MYTHBUSTERS Recap: Tanker Implosion? Crushed!

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This week’s “Tanker Crush” episode of MYTHBUSTERS definitely wasn’t a “been there, done that.” After crushing more than 900 explosions, the MYTHBUSTERS crew finally took on a program about implosions. And it was a single-minded effort to do but one implosion — that of a 67,000-pound cold-rolled half-inch steel rail tanker, something that’s been on the MYTHBUSTERS list since nearly day one.

Why so long to tackle this myth? Because of its complexity.

In the original story, two rail workers steam cleaned a rail tanker car at the end of the day, then sealed it up, closing every hole and hatch. It rained, cooling the steam and creating a temperature differential, which means the external pressure was greater than the internal pressure, and the steel tank caved in. But to recreate the effect required a lot of effort, finding someone willing to part with a tanker car for the test, locating somewhere safe to perform the experiment, and getting permits. It took the final season to bring everything together.

Typical of MYTHBUSTERS technique, Adam Savage and Jamie Hyneman first scaled down the experiment.

Adam began by demonstrating the effect of heating water in a gallon metal can, sealing it, and then letting it cool. And it collapsed quickly. Then Jamie and Adam did the same to a 55-gallon metal drum. Structurally more sound, it look quite a bit longer, but it too collapsed, taking more than 15 minutes.

To better prepare for the main event, Adam and Jamie reset the 55-gallon drum experiment to take data, measuring the temperature, pressure, and time to collapse. Heating the water to nearly 200º F, the pressure dropped 16 inches and took 8 minutes for the collapse. Then they set up another 55-gallon drum, this time using steam as they would in the rail tanker. The temperature rose to 203º F, the pressure dropped 17.5 inches, and it took 16 minutes for the collapse.

The MYTHBUSTERS crew had been working with drums. To scale as closely as possible to the real event, Adam and Jamie built a scale model of an actual tanker – minus bulkheads – and ran another test. It took only 7 minutes at an 11-inch drop of pressure for the tank to collapse, attributable to the weaker construction Jamie surmised.

Finally, everything was ready for the real test. Using a remote two-and-a-half-mile track of rail in Oregon, the myth and one of the biggest production efforts in MYTHBUSTERS history was on.

Thermometers and pressure gauges wired into the tanker, Adam, Jamie, and crew used a huge portable industrial steam cleaner to clean the inside of the tanker, bringing the interior temperature to 209º F. Adam, suited in a heat-resistant suit, climbed onto the car and sealed the tanker and then rushed back to the safety bunker to watch. The local fire department turned on a hose of cold water to simulate rain, and the suspenseful countdown to implosion began.

After an hour and an amazing pressure drop of 27 inches – to a nearly perfect vacuum – the tanker failed to collapse. In their eyes, the MYTHBUSTERS crew had performed a flawless experiment but didn’t get the same results as in the original story. But they wouldn’t settle for the results.

Perhaps the tanker in the original story had been damaged or corroded, reasoned Adam and Jamie. So they ordered a corroded tanker for another attempt at the myth. This time they used an industrial vacuum pump to get the same pressure differential in a fraction of the time, but after an hour the results were the same: no collapse!

When they have tried all reasonable results to replicate the original myth and have failed, you know the MYTHBUSTERS: Try to replicate the results. Adam and Jamie brought in a crane and dropped a hefty chunk of concrete on top of the corroded tanker, denting the top. Then they vacuum pumped the tanker again.

This time, after 10 minutes and a drop in pressure of 23 inches, the tank collapsed — flattened like an elephant had stepped on a soda can. “I’ve never seen anything quite like that,” said Jamie in wonder, “something that sturdy collapsing like that.” Adam agreed: “It was beautiful!”

Of course, they couldn’t reproduce the original results so…

  • Conclusion: Busted!

Missed the episode? MYTHBUSTERS repeats Wednesday night at 9:00 p.m. ET/6:00 p.m. PT and midnight ET/9:00 p.m. PT on the Science Channel.

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  • HolyBananas

    I like how they only rained on ONE SIDE of it. And they live in a hot ass place. I feel that the test wasn’t quite 100% accurate. BUT I could be wrong.

  • Alan Eggleston

    That bothered me, too. The hosing of the tanker car didn’t really replicate the equal-immersion effect of rain. And using an industrial vacuum, while reproducing the pressure differential, didn’t introduce the stress of hot metal turning suddenly cold because of the rain. But they gave it their best shot(s). Once the tanker did buckle, it was quite a collapse! Thanks for commenting.

  • Terry Shearer

    Google ” inploded tank cars” for a demonstration with a European tank car. I suspect that the tank car in the video had a thinner steel thickness on the tank. Also, the weather was raining and the temperature was not in the 90 F degree range.

  • Alan Eggleston

    That bothered me, too. The hosing of the tanker car didn’t really replicate the equal-immersion effect of rain. And using an industrial vacuum, while reproducing the pressure differential, didn’t introduce the stress of hot metal turning suddenly cold because of the rain. But they gave it their best shot(s). Once the tanker did buckle, it was quite a collapse! Thanks for commenting.

  • Alan Eggleston

    You could be right, although I would think that Adam Savage and Jamie Hyneman would have done the research and known that. Thanks for commenting.

  • rulingsword

    I can’t wait for the last episode because it’ll mean I don’t have to watch Adam and Jamie fumble their way through scientific concept ever again. They kept saying negative pressure when that’s rarely used as a term for closed systems. Also, inches of mercury? Why not stick to PSI, something more understandable and more indicative of the forces involved? We had to rely on Jamie claiming that -30 inHg is a “full vacuum”. Nobody measured the outside pressure to confirm this. Not that it really matters. Viewers would still have no idea what 90% towards a vacuum means without some math and some outside knowledge of the physics involved. A simple fix would have been a factoid about the magnitude of atmospheric pressure.

    Finally, busted? They took 3 tries, it didn’t happen with the full replication but I’d imagine had they tried the steam with the compromised tanker, they’d have gotten the result they wanted. Plausible at worst. Yet another episode in missing the forest for the trees.

  • variaatio

    No matter the the rain amount, the pressure gauge doesn’t lie. It was in near perfect vacuum already. No matter how much more they would have rained on it, it wouldn’t have have gotten bigger differential. It was already on vacuum aka maximum pressure differential possible. You can’t go below vacuum. You can pile up high pressure as much as you want, but at the low end vacuum is a hard limit. The simple fact is apparently the train tankers engineers did their math and flat out designed the tankers to just take a full vacuum inside and keep smiling.

    It’s all about geometry as said. Frankly it isn’t actually that surprising that the car could take it. 1 atmo pressure differential is relatively low on the engineering problem scale. As long as the is no geometry faults, and you have correct shape (note the correctly designed pressure taking bulk heads at both end of the tanker compared to the small scale) it doesn’t take that much to take 1 atmo. Heck space crafts have paper thin aluminium walls and those can take 1 atmo difference. Submersibles designed to go to Mariana Trench have to deal with a 1000 atmo differential against an implosion and we have designed vehicles made out of steel capable of withstanding that.

  • Steven W. Kirkpatrick

    They used the wrong type of tank car. Many of the DOT-111 tank cars are built with a slight slope from center to ends for more efficient unloading. Typical “funnel flow” slopes for 111 cars are 1/4-inch per foot. With this, you create a natural offset in the tank compression relative to the tank cylindrical geometry that will significantly reduce the buckling (implosion) pressure. In addition the joint at the center is a small stress riser under compression.

    From the video, they used a straight sided tank. I have done simulations and found that the straight sided tank is stable under a 1-atmosphere negative pressure but a funnel flow tank will collapse. I could have predicted the tank they selected would not collapse.

  • Ed
  • Alan Eggleston

    Thanks for commenting. That makes sense. The reason for the rain was to drop the temperature and, thus, to create the pressure differential, which as you said dropped to nearly perfect.

  • Alan Eggleston

    They didn’t use steam on the last couple of tankers because they could get the same effect of reducing the pressure without taking all the time of steam cleaning the interior to raise the temperature and then letting the temperature lower again, simply by using the industrial pump. They proved the reduction in pressure the first time, so no need to do it again and again. I’m cool with that. Thanks for commenting.

  • Alan Eggleston

    The idea was to replicate what Adam and Jamie saw in the original video as closely as possible. If the original had used a funnel flow tank that’s what they would have used. Unfortunately, this is their last shot at testing the myth or they could have tried the funnel flow tank on a redo some day. Thanks for commenting.

  • Alan Eggleston

    There seems to be something about tanker cars on rainy days… ;-) Thanks for posting!

  • rulingsword

    I’m completely in agreement that the vacuum truck has the identical effect of steam cleaning. My gripe was with the busted call. At the end Adam says, to the effect, the evidence points to this being busted because of how much they had to “stack the deck”. But that’s just the nature of catastrophic failure. They always involve multiple smaller failures. Other myths have been plausible or even confirmed with more caveats and hedging. Mythbuster’s is, to me, saying goodbye, and every call we’ve made doesn’t mean much – explosion.

    For everyone’s edification, I bothered to do what mythbusters didn’t do – I calculated the atmosphere’s force squeezing those tankers (btw, mythbusters consistently described the effect as the tanker “pulling itself in” or the vacuum “pulling” the tanker in). 27 inHg is 13.3 psi. That tanker had about 3500 square feet of surface area. That comes out to almost 3400 tons of force pushing the tanker from all directions or almost one ton per square foot. Yet I expect had they spelled this out for viewers, Jamie would have figured out a way to screw it up.

  • Steven W. Kirkpatrick

    The 1/4-inch per foot is still pretty subtle angles and you would not necessarily notice it unless you are looking along the length from the correct position. It may well have been in the original but not apparent from the point of view.

  • Alan Eggleston

    Maybe.

  • Alan Eggleston

    Given that they were finally able to collapse the tanker, it seems like plausible would have been the more accurate call.

  • Guest

    You must not be aware that “vacuum” can be measured a number of ways. “Inches of Mercury” is a common unit used for standard vacuum measurement, with 29.92 inches of mercury being the most that can be achieved at standard sea level and room temperature (or in other words “1 atmosphere of vacuum”). if you want a Differential or “Delta” Pressure measurement then yes, psi would be the correct unit, but take a look at any industrial or automotive vacuum gauge and you will see “inHg” along with “mmHg”. This is a measure of the height of a column of mercury that can be supported in a tube under vacuum, with “0″ being no vacuum and 29.92″ being the maximum.

    As an aside, “inches of water” is used in very low levels of vacuum such as in ventilation systems. Same principle applies.

    Notice that 760mm is the same as 29.92″

    “1 Torr” (named for 17th century Eye-Talliun physicist and mathematician Evangelista Torricelli (who invented the barometer among other things) is defined as the unit of measure of 1/760
    of an atmosphere or 1mm of vacuum.

    In terms of a perfect vacuum, meaning literally “absence of material” from the Latin “Vacuus,” 1 torr is not that great. There is a chart on Wikipedia which shows the various levels of vacuum and how they are typically designated, which I will not bother to reproduce here. If you will just search on “vacuum” and read the Wiki article, this will become clear.

    Thus, the particular level of vacuum being measured then would determine the proper “units”, not your personal aversion to their proper usage.

    Also the Mythbusters tank car was constructed of 1/2″ thick steel (though corrosion in places would have significantly weakened it from one fresh from the tank car manufacturer) while the video of the tank car with the “EVA” label is not the same type of tanker, and is constructed of steel that is nearer 1/4″ thick, obviously not possessing the same strength overall. That is why they had to create a severe deformity in the heavier wall tanker shell by dropping the concrete to enable the collapse.

  • Alan Eggleston

    Great information. Thanks for commenting and for clarifying.

  • rulingsword

    I’m a physicist and amateur pilot. A lab I’ve worked at would evacuate glass tubes to pressures in (positive) nanoTorr. And you won’t believe how often I’ve heard the number “two niner niner two” or “two niner niner” anything to calibrate the altimeter.

    I was critiquing their choice of language not what they were measuring. Watch it again; a layperson would have come away believing a vacuum “pulled in” the cans, drums, and the tanker. I can’t remember them ever using inHg before in the show, always PSI (see chicken air cannon, water heater rocket, etc.).

    Finally, I’ve had the privilege of teaching college freshman physics for a couple years now and unit conversion is absolutely lost on most of them until I can remediate it. They can find an app but can’t navigate SI units or be convinced that only knowing a couple numbers will let them jump between SI and imperial. They love to tell me about their “conversion” to science, though, and it frequently involves mythbusters.

  • elwyn5150

    If you don’t like it, don’t watch it.