2x2 rule sticky/pinned

[zenmic]

Does anyone still have a copy of the 2" or 2' rule for those 13ci tanks? The old forum had it sticky/pinned. A friend was asking as they are about to buy a few of these tanks, and I wanted to point them to the sticky for reference.

[Chuck E Ducky]

Every time I have needed it I just google it. 2” round less then 2’ length (Aluminum 3k HPA tanks) are exempt from hydro. It’s on the DOT website and Most hydro pages have the info as well. Never had an issue yet in +20 years after showing the rule in black and white.

https://www.law.cornell.edu/cfr/text/49/180.209

[Grendel]

govinfo.gov link:

https://www.govinfo.gov/app/details/CFR-2011-title49-vol3/CFR-2011-title49-vol3-sec180-209/context

https://www.govinfo.gov/content/pkg/CFR-2011-title49-vol3/pdf/CFR-2011-title49-vol3-sec180-209.pdf

Snap shot of relevent table out of 49 CFR 180.209:

[zenmic]

Thanks everybody!

[Nish]

Job well done.

[Frog of Peace]

I think it is silly they limited the outside Diameter.
That ist an incitation to make the walls as thin as you can to maximise capacity at the cost of security.

[lew]

Government was involved. What did you expect? Perverse incentive is their bag.

[SR_matt]

So I admit this is a bit of a necro post but I think the part you missed in your statement is as thin as possible as still meet the minimum safety factor. The tanks have to be better than a 1.66 safety factor (I.e. they are tested 66.66% above their working pressure). Thickness is pretty irrelevant as long as it meets the requirement. Just look at CF tanks from 20 years ago until now, they use probably 50% less materials.

At the end of the day someone is buying a tank for its capacity and rarely it’s outside dimensions. With the 2x2 rule the makers just extend the tank to get the volume they need since the thin profile of the tank is what allows them the exemption as it is proportionally stronger.

[Trbo323]

Question on this, aluminum tanks have no fixed life correct? So a 13/3k is good forever?

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[Grendel]

Question on this, aluminum tanks have no fixed life correct? So a 13/3k is good forever?

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This is based on US D.O.T. 49 CFR 1XX and bottles used in paintball. If you dig enough in these documents you can always find exceptions and more frustrating infinite loops that have no answer.

The short answer is no.

The longer answer is dependent upon the specific bottle and permits it is manufactured under as the original manufacturer applied for their permitting under. If the manufacturer applied for their permit under FRP-1 design testing the service life of the bottle is 15 years maximum and has to be clearly defined under their special permit (this is us typically). If they are working under ISO 11119-2 then the service life of the bottle is between 10-38 years and varies bottle to bottle (this 38 years is defined as "unlimited life" in the documents so not a literal definition but instead a bureaucratic definition). Under CFFC it is either 15 years or 30 years but 30 years requires specific administrator approval.

So one of our aluminum bottles that meets the 2x2 rules does not have to be hydrostatically tested but still has a max service life, most commonly 15years (never seen one that did not, does not mean there aren't any just never seen them). Carbon Fiber bottles have a max service life of 15 years period with no exceptions.

The table I posted in an above post is the requirements for retesting and does not include references to end of service life.