Risk assessment in tug boat towing system using fuzzy failure modes and effects analysis method

Throughout maritime history, various ship types have been developed to meet maritime transportation needs. The increasing demand for maritime transportation has led to an increase in the number and size of ships. In addition to merchant ships, tugboats began to be used to assist in the maneuvering of ships. The first tugboats were equipped with paddle wheels and steam engines. Later, with the invention of diesel engines, tugboat development continued. Furthermore, azimuth and Voith-Schneider propellers further enhanced tugboat maneuverability. Tugboats are complex vessels comprising many subsystems. The towing system, one of these systems, is a critical component of a tugboat. The smooth operation of the towing system is crucial for the safety of life and property. In this thesis, a tugboat towing system was technically examined and a risk analysis was conducted. In this context, failure modes for the tugboat towing system were identified by a group of experienced experts, and these were prioritized using the rule-based fuzzy FMEA method. Finally, preventive actions were proposed for risky failure modes. The results showed that the three most risky failure modes were, respectively, towing system rope failure (RPN=6.4), insufficient air supply to the towing system from the compressor (RPN=6.0), and cracking or breakage of system components (RPN=5.88). The effects of these failures, which generally occur due to operational or human-related causes, can be summarized as disruption or complete halt of towing operations, personnel injuries or deaths, and environmental disasters. The fundamental action required to prevent these failures is the systematic control and recording of relevant components and operations. Furthermore, regular and well-planned maintenance and repair programs were considered another important preventive action.