Operability analysis and line failure risk assessment for a tanker moored at berth

Abstract

Oil terminals are critical infrastructures for the safe transfer of oil between ships and facilities on land. However, the presence of waves can pose a substantial risk to the mooring system, particularly when dealing with period waves that exceed 8 s. To better understand this relationship and minimize potential risks such as displacement and line failure, physical model tests were conducted. These tests sought to analyse how waves interact with the mooring system, which consists of ships, lines, and fenders. The findings of the research indicate that under experimental conditions, the ship's ability to operate safely is largely determined by its sway and roll motion. Among the various lines in the mooring system, the force exerted on the breast lines was found to be the highest, making them more susceptible to failure. This highlights the importance of paying close attention to these specific lines during operations, and considering necessary adjustments to ensure safety. Furthermore, the study also evaluated the maximum allowable operating wave height of the ship, taking into consideration the limitations imposed by movement and mooring force. These test results can serve as a valuable reference for determining the safe operating conditions for ships in oil terminals, contributing to improved mooring safety. Lastly, the study also took into account the potential occurrence of mooring failure. The event of one breast-fore line failure (Case1) and two breast-fore lines failure (Case2) were both tested. The results showed that the most significant impact was on the adjacent headlines, which increased approximately 40% and 70% respectively. Furthermore, it is important to recognize that the failure of one line may trigger a cascade effect, leading to the gradual failure of other lines and significantly jeopardizing mooring safety.