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Mini-Challenge #587 - Transportation

Started 10 months ago | Discussions thread
NAwlins Contrarian Veteran Member • Posts: 7,964
The steam locomotive hazard

Yikes!

I wonder who determined that the steam locomotive was safe to be around. I can see vapour at extreme right, an indication that the boiler is under pressure. With the engine tilted onto its side, the crown sheet inside of the firebox is exposed partially, and will be above the water level in the boiler. If there's still a sizeable fire in the firebox, the crown sheet could melt and the boiler contents will explode outward, expanding 1600 times its liquid volume. Yes, steam expands at least 1600 times when it is released to atmosphere if it is contained in a pressurized vessel.

Insofar as the locomotive is on its side, the risk of failure may be less in the crown sheet--which is at the top of the firebox--than in the right side sheet (quite possibly fully exposed). And it's better but here worse: commonly crown sheets contain fusible plugs, which are designed to melt before the sheet fails, sending steam into the firebox and extinguishing the fire; but I'm not aware of side sheets having fusible plugs.

Of course a steam locomotive boiler explosion is a very bad thing, quite likely to kill anyone nearby and quite capable of killing people far away, so better safe than sorry. If the locomotive crew was not too injured, they should have made sure everyone was clear of the immediate area and then done something to release the pressure in the boiler. With common boiler pressures of not-super-ancient steam locomotives running about 175 to 250 psi (1.2 to 1.7 MPa) and superheating being more the rule than the exception on operational steam locomotives, there's a lot of energy = potential for trouble in that boiler.

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