Size Reduction and Material Handling: Mechanics and energy requirement in size reduction of agriculture produce; particle size analysis for comminuted solids; size separation by screening; fluidization of granular solids-pneumatic, bucket, screw and belt conveying; cleaning and grading; effectiveness of separation; centrifugal separation of solids, liquids and gases; homogenization; filtration and membrane separation.
Head pulley of a bucket elevator has an effective radius of 150 mm. In order to obtain the most satisfactory discharge from this elevator, the speed of the head pulley in rpm is
Options:
(A) 36
(B) 44
(C) 50
(D) 77
Official Answer Key:
D
Step-by-Step Solution & Explanation
For "satisfactory" (centrifugal) discharge in a bucket elevator, the optimum head-pulley peripheral speed is that at which the centrifugal force on the material just equals the gravitational force, i.e. v² = g·r, giving v = √(g·r).
v = √(9.81 × 0.150) = √1.4715 = 1.213 m/s.
Speed, N = v × 60/(2πr) = 1.213 × 60/(2π×0.150) = 72.78/0.9425 = 77.2 ≈ 77 rpm. Answer: (D) 77.
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