Historic Markers Across Alabama

The Blowing Engine Room

Marker ID:  
Location: Marker is located next to the north side entrance to the Blower Room, largest building on the grounds of Sloss Furnaces National Historic Landmark.
County: Jefferson
Coordinates: N 33° 31.234    W 086° 47.503
  33.52056666    -86.79171666
Style: Interpretative Sign **
Waymark: None


The Blowing Engine Room
Sloss Furnaces National Historic Landmark

The blast furnace required a tremendous amount of air - about two tons for every ton of iron produced. These three rooms, known collectively as the blower building, house the equipment used to pump air to the furnaces. Workers called this blast of air the" wind.” The eight giant steam-powered piston engine in the largest room date from 1890-1910 and were used until the early 1950s. At that time they were replaced by the two turbo-blowers in the adjoining rooms. Despite their size, the turbo-blowers 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. The two turbo-blower rooms were added when the turbos were installed.

The Process

Although built in the early twentieth century, the blowing engines represent the pinnacle of nineteenth-century technology. Reciprocating steam engines such as these powered the industrial revolution. Each engine had a steam cylinder (on bottom) and an air cylinder (on top). Steam drove the piston in the steam cylinder up and down, in turn driving the piston in the air cylinder. The moving piston pulled in air, compressed it, and pushed it out. Half the engines served Furnace No. 1, the remainder, 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. In operation they were magnificent to behold. The twenty-foot flywheels and the movement of the gears, cranks, and levers made the machines look almost alive. All these moving parts required constant attention, adjustment, and lubrication. The twentieth-century technology of the turbo-blowers replaced the blowing engines. The turbos were small, highly efficient air compressors driven by steam turbines. The turbos each blew an average of 43,000 cubic feet of air per minute into the furnace, at an average pressure of 20 psi. It took four blowing engines to produce the same volume of air. The turbo-blowers were in some ways the opposites of the blowing engines-in operation there was little to see, for their moving parts were under cover; and while great care was needed to install and repair them, they required maintenance only at infrequent intervals.

Erected by Sloss Furnaces Historic Landmark.

End of The Blowing Engine Room