Torsional Vibrations

Monitoring of Torsional Vibrations can be a very successful way to detect problems in drive systems and gearboxes such as bearing faliure.

Using an IME encoder, it is possible from a single device to track bearing run out and torsional vibrations. In the case of a transmission or gearbox, devices integrated to input and output shafts facilitate a detailed analysis that can show bearing failure, gear wear degradation, oil contamination, shaft imbalance, bearing rub and mechanical failure. The torsional vibration data sampling is intrinsically locked to the rotation and is ideal for phase analysis. Further enhancement can be achieved using additional units.  Magnetic based sensors can now be used in hostile environments inside gearboxes or internal combustion engines and turbines.

Example – Torsional Vibrations on 100mm heavily  loaded transmission shaft
A peak is observed at  ~150 cycles per rev-  but  only at high torque
Torsional Vibrations on 100mm heavily  loaded transmission shaft

Vertical and horizontal displacement shows a peak at the same frequency (~150 cycles per revolution)
Yellow vertical axis, cyan horizontal axis.
Vertical and horizontal displacement shows a peak at the same frequency

Orbit plot of this peak shows that it is always from the same direction

Orbit plot of this peak shows that it is always from the same direction

A series of phase plots of the above peak data (at ~ 150 cycles per rev) in torsional, vertical and horizontal modes.

A series of phase plots of the above peak data

This demonstrates that all aspects at this frequency are not phase locked to the speed of rotation (rotationally asynchronous vibration).

In addition this peak has a fixed frequency in Hertz. Unlike other features which are tied to the rpm