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Hey guys, I hate to break this to you, but mixing isn't rocket science. Fudge factors have more to do with your personal gauge and with the T in PV=NRT (tank overheating) than they have to do with compressibility and real gas laws. That combined with the fact that the O2 is really the only critical pressure, and you are doing that as a delta pressure in the midrange of the gauge means that if you're getting your mixes wrong, you're not doing it right. Next we'll be hearing about how oxygen analyzers have to be on a flow meter to be accurate. At 01:09 PM 3/28/2000 +0200, <Bjorn.Forshei@kv*.co*> wrote: >Capitan, >You may download a demo version of GASMIX 5.0 on Cobb's Trimix page. It's >not a full version, but you will find the compressibility (Z) factors for >He, O2 and N2 there for any pressure. As you see, Z may be below or above >unity, depending on type of gas and pressure. A fudge factor to compensate >for compressibility factors may thus not always work. The reason it works >anyway is probably because the main thing to compensate for is temperature >(hotfill), and not compressibility factors. > > >I've enclosed a listing from GASMIX, for Trimix 18/50, 2640 and 3500 psig, >for both Ideal and Real gas. The "Real gas" gas model should be >theoretically most accurate. > >-b- > > > >****************************************************** >* * >* Trimix from Helium + Oxygen + Air * >* * >****************************************************** > > Gas Model = Ideal Gas > Narcotic Oxygen = No > Registred User = Bjorn Forshei > > > Filling Data... > > Goal contents : 18.00 [%] O2 > 50.00 [%] He > 32.00 [%] N2 > 2640.00 [psi] > > The bottle to be filled is empty > > Filling Sequence : Helium -> O2 -> Air > HELIUM fill pressure : 1320.0 [psi] > Intermediate O2 cont.: 0.00 [%] > OXYGEN fill pressure : 1572.0 [psi] > Intermediate O2 cont.: 16.03 [%] > AIR fill pressure : 2640.0 [psi] > Final O2 contents : 18.00 [%] > > You have now mixed Trimix : 18.0 / 50.0 > > >****************************************************** >* * >* Trimix from Helium + Oxygen + Air * >* * >****************************************************** > > Gas Model = Real Gas > Narcotic Oxygen = No > Registred User = Bjorn Forshei > > > Filling Data... > > Goal contents : 18.00 [%] O2 > 50.00 [%] He > 32.00 [%] N2 > 2640.00 [psi] > > The bottle to be filled is empty > > Filling Sequence : Helium -> O2 -> Air > HELIUM fill pressure : 1319.5 [psi] > Intermediate O2 cont.: 0.00 [%] > OXYGEN fill pressure : 1557.3 [psi] > Intermediate O2 cont.: 16.03 [%] > AIR fill pressure : 2640.0 [psi] > Final O2 contents : 18.00 [%] > > You have now mixed Trimix : 18.0 / 50.0 > > > > >****************************************************** >* * >* Trimix from Helium + Oxygen + Air * >* * >****************************************************** > > Gas Model = Ideal Gas > Narcotic Oxygen = No > Registred User = Bjorn Forshei > > > Filling Data... > > Goal contents : 18.00 [%] O2 > 50.00 [%] He > 32.00 [%] N2 > 3500.00 [psi] > > The bottle to be filled is empty > > Filling Sequence : Helium -> O2 -> Air > HELIUM fill pressure : 1750.0 [psi] > Intermediate O2 cont.: 0.00 [%] > OXYGEN fill pressure : 2084.1 [psi] > Intermediate O2 cont.: 16.03 [%] > AIR fill pressure : 3500.0 [psi] > Final O2 contents : 18.00 [%] > > You have now mixed Trimix : 18.0 / 50.0 > > > > > > >****************************************************** >* * >* Trimix from Helium + Oxygen + Air * >* * >****************************************************** > > Gas Model = Real Gas > Narcotic Oxygen = No > Registred User = Bjorn Forshei > > > Filling Data... > > Goal contents : 18.00 [%] O2 > 50.00 [%] He > 32.00 [%] N2 > 3500.00 [psi] > > The bottle to be filled is empty > > Filling Sequence : Helium -> O2 -> Air > HELIUM fill pressure : 1723.2 [psi] > Intermediate O2 cont.: 0.00 [%] > OXYGEN fill pressure : 2031.8 [psi] > Intermediate O2 cont.: 16.03 [%] > AIR fill pressure : 3500.0 [psi] > Final O2 contents : 18.00 [%] > > You have now mixed Trimix : 18.0 / 50.0 > > >-- >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. ---------------------------------- Kevin Connell <kevin@nw*.co*> NW Labor Systems, Inc http://www.nwls.com Res tantum valet quantum vendi potest. (A thing is only worth what someone else is willing to pay for it) ---------------------------------- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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