1. Conveyor Belt Tension Calculation
The purpose of this section is to provide a simple and
efficient method to select the best conveyor belt for many
common applications. It may provide a way to quickly double
check a given design. If there are doubts or discrepancies,
get a recommendation from a reliable conveyor belt
manufacturer. The best selection will usually result in the
lowest total cost-per-ton over the service life of the conveyor
belt.
The best selection depends on acquiring complete operating
and environmental information. It is best to get this
information immediately and before any calculations are
attempted. This information should include:
1. Carrying Surface. State if load surface of belt is
supported by flat or troughed idlers or type of flat slider
bed surface. State angle of troughed idlers.
2. Drive Data.
a. Motor nameplate horsepower
b. Identify if single or multiple drive pulleys
c. Are drive pulleys bare or lagged?
d. Total belt wrap (degrees) on drive pulley(s)
e. Location of drive
3. Environment. Temperature, chemicals, oils, and any
special conditions.
4. Height. Vertical difference of head and tail (terminal)
pulleys, elevation (ft.).
5. Length. Distance (ft.) between head and tail pulley.
6. Loading Rate. Tons/hour.
7. Material. Type, temperature, weight per cu. ft., size and
percentage of maximum lumps.
8. Pulley Diameter. In addition to tail and head pulley, and
carry idlers, any pulley that changes belt direction
(identify each--include in system sketch).
9. Speed. (Ft./minute) of belt.

2. 10. Take-up. Type (mechanical screw or automatic),
location, and total amount of movement (included in
sketch).
11. Width of Belt. (Inches) Include width of pulley face
width, if known.
First, the Effective Belt Tension (TE) must be calculated. TE
is the sum of the tension required to move the empty belt
(TC), the tension required to move the load horizontally (TL),
and the tension required to lift the load (TH).
Example 1. TE = TC + TL + TH
Calculations
TC = F1 x L x CW
F1 = .035" [Normal friction factor for average conditions
(over 20°F) to move empty belt.]
L = Belt length (ft.)
CW = Weight of conveyor belt components. See Table
A.
TL = F2 x L x MW
F2 = .04" [Normal friction factor to move load
horizontally.]
L = Belt length (ft.)
MW = Material weight (lbs. per lineal foot).
MW = 33.3 TPH/Belt Speed (fpm) o rTotal material
load in lbs/L.
TH = H x MW
H = Difference in elevation of terminal pulleys (ft.)
TE = TC + TL + TH
(Continue with calculation of TS and then TO.)
Table A
Weight of Moving Conveyor Components

3. Belt Width CW Factor with
Regular 5"
Idlers (See Notes)
12" 12
18" 18
24" 24
30" 30
36" 36
42" 42
48" 48
54" 54
60" 60
NOTE:
For 4" idlers, multiply by .85
For 6" idlers, multiply by 1.33
For lengths (L) less than 150 gt., multiply by
100´ to 150´ -- 1.1
75´ to 99´ -- 1.2
50´ to 74´ -- 1.3
30´ to 49´ -- 1.5
15´ to 29´ -- 3.0
Table B
Drive Factor (D)
Screw
Take-Up
Gravity or
Flexible Take-
Up
Angle of
Belt
Wrap at
Drive
Type of
Drive
Bare
Pulley
Lagged
Pulley
Bare
Pulley
Lagged
Pulley
150 Plain 1.5 1.0 1.08 .67
160 Plain 1.4 .9 .99 .60
170 Plain 1.3 .9 .91 .55
180 Plain 1.2 .8 .84 .50
190 Snubbed 1.1 .7 .77 .45
200 Snubbed 1.0 .7 .72 ..42
210 Snubbed 1.0 .7 .67 .38
220 Snubbed .9 .6 .62 .35
230 Snubbed .9 .6 .58 .32

4. 240 Snubbed .8 .6 .54 .30
340 Tandem or
Dual
.5 .4 .29 .143
360 Tandem or
Dual
.5 .4 .26 .125
380 Tandem or
Dual
.5 .3 .23 .108
400 Tandem or
Dual
.5 .3 .21 .095
420 Tandem or
Dual
.4 .3 .19 .084
440 Tandem or
Dual
- - .17 .074
460 Tandem or
Dual
- - .15 .064
480 Tandem or
Dual
- - .14 .056
Additional tension must be added to the Effective Belt
Tension to prevent belt slippage on the drive pulley. This is
called Slack Side Tension (TS).
TS = D x TE Drive Factor - Table B
Total tension herein called Operating Tension (TO),
sometimes called Allowable Working Tension, is the value
used to select the reinforcement ply combinations.
TO = TE + TS/W
TE = Effective Belt Tension at drive
TS = Slack Side Tension
W = Belt Width (inches)
The next step is to select the proper reinforcement (usually
fabric) combinations. A number of alternatives are usually
available, and the final selection is narrowed by the
following considerations:
1. Flexibility to negotiate the pulleys. The minimum
recommended pulley diameters for each fabric -- the
number of plies combination must be considered at the
percent of rated tension of the combination. If this is
disregarded, service life will be shortened by ply
delamination, splice failure, and tracking problems.
See Table C, page 11-5.
2. Troughability. Eliminate combinations that will not

5. allow normal belt contact with carrying idlers, including
transition areas, while belt is empty. A belt with
inadequate transverse flexibility will result in poor
training and tracking which will cause edge wear,
spillage, poor loading, and early belt failure. See
Tables D1 and D2 on page 11-6.
3. Impact Resistance. The final selection must be rated
to handle the lump weights and the weight per lineal
foot of the material. Loading conditions will vary and
must be considered. Your selection must be rated for
the condition or the belt will be beaten into premature
failure. See Tables E1, E2, and E3 page 11-8.
4. Load Support. The final selection must be capable of
resisting the load weight at the juncture of the center
support idler and the troughing idlers. The belt
carcass will break down and split longitudinally in this
area if it is loaded beyond its capacity to support the
load. See Table F1 page 11-10.
The values of the belt carcass to pass the above
consideration should be available in the conveyor belt
manufacturer reference manuals or printed information for
belt selection.
The final selection of the alternate combinations should be
made by considering costs and availability from a reliable
source.
MOTOR HORSEPOWER (HP)
To determine the required motor horsepower given the
calculated Effective Belt Tension (TE) and belt speed (fpm).
HP = TE x fpm/33,000
To determine maximum Total Tension (TO) that a system
can generate given the nameplate horsepower of drive,
Drive Factor (D), width of belt (inches), and belt speed
(fpm).
TO-MAX = .9 HP x 33,000 x (1+D)/W x S
HP = Nameplate HP rating
D = Drive Factor (see Table B)
W = Belt Width (inches)
S = Speed of Belt (ft./min.)
NOTE:
If oversized motor is used, there is always the potential of

6. surge loading that could over stress the belt system.