The hull forms used for FPSOs and trading tankers look very similar. So similar in fact that it may appear that one could use the same design and design methods for both vessels. Both vessels will be subject to extreme and fatigue loading and both will have a similar design life. But each will have different design requirements and therefore different designs.The trading tanker spends most of its life moving oil from one location to another, in either one of two draft conditions, ballast or laden. They are dry-docked at regular intervals for maintenance, inspection and if necessary repair.FPSOs are stationary, i.e. they have zero forward speed, the vessel's draft is continuously changing, the maintenance and inspection is done in situ, and they are not usually dry-docked.These apparently subtle differences, see Table 1, in design requirements are not so subtle with respect to the load differences, both short term and long term for the two designs. This difference is the driver for the FPSO Integrity Joint Industry Project.The JIP was established to obtain fatigue load information on an FPSO through full-scale measurements. The main goals were as following.• Develop of a computational model for fatigue loading • Evaluate current practice.• Have the Classification Societies conduct a comparative study, and • Recommend a fatigue method for use in design of FPSOs.The work in this JIP is being further enhanced through a sister JIP "FPSO Fatigue Capacity" being administered by DnV. By combining the results of the two JIPs, the industry is gaining a better knowledge of the fatigue loads and fatigue resistance on FPSOs. Predictive methods are being developed to calculate the fatigue lifetime of FPSOs and this is leading toward more reliable systems.
The paper describes a design family for 'ship to ship' and 'ship to shore' transfer systems for LNG. The common design philosophy is explained and each configuration is described briefly. Auxiliary systems and equipment are discussed as are operational procedures.A case study is presented for a near shore LNG terminal, comprising a marine transfer system in combination with a regasification plant and a salt dome storage cavern. The regasification plant and the salt dome storage cavern are treated extensively.The systems described will greatly advance the implementation of offshore terminals for LNG. Although new, all of the components used are proven and have been applied in LNG terminals and offshore loading systems longtime.
This paper discusses the structural interface on FPSOs between the hull structure and the topsides modules. It identifies the most common topsides foundation concepts applied on FPSOs, and discusses the consequences of each configuration for the layout of the unit, the design of the hull structure and the topsides. The information needed by the hull designer and the topside designer is identified. Moreover, the differences between shipbuilding and offshore construction design practices are discussed, and it is identified where and how these fall short for FPSO purposes. Topics that are addressed are overall safety, operational aspects, such as tank entry and mechanical handling, and the design specifications for the hull and the topsides modules. In order to control the schedule and costs of FPSO projects, fabrication of the hull and topsides should be allowed without impractical or unduly strict specifications imposed on the shipyard or the topsides fabricator. At the same time the traditional design specifications for hull and topsides design may fall short to cover the functional needs for FPSO service.
This paper describes the conceptual design of an offshore liquidified natural gas (LNG) import terminal based on the "Bishop Process," sited on Vermilion block 179, offshore Louisiana. The Bishop Process comprises direct regasification of LNG in the dense phase and storage of the gas thus produced in salt caverns. (For conversion factors of units commonly used with LNG, please refer to Table 1.) The operating principles of this process are discussed, as well as the design considerations for the regas, storage, and send-out facilities. The single-point mooring (SPM) system for the offloading of LNG carriers is described, as well as the verification process thereof. The foreseen marine operations at the terminal are explained, and the work done confirms the technical and economical feasibility of the concept.
The objective of the Joint Industry project 'FPSO Integrity' is to provide insight in the fatigue loading of FPSO's and the accuracy and validity of computational models. The results should contribute to reliable life time prediction and site assessment studies for this relative new concept of production.Within the frame work of this JIP, 'Glas Dowr', a new build double hull FPSO operated by Bluewater for Amerada Hess at the Durward and Dauntless fields in the North Sea, has been instrumented extensively. The objective of the instrumentation was to measure sufficient signals to derive the fatigue loading on the vessel. The dedicated monitoring system comprised the instrumentation of two cross sections of the vessel with strain gauges, pressure transducers and wave height radar's. Also the deck and the turret were equipped with strain gauges. Both the wave induced motions and the low frequency positions and orientation of the vessel was recorded. For the analysis of the measured signals the wind, wave and current conditions have been recorded as well as the vessel parameters such as draft, trim and tank loads. Data from the Glas Dowr has been collected from October 1, 1997 to 1 August 1999. The data has been subjected to long term statistical analysis and for selected periods to more detailed spectral and statistical analysis as well as rain flow counts. The results have been used for validation of existing fatigue load calculation methods used by five classification societies and for the development of new fatigue load prediction software.
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