ISO INTERNATIONAL STANDARD 21940-1 First edition 2019-02 Mechanical vibration Rotor balancing - Part 1: Introduction Vibrations meécaniques - Equilibrage des rotors - Partie 1: Introduction Reference number IS0 21940-1:2019(E) [so @IS02019 IS0 21940-1:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ IS0 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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 CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2019 - All rights reserved IS0 21940-1:2019(E) Contents Page Foreword ..V Introduction. ..vi 1 Scope. 2 Normative references 3 Terms and definitions 4 Fundamentals of balancing 4.1 General .1 4.2 Unbalance of a single disc ..2 4.3 Unbalance distribution. .4 4.4 Unbalance representation 5 Factors to consider when balancing ..5 5.1 General .5 5.2 Rotors with rigid behaviour ..5 5.3 Rotors with flexible behaviour. .6 5.3.1 General ..6 5.3.2 Shaft-elastic behaviour .6 5.3.3 Component-elastic behaviour ..7 5.3.4 Settling behaviour. .7 5.4 Examples of rotor behaviours. .7 6 Selection of a balancing procedure .8 7 Unbalance tolerances .9 7.1 General .9 7.2 Permissible residual unbalance .9 7.2.1 General .9 7.2.2 Permissible residual unbalance for rotors with rigid behaviour .9 7.2.3 Permissible residual unbalance for rotors with flexible behaviour 7.3 Vibration limits ..10 7.4 Influenceofmodesaboveservicespeed 10 7.5 Factors influencing balancing procedures .11 7.5.1 General. ..11 7.5.2 Tolerances. ..1 7.5.3 Speed and support conditions ..12 7.5.4 Initial unbalance ..12 8 Selection of a balancing machine ..12 8.1 General. .12 8.2 Special requirements ..13 9 International Standards on balancing ..13 9.1 General ..13 9.2 Vocabulary ..14 9.2.1 ISO 21940-2— - Balancing vocabulary ..14 9.2.2 IS0 2041 Vibration and shock vocabulary ..14 9.3 Balancing procedures and tolerances. .14 9.3.1 General 14 9.3.2 Is0 21940-11 Procedures and tolerances for rotors with rigid behaviour... 9.3.3 IS0 21940-12 -— Procedures and tolerances for rotors with flexible behaviour.14 9.3.4 IS0 21940-13 Criteria and safeguards for the in-situ balancing of medium and large rotors ..14 9.3.5 IS0 21940-14 Procedures for addressing balancing errors .. 15 9.4 Balancing machines.. .15 9.4.1 Is0 21940-21 — Description and evaluation of balancing machines. .. 15 @ IS0 2019 - All rights reserved ii