12
Twin City IM-4800
Figure 5. Eliminate Slack
Figure 6. Belt Deflection
Figure 7. Alignment
Figure 8. Belts
Figure 9. 2-Groove Sheaves
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 tension
should be checked prior to start-up (see Figure 5).
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 6. 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 7). On units equipped with 2
groove pulleys, adjustments must be made so that there
is equal tension on all belts (see Figure 9).
1. Where tensioning rods are not available, 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
damaged internally by careless handling (see Figure 8).
3. Fan speed can be increased by closing the adjustable
motor pulley, or decreased by opening it. Two
and three groove adjustable pitch pulleys must be
adjusted an equal number of turns. (See Figure 9).
Always check load on motor when increasing fan
speed.
CORRECT
INCORRECT
When removing or installing belts, never force
belts over pulleys without loosening motor first to
relieve belt tension.
WARNING
