Lip seals are commonly used in a wide range of applications ranging from sealing electric motors, bearing housings, car engines, gear boxes etc. They are used to stop the ingress of fluids or solids from entering a chamber from the atmosphere whilst also simultaneously stopping egress of the lubricating fluids from escaping the equipment chamber. Essentially the aim of a lip seal is to therefore prevent the premature failure of rotating equipment through contamination or loss of the lubricating fluid.
In order to provide this fluid seal, lip seals comprise a single moulded rubber component, which fits into the equipment housing and contacts the rotating shaft. This, however, means that the seal that the lip seal provides deteriorates over time as the shaft and lip seal wear. This not only allows ingress of particulates and moisture into the chamber, thus reducing the bearing life, but also means that the shaft may be damaged in the process. This can, therefore, lead to extended downtime of equipment whilst lengthy and costly repair work is carried out, thereby resulting in reduced mean time before failure, which increases the operating costs of equipment.
An alternative to Lip Seals, which are widely used, are generically called bearing seals. Commonly these exist as two types: labyrinth seals; and mechanical seal bearing protectors. Labyrinth seals typically have a complex outer profile which is located adjacent and in close radial and axial proximity to a complex inner profile of the stationary component. Together these complex profiles provide a tortuous path preventing the passage of materials or fluids through the seal. Due to the non-contacting characteristics of the labyrinth design its use in flooded or pressurised environments is limited. Mechanical seal bearing protectors are therefore commonly used in these applications as contacting faces ensure that limited or no fluid is able to pass through the seal. The face pressure between the stationary and rotating faces, which ensures contact between the faces is maintained, is commonly produced through the use of magnets.
These bearing seals solve the limitations of a lip seal as they do not wear the shaft, however, due to inherent increased complexity and machined components they are more expensive and also require a larger cross sectional area to fit into and so are not suitable for all applications.