How to Calculate Conveyor Tension

Industrial conveyor belts must have a specific amount of tension to properly function.

Minimum conveyor belt tension is the amount of necessary tension for a conveyor belt to operate properly. It needs to be high enough so the belt conforms to the crown of any pulleys and will not slip even under the most demanding conditions. This metric, also known as effective tension, changes over the life of the belt. The amount and type of required tension change will depend on what the belt is made of; for example, polyester belts reach maximum stretch in the first 24 hours of use, whereas cotton and nylon stretch over their lifetimes and require periodic retensioning.

Instructions

1. Find the weight of your conveyor belt components (CW). With regular 5-inch idlers, CW is equivalent to the belt width in inches. If you have 4-inch idlers, multiply the belt width in inches by 0.85 to get CW; if you have 6-inch idlers, CW is the belt width multiplied by 1.33.

2. If your belt length is shorter than 150 feet, multiply CW as found in Step 1 by 1.1 for lengths between 100 and 150 feet, 1.2 for lengths between 75 and 99 feet, 1.3 for lengths between 50 and 74 feet, 1.5 for lengths between 30 and 49 feet or 3.0 for lengths between 15 and 29 feet.

3. Find the tension required to move the empty belt (TC) by multiplying CW (including any modifiers you may have added in Step 2) by the length of the belt in feet (L) by the normal friction factor for moving a conveyor belt under normal conditions, which is 0.035.

   TC = CW x L x 0.035

4. Find the tension needed to move your load horizontally (TL) by multiplying the weight of the load in pounds (MW) by the belt length in feet (L) by the coefficient of friction needed to move a load horizontally under normal conditions, which is 0.04.

   TL = MW x L x 0.04

5. Find the tension needed to move the load horizontally (TH) by multiplying MW by the difference in vertical elevation between terminal pulleys, in feet (H).

   TH = MW x H

6. Find the effective belt tension (TE) by adding TC, TL and TH.

   TE = TC + TL + TH

7. Find the drive factor (D) by looking at Table 2 on the site linked under Resource 1.

8. Find the slack side tension (TS) by multiplying D by TE.

   TS = D x TE

9. Find the total operating tension (TO) by dividing TS by the belt width in inches (W) and adding that to TE.

   TO = TE + TS/W

Tips & Warnings

• The required motor horsepower (HP) can be found using TE and the belt speed in feet per minute (S).

• HP = TE x S/33,000

• Alternately, the maximum total tension (TO-MAX) allowable with a certain amount of motor horsepower can be found using many of the figures found in this tutorial plugged into the following formula:

• TO-MAX = 0.9(HP) x 33,000 x (1 + D)/W x S

References

• Conveyorbelt.com: How to Calculate Conveyor Belt Tension
• Belting: Minimum Conveyor Belt Tension

Resources

• Legg Belting: Technical