Changing the frequency of heеling test for small fishing vessels during their operation

Abstract

Loss of stability of the vessel belongs to the category one of the most dangerous disasters, several ships perish each year from capsizing around the world, and in some years the number is measured in tens. Therefore, the ships should carry out constant of monitoring of the main parameters of stability. The displacement and height of the center of gravity above the main plane a of light ship increase during operation. This growth is due to repairs, modernization, bringing the vessel into compliance with the new requirements of the IMO Conventions, and improvements in working and living conditions. An analysis of the records of the ships MRTK of the Baltica type heeling test showed that their displacement increased by 0,5-14,8 tones and that the increase in height of the center of gravity above the main plane was about 5,47 centimeters, and a maximum increment has reached of 15 centimeters. Such changes in the characteristics of a light ship may result in a disruption of the vessel's stability in operational load cases. Calculations of changes in displacement and height of the center of gravity above the main plane of light ship for Baltika type MRTK and Obolon type SRTM (333 design) under the worst-case load in terms of stability were made in the article. Analysis of the plotted graphs changes static stability curve for MRTK Baltika type showed, that during 10 years of operation, maximum metacentric arm decreased by 0,05 m, and change of height of the center of gravity above the main plane of the light ship made 0,1 m. For the SRTM Obolon type the maximum shoulder of the dynamic stability curve decreased by 0,038 m and the change in the height of the center of gravity above the main plane for the light ship 0,05 m. All this suggests that a heeling test for small craft should be carried out more frequently than every 10 years.