----- Original Message -----
Sent: Thursday, January 12, 2006 10:14
PM
Subject: Re: [PSUBS-MAILIST] Re: Life
Support
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