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--=====================_15515212==_.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed At 06:03 PM 3/26/00 -0500, David B. Widen wrote: >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 There is a slight problem with going 100% by the ideal gas law here. Helium has a slightly lower compressibility and equal pressures yield a tad less helium than you want. If you go 54% helium -- 46% nitrox _by pressure_ it comes out right. The simplest way is to fill helium first and add nitrox. This way the cylinder heats during the nitrox filling and you get your fudge factor. Another rule of thumb is to fill a few bar / psi (5 - 10 bar / 100 psi) more helium than calculated. At any rate, the ratios are not critical as long as you verify and plan according to FO2. With trimix from helium and nitrox you may calculate the exact composition from the analyzed FO2. regards, Hans --=====================_15515212==_.ALT Content-Type: text/html; charset="us-ascii" <html> At 06:03 PM 3/26/00 -0500, David B. Widen wrote:<br> <blockquote type=cite cite>Ronald<br> <br> It looks like to me, using ones favorite mix program, do parcial pressure<br> mixing 50% of the gas is HE the rest is EAN36. Volume is not the issue PP<br> mixing. So a 2640 psi target would require 1320 psi HE and top to 2640 with<br> EAN36 will yield a 18/50/32 within a fudge factor. The 3500 target needs<br> 1750 HE and the rest EAN36 resulting in the required 18/50/32. Validate the<br> number withTrimix Blender 2.1.5 from GUE.<br> <br> David</blockquote><br> There is a slight problem with going 100% by the ideal gas law here. Helium has a slightly lower compressibility and equal pressures yield a tad less helium than you want. If you go 54% helium -- 46% nitrox _<b>by pressure</b>_ it comes out right. The simplest way is to fill helium first and add nitrox. This way the cylinder heats during the nitrox filling and you get your fudge factor. Another rule of thumb is to fill a few bar / psi (5 - 10 bar / 100 psi) more helium than calculated. At any rate, the ratios are not critical as long as you verify and plan according to FO2. With trimix from helium and nitrox you may calculate the exact composition from the analyzed FO2.<br> <br> regards,<br> <br> Hans<br> </html> --=====================_15515212==_.ALT-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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