FPSO Design and Conversion: A Designer's Approach

Abstract

As designer of FPSO vessels ample experience has been gained with both the design of new build FPSOs and the conversion of existing trading tankers into an FPSO. This experience covers FPSO hull design, topsides and topsides support design and the combined application of ship and offshore rules, regulations and standards during the design process.Items discussed in the paper will address the use of direct calculations versus traditional ship rules, and more generally the differences between naval architectural and offshoreorientated approach. A comparison will be made between new build and conversion projects. Integration of topsides and hull design is required, while maintaining sufficient flexibility to accommodate design changes. Moreover the FPSO hull influence on topsides design will be further examined. Attention should be paid to adherence to common shipyard practice.Two examples of FPSO hull design will be presented. One is a new build vessel, and the other a conversion. Both projects are comparable with regard to geographical location and mooring system. For both vessels, aspects of hull design and relation between hull and topsides design will be addressed. Typical aspects of hull design to be discussed are cargo and ballast arrangement, extreme bending moments and fatigue design. The impact of the module support arrangement on the hull design and piping design is evaluated.The general information presented in the paper, and supported by the cited examples, will provide guidance to the industry on how to merge shipbuilding practice and offshore standards. OTC 13210 FPSO DESIGN AND CONVERSION: A DESIGNER'S APPROACH 3

Systematically Varied Rogue Wave Sequences for the Experimental Investigation of Extreme Structure Behavior

“…These rules are empirically based and are intended to be applicable for a variety of ship types. Classification rules typically consider the North Atlantic wave environment as a design premise and are based on a 20 years return period corresponding to a significant wave height in the range of 16.5 m to 18.3 m (Terpstra et al [20]).…”

“…This exposure to extreme weather conditions in combination with high topside loads and a more box shaped form of new built FPSOs may lead to structural loads that are not covered by standard design rules. Terpstra [20] found that for a new built FPSO, the rule values for the maximum still water bending moment and shear forces are exceeded by up to 95%. From the analysis of the sinking of the M. V. Derbyshire Faulkner concludes that ship bending moments from abnormal waves may substantially exceed the present IACS standards and suggest a survival approach design (Faulkner [4]).…”

FPSOs: Design Considerations for the Structural Interface Hull and Topsides

“…Terpstra [6] distinguishes, two types of arrangements that are normally used for PAU supports: Multiple column supports, in which the PAU or grillage deck is supported on (multiple) rows of columns, fitted in line with the hull's transverse web frames. The columns are sniped at their ends and gusset plates aligning with the hull's under deck structure are fitted.…”

Hull Performance Assessment and Comparison of Ship-Shaped and Cylindrical FPSOs With Regards To: Stability, Sea-Keeping, Mooring and Riser Loads In Shallow Water

“…Initial FPSOs were dominantly produced from over aged oil tankers and known as converted FPSO. For this type of FPSOs, the prescriptive based shipbuilding standards were applied for hull design, while later experience shows this cannot answer all the design requirements as FPSO is more similar to a floating production platform [3]. Therefore, offshore design rules and standards have been developed and modified based on unique operational requirements of FPSOs.…”