I look at the 02 analysis as a backup to the PP fill. No, I don't bother 
checking immediatly after the fill, whats the point? I weight until the 
tanks are cool to the touch.
   Jim

Sender: Steve Hogan  Date: 4/9/99 11:59 AM

>Jim,
>
>Have you ever analysed your mix immediatly after mixing?
>
>I have noticed a difference (especially with hi O2 mixes)
>so I wait (I will not roll a tank as there is no mechanism
>to force turbulance inside the tank, waste of time).
>
>I would rather wait and get a correct reading the first time
>than try to figure out how soon after mixing I can measure. 
>
>Steve
>
>-----Original Message-----
>From: Jim Cobb [mailto:cobber@ci*.co*]
>Sent: Friday, April 09, 1999 8:25 AM
>To: Steve Hogan; pdisler@io*.ne*; silent@cu*.ne*
>Cc: Tech Diver
>Subject: RE: Trimix Question
>
>
>I really have a hard time getting my brain wrapped around this 
>stratification thing. When you are adding gas to a cylinder it not like 
>you are decanting it in like you are mixing a black and tan. You are 
>blasting high pressure gas through a tiny oriface in a violent fashion 
>into your tank and the goddamn molecules are flying all over the fucking 
>place. They hardly have a chance to delicately float down like a bunch of 
>snowflakes into a nice stack of different gas densities.
>
>When you are in a fire what do you do to avoid the smoke? Crawl on the 
>floor. The smoke/air mixture is up on the ceiling because of its 
>temperature, not because the house is not being rolled. As the 
>temperatures mix and even out the smoke is more than happy to fill the 
>room top to bottom.
>
>This rolling tank BS is an old wifes tail and cannot be explained via 
>physics. The inside of a tank is smooth, there are no vanes sticking out 
>to "mix" the gases, so how could rolling possibly help?
>
>The temp differences do not have to be measured in 100's of degress for 
>inversion layers to take place but eventually the temps even out and you 
>get a good mix measurement. You don't have to roll the goddamn tanks. 
>Can't you knuckleheads see this?
>
> Jim
>
>Sender: Steve Hogan  Date: 4/8/99 8:17 PM
>
>>Jim,
>>
>>Since I fill the cylinders slowly there is not much heating going
>>on. I suppose you could test this by doing a fast fill (with the O2)
>>and let us know. If we don't here from you we will pretty much know 
>>what happened (wink).
>>
>>If temperature were an issue then warming a tank after there is a known 
>>good mix should throw off the measurement. I always measure my mixes 
>>in my garage (my safe haven) so it is a bit on the cold side. I 
>>do not wait until I am on the boat to check the mix (that comes under
>>the heading of preparation).
>>
>>Comments.
>>
>>Regards
>>
>>Steve
>>
>>-----Original Message-----
>>From: Jim Cobb [mailto:cobber@ci*.co*]
>>Sent: Thursday, April 08, 1999 4:55 PM
>>To: Steve Hogan; pdisler@io*.ne*; silent@cu*.ne*
>>Cc: Tech Diver
>>Subject: RE: Trimix Question
>>
>>
>>I don't know about you guys but I think the problem we are dealing with 
>>here is the temperature of the mix rather than stratification. As the mix 
>>cools off the reading becomes more accurate.
>>
>>   Jim
>>
>>Sender: Steve Hogan  Date: 4/8/99 6:53 PM
>>
>>>
>>>I have run into this and have modified my mixing procedures 
>>>so that after I add the O2 to the helium I wait 1 day (I 
>>>usually mix at night so waiting around is not appealing)
>>>before measuring the O2 % (O2 & He). It is not hard to figure
>>>out what percentage I expect after mixing O2 with He.
>>>Next step is to add air, wait a few hours (usually doing 
>>>something else) and then measure again. 
>>>I fill about 50 psi/min so I expect to not get much mixing from 
>>>Brownian motion.
>>>
>>>Steve
>>>
>>>-----Original Message-----
>>>From: Patricia Disler [mailto:pdisler@io*.ne*]
>>>Sent: Friday, April 09, 1999 1:14 PM
>>>To: S I L E N T I M M E R S I O N
>>>Cc: techdiver@aquanaut.com
>>>Subject: Re: Trimix Question
>>>
>>>
>>>
>>>
>>>
>>>At 09:16 AM 4/8/99 -0700, you wrote:
>>>>Frank,
>>>>
>>>>>Not me, but I do let the filled tanks rest a day before analyzing. An if
>>>>>you want to tell me
>>>>>thats not neseccary I recommend that you try this: Fill oxygen, top with
>>>>>air, wait a minute,
>>>>>analyze mix, turn the tank so that the valve faces ground, wait another
>>>>>minute and than
>>>>>re-analyze the mix.
>>>>
>>>>And it's the same... or not?
>>>>When filling a tank the temperature and pressure are high which in turn
>>>>gives a high diffusion coefficient. Makes the mix homogeneous almost
>>>>instantaneoulsy (couple of seconds).
>>>>What kind of differences do you get?
>>>>What kind of analyser do you use, are you sure the hoses are drained when
>>>>using a regulator or something?
>>>>
>>>>Regards,>
>>>>THOMAS
>>>
>>>I have witnessed Nitrox mixtures take a while to fully homogenize. Several
>>>years ago while mixing 80/20, (Yeah I know don't start) it came out 63% O2
>>>approx 30 min after the very s-l-o-w top off to fill pressure. Yes I
>>>checked the calibration of the aynalizer (Teledyne TD-50). Each time I
>>>would check the O2 reading would climb. I did this over a period of
>several
>>>hours. Later it was right on 80%.
>>>I'd have to say stratification can and does occur, esp. if there is not
>>>enough turbulence during top off.
>>>I have never seen this with Trimix as the fill rates are much higher.
>>>However I suppose it could occur if they too were topped slowly.
>>>At any rate I never seem to dive my gas until they show the correct
>>mixture.
>>>
>>>
>>>
>>>"SILT HAPPENS"JD   JEFF DISLER
>>>  SAFE CAVING       NSS 26000
>>>--
>>>Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
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>>>
>>
>>
>> -------------------------------------------------------------------
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>>
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>>
>
>
> -------------------------------------------------------------------
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>
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