This is what happens when steam loco water levels get low!

[PaxmanValenta]

Ok so I've been researching building my own miniature gauge steam loco, and was curious on boiler safety and testing. I came across a fairly catastrophic true story of what can happen if the water gets too low.

This is my interpretation of what happened.

In East Germany steam locomotives had been used on scheduled services until the late 1980s. In November 1977 approaching Bitterfeld station, a DR class 01.5s normal driver was on a course and had been replaced by a driver not fully experienced with this type of locomotive. Lack of communication between the fireman and this temporary driver resulted in the water gauge not being checked.

The result was that the water got so low that it was no longer covering the firebox. In a period of 4 minutes the steel fire box had heated to nearly 800 degrees C, starting to cause the metal to fail. The train entered Bitterfeld station and as it came to a halt the inertia caused water in the boiler to swash forward and then back over the fire box.

(Now these locos have 9 cubic metres of water inside and as you know from physics that under pressure a liquid can remain liquid well above its boiling point and become a gas when pressure is released.)

The action of the water flowing back over the red hot fire box top resulted in it 1) instantly turning to steam, and 2) causing severe changes to the structure of steel in the firebox top. The result was a massive localised pressure build up over the top of the box, which caused the fire box top to collapse. In an instant 9 cubic metres of super heated water flashed to 3000 cubic metres of steam about 1 billion watts of energy. This blasted through the fire box opening into the cab like a rocket jet nozzle, ripping the entire boiler from its chassis and propelling it like a rocket 50 metres down the station! The 2 crew members were killed plus 7 bystanders in the station.

Just shows how a steam engine boiler can be like a bomb. Never underestimate the energy in compressed liquids and gases.

See: http://www.vapeur-dampf.ch/la-vapeur-pas-de-peur-mais-du-respect/?lang=en

An interesting topic to discuss. Please feel free to add any more storied or examples of boiler mishaps etc!

 

[oddiesjack]

Was there anything in the report about the fusible plug(s) failing to "drop" ?

I am struggling to get to grips with the firebox crown being totally uncovered yet the fusible plug remaining intact. However, I have seen a severely damaged firebox crown due to an operator ignoring a blown plug and firing more heavily to counteract the ongoing pressure loss due to the amount of steam/water escaping through the dropped plug.

 

[PaxmanValenta]

Was there anything in the report about the fusible plug(s) failing to "drop" ?

I am struggling to get to grips with the firebox crown being totally uncovered yet the fusible plug remaining intact. However, I have seen a severely damaged firebox crown due to an operator ignoring a blown plug and firing more heavily to counteract the ongoing pressure loss due to the amount of steam/water escaping through the dropped plug.

I thought the same thing. But maybe they didn't use fusible plugs on East German built boilers.
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Surely on new built steam locos like the A1 Tornado, there are safety systems and back up systems to stop this sort of thing happening such as loud warning alarms if water level reaches critical level?

 

[SWTH]

No, the warning alarm should be ringing loud and clear in both the driver and firemans heads when the water is showing less than an inch in the gauge glasses.
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To expand on my previous post, it is the responsibility of both the driver and the fireman to ensure there is an adequate level of water in the boiler. This is combined with knowing the road (i.e are there any steep gradients up or down ahead, distance of the journey, speed etc), and knowing the load (light engine? 10 bogie carriages? Slow freight?).

The fusible plugs act as the warning device, and are required in all locomotive boilers, certainly in EU countries at least.

Unfortunately most boiler explosions kill the crew, so it is hard to gain an understanding of how the boiler was allowed to fail - I suspect incompetence is the primary factor in more recent (post-1950) examples.

 

[ac6000cw]

Very fortunately it didn't actually turn into a full-scale boiler explosion, but on the Gettysburg Railroad in the US they had a serious firebox explosion in 1995. It was caused by a mixture of poor maintenance and an inexperienced crew who didn't realize the mortal danger they and the 310 passengers were in until it was almost too late (the crew survived but were seriously injured). It led to a complete review of the maintenance, inspection and operation of steam locomotives in the US, so something good did come out of it.

The full accident report is here - http://www.ntsb.gov/safety/safety-studies/Documents/SIR9605.pdf

(the locomotive - built in Canada in 1948 - didn't have fusible plugs, they are not a requirement in the US).

 

[edwin_m]

The excellent Railways Archive search facility finds five pages of British accidents described as boiler explosions, with the most recent being on the GCR in 1976. There was also an event on the narrow gauge railway at Shelley in 2011 which came near to being an explosion.

Various water gauge faults are responsible for several serious boiler incidents, including at least two on the S160 locomotives imported from the States during WW2. These had a different type of valve to shut off the water gauge, whose setting was not obvious to crews so they thought the gauge was reading correctly when in fact it was no longer connected to the boiler.

 

[Taunton]

My father was a child in Buxton, Derbyshire, when in 1921 an LNWR 0-8-0 exploded, killing the crew and waking up the whole town as it happened after midnight. It appears to have been a defective safety valve, and a pressure gauge where the pointer had gone so far round the dial it was regarded as defective itself; in fact the gauge had been changed multiple times beforehand because of a belief that if it was reading overpressure it must be a gauge fault rather than the safety valves. This was the less common but "classic" explosion, due to overpressure rather than water shortage.

http://www.railwaysarchive.co.uk/documents/MoT_Buxton1921.pdf

His greatest recollection of the event however was that the town newspaper, which rushed out a 4-page emergency edition in the middle of the night as was the custom in those days, had been put together so fast it had a gross misprint in the sub-heading which read "Two men burst when a boiler killed".

 

[oddiesjack]

If I remember correctly, some parts of the boiler were found in the churchyard of St Peter's in Fairfield, a distance of over 500 yards, and is quite a bit higher than the Down Sidings at Buxton.

 

[30907]

For those who read German, this link to the Bitterfeld tragedy might be interesting.

Amazingly, and worryingly, the same crew narrowly avoided the same issue with an 03 on the outward run.

http://www.gerdboehmer-berlinereisenbahnarchiv.de/Statistiken/BBU-DR-DB.html

 

[PaxmanValenta]

For those who read German, this link to the Bitterfeld tragedy might be interesting.

Amazingly, and worryingly, the same crew narrowly avoided the same issue with an 03 on the outward run.

http://www.gerdboehmer-berlinereisenbahnarchiv.de/Statistiken/BBU-DR-DB.html

Very interesting I will copy and paste it through Google Translate

 

[edwin_m]

Very fortunately it didn't actually turn into a full-scale boiler explosion, but on the Gettysburg Railroad in the US they had a serious firebox explosion in 1995. It was caused by a mixture of poor maintenance and an inexperienced crew who didn't realize the mortal danger they and the 310 passengers were in until it was almost too late (the crew survived but were seriously injured). It led to a complete review of the maintenance, inspection and operation of steam locomotives in the US, so something good did come out of it.

The full accident report is here - http://www.ntsb.gov/safety/safety-studies/Documents/SIR9605.pdf

(the locomotive - built in Canada in 1948 - didn't have fusible plugs, they are not a requirement in the US).

Thanks for this - an interesting read and in view of recent events in the UK also a relevant commentary on what was quite literally a "Mom'n'Pop" operation. I notice the S160 crown collapses in the UK that I mentioned above are also cited in this report - does this mean the Americans didn't have similar accidents of their own that they could quote?

 

[Elecman]

I don't believe that water waning over a dry firebox top would lead to the sudden production of that much steam that the safety valves couldn't deal with. This was finally proved by either a Railway Inspector or a Boiler expert from the Boiler Users Association assisting him back at the turn of the last century which laid to rest the oft quoted explosion due to excessive steam production when a dry firebox roof and sides were suddenly recovered in water. I have read the report somewhere but can't remember where, there is an excellent book on Railway Boiler accidents ( may now be out of print) that also quoted the above.

 

[edwin_m]

I don't believe that water waning over a dry firebox top would lead to the sudden production of that much steam that the safety valves couldn't deal with. This was finally proved by either a Railway Inspector or a Boiler expert from the Boiler Users Association assisting him back at the turn of the last century which laid to rest the oft quoted explosion due to excessive steam production when a dry firebox roof and sides were suddenly recovered in water. I have read the report somewhere but can't remember where, there is an excellent book on Railway Boiler accidents ( may now be out of print) that also quoted the above.

The steps leading to explosion are explained in the various accident reports and I also can't see how water washing over the firebox top makes any difference.

If there is no longer water to cool the firebox crown then it gets too hot and ultimately the steel weakens and fails under the normal working pressure of the boiler. Before this happens the water in the boiler is at well above boiling point, kept liquid by the high pressure, but when it fails the pressure drops and a lot of the water boils instantaneously to steam. At no time is the pressure more than the normal working pressure of the boiler (otherwise the water would stop boiling off) so the safety valves do not open. However the force appears to be quite enough for a rush of steam from the firebox into the cab, carrying the fire with it.

I'm not sure if it is enough to propel the boiler like a rocket - that seems to be more associated with accidents in earlier years when the safety valves failed for whatever reason to do their job, or the whole boiler was critically weakened by unnoticed corrosion and in either case it failed much more catastrophically. Not knowing about the Bitterfeld incident I can't say what might have happened there.

 

[broadgage]

I recall reading of a boiler explosion on a very recently overhauled steam locomotive in the 1950s?
It was found that during the overhaul that the safety valves had wrongly assembled and could never have opened.
Shortly after the overhaul, the fireman had trouble in raising enough steam, so he "built a fierce fire, and with the driver went for a cup of tea"
The resultant explosion would almost certainly have killed anyone in the cab.

Anyone got more details of this incident, I may be mistaken WRT the date, but clearly remember the rest.

 

[Elecman]

Wasn't that the Taff Vale incident where the safety valves had been made of 2 dissimilar metals and when heated the inner was wedged closed by the differential I'm expansion coefficients?

Was also a similar incident on I think the LMS where a fitter reassembled the safety valve retainer the wrong way round thus effectively holding the valves shut and unable to open.

As an aside would opening the cylinder drain cocks full not vent sufficient steam?

 

[SWTH]

It would help, but I very much doubt it would be sufficient. The total diameter of the drain cock pipes is significantly less than the diameter of even the regulator pilot valve, let alone main valve.
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What also has to be considered is that whilst there is heat in the firebox, steam is continuously being created.

If considered safe to do so, the best course of action would be to put both injectors on, open the drain cocks and remove the fire. This is significantly easier on locos with rocking grates (especially if they are steam operated) as a quick run through with the slicer to remove any clinker and lumps followed by rocking the grate until largely clear is a fast way to destroy the fire and stop the production of steam. It's perfectly possible to do in under 10 minutes.

Locos with fixed grates are far more problematic - you need to go in with the clinker shovel and scoop all the fire out onto the lineside.

However, in a situation where boiler structural failure is imminent, the only steps I would take are bloody big ones as fast as possible.

 

[Elecman]

LOL in which direction?

 

[oddiesjack]

Cylinder drain cocks will only release steam/condensate from the cylinders and potentially valve chests, ie beyond the regulator and wouldn't really do anything to reduce the pressure in the boiler on the other side of the regulator valve. As the previous poster said, putting both injectors on full would be the most effective way to lower boiler pressure, combined with shutting dampers and throwing the fire out as quickly as possible.

 

[edwin_m]

Hang something heavy on the whistle chain? This would also serve to warn anyone nearby...

 

[SWTH]

If there is anything to hand then yes. However, I can't think of anything sufficiently heavy and usually found in the cabs of the locos I fire that would work whilst the crew still need to be on the footplate. Resting a fire-iron against the chain would work though once the time came to leg it.

 

[edwin_m]

If there is anything to hand then yes. However, I can't think of anything sufficiently heavy and usually found in the cabs of the locos I fire that would work whilst the crew still need to be on the footplate. Resting a fire-iron against the chain would work though once the time came to leg it.

I would have thought it would be the time to leg it already.