Vibration analysis diagnostic chart - master machinery fault diagnosis

Complete reference guide for bearing defects, misalignment, unbalance & more

Comprehensive diagnostic chart covering spectral characteristics, waveform symptoms, and frequency calculations for all major rotating machinery failure modes. Your essential reference for accurate vibration analysis.

Low Severity
Medium Severity
High Severity
Critical Severity

Transform complex diagnostic procedures into a streamlined reference system that covers every major failure mode you'll encounter. This comprehensive guide consolidates spectral characteristics, waveform symptoms, and frequency calculations for unbalance, misalignment, bearing defects , looseness, gear issues, belt problems, rotor bow/rub, and electrical faults — all in one accessible format. No more flipping through multiple references or relying on memory during critical diagnostics, plus get proven analysis tips that enhance your diagnostic accuracy. Access your complete diagnostic reference toolkit and elevate your vibration analysis capabilities.

Unbalance

Medium

Spectral Characteristics

Frequency:

1× RPM dominant

Direction:

Radial vibration

Phase:

Consistent across similar points

Harmonics:

Minimal higher harmonics

Waveform Symptoms

  •  Sinusoidal waveform at 1× RPM
  •  Amplitude increases with speed
  •  Phase relationship maintained
  •  Smooth, repeatable pattern
Hands-on Analysis

Misalignment

High

Spectral Characteristics

Frequency:

1×, 2×, 3× RPM

Direction:

Radial & axial vibration

Phase:

180° out of phase

Harmonics:

Strong 2× and 3× harmonics

Waveform Symptoms

  •  High axial vibration (parallel misalignment)
  •  High radial vibration (angular misalignment)
  •  Clipped or distorted waveform
  •  Strong directional characteristics
Hands-on Analysis

Bearing Defects

Critical

Spectral Characteristics

Frequency:

BPFO, BPFI, BSF, FTF

Direction:

Radial, often random

Phase:

Non-coherent, random

Harmonics:

Multiple harmonics of defect frequencies

Waveform Symptoms

  •  Impulsive time waveform
  •  High crest factor (>4)
  •  Amplitude modulation
  •  Noise floor elevation
Hands-on Analysis

Looseness

High

Spectral Characteristics

Frequency:

1×, 2×, 3× RPM (broad)

Direction:

Multiple directions

Phase:

Unstable, varies

Harmonics:

Many harmonics, broad peaks

Waveform Symptoms

  •  Erratic, noisy waveform
  •  Unstable amplitude
  •  Broadband energy
  •  Non-linear behavior
Hands-on Analysis

Gear Defects

High

Spectral Characteristics

Frequency:

GMF ± sidebands

Direction:

Radial, perpendicular to mesh

Phase:

Consistent at GMF

Harmonics:

GMF harmonics with sidebands

Waveform Symptoms

  •  Amplitude modulation at GMF
  •  Impulsive components (tooth damage)
  •  Hunting tooth frequency patterns
  •  Load-dependent variations
Hands-on Analysis

Belt Defects

Medium

Spectral Characteristics

Frequency:

Belt pass frequency

Direction:

Radial, perpendicular to belt

Phase:

Consistent across pulleys

Harmonics:

Multiple harmonics of BPF

Waveform Symptoms

  •  Periodic impulsive pattern
  •  Beat frequency (multiple belts)
  •  Amplitude modulation
  •  Speed-dependent variations
Hands-on Analysis

Rotor Bow/Rub

Critical

Spectral Characteristics

Frequency:

1× RPM, fractional harmonics

Direction:

Radial, directional

Phase:

Varies with temperature

Harmonics:

Sub-synchronous components

Waveform Symptoms

  •  Temperature-dependent amplitude
  •  Directional sensitivity
  •  Thermal bow characteristics
  •  Speed-dependent behavior
Hands-on Analysis

Electrical Issues

Medium

Spectral Characteristics

Frequency:

2× line frequency

Direction:

Radial, all directions

Phase:

Consistent electrical sync

Harmonics:

Pole pass frequency sidebands

Waveform Symptoms

  •  120 Hz component (60 Hz power)
  •  Air gap variations
  •  Slip frequency components
  •  Load-dependent characteristics
Hands-on Analysis

Key Frequency Calculations

Bearing Frequencies
BPFO = (n/2) × (1 - d/D × cos φ) × RPM
BPFI = (n/2) × (1 + d/D × cos φ) × RPM
BSF = (D/2d) × (1 - (d/D × cos φ)²) × RPM
FTF = (1/2) × (1 - d/D × cos φ) × RPM

Where: n = number of balls, d = ball diameter, D = pitch diameter, φ = contact angle

Gear Frequencies
GMF = Number of teeth × RPM
Hunting Tooth = RPM / LCM(teeth₁, teeth₂)

Sidebands: GMF ± 1×, 2×, 3× shaft frequency indicate gear problems

Belt Frequencies
BPF = RPM × (π × D) / Belt Length

Where: D = pulley diameter, multiple belts create beat frequencies

Electrical Frequencies
Line Frequency = 2 × Power Frequency
Pole Pass = (Number of poles / 2) × RPM

Common: 120 Hz for 60 Hz power systems, 100 Hz for 50 Hz systems

Analysis Tips & Best Practices


  • Always compare trends over time - single measurements can be misleading
  • Consider operating conditions: load, temperature, speed variations
  • Use phase analysis to distinguish between different fault types
  • Crest factor >4 typically indicates impact-type defects (bearings, gears)
  • Amplitude modulation often indicates looseness or coupling issues
  • Sub-synchronous components may indicate oil whirl or rub conditions
  • Always correlate vibration data with other parameters (temperature, current, etc.)
  • Consider machine geometry and mounting when interpreting directional data