All are fitted with a spring to preload the sealing lip. All these types are for non-pressurised or low-pressure applications up to 0.5 bar for diameters of a limited size. For diameter of 500 mm or more, the maximum pressure is 0.1 bar. For higher pressures, special types or PTFE lip seals can be used.
A wide range of sealing devices are used in various machines.
Sealing devices serve the following functions:
An oil seal has two tasks: Keeping the lubricant in and keeping dirt and contaminants out of rotating components. This separation must be accomplished between surfaces in relative motion, usually a shaft or bearing inner ring and a housing. With correct installation, oil seals can also prevent seal leakage and maintain the lubricity of a bearing to ensure that the rotary shaft and its bearings remain fully functional.

Plug tube gasket
