Vane passing syndrome cavitation


A type of cavitation caused by the impeller/ cutwater clearance being too small. You will notice damage to the tip of the impeller caused by its passing too close to the pump cutwater.

  • The velocity of the liquid increases if the clearance is too small, lowering the pressure and causing local vaporization.
  • The bubbles collapse just beyond the cutwater and there is where you should look for volute damage. You will need a flashlight and mirror to see the damage unless it has penetrated to the outside of the volute.
  • The damage is limited to the center of the tip of the impeller vane and does not extend into the shrouds. You can prevent this problem if you keep a minimum impeller tip to cutwater clearance of 4% of the impeller diameter in the smaller impeller sizes (less than 14″ or 355 mm.), and 6% in the larger impeller sizes (greater than 14″ or 355 mm).
  • To prevent excessive shaft movement bulkhead rings can be installed in the suction eye. At the discharge, rings can be manufactured to extend from the walls to the impeller shrouds