2. Isothermal mixed lubrication

2.1 Tribological situation (and assumptions)

The film between the faces of a seal is not always thick enough to completely separate the surfaces, especially at low speeds. In this case, the seal faces are partially in contact, at the top of their asperities. This is called mixed lubrication (see definition in article [TRI 1 500] ). In this situation, the average film thickness h is of the order of the surface roughness height Sq. In the case of mechanical seals, h ≈ 2 to 4 Sq (figure 15 ).