Periodic Service and Maintenance
Setscrews are used to lock sheaves, locking collars, and fan wheels to their shafts. They must be checked periodically to see that they have not loosened. If this is not done, severe equipment damage could occur.
Using Table 30, check the tightness of all setscrews with a torque wrench. Note that if the return fan bearings setscrews must be retightened, a special procedure is required to equally load both bearings (see “Return Fan Bearing Setscrews” ).
Return Fan Bearing Setscrews
Because the return fan is mounted on a vertical shaft, the following procedure must be used to retighten any return fan bearing setscrews that have loosened. This procedure will provide that both bearings are equally loaded
If one bearing is carrying the entire weight of the fan, it could fail prematurely.
Source: MaintainX (Community Member)