Skeleton oil seal, often referred to as skeleton oil seals, are widely used
in rotating machinery to retain lubricants and exclude contaminants. Their
performance depends largely on the sealing principle of the lip and the proper
determination of lip interference.
Sealing Principle
The lip of the seal is designed to press against the shaft surface with a controlled radial force. This contact generates a thin lubricating film between the lip and the shaft. The film acts as a barrier: surface tension prevents oil leakage, while the elastic force of the lip maintains continuous contact. In practice, sealing is achieved through the combination of elastic compression and fluid film tension.
For double-lip seals, the secondary lip provides dust protection, ensuring
that external particles do not enter the system.
Determining Lip Interference
Lip interference refers to the dimensional difference between the seal’s inner diameter and the shaft diameter. Too little interference results in insufficient sealing force and leakage; too much interference increases friction, heat, and wear.
Key factors influencing interference include:
Shaft diameter: Larger shafts generally require proportionally smaller interference.
Operating temperature: Elevated temperatures soften elastomers, so interference may need to be increased.
Speed and pressure: High-speed or lightly pressurized conditions demand stable oil film formation, with interference carefully balanced to avoid overheating.
Material properties: NBR, FKM, and PTFE differ in elasticity and wear
resistance, which directly affects the recommended interference values.
Typical interference values range from 0.2 mm to 0.6 mm, depending on shaft size and application. International standards such as DIN 3760, ISO 6194, and GB/T 9877 provide guidelines for interference and installation dimensions, and engineers usually combine these references with real operating conditions to finalize the design.
The sealing principle of skeleton oil seal is straightforward, but achieving
reliable performance requires precise control of lip interference. It is both
the source of sealing force and a determinant of friction and service life. By
applying standard references and adjusting for specific operating conditions,
engineers can ensure that seals deliver consistent and durable performance in
industrial applications.
