The Mechanical Handling and Storing of Material

HANDLLNG BLAST-FURNACE STOCK 355 A long line of unloaders, fifteen in number, is placed at the dock front, thus making it possible to simultaneously attack every hatch in a large lake vessel. Each unloader manipulates a 5-ton grab, operated by one man, and makes sixty trips per hour, giving a gross capacity to the first half of the vessel of 3,000 tons per hour. The unloaders deliver the ore into trucks for carriage to distant points, or into the adjacent con- crete trough-shaped ore pocket in their rear. In this manner, practically the first half of the cargo is dis- charged in the first hour. The residue of the cargo has to be brought to a point beneath the hatchways before it can be taken out by the grabs. This is effected by a series of scrapers, one at each hatch, operated by an engine installed on the unloader on the shore, which controls the scrapers in the hold by light ropes. The diagram, Fig. 496, represents a part section through the vessel; whilst Fig. 497 is a part plan of the vessel showing method of mechanical trimming. The scraper has a resemblance to a giant hoe, and weighs more than a ton. Its form is shown in Fig. 498. The ore is handled by alternately moving this scraper backwards and forwards, the point to which it returns empty being regulated by changing the position of the sheaves as shown in the plan view of the vessel, Fig. 497. Thus the entire cargo can be unloaded without hand labour. The dis- charge of the cargo, with the necessary clean up to get the vessel ready for another load, has been accom- plished in four hours. The unloaders receive steam from the .blast- furnace boilers through a line laid in a conduit, and along the dock front in a tunnel within the concrete trough construction, each unloader being connected with the main by a flexible pipe. As regards soft or hard ores the capacity differs but little. The work of stocking the ore or trans- ferring it direct from the vessel to a trough 600 ft. long immediately in the rear of the unloaders, or from the stock pile to the furnace pockets, is accomplished by means of two high-level cranes, each 520 ft. long, which are traversed by electric trolleys, each of which contains mechanism for the control of 10-ton grabs, and commands all the various materials for the furnace, including a reserve stock of limestone and coke. Each crane is controlled by a single operator, Fig. 495. Elevation of Hoover & Mason's Ore-Handling Plant. who can at will pick up 10 to 15 tons, and transport it to the furnace hoist, the hoisting speed being 100 ft. per minute, while the conveying speed of the heavy trolley is 1,000 ft. a minute. '