High Bridge Blow-Down. DRGW K-28 #473 executes a firebox blow-down as she rumbles across the High Bridge at Tacoma, around MP 471.2. The blow-down involves opening valves in the boiler, just above the firebox mudring. Superheated water at boiler pressure flashes instantly to steam as it is expelled, taking with it sediment and boiler contaminants that can adversely affect the efficiency of the boiler. Crews do this procedure frequently during the trips to Silverton, mostly on bridges such as this one, where there is no risk of injuring anyone.
The High Bridge at Tacoma is a wrought-iron deck truss, which has been at this location since 1894. When first built, this bridge was designed to hold the small, inside-frame Consolidations that were the standard power at the time. Although able to hold some of the larger K-class Mikados, such as the K-27 and K-28 (pictured here), that was about the limit of the original design. When the line was sold to Charles Bradshaw in 1981, the newly-formed Durango & Silverton Narrow Gauge Railroad added considerable bracing to the existing design, to strengthen the bridge and allow it to carry the heavier K-36 and K-37 Locomotives that would be become the workhorses of the new tourist operation. Some of those "modifications" become pretty obvious when you stand at this location and study this century-plus year-old bridge. Oh, and needless to say, there's a slow-order here too.
The Cumbres & Toltec Scenic Railroad and the Durango & Silverton Narrow Gauge Railroad are all that remains of the legendary Denver & Rio Grande Western narrow gauge system. Here you'll find some of my favorites from these two beautiful railways.
