What are oil seals?

A shaft seal is a technical Sealing element, which acts as a seal between a rotating shaft and a stationary housing. The aim is to retain the lubricant inside - usually oil or grease - and at the same time prevent the ingress of dirt, dust or moisture.

 

The structure of a shaft seal typically consists of:

  • ElastomerSealing lipensures the actual sealing effect through defined contact pressure on the shaft
  • Elastomer dust lip: optional sealing lip on the dirt side for increased protection against foreign bodies
  • Metal reinforcementLends dimensional stability and ensures a tight fit in the housing
  • Tension spring: ensures uniform contact pressure of the sealing lip, even in the event of wear or temperature fluctuations

 

Sealing is achieved via a thin layer of lubricating film between the sealing edge and the shaft. This film prevents dry running and wear, while the controlled contact pressure minimises leaks. Shaft seals are available in countless variants from simple Sealing lips from double lip seals with dust lip to pressurised high-performance seals. Special microstructures on the sealing edge can also have a conveying effect on the medium, e.g. to minimise lubricant loss. Shaft seals are dimensioned according to internationally standardised dimensions.

 

Functions and applications of shaft seals

Shaft seals are crucial for the functional reliability and service life of rotating systems. They ensure lubrication and prevent contamination.

 

Functions at a glance:

  • Sealing rotating shafts against loss of lubricant
  • Protection against the ingress of dust, moisture or dirt
  • Pressure equalisation and retention of media at varying speeds
  • Lubricant film control to minimise friction, heat generation and energy loss
  • Vibration and noise damping through elastic material contact

 

Typical applications:

  • Automotive and commercial vehicle technology: crankshafts, gearboxes, axles and wheel hubs
  • Mechanical and plant engineering: motors, pumps, compressors and gearbox housings
  • Hydraulics and pneumatics: Sealing of shafts and piston rods
  • Electric motors: Protecting the bearings from dust and moisture
  • Agricultural and construction machinery: Sealing of drive and swivel joints
  • Building services and energy systems: Shaft sealing in fans, pumps and ventilators

 

Oil seals make a significant contribution to the reliability, maintenance-free operation and energy efficiency of rotating systems. Their failure can lead to loss of lubricant, increased friction or bearing damage, which is why material selection and installation conditions are crucial.

 

Components and materials of shaft seals

The choice of material for a shaft seal depends on the medium, temperature, speed and chemical load. The right Elastomer material ensures that the sealing ring remains elastic, operates with low wear and is chemically resistant.

 

Typical materials:

  • NBRoil and grease resistant, suitable for temperatures from -30 °C to +100 °C
  • HNBRimproved heat and oil resistance, high abrasion resistance
  • FKMhigh chemical resistance and temperature resistance up to approx. 200 °C
  • EPDMresistant to water, vapour and brake fluids, not oil-resistant
  • Siliconevery elastic, good low-temperature flexibility, for special applications

 

Metal support and tension springs:

  • Steel: Standard for general applications
  • Stainless steelCorrosion-resistant, suitable for humid or chemical environments
  • brassfor special applications, e.g. to prevent galvanic effects or flying sparks (EX areas)

 

Shaft seals can be adapted by design to optimise durability and sealing effect:

  • Sealing lip with contact line to the shaft
  • Dust lip to protect against external contamination
  • Metal armouring or coating for a tight fit in the housing
  • Tension spring for even contact pressure
  • Surface grooves or microstructures for targeted control of the lubricating film

 

Precise manufacturing and the right combination of elastomer, carrier material and geometry ensure long-lasting, reliable sealing under high speeds, changing temperatures and demanding operating conditions.