Stainless steel tanks

[Falcon99]

I'm not a metal expert, but from gut feelings, I really wouldn't want a tank made out of Titanium. Yeah, it's light and strong, but is WAY too brittle - IMHO.

You guys are scaring the h*ell out of with these tank posts. I recently borrowed some tanks from a friend who had not used them in a long time (having a kid does that). The last hydro was 1990!

They passed both hydro and VIP, but now I'm nervous anyway! One is a Catalina, though, so I don't feel too scared about that one...

:boom:

James

 

[Falcon99]

Just got home... just my luck... One is a Walter Kidde tank, made in 1979. The other is a USD tank, made in 1986, and marked with the exception number noted on the DOT alert text. Obviously, these are center of target, suspect tanks according to the DOT alert....

OK, question...

These things Hydro'ed OK with a VIP about 6 weeks ago.

What should I do with them?

James

 

[crispos]

Use them for flower pots. Splurge and buy new tanks. That's MHO.

 

[ew1usnr]

tcatdiver once bubbled...
sorry about that, in the reply that I just posted there is an error. it should read that the SS tank held 90 cubic inches, not cf.

It had to be 90 cubic feet. One cubic foot equals 12"*12"*12" = 1728 cubic inches. 90/1728 = 0.052 cubic feet. That would be a real little tank.

 

[nyresq]

get rid of the kiddie tank, cut in half make a flower pot.
The catalina- if its in mint condition (no dings or chips, and clean in and out) I'd get an eddy test and a neck inspection done, if they weren't done with the hydro (they're supposed to be done on those tanks automaticly).

If your short on cash, use the catalina if it passes and is like new condition.

If you can afford it, junk it too. New AL80 only cost about $120 from Liesurepro.
For $240 bucks, you gat some piece of mind and new shiny tanks.

 

[Pimbura]

High pressure cylinders are made of various materials for various applications. I have seen Stainless and Inconel in this country and they are in current production. You can order any size, pressure rating and neck configuration you want. The inconel tanks were around $4,000 each. I have also seen titanium tanks for sale in Europe. For the time being, we won't be seeing them imported for retail sale. They are welded, and the DOT requires that high pressure tanks be seamless. Don't flinch at the ti tanks being welded. They are electron beam welded and absolutely safe. Another problem with the ti tanks is that they can't be hydro tested. They don't expand and contract enough to give a legitimate reading. I may bring a couple back to the US just to thrill and amaze my friends.

Hello,

can anyone tell me the company who makes the DOT approved ss tanks for use in the US?

thanks,

Ed

 

[Scubaroo]

How on earth do you get a full fill in a Ti tank then? They must have a monstrous working pressure.

 

[Robert Phillips]

If those tanks passed hydro and a visual, they are okay. The 6351 alloy they are made with is susceptible to SLC (sustained load cracking) which is small cracks in the neck of the tank. Any shop that does VIP's should be usin a Current Eddy test to find SLC in older alloy tanks. Use them until they fail a visual inspection. Luxfer had a program that ended on Dec 31 that offered a $50 voucher for thier 6351 alloy, so you are late for that, but, like I said, the tanks are good until they fail a visual. Try this link

Just got home... just my luck... One is a Walter Kidde tank, made in 1979. The other is a USD tank, made in 1986, and marked with the exception number noted on the DOT alert text. Obviously, these are center of target, suspect tanks according to the DOT alert....

OK, question...

These things Hydro'ed OK with a VIP about 6 weeks ago.

What should I do with them?

James

 

[Bob3]

Use them until they fail a visual inspection.

I hear there are some shops [Canada & FL if memory serves] that won't fill the critters if they're 10+ years old.
If you have the misfortune of going to that shop, go to another shop that has a better "informed" attitude.

 

[Albion]

any one who has tried to work with stainless steel will tell you about heating and bending. unlike standard chromemoly and high carbon steels, stainless does not heat in a uniform and even pattern. try heating a straight piece of stainless bar stock and watch when it cools, it will twist and distort several inches away from the heating point. I think someone filling a stainless tank would run a very high risk of heat damage from filling too fast.
Now I know your all sitting at your computers saying to your selves "noooooooooo, who would fill a tank too fast??" But I'm here to tell you, it does happen from time to time.... yes it really does... no really I'm serious, I've seen scuba-doobas fill tanks in a shop a little too fast (when I say a little, I mean hotfill to 3600 and cool down to 2800).
So if your LDS has some kid fill your $600 stainless tank too fast, guess what... stainless ain't gonna take it the way high carbon steel would. Do that a couple of times and a stainless tank would probably develop stress fractures in the body from uneven heating.
Incidently, the same thing can happen from hot filling tanks that are only half immerssed in a water tank while filling. The uneven heating caused by the bottom being cooled by the water while the top half heats up can do som interesting things to the body. Thats why if your going to bother putting them in a water bath while filling, put them all the way under. (this is also a good way to look for any leaks.

I seam to remember a shop telling me about some stainless or titanium tanks that were being sold in europe but the manufacture was having trouble meeting DOT specs. that was probably in the area of 1994. never heard any thing about it since.

I dont know how the calculation works for holding gasses but when under pressure with liquids 316 St St is about 20% weaker than standard carbon steel, so against a Cro mo add a bit more. That means your tank will be around 25% thicker, now that is at room temperature, However as temperature increases 316SS gets weaker still and your looking at another 5% loss compared to Carbon steel at 200DegF (a possible hot fill temp), so we are now at least 30% thicker, and that is before looking in stress cracking issues. Stainless Steel is just not a good idea.