Oil seals prevent internal system fluids from leaking and keep external contamination from entering the system. Leakage and/ or contaminants paths occur between the shaft and the seal lip and between the seal and the housing. Oil seals need to seal both dynamically (on the shaft) and statically (on the outer diameter of the seal).

An oil seal normally consists of three basic components: the rubber sealing element, the metal insert (case) and the garter spring. The purpose of the sealing element is to stop the fluid from leaking between the shaft and housing. The metal insert will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The garter spring will help make the rubber sealing element more effective.

Where hydrodynamic aids have been provided it should be remembered that a pressure deficit can be produced in the space between primary and secondary lips which will increase the radial force. This situation can be alleviated by providing breathing holes in the secondary lip. It should also be remembered that contaminants which have penetrated past the secondary lip will eventually cause damage in the couterface region. A build-up of heat can also occur between the two lips; this promotes premature wear.

Oil Seals Groove Dimensions & Tolerances PDF