[PSUBS-MAILIST] over pressure valve

Sat Jun 20 22:50:16 EDT 2015

What happened to Captain K's snorkel float valve?  That was a snorkel and over pressure valve all in one which I have adopted.
Too big an OP valve at low differential will let water leak in if it is not in the right orientation.  If it is upside down like a pingpong ball on a kids dive snorkel then it wont leak water in while venting small quantities.
I have made a 1-1/2" float valve using Capn K's design concept but I have 3 seals.  Then I have a combination 2" ball valve valve with non-return and a pneumatic operated shuttle design leading into the cabin.  So if all valves are open there are two non check valve/OP valves in series both of which you can breathe out through.  Maybe a bit complex as I am using all that for the Engine intake into the cabin as well, however the concept remains the same as the float valve of the K350 and a non return with isolating valve.  

Better to get a consensus of process type drawings and have communal parts.  That way no-ones sub is a complete orphan.  Very good 20/20 hindsight.
Hugh

-----Original Message-----
From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Brian Cox via Personal_Submersibles
Sent: Saturday, 20 June 2015 11:16 a.m.

To: Personal Submersibles General Discussion
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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