National foreword

This British Standard is the UK implementation of ISO 21940‑21:2022. It supersedes BS ISO 21940‑21:2012, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee GME/21/5, Vibration of machines, vehicles and structures.

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

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute 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 31 December 2022.

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 of 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 www.iso.org/iso/foreword.html.

ISO 21940‑21 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 second edition cancels and replaces the first edition (ISO 21940‑21:2012), which has been technically revised.

The main changes are as follows:

the introduction of new computer based technology into balance machine indication systems;
the introduction of additional tests for repeatability and speed range (see Annex F and Annex G);
the introduction of greater clarification for use with automated and special purpose machines.

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

The purpose of this document is to provide a common framework for the specification, comparison and evaluation of balancing machines.

It describes a proforma on which the baseline balancing machine characteristics can be presented by the manufacturer enabling users to compare products from different manufacturers. Additionally, guidelines are given on the information by which users provide their data and requirements to a balancing machine manufacturer.

This document describes the tests to be performed during the acceptance testing of a balancing machine and later, on a periodic basis, to ensure that the balancing machine is capable of handling the actual balancing tasks. For periodic tests, simplified procedures are specified.

Methods and requirements for preparing proving rotors (which can be of Type A, Type B or Type C, or a user defined proving rotor e.g. based on a user supplied part) are specified, allowing a wide range of applications to be covered.

The accuracy of all balance machines is inherently non-linear over their mass and speed range. In normal practice, a hard bearing balance machine is calibrated over a particular part of its speed and mass range, but outside that its accuracy cannot be assumed. As a consequence, a rotor specific calibration should be performed to establish the machine accuracy at a specific speed and for a rotor of a particular mass. This is normal practice for soft bearing machines or where the manufacturer states that rotor specific calibration should be carried out.

1 Scope

This document sets out the requirements for evaluating hard and soft bearing balancing machines that support and rotate:

rotors with rigid behaviour at balancing speed (as described in ISO 21940‑11);
rotors with shaft elastic behaviour and balanced in accordance with low speed balancing procedures (as described in ISO 21940‑12).

2 Normative references

3 Terms and definitions

4 Capacity and performance data of the balancing machine

4.1 General

4.2 Data for horizontal balancing machines

4.3 Data for vertical balancing machines

5 Machine features

5.1 Principle of operation

5.2 Machine arrangement

5.3 Measuring system

5.4 Plane separation system

5.5 Setting and calibration of the measuring system

6 Production efficiency

6.1 General

6.2 Time per balance cycle

6.3 Unbalance reduction ratio, R_UR

7 Performance qualifying factors

8 Installation requirements

8.1 General

8.2 Supply requirements

8.3 Foundation

9 Proving rotors and test masses

9.1 General

9.2 Standardized proving rotors

9.3 User defined proving rotors

9.4 Test masses

10 Balance machine verification tests

10.1 General

10.2 Requirements for evaluating balance machine performance

10.3 Test speed

10.4 Test for establishing the minimum achievable residual unbalance, U_mar

10.5 Test for unbalance reduction ratio, R_UR

10.6 Test for couple moment interference on single-plane machines

10.7 Compensator test

10.8 Simplified tests

Bibliography

BS ISO 21940-21:2022

Mechanical vibration. Rotor balancing - Description and evaluation of balancing machines

Current

Published:

30 Nov 2022