Numéro : 2454 - Year : 2005
Selection of trading tankers for FPSO conversion projects
Vincent BONNIOL, Bureau Veritas, Division Marine – Paris (France)
Review of single and double hull tanker designs has been conducted to identify the relevant aspects of the hull structure in the context of conversion into future FPSO systems. Typical designs have been selected and structural analyzes procedures for verification of the hull girder strength and the primary and secondary structures have been reviewed regarding yielding, buckling and fatigue strength. The typical defects and the main degradation modes based on the return of experience with tankers are also identified and a set of hull design parameters are described in order to evaluate the hulls candidates to conversion.
The paper provides guidelines to assist the selection of trading tankers for conversion into FPSO. Based on a set of hull design parameters, different hull configurations are evaluated and the respective advantages and disadvantages assessed in order to identify the best candidates for conversion. Reserve of strength and corrosion margins have to be analyzed for each hull and compared with the FPSO project requirements, including field design life, environmental conditions and corrosion rates. Lists of typical defects and hazards based on the return of experience with tankers are also discussed. The paper also discuss the different designs based on the several parameters analyzed in order to provide guidelines to assess the hull structure condition, estimate the repair work at conversion and the inspection effort along the FPSO life.
Nevertheless, the decision making process regarding the selection of such hulls faces the higher cost of refurbishment of single hulls during the conversion and the high cost of purchase of more recent double hulls.
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