Study on Optimal Shaft Alignment of Propulsion Shafting System for Large Crude Oil Tanker Considering Ship Operating Conditions

The alignment of the propulsion shafting system is crucial to ensuring the safe and efficient operation of ships. As ships grow in size and engine output increases, the complexity of propulsion systems also escalates, making precise alignment more challenging. Traditional methods often neglect hull deformation caused by varying operational conditions, which can lead to uneven bearing loads, excessive vibrations, and potential bearing failures. This study addresses these challenges by analyzing the effects of hull deformation on bearing reaction forces in a large crude oil tanker. Shaft alignment analysis was conducted under six different loading conditions, ranging from dry docking to fully loaded states. The results indicated that hull deformation significantly alters the distribution of bearing loads along the propulsion shaft. Initial alignment, without considering hull deflection, showed satisfactory results, but when hull deformation was included, notable deviations in bearing loads emerged. These deviations pose risks of bearing overloads or underloads, which could accelerate wear or cause failure. To mitigate these risks, this study proposes an optimized bearing offset configuration, adjusting intermediate shaft bearings to maintain balanced loads across all conditions. The findings demonstrate that incorporating hull deformation data into shaft alignment improves the system’s reliability and safety, providing a foundation for better alignment practices for large vessels in varied operational conditions.