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Jim >David, without a doubt you have one over on me on any discussion regarding >mixing trimix. Shame, as you can't argue back :-). As I stated, I have only seen the analysis change on Trimix, not Nitrox. > But you are insinuating from your statement here is that all mixing >is done under pressures where gas supposidly becomes viscious. But the pressures >are variable, rangeing from zero to 3500 psi or more. Agreed. > At what point does this >viscosity take place? At what pressure do gasses decide that they don't want to >mix? I was merely referring to the mail I read yesterday where someone said the viscosity was 43% of that of water when at "full" cylinder pressure. *If* this is correct, it would explain the phenomenon, perhaps. >I will stick to my guns on that it is temperature which cause gases of >different dencitiys to layer. As time passes temps equalize and thus gases intermix. I can't believe this to be true. Higher temperatures create lesser viscosity and greater activity via Brownian motion. Thus the gases should mix quicker at higher temperatures. Brownian motion can be the only way gases mix once the gas has stopped any turbidity (is that the right word?) after having been "blast[ed at]high pressure through a tiny oriface in a violent fashion into your tank and the goddamn molecules are flying all over the fucking place". >If different gasses which have different thermdynamic characteristics are in a >container you can roll that bitch to the moon and back and it won't make one >tit of difference. And the fact that tanks get hot no matter how slowly you fill >them causes boundry temperature differences which complicate things even more. Agreed. BTW, I always hot fill with no cooling between gases. O2 goes in first but slowly. >Bottom line, do your mix according to your tables, let the tanks cool and test >the O2 with an analyzer. This stuff is not rocket science you bunch of >knukleheaded bubblebrains out there. And if I ever see someone rolling their tank after >doing a mix I am going to kick them square in the ass. Ah, here is the nub. "let the tanks cool and test the O2 with an analyzer" - during the time that the cylinders cool, the gases have had further time to mix. I repeat that I have seem changes after 3 hours (only on one occasion). You are essentially doing what I do. Wait before analysing. Kick the buggers rolling Nitrox, but be gentle with those picking up their twin sets and putting them on their shoulder and then back to the floor many times. I occasionally have to do this if I have to analyse Trimix immediately after filling and just about to depart on a boat. The reason to be gentle with them is that they may actually be right and secondly, they will have built up some muscles by the act and may take umbrage at being kicked square in the ass. David Shimell Project Manager, Sequent Computer Systems Ltd., Sandton, South Africa. Email: shimell@se*.co* <mailto:shimell@se*.co*> -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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