Turn the shaft by hand, if the impeller rubs the inside of the casing it must be realigned. The following
steps are used to align the impeller.
NOTICE:
Impeller rubbing is often caused by pipe strain or belt tension. Pipe strain must be eliminated
prior to impeller alignment. The impeller should aligned after proper belt tensioning.
Clearance measurement
The alignment worksheet Figure:
Impeller alignment worksheet,
is used to align the impeller of the AF
pump. The measurement procedure is as follows:
Make sure the cap screws fastening the casing to the elbow are tight (if applicable), so an accurate
measurement of the impeller clearances can be made prior to adjustment.
Mark each blade 1, 2, 3 and 4 and then align the impeller blades as shown on the impeller alignment
worksheet (approx. 2, 4, 8, and 10 o’clock).
Rotate the shaft and measure the gap between each blade and the casing at all four clock positions indi-
cated on the worksheet. The value of interest is the largest value of feeler gauge thickness that will slide
easily the whole length of the vane tip.
Add the measurements for all positions together and divide by the number of measurements. This will
give the average measurement.
Divide the average measurement by 2. This will give the minimum clearance.
If any blade has a clearance in any position smaller than the calculated minimum clearance the prop is
not sufficiently centered and should be adjusted.
4.5 Impeller Alignment
Model AF (42"/1200mm/54"/60"/66") LM/LMR Bearings Installation, Operation, and Maintenance Manual
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