Nitrox fill question

[faster7581]

I got my nitrox cert last week. From what I understand, there is 2 ways to fill a tank with it.. The DS will either order their nitrox premixed at 32, 36, whatever blend, and fill your tank with that.. or, they blend it themselves, adding pure oxygen to get the blend you request, up to 40%... I use 2 LDS's, one I really like all the guys there, and use them when i can, and then the closer one, that i usually pass on the way to the ramp..
question 1... I know that when they blend it themselves, and add the 100% o2, to get your ordered blend, the tanks must be oxygen cleaned for this fill... when you use the premixed nitrox, do the tanks still have to be o2 cleaned? and if you fill an o2 cleaned tank with the premixed, it cant be filled again at the LDS that blends it.. correct?

[mathauck0814]

A tank needs to be oxygen serviced if it will come into contact with gasses with O2 content 40% and above. If your serviced tank is filled with any gas that has not been filtered to the standards of oxygen service it needs to be serviced again.

If you're using a shop's banked mix and that mix is <40%, you do not need an oxygen serviced tank. Depending on how they are making their banked nitrox, that gas may or may not be oxygen compatible (if they're using partial pressure themselves, odds are that the air being blended is oxygen compatible. if they're using continuous blending through a stick odds are that it's not).

It's best to ask how their nitrox is being made and whether or not their nitrox is filtered to OCA standards (better filtered than E-grade air).

A couple of thoughts on best practices: If they're using partial pressure to blend nitrox for you (starting with 100% O2 and blending air to create the mix) you probably want dedicated cylinders for this purpose. The flip side of that argument is to keep all of your equipment oxygen serviced and only use providers that pump oxygen compatible air (it's cleaner to breathe than e-grade and safe for use in blending). This isn't always feasible depending on what shops you have near to you. In Florida, you might be lucky enough to have several.

[Scared Silly]

The above is a good explanation. If you are always filling with premixed nitrox your cylinders do not need to be O2 compatible. The same for regulators which are good up 40% O2 out of the box.

If the gas being put in your cylinders is O2 compatible then your cylinders will in theory remain O2 compatible. Each time the cylinders are filled with gas that is not O2 compatible they have the potential to become O2 incompatible. Notice the wording in theory and potential - meaning that there is no exact science.

[k ellis]

To be filled with premix most shops still will not fill the tank unless its O2 cleaned. One shop I go to fairly often is a place that sales banked nitrox and if it does not have its o2 cleaned certification on the bottle he will either give it back to you or at your request (and his available time) he will do it for you at his cost. (Not sure as he is not my tank certification place)

Best bet is to go ahead and have it O2 cleaned anyway as it does not hurt. Increased oxygen is still flamable though maybe not as much so as pure oxygen and thus always has a potential that it could ignite of foreign particles inside the tank. Though this is highly unlikely no one wants to take that chance that they wont need a few less fingers or hand or even their life.

Best bet is just get it certified so you NEARLY eliminate the possiblity of being declined a fill.

[Jim Lapenta]

Not with percentages below 40%. Any shop that will not put premix up to 40% in a tank without an O2 clean sticker is just being a pain. And likely trying to gouge you for a cleaning that is not necessary. Not much different than the asses who want a 6 inch wide bumper sticker that screams nitrox on it. Does nothing for the tank. I use a place that puts a combination O2 clean/vis sticker on that is about 3x3. Nothing else is necessary. Other than the duct tape with my name, MOD, mix, and date on it.

[faster7581]

heres why I asked originally... I had them all o2 cleaned, and filled with 36%, the shop(call them #1) I used blends their own nitrox... but another local shop(call them #2), that is more convienent for me, banks theirs... now if I go to shop #2 to fill my tanks next, will my tank still be o2 clean? I dont want to go back to shop #1 and have a problem.

[Jim Lapenta]

The answer to that is maybe. Depends on the grade of air he is using to mix with. Should be O2 compatible. Ask to see his last air analysis. The shops I use have it done quarterly. It's not just his air. Is he mixing his own stuff? What is the fill set up like? Clean fittings? Really need to see the shop to say for sure but ask your other LDS if they feel ok with partial pressure blending after a fill from the other shop. Or just have enough tanks to keep some dedicated for partial pressure. All the places I use do partial pressure so far. One is going to continuous blending but I know the air quality there. Course I rarely use nitrox any way. Not worth the hassle if only doing 2 or 3 dives a day and not going deeper than 60 feet.

[raftingtigger]

heres why I asked originally... I had them all o2 cleaned, and filled with 36%, the shop(call them #1) I used blends their own nitrox... but another local shop(call them #2), that is more convienent for me, banks theirs... now if I go to shop #2 to fill my tanks next, will my tank still be o2 clean? I dont want to go back to shop #1 and have a problem.

OK, a really simple question from a diver who is NOT Nitrox certified (thinking about it though). You get your tanks O2 cleaned and get the sticker to show that. Later you go to shop #2 and get their banked blend. Later when you go to shop #1 for a custom blend how do they know you have gone to shop #2? And while I am NOT suggesting this, how would they know if the tank was filled with regular air? Does a shop that fills with regular air deface or remove the O2 clean sticker?

[k ellis]

OK, a really simple question from a diver who is NOT Nitrox certified (thinking about it though). You get your tanks O2 cleaned and get the sticker to show that. Later you go to shop #2 and get their banked blend. Later when you go to shop #1 for a custom blend how do they know you have gone to shop #2? And while I am NOT suggesting this, how would they know if the tank was filled with regular air? Does a shop that fills with regular air deface or remove the O2 clean sticker?

Only based upon my experience

I have mostly seen shops refuse to fill air into a nitrox bottle unless the nitrox labels were removed with permission of or by the owner of the tanks. As I stated (In my own experience so this may just be a regional thing) if you take a tank into a store that even sales banked premixed nitrox. They will tell you no way unless its O2 cleaned. Again if your going to dedicate the bottle entirely for nitrox use here on out. Then it does not hurt anything to go ahead and get it O2 cleaned. If you choose not to and a shop localy will sell you prebanked nitrox then good deal. Id just hate to see you road trip to some place without the O2 cleaning and they deny the fill based on that. (Again this is entirely based on my personal experience)

[mathauck0814]

Only based upon my experience

I have mostly seen shops refuse to fill air into a nitrox bottle unless the nitrox labels were removed with permission of or by the owner of the tanks. As I stated (In my own experience so this may just be a regional thing) if you take a tank into a store that even sales banked premixed nitrox. They will tell you no way unless its O2 cleaned. Again if your going to dedicate the bottle entirely for nitrox use here on out. Then it does not hurt anything to go ahead and get it O2 cleaned. If you choose not to and a shop localy will sell you prebanked nitrox then good deal. Id just hate to see you road trip to some place without the O2 cleaning and they deny the fill based on that. (Again this is entirely based on my personal experience)

This is a prime example of why I loath dealing with most LDS. Call bull!@#$ when it's appropriate. If they're doing partial pressure blending to provide you nitrox then you need an O2 serviced tank. If they're not doing partial pressure then you do not need a dedicated, O2 clean tank to get a fill.

Similarly, just because you have a Nitrox or EAN or other sticker on your tank, doesn't mean that they can't put regular old air into it.

Any shop that won't take your money to provide a service that you're willing to pay for (within the safety confines practiced by the rest of the sane world) doesn't deserve any of your business.

[k ellis]

This is a prime example of why I loath dealing with most LDS. Call bull!@#$ when it's appropriate. If they're doing partial pressure blending to provide you nitrox then you need an O2 serviced tank. If they're not doing partial pressure then you do not need a dedicated, O2 clean tank to get a fill.

Similarly, just because you have a Nitrox or EAN or other sticker on your tank, doesn't mean that they can't put regular old air into it.

Any shop that won't take your money to provide a service that you're willing to pay for (within the safety confines practiced by the rest of the sane world) doesn't deserve any of your business.

I see your point. I am honestly not familiar enough with the practices of Oxygen handling to know one way or another. My intent by all means was not to discredit Jim or you or any other posters listing on here. It was simply to inform the O.P. that there is the potential that if he travels with his tanks there is a real possibility that some LDS will actually deny a fill based on the tank not being O2 cleaned.

Again just to be clear I am not in the business of oxygen handling so I am taught the bare minimum. Basicly that Pure Oxygen is flamable and highly combustible. Look for the placard on vehicles involved in accidents and respond with them accordingly.

As far as Nitrox in my class we were drilled on the reason that tanks have to be 02 cleaned was because of the partial blending practice. To be honest very little was said about banked nitrox if I recall having any effect on the fills. I just know I went to a shop once that banked Nitrox and he stated that he could fill my tank because it was 02 cleaned but had it not have been he would not be able to fill it.

This was not an attempt to put the O.P. on the wrong track or to prove or disprove any other statements in this thread. Merely an attempt to prepare the O.P. for the potential that it could happen to him/her.

[halocline]

You get your tanks O2 cleaned and get the sticker to show that. Later you go to shop #2 and get their banked blend. Later when you go to shop #1 for a custom blend how do they know you have gone to shop #2?

You have just put your finger on one of the prime questions and confusion surrounding O2 clean conditions, dive shops' practices, and recreational nitrox. Once you O2 clean a tank, and fill it once, you are now trusting the quality of the fills to retain O2 clean conditions. And since you yourself do not own and service the compressor, you (or any subsequent shop filling the tank) basically have no control over what the actual state of O2 cleanliness exists. This is one reason that O2 cleaning for nitrox use is a bit of a smokescreen. First, the risk of spontaneous combustion with recreational blends is extremely low, and because the O2 is added first in partial pressure blending, it's never under the high pressure that, for example, deco bottles with 100% O2 would be. The higher the pressure, the greater the risk, or at least that's the assumption. Second, I don't believe I have ever seen a dive shop in the U.S. using continuous blending that does NOT use modified grade E (that's O2 clean) air for their fills. I'm sure there are some out there, but I suspect that modified grade E is becoming the standard anyway. Certainly PTFE greases (like Christolube) are supplanting silicone as 'standard' lubricants in regulators and tank valves.

For these reasons, I see zero reason to pay for an O2 cleaning of a tank used with banked or continuous blend nitrox. OTOH, it's not a bad idea to avoid silicone (the PTFE greases are supposedly better lubricants anyway) and use viton o-rings in tank valves, especially for the tank neck o-ring, in any tank that will have nitrox in it, or I suppose, any tank period. Viton is a pretty good compound, and its higher price for the very few times you have to replace tank valve o-rings adds up to a few dollars/year at most.

[couv]

snip......For these reasons, I see zero reason to pay for an O2 cleaning of a tank .........

But you get that sticker that protects the tank from contamination. :-)