V-Belts - Carrier AERO 39MN Installation, Start-Up And Service Instructions Manual

string will touch them at the points indicated by the ar-
rows in Fig. 36.
Adjustable sheaves — To check the location of adjust-
able sheave on shaft, make sure that the centerlines of
both sheaves are in line and parallel with the bearing
support channel. See Fig. 36. Adjustable pitch drives are
installed on the motor shaft. Carrier recommends that
adjustable sheaves should only be used for initial bal-
ancing and be replaced with fixed pitch sheaves by the
air balancer prior to the final system air balance.
CAUTION
Do not exceed maximum fan speed rpm with adjustable
sheave.
3. Rotate each sheave one-half revolution to determine
whether the sheave is wobbly or the drive shaft is bent.
Correct any misalignment.
4. With sheaves aligned, tighten cap screws evenly and
progressively.
NOTE: There should be a
mating part hub and the bushing flange. If gap is closed, the
bushing is probably the wrong size.
5. With taper-lock bushed hubs, be sure the bushing bolts
are tightened evenly to prevent side-to-side pulley wob-
ble. Check by rotating sheaves and rechecking sheave
alignment. When substituting field-supplied sheaves for
factory-supplied sheaves, consider that fan shaft sheave
has been factory balanced with fan and shaft as an as-
sembly. For this reason, substitution of motor sheave is
preferable for final speed adjustment.
When installing or replacing belts, always use a
V-Belts —
complete set of new belts. Mixing old and new belts will re-
sult in the premature wear or breakage of the newer belts.
Fig. 36 — Determining Sheave-Shaft Alignment
1 / -in. to 1 / -in. gap between the
8 4
A39-137
Refer to label on inside of fan access door for information
on factory-supplied drive.
1. Always adjust the motor position so that V-belts can be
installed without stretching over grooves. Forcing belts
can result in uneven stretching and a mismatched set of
belts.
2. Do not allow belt to bottom out in sheave.
3. Tighten belts by turning motor-adjusting jackscrews.
Turn each jackscrew an equal number of turns.
4. Equalize belt slack so that it is on the same side of belt
for all belts. Failure to do so may result in uneven belt
stretching.
5. Tension new drives at the maximum deflection force
recommended (Fig. 37).
On current production, the correct tension information is
listed on the fan drive label. For older equipment or for units
with field-modified drives, use the deflection formula given
in the following example and the tension data from Fig. 37.
SMALL
BELT
SHEAVE
CROSS
PD RANGE
SECTION
(in.)
3.0- 3.6
A
3.8- 4.8
5.0- 7.0
3.4- 4.2
B
4.4- 5.6
5.8- 8.6
7.0- 9.4
C
9.6-16.0
4.4- 6.7
5V 7.1-10.9
11.8-16.0
12.5-17.0
8V
18.0-22.4
LEGEND
PD — Pitch Diameter, inches
Fig. 37 — Fan Belt Tension Data
EXAMPLE:
Given:
Belt Span
Belt Cross-Section A, Super Belt
Small Sheave PD
Deflection = Belt Span/64
Solution:
a. From Fig. 37 find that deflection force for type A,
super belt with 5-in. small sheave PD is 4 to 5
b. Deflection =
=
c. Increase or decrease belt tension until force required
for 1 / -in. deflection is 5 lb.
4
Check belt tension at least twice during first operat-
ing day. Readjust as required to maintain belt ten-
sion within the recommended range.
With correct belt tension, belts may slip and squeal mo-
mentarily on start-up. This slippage is normal and disappears
68
a39-1154
DEFLECTION FORCE (lb)
Steel Cable
Super Belts Notch Belts
Min Max Min Max Min
1 7 1
3 4 / 3 / 5 / 3
4 8 2
1 1 1
3 / 5 4 / 6 / 3
2 2 4
4 5 1 / 5 6 7 / 4
2 8
1 3
4 5 / 5 / 8 4
2 4
5 1 / 7 1 / 6 1 / 9 1 / 5
8 8 2 8
3 3 3 1
6 / 8 / 7 / 10 / 7
8 4 8 8
1 3 3 7
11 / 14 / 13 / 17 / 11
4 8 4 8
1 1 1 1
14 / 18 / 15 / 20 / 14
8 2 4 4
— — 10 15 —
1 3 7 3
10 / 15 / 12 / 18 / —
2 4 8 4
1
13 19 / 15 22 —
2
1
27 40 / — — —
2
30 45 — — —
16 in.
5 in.
16 /
64
/ -in.
1
4
Belts
Max
1
/ 4
4
3 3
/ 4 /
4 4
1 / 5 1 /
4 4
1 1
/ 5 /
2 2
3 / 7 1 /
4 4
3
8 /
4
1
/ 14
4
1 3
/ 17 /
4 4
—
—
—
—
—
1 / lb.
2