Bucket drive power requirement

DIN 22200 gives guidance on calculating the drive power requirements for bucket elevators. Here only a simplified method will be indicated, based on the fact that the term Ph representing the actual lifting power input is by far the dominant term in the equation (for comparison, see the equation for the inclined belt conveyor given earlier on), while the proportion required for overcoming frictional losses can be taken into account by means of a coefficient w ... 

Bucket elevators. The bucket elevators lift catalyst, at 900-1000°F., about 200 ft. Each elevator consists of two chains with a continuous line of alloy-steel buckets loosely supported between them (217). The upper shaft is fixed in position but the bottom shaft can move to offset thermal expansion and wear of the chain. Chain speeds are 90 to 125 ft./minute at catalyst-circulation rates of 100 to 150 tons/hour. Power requirement is 60 to 80 horsepower (241). Differential band brakes protect against reverse rotation in case of a power failure. Sprockets with renewable teeth were used at first (217), but a traction-wheel drive was later substituted because wear is more evenly distributed and life is longer (241). Repair techniques have been developed for extending chain life (316). Graphite is used to lubricate the chains (239). The upper shaft and main bearings are water-cooled and the bearings are lubricated with oil. 

Choose a bucket elevator to handle 150 tons/h (136.1 tonnes/h) of abrasive material weighing 50 lb/ft3 (800.5 kg/m3) through a vertical distance of 75 ft (22.9 m) at a speed of 100 ft/min (30.5 m/min). What horsepower input is required to drive the elevator The bucket elevator discharges onto a horizontal conveyor which must transport the material 1400 ft (426.7 m). Choose the type of conveyor to use and determine the required power input needed to drive it. 

Example.—Required the net operating cost of a 100-ft. double-strand (two chain) elevator handling sand weighing 120 lb. per cubic foot. Elevator to have malleable-iron buckets and combination chains. Power delivered at elevator drive commanding a value of 3 cts. per horsepower. Elevator to be used 1,500 hr. per year. Capacity 25 tons per hour. 

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