Performance of the radial shaft sealing system under the influence of shaft lead.

The performance of a radial shaft sealing system depends primarily on the main components radial shaft seal (RSS), shaft surface and lubricant and how they interact with each other. The dynamic sealing mechanism of the seal depends on many influencing factors, one of which is the shaft surface topography. Therefore, the shaft surface roughness parameters must be in an acceptable range. Now, different parameters or machining processes of the shaft can generate the same surface roughness but totally different surface topographies. To ensure the performance of the sealing system, in addition to the known roughness parameters, the shaft must be free of fluid-pumping structures. Those structures are known in the sealing technology community as shaft lead. Depending on the shaft lead characteristics, the lead can create an axial pumping effect of the fluid which disturbs the sealing mechanism. The latter expresses itself either in the form of direct leakage or poor lubrication conditions and therefore to an increased wear of the sealing edge. Different lead structures can be measured and quantified with state-of-the-art measuring and analyzing methods. Using these methods, the correlation between lead parameters and leakage resp. seal wear can be shown. The insights drawn, will be applied to unpressurized and pressurized radial shaft sealing systems. Based on those results, acceptable limits for shaft lead can be set to ensure a reliable sealing system.