Daikin RoofPak RPS Series Installation And Maintenance Manual page 111

Propeller Exhaust
For information, see Propeller Exhaust Fan Option on page
92.
Vibration Levels
Each unit as shipped is trim balanced to operate smoothly. To
provide satisfactory operation after shipping and installation,
use accepted industry guidelines for field balancing fans. See
Table 29.
NOTE: Excessive vibration from any cause contributes
to premature fan and motor bearing failure.
Monitor overall vibration levels every six months of
operation. An increase in levels is an indication of
potential trouble.
Table 29: Vibration Levels
Fan speed (RPM)
800 or less
801 or greater
Vibration Causes
1. Wheel imbalance.
a. Dirt or debris on wheel blades.
b. Loose setscrews in wheel hub or bearing-to-shaft.
c. Wheel distorted from overspeed.
2. Bent shaft.
3. Faulty drive.
a. Variable pitch sheaves—Axial and radial runout of
flanges; uneven groove spacing; out of balance.
Also similar faults in driven sheave.
b. Bad V-belts; lumpy, or mismatched; belt tension
too tight or too loose.
4. Bad bearings, loose bearing hold-down bolts.
5. Motor imbalance.
6. Fan section not supported evenly on foundation.
Periodic Service and Maintenance
1. Check all moving parts for wear every six months.
2. Check bearing collar, sheave, wheel hub setscrews,
sheave capscrews, and bearing hold-down bolts for
tightness every six months.
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Vibration
5 mils maximum displacement
0.20 in/sec maximum velocity
111
Setscrews
Setscrews are used to lock bearings, 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.
Refer to Table 30 and 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
Table 30: Setscrew Minimum Torque Specifications
Setscrew diameter (in .)
1/4
5/16
3/8
7/16
1/2
5/8
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.
1. Loosen the fan belts.
2. Support the weight of the fan and the fan shaft with
timbers or some other suitable means (see the fan shaft
support in Figure 121). Important: To maintain proper
drive alignment and fan-to-tunnel clearance, the fan
and shaft must not drop at all when the setscrews are
loosened in Step 4.
3. Verify that the upper shaft collar is securely fastened to
the shaft. Check the setscrew torque.
4. Loosen the upper and lower bearing setscrews. The
entire weight of the fan and shaft is now supported by
the fan shaft support.
5. Retighten all bearing setscrews to the torque
specification given in
support and re-tension the belts.
Figure 121: Return Fan Assembly
U p p e r B e a r i n g
F a n W h e e l
F a n S h a f t
S u p p o r t
IM 926-3 • ROOFPAK APPLIED SYSTEMS
Maintenance and Service
Setscrews).
Minimum torque (ft .lb .)
5.5
10.5
19.0
29.0
42.0
92.0
Table 30. Remove the fan shaft
F a n S h a f t
L o w e r
B e a r i n g