Wear ring clearance

Wear rings should be replaced when their clearance exceeds manufacturers recommendatrons. A general rule of thumb is to replace them when the originalclearance doubles. This additional clearance will increase the pump power requirements with the amount of power varying according to the specific speed (NS ) of the impeller

  • NS 200 14% increase
  • NS 500 7% increase
  • N2500 Insignificant increase

If the wear-ring clearance is too large the pump will take on excessive vibration caused by internal recirculation. This can cause seal and bearing component damage. Another problem is that the pump will not meet its designed capacity because of the internal recirculation.

If you cannot get a copy of the manufacturer’s clearance recommendations, you can use the following chart as a guide.

When replacing wear rings, it is not uncommon to bore out the stationary ring and machine the rotating ring oversize to get the correct clearance. If you do this on a double-ended pump, be sure to do both sides of the impeller to prevent upsetting the balanced hydraulic forces and thrusting the impeller to the end that was not bored oversize.

Also be aware that many wear rings supplied by OEM manufacturers are out of round and must be machined to get the proper clearance inside the stationary ring



  • On February 17, 2018