Transient Stress Analysis And Failure Mechanism Simulation For Liquefied Petroleum Gas Vessel

Wth the fast development of petroleum industry liquefied petroleuxn gas (LPG)is used increasingly in industrial and civil area. Because LPG is combustible andeXPlosive material, with increasing of its consUInPtion, accidents of LPG occursomctimes in tranSPortation and storage. Accordingly, accidellts of LPG are anachedgreat imPortance, and relevam research is developed. Ainong these researches,transient stress distriblltion calculation, predication of crack propagation and stUdy onthe failure mechhasm of LPG vessel under high temPeratUre has a great significancefor insuring safe transportation and storage of LPG.This paPer aims at the characteristics of thermal response of LPG vesse1 underhigh temPeratue, conjoining the prOject of "Study On TransPortation SafetyEarly-wdring System of LPG Dangerous Goods" suPported by TransportationDepartInen of China and the prOject of "Mechanism StUdy and Numerical Simulationof the ExPlosion of LPG Vessel" suPported by Science Foundation of Hubei Province.The interdisciplinary research has been done among temPerature field distribution ofLPG vessel under flame surroundings, intensity calculation, crack propagationpredication and mechanism of explosive accident, etc. Three parts are analyzed anddiscussed.First, the safety of a workPiece is related to stfCss it bears and its temPeta, sois LPG vessel. TemPeratUr field distribution and stress field distriblltion of LPGvessel are calcu1ated in order to eStimate its safety statlls. As to the calculation of thetemPedee fie1d distribulion. the heat transfer model of LPG vessel under flamesurroundings is set uP firSt, then the heat transfer boundary conditions of LPG vesselare determined according to the heat transfer theory and the heat exchange boundaryconditions of LPG vessel of global shaPe with 4l percellt fill rate is calculated interms of PLGS99 software, finaly the temPerafore field distribution of this model iscalculated and analyzed by ANSYS software. Wth regard to stfess calculation ofLPG vessel, the stress of LPG vessel is caused mainly by thermal stress andmechanical Stress. In order to make clear the influence of two kinds of stress to thetotal Stress, equivalellt thermal stress of LPG vessel under only temPertae load andits equlvalent mechanical stress under only inner wall stress are calculated andanalyZed, then its equivalent total stress is calculated, analyzed and comPared.' Second,Jhe failure process of LPG vessel usually includes two phasest the crackformation and the crack propagation. After the temPeratat field distribution and theIIl.stress field distribution of LPG vessel without cracks are calculated, the stress intensity factor of LPG vessel with initial radial crack as well as surface crack are calculated and analyzed.In the end, the mechanism of explosive accidents of LPG vessel under high temperature is analyzed. The major inducements of LPG vessel under high temperature are as follows: 1) sudden falling of pressure on valve opening; 2) material strength falling of vessel wall, which is caused by high temperature of vessel wall; 3) thermal stress that is caused by non-uniform temperature of vessel wall. Among usual measures of precaution and protection, spray system and thermal insulated layer are easy and effective. In addition, the improvement of the relief valve is propitious to prevent the explosion of LPG vessel.