A predictive maintenance department at a chemical customer in Antwerp was alarmed by high overall values on their Wi-care system, installed on a titanium exhaust fan on their production units.
The measurement history and trend data did not show anything in particular. Amplitudes did vary a lot over time as you can see in the plot on the right.
The imbalance value of the fan was low and acceptable. At moments when the overall value was high, a 35 Hz component was showing up in the spectrum with amplitudes over 10 mm/sec.
Sometimes, the amplitudes were above 20 mm/sec and absolutely not acceptable. A transient measurement with AMS 2140 showed a 35 Hz component with unstable amplitude, being most of the time higher than 10 mm/s RMS and dropping to less than 2 mm/s RMS every once in a while. Unfortunately most route measurements were taken during that low amplitude phase.
The transient waveform shows clearly the amplitude variation. And we can see in the waterfall that the dominant frequency is 35 Hz.
After adding stiffness to the structure, the fan was less sensitive to the 35 Hz component and it has been working now with low vibration levels. The Wi-care system caught the fan more often red
handed with double digit amplitudes and triggered the maintenance department to take some actions:
frame and machine setup were modified in order to get rid of the 35 Hz phenomenon. The following trend shows the overall values after the modifications made to the fan. The level remained below 3 mm/sec RMS and constant.
This is just one of the multiple examples where Wi-care can be a succesful babysitting tool.