Tank Age Anxiety

[happy-diver]

Time to start saving for some decent steel tanks and a stress free life

 

[mderrick]

I've run into several shops that have a 20 yr cut off for aluminum cylinders and even one that refused to fill a person's STEEL 72's that had passed hydro and were from the 70s. Age was the ignorance based reason.
I have heard of one hydro place that decided to stop doing older aluminums because they were getting all kinds of grief after passing a cylinder that some shops decided not to fill.
If it has a current hydro and vis we fill them.
6351 alloys the owner has decided not to and he owns the compressor.

Fill Express was one of the 'early adopters' in our area for refusing to fill the 6351's. At the time we were being told by industry experts and manufacturers they were perfectly safe to fill when 'properly inspected with an eddy current test' and based on the conventional wisdom that sustained load cracking in 6351's took years to develop and SLC would be detected by eddy current (thus rejecting the cylinder) well in advance of any concern regarding safety.

We would not accept 6351 cylinders for hydro test, because we had multiple experiences where the customer would pay us to hydro the cylinder and other shops (especially in the Keys) would refuse to fill them and the customer would boomerang back angry at us for passing a cylinder that 'failed'. However, prior to changing our policy not to fill them at all, we WOULD fill the 6351's if WE did the inspection. If a 6351 came in that didn't have our VIP decal on it, I would VIP once at no charge and then fill it.

Following the cylinder explosion and fatality during a fill at Bill Rennakers' Cave Excursions, there was a rumor heard from several sources the cylinder in question was a 3651 alloy (which later proved to be not the case and irrelevant in any case.) This served to further increase my anxiety regarding filling 6351's, but by this time 6351's coming in for fills were rare; mostly brought in by travelling divers from northern and midwest states where 6351 didn't seem to be much of a concern. Then a little while after Bill's misfortune, a good customer brought in half a dozen Walter Kidde SCUBA 80's he had picked up at a flea market, which of course were all made with 6351. I can still remember the feeling of dread I had when I first saw them coming in the door, the distinctive shape of the crown making them instantly recognizable as WK.

They of course all had expired hydro tests. I had to drain the cylinders to remove the valves, so no way of knowing how long they had sat filled (or the fill pressure, I didn't check) and unused, but certainly for several years. I personally inspected the crap out of the neck threads on all of these WK cylinders, both visually with two different devices and with one of the early eddy current test machines. Then I took them to Hydro Stat to get the hydro current and when I dropped them off Rick did me a favor and inspected the neck threads again using his tools and eddy machine while I watched.

After they came back from hydro, I did another visual (but not an third eddy current test) so I was confident there were no issues, and filled them regularly for a year. When time came to renew the VIP a year later, I decided to personally inspect the threads again.... as I was removing the valves I saw one that had a crack in the threads so significant that I could see it while standing next to it and looking down... much less needing any tools or eddy current testing. So much for the conventional wisdom that sustained load cracks take years to develop.

That was first day of the "no fill" policy for 6351's at Fill Express.

Fill station operators have the right to refuse to fill a cylinder for no reason or any reason. I've refused to fill cylinders because I didn't like the color of the paint.

 

[Belzelbub]

However they are older tanks, one of them is a Catalina with the first hydro test in 1993 and the other a Luxfer manufactured in 1990.

@DiveGearExpress addressed the main concern with older AL tanks. As yours are newer, this shouldn't be a problem. They weren't made with the alloy that was cause for concern, so from a safety perspective, as long as they are kept current on VIPs & Hydros, nothing to be concerned with.

You may, however, run into dive shops that won't fill them. I've heard of some shops using 1990 as a cutoff, and others using 20 years. The 1990 makes some sense as it's an easy number to remember, and doesn't rely on the diveshop employee remembering which brand were OK before then and which weren't. The 20 years, however, doesn't really make much sense. I can only imagine that that policy was instituted around 2010 and never updated.

Depending on where you are, the above may or may not be a real issue. As long as you can get the tanks filled, keep using them. Nothing wrong with them just due to the age.

 

[edwants2dive]

Came across this info in some of my own research. The exception to this is the 6351 alloy aluminum tanks but per DOT they are technically good until they fail eddy current testing. Most dive shops won't fill or test those so I stay away from them ( I now stay away from all AL tanks except my pony).

DOT-3AL gas cylinders must be tested every 5 years and have an unlimited life.

SP-Cylinders Special Permit

DOT-3AA gas cylinders must be tested every 5 years and have an unlimited life. (Unless
stamped with a star (*) in which case the cylinder meets certain specifications and can have a 10-year hydrostatic test life) (SCUBA cylinders are not eligible for the 10 year hydro per DOT regulations.)

 

[CT-Rich]

IF I were shopping for tanks, I would pass on a AL tank that old. That does not mean the tank is dangerous or “bad”, but you might run into a shop with a blanket policy that would decline to fill it. Since the tank is in hydro and vis and you have some place to fill it, dive the crap out of them. shops sometimes create blanket rules to avoid issues with their least component employees.