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Client: Australian Operator
Industry: Oil & Gas Operations
Asset: Floating Production Storage and Offloading Unit
Location: North-West Shelf Australia
Year: 2021-2022
Challenge
The facility was shut down by the Australian Regulator due to several safety concerns. Nobleseas Engineering was engaged to conduct hull structural strength assessment to ascertain the asset integrity for the remaining period on station and readiness for towing for decommissioning. The challenge was to analyse the entire hull model with a number of governing loading conditions incorporating critical structural anomalies with reduced scantlings.
Scope
- A surface model was prepared from the lines plan of the vessel.
- Established the critical loading conditions of SF and BM for extreme hogging and sagging loads.
- Wave hydrodynamics and pressure mapping for the cyclonic environment.
- Review of the critical anomalies.
- Comprehensive Finite Element Model (FEM) of the full ship is developed with projected thickness and more than 500 critical anomalies.
- Encompassing corrosion deductions in accordance with the class rules which are also incorporated into the FE Model.
- The stability assessment is conducted, and the watertight integrity evaluated against the major structural members and provided recommendations
- Pre-Assembled Unit (PAU) lumpsum weights are taken into consideration.
- Estimation of peak stresses from the global analysis and provided recommendations for the repair.
- Structural integrity in terms of the stress distribution and stress concentrations are observed and provide the recommendations.
Outcome
The holistic approach enabled a thorough analysis of the ship’s structural integrity with the FEA model to identify structural hotspots due to global loading, and provide the status of the anomalies to the client with a remark of severity of the anomaly. The overall scope of the work was reviewed and endorsed by the Classification Society.
