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

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68 POSTHARVEST INDUSTRY HANDBOOKThe total horsepower required is the sum of the powers calculated from the threeequations, plus that required for the tripper from Table 3.10.For example: A belt carrying 18 t/hour, 41 cm wide, traveling at 110 m/minute for adistance of 90 m, with a 3-m lift:110 0.25 + (.0014) (3.281) (90)hp 1 = ×= 2.390.3048 100.048 + (.10) (90)hp 2 = 18 ×100hp 3 =30.3048= 0.2518× 1.015 × = 0.181000Plus for the tripper (from Table 3.10) = 0.70Total hp = 3.523.35. Cross section of beltconveyor: A, drive pulley;B, idler; C, tripper, D, feedhopper; E, adjustable belttensioningpulley. (below)3.36. Belt loading arrangementshowing metal orwood frame with rubberskirt and extra set ofidlers. (bottom)A cross section of a belt conveyor with its major parts is shown in Figure 3.35.Note that the feed hopper is installed near the upper end of the belt. It has guides onthe side to prevent the paddy from splashing off as it feeds onto the belt. These guidesmay be metal or wood, 60-90 cm long, installed slightly above the belt surface toprevent wear on the belt. Details are shown in Figure 3.36.In Figure 3.35, the belt moves along the top idlers, which are spaced close togetherto carry the load. The tail pulley is adjustable to maintain the correct belt tension.Paddy is discharged by a belt tripper, which is movable along the length of the beltand incorporates a two-way discharge valve so that the paddy can be discharged on
69 CONVEYINGeither side of the belt.A standard set of top idlers is shown in Figure 3.37. The side idlers are positionedat the 20° angle required for paddy. They are designed for periodic lubrication. Thecenter roller has an extended grease pipe on the side for easy access. Figure 3.38shows dimensions of standard idlers. Tapered roller bearings with outer dust andwater seals are most commonly used.Self-aligning idlers (Fig. 3.39) are used for training troughed belts. They automaticallycorrect belt misalignment due to off-center loading, uneven belt stretch,misalignment of supports, or other common field working conditions. A selfaligningidler replaces a standard idler every 15-30 m.Self-aligning idlers should use the same rollers and bearings as the standard idlers.Self-aligning camber idlers (Fig. 3.40) installed on the return belt help train theloaded belt. The idlers are often overlooked in conveyor belt designs.Paddy generally is discharged from the belt conveyor over the end pulley or at anypoint along the conveyor by a scraper plow or a throw-off carriage known as atripper. The discharge over the end pulley of the belt is simple and does not requireany special mechanism. A common use of this type discharge is from a belt conveyorinto the boot of a bucket elevator.The discharge scraper plow is a board placed at an angle (usually 30 to 49°) to thelongitudinal axis of the belt and fastened on a frame that can be raised or loweredonto the belt as required. In the operating position, the plow rests on the belt,pressing against it with a rubber strip fastened to the board. The plow can be used todischarge paddy from either side of the belt. As the paddy grains traveling on the beltcome in contact with the plow, they are deflected to the side of the belt anddischarged. The discharge plow is not commonly used with paddy because smallpaddy grains often slide under the plow and are not discharged at the desired3.37. Standard idlers forbelt conveyors. (Courtesyof Continental ConveyorCorp.)
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: 67 CONVEYINGExample: Determine 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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