Comparative study of the safety of two tugboats using new harmonized stability rules

Tugboat operations present a high degree of risk and to prevent accidents, the crew must know and manage very well all the necessary maneuvers. Stability is a critical aspect for the safety of tugboats and towing operations, so recently new international regulations have been developed. The tugboats perform several functions, the main one being pulling, but by being equipped with certain equipment and installations, the tugboats are intended for rescue, firefighting, depollution, ice breaking and occasional transport. For this study, two categories of tugboats were considered to determine the geometric characteristics, hydrostatic, of stability and longitudinal strength. The Modelmaker module is used to create the ship's body (Geometry File), the superstructure and all appendages, after which the compartmentation is created and the types of compartments and tanks are positioned in the ship's body. To determine the safety of the two tugboats from the point of view of stability, the heeling moment (the heeling arm) that occurs during towing with the righting arm was checked. At the end, the safety status of the two categories of tugboats was analyzed and new projects were proposed for the future, regarding the use of stability criteria for tugboats.