How to Prevent Failures due to Shaft Damage

On the subject of impellers, the second common issue for a damaged shaft can be caused by and imbalanced impeller or rotor. An unbalanced shaft can lead to major issues for a shaft, in what’s known as “shaft whip”: “An unbalanced impeller will create ‘shaft whip’ while in operation. The effect is the same as if the shaft was bent and/or deflected, even though the shaft would measure straight if you stopped the pump and checked the shaft…The number of bending cycles in a given time frame is reduced, but the amplitude (strain) of displacement (due to the imbalance) remains in the same range as the higher-speed factors”3 In short, an imbalanced impeller can lead to deformation of a shaft, which will lead to lesser efficiency of the pump, as well as a need for a new shaft. Besides improper installation of an impeller, an improperly installed packing seal can also badly damage a shaft (see image). The best way to prevent impeller imbalances, simply, is to properly install the impeller and to also take into account any manufacturer specifications otherwise.