As with proper belt tensioning, good sheave alignment will result in both maximum performance and maximum belt life. Therefore sheave alignment should be checked at least annually.
To check alignment, place a straight edge across the driver and driven sheaves as shown.
When the drives are properly aligned, the straight edge will contact all points as indicated. There should be no more than 1/16″ deviation from four-point contact.
If realignment is necessary, loosen the motor sheave and align it with the fan sheave and be sure to allow approximately 1/4″ for draw-up as the bushing screws are retightened.