EANx Shaken or Stirred?

Orlando Eric · Jun 27, 2005

After reviewing eighty post from my search I did not see this discussed.

I was diving in South Florida this week and got Nitrox fills at a well known shop that is VERY reputable.

I saw several people ahead of me kicking their tanks back and forth rolling them to "stir up the gas."

My BS meter went into the red and my curiosity meter pegged!

I asked how could that work?

My thoughts are:

#1 That with partial pressure blending you get a partial fill of O2. Now you top that off with "air" at considerable force which in my mind (not an expert) would surely mix these gases.

#2 Even if you roll the tanks back and forth the tanks do not have paddles in them to stir anything up and you can recreate this experiement by adding some water and oil in a clear soda bottle and roll it around.. does not mix very well.

#3 If the O2 and Nitrogen seperated that severly what happens when you leave it upright in your house for a week and then dive it?

I am just looking for a Expert opinion. In my mind my three conclusions are very sound but it would not be the first time I am wrong.

I saw MANY people doing this and the shop said that this is a FACT and rolling the tanks makes a difference.

Eric

JWU42 · Jun 27, 2005

How would you mix a set of doubles?

I call BS on this one

bisonduquebec · Jun 27, 2005

According to my "experts", you may need to shake a nitrox bottle after filling before getting an accuratye O2 reading. BUT this will only happen if the EAN is very high (more then 40%).

Looks like the O2 and regular air will not mix completely when the bottle is slowly filled up (which is needed for O2 filling). Temperature seems to be the culprit here.

Notso_Ken · Jun 27, 2005

Orlando Eric:
I am just looking for a Expert opinion. In my mind my three conclusions are very sound but it would not be the first time I am wrong.

Eric

As a chemist, let me assure you that with gasses very nearly the same density (as are air and oxyegn), they will mix naturally very quickly due to the natural random motion of the molecules.

If one is very much more dense than the other, or if they are at a VERY cold tempreature, that won't be the case. By VERY cold temp, I am talking on an absolute tempreature scale such as Kelvin or Rankin. On a Celsius or Fahrenheit scale, we are talking multiple hundreds below zero.

Go ahead and raise the BS flag next time.

Ken

BlueWaterDiving · Jun 27, 2005

Both gases must be at the temp. To get a good reading . If rolling them will get them both at the same temp. Then roll away. I would like to see you roll my doubles.
I have been blending for a long time and I have NOT rolled one tank. And I do hit my mix.

jonnythan · Jun 27, 2005

Notso_Ken:
As a chemist, let me assure you that with gasses very nearly the same density (as are air and oxyegn), they will mix naturally very quickly due to the natural random motion of the molecules.

If one is very much more dense than the other, or if they are at a VERY cold tempreature, that won't be the case. By VERY cold temp, I am talking on an absolute tempreature scale such as Kelvin or Rankin. On a Celsius or Fahrenheit scale, we are talking multiple hundreds below zero.

Go ahead and raise the BS flag next time.

Ken

Huh. Chemist you say?

Mike Veitch · Jun 27, 2005

Definite BS, but must be entertaining if someone hits themselves on the toe!
I used to partial pressure up to 75 tanks a day, never once did i roll....but then again i am not a sheep like those you were watching....

Rick Murchison · Jun 27, 2005

Notso_Ken:
As a chemist, let me assure you that with gasses very nearly the same density (as are air and oxyegn), they will mix naturally very quickly due to the natural random motion of the molecules.

Ah, yes, but the question is "how quickly?"
My experience is that I need to wait a couple of hours after finishing a partial pressure blend to get a good final reading. Some folks say rolling the tanks around will speed the process; I don't see why it wouldn't (the close density makes rolling the tanks more effective than the oil/water example previously cited).
That said, since a two hour wait is convenient for me, I haven't explored the half-hour to just under two hour window to see if I could reasonably wait a shorter time - if anyone has, let us know. But I do know that in my experience, readings within a few minutes of a PP fill are unreliable.
Rick

The Kraken · Jun 27, 2005

Take a jar, put some clear water in it, say about 60% full, then take some water with a colored dye in it. Pour it in the jar to fill it up. Put the top on it. Place it on its side on the counter top. Roll it around . . . same thing.

the K

Curt Bowen · Jun 27, 2005

I have been PP mixing nitrox for 15 years and never had a problem.

But I have had it happen when mixing trimix (helium, oxygen, nitrogen) with a haskel booster. Seems the booster moves the helium so slow it stays seperated inside the cylinder. Rolling the tanks didnt seem to help. Just leaving them alone for several hours fixes the problem.

So what they are saying, might not be all BS.

Orlando Eric:
After reviewing eighty post from my search I did not see this discussed.

I was diving in South Florida this week and got Nitrox fills at a well known shop that is VERY reputable.

I saw several people ahead of me kicking their tanks back and forth rolling them to "stir up the gas."

My BS meter went into the red and my curiosity meter pegged!

I asked how could that work?

My thoughts are:

#1 That with partial pressure blending you get a partial fill of O2. Now you top that off with "air" at considerable force which in my mind (not an expert) would surely mix these gases.

#2 Even if you roll the tanks back and forth the tanks do not have paddles in them to stir anything up and you can recreate this experiement by adding some water and oil in a clear soda bottle and roll it around.. does not mix very well.

#3 If the O2 and Nitrogen seperated that severly what happens when you leave it upright in your house for a week and then dive it?

I am just looking for a Expert opinion. In my mind my three conclusions are very sound but it would not be the first time I am wrong.

I saw MANY people doing this and the shop said that this is a FACT and rolling the tanks makes a difference.

Eric

EANx Shaken or Stirred?

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