How long is too long for tanks to sit empty?

[jseteroff]

I am considering buying 2 catalina AL80s, both made in 1990, one had its last hydro in 2000 the other in 2005. Owner says they have been sitting empty, I don't know for how long. At what point would you be worried that the tanks are not longer capable of getting past hydro?

 

[miketsp]

If they were really made in 1990 they shouldn't be made from 6351 alloy. So that shouldn't be an issue.
6351 was subject to Sustained Load Cracking.

The Catalina Tank Company began making 3AL cylinders in 1986 using alloy 6061-T6.

Although this alloy is generally not subject to SLC, a very few Catalina cylinders have
been found with minor thread area cracks attributed to stress corrosion cracking.
Therefore, PSI, Inc. recommends that thread examinations, including a mirror-and-light
protocol be performed on all 3AL cylinders.

 

[Jim Lapenta]

They need a hydro and vis at least. If they pass both they may be worth 75 bucks each. If they have been sitting totally empty, which is real dumb on the part of the owner, they could have moisture in them, corrosion, etc and the only way to tell for sure is to do the vis. If you decide to go for them make sure you can get your money back if they are bad and won't pass. Otherwise you may have just paid whatever he charges you for 40-50 worth of scrap or some really neat windchime cylinders. Better yet if he's just left them sitting empty he should just give them to you because he does not know how to treat gear and they deserve a better home than what he has given them.

 

[MC]

I picked up a tank that was empty for about 3 yrs. it VIP'd with no issues. but as stated earlier, will not know until you get her vip'd. What you could do is pull the valves, then look inside to see if there is any corrossion (doubtful their will be unless he had left the valves open while under water).

If he is a local guy, see if he'll agree to you paying a little bit for them to see if they vip/hydro, and the balance when they pass. I did that with a few tanks in the past and had no issues with the seller.

 

[gypsyjim]

T Better yet if he's just left them sitting empty he should just give them to you because he does not know how to treat gear and they deserve a better home than what he has given them.

I like your thinking!

 

[theduckguru]

You are looking at $40-$60 each for vis and hydro on a 20 year old tank you can purchase new for <$150.

You can find both the procedure to remove the valves and perform a vis inspection
online if you wanted to perform your own evaluation before putting $ in the tanks.

 

[DevonDiver]

I'd just make the purchase conditional on whether they pass inspection or not. Or..ask him to get the VI done, then deduct the cost from the purchase price if they pass.

Without VI and hydro, and no guarantees, they are essentially just scrap metal. What's the going rate for a few lbs of Aluminium?

 

[cbrich]

I'd just make the purchase conditional on whether they pass inspection or not. Or..ask him to get the VI done, then deduct the cost from the purchase price if they pass.

Without VI and hydro, and no guarantees, they are essentially just scrap metal. What's the going rate for a few lbs of Aluminium?

I agree.

The going cost of aluminum as of last week was about $0.70/lb, but this can very from location to location.

 

[herman]

To a great extent it's a myth that somehow tanks are damaged by being empty. AL tanks are pretty much uneffected by moisture and while totally open steel tanks will rust inside this requires that the valves either be open or removed. To rust there must be moisture which has to come from somewhere and if there is a closed valve on the tank there is no point of entry. Even if the tanks are bleed totally down and the valves reclosed there is not way that moisture can get inside the tank and the remaining air is dry breathing air. To top it off, my bet is the tanks are not actually empty but have a a few to several hundred PSI and ANY pressure above ambient means that nothing can enter the tanks.
If the tanks fail hydro it's for another reason, not from being empty.

 

[halocline]

Herman's right, with AL tanks this is probably a non-issue. You just need to peak inside and see if there are any pits, or go for an actual VIS. If they really sat empty with the valves off for years, there might be some surface corrosion, but I bet a little tumbling would take care of it. Catalinas are a little better than luxfers IMO because they're about a half pound less positive.