The Reliability Analysis For Large-Scale LNG Tank Under Conditions Of Inner Tank Leak

LNG is one of the most crucial energy sources whose consumption is increasing year by year among the energy structure of China. A lot of LNG projects have been built in the coastal cities of China. The working condition of LNG tank is-162 °C. Once the cryogenic liquid leaks from inner tank, the LNG will flash and churn heavily. The low temperature causes large internal force and deformation to outer wall. Concrete cracking will cause further stress. Therefore carrying out the research on reliability of LNG tank in the condition of leakage will provide more guidance for the safety assessment.Firstly, the reliability analysis procedure, type of variables and analysis methods in ANSYS software were introduced. Then, the basic conception of structural system reliability, the limit state of structure analysis, the limit state equation, probability and the failure probability were briefly introduced. Finally, method for searching structure failure model failure mode and the calculation method of structure system reliability were stated briefly. Through analysis, it can be concluded that the thermal distribution is not constant when the leak had finished. The inner side is under the condition of tensile while the tank wall of the lateral compressive stress. The response surface method was used in analysis. The destruction of wall of tanks, which was composed by the liquid level of the tank wall and the bottom, was considered as the most primary modality. And the two main failure models, which consisted of the tank wall direction units in parallel, formed a series system. The reliability index unit and the linear functions were calculated by applying the JC method. The subsequent response surface equation, reliable index and linear function of units were calculated after internal force redistribution. The of each case could be achieved by using equivalent linear equation. Finally, the ranges of system reliability index and failure probability were calculated. As a consequence, it can be concluded that the reliability index of structure system is at the range of 2.5063 to 2.584 and its corresponding failure probability Pf is from 0.0049 to 0.0061. The is less than the value of norm.