Rick!!!!
Hang on there, I'm here to learn also!
I only stated what I have found and how I concluded what I have
concluded.
I sure don't claim to know all about any subject,
much less O2. In fact, what I stated was about ALL I know about
O2.
So then, am I correct when I say that, gathering
from you posting, high pressure O2 is more apt to self ignite something then a
high O2 environment at atmospheric pressure?
When a gas is decompressed it cools and that
sort of goes against the theory that a blast of high pressure O2 is more apt to
cause combustion, but on the other hand, there would be friction of the O2
molecules as they were racing through a valve. Again referring to my
torches, there is a HP bottle with a regulator that reduces the 2000+ PSI
O2 to 40 PSI. That regulator neither gets hot or cold.
So where is the actual danger with O2? Is it
when it's being decompressed from it's tank or when it's surrounding something
combustible? Or, is the ABS rule about tanks outside the
hull there because of the problems you could have with an uncontrolled
release of any pressurized gas in to an enclosed occupied space?
Are you sure there wasn't something more that
ignited you flame thrower rebreather.... like a chemical reaction that touched
off the fire in the first place?
Not professing to know anything about anything, Dan
H
----- Original Message -----
Sent: Friday, January 13, 2006 12:26
AM
Subject: Re: [PSUBS-MAILIST] Life
Support
Dan:
i really respect you for what
you have done with your sub but you need to look at o2 saftey a little more in
depth.
It sound like you have
expeience with med o 2 and welding o2. but not high pressure o2. high velocity
o2 can ignite metal at room temp., your motor controllers are hot enough to
ignite in a high o2 enviroment. oil from a wrech used when changing bottles
can cause an o2 fire. and just to say that it has not happen to you. will not
stop it from happening. My first rebreather suffered an o2 fire in the piping
due to use scuba tanks with quick opening valves. luckey it was durring
testing outside.nice flame thrower though
standard scuba valves are
quick opening and can cause scorching of regulators or piping ingition. open
all o2 valves slowly. abs requires that o2 tanks be carried outside due
to pressure reasons and the risk of high o2 levels in the cabin. So you have
high pressure o2 entering the cabin at least above ambient.
the question of carry tanks
outside and forgeting to open them needs to covered durring the predive check.
flow check and pressure readings prior to dive. how many of us have hit the
water durring a scuba dive with our tank turned off. i did it once! only once.
now i always check again before i dive.
that all said o2 can be
handled safetly but it requires a hell of a lot more respect then nornal
compressed air
rick m
----- Original Message -----
Sent: Thursday, January 12, 2006 8:18
PM
Subject: Re: [PSUBS-MAILIST] Life
Support
Ross,
I haven't dived my sub any deeper then I could
escape from yet but soon will be. I'll be installing O2 and a scrubber
before I do.
Your correct, I couldn't last long trapped
inside.
Dan H.
----- Original Message -----
Sent: Thursday, January 12, 2006 5:05
PM
Subject: Re: [PSUBS-MAILIST] Life
Support
Dan,
I think I would be afraid to dive with no scrubber or oxygen.
What would happen if I get tangled on something and can't get back
up? By the time anyone realizes I am in trouble I could
suffocate.
Rick,
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.
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.
Unless the tank or valve ruptures, I don't
see the danger of it being inside the sub. I know it's not leaki!
ng 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.
Any thoughts?
Dan H.
----- Original Message -----
Sent: Wednesday, January 11, 2006
9:41 PM
Subject: Re: [PSUBS-MAILIST] Life
Support
harry
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.
fire and
o2
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 h! ad success with hot soapy water wash, repeat until clean then
hot water rinse and cap lines until installed.
hope this helps
rick m
----- Original Message -----
Sent: Wednesday, Janu! ary 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 get! ting 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
?o! xygen 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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