In the making of steel, iron ore is converted to molten iron in a blast furnace, refined into steel in a steelmaking furnace such as a Bessemer converter, open hearth or basic oxygen furnace, cast into solid shapes and then squeezed into its final form in rolling mills.  Doing this work required a great deal of energy and horsepower.  In the days before the perfection of high horsepower electric motors and steam turbines, giant reciprocating steam engines were built to do the job.  Engines weighing upwards of 700 to 800 tons capable of producing up to 30,000 horsepower were built by several manufacturers in the time period of the 1890s through 1920.  Today only a handful of these engines still survive in North America.


Large steam engines were used in the steel industry for three main jobs.  The first was to provide the air blast to the blast furnaces.  These are called blowing engines.  The second type drove generators making electrical power.  These are generating engines.  The largest and most powerful engines though were used to drive the rolls at rolling mills.  These are rolling mill engines.  Steam engines are further classified by the size and configuration of their cylinders, whether they are reversing or non-reversing, and whether they exhaust into a condenser or to the atmosphere.


Let’s look at the full name of the Tod Engine.  It is officially a 34”and 68”x 60” cross compound non reversing merchant mill engine.  34” is the diameter of the high pressure cylinder; 68” the diameter of the low pressure cylinder; 60” is the length of the stroke; cross compound means that the cylinders are located across from each other on two separate bedplates; non reversing means that it runs in one direction only; and merchant mill means that it drove a 6 stand 24” merchant mill via drive shafts.  Now let’s look at the name of the engine that drove the blooming mill at the Brier Hill Works.  It was a 44” and 76” x 60” twin tandem compound reversing blooming mill engine.  Just as before, the numbers refer to cylinder dimensions, but “twin tandem” means that the engine has four cylinders, two low pressure and two high pressure, arranged so that each side has one of each.  Reversing means that it would change directions while in operation, and blooming mill indicates that it drove the rolling mill that rolled ingots into semi-finished shapes.  The blooming mill engines were among the largest and most powerful stationary steam engines ever built.


There were several manufacturers of rolling mill engines for the steel industry, but the largest producers were the William Tod Company in Youngstown, OH, Mesta Machine in Homestead, PA and Allis Chalmers in Milwaukee, WI.  Several others also built rolling mill engines but not in as great of numbers as the big three.  Where were the engines used at?  Practically all integrated steel plants built in the 1890 through 1920 time frame utilized at least one rolling mill engine. In the Youngstown district alone probably 40 to 50 engines were in use during the golden age of the steam driven rolling mill.  No complete listing of rolling mill engines has been created, but it is a long range goal of Youngstown Steel Heritage to compile such a list and to bring as much information about rolling mill engine technology under one roof at the Tod Engine in Youngstown, OH.

History Subpages

- Page 1

- Page 2

- Page 3

- Page 4

- Page 5

- Page 6

- Page 7

- Page 8

- Page 9

- Page 10