Oxygen ready tanks and filling

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MikeS

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Perhaps someone would be so kind to clarify the situation with oxygen ready tanks and filling. I would like to figure this out as I am getting ready to purchase several tanks and I’m trying to figure out what is the smart, safe, and/ or practical thing to do.

This is what I think I know so far:

Some tanks come “oxygen ready” from the manufacture.

If not, or if the “oxygen ready” status is compromised, it cost about $25 to have a tank “oxygen cleaned.”

“Oxygen ready” status is not necessarily required to get fills up to 40% O2, but only some LDSs can do so.

You can fill an “oxygen clean” tank with air (21% O2) without changing the “oxygen clean” status but the air is somehow special and not all LDSs can do it.

Thanks in advance for any help.

Mike
 
It cost about 25-30 to get your tanks 02 clean.If you have a good local dive shop he may tell you how to do it and observe you do it for a discounted rate.Dont expect to take your tanks home and clean them and have him certify them without him either doing the work or witnessing it.

The thing with the tanks is where the oxygen is mixed.If the oxygen is mixed in the tank it must be O2 rated.If the mixture is done outside the tank and then added to the tank at lets say 36% then it doesnt require the 100% O2 rating.Due to the popularity of eanx 1 & 2(32% & 36%) some places already have a premix of this and just add it to your tank already mixed.

In order to keep your O2 rating your tank must be filled with grade E air or you can lose your rating with a lesser air.

My LDS does the mixing in the tank which requires the O2 service rating and also lets me tailor the mix up to 40% depending on what my dive profile will be.Like i said before some places have an eanx 1(32%) and eanx2(36%) premade so all they do it is pump the mixture in your tank.Hope this helps
 
There is a lot of debate on this so without splitting hairs...If the tank (or whatever) is going to be in contact with high FO2 (fraction of O2) under presure then there is a risk of fire if the material is not suited for exposure to O2 or if it is not clean (free of highly combustable contamination). One way to blend nitrox is by partial presure. The first step is to pump pure O2 into the tank. During this phase the tank and the valve need to be O2 compatible and clean. How clean it needs to be is a much debated subject. It is common practice to run air through an extra filter stage (hyper filter) to ensure that more of the contaminants are removed. In theory even a small amount can build up over time and cause a problem. Therefore, some will not want to blend in your tank if they know that anything other than hyperfiltered air has gone in it.

If a methode of blending is used that does the mixing before it gets to the tank and the mix is under 40% then compatability and clenliness are not an issue. No the number 40 isn't magic but most agree on it.

Some blendors are more skiddish than others and some are even parenoid. But...if it blows it will be in their face.
 
their aluminum scuba cylinders are NOT shipped O2 Clean.

If a cylinder is O2 clean it should only be used for partial pressure filling. This status is only obtained by cleaning the cylinder to ensure that all hydrocarbons have been removed.

O2 clean cylinders can have an air fill if the air is hydrocarbon free which is obtained by hyper-filtration. Modified Grade E air that is properly filtered will not invalidate an O2 clean status.


If a cylinder is O2 serviced it can be filled with EANx mixes that are premixed.

In my area...$25 for actual O2 cleaning is a reasonable price.

I charge $40.

Hope this helps.

C_C
 
Thanks for the responses.

Lets see if I have this correct.

The crux of the matter is where are the gasses mixed, to safely mix in the tank, the tank must be “oxygen ready” because of the potentially high concentration of oxygen.

Regardless of where the gasses are mixed, if air is used, it must be grade E to maintain status. Air is normally hyper filtered to achieve this.

Filling a tank with other than hyper filtered (grade E) air compromises the “oxygen ready” status.

In conclusion:

If the LDS you use can premix to the highest oxygen concentration you intend to use, not more than 40 percent, the tank does not need to be “oxygen ready.”

If your tank is “oxygen ready” you should only have it filled with hyper filtered (grade E) air to maintain the “oxygen readiness.”

Thanks,
Mike
 
Close enough. Actually all air should meet grade E. The good stuff is modified grade E
 
There are three phrases that I've been told about.

O2 Compatibility means that all components of the tank and valve are made from materials that do not become more combustible under high levels of O2. These materials are 316L Stainless Steel, Monel Alloy 400, Inconel Alloy 600, Brass, Nylon 11, PTFE, Vitron/Nitrile, and TFE based plastics. This is important for the blending system as well.

O2 Cleaned means that your tank/valve (and the blending system/compressor) have had all hydrocarbons (grease, oil, manufacturing mold release, etc) removed from any surfaces that could come into contact with high O2 concentrations.

O2 Serviced is when the equipment is both O2 Cleaned and O2 Compatible and this should be documented on your VIS sticker.

And yes..... your tank and valve must be O2 serviced for any partial pressure blending. Faliure to use medical grade air may allow carbon or hydrocarbons to get into your tank. Oh in case you care CGA Grade E air (or DIN 3188, BS4275) can have no more than Oxygen: 20% to 22% (balance of gas predominantly nitrogen)
Water vapor: May vary depending on intended use (Not a good thing in scuba tanks IMHO)
Condensed hydrocarbons: 5 mg/m 3
Gaseous hydrocarbons (methane): 25 ppm
Carbon monoxide: 10 ppm
Carbon dioxide: 1000 ppm
Odor: none


Naui Modified standard Grade E air is Oxygen: 20% to 22% (balance of gas predominantly nitrogen)
Water vapor:128 ppm (v/v) -40 ºF Dew Point
Condensed hydrocarbons: 0.1 mg/m 3
Gaseous hydrocarbons (methane): 25 ppm
Solid particulate: none >2microns
Carbon monoxide: 2 ppm
Carbon dioxide: 500 ppm
Odor: none


Hope that this helps.
 

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