[PSUBS-MAILIST] over pressure valve
Alan James via Personal_Submersibles
personal_submersibles at psubs.org
Fri Jun 19 20:03:55 EDT 2015
Any link to it Brian?I think Emile posted his over pressure valve design at one time.It has a plunger for manually releasing the last bit of pressure.With a bit of thought you could incorporate a snorkel system &circulate air around the hull through it.Another thought is to use Vance's Top Hat valve design for ballast tanks,& use a weak spring.Alan
From: Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Saturday, June 20, 2015 11:15 AM
Subject: Re: [PSUBS-MAILIST] over pressure valve
I found a really nice 1" SS spring check valve that I think would work really nicely as an OP valve, the spring is so light that the differential would be next to nothing. I also looked at an interesting ball bearing check valve that works on just gravity, which would work as well, but it wasn't SS.
Brian
--- personal_submersibles at psubs.org wrote:
From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] over pressure valve
Date: Fri, 19 Jun 2015 14:28:43 -0700
Alec,
At first I resisted the notion of thermal expansion, but I was thinking in terms of heat generated from motor use. I didn't consider the temperature change from the sun on a black motor until the light went on :-)
I have changed my p trap ss tube to a larger hose so there is more air volume to work with. I am ready to test that part. Now I have to fix my bent up rudder :-(
Hank--------------------------------------------
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, 5:03 PM
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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