The Mechanical Handling and Storing of Material

CHAPTER XXVIII HANDLING RAW MATERIAL IN CONNECTION WITH BLAST-FURNACES FURNACE HOISTS Ordinary elevators are not serviceable for feeding blast-furnaces, the ore, limestone, and coke being too uneven in size, and each of these three materials must be handled separately, and in different proportions, and in addition to this the feeding must be more or less intermittent; all these conditions call for an elevator of a different type from the ordinary. The older appliances were ordinary platform lifts, similar to those used for passengers. The ore, after being weighed in tip trucks, was pushed on the lift and taken to the top of the furnace, and then tipped into it. Modern furnace hoists consist of a skip on wheels, which is raised on rails up a sharp incline to the top of the furnace, into which it automatically discharges its load. These furnace hoists or single-bucket elevators, not being automatic and continuous^ require some hand labour, however little it may be, for the purpose of filling the bucket at the lower terminal ; the discharge at the other terminal generally being automatic. A single-bucket elevator will do excellent service where it is necessary to raise occasional loads to a considerable height, as for the service of blast-furnaces. For this purpose elevators are almost universally used, and generally go under the name of furnace lifts or hoists. It is rarely now that one meets with the old-fashioned vertical hoist or lift. There are certain accessories to modern furnace hoists the use of which are calculated to greatly increase their efficiency. For instance, the opening of a slide is all that is necessary for the purpose of filling the buckets when they are ready for a charge, and it is in these accessories (on which the efficiency of the elevator more or less depends) that a great many ironworks are still very far behind. It is not an unusual sight to see the iron ore heaped up with a shovel and -filled into small gauge railway trucks which are pushed by hand to the lift, an operation which requires a large staff of men for loading and moving the wagons to and from the platform of the lift. Even if a modern elevator has been introduced, the full benefit will not be felt until the appliances conveying to it are automatic and mechanical. Therefore, in erecting installations of this kind, more or less automatic, it is most important that the whole plant should be worked in such a way as to be one mechanical installation divided into two sections, namely— (a) The section for conveying the material to the hoist, and (Z>) the hoist itself. It was in the United States that mechanical appliances for this purpose were first introduced, and many of the larger up-to-date furnaces are now fitted with a device of this class. It is essential that such elevators should be built in a very substantial manner, as breakdowns would stop the working of the furnace, with possibly disastrous results. The elevators are mostly so arranged as to obviate manual labour at the point of delivery at the top of the furnace, and the material, be it iron ore, limestone, or coke, is taken up a skip-load at a time and emptied automatically into the furnace. It