Vibration Analysis Troubleshooting

Applied Diagnostics Ltd - Precision with Pride

We use a range of specialist vibration monitoring techniques to trouble shoot and assess the condition of large rotational machines, such as steam turbines.

Some of the testing procedures we offer include: -

Resonance Assessment

The collection of cascade frequency data during run up or coast down allows rotor and casing critical resonant frequencies to be determined:

Fig. 1 Cascade Frequency Graph (click to enlarge)


Resonance Assessment

Rotor and casing critical resonant frequencies can also be determined/clarified by monitoring the Peak Vibration and Phase Angle during machine coast down:

Figs. 2a & 2b Peak Vibration & Phase Angle Graphs (click to enlarge)

*   *

Orbital Plots

A majority of large machines with sleeve bearings have X & Y axis displacement probes fitted. These usually terminate in a monitoring system which protects the machine when vibration levels become undesirable. By collecting simultaneous data from the probes orbital plots can be collected, allowing analysis of imbalances, oil whirl and other dynamic rotor problems:

Figs. 3a & 3b Orbital Plots (click to enlarge)

*   *

Transient Waveform Analysis

This allows collection of vibration data over a larger process cycle time. Normal vibration data only collects 2 to 8 seconds of this data so spurious impacts can easily be missed:

Fig. 4 Transient Waveform Analysis Graph (click to enlarge)


Phase Analysis

This allows our engineers to measure the phase angle of a vibration, by comparing readings in different planes and from different bearings. This data is used to confirm problems such as imbalance and shaft-to-shaft misalignments. It also gives invaluable information into understanding the relationship of movement across large rotors, for example a turbine rotor.