White lies told by your LDS when you first started

[rmediver2002]

A informational post on the Luxfer site about a year ago stated that fully 50% of the 6061 alloy tanks returned for failure of VIP testing did not have any damage...

Pretty big margin of error but as a friend of mine pointed out what about the 50% that did.

I am not at all suprised shops would require Visual plus, annual VIP, nor O2 cleaning procedures be performed by thier techs to get a fill... But the issue is one of money not diver safety in my opinion.

DOT only requires hydro testing at five year intervals. I support VIP testing but would like to see it explained to folks as a recommendation not a regulation.

Jeff

p.s. most of the tanks I have identified cracks on were within hydro specifications, they also showed distinct and multiple cracking easily visible to the naked eye but re-confirmed through use of visual plus testing. It is my belief that visual plus can be an aid to a tech in that it may cause them to more closely inspect an area with a slight or forming crack. I have also seen many shops that have defective or non-functinal components and had the techs explain to me that you had to hold the probe just so due to a short in the wire... (really effective testing there, well worth $30 huh?)

 

[Genesis]

at least not really.

Tanks are designed to fail in such a fashion that a crack will cause a leak of air BEFORE the material is compromised sufficiently to cause an explosion.

That is, it won't hold pressure before it goes "boom".

This is part of the engineering of ALL tanks, irrespective of the gas. There are multiple safety measures engineered into these things; the burst disk, the design of the neck, etc - all designed to insure that the tank will fail to hold pressure rather than turn into a bomb if it is approaching its failure point.

The 6351-problem is not yet fully understood, but there are suggestions that a batch of bad alloy was responsible, or that stress-related migration of alloy components and work hardening may be at the root of it. In any event, instead of the intended and designed-for leak what has happened in a few cases is a "boom" instead. Even so, VERY FEW tanks have gone "bang" - about a dozen, out of well over a million in circulation.

The problem with AL tanks is aggrevated by overfilling, which is sometimes done. AL alloys are not very elastic, and are much more succeptable to work hardening than steel. As a consequence overfilling is REALLY bad for AL tanks, and can lead to the neck cracks - this is INTENTIONAL, as that is the weak spot - intentionally - in the design of the tank.

Finding of a crack does not necessarily mean that the tank is about to blow up. There are, in fact, even specifications for what is and is not an acceptable "void" in the threads, as I'm sure you're aware if you're doing inspections.

But even a tank that DOES have a crack in the neck area that reaches unsafe levels SHOULD fail by releasing the pressure rather than exploding.

It is that failure of the design parameters of the original tanks that has puzzled the folks who do this stuff for a living (and who originally certified the 6351-alloy tanks as "ok" for sale in the US) when they started blowing up.

Again, there is no history of 6061-tanks exploding. In fact, I've been unable to find a report of ANY 6061 tank going "boom".

Leaks don't count - that is how these things are DESIGNED to fail - its part of the safety in the original design.

 

[diverjed]

Genesis & Jeff:

Both of my tanks were aluminum, way less than 10 yrs old.

Is that the 6061-alloy? More than likely?

 

[zeN||]

oops

 

[Genesis]

Both of my tanks were aluminum, way less than 10 yrs old.

Is that the 6061-alloy? More than likely?

Not more than likely.

Absolutely.

Luxfer and Kidde were the two major users of the 6351 alloy in the US; Kidde is no longer making scuba tanks, and Luxfer stopped making them out of that alloy in the late 80s.

All tanks made in '89 or later are made out of 6061. Catalina never used the bad alloy irrespective of the date of manufacture. Some tanks made in '88 by Luxfer were made of the bad alloy, and all made in '87 and earlier.

There is another alloy that is apparently just as bad as the 6351, but as far I know it was never used on tanks certified for use in the US. There have been a couple of European explosions traced to that alloy.

 

[diverjed]

That certainly explains a lot. Thnx.

 

[Gio]

runvus4 once bubbled...
My dive shops were pretty good, only "white lie" that I can remember them telling me was "Diving is not an expensive sport"

Ha ha....yes! I was told that too...actually, maybe thinking that that statement by itself was not strong enough they added: "Well, you know, once you own some of your gear, you just have to shell a couple of buck to get your tank filled: it's cheaper than a movie, and a lot more fun..."

 

[ZenSquirrel]

raviepoo once bubbled...
"The most important thing about scuba is looking cool." (In other words, make sure your gear is color coordinated.)

and

"You don't want to go deep. There's nothing good to see below 60 ft anyway."

I remember reading through my PADI OW book. Every section on gear listed the main things you look for in gear and then ended with "item X is available in a variety of colors and styles." Cracked me up every time.

 

[hotsoup631]

Like most people, I started my dive experience at the LDS. I don't think my LDS is bad, but I've been burned enough that I'm also wary of it. It annoys me how my expenses have doubled and doubled again. It reminds me of a game that I played in business school. The only winning strategy was not to play in the first place.

But, I really want to dive, and I want to avoid the majority of the "cattle". I know it sounds bad, but I really felt that some of the people in my OW class were a danger to themselves and to their buddies!

It sounds like many of the people posting have extensive dive experience, so you're not tied to the LDS's.

However, what is a beginner diver to do?

On one hand, my LDS are a source of information and instruction. On the other hand, my LDS is pressuring me to spend, spend, spend. I realize that I'm getting ripped off, but there seems to be little choice in the matter.

 

[Genesis]

However, what is a beginner diver to do?

On one hand, my LDS are a source of information and instruction. On the other hand, my LDS is pressuring me to spend, spend, spend. I realize that I'm getting ripped off, but there seems to be little choice in the matter.

There are indeed choices; you just need to make the effort to handle the decisions on your own.

The good news is that by doing so, you will become what you were promised in your OW class - the ability to dive independant of instructors and divemasters.

The bad news is that you will have to think, and evaluate, for yourself.

Oh wait - is that really "bad news"? No. Its really good news.

By thinking and evaluating for yourself, you become a better diver. You become more aware of how your gear works and why. You will know when its not working right, probably before you get in trouble as a consequence. You might even learn how to fix it on your own.

In short, there really is no downside to taking responsibility for your own diving. Start a "dive club" - find others who like to dive, set up a mailing list or phone circle, and go out and dive.

Instruction? What do you need to learn that can't be learned at least as well by spending the class money on actual time underwater? There isn't much, really...

Oh sure, there are classes you may want to take anyway, and that's ok. Rescue comes to mind, if you can find a good one.

But the problem with just running out and taking classes is that you don't know what you need to learn until you've had some time underwater, and have thrown away the "training wheels." And the LDS will help yourself to a fat chunk of the contents of your wallet in "helping" you.

What's worse, as you've seen, they might not actually be teaching you good things! It would really bite to be "taught" things that actually make you MORE dangerous, no?