Bearings support the rotating shaft and allow it to turn with a minimum amount of friction. There are three types of bearings used in centrifugal and positive displacement (PD) pumps:
In this illustration you can see:
- An inner race or ring
- An outer race or ring
- A series of balls between the races.
- You should also be able to see a cage between the balls to keep the balls from coming into contact
This bearing is often called a precision or anti-friction bearing.
These bearings are specified for radial loads only and therefore have limited use in centrifugal pumps where a combination of radial and axial loads are present.
This illustration shows a double row roller bearing
||Sleeve or journal bearings
When do you go from anti-friction ball and roller bearings to hydrodynamic (sleeve) bearings in a centrifugal pump?
- Any time the DN number exceeds 300,000 (Bearing bore x rpm)
- If the standard bearings fail to meet an L10 life of 25,000 hours in continuous operation or 16,000 hours at maximum axial and radial load and rated speed.
- If the product of the pump horsepower and speed in rpm is 2.7 million or greater.
A primer for magnetic bearings