LAPD blast containment truck fails, seventeen people injured 6

[jrs87]

https://www.dailymail.co.uk/news/ar...illegal-fireworks-LA-goes-terribly-wrong.html

Someone did not read the manual.

 

[Eufalconimorph]

"Federal authorities who weighed the larger ones sade they were about 5 ounces (142 grams)."

That says the federal authorities weighed the larger ones, not calculated. So the larger ones weighed about 5 oz, and that's 141.75g, or 140g for a bit less false precision. Somewhere between 100-200g, anyway. Probably not pure flash powder.

 

[TugboatEng]

The elephant in the room is that they knowingly put 16.5 lbs in which is still over the rated capacity. Me thinks the party was mathematically lacking. That is all.

15 lbs is the max reusable shot and you know they were planning to reuse the vessel because there were enough explosives left over for the feds to analyze and estimate the actual load.

 

[spsalso]

Using the word "knowingly" might be a little generous.


spsalso

 

[TugboatEng]

The responsible party said they put 16.5 lbs in, intentionally. They didn't know it was actually 42 lbs. Both measures exceeded the rating. It's as if they didn't know 16.5 lbs was greater than 15 lbs. With that bit of knowledge, I would be extremely surprised if they were able to do the multiplication to calculate the total charge.

 

[RedSnake]

The bomb technicians — estimated the weight of the homemade explosives and a counter-charge to be about 16.5 pounds (7.5 kilograms) in a standard flash powder measurement. That measurement is not the same as an item's physical weight and is instead calculated as a TNT equivalent because explosives have different concentrations and therefore have varying “explosive weights."

Federal authorities who weighed the remains after the blast calculated that the weight was actually more than 42 pounds (19 kilograms) in the standard measurement. The smaller explosives were actually 1.37 ounces (38.9 grams) and the larger ones were about 5 ounces (142 grams).

The detonation chamber's maximum capacity is 15 pounds (6.8 kilograms) for multiple uses or 25 pounds (11 kilograms) for a single use, Moore said.

2014

https://www.dhs.gov/sites/default/files/publications/TVC-MSR_0714-508.pdf

TNT equivalent 2014

https://store.mssdefence.com/home/1...f-closing-total-containment-vessels-home.html

The detonation chamber's maximum capacity is 15 pounds (6.8 kilograms) of what.
Here it says 15 lbs. MIL-C4

Since everything is recalculated in TNT equivalent it should have sade it could take multiple blasts of 19.4 lbs. (8,8 kg) TNT.
(8,8 x 4,6)/6,8 = 5,95MJ (Military C-4 (5,9 - 6,7 MJ/kg))

Energy density
TNT 4,6 MJ/kg
Military C-4 5.9 - 6,7 MJ/kg
Flash powder 9,2 MJ/kg

And one blast of 26 lbs. (11,8 kg) TNT equivalent.

Not sure the people on site got the 15 lbs. vs 16,5 lbs. wrong, it might have been Chief Moore that hadn't read the specs properly.

/A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[TugboatEng]

Why have a TNT rating for one value and C4 for another? I think your first link is correct and your second in error. Interesting that flash powder has a higher energy density than commercial explosives.

 

[RedSnake]

Well if the first link is correct then it would have been okey to put in 19.4 lbs. (8,8 kg) TNT equivalent.

And if so they are both correct as it is the same value in MJ
19,4 lbs. TNT 8,8 x 4,6 = 40,48 MJ
15 lbs. MIL-C4 6,8 x 5,95 = 40,46 MJ

/A


“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

Tug its to do with the amount of gas produced.

Explosives its a combination of speed of detonation, pressure front, temperature and a few other factors.

Flash powder takes up colossal volume, is relatively slow and produces lower pressure. So even though its got a higher energy yield it produces less of a bang with a lot of it being turned into heat slowly which lowers the pressure front......


This is going back 30 years now so distant memory of a lecture standing soaked on a pissing wet day in wales on Sennybridge ranges.

 

[TugboatEng]

Red, the patent calls out 15 lbs TNT.

The design charge weights for the present invention are:
3-lbs TNT—totally sealed system, repeatable detonations. The UTCV 10 will require decontamination and maintenance, but no repairs.
15-lbs TNT—repeatable detonations with venting. Minor repairs may be required which include mechanical components, ports 68, and flanges (at the yoke 16, door 14, and body 12).
26-lbs TNT—one-time event with venting. Major repairs may be required to all components of the system. However, the system will retain structural integrity during the event.

https://patents.google.com/patent/US20090044690

(same as posted earlier)


I think the manufacturer's description is poorly worded. It should state that it is rated for one time use at charges over 15 lbs and up to 26 lbs. I think the description isn't sufficient for non-engineer types.

 

[RedSnake]

Yes I remembered seeing some different values here, but then the Total Containment Vessels Market Survey Report
done by Space and Naval Warfare Systems Center Atlantic in 2014 for Homeland Security isn't correct.
And they claim they took the values from NABCOs homepage.
/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

They use factorisation with the TNT as the base line for loadings for some things.

But it doesn't really work in some situations.

You can cut metal with C4 with a sausage half the width of your finger with a bit of copper wire under it. It just won't work with TNT or powder using the same factorisation adjustments to amount. You will just get a big bang and smoke and the tank track will just be sitting there saying screw you buddy.

HE is actually good fun stuff to use and its very handy to do quick jobs. Much less hassle than using a cutting torch

 

[RedSnake]

More fun then snail dynamit I suppose.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

yep and less dangerous than real dynamite. There is pretty much no restrictions on HE mil explosives in how you carry it and naked flames etc. So you can just stick in in your Bergan and use it as required its relatively light. Dynamite/TNT comes in big metal boxes and you have to set up no flame zones around it and there is a heap of storage restrictions as well.

 

[TugboatEng]

Considering the patent is in pounds and the market survey report is in kilograms and we now know the people that surround these chambers are bad at math, I'd wager that there was an error in conversion to get the metric number.

 

[RedSnake]

Yes I have been thinking about that too but it would have been less then twice the amount and not three.
And there should be programs or ready made tables for this, I would think.

And Í wonder what "in a standard flash powder measurement" stands for?

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[dik]

bad at math... reminds me of the Gimli Glider...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Demented]

How did they weigh what was put in the unit? Sorry if that's already been answered before.

Precision guess work based on information provided by those of questionable knowledge

 

[waross]

How did they weigh what was put in the unit? Sorry if that's already been answered before.

Your tag line answers that question quite well.

Precision guess work based on information provided by those of questionable knowledge

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[RedSnake]

They X-rayed one, two, some, all and made a estimate and then recalculated it some way to TNT equivalents.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Demented]

Do we know what the specs of the X-ray device?
They measure through the side of the can, bottom of the can, through the open mouth? You'll get inaccurate readings of Al content if your calibration is off or you're too far away and you measure through the can.

Edit:
I've x-rayed my fair share of metals with XRF guns. You can get wildly different results if you use it incorrectly. So much so you could easily be lead to think the firework maker sucked and filled cans with mostly Al powder and not enough oxidizer, therefore putting more cans in than they should have. This could be simply failure to RTFM of the testing equipment.
I bet those bomb guys looked over every inch of that container before using it each time.