How to Calculate Inclined Roller Conveyor Belt Pull

This video shows how to calculate required belt pull and power to move packages on an inclined roller-supported conveyor belt. For more conveyor info, go to https://rulmecacorp.com/motorized-pul... 0:00 Start 0:30 Related Videos 1:53 Power equals force times velocity 5:15 Belt pull to overcome bearing friction 7:18 Belt pull to overcome gravity 8:00 Required power 9:30 Selection of drive 9:58 Sensitivity analysis Use this video with our other videos on how to calculate required belt pull and mechanical power to move: • Discrete packages on a horizontal roller-supported conveyor belt. • Discrete packages on an inclined slider bed supported conveyor belt. • Continuously flowing bulk materials on a inclined roller-supported conveyor belt. The power required to move a load on a belt conveyor may be calculated as follows: Required Power = Force x Velocity Required Power = Belt pull x belt speed The belt pull required to move packages on an inclined roller-supported conveyor belt equals the total weight of all packages plus the weight of the belt plus the weight of all rotating parts times the coefficient of bearing friction of the supporting rollers, as summarized in this equation: F = (0.04 x L x (2Pn +Ppr + Pm)) + (H x Pm) Where, L = conveyor length H = material lift height Pn = weight per foot of conveyor belt Ppr = weight per foot of all rotating parts Pm = weight per foot of product to be handled If a roller brand and belt supplier have not been selected, then we use: 0.04 as the roller bearing frictional coefficient 5 lbs per foot as the weight per foot of all rotating parts 5 lbs per foot of conveyor belt If the roller is especially long or if the roller has a thick wall, then you should consult your roller supplier for specific details. For example, consider a 100-foot-long, inclined, roller-supported, belt conveyor continuously moving 25 evenly spaced boxes, with an average weight of 50 lbs/box, at a belt speed of 100 fpm on a conveyor belt during an 8 hour shift. The belt pull is calculated as follows. Belt pull required to overcome roller bearing friction: • L = 100 ft • Pn = 2 x 5 lbs/ft of belt = 10 lbs/ft of belt • Ppr = 5 lbs/ft of rotating parts • Pm = (25 packages x 50 lbs/package) / 100 feet = 12.5 lbs/foot of product • Total weight on rollers = 27.5 lbs/ft Belt pull to overcome roller bearing friction = 0.04 x 100 ft x 27.5 lbs/ft = 110 lbs Belt pull required to overcome gravity: • H = 20 ft • Pm = (25 packages x 50 lbs/package) / 100 feet = 12.5 lbs/foot of product Belt pull required to overcome gravity = 20 ft x 12.5 lbs/ft = 250 lbs Total belt pull required to move packages = 110 lbs + 250 lbs = 360 lbs To determine required power use this equation: Required Power = Belt pull x belt speed Required power = 360 lbs x 100 fpm = 36,000 ft-lbs/min We can now convert that to a useful unit of measure. 1 HP = 33,000-foot-pounds per minute. Required power = (36,000 ft-lbs/minute) / (33,000 ft-lbs/ minute / HP) = 1.1 HP Now we can make a selection of an appropriate conveyor drive system. Here’s a tip to selecting an adequate amount of drive power for a conveyor. Select a power and then do a sensitivity analysis, verifying that all design assumptions are correct. Let’s select a conveyor drive of 1.5 HP and check the validity of the design rate. Suppose the design rate was based on a daily average handling rate calculated as follows: • Total package weight handled during 8 hour shift = 600,000 lbs • Total number of packages handled during 8 hour shift = 12,000 packages • Average package weight = (600,000 lbs/shift) / 12,000 packages/shift) = 50 lbs/package However, suppose while double-checking the design parameters you learn that heavy packages (120 lbs/box) are handled from 8:00am to 10:00 am and light packages (26.67 lbs/box) are handled from 10:00am to 4:00pm on every shift. Check required conveyor drive power from 8:00 am to 10:00am. Belt pull required to overcome roller bearing friction: • L = 100 ft • Pn = 2 x 5 lbs/ft of belt = 10 lbs/ft of belt • Ppr = 5 lbs/ft of rotating parts • Pm = (25 packages x 120 lbs/package) / 100 feet = 30 lbs/foot • Total weight on rollers = 45 lbs/ft Belt pull = 0.04 x 100 ft x 45 lbs/ft = 180 lbs Belt pull required to overcome gravity: • H = 20 ft • Pm = (25 packages x 120 lbs/package) / 100 feet = 30 lbs/foot of product Belt pull required to overcome gravity = 20 ft x 30 lbs/ft = 600 lbs Total belt pull required to move packages = 180 lbs + 600 lbs = 780 lbs Convert this required belt pull to required power. Required Power = Belt pull x belt speed Required power = 780 lbs x 100 fpm = 78,000 ft-lbs/min Therefore, Required power = (78,000 ft-lbs/minute) / (33,000 ft-lbs/ minute / HP) = 2.4 HP If we installed 1.5 HP the drive would not have enough power to move the heavy boxes from 8:00 am to 10:00am. The correct drive selection would be 3 HP.