Am I the dumb one?

[Sea_Jay]

I have seen several people do this; and FWIW I believe I've lost a few brain cells watching them:

At the analyzing station, with the whip & the O2 analyzer connected, and the tank valve open -- they're rocking the tank back & forth as if it's some type of cocktail. I have went out of my way to ask them "what are you doing?" and I always get the same response...."blending the gas so I get an accurate reading"

My basic knowledge of of physics tells me that a compressed gas cylinder, which is *UNDER PRESSURE* should not be affected by rocking the cylinder back-and-forth. It has bothered me enough to research the weight of oxygen vs. the weight of nitrogen. Even still, the difference appears to be negligible.....and this is assuming the gas is NOT under pressure.

Idk....I call bullsh*t

 

[Wookie]

Hahahaha!! I've blended hundreds of thousands of cubic feet of gas.

You are absolutely correct.

 

[grantctobin]

https://pubs.acs.org/doi/abs/10.1021/je60005a002

Mixed gases in compressed cylinders: some popular misconceptions and explanations (Technical Report) | OSTI.GOV

The U.S. Department of Energy's Office of Scientific and Technical Information

www.osti.gov

Having done some maths and mixed some mix, I’d encourage both @Sea_Jay and @Wookie to read the above. I don’t concern myself with nitrox, but I’d encourage a solid bashing of a wrench on a high helium concentration cylinder and ideally a second analysis the day of use.

 

[Wookie]

https://pubs.acs.org/doi/abs/10.1021/je60005a002

Mixed gases in compressed cylinders: some popular misconceptions and explanations (Technical Report) | OSTI.GOV

The U.S. Department of Energy's Office of Scientific and Technical Information

www.osti.gov

Having done some maths and mixed some mix, I’d encourage both @Sea_Jay and @Wookie to read the above. I don’t concern myself with nitrox, but I’d encourage a solid bashing of a wrench on a high helium concentration cylinder and ideally a second analysis the day of use.

I calculated roughly how much gas I have mixed. It came out to 50 million cubic feet.

I must say I never "mixed" it, I let Dalton do it for me.

It never failed.

 

[Pavao]

It most definitely makes a difference a certain scenarios.
Partial pressure mixing trimix for example will change the readings on the analyzer right in front of your eyes, drastically, by drastically I mean 10% + variance in less than a minute.

Can't say that every fill will have that effect, simply because I haven't used every possible technique, but the way I fill, slowly, veeery slowly filling O2 - He - Air. Put it on the analyzer right after filling and see the results, then just simply flip the bottle upside-down and watch what happens on the analyzer.
Could be wrong but it seems more drastic the smaller the cylinder, which for "scientific" purposes are easier to replicate, rebreather bottles are great for this, can flip them around back and forth while still connected to analyzer and see the change on the readings right before your eyes.

Can't remember if I've noticed or payed attention to this on partial pressure of nitrox fills.

 

[Wookie]

I fill, slowly, veeery slowly filling O2 - He - Air.

Ah. In this lies the issue.

I always add He first, and then the O2, and then blast in the air on top to get everything circulating nicely.

I've missed the mix, not enough for a rebreather to care, but never waited for a mix to settle out. I would mix 8 444 cu ft at a time.

 

[Pavao]

Ah. In this lies the issue.

I always add He first, and then the O2, and then blast in the air on top to get everything circulating nicely.

I've missed the mix, not enough for a rebreather to care, but never waited for a mix to settle out. I would mix 8 444 cu ft at a time.

I may have tried flipping the order of the gases, can't remember.
But my logical mind definitely prompted me to "blast" the air in last to mix everything, it did not do the trick however.

 

[Still Kicking]

I calculated roughly how much gas I have mixed. It came out to 50 million cubic feet.

I must say I never "mixed" it, I let Dalton do it for me.

It never failed.

It's the law!

 

[DeepSeaExplorer]

Ah. In this lies the issue.

I always add He first, and then the O2, and then blast in the air on top to get everything circulating nicely.

I've missed the mix, not enough for a rebreather to care, but never waited for a mix to settle out. I would mix 8 444 cu ft at a time.

I too would fill slowly, then at the end blast some air. There’s no way at the gases aren’t mixed after that.

I assumed the people having issues were filling slow and their measurements were distorted by the last gas in the manifold.

 

[34109411]

I have seen several people do this; and FWIW I believe I've lost a few brain cells watching them:

At the analyzing station, with the whip & the O2 analyzer connected, and the tank valve open -- they're rocking the tank back & forth as if it's some type of cocktail. I have went out of my way to ask them "what are you doing?" and I always get the same response...."blending the gas so I get an accurate reading"

My basic knowledge of of physics tells me that a compressed gas cylinder, which is *UNDER PRESSURE* should not be affected by rocking the cylinder back-and-forth. It has bothered me enough to research the weight of oxygen vs. the weight of nitrogen. Even still, the difference appears to be negligible.....and this is assuming the gas is NOT under pressure.

Idk....I call bullsh*t