So, how do you roll a set of doubles?

   Jim

Sender: Jeff Waugh  Date: 4/8/99 11:13 PM

>     I'm not sure about the temperature actually being that much of an 
>influence
>on the ending reading. I have found that generally low O2 % mixes such as 
>"deep"
>Tri-Mix'es generally homogenize to the final desired analysis over a 
>period of a
>few hours.
>     I've found that high O2 mixes that if filled with O2 and topped with 
>air and
>allowed to sit without agitation, can render an inaccurate analysis a day 
>later.
>At that point, a simple "roll" around the garage will suffice to get you 
>what you
>were looking for!
>
>Jim Cobb wrote:
>
>> 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
>> >--
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>>
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