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As a type, the "fireless" locomotive was indeed highly specialized, and few were manufactured.
The Heisler Works of Erie, Pa., produced by far the greatest number of examples of the fireless type, about 50.

Such a locomotive could only operate on trackage very near a large, stationary steam plant, to which the locomotive would return every few hours of operation for hookup to the stationary plant's boiler - in order to recharge the locomotive with superheated water - i.e. liquid water heated under high pressure and thus to temperatures well above 100 degrees C.

(Superheated water contained in the cylindrical "pressure vessel" that is the principal visible feature of the locomotive provided the short-term source of steam to run the pistons to propel the wheels.

By opening the throttle, the pressure within the vessel of superheated water was slightly reduced, and the slightly lowered pressure resulted in the generation of water vapor - saturated steam at the new pressure - to push the pistons.) There is no firebox to heat the water; hence the term, "fireless."



Object: Fireless Steam Locomotive, standard gauge. Acc. No. 1979.1027, Cat. No. 79.1027.01

Donor: Potomac Electric Power Co. (PEPCO), 1979.

Purchased new by Potomac Electric in 1938.

Description: 4-wheel, 35-ton locomotive, manufactured in 1938 by the Heisler Locomotive Works, Erie, Pa., Heisler construction no. 43.

Dimensions: 21 ft 4 in long, 11 ft 4 in high, 9 ft 6 in wide.