Vibration Analysis Of Vertical Pumps.

Abstract

Vibration field data was measured on several large motor-driven vertical cooling water pumps which experienced excessive wear of the impellers, wear rings and seals after a short period of operation. The data indicated that the problem was due to the operating speed being near the pump-motor system mechanical natural frequency, which resulted in excessive vibration levels on the motors and pump impellers. The mechanical natural frequency was very sensitive to the effective stiffness of the connections between the concrete, baseplates, pump base and motor flange. Tests were conducted to evaluate the advantages and disadvantages of lowering the natural frequency below the running speed and raising the natural frequency above the running speed. The results of these tests are presented with conclusions and recommendations.