
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.
Viton Oil Seals

synthetic rubber gasket.
1. Pressure: Many oil seals are used in high-pressure applications, so understanding the working pressure of your components is very important.
Oil seals are protective elements. They prevent the mixing of water and lubricants within a machine, thereby ensuring optimal machine functionality. Also, oil seals help to prevent lubricant leakage at high pressure like when the machine is working at an extremely high rate. Not only that, radial shaft seals stop foreign components from entering a machine. This is because they can contaminate the lubricant and even damage the machine.

Notes
1) ISO: International Organization for Standardization
2) 2) JIS: Japanese Industrial Standard