The Feasibility Analyzing Method Of The Offshore Platform Transportation By The Semi-Submersible Heavy-Lift Vessel

With a rig on board, the Semi-submersible heavy lift vessel has a very high center of gravity, poor stability and is easily damaged by wave and wind. For the sake of safety, it is necessary to check the feasibility of transporting. Farther more, feasibility analysis will be done for every transporting, even for the same heavy lift vessel because styles and weights of different rigs are so different.In this paper the characters of rig and heavy lift vessel, the transportation market of rig and heavy-lift vessel operation are introduced; the process and content of the feasibility analysis of rig transportation using heavy-lift vessel are described; the metocean database IMDSS and the Strip Theory used in feasibility analysis are introduced and evaluated.The equation of ship motion with six freedoms is listed. With the sample of longitudinal motion equation, calculating hydrodynamic coefficients by the potential fluid theory is introduced. The way to calculate the added-mass and the damping coefficient of the ship sections by conformal mapping and pulsating source method.A transporting is calculated by the method described in this paper. By analyzing the result, three most main factors influencing the calculation accuracy are found: the constitution of wave scatter diagram, interpolating the irregular wave and the estimating of roll damping coefficient. Tested in actual condition, by using the Strip Theory with precise forecast of wave and wind combined, the calculation accuracy of feasibility analysis of transporting will meet the requirement in engineering.