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[MeFi] Why liquid nitrogen containers have vents, or 1200 PSI is not your friend. - Adventures in Engineering — LiveJournal
The wanderings of a modern ronin.

Ben Cantrick
  Date: 2006-08-18 23:58
  Subject:   [MeFi] Why liquid nitrogen containers have vents, or 1200 PSI is not your friend.
Public
  Mood:Impressed
  Music:Nirvana - Blew
The cylinder had been standing at one end of a ~20' x 40' laboratory on the second floor of the chemistry building. It was on a tile covered 4-6" thick concrete floor, directly over a reinforced concrete beam. The explosion blew all of the tile off of the floor for a 5' radius around the tank turning the tile into quarter sized pieces of shrapnel that embedded themselves in the walls and doors of the lab. The blast cracked the floor but due to the presence of the supporting beam, which shattered, the floor held. Since the floor held the force of the explosion was directed upward and propelled the cylinder, sans bottom, through the concrete ceiling of the lab into the mechanical room above. It struck two 3 inch water mains and drove them and the electrical wiring above them into the concrete roof of the building, cracking it. The cylinder came to rest on the third floor leaving a neat 20" diameter hole in its wake. The entrance door and wall of the lab were blown out into the hallway, all of the remaining walls of the lab were blown 4-8" off of their foundations. All of the windows, save one that was open, were blown out into the courtyard.


http://pipeline.corante.com/archives/2006/03/08/how_not_to_do_it_liquid_nitrogen_tanks.php

Apparently the tank failed at 1200 PSI after some total moron welded the vent openings shut. A 20" diameter cylinder has a bottom circle area of 314 square inches. 314 times 1200 is 376,800 lbs... or 188.4 tons.
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MegaZone
  User: zonereyrie
  Date: 2006-08-19 01:10 (UTC)
  Subject:   (no subject)
Well, shit, someone plugged the pressure relief systems up. This thing was a fucking bomb just waiting to blow. Impressive - both in the explosion and the stupidity.
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Ben Cantrick
  User: mackys
  Date: 2006-08-19 07:49 (UTC)
  Subject:   (no subject)
The guy who "repaired" the vents on this tank is almost as smart as the guy who took an acetylene torch to a 10,000 gal tank of asphault emulsion. After two different people told him he was nuts and pointed out the sticker on the side of the tank that read "WARNING: FLAMMABLE." BOOM! A well deserved Darwin award.
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osmium_ocelot
  User: osmium_ocelot
  Date: 2006-08-20 01:40 (UTC)
  Subject:   (no subject)
or the guy who decided to tac weld his acetelyne tank to the metal roof he was working on...
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osmium_ocelot
  User: osmium_ocelot
  Date: 2006-08-19 01:25 (UTC)
  Subject:   (no subject)
ah, but lets not forget the sides of the tank... all the pressure they were holding back had to go somewhere, namely out the failed bottom of the tank.

From the picture, I'd say that tank looks to be about 60" tall.
So, area of a cylinder with diameter of 20" and height of 60"... (3.14 x D) x H = 3768 square inches... times 1200psi... 4,521,600 pounds, or about 2260.8 tons of force, plus 188.4 tons top and bottom, for a grand total of 2637.6 tons of pressure released explosively.
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Alex Belits
  User: abelits
  Date: 2006-08-19 04:26 (UTC)
  Subject:   (no subject)
But the sides didn't move, so at no point in time anything exploding was subjected to the force that you have calculated. Large volume of evaporating and expanding nitrogen increased the energy released (force integrated over distance -- so basically things flew farther) however the maximum force involved in this explosion (ignoring impact of sharp objects that flew as the result of explosion) was initial pressure multiplied by the surface of the breach (fallen out bottom of the tank) at the moment when the pressure over that surface was still close to the initial value.

If the tank's sides didn't hold, the total force involved would be what you have calculated, and since the energy released would be still the same, the tank wouldn't fly as far as it did, but would spread more damage over the lab.
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osmium_ocelot
  User: osmium_ocelot
  Date: 2006-08-20 01:38 (UTC)
  Subject:   (no subject)
That's what I meant. Unfortunately I was about as clear as mud in saying it. My bad.

My paranoia is still waiting for the day that the tank on the air compressor for the nail gun fails. Yeah, sure, that's only 120psi, but it's an 80 pound object. Parts will fly with lethal velocity. With my luck, they will be sharp steel parts.
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Coinneach Fitzpatrick: Eeeevil
  User: scarybaldguy
  Date: 2006-08-19 02:05 (UTC)
  Subject:   (no subject)
Keyword:Eeeevil
O.O

*looks disappointedly at shampoo bottle*

Where can I get me one of them liquid nitrogen tanks?

Note to DHS: I'm kidding! KIDDING!
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  User: (Anonymous)
  Date: 2006-08-19 02:42 (UTC)
  Subject:   (no subject)
LN2 works great on Denver Boots. Pour it on the main bolts, and tap it with a hammer Poof!
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