Many people regularly encounter oil seals, which are mechanical components designed to seal liquid media (including oil, water, etc.). They isolate lubricated moving parts from the external environment, preventing leakage of lubricants.
The image above shows a cross-sectional diagram of a TC oil seal.
The TC oil seal is the most widely used in modern industry. It features an internal metal skeleton, externally wrapped with rubber, and has dual lips (hence "T" for "two lips"). The "C" denotes external rubber coverage. The main lip prevents oil leakage, while the secondary lip acts as a dust guard.
The SC oil seal is a single-lip, rubber-wrapped skeleton seal ("S" for "single lip"). Compared to the TC type, it lacks the secondary dust-proof lip, making it suitable for dust-free environments.
The TF oil seal is less common in general applications. It is a fully rubber-encapsulated metal shell seal, significantly more expensive than TC types. It is designed for corrosive environments, as the rubber fully protects the carbon steel skeleton from corrosion. TF seals typically use fluorocarbon rubber (FKM) and stainless steel springs for durability in high-temperature or corrosive conditions.
Similar to the TF type, the SF seal is also fully rubber-encapsulated. The key difference is that the SF has a single lip (suitable for dust-free environments), while the TF has dual lips (oil and dust protection).
· All four types are only suitable for environments with pressure ≤ 0.3 bar.
· Material selection must account for temperature and rotational speed:
o Nitrile Rubber (NBR): Low cost, oil-resistant, and wear-resistant, but limited to <100°C.
o Hydrogenated Nitrile Rubber (HNBR) or Fluorocarbon Rubber (FKM): Required for >100°C.
o FKM: Mandatory for >150°C
Perfluoroelastomer (FFKM): Used for >200°C, withstanding up to 320°C and resistant to 1,600+ chemicals.
