OT: Tianjin explosion

Tell that to the people in Enschede... some of them are still looking for a conspiracy that explains how the explosion of a fireworks storage facility resulted in such a major blast as happened in may 2000. (with resulted in damage similar to what we see on the Chinese footage)

However, in China the pictures show large billowing fireballs more typical of a fuel thermobaric explosion, the Enschede explosion was a detonation.

On 14 Aug 2015 08:15:15 GMT, Rob Gave us:

There were fireworks flying all over the place, or do you not remember?

Not the case in Wednesday's explosion.

Fireworks do go off all at once, see the destruction from Danish fireworks factory a couple of years ago:

Cheers

Klaus

That was BEFORE the big explosions. Because it started as a small fire inside the work areas of the facility that caused one-by-one lighting of firecrackers and rockets, and only when a larger amount of stored fireworks exploded it resulted in two major detonations.

The latest report I heard is that there had been a fire in a storage area, which the fire brigade were putting out with quantities of water (as is the norm). Unfortunately, the storage contained a large store of calcium carbide - adding water produces acetylene gas. Such an eruption of acetylene does not take much to produce a massive explosion. To add to the fun, there was also a lot of artificial fertilizer nearby - this may or may not have contributed to the acetylene explosion.

(I don't know if calcium carbide is used in fireworks or not.)

A friend filmed a UK explosion from what turned out to be rather too close. He got away with it apart from ears ringing for days despite the fact that RSJs were landing behind him. A professional TV team in a block of flats half a mile away were cut to ribbons by flying glass.

From the fireball scale and timing it looked to be more like a fractional kT yield explosion rather than the 20T they are admitting to. I'd be very surprised if it turns out to be less than 100T.

It should be possible to estimate explosive yield from the groundwave seismic shocks which have been reported as Richter 3.5 equivalent.

Problem is when someone smokes in an explosives storage warehouse.

Very nasty accident with housing so close to such a dangerous site.

Newer information suggests that in was a storage warehouse where large amounts of ammonium nitrate and calcium carbide were stored.

Not explosives that would by themselves detonate because of someone smoking, but the combination of calcium carbide with water yields acetylene gas that of course can explode thermally, and in combination with ammonium nitrate as an oxidizer can detonate.

So when something unrelated caused a fire in the storage and it was extinguished with water, the recipe for a big detonation was created.

One can of course question if it is wise to store a strong oxidizer like ammonium nitrate together with a fuel or fuel-generating substance. But in fact ammonium nitrate can even detonate alone. But not because of someone smoking.

Ammonium nitrate explosions are rare and improbable, but they have been devastating in the past, and - because people can get away with doing stupid stuff for years, 20,000 times in one case - they'll probably keep on happening.

Bulk calcium carbide can get hot enough in contact with water to self ignite, but there may have been some commercial high explosive or other present to create a shockwave strong enough to make ammonium nitrate go. It will thermally decompose spectacularly but it melts and runs over things first. If the things that it runs over are flammable all bets are off once it gets to ignition temperature.

A fire can melt chemicals together in a way that it can make nasty unstable explosive compounds - one such occurring in Gateshead 1854 and well documented. It was a 100T class explosion.

It is not for nothing that fireworks factories keep certain chemicals exclusively in entirely separate sections of the works.

I suspect that the initial explosion ruptured storage tanks and the secondary was some kind of fuel air bomb of materials dispersed by it.

At least one major AN detonation disaster at BASF was because they used dynamite to break it up after it had set like rock in a storage silo and pickaxes were not good enough! It was a low kT yield explosion.

That didn't look to me as though it were primarily high explosive. HE makes a much bigger *crack* and a lot less flame--see e.g.

Cheers

Phil Hobbs

I mentioned that before, it looked more like a gas or fuel thermobaric explosion than a HE detonation. However the extensive damage on the ground suggests a detonation. Maybe the one I saw on the video was the fuel explosion and a second one, the detonation of the AN followed after that and was not clearly filmed.

NYT story this morning is the FD was putting out a car fire... then boom....

Some shots showed a sonic pressure wave so (the big bang) was not a fuel-air or gas explosion

That doesn't follow. A small shock wave propagating through an inflammable fuel-air mixture can create a condition where it speeds up combustion enough to make it a progressively larger shock wave.

Coal dust explosions in mines are the classic example - I seem to remember that it takes 400 feet of inflammable mixture to boost the shock-wave to the point where it becomes dangerous.

HE

hat

e fuel-air mixture can create a condition where it speeds up combustion eno ugh to make it a progressively larger shock wave.

r that it takes 400 feet of inflammable mixture to boost the shock-wave to the point where it becomes dangerous.

That's more like it. The so-called energetic HE material reaction is a form of shockwave that progresses through the material at a rate on the order o f meters per microsecond. The aftermath would include a large and deep crat er at ground zero and all the nearby material will be blown away or to bits . There was none of that here. Something originally dispersed a bunch of ra w material outward spherically and far enough to allow the follow-on igniti on to progress to shockwave status.

In military, the percussion is the factor that determines damage and death. I think the MOAB is a good example, it'll turn you into jelly.

Cheers

should have said a super-sonic shock wave - a basic property of high explosives.

Fuel - air (not fuel oxygen) explosions never reach that speed. An explosion can be 'Dangerous' even if not supersonic, so what; that is hardly relevant or surprising.

Since supersonic aircraft reach that speed, driven by fuel-air combustion, you may want to think that out again.