V-belts – Twin City BCRFS Belt Driven Centrifugal Filtered Supply Fans - IM-4310 User Manual

Page 4

Twin City IM-4310

Figure 1. Eliminate Slack

Figure 2. Belt Deflection

Figure 3. Alignment

Figure 4. Two-Groove Sheaves (Pulleys)

Figure 5. Belts

Deflection

Deflection =

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 paral-

lel and sheaves in alignment to prevent

unnecessary 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 oper-

ating 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 1). When

it becomes necessary to adjust belt tension, do not

over-tension as bearing damage will occur. Recommended

belt tension should permit

⁄

" deflection per inch of

span of the belt at the center of the belt span. To find

this point, measure halfway between the pulley center-

lines as shown in Figure 2. Extreme care must be exer-

cised when adjusting V-belts as not to misalign the

pulleys. Any misalignment will cause a sharp reduction

in belt life and will also produce squeaky, annoying

noises (see Figure 3). On units equipped with 2 groove

pulleys, adjustments must be made so that there is

equal tension on all belts (see Figure 4).

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 5).

WARNING: When removing or installing belts, never

force belts over pulleys without loosening motor first to

relieve belt tension.
3. Fan speed can be increased by closing the adjustable

motor pulley or decreased by opening it. Always

check the load on the motor when increasing the fan

speed.

CORRECT

INCORRECT