HP or LP double

[XS Scuba]

Hi PerroneFord:
As I stated in my prior post: They are no more safe or no more unsafe to pressurize beyond 2640 psi (2400+ psi) then any other 3AA 2400+ psi scuba cylinder.

None of the DOT3AA scuba cylinders are "overbuilt" beyond the DOT 3AA requirements. It is a myth that any manufacture's cylinders are actually "high pressure" cylinders with an underrated working pressure. Why would any manufacture do that? If that were the case, I would have the cylinders stamped with a higher working pressure (increasing the cylinder capacity and value) or use less steel & reduce my cost.

Is your argument, that your knowledge of past experience of overfilling is greater then the knowledge of DOT regarding safety margin and high pressure vessels? If that is the case why not grossly overfill 3AL (aluminum) cylinders? Why not grossly overfill cylinders with a DOT exemption? All scuba cylinders manufactured to meet DOT specifications have essentially the same safety margin.

My point is simple, we manufacture high pressure cylinders designed to meet the DOT requirements for a working pressure of 3442 psi. These are not low pressure cylinders which we have stamped with a higher working pressure. These cylinders are designed and manufactured with a high tensile steel alloy to meet the DOT requirements of 3442 psi. If you want a cylinder that is safe for high pressure, then purchase the cylinder that is designed for that purpose.

Would you characterize your cylinders as As safe, less safe, or more safe, than the Faber 3AA steel tanks that we have been overpressurizing for nearly 30 years? Are they equally as safe as the PST cylinders that people have been putting 3500-4000psi In since the 80s?

Since I intend to purchase some new LP cylinders this winter, I want to be sure that if I purcahse Worthington tanks, I am not getting an inferior product when I could purchase PSTs or Fabers.

Thank you.

-P

 

[CompuDude]

Hi CompuDude:
The information you read is not correct. We currently have Worthington manufacture 13 sizes of steel cylinders for us (Sea Pearls is the same). Four sizes are DOT3AA 2400+ psi, four sizes are DOT3AA 3130+ psi and five sizes are DOT E14157 3442 psi. The specifications can be viewed here: http://xsscuba.com/tank_steel.html We have no plans of discontinuing production of any of these cylinders. In fact, we plan to introduce two new sizes at the DEMA show in November. One is a 3AA 2400+ psi cylinder and the other is another X-Series cylinder 3442 DOT E14157.
Also, if you are of the belief that the DOT 2400+ psi cylinders are just "down rated" high pressure cylinders, you are wrong. Our low pressure steel cylinders are manufactured to meet all the requirement of the DOT 3AA classification for 2400+ psi, no more. They are not "overbuilt" in anyway to exceed the requirements of DOT. They are no more safe or no more unsafe to pressurize beyond 2640 psi (2400+ psi) then any other 3AA 2400+ psi scuba cylinder. I suggest if you plan to fill your cylinder beyond 2640 psi, then purchase an X-Series cylinder which is designed for fills to 3442 psi.

Good to know, thanks.

(Personally, I only use HP tanks so it's a moot point for me!)

 

[PerroneFord]

Hi PerroneFord:
As I stated in my prior post: They are no more safe or no more unsafe to pressurize beyond 2640 psi (2400+ psi) then any other 3AA 2400+ psi scuba cylinder.

Ok, that's the magic bullet.

None of the DOT3AA scuba cylinders are "overbuilt" beyond the DOT 3AA requirements. It is a myth that any manufacture's cylinders are actually "high pressure" cylinders with an underrated working pressure. Why would any manufacture do that? If that were the case, I would have the cylinders stamped with a higher working pressure (increasing the cylinder capacity and value) or use less steel & reduce my cost.

I was not under that impression. I've seen the difference in manufacture between the two different types of tanks.

Is your argument, that your knowledge of past experience of overfilling is greater then the knowledge of DOT regarding safety margin and high pressure vessels?

I have no argument. I merely asked a question. Empirical evidence has shown over many years that the 3AA tank specification allows the cylinders to be filled to a greater capacity than their working pressure with reliable results. Is this outside of specification? Yes. Does it carry more risk? Yes. Is it still done? Daily.

My point is simple, we manufacture high pressure cylinders designed to meet the DOT requirements for a working pressure of 3442 psi. These are not low pressure cylinders which we have stamped with a higher working pressure. These cylinders are designed and manufactured with a high tensile steel alloy to meet the DOT requirements of 3442 psi. If you want a cylinder that is safe for high pressure, then purchase the cylinder that is designed for that purpose.

While I appreciate your position, as a consumer, it is my obligation to purchase the tank I feel best meets my needs. As a distributor, XS Scuba has done a marvelous job. As such, I am likely going to be purchasing an XS SCUBA tank, or rather several. You have done your due diligence in educating the market about high density steel tanks and their intended use, versus low pressure cylinders.

I wish XS continued success with their fine product.

 

[XS Scuba]

Hi PerroneFord:
I appreciate your good words and understanding of our position.

 

[PhilEllis]

(snip)......My point is simple, we manufacture high pressure cylinders designed to meet the DOT requirements for a working pressure of 3442 psi. These are not low pressure cylinders which we have stamped with a higher working pressure. These cylinders are designed and manufactured with a high tensile steel alloy to meet the DOT requirements of 3442 psi. If you want a cylinder that is safe for high pressure, then purchase the cylinder that is designed for that purpose.

As I understand it, it is technically IMPOSSIBLE to "over engineer" a pressure cylinder for service under DOT standards. In order for a cylinder to pass the various DOT tests, it must withstand 10,000 cylcles to X pressure (depending on the working pressure of the cylinder tested) and then it MUST fail at some point after the 10,000 cycles to determine the failure mode. "Over engineering" the cylinder, apart from the absurd cost issues (adding metal where it is not needed), would prevent it from failing at X pressure, thereby preventing it from completing the test and being certified. That being the case, if you insist on overfilling a cylinder, an Aluminum 80 cylinder would be "just as safe" for overfilling as any steel cylinder.

I agree with Mike. Overfilling is not a good idea. Empirical data is often "clouded" by ommissions of facts. Empirical data is typically not gathered with the scientific control necessary to make valid conclusions from the data. This is not the case with data from a designed experiment.

Unfortunately, overfilling has become a routine practice in our part of the country. Thus far, the practice has resulted in few injuries (to my knowledge). For the sake of humanity, I hope this "empirical" track record continues. Anyway, just my opinion.

Additional Note: It is further sad when a company takes a testing standard like the 3AA standard and uses the 10,000 cycle test as "evidence" that THEIR cylinders, apart from all others, will withstand overfilling without problems. All the while, THEY KNEW that EVERY cylinder approved under that standard had exactly the same safety margin as their cylinders. I realize that the company I speak of never OFFICIALLY made that claim, but for years they did publish that information in a way that was designed to make consumers "arrive at a dishonest understanding" of what their cylinders would and would not do, as compared to other brands. How lucky that company was that there never was a litigated accident with their product. Again, just my opinion.

Phil Ellis

 

[PerroneFord]

Phil,

I have never owned a steel tank. As such, I have not seen advertising by any company that made claims that their cylinders could be safely overfilled. This would be foolhardy not only from an engineering standpoint, but from a legal one as well.

Your comments on AL tanks being "just as safe to overpressure" run into trouble from the sustained load cracking issues we've seen. That aside, you are correct that empircal evidence often lacks the hard facts needed to offer guarantees. There are very few guarantees in this business. We are all assuming risks.

From examining the evidence on record, it appears that there is minimal risk in overpressuring 3AA tanks that are clean, and in good order, within reason. I tend to put about 3000-3200psi in the 3AA tanks I've used. I have seen them pumped to 3800-4000 psi. I have no desire to do that. I am NOT advocating this is safe. I am merely saying that the risk/reward factor is sufficient for *me* to sustain the practice. Thousands of other divers seem to feel similarly.

I have every confidence that XS/Worthington is built to the same specification and with the same quality as others marketing 3AA tanks.

 

[PhilEllis]

I have never owned a steel tank. As such, I have not seen advertising by any company that made claims that their cylinders could be safely overfilled. This would be foolhardy not only from an engineering standpoint, but from a legal one as well.

I agree with you....foolhardy from both an engineering and a legal perspective. That didn't stop them from making that implication. You will notice I didn't mention the company. Those with lots of experience with steel cylinders will know EXACTLY what company I am speaking of. (they were not a manufacturer of cylinders, just a major marketing force in the cylinder business)

Your comments on AL tanks being "just as safe to overpressure" run into trouble from the sustained load cracking issues we've seen. That aside, you are correct that empircal evidence often lacks the hard facts needed to offer guarantees. There are very few guarantees in this business. We are all assuming risks.

The "sustained load cracking" problem was not a problem of overfilling. It was a problem with only a single aluminum alloy and manifested itself at the NORMAL working pressure. That aside, my statement was that from a viewpoint of the "robustness of a cylinder to withstand repetitive overfilling", an aluminum 80 would be just as safe when overfilled as any other pressure vessel submitted for this use under the DOT standards. Understand, I didn't say safe. I simply said "as safe". I personally don't advocate constant overfilling just because you can, especially on aluminum cylinders.

From examining the evidence on record, it appears that there is minimal risk in overpressuring 3AA tanks that are clean, and in good order, within reason. I tend to put about 3000-3200psi in the 3AA tanks I've used. I have seen them pumped to 3800-4000 psi. I have no desire to do that. I am NOT advocating this is safe. I am merely saying that the risk/reward factor is sufficient for *me* to sustain the practice. Thousands of other divers seem to feel similarly.

I stated in my previous post that we do live in a part of the country that routinely overfills steel cylinders. I even admit to doing it myself for select customers and for my personal use. That doesn't make it "safe" or "safe enough". Empirical data has all of the problems that have always been associated with empirical data. As to the "risk/reward" issue, I have think about that. As a gambling man, I realize that the "risk/reward" must be comparable. In the filling of cylinders, the two are not even close. The "reward" is a little more bottom time. The "risk" is death for the fill station operator. Again, I am not claiming that there have been a rash of failures on steel cylinders. I'm simply saying the "risk" if there is a failure far overpowers the "reward" of overfilling. You can choose to overfill, but don't do it because the "risk/reward" balances. It never will.

I have every confidence that XS/Worthington is built to the same specification and with the same quality as others marketing 3AA tanks.

On that, I think you can be absolutely confident. In fact, Worthington didn't like the base thickness of the PST model and choose to add metal to the bottom of the cylinder. That is the cause of the roughly 1 pound difference in the weight of the Worthington cylinders and other steel cylinders. (at least I think that is what I was told)

Thanks PF. I enjoy this type of back and forth. Again, I express only my opinion.

Phil Ellis

 

[Leadking]

Right on Phil!

Every tank design MUST pass a minimum of 10,000 fills at hydro pressure and then LLB (leak before burst) therefore all tanks have what is called "an equivalent level of safety". Therefore it's just as "safe" to fill an aluminum tank to hydro as steel.

Lee
www.seapearls.com

Just because you're getting away with it does not mean it is safe!

 

[PerroneFord]

On that, I think you can be absolutely confident. In fact, Worthington didn't like the base thickness of the PST model and choose to add metal to the bottom of the cylinder. That is the cause of the roughly 1 pound difference in the weight of the Worthington cylinders and other steel cylinders. (at least I think that is what I was told)

It also explains why the Worthington tanks trim better for me than other options and why I am seeking these tanks instead of others. The 108s should be nearly perfect for me, and the 121s very manageable should I go that route.

Thanks PF. I enjoy this type of back and forth. Again, I express only my opinion.
Phil Ellis

Agreed. Nothing but opinions expressed here, and it's nice to do so without namecalling, or bickering. I had a good sense about you when you were going through that B.S. in the spring, and I'm glad I spent money with you and your shop. We need more vendors like you.

 

[XS Scuba]

...and just as "unsafe."
My point: "If you want a cylinder that is safe for high pressure, then purchase the cylinder that is designed for that purpose."

Therefore it's just as "safe" to fill an aluminum tank to hydro as steel.

Lee
www.seapearls.com

Just because you're getting away with it does not mean it is safe!