Subject : Increasing the centrifugal pump performance by modifying the impeller.12-6

The following information will apply to closed, semi-open and open impellers unless noted otherwise:


  • We will be using the term Gap "A" to describe the clearance between the impeller shrouds to the volute or casing and
  • Gap "B" describes the clearance between the impeller vanes and the casing or volute.
  • "D" describes the diameters of the vanes and shrouds



What happens when you reduce the impeller vane diameter? Several things :

Although both the vanes and shrouds are often cut in end suction, volute type centrifugal pumps; it is not a good idea to do this in double suction designs. With these types of pumps you can reduce the vane diameters, but the shrouds should remain untouched.

Under filing the exit vanes is usually a good idea. Please look at the following diagram :

  • (d) is the distance before filling
  • (df) is the distance after filing


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