Accurate balancing is necessary to the operation, maintenance and repair of rotating machineries.
It has been known for a long time that misalignment and imbalance are the root cause of the majority of machine faults.
Whether turbines in a power plant, a fan, an electrical motor, there rotors needs to be balanced. Balancing of a rotor under normal operation condition can reduce the vibration amplitude and extend the life of machine components.

All balancing are done to International Standard, ISO 1940/1 ( Balance quality requirements of rigid rotors )

Imbalance in a rotor is the result of an uneven distribution of mass, which cause the rotor to vibrate. The vibration is produced by the interaction of an unbalanced mass component with the radial acceleration due to rotation, which together generate a centrifugal force. The vibration will be transmitted to the rotors bearing, and any points on the bearing will experience this force once per revolution.
Balancing is the process of attempting to improve the mass distribution of a rotor, so that it rotates in its bearings without uncompensated centrifugal forces.