Blow-down! The crew of Mt. Emily Lumber Company's Shay #1 executes an extended blow-down of the locomotive's boiler, just after crossing the Crooked River on the eastbound run to Prineville. The blow-down procedure is designed to rid the boiler of sediment that typically builds up in the base of the firebox area, which is known as the mud-ring. This sediment can interfere with heat transfer, and thus affect boiler efficiency. It can also promote corrosion, which is never a good thing. Periodically, the locomotive fireman will open the blow-down valve or valves, which are generally located on the sides of the firebox sheets. When the valve is opened, superheated water is expelled at boiler pressure and typically flashes instantly to steam. It makes quite a racket and produces an extensive plume. The blow-down is generally done when the locomotive is drifting and can afford a momentary loss of boiler pressure. Needless to say, the crew must be careful to ensure that the water level in the boiler is high enough so that the loss of water will not compromise the crown sheet. Obviously, the crew must also take care to ensure that the plume does not impact people or animals. The plume is obviously scalding hot right next to the locomotive, but beyond perhaps 15 yards, it is just wet.
