Switching between standard and enriched air

[MildlyDamp]

I recently purchased the Atomic Aquatics B2 regulator. Like many other regs, the instruction sheet specifically advises against swtiching back and forth between standard compressed air and enriched air. The salesperson at my LDS, who is a very experienced DM, said that this is just standard CYA language that's in most regulator manuals, and not to worry.

My question is - can I switch between standard and Nitrox? If so, do I have to take various precautions (e.g. having the reg cleaned first)?

 

[WarmWaterDiver]

Hop over to the "Tek Talk" forum, under "General Tek Discussions", and look for two threads began by a person going as "Deal Me In" for recent threads on this topic.

I personally do not choose to switch back and forth between "Grade E" air and O2 enriched air. I personally don't have a problem switching back and forth between "Grade J" air and O2 enriched air, But this is just my persoanl choice, due to the tendency of things like compressor oils to accumulate over time.

There's an article I ran across regarding testing NASA did on oil and oxygen and pressure regulators I posted in another thread. This was using 100% oxygen, but the oil quantities are not very large - milligrams are little things. Oils tend to spread as very thin films, coating surfaces (this is part of what makes them such good lubricants for things with tight tolerances like pistons & cylinders).


http://stinet.dtic.mil/cgi-bin/fulc...searchid=10772414666282&submitbutton=Citation

 

[Spectre]

It depends on if you have an O2 cleaned regulator. If you have an O2 clean reg, and you use it on non-hyper filtered air, or a tank that has has non-hyperfiltered air in it, then you'll have to re-clean the reg before using with nitrox exceeding EAN40. so if you're not using over 40% o2, you shouldn't need to have the first stage be cleaned.

 

[iflyprops]

My reg is only for use up to 40%. I have the Atomic Z1, very similar to your B2, and have never had a problem switching between air and nitrox (lean mixes). From what I have read, as I am no expert, if you only use rec mixes such as EAN32/36 you will have no problems.

 

[rescuediver009]

I would say that it all depends on the facility. If you are getting your gas from a place that does EAN then they are more than likely not to have problems with oil in the compressor. It is when you go to a place that does not have EAN mixes they may not be as careful as the EAN places and leave you with some oil in your tank. Just be careful where you are getting your fills I guess.

 

[SDAnderson]

I'd say that the DM is correct. If you're a recreational EAN user (EAN40 or less) I wouldn't worry about oxygen cleaning your regulators, even if you're using plain old Grade E air for your air fills instead of the hyperfiltered air that goes into EAN mixes. If your air fills are hyperfiltered then there is no reason to be concerned at all.

The same doesn't apply to mixes above EAN40, but it doesn't sound like this is your worry.

 

[Spectre]

That's a good point. I looked at the question from the regulator standpoint, but it's probably more important to answer it from a tank standpoint. The main issue is that you don't want high percentages of oxygen at high pressure passing through anything that's not clean. So this would include a 1st stage regulator being used for deco gasses, or a valve or tank when getting nitrox via partial pressure means.

So if you have your tanks cleaned for O2 service, this allows the valve and the tank to handle the 100% o2 involved in partial pressure nitrox blending. If you fill those tanks with non hyper filtered air, then there is a chance that the valve is now contaminated and you shouldn't put 100% o2 directly into the bottle anymore.

If you are getting your nitrox fills off of a banked system, or another type of mixing system that keeps the O2 percent going into the bottle around EAN40, then you don't need the tank cleaned for O2 service.

 

[MikeFerrara]

At 40% (about) FO2 or less I don't worry about it.

 

[iflyprops]

If you are getting your nitrox fills off of a banked system, or another type of mixing system that keeps the O2 percent going into the bottle around EAN40, then you don't need the tank cleaned for O2 service.

Most (if any at all) of the shops will not fill your tank with nitrox without the proper markings which usually entails O2 cleaning.


my 2 cents

 

[Genesis]

I'm with Mike on this.

Regs and such that will never see over 40% FO2 I don't worry about.

Anything over 50% I do. NASA has done a number of studies on this, and the short version of their results is that for any FO2 over 50% you may as well treat it as 100%.

BTW, you can provoke ignition on ANY reg, O2-cleaned or not, if you work at it hard enough. Don't do dumb things like slamming open valves and you greatly reduce the risks. O2 cleaning is not a panacea, but it IS a necessary component towards having REASONABLE safety (no such thing as "completely" safe)

O2 cleaning is really just kitchen science, and isn't tough, although things like an ultrasonic cleaner help a lot.