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Hi guys!
I've noticed on our membrane (DNAx) a slightly higher level of CO2 shown
in our lab tests. I'm guessing it makes it thru the membrane along with
the good stuff that isn't being dumped off. Since there's an amount
going in, and gas being removed via membrane, afterwords you get a
slightly higher percentage (same number of molecules, just less total
gas pressure after dumping N2.) Right? Has anyone found this to be a
problem when mixing for dives to "the dark side of the moon" as Billy
would say?
Also, as someone's already asked, if the point of heliair is to
eliminate the need for O2...(or if the point of using a membrane is to
eliminate the need for O2) how do you mix up your 50/50 and 100% deco
gases? The time I save in mixing my back gas using the membrane and no
pure O2 is totally wasted by running 10 miles and back over the bridge
to another shop that has O2 available.
-Case
Joel Silverstein wrote:
>
> Kent,
>
> there is no big deal handling oxygen, other than having the cylinders.
> Heliar was conceived
> for mixing in the field and home brewing where only helium and air was
> needed.
>
> But by taking the dilution concept a step further one can use the method of
> premix enriched air from a membrane system and combining that with helium
> to get
> a resultant mix, circumventing the need for having pure oxygen for mixing.
>
> It's another method that works well.
>
> When i do training at Olympus Diving Center in North Carolina they have a
> huge
> membrane system. They typically bank 36% enriched air, about 5,000 cubic
> feet of it
> at a time. By just using that and helium i can fill more sets of 18/50 in a
> few hours
> than i ever can by taking the oxygen/helium/air approach to mixing.
>
> The math on it is so simple.
>
> 3000 psi fill.
>
> 1500 psi helium (cold)
> top to 3000 with NN36
> analyze
> result 18/50 trimix
>
> Top Up
>
> have 1000 psi 18/50
> want 3000 psi 18/50
> add 1000 psi helium
> top to 3000 psi with NN36
> result ... 18/50 trimix
>
> Mogan Wells came up with this method of using the membrane system or premix
> for making trimix for the NOAA Monitor projects a few years back, it works
> so well.
>
> happy new year ......
>
> At 01:33 PM 12/31/99 -0900, Kent Lind 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'.
> >
> Joel Silverstein
> http://www.nitroxdiver.com
> --
> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'.
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--
\ \
^_ \ \ Case E. Harris
\ \ { \ US Deep Wreck Diving Team
{ \ / `~~~--__ diveman@cy*.co*
{ \___----~~' `~~-_
\ /// ` `~. ___ Oo
/ /~~~~-, ,__. , /// __,,,,) (___)o_o
\/ \/ `~~~; ,---~~-_`~= //====--//(_)
/ / \\ ^
'._.' Deep...Professional...The Standard!
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