There's another name for "conventional wisdom": urban legends.

Some are utterly, demonstrably true and have documentation.

Some are based on reality, but take a few liberties with the facts (another location, instigator, etc.).

Some are really, really good stories that may or may not have some passing familiarity with reality.

And some are outright hokum and balderdash, but "don't let the facts get in the way of a good story." ("Really! It happened to my aunt's friends' hairdresser's customer!")

What are we dealing with here in relation to "adding water to an exposed crownsheet makes it blow up"? I still don't know, and until someone like Mythbusters does a test (or many), I don't think we're going to know for sure.

But back to another question: What do "the experts", the people who have worked with this stuff professionally (the Strasburg guys, the TVRM guys, the 765 and 4449 and 261 guys, Tom Gears, etc.) think of the off-the-top-of-my-head idea of cracking open a blowdown valve to relieve pressure on a runaway boiler? I mean, honestly and seriously, at some point I also got it into my head that smashing out the sight glass would also help do the trick--not that I'd want to do it on a 200-300 psi boiler, but......

The discussion so far about this topic has brought out some interesting thoughts and ideas concerning low water in a locomotive boiler. I am an owner of two locomotive style boilers which are not on steam locomotives but rather are on traction engines. These boilers function the same way their larger counterparts do on locomotives. The idea of introducing water onto an exposed crown sheet is not a new topic of discussion; it has been covered many times. A recent discussion about this topic can be found here, http://www.smokstak.com/forum/showthread.php?t=115438. This is a discussion about BLEVE and pertains to what happens when a crown sheet is not adequately covered by water in the boiler.
For those that may not know, BLEVE stands for Boiling Liquid Expanding Vapor Explosion. Both in the steam locomotive and steam traction world there have been two recent examples of this occurring. Both were caused by low water over the crown sheet and resulted in serious injury and death. Both were caused by operator error. Once you have exposed the crown sheet to an extended period of heating and it has reached the point of being plastic you are in a failure mode. There is no way to know via visual inspection as to the condition of that crown sheet and if it is close to failure. Within the traction world we use fusible plugs in the crown sheets which if maintained act as a safety device for low water and blow out at a much lower temp. If you cannot detect water in the glass or with the tri cocks adding water is not advised. You remove the heat source by either pulling the fire or smothering it or in the case of an oil burner you shut off the fuel. A coal fire can be smothered with fresh coal on top of it. You can debate this all you want but unless you have x-ray vision and can see what is going on inside that boiler why would you take a chance.
This is a topic that should not be taken lightly by anyone who is or wants to become a steam locomotive fireman/engineer. It is also about maintenance of the equipment and making sure the various methods of putting water in a boiler are functioning and the water glasses, water columns and tri cocks are working properly. Training and proper operation are also part of the equation.
You can discuss all the theory you want about what might happen to a crown sheet when you introduce water from an injector or a steam pump to the boiler and the crown sheet is exposed but without knowing the exact condition of the sheet are you willing to be the test dummy. This may be a wives tale but is it worth the risk of life and limb of you and of others to find out. The best prevention from getting into this situation is competent operators, daily inspection and regular maintenance. From the world of steam traction I quote WATER, WATER, WATER.
John Deck

I was firing 1522 one time and took a big drink of ice water and the safety valve lifted.

Isn't this somewhat of a false dichotomy? There is nothing saying that if you have two sight glasses you can't have tri cocks. The one locomotive I was involved with was set up this way, 2 sight glasses, one set of tri cocks, and three injectors.

I want to clarify a couple of things in this topic. As has already been talked about ad nauseum, a crown sheet fails when the sheet is no longer covered with water, which functions as a coolant, and weakens as it increases in temperature until the pressure in the boiler forces the sheet from the crown stays. We all agree on this, I think.

The following phrase is contained within the instruction packet that a current steam locomotive operator, who I happen to otherwise have a great deal of respect for, gives to their volunteers:
"If the water level is unknown, or no water is visible in the glass, drop the fire. DO NOT ADD WATER."(emphasis added)

If we know that crown sheets overheat and fail because of LOW WATER, why would anyone instruct a fireman to not add water when the water condition is known to be low? This seems to me to be a very difficult philosophy to defend, and for it to be so pervasive you would think that facts supporting it would be readily available. What I was originally asking for was any proof, real documentation and not stories or conjecture, that adding water to a locomotive boiler has ever caused, rather than prevented, a crown sheet failure. I am willing to accept that there may be a situation in which this is possible, but I have seen no information that would indicate so, nor have I ever spoken with anyone who knows of any such information. I would be interested in this information if it does exist. Policies should be instituted or altered based on facts, and no one should be so wedded to their own beliefs that they ignore them when presented.

When we develop operating practices and training curriculum, emergency management must be a part of those practices. It would seem to me that in lieu of any real shred of evidence that supports the theory that "adding water to a boiler with low water causes it to blow up" is even plausible, let alone probable we should probably not be teaching this to operators. Emergency management instructions must be simple and instinctive, complicating matters leads to failures. A low water situation is an emergency, but there is a noteworthy time between the moment that water drops from view in the glass and the boiler goes Ka-BOOM. (In locomotives on level track, the water level must drop another 3 inches or more before any portion of the crown sheet even starts to uncover and then begins to rise in temperature) So, if we know that there are several minutes that must elapse between the time water disappears from the glass and when the critical moment of failure arises in this rumored, yet undocumented scenario, it seems that the odds are fairly stacked against calling this a real danger. LOW WATER causes crown sheet failures, the solution to low water is to ADD WATER. The proper emergency management instruction is, in the event of low water, to turn on the injector and put out the fire, in that order, NOW. I am willing to roll the dice on a 1:1Billion odds scenario where this doesn't work.



I presume you are referring to Medina and Gettysburg? After reading the reports on both, I did not get from them that adding water to the boiler after the crown sheet overheated caused the failures. If I am incorrect and you are referring to others, please advise. I am always interested in reading these reports.



Mr. Kennedy, your guess seems spot on... The following was published in the Journal of the Brotherhood of Locomotive Firemen and Engineers in 1920. The article is titled "Water Circulation in the Locomotive Boiler". You may want to check your sources, I think they are a bit dated.
Link to complete article:http://books.google.com/books?id=oLwOAQAAMAAJ&pg=RA2-PA21&lpg=RA2-PA21&dq=false+head+gauge+cocks&source=bl&ots=9F0fwMlB0D&sig=OPvTJ2XMs9KbdVykIK2zHmJWWHE&hl=en&sa=X&ei=KewbUb3RKrK-0QHno4HIAQ&ved=0CC0Q6AEwAA#v=onepage&q=false%20head%20gauge%20cocks&f=false

"The old established theory that the water glass was little more than a convenient auxiliary to the gauge cocks on a locomotive boiler and not to be depended upon and that the gauge cocks were the only true indicator of the water level has received a severe jolt and will have to give way to demonstrated facts as presented in the report of tests recently made by the Bureau of Locomotive Inspection Interstate Commerce Commission AG Pack Chief Inspector the first installment of which we publish herewith Little wonder is it that so many locomotive enginemen who had been taught to pin their faith to the gauge cocks have been the unfortunate victims of a theory that became a conviction and notwithstanding their previous good records suffered the loss of position and reputation if not their lives when they should have been held blameless Almost since the steam locomotive came into existence the scorching of a crown sheet has been considered about the worst offense in the line of dereliction of duty of which an engineman could be guilty for in nearly every case his protestation that the gauge cocks showed sufficient water in the boiler for safety has been ignored in fact disbelieved as the scorched sheet itself was considered conclusive evidence of low water and complete proof of incompetency on his part That the theory of gauge cock superiority as a water indicating appliance will now have to be revised is plainly evident...
...Practically all enginemen and others having to do with the operation of the locomotive true to a common understanding believe that the correct height of water over the crown sheet is always indicated by the gauge cocks and that the level indicated by the water glass is unreliable and not to be depended upon therefore it is reasonable to believe that engine men have frequently depended upon a level of water indicated by the gauge cocks as being correct when in fact the true level was much lower and as a consequence damaged crown sheets have resulted."

I think we're making a very large mistake in assuming that just because nobody who has contributed to this discussion knows scientifically whether adding water to a dry hot crown sheet is a good or bad idea, nobody knows. We're not the only or best engineering brains in the known universe. I'd be very surprised of there are not people capable of calculating materials response to specific stresses in changing combination........but I'm not at all surprised they aren't looking at this part of the web based universe.

Also, low water doesn't mean dry.....there's a lot of depth to lowness. How do you determine how low yoyur water is when it is below the level of the bottom of the glass or the lowest try cock? If it hasn't blown up, the crown is still covered? Look to see if the soot has burned off the crown sheet? That last one is another part of the Old School tradition. You look, I've dumped the fire and am far away.........

So, I'm wondering.......do we want to think about installing a third glass that reads from below the crown with a big red line on it labeled "PANIC?"

dave

I agree with this in concept, Dave. However, I am also relying on the over 250 years of combined steam experience of my co-workers, including the likes of Musser, Anderson and Moedinger. In my 10 years of professional steam I have never encountered any information or anyone with information that would support this policy. Considering that, I think I have been more than fair, especially because I am still willing to entertain the possibility at all.

Nukes have a "core spray" system. This is a bunch of sprinkler heads sitting directly above the fuel rods. Even if the rods are exposed to air, they are in a torrential rainstorm.

Someone is proposing that if such a sprinkler sat directly above a red-hot crown sheet, it would make the crown sheet more likely to fail than it already is.

Maybe.

That's not what's happening here though. Steel is a good conductor of heat. The boiler will refill gradually. Sure, the motion of the train is going to splash, but little more than it's already splashing. Think of waves on a beach, and how they progressively move up the beach from low to high tide. Despite the volatility of the waves, there's no sand that suddenly goes from bone dry to quenched... it's already fairly wet because of groundwater movement from past waves that didn't quite reach it. In this case it would not be groundwater bringing water closer, but steel's conductivity bringing heat closer to the water. The regiion about to get splashed next, has already cooled a lot. I don't believe it'd be possible to thermally shock a boiler by refilling it with normal feedwater devices.

I'd be more worried about a transition from smooth rail to rough, or entering a curve, grade or braking that suddenly shifts boiler water.

So it all seems like poppycock to me. A sad case of "overthinking", which is the direct result of brains doing what brains do. Think.

And no, I don't think some great epiphany will arise from it being carefully studied by a professional engineer, scientist or deity. One of the most basic scientific concepts is Occam's Razor: The simplest explanation is usually the correct one. Astronomers were going bananas trying to match the movement of planets to known physics, until they considered that the Church might be wrong about Earth being the center of the solar system. Then everything made sense.

I used to live next door to a retired SP steam engineer. He has since passed on but we used to talk about steam locomotives from time to time. Some of it was often over my head, but I do recall this subject coming up. He said he never worried about a crown sheet doing anything funny with water (of any temperature) being added other than getting 'more wet.'
He described the whole thing as silly paranoia and compared it to mothers not letting their kids swim until exactly an hour after they ate (a discussion about this topic is what led him to discuss the whole new water over the crown sheet to start with).

Call me conservative, but if I don't see water in the glass, the first thing I am going to do is open the drain at the bottom of the glass (using it as a "try cock") to see if I get water, steam, or nothing. If I get steam or nothing, I will drop the fire and exit the cab--fast--and de-board my passengers as quickly as possible to a safe distance away. When things cool down, I will come back and try to determine what kind of mess I left behind. I am not interested in personally conducting any tests of crown/flue sheet integrity. When the water disappears, the operation quits.

IMHO, of course.

Mike

I'm not suggesting anything else, Brandon......and I applaud your inquiry. I'd caution you about the difference between empirical and scientific knowledge, though......and most of what we know about steam operation is empirical, passed down because it was what worked at the time, and few people question it as you do.

I do think that if it were studied by somebody who has the ability to consider it completely - and there's a lot of complex stuff going on at once - there might be some answers that are scientifically sound on which to base a best practice.

I'm not the guy to do it, obviously........I just know enough to know that it's not simple or straightforward.

dave

Additional information:

1) I spoke today with a second-generation plumber/fitter/boiler serviceman, AND a decades-of-experience rail restorationist (steam, diesel, electric, marine, you name it) at one museum today. The latter repeated, to the letter, the "conventional wisdom" but could offer no proof, background data, etc.
The former said "In the case of small boilers, the kind that heat houses, YES, you CAN break a crown sheet by pumping cold water in on an exposed crown sheet. We've seen the results, and know why they happened. BUT.... We;re talking SMALL boilers you can flood that fast, working at 40 to 50 PSI, and MUCH thinner sheets than a locomotive or big power plant boiler. I can't see anyone ever flooding a locomotive or industrial boiler fast enough to do that, especially with the foaming the goes on at the top of the water...." Both of them then compared note on how fast injectors feed such boilers, where they feed, etc. The verdict was the same: Not that big a boiler, and not at locomotive pressures. "Water-tube" boilers/fireboxes at 1000+ psi? Maybe.

2) I brought home information from three 1901 and 1902 International Textbook Company/ICS books on steam engineering, and a fourth book I've yet to crack open. From "Boiler Management" section of "Steam Engineering", 1902:


Other sections of the other book emphasize that the greater danger to the crown sheet is from the entrance of colder air to the firebox, not additional water added to the boiler. Thus, dropping the fire or shutting off the oil burner completely may NOT be the best course of action! Indeed, all three books say specifically to bank the fire if the injectors fail on the road, in order to preserve remaining water and not pop the safeties.

I'll report more later.

I think of it as drop fire = SCRAM. So no, that does not seem conservative to me. In a nuke, you get 10% of your heat after you want it, so you still need to worry about uncovery. In a steam engine you do not.

And I'll accept "bank fire" in lieu of "drop fire" if it can be done quickly enough. The analogy in nukes is how submarines can rapidly set control rods to zero, having the same effect as SCRAM, but with the option to easily restart.

Just the same, I'd try to turn on the injector on the way out the door. Which segways to another interesting question.

What happens on our fire-dropped, abandoned locomotive, its feedwater pumps running amok on the remaining steam pressure, when the water rises to the steam done? Will water in the steam lines damage or destroy a feedwater pump? How about an injector?

In my experience, Robert, if you were dealing with an injector, you would be putting enough water into the boiler (assuming that it didn't go BOOM before then) to drop the pressure enough to cause the injector to drop out, probably well befofe the water reached the height of the dome. The injectors (lifting style) I have worked with seem to struggle to hang onto the water much below 110-120 psi. I can't speak to feedwater pumps; I have no experience with them.

The nice thing about firebox explosions (if you want to call them "nice") is that they tend to cause the boiler to fly up and forward in the direction of travel, away from the passenger cars. However, I imagine the concusive blast would still shatter window glass and eardrums. Anyway, when fleeing the engine, head in the direction fo the rear of the train. And say your prayers.

Mike

In my experience, a Sellers lifting 8.5 worked fine down to 45psi, and flooded the boiler as high as we wanted and then some.