The imploding can demo is an old classic, often done with an old square-sided oil tin though I’m personally rather partial to the Coke can version. This, however, is something else. Commentary around the web suggests the method used here is to steam-clean the tank then seal the valves while it’s still full of steam. Which sounds plausible, and it’s not ridiculous to suspect this has been done as part of an industrial safety course.
Years ago I remember talking to David Jones about trying this – he’d long fancied having a go with a petrol tanker lorry. Even for TV the costs had looked prohibitive, and I never did find him an end-of-life tanker to play with. There’s also the minor issue of disposal to consider. But at least we can now be reasonably confident we could have made it work.
One concern, though: I’m not 100% convinced by the video. It’s from an interlaced source so it’s hard to tell for sure, but frame-by-framing the implosion makes it look to me like it’s been sped up somewhat. That said, the movement of the bogies looks appropriate. Ah, YouTube, you do so tease us with your ripped-off sources and your dodgy recompression.