Rules Of Thumb : Conveyors For Particulate Solids

Part 1

1. Screw conveyors are used to transport even sticky and abrasive solids up inclines of 208 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 cuft/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 308 maximum. A 24 in. wide belt can carry 3000 cuft/hr at a speed of 100 ft/min, but speeds up to 600 ft/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 Â 20 in. capacity can reach 1000 cuft/hr at a speed of 100 ft/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 (400 ft) transport simultaneously from several sources to several destinations. Either vacuum or low pressure (6–12 psig) is employed with a range of air velocities from 35 to 120 ft/sec depending on the material and pressure. Air requirements are from 1 to 7 cuft/cuft of solid transferred.