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By the way, for the reasons I gave you about why
your tank will not hold pressure from opposite sides equally, that is exactly
why the knowledgeable experts here advise
against building a sub out of a propane tank. Yes
some people have done it, and it might even be ok to use to say maybe two
atmospheres (33 ft) DEPENDING ON THE
CONSTRUCTION AND THICKNESS OF THE TANK. But what
would happen if you had an unexpected
uncontrolled decent that took you past that depth? Likely implosion
and Death.
Yesterday I reposted an idea of mine regarding
using a propane tank as a 1 atm (surface pressure) sub to not exceed 2 atm (33
ft) depth while it was operating as a 1 atm sub. Then
the operator would pressurize the interior of the
sub to counteract the outside water pressure so they could dive deeper exactly
as in an ambient sub. I am not planning to, but if I WAS
planning to use a propane tank or some other kind
of existing tank that was not specifically designed to be a 1 atm pressure
vessel.....I would build a hybrid like I have described.
Some of the fellow here have said that they live in
non ocean inland areas and that the lake they plan to use their sub in is
relatively shallow and only 2 or 3 atmospheres. This idea
might be good for people like them. It would have
these advantages.....1. You could use the sub as a 1 atm sub down to 2 atm (33
ft) without having to pressurize the interior and you wouldn't have
to
subject your body to increased interior pressure
and the necessity of following dive tables at that depth. If this is
what someone normally dives to anyway in a shallow lake, this would work
fine. Then for those
occasional times you wanted to dive say an
atmosphere or two deeper, you could switch to ambient operation and operate the
boat exactly like an ambient and use dive tables. I think if
someone
built in a safe, redundant, automatic ambient
pressure control system (as Rick is doing with six scuba regulators) this might
be a good alternative to the expense of building a pressure hull and in
this
instance a propane tank might work and be much
safer than just trying to use the same tank without an ambient system to switch
over to. 2. The other safe thing about this idea is that if you had an
unexpected and uncontrolled
decent in your propane tank 1 atm/ambient
hybrid, you could quickly open a single valve leading to your
regulators and allow their air input to pressurize the hull so it would not
crush. Or, you could even build in valves that would
automatically open when you decended past 2 atm and
would automatically allow your ambient system to kick in. That way you would not
have to constantly keep your eye on the pressure gauge. It would automatically
switch from
1 atm to ambient operation. You still need an
interior air pressure gauge though so you will know what your dive table times
would allow for a given time at a given depth once switched to ambient
operation.
This system would save you from implosion from an unexpected and uncontrolled decent as long
as you did not decend past the depths that a normal ambient sub could
go.
I like this idea and hope someone
will make it. Basically it would simply be an ambient sub made out of a
propane tank that is able to shut off the regulator's air flow to enable it to
be a 1 atm sub
for use at shallow depths say to 2 atm (33ft).
Of course once you pressurized it and switched over to ambient operation, you
could not return to 1 atm interior pressure until you were at or near the
surface
(Carsten taught me that) because there is no way to
lose your pressurized over 1 atm interior atmosphere. You cannot exhaust it
until you allow the system to exhaust it as it would normally in an ambient
sub
as it accends. But I
do not see that as any more of a disadvantage than you would have in a
STRICLY ambient sub where you would have the same condition. I think using this
hybrid 1 atm/ambient system
could possibly enable a lot of us that do not have
the resources to build a pressure hull, to cheaply build a propane tank sub we
could cruise to 2 atm underwater in, while being at 1 atm interior hull
pressure, and then
switch to ambient operation for deeper diving.
Propane tanks might just have a use after all in this limited instance. Before
it was operated though, it should be pressure tested in its 1 atm mode to make
sure it can withstand
the pressure of 2 atm. Which of course for safety
means you should test it in 1 atm mode deeper than 2 atm of depth. What do you
fellow think of this idea?
Bill Akins.
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