Technical handbook for the paddy rice postharvest industry in ...

More documents

Recommendations

Info

74 POSTHARVEST INDUSTRY HANDBOOKcompared to other grains. Because these conveyors are seldom used for movingpaddy, their discussion is limited.Shaker conveyorShaker (also called vibrating, oscillating, or grasshopper) conveyors move paddy ina uniform, continuous flow by the upward and forward oscillating motion of acontinuous trough that is mounted on sturdy inclined reactor legs (Fig. 3.46). Theconveyor consists of a steel or wood trough mounted on flat spring, resilient supportlegs with a positive action drive. The drive consists of a motor turning a shaft onwhich an eccentric provides the oscillating action to the trough.The shaker conveyor is designed for horizontal conveying. It is particularly suitedfor moving wet paddy from the parboiling tanks to the dryer. In this case, the bottomof the trough is perforated to permit excess water from the parboiled paddy to drainbefore reaching the elevator leg.The carrying capacity of the shaker is small. A trough 30 cm wide by 10 cm deepwould be limited to about 5 t/ hour. A 46- × 10-cm trough would have a capacity ofabout 7.5 t/ hour. Horsepower requirements are low. A 5-t/ hour shaker conveyorwould be limited to a maximum length of 21 m and would require 1 hp.Chain conveyorChain conveyors are inexpensive, slow, noisy, and mechanically inefficient. To movepaddy, scrapers or drags used with the chain operating in a closed container ortrough incur excessive wear due to the abrasive paddy. Figure 3.47 shows the crosssection of the conveyor trough and the normal movement of paddy as it is draggedby the conveyor chain. Horsepower requirements for chain conveyors are more thanfor belt or shaker conveyors of the same capacity. Because of the highly abrasivenature of paddy, the expected life of the chain conveyor is considerably less than thatof the belt conveyor.3.46. Shaker or vibratingtypeconveyor showingspring mounting andpower drive.
75 CONVEYING3.47. Cross section ofchain-drag conveyor.Pneumatic conveyorPneumatic conveyors move material in a closed-duct system by a high-velocity airstream. The system uses a material feeder or collector, an air blower, ducts, and acyclone for collection or discharge. Figure 3.48 illustrates a common use of thepneumatic system — unloading ships or railcars and conveying the grain into astorage or another handling system.The power requirements for a pneumatic conveyor are high. A larger problem isthe excessive wear on the equipment caused by the highly abrasive paddy. Therefore,the pneumatic system is seldom used for moving paddy.The pneumatic conveying system is most useful in handling less dense paddy huskand other by-products such as bran and fine brokens. It is hard to beat for handlinghusk and bran. Wear is minimized by the proper duct design, velocity considerations(not too fast, not too slow), and matching the system to the requirements.3.48. Typical pneumaticconveying system.
Page 1 and 2: Chapter 3CONVEYINGIn the paddy post
Page 3 and 4: 47 CONVEYINGTypesBucket elevators a
Page 5 and 6: 49 CONVEYING3.6. Elevator discharge
Page 7 and 8: 51 CONVEYING3.7. Elevator head show
Page 9 and 10: 53 CONVEYING8.11. Boot section desi
Page 11 and 12: 55 CONVEYING3.15. Elevator with pla
Page 13 and 14: 57 CONVEYINGments vary with segment
Page 15 and 16: 59 CONVEYINGHorsepower requirements
Page 17 and 18: 61 CONVEYING3.24. Standard hangerbe
Page 19 and 20: 63 CONVEYING3.28. Drive arrangement
Page 21 and 22: 65 CONVEYINGWhen the auger is opera
Page 23 and 24: 67 CONVEYINGExample: Determine belt
Page 25 and 26: 69 CONVEYINGeither side of the belt
Page 27 and 28: 71 CONVEYING3.40. Self-aligning cam
Page 29: 73 CONVEYING3.44. Wing-type pulley.
Page 33 and 34: 77 CONVEYINGMost spouting is straig
Page 35 and 36: 79 CONVEYING3.54. Five-way distribu

Technical handbook for the paddy rice postharvest industry in ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?