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Professional Balancing Equipment & Calculators

Calculation Parameters

ISO 1940 - Maximum permissible shaft vibration displacement

Metric System Imperial System

Calculation Results

Permissible Vibration Displacement: —

Corresponding Velocity: —

Maximum Bearing Clearance: —

Frequency: —

Displacement Severity Assessment:

Good: Less than 30% of calculated value

Acceptable: 30-70% of calculated value

Marginal: 70-100% of calculated value

Unacceptable: Above calculated value

How the Calculator Works

Vibration Displacement and Balance Quality

Vibration displacement is directly related to the balance quality grade through the formula:

S = (G × 1000) / (2πf)

where:

S — vibration displacement (μm peak-to-peak)
G — balance quality grade (mm/s)
f — rotation frequency (Hz)

Relationship Between Displacement, Velocity, and Acceleration

For sinusoidal vibration:

Velocity: v = 2πf × S
Acceleration: a = (2πf)² × S

Bearing Clearance Classes

Bearing clearances affect permissible displacement:

C2: Used for high precision applications
CN: Normal clearance for general applications
C3: Used when operating temperature is higher
C4/C5: For high temperature or heavy load applications

Measurement Types

Peak-to-Peak: Total displacement range (most common)
Peak: Maximum displacement from center position
RMS: Root mean square value (0.707 × peak for sine wave)

Application Guidelines

Lower speeds generally allow higher displacement values
Displacement measurement is most effective below 1000 RPM
Above 1000 RPM, velocity measurements are preferred
Above 10,000 RPM, acceleration measurements are recommended

Critical Considerations

Ensure probe is properly calibrated and positioned
Account for thermal growth when setting cold clearances
Consider shaft surface condition for eddy current probes
Monitor trends rather than absolute values for best results

Usage Examples & Value Selection Guide

Example 1: Large Slow-Speed Motor

Scenario: 500 kW motor driving a mill at low speed

Speed: 300 RPM
Balance Quality: G 6.3 (process machinery)
Shaft Diameter: 200 mm
Bearing Clearance: CN (normal)
Measurement: Peak-to-Peak
Result: S_max ≈ 126 μm p-p
Good condition: < 40 μm p-p

Example 2: Precision Spindle

Scenario: Machine tool spindle for precision grinding

Speed: 6000 RPM
Balance Quality: G 0.4 (precision)
Shaft Diameter: 60 mm
Bearing Clearance: C2 (small)
Measurement: Peak-to-Peak
Result: S_max ≈ 1.3 μm p-p
Critical: Requires precision measurement

Example 3: Turbine Generator Shaft

Scenario: Steam turbine with proximity probes

Speed: 3600 RPM
Balance Quality: G 2.5 (turbines)
Shaft Diameter: 400 mm
Bearing Clearance: C3 (hot running)
Measurement: Peak-to-Peak
Result: S_max ≈ 13 μm p-p
Alarm: Set at 80% = 10 μm

How to Choose Values

Speed Range Guidelines

< 600 RPM: Displacement measurement preferred
600-1000 RPM: Either displacement or velocity
1000-10000 RPM: Velocity measurement preferred
> 10000 RPM: Acceleration measurement recommended

Balance Quality Selection for Displacement

G 0.4: Precision spindles, gyroscopes (1-5 μm typical)
G 1: Grinding machines, small armatures (5-15 μm typical)
G 2.5: Machine tools, pumps, fans (15-40 μm typical)
G 6.3: General machinery (40-100 μm typical)
G 16: Large slow machines (100-250 μm typical)

Bearing Clearance Selection

C2:
- High precision applications
- Low operating temperatures
- Light loads
CN (Normal):
- General applications
- Normal temperatures
- Standard loads
C3-C5:
- High temperature operation
- Heavy loads
- Thermal expansion concerns

Measurement Type Selection

Peak-to-Peak:
- Standard for displacement
- Total movement range
- Direct bearing clearance comparison
Peak (0-Peak):
- Half of peak-to-peak
- Used in some standards
- Stress calculations
RMS:
- Energy content
- 0.707 × peak (sine wave)
- Statistical averaging

Probe Setup Tips

Gap voltage: Set to mid-range (-10V typical)
Probe location: 45° from vertical on each bearing
Surface prep: Ensure smooth, clean shaft surface
Runout compensation: Record and subtract electrical/mechanical runout

📘 Vibration Displacement Calculator

Converts vibration velocity to displacement (oscillation amplitude). Used for clearance assessment and low-frequency vibration analysis. Relationship: S = V / (2πf) where S = displacement (μm), V = velocity (mm/s), f = frequency (Hz).

💼 Applications

Bearing Clearance Check: Velocity 4.5 mm/s at 25 Hz. Displacement: S = 4.5/(2π×25) = 29 μm pk-pk. Bearing clearance: 80 μm. Safe margin: 51 μm ✓
Low-Frequency Foundation: Frequency 3 Hz. Velocity: 1.2 mm/s. Displacement: 64 μm. Visible to eye (> 50 μm).
Unbalance Analysis: Shaft 1480 RPM = 24.7 Hz. Velocity: 7.1 mm/s. Displacement: 46 μm. Requires balancing.

When Displacement Matters:

Checking against mechanical clearances
Low-frequency vibration (< 10 Hz)
Foundation/building vibration
Proximity probe measurements

Permissible Vibration Displacement Calculator – ISO 1940 | Vibromera.eu

Published by admin on October 20, 2025 December 9, 2025

Permissible Vibration Displacement Calculator