3 ms·

it's not chemistry, but tangentially, I have another amazing read. Liquid N2 is held in a dewar, consisting of an internal and an external tank with vacuum in

by x0x0 11y ago

it's not chemistry, but tangentially, I have another amazing read. Liquid N2 is held in a dewar, consisting of an internal and an external tank with vacuum in between. In case of overpressure, there are blowout valves, designed to relieve pressure in a large hole rather than a small one. You'd rather have a large hole because a high pressure tank with a small hole is basically a rocket. Or a grenade. Also, the N2 liquid to gas expansion factor is roughly 1:700. In any case, some special person at Texas A&M noticed a N2 dewar with a presumably damaged overpressure blowout valve and fucking welded a brass plug in place. Eventually, the tank catastrophically failed, most likely due to corrosion of the internal tank, leading to temperature increase and the aforementioned 1:700 volume increase. According to I believe the tank manufacturer, the tank mechanically fails at 1200 psi. When it finally went boom, it shredded the room it was in, put a 24-in hole through a concrete floor, significantly damaged a concrete/steel support beam, and was eventually stopped by a 3-in water main and other stuff in a mechanical room. Miraculously it went at 3-am or so and no-one was present. When people determined what had happened, some unlucky dude who didn't get paid nearly enough got to frantically inspect every tank in the chemistry building to see if the mystery welder had "upgraded" any others. There's a report pdf somewhere on the internet that I can't find at the moment. I may have some details wrong but the boom part is definitely right =P edit: https://web.archive.org/web/20060901094515/http://finance.tamu.edu/ehsd/report_on_chemistry_301A.pdf https://web.archive.org/web/20060901094515/http://finance.ta... it's worth looking at the pictures in the pdf

HCIdivision17 11y ago
I think there should be a category of "there I fixed it" just for over zealous welders. I worked with a robot that had an aluminum tool that got mangled every time the robot got in a fight with the lift table. This was a Kuka 450 (as in kg), and it could really stack. A maintenance guy thought it was an enormous chore rebuilding the tool each time, so he bolted (literally) a 3/8 inch steel plate to the thin aluminum a frame. And when that tore welded the whole shebang. Next time the robot snapped its wrist, since the tool could no longer buckle and absorb the impact, and it rather impressed the service engineer with the... sturdiness of the tool. I wanted to share the story about environmental's efforts to put gas meters on the safety release valves on our large liquid argon dewars, but we thankfully convinced them that accidentally blowing a crater in the plant was a worse OSHA violation than upsetting our local regulators. (An accident in a nearby county with a truck hauling liquid gas dewars resulted in a death by displacing all the air in the intersection with Argon, leading the inert gas to be classified as a dangerous controlled substance that needed to be monitored and metered...)
gh02t 11y ago
Oh, I have a story about LN as well. I studied nuclear engineering in school and our department had a nuclear reactor in the building (important in a moment). Nuclear engineering labs usually have large LN tanks because some types of radiation detector require cryogenic cooling. One day of the week at about 3AM some [presumably students living on campus[ were walking by and heard the tanks venting exactly as you mentioned. They called it in to campus security, who panicked and assumed the reactor was melting down (not even possible with this reactor) and by 3:30 AM a full emergency response crew, in full HAZMAT gear and complete with heavy vehicles has surrounded the building only to discover that nothing is remotely wrong.
dsfyu404ed 11y ago
I'm surprised a 3" water main stopped it, pipes in general are typically made of very soft, low quality steel. It probably just ran out of energy after flying through everything else. The plug wasn't welded, it simply screwed into existing pipe threads replacing an overpressure valve.
- Someone 11y ago
  "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." => that concrete roof probably had more to do with the stopping than the pipes below it.

by x0x0 11y ago

HCIdivision17 11y ago

I think there should be a category of "there I fixed it" just for over zealous welders. I worked with a robot that had an aluminum tool that got mangled every time the robot got in a fight with the lift table. This was a Kuka 450 (as in kg), and it could really stack. A maintenance guy thought it was an enormous chore rebuilding the tool each time, so he bolted (literally) a 3/8 inch steel plate to the thin aluminum a frame. And when that tore welded the whole shebang. Next time the robot snapped its wrist, since the tool could no longer buckle and absorb the impact, and it rather impressed the service engineer with the... sturdiness of the tool. I wanted to share the story about environmental's efforts to put gas meters on the safety release valves on our large liquid argon dewars, but we thankfully convinced them that accidentally blowing a crater in the plant was a worse OSHA violation than upsetting our local regulators. (An accident in a nearby county with a truck hauling liquid gas dewars resulted in a death by displacing all the air in the intersection with Argon, leading the inert gas to be classified as a dangerous controlled substance that needed to be monitored and metered...)

gh02t 11y ago

Oh, I have a story about LN as well. I studied nuclear engineering in school and our department had a nuclear reactor in the building (important in a moment). Nuclear engineering labs usually have large LN tanks because some types of radiation detector require cryogenic cooling. One day of the week at about 3AM some [presumably students living on campus[ were walking by and heard the tanks venting exactly as you mentioned. They called it in to campus security, who panicked and assumed the reactor was melting down (not even possible with this reactor) and by 3:30 AM a full emergency response crew, in full HAZMAT gear and complete with heavy vehicles has surrounded the building only to discover that nothing is remotely wrong.

dsfyu404ed 11y ago

I'm surprised a 3" water main stopped it, pipes in general are typically made of very soft, low quality steel. It probably just ran out of energy after flying through everything else. The plug wasn't welded, it simply screwed into existing pipe threads replacing an overpressure valve.

Someone 11y ago
"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." => that concrete roof probably had more to do with the stopping than the pipes below it.