Buying old carbon fiber tank?

[dem66]

Sorry guys if this has been discussed but I did a search and could not find what I was looking for.

I have seen on ebay carbon fiber tanks that are 15+ years old for sale. Is it ok to use these tanks if you will fill them yourself? I understand you can't have them tested and certified after 15 years so no one can fill them for you. If they fail is it a catastrophic failure as in explode or is it that they will just develop a leak? If they have a catastrophic failure of course you would not want to use them but if they are just going to develop a leak over time I don't see where that would be a safety issue for airgun use. Now if you were a fireman in a fire that would be a different story.

So my main question is: Is it a bad idea to buy one of these tanks no matter how cheap they are for airgun use?

Thanks guys,

Dan

 

[ztirffritz]

Look about 10 posts down (currently) and you'll find details of my eBay tank build project. It includes a link to 65.5 cft tanks that still have 8-10 years of life left for $115. The guy has several hundred of them. I personally wouldn't use a tank that hasn't been tested/inspected. Yes, if you have the means to fill it yourself you could continue to use it. And it should be ok to use for about another 15 years if maintained. But you'll have a dangerous wildcard on your hands. After 15 years you can't get the tank inspected. No one will do it, or shouldn't at least. That means your using a tank of unknown provenance, that can't be verified, and may or may not fail at any time. I think the middle ground between new and expired is the better route. You get a verifiable tank, at a lower cost with useful life remaining.

Another option, would be to get one of these setups for $195. The tank is good for 5 years, but you should be able to replace the tank in 5 years with another used one from eBay for $100 or so. You'd still be ahead of a new system, and it would have a known good starting condition.

 

[ztirffritz]

I just came across this article linked on another forum:

http://tbo.com/news/st-pete-veteran-killed-by-exploding-scuba-tank-256967

I'm sure that this isn't common but it does make you understand the scope of the pressure inside the tanks we're playing with. His was probably a 3000PSI tank. Ours are 4500psi. A bomb indeed.

 

[FukoChan]

As to what would happen, I spoke with a scuba instructor about what could happen with a tank that is out of hydro. He replied it would blow anything within 600 square feet and possibly more away, acting as a bomb essentially. As to what would happen to your body? People have cut themselves with high pressure water(pressure washers) so you could imagine what would happen a 4500 pounds per square inch carbon fiber bottle with 75 cu Ft. Just don't do it and buy some safe verified ones. 

 

[dem66]

Thanks ztirffritz that is kind of what I was expecting to hear. I took a quick look at your post and will spend more time studying it when I got time. One of my issues is I live in a small isolated town in the mountains and will have to travel 100 miles to find someone to fill a tank so I plan on getting a compressor and doing it myself.

 

[ztirffritz]

That's completely reasonable. But that doesn't mean you can't get a tank that is at least within it's 15 years life span and get it tested. This place will let you ship a tank to them and they'll test it and return it. For a fee they'll remove the valve and put it back on too.

http://www.hydrotester.com/

Then you're good for another 5 years.

 

[dem66]

Thanks for the link on hydro testing I wasn't sure how I was going to get that done.

 

[snakedoctor9]

I saw a demonstration of a carbon fiber tank tested to the limits. It did not explode. It split. The air rushed out violently but there was no shrapnel. I'm sure that if you were on either side of the tank, you would not have a great day though.

 

[ajshoots]

Steel and aluminum tanks can and will explode in a bomb type fashion. Carbon scba bottles based on limited failures don't explode, but fracture and release air in a scary "poop your pants" kind of way.

I have a compressor, but will have my tanks hydroed and after 15 years, they will get holes drilled in them and I will buy new. I understand saving money and being frugal, but this hobby is not cheap and tanks are not the place I would try to save money by using them after there DOT service life.

 

[Nancy-Liu]

The most important matter for using a tank is the safety. Carbon fiber cylinder is safer compare with metal tanks, because it is wrapped with carbon fiber and glass fiber and could bear more than 102 Mpa burst pressure. But still a new and good quality tank is recommended when you choose tanks. Safe and good quality come first and price come second. Of course, cheaper one is always better if it is in high quality. That is my suggestion. Any other concerns you may feel free to ask.