Re: [PSUBS-MAILIST] Sgt. Peppers O2 consumption rate question.

[MerlinSub@t-online.de (Carsten Standfuß)]

Hi Pat

Captain Nemo schrieb:
> 
> ----- Original Message -----
> From: "Carsten Standfuß" <MerlinSub@t-online.de>
> 
> "Hi Pat .. I do not like cubic feet.. "
> 
> Hi Carsten!
> 
> I don't blame you!  I didn't think the conversion would be this complicated,
> but I appreciate your efforts.
> 
> Over here, when they say a pressure bottle holds 20 cubic feet of Oxygen,
> they mean it contains the amount of pure O2 that would fill an area of 20
> cubic feet at one atmosphere pressure, which has then been compressed to fit
> inside the tank.  My "20 cubic foot tank" is about 13 inches tall (32.5 CM)
> and about 5-1/4 inches in diameter (13.125 CM).  I just bought it; and
> assuming it was properly filled (and there is the chance it might not be
> completely full, and/or that my old pressure gauge is a little inaccurate),
> the O2 inside seems to be compressed to about 1800 PSI (about 122
> atmospheres).
> 
> Now, let me make sure I understand the rest of your equations:
> 
> "the equal of 20 cubic feet = 0,566 cubi meter or 566 liter  (Hope thats
> right..)"
> 
> OK.  So 20 cubic feet equals about 566 liters, correct?

Your tank is diamter 0,1325 m length 0,325 m 
so volume (without any correction for the tickness) is : 

((0,1325 x 0,1325) x 3,1415)/4 x 0,325 
= 0,00448 cubic meter or 4,48 Liter, with 122 bar it should be
4,48 x 122 = 547 Liter - so figures seems right. 
But is that a new bottle ? we use here normally 225 bars (atm.)

> 
> " With a "You need at least 0,25 Liter/minute O2 each person.   566/ 0,25 =
> 2264 Minutes  divided by 60 Minutes = 37,73 hours.   One day, one night,
> another day and the game is over."
> 
> So, figured on an average Oxygen consumption rate of about 0.25 liters of O2
> per person / per minute: one liter of O2 would last one person about 4
> minutes; and 566 liters would last 2264 minutes, or 37.73 hours; right?
> 
right - but see also message to Stan 

> Not meaning to doubt you, (you are admittedly better at converting Metric
> than I am) but are you SURE we didn't drop a decimal point some place?  I
> would be extremely happy to get 37 hours out of my little O2 bottle; but
> that seems almost too good to be true.  Are we sure it's not more like 3.73
> hours?

I make a decimal point error 12 years before - I calculate the inside
air
and CO2 poision rate with 4 minutes before I close the hatch to find out
the right figures for the spare air inside the cabin without using the
L.S.S.
I was wondering after 40 Minutes thats I am still alive - but the last
36 
minutes I feel a little uncomfortable.. 

> " Sgt.Peppers use a pure O2 closed cycle rebreather"

.. without a blower - use a jetfighter-halfmask and my lungs to
ventilate, 
not so comfortable as an blower system - but works so long as I work..
and 02 and scrubber are in the system.

> 
> In the NAUTILUS, I'm removing the CO2 from the atmosphere with a SODASORB
> scrubber; recycling the same old nitrogen; and adding O2 as it is depleted.
> 
Thats the normal way, maybe I have more to do after one week on the
bottom
in CSSX with 3 friends producing some other toxic gases..

> "Normaly the free air inside my sub works for a maximium of 40 minutes
> (starting strong  headeges)"
> 
> That's about what I was getting in the NAUTILUS without any life support
> system; after about 45 minutes, it started getting hard to breathe.  I
> figure the volume of the pressure hull was about 35 cubic feet (about 991
> liters?), and she displaces about 2225 lbs. about 1011.36 kilos).

But the inside volume is more less - you body, all equipment the bottles
displace some of this volume. 
So your inside volume must be calculate to 991 minus 75-95 Liters for 
your body minus 4,5 Liter for the o2 bottle, minus ... etc.etc. 

> 
> So, given these specifications about my submarine hull and life support
> system, do you still think my new 20 cubic foot O2 bottle will last me about
> 37 hours?

I am working allways with security factors .. 
so use maybe 0,5 l/min consumption and figure out 37/2 = 18,5 hours..

Before you start the lomg travel mission. Get into your shop 
-in your sub, close hutch, note O2 indicator gauge, 
use the L.S.S for just 1 hour, note gauge again. Tell us the result. 

My breathing rate (and 02 consumption) during scuba diving
is about 25-30 less than the rate of my friend - he is an smoker..

I have here - somewere in my liberay,  nice figures from a test during 
WWII on a german VIIC boat. The sunk it to the harbour bottom with
a doctor on board and make all the meassuring without the
L.S.S working - will look for it.

Remember that the fat mans and the older mans get much earlier
problems with breathing as the young or the small ones. They 
stopped the test after some days for the reason that one older
crew member gets feelings very similar to a heart attack. 

Today I get the steel anticollision bulkhead (3,2 feet in diameter, 
half inch strong)  and the stiffners for it. 
Its forward on the bow-main ballast tank and will later covered
by a GRP /GFK nose with the sounder, video, lamps etc. 
Something to weld for the weekend. 

Carsten

> 
> " Hope helps a little - keep me inform if you get the scrubber consumtion
> figure for different materials out. "
> 
> It helps a lot; thanks for all your efforts.  Muchly appreciated.
> 
> " Hope to send new pictures at the end of this week."  Carsten"
> 
> Looking forward to seeing them.
> 
> Thanks again!
> 
> Pat