5. Lubrication

Lubricant formulation and production have a major influence on the service life and suitability of a seal for its intended purpose. Specific greases and additives are generally used; for ball joints, molybdenum disulphide is added in varying percentages (2-4%).

The viscosity must be chosen so as to ensure lubrication of the seal at low temperatures (– 30°C, or – 40°C at engine start-up), with the least possible interference with the sealing bellows, while guaranteeing physico-chemical stability at high temperatures (120°C, or even 150°C) and high speeds.

Other imperative tasks include fast but careful running-in of the seal, the lowest possible coefficient of friction, correct heat transfer, material compatibility with the bellows seal, and so on.