Overfill at Castaway Scuba

[PhilEllis]

That's very interesting, because is still sounds like you are. I mean, hell, if the burst pressure is 7,500, we can go on ahead and jack those babies up to 6,000 easy and get double the dive!

Steel is not aluminum... why don't you take a look at the statistics for tank failures and see how many were steel?

Actually doing it is one thing, acting as the expert and brushing it off to the point of advocation is a whole other thing.

Well, on this issue of "looking at the statistics of cylinder failures", I think with some DEEP research, you might be surprised which material has more failures. You assume that by quoting the DOT qualification procedures for qualification, people are supporting the practice of overfilling....that simply isn't so.

This is what I said in my original post.....................

...it is equally as safe (or unsafe, depending on your viewpoint) to overfill an aluminum cylinders as it is to overfill a cylinder made of any other material under the DOT standards. Regardless of the material, they are all subjected to EXACTLY the same qualification tests. ALL OF THEM (even steel cylinders) must fail in a leak-before-burst mode at some time after 10,000 cycles to be approved. If a cylinder never fails during the testing, the test is a failure.

Many will CLAIM that there is some sort of evidence that aluminum is less safe than steel for overfilling, but few can produce anything other than anecdotal evidence. Overfilling cylinders, while done fairly frequently, is entering into completely unknown (from an engineering perspective) territory. I don't know of ANY scuba cylinder company that has completed and published any engineering tests on the impact of overfilling scuba cylinders.

I cannot back off of this statement, because it is absolutely, 100% correct. There is no dispute about it. Now, I phrased this statement to say it is equally as safe, OR UNSAFE, to overfill either. Personally, since that is a complete absence of an engineering data and testing by any cylinder manufacturer about the impact of overfilling cylinders, regardless of material construction, I don't suggest overfilling aluminum cylinders, steel cylinders, composite cylinders, or clay cylinders. But regardless, NO MATTER WHAT MATERIAL IS USED....IF it is safe to overfill a steel cylinder, the evidence indicates that it is equally safe to overfill an aluminum cylinder. There is no quantified, document engineering study that says one is "stronger" or "safer" than the other.

Now, you are one brightgator. You KNOW that the anecdotal evidence on overfilling steel cylinders in cave country is exactly what it is.......anecdotal evidence. Engineers and scientists may START a study as a result of anecdotal evidence, but they NEVER use it for statistically valid conclusions.

There is a bottom line from a testing, engineering, design, and qualification perspective.......it is EQUALLY as safe or unsafe to overfill aluminum cylinders as it is steel cylinders. But then, if you whistle through the graveyard, it makes the walk a little less scary.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

 

[mike_s]

That's very interesting, because is still sounds like you are. I mean, hell, if the burst pressure is 7,500, we can go on ahead and jack those babies up to 6,000 easy and get double the dive!

.

Hmmm...... So have you tried this yet ?


Seeing how your 1st stage is most likely not rated for more than 4000psi or maybe 5000psi, I'm sure the explosion of the 1st stage you would hear behind your head would be quickly deafened by the parts of the 1st stage entering the rear of you skull...

Let us know your test results

 

[OneBrightGator]

sho fly.

Well, on this issue of "looking at the statistics of cylinder failures", I think with some DEEP research, you might be surprised which material has more failures. You assume that by quoting the DOT qualification procedures for qualification, people are supporting the practice of overfilling....that simply isn't so.

The use of the material is what counts, the number of soda pop cylinder failures or storage cylinder failures or whatever type cylinders doesn't have much to do with scuba cylinder failures unless the working conditions are similar, which they aren't.

When you throw out that you can fill a cylinder to whatever pressure you quoted 10,000 times you are giving people the impression, unintentionally or not, that is it safe to overfill cylinders. I am positive some divers have read this thread and will have no problem pushing hot fills because of the information you provided.

 

[PhilEllis]

sho fly.


The use of the material is what counts, the number of soda pop cylinder failures or storage cylinder failures or whatever type cylinders doesn't have much to do with scuba cylinder failures unless the working conditions are similar, which they aren't.

When you throw out that you can fill a cylinder to whatever pressure you quoted 10,000 times you are giving people the impression, unintentionally or not, that is it safe to overfill cylinders. I am positive some divers have read this thread and will have no problem pushing hot fills because of the information you provided.

Well, if quoting the qualification relationship of both aluminum and steel cylinders accurately encourages people to think they can overfill, I don't understand why. It certainly isn't my attempt, since I am TOTALLY AGAINST overfilling, regardless of what the cylinder is made from. But the point is.....if a person thinks it is "safe" to overfill a steel scuba cylinder, then they have to conclude that it is "safe" to overfill an aluminum scuba cylinder. After all, the design, qualification, testing, and certification of the two are identical. Anyway.

Phil Ellis
Discount Scuba Gear at DiveSports.com - Buy Scuba Diving Equipment & Snorkeling Equipment

 

[The Chairman]

Castaway Scuba is Great! Like any shop, with any new employee, there are BOUND to be mistakes. No, you don't need a new burst disc, and no, you don't need to have your valve re-done. Marta has seemed to have already addressed this issue and you won't find me hesitating ONE BIT to use her shop. Really, really.

 

[TommyinMiami]

Wow, you guys are just over the top. I go diving 2-3 times per week and have 2 friends that dive everyday for a living. We get our tanks filled together all the time. every time we fill them we get them filled to no less than 3,300 and the norm is 3600. FOR YEARS!!! with the same tanks. I've had them as high as 3,900 with no issues what so ever. Now I would not leave my tanks in a car trunk, but I have no problem with a dive shop overfilling tanks for REPEAT customers that have common sense and that KNOW the tank will be overfilled.

STOP SPEADING UNFOUNDED FEAR.

the working psi of your first stage is 3000, but its max pressure is 7500. So why are you people telling people their tanks and 1st stages are going to blow up and kill them and go into their skulls.

COME ON PEOPLE GET A LIFE!

 

[D_B]

.. for years? ... what number of tanks tested and at anywhere near 10000 cycles?? ... Data???

I like the "I've done it, know others that have done it, and we're still fine" attitude that is displayed in only this one area of scuba diving

 

[TommyinMiami]

DB you are ridiculing me for something that I've experienced first hand, when you're talking about something you have no experience in. You dont know anyone whos tank or 1st ever blew, and you don't overfill, so why even chime in here. I am at least adding my first hand experiences.

FACT:
Manufacturer MINIMUM burst pressure is 7,500PSI so NO 3,600 or even 3,900 would not burst a tank or even cause the burst disk to act.

Personally I would not exceed 3,800-3,900 not for fear of bursting, but for fear of premature wear on equipment, and gaskets.

So the minimum tank burst pressure is 7,500 the minimum bust disck pressure is 4200psi
If a Leaving a 3000psi tank in 140degree trunk for an entire day would result in an increase of 215 degrees. Still more than 1000PSI before the burst disk activates.

For a living. I deal with small rubber hoses and machines that operate at a service pressure of 4,000PSI If these little fleible hoses I use and abuse can withstand 4,000PSi trust me your tank and 1st can. The hoses I use also go from 2200psi to 4000psi every couple seconds. The quick change in pressure is even worse for a hose, but yet never a problem.

I'm not telling people to go out and get your tanks overfilled, But I am saying you guys are freeken out at this dive shop for no reason. Do you really have nothing better to do than to take up this stupid cause. That mathmatically speaking you have no back bone for the argument to stand on.

 

[The Chairman]

Dang Tommy,

Both of your posts warrants a "Lighten up Francis"! Tanks are tested to 4/5s of their rated pressure. Their elasticity is then measured. Quite often tanks which are consistently filled in excess of %20 of their rated capacity are FAILED due to work hardening. Please, go ask any hydro operator in the state about this.

BTW, your post was dripping with ridicule for people who err on the side of caution, and you bristle at someone questioning your anecdotal evidence? You have nothing in your profile to suggest that you are even certified to VIP a tank. Are you? If not, then stop with the aggressive nature.

BTW, you might want to check those "rubber hoses" you work with. You will find that they have more than rubber in them, and it ain't aluminum.

 

[Dive-aholic]

I've had a burst disk go at about 3300 psi. It was less than a year old.