmental loads on risers. The deep draft semi-submersible platform is one of these concepts [1]. The semi-submersible deep draft platform is described in a simplified way as a deck supported by columns connected by pontoons. This particular geometry can make this structure susceptible to a significant low frequency vibration movement caused by vortex shedding. This phenomenon is usually known as VIM (Vortex Induced Motions). The amplitude of these motions depends on some parameters such as current velocity, hydrodynamic diameter of the column, natural frequency of the platform due to the mooring system and structural damping (hull, mooring lines and risers). One of the consequences of these motions is the increase of the fatigue damage on the risers connected to the platform.
In a previous work presented by the authors in 2009[2], a time domain methodology based on a Van der Pol equation was described. This methodology was developed in order to represent the vortex shedding phenomenon. In this paper the Van der Pol methodology is improved by considering the VIM phenomenon acting on a multicolumn structure.
VIV Safety Factors for Drilling Risers: Propagating Model Uncertainty in a Long-Term Reliability Analysis
Authors: Tognarelli Michael A. , Panicker Nikhil , Campbell Mike , Winterstein Steven R. 
Published: November 2013

Previous work [1] has given an approach to estimate vortex-induced vibration (VIV) factors of safety (FOS) for deepwater drilling risers. This work compared fatigue predictions from the industry-standard fatigue analysis software SHEAR7 with full-scale measured data. The field data have been collected over the past several years from five drilling risers without VIV suppression devices. These risers are on rigs under contract to BP worldwide, at sites susceptible to high currents. Collectively, the data correspond to 9,600 10-minute field measurements, equivalent to 0.18 years of continuous monitoring.
A worked example for a deepwater drilling riser in the Gulf of Mexico was used to show how the FOS methodology can be applied in the case of multiple design currents each with a different annual probability of occurrence. However, the paper cited future work that included development of a mathematical approach that would permit a designer to calculate a modified FOS that accounts for the number of events (currents or wave seastates) analyzed.
This paper documents a mathematical approach developed that can be used to calculate the riser design FOS based on multiple events of varying fatigue damage amplitude and probability. Note that the approach is not limited to VIV. It can be used for long-term wave fatigue life for example, assuming the designer has an understanding of the statistical differences between software predictions and actual field response.
Gap Effects at Side-by-Side LNG-Transfer Operations
Authors: Clauss Günther F. , Dudek Matthias , Testa Daniel 
Published: November 2013

The current demand of liquefied natural gas (LNG) from remote marine locations pushes the design of floating LNG (FLNG) liquefaction or regasification facilities, where LNG is transferred between shuttle carrier (LNGC) and terminal. Even if the tandem configuration is the primary choice for LNG transfer at rough offshore locations, side-by-side configurations would be the preferred option because of existing midship coupling manifolds on the present carrier fleet (no need for manifold modifications) as well as standard mooring systems and transfer-process-chains similar to oil-transfer. Therefore, the operation conditions at rough seas have to be improved to allow side-by-side LNG-transfer and to reduce offloading downtime.
Within the SOTLL-project, side-by-side LNG transfer up to HS = 3 m is reached as a transfer limit using a new flexible pipe design, the advantages of sheltered areas at the leeside of the terminal barge and an optimized ship transfer position due to a flexible longitudinal offloading position. In addition to the evaluation of the hydrodynamic characteristics of this multibody system, one key aspect is the analysis of the exciting forces and motions due to wave amplification between the ships. In the gap between the hulls, the incoming wave field is amplified and changes dramatically. Depending on gap width, longitudinal offset, wave heading and length, large wave amplifications, standing waves and other resonance phenomena are observed which may result in high relative motions and increased forces of the entire mooring system. In this paper, the gap effects are investigated in detail with numerical approaches in frequency domain, validated by model tests at TU Berlin. A typical offloading scenario with barge and carrier is investigated for different gap sizes to identify suitable transfer configurations and ensure safe LNG offshore transfer up to HS = 3 m.
Statistics of Extreme Wind Speeds and Wave Heights by the Bivariate ACER Method
Authors: Naess Arvid , Karpa Oleh 
Published: November 2013

In the reliability engineering and design of offshore structures probabilistic approaches are frequently adopted. They require the estimation of extreme quantiles of oceanographic data based on the statistical information. Due to strong correlation between such random variables as e.g. wave heights and wind speeds, application of the multivariate, or bivariate in the simplest case, extreme value theory is sometimes necessary.
The paper focuses on the extension of the ACER method for prediction of extreme value statistics to the case of bivariate time series. Using the ACER method it is possible to provide an estimate of the exact extreme value distribution of a univariate time series. This is obtained by introducing a cascade of conditioning approximations to the exact extreme value distribution. When this cascade has converged, an estimate of the exact distribution has been obtained. In this paper it will be shown how the univariate ACER method can be extended in a natural way to also cover the case of bivariate data. Application of the bivariate ACER method will also be demonstrated at the measured coupled wind speed and wave height data.
Effect of Pipeline Thermal Expansion on Direct Electric Heating Cable
Authors: Brany Ahmad Makintha , Damsleth Per , Gil Cyprian 
Published: November 2013

Subsea Direct Electrical Heating (DEH) of pipelines has been in operation for more than 10 years and is therefore considered by most Operators as proven technology. Aside from the electrical aspects, there are mechanical design challenges with installing a cable piggyback fashion onto a HPHT flowline that expands and contracts with the temperature of the flowing wellstream. The cable may also need protection against fishing gear which becomes an integral part of the DEH pipeline system.
Depending on the pipeline operating temperature, the DEH cable may experience excessive axial tensile strain due to thermal expansion and global buckling unless sufficient cable overlength is incorporated during pipeline installation. The cable will be subjected to additional strains at a thermal buckle location when subject to trawl gear pullover. During DEH cable operation, the flowline will initially be cold and contracted but the cable expands due to heating of the cable itself, adding to any installed compression to provide overlength. The following study has been performed to investigate strains in the cable and pipeline due to their responses to thermal and trawlboard loads and to determine the required overlength to keep the cable within strain limits.
Finite Element models of the flowline with piggybacked DEH cable was developed with both ANSYS and ABAQUS in order to analyse their interaction during installation and operation on the seabed. The influence of friction between cable and protection system, and position of the cable on the flowline was simulated in order to quantify the required overlength to be installed during pipelay to avoid overstraining the cable in tension as well as compression.
The Effect of Measured Whipping and Springing on LNG Vessels
Authors: Storhaug Gaute , Oma Narve , Blomberg Bjarne , Hirota Kazuhiro 
Published: November 2013

Strain measurements of structural members onboard two LNG vessels have been collected for a period of 5 years. The vessels have been sailing in the world wide trade except for the North Pacific area. The time spent in the North Atlantic is about 40%, which is higher than for typical LNG vessels. The vessel speed has been relatively low in average and well below the service speed, still the effect of springing and whipping has been significant on the fatigue and extreme loading. Previously, results from the strain sensors have been presented versus the fatigue and extreme loading on a general level, independent on the environmental conditions. In this paper the focus is more towards how the vessel behaves in wind/waves with respect to springing and whipping in order to understand more of the relationship between accumulated fatigue damage, heading and loading condition.
The vessels have been equipped with wave radars and wind sensors. The effect of whipping and springing on accumulated or part fatigue damage versus relative heading is demonstrated. The effect as a function of the wave height/wind speed is shown for selected headings. One of the objectives is to check if the wind sensor can be a useful alternative to the wave sensor to capture the physics. Some of the data is studied for ballast and cargo condition separately in order to see if these loading conditions can be merged, which is desirable from an assessment point of view.
Proposals for Integrity Management of Flexible Pipe
Authors: Yuan Shuai , Tang Gao , Bai Jie , Badaruddin Mohd Fauzi 
Published: November 2013

The increasing use of flexible pipes in subsea with high pressure/high temperature brings about much more challenges, for example flexible riser fatigue, bird-caging and armour wire disorganization, development of flexible pipes with smooth bore and ones with anti-H2S layer, which demand operators to adopt an effective integrity management program including every phase of flexible pipe industry to avoid reduction of production. To date, much research work has been carried out on this topic.
In this paper, the applicable inspection and monitoring measures are presented as proposals to develop the integrity management of flexible pipes. Meanwhile, this paper takes a practical project as an example to show the whole process of integrity management study clearly. The process can be used as reference for the other similar integrity management projects.
Whistling of Pipes With Narrow Corrugations: Scale Model Tests and Consequences for Carcass Design
Authors: Golliard Joachim , Belfroid Stefan , Bendiksen Erik , Frimodt Casper 
Published: November 2013

Pipes for gas production and transport with a corrugated inner surface, as used in flexible pipes, can be subject to Flow-Induced Pulsations when the flow velocity is larger than a certain velocity. This onset velocity is dependent on the geometry of the corrugations, the operational conditions and the geometry of the topside and subsea piping.
In this paper, small-scale tests performed on corrugated tubes are reported. The tested geometries include both “classical” profiles, similar to the inner profile of agraff flexible risers, and profiles with less typical variations, such as narrower and/or deeper cavities, or irregular pitch. These tests were performed in order to evaluate the validity of a prediction model developed earlier for the onset of pulsations, for corrugated pipes with these kinds of atypical variations, which are found on a new type of carcass designs. The mechanism of Flow-Induced Pulsations in corrugated pipes is discussed, as well as the principle of the prediction model. The experimental results show that the validity of the model remains reasonable in most cases, except when the cavities are very narrow. In this case, the model becomes overly conservative. This limitation can be attributed to the fact that, for very narrow cavities, the cavity opening becomes too small compared to the boundary-layer momentum thickness, effectively destroying any instability of the shear layer. Furthermore, the shift towards higher frequencies of the acoustic source term due to narrower cavities, and the possible coupling with higher acoustic modes, is considered.
The results of the analysis are used to evaluate the onset velocity and whistling behavior of a newly developed carcass design of flexible risers. A previous analysis has indicated that the particular geometry profile of the new design improves the whistling behavior by pushing the onset velocity outside the typical operational envelope of flexible risers. The analysis confirms that the new design will be less prone to whistling than flexible risers with classical agraff carcasses.
Fatigue, Creep and Electrical Performance of Subsea Power Cable
Authors: Buitrago Jaime , Swearingen Sean F. , Ahmad Sana , Popelar Carl F. 
Published: November 2013

Subsea processing is a key aspect of ExxonMobil’s subsea technology qualification efforts. Consequently, the reliable delivery of high voltage power to subsea equipment offshore, such as multi-phase pumps, is essential. The base case involves power delivery up to 30 kV via copper cables embedded in umbilicals to a water depth of 1,500m over a design life of 30 years. Since umbilicals are often suspended from a floating facility in deepwater, the power cables are subjected to static load due to the umbilical weight and to cyclic loads in response to the floating facility motions. Therefore, sufficient mechanical resistance to preclude electrical failure is needed to achieve safe and cost-effective designs.
To that end, an experimental program was completed aimed at developing a qualification methodology and collecting data on the effect of static and cyclic loads on the mechanical and electrical performance of copper power cables. This paper presents the experimental approaches and results obtained from creep, fatigue, and electrical tests performed on 18/30kV, 95mm2 copper conductor cable specimens.
Specifically, the program included (a) five monotonic tension tests to failure to characterize the cable, (b) 11 creep tests to develop a load-time performance curve, and (c) 59 fatigue tests under pulsating tension, of which 50 used short-cable samples to evaluate the effect of mean load and nine used long samples for electrical testing following fatigue. A fatigue curve is proposed that includes the effect of mean load and temperature. However, fatigue results can be sensitive to the cable material and mechanical characteristics of a particular cable.