Torsional Oscillation Analysis by

FUNCTIONS

Measuring, recording and analyzing torque variations.

Trend analysis of torque oscillations is a tool for preventive maintenance and corrective actions.

ANALYSING MODES

The measured values can be presented in three ways:

• Graph showing torque as a function of time
• Graph showing torque as a function of the rotational angle
• Torsional oscillation frequency spectrum

Analysis may be performed in real-time (on-line) or on recorded files of data: Advantage of analysing recorded data: View the same data in three different modes which may give additional information compared to single mode real-time analysis.

DATA LOGGING

May be performed for one shaft or for two shafts simultaneously

Continuous logging:

• Records the shaft continuously

Interval logging:

• Records the shaft for a short period at chosen intervals
• Ideal in order to study the performance changes over some time without generating too much data

Overload logging:

• Records the shaft when torque or power exceeds preset levels
• Data is kept in a buffer some time before discarded. This makes it possible to record data generated some seconds before the log-state occurred, as well as some time after the log-state is over

REAL WORLD EXAMPLE

The following image is from a ship with a 6 cylinder two stroke engine. The ship owner was suspicious that something was wrong with the engine, because of erratic performance. With TOA installed, the suspicion was confirmed. As you can see on the picture, one of the cylinders has a serious misfire.

Click on image to enlarge

Upper graph displays torque/time recordings. Lower graph displays the corresponding torque frequency spectrum (based on FFT analysis)

Click on image to enlarge

Torque as a function of the rotational angle. The image displays five consecutive shaft revolutions