Overhung fan balancing

The characteristic vibration of overhung fan is shown in figure 1.

Figure 1. Overhung Fan

Bearing B vibration is related with plane C and bearing A vibration is related with plane D.

Step for onsite balancing for overhung fan are as below:

1. Connect accelerometer in bearing A and perform single plane balancing on plane D or put your accelerometer on bearing B and perform single plane balancing on plane C. See vibration correlation between bearing and plane in figure 1.

2. If the vibration level on bearing A (if you choose bearing A on the first step) are acceptable, move your accelerometer to bearing B and measure vibration.

3. If the vibration on bearing B is not acceptable, then put weight on plane D that equal with trial weight in plane C but 180^o apart.

4. Perform static balancing on plane D till vibration is acceptable. Sometime it’s may needed to put equal trial weight on plane C on 180^o opposite when you put trial weight on plane D.