As you note, careful attention to the water level in the boiler is a must. Two methods are used to determine the water level. The first as previously described in this thread is the sight-glass. The second method is by means of the tri-cocks, which are three valves which are spaced at different levels on the backhead of the boiler. When opened, the top valve should produce steam, the middle valve should produce a mix of steam and water, and the bottom valve should produce water. If this is not the case, then “adjustments” must be made. The use of both methods should be done as a check against the other. If one were to enter the cab of a steam locomotive and observe a sight-glass devoid of water, and a bottom tri-cock blowing steam, one’s first course of action, besides running away, would be to kill the fire by closing the firing valve on an oil burner or dumping the grates on a coal-fired engine. The key point here is that the observer is ignorant of the time elapsed since the water disappeared from view. Otherwise, if the fireman saw the water in the glass disappear as the locomotive nosed over the hump of a grade, the course of action would be to add water. Of course a good fireman would know the territory and know his engine, and he would not allow that to happen. The best way to empty the boiler would be to open the blow-down valve, which is located at the bottom of the boiler. Under normal circumstances this valve is used to clear sediment from the boiler. Just as a point of discussion, I wonder if dumping the water or steam would be good practice. The water temperature in a boiler, which is working 200 psi, is about 380 degrees. As one lowers the boiler pressure, more of the water is turned to steam and thus would lower the water level. It might be just as good to let the boiler cool slowly, and avoid the additional stress induced by dumping the water.
Karl's post is very informative. I did not know about trycocks, but they certainly provide a useful cross-check. A good operator would use both trycock and sight glass for awareness of the system's state. I forgot about dumping the fire on a coal-fired locomotive, but that carries its own hazards. Dumping the water through the blow-down valve probably would be bad practice for reasons mentioned. Apparently there was no quick way to just vent steam by itself. That would be rapid way to remove heat because of the higher heat content of steam relative to liquid water. It then appears the best remedy for extremely low water would be to drop the fire, let the locomotive stand and cool. Thanks George
When did low-water alarms come into play? Dates, manufacturers, and of course application to any Frisco motive power? Granted, it is comparing apples to...well, sledgehammers, but while taking Disney's "Behind the Steam" backstage tour of their operating steam locomotives, the engineer was careful to point out the low-water alarm device as an added safety precaution. Karl's excellent explanation also reminds me of reading an article years ago of a novice fireman on an Espee Mallet who mistakenly identified an empty sight class on the Tehachapi run. He had been scared by safety posters with photographs such as what Don has shown. He added so much additional water that the locomotive eventually created its own artificial rainstorm. It was in a Kalmbach publication, but I do not remember which one.
As Chris notes, the railroads applied safety devices to prevent such explosions, including low-water alarms, fusible plugs in the crown sheet, and thermic syphons. I cannot remember, whether it was Collias or Stagner, but one of these authors states that the Frisco removed its low-water alarms, after it equipped its steam locomotives with the syphons. Although designed to improve boiler-water circulation, syphons added heating surface and helped to keep the crown sheet covered.
Most mainline steam today has an added safety feature. On the 4-8-2 SLSF 1522 we added a second water glass on the fireman's side, so we had two water glasses and the tri-cocks. Suspenders and a belt. The appropriate action on 4-6-0 SLSF 1104 would have been something like kill the fire and run like hell. I would not release any steam, just let it cool naturally. When it cools, the water level will drop even more. May have been some crown sheet damage from overheating, but the cold water set it off. Important thing is to get rid of the fire.
We will never know what was going threw his mind at the time, but running like hell would have been on mine. He was a young man, in his mid thirties. I would bet he never gave it a second thought and just turned the water on. Had he thought about it, the end results would have probably been different.
From Richard Crabtree on Frisco Rails Across Missouri: This is what happens when you are not paying attention doing your job!!! May 1st. 1933, Frisco No. 1104 4-6-0 Ten Wheeler built by the Schenectady Locomotive Works in 1907; boiler exploded! George Keener, a 35 year old locomotive watchman, 18 years with the Frisco, was in the cab and had permitted the water level in boiler to get too low. He must have turned on the water injector allowing very cold water to hit the boiler, and that is all she wrote! The boiler blew 75 feet away from the frame and the cab that he was in flew 125 feet. He did not survive the explosion. He had been doing this job for the last 5 years, so he knew how to do it. He left behind a wife and eight kids.
