What to do with outdated Kevlar O2 bottles

I came across a Kevlar O2 bottle manufactured in 1986. It looks perfect, but it is beyond the 15 year lifetime mandated by the DOT.

Anyone know of a way to rejuvenate this thing.

Thanks,

ox

That's a hard time. Use at your own risk.

This came off the Mountain High glider site...

If the cylinder is to be used in type certified aircraft, by current DOT protocol, it must be hydro tested every 3 years and taken out of service if it fails or after 15 years from the first hydro test date comes about. Even if the cylinder passes hydro test. DOT protocol does not specifically detail any requirements for these cylinders if used in experimental aircraft. As of July of 2006, any Kevlar cylinder tested after that date can be hydro tested every 5 years (instead of 3). That is true for cylinders manufactured before that date.

Some more research into the DOT wording is needed...

I've been involved with the use of the composite bottles since they first came out, the 15-year life limit on the bottles was based on a lack of knowledge during the early years of how the bottles would stand up to age under use, not due to any real or perceived failure mode. There was simply no knowledge of how this "new material" would react after 25 or 30 years and so DOT reacted with an abundance of caution and put the 15 year life limit on all composite bottles.

There is still no evidence today indicating that there is any significant age-related failure mode (exclusive of physical or heat damage) that would preclude use of the composite bottles into the 20-30 year range, but the rules have not been changed due to lack of review. The industry has no driving need to force the review, since they keep selling new bottles as the old ones expire, and the market can't force the review since DOT will only accept the data from the manufacturers. I can tell you this though - I personally have a 3000psi composite bottle (42 SCF capacity) that I have had in service with compressed air (literally thousands of cycles) continuously since 1986 and it shows zero degradation. I have done my own hydro's on it annually (no, I'm not a certified hydro shop but I am an engineer and I can read the specs, I built my own unofficial rig) and it continues to pass the spec at 1.5x rated pressure. YMMV. I do not use it for any commercial purpose.

Officially, by rule, the tank has to be taken out of service at 15 years - meaning that no reputable shop will fill it for you, and no certified hydro shop will return the bottle to you in serviceable condition (they will punch a hole in it first). There are regulatory teeth in the law for commercial operations that fill, test, or service these outdated bottles, but I am not aware of any enforcement action they can take against private citizens using the outdated bottles for their own private (non-commercial) use. You can fully expect FBO's to refuse to fill the bottles if you need oxygen on the road, but if you have your own transfill equipment there is nothing to stop you from filling it other than your conscience based on inspection of the bottle, and a healthy dose of Darwinism.

I totally agree that the composite bottles will last as long as you care to use them (technically, not legally of course).
I did composite design for Boeing and McDonnell Douglas a while back, and for this type of application, the composite bottles likely grow stronger with age. Plus the concept of rapid failure due to crack propagation that metal has does not exist with composites. You could drill a hole in the composite bottle, patch the hole, and the only issue will be whether the patch will hold (not recommended of course, but you get the point).
Despite all that, the legalities will trump the engineering. I totally agree with airguy's comments.

They would destroy it?

Sounds like I better not take it to a certified shop for hydro testing or they will return it to me with a hole in it! That would be disappointing.