FPSO Spectral Fatigue Analysis

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Client: Australian Operator

Industry: Oil & Gas

Asset: Floating Production Storage and Offloading Unit

Location: North-West Shelf Australia

Year: 2020



To support the RBI process, Nobleseas performed the FPSO hull spectral fatigue assessment Level 2 and Level 3. The detailed analysis to be performed in the Class proprietary tool while in a close interface with the technical solution team and the analysis outcome to be verified and endorsed by the Class prior to implementation.


The detailed modelling and analysis was required to address the following:

  • Take credit of all the hull upgrades/special survey made till date
  • Identify critical structure or conditions that could fail over the remaining life
  • Identify if fatigue life of the hull can be extended beyond the required year by revised and improved engineering analysis


The scope of work consist of following tasks:

  • Prepared section model in FDA L2 modeller for structure iwo midship and other sections based on the longitudinal structural arrangement.
  • Implemented structural scantling with major updates in the latest drydock campaign and prepared the model close to the current condition of the vessel.
  • Used voyage simulation to derive fatigue damage during vessel operating as tanker.
  • Generated hydrodynamic loads using Class in-built tools.
  • Load set up and Conducted FDA Level 2 analysis.
  • Assessed fatigue prone area of vessel for subsequent check in FDA L3 and established broad level fatigue life for longitudinal members.
  • Developed global hull hydrodynamic model and conducted mean heading analysis under combined effect of wave current and wind
  • Carried out hydrodynamic analysis and mapped pressure load to FEA model.
  • Carried out unit load response of hull under environmental load.
  • Carried out fatigue check coarse model and identified hotspots.
  • Carried out voyage simulation to derive fatigue damage during tanker life.
  • Fatigue check area identification of local hotspots and Class recommended locations for fine mesh FDA L3 analysis.
  • Using the analysis result in Class tool, the Fatigue Critical Locations was identified which showed critical behaviour under cyclic loading.
  • For each selected fatigue check area, a local fine mesh sub-model was created for fatigue damage study.
  • Sub-model was analysed critically to review fatigue damage under given conditions.


The detailed analysis results supported the client to develop and implement Risk Based Inspection strategy to replace the traditional periodical Class special survey scheme to achieve area focused target inspection campaign and improved management of hull integrity.

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