Non-steel, non-aluminum scuba tanks

[BoltSnap]

I personally saw the Titanium scuba tanks made in the Russia, after the collapse of the USSR and Russia had so much titanium they didn't know what to do with at that time they used in their submarines and other weapon systems during the times of the cold war. They exhibited the Tanks at DEMA. These tank were rated to 10,000 PSI. They fizzled away and never saw them again. I believe that their cost was so high and, perhaps, couldn't get the international approvals, DOT, etc.

 

[lowwall]

Now that I think about it. Higher pressure is the path to lighter system weight. If you can cram the same amount of air into a smaller volume, then you'll need less ballast to counteract your lower displacement when the tank is empty.

So carbon fiber or titanium could be advantageous if their strength allowed you to pump them up well beyond the 300bar/4350psi you can get in steel tanks (where legal).

But you still have cost and durability and fill issues. One huge issue is failure modes. Both CF and Ti have a tendency to explode under high pressure if they get nicked.

Everything is a trade-off. Steel and Al are the preferred options because they offer the best combination of pros and cons of the materials currently available.

 

[rx7diver]

... But you still have cost and durability and fill issues. ...

And you still have the buoyancy swing issue, too, maybe. For example, 330 ft^3 of air/nitrox still weighs ~26# (= ~0.08 * 330) regardless of how small a volume it is compressed into (within reason). So, breathing two-thirds of this amount on a given dive means a buoyancy swing of ~18#.

rx7diver

 

[rx7diver]

... I made a note on the cylinder spec page of my Cave Diving Manual, I think, because of my "forever" interest in smaller, lighter, and simpler scuba. I'll look this up when I return home this evening.

I am home now. My handwritten, undated notes in my "NSS Cave Diving Manual" read:

Larry Elsevier, Pacific Development Company:

1. Titanium 85, 4,400 psig, ~20" length, 6" outer diameter, ~17# empty weight in air. Empty buoyancy in fresh water not specified.

2. Titanium 158, 4,400 psig, ~20" length, 8" outer diameter, ~37# empty weight in air. Empty buoyancy in fresh water not specified.

So, these were 300 Br cylinders. (So, not outrageous high-pressure.)

I remember being so jazzed when I first read about these, that I began budgeting to purchase a couple of the small ones. (They weren't going to be inexpensive!)

rx7diver

 

[Tracy]

Even the carbon fiber tanks are around an aluminum liner. Metal has an unlimited lifespan. The composite materials age poorly (long term, none will be serviceable by the age of 20 years)

There are thousands and thousands of fiber wrapped SCBAs that are beyond 20 years and will live to their 30 year lifespan.
30 years is a solid life on a tank that sees daily use and hot fills.
How long do you think it needs to last?

 

[broncobowsher]

There are thousands and thousands of fiber wrapped SCBAs that are beyond 20 years and will live to their 30 year lifespan.
30 years is a solid life on a tank that sees daily use and hot fills.
How long do you think it needs to last?

The SCBA tanks I know of have a 15 year service life. Did not know of any that were rated for more than that. News to me.

 

[Jonn]

Would a half century really be too much to ask? Or a full one or more? This low pressure steel has six little feet forged into the bottom so it stands without a boot, nifty feature.

 

[Tracy]

View attachment 717217Would a half century really be too much to ask? Or a full one or more? This low pressure steel has six little feet forged into the bottom so it stands without a boot, nifty feature.

Those are called "toed" 72s. I have a collection of them. They were sold by Sears Roebuck under the Nemrod brand. I could use another one, would you like to sell it?

 

[Tracy]

The SCBA tanks I know of have a 15 year service life. Did not know of any that were rated for more than that. News to me.

Most have an original service life of 15 years. DOT has now allowed an additional test to certify for another 15 years of service. Here is the company currently providing the retesting.
It has been gaining a lot of ground with fire departments. For a third the cost, you get the same life as purchasing new.

 

[Ghost95]

Now that I think about it. Higher pressure is the path to lighter system weight. If you can cram the same amount of air into a smaller volume, then you'll need less ballast to counteract your lower displacement when the tank is empty.

So carbon fiber or titanium could be advantageous if their strength allowed you to pump them up well beyond the 300bar/4350psi you can get in steel tanks (where legal).

But you still have cost and durability and fill issues. One huge issue is failure modes. Both CF and Ti have a tendency to explode under high pressure if they get nicked.

Everything is a trade-off. Steel and Al are the preferred options because they offer the best combination of pros and cons of the materials currently available.

I don't have the book in front of me but weren't carbon tanks experimented with in the Wakulla exploration? I thought i read something about them leaking helium and messing up the mixes. That may be another issue with those particular materials for diving.