Question on tank life and hydro

[Gadget Soldier]

After playing for so many years, all of my tanks will be reaching their end of their 15 year life next year and I'm starting the process of looking for replacements.

While perusing online paintball stores, I noticed that First Strike Tanks are UNISO certified and that they have a never ending lifespan.

I have tried google and I don't think I got a clear answer (or probably looking in the wrong place) on how and why First Strike Tanks have a long lasting lifespan.

[Seajay]

• Tri-Label UN ISO Certification–Universal Acceptance
• Lifetime use bottle (still required 5 year re-hydro)

https://first-strike.com/first-strik...on-fibre-tank/

It's the construction of the tank which doesn't expire. Hydro still required though.

[DocsMachine]

Adding a little detail, the issue is fatigue life. The more a material flexes, the weaker it gets- the classic example is bending a paperclip back and forth 'til it breaks.

Some materials, like spring steels, have a very long fatigue life. You can bounce that spring millions of times and it'll come back to shape each time. Others have a limited fatigue life, such as aluminum. If you made an aluminum spring, after a much shorter time than the steel, it would no longer 'spring back' all the way, and not much past that, it would break- and with a lot less force needed than on un-fatigued metal.

In the case of our tanks, they of course expand and contract, very slightly, each time they're filled and emptied. For a steel tank, this minor movement is well within it's very long fatigue life- it's not uncommon to find gas-torch tanks, today, that still have WW2 or even Nazi Germany hydrotest marks. (I once had a 20-pound CO2 tank whose first hydro stamp was 1944.)

With an aluminum tank, under a certain size- the classic 2"- the amount of flex is so small that it has little or no effect on the life or strength of the bottle. But larger ones do, and so are periodically hydrotested.

And basically, hydrotesting means they over pressurize the tank (filled with water in case it ruptures) and see how far it 'returns to normal' afterward. That is, if the tank expands and stays expanded after the overpressure, then the metal is getting weak- fatigued- and will no longer "spring back" anymore.

With the older fiber-wrapped tanks, you had a thin aluminum shell, wrapped with fiberglass or carbon fiber to give it the strength. The problem there is that both the aluminum and the wrapping had a finite fatigue life, so unlike the big steel tanks which can be used essentially forever, the fiber-wraps had to be decommissioned after a certain amount of time.

But, technology marches on. The original fiberglass-wrapped tanks had to be hydroed every three years. Later, the better carbon-fiber and/or kevlar-fiber wrapped tanks were allowed to push that out to five years. And now, modern tanks are good enough to do away with the 15-year overall lifespan. I seem to recall one company was using a thin stainless steel inner shell, but honestly, I don't know if that's still the hot trick.

Personally, I just wish one of these makers would reintroduce a 68-ci size 3K tank with the new build quality, for those of us that still have a ton of old 3K systems floating around. (I think I have half a dozen Flatlines alone. )

Doc.

[Cyberpyr8]

I own one of these first strike tanks and my concern is when it does expire, am I going to be able to get it re-hydro'd for a reasonable price. Since I uncontrollably seem to keep buying tanks these days, I will probably just throw it in the shed and use it for around the house testing, refilling it with my scuba tank rather than mess with it. But it would be nice to know if/when it needs to be re-done that I won't have to send it back to First Strike to get it done or cost me almost as much as a new tank. It also seems that most of the FS tanks I have bought the last few years all had 2018 born dates. That means it will need to be done again in 2 years.

[Seajay]

UNSI is just the lifespan of the tank as Doc amazingly described!
You still need a DOT certification which is the hydro test every 5 years. There is no 15 year lifespan, that's all it means, so in 20 years you can still use that tank if it passes a hydro test. You can get a hydro test done wherever you normally would, I don't have anything local so I just use Ninja.

[Gadget Soldier]

Thank you everyone for your input, at least I have a better understanding on why First Strike tanks have a long life. I'll probably go with those tanks when the time comes to replace my current ones.

[djeclypse]

The FS Hero tanks and the Immortal Air tanks are the same bottle from the same manufacturer as I was told. If you can purchase just a bottle directly from the manufacturer you'd definitely save some coin, just swap your current regulators over to the new bottle. Immortal has a tank only option for their 77/4500 for 170 as opposed to 220 with reg.

EDIT: The tanks are made by AMS Composite Cylinders based in England with manufacturing in Korea. Their website does not seem to offer retail purchases.

https://ams-composites.com/lightweight-carbon-composite-cylinders/

[custar]

With an aluminum tank, under a certain size- the classic 2"- the amount of flex is so small that it has little or no effect on the life or strength of the bottle. But larger ones do, and so are periodically hydrotested.

To OP: Doc touched on this. If a smaller tank is an option for you, tanks under 2" in diameter and 2" in length do not require re-hydro.

[Grendel]

2" OD and 24" length I believe was your intent, typos are a bitch

[custar]

To OP: Doc touched on this. If a smaller tank is an option for you, tanks under 2" in diameter and 2" in length do not require re-hydro.

You are right; 2" x 2'.