Shaft wear
Shaft wear in the area of contact between the shaft (protection sleeve) and a mechanical seal's secondary seal on the shaft side arises when two conditions are fulfilled: The medium to be sealed contains fine-grained, hard solids, and the secondary seal makes involuntary axial movements and/or run-outs on the shaft. The solids become embedded in the soft secondary seal (figure …) and exert an abrasive action on the shaft and often on the secondary seal, too, during the axial movements and run-outs (cf. wear abrasion on O-rings).		Coating the shaft with a hard wear-resistant material delays shaft wear but cannot prevent it totally. To avoid shaft wear, its causes must be eliminated (by fitting a cyclone separator, flushing, preventing axial movement and run-out or reducing it to a tolerable limit) or use must be made of elastomer bellows mechanical seals or metal bellows mechanical seals.
A shaft sleeve worn at the area of contact with the secondary seal (O-ring)		Dynamic O-ring with embedded solids