Baking Tanks in the Oven for O2 Cleaning

[evensplit]

...I have heard many people on various boards say they need to "inspect" the cylinder to determine if it is oxygen clean. I would love to know what they are looking for and with what device they are looking.

Phil Ellis

I have looked into quite a few "O2 clean" cylinders that I thought suspicious. While we may not be able to tell if a cylinder is O2 clean, It is often easy to spot one that is not. It's amazing how many times we've found non O2 compatible grease, O-rings, and other contaminants in cylinders that are supposed to be (and were marked as) O2 clean.

 

[ekewaka]

I have heard many people on various boards say they need to "inspect" the cylinder to determine if it is oxygen clean. I would love to know what they are looking for and with what device they are looking.

My guess is that most of them are looking for dollar bills in the customers wallet, but some use UV lights to look for hydrocarbons in the tank. I have never used one, and I don't know how effective it is. I don't doubt that it is possible to see some hydrocarbons with a good UV light that is designed for that purpose, but it certainly is not guaranteed to find all of them.

 

[Gilldiver]

Heat can damage aluminum long before the melting point. Luxfer and DOT say that the cylinders should never be exposed to heat above 130F. You would probably be safe a bit higher than that, but you definitely shouldn't be heating them in an oven.

130F, that is a hot day in the gulf with the boys wearing sand colored leasure suits and boots.

Aluminum heat treat temps range between 250 and 600F depending on the alloy. It is all a time at temperature thing. The heat treat are what the -T3 or -T6 mean after an alloy number like 6061-T6.

For all of the alloys that tanks are made out of you start changing the micro structure between 225 and 250F. A usual heat treat will be between 2 and 24 hours at temp depending on just what you want the metal to do. The problem is that the time is cumulative over the life of the tank. So, it may already have the equivelent 1 or 2 hours when you buy it from the working temps the metal reaches as it is formed.

Back to tanks, using hot water that can not be hotter then 212F and if from a sink most likely will not be hotter then 120 or 130F is not a problem.

Putting it through a powder coat process that bakes the powder paint at 350F, now that is a problem and will result in a tank that can, and will, explode at pressure. Also, some paint shops will Bake paint with IR which can result in surface temps into the 225-250F range, if they bake for 1 or 2 hours, the heat treat was just blown and the microstructure will be brittle. Both of these are why some shops will not touch a repainted tank. They just don't know how it was processed.

 

[Gilldiver]

Here are two photos of how I just cleaned some tanks. The "tools" are a tooth brush for getting the neck threads clean, a "stand" made from PVC couple and a 90 eletrical conduit bend. I use clean NITROX to blow dry the tanks.

1) Put in about a quart of your cleaner using hot water - as hot as your sink will deliver, slosh it around for a while. I will plug the neck with a stopper and roll quickly back and forth turning the tank 1/3 around 3 or 4 times to make sure I get good mechanical cleaning (impingement) on all areas of the tank.

2) Dump it out and repeat.

Use the tooth brush each time to get the threads

3) Dump out the cleaning solution and use a quart of clean hot water. Slosh it around just like the cleaner

4) Repeat

5) Dump out the last rinse and completely fill the tank with hot water. By this time the tank will be unpleasent to "this hurts" hot from the water. Dump it out, place the "stand" and tube into the neck, flip over and blow it dry.

I can feel the air comming out and tell the diffrence when the water is all gone. But a slow could to 30 is all I need for tanks up to an 80. You may want to do a slow count to 60 for 100's and bigger.

The tank on the "stand" is an aluminum 40.

Pete

 

[hydro12]

Cool, that looks pretty slick. For my situation, I'm just worried about using any of my air tanks to blow-dry the O2 clean tank b/c the air I have is definitely not oxygen-compatible.

I assume that's an AL40 in upside down, so that is a 5.25 inch pvc coupling?

Thanks again for the pictures.

 

[JeffG]

Cool, that looks pretty slick. For my situation, I'm just worried about using any of my air tanks to blow-dry the O2 clean tank b/c the air I have is definitely not oxygen-compatible.

Your tank is open to the atmosphere, but your worried about blowing in "non-O2 compatible" air?

Make sure you O2 clean your mask too. If you breath out of your nose your mask could exploded.

 

[hydro12]

Actually, I'm performing all the decontaminating in my hermetically sealed oxygen-clean kitchenette with filtered hyper-clean, dehumidified air.

I'm definitely on the same page as you though - I've already O2 cleaned my mask AND snorkel for such reasons as you list.