Spectral analysis is an essential tool for evaluating the dynamic behavior of rotating components under extreme conditions. In spin testing, where rotors are subjected to high speeds and extreme temperatures, subtle changes in vibration signatures can reveal emerging mechanical faults before they lead to failure.
At Barbour Stockwell, Inc., we incorporate Fast Fourier Transform (FFT)-based spectral analysis into our spin testing services to extract meaningful frequency-domain insights from complex vibration data. Our spin testing systems, which achieve rotational speeds up to 250,000 RPM and temperatures ranging from cryogenic to 1100 °C, are equipped with spectral monitoring tools that allow us to detect faults early on.
What FFT Reveals About Vibration
Fast Fourier Transform (FFT) is a mathematical algorithm used to convert vibration signals from the time domain to the frequency domain. Rather than viewing how a signal changes over time, FFT shows what frequencies are present and with what intensity, which is crucial information when assessing rotor dynamics.
Named after French mathematician Joseph Fourier, this technique allows engineers to identify specific vibration patterns that correlate with faults like imbalance, misalignment, gear mesh issues, and bearing defects.
Spectral data can be gathered from various sensors integrated into our spin test systems, such as:
- Accelerometers
- Velocimeters
- Non-contact proximity sensors
- Displacement Sensors
- Strain gauges
- Microphones
Barbour Stockwell’s Spin IV spectral analysis module expands our testing capabilities by offering real-time monitoring, display, and recording of spectral data across four analog input channels (-10V to +10V). This tool allows operators to zoom in on specific frequencies to isolate fault frequencies, and capture snapshots for later review. Spectral analysis allows us to set fault thresholds as a function of frequency.
When to Employ Spectral Analysis
In spin testing, the ability to discern frequencies allows for higher trip levels to be set for low energy sub-synchronous vibration thereby eliminating unnecessary shutdowns. Beyond that, the employment of Spectral analysis is also very useful for monitoring the health of rotating machinery; whether components of BSi’s drive systems or other high speed machinery.
Spectral tools can be employed for:
- Variable Speed Machinery. Traditional tools may miss changes that occur with speed or RPM variation. Spectral tools track frequency shifts and correlate them with speed.
- Diagnosing Harmonics, Sidebands, and Resonance. Patterns in the frequency spectrum often indicate issues with bearings or gears that you can’t see in time-domain data.
- Early Fault Detection. Small issues often appear first in the frequency domain long before failure occurs.
- Rotating Equipment with Multiple Components. When there are multiple vibration sources (i.e., shafts, motors, gears), spectral tools can isolate and identify each source based on its frequency.
Spectral tools also offer the added benefit of being able to produce waterfall plots, which are graphs that stack frequency spectra over time or speed. This provides the insight required to determine whether the resonance is that of the rotor or the stator of the machine.
Spectral Analysis Solutions from Barbour Stockwell
Spectral analysis plays an important role in rotor testing. It offers engineers a stronger understanding of how rotating components perform under demanding conditions and allows for earlier identification of faults. Our expertise in spin testing, combined with advanced spectral analysis tools, allows us to gain a better understanding of the source of high vibration levels and facilitate measures to mitigate the problem.
For more information about our spectral analysis capabilities, or to get started on your next project, request a quote today.