49 manhole covers blown into the air in Tokyo's Shinagawa

It"S MENov. 05, 2014 - 03:38PM JST So blowing a 20kg manhole cover is easier than the pressure flowing down an empty pipe.

When the pressure is "flowing" at 2000m/s? ... Then no.

Would like dynamic the flowing formulates for that, etv.

I'm too lazy. Do it yourself.

I have seen gas tanks under cars blow up and that barely lifted the end of the car 2 feet if at much. Just a bang/smoke some lifting and end of show. Nothing like what you seen in Hollywood movies.

The key to the explosive power of gasoline is the degree of vaporization and the mixture of air.

The reason the Twin Towers explosions were so powerful was because the tanks were less than half full of fuel, the other half being air, which created a far more explosive combination than if they had been full.

Had those airplanes been setting off on an international flight with mostly full tanks the explosions would have been minor, and the main worry would have been the impact of the airplanes.

So blowing a 20kg manhole cover is easier than the pressure flowing down an empty pipe.

Would like dynamic the flowing formulates for that, etv.

I have seen gas tanks under cars blow up and that barely lifted the end of the car 2 feet if at much. Just a bang/smoke some lifting and end of show. Nothing like what you seen in Hollywood movies.

Motor home methane from visiting Octoberfest tour group of Germans and their Mexican chef.

Okay, there seems to be some discussion about whether 10l of gasoline could blow up 49 manhole covers.

Would it be more believable if someone said 1/2 a pound of plastic explosive?

10l of gasoline, exaporated and mixed with air (with a standard oxygen content) = 134GW of explosive force. 1 pound of plastic explosive is 240GW.

Let's guestimate the weight of the manhole covers at 50 kilograms each (for argument's sake).

The equation for lifting power is: power = mass x 10 x distance / time

Let's set the time at 1 second, the mass at (49 x 50kg =) 2450kg and the distance 1 meter in 1 second. P = 2450 x 10 x 1/1 P = 24500W

Since the total power of the explosion was around 134 000 000 000 Watts I'd say this is totally believable. Of course the reason the vast majority of the energy would have been dispersed up and down the pipe (least resistance).

... still, it it was my pipe I'd be checking it carefully for damage, since that's a LOT of explosive force.

People forget that gasoline (petrol) in vapor form is HIGHLY explosive. If the vapors from this spill started to waft through the sewer lines (which already has a buildup of methane gas at times) and there is a spark somewhere among the sewage pipe, the results are obvious.

Tokyo's storm drains are not isolated from their sewage lines?

manhole covers(those are heavy) over a 200 metres stretch and that the explosive force would spread along the tube = easiest route.

That's not correct. The explosive force will spread along any route it can find until it runs out of power - which includes weak points where the manholes are. The weight of the manhole covers would have to be heavier than the force which is propelling them from underneath for them not to fly into the air. As is evidenced by this case, they weren't heavy enough to repel the propulsion from underneath, and therefore they flew into the air.

" I never seen 49 manhole covers(those are heavy) over a 200 metres stretch and that the explosive force would spread along the tube "

Well, now you have. And the explosive force of course spreads everyhwere it can.. including out of manholes.

So once again its is your "belief" versus reality...

WilliB.

A friend of mine does bomb disposal.

Further talk about 10ltrs of volume distribution over 200 metres, add in that I never seen 49 manhole covers(those are heavy) over a 200 metres stretch and that the explosive force would spread along the tube = easiest route.

Itsme:

" I agree 10ltr of fuel is nearly a full tank on many models. 49 manholes over 200 metres takes a lot more. "

And you know that how? How many times have you tried to blow up manhole covers?

Keep in mind that 10 Liters are enough to propel you and your bike for 400 kilometers or so (or 30 kilometers, if you use a car). That is a hell of a lot of energy right there.

One more time. Yes gas/petrol vapour can be extremely explosive. One extreme example is Buncefield, UK, 2005 one refinery tank of fuel overflowed, creating a big cloud of petrol vapour. Quotes from the time include " blast wave woke people 150 kilometres (93 mi) away", "smoke cloud approaching France". So, lifting 49 covers is kind of plausible.

There's a saying that if gas/petrol was discovered today, you'd need a special licence to buy it, being flammable (and so explosive), toxic and.carcinogenic.

So what happened to the cars that just happened to be stopped over one of them?

10 liters of gasoline could easily do that, it floats on top of the water (or whatever brown liquids flow in sewers), it evaporates and forms gas clouds and it gives a lot of gas on explosion(that's what gasoline is supposed to do anyway). People here seem not to know how destructive even 100ml of gasoline can be, in the right conditions.

Godzilla is flexing his tail muscles.....

um adam shrimpton, it was 49 covers, not 10

heads or tails?

With the unrelenting stench that seeps out of these manholes in Tokyo, it's no wonder...

People forget that gasoline (petrol) in vapor form is HIGHLY explosive. If the vapors from this spill started to waft through the sewer lines (which already has a buildup of methane gas at times) and there is a spark somewhere among the sewage pipe, the results are obvious.

(Indeed, a recent episode of Discover Channel's MythBusters showed that if an explosive gas ignites in a confined space of a sewer line, it can literally blow a 40 to 50 kg manhole cover pretty high up in the air.)

Here you have it. That's why no smoking on the streets in Tokyo ;)

I'm sure a dozens people were walking down the street when it happened — and all of them had their heads buried in their smartphones, forever oblivious to the what was happening around them.

Too bad none of them bothered to look up, switch the smartphone into video mode and actually record some of the explosions.

It's probably caused by the mixture of the gasoline and the methane gas that's currently down in the sewer line. One lit cigarette can make a nasty mess.

Static electricity may have ignited the gasoline.

Lucky no one was killed or hurt.

So did he also open the tank cover and fuel tap?

Worked on my bikes many times never spilled a drop

" How in the world do you spill 10 liters of gasoline while working on a motorcycle? "

On TV they said he was repairing his bike, removed the (full) fuel tank, and placed this in the gutter. Et voila...

gas itself maybe not but if evaporated and created big cloud in sewer it could quite conceivably create a pretty powerful explosion formula is vmt*bf = BB

I agree 10ltr of fuel is nearly a full tank on many models.

49 manholes over 200 metres takes a lot more.

I don't buy this explanation at all,10 litres of gas wouldn't blow 49 manhole covers esp for 200 feet

10 litres of gas is enough to drive a vehicle that is hundreds or even thousands of pounds, many kilometers. Depending on how much pressure had built up, it's entirely plausible that an explosion of it could blow 49 manhole covers.

I don't buy this explanation at all,10 litres of gas wouldn't blow 49 manhole covers esp for 200 feet...wonder what it really was

How high we talking here? Blown up to the air? Like 10 meters?

How in the world do you spill 10 liters of gasoline while working on a motorcycle? Sounds fishy to me. I see bike and scooter shops cleaning their shop floor by spray washing it into the storm drain all the time.

I would have had trouble controlling myself from laughter. Maybe it's because I've seen too many gags involving exploding manhole covers.

Scary! At least it was only 10 manhole covers and not whole streets caving in like what happened in Kaohsiung in Taiwan earlier this year. I hope no-one got injured!