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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