Charging Crane, Underslung

a machine used with steel-smelting furnace units to load the charge (scrap, ore, and flux) into the furnace. Underslung charging cranes may be floor-mounted (with or without rails) or of the overhead type.

Floor-mounted underslung charging cranes with rails are usually installed in open-hearth shops with large furnaces (capacity of 150 tons or more). All machine assemblies are mounted on a bridge, which moves along rails laid on the operating platform of the furnace bay along the front sides of the furnaces. A carriage with a charging bar that is used to introduce the charging box into the charging door of the furnace moves within the bridge. The load capacity of such cranes is 7 to 15 tons. They are simple in design and reliable in operation, and their output is high (one machine can service four furnaces); however, they require the construction of a reinforced operating platform. Floor-mounted cranes without rails are intended to service low-capacity furnaces (5–20 tons). In contrast to the floor-mounted cranes on rails, they can move in any direction and can be turned around easily, even on small operating platforms.

Charging cranes of the overhead type are usually used to service furnaces of medium capacity (20–150 tons). A machine of this type consists of a bridge crane with a main carriage and an auxiliary (crane) carriage, which is intended for repair work and slag removal. The load capacity of the overhead charging machines is as follows (the numerator denotes the mass of the charge in the charge box: the denominator shows the load capacity of the auxiliary carriage): 1.5/20, 3/10, 5/20, and 8/20 tons. The advantage of overhead charging cranes is that the absence of rails makes the servicing of furnaces easier. Its disadvantages include its complexity of design and comparatively low output (each machine services two to three furnaces) and the fact that it is impossible to operate the charging and casting cranes in the same bay.