What is the chemistry behind this?
16 years ago
What is the chemistry behind this?
Maybe there was some oil or dust in the valve that ignited when the fast stream of O2 was released. Randy
Grease will explode if subjected to 2,000-psi oxygen. A dab will do.
I was first inclined to think, "No... that was just a loose cylinder" until I saw the evidence of fire and the ruptured tank.
This was probably caused by friction: Some folks have surmised there may have been oil or grease in the valve. That's not likely, even if the guy was dumb enough to squirt some PB or Liquid Wrench on the valve. It probably would not have gotten past the thread seals. It MIGHT have gotten exposed to O2 if he had the valve loose enough. They didn't say anything about the application of a rust-breaker oil, though, and I think they would have, if that had been the case.
However, a tightly installed pipe thread engages metal-to-metal, even with sealant present. Wrenching a threaded component apart always causes extreme friction until the taper relieves the fit. Some metal would have been abraded away as a fine powder, along with the generation of enough highly localized heat to initiate combustion.
Once the fire started, it was self-sustaining. Then the O2 pressure (likely above 2500psi to start with) rose high enough from the addition of heat and combustion products to rupture the tank.
That slide show is definitely not breakfast fare.
Total agreement with Lloyd. That is why it is emperative to have the vessel empty before disassembly.
At 2000 psi is the generation of heat even a requirement for a small shaving/dust particle of steel to combust?
At STP, most metals become pyrophoric at sizes smaller than about 1000 mesh (around 0.5 micron).
I don't have the tables on it, but I'd guess that pure pressurized O2 would lower that to more like 300 mesh.
Such small particles are the normal result of friction between threads.
That said, there WOULD be very high localized heating, so the two together are almost a "gimme".
A belt-and-suspenders approach to blowing your own poor ass up-
I am never going to feel as comfortable around the welding tanks again. Yikes!
Imagine cutting into a big one with a disc grinder or a torch...D
At least Argon shouldn't be able to do that.
I'd bet that hey have killed or injured far fewer people than, say, light fixture falling off ceilings.
Don't grease them, dont try moving them about without the cover over the valve, don't do stupid shit like trying to remove valves while they are under pressure. You'll be fine.
Figure out the explosive energy potential in the gas tank of your car, if you need some perspective. Then you can try to find a nice couch to hide under while you try to stay safe.
Cheers Trevor Jones
Did you check out the valve stem, its threads, and the tank portion?? There was corrosion as well as tearing. Maybe an organic peroxide from oil etc. built up in there over time, and the wrenching touched it off? MadDog
And if the tank was empty - there would not have been the massive oxidizer ready for fire. Drain down the tank and fill with water.
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member
Pete C. wrote:
Boris Mohar wrote:
Well, the damage was a LOT less than I expected. The actual situation was a metal fire INSIDE the cylinder, as the narrator essentially states at the end. I'm guessing that the action of breaking the metal-metal bond or maybe the sealing compound produced enough heat to ignite the metal in the high-pressure pure O2 environment in the cylinder. The valve must have been totally frozen, and he began to unscrew the valve from the cylinder.
The pegboard stayed on the wall, and all that!
I heard of a somewhat related incident that happened a year before I started work at NASA, so it would have been 1971-72, in the radio-TV section at NASA Wallops Station, Eastern Shore of Va.
They had a big O2 cylinder in the shop, and a small braided hose so they could recharge the portable O2 tanks for welding/cutting jobs that they carried on the work trucks. Some greasy gunk had accumulated on the side of the big tank, which is not a real good idea. One time, a guy set up to refill a small tank, and apparently had a small leak where the hose attached to the big tank. It was leaking pure O2, which apparently formed a film sliding down the side of the tank. (O2 is denser than ordinary air, and would be cold after expanding from the pressure in the bottle.) It ignited the greasy stuff. The guy tried to beat out the flames (fat chance, in a pure Oxygen-fed fire) and then realized the tank was heating up. The story goes that he saw a red spot deveol and grow where the fire was. I rather doubt that - when the tank wall got hot enough to glow, the raging fire at 2000 PSI inside would blow the tank in milliseconds, it seems to me. Anyway, he screamed "the Oxygen tank is going to blow, get the hell out!" and pulled the fire alarm on the way out. Some of the guys, hearing the warning, and knowing the normal way out meant running PAST the room with the tank, threw a chair through a window and dived out. This was a big one-story shed, basically. They had bunkers there because a rocket launch facility was only 6 miles away, so everybody got in the bunker. As the last guy dove in, the tank blew, and the entire building was launched hundreds of feet in the air. They heard all manner of stuff raining down, radios, oscilloscpes, TV cameras in blast-proof housings, tool cabinets, etc.
They eventually got a new building, made of BRICK! And, they were told in no uncertain terms that there's be NO refilling of any kind of tank, whatsoever, unless it was a water bottle.
The tank in this story was a LOT larger than the little medical Oxygen tank in the Youtube video.
No chemistry involved - a simple fracture from stressing the tank with a chain vice and cranking on the valve with the wrench. I doubt heet was involved with ANY of the damage shown. There was 2200 psi MINIMUM pressure in that tank - and it ALL got out at once.
True, it wont burn but there is still an awful lot of energy stored in it just as Pressure X Volume . If the tank ruptures it still has plenty of destruction available to do you in.
There is obvious fire damage on all the exposed parts.
But Martin, that's the whole thesis of this accident review... He COULDN'T drain down the tank. The valve was either frozen or broken -- so he intended to just loosen the fitting, and let the tank drain that way.
And that's a big mistake.
In the Navy, if a tank top was damaged in any way whatsoever, the whole tank got AXED in our guillotine "tank disposer-of-er". Cam Rahn Bay got its share of empty tanks with no valves...
Now, the military is a lot more cavalier about throwing away money than a civvy company would be, but in this case, they should have a policy in place to waste a little to save a lot.
Yes, but the procedure the guy who blew his arm off was trying would likely have worked without incident.
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