Dynamic Tracking of Noncontacting Face Seals

Abstract

A model is presented here to predict the maximum frequency attainable for a typical noncontacting face seal (for gas service) to be run successfully in the presence of axial runoul. This work has been carried out because the determination of maximum allowable speed by laboratory testing results in serious and costly damage to seal rings. The circumferential variation in gas film thickness, spring load, seal gas pressure, and seal geometry are considered in estimating the applied torque to the stator enabling it to dynamically track the misaligned rotor. The mathematical expression arrived at shows that, for a fixed seal geometry, the maximum frequency is proportional to the square root of the closing force and inversely proportional to the square root of both axial runoul and mass. Calculations and laboratory experience available for testing the model, though very limited, are in reasonable agreement.