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antique diver
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Bottle went "BOOM"

Fri Jul 15, 2016 7:15 pm

tank in trunk.JPG
How many other old timers remember the late 1960's poster this was on? :shock:
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The older I get the better I was.

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Bryan
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Re: Bottle went "BOOM"

Fri Jul 15, 2016 7:33 pm

NASDS Safe Scuba hardback edition and it was also on the big VIP posters they put in the stores....At least thats as early as I can remember it...

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Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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antique diver
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Re: Bottle went "BOOM"

Fri Jul 15, 2016 7:54 pm

Bryan wrote:NASDS Safe Scuba hardback edition and it was also on the big VIP posters they put in the stores....At least thats as early as I can remember it...

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Right! And you aren't even "old".

I had one of those posters in the shop in the early 70's, and it sure helped to drive home the importance of "VIP's". I recently got the gift of another one, still rolled up in new condition, from the Vintage friendly folks at Arlington Scuba. (Arlington, Texas)
NASDS VIP Poster.JPG
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The older I get the better I was.

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Bryan
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Re: Bottle went "BOOM"

Fri Jul 15, 2016 7:59 pm

Close...our posters were all that hideous gold color NASDS was so fond of in the late 70s. And there was a picture of the oval VIP sticker and the silhouette At-Pac diver on them. It was right above the fill station where I filled several chrome plated 72's.

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Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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1969ivan1
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Re: Bottle went "BOOM"

Sun Aug 21, 2016 9:13 pm

That is a very cool poster. It reminds me of the tank in the red coral diver video that the diver showed Cousteau.

DAAquamaster
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Re: Bottle went "BOOM"

Tue Aug 23, 2016 7:54 am

It's an interesting picture for a couple reasons:

Steel tanks tend to split like this one, usually with no large fragments. Aluminum tanks are not as friendly as they then tend to shatter and send several large fragments flying through the area.

The tank in the picture appears to have failed due to a line of rust pits along the side of the tank. Add water to a tank, leave it on it's side a couple years and don't inspect it, and this is the result. The thicker metal in the bottom of a tank, along with any rust or pits being more obvious in the bottom of the tank, are reasons why they advise storing tanks vertically, but the reality is you need to look inside a steel tank every year or so.

3AA steel tanks are over engineered enough that they effectively have no fatigue life and the only thing that kills them is rust.

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luis
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Re: Bottle went "BOOM"

Tue Aug 23, 2016 10:33 pm

DAAquamaster wrote:
3AA steel tanks are over engineered enough that they effectively have no fatigue life and the only thing that kills them is rust.

Even rental tanks that are filled daily (or even a few times a day) don't experience enough cycles to make a dent into fatigue life curves. The fatigue life curves are normally plotted on a logarithmic scale.

Fatigue failure is a big issue with the number of cycles experienced in rotating machinery or a vibrating object, not so much for a recreational scuba cylinder.

Also most fatigue life curves are based on reversing stresses. In other words stresses that cycle in both direction (positive and negative cycles), like bending a beam back a forth. A pressure vessel only sees positive tensile stresses, which is less of a fatigue issue.

The statement that "3AA steel tanks are over engineered" is not really a true statement. A cylinder is just a very simple geometry and it is very predictable. The stresses can be easily calculated for a theoretically perfect cylinder without imperfections. It just happens that the fabrication methods also produce a fairly reliable, uniform wall thickness cylinders.

Yes, rust pits is what will destroy a steel cylinder.
Luis

Buceador con escafandra autónoma clásica.

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