The below images depict discharge recirculation on an axial flow pump propeller. Recirculation occurs when the flow is reversed back through the impeller/propeller of the pump. The damage can be seen on each vane at the same location. When there is recirculation in a pump it experiences cavitation and surging that can cause considerable damage.
How do we correct this?
- Increase the output flow of the pump so that it is not operating below its minimum flow requirements.
- Modify the impeller design to more appropriately meet your station design.
- Install a bypass line between the discharge and suction of the pump to allow your pump to meet its minimum flow requirements.
- Upgrade the impeller material to something more resistant to cavitation (Ni-Al-Brz or Stainless Steel for example).