Thanks and Tanks

[potato cod]

Hi there,

First, I'd like to thank everyone who has graciously offered input into a number of my pesky questions about gear over the last few months. I'm so excited to report that my SO I just purchased our very own regs and bcs to complete our scuba kit. I learned a lot from everyone and am glad I got some great advice before buying because we ended up getting very different gear than what we were originally looking at.

The final choices included back inflate bcs (SeaQuest Balance for the boy, Zeagle LaZer for me) and AL Titan LX Supreme regs for both of us. Stuff we can travel with, and also grow into for future diving in the local, colder waters. We also put the regs on 7' hoses with bungeed octos, which our LDS showed us how to deploy. When I tried this setup out in the pool I absolutely loved how easy it was to deal with when practicing OOA drills.

In addition to the gear we just bought, we had an unexpected early "scuba christmas." A friend of a neighbor has gotten out of diving and gave us a bunch of equipment (bag, soft weights, float, lights) and 3 tanks. From the sticker it is obvious that the tanks have not been inspected since 2003. I don't really know much about tanks in general or the history of this equipment in particular since the donor is a very casual acquaintance, which leads to a couple of questions:

-Is it possible to tell just by looking if the tanks are steel or aluminum?

-If aluminum, is it possible to tell if they are the regular sort or the neutrally bouyant type?

-They are labeled for Nitrox. I'm doing my nitrox certification Saturday, but nitrox would be overkill for things like shallow local drift dives, but good for deeper wrecks, etc. Can I switch some of them back to air?

I can certainly take these into my LDS to figure this stuff out, but since I won't be diving around here until next spring, I don't really want to haul them around or have the hydro/inspection done until closer to the date that I'll use them.

Thanks!

P-Cod

 

[Jimmer]

If the tank has a flat bottom, it's aluminum. Look at the markings on the shoulder, if you can see 3AA, it's steel, if you see 3AL, it's aluminum.

Well all of the neutral 80's I've dealt with were rated for 3300 psi, not 3000. So if you see 3300 marked on the shoulder, it's likely a neutral tank.

 

[spectrum]

Congratulations on the gear!

Jimmer gave good clues on spotting AL and neutral models.

You certainly can revert to regular compressed air service if that's what makes sense for you.

If you can respond with the actual numbers stamped in the cylinders folks can add more information.

Pete

 

[potato cod]

Thanks for the info Jimmer and Spectrum!

2 of the tanks say 3AL-3000 and have flat bottoms, so it looks like they're aluminum. The other tank is a bit smaller, has a convex bottom under its boot, doesn't say AL on it anywhere, but is inscribed with: IA 636079 81 -3500 (plus the DOT serial number). Any guesses on that one?

 

[Jimmer]

Thanks for the info Jimmer and Spectrum!

2 of the tanks say 3AL-3000 and have flat bottoms, so it looks like they're aluminum. The other tank is a bit smaller, has a convex bottom under its boot, doesn't say AL on it anywhere, but is inscribed with: IA 636079 81 -3500 (plus the DOT serial number). Any guesses on that one?

The first 2 are standard Al80's. The third one, if it's just a little bit smaller, sounds like a 3500 psi high pressure steel 100 cubic foot tank. Is the valve offset and angled back?

 

[spectrum]

Can you locate the original hydro date on the AL cylinders? That would be 2 digits, a symbol and 2 more digits.

Are they made by Luxfer or Catalina?

 

[rstofer]

If the tanks have been cleaned for Oxygen Service (there will be a tag) and labeled for Nitrox, it is still possible to fill them with what my LDS calls 'Safe Air' Basically, this is clean air that is normally mixed with oxygen to create Nitrox. They just don't increase the percentage of oxygen.

This assumes the tanks are really clean. I would have a tendency to want to get the tanks hydro's well in advance of the need, get the Visual Inspection and have them cleaned for Oxygen Service as soon as possible.

If the Al 80 tanks are from before 1990, you may find they are rejected for filling even if they pass hydro. You can research this over on the Tanks and Valves forum. There seem to be a couple of ideas floating around: reject all tanks made before 1990 on the suspicion they are made from 6351 aluminum alloy (whether they are or not) and reject all aluminum tanks that are more than 20 years old. Check to see what the hydro and visual will cost on your tanks. At some point, depending on age and alloy, the cost will approach that of a new tank.

You have to continually keep track of what is in the tank. My LDS uses a tape type label and I have to fill in the MOD and the O2 concentration. So, I put in 187' and AIR when I have them filled with Safe Air. This is just something to keep track of because I sometimes put up to EANx 36 in the same tank.

Richard

 

[potato cod]

The tank with 3500 on it is a little smaller, but the valve position and orientation looks normal.

The tanks are all made by Luxfer. The original hydro dates are '98 on one of the Al and the mystery tank and '97 on the other Al tank.

Rstofer, why do you think getting the tanks tested and inspected well before you need them is good? Does it take a long time? I figured if I did this now they'd just spend 6 months getting closer to being out of hydro before I even used them--there's no local ice diving in my future this winter, just some nice tropical diving! Also, how much does the testing typically run?

Thanks!

 

[divad]

get the Visual Inspection and have them cleaned for Oxygen Service as soon as possible.








You don't have to have them cleaned at all if you just use banked nitrox. Don't let tthem sell you that sticker that someone from another shop may not honor. Just politely tell them you're only using banked nitrox.