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 The vaneaxial fan has a set of stationary vanes placed ahead of or after
the propeller. These vanes help straighten the air and convert the rotation
energy to static pressure energy. The fan blades may be fixed or adjustable
to meet the specific application. Vaneaxial fans can develop static
pressures comparable to that produced by the centrifugal fans. They have
the advantage of a straight-through design, and are well suited to
installation in a straight run of ductwork. Some vaneaxial fans have higher
noise characteristics than comparable capacity centrifugal fans.
The fan is mechanically connected to its shaft
2.6 FAN-TO-SHAFT CONNECTION.
by one of three methods:
Set screw
a.
Set screw and key
b.
C.
Expanding hub
The same methods are used for fastening pulleys (sheaves) to shafts.
Figure 2-11 shows the simplest type of fan-to-shaft attachment. The set
screw threads through the fan hub, and bottoms out on the fan shaft. When
installing a fan with a set screw, there will be one flat side on the
shaft. It is imperative that the set screw be lined up with this flat
spot. If it is not, the fan may be secure to the shaft, but it will soon
work its way loose.
FIGURE 2-11
Fan Hub Fastened to Shaft With a Set Screw
Figure 2-12 shows a key fastening arrangement. This is much stronger
than the simple set screw method. It is used for more severe fan duty.
When removing a fan that is fastened in this manner, take care not to lose
the key.
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