Excessive wear-ring clearances can impact the tendency for formation of both classical and recirculation cavitation. 2 disturbs the flow pattern into the eye, the tendency for pockets and bubbles to form is increased. As both types of cavitation generate noise and vibration, about the only way to distinguish between them is by a careful inspection of the damaged impeller. The following two simple statements and Fig. 2 can be used to guide the inspection.
Damage is located on the non-visible or underside of the vane.
It starts near the leading edge and can extend up to approximately two-thirds of the vane length before the pressure implodes the bubbles. Either feeling or looking at the underside of the vane with a mirror is necessary to evaluate the damage.