Erosion (abrasive jet wear). Unlike corrosion – where material is damaged by (electro-) chemical processes – erosion is a mechanical attack on the surface of the material. It occurs in fast flowing liquids and gases and is usually intensified considerably by solid particles in the flowing medium. Erosion and corrosion can reinforce each other in their destructive effect. Corrosion-inhibiting protective coatings can be worn away by erosion, while the roughening caused by corrosion provides erosion with a larger surface to attack. Erosion damage to mechanical seals can be categorized by cause and damage profile in two groups: Erosion damage to sliding faces has been observed frequently in high-duty mechanical seals for feed water pumps which were exposed to differential pressures > 30 bar over a long period of time, including standstill.

Pressure-induced minimal deformations of the seal face and stationary seat (sealing gap shapes) produced tiny channels, in which the resultant high-velocity leakage flow first washed the binder out of the face materials tungsten carbide with nickel binder and then attacked the base material. Erosion damage to sliding faces is prevented nowadays by using face materials with better geometrical stability and a modified sealing gap geometry.

Erosion damage to the other parts of mechanical seals occurs when

• the mechanical seal runs in overtight stuffing boxes in media containing solids or
• the circulation flow of a medium containing solids impacts radially against mechanical seal parts at high velocity.

Damage of this type is prevented by bigger stuffing box diameters and a circulation flow entering tangentially against the direction of rotation.