22
McQuay IM 777-6
Operation Guidelines
Figure 37: Torque Requirements at 100% WOV for
SWSI Plenum Fans with NESTED Inlet Vane
Fan Vibration Levels
Each unit as shipped is trim balanced to operate smoothly. To
provide satisfactory operation after shipping and installation,
use the accepted industry guidelines for field balancing fans.
See
Table 14
.
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 set screws in wheel hub or bearing-to-shaft.
c
Wheel distorted from overspeed.
2
Bent shaft.
3
Drive faulty.
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
Table 12: Operating Limits—Plenum Fans
Fan operating limits
Plenum fans
Diameter
13.5
15
16.5
18.25
20
22.25
24.5
27
30
33
36.5
40.25
44.50
49
54.25
60
Class
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Maximum rpm
3,909
3,468
2,820
2,930
2,674
2,403
2,183
1,860
1,783
1,620
1,465
1,329
1,202
1,091
986
891
Maximum motor HP
7.5
10
15
15
15
20
25
30
40
40
50
60
75
75
75
75
Table 13: Operating Limits—Inline Fans, Twin Fans
Fan operating limits
Inline fans
Diameter
18.25
20
22.25
24.5
27
30
33
36.5
40.25
44.50
49
54.25
Maximum rpm Class I
2727
2488
2236
2041
1835
1665
1476
1330
1208
1072
973
880
Maximum rpm Class II
3409
3111
2796
2551
2294
2082
1846
1662
1510
1340
1216
1100
Twin fans
Diameter
9 x 9
10.62
12.62
15
18.12
20
Maximum rpm
2575
2400
2000
1700
1400
1200
Maximum HP
10
15
15
30
40
40
6
0
0
700
600
500
400
100
900
300
200
To
rq
ue
(
lb
./i
n.)
Fan Speed (rpm)
800
900
1
000
1
500
2000
400
500
600
700
300
200
3000
800
1000
2000
3000
4000
5000
5
4
2
4
9
0
4
4
5
4
0
2
3
6
5
3
3
0
3
0
0
2
7
0
2
4
5
To
rq
u
e
(
in
-l
b
)
Table 14: Vibration Levels
Fan speed (rpm)
Vibration
800 or less
5 mils maximum displacement
801 or greater
0.20 in/sec. maximum velocity
Summary of Contents for Skyline IM 777-6
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