Tank comparison Steel V Aluminum

[Zoomer]

I was shopping for a dedicated Nitrox tank the other day and discovered something. Aluminum 80, working pressure 3000 psi, HP Steel 80 working pressure 3345 psi... so what is the big advantage to justify the large price difference? Yes I understand the buoyancy thing...

Discuss

 

[Jimmer]

The large price difference is mainly due to the price difference in the cost of raw materials. Steel is a fair bit more expensinve than aluminum. In addition to that it is a different manufacturing process used to make steel tanks versus aluminum. I'm pretty certain it takes a lot longer to manufacture steel tanks.

 

[String]

Works the other way round here, Aluminium costs far more than Steel to buy and an awful lot more to get tested (roughly twice the price). Steel is also lighter out of the water per same capacity of Aluminium.

Due to Aluminium holding less gas per size than steel and having annoying buoyancy characteristics they are generally only used here for stage cylinders with back gas always on steel.

 

[Divin'Papaw]

It's the buoyancy thing primarily. You say you got that, so what else are you looking for?

Here are a few additional points to consider:
- Steel will also pretty much last forever while an aluminum tank has a life span of approx. 10-15 years I believe.
- Steel will be smaller and more compact than the aluminum. There is a significant size difference between a HP80 and an AL80. An AL80 is actually closer in size to a HP100, which IMO is a better option for most than a HP80 which is often too small and therefore causes trim issues. The AL80 is actually bigger than a HP100.

 

[Zoomer]

Well I thought the biggest advantage was more psi, thus requiring the DIN valve, which would result in more air in the same sized cylinder with the addition of not becoming negatively buoyant toward the end of the dive. But after weighing the options, to me it doesn't justify the added cost.... I have found new AL80's for 139.00 where most steel HP80's are more than double the cost.

I don't know maybe I am looking at this wrong.

 

[Nick_W]

- Steel will also pretty much last forever while an aluminum tank has a life span of approx. 10-15 years I believe.

Not to pick on you or anything, but I'm not sure where people get this 10-15 years stuff. I have some aluminum tanks that are 32 years old. They still pass hydro and VIP with flying colors.

With just about all of your gear, tanks included, if you take care of it, you're probably going to want to buy new gear before you need to buy new gear.

As for which is better, well that all depends upon where and how you're diving.

 

[Divin'Papaw]

Well I thought the biggest advantage was more psi, thus requiring the DIN valve, which would result in more air in the same sized cylinder with the addition of not becoming negatively buoyant toward the end of the dive. But after weighing the options, to me it doesn't justify the added cost.... I have found new AL80's for 139.00 where most steel HP80's are more than double the cost.

I don't know maybe I am looking at this wrong.

The new steel HP tanks are 3442 service pressure and do not require a DIN valve. Most come with a Thermo Pro valve that can be either DIN or Yoke.

Better buoyancy characteristics is key. Steels are not "floaty" at the end of the dive.
Yes, steels also hold more air in a more compact tank than aluminum tanks.

You have to judge for yourself if the cost is justified. Those of us who dive drysuits in cold water, we MUCH prefer steel tanks. If you are primarily a warm water diver wearing a thin wetsuit, an aluminum tank is probably the better choice.

 

[Jimmer]

Works the other way round here, Aluminium costs far more than Steel to buy and an awful lot more to get tested (roughly twice the price). Steel is also lighter out of the water per same capacity of Aluminium.

Due to Aluminium holding less gas per size than steel and having annoying buoyancy characteristics they are generally only used here for stage cylinders with back gas always on steel.

Over here it costs exactly the same amount to be hydro or visually inspected. But we do have the same unofficial use of them over here. Most of the guys I dive with, myself included, use steel for the back gas exclusively and aluminum on stages.

Well I thought the biggest advantage was more psi, thus requiring the DIN valve, which would result in more air in the same sized cylinder with the addition of not becoming negatively buoyant toward the end of the dive. But after weighing the options, to me it doesn't justify the added cost.... I have found new AL80's for 139.00 where most steel HP80's are more than double the cost.

I don't know maybe I am looking at this wrong.

Where you are maybe going wrong is that an HP80 is WAY smaller than an AL80. The HP100 is close in size to an AL80, and have 25% more gas. That is where a big part of the advantage comes in, also the steel tanks allow you to drop some weight off the belt.

 

[Divin'Papaw]

Not to pick on you or anything, but I'm not sure where people get this 10-15 years stuff. I have some aluminum tanks that are 32 years old. They still pass hydro and VIP with flying colors.

With just about all of your gear, tanks included, if you take care of it, you're probably going to want to buy new gear before you need to buy new gear.

As for which is better, well that all depends upon where and how you're diving.

I assume then that it's not the 6351 alloy? Tanks made with 6351 alloy are going to become harder and harder to fill, even if they pass the eddy current test. It's just too risky for most shops.

Maybe the newer 6061 alloy tanks will last longer. I hope so. I own two Luxfer 6061 aluminum tanks and I'd love it if they last 32 years.

 

[String]

A-clamp is generally rated at 232 bar (3410 psi).
DIN is rated to max 300 bar (4410psi).

Most aluminium tanks ive seen are rated to 206 bar (3028psi) maximum.

As far as im concerned i dont like having to wear additional lead to keep an empty tank from floating so i go for steel. The more cold water diving you do the more lead you need anyway so shaving some off anywhere is good.