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Technical

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     A Printable Data Sheet for your conveyor information.

Tension Calculations

The best place to start with your tension calculations is to gather all the data that you will need.  Click here for a printable form that will aid you in your Data gathering and calculations.  You can enter data in the form and then print it, or print it and fill it in by hand.  This is good information to have on hand for many aspects of conveyor system management.  Legg Co. recommends that these Data Sheets be filled out and filed for all of your conveyor systems.

Quick Calculation

The quickest way to determine what tension rating a new belt for your system would require is to figure the maximum amount of tension that your system could put on the belt.  Below is the formula for calculating how much belt tension your system can generate.  

Note:  This formula is assuming that your system is not over horse powered.  If it is this formula will indicate a heavier belt tension rating than is required by the system.  It is important that you understand that required tension rating is only one part of the belt selection process and that other considerations such as, but not limited to, Troughability and Load Support need to be made.

To determine Maximum Total Tension (M_TT) that a system can generate given the nameplate horsepower of the drive, Drive Factor (D_F) (Table 2), width of belt (inches), and belt speed (fpm).

HP = Nameplate HP rating

D_F = Drive Factor (see Table 2)

BW = Belt Width (inches)

S = Speed of Belt (ft./min.)

Below is a simplified belt tension calculation formula that will give you the required belt tension rating for your system.  It should be understood that this is ONLY a simplified formula for calculating belt tension on simple conveyor systems.  Accurate belt tension requirements should be supplied by the conveyor system manufacturer and/or engineering firm responsible for the design of the system.  Legg Co. recommends that the formulas and calculations found in the CEMA manual be followed for the most accurate required belt tension calculations.

First you must calculate the Effective Belt Tension (EBT).   EBT = T_EB + T_LH + T_LL    EBT is the sum of the tension required to move the empty belt (T_EB), the tension required to move the load horizontally (T_LH), and the tension required to lift the load (T_LL).

NF₁ = .035 [Normal friction factor for average conditions (over 20°F) to move empty belt.]
BL = Belt Length (ft.)
W_t = Weight of conveyor belt components. See Table 1.

NF₂ = .04 [Normal friction factor to move load horizontally.]
CL = Conveyor Length (ft.)
MW = Material weight (lbs. per lineal foot).
MW = 33.3 TPH/Belt Speed (fpm) or Total material load in lbs/L.

LF = Lift, difference in elevation of terminal pulleys (ft.)

Additional tension must be added to the Effective Belt Tension to prevent belt slippage on the drive pulley. This is called Slack Side Tension (T_SS).

T_SS = D x EBT 

D = Drive Factor - Table 2  

Total tension herein called Allowable Working Tension (AWT), is the value used to select the reinforcement ply combinations.

EBT = Effective Belt Tension at drive

T_SS = Slack Side Tension

W = Belt Width (inches)

NOTE:    For 4" idlers, multiply by .85
                For 6" idlers, multiply by 1.33
                For lengths (L) less than 150 ft., 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

Next, select the proper belt reinforcement member.  Consideration needs to be given to Flexibility, Troughability, Impact Resistance, and Load Support (Idler Junction Support).  Consult Legg Company or your Legg Belting Distributor for final recommendation.  Be sure to have previous belt failure cause available.

Coefficient of Friction

Table Fs-1 gives some generalizations for the coefficient of friction of conveyor belting to polished steel or aluminum sheeting.

Table Fs-1

*xx* - The coefficient of friction for a rubber cover will very greatly depending on the type and duro of the rubber cover.

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