Document ykrQ4wOBVDN6zoYOyRnwBNnRD

TANKS AND SILOS HORIZONTAL BUNKERS Ovtld.tlio.|>lear tfrag* iTrvtTvrti Include cylindrical ! lackt, sllac. Illo* may hare thro end dead ttorago, cenfer, or tingle icerege ipcce, biltw McrUwfgf ovorttaotf bunkoes afro# eye el mitpended cenitmrtleii, left above. Multiple hepper-bclten declge, rtgki, ellmlnalee dead cpacei between eatletc SWING-TYPE C0AI GATES SLIDING GATE Ibdnrge outlets of iwra|* v*li< ore fln*d wlffe goto* to sontrol flow of cooL IWm bmmI open quickly and positively. Oates shewn above ere ef the swing typo, is wit on the left being o simplex design and that an the right being a duplex. Ui gotes ore usuelly mode ef cost Iren to rsslst abrasive action ef moving cool Kldtng design reqolres little headroom. Protected double rock and pinions drive the gale, which moves on roller bearings In side pockets away from flow of coal For storing coal under cover... bins, silos and bunkers prove their versatility Day-to-day supply (or firing units nearly always comes from covered storage -- bins, silos, bunkers. Some time* these units provide the only storogc so there is no separate reserve. Or, as in many silos, live and dead storage ere included in same structure, but physically separate. Capacity required often dictates type of storage unit. For small plants, the simple bin may serve. Larger ca pacity needs point to use of tanks, silos and bunkers designed to save ground space and give more convenient flow to firing units. Oulside-the-plant structures include cylindrical tanks, and silos. Steel tanks, like the one pic tured above, left, serve for storage up to about 100 tons where roof .location is attractive. Silos, usually sued to hold a week's supply, are rarely used for less than 100 tons. FUtl HANOUNO AND STOIAGE Silos. Often attractive costwise, silos are built of concrete (poured, block or stave construction) and of hollow tUe. Usual practice puts a live-storage compartment above, for gravity flow to firing units, and o reserve sectloa below. When live storage is full, cost spills over to reserve, whleh dUehsigcs to pickup point of elevator or convey or. Thus eoal con be fed to live storage directly from unloading point, or fro reserve section. With relatively modest live-storage eapaeity (say. one day'* supply) operator can recirculate often from reserve. Live-storage compartment is usually formed by a sloping shelf (about 50 deg). Some silos, how ever, have a cone-bottom steel hopper for live storage^ diameter being about 7 ft less than silo's. Alternative construction for 1^ has no separation of live and dead rowtt detage, and a flat bottom. Unit lllusfasted, left, has bottom above level of iring-unit hoppers and feeds them by * monorail system. Ivipondod Bunkers. Ovcrheod stor*ge units of generally horizontal lay*ut have been built of concrete, menry and cast iron, but today's bmunon construction Is steel plate, of the suspended design. In its familiar form, the suspension linker consists of plates (W to V6 In.) tag in a catenary between parallel girder*. Plates are in tension only, protect against corrosive action of *1| steel bunkers are often lined with crete or other protective coatings. Mother suspended construction has ***1 straps on about 3-ft centers, oct^1 as bearing members for light-gage formed steel sheets. These are lined concrete applied by {uniting. IMJ Discharge efficiency. Horizontal bunkers of suspension and other types hove discharge outlets and gotes at in. tervats along the length. Cates, as il lustrated above, may be of either winging or sliding design. Discharge efficiency suffers because of dead spaces between outlets, and trimming these dead spaces can be difficult. One onswer la to increase the number of outlets wherepractleal. Another solu tion uses multiple hopper-bottom con struction to eliminate d^ad spaces. Moisture ond compacting .can raise cool's angle of repose from about 4$ deg to 60 or 70 deg. This may lead to flow problems at storage outlets. Coal immediately above opening drop* free ly but the remainder arches over and hangs up, stopping flow. Hew la Prevent Arching. If good space above opening con be kept free ruet HANDLING AND StOIAOf of coal, say 3 ft or more, arch spon becomes too great and flow utuolly can be maintained. Poke holes, looped chains reaching down to openings, and the modern vibrator all aim at keeping arches from forming. Another ap proach is to make slopes to outlets steeper,.For existing bunkers, this ef- ' feet can be achieved in some cases by putting a vertical plate above open ing's centerline. In new bunkers this is a matter of deiign -- some recommend bunkers with three vertical sides and one sloped. . Crushors. In these pages we've men tioned the common practice of crush ing coal before putting it into storage. Limited space makes it necessary to confine this discussion to handling and storing equipment. For comprehen sive roundup on crashers, see Power, July 1951, PP 73-75: Aug. pp 84-85. 17