Daikin RDT-135c, Installation And Maintenance Manual

Page: 117 / 132

IM 738-2
115
Maintenance: Setscrews
Fan Shaft Bearings
Relubricate fan shaft bearings periodically. Relubricate
according to the schedule shown in Table 26. If the bearings
are exposed to wet conditions, wide temperature variations, or
other severe atmospheric conditions, relubricate more
frequently. Use one of the greases shown in Table 25.
While the bearing is at normal operating temperatures, rotate
the fan by hand and add only enough grease to purge the seals.
The seals bleed slightly when this occurs. Do not overlubricate.
Propeller Exhaust
For more information, see page 96.
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 27.
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.
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, and wheel hub setscrews,
sheave capscrews, and bearing hold-down bolts for
tightness every six months.
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.
Using Table 28, 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”
below) .
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 114).
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 bearings to the torque specification given in
Table 28. Remove the fan shaft support and retension the
belts.
Table 25: Recommended greases
Manufacturer Product name Temp. range (°F)
Texaco Lubricants Co. Premium RB -30 to 300
Keystone Ind. Lubricants 84EP-2 -40 to 200
Mobil Oil Corporation Mobilith AW2 -40 to 325
Chevron U.S.A. Inc. SRI-2 -20 to 325
Exxon Company. U.S.A. Ronex MP -40 to 300
Shell Oil Company Alvania No. 2 -20 to 240
Table 26: Recommended fan shaft bearing lubrication
intervals
Operating
duty
Bearing ambient temperature
To 130°F To 150°F Over 150°F
Continuous 6 months 4 months 2 months
12 Hrs./Day 12 months 12 months 6 months
Table 27: Vibration levels
Fan speed (RPM) Vibration
800 or less 5 mils maximum displacement
801 or greater 0.20 in/sec maximum velocity
Table 28: Setscrew minimum torque specifications
Setscrew diameter (in.) Minimum torque (ft.lb)
1/4 5.5
5/16 10.5
3/8 19.0
7/16 29.0
1/2 42.0
5/8 92.0