The Research Of Fatigue Life Analysis Method On Large-Scale LNG Pump Tower Under Sloshin Load

It becomes increasingly important that the strength and fatigue problems of the inner parts under sloshing load in the tanks of large-scale LNG and LPG ships for oil transport. In this paper, a model of a pump tower in a LNG ship is established for analyzing. After using the dynamic load method to calculate the wave load and choosing the most serious states to the sloshing movement of the ship, a systematic analyzing method of pump tower fatigue strength is obtained. The main contents of this paper are listed as follows:1) The seakeeping of the ship is calculated using the dynamic load method. The motion and the frequency of ship under hydrodynamic load are calculated under long-term forecasting.2) The rule to choose the ship moving conditions most serious to the sloshing movement is obtained based on comparison of the natural period of the tanks and the motion period of the ship.3) The velocity and the acceleration of sloshing liquid are obtained by 2D-sloshing program and Morison equations for the choosing of the most dangerous sloshing load to the pump tower.4) Fatigue strength and reliability of pump tower are assessed by using the theory of the cumulative fatigue damage theory based on S-N curves. Further, the most dangerous fatigue points on the pump tower are predicted while the influence of the loading level to the fatigue life of pump towers is analyzed.