Vibration Analysis: The FFT spectrum is the core diagnostic tool (Source: Tractian); Golden Rule: 1x = Unbalance, 2x = Misalignment (Source: Tractian); Core Concept: Fault characteristic frequencies (Source: iFactory)—Note: Sampling rate ≥ 2x the highest frequency (Source: Industrial).
I.
FFT Spectrum
FFT: Fast Fourier Transform (Time Domain → Frequency Domain) (Source: PLC IO); Spectral Lines: Each peak = one vibration source (Source: PLC IO); X-axis: Frequency; Y-axis: Amplitude (Source: STEM); Diagnosis: Peak location identifies the fault (Source: Tractian)—FFT: Spectral localization (core method).
II.
Characteristic Frequencies
1x: Rotational frequency = Unbalance (Source: Tractian); 2x: = Misalignment (Source: Tractian); BPFI/BPFO: Bearing raceway defects (Source: iFactory); BSF/FTF: Rolling element/Cage (Source: iFactory); GMF: Gear Mesh Frequency (Source: iFactory)—Characteristics: 1x/2x/BPFO/GMF (Fault fingerprints).
III. Sensor Selection
Accelerometer: Most common, wide-bandwidth, and durable (Source: STEM); Type: Piezoelectric/MEMS (Source: STEM); Sensitivity: mV/g (Source: STEM); Mounting: Stud-mount offers the best frequency response (Source: STEM); Low Speed: Use velocity/displacement probes for low speeds (Source: STEM)—Sensor: Accelerometer + stud-mount (mounting is critical).
IV.
Measurement Selection
Acceleration: g (high frequency) + bearing envelope (Source: Engineering); Velocity: mm/s RMS per ISO 10816 (Source: Engineering); Displacement: µm peak-to-peak (low frequency, shaft-relative) (Source: Engineering); Envelope: Demodulation of high-frequency impacts (Source: F7i); Ultrasonic: Heterodyning down to audible range (Source: F7i)—Measurement: High-frequency acceleration + ISO velocity (dual-track).
V.
Sampling Requirements
Nyquist: Sampling rate ≥ 2× maximum frequency (Source: Industrial); Example: 5 kHz analysis requires 10 kS/s (Source: Industrial); Data Volume: 12 seconds @ 10 kS/s = 120,000 points (Source: Industrial); Baseline: Spectrum capture at normal speed and load (Source: Cryotos); Operating Conditions: Record speed, load, and temperature (Source: Cryotos)—Sampling: 2× frequency (for valid data).
VI. Diagnostic Process
Time Domain: Check raw waveforms for impacts (Source: Cryotos); Frequency Spectrum: Use FFT to identify characteristic peaks (Source: Cryotos); Phase: Analyze coupled systems to pinpoint the source (Source: Dynamox); Trend: Monitor amplitude growth (Source: PLC IO); CMMS: Establish baselines in the asset database (Source: Cryotos)—Process: Time Domain + Spectrum + Trend (Three-step diagnosis).
VII.
Procurement Recommendations
First, select sensors (accelerometers); second, measure quantitatively (velocity/ISO standards); third, configure sampling (2× frequency); fourth, establish baselines (asset database);
fifth, incorporate phase analysis (coupling/source identification)—Vibration Analysis: Spectrum + Sensors + Baseline (Three-element closed loop).
