Technical data are subject to change without notice.
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Checking accuracy
With the help of the lowest reading, (V
2
= 3.2) one can predict the likely result of the balancing
work before the weight is welded to the rotor.
Draw an arc with radius V
2
= 3.2 from point 2 so that it intersects the other arcs.
If machine vibration is mainly due to out-of-balance, all three arcs will intersect at the same point.
This means that the calculated weight and position of the correction mass are sufficiently accurate
to reduce vibration to a value considerably lower than V
0
.
Other Causes of Vibrations
If a significant part of the measured vibration is due to other mechanical faults, the arcs will have no
common point of intersection. They will either form a triangle or, in some cases, not intersect at all.
The smaller the triangle between the arcs, the better the result of the balancing works. A large
triangle means that one has to find and remove other possible causes of vibration before achieving
accurate balancing results.
Measuring Angles
For rotors that will need balancing at least once every year, it is well worth taking time to prepare
mounting positions for the weights or at least to marks angles on the rotor when the machine is
next stripped down for repair or overhaul.
If only a small part of the rotor is accessible through a hatch or cover, a tape measure can be used
to mark off the angles. An arc of 120° has a length of 2.1 x radius. 1° is an arc of 0.0175 x radius.
If is also possible to mark ”trial points” at 120° intervals on the end of a shaft, a hub or some other
accessible part which turns with the rotor. Align the first ”trial point” on the shaft end with a fixed
point on the bearing housing or casing and attach the trial weight to the rotor. For the second and
third measurements align the other ”trial points” on the shaft end with the same fixed mark and
attach the trial weight through the same access point, hatch etc.
Out - of - balance
plus
other vibration
Mainly
out - of - balance
Balancing with T30 71
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