Belt Conveyor Effective Tension and Drive Power

EFFECTIVE TENSION is the force the drive pulley must produce. The FRICTION term is everything that resists motion along the run -- the belt itself counted on BOTH the carrying and the return sides, the material, and the rotating mass of the idlers -- multiplied by a friction factor around 0.022 for a well-maintained conveyor and by the length. The LIFT term is the potential energy being added, and it is the material weight per foot times the rise. Nothing else. Which term dominates decides what to fix, and that is the whole point of printing them separately. A 100 ft conveyor lifting 20 ft with 200 tons an hour at 300 fpm carries 22.2 lb of material per foot, and its lift term of 444 lb is five times its friction term of 88 lb: perfect idlers would save under a horsepower and cutting the rise in half would save two and a half, so if the motor is marginal the answer is the profile, not the maintenance. Reverse the geometry to 500 ft of flat run at the same tonnage and the friction term becomes 442 lb with no lift term at all, and now idler condition and alignment are the entire conversation. On a long flat conveyor friction is nearly everything; on a short steep one lift is nearly everything and the only ways down are less material or less rise. Effective tension and drive power only, on the simplified CEMA form. It does not compute the tension distribution around the loop, the slack-side tension needed to prevent drive-pulley slip or to keep the belt from sagging between idlers, or the take-up travel that maintains it, and it does not size the belt itself -- carcass rating, ply, cover, or splice. Acceleration, braking, and the runaway condition on a declining conveyor are separate and important problems, as is the belt tension the starting method produces. Skirtboard, plow, and tripper losses, material acceleration at the loading point, and the effect of temperature and belt condition on the friction factor are all outside it. CEMA's Belt Conveyors for Bulk Materials, the belt and idler manufacturers, and the engineer of record govern.

material load Wm = tph x 2000 / (speed x 60); friction = f x L x (2 Wb + Wm + Wrot); lift = H x Wm; Te = friction + lift; belt hp = Te x speed / 33,000; motor hp = belt hp / drive efficiency.

The simplified CEMA effective-tension form with the belt counted on both the carrying and return sides, and belt horsepower = Te x speed / 33,000, by name; the friction factor (about 0.022 for a well-maintained conveyor) and the idler rotating weight are entered rather than tabulated. Effective tension and drive power only. CEMA's Belt Conveyors for Bulk Materials, the belt and idler manufacturers, and the engineer of record govern.

The simplified effective-tension form is stated and cited to CEMA rather than reproduced from it; every weight and factor is user-entered.

Estimate. AHJ and licensed professional govern.

Field names used by the API: tons_per_hour, belt_speed_fpm, length_ft, lift_ft, belt_weight_plf, idler_weight_plf, friction_factor, drive_efficiency, material_load_plf, friction_term_lb, lift_term_lb, effective_tension_lb, belt_hp, motor_hp

• The belt counts twice carrying and return sides both appear in the friction termCEMA Belt Conveyors for Bulk Materials
• Which term dominates sets the lever lift-dominated means the profile; friction-dominated means idlers and alignmentCEMA Belt Conveyors for Bulk Materials
• Not a conveyor design no tension distribution, slack side, take-up, belt selection, acceleration, or brakingCEMA Belt Conveyors for Bulk Materials