Load Support and Leakage from Microasperity-Lubricated Face Seals

Abstract

Observations of load support from various shapes of microasperities placed on the surface of a rotary-shaft face seal indicate that all are comparable in this respect and generally follow the theory developed previously for cylindrical asperities. Both positive (protrusions) and negative (valleys) asperities produce similar load support, developing stable hydrodynamic lubricant films of the order of 10−5 in. for linear velocity of at least 50 in./sec, lubricant viscosity as low as 1 cp, and loads of the order of 100 pounds or higher. Variations in the film thickness with these parameters is predicted by the theory developed on the basis that an effective small tilt exists on the tops of the asperities. Leakage from microasperity-lubricated seals on the average follows the predictions of Poiseuille flow, with the exception that a significant effect of rotor rotation is observed. For a leakage channel height of 10−4 in., leakage was typically of the order of 0.2 in.3/hr for a pressure drop of 10 psi across the seal.