Mixed lubrication in mechanical face seals with plain faces

Abstract

For the purposes of design and analysis of plain-face contacting mechanical face seals, it is necessary to predict the seal leakage and the friction power as functions of the face profile and the operating conditions. Thus a model of mixed friction behaviour for face seals is required. A complete model is presented. Load support is based on the sum of three components of pressure: hydrostatic, hydrodynamic and contact. Prediction of the hydrostatic pressure is straightforward. Empirical data are developed for the prediction of hydrodynamic load support. Both a plastic and an elastic model for contact pressure are presented. Complete equations are given for load support, load support equilibrium and friction. It is shown how the model is used to predict the film thickness and leakage for any combination of fluids and operating conditions. Predictions from the model are compared with some test data and agreement is encouraging. While the model is currently used as a practical tool to predict the seal performance, the weaknesses of the model are discussed, and it is shown where further research is needed.