WHEN SHOULD YOU PERFORM A LOW-SPEED BALANCE?

WHEN SHOULD YOU PERFORM A LOW-SPEED BALANCE MACHINE?

In general, balancing should be performed on any in-service rotor in which a significant amount of work has been performed. 

Changes made during the course of servicing a machine often create changes in its mass  distribution.

Also, rotors that have higher vibrations from wear will benefit from a low-speed balance.

Low-speed balancing machine is only appropriate for rigid rotors.

The technical definition of a rigid rotor is a rotor that operates 30% or more below its resonant speed. 

Practically, rotors that operate above their first critical, but  below their second critical, can be successfully low-speed  balanced provided that it has low run out.

Turbine spindles are the most likely candidates for a low speed balance depending on their flexibility.

Due to their larger relative stiffness and large diameters, low pressure (LP) spindles are especially well-suited for low-speed  balances.