Overfilling Scuba Cylinders

[dmoore19]

apples and oranges

I think it is at least similar in that the tanks are engineered for X if you increase X by 40% you are taking a chance. While running a red light is also taking a chance. If you continue to push engineering limits you will eventually have a failure. Maybe not as soon as getting hit by running a red light but IT WILL HAPPEN.

If the tanks are designed for 4200 psi you in your lifetime will not have a failure the odds are against it. If it is designed for 3000 psi the same can be said. Engineers and metalurgists are educated and specialize in determining these things. It is taking a chance everytime to exceed the recommended limits. They don't just throw a number out there and say OK 3000 psi it is. The engineers that designed the specifications for the tanks have far more information backing them up than the average cave diver. It is their job. Don't flame me I am not saying anything detrimental about cave divers, just that manufacturing a tank is generally not their specialty.

As I said in an earlier post, even if it is designed for 3000 psi working pressure there is still a chance of failure. Much less than pushing it to 5000 psi. I have witnessed things coming apart with 3000 psi on them that were designed for 3000 psi. It is often something you would have to see to belive. It is just flat out dangerous to push the engineered limitations of anything just because you can or because you did it before without problems. I am a quasi engineer. I do not have any experience in designing a tank. I do have experience in designing different fluids and their properties. Failures do occurr and can occurr even if operating guidelines are adhered to.

 

[Rhone Man]

Not sure I buy that. They hydrostatically test tanks to 5/3rds rated pressure. Some tanks do a lot of hydros (and by definition are thereby very old tanks), and I have not yet once seen a warning "don't hydrostatically test your tanks too often as it will weaken them."

 

[dmoore19]

Not sure I buy that. They hydrostatically test tanks to 5/3rds rated pressure. Some tanks do a lot of hydros (and by definition are thereby very old tanks), and I have not yet once seen a warning "don't hydrostatically test your tanks too often as it will weaken them."

We test things to higher pressures all the time, that just it Test them. We do not expect them to operate at that pressure.

I doesn't matter though. This is just my opinion. If you want to put that much pressure in the tank OK. It just makes me firm on the idea that when I buy a tank it will be new, not used. That way I know that it has not been stressed beyond it engineered limits. Again thats just my personal preference. Don't mean to argue. Thanks for your input.

 

[tgsmith]

For all this conjecture, it sure is a lot of bull when you look at what happens in real life under real circumstances.

Plain and simple........steel cylinders have been overfilled by technical divers for YEARS upon years without negative effects. Some of you really want to argue with reality?

Instead, you might just want to ask reality to leave a message since some of you are(without doubt) on lunch break.

EDIT: Remember I'm talking about steel cylinders.

EDIT #2: The data sample is pretty big. I wouldn't call it "you're probably just lucky and your tank is an outlier." The standard fill in North Florida is 3600psi for steel tanks. If you want something else, you ask. Considering how many people go through there every year......yeah. Right. OK guys.

Just because we don't have phd's, aren't metallurgists, aren't arm-chair internet smarty-pants, doesn't mean our evidence doesn't matter. Our evidence is the reality that technical diving(with N Florida being the flagship here) has proven it's OK.

But, some of you still are smarter than that, I guess. I've got some nice ocean-front property for you in Arizona, too.

 

[fppf]

with N Florida being the flagship here

Yeah like there are no underwater caves or deep water anywhere else in the world
Give me a break.

 

[tgsmith]

Yeah like there are no underwater caves or deep water anywhere else in the world
Give me a break.

Flagship. Get the meaning? As in there's other ships in the fleet but this is the big momma.

Give ME a break! Reading comprehension, people! You're all great at equations though, so whatever.......

Our evidence is the reality that technical diving(with N Florida being the flagship here) has proven it's OK.

Where in there did I EVER say that N Florida is the ONLY place that has caves or deep water columns? Come on man, really?

-Tyler
NOT an engineer.

 

[themagni]

As for "I"m an engineer", cylinders are not cast. Cylinders are mfgred by cold drawing. Basiclly they take a slug of aluminum, or a thick disk in the case of steel cylinder, and press it through a die. To form the neck the spin the cylinders and close it up. Then drill tap and turn the valve seat.

Sorry, it was way past my bedtime. Thanks for the correction and the links to the videos.

The rest of my post is still valid. You can't know the specifics of your tank, and after fatigue sets in you end up with a dangerous practice. Steel has a stress knee; Aluminum does not.

There was a post earlier about the shops doing light fills - I got a whopping 2400 on my last dive.

 

[clAwnU]

Just to be safe maybe no one should even use compressed gas cylinders. After all the manufacturing process is not perfect and any cylinder could explode at any moment. Run for the hills!!! Stay away from scuba divers lest one of their crazy tanks were to explode and kill us all!!!!! I sure am glad we have ELECTRICAL engineers that can come on here and tell us we should know better.

First of all last time I checked DOT was not a law enforcement agency. Their REGULATIONS NOT LAWS!!!) are limited to pressure vessels used in INTERSTATE COMMERCE. Secondly, metalurgists are not the ones coming up with these arbitrary numbers, it is some pencil pusher afraid of litigation. The same EXACT tanks in Europe are rated higher. The only difference between my low pressure Fabers and the high pressure are what's stamped on the neck. If a tank is going to explode because of faulty manufacturing it's not going to be better if it blows at 2400 than at 3500. You're still getting effed up. By overfilling you are shortening the lifespan of the tank, but they'll still out live you by a few decades. Next, DO NOT OVERFILL ALUMINUM TANKS! Steel handles fatigue MUCH better than aluminum and aluminum tanks only have a lifespan of about 15 years.

But then I'm probably wrong, I dive several times a month so I don't get the knowledge that comes from going down to the carribean once a year for a week and getting in all my dives then.

 

[tlt]

 

[Killer&Griller]

Ummmmm, more butter please.....I got two cause I was hoping to see a double feature...... How much for a small soda? What!! I can buy an old overstressed al80 for that price....