ISO 21940-11:2016 pdf free
ISO 21940-11:2016 pdf free.Mechanical vibration一Rotor balancing一Procedures and tolerances for rotors with rigid behaviour
Resultant unbalance and resultant moment unbalance (the latter can also be expressed as resultant couple unbalance) have different effects on forces on the bearings and on the vibration of the machine.In practice, therefore, both unbalances are often considered separately. Even if the unbalance is stated as a dynamic unbalance in two planes, it should be noted that in most cases there is a difference in effects if the unbalances predominantly form either a resultant unbalance or a resultant moment unbalance.
It is recommended to use reference planes to state the unbalance tolerances. For these planes, only the magnitude of each residual unbalance needs to stay within the respective balance tolerance whatever the angular position may be.
The aim of balancing is usually to reduce vibrations and forces transmitted through the bearings to the environment. For the purposes of this document, the reference planes for unbalance tolerances are taken to be the bearing planes. However, this use of bearing planes does not always apply.
NOTE For a component without a shaft (e.g. a disc shaped element), but where the final bearing positions are known (or can be estimated), these planes can be used.
Rotors that are out of unbalance tolerance need correction. These unbalance corrections often cannot be performed in the planes where the unbalance tolerances were set, but need to be performed where material can be added, removed or relocated.
The number of necessary correction planes depends on the magnitude and distribution of the initial unbalance, as well as on the design of the rotor, e.g. the shape of the correction planes and their location relative to the tolerance planes.
If a rotor with rigid behaviour does not comply with the conditions specified in 4.5.2, the moment unbalance needs to be reduced as well. In most cases, resultant unbalance and resultant moment unbalance are assembled into a dynamic unbalance: two unbalance vectors in two planes; see Figure 1 d). ISO 21940-11 pdf free download.
