Need help on used AL tanks

[jlwest63]

I have someone that wants to sell me some used AL tanks. Here is what he has.

2 - 80cu AL standard tank that has been Nitrox cleaned and he says it can be used for either air or nitrox for $100.00ea
Can you use air or nitrox in the same tank??

2 - High pressure Neutral Buoyancy tank with sherwood valves for $120.00ea
How can you tell this?

each are 1 1/2 years old.

Are these worth buying for the price? I know you can buy new ones for $125.00 so I do not know if this is a good deal or if the guy is being stright with me.
Thanks

 

[TwoBitTxn]

Yes, you can use air and nitrox in the same tank.

Here is the catch. According to some nitrox fill stations, as soon as you put air into a nitrox tank, it is no longer oxygen clean and must be recleaned.

If the air is comming from a compressor that is also used to pump nitrox, it shouldn't be a problem. Also if the nitrox is either banked or a membrane fill, it shouldn't be a problem. Nitrox clean that is. This was probably more information than you wanted.

If you can get a brand new tank for $5 more, spend the $5.

TwoBit

 

[jlwest63]

Yes, you can use air and nitrox in the same tank.

Here is the catch. According to some nitrox fill stations, as soon as you put air into a nitrox tank, it is no longer oxygen clean and must be recleaned.

If the air is comming from a compressor that is also used to pump nitrox, it shouldn't be a problem. Also if the nitrox is either banked or a membrane fill, it shouldn't be a problem. Nitrox clean that is. This was probably more information than you wanted.

If you can get a brand new tank for $5 more, spend the $5.

TwoBit

Interesting. I could get the Nitrox ones for 100.00 ea. That would save me 50.00 on the 2 of them if I just bought regular air tanks.

What about the other 2?

 

[DEEPLOU]

I have someone that wants to sell me some used AL tanks. Here is what he has.

2 - 80cu AL standard tank that has been Nitrox cleaned and he says it can be used for either air or nitrox for $100.00ea
Can you use air or nitrox in the same tank??

2 - High pressure Neutral Buoyancy tank with sherwood valves for $120.00ea
How can you tell this?

each are 1 1/2 years old.

Are these worth buying for the price? I know you can buy new ones for $125.00 so I do not know if this is a good deal or if the guy is being stright with me.
Thanks

First of all there is a difference between Nitrox cleaned and O2 cleaned.
Nitrox cleaned indicates the tank has been cleaned suitable for pre-mixed nitrox.
If tank is going to get nitrox from partial pressure blending, it has to be O2 clean as pure O2 is put into the tank and then topped off with "clean" air.

Most AL tanks don't come from the factory O2 cleaned so it would be an extra expense to O2 clean a tank for nitrox use.
However, for your $100 you are getting a tank that needs a VIP in 6 months and a hydro in 3 1/2 years vs a new tank that will need a VIP a year from when you get it and 5 years from when it was stamped (new tank should have stamp w/in few months of purchase date).

 

[rcmcg]

Hi, I think the guy is being straight with you as long as the hydro is good and the visual inspection is current. Nitrox cleaned tanks can be used with air or nitrox but not both. Once you put regular air in the tank you must get it cleaned again if you want to use it for nitrox. Another alternative is to have it filled only with super cleaned air or nitrox and not use regular air. You should have learned about tank markings in your open water class as the tanks working pressure
(maximum fill pressure) is clearly imprinted on the tank. The neutral density tank is probably marked to 3300. Its advantage is you can wear less weight on your belt or in your bc. The disadvantage is it will probably cost more to get it filled. It still only holds as much air as the regular 80's, not more. Hope this was helpful. Rich

 

[jlwest63]

I just found a big thread on the 3300 tanks. Sounds like most people think they are a waste of time.

I thought that if you used the tanks that are cleaned for Nitrox with air you would have to get them re-cleaned.

I do not have a Nitrox cert. yet so I see no advantage of that because I would just be using them with air for now.

Keep the info coming.

 

[Ontario Diver]

This has been covered before in depth but here it is again.

Tanks to be used for nitrox must be "O2 Serviced". or "Suitable for O2 Service".

This means that all hydrocarbons must be removed from the tank and valve (O2 Cleaned) and all materials/lubricants in the valve and tank must be replace with O2 resistant materials (O2 Compatable).

Once this is done, any air that is put into the tank must be properly filtered in order to remove hydrocarbons from the air. This goes for either straight air or enriched air.

If the air you put into the tank is not properly filtered, it may contain hydrocarbons and then you tank is no longer O2 Clean and is then no longer suitable for nitrox.

You can put all of the air you want into a nitrox tank as long as it is properly filtered AND you lable the tank as containing 21%.

Or remove the durn sticker and put whatever air you want in.

 

[pasley]

If pure O2 is introduced into the tank, as in partial pressure blending, and if there is a contaminant, then there could be a problem, and you would not need any experts to tell you either, it potentially could be painfully obvious.

Personally, for the price, I would just get new tanks. But that is me.

 

[jlwest63]

If pure O2 is introduced into the tank, as in partial pressure blending, and if there is a contaminant, then there could be a problem, and you would not need any experts to tell you either, it potentially could be painfully obvious.

Could you give more details on this?

 

[Boogie711]

Pure O2 has a tendency to go very very BOOM when it hits contaminants at high pressure.

A woman at a dive shop in Florida was killed about 6 weeks ago after an incident with a pure O2 cylinder. It's not something you want to mess around with.

Is that detailed enough? Or did I misread your question?