What is O2 clean?

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BILLB

Contributor
Scuba Instructor
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Location
Hatboro, PA
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My dive friend who always is looking for another angle on the industry sent this link to me.

http://www.alldiver.com/

Check out this site.

Here is the text of the essay on O2 cleaning.

Comments are welcome. Again, there may be something to learn here.

Oxygen Cleaning



The dive industry, as any other, is constantly looking for new ways to make money. Every year products are “improved” and new products are introduced in the hopes that scuba divers, who are very technical by nature, will part with their money and keep the local dive shop in business.



One of the ways dive shops earn money is by requiring that equipment, which will be exposed to mixtures other than air, be “oxygen cleaned”. The equipment includes, but may not be limited to, cylinders, cylinder valves and manifolds, regulators, pressure gauges, and almost anything else they can convince you to have cleaned.



Let’s all first agree that no one wants to breathe dirty gas or have fires and/or explosions because of their equipment – no matter what the cause. That means that everyone needs to maintain their gear as though their life depends on it – which by the way, it does. If you didn’t already know that, please sell your gear on eBay and take up golf. What ever you do, don’t go diving. You’ll hurt or kill yourself and maybe take others with you.



So what is Oxygen cleaning and what does it mean to be Oxygen cleaned?



For the purposes of this discussion, consider that there are three components of fire/explosion. They are, heat, fuel, and Oxygen. If any one of these is missing, you can’t have a fire or an explosion. If all of these are present in adequate quantities, you can have a great deal of fire and/or an explosion.



Oxygen cleaning addresses the fuel component of the fire triangle. Remove all traces of fuel and you can have as much of the other two components as you want and you will still not have a fire or explosion. For all intents and purposes, that’s true although, given enough heat, a cylinder of Oxygen will expand enough to explode but that and any other scenarios one can come up with are not part of this discussion.



So how clean is Oxygen clean? You just paid your $25 to have your cylinder O2 cleaned. What was done? For $25, your cylinder, after being VIP’d, was probably tumbled with soapy water and an aggregate to dissolve any hydrocarbon containing substances that might have been in there. The soapy water and aggregate were emptied out and the cylinder rinsed and dried.



For some more money, your cylinder valve was disassembled and all the parts were placed in an ultrasonic cleaning bath of soapy water or a chemical cleaning compound for a few minutes. They were then rinsed and dried and reassembled using inert seals and lubricants.



Your Oxygen clean valve was rejoined with your Oxygen clean cylinder and the VIP sticker was punched for partial pressure filling as opposed to premixed gasses up to 40% Oxygen.



This all sounds great, right? Yes it does! Now comes the fun part. So how long does scuba gear stay Oxygen clean?



Let’s say the technician cleaning your valve was in a hydrocarbon free area and used gloves, since the natural oils on the skin of your fingers contain hydrocarbons and would render the valve O2 dirty. What’s the next thing that happens? They fill your cylinder for you, right? When was the last time the fill system was O2 cleaned? Your cylinder gets filled say 100 times each year from their fill station and they want you to pay them every year to have it O2 cleaned. The hydrocarbons they are cleaning out came from their filling system. You are only one of hundreds of people they fill cylinders for. If your cylinder can dirty enough in 100 fills to warrant O2 cleaning, then just imagine how dirty their fill system is if they fill thousands of cylinders each year. When was the last time they cleaned all the valves and gauges that comprise their fill system after the hyper filtration system?



So right after cleaning, your cylinder now contains at least 1% of the hydrocarbons it will accumulate over a year (based on 100 fills per year) and you received them from the people that you paid to clean it out. Did you ever touch the inside of a DIN valve or the surface of a yoke valve? Guess what? It’s not O2 clean any more.



Given that you need all three sides of the fire triangle (heat, fuel, Oxygen) to have a problem, minimizing the fuel and the heat lets us safely use Oxygen at high pressures. The truth is that O2 cleaning is only one part of safely handling Oxygen, but it’s good practice to have your equipment checked, serviced, and cleaned, regularly. Selling “O2 clean” regulators and other equipment at higher prices is a scuba con game. I’m sure oxy-acetylene gas welders laugh every time they hear about O2 cleaning in the dive business.
 
Do shops clean new gear? New tanks from reputable sources like PST and Faber are clean enough to be used with oxygen as they come from the factory. The valves are likewise clean. I'm referring to Sherwood which are not only clean but use teflon washers ( no O ring) in their single valves, and 'tech' sources like SeaElite or Diverite which advertise Nitrox clean but are really O2 ready.

I don't see any reason to clean a tank which is filled with > grade E air (hyper filtered). However, it would seem prudent to clean a tank which has been consistently filled from a portable compressor with small condensator and filter. I don't know how often but might suggest per 100 fills. Even this may be too frequent. If I were filling steel tanks I would look for moisture or rust. If none, wouldn't worry about oil either. A trace, non visable oil film such as might be left by a fingerprint is irrelevant. A larger area non visible oil film which can only be illuminated by black light or similar might cause a problem by emitting a trace of carbon dioxide. Industry types would have you believe that carbon monoxide will be produced but I am skeptical that CO can form in a pure oxygen environment. Certainly not any significant amount, not enough fuel. In any case, such minor combustion would leave an odor. With aluminum tanks, well, aluminum can burn in presense of pure o2. I think that this has happened once or twice but the circumstances were unusual involving a neck crack. This is an area that I'm not too familiar with. It is said that particles of aluminum oxide can burn but I'm not sure of the actual history, eg whether anyone has identified a smoldering (G) problem here. I might choose to be more cautious in examining and maintaining aluminum tanks if I were to own them.
 
Furthermore to the above points, does anyone seen or heard of a tank exploding because it was not oxygen cleaned?


What is the tank internal temperature when being filled?
 
VIP+ = $$$ for LDS

Can we make the same marketing agrument for VIP+??
 
During my nitrox class the instructor made a big deal about 02 cleanliness. Really beat it into our heads.

He then demonstrated the proper filling technique using a "02 clean" tank that had been left empty with the valve open for quite some time.

I was the only one to see the humor. Sigh.

Anyway, I think that tanks that contain 02 should be cleaned. I also think that the typical LDS approach is not optimal.

Peter Doege
 
The VIP+ is another way to extract dollars from the unknowing. As I understand it the alloy now used by all AL tank manfactures has never exhibited any stress fractures that were the cause of tank explosions on the older alloy tanks. In fact I know of a LDS that failed several tanks when nothing was wrong. The problem is the Visual Plus system simply was not designed for the AL tanks now in use. In fact, several articles on Visual Plus has stated that this method is basically useless on AL tanks manufactured after 1991.
 

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