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Sember W.J.,ABS
Hydrocarbon Engineering | Year: 2011

Classification society ABS is closely involved in addressing the technical and operational issues surrounding increased production, transport, and storage of LNG. In this direction, ABS is undertaking a design review of a number of FLNG plant designs, and looking at design and containment system parameters for LNG carriers operating in the Arctic. ABS has participated in a joint industry project (JIP) with Korea's Daewoo Shipbuilding & Marine Engineering (DSME) examining critical wave conditions for sloshing model tests and computational fluid dynamics (CFD) in the cargo tanks of FLNG vessels. The total sloshing wave energy and severity computation developed jointly by ABS and DSME provides an alternative to selecting relevant sea states in sloshing model testing and analysis. ABS has also collaborated with South Korean shipbuilder Hyundai Heavy Industries (HHI) to evaluate the basic design and containment system parameters for an LNG carrier operating in an Arctic environment. Source

Wang S.,ABS | Donnarumma S.,University of Genoa
Proceedings of the 17th Offshore Symposium: Pushing Boundaries in the Global Industry | Year: 2012

It is important that a floating drilling unit is able to disconnect from the wellhead in a timely manner during a loss of position to minimize risk to personnel, the environment, and equipment. For most dynamically positioned (DP) vessels, the concept of watch circles has been used for that purpose. The watch circles define when to initiate disconnecting action. Typical watch circles are referred to as green, yellow and red circles. When a vessel is in the yellow circle, the operation should be halted, while in the red circle, the Emergency Disconnect System (EDS) should be initiated. Drift-off and drive-off assessment can be utilized in the determination of the green, yellow and red watch circles. Drift-off is a scenario of the vessel drifting away after a loss of thruster power, while drive-off is of the vessel being pushed away by excessive thruster force. Drift-off and drive-off are functions of a vessel's characteristics and the prevailing environmental conditions. This paper presents the study on the drift-off and drive-off scenarios of a DP drillship under different environmental conditions. The vessel's excursion as a function of time is simulated using a time-domain simulation program aNySIM. The comparison of drift-off and drive-off speed under different environmental conditions will be made. The effect of environmental conditions on the determination of watch circles is assessed. Source

Chen N.-Z.,Abs Consulting | Wang G.,ABS | Guedes Soares C.,University of Lisbon
Engineering Fracture Mechanics | Year: 2011

A Palmgren-Miner's rule and fracture mechanics (FM) based approach coupled with Bayesian updating in order to establish inspection plans for marine structures is proposed. A FM formulation based upon the British Standard (BS) 7910 is calibrated by S-N curves and Palmgren-Miner's rule. A model is developed taking account of the uncertainties associated with S-N curves and Palmgren-Miner's rule to quantify the random growth of a flaw predicted by the calibrated FM formulation. The long-term stress range acting on a structural component is fitted to a two-parameter Weibull distribution, according to the rules of the American Bureau of Shipping (ABS). The reliability after inspection is updated by the Bayesian approach accounting for the probability of detection (POD) and inspection results. An inspection plan is then set up on the basis of the comparison between the updated reliability and a target reliability index. Typical fatigue-prone structural details from a tanker are utilized for demonstration of the capabilities of the approach proposed. © 2011 Elsevier Ltd. Source

Chen N.-Z.,Abs Consulting | Wang G.,ABS | Guedes Soares C.,University of Lisbon | Teixeira A.P.,University of Lisbon
Advances in Marine Structures - Proceedings of the 3rd International Conference on Marine Structures, MARSTRUCT 2011 | Year: 2011

A case study was conducted to investigate the extreme value of the combination of Still-Water Bending Moment (SWBM) and Vertical Wave-Induced Bending Moment (VWBM). Three wave scatter diagrams, namely ABS Base 1, Base 2, and one from IACS Rec No. 34, were used for the prediction of the extreme value of the VWBM based on the extreme value theory and Response Amplitude Operators (RAOs). The SWBM is modeled as an alternating renewal pulse process. The pointcrossing method, load coincidence method, and Ferry Borges-Castanheta method are utilized for the prediction of the extreme value of the combination of SWBM and VWBM. A sample tanker under sagging condition is utilized for the case study and results show that for the predicted extreme values of the combination of SWBM and VWBM: 1) the results predicted based on the wave scatter diagram of ABS Base 1 are higher than those predicted based on ABS Base 2 or IACS; 2) the results based on the wave scatter diagrams of ABS Base 2 and IACS are very close; 3) the point-crossing method and load coincidence method yield almost identical results; 4) The Ferry Borges-Castanheta method yields higher values than those predicted by the point-crossing method or the load coincidence method; 5) the highest value with a design period less than 20 years is 93.3% of the total design bending moment, which is predicted by the Ferry Borges- Castanheta method based on the wave scatter diagram of ABS Base 1. © 2011 Taylor & Francis Group, London. Source

Bone C.,ABS | Eccles T.,NAVSEA
Marine Technology | Year: 2011

The agreement between the NAVSEA and ABS led to the publication of the first edition of ABS Rules for Building and Classing Naval Vessels (NVR) in 2004. ABS provides classification services to a number of federal agencies, including the fleets of the Military Sealift Command and the Maritime Administration. Under the joint NAVSEA-ABS management of the NVR, the navy maintains its role as the ultimately technical authority. To ensure the NVR would remain a living document, NAVSEA and ABS worked together to create an annual update process modeled after the process ABS used for its commercial rules. The coast guard has embraced the NVR as the central standard for cutter construction and is currently applying the NVR to the new offshore patrol center. Since the establishment of the initial cooperative relationship between NAVSEA and ABS, developments of the NVR and ASLP (Achieving Life Assessment Program) have brought great benefits to the navy through the adoption of independent third-party certification. Source

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