Abstract: The LPG tanks with the form of cylinder shape are taken into investigation, the root cause of the overpressurization is that the fire increases the pressure in the tank, then the pressure promotes the leak, and the leak aggravates the fire again. Combining the equations of mass and energy conservation, the Hertz-Knudsen equation, the prediction formula for pressure vessel rupture and so on, the model for overpressurization of cylinder tank of LPG due to leakage fire is established and then verified by an accident. Through the analysis of the pressure in the tank during the accident, when the liquid phase of LPG in the tank is heated by fire, both the jet fire and pool fire of LPG can cause the tank to fail due to overpressure, and the tank is broken more quickly under jet fire. The overpressurization time for the tank is shorten with high filling coefficient. With the analysis of tank overpressurization under the conditions of various leak sizes, the tank will not fail when the leak size is less than the safety critical leak size, and the tank fails fastest when the leak size is equal to the most dangerous leak size. In the event of a leakage fire of LPG tank, it is recommended to judge the accident situation carefully according to gas phase or liquid phase heating, fire types, leak sizes, etc., then decide on the emergency plan, and always beware of explosion caused by overpressure failure of tank.

Key words: LPG; cylinder tank; leakage fire; overpressure failure