BS ISO 21940-11:2016 pdf download

BS ISO 21940-11:2016 pdf download.Mechanical vibration — Rotor balancing — Part 11: Procedures and tolerances for rotors with rigid behaviour
1 Scope
This document establishes procedures and unbalance tolerances for balancing rotors with rigid behaviour. It specifies
a) the magnitude of the permissible residual unbalance,
b) the necessary number of correction planes,
c) the allocation of the permissible residual unbalance to the tolerance planes, and
d) how to account for errors in the balancing process.
NOTE In ISO 21940-14, the assessment of balancing errors is considered in detail. Fundamentals of rotor balancing are contained in ISO 19499 which gives an introduction to balancing.
This document does not cover the balancing of rotors with flexible behaviour. Procedures and tolerances for rotors with flexible behaviour are dealt with in ISO 21940-12.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21940-2 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
4 Pertinent aspects of balancing
4.1 General
Rotor balancing is a procedure by which the mass distribution of a rotor is examined and, if necessary,adjusted to ensure that the residual unbalance or vibration in service is within specified limits. It should be noted that the vibration in service can originate from sources other than unbalance.
Rotor unbalance can be caused by design, material, manufacturing and assembly. Every rotor has an individual unbalance distribution along its length, even in series production.
4.2 Representation of the unbalance
For a rotor with rigid behaviour, different vectorial quantities can be used to represent the same unbalance as shown in Figure 1.
Figure 1 a) to c) shows different representations in terms of resultant unbalance and resultant couple unbalance, whereas Figure 1 d) to f) shows different representations in terms of a dynamic unbalance in two planes. NOTE 1 The resultant unbalance vector can be located in any radial plane (without changing magnitude and angle), but the associated resultant couple unbalance is dependent on the location of the resultant unbalance vector. NOTE 2 The centre of unbalance is that location on the shaft axis for the resultant unbalance, where the resultant couple unbalance is a minimum. If single-plane balancing is sufficient (see 4.5.2) or when considerations are made in terms of resultant unbalance and resultant couple unbalance (see 4.5.4), the representation in Figure 1 a) to c) is preferable. In the case of typical two-plane considerations, the representation in Figure 1 d) to f) is advantageous.