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MVA 02 rev 5 - December 2017
6.- Lift and remove the impeller (Photo 18): when
carrying out this operation, take care not to damage
or deform the impeller blades.
Photo 18
10.1.3 Adjusting blade angle
Blade angle adjustments may alter impeller balance. It is therefore advisable to check impeller balance after
adjusting blade angles, to prevent any abnormal vibration due to blade angle adjustment. Note that an
increase in blade angle also produces higher power absorption by the fan.
CAUTION:
Check that the available installed power has not been exceeded by checking power
absorption while running, and consult the data on fan characteristics to assess the permitted
variation.
This operation can be carried out with the impeller still fitted to the fan. Without removing them, slacken the
four fixing bolts (Fig. 10.1) at the base of each blade. Rotate the blade to alter its angle. The original angle is
shown on the blade by a mark on the ring between the base of the blade and the hub. A Model G1
goniometer, if supplied, can be used, or any other instrument for measuring angles. Tighten the four blade
fixing bolts in opposite pairs until the tightening torque indicated in 12.2 is reached
.
Fig. 10-1 Blade angle adjustment for impellers with steel hubs
.
