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

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60 POSTHARVEST INDUSTRY HANDBOOKThe next standard size electric motor above 5 hp should be used. The followingspecifications apply:Conveyor size: 30 cmConveyor speed: 92 rpmConveyor horsepower: 7.5Screw conveyors can be operated in an inclined position with the flow of materialsupward. However, the allowable capacity rapidly decreases as the angle of inclinationincreases. A standard conveyor inclined 15 degrees will carry about 75% of itsrated horizontal capacity. At an incline of 25 degrees it will carry about 50% of itsrated horizontal capacity.The additional horsepower required over the horizontal horsepower requirementsis roughly 25% for a 15° inclined conveyor and 50% for a 25° inclinedconveyor. For a screw conveyor operated at an incline greater than 25°, a tubularcasing or a shrouded U trough should be used. It also becomes necessary at this angleto use shorter-than-standard pitch flights.Hangers and end bearingsThe end thrust on a conveyor screw is against the direction of material flow. An endthrust bearing assembly absorbs this force and prevents excessive wear of theoperating parts. A number of thrust arrangements are possible. One of the mostfrequently used is an outside-type thrust bearing (Fig. 3.23). Preferably, the conveyordrive should be installed to drive through the end thrust because the shaft isfixed in position and cannot “float” in the end bearing. However, the drive is ofteninstalled on the feed end of the conveyor because of space or other limitations.A standard-type hanger bearing used for screw conveyors designed for paddy isillustrated in Figure 3.24. The 3.175 mm pipe tap provides a connection for a greasefitting and is most often used with a pressure-type grease cup. Additional life can beobtained by using ball bearings with dust seals in the hanger. Shields should beplaced on the upstream side of the bearing to protect it from grain pressure and wear.Inlets and discharge openingsGenerally, inlet openings may be cut into the conveyor trough cover whereverneeded. Figure 3.20 shows inlet spouts at two locations. Inlet openings should bekept at a sufficient distance from hanger bearings to prevent clogging or choking at3.23. Outside type thrustbearing for heavy dutyservice.
61 CONVEYING3.24. Standard hangerbearing.that point. For general use, the inlet opening is square and of the same dimensions asthe inside width of the trough. The opening may be flared or an inlet spout may bedesigned to meet specific needs. Special side opening inlets can also be designed tocontrol the depth of material fed to the trough at that point.Discharge spouts may be flared or made longer to meet special machinery needs.A standard opening is square and equal to the inside width of the trough. Severaltypes of discharge openings and spouts are illustrated in Figure 3.25.3.25. Screw conveyor dischargeopenings andspouts.Troughs and coversA variety of screw conveyor troughs exist. Two types common to paddy requirementsare shown in Figure 3.26: the flanged type with flanged cover installed (A) andthe angle flanged type without cover (B). Most troughs for handling paddy are madeof high carbon steel or abrasive-resistaat alloys to withstand the severe wear.Other types of trough covers are illustrated in Figure 3.27. The flat cover is usedindoors where waterproofing is not necessary. For most outdoor conveyors where
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: 59 CONVEYINGHorsepower requirements
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 and 30: 73 CONVEYING3.44. Wing-type pulley.
Page 31 and 32: 75 CONVEYING3.47. Cross section ofc
Page 33 and 34: 77 CONVEYINGMost spouting is straig
Page 35 and 36: 79 CONVEYING3.54. Five-way distribu

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