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ISO 21940-31 1st Edition, August 15, 2013 Mechanical vibration - Rotor balancing - Part 31: Susceptibility and sensitivity of machines to unbalance
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Availability date: 07/13/2021
Description / Abstract:
This part of ISO 21940 specifies methods for determining machine
vibration sensitivity to unbalance and provides evaluation
guidelines as a function of the proximity of relevant resonance
rotational speeds to the operating speed. This part of ISO 21940 is
only concerned with once-per-revolution vibration caused by
unbalance. It also makes recommendations on how to apply the
numerical sensitivity values in some particular cases.
It includes a classification system that can be applied to
machines which is related to their susceptibility to a change in
unbalance. Machines are classified into three types of
susceptibility and five ranges of sensitivity. The sensitivity
values are intended for use on simple machine systems, preferably
with rotors having only one resonance speed over their entire
operating speed range. The sensitivity values can also be used for
machines that have more resonance speeds in their operating speed
range if the resonance speeds are widely separated (e.g. by more
than 20 %).
The sensitivity values given are not intended to serve as
acceptance specifications for any machine group, but rather to give
indications regarding how to avoid gross deficiencies as well as
specifying exaggerated or unattainable requirements. They can also
serve as a basis for more involved investigations (e.g. when in
special cases a more exact determination of the required
sensitivity is necessary). If due regard is paid to the values
given, satisfactory running conditions can be expected in most
cases.
The consideration of the sensitivity values alone does not
guarantee that a given magnitude of vibration in operating is not
exceeded. Many other sources of vibration can occur which lie
outside the scope of this part of ISO 21940.