6.1 FANS AND BLOWERS. The maintenance frequency required for fans and
blowers is influenced tremendously by the operating conditions. Fans
operating under dusty or corrosive conditions require far more frequent
attention than those handling clean air in a dry location.
Fan blades may be inspected for buildup of foreign material which may
cause imbalance or loss of capacity. Centrifugal fans with FC wheels are
especially susceptible to capacity loss due to dust packing the blades. Ap-
plications where buildup of foreign material should be anticipated are paint
spray booths, kitchen exhausts, and machine shops where normal dust in the
air is more likely to stick to a coated fan blade or support.
When cleaning accumulations from fan blades or wheels, use air hoses,
solvents, or soft brushes. Take care not to bend propeller fan blades when
cleaning, as this will cause a permanent vibration and require the replace-
ment of the blade.
6.2 MOTORS. Information on the maintenance of motors that is generally
applicable to fan motors is included in MO-116, Facilities Engineering
Electrical Interior Facilities.
Fan bearings of three types are in general use:
6.3 FAN BEARINGS.
The failure of bearings may usually be attributed to overheating or
The condition of bearings may be indicated by temperature dur-
ing operation. Temperatures over 140 F should be investigated further for
proper lubrication and load. For fans operating in high temperature
environments, special high temperature lubricants should be used. Standard
lubricants lose too much viscosity above 140 F. In all cases, the
lubricant recommended by the manufacturer is the best choice.
When lubricating fan bearings, do not use large quantities of grease or
oil. A few drops of oil properly distributed over the running surfaces of
the bearing will provide satisfactory lubrication. Too much lubricant may
cause high operating temperatures due to the working and churning of the
lubricant by the rolling elements. A potential fire hazard can also be
created by too much lubricant.
Overloading of bearings is most commonly caused by belt tensions that
are too tight. The fan bearing and motor bearing are both in jeopardy from