How old is "too" old for aluminum cylinders?

[Tracy]

Interesting exchanges and information. I am not an expert and did not sleep in a Holiday Inn to qualify as one...as others I have vip'd and hydro'd many, many bottles....do have a question: If crack was within the "crown" why and how did it fail? Crown I am imaging is not a sealing surface as are the threads and of course o-ring/seats. Did it just start a slow leak or a rapid one? New one on me.

Old 72cf 2250 bottles? The steel 72cf I bought in 1955 just past it's 19 [hope I count correctly] hydro and yes bottle always kept full...only death knell for a steel bottle is to get water, particularly salt water, inside and not dry it out; then pump in high O2 and rust city. Or be really dumb and pump it way over rated pressure repeatedly.

Thanks again for everyone's input....I am always learning...

Literally started leaking through the tank. The paint flaked off and air was coming from the crack within the tank itself. I cut the crown off and examined the inside, the crack was along the side of a fold in the aluminum.

 

[Tracy]

The 72s that fail are dry and rust free, and have never seen more than 21 percent. A small minority of tanks overall for sure but there is no mistake when you test one - massive expansion and not much elasticity.

I have tested and sold several hundred steel 72s in the last decade, only had the one fail. It had no elasticity. I honestly don't remember if it was high expansion or no. I still have the tank, I could test it again and see what the numbers say.

 

[ScubaBunga]

The 72s that fail are dry and rust free, and have never seen more than 21 percent. A small minority of tanks overall for sure but there is no mistake when you test one - massive expansion and not much elasticity.

did they go through the rounding out process. Seems they may (when sitting a long time) constrict or something and need a rounding out before testing so the initial expansion is covered in that rounding out. Never had a steel 72 fail hydro other than the one the shop condemned because it had a thin liner (clueless folks). I'm sure some do eventually fail but many get erroneously failed because they were not rounded out.

 

[Tracy]

did they go through the rounding out process. Seems they may (when sitting a long time) constrict or something and need a rounding out before testing so the initial expansion is covered in that rounding out. Never had a steel 72 fail hydro other than the one the shop condemned because it had a thin liner (clueless folks). I'm sure some do eventually fail but many get erroneously failed because they were not rounded out.

Very few tanks ever require that process and it certainly wouldn't be needed on an old cylinder that has sat full. It is only ever needed on new galvanized cylinders. Specifically worthington galvanized cylinders. They used a very thick galv coating that would show brittle if they hadn't been used much. Once they have been overfilled or hydroed a few times, it is never an issue again.

 

[Still Kicking]

Wow...do you happen to remember who made the steel bottles that had that huge expansion with little recovery? Oh, I meant "knell" not "knoll"...old fingers and older mind!

I will check records and see if there is any pattern. Many are Norris I would guess just because they are most common 72s.

 

[ScubaBunga]

Very few tanks ever require that process and it certainly wouldn't be needed on an old cylinder that has sat full. It is only ever needed on new galvanized cylinders. Specifically worthington galvanized cylinders. They used a very thick galv coating that would show brittle if they hadn't been used much. Once they have been overfilled or hydroed a few times, it is never an issue again.

It's needed for ALL old galvanized steel PST's - per PST's docs. I would think norris (being the same type of tank) could use it as well.

 

[Tracy]

It's needed for ALL old galvanized steel PST's - per PST's docs. I would think norris (being the same type of tank) could use it as well.

While I appreciate your vast internet knowledge of tanks, Show me an old PST tank that fails the hydro on the first round and passes after a round out.
Find one, and I'll eat my words.
PST galvanizing wasn't as thick and didn't cause issues. The document was made as a "just in case" back when those tanks were new. It just didn't come into play in real life. Same with Faber and Norris. Never seen it, never heard of it happening.
It isn't that hard to do with worthingtons. It is getting harder as they are getting old enough that it is hard to find a pristine virgin tank, but it does still happen.

 

[ScubaBunga]

While I appreciate your vast internet knowledge of tanks, Show me an old PST tank that fails the hydro on the first round and passes after a round out.
Find one, and I'll eat my words.
PST galvanizing wasn't as thick and didn't cause issues. The document was made as a "just in case" back when those tanks were new. It just didn't come into play in real life. Same with Faber and Norris. Never seen it, never heard of it happening.
It isn't that hard to do with worthingtons. It is getting harder as they are getting old enough that it is hard to find a pristine virgin tank, but it does still happen.

yeah, I probably won't have one as I paste the process to my tanks when they go in for hydro. It was obviously enough of an issue that the manufacturer published the procedure: PST Technical Bulletin D100-E
This forum has several long chains with discussions on this - there may be some that had failed hydros in that list.

 

[happy-diver]

Aluminium cylinders are never too old to keep out of the tip

 

[Wallowa]

Nice Aqua Master DA reg ['69?].....how does it breath on that bottle? The Land of Oz indeed!

Your AO looks very sharp and organized.....jealous!