I want to be really clear: the odds of a manhole in a London street suddenly
exploding while you're next to it are tiny. This is not something to worry about. And the company that handles the
cables under London's streets is spending a lot of money fixing them up. But, yeah, about once or twice a month
on average, somewhere in London, a bit of pavement just goes... boomf. But no-one wants to license security camera
footage of actual pavement explosions to just someone on YouTube, and no-one wants
to be interviewed about it either. So instead, we are going to create our own
underground explosion right here with the help of a friendly pyrotechnician. And the easy answer to why London's pavements
keep exploding... well, it would be "electrical faults", and
that's what the news often blames. As seasons change, the ground is going to
get warmer and cooler, it's going to expand and contract,
rain and subsidence will move the soil, and over the course of decades that is going to steadily wear out
the 36,000km of electrical cables and 100,000 electrical junction boxes
that are under London. Most of those were laid decades ago.
It's a big city. Things will break. But an electrical fault won't make an explosion. If electricity goes somewhere it shouldn't, then the circuit breakers that
control the grid will detect that and shut it off right away. The trouble is that there's a lot of other
old stuff under London's streets. Including gas pipes. A steady, slow gas leak in a pipe might not
be detected for a while, and in that time the gas can spread a long
distance through narrow underground tunnels. So if you've got gas in a tight underground
space where it can't expand, thank you, and an electrical spark
to set it off... well, that's all we're doing here: under that cover there is a fuel source,
not enough room for it to expand, and something to make an electrical spark. That's all you need for an explosion. Fire in the hole. "This looks devastating in slow motion. "The burst of flame, the flying manhole cover, "at 1800 frames per second on a zoom lens
it looks like it could do serious damage. "But even this dramatised explosion, made
with the help of a pyrotechnician, "this worst-case-scenario...
is actually not that bad. "I tried to do the 'cool guys don't look at
explosions' shot, "and when you take away all this style..." Fire in the hole. "It'd hurt if you were standing on it, sure, "but like I said, it's not something to be
worried about."
Nothing to worry about. It's just fire.
Isn't the fastest object ever launched a manhole cover by accident? (no-joke)
Edit: Here is the must read story.
I work for a UK Electricity Distributor (we handles the cables overhead and underground in certain areas). All of the power distributors now have these fire blankets that they lay in these. We call the equipment sunken in the ground like this a link box. We cover the link box with this fire proof blanket and it helps stop the explosions damage.
London is a real pain because the equipment is so damn old and there isn't enough money in the country to do all the works to change it all out. So the distributors that cover that area have to just change things mostly as and when they break. London has an entirely underground network, which is safer but much more time consuming to find faults with.
good video
True?
not seen or heard of any manhole covers in London exploding. Very odd.
Sewer jihad