NA 121

DIN Standards Committee Tools and Clamping Devices

Standards [CURRENT]

DIN ISO 21940-21
Mechanical vibration - Rotor balancing - Part 21: Description and evaluation of balancing machines (ISO 21940-21:2012)

Title (German)

Mechanische Schwingungen - Auswuchten von Rotoren - Teil 21: Beschreibung und Bewertung von Auswuchtmaschinen (ISO 21940-21:2012)


This part of ISO 21940 specifies requirements for evaluating the performance of machines for balancing rotating components by the following tests: a) test for minimum achievable residual unbalance, Umar test; b) test for unbalance reduction ratio, URR test; c) test for couple unbalance interference on single-plane machines; d) compensator test. These tests are performed during acceptance of a balancing machine and also 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. Tests for other machine capacities and performance parameters, however, are not contained in this part of ISO 21940. For these tests, three types of specially prepared proving rotors are specified, covering a wide range of applications on horizontal and vertical balancing machines. An annex describes recommended modifications of proving rotors prepared in accordance with ISO 2953:1985. Moreover, this standard also stresses the importance attached to the form in which the balancing machine characteristics are specified by the manufacturer. Adoption of the format specified enables users to compare products from different manufacturers. Additionally, in an annex, guidelines are given on the information by which users provide their data and requirements to a balancing machine manufacturer. This standard is applicable to balancing machines that support and rotate rotors with rigid behaviour at balancing speed and that indicate the amounts and angular locations of a required unbalance correction in one or more planes. Therefore, it is applicable to rotors with rigid behaviour as well as to rotors with shaft-elastic behaviour balanced in accordance with low-speed balancing procedures. It covers both soft-bearing balancing machines and hard-bearing balancing machines. The International Standard ISO 21940-21:2012 "Mechanical vibration - Rotor balancing - Part 21: Description and evaluation of balancing machines" has been 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", the secretariat of which is held by DIN. The responsible German body involved in its preparation was Working Committee NA 001-03-06-01 (NALS/VDI C 6.1) "Auswuchten und Auswuchtmaschinen" ("Balancing and balancing machines") of the Acoustics, Noise Control and Vibration Engineering Standards Committee (NALS) in DIN and VDI.

Document: references other documents

Responsible national committee

NA 001-03-06 AA - Balancing and balancing machines 

Edition 2013-09
Original language German
Translation English
Price from 130.60 €
Table of contents


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