Air cylinders

[TheHuth]

Alright, I dropped both tanks off at the local scuba store. They're both Aluminum. One is a LUXFER Dive Tank 3AL3000-S63. The other is an Aluminum 80, but I didnt catch the brand. One had air, the other didnt. They cracked open the one that did not have air, and he said it looked fine inside. The AL80 had 1000 psi left in the tank. So all in, I'll have gambled $155 on the pair. I may get two good tanks, I may get none. We'll see

 

[Tracy]

Alright, I dropped both tanks off at the local scuba store. They're both Aluminum. One is a LUXFER Dive Tank 3AL3000-S63. The other is an Aluminum 80, but I didnt catch the brand. One had air, the other didnt. They cracked open the one that did not have air, and he said it looked fine inside. The AL80 had 1000 psi left in the tank. So all in, I'll have gambled $155 on the pair. I may get two good tanks, I may get none. We'll see

Wow, that is a big whups. You have $155 into 2 tanks that costs $100 each with a fresh hydro and free air for a year.

 

[TheHuth]

Well, I'm going to be learning as I go. If both pan out, it should be about a break even.

 

[shurite7]

And I'm pretty damn sure if you leave an aluminium and a steel tank in salt water for a while, the aluminium will be looking much better than the steel one

According to the University of Rhode Island report a steel tank took 30 days to rust to the point they would not hydro the cylinder; the aluminum tank took 249 days.

 

[Remy B.]

A good thing about the EU, is that 300Bar / 4380psi are common, and if you have spare money you can get Carbon Tank that weight less than AL, are smaller in size as well, or you can get the inexpensive Steel tanks that are heavy, good thing you don't need to carry to much weight. for any type of diving they are very convenient, high capacity less gear better regulators design.

 

[runsongas]

carbon fiber tanks have pretty terrible buoyancy for scuba.

 

[undrwater]

If the 63 is good, it'll be a decent tank for diving in Laguna or other shallow sites. I believe it's about the same size and weight as the 80, though isn't it?

Still, you've got some of your own gear! Woot!

OH! And learning (IMO) is priceless.

 

[2airishuman]

hm beyond price of course, I wonder why they don't make titanium tanks, a super light metal certainly stronger than aluminium but not as much as steel, seems ideal really if somebody were willing to pay the price

I guess there are some Russian ones that don't meet regulatory requirements for U.S. use because they have welded seams.

U.S. regulations require high-pressure cylinders to be made in one piece. Titanium, I understand, does not lend itself well to the deep-drawn process usually used to do this.

Based on what I'm reading, there is no real up side to aluminum.

There is:
1) Cost
2) Practical lifespan in frequent use as a SCUBA cylinder, due primarily to greater inherent corrosion resistance
3) Greater positive buoyancy, which is helpful in some situations.
4) Less weight when being handled out of the water

Aluminum is the material of choice for stages and pony cylinders , in most cases, because the combination of a cylinder, valve, and regulator is more neutrally buoyant in the sizes used for these purposes than HP steel.

With steel there are two choices, hp and lp. Why choose one over another?

LP tanks have advantages in certain situations, some of them mentioned upthread:
1) HP fills are not always available, which prevents HP tanks from being used to their full potential
2) Some shops charge more for an HP fill
3) Some people overfill LP tanks and believe this is safe, but do not believe that HP tanks can be overfilled with a comparable margin of safety
4) Some LP tanks have buoyancy and trim characteristics that are preferable in certain situations, or are available in sizes and shapes that have no HP equivalent (e.g. LP50 doubles)
5) Cost and availability, in some cases, particularly for used tanks

The main advantage of HP tanks is that, when comparing tanks filled to their intended working pressure, HP tanks are smaller and slightly lighter.

Second hand tanks can be good value, however remeber you might have to have a hydro done as well as a valve service and that adds to the final cost over a new one which is perfect and has 12 months use until next vis/hydro.

For secondhand tanks, consider the total amount of work that will have to be done to make the cylinder suitable for use in your particular situation and look at the costs. Be sure you have someone lined up who is willing to do the work. For galvanized HP steel tanks be sure you have a hydro tester lined up who is willing to follow the 90% pressure "test" to re-round the cylinder. For older tanks be sure there is someone who will fill them. Consider the possibility that the cylinder will fail hydro, particularly for steel tanks with internal corrosion. If the valves are 300 bar DIN and your regulators are yoke, consider the cost of new valves.

 

[Patoux01]

4) Less weight when being handled out of the water

Out of the water, for same internal volume, aluminium tanks are typically the heaviest there is. The ones that beat them are the short steel tanks (also known as "compact").

 

[Rred]

Titanium was classed as a ":strategic metal" because most of the world supply was inconveniently located in the USSR. After that collapsed, the price of titanium plummeted and it became arguably affordable. It was, and is, so expensive that the USSR managed to build two submarines with titanium hulls--and the US never built any. The USN couldn't afford to buy that much titanium, at all. Then or now.
The armor plated "bathtub" surrounding the cockpit on the Warthog ground attack aircraft is built of titanium because the USAF said "We don't care what it costs, we don't want the pilot getting shot" and the Warthog, btw, has a reputation for taking incredible damage and simply ignoring it.

As to making tanks from titanium? There are four primary titanium alloys in common use. All of them are so difficult to machine (strong and hard) that if you say "titanium" to a machinist, they will run and scream "MOMMY! MOMMY!" and you'll never see them again.

Titanium tanks? I'm sure someone could make them for you. Maybe ten grand a piece, after the machining and setup costs? When you're ready to play in that ballpark, you can start soliciting quotes.

Secondhand tanks are best ignored, unless the seller has JUST had them hydro'd and VIP'd so you can be sure that you are getting something that can be used. Otherwise, you risk $45? $65? to send it out for testing and tumbling and when you add that to the price of the used tank, knowing the tank may be trash and certainly will need oxygen cleaning if you plan to use it for nitrox....New tanks are often cheaper.