Oil Seals

oil seals
The purpose of oil seals is to provide sealing between the rotating crankshaft and the outside. Classical oil seals consist of a metal housing that carries the dynamic sealing lip and also provides the static sealing function. The sealing lip of oil seals is usually manufactured of elastomer material, and is in contact with the surface of the rotating shaft. Hereby, the lip is pressed onto the shaft surface by means of a spring ring. As a result of the rotational movement, there is a sealing gap of approx. 1 μm at the lip edge. Oil can enter this gap, which serves to lubricate the sealing lip.



Construction of a conventional oil seal with spring ring.

A Perfect Combination – Oil Seals and PTFE

The material for future oil seals is named polytetrafluoroethylene – or simply PTFE.

Low friction and minimum power consumption are the decisive advantages offered by PTFE oil seals. These seals can be used without problems also with dry operation or insufficient lubrication. The material’s excellent thermal properties, with an operating range of -130ºC to +200ºC, are unrivalled. Moreover, PTFE is featured by high chemical resistance and a low breakaway torque after standstill.



Construction of an oil seal with PTFE sealing lip.
 

Integrated oil seal Design and Construction
The outer housing is made of stainless steel. An O-ring of fluoroelastomer ensures optimal static sealing. The internal diameter is perfectly concentric with the outer diameter. The actual sealing lip is made of highly wearresistant and low-friction PTFE. An additional dust seal (rubber lip or felt strip) provides an effective barrier against contaminating particles.

Special Type With Integrated Oil Seal
Integrated oil seals reduce the manufacturing time of series production engines. As only one component needs to be installed, work on the assembly line as well as subsequent leakage is reduced by about one third. Similarly, significant time savings are achievable when replacing the radial crankshaft seals.

 

Integrierter Radial-Wellendichtring

TIP FROM THE EXPERTS
When installing integrated oil seals, please note that it is usually necessary to slightly loosen the oil pan to enable the radial seal to be pushed onto the crankshaft.

Installation of PTFE Oil Seals

TIP FROM THE EXPERTS

  1. Only remove PTFE oil seals from their protective packaging immediately before installation, to protect them from dust and other contamination.
  2. The sealing lip of PTFE oil seals is protected by a plastic sleeve, which can normally be used as an assembly aid. Therefore, the sleeve should remain in place until the seal has been installed.
  3. If the seal is to be installed without the sleeve, use the special tool provided by the manufacturer.
  4. Both the PTFE sealing lip and the shaft surface must be completely dry. Do not use any grease or oil.
  5. The shaft may not exhibit any sharp-edged chamfers – if necessary, have the edges removed by an engine expert.
  6. The shaft surface must be in a perfect condition – also here, possible damage must be repaired by an expert.
  7. Position the assembly sleeve with the PTFE oil seal on the shaft.
  8. Make sure that the sealing ring is aligned correctly – the sleeve must be located so that the seal can be pushed onto the shaft smoothly.
  9. Push the sealing ring onto the shaft with an even motion.
  10. When replacing, the PTFE lip of the new seal should not run in the same position as the old one.
  11. You can now remove the assembly sleeve.
  12. Do not start the engine sooner than four hours after installation – this permits the new sealing lip to adapt perfectly to the shaft.


Failure of PTFE Oil Seals

Damaged PTFE Sealing Lip
The most frequent cause for failure is damage to the PTFE sealing lip during assembly. If the seal is installed without the help of a sleeve or special tool, and is shifted or even turned inside out, reliable sealing will hardly be possible. Similarly, the use of oil or grease – as with classical oil sealing rings – will result in total failure of the PTFE oil seal immediately after installation.


TIP FROM THE EXPERTS
If available, new oil seals with PTFE sealing lip can be used as replacements for conventional oil seals.


Left: Damaged PTFE sealing lip as the cause of failure.
Right: Greased PTFE sealing lip as the cause of failure.

Practical Information

PTFE Oil Seals and Their Installation