O2 clean regs for back mount doubles?

[geoff w]

So you don’t “need” o2 clean regs on your back.

However, I believe it makes sense to keep all your stuff o2 clean. I have cannibalized my backgas regs to create a deco reg for a buddy on more than one occasion. Oh your 1st stage is creepin? Here bro take this. Enjoy.

How do you keep everything O2 clean? O2 clean tanks and only gas fills with partial pressure blending? That rules out membranes and sticks for nitrox, which is pretty impractical around here at most shops. I'm not willing to put a blending station in my garage

 

[rjack321]

How do you keep everything O2 clean? O2 clean tanks and only gas fills with partial pressure blending? That rules out membranes and sticks for nitrox, which is pretty impractical around here at most shops. I'm not willing to put a blending station in my garage

Making OCA is ridiculously easy. Just because the 32% is made by membrane or a stick doesn't mean its dirty gas.

 

[rjack321]

To answer the original question.

Every new regulator bought today is O2 clean-even ones that state 'only use up to 40%'.

Sighs so much misinformation in here. As a general rule, whenever you say "all" or "every" stop for a moment. Have you experience with EVERY regulator on the market? If the answer is no, then perhaps you can't really be this authoritative.

There are several regulators on the market right now which may be scrupulously clean out of the box, but contain materials which are completely incompatible with high pressure O2. For instance, aluminum or titanium 1st stages should never be used with oxygen

 

[tbone1004]

How do you keep everything O2 clean? O2 clean tanks and only gas fills with partial pressure blending? That rules out membranes and sticks for nitrox, which is pretty impractical around here at most shops. I'm not willing to put a blending station in my garage

what @rjack321 said. Just because it's not air being used to pp blend doesn't mean the compressors aren't kept O2 clean. Why would a membrane or a stick automatically make it not O2 clean? Now some peoples pumps may not be O2 clean at all, but all of the ones that I frequent in cave country and NC are.

 

[CptTightPants21]

Sighs so much misinformation in here. As a general rule, whenever you say "all" or "every" stop for a moment. Have you experience with EVERY regulator on the market? If the answer is no, then perhaps you can't really be this authoritative.

There are several regulators on the market right now which may be scrupulously clean out of the box, but contain materials which are completely incompatible with high pressure O2. For instance, aluminum or titanium 1st stages should never be used with oxygen

Perhaps additional detail with the titanium could have been added-I thought I had covered it and mentioned the T series when I was listing out the other Atomic series, but I can see from my post I did not. The S series should be fine because all the titanium parts are in the 2nd stage.

Point was a regulator doesn't need to be 'green' to be O2 clean, nor is there anything magic about O2 cleaning. I was referring to new regulators because the days of manufacturers using oil for sealing or using non-oxygen compatible lubricants are over. But I will admit, perhaps I am sheltered in my diving--just about everyone I know dives Apeks XTX series, Scubapro/Halcyon (Mk17, MK20, MK25, Atomic (Z,B,M), or Deep Six.

It would be easier to list the regulators that could not be used for deco bottles. Scubapro and Atomic have a titanium regulator and they both cost close to 2K, any others? You mentioned aluminum, which regulators are using aluminum in the their first stage?

 

[NAM001]

I'm planning to start tech training some time in the near future, depending on scheduling everything with the pandemic. From talking to several people, they all use Atomic M1s for their back mount double regs because they're O2 clean and rated for higher percentage O2 right out of the box. After thinking about this for a little bit, it didn't make sense, because you'd need O2 clean for a deco bottle, not back gas. I asked one friend who has his set up this way, he didn't know the reason, and said it's because that's what an instructor recommended to him

Is there any reason to use something like an Atomic M1 for back gas, or is a properly configured Atomic ST1 or similar fine for doubles, and use an M1 for higher percentage O2 stage bottle?

I have to try to remember but if I do correctly all regs are clean from the maker now days. IMO for O2 use but sold as 40% and less use. atomic had an issue with their titanium regs in that they say not to use O2 with them because of the titanium parts. I did some reserarch a long while back and what I found is that there is a hazzard with titanium in an O2 rich environment. However that environment was 14,000 psi and above. What that means I do not know. the obvious says it is not an issue but that 14k number may be related to being say a titanium pipe and not making sharp turns where heat is generated I forget the name of the principle that means heat generated from gas impacting at a sharp bend. What the PSI is with that involved I can not say. And that , that psi was pure O2 not a fractional gas. Personally I will never clean a reg for nitrox 40 and less service.

 

[Rose Robinson]

I'm planning to start tech training some time in the near future, depending on scheduling everything with the pandemic. From talking to several people, they all use Atomic M1s for their back mount double regs because they're O2 clean and rated for higher percentage O2 right out of the box. After thinking about this for a little bit, it didn't make sense, because you'd need O2 clean for a deco bottle, not back gas. I asked one friend who has his set up this way, he didn't know the reason, and said it's because that's what an instructor recommended to him

Is there any reason to use something like an Atomic M1 for back gas, or is a properly configured Atomic ST1 or similar fine for doubles, and use an M1 for higher percentage O2 stage bottle?

Hello Jeff,

I dive back-mounted doubles full time, as well as diving with blended gas full time.

My regulators of choice are current generation Poseidon Jet-Streams, I own four sets, two sets configured for doubles, two sets configured for stage/deco bottles.

As far as O2 cleaned, I was always told that the viability of your O2 cleaned regs is based solely on the quality of your fills, one bad fill and your regs are no longer O2 clean, as we consider the term ''100% O2 clean", and that goes for your O2 cleaned tanks as well.

I rely on a certain professional to service all my gear, and me like thousands of others do the same and have to rely on their expertise/knowledge and advice.

All my regs are serviced annually, regardless of amount of use, and primarily to ensure 100% O2 cleanliness.

Rose.

 

[geoff w]

Making OCA is ridiculously easy. Just because the 32% is made by membrane or a stick doesn't mean its dirty gas.

How so? Putting a filter stack between the fill whip and an O2 clean set of doubles? Dive shops around me tend not to have those, unless it's a shop catering specifically to tech divers. As someone above said, once you do a fill that isn't O2 clean, all bets are off as far as tank, attached regulators, etc., and to get everything back so it qualifies as O2 clean you would have to clean everything and from that point on make sure everything that touches is O2 clean.

With either a membrane or blending stick for nitrox, the compressor is never ingesting pure O2. The blending stick needs to be O2 clean to mix pure O2 and air for the input stream to the compressor, and being rated at 40% O2 or less by policy is the same as air (per NOAA or OSHA), and the membrane basically filters out the nitrogen leaving a higher percentage of O2. Oxygen clean and oxygen compatible are very different.

My original question was Atomic regulator related and basically why use an M1 (intended for high O2 % applications) for back mount doubles instead of any other Atomic (I have ST1s), since my back gas won't be high O2, and I think I got a lot of good answers to think about. Bottom line from the answers is there's no reason to go with M1s for back gas, and better to use an M1 for a deco stage bottle, and just apply my (possibly O2 compatible and most definitely not O2 clean) ST1s for my double regs. Although there are several very good reasons for making and keeping everything O2 clean if I was serious about tech diving a lot (I'm not, too old for that sort of stuff and mostly interested for the knowledge and skills).

At one of the local scuba shows a couple of years ago, I talked to Dean Garraffa from Atomic. He indicated they did destructive testing on regulators in high O2 environments. I don't recall the specifics he quoted as far as test pressure, but he confirmed the titanium regulators can very violently self disassemble into very small and rough pieces during testing

 

[Woolfie19]

How do you keep everything O2 clean? O2 clean tanks and only gas fills with partial pressure blending? That rules out membranes and sticks for nitrox, which is pretty impractical around here at most shops. I'm not willing to put a blending station in my garage

Personnal filter for every fill in my tanks, regardless where I fill them ( even if the shop tells me they maintain their compressor filters meticulously).

 

[tbone1004]

@geoff w you don't need extra filter stacks between whips and what not. Personal filters don't really do anything as the fill rates are far too fast and there isn't a back pressure regulator on them. Dwell time is woefully inadequate to really do anything but if it makes you feel better, then go for it.

MOST all compressors come with filters that are capable of spitting out O2 clean air from a capacity and it's then up to the owner of said compressor to put filter cartridges in that will give OCA which really is ridiculous
So OCA vs CGA Grade E vs EN12021 *divers
CO is <2 vs <10 vs<15 -this has no bearing on oxygen compatibility
OCA does not have a dewpoint spec, but CGA is -65F and again has no bearing on O2 compatibility
Oil is <0.1 vs <5 vs <0.5 mg/m3

So the oil is obviously the most important part of this since it is what actually matters for oxygen compatibility. Now, pretty much all modern compressors if properly maintained and using synthetic oil can meet the <5mg/m3 without any filtration at all. No water knock out, no filters, literally at the outlet of the final stage. The moisture separator will take quite a bit of oil out with it as the water condenses and that's why in Europe especially the effluent from the traps has to be captured. @iain/hsm knows a lot more about this, but it's one of the perks of having a Rix where it's just distilled water. The rest of the oil is taken out by activated carbon in the filter stacks. So long as the AC bed is big enough and replaced at the right time *calculated based on volume pumped through* and the PMV is set properly, the air coming out will have essentially non detectable oil levels. This is also why it's important to get your air checked at the END of the filter life to make sure that your PM frequency is sorted out.
The math for the AC bed life is basically assuming 5mg/m3 incoming to the filter, the mass of the AC bed so for easy math say 100g, and the AC beds can absorb somewhere around 8% of its weight in oil IIRC but call it 5% for easy math and conservatism. So the filter can absorb 5g of oil. 5/.005=1000m3=35k cf. Say the dive shop has a 10cfm pump, so every 3500mins/60hrs the filters have to be changed. Obviously adjust for the actual mass of AC in your specific filter and your compressors fill rate and I would double check the % absorption of the AC if you're running your own compressor, but that's how the calculation works.

So, all this to say that if you are getting gas from a compressor that has an adequately sized filtration stack, that has an AC bed in it, and it is changed at the right frequency, you should be receiving what we call "OCA" from the pump. Ask the dive shop to look at their last analysis and if they don't show it to you run away very quickly. If the oil level is <0.5mg/m3, then I wouldn't worry about it. Of note fresh analysis is usually <0.05mg/m3 so it's not something you have to worry about...