Vibration and stability problems with axial-flow pump blades in cavitating off-design operation

Hydraulic machinery (pumps, fans) is often operated far away from its design point.

Hydraulic machinery (pumps, fans) is often operated far away from its design point. This is mostly due to an imprecise understanding of equipment resistances and the subsequent imprecision of pump and equipment coordination. If the pump output is too great, in many cases the pump will be throttled back to partial load (working point on the pump characteristic curve to the left of the design point, Fig. 1) by a shut-off device. This applies in particular to the impellers of axial-flow pumps with greater torque when running at partial load rather that at the design point, where the stress on the vane of the blade is greater.