Tank storage question - in case of fire

[dumpsterDiver]

Aluminum is VERY sensitive to weakening from rather moderate heating....It occurs way before melting......

 

[Jax]

Aluminum is VERY sensitive to weakening from rather moderate heating....It occurs way before melting......

But after it cools? it passes hydro?

 

[dumpsterDiver]

NO, it will almost definitely fail in hydro.. It weakens it severely. Al tank in a fire should be scraped, not worth testing, my buddy's shop burned down and he did salvage the brass valves,,,,

 

[Jax]

NO, it will almost definitely fail in hydro.. It weakens it severely. Al tank in a fire should be scraped, not worth testing, my buddy's shop burned down and he did salvage the brass valves,,,,

No, not a fire. A tank that has been exposed to 350F or greater . . . like baked on paint.

The book says it could pass hydro, but fail in the dive shop.



EDIT: That sounds like splitting hairs, but I don't want to recite anything not in the book.

 

[Dsix36]

I do not know of any paint baking that takes it to 350 degrees. In the olden days the paint had to be heated to 300 degrees to harden properly, but with todays newer paints the temps can be much lower. Powercoating ovens do not even have to be that high to melt the powders. Most paints can be baked at anywhere between 100-200 dgrees to harden properly nowadays.

 

[PfcAJ]

I know the idea behind the recommendation for burst disks, I get it. But the weak part of all this isnt the tan or burst disk, it's the oring. They melt in fires... Before 350 degrees...

 

[Scared Silly]

Jax, Wookie has most of your answer. When the cylinder is heated it loses it annealing - i.e. embrittle. At this point you have a material that is more brittle than it should be. During hydro it gets a nice slow fill and the cylinder is able to expand accordingly. All is well. Back in the shop the fill monkey slams 3000psi in it. Kaboom, the cylinder was shock loaded and was not able to expand fast enough.

You can do the same thing with a brick. Set it between two supports. Start adding weight in the middle - you can put a lot on it before it breaks. Now do the same with another brick. Smack it with an hammer and it breaks. That is an example of a shock load. The energy produced by the hammer blow can be substantially below the energy from adding the weight but the time involved makes a difference.

There is another explain that I need to think about. During hydro the cylinder can hold the test pressure but enough damage is done that the next time it is pressurized that it is not able to. I have to think about those mechanics.

 

[Jax]

Cool! Thanks, Silly. I learned that hydro testing is much slower than the 300-600psi/min of tank (air) filling.