Is it true? Can you use some EANx blends in tanks not O2 cleaned?

[orch1ds]

So I signed up for a boat trip this coming weekend and I'm told that they will have Nitrox blends that can be filled in tanks that are not O2 cleaned?

Is that true? I guess I'm kind of a stickler about the rules I learned from my Nitrox class and I could have sworn I needed to get my tank O2 cleaned before putting Nitrox blends. So am I to understand that its only necessary to have your tank O2 cleaned if you plan on putting pure O2 to create a mix. But if you have a blend going into your tank you do not need to have your tank O2 cleaned?

Could someone please clarify and point me in the right direction?

Thanks!
cmk

 

[Scubakevdm]

Nitrox mixes equal to or less than 40% are treated the same as air. Over 40% is treated as pure O2, so if your tanks are filled with premixed recreational blends of nitrox (40% and below) it is not necessary to O2 clean the tank. If however, they mix the nitrox in the tank, the tank must meet O2 cleanliness and compatibility requirements.

 

[GrimSleeper]

So am I to understand that its only necessary to have your tank O2 cleaned if you plan on putting pure O2 to create a mix. But if you have a blend going into your tank you do not need to have your tank O2 cleaned?

For mixes up to 40% O2 (ie. normal recreational EANx blends), yup, you understand correctly. If the breathing tanks are being filled from a bank, or from a Nitrox-producing compressor, then they don't have to be O2 clean.

For mixes over 40%, or for partial pressure blending any mix (ie. putting in pure O2 then adding air), the tanks do have to be O2 clean.

 

[orch1ds]

Nitrox mixes equal to or less than 40% are treated the same as air. Over 40% is treated as pure O2, so if your tanks are filled with premixed recreational blends of nitrox (40% and below) it is not necessary to O2 clean the tank. If however, they mix the nitrox in the tank, the tank must meet O2 cleanliness and compatibility requirements.

Yes he said that it is premixed and it will definitely be less than 40% for me. Cool. Thanks for the clarification.

 

[Teamcasa]

Nitrox mixes equal to or less than 40% are treated the same as air. Over 40% is treated as pure O2, so if your tanks are filled with premixed recreational blends of nitrox (40% and below) it is not necessary to O2 clean the tank. If however, they mix the nitrox in the tank, the tank must meet O2 cleanliness and compatibility requirements.

Exactly right and well stated. However, many Nitrox operations don't follow this procedure. And don’t even think of trying to explain it to them.

 

[FinMaky]

Just did my nitrox course and this is what I've learned so far. There is basically 3 ways to get nirox in to your tank. First is to add o2 from separate tank. Second is reduce nitrogen from air so that o2 adds up. Third is mix it ready for use in to separate fill tank. You only need o2 cleaned tanks if at any point your tank comes in contact with 40% or more o2 mix.

So method three. No need for o2 clean as mixture is ready and below 40%. In the second it basically the same. No more than 40% o2 again no need for o2 clean. Then the first method. If they mix it so that you first add near 100% o2 to your tank, then air on top to get your mix, then you need o2 clean tanks. But it can also be done so that they mix near 100% o2 from tank with air BEFORE they are added to your tank. If they do it this way and make sure that o2 levels are below 40% you don't need o2 clean tanks.

 

[=C=]

Just did my nitrox course and this is what I've learned so far. There is basically 3 ways to get nirox in to your tank. First is to add o2 from separate tank. Second is reduce nitrogen from air so that o2 adds up. Third is mix it ready for use in to separate fill tank. You only need o2 cleaned tanks if at any point your tank comes in contact with 40% or more o2 mix.

So method three.....

I'm not sure if this fits in your #2 but I've mainly seen continuous blending here... Theres a line from an O2 tank that meters oxygen into the inlet of the compressor.

Heres good link from Wikipedia

 

[TMHeimer]

The shop where I did the Nitrox course uses the "membrane" to mix gas. They have filled my air tanks with nitrox and said it was fine. Interesting that this is not mentioned in the PADI course book. Maybe the book came out before the "membrane"?

 

[hdugan]

Interesting that this is not mentioned in the PADI course book. Maybe the book came out before the "membrane"?

I can quickly think of 2 reasons PADI would say clean the tank.

1. The Compressed Gas Association specifies any gas containing over 22% Oxygen to be in a O2 clean tank. PADI just Loves to CYA on everything that might be a liability.

and

2. The shop makes money from doing the cleaning.
good ole Put Another Dollar In.

 

[matts1w]

The shop where I did the Nitrox course uses the "membrane" to mix gas. They have filled my air tanks with nitrox and said it was fine. Interesting that this is not mentioned in the PADI course book. Maybe the book came out before the "membrane"?

It does. See page 25-26 in the PADI Enriched Air Diving manual.

I can quickly think of 2 reasons PADI would say clean the tank.

1. The Compressed Gas Association specifies any gas containing over 22% Oxygen to be in a O2 clean tank. PADI just Loves to CYA on everything that might be a liability.

and

2. The shop makes money from doing the cleaning.
good ole Put Another Dollar In.

The course does make clear between an O2 clean and marked for EANX. Nice swipe at PADI though. We are just rolling in the money from cleaning tanks that dont need it.