Banked EANx 32

The shop I go to for my fills banks 32 & 36

I went in for a fill today, and got 32 but the last two times I have been in they have been high 33.5 % today and 33.1 % another time.

But when I go, and the old man is there he's low 31% and 30.8 %

It just kinda sucks since you lose 5 feet one day, then ten feet the next fill.

I thought with it would be almost dead on since its "banked" not off by 1.2% or etc ?

Or is banked just in the "ballpark"?

Ya think it would be closer, but you can screw filling a bank cylinder just as easy as filling a scuba cylinder.

Another possiblity is that both temperature and humidty affect the analyzer. Was the analyzer calibrated using dry air out of scuba cylinder?

Otter:

Ya think it would be closer, but you can screw filling a bank cylinder just as easy as filling a scuba cylinder.

Another possiblity is that both temperature and humidty affect the analyzer. Was the analyzer calibrated using dry air out of scuba cylinder?

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Calibrated off room air,

Really it can be off that bad from temperature and humidty?

Heck 31% is damn close. I know a lot of guys like to toute how accurate they are, but the reality that I see is anybody within 1% is batting fairly well. Sometimes I'm bang on, other times I'm 1% out........sometimes I lie to myself and say 1% when I'm really 1.2% off. I also like to err low.

It happens. And it doesn't take much.

Plus or minus one percent is close enough. If you are pushing your oxygen partial pressure, I would re-think diving with that mix anyway. Better to go with a lower mix and then use a deco gas.

Since even an "accurate" O2 analyzer can have a variance of +/- 1%, I would be happy with a mix that came out 31-33%.

Lil' Irish Temper:

The shop I go to for my fills banks 32 & 36

I went in for a fill today, and got 32 but the last two times I have been in they have been high 33.5 % today and 33.1 % another time.

But when I go, and the old man is there he's low 31% and 30.8 %

It just kinda sucks since you lose 5 feet one day, then ten feet the next fill.

I thought with it would be almost dead on since its "banked" not off by 1.2% or etc ?

Or is banked just in the "ballpark"?

Click to expand...

Out of curiosity, what did you have in your tanks before you filled them? If they were thinking it was 32 but you previously had 36 with several hundred pounds left, that would push you higher. As far as it being on the low side, have the tanks been sitting long enough to fully homogenize? After sitting for a while, the old man's tanks may show a higher reading. Oh, and 1.2% isn't TOO horrible--it should be within 1%. As others mentioned, it could be a poorly calibrated analyzer, especially if it is not calibrated on an air tank.

A lot of it depends on the skill of the blender... A buddy of mine went in for 32% only to find that his tanks weren't done yet, so they filled it on the spot for him and he ended up with 28 (novice blender who assured him he knew how to do it). Fortunately he was able to call and they just swapped a set out for him w/ 32. Would've really made our SITs imcompatible w/ me diving on 34.

The guy that normally does it at my shop is truly a pro... my tanks that I picked up Wednesday were 32.0 and 32.1 (req. was 32).

rtkane:

Out of curiosity, what did you have in your tanks before you filled them?

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I would assume empty - because they just tumbled & O2 cleaned them before the fill.

Other shops around here that I use do partial pressure blending, so I thought I better have them O2 cleaned ~ Just to be safe.

I play it safe anyway, if it's 33.1% I treat it like it's 34% MOD.
No shakey baby for this kid

Lil' Irish Temper:

I play it safe anyway, if it's 33.1% I treat it like it's 34% MOD.
No shakey baby for this kid

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For calculating your MOD, round up (the %) to be more conservative. You should get a shallower MOD.

If you use a Nitrox computer or tables, round down to be more conservative. The computer or table will "think" that you are loading more nitrogen.

Of course, to paraphrase what was stated earlier, don't push the tables/limits

do it easy:

For calculating your MOD, round up (the %) to be more conservative. You should get a shallower MOD.

If you use a Nitrox computer or tables, round down to be more conservative. The computer or table will "think" that you are loading more nitrogen.

Of course, to paraphrase what was stated earlier, don't push the tables/limits

Click to expand...

As part of the close to 50 crowd, I use "old man's tables." I round down and subtract one for the computer, and round up and add 1 for MOD. Thus, 32.3% would be 31% on the computer (helps when you have a very liberal computer - Oceanic), but 34% for MOD calculation. My backup computer would be set for 32% to better track 24 hour O2 on liveaboards.