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Good point, kent. What's the trouble with handling oxygen? Shoot, it adds all of about 3 bucks to the price of heliar fill, and you end up with proper mix. If it were dangerous, we'd have a lot more dead welders If I were "in the field" I'd be damn sure I had some oxygen. I carry oxygen to every dive, since I am a nice guy and would offer it to someone who needed it (unlike some other people I know around here) At 01:33 PM 12/31/1999 -0900, you wrote: >Maybe I'm missing something here but any technical diving that I've ever been >involved in necessitates the handling of pure oxygen. > >How do you guys fill your 50/50 and 100% O2 deco bottles if not with an oxygen >cascade? > >Since you already have to cascade oxygen to fill your deco bottles, what's the >big deal about mixing a proper trimix at the same time? > >Doing it right is not that difficult. In my mind, if you don't know how to >handle oxygen then you have no business using it for deco either. > >Kent Lind >Juneau, Alaska > >-----Original Message----- >From: Joel Silverstein [mailto:joelsilverstein@wo*.at*.ne*] >Sent: Friday, December 31, 1999 11:18 AM >To: dmdalton; tgunther@co*.co*; Kevin Connell >Cc: techdiver@aquanaut.com >Subject: Re: HELIAIR > > >The concept of heliar was to eliminate the need to handle pure oxygen in >the field, nick named poor mans trimix the method of mixing works its >resulting diving gas is less than favorable. One can still use this mixing >methods and still get a more appropriate mix by using premix enriched air >nitrox and helium. > >For example: >to make an 18/50/32 trimix which has a very good working depth range > >one would fill the scuba cylinder with 50% of the final pressure with helium >then top off with 36% enriched air from either a premix bank or a >denitrogenation (DNAx) system to final pressure, or from an ANX system >(this uses oxygen). > >Poof -- you have 18/50 trimix ------ no oxygen handling > >take it a step further and the premix of 36% is now you intermediate >110 (120) decompression gas > >trans fill some oxygen in the o2 deco bottles and you are set ... > >The primary problem with heliar is it will ALWAYS give you a hypoxic (on >the surface) mix simply due to the fact that the oxygen in the air gets >diluted by the helium. If you want 50% helium you will have 11-12% oxygen >--- its direct proportion to the helium added. > >25% helium would yield .1575 oxygen fraction in the mix. The o2 is low >enough for a relatively deep dive but the helium just is not enough. > >I've got some charts on the premix / helium method I will put on the web >site in a few days to make mixing trimix very simple with premix OEA. > >Happy New Year. > >Joel Silverstein >http://www.trimixdiver.com > > > > > > >At 12:12 AM 12/31/99 -0500, dmdalton wrote: > >Kevin, > > > >I think you are quite right that Heliair isn't the "perfect" gas because it > >locks you into a very rigid set of mixtures as you pointed out in your > >chart. In some cases, however it might be a reasonable way to go. Try this > >on for size, unless my math is wrong (wouldn't be the first time :) I think > >the gas you suggested (12/40) would actually be quite suitable for use at > >200 fsw. > > > >Correct me if I am wrong but I think the formula is: > > > >Atmospheres Absolute (ATA) X % (Percent of Gas in Mixture) = PP > >(Partial Pressure) > > > >If we want an equivalent nitrogen depth max of 100 fsw then we would be > >looking at a PP of 3.16. > > > >4 (ATA) X .79 (%) = 3.16 (PP) > > > >Breathing 12.6 / 40 / 47.4 at 200 fsw you would have a N2 PP of 3.318 which > >would result in an END of 105.6 fsw. > > > > 7 (ATA) X 47.4 (%) = 3.318 (PP) > > 3.318 / .79 = 4.2 (ATA) > >( 4.2 -1) X 33 = 105.6 fsw (END) > > > >You would have an O2 PP at this depth of .882 which would be fine. Remember > >your O2 PP at the surface breathing air is only .21 . > > > >On the other hand the 18/40 you mentioned would give you an O2 PP of 1.27 > >and if you strayed down to 220 it wold take you right to the edge for a > >working dive with a PP of 1.379. Remember air maxes out at 218 fsw as far as > >O2 PP goes. > > > >7.6 (ATA) X .21 (%) = 1.59 PP ( O2 PP of 1.6 at rest considered the max ) > > > >One down side to the 12/40 mix is that this mix is hypoxic from the surface > >where your O2 PP would be only .126 until you got to about 20 fsw where it > >would increase to .20 . Consequently you need something else to breathe > >from 0 to 20 and from 20 to 0. > > > >Comments anyone??? > > > >Dave Dalton > > > >----- Original Message ----- > >From: Kevin Connell <kevin@nw*.co*> > >To: <tgunther@co*.co*> > >Cc: <techdiver@aquanaut.com> > >Sent: Thursday, December 30, 1999 5:32 PM > >Subject: Re: HELIAIR > > > > > >> Heliar is DIW. There is only one depth that the heliar mix curve matches > >> PPO2 and END, and it's not anywhere under 200fsw. > >> > >> Here is a mix chart for heliar for a 3000psi tank (I think) > >> (ftp://ftp.nwls.com/pub/kevin/mixing.xls) > >> > >> He psi he% n2% o2% > >> 100 3.3% 76.4% 20.3% > >> 200 6.7% 73.7% 19.6% > >> 300 10.0% 71.1% 18.9% > >> 400 13.3% 68.5% 18.2% > >> 500 16.7% 65.8% 17.5% > >> 600 20.0% 63.2% 16.8% > >> 700 23.3% 60.6% 16.1% > >> 800 26.7% 57.9% 15.4% > >> 900 30.0% 55.3% 14.7% > >> 1000 33.3% 52.7% 14.0% > >> 1100 36.7% 50.0% 13.3% > >> 1200 40.0% 47.4% 12.6% > >> 1300 43.3% 44.8% 11.9% > >> 1400 46.7% 42.1% 11.2% > >> 1500 50.0% 39.5% 10.5% > >> > >> as you can see, none of these mixes make any sense. > >> > >> For example, a mix for 200fsw would be something like 18/40, and you can't > >> get the right combination here. You could dive 12/40, but that is a > >little > >> low on the O2, and unnecessarily hypoxic. > >> > >> > >> > >> At 01:26 PM 12/30/1999 -0800, you wrote: > >> >Team: > >> > > >> >I am told that many members create their own mixes using personal cascade > >> >systems. > >> > > >> >Because heliair would probably be the easiest introduction to this > >method, and > >> >also increase the safety of ones mix (only interested in < 200fsw at this > >> >point), I was wondering if anyone would like to share their experiences > >in > >> >this > >> >area. Pros, cons, concerns, applicability, etc. > >> > > >> >Thanks, > >> >Tod > >> > > >> > > >> >-- > >> >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 > >> > >> > >> ---------------------------------- > >> > >> -- > >> 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'. > > >Joel Silverstein >http://www.nitroxdiver.com >-- >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'. ---------------------------------- Kevin Connell <kevin@nw*.co*> NW Labor Systems, Inc http://www.nwls.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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