Overfilling Scuba Cylinders

[rstofer]

regardless din or yoke, you get more wear and tear on a regulator with higher pressures, so the question becomes how high is too high?

Whatever the manufacturer recommends.

I suspect you do get more high pressure seat erosion with higher pressures. I have no idea if the regulators have ever been rated for burst pressure. Maybe the idea is that the IP prevents overpressure because the 2d stages will freeflow.

I don't think the regulators are being overpressured by all that much. I don't know how much pressure they put in the LP tanks but the modern reg is clearly designed to handle 3442 psi, probably 3500 psi. In Europe, the CE models may handle 4000 psi (I'm guessing) and there would be no reason to have separate designs.

I was worried only about stretch in the yoke and subsequent failure. I'm not worried about the regulator housing.

A 50% overfill of a LP tank probably isn't much of an issue for a modern regulator as the Owner's Manuals I have read mention 3500 psi and the yokes are rated for 3500 psi.

Richard

 

[GrandpaScuba]

... Nevertheless, cave divers know metallurgy and stress analysis far better than tank designers ...

No, they just think they do.

 

[Kevin Carlisle]

Obviously they do.. They have no where near the accidents you open water guys have and its no wonder why. Now if you really want to learn something go find out what the little + means on a LP cylinder that has come from hydro. The OP asked a question, got called a troll and since then NOT one of you has answered his question. All you can do is speculate and run around bashing people you dont know.

No, they just think they do.

 

[deepn0va]

other than law, what are the limits of these lp tanks? This topic has been beaten like a dead horse in other threads but no conclusion has been defined. if the DOT did not regulate pressurized gas cylinders, what could the lp tanks (rated for 2400psi + a 10% overfill to 2640) take without adverse effects to the metal or regulator? what is the weakest link in the equation.

 

[rstofer]

Now if you really want to learn something go find out what the little + means on a LP cylinder that has come from hydro//QUOTE]

I think I know exactly what it means. If a tank passes an additional, higher pressure, test without violating an expansion limit (indicated by the REE number) then the very same 49 CFR 173 that says don't overfill a tank allows this particular tank to be overfilled by 10%. So a 2240 psi tank can be filled to 2460 psi is it has the '+' stamp.

That's exactly the case with my LP 72. There are also 2400 psi LP '+' rated tanks that can be filled to 2640 psi.

There are some Faber '+' rated MP tanks but when the additional pressure is added, they seem to max out around 3490 or 3500 psi.

I thought I answered the question properly and succinctly. 49 CFR 173 prohibits filling a tank beyond its working pressure with the exception that '+' rated tanks can be overfilled by 10%. But this is all well known, everyday stuff. It is also known that the '+' rating can be lost over the lifetime of the tank or the test simply omitted. If the tank subsequently passes the test, the '+' rating can be restored. Again, all this stuff is in 49 CFR 173.

The question was regarding the wild overfills that cave divers think should be the norm. These are prohibited by 49 CFR 173 and the DOT should close down the facilities that do them (IMNHO). I pointed that out as well. Complaining about their inaction.

The fact that a tank hasn't blown up YET doesn't mean the stress is allowable or somehow justifiable. It's kind of like the Challenger disaster. NASA management describes the safety of the space shuttle as 1 accident in some huge number (like 100,000). The engineers that designed the shuttle rate it as no better than 1 in 100. Their opinions differ by more than 1000x. See Feynman's Appendix to the Rogers Commission Report on the Space Shuttle Challenger Accident

I suspect the tank designers would have the same point of view. The tanks weren't designed for the wild overpressures and the fact that they haven't exploded YET is just luck. Not one credible Registered Professional Engineer has ever said that this practice is acceptable. Nor would they with their E&O insurance on the line.

Richard

 

[Doc Harry]

 

[deepn0va]

Now if you really want to learn something go find out what the little + means on a LP cylinder that has come from hydro//QUOTE]

I think I know exactly what it means. If a tank passes an additional, higher pressure, test without violating an expansion limit (indicated by the REE number) then the very same 49 CFR 173 that says don't overfill a tank allows this particular tank to be overfilled by 10%. So a 2240 psi tank can be filled to 2460 psi is it has the '+' stamp.

That's exactly the case with my LP 72. There are also 2400 psi LP '+' rated tanks that can be filled to 2640 psi.

There are some Faber '+' rated MP tanks but when the additional pressure is added, they seem to max out around 3490 or 3500 psi.

I thought I answered the question properly and succinctly. 49 CFR 173 prohibits filling a tank beyond its working pressure with the exception that '+' rated tanks can be overfilled by 10%. But this is all well known, everyday stuff. It is also known that the '+' rating can be lost over the lifetime of the tank or the test simply omitted. If the tank subsequently passes the test, the '+' rating can be restored. Again, all this stuff is in 49 CFR 173.

The question was regarding the wild overfills that cave divers think should be the norm. These are prohibited by 49 CFR 173 and the DOT should close down the facilities that do them (IMNHO). I pointed that out as well. Complaining about their inaction.

The fact that a tank hasn't blown up YET doesn't mean the stress is allowable or somehow justifiable. It's kind of like the Challenger disaster. NASA management describes the safety of the space shuttle as 1 accident in some huge number (like 100,000). The engineers that designed the shuttle rate it as no better than 1 in 100. Their opinions differ by more than 1000x. See Feynman's Appendix to the Rogers Commission Report on the Space Shuttle Challenger Accident

I suspect the tank designers would have the same point of view. The tanks weren't designed for the wild overpressures and the fact that they haven't exploded YET is just luck. Not one credible Registered Professional Engineer has ever said that this practice is acceptable. Nor would they with their E&O insurance on the line.

Richard

I must have missed the point to this, so let me rephrase my question.

Without 49 CFR 173 and the DOT regulating fill pressures (like outside the US), what can 2400psi tanks take before they cause irreversible damage to the tanks or rupture? Is this pressure higher or lower than what today's first stages are able to handle?

 

[deepn0va]

Doc, What was that tank filled to before it exploded? most of us have see what a scuba tank looks like after it ruptures. Was it a bad alloy?

 

[UCFKnightDiver]

thats an aluminum tank were talking lp steel here... possibly a bad alloy? Where did you get that picture from?

 

[dmoore19]