Simpler method for volatile medium pump mechanical seals

Mechanical face seals operating with volatile media, such as liquid ammonia, hot water, and light hydrocarbons, generally fail as a 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. In this article, correlations for calculating thermophysical properties of typical single volatile process media in petrochemical plants are presented. Taking a parallel face seal as the model, a simpler method is given for determining average face temperature T_f and fluid film pressure coefficient K_m which can be used as criteria for identifying phase states and phase state stability of such a seal. On the basis of the criteria and the curves relating K_m to T_f, a new idea is proposed for monitoring the phase states of the fluid film between the two faces. Taking the face seals of liquid ammonia and hot water pumps as examples, the calculation results of average face temperature are in excellent agreement with the test results on-site.