Rigid Rotors
Maximum operating speed below 70% of natural frequency or first critical speed.
Can be balanced at any speed:
Will remain in balance throughout speed range provided
tolerance, calculated to maximum service speed, is achieved.
tolerance, calculated to maximum service speed, is achieved.
Balance corrections made in any two arbitrary correction planes.
Flexible rotor
Does not satisfy the definition of a rigid rotor and has a tendency
to bend or distort due to centrifugal and unbalance forces
High speed flexible shaft
balance correction (low speed) balance correction (low speed)
rotat
ng center
ne
mass centreline
initial unbalance
High speed flexible shaf
effect at high speed
Correcting Unbalance In-Situ Requirements
In-situ balancing is best. Unbalance is primary problem.
In-situ balancing is not always Access to add / remove weight.
possible. Ability to start / stop machine "at will"
Balance Tolerances ISO 1940/1 has also been adopted by:
Manufacturers' recommendation.
BS 6861 Part 1 (British Standards)
International standards ISO 1940/1. ANSI S 2.19-1975 (American National
Standards Institute)
VDI 2060 (German Standards)
19
C of G
C of G
