Study of stability improvement measures meeting the effects of new use of a secondhand cement carrier vessel

Abstract: Secondhand ship is an option to improve marine business competitiveness. It provides a way for ship owners to integrate customer market rapidly without spending many resources on producing new ships. However, secondhand ships that perfectly suit owner's requirements becomes unavoidable challenge. Ship owners may decide to modify their ships to completely fulfill their requirements. A modification method that is often implemented is cargo replacement as observed from customer and global trends. It impacts ship stability due to different cargo properties which leads to different ship physical properties, such as position of center of gravity and buoyancy. Due to this impact, some ships may have excessive or reduced stability which causes potential damages. To ensure that cargo replacement does not negatively impact ship stability, it is evaluated according to the stability regulation of International Maritime Organization and classification society. A cement carrier vessel named MV Cemfjord is used as an example ship. The cargo is replaced from cement (ρ=1.35 tons/m3) to iron ore (ρ=3.03 tons/m3) and fly ash (ρ=0.794 ton/m3). Some modifications such as cargo position and total payload weight will be adjusted to some requirements. After implementing those modifications, some stability issues due to ship center of gravity shifting are considered. Therefore, the possibility of excessive and reduced stability may follow because of this effect. This study will investigate those stability issues and define the solution to overcome them. In this study, two solutions are offered. Firstly, the ship center of gravity is adjusted bymodifying the general arrangement. Other solution is conducted through adjusting the ship center of buoyancy by adding sponsons that affects buoyancy force on the ship hull. After defining the solution, it will be visualized into physical manners, in form of the new general arrangement or the sponsons dimension. Advantages and disadvantages of the chosen solution will also be discussed.