over fill a low pressure steel tank?

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I heard of steel tanks rupturing. Admittedly by design.

In one case a surplus tank had a groove milled into it to 50% of the wall thickness in order to test a tank-explosion-proof shelter. It was a 200bar rated tank. it blew at 230bar iirc.

The second case was a tank that failed hydro due to too much surface rust. So... it was filled with water and, since we have access to this nifty high pressure booster, let's see what happens.... it was a 20 year old Mannesmann 4L SCBA steel tank used in water w/o being galvanised and repainted before re-purposing. It popped around 3x service pressure...

The only cases I heard of problems with steel was due to rust. There's WW2 vintage steel tanks still in service, but they were only filled with good air.

I'd not hesitate to fill steel tanks to 10% over service (232bar rated, 250 cold I'm not going to lose sleep over) but I don't like loading tanks with more than that into my car, since in an accident, it may end up against me. I'm not going to fill AL to more than rated, because aluminium sucks as far as fatigue limit is concerned. (Fun fact: Al will fatigue no matter what. The steel fatigue limit is about 1/2 of ultimate tensile strength - below that cycling does not change the material. The fatigue limit is usually set to the hydro limit...)

Anyway, enough rambling... I always thought that the p(s) and p(t) on tanks were the pressure rating for sports- and technical diving respectively... :wink:


Gerbs - has helped test tanks before
 
In the article, Bill is talking to professional tester/inspectors thus the wording.

I, like others, do all sorts of things that bend or break safe diving practices and my opinions are not directed towards what individuals choose to do themselves. It has to do more with what we advise strangers to do in the forums. Just recently, a series of threads were heavily moderated because they advocated a violation of safe diving practices. Yet here we have people advising others to tamper with their burst discs and pump up tanks to nearly twice the DOT service rating. Show me the agency that considers this a safe diving practice. Litehedded. I suspect we will both need some popcorn for this one.

A lot of what is being passed on a routine comes with some caveats: Those who overfill probably know the history of their tanks and hopefully wouldn't just pump up any old tank they buy second hand. As Fdog pointed out, European tanks without burst discs or that run much higher pressures are made of different alloys or design specs. Cousteau dove the Britannic with 4000 psi in his tanks but that doesn't mean one should imagine their tanks were designed the same way.

IMO There are some subjects that should have a certain degree of opt in or selectivity to them. We seem to agree that solo diving fits this description. The tech forums are another example. We probably shouldn't teach folks how to cave dive over the internet without some form of filter and, IMO, we shouldn't just advice total strangers to seal off the burst discs and pump up the volume on tanks we have no insight into.

Funny how the mods choose to be selective in their interventions and leave it up to some individual member to try and make this point.
 
DaleC:
In the article, Bill is talking to professional tester/inspectors thus the wording.

I, like others, do all sorts of things that bend or break safe diving practices and my opinions are not directed towards what individuals choose to do themselves. It has to do more with what we advise strangers to do in the forums. Just recently, a series of threads were heavily moderated because they advocated a violation of safe diving practices. Yet here we have people advising others to tamper with their burst discs and pump up tanks to nearly twice the DOT service rating. Show me the agency that considers this a safe diving practice. Litehedded. I suspect we will both need some popcorn for this one.

A lot of what is being passed on a routine comes with some caveats: Those who overfill probably know the history of their tanks and hopefully wouldn't just pump up any old tank they buy second hand. As Fdog pointed out, European tanks without burst discs or that run much higher pressures are made of different alloys or design specs. Cousteau dove the Britannic with 4000 psi in his tanks but that doesn't mean one should imagine their tanks were designed the same way.

IMO There are some subjects that should have a certain degree of opt in or selectivity to them. We seem to agree that solo diving fits this description. The tech forums are another example. We probably shouldn't teach folks how to cave dive over the internet without some form of filter and, IMO, we shouldn't just advice total strangers to seal off the burst discs and pump up the volume on tanks we have no insight into.

Funny how the mods choose to be selective in their interventions and leave it up to some individual member to try and make this point.
Click to expand...

I dont spend a lot of my time waiting for a dive agency to tell me what I can and can't do with my tanks, chief. but I would say IANTD, NACD, NSSCDS, GUE dont seem to think it's unsafe. give them a call and ask. then once they feed your opinion to you you can start overfilling tanks like the rest of us.

comparing the safety of overfilling a steel tank to diving deep on air or solo diving is ludicrous. the people dreaming this up no doubt breathe through their mouths and move their lips when they read our posts on here.

oh, and every tank I own is second hand. all twenty of them or so...
 
lel agencies and safe diving practices? The same ones with "Narcosis Management" and "Deep Air"? Things that are routinely implicated in diving fatalities. That's your standard?

I operate in the real world, and I know what works (clearly). 2400psi rated steel tanks that are in Hydro and VIP filled to ~3600psi simply don't hurt anyone. Its NEVER happened. Ever. Like I said, if you can show me where it has happened, I'll kiss your butt in a Macy's window so everyone can see it. Till then...

Also, Dale, the Euro's aren't required to have burst disks on Al tanks either (including US spec tanks). I don't hear about anything happening over there, either. Coincidence? Burst disks don't make a lot of sense, and as such, I see no value to them. Since you can't get manifolds and valves without them in the US, I do the next best thing and plug them. Burst disks are one of the most questionable aspects of valves, and I don't have the time to deal with silly failures for no reason.
 
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