[SML] Taiwan water park explosion

[Jerry Durand]

{bang lesson for the day}

Actually, something that explodes may or may not be chemical in nature
(see BLEVE).   An explosion is a rapid release of gas without specifying
the source of the gas.

Deflagration may or may not produce an explosion, it would normally need
to be confined to allow the container to burst.

A detonation is when the reaction moves through the material at greater
than the speed of sound in that material.  A material detonating does
NOT need a container to cause an explosion.  A small pile of flash
powder on a shelf in a shed will reduce the shed to toothpicks.

You can tell a detonation a couple of ways.  One is you get a CRACK
sound before or instead of the BANG.

Second, you can often see the shock wave traveling through the air if
you're lucky to be far enough back.  It will also raise dust on the
ground.  At the begging of this video
http://interstellar.com/photos/Western_Winter_Blast_2008/Burn_Pile_WWB-19.wmv
there will be a small bang, then you'll see a semicircular dust cloud
appear on the ground followed by everything else going off.  The dust
cloud was from a Barney doll that was sitting on some "special sauce".

Oh, and black powder (the real stuff, not a substitute) is a bit funny. 
In small quantities like you would use in a gun it deflagrates.  If you
have a larger quantity of it, it will "go high order" and detonate. 
Doesn't need a container.  That's why you find it hard to get.  The
substitutes like Pyrodex are actually a version of smokeless powder
that's been speed adjusted to mimic black powder burning in a gun.  But,
it will NOT detonate.  That's why you can buy it mail order and have UPS
leave 20 pounds of it on your porch without so much as a signature.

Oh, and regular smokeless powder?  Single base stuff is nitrocellulose
(gun cotton) with stabilizers and graphite powder to reduce static. 
When it first came into use it didn't have the stabilizers in it and
could go off because it was Tuesday.  This is the same stuff old movie
film was made of, model airplane dope, and also ping pong balls.  Really!

Double base adds nitroglycerin, the active component in dynamite.


On 06/30/2015 02:42 PM, Chip Wood via Stagecraft wrote:
> Where is the boundary in "speed" between deflagration and explosive? 
> Is there a jump or is it a continuous ramp up depending on source?  Or
> is this just experts letting us in on the details or something
> practical we can use for pyro staging?
>
> Chip 1
>

-- 
Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
tel: +1 408 356-3886, USA toll free: 1 866 356-3886
Skype:  jerrydurand 

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