Complete guide to rotary shaft oil seals including TC, TG, SC/DC types, materials, and selection criteria for industrial use.
An oil seal, also known as a rotary shaft seal, is a device used to prevent the leakage of oil or grease from rotating shafts while also keeping contaminants out. Oil seals are essential components in virtually all rotating machinery, from small electric motors to large industrial gearboxes.
The TC type is the most common oil seal design. It features a primary sealing lip with a garter spring for positive contact with the shaft, and a secondary dust lip to prevent contaminant ingress.
Applications: General-purpose applications including gearboxes, pumps, motors, and automotive components. The TC type is the default choice for most industrial applications.
The TG type features only a primary sealing lip with a garter spring, without a dust lip. This design is used when external contamination is not a concern.
Applications: Clean environments, enclosed gearboxes, and applications where the seal is protected from external contaminants.
The SC type features a single metal case with double sealing lips. It provides a more compact design than the TC type while maintaining dual-lip sealing.
Applications: Space-constrained applications, automotive transmissions, and compact machinery.
The DC type features two metal cases for enhanced rigidity and improved bore sealing. This design provides better retention in the housing.
Applications: Heavy-duty applications, large bore housings, and applications with significant bore tolerances.
The most common oil seal material. NBR provides excellent compatibility with petroleum-based oils and greases. Temperature range: -40°C to +120°C. Suitable for shaft speeds up to 12 m/s.
Used for high-temperature applications and aggressive chemical environments. Temperature range: -20°C to +200°C. FKM oil seals are essential for applications involving synthetic oils, biodegradable fluids, and high operating temperatures.
PTFE oil seals offer the broadest chemical compatibility and lowest friction. They can operate at higher shaft speeds (up to 30 m/s) and temperatures (-200°C to +260°C). PTFE seals are used in food processing, pharmaceutical, and chemical applications.
Shaft Diameter: Measure the shaft diameter accurately. Oil seals are specified by shaft diameter, bore diameter, and width.
Shaft Speed: Higher shaft speeds generate more heat at the sealing lip. For speeds above 12 m/s, consider PTFE seals or special high-speed designs.
Temperature: Consider both the ambient temperature and the heat generated by shaft rotation. Select a material that can handle the maximum expected temperature.
Media: Ensure the seal material is compatible with the oil or grease being sealed. Check compatibility charts for unusual fluids.
Pressure: Standard oil seals are designed for near-zero pressure differential. For pressurized applications (above 0.05 MPa), use pressure-rated oil seals with reinforced designs.
Proper installation is critical for oil seal performance and longevity:
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