Why are not all seals called oil seals?
Seals are a general term for all products that play a sealing role, including static seals, O-rings, oil seals, hydropneumatic seals, etc. The oil seal refers to the skeleton oil seal used for rotation, also known as the rotary shaft lip seal. It has two main functions in the process of rotating the shaft: to prevent sediment, dust, water vapor, etc., from invading the bearing from the outside, and to limit the leakage of the lubricating oil of the bearing.
Therefore, the oil seal is a specific type of seal, which is specially used for the sealing of the rotating shaft. Not all seals are called oil seals because the range of seals is broader and includes a variety of components and products used to prevent leaks and maintain environmental isolation.