Shaft seals consist of a metal case, a sealing element and a garter steel spring.
Working principle of rotary shaft seals.
The sealing effect is achieved by interference between lip and shaft, the spring allows the lip to maintain a radial load.
After a short period the sealing edge is transformed in a defined contact band which sizes are between 0,4 and 1,3 mm.
An oil film forms under the lip contact area, its thickness is between 1 and 3 µm, the meniscus is maintained through capillary action between shaft and the atmosphere in
order to avoid leakage.
An increase of the film thickness means increasing pressure of the fluid to be sealed reaching bigger values which determine the meniscus break and therefore leakages.