1、BSI Standards PublicationBS ISO 21940-31:2013Mechanical vibration RotorbalancingPart 31: Susceptibility and sensitivity ofmachines to unbalanceBS ISO 21940-31:2013 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO21940-31:2013. It supersedes BS ISO 10814:1996 whi
2、ch is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee GME/21/5, Mechanical vibration, shock and conditionmonitoring - Vibration of machines.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not
3、 purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 79296 0ICS 21.120.40Compliance with a British Standard cannot confer immunity fromlegal obliga
4、tions.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2013.Amendments issued since publicationDate Text affectedBS ISO 21940-31:2013 ISO 2013Mechanical vibration Rotor balancing Part 31: Susceptibility and sensitivity of machines to
5、unbalanceVibrations mcaniques quilibrage des rotors Partie 31: Susceptibilit et sensibilit des machines aux balourdsINTERNATIONAL STANDARDISO21940-31First edition2013-08-15Reference numberISO 21940-31:2013(E)BS ISO 21940-31:2013ISO 21940-31:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED D
6、OCUMENT ISO 2013All 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
7、can be requested from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 21940-31:2013ISO 21940-31:201
8、3(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction vi1 Scope . 12 Normative references 13 Terms and definitions . 14 Machine susceptibility classification 14.1 General . 14.2 Type I: Low susceptibility 24.3 Type II: Moderate susceptibility 24.4 Type III: High susceptibility .
9、24.5 Machine susceptibility correction factors . 25 Modal sensitivity 25.1 General . 25.2 Modal sensitivity ranges . 35.3 Characteristics of modal sensitivity ranges . 35.4 Values of modal sensitivity . 35.5 Operating speed . 75.6 Transient speed 96 Experimental determination of modal sensitivity ne
10、ar resonance speed under operational conditions 106.1 General 106.2 Nyquist diagram procedure 106.3 Bode diagram procedure . 107 Numerical values for the local sensitivity .118 Experimental determination of the local sensitivity .128.1 General 128.2 Procedure . 129 Damped unbalance sensitivity analy
11、sis 13Annex A (informative) Explanations of terms 14Annex B (informative) Example of polar plot diagram procedure .16Annex C (informative) Examples of classification according to modal sensitivity 17Annex D (informative) Example of mathematical model applied unbalance .18Bibliography .19BS ISO 21940
12、-31:2013ISO 21940-31:2013(E)ForewordISO (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
13、 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 Comm
14、ission (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 s
15、hould be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2, 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 ident
16、ifying 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, www.iso.org/patents.Any trade name used in this document is information given for the convenience o
17、f users and does not constitute an endorsement.The committee responsible for this document is 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 e
18、dition of ISO 21940-31 cancels and replaces ISO 10814:1996, of which it constitutes a technical revision. The main change is modification to the modal amplification factors to make this part of ISO 21940 more consistent with relevant parts of ISO 7919, e.g. machines predicted to operate in ISO 7919-
19、22zone A would be classified as very low (range A) and machines predicted to operate in ISO 7919-22zone B would be classified as low (range B).ISO 21940 consists of the following parts, under the general title Mechanical vibration Rotor balancing: Part 1: Introduction1) Part 2: Vocabulary2) Part 11:
20、 Procedures and tolerances for rotors with rigid behaviour3) Part 12: Procedures and tolerances for rotors with flexible behaviour4) Part 13: Criteria and safeguards for the in-situ balancing of medium and large rotors5) Part 14: Procedures for assessing balance errors6)1) Revision of ISO 19499:2007
21、, Mechanical vibration Balancing Guidance on the use and application of balancing standards2) Revision of ISO 1925:2001, Mechanical vibration Balancing Vocabulary3) Revision of ISO 1940-1:2003 + Cor.1:2005, Mechanical vibration Balance quality requirements for rotors in a constant (rigid) state Part
22、 1: Specification and verification of balance tolerances4) Revision of ISO 11342:1998 + Cor.1:2000, Mechanical vibration Methods and criteria for the mechanical balancing of flexible rotors5) Revision of ISO 20806:2009, Mechanical vibration Criteria and safeguards for the in-situ balancing of medium
23、 and large rotors6) Revision of ISO 1940-2:1997, Mechanical vibration Balance quality requirements of rigid rotors Part 2: Balance errorsiv ISO 2013 All rights reservedBS ISO 21940-31:2013ISO 21940-31:2013(E) Part 21: Description and evaluation of balancing machines7) Part 23: Enclosures and other p
24、rotective measures for the measuring station of balancing machines8) Part 31: Susceptibility and sensitivity of machines to unbalance9) Part 32: Shaft and fitment key convention10)7) Revision of ISO 2953:1999, Mechanical vibration Balancing machines Description and evaluation8) Revision of ISO 7475:
25、2002, Mechanical vibration Balancing machines Enclosures and other protective measures for the measuring station9) Revision of ISO 10814:1996, Mechanical vibration Susceptibility and sensitivity of machines to unbalance10) Revision of ISO 8821:1989, Mechanical vibration Balancing Shaft and fitment k
26、ey convention ISO 2013 All rights reserved vBS ISO 21940-31:2013ISO 21940-31:2013(E)IntroductionRotor balancing during manufacture (e.g. as described in ISO 1940-11and ISO 113424) is normally sufficient to attain acceptable in-service vibration magnitudes if other sources of vibration are absent. Ho
27、wever, additional balancing during commissioning may become necessary and after commissioning, some machines may require occasional or even frequent rebalancing in situ.If vibration magnitudes are unsatisfactory during commissioning, the reason may be inadequate balancing or assembly errors. Another
28、 important cause may be that an assembled machine is especially sensitive to relatively small residual unbalances which are well within normal balance tolerances.If vibration magnitudes are unsatisfactory, the first step often is an attempt to reduce the vibration by balancing in situ. If high vibra
29、tion magnitudes can be reduced by installing relatively small correction masses, high sensitivity to unbalance is indicated. This can arise, for example, if a resonance rotational speed is close to the normal operating speed and the damping in the system is low.A sensitive machine which is also high
30、ly susceptible to its unbalance changing, may require frequent rebalancing in situ. This may be caused, for example, by changes in wear, temperature, mass, stiffness, and damping during operation.If the unbalance and other conditions of the machine are essentially constant, occasional trim balancing
31、 may be sufficient. Otherwise it may be necessary to modify the machine to change the resonance speed, damping or other parameters to obtain acceptable vibration magnitudes. Therefore, there is a need to consider permissible sensitivity values of the machine.The repeatability of the unbalance sensit
32、ivity of a machine is influenced by several factors and may change during operation. Some thermal machines, especially those with sleeve bearings, have modal vibration characteristics which vary with particular operational parameters (e.g. steam pressure and temperature, partial steam admission or o
33、il temperature). For electrical machines, other parameters such as the excitation current may influence the vibration behaviour. In general, the machine vibration characteristics are influenced by the design features of the machine, including coupling of the rotor and its support conditions includin
34、g the foundation. It should be noted that the rotor support conditions may vary with time (e.g. wear and tear).This part of ISO 21940 is only concerned with once-per-revolution vibration caused by unbalance; however, it should be recognized that unbalance is not the only cause of once-per-revolution
35、 vibration.vi ISO 2013 All rights reservedBS ISO 21940-31:2013INTERNATIONAL STANDARD ISO 21940-31:2013(E)Mechanical vibration Rotor balancing Part 31: Susceptibility and sensitivity of machines to unbalance1 ScopeThis part of ISO 21940 specifies methods for determining machine vibration sensitivity
36、to unbalance and provides evaluation guidelines as a function of the proximity of relevant resonance rotational speeds to the operating speed. This part of ISO 21940 is only concerned with once-per-revolution vibration caused by unbalance. It also makes recommendations on how to apply the numerical
37、sensitivity values in some particular cases.It includes a classification system that can be applied to machines which is related to their susceptibility to a change in unbalance. Machines are classified into three types of susceptibility and five ranges of sensitivity. The sensitivity values are int
38、ended for use on simple machine systems, preferably with rotors having only one resonance speed over their entire operating speed range. The sensitivity values can also be used for machines that have more resonance speeds in their operating speed range if the resonance speeds are widely separated (e
39、.g. by more than 20 %).The sensitivity values given are not intended to serve as acceptance specifications for any machine group, but rather to give indications regarding how to avoid gross deficiencies as well as specifying exaggerated or unattainable requirements. They can also serve as a basis fo
40、r more involved investigations (e.g. when in special cases a more exact determination of the required sensitivity is necessary). If due regard is paid to the values given, satisfactory running conditions can be expected in most cases.The consideration of the sensitivity values alone does not guarant
41、ee that a given magnitude of vibration in operating is not exceeded. Many other sources of vibration can occur which lie outside the scope of this part of ISO 21940.2 Normative referencesThe following documents, in whole or in part, are normatively referenced in this document and are indispensable f
42、or its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 1925, Mechanical vibration Balancing Vocabulary11)3 Terms and definitionsFor the purposes of this document, the terms
43、 and definitions given in ISO 1925 apply.NOTE Some of the terms used are explained in Annex A.4 Machine susceptibility classification4.1 GeneralMachine susceptibility classification is based on the likelihood of a machine experiencing significant unbalance during operation. Machines with low suscept
44、ibility are allowed higher sensitivity values 11) To become ISO 21940-2 when revised. ISO 2013 All rights reserved 1BS ISO 21940-31:2013ISO 21940-31:2013(E)(require less damping), and machines with high susceptibility are restricted to lower sensitivity values (require more damping).4.2 Type I: Low
45、susceptibilityMachines of this type have a low likelihood of experiencing significant unbalance changes during operation. Typically they have a large rotor mass in comparison to their support housing and operate in a clean environment, have negligible wear and exhibit minimal rotor distortion caused
46、 by temperature change.EXAMPLES Paper machine rolls, printing rolls, and high-speed vacuum pumps.4.3 Type II: Moderate susceptibilityMachines of this type have a moderate likelihood of experiencing significant unbalance changes during operation. Typically they are machines which operate in environme
47、nts with large temperature changes or experience moderate wear.EXAMPLES Pumps in clean media, electric armatures, gas and steam turbines, generators, and turbo compressors.4.4 Type III: High susceptibilityMachines of this type have a high likelihood of experiencing significant unbalance changes duri
48、ng operation. Typically they are machines which run in deposit producing (e.g. pumps operating in sludge) or corrosive environments.EXAMPLES Centrifuges, fans, screw conveyors, and hammer mills.4.5 Machine susceptibility correction factorsThe remainder of this part of ISO 21940 focuses on moderate s
49、usceptibility classification machines (type II). For evaluation of low susceptibility or high susceptibility machines, a correction factor can be applied to adjust the sensitivity range. Table 1 shows correction factors that are applied to the sensitivity values (see Clause 5) based on machine susceptibility type (see 4.2 to 4.4).Table 1 Correction factorsMachine typeMachine susceptibility classificationCorrection factorI Low susceptibility 43II Moderately susceptibility 1 (Base)III High susc
