ISO INTERNATIONAL STANDARD 21940-31 Firstedition 2013-08-15 Mechanical vibration Rotor balancing - Part 31: Susceptibility and sensitivity of machines to unbalance Vibrationsmeécaniques-Equilibragedes rotors- Partie31:Susceptibiliteetsensibilitedes machinesauxbalourds Referencenumber IS021940-31:2013(E) LSO @IS02013 ed without license from IHS Not for Resale IS021940-31:2013(E) COPYRIGHTPROTECTEDDOCUMENT ISO2013 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 Casepostale 56.CH-1211Geneva20 Tel. + 4122 749 01 11 Fax +4122749 09 47 E-mail [email protected] Web www.iso.org Published in Switzerland CopyrightintenatonalOrganizatonforStandardization @ IS0 2013 - All rights reserved No reproduction or networking permited without license from IHS Not for Resale IS0 21940-31:2013(E) Contents Page Foreword ..iv Introduction. ...vi 1 Scope. 2 Normative references 3 Terms and definitions .1 4 Machinesusceptibilityclassification .1 4.1 General .1 4.2 Type I: Low susceptibility .2 4.3 Type Il:Moderate susceptibility .2 4.4 Type III: High susceptibility. .2 4.5 Machine susceptibility correction factors 2 5 Modal sensitivity .2 5.1 General 2 5.2 Modal sensitivity ranges .3 5.3 Characteristics of modal sensitivity ranges .3 5.4 Values of modal sensitivity .3 5.5 Operating speed .7 5.6 Transient speed .9 6 Experimentaldetermination of modal sensitivitynear resonance speed under operational conditions .10 6.1 General .10 6.2 Nyquist diagram procedure .10 6.3 Bode diagram procedure. ..10 7 Numerical valuesforthe local sensitivity ..11 8 Experimentaldeterminationofthelocalsensitivity ..12 8.1 General .12 8.2 Procedure .12 9 Damped unbalance sensitivity analysis ..13 AnnexA(informative)Explanationsofterms ..14 AnnexB(informative)Exampleofpolarplotdiagramprocedure ..16 Annex c (informative)Examples ofclassification accordingto modal sensitivity ..17 AnnexD (informative)Exampleofmathematicalmodelappliedunbalance ..18 Bibliography ..19 orStana ili lout license from IHS Not for Resale