The balancing of rotating bodies is important to avoid vibration. The aim of rotor balancing is to achieve satisfactory running when installed on site. It means no more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. In heavy industrial machines such as gas turbines and electric generators, vibration can cause catastrophic failure, as well as noise and discomfort. For a system to be in complete balance both force and couple polygons should be close in order to prevent the effect of centrifugal force.