Wear

Wear is an attrition phenomenon (i.e. the gradual loss of material from the surface of a solid body) which is caused by mechanical factors such as contact with and motion relative to a solid, liquid or gaseous counter body (see abrasion).  

One of the main ways to extend the service life of machines and equipment is to reduce the level of wear. There are various types of wear, but certain types are more common in centrifugal pumps than others. See Fig. 1 Wear