ISO 21940-11:2016
Mechanical vibration — Rotor balancing — Part 11: Procedures and tolerances for rotors with rigid behaviour
ISO 21940-11:2016 establishes procedures and unbalance tolerances for balancing rotors with rigid behaviour. It specifies
a) the magnitude of the permissible residual unbalance,
b) the necessary number of correction planes,
c) the allocation of the permissible residual unbalance to the tolerance planes, and
d) how to account for errors in the balancing process.
NOTE In ISO 21940‑14, the assessment of balancing errors is considered in detail. Fundamentals of rotor balancing are contained in ISO 19499 which gives an introduction to balancing.
ISO 21940-11:2016 does not cover the balancing of rotors with flexible behaviour. Procedures and tolerances for rotors with flexible behaviour are dealt with in ISO 21940‑12.
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Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Pertinent aspects of balancing
4.1 General
4.2 Representation of the unbalance
4.3 Unbalance effects
4.4 Reference planes for unbalance tolerances
4.5 Correction planes
4.5.1 General
4.5.2 Rotors which need one correction plane only
4.5.3 Rotors which need two correction planes
4.5.4 Rotors with more than two correction planes
4.6 Permissible residual unbalance
5 Similarity considerations
5.1 General
5.2 Permissible residual unbalance and rotor mass
5.3 Permissible residual specific unbalance and service speed
6 Specification of unbalance tolerances
6.1 General
6.2 Derivation of the unbalance tolerances
6.3 Balance quality grade G
6.3.1 Classification
6.3.2 Special designs
6.3.3 Permissible residual unbalance
6.4 Experimental evaluation
6.5 Unbalance tolerances based on bearing forces or vibrations
6.5.1 Bearing forces
6.5.2 Vibrations
6.6 Methods based on established experience
7 Allocation of permissible residual unbalance to tolerance planes
7.1 Single plane
7.2 Two planes
7.2.1 General
7.2.2 Limitations for inboard rotors
7.2.3 Limitations for outboard rotors
8 Allocation of unbalance tolerances to correction planes
8.1 General
8.2 Single plane
8.3 Two planes
9 Assembled rotors
9.1 General
9.2 Balanced as a unit
9.3 Balanced on component level
10 Accounting for errors in the verification of permissible residual unbalances
10.1 General
10.2 Unbalance tolerance
10.3 Combined error of unbalance measurements
10.4 Verification of the permissible residual unbalance
10.4.1 General
10.4.2 Unbalance readings within tolerance
10.4.3 Unbalance readings out of tolerance
10.4.4 Region of uncertainly
Annex A (informative) Example of the specification of permissible residual unbalance based on balance quality grade G and allocation to the tolerance planes
Annex B (informative) Specification of unbalance tolerances based on bearing force limits
Annex C (informative) Specification of unbalance tolerances based on established experience
Annex D (informative) Rules for allocating unbalance tolerances from tolerance planes to correction planes
Bibliography
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BS ISO 21940-11:2016+A1:2022
Mechanical vibration. Rotor balancing, Procedures and tolerances for rotors with rigid behaviour
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Pertinent aspects of balancing
4.1 General
4.2 Representation of the unbalance
4.3 Unbalance effects
4.4 Reference planes for unbalance tolerances
4.5 Correction planes
4.5.1 General
4.5.2 Rotors which need one correction plane only
4.5.3 Rotors which need two correction planes
4.5.4 Rotors with more than two correction planes
4.6 Permissible residual unbalance
5 Similarity considerations
5.1 General
5.2 Permissible residual unbalance and rotor mass
5.3 Permissible residual specific unbalance and service speed
6 Specification of unbalance tolerances
6.1 General
6.2 Derivation of the unbalance tolerances
6.3 Balance quality grade G
6.3.1 Classification
6.3.2 Special designs
6.3.3 Permissible residual unbalance
6.4 Experimental evaluation
6.5 Unbalance tolerances based on bearing forces or vibrations
6.5.1 Bearing forces
6.5.2 Vibrations
6.6 Methods based on established experience
7 Allocation of permissible residual unbalance to tolerance planes
7.1 Single plane
7.2 Two planes
7.2.1 General
7.2.2 Limitations for inboard rotors
7.2.3 Limitations for outboard rotors
8 Allocation of unbalance tolerances to correction planes
8.1 General
8.2 Single plane
8.3 Two planes
9 Assembled rotors
9.1 General
9.2 Balanced as a unit
9.3 Balanced on component level
10 Accounting for errors in the verification of permissible residual unbalances
10.1 General
10.2 Unbalance tolerance
10.3 Combined error of unbalance measurements
10.4 Verification of the permissible residual unbalance
10.4.1 General
10.4.2 Unbalance readings within tolerance
10.4.3 Unbalance readings out of tolerance
10.4.4 Region of uncertainly
Annex A (informative) Example of the specification of permissible residual unbalance based on balance quality grade G and allocation to the tolerance planes
Annex B (informative) Specification of unbalance tolerances based on bearing force limits
Annex C (informative) Specification of unbalance tolerances based on established experience
Annex D (informative) Rules for allocating unbalance tolerances from tolerance planes to correction planes
Bibliography