Re: [PSUBS-MAILIST] Life Support

On 9/28/05, Marie-Andrée et Pierre <poulin.carrier@videotron.ca> wrote:

Hi Phil and others,

I'm in the process of building a scrubber/O2 monitor system for my
dry-ambient sub.

My question is: If I stay at 66 feet for some time and monitor PP O2. Will
there be a problem when I surface? The PP O2 should be like 3 times lower on
surface then at 66 feet right? Will I have to have atleast 3 times the
minimum PP O2 (0.21 X 3 = 0.63) before I begin to surface? Otherwise I may
lack O2 in the cabin and pass-out or something?

It remind me of the technique you just mentionned about raising cabin
pressure in a 1atm sub. I think there could be the same issue there.

Any thought?

Pierre Poulin

----- Original Message -----
From: "Phil Nuytten" < pnuytten@compuserve.com>
To: <personal_submersibles@psubs.org>
Sent: Sunday, September 25, 2005 4:04 PM
Subject: [PSUBS-MAILIST] Life Support

> Hi, Daniel:
>        Sunday, again - a little time to wander thru' the debbil box! If
> you need ultra lo-cost LSS, put in an oxygen tank with a medical regulator
> that has a needle valve/ flowmeter on it - these are nickles and dimes on
> eBay - less than a 100 bucks will get you a 40 cu ft tank and reg - if you
> want 72 hours, get two. Get an O2 analyzer/monitor ( another 50 -100 bucks
> in eBay 'scuba') - buy a 10 dollar wind - up oven timer and set for 5
> minutes to remind you to check 02 level (buzz! /rewind) and adjust flow (
> once you get it dialed in, you may only touch it a couple of times during
> a
> 6-8  hour dive) For scrubbers, get a low voltage hair dryer and snip the
> heating coil out of it - or a 12 volt automotive heater blower, etc, and
> attach to the end of a piece of 6 inch PVC pipe- or clear acrylic if you
> are using color indicating absorbent.Screen both ends ( 2 layers of
> plastic
> bug screen mismatched so holes dont line up!) Stuff it full of Sodasorb,
> Sofnolime or  soda lime of choice, and there y'go ! For a passive
> scrubber,
> get some 400 foot, 16mm movie reels, make plastic snap-on plastic bug
> screen covers - they're good for a couple of hours each, and the center
> sprocket hole makes a convenient mounting point.
>        For a virtually  no-cost LSS, install a large diameter vent valve (
> light cracking pressure non-return valve) and instead of coming to the
> surface every two hours, double your cabin pressure from your air ballast
> supply tank or from an interior scuba bottle after the intitial  2 hours
> bottom time ( if you're happy with the '2 hours before surfacing to
> replace
> cabin air' scenario) - this will halve the PP C02 and still provide
> sufficent  02. After another 2 hours at 33 feet cabin pressure, you can
> increase it to 66 feet to gain additional time, but must be mindful of
> the
> air no-decompression limits. The excess cabin pressure will vent on ascent
> - or rig your hatch with a couple of bungee cords so it will burp on a
> couple of pounds excess pressure - if you're concerned about the vent
> valve
> sizing or your ability to make a relatively controlled surfacing.
>        Obligatory disclaimer: Please note that I don't recommend either of
> these approaches, only offer this info as examples of what has been done
> in
> the past. FYI, the 02 tank/liter flow reg/oven timer/ manual adjustment
> was
> the way most commercial deep-diving subs provided LS in the 50's and 60's
> and even into the 70's. The pressure-down system was used a lot during
> early (60's)bounce bell one-at observation dives when a lock-out wasn't
> contemplated, only a look-see at problem - and the bounce bells weren't
> fitted with scrubbers.
> Phil Nuytten
>
>
>
>
>
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