WHY MEASURE TORSIONAL VIBRATION?
We measure torsional vibration to determine the amount of dynamic stress which the components of the system are being subjected to. If all components of a rotating system exhibited identical torsional vibration then there would be no significant additional stress on the components. In practice the dynamics of the various system components are different and as a result the instantaneous movements are not equal and in phase. Since the shaft must still connect the components rigidly it follows the shaft must be subjected to twisting. The twisting of the shaft creates stress in the shaft. If the stress is to high or repeated to many times the component will eventually fail by fatigue. Torsional vibration occurs with in the system and does not typically evidence itself in any external symptoms. It is not unusual for the first evidence of a torsional problem to be instantaneous catastrophic failure of the system shaft. HOW TO MEASURE TORSIONAL VIBRATION ? There are two common methods of meas