Converting tanks to Nitrox

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BEM

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1000 Island Parkway, Ontario, Canada
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Has anyone any suggestions on this idea?

As EAN certified divers, my wife and I were thinking of converting our Al tanks, (1 year old), to Nitrox.

Our LDS says that this is possible. This way we can dive using mixtures from 21% to 36%, not have to rent Nitrox tanks and we only get fills at our LDS. Our computers can be set to 21% Oxygen and the regs, BCs and guages are only 1 year old and can be used with EAN.

Anyone gone this route?
 
Yes lots have done it. As long as you have the tanks filled at a LDS with "clean" air you'll be fine. The moment you have an air fill from a regular compressor you'd have to get the tanks cleaned again.


Which end of Ottawa are you in? We could be neighbours!
 
. Our computers can be set to 21% Oxygen and the regs, BCs and guages are only 1 year old and can be used with EAN.

BEM, why would you set your computer to 21% oxygen?

The concern with NITROX is tank and valve cleanliness. This is related to the practice of partial pressure filling where the tank is prefilled with a certain pressure, usually around 400 psi, of pure O2 and then topped off with compressed air. Most new tanks and valves are usually clean enough from the factory to tolerate O2. However, there is a great deal of conservatism and black magic surrounding this subject. It involves special O ring materials and routine cleaning with special chemicals or detergents, and unique NITROX certification and stick on labels.

Filling a NITROX clean tank with a standard compressor of modern design will not have any appreciable effect on tank cleanliness. However, after many such fills it is theoretically possible to deposit enough hydrocarbon film in the valve or tank to cause a mini O2 combustion resulting in some fumes inside the tank. Actually finding a case where this has happened is difficult. When actual problems have been documented they almost always involve a tank valve or regulator which has been heavily lubed with silicone grease. That stuff, in visible quantities, is combustible in high pressure O2.

There are alternate methods of filling called membrane separation, decanting and mixing, and/or continuous blending which do not inject pure O2 into the tank, and cleanliness is less of a concern to the industry. Still, individual shops may impose their own rules or requirements. They own the equipment and the gas and they do the filling.

One note about aluminum. Aluminum, although a metal, is combustible. The source of combustion can be small metal chips, oil or grit inside the tank. Also, older tanks are sometimes subject to stress cracking. For these reasons, it is a good idea to keep NITROX tanks made from this metal as clean as possible of oils and grit. Not to scare anyone unnecessarily as this is more of a curiosity at recommended O2 fill rates and pressures. However, hot filling an aluminum tank with pure O2 to 3000 psi would raise such concerns to a serious level. Therefore, cleanliness is doubly important in such cases.
 
Originally posted by pescador775


BEM, why would you set your computer to 21% oxygen?


I'm not BEM, but I did stay at a Holiday Inn Express last night!

I have a Vyper and it has a good reason to use a 21% mix. Once you set it into Nitrox mode, it has to stay in Nitrox mode with no diving for 24 hrs before it can be changed out (It does the same with Guage Mode as well)

The reason is so that it continues to track O2 Tox units etc.

So if you want to dive a mix of Nitrox and Air - the only way to do it is to set up in Nitrox and do your air dives as if they were a 21% Nitrox mix.

Just a built in safety thing......

Dive Safe
 
Originally posted by BEM
Our LDS says that this is possible. This way we can dive using mixtures from 21% to 36%
up to 40%, actually. :)
 
I'll talk to my LDS to investigate further - thanks for all the input.

DivingGal - I live in Kanata - close to the Corel Centre (where the Sens will win the Cup!)

One reason I'm looking into this is I just finished my DAN Oxygen - First Aid for Scuba Diving Injuries and am the middle of the Rescue Diver course and the diving season is almost here (still a bit cool for my 7mm.)
 
Originally posted by metridium
up to 40%, actually. :)
Depends. If the shop banks 36%, that would be in fact a true statement, though a "basic" Nitrox certification covers up to 40%...

Roak
 
Originally posted by BEM
I'll talk to my LDS to investigate further - thanks for all the input.

DivingGal - I live in Kanata - close to the Corel Centre (where the Sens will win the Cup!)

One reason I'm looking into this is I just finished my DAN Oxygen - First Aid for Scuba Diving Injuries and am the middle of the Rescue Diver course and the diving season is almost here (still a bit cool for my 7mm.)

Don't forget to (quickly) cast your vote for the mascot we should use for the Ontario Chapter of Neptune Divers International over in the Ontario Forum.

Drop me a PM and we can talk about this stuff "live and in person" if you want..... Go Sens Go hehehe
 
In a perfect world it would be no problem to invest a ton of money getting everything you own oxygen cleaned and it would make a discernable difference. In reality though, for the low percentage nitrox you're talking about, you likely won't even notice an increase in the life of your o-rings. A safety benefit? I doubt it.

Again, in my opinion only, for low level nitrox, a cool green sticker will do the trick.

Tom

ps- You didn't really check to see if your BC was nitrox compatible, did you?



:confused:
 
https://www.shearwater.com/products/perdix-ai/

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