International Journal of Multidisciplinary Research and Growth Evaluation

Failure Modes and Reliability of Single Point Mooring (SPM) Systems: A Review of West African Offshore Terminal Experience

Paul Chibuike Obetta¹, Nwakamma Ninduwezuor-Ehiobu², Henry Chukwuemeka Olisakwe³

1. ¹
2. ²
3. ³

Abstract

Single Point Mooring (SPM) systems, particularly Catenary Anchor Leg Mooring (CALM) buoys, are the principal means of crude oil export and refined product import along the West African coast, where shallow draft restrictions, limited port infrastructure, and long swell conditions make conventional berthing of large tankers impractical. Terminals in Nigeria, Angola, Ghana, Cote d’Ivoire, and neighbouring states have accumulated more than five decades of operational experience with these systems, and this experience provides a valuable but under-synthesised record of how SPM systems fail and how their reliability can be managed. This review consolidates published literature, industry guidance, incident records, and regional operating experience up to 2021 in order to characterise the dominant failure modes of SPM systems in West African service. The evidence shows that floating and submarine hose failures, mooring hawser degradation, anchor chain wear and corrosion at the touch-down and inter-link zones, main bearing and swivel deterioration, and Pipeline End Manifold (PLEM) related defects are the most frequent and consequential failure categories. Regional aggravating factors include persistent Atlantic swell, high humidity marine atmospheric corrosion, biofouling, third party interference and security incidents, supply chain constraints for spares, and irregular inspection and maintenance intervals. The review then examines the reliability assessment methods that have been applied to SPM systems, including Failure Mode, Effects and Criticality Analysis (FMECA), Fault Tree Analysis (FTA), Reliability Block Diagrams, Markov and Bayesian approaches, and risk-based inspection frameworks aligned with OCIMF, API, ISO, and classification society guidance. Reported findings indicate that structured integrity management, condition monitoring of hoses and hawsers, and disciplined change-out regimes materially reduce spill frequency and terminal downtime. The paper concludes by identifying research gaps, including the scarcity of publicly available regional failure rate data, limited application of digital condition monitoring, and the need for reliability models calibrated to West African metocean and operational conditions.

Keywords: Single Point MooringCALM buoyfailure modesreliabilityoffshore terminalsWest Africamarine hosesintegrity management

How to cite

Licensed under CC BY 4.0.