Abstract:The diffusion of permeable gas media such as helium,argon and Freon in the reverse leak direction of mechanical seals was studied.Aimed at the dual face mechanical seal of a main pump which used No.32 turbine oil as barrier media to seal gas media,the mean square displacement(MSD)of argon and Freon molecular in No.32 turbine oil was calculated based on molecular dynamics.The approximate diffusion factors of argon and Freon molecular in No.32 turbine oil were obtained by linear line fitting method.The leakage of the dual face mechanical seal was calculated and was compared with permeation flux of argon and Freon molecular.The results show that,during the normal working process of this type of mechanical seal,there is no possibility that the permeable gas media such as argon and Freon can escape to ambient along the reverse direction of mechanical seal end face.