Perhaps I dont watch or read the news enough but do steel 72s or any tank for that matter explode? Has this happened often? I was under the impression that the relief valve would blow before the tank would.
Overpressurizing / Overfilling steel tanks
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pescador775
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Late to the party? Yes, six months ago, on this board, were posted pics of an incident in Mexico. A yellow painted USD 72 exploded turning a sedan into a Ranchero. The problem was external rust. Rust inside is a more common problem leading to failure.
quimby
Contributor
Got to agree with you gen I would not want to be standing next to one when it bannana peeled which is my understanding of the actual shape of it afterwards. I also have to add that I filled thousands of them when I had a shop in the 60's and 2800 was pretty much the norm. Of course they and I were much younger then but I really wouldnt worry about stressing them within reason(whose definition?) I have also seen a lot of fire bottles converted and mistreated to the point of having a quart of water in them. Twice in my tenure I saw tanks leaking (bubbling ) out of the side wall during fill, both bottles had water in them and it was pitted clean clear through. (maybe Vance Harlow's buddy Cale would have used some JB weld and gone on forever but even then I questioned immortality) My understanding of mode of failure of CM is quite diff than AL and verifys what I saw was explainable and why I love my steels 72s 104,120etc.
The Curly One
Registered
If you are filling your own tanks why take any chances? It may give you 5 minutes more time under water or it may take your life! I realize that tank explosions are rare but why take any chances? They put the maximum pressure on there for a reason.
Curly
Curly
The Curly One
Registered
If I am not mistaken the burst discs on the 80 cu ft Aluminum 3000 psi tanks is 4250 psi and the 4500 psi carbon fiber tanks is 5750. Now that is way over any safe fill pressures and most tank explosions have happened when the tank was not even filled to its maximum rated pressure. Curly
... While I was in here playing on the computer and the compressor was pumping up a couple of 104s with EAN32.
It shut off at 3700.
It shut off at 3700.
... are not actually "overfilled" if they are taken to 2475 (@ 70F)
Realize that all these pressures are at 70F. If the bottle is at 90F then it is perfectly acceptable for the pressure to be about 3.7% higher, or 2567 psi, as that is the expected change at that temperature (a bit under 2% for each 10 degrees F)
However, similarly, if your tank cools to 50F, then you should have a "cold" fill pressure of 3.7% LESS than rated.
The "+" rating is often not renewed, usually because the hydro station either isn't asked to do the computation for it or simply fails to do so. Not all that many tanks fail the "+" test, but they can! Nonetheless, going to the "+" pressure on a tank that originally had a "+" rating probably isn't very unsafe, but beyond that, you're on your own.
I've seen the claims of 10,000 cycles at hydro test pressure made for some LP steel tanks, but I'm not pumping MINE to that pressure. I have no intention of finding out first-hand if they will take it or not.
PS: My compressor pops off at 4500, and I've gone there against a closed outlet valve. I ain't taking NOTHING I have around here in the form of a scuba tank to that pressure.
Realize that all these pressures are at 70F. If the bottle is at 90F then it is perfectly acceptable for the pressure to be about 3.7% higher, or 2567 psi, as that is the expected change at that temperature (a bit under 2% for each 10 degrees F)
However, similarly, if your tank cools to 50F, then you should have a "cold" fill pressure of 3.7% LESS than rated.
The "+" rating is often not renewed, usually because the hydro station either isn't asked to do the computation for it or simply fails to do so. Not all that many tanks fail the "+" test, but they can! Nonetheless, going to the "+" pressure on a tank that originally had a "+" rating probably isn't very unsafe, but beyond that, you're on your own.
I've seen the claims of 10,000 cycles at hydro test pressure made for some LP steel tanks, but I'm not pumping MINE to that pressure. I have no intention of finding out first-hand if they will take it or not.
PS: My compressor pops off at 4500, and I've gone there against a closed outlet valve. I ain't taking NOTHING I have around here in the form of a scuba tank to that pressure.
...was pretty clearly the result of MASSIVE corrosion of the bottom of the tank due to a boot that didn't drain, and complete ignorance of the condition of the tank.
Internal rust on steels is a problem though, and one that can bite you without warning if you're less than careful. The problem arises in that fills on a boat or in a shop can be somewhat carelessly done, and water can get blown into the tank. All it takes is for the fill whip to get some water in it and not have it blown clear before being attached, or water in the valve that is not blown clear before the filler is put on. When the valve is opened to fill, the water is then blown into the tank.
It takes surprisingly little water to cause trouble.
Internal rust on steels is a problem though, and one that can bite you without warning if you're less than careful. The problem arises in that fills on a boat or in a shop can be somewhat carelessly done, and water can get blown into the tank. All it takes is for the fill whip to get some water in it and not have it blown clear before being attached, or water in the valve that is not blown clear before the filler is put on. When the valve is opened to fill, the water is then blown into the tank.
It takes surprisingly little water to cause trouble.
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I know it is a standard practice to overpressurize lp steel tanks in technical diving. I have to admit to fudging a couple of hundred psi on occasion. A couple of very well know dive areas and will take them to 3500 and above. Whenever I've asked why, they just look at me funny and say, they do it in Europe all the time. Yes I know why it is done, but with tec agencies pushing rules,regulations and standards, my way or the highway, all the time, it is like, these are the rules obey them religiously, except for the ones we choose too ignore.
What is your justification for overpressurizing
What is your justification for overpressurizing
Boogie711
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No one has ever died from a tank exploding on them.
Lots of divers have drowned by running out of air.
'nuff said.
Lots of divers have drowned by running out of air.
'nuff said.
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