Aluminum Hydro Problem

[pasley]

Please, someone find one article in the last decade were a Luxfer Cylinder went boom and sent pieces everywere..I double dare you to find one!

Oh this one was just too easy.

In addition to the above, would you believe the U.S. government Department of Transportation?
http://hazmat.dot.gov/not99_11_3al.supp.pdf
http://hazmat.dot.gov/3al_mainreport.pdf

If Luxfer is not listed by name, just keep in mind they were the principal mfg of tanks using the suspect alloy either under thier own name or mfg for others. I also figure they did not do the $50.00 rebate offer last year for fun. There was a reason for it, like wanting to get the suspect tanks off the street. But that is just IMHO.

A more recent article, that is not related to the composition of the tank is from LUXFER themselves: http://www.luxfercylinders.com/support/bulletins/20040809.shtml

 

[Groundhog246]

I'm told by a local LDS, that steel cylinders with internal coatings are no longer allowed (ie, when they come in for testing, vsisual or hydro) they are condemmed. Some shops don't seem to keep up with the regulations though. I was there when they pulled the valve out of an older AL tank that had passed hydro and vis at a large Toronto shop last year. The valve had a plastic pitot tube, the use of which has be banned for many years. A minor matter to replace it with a metal tube, but it should have been done long ago. If they miss or skip that, how good is their visual? I've been told the same shop does not do Eddy testing, just a visual!
At both of the 2 local shops where I've had visuals done, the boots are removed to inspect the area, eddy current is done on all AL tanks (some don't do it on newer alloy tanks), as well as a thorough visual examination and ALL exterior labels not applied by the manufacturer are removed to ensure they are not covering up damage.

 

[Ontario Diver]

I'm told by a local LDS, that steel cylinders with internal coatings are no longer allowed (ie, when they come in for testing, vsisual or hydro) they are condemmed. Some shops don't seem to keep up with the regulations though. I was there when they pulled the valve out of an older AL tank that had passed hydro and vis at a large Toronto shop last year. The valve had a plastic pitot tube, the use of which has be banned for many years. A minor matter to replace it with a metal tube, but it should have been done long ago. If they miss or skip that, how good is their visual? I've been told the same shop does not do Eddy testing, just a visual!
At both of the 2 local shops where I've had visuals done, the boots are removed to inspect the area, eddy current is done on all AL tanks (some don't do it on newer alloy tanks), as well as a thorough visual examination and ALL exterior labels not applied by the manufacturer are removed to ensure they are not covering up damage.

The steel tanks that you are referring to had a vinyl coating applied to the inner surface. The problem is that if the vinyl sleeve gets a pinhole in it, water gets in and the visual inspector cannot see the pitting. PSI standards call for a failure on any tank that you cannot see the metal to check for pitting.

The plastic dip tubes are expected to be replaced but are so rare now that a lot of people don't know about it.

Doing an eddy current exam on all AL tanks can be counter productive. You would in fact need two machines because it is "tuned" for a specific alloy. A good shop will use a eddy system in conjunction with a trained visual inspection. There are many who believe that a good inspection will detect any cracks before they become an issue. I have been told by a PSI trainer that it takes at least 4 years for a crack to become dangerous and it should be detectable by visual inspection for at least three of those years.

Visual inspections are not rocket science. They are fairly easy to do once you learn what to look for and have a few good tools.

 

[hecker-the-wrecker]

Just talked to my lds again (for another fill) They do utilize the"eddy current" inspection, and most steels they see problems with have come from "out of our area", the shop is highly reputable, and there are alot of divers from out of the area(tourist town). Thanks for advice regarding the eddy current testing, and links of exploding tanks, Pasley. What an eye opener!!

 

[wedivebc]

The steel tank referenced is mostly intact also judging by the pics it was one of those tanks that had an internal coating that was well know for hiding problems! The tank didn't break into several pieces like usually happens with Al tanks it became a projectile.

Here are some al failures
http://www.scubabomb.freeservers.com/Scubadag.htm
http://www.scubabomb.freeservers.com/Cscuba.htm
http://www.connected.bc.ca/~baquatics/explode.html (luxfer - also below)
http://www.airsource-one.com/rupture1.html (several pages of photos)
http://www.airsource-one.com/beaver.html (this is a luxfer)

Which one is the steel tank?
It is pretty amazing that with so many dive tanks out there there are so few tank accidents.
I recently filled a 1975 usd al 80 that was vis'ed by Beaver Aquatics, the victim of this explosion http://www.connected.bc.ca/~baquatics/explode.html
They seem to be OK with the older tanks.
Anyone know of a steel tank exploding?

 

[rbeck]

We also have had some steel tanks that have lasted a VERY long time. All of these we bought used so don't know how they were treated before we had them, but we kept them up to date on hydros and VIPS. Many of them were probably 30-40 years old, at least. Now, it seems that everytime we take them in for hydos one or more fails. Has the testing equipment gotten more sensitive or the thresh holds for failure changed? Or, have our tanks just run through their life times?

 

[Bob3]

Anyone know of a steel tank exploding?

Yah, the latest US fatality was from a steel HP bottle, happened last month in FL.

That being said, ALL aluminum tanks will fail if they get enough fill cycles.
Fortunately they're engineered to handle a minimum of 10,000 cycles, so a person would have to be doing a heck of a lot of diving to reach the magic number.

 

[wedivebc]

Yah, the latest US fatality was from a steel HP bottle, happened last month in FL.

That being said, ALL aluminum tanks will fail if they get enough fill cycles.
Fortunately they're engineered to handle a minimum of 10,000 cycles, so a person would have to be doing a heck of a lot of diving to reach the magic number.

Wow sorry to hear that! Do you have any info? I believe steel tank failure is much rarer than AL. I know of one steel tank that went up like a rocket leaving the bottom as a base due to ring pitting. No-one hurt though just some new underwear required.

 

[Bob3]

http://www.keynoter.com/articles/2004/08/06/news/news17.txt
is for the FL incident. From what I know, there actually was oxygen involved, & not just the usual bad reporting where air = oxygen to those bonehead reporters.

.

Or, have our tanks just run through their life times?

Actually, having your tanks hydroed could well be the reason for the steady rate of failures. Pumping the critters up to 3x their working pressure can put a strain on the things.

 

[Groundhog246]

Yah, the latest US fatality was from a steel HP bottle, happened last month in FL.

From another thread. From another board...

It has been reported to PSI headquarters that the cylinder was manufactured by Luxfer in 1987, made from 6351 T6 alloy. Eyewitness accounts indicated that the cylinder had been dropped in the parking lot prior to being taken in for filling.

NOT a steel tank it was a 30CF AL. See http://www.luxfercylinders.com/news/releases/20040809.

Wonder if maybe the valve/tank O ring wasn't replaced before filling with O2 (pure speculation on my part).

Also, Hydro test is to 5/3 (1.66666 times) not 3X the working pressure.

And just found another Luxfer release http://www.luxfercylinders.com/news/releases/20040823.shtml it was a 6061 alloy, not the old one.