Industrial Fans, Blowers & Air Movement Equipment worked example

Impeller Balance Tolerance with allowable residual unbalance of 310 g-mm: a worked example

Push allowable residual unbalance up to 310 g-mm and the picture changes. This example computes every intermediate figure at that operating point. Use it when checking whether an impeller, wheel, rotor, or blower assembly has enough balance margin before shipment.

The inputs for this scenario

  • Allowable residual unbalance: 310 g-mm (raised for this scenario; the documented default is 125)
  • Measured residual unbalance: 92 g-mm (unchanged)
  • Reference balance tolerance: 125 g-mm (unchanged)

Working through the calculation

  • Applying the documented formula (Impeller balance tolerance margin = allowable residual unbalance - measured residual unbalance) to the inputs above produces each figure below.
  • At this operating point the engine returns 174 % for balance margin percent, the number this scenario is built around.
  • At this operating point the engine returns 218 g-mm for impeller balance tolerance margin.
  • At this operating point the engine returns 310 value for allowable residual unbalance.
  • At this operating point the engine returns 92 value for measured residual unbalance.

How this compares with the baseline

  • Against the tool's baseline example, where allowable residual unbalance sits at 125 g-mm and the headline result is 26.4 %, this scenario comes in 561% above the baseline at 174 %.
  • It subtracts measured residual unbalance from the allowable residual unbalance to get a balance margin in g-mm, then divides by a reference tolerance for a percent margin. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Balance margin percent: 174 % (headline result)
  • Impeller balance tolerance margin: 218 g-mm
  • Allowable residual unbalance: 310 value
  • Measured residual unbalance: 92 value

Run it with your numbers

  • Every input above is editable in the live Impeller Balance Tolerance calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.