Historically the most common way of protecting bearings was to use a lip seal  .  They rely on surface contact between the seal lip and the shaft to form the seal.  This surface contact often results in costly damage to the shaft itself  . In addition, as a consequence of this rubbing, lip seals can’t fully protect the bearing from moisture or particle ingress, which ultimately results in bearing failure. Today however it is generally accepted that lip seals have limitations, but due to inexpensive initial cost they continue to be widely applied.

Bearings are important basic components of all kinds of mechanical equipment. Its accuracy, performance, longevity and reliability play a decisive role in the accuracy, performance, life and reliability of the main engine. In mechanical products, bearings are high-precision products, which not only require comprehensive support of many disciplines such as mathematics and physics, but also require materials science, heat treatment technology, precision machining and measurement technology, numerical control technology and effective numerical methods and powerful computers. Technology and other disciplines serve it.