[PSUBS-MAILIST] over pressure valve

Fri Jun 19 17:03:34 EDT 2015

Oh! Well I suppose it just depends on the volume the valve can handle. This
is an interesting calculation, which I have not done but should. In
general, these valves should handle pretty huge flow rates. But you're
right, its basic to surface very slowly when there's any over-pressure -
normally we dive with under-pressure. For a K-boat sized hatch, an
over-pressure of 1/4 psi translates to a force of 95lbs trying to pull the
dome out of the hatch ring. I know Snoopy's dome stays put at 1/4 psi, but
I wouldn't take it any further than that just in case.

BTW, on the subject of calculations and changing topics back to the recent
thruster compensation thread, you were right about the temperature change.
The volume I had to compensate was a combination of thermal contraction and
air bubble. The air bubble was of unknown size, but I ran the numbers on
the thermal contraction alone and it is enough to cause the problem. The
little hose only has a an internal volume of 10ml. The thermal contraction
of the oil turned out to be 16ml - add to that the volume of the unknown
bubble, and you can see the hose was inadequate even if it squashed to zero
internal volume. I am now installing bellows bottles in place of the little
hoses, with a capacity of 60ml. And a better filling method that should
eliminate the bubble. You'd think I wasn't an engineer, assuming the effect
of thermal contraction to be negligible. Its easy to focus the calculations
on big items like hull strength or stability and make assumptions about the
little stuff.

Best,

Alec

On Fri, Jun 19, 2015 at 4:19 PM, hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

>
> You have to be experienced to surface slowly and hover while the valve
> leaks out the air.--------------------------------------------
> On Fri, 6/19/15, Alec Smyth via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>  Subject: Re: [PSUBS-MAILIST] over pressure valve
>  To: "Personal Submersibles General Discussion" <
> personal_submersibles at psubs.org>
>  Received: Friday, June 19, 2015, 4:16 PM
>
>  I
>  don't get the "in the hands" part... its
>  completely automatic.
>  On Fri, Jun 19, 2015 at
>  4:09 PM, hank pronk via Personal_Submersibles <
> personal_submersibles at psubs.org>
>  wrote:
>
>
>  Agreed,
>
>  In the hands of an experienced submarine operator an over
>  pressure valve is safe, providing it is large enough.  I
>  have not seen an example of a large enough OPV.  A simple
>  valve in the hatch will do the same job, just need an
>  umbrella :-)
>
>  The noise of a compressor is a welcome sound if it means
>  keeping the dome on the sub :-)
>
>  Hank--------------------------------------------
>
>  On Fri, 6/19/15, Carsten Standfuß" via
>  Personal_Submersibles <personal_submersibles at psubs.org>
>  wrote:
>
>
>
>   Subject: Re: [PSUBS-MAILIST] over pressure valve
>
>   To: "Personal Submersibles General Discussion"
>  <personal_submersibles at psubs.org>
>
>   Received: Friday, June 19, 2015, 2:47 PM
>
>
>
>   But a overpressure vale works
>
>   full auto. A compressor
>
>   not.
>
>
>
>   A OPV needs
>
>   no energy - but a compressor did.
>
>
>
>
>
>   A OPV needs no room - but
>
>   a compressor did.
>
>
>
>   And a
>
>   compressor is
>
>   a noisy solution..
>
>
>
>   vbr
>
>   Carsten
>
>
>
>
>
>
>
>   "hank
>
>   pronk via Personal_Submersibles" <personal_submersibles at psubs.org>
>
>   schrieb:
>
>   > Personally I think an onboard
>
>   compressor is a much safer option than an over pressure
>
>   valve.  There are multiple safety benefits to an
>  onboard
>
>   compressor, over pressure being the biggy.  With a
>
>   compressor you can get rid of the pressure without
>  surfacing
>
>   and trying to control a perfect ascent.  With the OPV
>  you
>
>   have to surface a bit and let air out and wait then
>  surface
>
>   more and wait and so on. You can't just surface and
>  hope
>
>   the valve keeps up with the demand. This is more
>  important
>
>   for subs with large domes.
>
>   > The next
>
>   benefit to a compressor is, if you lost all your air,
>  you
>
>   surface by dropping your weight.  In my case the weight
>  is
>
>   small and I would also drop the thruster and tail
>  assembly.
>
>   Still, not much sub out of the water.  With the
>  compressor,
>
>   I can open my vent valve in the hatch and use the
>  compressor
>
>   to fill the ballast tanks.
>
>   > Hank
>
>   >
>
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