Research on the navigational risk of liquefied natural gas carriers in an inland river based on entropy:A cloud evaluation model

Due to the flammability and explosive nature of liquefied natural gas(LNG),an extremely strict process is followed for the transporta-tion of LNG carriers in China.Particularly,no LNG carriers are operating in inland rivers within the country.Therefore,to ensure the future navigation safety of LNG carriers entering the Yangtze River,the risk sources of LNG carriers’navigation safety must be identi-fied and evaluated.Based on the Delphi and expert experience method,this paper analyses and discusses the navigation risk factors of LNG carriers in the lower reaches of the Yangtze River from four aspects(human,ship,environment and management),identifies 12 risk indicators affecting the navigation of LNG carriers and establishes a risk evaluation index system.Further,an entropy weight fuzzy model is utilized to reduce the influence of subjective judgement on the index weight as well as to conduct a segmented and overall evaluation of LNG navigation risks in the Baimaosha Channel.Finally,the cloud model is applied to validate the consistent feasibility of the entropy weight fuzzy model.The research results indicate that the method provides effective technical support for further study on the navigation security of LNG carriers in inland rivers.

Research on Temperature Field and Thermal Stress of Liquefied Natural Gas Carrier with Incomplete Insulation

The insulation of membrane type liquefied natural gas(LNG) carrier is composed of plywood boxes filled with perlite.Within the service period,considering of the effects of load conditions,such as sloshing,wave load,it is possible to have some damage of the plywood box,leakage of perlite,and failure of the insulation box.LNG carrier without whole protection of effective insulation is dangerous.Hull structure is extremely fragile when exposed to ultra-low temperature.In order to solve these problems,firstly a study on insulation boxes' character and work condition is carried out and some presuppositions of partial disabled insulation are put forward.Secondly the thermal system of LNG carrier is analyzed to find out an effective way to simulate the thermal action of close air between outer and inner hull.Then a calculation about temperature field and thermal stress is done by MSC/PATRAN&NASTRAN.At the end it is concluded that LNG carrier with incomplete insulation is dangerous and needs to be avoided.