O2 tank explosion

[05sportsman]

Thanks for your clarification.
Why would the term "sustained load cracks" be confined/restricted/apply to only the threaded neck area of the tank? I would have guessed that they could appear anywhere on the tank including body and shoulder.

As its applied, having had an eddy-current test would not have prevented this accident anyway.

The term "SLC" is just what they use to describe the fact that the 6351 alloy tanks crack on the threads. Generally the cracks start in a deep valley but not always. But you are right the eddy current test is meant to test the threads and since it doesn't appear the threads split I don't think it is at fault.

 

[Puffer Fish]

Of course I have. I also know that the temperature at which your skin will burn is LOWER than the ignition point of gasoline. I looked for the Mythbusters episode which clearly demonstrated this but it isn't online. There are several other videos on Youtube that bust this myth.

I never ceases to amaze me how pervasive the Hollywood nonsense effects have become. I guess we all repeatedly view the scene where the bad guy pours gasoline over the hero's car and then throws a lit cigarette at it and the car explodes into flame. Great effect, but total crap.

It seems that in this thread, many of the posters believe that a "room full of O2" will also explode. Maybe like the scene in the movie where the bad guy rips the stove away from the wall opening a city gas pipe and shortly thereafter, the entire house is blown into tiny pieces. There are really two problems here. One, O2 doesn't explode. Two, city gas will not produce an explosion of this magnitude. Yes, the city cooking gas IS quite explosive, but it will not blow the entire house into tiny pieces. It'll overpressure and shatter windows windows but that's about it. Again, Mythbusters has videos where they tried to replicate the Hollywood outcome without success. The Hollywood effects artists cheat it because a city gas explosion in a house just isn't all that dramatic.

-Charles

While it is true that normally one does not get a huge explosion from natural gas, and it is very difficult to duplicate (as one has to have the right mix of fuel and oxygen... it does happen, Knoxville had one last year that just left a slab where the house used to be.

Likewise, it is not easy to get a cigarette to ignite gas, but the worst burn situation I have every seen was at a parts depot in Camron Bay (Vietnam)..the poor guy was carrying a pail with gasoline in it, and smoking. The wind blew some of the embers off the cigarette and ignited the gas. I was maybe 20 ft from him...the three of us that rushed to help all got burns, but nothing like what he got.

Closed cup flash point is exactly that, the temperature where something will sustain a fire, after something hotter than the auto ignition temperature is introduced. Gas has a -45 F flash point (it will burn easier down to that temperature), and a 495 autoignition temperature. So the spark in an engine has to be hotter than 495 F to ignite the fuel. The autoignition temperature is hot enough to burn someone, so one can heat gas up to say 400 F, and it will not explode without a heat source, but it will burn you. Cigarette ends, if there is air blowing on them, are way past 500F, but typically for a very short time

 

[akdeepdiver]

The tank just passed hydro less than 6 months before the accident (Shows 6/10 hydro on video). If a hydro shop is using correctly calibrated equipment and knows what they are looking for on the visual inspection a tank that is going to rupture will NOT even make it into the test jacket. Not to mention the required eddy current testing that the tank must have passed to have a current hydro.

But on a side note, while testing the other day I had an AL80 1973 USD. Visual Plus 3 pointed out 4 cracks longer than 2 threads and 1 that was 4 threads. Not to mention when I went to pick it up from the dive shop I had to drain the air out myself. Made me think twice!

I will first start out by saying 1. I could not tell if the "VE" stamp was following the Hydro date in the pictures, and 2. No one has mentioned if the stamp was present.

That being said, due to the dammage and injury, I am sure the DOT is also involved. If so, if the "VE" stamp was not on the cylinder after the 2010 Hydro stamp, I would not want to be that Hydro facility. The lack of the stamp will be a hefty fine at the least when the DOT comes knocking and possibily also a lawsuit from the injured party if SLC is determined to be the culperate.

With that, My heart goes out to the family and wish them the speediest recovery

 

[John C. Ratliff]

I too have been thinking about the Rick and Cindy. That is one reason why I have been directing thinking toward the generic situations of oxygen and gasoline explosions, and not focusing on this particular situation. I have been praying for Rick's speedy recovery, and hope he is doing well.

On the subject of gasoline explosions, and the "difficulty" of igniting gasoline with a cigarette, I have a story to relate. I don't know the temperature of a metal-on-metal spark, but I watched while SSgt. Draper climbed up the tail pipe of a HH-43B Husky helicopter to do an inspection. He forgot about his USAF belt buckle, which scraped along the metal of this pipe he was in. He watched what he said was a blue flame go up by his nose, and a flash of light happened at the engine. The next thing he remembers is being on the ground outside the helicopter, after it had "spit him out." Now, JP-4 is a mixture 50-50 of kerosene and gasoline. It is less flammable than gasoline. So it seems strange that this would happen, if a cigarette cannot easily ignite gasoline. Sparks must be a fairly high temperature to ignite that mixture, which seems reasonable.

But a pure oxygen atmosphere is another story, especially one where there is pressure involved. Take a good look at that video I posted in the last page of the oxygen tank explosion. There was no obvious ignition source, except the friction of the metal valve on the cylinder threads, and the friction of the gas escaping. But it resulted in an explosion hot enough to melt the threads, and violent enough to rupture the tank.

SeaRat

 

[k ellis]

Prayers go out to this couple.

The manufacture date, if I'm making it out correctly, is 4/88 which depending on the manufacturer and size could mean it is indeed a 6351 AL alloy. See

Well I would say at first guess that there was some sort of oxygen build up below the dust cover. It would appear as if though this may have been from a leaking valve to which it was releasing a small amount of oxygen into the dust cover over a period of time.

It appears that when this flame ignited for what ever reason it may have went up the oxygen trail and through the source of the leaking oxygen and entered into the main bottle of the oxygen which would have caused an explosion from the inside out.

Without more photos this would be hard to tell for sure but had the oxygen ignited it would have been almost instantaneous. The photo suggest that the actual ignition took place with in the bottle itself.

Again these are just theoretical since with out actually examing the bottle itself and in person.

Anyway thats just my speculation.

 

[bleeb]

I will first start out by saying 1. I could not tell if the "VE" stamp was following the Hydro date in the pictures, and 2. No one has mentioned if the stamp was present.

Maybe someone more knowledgeable can comment, but IIRC, in another thread somewhere on here, I thought it was mentioned by some hydro or metalurgical professionals that stamping "VE" on a tank was not legal marking, and a literal interpretation of the federal regulations would require an immediate condemnation of the tank, not that I imagine most inspectors would be that literal.

 

[akdeepdiver]

Thats wrong, the DOT Specifies that at time of Hydro, 6351-T6 Alloy tanks will recieve a Eddy Current test. After passing the Hydro, and EC the letters VE will be stamped after the Hydro Retest stamp. I am not at my shop right now, but if people want, later I can dig through 49CFR and find the exact reference number.

 

[charlesml3]

It appears that when this flame ignited for what ever reason it may have went up the oxygen trail and through the source of the leaking oxygen and entered into the main bottle of the oxygen which would have caused an explosion from the inside out.

No. Again, Oxygen alone is NOT explosive and will NOT burn. It's not the O2 that burns, it's the fuel that burns. O2 is an Oxydizer and a required part of combustion. Go back to your elementary school science class where you lit some paper in a jar and then covered the top. In a couple of seconds, the fire consumes all of the O2 in the jar and combustion ceases.

-Charles

 

[charlesml3]

Ahhh Mythbusters again! When under graduate and post graduate degrees in materials science are boring, take too long to complete, or leave questions to be answered, Mythbusters to the rescue.

Please post references to more complete studies that support your point and aren't "boring" or "take too long to complete."

 

[sharksdelight]

And please remember that this thread was to started out of concern for Rick and Cindy. Rick has a long and painful road ahead of him and will be in the hospital for, at least, the next 2-3 months. With no income coming in and Cindy not even being able to stay at the much destroyed house, please find it in your hearts to donate something to them either through me or their Paypal 'Get Well Rick' link elsewhere in this thread.
Thank you,
Steve