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Ronald It looks like to me, using ones favorite mix program, do parcial pressure mixing 50% of the gas is HE the rest is EAN36. Volume is not the issue PP mixing. So a 2640 psi target would require 1320 psi HE and top to 2640 with EAN36 will yield a 18/50/32 within a fudge factor. The 3500 target needs 1750 HE and the rest EAN36 resulting in the required 18/50/32. Validate the number withTrimix Blender 2.1.5 from GUE. David -----Original Message----- From: Ronald D Thompson [mailto:rthomps@co*.or*] Sent: Sunday, March 26, 2000 1:29 PM To: techdiver@aquanaut.com Subject: Tri-Mix fudge factors Experienced tri-mix home brewers on the List: I'm considering blending some helium and EAN36 to yield a specific tri-mix (this would be my first attempt at blending tri-mix), and I'd like some guidance regarding fudge factors to use in order to compensate for helium compressibility. My ideal gas calculations would have me first half-fill an "empty" cylinder with helium and then top off with EAN36, to obtain a tri-mix consisting of 18% O2, 50% He, and 32% N2. (At MOD = 225 fsw, this mix has PO2 = 1.41 ata, END = 71.5 ata, and AED = 96 fsw.) Now, my admittedly naive understanding of helium compressibility suggests that I really need to start with more than half-filling the cylinder with helium to obtain the desired mix. My question is: How much more? Specifically, if I'm using twin LP 112's with an ending pressure of 2640 psig, what fudge factor should I use to end up with tri-mix 18/50? Same question if, instead, ending pressure is 3500 psig? Thanks in advance for your suggestions. Ronald -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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