8
with field-modified drives, use the deflection formula in
the following example and the tension data from Table 3.
EXAMPLE:
Given
Belt Span
16 in.
Belt Cross-Section A, Super Belt
Small Sheave PD
5 in.
Solution
a. From Table 3 find that deflection force for a new
type A, super belt with 5-in. small sheave PD is
8 lb.
b.
Tension Measurement Procedure
1. Measure the belt span (see Fig. 11).
2. Position bottom of the large O-ring on the span scale at
the measured belt span.
3. Set the small O-ring on the deflection force scale to zero.
4. Place the tension checker squarely on one belt at the cen-
ter of the belt span. Apply a force on the plunger and per-
pendicular to the belt span until the bottom of the large O-
ring is even with the top of the adjacent (next) belt or with
the bottom of a straight edge laid across the outside diam-
eters of the v-belt sheaves.
5. Remove the tension checker and read the force applied
from the bottom of the small O-ring on the deflection
force scale.
6. Compare the force you have applied with the values giv-
en in Table 3. The force should be between the “Used
Belt” and “New Belt” values shown. The maximum val-
ue is shown for “New Belt” and new belts should be
tensioned at this value to allow for expected tension loss.
“New Belt” tensions should be used at initial installation
and after job start or 1 to 3 minutes of operation. Used
belts should be maintained at the value as indicated in the
chart. “Used Belt” tensions should be used for the 8-hour
and subsequent checks. If the belt span was measured in
centimeters, then use the kilograms of force values for
comparison.
NOTE: The ratio of deflection to belt span is 1:64 in either
unit of measurement.
Whenever possible, jog start for a few revolutions or prefer-
ably run drive for approximately 1 to 3 minutes and then re-
tension in accordance with Steps 1-6. Running the drive for a
few revolutions or minutes will help seat the belt(s) in the
groove(s). This relatively early re-tensioning may reduce or
minimize the amount of re-tensioning required in the first 24
hours of drive service. Record information on the label
(Fig. 12) found on the door of the fan section.
Yearly
1. Lightly lubricate dampers and linkages.
2. Inspect both sides of coils for cleanliness. After cleaning,
check again by flashlight from one side to the other by
observing amount of light emission through the coil. Dirt
and debris can collect deep within a multi-row coil. Use
low pressure compressed air to blow through fins or de-
tergent water from clean side to dirty side to clear.
3. Lubricate control valve linkages.
Deflection =
(Belt Span)
64
Deflection =
16
=
1
/
4
in.
64
50
100
1
50
SP
AN
INC
HES
1
5
20
2
5
30
50
10
0
1
50
SP
AN
IN
C
H
ES
05
10
15
20
25
30
5
0
10
0
1
50
S
P
AN
IN
C
H
ES
0
5
10
15
20
2
5
30
DEFLECTION
FORCE
(LB.)
SMALL
“O” RING
SPAN SCALE
STRAIGHT
EDGE
LARGE “O” RING
V-BELT
ADJACENT
V-BELT
BELT
SPAN
Fig. 11 — Belt Tensioning
