Hydrostatic Effects in a Mechanical Face Seal

In a mechanical face seal, the total applied load is supported by hydrostatic and hydrodynamic fluid pressures and often by partial contact of the seal faces. Hydrostatic load support is affected by the initial seal interface geometry and the modification of this geometry due to component distortions. A model developed for static (non-rotating) conditions demonstrates effects of face convergence, spring pressure, and secondary seal friction on the hydrostatic fluid film thickness. The previously reported film thickness probe system has been used to measure the fluid film geometry in a standard wedge-type seal up to 4.5 MPa pressure, for comparison with theory. It is shown that the experimental results verify the hydrostatic model, in particular, confirming the prediction of the hysteresis effect due to the secondary seal friction. Application of the model for a hydrostatic seal design is also discussed.