Wear rings can be defined as a device used to seal the pressure leakage of the liquid between the inlet of the impeller and the pump casing. Wear rings are typically
found on pumps with closed impellers. A similar device that serves the same function called a wear plate can be found on some pumps with a semi-open impeller.
The typical reason for using a wear ring is to decrease the amount of leakage loss around the impeller. Due to more work available to push the pumped liquid out the discharge there is a slight improvement in pump efficiency.And also as name indicates 'WEAR' which is a ring can sacrifice its size by taking friction generated between stationary and rotating elements.The replacement of rings is easier & cheaper than replacing impellers/casing.