Oil seals bearings usually are grease, fluid, or dirt seals bearing. These seals close spaces between stationary and moving components in mechanical equipment.
People design oil seals bearing to prevent the escape of lubricant. So, they also block contaminants from entering machinery. And this is especially important in severe environments where heat and foreign objects may be frequently present. They also prevent the mixing of different mediums like lubricating oil and water.
Oil seals come cataloged as metric oil seals or imperial sized oil seals. The seals are custom-made to match the bearings in new types of machinery. Install them in practically every type of machine including vehicles, protecting all kinds of precision, precisely-fitted ball bearings, sleeve bearings, and roller bearings.
The oil seal gets its structural stability from an interior metal ring which serves as an inner skeleton. The outer skin is a more flexible material like nitrile rubber or other materials based on the physical environment of the seal. A spring on the lip of the seal supports the lip and keeps the lubricant from leaking. The lip construction is what blocks contaminants from outside.
Where loads are light, the outer skin layer can be made of silicone. Fluoroelastomer (or Viton) can make it protect under high temperatures (more than 120 degrees Celcius). People can also use Poly Acrylate or Polytetra-FluroEthylene to make the skin.
The shaft on which the oil seal is mounted has to be ground to a rough surface finish. The shaft also should be hardened to prevent grooves forming on the shaft when the pressure is exerted by the spring on the seal. The area where the seal is fitted also has to be ground to prevent grooves that tend to wear out the lip of the oil seal faster than normal.
Oil seals have a flexible lip that actually rubs against the rotating shaft or housing to prevent leakage. The spring keeps the lip in contact with the shaft. Bearing isolator oil seals are dynamic seals that incorporate a rotor or rotating member and a stator or stationary member. The rotor actually turns with the shaft. Some oil shafts are bearing isolators with a "labyrinth" construction. Others incorporate simpler O-rings.
Types of oil seals include:
Single and double lip
Rubber or polymer
The internal, external and axial orientation