A simpler method for volatile medium pumps mechanical seals

Mechanical face seals operating with volatile mediums, e.g., liquid ammonia, hot water, LPG, and light hydrocarbons, generally fail as the result of phase state instability of the fluid film between the two faces. Therefore, determining face temperature and identifying phase states and phase state stability of such a face seal are very important. The correlations for calculating thermophysical properties of single volatile process mediums were presented, mainly including fluid density, vapor pressure and fluid velocity, etc. With the same temperature variation, change of fluid film pressure coefficient in quasi-vapor phase region (QVPR) was larger than that in quasi-low phase region. A volatile medium mechanical seal would consume more energy to be in stable or quasi-stable phase state when operating pressure was higher or seal face was wider. The reverse was that when medium pressure was very low or seal face was very narrow, the narrow QVPR would lead a seal in VPR adjacent to QVPR to vary quickly and repeatedly from one phase state to another with slightly change of operating conditions, which caused the seal to be in unstable and caused the leakage. To verify the presented method, tests on site were conducted in Qilu Petrochemical Co Ltd in China. This is an abstract of a paper presented at the Technische Akademie Esslingen 14th International Colloquium Tribology (Stuttgart/Ostfildern, Germany 1/13-15/2004).