5
Adjusting Fan Blade Pitch
The trial pitch is the calculated setting for design conditions
(water rate , heat load, air density, and brake horsepower)
. The trial
pitch is provided by SPX (see page 2).
1–Select a position on the fan circumference and rotate each blade
to this common location when setting or checking blade pitch. Sup-
port the blade tip to maintain a common rotation plane while setting
the fan pitch. The pitch is set
3
⁄
16
" (5 mm) inboard of the blade tip
by placing a protractor on top of a parallel sided straight edge that
extends across blade width as shown in
Figure 4.
2–Be sure all blades are positioned correctly on hub, then set the
pitch. Blades should be within ±
1
⁄
4
° of the desired pitch angle. After
the desired setting is obtained, progressively tighten the hardware
according to
Table 5. Recheck the pitch angle. If required, loosen
the hex nuts and reset the pitch as necessary until the proper pitch
angle is obtained.
Note
Figure 4
Table 5
Bolt
Diameter
3
⁄
8
"
5
⁄
8
"
ft·lb
ƒ
40
100
N·m
55
136
Torque Wrench Setting