Page 338 - Machinery Component Maintenance

320 Machinery Component Maintenance and Repair

stalled. The operation of the instrument and the determination of the
masses required to correct the unbalance is carried out by trained person-
nel. Not only does this result in considerable cost savings but the method
also provides a significant saving in time compared to rebalancing on a
balancing machine. With careful preparation, field balancing of a blower
need not take more than 30-60 minutes.
It has been shown in practice that in over 95 percent of all blowers field
balancing in one plane is sufficient to reduce unbalance vibrations to per-
missible and safe values. The method is as follows:

1. The balancing instrument is used to measure the unbalance vibra-
tion at the bearing positions nearest to the blower rotor (Figures
6-41 and 6-42). The instrument suppresses with a high degree of
separation any extraneous vibration and shows the amount and the
angular position of the rotational frequency vibrations. Both mea-
sured values-also designated as “initial unbalance”-are entered
on a vector diagram (Figure 6-43).

Figure 6-41. Individual stages in the field balancing of a blower using balancing and vibra-
tion analyzer “VIBROTEST.”