Three-dimensional structure-based approach for the analysis of macroscopic lead structures on sealing counterfaces

The seal failure of an elastomer rotary shaft seal is often caused due to lead on the shaft counterface. In sealing technology, the term ‘lead’ includes all structures on sealing counterfaces that are capable of transporting fluid in axial direction through the sealing contact and thus disrupting the sealing mechanism. Lead structures are created during the manufacturing process of the shaft surface or throughout the handling. They occur in various shapes and sizes. Depending on the characteristics of the lead structures, several specialized measurement and evaluation methods exist which have to be applied in combination. However, not all types of lead can be covered with the methods known so far. State of the art are frequency-based and model-based analysis methods, which are only able to detect periodic lead structures. Aperiodic and stochastically distributed lead structures cannot be detected due to the functional principle. This article provides an approach for a structure-based evaluation of macroscopic lead structures based on optical topography measurement data. This allows to detect all known types of macroscopic lead on the shaft surface and in future to measure microscopic and macroscopic lead with a single measurement procedure.