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Applying FPSO-specific loading conditions

This program has been developed to perform the environmental sea loads calculations, determine the environmental severity factors and perform fatigue and strength assessment for both newbuild FPSO/FSOs and conversions.

The FPSO program is comprised of three main components:

  1. Sea Environmental Assessment Systems (SEAS)
    • Seakeeping analysis to generate Transfer Functions for vessel motions and wave loads
    • Factors accounting for different wave climates during lifetime as a trading tanker (applicable to FPSO conversion), in transit and onsite
  2. Initial Scantling Evaluation (ISE)
    • Rule-based strength and fatigue evaluation
  3. Total Strength Assessment (TSA) – Two Options
    • Three cargo hold FEA, FE-based strength and fatigue evaluation
    • Cargo block FEA, first principle based, as an alternative to the three-hold finite element analysis

Revised ABS requirements apply FPSO-specific loading conditions and prescribe strength assessment procedures for both newbuilds and conversions. Realistic tank load patterns and appropriate load combination factors are used in the structural assessment of FPSOs. Site operations include variations in tank loadings due to the many loading and offloading cycles.

Requirements include:

  • Consideration of the sea and swell in non co-linear directions for the onsite condition
  • On-site fatigue strength assessment by including high cycle fatigue due to waves and low cycle fatigue due to cargo loading and offloading
  • An evaluation of the interface structure between the hull and topside and also between the hull and position mooring system using FEA
  • An evaluation of hull girder ultimate strength
  • Scantling verification based on finite element structural analysis

Additional requirements for Conversions:

  • Remaining fatigue life calculation based on the vessels past trading history, expected transit route and projected on-site location
  • A determination of the renewal scantlings
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