dehusman wrote: marknewton wrote:Why do you think that? How many instances where a collision or derailment has lead to a boiler explosion can you cite?The most famous example is the staged collision on the MKT between two steam engines. The boilers did explode and resulted in several fatalites and numerous injuries.Dave H.
marknewton wrote:Why do you think that? How many instances where a collision or derailment has lead to a boiler explosion can you cite?
The most famous example is the staged collision on the MKT between two steam engines. The boilers did explode and resulted in several fatalites and numerous injuries.
Dave H.
I think that was the one where the newsreel photographer a quarter mile away lost an eye to a bolt sailing like a bullet.
Steam locomotives are a series of long narrow steel tubes holding steam under high pressure. If in a crash one of the pipes got even a whole in it, all the steam in the entire engine would try to escape through that hole all at once - causing an incredible explosion.
I would think a steam engine speeding along and crashing into a large modern tank could sustain damage to a steam pipe causing an explosion. If it would happen every time, or one time out of 10, or whatever, I don't know. It maybe isn't even likely, but it is plausible.
wjstix wrote:Steam locomotives are a series of long narrow steel tubes holding steam under high pressure.
Almost. They are long narrow steel tubes holding very hot water under high pressure.
What actually causes the explosion isn't the pressure, its a sudden drop in pressure. When the the boiler develops a major leak and drops the pressure from 250 psi to atmosphere within seconds, all the superheated water in the boiler immediately turns to steam and attempts to expand. Followed by a big boom.
Dave H. Painted side goes up. My website : wnbranch.com
marknewton wrote: 2-8-8-0 wrote: As has been mentioned a steam explosion could well result...Why do you think that? How many instances where a collision or derailment has lead to a boiler explosion can you cite?Cheers,Mark.
2-8-8-0 wrote: As has been mentioned a steam explosion could well result...
As has been mentioned a steam explosion could well result...
lets not compare hitting a car to hitting a tank. Rather lets imagine what would happen if the loco hits another extremely massive object, like....68 tons of M1 tank. In "Reflections of the Nickel Plate Road" one of the first photographs is of a pair of steamers (i think both are 4-6-0s) that had a head on collision in western ohio. One loco was smashed underneath its own tender, the second had disintegrated into unrecognizable components. In both locomotives it was painfully obvious that the boiler would not be able to maintain pressure. I dont mean "explosion" as in KABOOM, destroying the entire locomotive. What perhaps should have been said was that a "rapid, vigorous, and potentially harmful" escape of steam could have resulted. I dont know why you have so much reason to doubt this, but if a collision like this were a real world scenario, i would definately want to be somewhere else.
M 1's have Chabum armor, so the occupants would be in the "safest" place. Still, he should have parked it head on facing the oncomingtrain with the turret turned away. Hey, they may find a round or two....
Tilden
bportrail wrote:It was a fun episode! I am glad that show is back on, and Hawkins is greatness! The premise was the "Bad" town got a Loco working to launch a flank attack on Jericho. Hawkins had the right idea, and drove the M-1 on the tracks to stop it. It was a pretty cool scene! Keith
It was a fun episode! I am glad that show is back on, and Hawkins is greatness! The premise was the "Bad" town got a Loco working to launch a flank attack on Jericho. Hawkins had the right idea, and drove the M-1 on the tracks to stop it. It was a pretty cool scene!
Keith
ahhh i was wondering what a steam loco was doing on the show . thanks !
Tilden wrote:Of course it would have helped if he had put a round through the train. One armour piercing round would take out the boiler front to back...
Of course it would have helped if he had put a round through the train. One armour piercing round would take out the boiler front to back...
Steam locomotives are a series of long narrow steel tubes holding steam under high pressure.
If in a crash one of the pipes got even a whole in it, all the steam in the entire engine would try to escape through that hole all at once - causing an incredible explosion.
2-8-8-0 wrote:lets not compare hitting a car to hitting a tank.
Rather lets imagine what would happen if the loco hits another extremely massive object, like....68 tons of M1 tank.
In "Reflections of the Nickel Plate Road" one of the first photographs is of a pair of steamers (i think both are 4-6-0s) that had a head on collision in western ohio. One loco was smashed underneath its own tender, the second had disintegrated into unrecognizable components. In both locomotives it was painfully obvious that the boiler would not be able to maintain pressure. I dont mean "explosion" as in KABOOM, destroying the entire locomotive. What perhaps should have been said was that a "rapid, vigorous, and potentially harmful" escape of steam could have resulted.
I dont know why you have so much reason to doubt this...
As I mentioned in a previous post, loco boilers typically have a factor of safety of four or more. They are designed to take a terrific amount of abuse, and the historical record shows that there were a miniscule number of collisions of derailments on US railroads that caused boiler explosions. Don't take my word for it, do some research of your own - the ICC accident reports are available for study.All the best,Mark.
But Mark, that would mean actually looking things up to obtain facts. Even though it's a lot easier now than before the Internet, it still involves taking some initiative. You can't ask people to do that.
In any case, isn't "boiler explosion" a misnomer as an actual explosion would involve the catastrophic failure of the boiler shell and those were extremely rare indeed. There's a book by a now deceased locomotive engineer (driver) called "Three Barrels Of Steam" in which the history of Southern Pacific's 4-10-2's is discussed. In 1948, near Bosque, Arizona, one of them suffered a catastrophic crown sheet failure. There are ample pictures of the event in the book and one thing that stands out is the essential integrity of the boiler shell, which was hurled about 150 yards forward of the locomotive and landed with the smokebox end facing the locomotive chassis. The boiler shell was kind of egg shaped at one end, due to impact with the earth, but there was no evidence of any failure of the boiler shell. Pictures of the chassis show that the superheater flues remained with the engine. The front tube sheet was blown into the cab of an ALCO S-2 which was being used as a point helper.
Andre
Another example of mis-planned 'movie magic'-- the head-on collision of two actual narrow guage locomotives in the 1952 Paramount film DENVER AND RIO GRANDE. Both trains were going about 35 miles an hour when they collided, and after all of the steam and dust (some of it studio created) cleared, the two locomotives were sitting on the track with just minor damage to the stacks and pilots. The movie company had to go in and bash them up to make them look more damaged for the subsequent close-up shots. Even had to stage a fake boiler explosion for one scene.
After all of the fancy plot-build up to the collision, the collision itself was an anti-climax (except to those of us who were appalled that Hollywood would actually destroy two 19th-century locomotives).
Tom
Tom View my layout photos! http://s299.photobucket.com/albums/mm310/TWhite-014/Rio%20Grande%20Yuba%20River%20Sub One can NEVER have too many Articulateds!
dehusman wrote: wjstix wrote:Steam locomotives are a series of long narrow steel tubes holding steam under high pressure. Almost. They are long narrow steel tubes holding very hot water under high pressure.What actually causes the explosion isn't the pressure, its a sudden drop in pressure. When the the boiler develops a major leak and drops the pressure from 250 psi to atmosphere within seconds, all the superheated water in the boiler immediately turns to steam and attempts to expand. Followed by a big boom.
d:
One big steel tube, actually, holding hot water under high pressure, full of tubes that hold hot gases. In a locomotive-type fire-tube boiler, the water is outside the tubes. The exception is the superheater; here we have large fire-tubes that contain multiple small tubes full of high-pressure steam.
The big boom you describe is what happens in a catastrophic crownsheet failure, but the situation here is a little different, because the crownsheet, without water covering it, will have already been heated to the point of softening, becoming the weakest part of the vessel, until suddenly the sheet isn't able to hold back boiler pressure. That heating and weakening hasn't occurred in an accident situation like this one. There have been examples of boilers exploding from collision damage, like that MKT example, but it would have to be a pretty big rupture all at once to do something similar to a crownsheet failure.
Autobus Prime wrote:The big boom you describe is what happens in a catastrophic crownsheet failure, but the situation here is a little different, because the crownsheet, without water covering it, will have already been heated to the point of softening, becoming the weakest part of the vessel, until suddenly the sheet isn't able to hold back boiler pressure. That heating and weakening hasn't occurred in an accident situation like this one. There have been examples of boilers exploding from collision damage, like that MKT example, but it would have to be a pretty big rupture all at once to do something similar to a crownsheet failure.
A pressure vessel explosion requires at least these two things: a catastrophic structural failure, and a relativel large volume of compressible (and compressed) gas trapped inside.
Nearly all loco boiler explosions were the result of the crownsheet no longer having the heat-absorbing blanket of water over it. Result: the crownsheet overheats and softens, resulting in a catastrophic structural failure of the pressure vessel. Why was the crownsheet uncovered? The water level was too low, meaning the steam volume was too high. Large volume of steam expanding means big bang! (Why was the water level too low? Because scale would clog the sight glass and it would show ample water, when the boiler was actually low on water. That's why there are both try-cocks - small water valves at various levels in the backhead - AND sight glasses on steamers. Good engineers and firemen look at the glass and open the try-cocks to make sure water drips out at the correct water level for the boiler).
Only a relatively small amount of the boiler water will generally flash to steam, even though the boiling point will drop as the pressure drops, and the water may be hotter than it's boiling point at atmospheric pressure. But the latent heat of vaporization (the non-sensible heat required to convert a material from a liquid to a gas) of water is high, so a small amount of water flashing to steam will immediately drop the temperature of the remaining water below boiling, leaving it only scaldingly hot. So you get a lot of very hot water with lots of tiny bubbles in it.
WAY oversimplified, but that's the gist of it, I think.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Nelson
Ex-Southern 385 Being Hoisted
Well Mark, we are kinda talking apples and oranges here. An RPG is a rocket propelled grenade, which usually has a shaped charge. Now. if there is something to ignite, an RPG should set it off. A boiler on the other hand has water, which if atomized would tend to smother any fire. You are correct about kenetic armor piercing rounds and they all generate a lot of heat. The older style, with tungsten penetrators, do tend to shred and make a big mess inside. However, that is after penetrating hardened protective armor. I don't believe a loco boiler would have the strength and density to cause an AP round to do this, it would probally go straight through the loco and tender. The newer Depleted Uranium rounds are even more dense (the 120mm round has about 4.5kg's of DU packaged into a fin stablized dart about 1 inch in diameter with 4.5 inches of powder behind it, thus the kenetic part), are self sharpening and pyrophoric (they burn). Contact temprature is over 1100 degrees C. So, this should be enough heat, mass and energy to cause a boiler to explode regardless of other fuel.
Either way, I don't want to be around when it happens.
Brunton wrote: Autobus Prime wrote:The big boom you describe is what happens in a catastrophic crownsheet failure, but the situation here is a little different, because the crownsheet, without water covering it, will have already been heated to the point of softening, becoming the weakest part of the vessel, until suddenly the sheet isn't able to hold back boiler pressure. That heating and weakening hasn't occurred in an accident situation like this one. There have been examples of boilers exploding from collision damage, like that MKT example, but it would have to be a pretty big rupture all at once to do something similar to a crownsheet failure.Right, Autobus.A pressure vessel explosion requires at least these two things: a catastrophic structural failure, and a relativel large volume of compressible (and compressed) gas trapped inside.Nearly all loco boiler explosions were the result of the crownsheet no longer having the heat-absorbing blanket of water over it. Result: the crownsheet overheats and softens, resulting in a catastrophic structural failure of the pressure vessel. Why was the crownsheet uncovered? The water level was too low, meaning the steam volume was too high. Large volume of steam expanding means big bang! (Why was the water level too low? Because scale would clog the sight glass and it would show ample water, when the boiler was actually low on water. That's why there are both try-cocks - small water valves at various levels in the backhead - AND sight glasses on steamers. Good engineers and firemen look at the glass and open the try-cocks to make sure water drips out at the correct water level for the boiler).Only a relatively small amount of the boiler water will generally flash to steam, even though the boiling point will drop as the pressure drops, and the water may be hotter than it's boiling point at atmospheric pressure. But the latent heat of vaporization (the non-sensible heat required to convert a material from a liquid to a gas) of water is high, so a small amount of water flashing to steam will immediately drop the temperature of the remaining water below boiling, leaving it only scaldingly hot. So you get a lot of very hot water with lots of tiny bubbles in it.WAY oversimplified, but that's the gist of it, I think.
At 200 PSI, the boiling point of water is 373 degrees F, 160+ degrees above the boiling point of water at atmospheric pressure. The catastrophic failure of a crown sheet due to low water will almost instantaneously drop the pressure necessary to keep water in a liquid state, causing that water to flash into steam as the latent heat required for steam generation is already there. In an earlier post, I mentioned an SP 4-10-2 that suffered such a failure at Bosque, AZ, in 1948. The working pressure of an SP 4-10-2 is 225 PSI and it was rated at around 4,000 HP under normal operating conditions. According to the book I mentioned, the crownsheet failure and subsequent steam flashover created energy estimated to be well in excess of 1 million HP.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
andrechapelon wrote:...Don't take my word for it, do some research of your own - the ICC accident reports are available for study.But Mark, that would mean actually looking things up to obtain facts. Even though it's a lot easier now than before the Internet, it still involves taking some initiative. You can't ask people to do that.
...Don't take my word for it, do some research of your own - the ICC accident reports are available for study.
In any case, isn't "boiler explosion" a misnomer as an actual explosion would involve the catastrophic failure of the boiler shell and those were extremely rare indeed.
There's a book by a now deceased locomotive engineer (driver) called "Three Barrels Of Steam" in which the history of Southern Pacific's 4-10-2's is discussed. In 1948, near Bosque, Arizona, one of them suffered a catastrophic crown sheet failure...
BRAKIE wrote:Last time I checked those small round tubes was called flues...
Brunton wrote:A pressure vessel explosion requires at least these two things: a catastrophic structural failure, and a relativel large volume of compressible (and compressed) gas trapped inside.Nearly all loco boiler explosions were the result of the crownsheet no longer having the heat-absorbing blanket of water over it. Result: the crownsheet overheats and softens, resulting in a catastrophic structural failure of the pressure vessel. Why was the crownsheet uncovered? The water level was too low, meaning the steam volume was too high. Large volume of steam expanding means big bang!
Nearly all loco boiler explosions were the result of the crownsheet no longer having the heat-absorbing blanket of water over it. Result: the crownsheet overheats and softens, resulting in a catastrophic structural failure of the pressure vessel. Why was the crownsheet uncovered? The water level was too low, meaning the steam volume was too high. Large volume of steam expanding means big bang!
(Why was the water level too low? Because scale would clog the sight glass and it would show ample water, when the boiler was actually low on water.
That's why there are both try-cocks - small water valves at various levels in the backhead - AND sight glasses on steamers. Good engineers and firemen look at the glass and open the try-cocks to make sure water drips out at the correct water level for the boiler).
Only a relatively small amount of the boiler water will generally flash to steam, even though the boiling point will drop as the pressure drops, and the water may be hotter than it's boiling point at atmospheric pressure. But the latent heat of vaporization (the non-sensible heat required to convert a material from a liquid to a gas) of water is high, so a small amount of water flashing to steam will immediately drop the temperature of the remaining water below boiling, leaving it only scaldingly hot. So you get a lot of very hot water with lots of tiny bubbles in it.WAY oversimplified, but that's the gist of it, I think.
Tilden wrote: Well Mark, we are kinda talking apples and oranges here. An RPG is a rocket propelled grenade, which usually has a shaped charge.
Well Mark, we are kinda talking apples and oranges here. An RPG is a rocket propelled grenade, which usually has a shaped charge.
You are correct about kenetic armor piercing rounds and they all generate a lot of heat. The older style, with tungsten penetrators, do tend to shred and make a big mess inside...I don't believe a loco boiler would have the strength and density to cause an AP round to do this...
The newer Depleted Uranium rounds are even more dense (the 120mm round has about 4.5kg's of DU packaged into a fin stablized dart about 1 inch in diameter with 4.5 inches of powder behind it, thus the kenetic part), are self sharpening and pyrophoric (they burn). Contact temprature is over 1100 degrees C. So, this should be enough heat, mass and energy to cause a boiler to explode regardless of other fuel.
Mark - my impression was that there isn't enough heat in the boiler for all the hot water to flash to steam. Like you, I've been lucky enough to avoid encounters with boiler explosions - the worst thing I have seen is a fusible plug dropping (fortunately not on an engine I was running, although I'm embarrassed to admit I got too close for comfort once!).
A good portion of the water certainly will flash to steam, but (for example) when blowing down gauge glasses I know a good amount of water ends up in the bucket at the bottom of the drain.
As an aside, I'm sure you would agree that boiler safety should be foremost in any operator's mind - having read through the NTSB report on the firebox collapse of 1278 at Gettysburg, and while I believe the operating practices I use and am familiar with are a lot better than theirs, it is well worth reading, just to remind you WHY it is so important to blow down that gauge glass at least every day (and a multitude of other things they failed to do!).
marknewton wrote: BRAKIE wrote:Last time I checked those small round tubes was called flues...Then you should check again. Those small tubes are called "tubes". The large diameter tubes that have superheater elements in them are called "flues".
I don't know what they are called in Austria but,I been around long enough to know those tubes are called flues and that includes both types(heat and gasses) even by 2 license steam boiler operators I know.
Maybe betwixt me and thee there's a term difference.Reckon?
BRAKIE wrote: marknewton wrote: BRAKIE wrote:Last time I checked those small round tubes was called flues...Then you should check again. Those small tubes are called "tubes". The large diameter tubes that have superheater elements in them are called "flues". I don't know what they are called in Austria but,I been around long enough to know those tubes are called flues and that includes both types(heat and gasses) even by 2 license steam boiler operators I know.Maybe betwixt me and thee there's a term difference.Reckon?
Perhaps. In Austria, they're called Feuerrohr
In Australia, they generally speak English. Well, an offshoot of English, anyhow.
marknewton sez:
As you say, the boiler shell suffered surprisingly little damage - but what always amazes me is the photo on the top of page 88, showing the distortion of the mud ring. Now that takes some force.(I'm sorry to read that Mr. Boynton passed away - he told a good story, I reckon!)All the best,Mark.
Yeah, I can close my eyes and see that picture, even though my copy of the book is packed away and not easily obtainable.
Which reminds me, how close did I come to the actual numbers cited in the book? I was doing it from memory, and I was probably off a bit.
Sometimes, Hollywood gets it right...
http://www.youtube.com/watch?v=KfNB2giXz-I
-George
"And the sons of Pullman porters and the sons of engineers ride their father's magic carpet made of steel..."
marknewton wrote:No, sadly that is not the case. In crown sheet failures, ALL of the remaining water flashes over to steam. There is a fair bit of literature on the subject, discussing the physics involved, as well as the failure mode in detail. I can recommend a few publications if you're interested in learning more.
m:
There isn't enough energy for that. Even though all the water is well above its boiling point, vaporizing the water will take a certain amount of energy. Say the water is at 412 degrees - the energy released as the water cools to its atmospheric-pressure boiling point will only be enough to boil a fifth of the water into steam. In practice, though, this will happen fairly evenly through the whole vessel, so you'll end up with a lot of water atomized into droplets and carried off with the steam.
No if I ever saw a good movie about the fact that it's safer to use water in your steamer rather then gasoline thats the one. I bet no one ever did that mistake ever again. Thank you Hollywood.
Magnus