Strength Analysis And Structural Improvement Of A Liquefied-Gas Cryogenic Tank

Liquefied-gas cryogenic tank is widely used in chemical, metallurgy, medical, aerostatical industries and many other fields. With the rapid development of the modern industries, more and more liquefied-gas is required and as a result, larger and larger liquefied-gas cryogenic tanks are needed. A large tank calls for more reasonable structure design. In this paper, finite element method was used to conduct stress analysis for a liquefied-gas cryogenic tank and a structural improvement had been made to make sure that the tank can pass the strength check in all load cases. In addition, the stability analysis of the head under complex loadings was also performed.First, for the strength analysis, eight load cases combined by the internal pressure, external pressure, gravity, thermal load, wind load, seismic load and transport load were considered. Stress distribution in the liquefied-gas cryogenic tank was obtained and strength was checked confirmed to the pressure vessel design standard JB4732-1995 Steel Pressure Vessel—Design by Analysis. Results show that in some load cases especially when the thermal loanding is presented, stress intensities in some key components are much higher than the allowable values or in other words, strength requirement is hard to be satisfied. Further analysis indicates that the structure of the tank is not so reasonable and needs to be improved.Secondly, structural improvement of the tank had been made, including the structure of the lifting bar and the way for connecting the inner vessel and the outer jacket. Results show that stress intensities in the new structure are decreased remarkably and all the strength checks are passed for all the load cases.Finally, linear as well as non-linear finite element stablility analysis was performed on the head of the liquefied-gas cryogenic tank and loaded with external pressure and reaction forces of supporters. The critical instability pressure and the critical instability vertical force of the head were calculated and the effect of the reinforcing plates was investigated. Results show that the critical instability pressure is not affected by the presence of the supporters. Instabilities of the head induced by the external pressure or the vertical force are independent from each other. The reinforcing plates have little influence on the critical instability pressure, but they increase the critical instability vertical force.