Rotor will create vibration due to lots of reasons during running rotation. Any arbitrary unbalanced amount act a force on these while rotating lead machine vibration. Therefore, we need add additional counteracting weight at the corresponding point where is detected by dynamic balancing equipment.

 

However, different rotor use different balancing machine in point detection. We category rotors into two divisions, rigid rotor and flexible rotor. While according to ISO standards, rigid rotors’ running speed is generally under critical speed. The rigid rotor is defined more precisely as "the balance can be corrected at any speed of one, or any of the selected two correction planes at any speed below the rotor operating speed. After correction, at the maximum operating speed and below the operating speed any speed and close to the actual working conditions, the unbalance does not significantly exceed the specified balance requirements”. Except this category, other rotors are classified as flexible rotors. Flexible rotor balancing is significantly more complex than rigid rotor balancing. The flexible rotor continually changes its elastic configuration as more critical speeds are encountered, and additional balance planes may be required.