pony bottle question

[TMHeimer]

Yes, as pointed out, my question was pretty much hypothetical. Mine was new in '07. I used it (had it with me on dives, no breathing from it other than to test it worked OK) several times then had it visualed and refilled. After a while was also checking it out and found that the pony reg wasn't breathing, so I got that fixed. The technician said stuff can sieze up in regs from lack of use. Anyway, I haven't used the pony since then and was somewhat curious as to whether it would be wise to take it on a dive say 3-4 years after the visual, with the 5 year hydro date expired (even though, as pointed out, it was still full and would not need a re-fill if I were willing to breathe 3-4 year old air). Just got me thinking-- You have a pony but hardly ever use it-- do you still get it visualed & hydroed every 1 & 5 years --or do you take care of that just before the next time you do use it, or do you just use the air in it then get the visual/hydro/refill? Not at all trying to cut corners, but not sure if it's necessary to pay for this stuff when I'm using it so infrequenty, and I'm not made of money. Someone mentioned a 2 1/2 year visual "rule" -- anyone else heard of that? I always thought pony's were yearly like any other tank.

 

[DandyDon]

I work at a dive shop and I take care of tank visuals and sending them out for hydro. The tanks that I usually fail hydro are the ones that have been stored without pressure in them, and pony tanks that are just left at full pressure all the time. I'm sure someone will have something to say about that, but in my experience that's what I've seen. Tanks are designed to be filled and emptied, and not fail.

Sent during my 10' deco stop

I'm very surprised.

 

[NAM001]

Use has no bearing on periodicity of testing and inspection requirements. If it did , everyone would go in saying it was only used once. hydro every 5 vis every year

Question for pony bottle users. I've made use of mine once. Ideally you never use it. How often do you get it visualed and re-filled? Hydros are done to check on metal fatigue, which is generally cause by repeated filling and emptying of a tank. So how often would you have to get it hydroed if it was almost never used and there wasn't a 5 year (US/Can.) rule?

 

[Superlyte27]

If your interpretation were correct, why do you think they chose to write "no cylinder ... may be charged or filled...." rather than the much clearer, "no cylinder may be used...." ? It would have been so much simpler.

Are you suggesting that it is OK for a tank to sit for 5 years or lwess with a cup of water inside; but not 8 years? BTW, that cup of water has little effect on the metal of my aluminum tanks.

No, I'm not suggesting 5yrs vs 8yrs, hence the need for an annual vip.
and, we weren't talking about rules for just aluminum or just steel. I'm assuming worst case scenario, not best case scenario, which is what I believe the DOT does also.

"be used" vs. "be filled" it's a lot harder to enforce one with hundreds of thousands of people using, vs enforcing the other with just a few thousand filling. Just my assumption. But, like I've already conveyed, I'll stick with the standards. You guys do whatever you want. It won't affect me one way or another.

 

[Bob DBF]

I get my tanks tested when they need it before they are filled. Sometimes it may be well past the "official" expiration date, I'm not inclined to drain a tank just to test it. The AL tanks wait the longest since They are not my favorites in NorCal waters.



Bob
---------------------------
I may be old, but I'm not dead yet.

 

[Edward3c]

... Someone mentioned a 2 1/2 year visual "rule" -- anyone else heard of that? I always thought pony's were yearly like any other tank.

In the UK cylinder testing for diving is:

* 15 Months - O2 cleaned.
* 30 Months - visual.
* 60 Months - hydro.

The values must also be inspected.

 

[redacted]

I believe that is exactly what the DOT regs say about hydro. A tank with expired hydro must be requalified before it can be filled but there is no prohibition against continuing to use the tank until a refill is required. For example, just because your emergency O2 tank has an expired hydro, there is no requirement to immediately drain and inspect the tank. It can continue in service until it is used and requires a refill.

"(ii) No cylinder required to be retested by paragraph (e)(1)(i) of this section may be
charged or filled with a hazardous material and transported in commerce unless that cylinder has been inspected and retested in accordance with this section and the retester has marked the cylinder by stamping the date of retest, the cylinder retester identification number unless excepted under this section, and any other marking required by this section. No person may mark a test date or a retester identification number on a DOT specification or exemption cylinder unless all applicable requirements of this section have been met. "

So what was it you found to be so funny?

Perhaps this update is a clearer:

§ 173.301
General requirements for shipment of compressed gases and other hazardous materials in cylinders, UN pressure receptacles and spherical pressure vessels.

....



(6) No person may fill a cylinder overdue for periodic requalification with a hazardous material and then offer it for transportation. The prohibition against offering a cylinder for transportation that is overdue for periodic requalification does not apply to a cylinder filled prior to the requalification due date.

 

[CT-Rich]

I had a AL80 sitting full in a closet at my parents house for about 2 years. the burst disk went and scared the sh*t out of them. They never let me store tanks in there house ever again. My understanding is that as long as the tank is never transported, no visual or hydro is required. (DOT= Department of Transportation). Is it a good idea? probably not.

I wonder if you have the cup of salt water in the steel tank scenario, would the oxidizing of metal significantly change the composition of the air over years? 80cu (72s actually would be most likely since they were the standard steel size for decades) is alot of O2. Roughly guessing about one pound of highly reactive oxygen. Plenty of Iron to make FeO2. Might be a fun problem for one of the chemist/engineer types. Of course this assumes alot of things about the tank, i.e. no coating on the interior and all sorts of things I probably haven't thought of....

Always fun seeing something blow up (in a controlled environment....)
MythBusters: Air Cylinder Rocket - YouTube

Any thoughts?

 

[windapp]

Unless you're talking about Aluminum 6351 tanks that suffer from sustained load cracking at the threads. I wouldn't knock metal fatigue under constant pressure. Keep in mind there is 3000psi pounding back and forth on the walls of a tank; its gotta do something. Air molecules aren't completely static.

No. The 3000 psi is a static load. It is not pounding back and forth on the walls of the tank. Air molecules move just as much when there is 15 psi air in the tank as they do when there is 3000 psi. The air molecules bumping into the walls of the tank do not cause fatigue. Variations in pressure due to temperature changes would cause a bit of cyclic loading because of the pressure change, so I suppose if you constantly expose your tank to different temperatures, this would contribute a little to fatigue. However as I stated, tanks are designed for over 100,000 cycles of loads cycling from 15-3000 psi. A 300 psi swing in pressure happening at most 10-20 times a year due to exposing the tanks to differing temperatures would not tend to make a huge contribution to the fatiguing of the metal.

The 6351 tanks were a case of bad design where the material was not suited to the application. Essentially, the threads fatigued much earlier than was designed for. This was an Engineering error.

And, to respond to Dumpster Diver:

Poorly constructed tanks will also fail prematurely because they are poorly constructed.
You are correct that not all properly tanks fail due to mishandling. Corrosion is also a factor, although one might technically consider this to be mishandling as well.
My understanding is that when aluminum tanks fail, it is usually due to mishandling, and when steel tanks fail it is usually due to excessive corrosion.

I am not sure exactly how steel tanks are designed, but an interesting thing to note is that steel has a fatigue limit while aluminum doesn't. You can design something to be made out of steel such that it will never fatigue under the loads being applied. Aluminum will eventually fail due to fatigue if it is continued to be cyclically loaded.

 

[FoxHound]

Hmm, rules rules rules.......

So its the scuba industry that requires vis done each year.....DOT only requires it at hydro....

As per luxfer's inspection guide it requires tanks be visual inspected at least once in a 12 month period.

Now this is a bit off topic, but interesting none the less seeing as how people here are pretty against breaking the rules.....how many have a O2 cleaned luxfer tank.....how many dive nitrox in a luxfer tank......technically from their inspection manual, this is a no go "To eliminate the risk of fire and serious injury, never fill a Luxfer scuba cylinder with pure oxygen or oxygen-enriched air mixture or any other special gas"

No where in the manual does it say that you can o2 clean a luxfer cylinder.

(catalina is a lot different rules surprisingly)

So it seems we really only partially follow the rules.

That being said, would I VIP a pony bottle every year......yeah prolly, just because I can do it myself. But I would not be concerned by it going over by a few months or so.