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UCFKnightDiver
11-01-2007, 23:44
Hey is there any difference between a tank labeled nitrox vs just a regular one for air? can they be used interchangeably? could I buy a nitrox labeled tank and use it for air?

fireflock
11-01-2007, 23:50
The definitive answer is well......it depends.

It depends to some extent on the fill station, how they make Nitrox, and to some degree how much they understand about the issue.

In real life, I have tanks with big green and yellow Nitrox bands, that have never been O2 cleaned, and I get either air or nitrox in them with no problems. However, I don't ask for Nitrox at shops that only use partial pressure blending (for that, tanks and valves need to be O2 cleaned). I have friends whose tanks have no green and yellow Nitrox bands, and they get air and nitrox too.

So.....you might have to ask around at the places you plan to get the most fills and see what they require. Requirements, for better or worse, can really vary.

Rich

divingbuddy
11-03-2007, 14:00
Hey is there any difference between a tank labeled nitrox vs just a regular one for air?

Some shops use a partial pressure blending system to 'create' the desired nitrox mix. To do this, they add pure oxygen to a cylinder, then top up/fill the cylinder with a different gas (usually air). Since you are putting 100% oxygen in the tank, the tank and valve must be 'oxygen cleaned' or 'oxygen compatable'. This means it has been cleaned to oxygen service specifications (no hydrocarbon contamination) and the lubricants (Crystolube) and o-rings (usually viton or EPMD) are also O2 compatible. You will see a special stamp or punch on the VIP sticker to indicate whether or not a tank has been O2 cleaned.

If your shop uses a different method (membrane system/Nitrox stick, banked mixes, etc.), you may not need this O2 cleaning of the tank and valve (although you are limited to a maximum blend of 40 percent oxygen).


can they be used interchangeably? could I buy a nitrox labeled tank and use it for air?

Again...it depends on whether or not your tank/valve has been O2 cleaned for partial pressure fills.

If you don't need an O2 cleaned tank/valve, then air fills are easy (fill it like normal).

If you did O2 clean your tank, then as long as the air station you are getting a fill from uses O2 compatible air (Grade E modified), you can put air in your nitrox tank (hey...air is just another way of saying '21% nitrox'). If the air fill does not meet O2 compatibility, the tank/valve needs to be oxgyen cleaned again before putting 100% oxygen in the cylinder.

Just my two cents...Cheers!

Puffer Fish
11-03-2007, 14:16
Hey is there any difference between a tank labeled nitrox vs just a regular one for air?

Some shops use a partial pressure blending system to 'create' the desired nitrox mix. To do this, they add pure oxygen to a cylinder, then top up/fill the cylinder with a different gas (usually air). Since you are putting 100% oxygen in the tank, the tank and valve must be 'oxygen cleaned' or 'oxygen compatable'. This means it has been cleaned to oxygen service specifications (no hydrocarbon contamination) and the lubricants (Crystolube) and o-rings (usually viton or EPMD) are also O2 compatible. You will see a special stamp or punch on the VIP sticker to indicate whether or not a tank has been O2 cleaned.

If your shop uses a different method (membrane system/Nitrox stick, banked mixes, etc.), you may not need this O2 cleaning of the tank and valve (although you are limited to a maximum blend of 40 percent oxygen).


can they be used interchangeably? could I buy a nitrox labeled tank and use it for air?

Again...it depends on whether or not your tank/valve has been O2 cleaned for partial pressure fills.

If you don't need an O2 cleaned tank/valve, then air fills are easy (fill it like normal).

If you did O2 clean your tank, then as long as the air station you are getting a fill from uses O2 compatible air (Grade E modified), you can put air in your nitrox tank (hey...air is just another way of saying '21% nitrox'). If the air fill does not meet O2 compatibility, the tank/valve needs to be oxgyen cleaned again before putting 100% oxygen in the cylinder.

Just my two cents...Cheers!

Excellent points... but I do have O2 cleaned tanks.. and the only way a shop would know that is by looking at the sticker...which means one should never get a nitrox tank filled with regular compressed air... or it is no longer a nitrox tank. Problem is, a shop that does not have Nitrox usually will happily fill Nitrox tanks.. and now it is up to the owner to void the sticker.. something many people would be reluctant to do... so there is a bit of a loop hole in things.

divingbuddy
11-03-2007, 14:33
Excellent points... but I do have O2 cleaned tanks.. and the only way a shop would know that is by looking at the sticker...

A shop using a partial pressure filling method will most certainly check to ensure the tank/valve have been properly serviced (for their own safety). If the shop uses partial pressure filling, and the tank is not O2 cleaned, the customer can either pay to have it cleaned, or will have to go elsewhere for his fill.


which means one should never get a nitrox tank filled with regular compressed air... or it is no longer a nitrox tank.

As someone who owns (and fills) mixed gas cylinders, I would agree with your assessment that the tank is no longer O2 clean - the tank can no longer be filled using 100% O2 (but you could still safely use other nitrox filling methods).


Problem is, a shop that does not have Nitrox usually will happily fill Nitrox tanks.. and now it is up to the owner to void the sticker.. something many people would be reluctant to do... so there is a bit of a loop hole in things.


The danger isn't for the user, it is for the poor guy/girl who has to fill the tank using 100% oxygen. You have to ask yourself if his/her life is worth the small cost of having the tank/valve re-cleaned if you have been using an unknown air source. Most shops have an analysis certificate that will let you know the quality of their air (at least they should). Ask if you're not sure, but if in doubt, re-clean the tank/valve.

fireflock
11-03-2007, 14:50
As you can see, things get confusing very quickly. The easiest thing for you to do is see what method your regular fill stations use to produce Nitrox and go from there. If they use something besides partial pressure blending, your life will be a lot easier (and cheaper, and safer).

Rich

divingbuddy
11-03-2007, 17:36
I would say that partial pressure blending can be cheaper - when a nitrox tank comes in I analyze the contents and determine the pressure of the contents of the tank. I then feed that information into a blender program with the tank size and working pressure to determine how much oxygen and how much air I need to add. The customer is charged for the oxygen by the cubic foot. This system makes it cheaper for someone who does not require a complete fill, or is blending from a higher O2% to a lower O2%.

Just my two cents...Cheers!

fireflock
11-03-2007, 17:48
I meant it would be cheaper because you don't have to get your stuff O2 cleaned at regular intervals (assuming you don't DIY). I would expect the fills to be about the same price no matter the method.

Rich