1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 21940-14:2012Mechanical vibration RotorbalancingPart 14: Procedures for assessing balanceerrorsBS ISO 21940-14:2012 BRITISH STANDARDNational forewordThis British Standard
2、is the UK implementation of ISO21940-14:2012. It supersedes BS 6861-2:1997 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee GME/21, Mechanical vibration, shock and conditionmonitoring.A list of organizations represented on this committee can beobtained o
3、n request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 72049 9ICS 21.120.40Compliance with a Brit
4、ish Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2012.Amendments issued since publicationDateT e x t a f f e c t e dBS ISO 21940-14:2012 ISO 2012Mechanical vibration Rotor bala
5、ncing Part 14: Procedures for assessing balance errorsVibrations mcaniques quilibrage des rotors Partie 14: Modes opratoires dvaluation des erreurs dquilibrageINTERNATIONAL STANDARDISO21940-14First edition2012-07-01Reference numberISO 21940-14:2012(E)BS ISO 21940-14:2012ISO 21940-14:2012(E)ii ISO 20
6、12 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either
7、 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 21940-14:2012ISO 21940-14:2012(E) ISO 2012 All rights res
8、erved iiiContents PageForeword ivIntroduction . vi1 Scope 12 Normative references . 13 Terms and definitions . 14 Balance error sources 14.1 General . 14.2 Systematic errors 24.3 Randomly variable errors 24.4 Scalar errors . 35 Error assessment 35.1 General . 35.2 Errors caused by balancing equipmen
9、t and instrumentation . 35.3 Balance errors caused by component radial and axial runout . 35.4 Assessment of balancing operation errors 45.5 Experimental assessment of randomly variable errors 55.6 Experimental assessment of systematic errors . 66 Combined error evaluation . 67 Acceptance criteria .
10、 7Annex A (informative) Error examples, their identification and evaluation 8BS ISO 21940-14:2012ISO 21940-14:2012(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standa
11、rds 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 tak
12、e part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is t
13、o prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility t
14、hat 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.ISO 21940-14 was prepared by Technical Committee ISO/TC 108, Mechanical vibration, shock and condition monitoring, Subcommittee SC 2, Measure
15、ment and evaluation of mechanical vibration and shock as applied to machines, vehicles and structures.This first edition of ISO 21940-14 cancels and replaces ISO 1940-2:1997, of which it constitutes a technical revision. The main change is extension of the applicability to rotors with flexible behav
16、iour.ISO 21940 consists of the following parts, under the general title Mechanical vibration Rotor balancing: Part 1: Introduction1) Part 2: Vocabulary2) Part 11: Procedures and tolerances for rotors with rigid behaviour3) Part 12: Procedures and tolerances for rotors with flexible behaviour4) Part
17、13: Criteria and safeguards for the in-situ balancing of medium and large rotors5) Part 14: Procedures for assessing balance errors6) Part 21: Description and evaluation of balancing machines7) Part 23: Enclosures and other protective measures for the measuring station of balancing machines8)1) Revi
18、sion of ISO 19499:2007, 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 const
19、ant (rigid) state Part 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-si
20、tu balancing of medium and large rotors6) Revision of ISO 1940-2:1997, Mechanical vibration Balance quality requirements of rigid rotors Part 2: Balance errors7) Revision of ISO 2953:1999, Mechanical vibration Balancing machines Description and evaluation8) Revision of ISO 7475:2002, Mechanical vibr
21、ation Balancing machines Enclosures and other protective measures for the measuring stationiv ISO 2012 All rights reservedBS ISO 21940-14:2012ISO 21940-14:2012(E) Part 31: Susceptibility and sensitivity of machines to unbalance9) Part 32: Shaft and fitment key convention10)9) Revision of ISO 10814:1
22、996, Mechanical vibration Susceptibility and sensitivity of machines to unbalance10) Revision of ISO 8821:1989, Mechanical vibration Balancing Shaft and fitment key convention ISO 2012 All rights reserved vBS ISO 21940-14:2012ISO 21940-14:2012(E)IntroductionThe balance quality of a rotor is assessed
23、 in accordance with the requirements of ISO 1940-1 or ISO 11342 by measurements taken on the rotor. These measurements might contain errors which can originate from a number of sources. Where those errors are significant, they should be taken into account when defining the required balance quality o
24、f the rotor.ISO 1940-1 and ISO 11342 do not consider in detail balance errors or, more importantly, the assessment of balance errors. Therefore this part of ISO 21940 gives examples of typical errors that can occur and provides recommended procedures for their evaluation.vi ISO 2012 All rights reser
25、vedBS ISO 21940-14:2012INTERNATIONAL STANDARD ISO 21940-14:2012(E)Mechanical vibration Rotor balancing Part 14: Procedures for assessing balance errors1 ScopeThis part of ISO 21940 specifies the requirements for the following:a) identifying errors in the unbalance measuring process of a rotor;b) ass
26、essing the identified errors;c) taking the errors into account.This part of ISO 21940 specifies balance acceptance criteria, in terms of residual unbalance, for both directly after balancing and for a subsequent check of the balance quality by the user.For the main typical errors, this part of ISO 2
27、1940 lists methods for their reduction in an informative annex.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document
28、(including any amendments) applies.ISO 1925, Mechanical vibration Balancing Vocabulary11)ISO 1940-1, Mechanical vibration Balance quality requirements for rotors in a constant (rigid) state Part 1: Specification and verification of balance tolerances12)ISO 11342, Mechanical vibration Methods and cri
29、teria for the mechanical balancing of flexible rotors13)ISO 21940-21, Mechanical vibration Rotor balancing Part 21: Description and evaluation of balancing machines3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 1925 apply.4 Balance error sources4.1 G
30、eneralBalancing machine balance errors can be classified into:a) systematic errors, in which the magnitude and angle can be evaluated either by calculation or measurement;b) randomly variable errors, in which the magnitude and angle vary in an unpredictable manner over a number of measurements carri
31、ed out under the same conditions;11) To become ISO 21940-2 when revised.12) To become ISO 21940-11 when revised.13) To become ISO 21940-12 when revised. ISO 2012 All rights reserved 1BS ISO 21940-14:2012ISO 21940-14:2012(E)c) scalar errors, in which the maximum magnitude can be evaluated or estimate
32、d, but its angle is indeterminate.Depending on the manufacturing processes used, the same error can be placed in one or more categories.Examples of error sources which may occur are listed in 4.2, 4.3, and 4.4.Some of these errors are discussed in greater detail in Annex A.4.2 Systematic errorsExamp
33、les of balancing machine systematic error sources are:a) inherent unbalance in the drive shaft;b) inherent unbalance in the mandrel;c) radial and axial runout of the drive element on the rotor shaft axis;d) radial and axial runout in the fit between the component to be balanced or in the balancing m
34、achine mandrel (see 5.3);e) lack of concentricity between the journals and support surfaces used for balancing;f) radial and axial runout of rolling element bearings which are not the service bearings and which are used to support the rotor;g) radial and axial runout of rotating races (and their tra
35、cks) of rolling element service bearings fitted after balancing;h) unbalance due to keys and keyways;i) residual magnetism in the rotor or mandrel;j) reassembly errors;k) balancing equipment and instrumentation errors;l) differences between service shaft and balancing mandrel diameters;m) universal
36、joint defects;n) temporary bend in the rotor during balancing;o) permanent bend in the rotor after balancing.4.3 Randomly variable errorsExamples of balancing machine randomly variable error sources are:a) loose parts;b) entrapped liquids or solids;c) distortion caused by thermal effects;d) windage
37、effects;e) use of a loose coupling as a drive element;f) transient bend in the horizontal rotor caused by gravitational effects when the rotor is stationary.2 ISO 2012 All rights reservedBS ISO 21940-14:2012ISO 21940-14:2012(E)4.4 Scalar errorsExamples of balancing machine scalar error sources are:a
38、) changes in clearance at interfaces that are to be disassembled after the balancing process;b) excessive clearance in universal joints;c) excessive clearance on the mandrel or shaft;d) design and manufacturing tolerances;e) runout of the balancing machine support rollers if their diameters and the
39、rotor journal diameter are the same, nearly the same or have an integer ratio.5 Error assessment5.1 GeneralIn some cases, rotors are in balance by design, are uniform in material and are machined to such narrow tolerances that they do not need to be balanced after manufacture. Where rotor initial un
40、balance exceeds the permitted values given in ISO 1940-1 or ISO 11342, the rotor should be balanced.5.2 Errors caused by balancing equipment and instrumentationBalance errors caused by balancing equipment and instrumentation can increase with the magnitude of the unbalance present. By considering un
41、balance causes during the design stage, some error sources can be completely eliminated (e.g. by combining several parts into one) or reduced (e.g. by specifying decreased tolerances). It is necessary to weigh the cost due to tighter specified tolerances against the benefit of decreased unbalance. W
42、here the causes of unbalance cannot be eliminated or reduced to negligible levels, they should be mathematically evaluated.5.3 Balance errors caused by component radial and axial runoutWhen a perfectly balanced rotor component is mounted eccentrically to the rotor shaft axis, the resulting static un
43、balance, Us, of the component, in gmm, is given by Formula (1):Us= me (1)wherem is the mass of the component, in g;e is the eccentricity of the rotor component relative to the rotor shaft axis, in mm.NOTE The mass can be stated in kg, the eccentricity in m, but the static unbalance remains in units
44、of gmm.The static unbalance of the component creates an identical static unbalance of the assembled rotor. An additional moment unbalance results if the component is mounted eccentrically in a plane other than that of the centre of mass. The further the plane distance is from the centre of mass, the
45、 larger the moment unbalance.If a perfectly balanced component is mounted concentrically, but with its principal axis of inertia inclined to the rotor shaft axis, a moment unbalance results; see Figure 1. ISO 2012 All rights reserved 3BS ISO 21940-14:2012ISO 21940-14:2012(E)For a small inclination a
46、ngle, , between the two axes, the resulting moment unbalance. Pr, in gmm2, is approximately equal to the difference between the moments of inertia about the component x- and z-axes, multiplied by the angle, , in radians; see Formula (2):Pr (Ix- Iz) (2)whereIxis the moment of inertia about the transv
47、erse x-axis through the component centre of mass, in gmm2;Izis the moment of inertia about the principal z-axis of the component, in gmm2; is the small angle between the component principal axis of inertia and the rotor shaft axis, in radians.Formula (2) is valid only if the component is symmetric a
48、bout its rotational axis and is therefore particularly applicable to the balancing of disks on arbors.The effects of radial runout and axial runout of a component mounted on the rotor can be calculated separately.For rotors with rigid behaviour, the separate unbalance components can be allocated to
49、the bearing or correction planes and then combined vectorially.For rotors with flexible behaviour, a rigid balance quality might be maintained, but accumulated axial disk runout errors (often described as skew) can lead to significant vibration due to the moment unbalance generated by the skewed disk(s).Key1 rotor plane, perpendicular to the rotor shaft axis x component transverse axis2 component plane y component transverse axisX rotor shaft transverse axis
