This standard provides guidelines for designing and selecting vibration isolation systems for machine foundations. It covers fundamental concepts of vibration, effects on structures and humans, principles of isolation, properties of different isolation materials, and methods for measuring vibration.
Vibration isolation for machine foundations - Guidelines
Quick Reference Values
Required frequency ratio for isolation> 1.414
Preferred frequency ratio for good isolation3 to 5
Transmissibility goal for sensitive installations< 0.1
Typical damping ratio for steel springs0.005
Typical damping ratio for elastomers0.05 to 0.15
Vibration velocity limit for medium machines (Class II)4.5 mm/s RMS (Good)
Human perception threshold for vibration (vertical)approx 0.15 mm/s RMS at 10 Hz
Key Formulas
T = sqrt( [1 + (2ζr)²] / [ (1-r²)² + (2ζr)² ] ) — Transmissibility Formula, where r is frequency ratio and ζ is damping ratio
r = ω / ωn — Frequency Ratio, where ω is disturbing frequency and ωn is natural frequency
ωn = sqrt(k/m) — Natural Frequency of a single degree of freedom system
Practical Notes
The effectiveness of an isolation system is highly dependent on accurately determining the machine's operating frequency and the natural frequency of the foundation system.
For variable speed machines, ensure the operating frequency range does not pass through or dwell on the natural frequency of the isolated system to avoid resonance.
Always verify the static deflection of the chosen isolators under the machine's weight to ensure it matches the design natural frequency.