Document 3ZGpvzDJqBnw5vgkZ60gYjJE

r MONORAILS, BUCKET CARRIERS, BEITS Some idea of the wide variety of conveying equipment can be gained by looking at designs illustrated here, plus those on the preceding page. Here we have, left, the monorail carrier, used in smaller plants for essentially horisontal distribution, from bin to stoker hoppers, for example. The pivoted-bucket or Peck carrier, above, serves equal, ly well (or vertical and horisontal runs. It was once exten sively used in a closed-circuit arrangement, distributing coal to bunkers or hoppers along the top run and handling osh removal on the bottom run. Gravity-discharge bucket elevators, righf, above, can hondle short horisontal mas after the vertical lift. Two popular units in today's plants are the flight snd tell conveyor, r/ghf. Drawings illustrate basic flight and ktt construction and the trippers and shuttle conveyora red with belts for horisontol distribution. It is common practice to equip belt conveyors with esgoetk pulleys to separate tramp iron from coal before driimy. In addition to the electromagnetic detigns, perBtaait magnets have come into use. Magnetic separators in sometimes used at other points in the handling system. ... others serve best on horizontal runs, and... ,.. many do both jobs flight conveyors, like elevators, use endless chains but hove spaced scrapers or flights to push or drag coal along a trough. In simplest form, they eon be several hundred feet long, travel up inclines of os much as IS deg without backward cascading of coal. Above about 40 to 4S deg, capacity loss becomes too great. A typical 2-chain conveyor of this type handies 250 tph at 100 fpm. Discharge may be at end or at intermediate points through gates in the trough. On horisontal runs, flight conveyors require little headroom. Continuous-flow or Redler design employs a duct within which closely spaced skeleton flights act as the conveying element. The conveyor feeds itself at any point with a uni form load that Alls the duct and entirely surrounds the conveying element When the flights move they cause the material to flow upward or forward with them In a solid column. Coal can be discharged at any opening where it can fail away from the flights. The Redler type requires no deep loading pit. only enough room for gravity feed. Skeleton flights are detachable from the central chain. Connecting joints are flexible, to permit moving around corners. There is normally no metal-tometal contact in the carrying run since coal completely surrounds the flights. Cosings are dust-tight and connections can be made dust-tight also. This design serves equally well for horisontal, vertical or inclined runs. Bolt Conveyors. Relative simplicity, few moving parts, minimum friction and hence low power needs, make belt conveyors a popular choice. In comparing belts with other conveyors, however, supporting bridge, sheathing, walk* ways etc, must be reckoned in the cost With belts, as with bucket elevators, only relotive motion between coal ond conveyor occurs at loading and discharge. But this holds true for belts only up to on incline oi roughly 15 to 20 deg. By varying belt width and speed a wide range of capacity needs ean be met. Belt conveyors in horisontal runs need little headroom except for trippers. Simple construction of the belt eonveyor involves carrier or troughing idlers and return idlers. Carrying idlers ere atmost always of the 3-pulley type. Spacing and diameter of idlers is Important: too mueh space leads to belt sag snd shock as it meets each roll. If idlers are too small, belt bend is sharp. Either reduces belt life. Most belt wear, though, develops at the loading point So every effort goes into reducing shock there. Oncoming coal is accelerated in direction of belt movement to lower relative motion between coal and belt. Coal should never land directly over a solid pulley: hammer-anvil action wears belt. Hence loading chute should deliver between idlers preferably, but far enough ahead of toll pulley to put in at least one belt.fteadying carrier pulley. Weather, cuts, gouges prove worst enemies of belts. Fabric exposed to weather absorbs moisture If protective covet is gone. In warm weather mildew and rat may set in; in cold weather ice crystals may gnaw from within as belt floes- FUCt MANDUNO AND STOBAOE POWfl Amplest discharge setup is from the end. When distribu te along belt length is needed, as over a long bunker, trippers are used. These may be Axed or movable. In the rouble type, snub pulleys that bend back the belt for discharge at the tripper ore mounted on a hand- or motorpopelled frame riding on a runway. When it is necettory to pUe coal either side of a conveyor, o high tripper discharging to o transverse reversible belt ean be used. Such heavy trippers are almost always motor-propelted. Another distribution scheme uses the shuttle conveyor. 11 consists of o reversible belt mounted on a frame for rogltudinol travel; the frame is hand- or motor-propelled. Coal can be discharged from either end. A shuttle with tout 75-ft centers will cover up to 160 ft from a loading aaveyor midway in its length. Short shuttles suffer from htquent impacts per unit of belt length. krsw Conveyers. In smaller plants, screw conveyors, acntloned before as feeders, often serve. Inclined units lift *al to storage bins and frequently directly to stoker hoptoi Horisontal screw conveyors ore often used as bln-to*fcer feeders. Simplicity, dust-tightness and compactness 01he the screw type attractive. tonoroil systems are also used in smaller plants for |ri*ontol movement -- often from bunker to individual tog units. Hand-operated systems have tip-over buckets 41 chain hoists. Carriers may be motor-propelled, with elechie hoists and side-dump buckets. Scales may be built-in. *UMSfca 1933 91