VectoraLab Lab

Why Bearings Fail Bearings are the most common source of vibration-based failures in rotating machinery, accounting for ∼40-50% of machine faults. Main Failure Modes: • Fatigue spalling (most common) • Wear (abrasive, adhesive) • Corrosion / fretting • Plastic deformation • Lubrication failure • Misalignment and overload Vibration Analysis Techniques: 1. RMS Trending: overall energy increase 2. Kurtosis: early impact detection (K>4 investigate, K>6 urgent) 3. Envelope Analysis: identify specific fault frequency (BPFO/BPFI/BSF/FTF) 4. Spectral Analysis: track harmonics of fault frequencies Bearing Fault Frequencies: • BPFO = (Nb/2) × f × (1 - Bd/Pd × cosα) • BPFI = (Nb/2) × f × (1 + Bd/Pd × cosα) • BSF = (Pd/2Bd) × f × (1 - (Bd/Pd × cosα)²) • FTF = (f/2) × (1 - Bd/Pd × cosα) Fault Development Stages (ISO 13374): Stage 1: Ultrasonic frequencies elevated (kHz+) — earliest sign Stage 2: Fault frequencies appear in envelope spectrum Stage 3: Fault frequency harmonics grow, sidebands appear Stage 4: Broadband noise rises; fault frequencies may merge into noise Important: These techniques indicate possible bearing defects. Confirmed diagnosis requires correlation with multiple indicators, trend analysis, and engineering judgment. False positives occur.