BISOPE series
19- Field balancing, dynamic balancing
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Representative forces that generate vibration include
'shock excitation force' and 'centrifugal imbalance force'. Among them,
centrifugal imbalance acts as a centrifugal imbalance force (F = mrw²) and
accounts for more than 80% of the defects of the entire rotating machine. It is
also a very important cause of defects that occupy But can this centrifugal
unbalance force (1X, 1Order) be removed?
The meaning of "imbalance must exist during
rotation" in vibration analysis is the same as "unbalance can be
reduced but not eliminated". Therefore, so-called 'balancing' is necessary.
Correction of rotational unbalance force reduces unbalance force. It can be
divided into single-sided balancing and multi-dynamic (Dynamic) depending on
the plane of occurrence. It is divided into field balancing and shop(lab)
balancing.
Multi (Dynamic) balancing
If you are balancing a plane whose thickness is almost
small compared to its diameter, it is enough to attach a mass of the same
moment in the opposite direction to the axis of the point where the unbalanced
mass is located on the single plane. Even with single-sided balancing, it cannot
be corrected if the plane is over 1/4 thickness. This is because the ‘coupling
force’ occurs in the Z direction rather than the X and Y directions. Therefore,
the
amount of unbalance exists in each of the two planes, and the amount of
vibration can be reduced only by correcting the two planes at the same time.
Field balancing
Usually, the rotating body constitutes a large machine
including the rotating shaft, so it is better to perform balancing at the site
that can produce the same number of rotations as the rotating shaft. However,
when the environment is not favorable (in the case of an important facility
that needs to be operated by replacing the spare facility immediately), the
Rotor is transported to the shop, lab, and corrected and then reassembled.
At this time, the important point is that balancing should be performed
in a normal rotation state. However, balancing in the shop is performed by
measuring at a low speed and optimum rotation speed rather than the normal
operating rotation speed, so the plane is balanced, but the unbalance force of the
shaft is not taken into account. Most of the unbalance force is measured by phase and
vibration amount and the calibration result is checked, so it is vulnerable to
the second unbalance force produced by the frame, restraint facilities, and
other 'resonance' during reassembly.
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BISOPE , vs72@naver.com, 070-4388-0415, www.kCBM.kr
