Understanding Baseline in Vibration Analysis

Devices

Portable balancer & Vibration analyzer Balanset-1A

Parts

Optical Sensor (Laser Tachometer)

Complete vibration diagnostics and balancing kit from Vibromera, including four vibration sensors with cables, a signal interface module, laser tachometer with magnetic stand, digital scale, USB cable, and a carrying case. The system is designed for field rotor balancing and condition monitoring on industrial equipment.

Devices

Dynamic balancer “Balanset-1A” OEM

Definition: What is Baseline?

Baseline (also called baseline data or reference signature) is the initial set of vibration measurements recorded when equipment is new, freshly commissioned, or in known good operating condition. This reference data serves as the standard for comparison in all future measurements, enabling detection of changes that indicate developing faults. The baseline typically includes overall vibration levels, frequency spectra, time waveforms, and phase information at all measurement locations and directions.

Establishing accurate baseline data is the foundation of effective predictive maintenance programs because it provides the “fingerprint” of healthy equipment operation. Without a proper baseline, trending analysis loses its reference point, making it difficult to determine whether current vibration levels represent normal operation or deteriorating condition.

Importance of Baseline Data

Enables Change Detection

Current measurements compared to baseline
Changes indicate developing problems
Small deviations detected early (before severe)
Quantifies severity (% increase from baseline)

Establishes Normal Operating Characteristics

Documents what “good” looks like for this specific machine
Accounts for design characteristics (some machines inherently higher vibration)
Sets realistic expectations
Differentiates normal from abnormal

Provides Alarm Limits Reference

Alarm levels often set as multiples of baseline (2×, 3×, 4× baseline)
Machine-specific rather than generic limits
More sensitive to equipment-specific changes
Reduces false alarms

Enables Meaningful Trending

Plot current data vs. baseline over time
Shows rate of change
Predicts when intervention needed
Validates effectiveness of corrective actions

When to Establish Baseline

Ideal Times

New Equipment Commissioning: After installation, alignment, and initial run-in (best time)
After Major Overhaul: Following rebuild, rewind, or bearing replacement
After Balancing: Once vibration reduced to acceptable levels
After Known-Good Condition Verified: When equipment confirmed operating correctly

Acceptable Times

Program Startup: When initiating condition monitoring (use current state if equipment functional)
After Minor Maintenance: Following routine maintenance that doesn’t affect major components
Fleet Baseline: Average of multiple identical units in good condition

Poor Times (Avoid if Possible)

When equipment has known problems
During abnormal operating conditions
When trending shows increasing vibration
Immediately after startup before thermal stabilization

What to Include in Baseline

Vibration Parameters

Overall Levels: RMS velocity, peak, or acceleration at each measurement point
Frequency Spectra: FFT showing all frequency components
Time Waveforms: Raw vibration signal over time
Phase Measurements: Phase angles at dominant frequencies
Multiple Directions: Horizontal, vertical, axial at each bearing

Operating Conditions

Speed: Actual RPM during measurement
Load: Operating load or output
Temperature: Bearing and process temperatures
Pressure/Flow: Process parameters for pumps, fans, compressors
Environmental: Ambient temperature, humidity if relevant

Equipment Information

Equipment ID, location, description
Date of baseline measurement
Measurement locations and sensor types
Instrument settings (frequency range, resolution, averaging)
Any special notes or observations

Baseline Data Quality Requirements

Measurement Conditions

Thermal Equilibrium: Equipment at operating temperature
Steady-State: Stable operating conditions (not transient)
Representative: Normal operating point, not startup or shutdown
Repeatable: Conditions that can be duplicated in future measurements

Data Quality

Multiple Measurements: Take 3-5 measurements, average or verify consistency
Adequate Resolution: Sufficient to identify important frequency components
Full Frequency Range: Capture all relevant frequencies (DC to >10kHz for bearing defects)
Low Noise: Good signal-to-noise ratio

Using Baseline for Comparison

Numerical Comparison

Calculate percent change: [(Current – Baseline) / Baseline] × 100
Typical alarm criteria: +50% change, +100% change, +200% change
Different thresholds for different parameters

Spectral Comparison

Overlay current spectrum on baseline spectrum
Look for new peaks (new faults)
Look for amplitude increases in existing peaks
Identify changed frequency components

Waveform Comparison

Compare time waveform shapes
Detect changes in periodicity, impacting, clipping
More subjective but reveals character changes

Baseline Updates and Maintenance

When to Update Baseline

After Major Repairs: New baseline after overhaul, rebalance, alignment
Equipment Modifications: Changes to machine configuration
Operating Condition Changes: Permanent change in speed, load, or process
Improved Condition: After successful vibration reduction

When NOT to Update

After vibration has increased (losing trending history)
During abnormal conditions
After minor maintenance not affecting vibration characteristics
Just because time has passed (baseline should be stable reference)

Baseline Version Control

Archive old baselines (don’t overwrite)
Document reason for baseline change
Date and identify each baseline version
Maintain historical record

Fleet and Generic Baselines

Fleet Baseline

For facilities with multiple identical units:

Average baseline from several units in good condition
Represents typical healthy machine signature
Useful for new units or after repairs
Still establish individual baselines over time

Generic Industry Baselines

Typical vibration levels for machine types
From standards (ISO 20816) or industry experience
Less specific but better than nothing
Use only when machine-specific baseline unavailable

Common Baseline Mistakes

Mistakes to Avoid

No Baseline: Starting monitoring without establishing reference
Poor Quality Baseline: Taken during abnormal conditions or with poor technique
Single Measurement: Not verifying repeatability
Inadequate Documentation: Not recording conditions and settings
Baseline When Faulty: Establishing baseline when fault already present
Frequent Updates: Changing baseline too often, losing trending history

Best Practices

Baseline Establishment

Comprehensive measurements at all points and directions
Multiple measurements to verify repeatability
Complete documentation of conditions
Store spectra, waveforms, not just overall levels
Photograph measurement locations

Baseline Management

Centralized database for all baseline data
Version control and change documentation
Regular review and validation
Archive historical baselines
Train personnel on baseline importance and proper use

Baseline data is the cornerstone of effective vibration monitoring and predictive maintenance programs. Establishing high-quality baseline measurements when equipment is in good condition, properly documenting all associated information, and maintaining baseline integrity while updating appropriately after major changes enables meaningful trending analysis and early fault detection that maximizes equipment reliability and optimizes maintenance interventions.

← Back to Main Index

What is Baseline in Vibration Analysis? Reference Data

Published by admin on October 31, 2025 October 31, 2025