National foreword

This British Standard is the UK implementation of ISO 21940‑1:2019. It supersedes BS ISO 19499:2007, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee GME/21/5, Mechanical vibration, shock and condition monitoring - Vibration of machines.

A list of organizations represented on this committee can be obtained on request to its secretary.

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2019.

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 voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and condition monitoring, Subcommittee SC 2, Measurement and evaluation of mechanical vibration and shock as applied to machines, vehicles and structures.

This first edition of ISO 21940‑1 cancels and replaces ISO 19499:2007, which has been technically revised. The main changes are as follows:

reference made to all International Standards in the ISO 21940 series;
deletion of former Table 2 "Guidelines for balancing procedures";
deletion of former Annex C "How to determine rotor flexibility based on an estimation from its geometric design".

A list of all parts in the ISO 21940 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

Vibration caused by rotor unbalance is one of the most critical issues in the design and maintenance of rotating machines. It gives rise to dynamic forces which adversely affect both machine and human health and well-being. The purpose of this document is to give guidance on the usage of the other parts of the ISO 21940 series.

Balancing is explained in a general manner, using the specific terms and definitions, to help readers to select the appropriate balancing approach for their application.

1 Scope

This document provides a general background to balancing technology, as used in the ISO 21940 series, and directs the reader to the appropriate parts of the series that include vocabulary, balancing procedures and tolerances, balancing machines and machine design for balancing.

Individual procedures are not included here as these can be found in the appropriate parts of ISO 21940.

2 Normative references

3 Terms and definitions

4 Fundamentals of balancing

4.1 General

4.2 Unbalance of a single disc

4.3 Unbalance distribution

4.4 Unbalance representation

5 Factors to consider when balancing

5.1 General

5.2 Rotors with rigid behaviour

5.3 Rotors with flexible behaviour

5.4 Examples of rotor behaviours

6 Selection of a balancing procedure

7 Unbalance tolerances

7.1 General

7.2 Permissible residual unbalance

7.3 Vibration limits

7.4 Influence of modes above service speed

7.5 Factors influencing balancing procedures

8 Selection of a balancing machine

8.1 General

8.2 Special requirements

9 International Standards on balancing

9.1 General

9.2 Vocabulary

9.3 Balancing procedures and tolerances

9.4 Balancing machines

9.5 Machine design for balancing

Bibliography

BS ISO 21940-1:2019

Mechanical vibration. Rotor balancing - Introduction

Current

Published:

28 Feb 2019