Stability Judgment of the Semi-Submersible Vessel Before Laden

For semi-submersible vessels carrying special heavy cargo,most authorities only provides a minimum limit of GM,without a provision for the maximum limit of GM.However,when GMis too high,the rolling period of the vessel will become shorter,which will cause severe shaking.From the aspects of providing sufficient righting arm and avoiding harmonic shake,this paper deduces a formula to calculate the feasible range of GM to maintain the stability of the semi-submersible vessel.Before the semi-submersible vessel loading a specific special heavy cargo,this formula can be used to preliminary judge whether the GM of this vessel meeting the requirement to load this cargo.Finally,a semisubmersible vessel carrying ajack up drilling platform is taken an example,by using this calculation formula,the stability of the semi-submersible vessel is analyzed and some methods improving sailing stability have been put forward.