The Blowing Engine Room

The blast furnaces required a tremendous amount of air, about two tons for every ton of iron produced, and the three rooms known collectively as the blower building housed the equipment that pumped this air, or “wind,” to the furnaces. The eight giant steam-powered piston engines in the largest room dated from 1890-1910 and were used until the early 1950s, when they were replaced by two turbo-blowers in the adjoining rooms that could do the work of all the old blowing engines. The room containing the giant blowing engines was built in 1902 and is the oldest structure at Sloss, while the two turbo-blower rooms were added when the turbos were installed. Built in the early twentieth century, the blowing engines represented the pinnacle of nineteenth-century technology, as reciprocating steam engines like these powered the industrial revolution. Each engine had a steam cylinder on the bottom and an air cylinder on the top; steam drove the piston in the steam cylinder up and down, which in turn drove the piston in the air cylinder, pulling in air, compressing it, and pushing it out. Half the engines served Furnace No. 1 and the remainder served Furnace No. 2. The blowing engines operated at 32 to 35 rpm on 125 pounds of steam pressure and produced an average blast pressure of 20 psi. Their twenty-foot flywheels and the movement of gears, cranks, and levers made them appear almost alive, but all of these moving parts required constant attention, adjustment, and lubrication. The turbo-blowers that replaced them were small, highly efficient air compressors driven by steam turbines. Each turbo blew an average of 43,000 cubic feet of air per minute into the furnace at an average pressure of 20 psi, and it took four blowing engines to produce the same volume of air. In operation, the turbo-blowers contrasted with the blowing engines because their moving parts were under cover and, although great care was needed to install and repair them, they required maintenance only at infrequent intervals.

Birmingham, Alabama · United States