Document pmnwk215q6mkLaYmxBXyrKe2X

lUllDOZIB mount'd on a trowltr tractor ICBAPIB with rwbbur-tlrod prtm^ ntavtr INOUITBIAl LIFT TBUCK li tomotlmoi uaod In mm It plant* to transfer coal dtroctly tram outdoor *torafla to firing unit* Use of mobile equipment for coal stockpiling has grown enormously in the past 10 years. Reasons are: (1) suitability for building layered, com* pacted piles (1) adaptability to var ious site conditions and changes (3) relatively modest first cost (4) possi bilities of using equipment for other purposes, such as. snow clearing, etc. To the original crawler-tractor bulldoser has been added an array of crawler and rubbcr-tlred With either crawler or mbber-tired tractor, the bulldoscr fits best for re. latlvely modest production rstes on shorter hauls, say up to about 300 ft Adding wings to the doser blad ralsa capacity per push. On large piles, bull, dosers ore used for dressing, cleanup. Pulling rubber-tired carry-type scrapers extends the economical work range of tractors. Units of this elsn can pick up from 10 to 20 tons of coal and houl It well over 1000 feet at rel atively low cost (Powsb, Aug IMS, p 80). Por larger stockpiles (say, over ^4N8INI KBAPfB, rubber-fired and lelMoadlng, fin belt In large operation* 0,000 tons with piling end reclaiming of more than ISO tph) there mw a 2-engine scraper (PowBff, Jan PP W-96). One engine powers ^0per wheels, and the other the trac- itordrive wheels. **'8decting mobile equipment thus de*paub on an economic comporison of Jit' various types in relation to the distances involved and the hourly pro:gocdon rates required. The operation b always much the same. Por moving cesl out to storage the starting point is a "Cushion" pile from which bulldoser er scraper can take its load. (Serapers are also loaded from overhead hoppen for quicker filling.) The cushion is formed in any one of a variety of ways by the conveying equipment working out of the unloading point Coal Is spread on the pile in thin layers and the normal traffic of mobile units usually proves odequate for com pacting. If not, oddltional trips ean be made just for compacting. In some cates, weighted rollers have been used, but this seems unnecessary. In re claiming operations, the bulldoser or scraper usually unloads to a hopper or pit feeding conveying equipment. HOPPCB IOAOINO till* icrapen quUker tfcaa they <a telf-leod, I* lamellate* vied In larger stockpiling operatlent For the outdoor stockpile: fixed and mobile... Coal storage may be divided into two types according to purpose: five, or active, storage from which firing equip ment feeds directly, end dead or reserve storage to guard against delays in shipments, etc. Usually, live storage is under cover and reserve storage is outdoors. But in some plants, one storage, covered or outdoor, does both Jobs. So on this pair of pages, and the next, let's look first at outdoor storage, keeping in mind thot while it's usually reserve storage it may be live storage as well. That's true in many smaller plants, which may have outdoor storage under a rail-siding trestle or in some corner of the plant yard where trucks dump deliveries. In such coses, and others, industrial lift trucks with scoops (photo above) or special ised motor loaders are used to bring coal from the pile directly into ground-floor boiler rooms. Stockpiling Iqvlpmenf. When It comes to outdoor stock piling, a tremendous variety of means is available. But they break down into two broad elasses: Axed and mobile. Perhaps most widely used of the fixed group are drag scrap, era. As sketched and dlteussed at the right, drag scrapers can be adapted to o wide variety of site conditions. Locomotive crones, and other types, fitted with clamshell buckets, are used for stockpiling. These can pile and reclaim only a limited distance either side of the track, but track can be looped or paralleled to At many ground plans. Por large operations, gantry or bridge crones are used, spanning the distance between paralleled sets of tracks and carrying one or more trolleys with clamshell buckets. Such equip ment often handles unloading from barges and ships, or railroad cars, as well os stocking for storage. In recent years, use of .mobile equipment hos grown rap idly. In this group we have what are primarily earth-moving machines -- tractors, bulldoiers, scrapers, etc -- adapted to handling coal. All they need is on initial pile to work from and a point to reclaim to, both of which are normally provided by the equipment for unloading cool and moving It directly Into the plant. Thus mobile methods eall for oo fixed structures and give a high degree of flexibility is utilising available ground space. Type of equipment selected for any given installation will depend on a great many factors, an Important one being first cost. The fact that eooMiandling equipment is I*' quently used Just one shift per day makes it desirable to keep investment down. But experience shows it pays to mechanise to keep down labor costs, so the trick Is to secui* the best balance between first costs and operating costs. Storage Procedure. Where outdoor storage serves as a reserve, normal practice U to. take part of incoming ship* menta directly Into storage within the plant and divert portion to the outdoor pile. As needed, reclaimed coal b routed into the plant. Kow much transfer between outdoor and Indoor storage there is, and how often stockpile coal b reclaimed depends on the nature of the coal and its storing qualities, fixe of pile In relation to plant use, etc. Regardless of equipment used, economical end safe star* age colls for know-how. See next spread for the methods. li run HANDIINO AMD STOBAOf *>wf* ... equipment meets varying site needs, but .. IUO SCSAPCfl on bark pe*r and brirfto MONOBAtl end trolley more* tall pulley DRAG-SCRAPER LAYOUTS *4IAl IITUPi back pe*t move* on track PABAUCt. 1-tower layout fur lorgu pile KtMiit mi ruci HANOMNO AMO STOIACI Simplest drag scraper has fixed back posts. Cable from scraper drive, near head post, posset over one head block, out to scraper bucket, then to tail block and bock to second head block and drive. To build pile, bucket works out from initial pile near head post; to reclaim, the bucket is reversed. Baek post height depends on storage depth and distance hauled. As a gen eral rule, back posts run 8 ft tall for 15- to 20>ft storage depth. Jn this lay out, toll block is shifted by bond. For larger piles and longer hauls, tail blocks are heavier and easier shift ing becomes important. One scheme uses a monorail and trolley, with fixed bock posts. Dut In most larger installa tions, some form of mobile tower Is used, often on a redial track. Towers have outriggers end rail clomps, may be shifted monualty or may be motorised. Fully mobile towers have propulsion motors end brakes controlled from op erator's cab; two may be used In par allel layout as sketched. Por dregscraper details, see Powbb, May 1948. pp 66-89, and July 1946, pp 74-7$. IS