Use of O2 clean tanks in remote areas...

[pescador775]

Brian,
By its nature, 'technical' diving is confusing. That's why we have all the dive courses........ to confuse you further. I recommend the 'oxygen hackers companion' for an irreverent look at the technology and practice.

As to your problem, we will solve it. Look, you basic requirement is for a metal pipe with threaded, O ring sealed end caps. Accumulators (devices used in pneumatic systems to capture and store air) are available from Protecair and Plans and Kits. Talk to them on the phone and explain that you need a small 3000 psi canister which accepts a Lawrence Factor cartridge. Or, if you desire, I will put you in contact with someone who may be available to machine a canister from scratch. He has plenty of experience in designing and fabricating similar devices. It won't cost an arm and leg, certainly not a ridiculous $1500 for which you, incidentally, could buy a good used compressor and bypass the dive shop altogether.

 

[diverbrian]

I will pick this comment as I am finding this to be interesting reading. I am not trying to "bypass the shop". The fact of the matter is that the "local shops" all have Grade E air. The problem is that I travel to do much of my diving. Check out my trip reports in the Great Lakes Wrecking Crew and you will see what I mean. The operators in the Straits may have air that is perfectly clean enough or maybe they don't. They won't stand by it for me to tell. They just play it safe and say that their air is not suitable for PP blending. Seeing that my "divemobile" is an overworked Ford Mustang, I am not taking a compressor w/ Nitrox system with me to dive in the Upper Peninsula.

What I am trying to avoid doing is buying another set of doubles just for places that don't have Nitrox Compatible air. I may just buy bands and a manifold for two of my eighties (which are not O2 clean as the LDS fills them and they have premix). That would get me a set of doubles that I could have filled in such areas. But that is just a thought right now.

Keep the conversation going!

Brian

 

[pescador775]

Keep it going?
LOL, I'm done. I'm in the 'can do' business. As such I will never try to tell you your question is dumb or suggest you do what I'm doing instead of what you want to do. There is already plenty of that here. There are solutions to most problems. People come on these boards and, in the end, hear two strategies--- buy an Apeks (answer to most questions around here) or 'build it yourself' (me and hacker, heh). Kidding.

Building a filter canister is not a laughing matter, eg a piece of water pipe with end caps simply won't do. That falls into the category of 'pipe bomb'.On the other hand, it is not rocket science although some calculations (Barlow's formula) and a knowledge of metallurgy are helpful. If aluminum is used the specific alloy must be traceable and verifiable and subject to Brinell test. Stainless steel is weird stuff so one might add some thickness above what the formulae indicate, but normally the pipe already has a specific press rating and I go with that. The first step is to settle on the filter cartridge, then the canister is built around it. People like those at Clark Yacht Center could advise on a smallish LF cartridge which contains dessicant and charcoal. The rest is selecting a piece of pipe and finding matching end caps. This is fairly easy to do for someone 'in the business' and is much cheaper than machining the various pieces. Machining is mostly confined to cutting the pipe, threading the ends and cutting O ring channels including the gas seal where the cartridge fits into the the canister end cap. Drilling and tapping the caps pretty much takes care of the rest.

 

[diverbrian]

I actually understand some of what you are talking about. They taught me basic metallurgy and chemistry in Nuclear Power School. Yes, stainless can be a little weird as far as characteristics go. (Try adding heavy ionizing radiation to the mix, LOL). Personally, I tend to trust pressure ratings or like designs with added Stainless if you intend to hold a pressure. Run air through there and things heat up or cool down rather quickly. That can crack the metal and cold, brittle metal (while having a great deal of hardness) gives little or no warning before it blows.

Thanks,

Keep it going?
LOL, I'm done. I'm in the 'can do' business. As such I will never try to tell you your question is dumb or suggest you do what I'm doing instead of what you want to do. There is already plenty of that here. There are solutions to most problems. People come on these boards and, in the end, hear two strategies--- buy an Apeks (answer to most questions around here) or 'build it yourself' (me and hacker, heh). Kidding.

Building a filter canister is not a laughing matter, eg a piece of water pipe with end caps simply won't do. That falls into the category of 'pipe bomb'.On the other hand, it is not rocket science although some calculations (Barlow's formula) and a knowledge of metallurgy are helpful. If aluminum is used the specific alloy must be traceable and verifiable and subject to Brinell test. Stainless steel is weird stuff so one might add some thickness above what the formulae indicate, but normally the pipe already has a specific press rating and I go with that. The first step is to settle on the filter cartridge, then the canister is built around it. People like those at Clark Yacht Center could advise on a smallish LF cartridge which contains dessicant and charcoal. The rest is selecting a piece of pipe and finding matching end caps. This is fairly easy to do for someone 'in the business' and is much cheaper than machining the various pieces. Machining is mostly confined to cutting the pipe, threading the ends and cutting O ring channels including the gas seal where the cartridge fits into the the canister end cap. Drilling and tapping the caps pretty much takes care of the rest.

 

[pescador775]

An aluminum pipe with 10,000 psi burst press (compensate for thread depth) is sufficient but my machinist buddy usually goes a bit stronger. Same with stainless pipe. He has taken some flack from the class of people known as experts in nothing, owners of competing business, mostly. It worked, because my cautious friend decided to make his product so strong that he was flack proof. Anyway, that's a good reason to go small, to cut the overall weight. Not much extra filtration is needed anyway, just enough to erase the one drop of water and 1/100 drop of oil that the average compressor puts into a SCUBA tank. BTW, that is pretty good air and not a cause of concern for rust, etc. The water, in particular, is gas vapor and the SCUBA tank would have to be cold indeed for the water vapor to condense.

I actually understand some of what you are talking about. They taught me basic metallurgy and chemistry in Nuclear Power School. Yes, stainless can be a little weird as far as characteristics go. (Try adding heavy ionizing radiation to the mix, LOL). Personally, I tend to trust pressure ratings or like designs with added Stainless if you intend to hold a pressure. Run air through there and things heat up or cool down rather quickly. That can crack the metal and cold, brittle metal (while having a great deal of hardness) gives little or no warning before it blows.

Thanks,

Anthatcomp

 

[m7scuba]

Sorry to resurrect an old thread, but I'm having the same essential question. I'm looking to get a tank soon, but my LDS does not fill with O2 compatable air. I'd like to keep it O2 clean if possible to open up to opportunity to get Nitrox fills. So, what was the eventual outcome of this discussion diverbrian?
Thanks,
Brian

 

[ScubaSixString]

Could someone clarify the issue with filling O2 clean tanks with regular air? I'm new to diving. I've just purchased tanks recently, and I'm going to get them O2 cleaned for partial blending Nitrox (I am Nitrox certified). Isn't regular air the same as Nitrox? It's just at EAN21. Is it the case when you go with partial blending of Nitrox you always have to go this route?

Thanks
oharag

Recreational NITROX is a blend from 21 to 40 % O2. As long as you are using "banked" nitrox below 40% there is minimal fire hazards associated with your tanks and regs (most now advertise "ready for nitrox up to EAN40 right out of the box". When either your tanks, valves or regs come into contact with anything over 40%, they have to be O2 cleaned and serviced, to make sure there are no contaminants or parts of the equipment that pose a fire hazard (or explosion hazard).

With regs and recreational nitrox there is little concern. However if the diveshop uses a partial pressure blending method, the tank will be in contact with 100% O2 during it, regardless of what the end mix is. They add O2 first, and then add air. If this is the case, the tank needs to be o2 rated.

Grade E, as i understand it, is oxygen compatible air. If you fill an O2 cleaned and serviced tank with non "oxygen compatible" air, it loses its rating and you'll have to have it redone.

 

[oxyhacker]

Grade E is standard scuba air, not O2-compatible. Though if you follow the literature, you will find a lot of people in the industry are beginning to feel that Grade E is fine for mixing - as long as it is really grade E!

If there was a problem, it would be gradual, occuring over many tankfills before the tank could be contaminated enough to present probems - it's not like virginity. So most of the people I know don't worry about an occasional fill of Grade E air in their O2- clean tanks.

If the filter has failed, and the system is not producing Grade E air anymore, then you may have a problem. So the above only applies to well-maintained systems, preferably equipped with some sort of moisture monitor on the output, since that gives good warnng of filter failure. That's why a lot of people feel the main benefit of extra hyper filters in an O2-compatible air system is providing a second line of defense in case the primary filter fails, rather than for any miniscule extra amount of filtering it provides.

However, if you are thinking about buying a nitrox tank now, for possible use later, it would make a lot more sense to buy a regular tank now, and nitrox clean it when and if you ever need PP mixed nitrox.

BTW, a air test lab told me awhile back that most of the air they test from Grade E systems actually meets O2-compatible standards.

Grade E, as i understand it, is oxygen compatible air. If you fill an O2 cleaned and serviced tank with non "oxygen compatible" air, it loses its rating and you'll have to have it redone.

 

[Tom Winters]

Uh, wouldn't it be a whole lot easier to just buy a few extra tanks so you can avoid stuff like this?

 

[ScubaSixString]

Grade E is standard scuba air, not O2-compatible. Though if you follow the literature, you will find a lot of people in the industry are beginning to feel that Grade E is fine for mixing - as long as it is really grade E!

If there was a problem, it would be gradual, occuring over many tankfills before the tank could be contaminated enough to present probems - it's not like virginity. So most of the people I know don't worry about an occasional fill of Grade E air in their O2- clean tanks.

If the filter has failed, and the system is not producing Grade E air anymore, then you may have a problem. So the above only applies to well-maintained systems, preferably equipped with some sort of moisture monitor on the output, since that gives good warnng of filter failure. That's why a lot of people feel the main benefit of extra hyper filters in an O2-compatible air system is providing a second line of defense in case the primary filter fails, rather than for any miniscule extra amount of filtering it provides.

However, if you are thinking about buying a nitrox tank now, for possible use later, it would make a lot more sense to buy a regular tank now, and nitrox clean it when and if you ever need PP mixed nitrox.

BTW, a air test lab told me awhile back that most of the air they test from Grade E systems actually meets O2-compatible standards.

I stand corrected. I wondered why the term "Grade E" wasn't used in my nitrox course