Investigation of the Effect of Underpressure Between Main and Dust Lip on the Performance of Radial Shaft Seals Under Instationary Shaft Movements

Abstract

Radial shaft seals (RSS) are increasingly used in applications with highly dynamic rotational shaft movement, high accelerations, and frequent changes in the rotational direction, e.g. positioning robots. For such instationary conditions, the behavior of radial shaft seals has not been adequately understood yet. Therefore, under such conditions, radial shaft seals show leakage much more frequently than under stationary conditions. This is a problem especially in food processing or surface treatment processes where even the smallest amount of oil leakage can cause significant financial and reputational damage. Previous investigations have shown that leakage does mostly occur with shaft seals equipped with a contacting dust lip. Consequently, it is assumed, that the build up of negative pressure between dust and the main lip plays a role in the leakage mechanism. A measuring setup and evaluation strategy for measuring this underpressure during instationary shaft movements have been developed. A measurement regime with variation of different influential parameters has been conducted. Results show build up of a much higher underpressure when compared to stationary shaft rotation with severe impacts on the RSS’s operational behavior.