Manual

8 Aerovent IM-121
Figure 4. Eliminate Slack Figure 5. Belt Deflection
Figure 6. Alignment Figure 7. Two-Groove Sheaves (Pulleys)
Figure 8. Belts
Deflection
Deflection =
Belt Span
64
Belt Span
Slack belts wear excessively, cause slippage
and deliver less power. For longest belt life,
always provide proper tension
Mount belts straight. Shafts must be parallel
and sheaves in alignment to prevent unnec-
essary belt wear.
Two-groove variable pitch
sheaves must be opened the
same number of turns on
both sides; otherwise, slip-
page occurs, wearing belts
rapidly.
Do not force belt. Forcing the belt will
break the cords and cause belt failure.
V-Belts
V-belts on these belt driven fans are oil, heat, and static
resistant type and oversized for continuous duty. With
proper installation and maintenance, years of operating
efficiency can be added to the lifespan of the V-belt
drive.
The condition of V-belts and the amount of belt ten-
sion should be checked prior to start-up (see Figure
4). When it becomes necessary to adjust belt tension,
do not over-tension as bearing damage will occur.
Recommended belt tension should permit
1
64" deflection
per inch of span of the belt at the center of the belt
span. To find this point, measure halfway between the
pulley centerlines as shown in Figure 5. Extreme care
must be exercised when adjusting V-belts as not to mis-
align the pulleys. Any misalignment will cause a sharp
reduction in belt life and will also produce squeaky,
annoying noises (see Figure 6). On units equipped with 2
groove pulleys, adjustments must be made so that there
is equal tension on all belts (see Figure 7).
1. Where tensioning rods are not provided, adjustment is
more easily obtained by loosening and adjusting one
side of the motor bracket at a time.
2. Always loosen tension adjustment enough to place
belts on sheaves without running belts over the edge
of either sheave. A new belt may be seriously dam-
aged internally by careless handling (see Figure 8).
WARNING: When removing or installing belts, never force
belts over pulleys without loosening motor first to relieve
belt tension. The fan has been checked for mechanical
noises at the factory prior to shipment. If mechanical
noise should develop, then some suggestions are offered
here as a guide toward remedying the cause.
1. Check rotating members for adequate clearance.
2. Check proper belt tension and pulley alignment.
3. Check installation and anchoring.
4. Check fan bearings.
CORRECT
INCORRECT