Industrial Fans, Blowers & Air Movement Equipment worked example

Vibration Margin with allowable fan vibration velocity of 0.09 in/s: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop allowable fan vibration velocity to 0.09 in/s, then walk the calculation through step by step. Calculate vibration margin by comparing allowable vibration level with measured fan vibration and a reference limit.

The inputs for this scenario

  • Allowable fan vibration velocity: 0.09 in/s (the input this scenario stresses; the baseline uses 0.18)
  • Measured fan vibration velocity: 0.11 in/s (held at the documented default)
  • Reference vibration limit: 0.18 in/s (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Vibration margin = allowable vibration level - measured vibration level.
  • Vibration margin percent works out to -11.11 % at these inputs, and this is the headline figure for the scenario.
  • Vibration margin works out to -0.02 in/s at these inputs.
  • Allowable vibration level works out to 0.09 value at these inputs.
  • Measured vibration level works out to 0.11 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where allowable fan vibration velocity sits at 0.18 in/s and the headline result is 38.89 %, this scenario comes in 129% below the baseline at -11.11 %.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to allowable fan vibration velocity, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. A single overall velocity number hides the diagnosis — two fans can share the same margin while one has imbalance and the other a failing bearing, so confirm with spectral analysis.

Results at a glance

  • Vibration margin percent: -11.11 % (headline result)
  • Vibration margin: -0.02 in/s
  • Allowable vibration level: 0.09 value
  • Measured vibration level: 0.11 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Vibration Margin calculator, set allowable fan vibration velocity to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.