Development of 90 Persons New Type Free Fall Lifeboat for the Evacuation System on Offshore Paltform

Abstract

The trend of the offshore structure development shows the increment on the height of the platform. Since the height of an offshore platform to the water surface is significantly high, the alternative of a particular hull form design is needed to reduce the acceleration response induced by the slamming load during launching. The main purpose of the research is to develop an alternative hull form of the free fall lifeboat in order to reduce the acceleration response during the water entry which may cause an injury to the occupants. For an offshore platform, an accident during the launching of the lifeboat is not acceptable, because the evacuation system should be able to embark and launch safely, when clearing the ship or offshore platform in critical conditions. The theory of a free fall lifeboat during launching was discussed. The analytical and numerical approach has been illustrated as the fundamental analysis of the development of a new hull form design of free fall lifeboat. The simulation approach and the theory of Arbitrary Lagrangian Eulerian method of LS-DYNA also has been explained in this thesis. The LS-DYNA FSI technique has been used to capture the physics phenomena of the launching of the free fall lifeboat. In the chapter three, the procedure of the development of a free fall lifeboat simulation model has been presented. The free fall lifeboat model and the fluid model are developed by using the lagrange element and euler element. The single material ALE and multi material ALE was examined; the both method results have been compared with the experiment data. Parametric studies have also been made to check the sensitivity and validity of simulation analysis. Nevertheless, the results of the simulation have shown a good agreement with the experiment data, therefore the proposed simulation model will be reliable for estimating the acceleration response of the new type of free fall lifeboat The development of a new hull forms for the free fall lifeboat has been presented, in the chapter four. The deep V-shaped chine type hull form has been proposed as an alternative design for the free fall lifeboat. The comparison of the proposed hull form performance with the existing free fall lifeboat has shown an improvement on the acceleration response performance. Furthermore, the investigation launching parameters on the motion pattern and evaluation of structure strength during slamming load will be made by using the LS-DYNA FSI technique. According to the numerical investigation on the effects of the launching parameter such as: drop height, sliding distance and the angle of skid on the motion pattern and forward velocity of the new type lifeboat, the new type of free fall lifeboat should be installed on the sliding distance of 10.97 meters, the angle of skid is 35 degrees and the maximum drop height is 45 meters. In the chapter five, an assessment of the performance of the new type lifeboat design has been reviewed. The acceleration response induced by the impact with the water has been investigated by using numerical analysis. The strength of the free fall lifeboat structure was examined in the thesis. The evaluation of the lifeboat structure during the water entry has shown that maximum effective stress induced by the slamming load is acceptable. Although the maximum stress is higher than the torpedo type, however the improvement has been shown on the other wedge bow type (middle navigation and conventional). The LS-DYNA FSI Technique has been confirmed as a useful method which captures the physical phenomena that occurs during the launching of the free fall lifeboat.