Fluke VIBXPERT II, Руководство по эксплуатации

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VIBXPER
T II Balancing 12.2019
Introduction
Balancing on machines with rotating masses
The VIBXPERT balancing module is based on the well-known 'influ-
ence coefficients method':
First, VIBXPERT measures the vibration amplitude and phase angle
and the vibration caused by the imbalance or so-called 'initial imbal-
ance'. A defined trial weight* is then attached and the instrument
measures the resulting change in amplitude and phase. VIBXPERT
calculates the influence coefficients from the difference between both
vibrations according to magnitude and phase which precisely indi-
cates the location and magnitude of the balancing weight with regard
to the position and size of the trial weight. In the case of two-plane
balancing, the calculation of the influence of the mass is also taken
into account in the other plane. All so-called 'rigid' rotors are balanced
using this method.
A rigid rotor mainly exhibits proportional vibration behavior if the
balancing weight and angle change. In the case of fixed rotational
speed, weaknesses or resonances in the mounting have no influence
on the vibration behavior. If the machine rotates at a variable speed,
it frequently exhibits different vibration behavior for each revolution
and, therefore, has to be balanced several times over the range of low-
speed to high-speed running.
Soft rotors do not exhibit the expected proportional behavior with the
calculated balancing weight, and the coefficients method does not ap-
ply. Such rotors can normally only be balanced in balancing machines
using a force measuring procedure.
* VIBXPERT calculates the weight and
location for the required trial mass in
such a manner that it usually results in a
reduction in the existing imbalance and
in the associated vibration load. This has
the added advantage that the trial mass
does not have to be removed again but
can remain on the machine indefinitely.