The separation of a mechanical seal's rotating sliding face from its stationary seat, resulting in excessive leakage. Separation occurs when the mechanical seal's opening forces surmount its closing forces. The reasons are:

• Gasification of the medium in the sealing gap due to cavitation or undershooting of the vapour heat); the rapid increase of volume separates the sliding faces, which close again after the pressure is balanced. Repeated periodically, this cycle produces vibrations which may result in the destruction of the mechanical seal.
• Sudden axial movement of the shaft
• Excessive hydraulic balancing of the sliding faces caused by a reversal of pressure at the mechanical seal (e.g. if the buffer fluid pressure fails)

Warping of the sliding faces that results in a lower load factor k.