Introduction:
To showcase VibScope’s capability in detecting and tracking unbalances, particularly in fan assemblies, we conducted tests by introducing unbalances to a controlled setup operating at a fixed RPM.
Configuration of FFT Automation: Anticipating a correlation between the running RPM (568 = 9.4 Hz) and the added weight, we established an automated FFT analysis with a search window from 5Hz to 15Hz. Following waveform acquisition, the analysis results are transmitted back. The calculated confidence factor reflects the relationship between the highest peak and other peaks in the search window. We expect a higher confidence factor with increased unbalance, as the amplitude at 1x running RPM should rise relative to other peaks.
Test Setup:
Our setup comprises an electrical motor controlled by a VFD, rotating a cylinder with threaded holes for weight installation. These weights, threaded with additional nuts, are attached to the cylinder. VibScope is mounted on the main bearing housing at the non-drive end.
Results in the App:
Using an iPhone with the IMBU Connect app, we acquired waveforms at a 1600Hz sample frequency, 2g scale, and 1200 samples. The immediate feedback from the server is depicted below. As expected, the confidence factor drops when weights are removed. Although the confidence factor slightly increases with the final step, it’s due to the highest peak dropping while other smaller peaks grow within the search window.
Results in the VibScope Web Portal:
In the web portal, we selected the four waveforms acquired during the four test runs. Test #4 showed the highest unbalance, while test #1 involved complete removal of the thread and nuts. Clear observation reveals that the amplitude at 9.4Hz consistently decreases with each weight removal.
Conclusion:
This test underscores VibScope’s user-friendliness for operations personnel to gauge readings on couplings and cooling fans for potential unbalance. Comparing readings over time is effortless, enabling trend analysis and stability assessment. VibScope emerges as an indispensable tool for proactive maintenance and performance optimization in various industrial applications.
