Is this relevant, you ask?

I've heard, from what I consider two reliable sources, of this situation arising in real life many years ago on one well-known excursion line. Supposedly a malfunctioning injector and a wild attempt to run back "home" were involved, as well as a fish supposedly clogging the injector...... But of course, this is all apocryphal, so.....

Robert, I can't help but resent your sentiments to some degree. As far as whether or not you like the topic, I simply don't care. However, I have to disagree with your questioning of the relevance in relation to railway preservation. I cannot think of a more relevant topic than the preservation of the skills necessary to operate preserved historic equipment. Without maintaining the skills, preserving the equipment seems to be a moot point. What good is a preserved steam engine as a teaching tool if nobody knows how the thing works (and please don't mistake that thought for some frothy arguement for restoring every rusting hulk in a county park to operation, I advocate no such policy). The bottom line is that those of us who are operating steam must do so safely and more importantly must ensure that when we teach others we teach them the best possible methods. When questionable practices come to light, they need to be discussed frankly and openly and without regard to the amount of valuable space on an internet forum consumed in the process. One catostrophic boiler failure that results from the actions of a well intentioned, but poorly trained, operator can potentially have a great effect on all aspects of railway preservation. On a much more personal level, it's a relevant topic because I, and a number of others that frequent this board, depend on railway preservation, and steam in particular to pay the mortgage. I guarantee I can do a great deal more for preservation in my current position than I could working in another field and volunteering on the side, and I gaurantee the next time somebody turns a firebox inside out I will be seeking a new line of work.

Kyle, your point is well taken. I would be very interested in seeing numbers and information to support any scenario. I make my assertions in this case based solely upon well reasoned arguements that I, and many others have put forth. I didn't intend to suggest that this scenario is entirely beyond the realm of possibility. Quite frankly, I don't know if it is or not. I am not an ME, just a curious layman with a fair amount of experience. I started this thread with a question because I am genuinely interested in getting the real story for the benefit of anyone interested. In regards to the conclusions I have come to, I simply feel that in light of the lack of evidence supporting the notion, and given the reasonable arguements presented to the contrary, we probably should give up on perpetuating what is at best a poorly documented theory and at worst a dangerous non-truth. Most importantly, the last thing I want to see is some 20 year old fireman get vaporized because he is standing on the foot plate trying to decide whether or not to turn on the injector after he forgot what he was doing and the water dropped out of the glass.

I enjoy the discourse going on here and feel that nearly all discussions I have seen on RYPN have some merit, even the ones I am not interested in. Thanks to everyone who has had something to add.

A great reply Brendan, and I agree with with you fully. It's something I would love to run some more numbers on myself, but the engineering "tools" for that are a few classes ahead of where I'm at now. The numbers I did run, though approximated, expressed in terms of volume, should help visualize the forces we deal with on a somewhat regular basis, as well as the catastrophic forces that have a potential to occur. It's not usually something expressed in a form that we can visualize both accurately and easily. Though its good to know how you probably should react if you are in this particular situation, I feel it's best practice to know your locomotives enough to know where you can operate with enough room to "play" and keep the boiler tame while you fix the mishap, be it broken blowdown, stuck safeties, etc. If you start the injectors before reaching near catastrophic levels, you are definitely buying good time to react with potential to not harm the locomotive at all.

Kyle
The 20 year old fireman/ ME student

Maybe on the Old Wive's Railroad (OW = Ontario Western?), incoming boiler water was directed onto the crown sheet?

Surprised this thread took off as it did.

However, I think it behooves any steam pressure vessel operator to have a decent notion of the physics of what they are operating. This issue got a lot of discussion on Smokstak because traction boiler operators are far more likely to suffer from exposed crown sheets, or encounter the situation. At that point, it's a matter of containing the danger and getting things under control--which is what I think most steam locomotive engineers would have in mind if faced with similar circumstances. Thus, this topic is very relevant to the steam tourist railroad industry.

At a local pulp mill (now closed) there was a failure of a large water tube process recovery boiler. The failure came not from a water condition, but by an "upset" of combustion forces in thie boiler (a structure roughly six stories tall). To think that there are not evaporative forces in a boiler that could lead to failure of a temperaure compromised sheet is a bit naive.

Has the ASME/NBIC ever done research into internal boiler dynamics in a FIRE tube boiler suffering from crown sheet overheating? I realize that firetube boilers aren't the state of the art anymore, but such research would be interesting from a material science point of view.

Anybody care to comment?

Michael Seitz
Missoula MT

Not that I'm aware of... But I think we have an example from modern times that could be looked at.

If you recall the incident on the Gettysburg Railroad in the nineties, you will remember that the engine was operated with the water glass nipples plugged with scale, and without an accurate reading of the water level, was worked until the front end of the crown sheet became uncovered, The sheet then sagged and pulled off the first row of stays; the second row in this Canadian Pacific designed engine were button head stays, and they held, preventing the entire sheet from dropping.

For sake of discussion here, I contend that when the sheet pulled off the first stay, opening that hole would have caused turbulence and flow that would have carried water over the sheet toward the hole, the same as the flow toward the throttle valve of a hard working engine can carry water over the valve. If this was the case, it should have had exactly the same effect as raising the water level on an overheated sheet by opening the injector/turning on the feedwater pump, yet the locomotive did not explode. Instead the sagging progressed across the width of the exposed area of the sheet, as one would have expected, and was stopped by the row of button head stays, and possibly the fact that the sheet in the area of those stays was not uncovered, or had not been uncovered as long.

Re:
From time to time the old notion "Never put water into a boiler that has low water or the crown sheet will shatter" comes up and I am concerned that in the face of rational thought this poor idea, as I see it, continues to be passed down.

I've never heard the term "shatter" used to refer to crownsheet damage. What happens is that the sheet overheats, becomes soft and pliable, and tears away from the staybolts. Firebox temperatures run, conservatively, around 2000 degrees F. The steel surrounding this fire that still has water against it is much cooler. A dry crownsheet will heat up quickly, and assessing how hot it has become is hard to do. If its temperature approaches 1400 F., then it is a dull cherry color and has become flexible, along with parts of its staybolts. If the injector is put on, say, for sixty seconds, the incoming water will hit some small part of the 1400 degree steel, and flash into steam with greater rapidity than the water already in the boiler that is against steel that it has already cooled. The soft crownsheet is fragile. This is why the situation is so serious. Any rise in pressure or sudden drop in pressure can cause it to fail. If the infusion of water causes a mere two psi rise against a 30-square-foot crownsheet in questionable state, that's 8,640 pounds of extra weight on the sheet, or two Ford pickup trucks. Even if the safeties lift suddenly, that will provide a subtle shock to the boiler that can be enough to set off a severely overheated sheet.

A dry crownsheet in a boiler under steam is an unknown factor that should be treated with the highest level of caution. When in doubt, the safest response is always best, and that seldom, if ever, includes using the injector.

The entire reason this discussion is going on is because we have yet to adequately agree on precisely the "safest" course of action.

Right now, as objectively as I can look at the hypothetical situation (a crown sheet exposed by low water and now heated to the point of potential/eventual failure under pressure), we have two possibilities: remove additional heating/pressure as fast as possible and flee (drop/extinguish the fire, maybe throw open a blowdown valve), AND/OR attempt to cool the potentially failing sheet with gradual cooling (nail the injector/feedwater pump).

We are not dumping three hundred gallons of cold water into the boiler instantaneously. It's agreed that the water, fairly warm at the bottom of the boiler, would inch up slowly with the injectors on. Also, we're also not talking a glowing orange two-thousand-degree patch of crown sheet with four-hundred degree steel/water a tenth of an inch away. There's a gradual transition from hot to glowing-hot, and that transition is where the rising water is going to hit first.

So, assuming I've now hit the injectors before running for the hills, presumably as fast as the water is hitting the hotter part of the firebox at the edges of the water, it's also cooling down the metal gradually--not like quenching a red-hot iron in a cold water or oil bucket all at once (yes, I've seen iron crack doing that), but easing it in gradually to a heated quench liquid.

The scientist part of me continues to assert that"you can't prove a negative," and we also have the previously-alluded-to problem that we seldom have survivors of boiler explosions to question as to what they did or didn't do (and the dead make great scapegoats). In my mind, the jury is still deliberating. And we really do want a decision, hoping to whatever deity you like we never have to use the resulting decision.

I think the actual best answer is a combination of your two options.

I would hope that everyone would agree you should kill the fire as soon as possible. I also hope that everyone agrees you should not put yourself or others at risk any more than absolutely needed to prevent catastrophic failure. The time to worry about damaging the firebox was before the water got low in the first place. Now the concern is stopping it from exploding.

So you kill the fire as quickly as possible. However, while you're doing that, if you cannot do it essentially instantly, i.e. Oil Burner, should you also open the injector to try and cool the crown sheet while you dump the fire? Bonus question, once you've dumped the fire, should you leave the injectors on while you vacate the area, assuming you said to use them in the first place?

You've also added a new question. Do you open a blowdown? Doing so would expose even more of the crown sheet. On the other hand, it would also reduce the pressure quickly. Interesting idea, and one that I don't recall hearing suggested before.

My first instinct is that it's a very bad idea to expose more of the crown sheet by using the blowdown, but then again, if you have a portion of the crown sheet that's already overheated and possibly close to failing, the part you expose by opening the blowdown won't be the issue, it will be the part that's already exposed when you encounter the situation. The part you're exposing will be cooler than the other portion, and maybe removing the pressure from that section as quickly as possible is a good idea?

Cool the pressure vessel by any means possible and reduce the pressure by any means possible (Injectors and blowdown for example) seems logical enough. But we seem to have already proven that this question isn't nearly as simple as it appears.

Brendan: As I said at the start of this thing, you are going to get a lot of flack. This situation is similar to someone crossing the road in front of a truck and insisting they are "right" and they wind up being dead right! I learned a long time ago to never argue with anything bigger than you are. This is a similar situation. You go right ahead and pull the injector on to prove you are "right" just make sure you tell everyone else anywhere nearby what you are about to do so they can get the Hell out of there.

As for the comment someone made "how do you know what happened?" as far as whether or not the injector was pulled on. Examination of the wreck would reveal the position of the injector handle.

By the Way, the only thing that saved those people on the 1278 was the CPR's design of buttonhead stays alternating with regular ones. This was done to prevent the worst reaction/explosion. The fools running that RR were entirely to blame. Gettysburg was one of only two or three tourist RR's where I turned down a cab ride because one look told me these people were trouble!

Incidentally, the outcome that resulted in TWO water glasses being put on is stupid. If you are not maintaining one glass what makes anyone think you would maintain two? The second glass replaced the gauge cocks. I was taught the gauge cocks were more accurate than the glass. Another old wives tale I guess.

Why would the addition of a second glass be stupid?? back in the days many locomotives exploded due to plugged orfices. A second glass gives you a second chance...If one is blocked the other may and probably won't be. Also many don't even know how to properly use tri-cocks but being able to look at 2 different glasses is wise and should have been done in the early days of steam. I am also a firm believer in blowing down your glass at least once per day.

And once again, we come full circle to the heart of the matter. Your words make you appear to accept it as Utterly Gospel Truth that pulling the injector on is going to blow up the boiler. We lack proof of that. The exposed crown sheet is enough of a reason to run for the hills. The injector might hurt, might help.... we don't know.

I'm reminded of the time, years ago, a friend's car in his driveway had a fuel line rupture, and smoke started coming out from under the hood. He popped open the hood, and I grabbed the garden hose, turned on the water, and got the water out of the nozzle into a "fog" to start quenching the flames that erupted when the hood went up. While I was knocking down the fire, the nearby kids were screaming, "Get away! Run away!! It's gonna blow up!" In mere seconds I had the flames extinguished (just by basically "blowing out" the flame on the ruptured fuel line), and I looked at the one girl, maybe ten or twelve years old, with an expression on my face that might have said "Well?", and she replied with a dumbfounded face, "Don't you watch 'CHiPS'?!? Don't you watch 'Emergency: One'?!?" [Two then-popular prime-time shows that featured inevitable dramatic explosions at every accident or fire scene, from which folks inevitably had to be rescued or dive for cover from.] I think the kids were learning right then and there that TV-Land was more explosive than real life. (Come to think of it, that car may have been a Ford Pinto station wagon....)

And I'm starting to thing that, absent demonstrable proof, the adage of not adding water to an overheated crownsheet stems from a similarly fertile imagination or parallel universe.

So what do we do: Call in Mythbusters! and let THEM test the hypothesis? Who's got a spare locomotive or thresher boiler we can put to the test??? Look, we've got the prospect of a truly spectacular show for them if this theory proves to be true! That's gotta be worth some money!

No, it stems from the working man's existence, something I tried to give an example of the other day, but no one picked up on it.

I don't ever recall this issue addressed in any trade press of the day, or accident reports, either. I just tried to search the ICC accident reports on the DOT web site, but only found one pertaining to a boiler explosion, and it is mute on the subject. I've tried to find the report on the C&O H-8 that blew up in Hinton, WV in '53 (I thought it was on the web) but couldn't find it. As far as I can recall, I've never seen this issue addressed, other than in popular lore.

It's conventional wisdom, which to me means it's the wisdom of conventional men, the kind that went to work, and hoped to go home to their families at the end of their shift. They weren't knighted members of the peerage. They didn't have "gentleman's honor" to uphold. They weren't ship's captains, and weren't expected to go down with their ship. They were just working stiffs who wanted to make it through their trick alive.

Now I think we can all agree that when faced with an empty water glass (which shouldn't ever happen) no one will really know how it got empty (or they would have taken corrective action) or even how long it had been empty. So, they now realize that the boiler could blow in a heartbeat, before they even draw their next breath. What to do? I'm sure management's position is they should do their job, refill the boiler, and everything will be fine. Or not.

The working stiff is going to view the situation a bit differently, and get his ass off the engine while he still can, and all that talk about adding water will cause the explosion is just rationalization to justify that action.

I'm still waiting for a citation of discussion of this in period trade literature, engineering texts, or accident reports. I don't think it exists, because I don't think it is a true premise. That's not to say that some poor SOB didn't get blown to kingdom come with his hand on the injector, but that was because the boiler was going to go at that moment no matter what he did.

Another Old Wive's Tale is that some steam engines had 2 sight glasses so that both the engineer and the fireman could see the water level without stretching their necks.

I would far rather fire an engine with one glass and tri-cocks than two glasses. Why? Because if a tri-cock is blocked you instantly know it. There is no doubt whether you're getting water or steam (or nothing) when you open the cock. You know exactly where your water is.

Now, I'm OK with two glasses, but don't take away my tri-cocks!

Perhaps, in new or heavily rebuilt boilers, two glasses and tri-cocks could be incorporated?

This is an interesting discussion. Hopefully the low water condition will never again happen due to proper training and careful observation- both the fireman and hogger need to be acutely aware of the water level at all times. Let's come back after every trip!

Steve Hunter