O2 Cleaning

[GLiebmann]

I have a question and please excuse my ignorance. I purchased two fairly new Al80s. I had them visually inspected and asked that they were to be O2 cleaned and filled with NOX32. When I picked them up my shop told me that they didnt need to O2 clean them because they used a Membrane system for filling and at that percentage it was not necessary. They wanted to save me money which I appreciate. If they are filled somewhere else, however, that does not use this type of system its a different story.

My question is after a year of 32% fills, what would be the harm if I had another shop that did not use a Membrane system for filling? Is it really necessary to have them O2 cleaned or at this point would it be okay? I assume that if there would be an issue it would be in the filling process. Of course I dont want to put anybody at risk by neglecting to identify that they were not cleaned. Any advice would be appreciated.

 

[ScubaBunga]

To the OP, this is generally a hot topic as the actual reqs say O2 cleaning is required at 23 or 23.5%. I clean my own tanks so it’s not a big deal for me, but it would be pretty expensive for my fleet of tanks to have it done at a shop. Here is another thread on the topic O2 Cleaning for Nitrox
There are a few on scubaboard. The history goes back to at least the Apollo 1 accident.
End result is it will be up to the dive shop and the only way (if the shop even accepts the sticker) to be accepted everywhere is to state O2 clean. Happy diving.

 

[Divin'Papaw]

To the OP, this is generally a hot topic as the actual reqs say O2 cleaning is required at 23 or 23.5%. I clean my own tanks so it’s not a big deal for me, but it would be pretty expensive for my fleet of tanks to have it done at a shop. Here is another thread on the topic O2 Cleaning for Nitrox
There are a few on scubaboard. The history goes back to at least the Apollo 1 accident.
End result is it will be up to the dive shop and the only way (if the shop even accepts the sticker) to be accepted everywhere is to state O2 clean. Happy diving.

Good advice.

As I mentioned in my post above, a select few shops require O2 clean tanks to fill with banked nitrox. In my experience, they are the exception and not the rule in the US. I have taken my own tanks to many diving hot spots in the US including Morehead City NC, Key Largo FL, Cave Country FL, Southeast FL including Jupiter-Palm Beach-Boca Raton-Pompano Beach-Ft Lauderdale, Southwest FL (Naples & Ft. Myers), and multiple locations around the Great Lakes including Canada, MI, WI, OH and NY. I've had my non-O2 clean tanks filled with banked 32-36% at least 500+ times. Out of that experience, I've run into ONE shop that requires O2 clean tanks to fill with their banked nitrox. I've used at least three dozen other shops for banked nitrox fills that have had no issue filling my non-O2 clean tanks with banked nitrox. Not a massive data set, but not insignificant. I choose to not go through the cost and hassle to have my tanks O2 cleaned. I have plenty of shops available in the areas that I dive where I can easily get banked nitrox fills. It works for me. YMMV.

 

[OMyMyOHellYes]

I wonder - and I'm being serious - how much hydrocarbon mass needs to be present in a closed environment like a tank to pose a risk in a 100% O2 environment introduced in partial pressure blending?

Oxygen is not combustible. The chemical stoichiometry of the reaction says that fuel and oxygen will only combine, in the presence of ignition, in a certain ratio. Once the fuel is gone, no more burn and you get leftover oxygen. If all the oxygen is consumed before the fuel, no more burn and you get leftover fuel. Kind of a limiting reagent thing going on.

If you have a few million stray hydrocarbon molecules farting around in the tank and you suddenly introduce a bunch of pounds pressure of O2 and it somehow finds an ignition source, does anything happen besides a tiny "pfffft" and that it? Maybe a tiny amount of CO2 or even dramatically less CO and some marginal heat.

I'm not advocating doing away with O2 cleaning (or more precisely, igonoring) in environments handling O2, but it's an academic question as to how much in the way of hydrocarbon would be needed in the tank to pose a problem or risk to safety?

Never ever gonna get to absolute -0-.

 

[rjack321]

I wonder - and I'm being serious - how much hydrocarbon mass needs to be present in a closed environment like a tank to pose a risk in a 100% O2 environment introduced in partial pressure blending?

Oxygen is not combustible. The chemical stoichiometry of the reaction says that fuel and oxygen will only combine, in the presence of ignition, in a certain ratio. Once the fuel is gone, no more burn and you get leftover oxygen. If all the oxygen is consumed before the fuel, no more burn and you get leftover fuel. Kind of a limiting reagent thing going on.

If you have a few million stray hydrocarbon molecules farting around in the tank and you suddenly introduce a bunch of pounds pressure of O2 and it somehow finds an ignition source, does anything happen besides a tiny "pfffft" and that it? Maybe a tiny amount of CO2 or even dramatically less CO and some marginal heat.

I'm not advocating doing away with O2 cleaning (or more precisely, igonoring) in environments handling O2, but it's an academic question as to how much in the way of hydrocarbon would be needed in the tank to pose a problem or risk to safety?

Never ever gonna get to absolute -0-.

"O2 clean" is generally defined as less the 0.1 mg hydrocarbons per meter squared area. Aluminum is also combustible in the presence of high O2 and an ignition source. The ummm "tiny pfft" of hydrocarbons tends to end up with an exploding cylinder.

The Apollo 11 astronauts would like a word with you about what a "small" o2 fire turns into.

 

[Bob DBF]

Did you clean the threads on the tank first? For all you know the previous owner could have been using vaseline on them.

Makes you wonder what the previous owner was doing with the tank.

 

[Marie13]

"O2 clean" is generally defined as less the 0.1 mg hydrocarbons per meter area. Aluminum is also combustible in the presence of high O2 and an ignition source. The ummm "tiny pfft" of hydrocarbons tends to end up with an exploding cylinder.

The Apollo 11 astronauts would like a word with you about what a "small" o2 fire turns into.

Apollo 1, I think.

 

[rjack321]

Apollo 1, I think.

my fat fingers going on and on lol

 

[OMyMyOHellYes]

The Apollo 11 astronauts would like a word with you about what a "small" o2 fire turns into.

Why?

 

[happy-diver]

Do not Gus Grissom and Gil Grissom, look quite similar

I blow my tanks out with 300bar air hydrocarbons gorn

 

[edwants2dive]

More fuel on the fire (pun intended) I happened to come across this from Luxifer. They require O2 cleaning for anything over 23.5% O2. I am not saying I agree with them just providing the link to their FAQ.

Aluminum scuba cylinders in oxygen-enriched and oxygen service - why does Luxfer require cleaning for oxygen concentrations above 23.5%?

Few concepts have caused more confusion and controversy in the recreational diving industry than the so-called "40% rule." While there seems to be general agreement that special cleaning is required when a pressurized oxygen concentration reaches a particular "threshold" percentage, there is...

www.luxfercylinders.com