CONVEYORS RULE OF THUMB.......!!!!! 1. Screw conveyors are used to transport even sticky and abrasive solids up inclines of 20° or so .They are limited to distances of 150 ft or so because of shaft torque strength. A 12 in. dia conveyor can handle 1000–3000 cu ft/hr, at speeds ranging from 40 to 60 rpm. 2. Belt conveyors are for high capacity and long distances (a mile or more ,but only several hundred feet in a plant),up inclines of 30° maximum. A 24 in. wide belt can carry 3000 cu ft/hr at a speed of 100ft/min, but speeds up to 600ft/min are suited for some materials. The number of turns is limited and the maximum incline is 30 degrees. Power consumption is relatively low. 3. Bucket elevators are used for vertical transport of sticky and abrasive materials. With buckets 20×20 in. capacity can reach 1000 cu ft/hr at a speed of 100ft/min, but speeds to 300 ft/min are used. 4. Drag-type conveyors (Redler) are suited for short distances in any direction and are completely enclosed. Units range in size from 3 in. square to 19 in. square and may travel from 30 ft/min (fly ash) to 250 ft/min(grains). Power requirements are high. 5. Pneumatic conveyors are for high capacity, short distance (400ft) transport simultaneously from several sources to several destinations. Either vacuum or low pressure (6–12psig) is employed with a range of air velocities from 35 to 120ft/sec depending on the material and pressure. Air requirements are from 1 to7 cu ft/cu ft of solid transferred.
Posted on: Thu, 23 Jan 2014 07:33:58 +0000
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