Harry,
No, I don't have any O2 measuring device in my sub
at this time. What I based twenty minutes with two people on is, the
designer of the K sub Captain Kittredge dove for years venting every hour and
had no problems. John Maynard told me he once sat in his K-350, with a
person monitoring from outside, and he had no ill effects for five hours.
With that to go by, I figured John at rest may burn
about half what I would burn actively operating the sub so that gives one
active person two and a half hours. To be on the safe side the
Captain suggested surfacing every hour with one person so with two I open the
hatch every half hour. Twenty minuets down and a few minutes back and to
unlatch. If I'm diving alone, I vent each hour. Maybe not very
scientific but proven.
I intend to add O2, a scrubber and a monitoring
system some day. Entanglement is by far my biggest fear. It's been
on my mind even through the building phases where I tried to reduce snags, if
possible, and is foremost on my mind when diving. So far I haven't been
deeper then I could safely escape from the sub. Now that the hull was
tested to 540 feet, I know I'll want to go deeper.
I guess a O2 monitor could detect if I have an
O2 leak and it's rising. Actually, if I have a leak that is more
then I would absorb, I would hear it when submerged. I would probably
hear a leak before it would raise the O2 level. It's really quiet
down below.
I know O2 supports combustion, but it's
not all that dangerous. You want to keep it away from any ignition
sources and keep the lines and valves oil free. Sure, if you have
something that gets hot it will burst into flames in a oxygen rich atmosphere
far faster and more furious then it otherwise would, but things don't
just go BOOM because they come in contact with oxygen. If it was that
sensitive, I would never have to strike a spark to start my torch.
Acetylene is a very volatile gas, but mixing it with pure oxygen won't make it
ignite. If I am using the torch and get a "flame out," I can blow the
combine gases on a hot piece of steel an it reignites, but if the steel is under
about a thousand degrees F, it won't.
I'm not saying you can't have big problems in an O2
rich environment, but it's not a bomb unless something gets it, and something
that can burn, hot.
I routinely get oxygen for industrial use. My
supplier has a manifold distribution system that he hooks medical cylinders and
industrial cylinders to. I don't see any difference in what they get
filled with but the medical cylinders look cleaner. They may be cleaner
inside also, but I'm only guessing.
Most likely If I purchased a small medical cylinder
from my supplier, he would fill it repeatly with no problem since he knows about
my sub. But your correct, here in the USA you need a doctors
prescription for O2 for medical use. But, I used to get the cylinders
refilled for our community ambulance with no questions asked so I don't think
their real strict about it. It's not regulated like pain killers and stuff
like that..
Scrubber, O2 and a monitoring device is
soon to be added to my sub.
Dan H.
----- Original Message -----
Sent: Thursday, January 12, 2006 12:14
PM
Subject: [PSUBS-MAILIST] Re: Life
Support
As of yet, I don't have a scrubber
or O2 supply in my sub. For now, I never stay down with two people in
the sub over twenty minutes. That's my rule. I set a timer and
return to the surface when it times out. So in actually, it's about
thirty minutes from closing the hatch to opening it again. There is a
pretty good cushion as I do it. Besides, my wife is more comfortable
with me touching base on a schedule like that. (she muttered something
about the life insurance not being paid up or something) I had
considered an O2 tank when building my sub. It would be nice to extend
my bottom time.
Even though you do
not have O2 on board do you still have gauges to measure CO2 and O2 content in
your sub to back up your 20 minute dive rule?
Kittredge used to carry a 02 tank
inside his sub, and then after the space capsule disaster, he moved it outside
and piped the O2 in through a hull penetration to a valve in the
sub. I was debating when building my hull whether to put the through
hull in or not. My thoughts were and still are; a tank inside the hull
is not leaking or it would be empty. A tank outside of the hull would
have to be turned on before putting the sub in the water. The valve
inside the hull may be leaking a bit and I may not know.
I would have thought
if you had the contence gauge inside with you, along with a separate O2
monitor you would be able to detect a leak and act
accordingly.
Unless the tank or valve ruptures,
I don't see the danger of it being inside the sub. I know it's not
leaking O2 at the time I'm in the sub if it has sat in there for a month or so
already. If I want to extend my bottom time with supplemental O2 and
discover my tank is empty I have to surface and go back to my twenty minute
schedule. I could carry two smaller medical tanks.
I believe the ABS
regs state that gas cylinders should be mounted outside so that a leak will
not increase the internal pressure to a toxic / dangerous level. By the same
token the volume of gas stored in internal pipelines should be kept to a
minimum (by the use of regulators or short runs of pipe) so that if released
it will not increase the internal pressure beyond a certain level. This all
seems to make sense but it does mean at least one more penitrator through your
hull and another stop on the inside.
H
----- Original Message -----
Sent:
Wednesday, January 11,
2006 9:41
PM
Subject: Re:
[PSUBS-MAILIST] Life Support
The normal
human consumes about one cubic foot of oxygen per hour and will feel no
effects of oxygen deprivation at an o2 level above 18% the osha level is
19.5% minimum. air contains 21 % o2. So dependent upon the size of your
cabin you need to run the numbers to see how much o2 you will
have.
A co2
scrubbber can be made from a piece of plastic pipe with screens at the end
to hold the absorbent. mount a fan at the top and for under 100$ you have a
co2 scrubber.
one caution
when using o2 addition it does make things burn rapidly. and abs says
that o2 tank most be mounted outside.
the biggest
problem using pure o2 is the risk of fire in the system piping. high
velocity o2 can ignite lots of things . needle valves are used here. Trust
me on this i turned a rebreather in to a flame thrower the hard
way.
most valves can be ordered o2
clean and should be, the packing and grease needs to be o2 compatible. yes
o2 needs a special grease. piping will need to be cleaned prior to use. I
have had success with hot soapy water wash, repeat until clean then hot
water rinse and cap lines until installed.
----- Original Message -----
Sent:
Wednesday, January 11, 2006 2:51 PM
Subject:
[PSUBS-MAILIST] Life Support
Hello
folks,
It has been a long time since
my last post but I still have questions!
Is it correct to think that
in an enclosed space, like your pressure hull you will suffer from the
negative effects of excess CO2 before you suffer from a lack of O2? What I
am getting at is, could you upgrade a simple sub with no life support by
adding just a scrubber to extend your usable bottom time or would you only
gain a little bit of extra time before the O2 would need replenishing as
well.
What sort of equipment is
used by those of you who do replenish the O2? It is sufficient to have an
O2 tank, conten gauge, regulator (and gauge?), and a flow meter (with a
separate O2 sensor and meter). Or does the equipment need to be more
sophisticated than this.
What do you do about ?oxygen
cleaning? Do you have to just concentrate on the O2 supply kit or all of
the equipment within the sub?
How many of you provide
yourselves with CO2, O2, and internal pressure gauges to monitor the
environment but do not fit additional life support.
Thanks in advanced
guys,
Harry
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