Nitrox fill question

[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.