Steel 72’s passed hydro, but .

[Luis H]

Some people are just weird about anything old. They figure that just because they are getting weaker and more brittle as they age, everything else must be too. Actually, some metals age harden and can become brittle from time alone, but steel isn't one of them. It's cycles, not age that matter, and even cycles only matter a little. Dive shop people might not understand this, but a hydro tester ought to.

You might try to cheer them up by pointing out that your tanks are newer than the USA's main line bomber, the B-52, which is still in full time service!

I agree.

I just looked up an S-N curve (stress versus number of fatigue cycles) for ASTM 4130.
ASTM 4130 is the steel that most 3AA steel tanks are made out of.

With a maximum repeated load of 49,600 psi the maximum number of cycles it can experience is in excess to 10,000,000.

The 49,600 psi is the hoop stress a steel 72 will experience at a fill pressure of 2500 psi.

Even with stresses close to those experienced at hydro, the fatigue life of a steel 72 is close to 200,000 cycles.

The above assumes a cylinder structure that has not being compromised by rust or heat.

All 3AA cylinders are design to the same test stress of 70,000 psi (based on an equation provided on CFR49). The stamped working pressure is 60% of the test pressure (60% is just the inverse of the test pressure of 5/3).


Nemrod
Who is Lewis? I have seen my name commonly misspelled as Louis…but…

 

[DA Aquamaster]

To put 200,000 cycles in perspective - that would be three fills per day for 182 years.

 

[Jim Lapenta]

I have a set of newer 72's- 1973 and 75. I had one of the epoxy lined ones and one shop tried to tumble it out. Stubborn little bugger would not get clean enough for him to mate it with the 73 tank. I had them O2 cleaned as well. He just pulled the 75 out of his basement, Had it hydro'd and gave it to me for my old one and the price of the hydro. My other two are from 55 and 56. They have the pipethread. Great tanks for pool and checkouts. I just bought an al80 to use as a stage/deco/pool tank. I'm betting the 55 and 56 outlast it.

 

[pescador775]

About the comment that wall thickness of the 72 is less than the modern LP's. One reason is that the diameter of the 72 is less than an LP. I wonder if the same person has ever considered the wall thickness of the HP? Heh heh.

 

[Couv]

......

Nemrod
Who is Lewis? I have seen my name commonly misspelled as Louis…but…

What do you want? He doesn't even know how to spell Nimrod I know, I know, I used to own a Nemrod Snark III...just yanking his chain. ;-)

... Back in the 60's the local dive shop was Roland's Surplus and Sporting Goods. They stamped ROL behind the month and date.

By the way Captain, I used to work at Roland's. Actually it was called New Orleans Skin Diving and Scuba School, but everyone called it "Roland's." It was the first dive shop in New Orleans and was opened by the son of the hardware store owner. Roland's father "taught" him to dive by putting him in the water with the gear and hit him on the hands with a hard rubber hose if he tried to get back in the boat.

couv

 

[captain]

What do you want? He doesn't even know how to spell Nimrod I know, I know, I used to own a Nemrod Snark III...just yanking his chain. ;-)




By the way Captain, I used to work at Roland's. Actually it was called New Orleans Skin Diving and Scuba School, but everyone called it "Roland's." It was the first dive shop in New Orleans and was opened by the son of the hardware store owner. Roland's father "taught" him to dive by putting him in the water with the gear and hit him on the hands with a hard rubber hose if he tried to get back in the boat.

couv

I have a few years on you and go back a little farther. The tank I have is stamped ROL 4-67, and I was the owner at the time.
Actually Roland's started as Roland's Army Surplus and Sporting Goods store on North Rampart St. in the 1950's. Roland Riviere was a US Divers dealer and the first to bring scuba to New Orleans in the mid 50's. As a 10 year in 1954, I would go in the store and look at the diving equipment on display along with all the World War ll surplus items.
After the store closed sometime in the 60's he opened the New Orleans Skin Diving and Scuba School. I can't recall the street but it was around Napolean Ave. and St Charles Ave. He is mentioned in this, Time Line of Scuba: A Chronology of the Recreational Diving Industry

http://www.hanaumabay-hawaii.com/About_scuba_diving.htm

 

[Couv]

Captain, my captain,

For someone who has a few years on me, you sure do have a good memory. We were located on Dryads St. just off of Napoleon (cattycorner from Pascal Manale's Restaurant.) The new dive shop was an old swimming club building dating back to who knows when.

Roland Jr, (I never knew Sr.) was quite the character. I was imagining a New Orleans area dive shop family tree and I would say that, probably, until the late 1980ies most dive shop owners, with the exception of Aqua Tech, had roots of some sort going back to Roland. Either having worked for him or trained by him or someone he trained.

You could walk around in the shop and see all sorts of memorabilia. Old equipment, spear guns-a picture of him an Jacques Cousteau, one giving the other a trophy. I asked him who was giving who was getting the trophy, he said, "It doesn't matter."

Thanks for the great link.



couv