Digital Wave is the only company I know of that is authorized to perform Modal Acoustic Emission (MAE) testing to extend service life of CFFC cylinders. From what I can tell you send them the cylinder, they test and send back. If your cylinder fails the test they still send you a used one that has passed the test. They cover over the original cert and glue on an updated cert that extends your cylinder for an additional 5 years. You can do this two more times for a total extension of 15 years or 30 years total service life.Info on CFFC tank life.
http://media.wix.com/ugd/d00b78_72625b919876457fb9191418c1259c6b.pdf Digital Wave Corp does this, but when I checked into it, the cost was more than just buying another CFFC tank that had 3 to 5 years remaining service (~$300).
What I do with expired tanks that are in good condition is have them hydro’d, but NOT ask for recertification. Some shops will perform the one minute 7500 psi hydro, some won’t. Shouldn’t be any skin off their backs, you are paying (approx. $30) for the labor to hydro the tank. You don’t care if they put a sticker on it or not, you just want to know if its safe. I’d say only dive shops that do their own hydros are candidates for this.
Another option is to drain down the tank, take off the valve, and inspect the tank yourself looking for moisture, cracks, discoloration, etc. You can’t see the entire inside unless you have a boroscope, but you can get a pretty good idea with a bright flashlight. Then if its OK, change out the software (o-ring) and put the valve back on the tank. If your tank was made IAW ISO 11119-2, and is a DOT-E11194, DOT-E-10915 or DOT-E-10945 tank, then it was DESIGNED for a 30 year service life.
If you have tanks that are within a few months of end of service life, then take them to get hydro'd, at least you'll get another 5 year sticker and be good for that amount of time. You'll need to fill your own tanks after the service life expiration of course.
