The Mechanical Handling and Storing of Material

RKs STORING OF COAL AND OTHER MINERALS 653 Mr G. H. Hutchinson, chief engineer to the North-Western Fuel Co., St Paul, Minneapolis, United States of America, says :1 “ The first step in handling a coal fire is to get direct access to the fire by rehandling the hundreds. -- a-r ------ ------- the fire by rehandling the hundreds, and frequently thousands, of tons of coal within the inverted cone tributary to the also the where the fire starts; It is sometimes to prevent the fire spreading. After small area at the bottom of the pile, necessary to isolate the burning area fire is uncovered, it can be extinguished by the use of water and the rehandling of the smouldering or burning coal. The application of water, however, to the top of the original coal pile is ordinarily useless and frequently increases the fire. While the liability to spontaneous combustion cannot be entirely eliminated, a clean dock surface and the absence of combustible foreign matter within the coal pile, and, after the coal is in storage, careful watching and prompt rehandling upon the first indication of heating, reduce the liability to a minimum.” As all mechanical appliances for mineral stores have been fully dealt with in previous chapters, it will suffice to give a number of the typical examples showing the general arrangement without entering into the details of their construction. Stock Piles on the “Dodge” System.—Such installations are essentially American. In this country they are not so necessary, owing to the closer proximity of the coal fields to the principal centres of consumption—such as blast-furnaces—and the facilities for rapid and regular delivery, except perhaps as a safeguard against the effects of labour troubles, trade booms, etc. Stock piles on this system are almost exclusively used for storing anthracite coal, as bituminous coal cannot be stored in such high piles, which are frequently 60 ft. high and 200 ft. in diameter. There seems, however, no reason why such appliances should not answer equally well for storing other minerals. For storing anthracite coal the “ Dodge ” system is eminently useful, as the demand for that coal fluctuates greatly, and if stored in large quantities between the coal fields and the market, a continuous instead of a spasmodic working of the mines becomes possible and a convenient base of supply is provided. Mr George E. Titcomb, of New York, read an interesting paper on “Hoisting and Conveying Machinery” before the American Society of Mechanical Engineers in 1908, from which the following description has been taken. The standard 11 Dodge ” plant consists essentially of a push-plate or chain and flight conveyor supported by shear trusses D d (Fig. 919), constituting a trimming machine which piles the coal with a minimum of breakage, delivering it upon the ground or at the ascending apex of a conical pile as it is formed. The withdrawal or reclaiming of the coal is begun by the open side conveyor a b, which is pivoted at a and runs on a number of circular ground-level tracks extending between and over the area to be covered by the piles. This conveyor works against the edge of the pile, and follows up the receding edge as the coal is removed; it is operated by power and is so devised as to be fully under the control of one man. All the coal is tributary to the reloading conveyors, and is carried without intermediate transfer up the incline to the reloading tower c, where it can be delivered either directly into cars or after having first been screened. In detail the “ Dodge ” system, as usually applied to open-air storage on levelled ground, consists of two trimming machines and the pivoted ground conveyor which travels radially between them (see Figs. 918 and 919), forming one group or unit. A 1 In a paper on “ The Handling of Coal at the Mead of the Great Lakes,” presented at the Spring Meeting, St Paul, Minneapolis, 1914, of the American Society of Mechanical Engineers. I I