Predicted Effects of Bearing Sump and Injection Pressures on Oil Labyrinth Leakage

Abstract

New information and an enhanced understanding concerning the oil vapor contaminant leaking through nonflooded oil labyrinth seals are provided. The results were obtained using a finite volume Navier-Stokes computer code that was extended to include the concentration transport equation. The minimum (i.e., critical) pressure and flow rate at which uncontaminated buffer gas must be injected to prevent oil vapor from leaking to the process gas was determined for a range of seal geometries and operating conditions. It was found that the variation of the critical buffer-gas injection pressure with bearing gas and process gas pressures, for example, was surprisingly small for the cases considered. In addition, the bearing gas and oil vapor flow rates for a wide range of bearing and injection (where present) pressures and geometries were determined for both buffered as well as nonbuffered seals.