Abstract: The deviation of non-equilibrium phase change from the Clapeyron-Clausius Equation for equilibrium phase change is analyzed. A model for determination of the superheat and boiling delay of saturated liquids during depressurization is proposed, which takes bubble generation, bubble growth and liquid surface evaporation into consideration. Various depressurization aspects of the LPG tanks at different initial temperature (pressure) and different depressurizing rate are calculated with this model. The superheat temperature, boiling delay mass and delay time decrease when the initial temperature rises, and increase as the de-pressurizing rate increases.