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Radial Gap, Overlap and Wheel Alignment
Wheels must rotate freely and not rub on the
inlet cone. Models USF with BI (backward-
inclined) or AF (airfoil) wheels overlap the
inlet cone. There is a gap between the inlet
cone and wheel on models USF with FC
(forward-curved) wheels. Refer to the tables
for the proper dimension.
Radial Gap and Alignment
Efficient fan performance can be maintained
by having the correct radial gap, overlap
and wheel alignment. These items should be
checked after the fan has been in operation
for 24 hours and before start-up when the
unit has been disassembled.
Radial Gap:
Adjust inlet cone position
such that the radial gap between the wheel
cone and inlet cone is evenly distributed
around the wheel.
Radial gap is adjusted by loosening the inlet
cone/ring bolts and centering the cone/ring
on the wheel. If additional adjustment is required to maintain a
constant radial gap, loosening the bearing bolts and centering
the wheel is acceptable as a secondary option.
Overlap:
Overlap is adjusted by loosening the wheel hub
from the shaft and moving the wheel to the desired position
along the shaft.
The transition between the inlet cone and wheel should be as
shown; there is a smooth feel to the profile when moving from
one component to the other.
Method for Centering Wheel:
centering can be accomplished by (a) loosening the inlet cone
bolts to move the inlet cone or by (b) loosening the bearings
in order to move the shaft. Wheel and inlet cone overlap
can be adjusted by loosening the wheel hub set screws and
moving the wheel to the desired position. Tighten all fasteners
and set screws securely and realign drive pulleys after
adjustment.
Forward-Curved
Gap Size
Inlet
Cone
12
Universal Single Width Fans
Backward-Inclined
Radial
Gap
Straight
Straight
Edge
Edge
On belt drive units,
Gap Dimensions
Series 100
Size
Gap
Direct Drive
6
⁄
(10)
3
8
Wheel
7
⁄
(10)
3
8
9
⁄
(13)
1
2
10
⁄
(13)
1
2
Belt Drive
9
⁄
(6)
1
4
10
⁄
(6)
1
4
12
⁄
(6)
1
4
15
⁄
(6)
1
4
18
⁄
(6)
1
4
20
⁄
(6)
1
4
22
⁄
(6)
1
4
24
⁄
(6)
1
4
Radial Gap and Overlap Dimensions
Overlap
Direct Drive
Size
4
6
8
10
A
13
15
16
18
Radial
Gap
Belt Drive
Size
4
Inlet
Inlet
Wheel
6
Cone
Cone
Cone
8
10
13
15
16
18
20
24
Radial Gap and Overlap Dimensions
Series
Series
300
500
6
7
8
10
7
8
9
10
12
12
13
13
15
15
16
16
18
18
20
20
22
22
24
24
27
27
30
30
33
33
36
36
40
40
44
44
49
49
54
60
66
73
Series 100
Overlap
A
Overlap
Tolerance
inches (mm)
4
⁄
⁄
⁄
(121)
(3)
(2)
3
1
1
4
8
16
4
⁄
⁄
⁄
(121)
(3)
(2)
3
1
1
4
8
16
4
⁄
(121)
⁄
(3)
⁄
(2)
3
1
1
4
8
16
5
⁄
(145)
⁄
(3)
⁄
(3)
11
1
1
16
8
8
5
⁄
⁄
⁄
(150)
(3)
(3)
7
1
1
8
8
8
7 (178)
⁄
(10)
⁄
(3)
3
1
8
8
7
⁄
(191)
⁄
(3)
⁄
(3)
1
1
1
2
8
8
9 (229)
⁄
⁄
(6)
(3)
1
1
4
8
Overlap
A
Overlap
Tolerance
inches (mm)
4
⁄
⁄
⁄
(121)
(3)
(2)
3
1
1
4
8
16
4
⁄
(121)
⁄
(3)
⁄
(2)
3
1
1
4
8
16
4
⁄
(121)
⁄
(3)
⁄
(2)
3
1
1
4
8
16
4
⁄
(121)
⁄
(3)
⁄
(2)
3
1
1
4
8
16
5
⁄
(146)
⁄
(6)
⁄
(3)
3
1
1
4
4
8
6
⁄
⁄
⁄
(165)
(13)
(5)
1
1
3
2
2
16
7
⁄
(181)
⁄
(13)
⁄
(5)
1
1
3
8
2
16
8
⁄
⁄
⁄
(219)
(16)
(6)
5
5
1
8
8
4
7
⁄
(197)
⁄
(16)
⁄
(6)
3
5
1
4
8
4
10
⁄
⁄
⁄
(259)
(19)
(10)
3
3
3
16
4
8
Overlap
A
Overlap
Tolerance
inches (mm)
2
⁄
(70)
⁄
(10)
⁄
(3)
3
3
1
4
8
8
5 (127)
⁄
⁄
(10)
(3)
3
1
8
8
3
⁄
(79)
⁄
(10)
⁄
(3)
1
3
1
8
8
8
5 (127)
⁄
(10)
⁄
(3)
3
1
8
8
1
⁄
(29)
2
⁄
(73)
⁄
(3)
1
7
1
8
8
8
3
⁄
⁄
⁄
(79)
(22)
(3)
1
7
1
8
8
8
3
⁄
(86)
⁄
(16)
⁄
(3)
3
5
1
8
8
8
3
⁄
(95)
⁄
(6)
⁄
(3)
3
7
1
4
32
8
4
⁄
⁄
⁄
(108)
(9)
(3)
1
11
1
4
32
8
4
⁄
⁄
⁄
(119)
(10)
(3)
11
3
1
16
8
8
5
⁄
(132)
⁄
(11)
⁄
(3)
3
7
1
16
16
8
5
⁄
(146)
⁄
(11)
⁄
(3)
3
7
1
4
16
8
6
⁄
⁄
⁄
(162)
(12)
(3)
3
15
1
8
32
8
7 (178)
⁄
⁄
(13)
(5)
1
3
2
16
7
⁄
(198)
⁄
(13)
⁄
(5)
13
17
3
16
32
16
8
⁄
(219)
⁄
(14)
⁄
(6)
5
9
1
8
16
4
9
⁄
⁄
⁄
(240)
(17)
(6)
7
11
1
16
16
4
10
⁄
⁄
⁄
(268)
(17)
(10)
9
11
3
16
16
8
11
⁄
(291)
⁄
(24)
⁄
(10)
7
15
3
16
16
8
12
⁄
(324)
⁄
(24)
⁄
(10)
3
15
3
4
16
8
14
⁄
⁄
⁄
(360)
(23)
(10)
3
29
3
16
32
8
15
⁄
1
⁄
⁄
(395)
(29)
(10)
9
1
3
16
8
8
17
⁄
(435)
1
⁄
(32)
⁄
(13)
1
1
1
8
4
2
18
⁄
(478) 1
⁄
(39)
⁄
(13)
13
17
1
16
32
2
20
⁄
1
⁄
⁄
(532)
(40)
(13)
15
9
1
16
16
2
22
⁄
1
⁄
⁄
(581)
(48)
(13)
7
29
1
8
32
2
25
⁄
(648)
1
⁄
(48)
⁄
(13)
1
29
1
2
32
2
®
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