Belt Pull and Power for Inclined Conveyors

Mike Gawinski explains how to calculate required belt pull and required conveyor drive power on an inclined package handling belt conveyor. For a free copy of the company's power calculation program go to:
https://rulmecacorp.com/bulk-handling...
0:00 Introduction
0:19 Inclined Conveyors
0:41 Belt Pull Calculation
0:56 Belt Pull to Overcome Friction
2:02 Belt Pull to Overcome Gravity
2:46 Converting to HP
4:06 Comparison of Horizontal and Inclined Conveyors

This video explains how to calculate belt pull and required power to move discreet packages on an inclined slider bed conveyor. An understanding of the basic aspects of conveyor bulk pull is essential to properly designing, operating and maintaining belt conveyors. We know that the power required to move a load on a belt conveyor equals belt pull times belt speed.

Required Power = Belt Pull x Belt Speed

The belt pull required to move packages on an inclined slider bed conveyor equals the belt pull required to overcome friction plus the belt pull required to overcome gravity.

Belt Pull Required to Overcome Friction:
The belt pull required to overcome friction equals the total weight of all packages, plus the weight of the belt times the coefficient of friction between the bottom of the conveyor belt and the top of the slider bed.

For example, if a 10 foot long conveyor moves five 50 pound boxes simultaneously at a belt speed of 50 feet per minute on a conveyor belt with a weight of 3 lbs/ft, on a slider bed with a frictional coefficient of 0.5, then the belt pull to overcome friction is calculated as follows. First, calculate total weight.

Total Weight = 5 packages x 50 lbs/package + 10 feet of belt x 3 lbs/ft
Total Weight = 250 lbs + 30 lbs = 280 lbs

Belt pull required to overcome friction equals total weight times frictional coefficient between the bottom of the belt and the top of the slider bed.

Belt Pull = Total Weight x frictional coefficient
Belt Pull = 280 lbs x 0.5
Belt Pull = 140 lbs

Belt Pull Required to Overcome Gravity:
Belt pull required to overcome gravity equals the weight per foot of the load on the conveyor times the change in elevation of the conveyor. In this example, we have five boxes at 50 lbs/box, which equals a total load of 250 lbs.

Since the conveyor is 10 feet long, the average weight per foot of load on the belt equals 250 lbs divided by 10 ten, which equals 25 lbs/foot.

Belt pull = Weight per Foot of Load x Change in Elevation
Belt pull = 25 lbs/ft x 3 feet
Belt pull = 75 lbs.

Total Required Belt Pull = Belt Pull to Overcome Friction + Belt Pull to Overcome Gravity
Total Required Belt Pull = 140 lbs + 75 lbs
Total Required Belt Pull = 215 lbs

Then, convert this to required power.

Required Power = Belt Pull x Belt Speed

Required Power = 215 lbs x 50 fpm = 10,750 ft-lbs/min

Convert that to a useful unit of measure. One horsepower (HP) equals 33,000 ft-lbs/min. Therefore, our power requirement can be converted as follows.

Required Power = (10,750 ft-lbs/min)/(33,000 ft-lbs/min per HP)

Required Power = 0.33 HP

Now we can select an appropriate conveyor drive system.

Compare this "inclined conveyor" example with the "horizontal conveyor" described in our previous video. Note that a change from a horizontal conveyor to an inclined conveyor with a 3 foot change in elevation (all other parameters remaining constant) results in a power requirement which is more than 50% higher.

The inclined conveyor requires 0.33 HP while the horizontal conveyor only requires 0.2 HP. This underlines the fact that it is always important to calculate belt pull required to overcome gravity as well as belt pull required to overcome friction in inclined conveyors.