Vibration Analysis: Complete Guide for Predictive Maintenance

Meta Description: Learn vibration analysis for condition monitoring and predictive maintenance. Discover techniques, equipment, and interpretation skills.

---

Introduction

Vibration analysis is one of the most effective condition monitoring technologies for rotating equipment. It detects developing faults early, allowing planned intervention before catastrophic failure.

Why Vibration Analysis?

┌─────────────────────────────────────────────────────────────────┐
│              Vibration Analysis Value                            │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  EARLY FAULT DETECTION                                          │
│  • Detects bearing faults months before failure                 │
│  • Identifies misalignment and unbalance                        │
│  • Finds gear wear, looseness, resonance                         │
│                                                                 │
│  BENEFITS:                                                      │
│  • Prevents catastrophic failure                                 │
│  • Plans maintenance during downtime                             │
│  • Extends equipment life                                       │
│  • Reduces maintenance costs                                    │
│  • Improves reliability                                         │
│                                                                 │
│  TYPICAL ROI:                                                   │
│  • 30-50% reduction in maintenance costs                        │
│  • 50-70% reduction in unplanned downtime                       │
│  • 20-40% extension in equipment life                           │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Vibration Fundamentals

What Is Vibration?

Vibration is the oscillation of an object about its reference position. In machinery, it's caused by rotating and reciprocating forces.

VIBRATION PARAMETERS:
• Displacement: Total distance traveled (mils)
• Velocity: Speed of oscillation (in/sec)
• Acceleration: Rate of change of velocity (g's)

FREQUENCY RANGES:
│ Parameter │ Frequency Range │ Application          │
│──────────│─────────────────│───────────────────────│
│ Displacement│ 0-600 Hz      │ Low speed, general     │
│ Velocity  │ 600-60,000 Hz   │ Most rotating equipment│
│ Acceleration│ 60,000+ Hz    │ High frequency, bearings│

Common Machinery Faults

Fault Detection

Vibration Measurement Equipment

Hardware Types

PORTABLE DATA COLLECTORS:
• Handheld devices
• Route-based collection
• Single or multi-channel
• Download to PC for analysis
• Best for periodic monitoring

ONLINE SYSTEMS:
• Permanent sensors
• Continuous monitoring
• Alarms and alerts
• Integration with DCS/PLC
• Best for critical equipment

WIRELESS SENSORS:
• Easy installation
• Battery powered
• Cloud connectivity
• Lower cost
• Emerging technology

Measurement Points

Where to Measure

STANDARD MEASUREMENT LOCATIONS:
• Bearing housings (radial and axial)
• Motor bearings (DE and NDE)
• Pump/fan/compressor bearings
• Gearbox bearings

MEASUREMENT AXES:
• Horizontal: Most common for detecting unbalance
• Vertical: Foundation and stiffness issues
• Axial: Misalignment, thrust bearing problems

SENSOR MOUNTING:
• Stud mounting for permanent measurements
• Magnet mounting for portable measurements
• Consistent location critical for trending

Data Analysis

Time Waveform vs. Spectrum

TIME WAVEFORM:
• Amplitude vs. time
• Shows transient events
• Identifies impacts
• Reveals waveform shape

SPECTRUM (FFT):
• Amplitude vs. frequency
• Identifies frequency components
• Shows fault frequencies
• Primary analysis tool

BOTH REQUIRED for complete analysis

Alarm Levels

Setting Limits

TYPICAL ALARM STRUCTURE:

General Machinery (Below 3600 RPM):
• Alert: 0.3 in/sec velocity
• Alarm: 0.5 in/sec velocity
• Danger: 0.8 in/sec velocity

Small Motors (above 3600 RPM):
• Alert: 0.2 in/sec velocity
• Alarm: 0.35 in/sec velocity
• Danger: 0.5 in/sec velocity

ISO 10816 Standards:
Zone A: Good (0.11 in/sec)
Zone B: Satisfactory (0.28 in/sec)
Zone C: Unsatisfactory (0.71 in/sec)
Zone D: Unacceptable (above 0.71)

CUSTOMIZATION:
Set alarms based on:
• Equipment type
• Operating speed
• Industry standards
• Historical data
• Manufacturer recommendations

Bearing Fault Frequencies

Calculations

Bearing Fault Frequencies are based on bearing geometry:

FTF = f/2 × (1 - d/D × cos(α))
BPFI = n/2 × f × (1 + d/D × cos(α))
BPFO = n/2 × f × (1 - d/D × cos(α))
BSF = D/2d × f × (1 - (d/D × cos(α))²)

Where:
f = RPM/60
d = Rolling element diameter
D = Pitch diameter
α = Contact angle
n = Number of balls/rollers

Many software programs automatically calculate these frequencies
from bearing numbers.

Analysis Process

Step-by-Step Approach

1. COLLECT DATA
   • Measure at defined points
   • Use consistent technique
   • Record all parameters
   • Note operating conditions

2. REVIEW OVERALL LEVELS
   • Compare to alarms
   • Check for changes from baseline
   • Note any exceedances

3. ANALYZE SPECTRUM
   • Identify frequency peaks
   • Match to fault frequencies
   • Note harmonics and sidebands

4. ANALYZE WAVEFORM
   • Look for impacts
   • Check for truncation
   • Identify modulation

5. IDENTIFY FAULTS
   • Match patterns to known faults
   • Determine severity
   • Estimate time to failure

6. RECOMMEND ACTION
   • Schedule maintenance
   • Plan repairs
   • Recommend additional monitoring

Severity Assessment

How Bad Is It?

BEARING CONDITION (High Frequency Analysis):
EARLY STAGE:
• Slight increase in high frequency
• No harmonics
• Low amplitude

MODERATE STAGE:
• Clear bearing frequency peaks
• Harmonics present
• Increasing amplitude

LATE STAGE:
• High amplitude at bearing frequencies
• Harmonics and sidebands
• Raised noise floor
• Changes in waveform

SEVERE:
• Very high amplitude
• Bearing frequency dominant
• Significant harmonics
• Imminent failure

ESTIMATED TIME TO FAILURE:
• Early stage: 6-12 months
• Moderate: 3-6 months
• Late: 1-3 months
• Severe: Days to weeks

Best Practices

Data Collection

COLLECTION GUIDELINES:
☐ Same location each time
☐ Same measurement parameters
☐ Consistent operating conditions
☐ Same sensor type
☐ Calibrated equipment
☐ Trained analysts

FREQUENCY:
• Critical: Monthly
• Important: Quarterly
• General: Semi-annual

ROUTES:
• Organize by location
• Plan efficient route
• Allow adequate time
• Include safety considerations

Common Mistakes

Training Requirements

Skill Levels

LEVEL I - BASIC:
• Understanding vibration fundamentals
• Equipment operation
• Data collection
• Basic alarm recognition
• Trending

LEVEL II - INTERMEDIATE:
• Spectrum analysis
• Fault identification
• Severity assessment
• Advanced measurement techniques
• Report writing

LEVEL III - ADVANCED:
• Detailed fault analysis
• Resonance identification
• Phase analysis
• Balancing
• Modal analysis
• Program management

CERTIFICATION:
• ISO 18436-2: Vibration Analyst
• ASNT: Vibration and Analysis
• Vibration Institute Certification

Integration with Maintenance

Actionable Information

ALERT RESPONSE PROCESS:
1. Alarm triggered
2. Verify measurement (retest)
3. Confirm trend (look at history)
4. Assess severity
5. Schedule inspection/repair
6. Document findings
7. Monitor after repair

INTEGRATION WITH CMMS:
• Equipment registry linked
• Work orders generated
• Results stored
• History tracked
• Reports generated

ROI Example

Financial Justification

Before Vibration Analysis:
• Bearing failure every 18 months
• Emergency repair cost: $20,000
• Production loss: $40,000
• Total every 18 months: $60,000
• Annualized: $40,000

After Vibration Analysis:
• Annual monitoring: $5,000
• Planned bearing replacement: $8,000
• Production during planned downtime: $0
• Total annual: $13,000

Annual Savings: $27,000
ROI: 208%
Payback: <6 months

Conclusion

Vibration analysis is a powerful tool for early fault detection and predictive maintenance. Success requires trained analysts, consistent data collection, and integration with maintenance processes.

Ready to implement vibration analysis? Contact us for assessment and implementation support.

---

Related Topics: Condition Monitoring, Predictive Maintenance, Bearing Analysis