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Integrity Assurance of FSO Turret Mooring Systems: A Review of Inspection, Monitoring and Life-Extension Strategies
Subject area: Science,Engineering and Technology · Area of research: Turret Mooring Systems
DOI: https://doi.org/10.64388/IREV3I6-1722581
Abstract
Floating Storage and Offloading (FSO) units moored through turret systems represent critical infrastructure in offshore hydrocarbon production, and their station-keeping systems are permanently exposed to cyclic environmental loading, corrosion and mechanical wear over service lives that frequently exceed twenty years. Industry experience over the past two decades has shown that mooring line failures occur at rates far higher than the nominal annual probabilities assumed in design, with several multiple-line failure events resulting in vessel drift-off, riser rupture and production shutdown. This paper reviews the state of practice and the state of the art in integrity assurance for FSO turret mooring systems as of 2019. The principal degradation mechanisms affecting chain, wire rope, connectors and turret bearing assemblies are summarised, including uniform and microbially influenced corrosion, fatigue in the splash zone and thrash zone, out-of-plane bending of chain links, and wear at interlink contact surfaces. Conventional inspection techniques based on general visual inspection and close visual inspection by divers and remotely operated vehicles are critically assessed against their known limitations in defect detectability. Emerging monitoring technologies are then reviewed, covering direct tension monitoring, inclination-based load inference, sonar and vision-based line tracking, and vessel position monitoring using differential global navigation satellite systems, together with data-driven anomaly detection methods. Frameworks for mooring integrity management contained in API RP 2MIM, ISO 19901-7 and DNVGL offshore standards are compared, and life-extension methodologies encompassing residual fatigue assessment, corrosion allowance re-evaluation, component replacement and requalification are discussed. The review concludes that a risk-based integrity management strategy that integrates periodic inspection with continuous monitoring and probabilistic remaining-life assessment offers the most credible pathway for safe life extension of ageing FSO turret mooring systems, and identifies research gaps in corrosion prognosis, chain fatigue under combined degradation, and the validation of indirect monitoring methods.
Keywords
FSO; turret mooring; mooring integrity management; inspection; structural health monitoring; life extension; fatigue; corrosion.
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How to cite this paper
@article{1722581,
author = {Paul Chibuike Obetta, Nwakamma Ninduwezuor-Ehiobu},
title = {Integrity Assurance of FSO Turret Mooring Systems: A Review of Inspection, Monitoring and Life-Extension Strategies},
journal = {Iconic Research And Engineering Journals},
year = {2019},
volume = {3},
number = {6},
pages = {599-629},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1722581.pdf},
abstract = {Floating Storage and Offloading (FSO) units moored through turret systems represent critical infrastructure in offshore hydrocarbon production, and their station-keeping systems are permanently exposed to cyclic environmental loading, corrosion and mechanical wear over service lives that frequently exceed twenty years. Industry experience over the past two decades has shown that mooring line failures occur at rates far higher than the nominal annual probabilities assumed in design, with several multiple-line failure events resulting in vessel drift-off, riser rupture and production shutdown. This paper reviews the state of practice and the state of the art in integrity assurance for FSO turret mooring systems as of 2019. The principal degradation mechanisms affecting chain, wire rope, connectors and turret bearing assemblies are summarised, including uniform and microbially influenced corrosion, fatigue in the splash zone and thrash zone, out-of-plane bending of chain links, and wear at interlink contact surfaces. Conventional inspection techniques based on general visual inspection and close visual inspection by divers and remotely operated vehicles are critically assessed against their known limitations in defect detectability. Emerging monitoring technologies are then reviewed, covering direct tension monitoring, inclination-based load inference, sonar and vision-based line tracking, and vessel position monitoring using differential global navigation satellite systems, together with data-driven anomaly detection methods. Frameworks for mooring integrity management contained in API RP 2MIM, ISO 19901-7 and DNVGL offshore standards are compared, and life-extension methodologies encompassing residual fatigue assessment, corrosion allowance re-evaluation, component replacement and requalification are discussed. The review concludes that a risk-based integrity management strategy that integrates periodic inspection with continuous monitoring and probabilistic remaining-life assessment offers the most credible pathway for safe life extension of ageing FSO turret mooring systems, and identifies research gaps in corrosion prognosis, chain fatigue under combined degradation, and the validation of indirect monitoring methods.},
keywords = {FSO; turret mooring; mooring integrity management; inspection; structural health monitoring; life extension; fatigue; corrosion.},
month = {December},
doi = {https://doi.org/10.64388/IREV3I6-1722581}
}