The operation of radial lip seals in contaminated environments and the significance of the test rig design

Abstract

The performance and basic rating life of rotating contact ball bearings have increased substantially over recent years, but the performance of radial lip seals, designed to protect these bearings against the ingress of contaminants, has not. In particular, the failure of the lip seals used to protect self-lubricating ball bearings has been identified as a major cause of bearing failure. To understand in detail the mechanisms of failure, these bearings and seals have to be assessed by performing carefully controlled experimental tests. As elastomeric lip seals are intrinsically sensitive to test conditions, their performance is often subject to statistical scatter. Therefore, the design of test rigs to carry out this research is vital so as to eliminate as many unwanted variables as possible. Typical test rigs and the usual tests previously carried out by the major bearing manufacturers are detailed, and the performance of both the test rigs and the seals are discussed. A new radial lip seal test rig, designed specifically for assessing seal performance is shown, and improved test methods and data logging are detailed. Typical lip seal test results are presented and analysed. The aim of this work is to characterize empirically lip seal behaviour under both contaminated and uncontaminated conditions, enabling a deeper understanding of lip seal performance to aid future improved lip seal designs to be formulated.