Re: [PSUBS-MAILIST] re: 1atm subs

["Alan D. Secor" <secor@btv.ibm.com>]

If you trickle O2 in at the rate you metabolize it and have a CO2 
scrubber, the net cabin pressure should not increase at all.  A simple 
atmospheric barometer could monitor cabin pressure to make sure your 
injection rate does go bonkers.

Al

>You wrote:
>a
>blowoff valve will not work if the pressure outside is greater
>than inside
>so do you use a air pump to pump it out (more calculations what
>size pump)
>Troy
>
>Troy, when designing my sub (I have extremely limited personnel space), I 
>had to take this into consideration. I thought about a small vacuum pump, 
>but considering I'd only be down an hour, and the pressure from O2 and - CO2 
>scrubber, would only build up to an additional 7 psi after 6 hrs (5 hr 
>reserve). This is assuming staying below 15 ft for the entire hr (not 
>likely, but possible). Upon ascending, a check valve (pressure relief valve) 
>would open and start bleeding off air. I'm looking at a pilot operated SRV, 
>which is actually safer, but more complex. Anyway, it depends on your 
>approach. If you want to pump it out, you still have to have an opening and 
>a check valve. The pump size can be extremely small similar to one of those 
>emergency tire inflators for your car.
>Suds
>
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--
Alan D. Secor
e-mail: secor@btv.ibm.com