Pendulum Effect

The “Pendulum Effect” created by inherently imbalanced, heavy, cast metallic impellers, which are not only hydraulically and mechanically Imbalanced, but often corrode, erode, and cavitate. The imbalance of the metallic impellers (both Hydraulic and Mechanical) in combination with the reduction of bearing supports in metallic pumps being cast overseas today creates a tremendous problem knows as the Pendulum Effect!

Whether the pump is Horizontal, or Vertical, the heavy weight and inherent imbalance of the cast metallic impellers sets up a condition for premature pump failure. Like the Pendulum on a clock, the heavy impeller acts like a weight at the end of the shaft and starts to wobble, or deflect. Any Corrosion, Erosion, or Cavitation increases the Pendulum Effect Problem! The motor bearings cannot hold the stresses that are set up by the Pendulum Effect and the Mechanical Seals, Sleeves, Bushings, Motor Bearings, and Motor fail prematurely. In extreme cases even the shaft break.

This Pendulum Effect is exacerbated by the Hydraulic and Mechanical Imbalance of the impeller. To reduce costs, the impellers are often cast with differences in the vane channels, which causes Hydraulic Imbalance.