DIN ISO 21940-12:2016-09

The aim of balancing any rotor is to achieve satisfactory running when installed in-situ. In this context, “satisfactory running” means that not more than an acceptable magnitude of vibration is caused by the unbalance remaining in the rotor. In the case of a rotor with flexible behaviour, it also means that not more than an acceptable magnitude of deflection occurs in the rotor at any speed up to the maximum service speed. This part of ISO 21940 presents typical configurations of rotors with flexible behaviour in accordance with their characteristics and balancing requirements, describes balancing procedures, specifies methods of assessment of the final state of balance, and establishes guidelines for balance quality criteria. This part of ISO 21940 also shows how criteria can be derived for use in balancing in a balancing machine, both from limits of vibration specified for the assembled and erected machine and from limits of unbalance specified for the rotor. If such limits do not exist, this part of ISO 21940 shows how they can be derived from ISO 7919 and ISO 10816 when it comes to vibration values, or how they can be derived from ISO 21940-11 when it comes to values of permissible residual unbalance. This part of ISO 21940 is not intended to serve as an acceptance specification for any rotor, but rather to give indications of how to avoid gross deficiencies and unnecessarily restrictive requirements. Structural resonances and modifications thereof lie outside the scope of this part of ISO 21940. The underlying International Standard ISO 21940-12:2016 "Mechanical vibration - Rotor balancing - Part 12: Procedures and tolerances for rotors with flexible behavior" 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. German cooperation was provided by the committee NA 001-03-06-01 UA (NALS/VDI C 6.1) "Auswuchten und Auswuchtmaschinen" ("Balancing and balancing machines") at Standards Committee Acoustics, Noise Control and Vibration Engineering (NALS) at DIN and VDI.