ISO 21940-12:2016

Mechanical vibration — Rotor balancing — Part 12: Procedures and tolerances for rotors with flexible behaviour

ISO 21940-12:2016 presents typical configurations of rotors with flexible behaviour in accordance with their characteristics and balancing requirements, describes balancing procedures, specifies methods of assessment of the final state of balance, and establishes guidelines for balance quality criteria. ISO 21940-12:2016 can also serve as a basis for more involved investigations, e.g. when a more exact determination of the required balance quality is necessary. If due regard is paid to the specified methods of manufacture and balance tolerances, satisfactory running conditions can be expected. ISO 21940-12:2016 is not intended to serve as an acceptance specification for any rotor, but rather to give indications of how to avoid gross deficiencies and unnecessarily restrictive requirements. Structural resonances and modifications thereof lie outside the scope of this part of ISO 21940. The methods and criteria given are the result of experience with general industrial machinery. It is possible that they are not directly applicable to specialized equipment or to special circumstances. Therefore, in some cases, deviations from this part of ISO 21940 are possible.

Vibrations mécaniques — Équilibrage des rotors — Partie 12: Modes opératoires et tolérances pour les rotors à comportement flexible

General Information

• Status: Published
• Publication Date: 28-Mar-2016
• ICS: 21.120.40 - Balancing and balancing machines
• Technical Committee: ISO/TC 108/SC 2 - Measurement and evaluation of mechanical vibration and shock as applied to machines, vehicles and structures
• Drafting Committee: ISO/TC 108/SC 2/WG 31 - Balancing
• Current Stage: 9093 - International Standard confirmed
• Start Date: 02-Sep-2025
• Completion Date: 06-Sep-2025

Relations

• Revises: ISO 11342:1998 - Mechanical vibration — Methods and criteria for the mechanical balancing of flexible rotors
• Effective Date: 28-Feb-2009

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21940-12
Second edition
Mechanical vibration — Rotor
balancing —
Part 12:
Procedures and tolerances for rotors
with flexible behaviour
Vibrations mécaniques — Équilibrage des rotors —
Partie 12: Modes opératoires et tolérances pour les rotors à
comportement flexible
PROOF/ÉPREUVE
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved

Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fundamentals of dynamics and balancing of rotors with flexible behaviour .2
4.1 General . 2
4.2 Unbalance distribution . 2
4.3 Mode shapes of rotors with flexible behaviour . 2
4.4 Response of a rotor with flexible behaviour to unbalance . . 3
4.5 Aims of balancing rotors with flexible behaviour . 5
4.6 Provision for correction planes . 5
4.7 Coupled rotors . 5
5 Rotor configurations. 6
6 Procedures for balancing rotors with flexible behaviour at low speed .8
6.1 General . 8
6.2 Selection of correction planes . 8
6.3 Service speed of the rotor . 8
6.4 Initial unbalance . 9
6.5 Low-speed balancing procedures . 9
6.5.1 Procedure A — Single-plane balancing . 9
6.5.2 Procedure B — Two-plane balancing . 9
6.5.3 Procedure C — Individual component balancing prior to assembly . 9
6.5.4 Procedure D — Balancing subsequent to controlling initial unbalance . 9
6.5.5 Procedure E — Balancing in stages during assembly .10
6.5.6 Procedure F — Balancing in optimum planes .10
7 Procedures for balancing rotors with flexible behaviour at high speed .10
7.1 General .10
7.2 Installation for balancing .11
7.3 Procedure G — Multiple speed balancing .11
7.3.1 General.11
7.3.2 Initial low-speed balancing .12
7.3.3 General procedure .12
7.4 Procedure H — Service speed balancing .14
7.5 Procedure I — Fixed speed balancing.14
7.5.1 General.14
7.5.2 Procedure .14
8 Evaluation criteria .15
8.1 Choice of criteria .15
8.2 Vibration limits in the balancing machine .15
8.2.1 Overview .15
8.2.2 General.16
8.2.3 Special cases and exceptions .16
8.2.4 Factors influencing machine vibration .16
8.2.5 Critical clearances and complex machine systems.16
8.2.6 Permissible vibrations in the balancing machine .16
8.3 Residual unbalance tolerances .17
8.3.1 Overview .17
8.3.2 General.18
8.3.3 Limits for low-speed balancing .18
8.3.4 Limits for multiple speed balancing .18
9 Evaluation procedures .19
9.1 Evaluation procedures based on vibration limits .19
9.1.1 Vibration assessed in a high-speed balancing machine .19
9.1.2 Vibration assessed on a test facility .19
9.1.3 Vibration assessed on site .20
9.2 Evaluation based on residual unbalance tolerances .20
9.2.1 General.20
9.2.2 Evaluation at low speed .20
9.2.3 Evaluation at multiple speeds based on modal unbalances .21
9.2.4 Evaluation at service speed in two specified test planes .22
Annex A (informative) Cautionary notes concerning rotors when installed in-situ .23
Annex B (informative) Optimum planes balancing — Low-speed three-plane balancing .24
Annex C (informative) Conversion factors .26
Annex D (informative) Example calculation of equivalent residual modal unbalances .27
Annex E (informative) Procedures to determine whether a rotor shows rigid or
flexible behaviour .30
Annex F (informative) Method of computation of unbalance correction .32
Bibliography .33
iv PROOF/ÉPREUVE © ISO 2016 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Suppleme
...

INTERNATIONAL ISO
STANDARD 21940-12
First edition
2016-04-01
Mechanical vibration — Rotor
balancing —
Part 12:
Procedures and tolerances for rotors
with flexible behaviour
Vibrations mécaniques — Équilibrage des rotors —
Partie 12: Modes opératoires et tolérances pour les rotors à
comportement flexible
Reference number
©
ISO 2016
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2016 – All rights reserved

Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Fundamentals of dynamics and balancing of rotors with flexible behaviour .2
4.1 General . 2
4.2 Unbalance distribution . 2
4.3 Mode shapes of rotors with flexible behaviour . 2
4.4 Response of a rotor with flexible behaviour to unbalance . . 3
4.5 Aims of balancing rotors with flexible behaviour . 4
4.6 Provision for correction planes . 5
4.7 Coupled rotors . 5
5 Rotor configurations. 5
6 Procedures for balancing rotors with flexible behaviour at low speed .7
6.1 General . 7
6.2 Selection of correction planes . 8
6.3 Service speed of the rotor . 8
6.4 Initial unbalance . 8
6.5 Low-speed balancing procedures . 8
6.5.1 Procedure A — Single-plane balancing . 8
6.5.2 Procedure B — Two-plane balancing . 8
6.5.3 Procedure C — Individual component balancing prior to assembly . 9
6.5.4 Procedure D — Balancing subsequent to controlling initial unbalance . 9
6.5.5 Procedure E — Balancing in stages during assembly . 9
6.5.6 Procedure F — Balancing in optimum planes .10
7 Procedures for balancing rotors with flexible behaviour at high speed .10
7.1 General .10
7.2 Installation for balancing .10
7.3 Procedure G — Multiple speed balancing .11
7.3.1 General.11
7.3.2 Initial low-speed balancing .11
7.3.3 General procedure .11
7.4 Procedure H — Service speed balancing .13
7.5 Procedure I — Fixed speed balancing.14
7.5.1 General.14
7.5.2 Procedure .14
8 Evaluation criteria .14
8.1 Choice of criteria .14
8.2 Vibration limits in the balancing machine .15
8.2.1 Overview .15
8.2.2 General.15
8.2.3 Special cases and exceptions .15
8.2.4 Factors influencing machine vibration .15
8.2.5 Critical clearances and complex machine systems.16
8.2.6 Permissible vibrations in the balancing machine .16
8.3 Residual unbalance tolerances .17
8.3.1 Overview .17
8.3.2 General.17
8.3.3 Limits for low-speed balancing .17
8.3.4 Limits for multiple speed balancing .18
9 Evaluation procedures .18
9.1 Evaluation procedures based on vibration limits .18
9.1.1 Vibration assessed in a high-speed balancing machine .18
9.1.2 Vibration assessed on a test facility .19
9.1.3 Vibration assessed on site .19
9.2 Evaluation based on residual unbalance tolerances .20
9.2.1 General.20
9.2.2 Evaluation at low speed .20
9.2.3 Evaluation at multiple speeds based on modal unbalances .20
9.2.4 Evaluation at service speed in two specified test planes .21
Annex A (informative) Cautionary notes concerning rotors when installed in-situ .23
Annex B (informative) Optimum planes balancing — Low-speed three-plane balancing .24
Annex C (informative) Conversion factors .26
Annex D (informative) Example calculation of equivalent residual modal unbalances .27
Annex E (informative) Procedures to determine whether a rotor shows rigid or
flexible behaviour .30
Annex F (informative) Method of computation of unbalance correction .32
Bibliography .33
iv © ISO 2016 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The comm
...