Question regarding tank fills

[CT-Rich]

Do you have a link to a good reference? I’m genuinely interested.

Don’t even think about asking for an overfill in your aluminum cylinder…

 

[tridacna]

Don’t even think about asking for an overfill in your aluminum cylinder…

That’s interesting but I’d like to see real results based on real numbers. I’m not volunteering - @lowviz you listening? - but it would be interesting to pump up a few 3ALs and 3AAs a few hundred times each and compare elasticity after a hydro.

 

[Divin'Papaw]

Do you have a link to a good reference? I’m genuinely interested.

Not readily at hand, no. If I have time and can find anything that summarizes it clearly, I’ll share it.

 

[Divin'Papaw]

Do you have a link to a good reference? I’m genuinely interested.

Duplicate post … removed

 

[CT-Rich]

That’s interesting but I’d like to see real results based on real numbers. I’m not volunteering - @lowviz you listening? - but it would be interesting to pump up a few 3ALs and 3AAs a few hundred times each and compare elasticity after a hydro.

I think you are missing the point. Steel and aluminum do not have the same properties. Aluminum has a lower density than steel, is more brittle and softer. Steel has more tensile strength, that is why steel tanks from the 1960s are still readily available and are used in HP cylinders. Aluminum is less prone to corrosion (an attractive feature in the tropics and when being constantly refilled by low wage resort employees).

If you think aluminum tanks are okay to overfill, feel free to post supporting evidence. I posted an article that articulated why it isn’t a good idea. It is on you to find the data you seek.

 

[tridacna]

I think you are missing the point. Steel and aluminum do not have the same properties. Aluminum has a lower density than steel, is more brittle and softer. Steel has more tensile strength, that is why steel tanks from the 1960s are still readily available and are used in HP cylinders. Aluminum is less prone to corrosion (an attractive feature in the tropics and when being constantly refilled by low wage resort employees).

If you think aluminum tanks are okay to overfill, feel free to post supporting evidence. I posted an article that articulated why it isn’t a good idea. It is on you to find the data you seek.

Agree with you regarding the metallurgical properties. No question. But the manufacturers compensate by using much thicker walls in the 3AL tanks. Does that impact the long term impact of high intensity use? There must be studies somewhere.

 

[CT-Rich]

Agree with you regarding the metallurgical properties. No question. But the manufacturers compensate by using much thicker walls in the 3AL tanks. Does that impact the long term impact of high intensity use? There must be studies somewhere.

1) Aluminum scuba tanks, according to the US DOT have a service life of 20 years.
2) Steel tanks have one of 50 years.
The experiment has been done. Look up the technical data yourself if you wish. I am sure your local engineering college has an article from 1985 on microfiche in the basement that explains how they determined that. They also articles that document catastrophic failures of scuba tanks that led to all sorts of regulations about testing, recalls etc…

steel tanks are heavier and more expensive than aluminum, but they can be made to withstand much higher pressures than AL. They don’t make HP AL tanks for a reason.

 

[Gone for diving]

Any one that works with steel know the difference (in general how steel and aluminum behaves... aluminum cracks way easier. Look a aluminum trailers there are vibration cracked all over. There's alot less wear and tear on a steel trailer but steel rusts.... grab to identical peices of steel and aluminum. Put it in a vice and hammer it back and forth. Aluminum will stress crack right away.
Some bridges are made of steel that's meant to rust and that is the protective layer. It doesn't need painting for the rest of its life...
Every everything has its advantages and disadvantages.

I away say aluminum tanks hold air pressure by rigidity... as soon as the aluminum stretches the tank is done...
Steel is allowed to stretch a bit...

PS what is the hydro pressure for an 80 aluminum?

 

[tridacna]

1) Aluminum scuba tanks, according to the US DOT have a service life of 20 years.
2) Steel tanks have one of 50 years.
The experiment has been done. Look up the technical data yourself if you wish. I am sure your local engineering college has an article from 1985 on microfiche in the basement that explains how they determined that. They also articles that document catastrophic failures of scuba tanks that led to all sorts of regulations about testing, recalls etc…

steel tanks are heavier and more expensive than aluminum, but they can be made to withstand much higher pressures than AL. They don’t make HP AL tanks for a reason.

Lots of speculation. I doubt that “my local engineering school” has anything on MF. Dang, I remember using that in college in the 70s and 80s. As an aside, my wife had a lawsuit against GM - she and her staff spent days poring through MF in Detroit researching their archives which are not digitised. They do it on purpose to make it as difficult as possible for plaintiff’s attorneys. (She won the lawsuit).

 

[tridacna]

PS what is the hydro pressure for an 80 aluminum?

5/3 of working pressure.