condensing steam railcar implosion demo

[Joe Frickin' Friday]

 

If you've never seen this demo done on a smaller scale in a chemistry/physics lab, there's a couple of ways to do this. One way of course is with a vacuum pump, but the other is more interesting. They don't say how they did it, but in all likelihood, here's what's happening:

 

A closed vessel (in this case, the railroad tanker car) is filled with a small amount of liquid water. The water is heated until it boils, filling the rail car with steam (water vapor), and shoving most of the air out of the rail car.

 

The rail car is then sealed and allowed to cool. The steam condenses back into liquid form, but since no air is allowed back in, the pressure inside the rail car (formerly at atmospheric pressure) begins to drop. THe rail car is pretty rigid, though, so it's able to resist the crushing pressure of the atmosphere - at first. But eventually, as the temperature drops and continues lowering the internal pressure, some little part of the railcar crinkles just a smidge (ever stood on an empty beer can?), and then WHAM! the whole thing gives up the ghost and collapses in on itself in spectacular fashion.

 

I saw this done in high school with a 1-gallon metal paint thinner can. In that case the collapse happed slowly because it was a rectangular can, so the sides caved in gradually and easily. I also saw Bill Nye (The Science Guy) do it once with a 55-gallon drum; he boiled the water inside on a charcoal grill, capped the drum, and then floated it in a kiddie pool filled with ice water until it did pretty much the same thing as the rail car.

 

Cool stuff.

[Mike O]

...A closed vessel (in this case, the railroad tanker car) is filled with a small amount of liquid water. The water is heated until it boils, filling the rail car with steam (water vapor), and shoving most of the air out of the rail car....

What's a 'small amount'? Seems like that would take a fair amount of liquid for a vessel that size (10's of gallons?). And how would they boil it? And with what?

 

Mike O

[Joe Frickin' Friday]

...A closed vessel (in this case, the railroad tanker car) is filled with a small amount of liquid water. The water is heated until it boils, filling the rail car with steam (water vapor), and shoving most of the air out of the rail car....

What's a 'small amount'? Seems like that would take a fair amount of liquid for a vessel that size (10's of gallons?). And how would they boil it? And with what?

 

According to these guys, a comparable tanker car has a capacity of 24,000 gallons, or 3200 cubic feet. That much steam (at 212F) weighs about 120 pounds; condensed to liquid, that's about 1.9 cubic feet, or 14 gallons of water.

 

As for how to heat it... a large burner under the tanker? Note that it's not necessary to fill the entire volume of the railcar with steam; there's so much surface area involved, it doesn't take much of a pressure differential to cause collapse.

 

See attached for a prior, accidental case of tanker implosion. As this suggests, you could supply the required steam with an external steam generator.

1027758-CollapsingSteam.zip

[Matts_12GS]

wow! that's cool as can be!

 

Smashlab take me away!

[George Brown]

I spent a few years working in the process industry. From my experience I would venture to say that more vessels are imploded due to vacuum or partial vacuum usually caused by undersized or restricted vents than exploded (or, as we used to write in our incident reports: "vessel failed to do a rapid pressure increase after dust or vapors ignited"

[Joe Frickin' Friday]

...A closed vessel (in this case, the railroad tanker car) is filled with a small amount of liquid water. The water is heated until it boils, filling the rail car with steam (water vapor), and shoving most of the air out of the rail car....

What's a 'small amount'? Seems like that would take a fair amount of liquid for a vessel that size (10's of gallons?). And how would they boil it? And with what?

 

Mike O

 

I took another look at the video,and noticed a rather large hose connected to the middle of the tanker. That could be connected to an external steam source, or to a vacuum pump. Either way, it would obviate the need for boiling up any liquid water inside the tanker.

[Mike O]

...A closed vessel (in this case, the railroad tanker car) is filled with a small amount of liquid water. The water is heated until it boils, filling the rail car with steam (water vapor), and shoving most of the air out of the rail car....

What's a 'small amount'? Seems like that would take a fair amount of liquid for a vessel that size (10's of gallons?). And how would they boil it? And with what?

 

Mike O

 

I took another look at the video,and noticed a rather large hose connected to the middle of the tanker. That could be connected to an external steam source, or to a vacuum pump. Either way, it would obviate the need for boiling up any liquid water inside the tanker.

Mitch,

 

That seems far more practical, don't you think? Every time I've tried to head 10's of gallons of water (especially at our altitude) it take lots of BTU's to accomplish.

 

Mike O